Cash Convertible Senior Notes and Related Transactions, Carrying Amount Table (Details) (USD $) In Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010		Dec. 31, 2010
Principal amount carrying amount and interest expense of notes
Carrying amount, net of discount	$ 146.3				$ 146.3				$ 141.4
Convertible Debt [Member]
Principal amount carrying amount and interest expense of notes
Principal amount	175.0				175.0				175.0
Less: unamortized issuance discount	(28.7)				(28.7)				(33.6)
Carrying amount, net of discount	146.3				146.3				141.4
Contractual coupon interest	2.0		1.9		5.9		3.9
Amortization of discount and deferred financing costs	2.0		1.8		5.8		3.6
Total interest expense	$ 4.0	[1]	$ 3.7	[1]	$ 11.7	[1]	$ 7.5	[1]

[1] A portion of the interest relating to the Notes is capitalized as Construction in progress.