CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Revenues	$ 397,159	$ 343,760	$ 789,006	$ 672,185
Cost of revenues	74,040	71,918	152,949	143,071
Gross profit	323,119	271,842	636,057	529,114
Operating expenses:
Selling and marketing (excluding customer base amortization)	130,461	119,075	255,568	207,169
Software development	39,001	28,455	80,611	56,383
General and administrative	57,403	42,337	116,276	82,413
Customer base amortization	14,935	7,175	26,419	14,857
Total operating expenses	241,800	197,042	478,874	360,822
Income from operations	81,319	74,800	157,183	168,292
Interest (expense) income	(3,596)	4,678	(1,945)	8,890
Other (expense) income	(474)	538	367	539
Income before income taxes	77,249	80,016	155,605	177,721
Income tax expense	16,889	16,768	22,452	29,304
Net income	$ 60,360	$ 63,248	$ 133,153	$ 148,417
Net income per share-basic (in dollars per share)	$ 1.61	$ 1.74	$ 3.60	$ 4.09
Net income per share-diluted (in dollars per share)	$ 1.60	$ 1.73	$ 3.57	$ 4.06
Weighted average outstanding shares-basic (in shares)	37,524	36,310	36,998	36,273
Weighted average outstanding shares-diluted (in shares)	37,734	36,627	37,256	36,597