Treasury Stock (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended		1 Months Ended	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Aug. 30, 2011 Stock Repurchase Program [Member]	Mar. 31, 2012 Stock Repurchase Program [Member]	Mar. 31, 2012 Stock Repurchase Program [Member] Since Equity Inception [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount			$ 150,000,000	$ 300,000,000
Treasury Stock, Shares, Acquired				1.0	29.5
Treasury Stock, Value, Acquired, Cost Method	353,000	696,000		4,500,000	133,400,000
Share Repurchase Program Commission Incurred				600,000
Treasury Stock Acquired, Average Cost Per Share				$ 4.62
Stock Repurchase Program, Remaining Authorized Repurchase Amount				166,600,000
Shares Paid for Tax Withholding for Share Based Compensation	0.1
Adjustments Related to Tax Withholding for Share-based Compensation	$ 400,000	$ 700,000