Stockholders' Equity (Details)		12 Months Ended
	Feb. 14, 2014	Dec. 31, 2015 USD ($) vote $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($)	Nov. 20, 2015 USD ($)	Mar. 31, 2015 USD ($) shares	Nov. 30, 2014 USD ($)	May. 16, 2014 $ / shares shares	May. 15, 2014 shares	Aug. 31, 2011 USD ($)
Class of Stock [Line Items]
Aggregated regular quarterly dividends on common stock		$ 91,551,000	$ 77,656,000	$ 55,236,000
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 | shares		300,000,000	300,000,000					300,000,000	150,000,000
Common stock, par value per share | $ / shares		$ 0.01	$ 0.01					$ 0.01
Common stock, shares issued | shares		134,663,244	134,679,064
Common stock, sinking fund		$ 0
Common stock, voting rights | vote		1
Ordinary Dividend [Member]
Class of Stock [Line Items]
Aggregated regular quarterly dividends on common stock		$ 91,551,000	$ 77,656,000	$ 55,236,000
2011 Program [Member]
Class of Stock [Line Items]
Stock repurchase program, authorized amount										$ 100,000,000
Stock repurchase 2011 program, shares repurchased | shares						1,944,161
Aggregate purchase price of common stock repurchased						$ 100,000,000
2014 Program [Member]
Class of Stock [Line Items]
Stock repurchase program, authorized amount					$ 150,000		$ 250,000,000
Stock repurchase 2014 program, shares repurchase | shares		2,682,489