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Stockholders' Equity - Stock Options (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-tax intrinsic value			$ 52,600	$ 157,900
Vesting of early exercised stock options			$ 8,300	$ 6,500
Granted (in shares)	0	0	0	0
Stock-based compensation expense	$ 36,636	$ 12,142	$ 100,900	$ 34,752
Modification expense	2,400	400	3,700	400
Modification expense, incremental fair value	2,100	300	3,300	300
Unrecognized stock-based compensation cost	14,500		14,500
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	5,300	1,800	$ 13,400	5,700
Weighted-average period of recognition			1 year 2 months 23 days
Stock options \| 2011 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period			10 years
Award vesting period			4 years
Stock options \| 2011 Equity Incentive Plan \| First Year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage			25.00%
Stock options \| 2011 Equity Incentive Plan \| Remaining Period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			36 months
Stock options \| 2019 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period			10 years
Award vesting period			4 years
Stock options \| 2019 Equity Incentive Plan \| First Year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage			25.00%
Stock options \| 2019 Equity Incentive Plan \| Remaining Period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			36 months
Vesting of restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			4 years
Stock-based compensation expense	23,000	$ 10,600	$ 52,000	28,000
Modification expense	$ 3,900		$ 3,900	$ 4,800
Weighted-average period of recognition			2 years 8 months 12 days
Vesting of restricted stock units \| First Year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			4 years
Award vesting percentage			25.00%
Vesting of restricted stock units \| Remaining Period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			36 months