Stock Repurchase Program (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended	0 Months Ended	1 Months Ended	12 Months Ended
	Jan. 29, 2012	Nov. 14, 2011	Jan. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Stock Repurchase Program [Abstract]
Stock repurchase during period, shares			6.1	8.1
Stock repurchased during period, value			$ 56,400,000	$ 150,445,000	$ 154,913,000	$ 199,811,000
Average price of shares repurchased, per share			$ 9.29	$ 18.67
Amount available under authorized stock repurchase program to repurchase outstanding shares of common stock	183,300,000			239,800,000
Additional authorized stock repurchase program		$ 100,000,000