Stock Plans (Details 4) (USD $)	12 Months Ended				1 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Apr. 30, 2011 Maximum	Aug. 31, 2010 Maximum	Dec. 31, 2011 Warrants	Dec. 31, 2010 Warrants	Dec. 31, 2012 Restricted Stock Units	Dec. 31, 2011 Restricted Stock Units	Dec. 31, 2012 Restricted Stock Units Maximum	Dec. 31, 2012 Restricted Stock Units Minimum	Dec. 31, 2012 Restricted Stock	Dec. 31, 2011 Restricted Stock	Dec. 31, 2010 Restricted Stock	Dec. 31, 2012 Restricted Stock Maximum	Dec. 31, 2012 Restricted Stock Minimum
Restricted Stock information
Fair value of restricted stock granted during the period (in dollars)									$ 20,000,000	$ 4,900,000			$ 0	$ 400,000	$ 500,000
Recognized compensation costs (in dollars)	17,470,000	12,430,000	4,805,000						7,900,000	2,400,000			100,000	1,800,000	2,400,000
Vesting period											3 years	1 year				3 years	1 year
Weighted average remaining vesting period									2 years 6 months
Intrinsic value of outstanding awards (in dollars)									18,600,000
Intrinsic value of RSU shares vested, but not issued (in dollars)									3,100,000
Grant date fair value of restricted stock vested during the period (in dollars)									5,500,000	0.0			100,000	2,800,000	2,100,000
Grant date fair value of forfeited shares (in dollars)																100,000
Summary of restricted stock and warrant activity
Nonvested shares at beginning of period (in shares)									149,340				6,668
Outstanding at the beginning of the period (in shares)							1,898	688,170
Granted (in shares)									1,590,567	149,340
Exercised (in units)								(678,187)
Forfeited/Cancelled (in shares)									(35,000)				(1,334)
Forfeited/Cancelled (in units)							(1,898)	(8,085)
Vested (in shares)									(284,674)				(5,334)
Nonvested shares at end of period (in shares)									1,420,233	149,340				6,668
Outstanding at the end of the period (in shares)								1,898
Weighted-Average Exercise Price For Warrants
Nonvested outstanding at beginning of period (in dollars per share)									$ 32.83				$ 26.12
Outstanding at the beginning of period (in dollars per shares)							$ 474.24	$ 11.68
Granted (in dollars per share)									$ 12.60
Forfeited (in dollars per share)									$ 9.20				$ 19.07
Vested (in dollars per share)									$ 19.19				$ 27.88
Exercised (in dollars per share)								$ 10.09
Cancelled (in dollars per share)							$ 474.24	$ 36.36
Nonvested outstanding at end of period (in dollars per shares)									$ 13.49	$ 32.83				$ 26.12
Outstanding at the end of period (in dollars per shares)								$ 474.24
Stock Repurchase Program
Common stock authorized to be purchased in open market or unsolicited negotiated transactions (in dollars)					80,000,000	30,000,000
Total share repurchases to date (in dollars)		34,700,000
Amount available for future share repurchases (in dollars)		45,300,000
Purchase of common stock under previous share repurchase program (in dollars)		$ 21,547,000	$ 13,148,000	$ 900,000