Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Stock Incentive Plans and Stock Purchase Plans - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	May 12, 2021	May 11, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, aggregate shares authorized	200,000,000		200,000,000				200,000,000
Aggregate number Shares issued under Stock Purchase Plans			0
Stock-based compensation expense	$ 5.8	$ 9.5	$ 6.4	$ 13.7
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, reserved for issuance	100,000		100,000
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
Stock Option [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of options, maximum years			10 years
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
1996 Non-Qualified Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares common stock reserved					9,900,000
Percentage of market value of common stock at which employees are permitted to purchase			85.00%
2015 Non-Qualified Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of market value of common stock at which employees are permitted to purchase			90.00%
Amended and Restated 2008 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares common stock reserved					34,975,000	27,775,000
Amended and Restated 2008 Plan [Member] \| Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grants and awards under Stock Incentive Plans	3,600,000		3,600,000
Amended and Restated 2008 Plan [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period			728,290
1996 Non-Qualified Employee Stock Purchase Plan and 2015 Non-Qualified Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate number Shares issued under Stock Purchase Plans			100,000
Common stock, reserved for issuance	400,000		400,000
1996 Non-Qualified Employee Stock Purchase Plan and 2015 Non-Qualified Stock Purchase Plan [Member] \| Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, reserved for issuance	61,000		61,000