Common Stock and Stockholders' Equity - Compensation Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Compensation costs charged as an expense
Stock-based compensation	$ 21,928	$ 17,368	$ 40,243	$ 30,891
Administrative And Marketing
Compensation costs charged as an expense
Stock-based compensation	1,544	1,317	2,803	2,138
Sales
Compensation costs charged as an expense
Stock-based compensation	3,271	2,528	6,190	4,658
Technology And Development
Compensation costs charged as an expense
Stock-based compensation	2,559	2,141	4,663	4,039
General and administrative expenses
Compensation costs charged as an expense
Stock-based compensation	$ 14,554	$ 11,382	$ 26,587	$ 20,056