PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Benefit Obligations, Fair Value of Plan Assets, and Net Funded Status) (Details) - USD ($)
$ in Millions |
12 Months Ended |
|
|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
Dec. 31, 2015 |
Dec. 31, 2014 |
| Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |
|
|
|
|
|
| Fair value of plan assets — beginning of year |
$ 188.1
|
$ 169.8
|
|
|
|
| Employer contributions |
3.5
|
5.5
|
|
|
|
| Fair value of plan assets — end of year |
193.4
|
188.1
|
$ 169.8
|
|
|
| Funded status at December 31: |
|
|
|
|
|
| Defined Benefit Plan, Fair Value of Plan Assets |
$ 188.1
|
169.8
|
169.8
|
$ 193.4
|
$ 188.1
|
| Amounts recognized in Statements of Financial Position: |
|
|
|
|
|
| Noncurrent liabilities |
|
|
|
(221.0)
|
(268.3)
|
| Amounts recognized in accumulated other comprehensive income: |
|
|
|
|
|
| Retirement And Defined Compensation Plans Disclosures [Table Text Block] |
The following table summarizes the annual expense recognized related to the retirement plans for 2015, 2014 and 2013:
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(In Millions) |
|
2015 |
|
2014 |
|
2013 |
Defined benefit pension plans |
$ |
23.9 |
|
|
$ |
26.2 |
|
|
$ |
46.8 |
|
Defined contribution pension plans |
3.6 |
|
|
4.4 |
|
|
5.0 |
|
Other postretirement benefits |
4.4 |
|
|
(2.5 |
) |
|
3.2 |
|
Total |
$ |
31.9 |
|
|
$ |
28.1 |
|
|
$ |
55.0 |
|
|
|
|
|
|
| Pension Benefits [Member] |
|
|
|
|
|
| Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |
|
|
|
|
|
| Benefit obligations — beginning of year |
$ (998.0)
|
(891.2)
|
|
|
|
| Service cost (excluding expenses) |
22.7
|
26.1
|
32.9
|
|
|
| Interest cost |
37.7
|
40.3
|
36.4
|
|
|
| Plan amendments |
0.0
|
0.0
|
|
|
|
| Actuarial loss |
(20.8)
|
(14.0)
|
(27.0)
|
|
|
| Defined Benefit Plan, Change in Actuarial (gain) loss |
(67.7)
|
113.4
|
|
|
|
| Benefits paid |
(78.7)
|
(71.4)
|
|
|
|
| Participant contributions |
0.0
|
0.0
|
|
|
|
| Federal subsidy on benefits paid |
0.0
|
0.0
|
|
|
|
| Benefit obligations — end of year |
(910.8)
|
(998.0)
|
(891.2)
|
|
|
| Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |
|
|
|
|
|
| Fair value of plan assets — beginning of year |
749.8
|
712.5
|
|
|
|
| Actual return on plan assets |
(6.4)
|
59.1
|
80.3
|
|
|
| Participant contributions |
0.0
|
0.0
|
|
|
|
| Employer contributions |
35.7
|
49.6
|
|
|
|
| Assets Transferred to (from) Plan |
0.2
|
0.0
|
|
|
|
| Benefits paid |
(78.7)
|
(71.4)
|
|
|
|
| Fair value of plan assets — end of year |
700.6
|
749.8
|
712.5
|
|
|
| Funded status at December 31: |
|
|
|
|
|
| Defined Benefit Plan, Fair Value of Plan Assets |
749.8
|
712.5
|
712.5
|
700.6
|
749.8
|
| Defined Benefit Plan, Benefit Obligation |
(998.0)
|
(891.2)
|
(891.2)
|
(910.8)
|
(998.0)
|
| Underfunded status of plan |
|
|
|
(210.2)
|
(248.2)
|
| Amount recognized at December 31 |
|
|
|
(210.2)
|
(248.2)
|
| Amounts recognized in Statements of Financial Position: |
|
|
|
|
|
| Current liabilities |
|
|
|
(0.5)
|
(2.2)
|
| Noncurrent liabilities |
|
|
|
(209.7)
|
(246.0)
|
| Net amount recognized |
|
|
|
(210.2)
|
(248.2)
|
| Amounts recognized in accumulated other comprehensive income: |
|
|
|
|
|
| Prior service cost |
|
|
|
7.5
|
9.8
|
| Net actuarial loss |
|
|
|
290.9
|
311.8
|
| Net amount recognized |
|
|
|
298.4
|
321.6
|
| The estimated amounts that will be amortized from accumulated other comprehensive income into net periodic benefit cost in 2013: |
|
|
|
|
|
| Net actuarial loss |
21.1
|
|
|
|
|
| Prior service cost |
2.2
|
|
|
|
|
| Net amount recognized |
23.3
|
|
|
|
|
| Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments |
(1.2)
|
(1.5)
|
|
|
|
| Other Benefits [Member] |
|
|
|
|
|
| Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |
|
|
|
|
|
| Benefit obligations — beginning of year |
(295.8)
|
(265.1)
|
|
|
|
| Service cost (excluding expenses) |
6.4
|
1.8
|
4.0
|
|
|
| Interest cost |
13.4
|
11.9
|
12.6
|
|
|
| Plan amendments |
0.0
|
(0.9)
|
|
|
|
| Actuarial loss |
(6.6)
|
(4.5)
|
(10.2)
|
|
|
| Defined Benefit Plan, Change in Actuarial (gain) loss |
(27.0)
|
37.4
|
|
|
|
| Benefits paid |
(20.6)
|
(25.3)
|
|
|
|
| Participant contributions |
4.0
|
4.8
|
|
|
|
| Federal subsidy on benefits paid |
0.4
|
0.9
|
|
|
|
| Benefit obligations — end of year |
(266.0)
|
(295.8)
|
(265.1)
|
|
|
| Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |
|
|
|
|
|
| Fair value of plan assets — beginning of year |
269.3
|
251.8
|
|
|
|
| Actual return on plan assets |
(3.9)
|
31.9
|
11.0
|
|
|
| Participant contributions |
0.4
|
0.8
|
|
|
|
| Employer contributions |
1.3
|
5.2
|
|
|
|
| Assets Transferred to (from) Plan |
0.0
|
0.0
|
|
|
|
| Benefits paid |
(16.5)
|
(20.4)
|
|
|
|
| Fair value of plan assets — end of year |
250.6
|
269.3
|
251.8
|
|
|
| Funded status at December 31: |
|
|
|
|
|
| Defined Benefit Plan, Fair Value of Plan Assets |
269.3
|
251.8
|
251.8
|
250.6
|
269.3
|
| Defined Benefit Plan, Benefit Obligation |
(295.8)
|
(265.1)
|
$ (265.1)
|
(266.0)
|
(295.8)
|
| Underfunded status of plan |
|
|
|
(15.4)
|
(26.5)
|
| Amount recognized at December 31 |
|
|
|
(15.4)
|
(26.5)
|
| Amounts recognized in Statements of Financial Position: |
|
|
|
|
|
| Current liabilities |
|
|
|
(4.1)
|
(4.2)
|
| Noncurrent liabilities |
|
|
|
(11.3)
|
(22.3)
|
| Net amount recognized |
|
|
|
(15.4)
|
(26.5)
|
| Amounts recognized in accumulated other comprehensive income: |
|
|
|
|
|
| Prior service cost |
|
|
|
(39.5)
|
(42.9)
|
| Net actuarial loss |
|
|
|
91.5
|
99.3
|
| Net amount recognized |
|
|
|
52.0
|
56.4
|
| The estimated amounts that will be amortized from accumulated other comprehensive income into net periodic benefit cost in 2013: |
|
|
|
|
|
| Net actuarial loss |
5.5
|
|
|
|
|
| Prior service cost |
(3.7)
|
|
|
|
|
| Net amount recognized |
1.8
|
|
|
|
|
| Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments |
0.0
|
0.0
|
|
|
|
| Salaried Employees [Member] | Pension Benefits [Member] |
|
|
|
|
|
| Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |
|
|
|
|
|
| Benefit obligations — beginning of year |
(379.2)
|
|
|
|
|
| Benefit obligations — end of year |
(340.0)
|
(379.2)
|
|
|
|
| Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |
|
|
|
|
|
| Fair value of plan assets — beginning of year |
288.3
|
|
|
|
|
| Fair value of plan assets — end of year |
258.3
|
288.3
|
|
|
|
| Funded status at December 31: |
|
|
|
|
|
| Defined Benefit Plan, Fair Value of Plan Assets |
288.3
|
288.3
|
|
258.3
|
288.3
|
| Defined Benefit Plan, Benefit Obligation |
(379.2)
|
(379.2)
|
|
(340.0)
|
(379.2)
|
| Underfunded status of plan |
|
|
|
(81.7)
|
(90.9)
|
| Salaried Employees [Member] | Other Benefits [Member] |
|
|
|
|
|
| Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |
|
|
|
|
|
| Benefit obligations — beginning of year |
(41.6)
|
|
|
|
|
| Benefit obligations — end of year |
(38.2)
|
(41.6)
|
|
|
|
| Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |
|
|
|
|
|
| Fair value of plan assets — beginning of year |
0.0
|
|
|
|
|
| Fair value of plan assets — end of year |
0.0
|
0.0
|
|
|
|
| Funded status at December 31: |
|
|
|
|
|
| Defined Benefit Plan, Fair Value of Plan Assets |
0.0
|
0.0
|
|
0.0
|
0.0
|
| Defined Benefit Plan, Benefit Obligation |
(41.6)
|
(41.6)
|
|
(38.2)
|
(41.6)
|
| Underfunded status of plan |
|
|
|
(38.2)
|
(41.6)
|
| Hourly Employees [Member] | Pension Benefits [Member] |
|
|
|
|
|
| Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |
|
|
|
|
|
| Benefit obligations — beginning of year |
(603.9)
|
|
|
|
|
| Benefit obligations — end of year |
(558.6)
|
(603.9)
|
|
|
|
| Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |
|
|
|
|
|
| Fair value of plan assets — beginning of year |
454.9
|
|
|
|
|
| Fair value of plan assets — end of year |
436.7
|
454.9
|
|
|
|
| Funded status at December 31: |
|
|
|
|
|
| Defined Benefit Plan, Fair Value of Plan Assets |
454.9
|
454.9
|
|
436.7
|
454.9
|
| Defined Benefit Plan, Benefit Obligation |
(603.9)
|
(603.9)
|
|
(558.6)
|
(603.9)
|
| Underfunded status of plan |
|
|
|
(121.9)
|
(149.0)
|
| Hourly Employees [Member] | Other Benefits [Member] |
|
|
|
|
|
| Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |
|
|
|
|
|
| Benefit obligations — beginning of year |
(254.2)
|
|
|
|
|
| Benefit obligations — end of year |
(227.8)
|
(254.2)
|
|
|
|
| Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |
|
|
|
|
|
| Fair value of plan assets — beginning of year |
269.3
|
|
|
|
|
| Fair value of plan assets — end of year |
250.6
|
269.3
|
|
|
|
| Funded status at December 31: |
|
|
|
|
|
| Defined Benefit Plan, Fair Value of Plan Assets |
269.3
|
269.3
|
|
250.6
|
269.3
|
| Defined Benefit Plan, Benefit Obligation |
(254.2)
|
(254.2)
|
|
(227.8)
|
(254.2)
|
| Underfunded status of plan |
|
|
|
22.8
|
15.1
|
| Mining Employees [Member] | Pension Benefits [Member] |
|
|
|
|
|
| Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |
|
|
|
|
|
| Benefit obligations — beginning of year |
(9.2)
|
|
|
|
|
| Benefit obligations — end of year |
(8.6)
|
(9.2)
|
|
|
|
| Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |
|
|
|
|
|
| Fair value of plan assets — beginning of year |
6.6
|
|
|
|
|
| Fair value of plan assets — end of year |
5.6
|
6.6
|
|
|
|
| Funded status at December 31: |
|
|
|
|
|
| Defined Benefit Plan, Fair Value of Plan Assets |
6.6
|
6.6
|
|
5.6
|
6.6
|
| Defined Benefit Plan, Benefit Obligation |
(9.2)
|
(9.2)
|
|
(8.6)
|
(9.2)
|
| Underfunded status of plan |
|
|
|
(3.0)
|
(2.6)
|
| Supplemental Executive Retirement Plan S E R P [Member] | Pension Benefits [Member] |
|
|
|
|
|
| Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |
|
|
|
|
|
| Benefit obligations — beginning of year |
(5.7)
|
|
|
|
|
| Benefit obligations — end of year |
(3.6)
|
(5.7)
|
|
|
|
| Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |
|
|
|
|
|
| Fair value of plan assets — beginning of year |
0.0
|
|
|
|
|
| Fair value of plan assets — end of year |
0.0
|
0.0
|
|
|
|
| Funded status at December 31: |
|
|
|
|
|
| Defined Benefit Plan, Fair Value of Plan Assets |
0.0
|
0.0
|
|
0.0
|
0.0
|
| Defined Benefit Plan, Benefit Obligation |
(5.7)
|
(5.7)
|
|
(3.6)
|
(5.7)
|
| Underfunded status of plan |
|
|
|
$ (3.6)
|
$ (5.7)
|
| Pension Costs [Member] | Pension Benefits [Member] |
|
|
|
|
|
| Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |
|
|
|
|
|
| Interest cost |
|
40.2
|
|
|
|
| Pension Costs [Member] | Other Benefits [Member] |
|
|
|
|
|
| Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |
|
|
|
|
|
| Service cost (excluding expenses) |
1.9
|
$ 1.9
|
|
|
|
| Interest cost |
$ 11.5
|
|
|
|
|