Summary of Significant Accounting Policies (Unrecognized Stock-based Compensation Expense Before Income Taxes and Adjusted for Estimated Forfeitures) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 Y
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Expense	$ 49,673
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Remaining Expense Life (Years)	3.0
Unrecognized Expense	36,530
Performance Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Remaining Expense Life (Years)	2.6
Unrecognized Expense	10,871
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Remaining Expense Life (Years)	1.8
Unrecognized Expense	1,907
Deferred Issuance Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Remaining Expense Life (Years)	1.2
Unrecognized Expense	247
Employee Stock Purchase Plan Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Remaining Expense Life (Years)	0.2
Unrecognized Expense	$ 118