Benefits (Details 1) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2015	Mar. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Current pension plan asset allocation in equity investments	45.00%				35.00%
Current pension plan asset allocation in fixed income investments	55.00%				55.00%
Current pension plan asset allocation in real estate investments					10.00%
Amounts recognized in Consolidated Balance Sheets
Other long-term liabilities	$ 203,800,000	$ 173,200,000
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	1,504,600,000	1,409,500,000
Defined Benefit Plan, Benefit Obligation	1,505,500,000	1,410,200,000	1,508,500,000
Change in Plan Assets
Fair Value at January 1	1,451,000,000	1,385,400,000
Actual earnings (loss) on plan assets	88,500,000	147,300,000
Employer contributions	8,400,000	8,700,000
Participants' contributions	0	0
Gross benefits paid	(103,300,000)	(90,400,000)
Fair Value at December 31	1,444,600,000	1,451,000,000
Amounts recognized in Consolidated Balance Sheets
Other deferred charges	39,200,000	138,700,000
Other long-term liabilities	100,100,000	97,900,000
Net Liability	60,900,000	(40,800,000)
Amounts not yet been recognized in net periodic benefit cost
Net actuarial loss	622,700,000	528,800,000
Prior service costs (credits)	6,800,000	8,800,000
Total	629,500,000	537,600,000
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation	397,700,000	362,700,000	381,200,000
Change in Plan Assets
Fair Value at January 1	327,600,000	285,400,000
Actual earnings (loss) on plan assets	17,700,000	45,500,000
Employer contributions	5,500,000	14,100,000	17,700,000
Participants' contributions	9,100,000	8,900,000
Gross benefits paid	(26,400,000)	(26,300,000)
Fair Value at December 31	333,500,000	327,600,000	285,400,000
Amounts recognized in Consolidated Balance Sheets
Other deferred charges	39,500,000	40,200,000
Other long-term liabilities	103,700,000	75,300,000
Net Liability	64,200,000	35,100,000
Amounts not yet been recognized in net periodic benefit cost
Net actuarial loss	44,100,000	9,800,000
Prior service costs (credits)	(4,600,000)	(1,700,000)
Total	39,500,000	8,100,000
Pension, Qualified [Member] | Pension Plans [Member]
Change in Plan Assets
Employer contributions	$ 0	$ 0	$ 95,600,000	$ 100,000,000