Stock-based Compensation Plans and Awards - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Stock-based Compensation Plans and Awards
Stock-based compensation expense	$ 2,523	$ 2,209	$ 5,227	$ 4,130
Service Costs
Stock-based Compensation Plans and Awards
Stock-based compensation expense	366	262	737	443
Sales and Marketing
Stock-based Compensation Plans and Awards
Stock-based compensation expense	363	171	728	251
Product Development
Stock-based Compensation Plans and Awards
Stock-based compensation expense	637	564	1,342	1,156
General and Administrative
Stock-based Compensation Plans and Awards
Stock-based compensation expense	$ 1,157	$ 1,212	$ 2,420	$ 2,280