Stockholders' Equity (Narrative) (Details) (USD $)	0 Months Ended	1 Months Ended		12 Months Ended
	Feb. 25, 2011	Mar. 31, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Cumulative number of shares authorized for repurchase	Mar. 31, 2011 Cumulative number of shares authorized for repurchase	Aug. 31, 2007 Cumulative number of shares authorized for repurchase	Dec. 31, 2011 Shares authorized for repurchase	May 12, 2011 Before amendment to amended and restated certificate of incorporation	May 12, 2011 After amendment to amended and restated certificate of incorporation
Stockholders' Equity [Line Items]
Authorized stock repurchase, shares							75,000,000	60,000,000	30,000,000	15,000,000
Stock split conversion ratio (as a ratio)	2	2	2
Value of common stock repurchased				$ 91,100,000	$ 114,000,000	$ 164,400,000
Remaining shares available for purchase (in shares)				15,100,000
Common stock, shares authorized (in shares)				600,000,000	600,000,000						300,000,000	600,000,000
Cash dividends declared				$ 0	$ 0	$ 0