Derivative Instruments (Narrative) (Details) (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]
Derivative assets	$ 1,409.1		$ 1,409.1		$ 1,204.2
Cross-currency and interest rate derivative contracts
Derivative [Line Items]
Valuation adjustment in asset cross currency and interest rate derivative contracts	7.7		7.7		9.8
Valuation adjustment in liability cross currency and interest rate derivative contracts	122.6		122.6		173.0
Loss on change in credit risk valuation included in realized and unrealized gains (losses) on derivative instruments, net	19.4	13.0	48.9	45.5
Derivative assets	980.6		980.6		769.2
Counterparty Credit Risk [Member]
Derivative [Line Items]
Derivative assets	$ 626.7		$ 626.7