Stockholders' Equity (Details 5) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($)	Oct. 31, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2008 item $ / item
Share Repurchase
Period over which shares may be purchased under share repurchase program			1 year
Cost of shares repurchased		$ 394,484	$ 483,077	$ 42,439
Shareholder Rights Plan
Purchase price of each Right, before the amendment and restatement of the Rights (in dollars per one one-thousandth of a share) | $ / item							64.75
Purchase price of each Right, after the amendment and restatement of the Rights (in dollars per one one-thousandth of a share) | $ / item							400.00
Number of shares of Series A Junior Participating Preferred Stock each Right entitles a holder to purchase | item							0.001
Minimum ownership percentage in the outstanding shares of voting stock from the commencement of a tender offer that would result in the exercise of shares under one condition of the Agreement (as a percent)							15.00%
2015 Share Repurchase Program
Share Repurchase
Authorized aggregate repurchases of common stock					$ 500,000
Repurchased shares of common stock | shares	280,000
Cost of shares repurchased	$ 37,800
2014 Share Repurchase Program
Share Repurchase
Authorized aggregate repurchases of common stock						$ 500,000
Repurchased shares of common stock | shares		2,368,645	887,114
Cost of shares repurchased		$ 394,500	$ 105,500