CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net income	$ 50,430	$ 58,269	$ 51,614
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation & amortization	12,610	9,117	6,929
Stock-based compensation expense	6,769	6,338	5,464
Deferred income taxes	1,682	1,448	1,640
Provision for losses on accounts receivable	782	852	552
Loss on disposal of property and equipment	89	88	49
Changes in operating assets and liabilities:
Trade accounts receivable, net	(4,826)	22,182	(21,769)
Prepaid expenses & other current assets	789	(887)	2,191
Other assets	4,430	1,810	(1,509)
Accounts payable	3,593	(28,828)	15,669
Accrued expenses	1,788	(2,351)	2,251
Other current liabilities	1,132	1,262	522
Other long-term liabilities	(7,218)	536	1,233
Net cash provided by operating activities	72,050	69,836	64,836
Cash flows from investing activities:
Purchases of property and equipment	(4,253)	(5,410)	(4,771)
Business combination	(10,000)	0	0
Asset acquisition	(3,486)	(3,555)	0
Proceeds from sale of property and equipment	0	0	7
Capitalized software development costs	(8,671)	(8,580)	(3,565)
Net cash used in investing activities	(26,410)	(17,545)	(8,329)
Cash flows from financing activities:
Cash dividends on common stock	(21,649)	(21,521)	(21,393)
Proceeds from employee common stock purchases	1,443	1,382	1,330
Tax withholdings related to stock-based compensation awards	(2,754)	(1,229)	(2,676)
Net cash used in financing activities	(22,960)	(21,368)	(22,739)
Net increase in cash	22,680	30,923	33,768
Cash, beginning of period	191,700	160,777	127,009
Cash, end of period	214,380	191,700	160,777
Non-cash investing activities:
Contingent consideration - business combination	960	0	0
Capital expenditures accrued but not yet paid	0	0	855
Cash payments:
Income taxes paid, net of refunds	$ 16,035	$ 13,707	$ 21,303