Quarterly Operating Results (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 198,941	$ 208,963	$ 212,272	$ 196,245	$ 193,425	$ 216,321	$ 197,683	$ 163,435	$ 816,421	$ 770,864	$ 598,776
Net income (loss)	18,422	(35,535)	74,438	16,637	22,994	38,248	26,583	7,170	73,962	94,995	73,543
Net income (loss) attributable to the Company	18,358	(35,423)	74,190	16,579	22,915	38,119	26,491	7,143	73,704	94,668	72,866
Net income (loss) attributable to common shareholders	$ 14,334	$ (43,897)	$ 69,949	$ 6,566	$ 16,428	$ 31,631	$ 20,004	$ 655	$ 46,952	$ 68,718	$ 47,787
Net income (loss) per share available to common shareholders, basic (in usd per share)	$ 0.20	$ (0.61)	$ 0.97	$ 0.09	$ 0.23	$ 0.44	$ 0.28	$ 0.01	$ 0.65	$ 0.95	$ 0.72
Net income (loss) per share available to common shareholders, diluted (in usd per share)	$ 0.20	$ (0.61)	$ 0.96	$ 0.09	$ 0.23	$ 0.43	$ 0.27	$ 0.01	$ 0.64	$ 0.94	$ 0.71