Condensed Consolidated Statements of Changes in Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Redeemable Convertible Preferred Stock	Class A and Class B Common Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Beginning balance at Dec. 31, 2019	$ (1,087,582)			$ 460	$ 8,788	$ (1,096,830)
Redeemable convertible preferred stock, Beginning balance, Shares at Dec. 31, 2019		126,046
Redeemable convertible preferred stock, Beginning balance at Dec. 31, 2019		$ 737,009
Beginning balance at Dec. 31, 2019				229,750
Stock options exercised	692			$ 1	691
Stock options exercised, Shares				467
Stock-based compensation	2,501				2,501
Net income	27,346					27,346
Ending balance at Mar. 31, 2020	(1,057,043)			$ 461	11,980	(1,069,484)
Redeemable convertible preferred stock, Ending balance, Shares at Mar. 31, 2020		126,046
Redeemable convertible preferred stock, Ending balance at Mar. 31, 2020		$ 737,009
Ending balance at Mar. 31, 2020				230,217
Beginning balance at Dec. 31, 2020	711,359		$ 39		2,101,773	(1,390,453)
Beginning balance at Dec. 31, 2020			391,660
Stock options exercised	2,680				2,680
Stock options exercised, Shares			513
Stock-based compensation	48,254				48,254
Vesting of restricted stock awards, Shares			608
Common stock withheld for tax obligations and net settlement	(14,902)				(14,902)
Common stock withheld for tax obligations and net settlement, Shares			(324)
Net income	1,668					1,668
Ending balance at Mar. 31, 2021	$ 749,059		$ 39		$ 2,137,805	$ (1,388,785)
Ending balance at Mar. 31, 2021			392,457