Equity-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining vesting period	4 years
Weighted Average Grant Date Fair Value per Share, Granted				$ 63.13
Number of Shares, Granted				354,072
Additional vesting of shares				50,946
Unrecognized equity-based compensation expense related to restricted stock		$ 19.9		$ 19.9
Weighted average grant date fair value per share		$ 105.17	$ 13.38	$ 50.73	$ 8.55
Total intrinsic value of stock options exercised		$ 171.3	$ 0.9	$ 255.8	$ 1.7
Unrecognized compensation cost related to stock options		$ 120.8		$ 120.8
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Grant Date Fair Value per Share, Granted	$ 57.71
Number of Shares, Granted	259,839
Weighted average period of unrecognized compensation costs				2 years 9 months 18 days
RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining vesting period				1 year 2 months 12 days
Weighted Average Grant Date Fair Value per Share, Granted				$ 15.05
Number of Shares, Granted				42,860
Additional vesting of shares				26,235
Accelerated vesting of shares				21,430
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period of unrecognized compensation costs				3 years 2 months 12 days
2015 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining vesting period				3 years
Description of stock options granted under the Plan				Stock options granted under the 2015 Plan generally vest 25% on the first anniversary of the original vesting date, with the balance vesting monthly over the remaining three years, unless they contain specific performance-based vesting provisions. The maximum term of stock options granted under the 2015 Plan is ten years.
2015 Plan [Member] | First Anniversary of Original Vesting Date [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vest percentage on the first anniversary				25.00%
2015 Plan and the 2016 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance		3,787,307		3,787,307
Percentage of cumulative increase in number of shares for future issuance				4.00%
2016 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance		500,000		500,000
Percentage of cumulative increase in number of shares for future issuance				1.00%
Maximum [Member] | 2015 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum term of stock options granted				10 years