CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 68,594	$ 50,430	$ 58,269
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation & amortization	14,245	12,610	9,117
Stock-based compensation expense	7,158	6,769	6,338
Deferred income taxes	(1,483)	1,682	1,448
Provision for losses on accounts receivable	1,505	782	852
Loss on disposal of property and equipment	0	89	88
Changes in operating assets and liabilities:
Trade accounts receivable, net	(71,134)	(4,826)	22,182
Prepaid expenses & other current assets	(10,694)	789	(887)
Other assets	2,940	4,430	1,810
Accounts payable	18,679	3,593	(28,828)
Accrued expenses	35,124	1,788	(2,351)
Other current liabilities	2,084	1,132	1,262
Other long-term liabilities	(4,181)	(7,218)	536
Net cash provided by operating activities	62,837	72,050	69,836
Cash flows from investing activities:
Purchases of property and equipment	(3,354)	(4,253)	(5,410)
Capitalized software development costs	(8,481)	(8,671)	(8,580)
Business combination	0	(10,000)	0
Asset acquisition	0	(3,486)	(3,555)
Net cash used in investing activities	(11,835)	(26,410)	(17,545)
Cash flows from financing activities:
Cash dividends on common stock	(24,398)	(21,649)	(21,521)
Proceeds from employee common stock purchases	1,509	1,443	1,382
Shares surrendered upon vesting of restricted stock to satisfy tax withholdings	(2,036)	(2,754)	(1,229)
Repurchase of shares	(3,944)	0	0
Net cash used in financing activities	(28,869)	(22,960)	(21,368)
Net increase in cash	22,133	22,680	30,923
Cash, beginning of period	214,380	191,700	160,777
Cash, end of period	236,513	214,380	191,700
Non-cash activities:
Contingent consideration - business combination	0	960	0
Cash payments:
Income taxes paid, net of refunds	$ 19,649	$ 16,035	$ 13,707