Stockholders' Equity (Details) (USD $)	0 Months Ended		1 Months Ended	12 Months Ended			3 Months Ended	0 Months Ended
	Nov. 21, 2014	Feb. 14, 2014	Aug. 31, 2011	Dec. 31, 2014 vote	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2012	Dec. 12, 2012	May 16, 2014	May 15, 2014
Class of Stock [Line Items]
Aggregated regular quarterly dividends on common stock				$ 77,656,000	$ 55,236,000	$ 285,521,000
Description of common stock voting rights				Each share of common stock entitles the holder to one vote on all matters on which holders are permitted to vote, including the election of directors. There are no cumulative voting rights.
Description of common stock subscription rights				The Company's common stock has no preemptive or conversion rights or other subscription rights.
Common stock, redemption provision				0
Stock split conversion ratio		2
Common Stock, Shares Authorized				300,000,000	150,000,000				300,000,000	150,000,000
Common stock, par value				$ 0.01	$ 0.01				$ 0.01
Common stock, shares issued				134,679,064	134,580,208
Stock Repurchase Program, Authorized Amount	250,000,000		100,000,000
Treasury Stock, Shares				1,787,546	1,252,922
Common stock, sinking fund				0
Voting rights per share				1
Ordinary Dividend [Member]
Class of Stock [Line Items]
Aggregated regular quarterly dividends on common stock				77,656,000	55,236,000	34,877,000
Common stock dividends paid							$ 0.0938
Special Dividend [Member]
Class of Stock [Line Items]
Aggregated regular quarterly dividends on common stock								$ 250,644,000
Common stock dividends paid							$ 1.875