Equity (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Components of accumulated other comprehensive income (loss)
Balance at beginning of the period	$ 277.8
Current period change	(21.0)	(73.5)	(1.2)
Balance at end of the period	256.8	277.8
Investment and Interest Rate Swaps Unrealized Holding Gains (Losses)
Components of accumulated other comprehensive income (loss)
Balance at beginning of the period	261.6
Current period change	(9.3)
Balance at end of the period	252.3
Currency translation adjustment
Components of accumulated other comprehensive income (loss)
Balance at beginning of the period	16.2
Current period change	(11.7)
Balance at end of the period	$ 4.5