Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 593,566	$ 587,613	$ 577,263	$ 566,184	$ 578,522	$ 575,982	$ 569,239	$ 560,792	$ 2,324,626	$ 2,284,535	$ 2,158,628
Net income	167,671	279,709	168,305	170,418	385,636	192,407	254,543	141,590	786,103	974,175	876,660
Net income attributable to common stockholders	$ 167,650	$ 279,677	$ 168,281	$ 170,366	$ 385,734	$ 192,486	$ 254,662	$ 141,643	$ 785,974	$ 974,525	$ 876,921
Net income per common share - basic (in dollars per share)	$ 1.20	$ 2.00	$ 1.21	$ 1.23	$ 2.79	$ 1.39	$ 1.84	$ 1.03	$ 5.64	$ 7.05	$ 6.36
Net income per common share - diluted (in dollars per share)	$ 1.20	$ 2.00	$ 1.21	$ 1.23	$ 2.79	$ 1.39	$ 1.84	$ 1.03	$ 5.63	$ 7.05	$ 6.35