CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 5,534	$ 12,120	$ 5,464
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	6,772	6,390	5,810
Stock-based compensation expense	7,843	8,359	5,992
Deferred income taxes	3,724	1,561	4,145
Loss on disposal or sale of assets	0	0	254
Allowance for doubtful accounts	1,143	(136)	1,764
Excess tax benefits from stock-based awards	0	(539)	(948)
Impairment of investments	1,032	0	4,000
Other non-cash income (charges)	211	328	(555)
Changes in operating assets and liabilities:
Decrease (increase) in accounts receivable	2,640	429	(6,454)
Decrease in inventories	0	0	386
Decrease (increase) in other assets	(635)	(108)	1,502
(Decrease) increase in accrued compensation and benefits	(64)	128	(212)
(Decrease) increase in accounts payable and accrued expenses	(1,634)	1,796	613
(Decrease) increase in deferred revenue	(2,639)	(1,888)	1,740
Decrease in deferred rent	(355)	(766)	(681)
(Decrease) increase in other liabilities, net	(43)	(500)	732
Net cash provided by operating activities	24,799	27,390	20,548
CASH FLOWS FROM INVESTING ACTIVITIES
Acquisitions, net of cash acquired	(3,150)	(1,359)	(5,647)
Additions to capitalized software	(4,689)	(4,142)	(3,096)
Payment to acquire investments	0	(295)	(2,500)
Maturity of U.S. Treasury Bills	1,248	3,842	2,600
Purchases of U.S. Treasury Bills	(1,232)	(2,490)	(2,595)
Purchases of property and equipment	(880)	(155)	(453)
Other investing activities, net	(113)	(202)	114
Net cash used in investing activities	(8,816)	(4,801)	(11,577)
CASH FLOWS FROM FINANCING ACTIVITIES
Surrender of restricted common stock for income tax purposes	(3,777)	(2,904)	(3,055)
Repurchase of common stock	(13,322)	(3,961)	(8,807)
Excess tax benefits from stock-based awards	0	539	948
Proceeds pursuant to employee stock-based compensation plans	1,505	931	497
Net cash used in financing activities	(15,594)	(5,395)	(10,417)
Increase (decrease) in cash and cash equivalents	389	17,194	(1,446)
Cash and cash equivalents at beginning of year	105,703	88,509	89,955
Cash and cash equivalents at end of year	106,092	105,703	88,509
Supplemental information:
Cash paid for income taxes, net of refunds	$ 2,826	$ 3,519	$ 4,305