Quarterly Operating Results (Unaudited) - Schedule of Quarterly Operating Results (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 642,111	$ 673,962	$ 598,806	$ 698,495	$ 578,989	$ 618,683	$ 575,219	$ 619,280	$ 2,613,375	$ 2,392,171	$ 2,014,246
Total expenses	511,195	515,434	469,405	493,242	476,940	466,845	451,697	470,760	1,989,276	1,866,242	1,551,784
Income before income taxes	130,916	158,528	129,401	205,253	102,049	151,838	123,522	148,520	624,099	525,929	462,462
Net income	$ 97,320	$ 133,979	$ 96,784	$ 152,400	$ 76,519	$ 115,506	$ 92,593	$ 113,896	$ 480,483	$ 398,514	$ 344,255
Net income per share:
Basic	$ 0.34	$ 0.47	$ 0.34	$ 0.54	$ 0.27	$ 0.41	$ 0.33	$ 0.41	$ 1.70	$ 1.42	$ 1.24
Diluted	$ 0.34	$ 0.47	$ 0.34	$ 0.54	$ 0.27	$ 0.41	$ 0.33	$ 0.40	$ 1.69	$ 1.40	$ 1.22