Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Total revenue	$ 392,158	$ 359,890	$ 412,746	$ 466,490	$ 498,362	$ 452,459	$ 446,014	$ 467,604	$ 1,631,284	$ 1,864,439	$ 1,780,858
Total cost of revenue	166,167	157,152	189,645	207,181	231,098	201,480	201,709	211,805	720,145	846,092	814,091
Net revenue	225,991	202,738	223,101	259,309	267,264	250,979	244,305	255,799	911,139	1,018,347	966,767
Total expenses and other income	182,884	185,052	185,912	213,592	195,746	202,015	199,019	196,956	767,440	793,736	761,458
Net income	$ 32,726	$ 15,062	$ 25,873	$ 32,918	$ 54,154	$ 34,761	$ 33,048	$ 42,655	$ 106,579	$ 164,618	$ 153,206
Diluted income per share:
Net income per diluted share (in dollars per share)	$ 0.79	$ 0.36	$ 0.62	$ 0.78	$ 1.27	$ 0.81	$ 0.76	$ 0.98	$ 2.56	$ 3.81	$ 3.41
Diluted weighted-average shares	41,331	41,536	41,531	42,007	42,760	43,167	43,256	43,658	41,600	43,208	44,884