Stockholders' Equity Matters - Dividends Declared (Details) - USD ($) $ / shares in Units, $ in Thousands																			1 Months Ended	12 Months Ended
	Dec. 15, 2015	Oct. 29, 2015	Sep. 30, 2015	Aug. 27, 2015	Jun. 26, 2015	May. 28, 2015	Mar. 20, 2015	Feb. 19, 2015	Dec. 22, 2014	Dec. 15, 2014	Nov. 17, 2014	Nov. 04, 2014	Oct. 15, 2014	Sep. 15, 2014	Jul. 15, 2014	May. 28, 2014	Apr. 15, 2014	Mar. 14, 2014	Nov. 30, 2012	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity [Abstract]
Dividends declared (in dollars per share)		$ 0.4850		$ 0.4750		$ 0.4750		$ 0.4750			$ 0.4750			$ 0.4750		$ 0.2700		$ 0.2700		$ 1.91	$ 5.3713	$ 1.0800
Special distribution declared (in dollars per share)														$ 3.6144
Catch-up distribution declared (in dollars per share)											$ 0.2550
Dividends declared	$ 102,438		$ 100,213		$ 100,119		$ 99,795		$ 99,617				$ 91,993		$ 52,033		$ 51,812			$ 405,906	$ 493,513	$ 208,900
Special distribution paid												$ 700,000							$ 700,000		$ 700,000
Catch-up distribution declared										$ 53,450