Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Total revenue	$ 498,362	$ 452,459	$ 446,014	$ 467,604	$ 481,208	$ 429,878	$ 419,972	$ 449,800	$ 1,864,439	$ 1,780,858	$ 1,779,822
Total cost of revenue	231,098	201,480	201,709	211,805	219,208	192,620	191,544	210,719	846,092	814,091	832,316
Net revenue	267,264	250,979	244,305	255,799	262,000	237,258	228,428	239,081	1,018,347	966,767	947,506
Total expenses and other income	195,746	202,015	199,019	196,956	198,824	193,175	186,157	183,302	793,736	761,458	775,194
Net income	$ 54,154	$ 34,761	$ 33,048	$ 42,655	$ 48,075	$ 33,325	$ 30,171	$ 41,635	$ 164,618	$ 153,206	$ 143,892
Diluted income per share:
Net income per diluted share (in dollars per share)	$ 1.27	$ 0.81	$ 0.76	$ 0.98	$ 1.09	$ 0.76	$ 0.67	$ 0.90	$ 3.81	$ 3.41	$ 3.00
Diluted weighted-average shares	42,760	43,167	43,256	43,658	43,936	44,116	45,043	46,479	43,208	44,884	47,888