Quarterly Financial Information (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 revenue	$ 518,240	$ 516,211	$ 502,307	$ 508,498	$ 480,840	$ 475,360	$ 457,459	$ 442,367	$ 2,045,255	$ 1,856,028	$ 1,685,061
Net income	242,183	356,329	197,319	237,877	155,352	206,076	172,253	208,053	1,033,708	741,733	697,327
Net income attributable to common stockholders	$ 242,235	$ 356,392	$ 197,444	$ 237,931	$ 155,428	$ 206,142	$ 172,324	$ 208,144	$ 1,034,002	$ 742,038	$ 683,567
Net income (loss) per common share - basic (in dollars per share)	$ 1.76	$ 2.60	$ 1.44	$ 1.73	$ 1.13	$ 1.54	$ 1.30	$ 1.57	$ 7.53	$ 5.54	$ 5.22
Net income (loss) per common share - diluted (in dollars per share)	$ 1.76	$ 2.59	$ 1.44	$ 1.73	$ 1.13	$ 1.53	$ 1.29	$ 1.56	$ 7.52	$ 5.51	$ 5.21