Condensed Consolidated Statements of Changes in Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) - USD ($) $ 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)	$ 737,009		$ 460	$ 8,788	$ (1,096,830)
Redeemable convertible preferred stock, Beginning balance, Shares at Dec. 31, 2019		126,046,000
Beginning balance at Dec. 31, 2019				229,750,000
Stock options exercised	692			$ 1	691
Stock options exercised, Shares				467,000
Stock-based compensation	2,501				2,501
Net income	27,346					27,346
Ending balance at Mar. 31, 2020	(1,057,043)	$ 737,009		$ 461	11,980	(1,069,484)
Redeemable convertible preferred stock, Ending balance, Shares at Mar. 31, 2020		126,046,000
Ending balance at Mar. 31, 2020				230,217,000
Beginning balance at Dec. 31, 2019	(1,087,582)	$ 737,009		$ 460	8,788	(1,096,830)
Redeemable convertible preferred stock, Beginning balance, Shares at Dec. 31, 2019		126,046,000
Beginning balance at Dec. 31, 2019				229,750,000
Net income	54,683
Ending balance at Jun. 30, 2020	(1,026,735)	$ 737,009		$ 462	14,950	(1,042,147)
Redeemable convertible preferred stock, Ending balance, Shares at Jun. 30, 2020		126,046,000
Ending balance at Jun. 30, 2020				230,439,000
Beginning balance at Dec. 31, 2019	(1,087,582)	$ 737,009		$ 460	8,788	(1,096,830)
Redeemable convertible preferred stock, Beginning balance, Shares at Dec. 31, 2019		126,046,000
Beginning balance at Dec. 31, 2019				229,750,000
Ending balance at Dec. 31, 2020	711,359		$ 39		2,101,773	(1,390,453)
Redeemable convertible preferred stock, Ending balance, Shares at Dec. 31, 2020		0
Redeemable convertible preferred stock, Ending balance at Dec. 31, 2020		$ 0
Ending balance at Dec. 31, 2020			391,660,000
Beginning balance at Mar. 31, 2020	(1,057,043)	$ 737,009		$ 461	11,980	(1,069,484)
Redeemable convertible preferred stock, Beginning balance, Shares at Mar. 31, 2020		126,046,000
Beginning balance at Mar. 31, 2020				230,217,000
Stock options exercised	531			$ 1	530
Stock options exercised, Shares				222,000
Stock-based compensation	2,440				2,440
Net income	27,337					27,337
Ending balance at Jun. 30, 2020	(1,026,735)	$ 737,009		$ 462	14,950	(1,042,147)
Redeemable convertible preferred stock, Ending balance, Shares at Jun. 30, 2020		126,046,000
Ending balance at Jun. 30, 2020				230,439,000
Beginning balance at Dec. 31, 2020	711,359		$ 39		2,101,773	(1,390,453)
Redeemable convertible preferred stock, Beginning balance, Shares at Dec. 31, 2020		0
Beginning balance at Dec. 31, 2020			391,660,000
Stock options exercised	2,680		$ 0		2,680
Stock options exercised, Shares			513,000
Stock-based compensation	48,254				48,254
Vesting of restricted stock units	0		$ 0		0	0
Vesting of restricted stock awards, Shares			608,000
Common stock withheld for tax obligations and net settlement	(14,902)		$ 0		(14,902)	0
Common stock withheld for tax obligations and net settlement, Shares			(324,000)
Net income	1,668					1,668
Ending balance at Mar. 31, 2021	749,059		$ 39		2,137,805	(1,388,785)
Redeemable convertible preferred stock, Ending balance, Shares at Mar. 31, 2021		0
Redeemable convertible preferred stock, Ending balance at Mar. 31, 2021		$ 0
Ending balance at Mar. 31, 2021			392,457,000
Beginning balance at Dec. 31, 2020	711,359		$ 39		2,101,773	(1,390,453)
Redeemable convertible preferred stock, Beginning balance, Shares at Dec. 31, 2020		0
Redeemable convertible preferred stock, Beginning balance at Dec. 31, 2020		$ 0
Beginning balance at Dec. 31, 2020			391,660,000
Net income	32,729
Ending balance at Jun. 30, 2021	824,394	$ 0	$ 39		2,182,079	1,357,724
Redeemable convertible preferred stock, Ending balance, Shares at Jun. 30, 2021		0
Ending balance at Jun. 30, 2021			395,393,000
Beginning balance at Mar. 31, 2021	749,059		$ 39		2,137,805	(1,388,785)
Redeemable convertible preferred stock, Beginning balance, Shares at Mar. 31, 2021		0
Redeemable convertible preferred stock, Beginning balance at Mar. 31, 2021		$ 0
Beginning balance at Mar. 31, 2021			392,457,000
Stock options exercised	13,291				13,291
Stock options exercised, Shares			2,609,000
Stock-based compensation	42,366				42,366
Vesting of restricted stock awards, Shares			631,000
Common stock withheld for tax obligations and net settlement	(11,383)				(11,383)
Common stock withheld for tax obligations and net settlement, Shares			(304,000)
Net income	31,061					31,061
Ending balance at Jun. 30, 2021	$ 824,394	$ 0	$ 39		$ 2,182,079	$ 1,357,724
Redeemable convertible preferred stock, Ending balance, Shares at Jun. 30, 2021		0
Ending balance at Jun. 30, 2021			395,393,000