Selected Quarterly Financial Data (Unaudited) (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2011	Mar. 31, 2010	Jun. 30, 2011	Jun. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Total cash provided by (required by):
Operating activity	$ (11.5)	$ (16.2)	$ (3.2)	$ 6.1	$ 28.6	$ 47.5	$ 104.3	$ 170.5	$ 707.3
Investing activity	(35.6)	(268.4)	(58.3)	(304.0)	(125.6)	(333.0)	(85.0)	(308.2)	(187.4)
Financing activity	(46.6)	(69.5)	(35.4)	(103.6)	15.8	(175.1)	(22.2)	(120.1)	(69.9)
Net increase (decrease) in cash and cash equivalents	(93.7)	(354.1)	(96.9)	(401.5)	(81.2)	(460.6)	(2.9)	(257.8)	450.0
Restatement Adjustment [Member]
Total cash provided by (required by):
Operating activity	(5.6)	(16.0)	2.7	6.3	49.7	47.8		170.5
Investing activity	(35.6)	(268.4)	(58.3)	(304.0)	(125.6)	(333.0)		(308.2)
Financing activity	(52.5)	(69.7)	(41.3)	(103.8)	(5.3)	(175.4)		(120.1)
Net increase (decrease) in cash and cash equivalents	$ (93.7)	$ (354.1)	$ (96.9)	$ (401.5)	$ (81.2)	$ (460.6)		$ (257.8)