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The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation.

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The interest rate used to adjust for the time value of money for the plan.

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Expected rate of compensation increases (for pay-related plans).

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An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Expected Long-Term Rate of Return on Plan Assets

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-Paragraph 1

-Subparagraph (k)(3)

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Expected rate of compensation increases (for pay-related plans).

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1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

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The increase in the fair value of plan assets from contributions made by the employer.

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Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

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Amount of benefits from a defined benefit plan expected to be paid in the five fiscal years after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of benefits from a defined benefit plan expected to be paid in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of benefits from a defined benefit plan expected to be paid in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of benefits from a defined benefit plan expected to be paid in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of benefits from a defined benefit plan expected to be paid in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of benefits from a defined benefit plan expected to be paid in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets.

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Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

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The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

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The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments.

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The amount of net gain (loss) recognized in net periodic benefit cost as a result of an event that significantly reduces the expected years of future service of present employees or eliminates for a significant number of employees the accrual of defined benefits for some or all of their future services.

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Amount of net gain (loss) recognized in net periodic benefit cost as a result of an irrevocable action that relieves the employer (or the plan) of primary responsibility for a benefit obligation and eliminates significant risks related to the obligation and the assets used to effect the settlement. Examples of transactions that constitute a settlement include, but are not limited to, lump-sum cash payments to plan participants in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contracts to cover vested benefits.

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The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

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The carrying amount as of the balance sheet date of the obligations recognized for the various benefits provided to former or inactive employees, their beneficiaries, and covered dependents after employment but before retirement.

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Current pension plan asset allocation in equity investments.

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Matching contributions under Savings Plans

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Rate to which assumed health care cost rate gradually adjusted.

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Benefits (Details 2) (USD $)	12 Months Ended			1 Months Ended
Benefits (Details 2) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2015	Mar. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Matching contributions under Savings Plans	$ 14,200,000	$ 14,200,000	$ 13,800,000
A one-percentage-point change in assumed health care cost trend rates effects
1% Increase, in assumed health care cost trend rates, Effect on, Post-retirement benefit obligation	30,200,000
1% Decrease, in assumed health care cost trend rates, Effect on, Post-retirement benefit obligation	(25,400,000)
1% Increase, in assumed health care cost trend rates, Effect on, Total of service and interest cost components	3,100,000
1% Decrease, in assumed health care cost trend rates, Effect on, Total of service and interest cost components	(2,500,000)
Benefits (Textuals) [Abstract]
Health care cost trend rate up to specified age	65
Health care cost trend rate post specified age	65
Current pension plan target asset allocation in equity investments	45.00%				35.00%
Current pension plan target asset allocation in fixed income investments	55.00%				55.00%
Other Post-Retirement Employee Benefits target asset allocation in equity investments					60.00%
Other Post-Retirement Employee Benefits target asset allocation in fixed income investments					40.00%
Matching contributions under Savings Plans	14,200,000	14,200,000	13,800,000
Postemployment benefits liability	3,300,000	4,200,000
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation	1,505,500,000	1,410,200,000	1,508,500,000
Defined Benefit Plan, Amortization of Previously Unrecognized Benefit Costs	48,300,000
Net Periodic Benefit Cost
Service cost	10,100,000	14,600,000	21,700,000
Interest cost	68,100,000	60,400,000	65,500,000
Expected return on plan assets	(98,600,000)	(95,800,000)	(89,600,000)
Amortization of:
Transition obligation	0	0	0
Prior service cost (credit)	2,100,000	2,300,000	2,200,000
Actuarial loss	36,700,000	54,500,000	41,000,000
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements	0	2,500,000	0
Curtailment (gain)	0	0	400,000
Net Periodic Benefit Cost	18,400,000	38,500,000	41,200,000
Weighted-Average assumptions used to determine benefit obligations as of Dec. 31
Discount rate	4.15%	5.00%	4.10%
Rate of compensation increase	4.00%	4.00%	4.00%
Weighted-Average assumptions used to determine net cost for year ended Dec. 31
Discount rate	5.00%	4.10%	5.05%
Expected return on plan assets	7.25%	7.25%	7.25%
Rate of compensation increase	4.00%	4.00%	4.00%
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	1,444,600,000	1,451,000,000	1,385,400,000
Employer contributions to defined benefit plan
Employer contributions	8,400,000	8,700,000
Expected benefit payments in future
2012	104,700,000
2013	103,600,000
2014	104,300,000
2015	102,300,000
2016	102,400,000
2017-2021	491,800,000
Pension Plans [Member] \| Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	760,600,000	873,200,000
Pension Plans [Member] \| Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	672,400,000	577,800,000
Pension Plans [Member] \| Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	11,600,000	0
Pension Plans [Member] \| Cash And Cash Equivalents [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	6,400,000	21,000,000
Pension Plans [Member] \| Cash And Cash Equivalents [Member] \| Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	6,400,000	21,000,000
Pension Plans [Member] \| Cash And Cash Equivalents [Member] \| Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
Pension Plans [Member] \| Cash And Cash Equivalents [Member] \| Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
Pension Plans [Member] \| U.S. Equity [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	503,800,000	519,500,000
Pension Plans [Member] \| U.S. Equity [Member] \| Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	503,800,000	519,500,000
Pension Plans [Member] \| U.S. Equity [Member] \| Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
Pension Plans [Member] \| U.S. Equity [Member] \| Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
Pension Plans [Member] \| International Equity [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	158,400,000	181,900,000
Pension Plans [Member] \| International Equity [Member] \| Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	128,600,000	146,200,000
Pension Plans [Member] \| International Equity [Member] \| Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	29,800,000	35,700,000
Pension Plans [Member] \| International Equity [Member] \| Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
Pension Plans [Member] \| U.S. Bonds [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	641,800,000	613,600,000
Pension Plans [Member] \| U.S. Bonds [Member] \| Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	42,500,000	108,400,000
Pension Plans [Member] \| U.S. Bonds [Member] \| Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	599,300,000	505,200,000
Pension Plans [Member] \| U.S. Bonds [Member] \| Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
Pension Plans [Member] \| International Bonds [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	122,600,000	115,000,000
Pension Plans [Member] \| International Bonds [Member] \| Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	79,300,000	78,100,000
Pension Plans [Member] \| International Bonds [Member] \| Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	43,300,000	36,900,000
Pension Plans [Member] \| International Bonds [Member] \| Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
Pension Plans [Member] \| Private Placement [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	11,600,000
Pension Plans [Member] \| Private Placement [Member] \| Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0
Pension Plans [Member] \| Private Placement [Member] \| Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0
Pension Plans [Member] \| Private Placement [Member] \| Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	11,600,000
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation	397,700,000	362,700,000	381,200,000
Defined Benefit Plan, Amortization of Previously Unrecognized Benefit Costs	900,000
Net Periodic Benefit Cost
Service cost	8,500,000	10,000,000	10,300,000
Interest cost	17,800,000	15,600,000	20,300,000
Expected return on plan assets	(23,700,000)	(21,300,000)	(19,000,000)
Amortization of:
Transition obligation	0	0	300,000
Prior service cost (credit)	(1,800,000)	(2,000,000)	(1,900,000)
Actuarial loss	1,200,000	3,700,000	7,300,000
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements	0	0	0
Curtailment (gain)	0	0	0
Net Periodic Benefit Cost	2,000,000	6,000,000	17,300,000
Weighted-Average assumptions used to determine benefit obligations as of Dec. 31
Discount rate	4.20%	4.95%	4.15%
Weighted-Average assumptions used to determine net cost for year ended Dec. 31
Discount rate	4.95%	4.15%	5.20%
Expected return on plan assets	7.50%	7.50%	7.50%
Assumed health care cost trend rates as of Dec. 31
Health care cost trend rate assumed for next year, Pre 65	0.075	0.075	0.075
Health care cost trend rate assumed for next year, Post 65	0.075	0.075	0.075
Rate that the cost trend rate gradually adjusts to	0.050	0.050	0.050
Year that the rate reaches the rate it is assumed to remain at (Pre 65 / Post 65)	2021/2021	2021/2021	2017/2017
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	333,500,000	327,600,000	285,400,000
Employer contributions to defined benefit plan
Employer contributions	5,500,000	14,100,000	17,700,000
Expected benefit payments in future
2012	25,500,000
2013	22,300,000
2014	22,800,000
2015	23,300,000
2016	24,100,000
2017-2021	122,500,000
OPEB [Member] \| Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	210,600,000	222,700,000
OPEB [Member] \| Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	121,900,000	104,900,000
OPEB [Member] \| Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	1,000,000	0
OPEB [Member] \| Cash And Cash Equivalents [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	1,400,000	2,600,000
OPEB [Member] \| Cash And Cash Equivalents [Member] \| Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	1,400,000	2,600,000
OPEB [Member] \| Cash And Cash Equivalents [Member] \| Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
OPEB [Member] \| Cash And Cash Equivalents [Member] \| Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
OPEB [Member] \| U.S. Equity [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	146,000,000	148,000,000
OPEB [Member] \| U.S. Equity [Member] \| Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	146,000,000	148,000,000
OPEB [Member] \| U.S. Equity [Member] \| Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
OPEB [Member] \| U.S. Equity [Member] \| Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
OPEB [Member] \| International Equity [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	44,700,000	49,700,000
OPEB [Member] \| International Equity [Member] \| Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	42,200,000	46,900,000
OPEB [Member] \| International Equity [Member] \| Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	2,500,000	2,800,000
OPEB [Member] \| International Equity [Member] \| Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
OPEB [Member] \| U.S. Bonds [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	115,900,000	104,700,000
OPEB [Member] \| U.S. Bonds [Member] \| Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	3,500,000	8,400,000
OPEB [Member] \| U.S. Bonds [Member] \| Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	112,400,000	96,300,000
OPEB [Member] \| U.S. Bonds [Member] \| Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
OPEB [Member] \| International Bonds [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	24,500,000	22,600,000
OPEB [Member] \| International Bonds [Member] \| Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	17,500,000	16,800,000
OPEB [Member] \| International Bonds [Member] \| Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	7,000,000	5,800,000
OPEB [Member] \| International Bonds [Member] \| Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
OPEB [Member] \| Private Placement [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	1,000,000
OPEB [Member] \| Private Placement [Member] \| Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0
OPEB [Member] \| Private Placement [Member] \| Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0
OPEB [Member] \| Private Placement [Member] \| Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	1,000,000
Pension, Qualified [Member] \| Pension Plans [Member]
Employer contributions to defined benefit plan
Employer contributions	0	0	95,600,000	100,000,000
Pension, Non-Qualified [Member] \| Pension Plans [Member]
Employer contributions to defined benefit plan
Employer contributions	$ 8,400,000	$ 8,700,000	$ 7,100,000