Stockholder's Equity (Details) (USD $)			0 Months Ended	3 Months Ended			12 Months Ended	0 Months Ended			9 Months Ended	0 Months Ended			12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 09, 2011 2% Senior Convertible Notes Due 2017	Jun. 30, 2013 2% Senior Convertible Notes Due 2017	Sep. 30, 2013 2% Senior Convertible Notes Due 2017	Mar. 26, 2007 2% Senior Convertible Notes Due 2017	Dec. 31, 2011 Common Stock	Sep. 07, 2012 Common Stock and-or Convertible Debt	Sep. 14, 2011 Common Stock and-or Convertible Debt	Mar. 09, 2011 Common Stock and-or Convertible Debt	Sep. 30, 2013 Common Stock and-or Convertible Debt	Sep. 07, 2012 Common Stock and-or Convertible Debt 2% Senior Convertible Notes Due 2017	Sep. 14, 2011 Common Stock and-or Convertible Debt 2% Senior Convertible Notes Due 2017	Mar. 09, 2011 Common Stock and-or Convertible Debt 2% Senior Convertible Notes Due 2017	Dec. 31, 2012 Open Market Purchases And Pre-Established Trading Plan Common Stock
Equity, Class of Treasury Stock
Preferred stock, shares authorized	5,000,000	5,000,000
Share repurchase program, authorized amount								$ 200,000,000	$ 200,000,000	$ 150,000,000
Share repurchase program, remaining authorized repurchase amount											200,000,000
Interest rate on senior convertible notes (as a percent)					2.00%	2.00%						2.00%	2.00%	2.00%
Convertible notes maturity date												2017	2017	2017
Total number of shares repurchased							9,200,000								6,900,000
Average price per share of common stock repurchased (in dollars per shares)							$ 18.52								$ 26.20
Cost of reacquired shares							169,700,000								180,300,000
Common stock trading days			20 days
Consecutive common stock trading days			30 days
Percentage of excess conversion price in effect on last trading day			130.00%
Conversion price of senior convertible notes (in dollars per share)						$ 18.87
Face value of converted notes				$ 12,000
Shares issued to convertible note holders				634