Fair Value Disclosure (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Derivative [Line Items]
Property, Plant and Equipment, Net	$ 5,688.7		$ 5,688.7		$ 5,070.3
Asset impairment	0	1.1	0.3	2.0
Fair Value Disclosure (Textual) [Abstract]
Derivative Asset, Notional Amount	500.0		500.0		200.0
Derivative, Notional Amount	118.7		118.7		163.6
Cash Flow Hedge Pre Tax Gain Loss to be Reclassified within Twelve Months			(5.8)
Expected After tax reclassification of net losses from accumulated other comprehensive income to earnings in Next Twelve Months			3.7
Aggregate fair value of all derivative instruments with Net liability position	$ 3.6		$ 3.6
Fair Value Hedging [Member]
Fair Value Disclosure (Textual) [Abstract]
Number of instruments, outstanding	6		6		3
Maturity Date Range of Derivative Instruments	2015 to 2019
Cash Flow Hedges [Member]
Fair Value Disclosure (Textual) [Abstract]
Number of instruments, outstanding	4		4		6
Maturity Date Range of Derivative Instruments	2019 to 2020