Derivative Instruments and Hedging Activities - Impact of Derivative Instruments on Consolidated Statements of Income and OCI (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Net Gain (Loss) Recognized in Accumulated OCI (Effective Portion)	$ (25.1)	$ (28.6)
Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(5.7)	(5.7)	0.4
Treasury Locks, Net Of Tax
Derivative Instruments, Gain (Loss) [Line Items]
Net Gain (Loss) Recognized in Accumulated OCI (Effective Portion)	(24.7)	(28.2)
Foreign Exchange Contract
Derivative Instruments, Gain (Loss) [Line Items]
Net Gain (Loss) Recognized in Accumulated OCI (Effective Portion)	$ (0.4)	$ (0.4)