Leases - Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Lessee, Lease, Description [Line Items]
Total operating lease costs	$ 2,144	$ 4,288
Cost of revenue
Lessee, Lease, Description [Line Items]
Total operating lease costs	192	392
Sales and marketing
Lessee, Lease, Description [Line Items]
Total operating lease costs	443	882
Technology and development
Lessee, Lease, Description [Line Items]
Total operating lease costs	893	1,764
General and administrative
Lessee, Lease, Description [Line Items]
Total operating lease costs	$ 616	$ 1,250