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Stock Incentive Plans and Stock Purchase Plans - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
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
Stock-based compensation expense	$ 4.5	$ 7.6	$ 18.2	$ 27.6
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]
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] \| 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	5,000,000.0		5,000,000.0
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			1,400,000
Amended and Restated 2008 Plan [Member] \| Non Qualified Stock Options [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			1,000,000.0
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]
Common stock, aggregate shares authorized	2,600,000		2,600,000
Aggregate number Shares issued under Stock Purchase Plans			400,000
Common stock, reserved for issuance	600,000		600,000