Revenue - Contract Balances (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Trade and client receivables, net of allowance	$ 33,230	$ 30,156
Deferred revenue	14,984	13,799
Deferred revenue (component of other liabilities, noncurrent)	3,552	3,153
Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Trade and client receivables, net of allowance	$ 33,230	$ 30,156