Leases - Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Lessee, Lease, Description [Line Items]
Total operating lease costs	$ 2,134	$ 6,421
Cost of revenue
Lessee, Lease, Description [Line Items]
Total operating lease costs	186	578
Sales and marketing
Lessee, Lease, Description [Line Items]
Total operating lease costs	433	1,314
Technology and development
Lessee, Lease, Description [Line Items]
Total operating lease costs	611	1,861
General and administrative
Lessee, Lease, Description [Line Items]
Total operating lease costs	$ 904	$ 2,668