Stock-Based Compensation Expense and Employee Benefit Plans - Stock Option and Stock Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Outstanding Options/RSUs, Number of Shares
Outstanding (in shares)	15,354,271
Exercised (in shares)	(2,597,003)
Cancelled (in shares)	(973,720)
Outstanding (in shares)	11,783,548	15,354,271
Outstanding Options Weighted Average Exercise Price
Outstanding (in dollars per share)	$ 21.27
Exercised (in dollars per share)	23.90
Cancelled (in dollars per share)	14.94
Outstanding (in dollars per share)	$ 21.22	$ 21.27
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Vested and expected to vest (in shares)	11,619,420
Exercisable (in shares)	9,328,149
Vested and expected to vest, weighted average exercise price (in dollars per share)	$ 21.38
Exercisable, weighted average exercise price (in dollars per share)	$ 24.26
Outstanding, remaining contractual life	5 years 4 months 24 days	6 years
Outstanding, aggregate intrinsic value	$ 50,366	$ 129,855
Vested and expected to vest, remaining contractual life	5 years 4 months 24 days
Exercisable, remaining contractual life	4 years 10 months 24 days
Vested and expected to vest, aggregate intrinsic value	$ 48,719
Exercisable, aggregate intrinsic value	$ 25,881