Benefits (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation	$ 1,507,100,000	$ 1,329,400,000
Matching contributions under Savings Plans	13,800,000	14,100,000	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	27,800,000
1% Decrease, in assumed health care cost trend rates, Effect on, Post-retirement benefit obligation	(23,500,000)
1% Increase, in assumed health care cost trend rates, Effect on, Total of service and interest cost components	4,000,000
1% Decrease, in assumed health care cost trend rates, Effect on, Total of service and interest cost components	(3,200,000)
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%
Current pension plan target asset allocation in fixed income investments	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	13,800,000	14,100,000	13,800,000
Postemployment benefits liability	4,000,000
Pension, Qualified [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Funded Status of Plan	(20,900,000)	24,400,000
Pension, Non-Qualified [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Funded Status of Plan	(102,200,000)	(92,500,000)
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation	1,508,500,000	1,330,600,000	1,222,800,000
Defined Benefit Plan, Amortization of Previously Unrecognized Benefit Costs	56,000,000
Net Periodic Benefit Cost
Service cost	21,700,000	15,900,000	23,700,000
Interest cost	65,500,000	67,600,000	68,400,000
Expected return on plan assets	(89,600,000)	(82,100,000)	(78,200,000)
Amortization of:
Transition obligation	0	0	0
Prior service cost (credit)	2,200,000	2,200,000	2,200,000
Actuarial loss	41,000,000	34,000,000	26,800,000
Curtailment (gain)	400,000	0	0
Net Periodic Benefit Cost	41,200,000	37,600,000	42,900,000
Weighted-Average assumptions used to determine benefit obligations as of Dec. 31
Discount rate	4.10%	5.05%	5.60%
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	5.05%	5.60%	6.05%
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	1,385,400,000	1,262,500,000	1,059,500,000
Employer contributions to defined benefit plan
Employer contributions	102,700,000	242,900,000
Expected benefit payments in future
2012	101,400,000
2013	99,500,000
2014	98,900,000
2015	99,100,000
2016	99,800,000
2017-2021	489,400,000
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	763,100,000	681,800,000
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	622,300,000	580,700,000
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	0	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	13,700,000	8,500,000
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	13,700,000	8,500,000
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	466,300,000	455,100,000
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	466,300,000	455,100,000
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	165,100,000	134,300,000
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	134,700,000	100,400,000
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	30,400,000	33,900,000
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	614,300,000	579,700,000
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	67,700,000	76,900,000
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	546,600,000	502,800,000
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	126,000,000	84,900,000
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	80,700,000	40,900,000
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	45,300,000	44,000,000
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
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation	381,200,000	389,700,000	368,300,000
Defined Benefit Plan, Amortization of Previously Unrecognized Benefit Costs	1,500,000
Net Periodic Benefit Cost
Service cost	10,300,000	10,400,000	11,200,000
Interest cost	20,300,000	20,800,000	21,200,000
Expected return on plan assets	(19,000,000)	(16,900,000)	(14,300,000)
Amortization of:
Transition obligation	300,000	300,000	300,000
Prior service cost (credit)	(1,900,000)	(1,900,000)	(11,900,000)
Actuarial loss	7,300,000	6,200,000	10,800,000
Curtailment (gain)	0	0	(400,000)
Net Periodic Benefit Cost	17,300,000	18,900,000	16,900,000
Weighted-Average assumptions used to determine benefit obligations as of Dec. 31
Discount rate	4.15%	5.20%	5.70%
Weighted-Average assumptions used to determine net cost for year ended Dec. 31
Discount rate	5.20%	5.70%	5.75%
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	0.080	0.075
Health care cost trend rate assumed for next year, Post 65	0.120	0.120	0.16
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)	2017/2017	2017/2017	2015/2016
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	285,400,000	255,400,000	216,700,000
Employer contributions to defined benefit plan
Employer contributions	17,700,000	48,400,000	4,900,000
Expected benefit payments in future
2012	23,300,000
2013	20,800,000
2014	21,000,000
2015	21,500,000
2016	22,200,000
2017-2021	113,900,000
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	187,900,000	165,000,000
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	97,500,000	90,400,000
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	0	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	1,700,000	2,400,000
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	1,700,000	2,400,000
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	125,900,000	113,600,000
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	125,900,000	113,600,000
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	42,100,000	34,400,000
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	39,900,000	32,100,000
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	2,200,000	2,300,000
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	94,900,000	91,200,000
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	5,000,000	8,200,000
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	89,900,000	83,000,000
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	20,800,000	13,800,000
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	15,400,000	8,700,000
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	5,400,000	5,100,000
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
Pension, Qualified [Member] | Pension Plans [Member]
Employer contributions to defined benefit plan
Employer contributions	95,600,000	236,400,000	0
Pension, Non-Qualified [Member] | Pension Plans [Member]
Employer contributions to defined benefit plan
Employer contributions	$ 7,100,000	$ 6,500,000	$ 6,800,000
Cash Balance Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Loss Contingency Range Of Possible Loss, Per Share, Maximum		$ 0.04