Stock-Based Compensation Expense - Additional Information (Detail)	12 Months Ended
Dec. 31, 2018 USD ($) Employees $ / shares shares	Dec. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of groups within the employee population \| Employees	2
Estimated forfeiture rate for unvested options for senior management	8.00%
Estimated forfeiture rate for unvested options for all non-senior management	12.00%
Increase in compensation expense due to revised estimated forfeiture rates	$ 1,283,000	$ 673,000	$ 334,000
Weighted-average grant-date fair values of stock options granted \| $ / shares	$ 20.84	$ 15.59	$ 6.33
Total intrinsic values of stock options exercised	$ 52,629,000	$ 136,672,000	$ 55,580,000
Total fair values of stock options vested	31,106,000	21,519,000	18,114,000
Total unrecognized compensation expense related to non-vested stock options	$ 49,229,000
Recognition period for unrecognized compensation expense	1 year 6 months 21 days
Stock-based compensation expense	$ 41,090,000	31,942,000	20,558,000
Income tax benefit recognized related to stock-based compensation expense	7,317,000	10,473,000	6,747,000
Compensation expense capitalized	$ 0	$ 0	$ 0
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant under stock option plans \| shares	19,578,752
Vesting period for stock option plans	4 years
Expiration period of stock option plan	10 years
Minimum [Member] \| Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for stock option plans	4 years
Minimum [Member] \| Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for stock option plans	1 year
Maximum [Member] \| Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for stock option plans	5 years
Maximum [Member] \| Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for stock option plans	3 years

Employee service share based compensation recognized period costs capitalized amount.

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- Definition

Estimated forfeiture rate for unvested options for all non-senior management.

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Estimated forfeiture rate for unvested options for senior management.

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Expiration period of stock option plan.

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Increase (decrease) in compensation expense due to revised estimated forfeiture rates.

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Number of groups within employee population.

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- Definition

Share based compensation arrangement by share based payment award options vested fair value.

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- Definition

Shares based compensation arrangement by shares based payment award options exercisable intrinsic value.

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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