Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net income	$ 44,597	$ 45,586	$ 33,712
Reconciliation of net income to net cash provided by operating activities
Deferred income taxes	3,881	4,241	7,581
Change in earn-out liability		(85)	(445)
Depreciation and amortization of property and equipment	14,788	13,127	11,123
Amortization of intangible assets	10,126	5,538	5,315
Provision for credit losses	4,717	5,660	3,499
Stock-based compensation	27,574	18,936	14,690
Other, net	323	(24)	(574)
Changes in assets and liabilities, net of effects of acquisition
Accounts receivable	(4,959)	(5,922)	(6,771)
Deferred costs	(9,299)	(3,414)	(1,441)
Other current and non-current assets	(6,181)	1,201	(2,768)
Accounts payable	2,259	1,214	(489)
Accrued compensation	6,775	(1,257)	319
Accrued expenses	1,017	563	706
Deferred revenue	14,483	4,432	6,366
Operating leases	2,792	(1,234)	971
Net cash provided by operating activities	112,893	88,562	71,794
Cash flows from investing activities
Purchases of property and equipment	(19,588)	(16,467)	(13,585)
Purchases of investments	(121,242)	(74,797)	(73,700)
Maturities of investments	111,193	69,461	84,472
Acquisition of business and intangible assets, net	(17,066)	(98,666)	(11,500)
Net cash used in investing activities	(46,703)	(120,469)	(14,313)
Cash flows from financing activities
Repurchases of common stock	(20,430)	(18,950)	(20,618)
Net proceeds from exercise of options to purchase common stock	9,374	18,592	6,207
Net proceeds from employee stock purchase plan activity	4,737	3,374	2,269
Payment for contingent consideration	(2,042)	(688)
Net cash provided by (used in) financing activities	(8,361)	2,328	(12,142)
Effect of foreign currency exchange rate changes	31	19	54
Net increase (decrease) in cash and cash equivalents	57,860	(29,560)	45,393
Cash and cash equivalents at beginning of year	149,692	179,252	133,859
Cash and cash equivalents at end of year	207,552	149,692	179,252
Supplemental disclosure of cash flow information
Cash paid for income taxes, net	9,979	1,656	1,545
Non-cash financing activities:
Net purchases of property and equipment on account	$ (683)	$ (551)	$ 322