Summary of Significant Accounting Policies (Income Taxes) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Income Tax Contingency [Line Items]
Unrecognized tax benefits	$ 21,900,000		$ 21,900,000		$ 42,300,000
Unrecognized tax benefits that would impact effective tax rate	6,800,000		6,800,000
Income tax penalties and interest accrued	8,200,000		8,200,000		12,600,000
Income tax benefit	5,450,000	(911,000)	(833,000)	2,197,000
Internal Revenue Service (IRS)
Income Tax Contingency [Line Items]
Decrease in unrecognized tax benefits			20,800,000
Income tax examination, change in unrecognized tax benefits which impacted effective tax rate			100,000
Reduction in interest expense from examination			5,100,000
Income tax benefit			$ 3,400,000