Summary of Significant Accounting Policies (Convertible Debt) (Details) (Three Point Seven Five Percent Exchangeable Senior Notes [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Three Point Seven Five Percent Exchangeable Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate stated on the Exchangeable Notes	3.75%
Debt Instrument, Interest Rate, Effective Percentage	5.62%
Interest Expense Reconciliation [Abstract]
Interest expense on Exchangeable Notes, excluding effect of accounting for convertible debt	$ 5,769	$ 7,136	$ 14,850
Effect of accounting for convertible debt	2,090	2,474	5,024
Total interest expense on Exchangeable Notes	$ 7,859	$ 9,610	$ 19,874