Revenue - Impact of Adoption on Cash Flow Statement (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income	$ 4,294	$ 3,580	$ 13,191	$ 6,276
Deferred income taxes			987	1,781
Decrease in accounts receivable			(2,193)	1,691
Increase in prepaid expenses and other assets, net			(84)	(871)
Decrease in accrued compensation and employee benefits			(844)	(2,045)
Increase in accounts payable, accrued expenses, and other			3,108	321
Increase/(decrease) in deferred revenue			$ 1,196	(2,442)
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income		3,580		6,276
Accounting Standards Update 2014-09 | As Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income		3,341		5,094
Deferred income taxes				986
Decrease in accounts receivable				3,106
Increase in prepaid expenses and other assets, net				(895)
Decrease in accrued compensation and employee benefits				(2,170)
Increase in accounts payable, accrued expenses, and other				321
Increase/(decrease) in deferred revenue				(1,731)
Accounting Standards Update 2014-09 | Adoption of ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income		$ 239		1,182
Deferred income taxes				795
Decrease in accounts receivable				(1,415)
Increase in prepaid expenses and other assets, net				24
Decrease in accrued compensation and employee benefits				125
Increase in accounts payable, accrued expenses, and other				0
Increase/(decrease) in deferred revenue				$ (711)