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Stock Incentive Plans and Stock Purchase Plans - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	May 16, 2019	May 15, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, aggregate shares authorized	200,000,000	200,000,000
Stock-based compensation expense	$ 35.4	$ 37.9	$ 28.8
Aggregate fair value of restricted and deferred stocks vested	$ 31.5	$ 27.4	$ 29.3
Weighted average grant-date fair value of restricted and deferred stock awards granted	$ 33.28	$ 51.99	$ 54.22
Aggregate intrinsic value of stock options exercised	$ 0.6	$ 2.8	$ 5.5
Cash proceeds received from the exercise of stock options	$ 0.1	$ 3.7	$ 4.8
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
Restricted and Deferred Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to non-vested restricted stock, weighted-average period in years	1 year 4 months 24 days
Unrecognized compensation expense related to non-vested restricted shares	$ 22.1
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]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation authorized shares				27,800,000	19,500,000
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	8,300,000
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
Aggregate number Shares issued under Stock Purchase Plans	500,000
Common stock, reserved for issuance	1,100,000

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

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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