Stock Repurchases (Details) (USD $)	12 Months Ended		0 Months Ended		12 Months Ended	1 Months Ended	12 Months Ended
	Dec. 31, 2011	May 31, 2009	Feb. 10, 2011 Previous Stock Repurchase Program [Member]	Feb. 10, 2009 Previous Stock Repurchase Program [Member] years	Dec. 31, 2011 Previous Stock Repurchase Program [Member]	Apr. 30, 2011 Current Stock Repurchase Program [Member] years	Dec. 31, 2011 Current Stock Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, amount authorized				$ 150,000,000		$ 200,000,000
Stock repurchase program, shares				15,000,000
Stock repurchase program, authorized repurchase period (in years)				2		3
Common stock repurchased					5,000,000	3,000,000
Repurchase of shares of common stock	51,462,000	51,547,000
Stock repurchase program, remaining amount authorized			$ 98,000,000				$ 149,000,000