Stockholders' Equity (Details) (USD $)	1 Months Ended	12 Months Ended			3 Months Ended	12 Months Ended			0 Months Ended	3 Months Ended
	Aug. 31, 2011	Dec. 31, 2013 vote	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Ordinary Dividend [Member]	Dec. 31, 2013 Ordinary Dividend [Member]	Dec. 31, 2012 Ordinary Dividend [Member]	Dec. 31, 2011 Ordinary Dividend [Member]	Dec. 12, 2012 Special Dividend [Member]	Dec. 31, 2012 Special Dividend [Member]
Class of Stock [Line Items]
Aggregated regular quarterly dividends on common stock		$ 55,236,000	$ 285,521,000	$ 18,265,000		$ 55,236,000	$ 34,877,000	$ 18,265,000	$ 250,644,000
Common stock dividends paid					$ 0.1875					$ 3.75
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 Repurchase Program, Authorized Amount	100,000,000
Treasury Stock, Shares		626,461	284,493
Common stock, sinking fund		$ 0
Voting rights per share		1