Derivative Instruments And Hedging Activities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				12 Months Ended	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	May 31, 2008	May 07, 2008	Dec. 31, 2010 Series 2005 - 1 Swap [Member]	Mar. 31, 2012 Interest Expense [Member] Interest Rate Swaps [Member]	Mar. 31, 2011 Interest Expense [Member] Interest Rate Swaps [Member]
Derivative [Line Items]
Interest rate swaps notional amount			$ 150	$ 150	$ 300
Floating interest rate base					3-month LIBOR
Net interest income (expense) recognized						(0.8)	1.1
Gain (loss) on foreign currency derivatives	$ 1.0	$ 3.2