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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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Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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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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General descriptive information regarding an arrangement under which employees and directors receive: (a) awards of equity shares, equity share options, or other equity instruments; or (b) the entity incurs liabilities to them: (1) in amounts based, at least in part, on the price of the entity's shares or other equity instruments; or (2) that require or may require settlement by issuance of the entity's shares. Such an arrangement is usually provided to employees and directors to compensate them, provide performance incentives to them, and to attract or retain their services. May also include pertinent information particular to a plan that is not elsewhere specified in the taxonomy.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

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The highest quantity of shares an employee can purchase under the plan per period.

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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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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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Price of a single share of a number of saleable stocks of a company.

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Purchase price of common stock expressed as a percentage of its fair value.

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Per share or per unit amount of equity securities issued.

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Stock-Based Compensation - Additional Information (Detail) - USD ($)	1 Months Ended						12 Months Ended
	Jan. 31, 2019	Jul. 31, 2018	Jan. 31, 2018	Jul. 31, 2017	Jan. 31, 2017	Jul. 31, 2016	Dec. 31, 2018	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted							790,000		939,000	1,471,000
Weighted average grant date fair value of restricted stock units granted							$ 45.99		$ 28.91	$ 18.95
Tax benefit from compensation expense							$ 12,036,000		$ 10,462,000	$ 8,752,000
Total unrecognized expense related to non-vested restricted stock unit awards and stock options							$ 44,000,000
Unrecognized expense related to non-vested restricted stock unit awards and stock options expected to be recognized over weighted average period, in years							2 years 4 months 24 days
Maximum percent of shares allowed to purchase							10.00%
Fair market value							$ 25,000
Maximum number of shares allowed to purchase							6,000
Percentage of common stock price paid							85.00%
Common stock issued to employees		300,000	300,000	300,000	400,000	500,000
Value of common stock issued to employees per share		$ 32.36	$ 35.59	$ 25.53	$ 21.59	$ 16.74		$ 35.59
Number of shares available for grant							7,874,000		8,605,000	9,546,000	10,914,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Cash received from employees, employee stock options exercises							$ 1,000,000		$ 6,800,000	$ 2,900,000
Tax benefit from compensation expense							$ 400,000		$ 2,500,000	$ 800,000
Percentage of common stock price paid							100.00%
Stock Options \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Period of stock granted to employees and executive officers vest in equal installments							4 years
Stock Options \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Period of stock granted to employees and executive officers vest in equal installments							7 years
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted							790,000		939,000	1,471,000
Restricted Stock Units \| Employees
Share-based Compensation Arrangement by Share-based Payment Award
Period of stock granted to employees and executive officers vest in equal installments							4 years
TSR Performance-Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Total shareholder return performance measurement period							3 years
Share-based compensation arrangement by share-based payment award, description							Capped at four times the grant date value
Minimum age of retirement to be eligible for PRSUs							60 years
Minimum years of service for retirement to be eligible for PRSUs							10 years
Restricted stock unit awards granted							100,000		100,000	100,000
Weighted average grant date fair value of restricted stock units granted							$ 54.85		$ 35.66	$ 20.29
Stock price							47.70		28.56	19.43
TSR Performance-Based Restricted Stock Units \| Measurement Input, Expected Dividend Payment [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Estimated annual dividend amount per share							$ 0.36		$ 0.28	$ 0.24
TSR Performance-Based Restricted Stock Units \| Share-based Compensation Award, Tranche One
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of vesting of target shares upon performance achieved								200.00%
TSR Performance-Based Restricted Stock Units \| Share-based Compensation Award, Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of vesting of target shares upon performance achieved								0.00%
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares available for grant							2,500,000
PBIT Performance-Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Total shareholder return performance measurement period							3 years
Restricted stock unit awards granted							100,000		100,000	100,000
Weighted average grant date fair value of restricted stock units granted							$ 46.62		$ 27.72	$ 18.71
Service-Based Restricted Stock Units \| Employees
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted							600,000		800,000	1,200,000
Weighted average grant date fair value of restricted stock units granted							$ 45.92		$ 28.19	$ 18.88
Service-Based Restricted Stock Units \| Non Employee Directors And Certain Employees
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted							100,000		100,000	100,000
Weighted average grant date fair value of restricted stock units granted							$ 35.81		$ 34.48	$ 18.71
Service-Based Restricted Stock Units \| Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted							100,000		100,000	100,000
Weighted average grant date fair value of restricted stock units granted							$ 12.17		$ 7.13	$ 5.30
Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award
Common stock issued to employees	400,000
Value of common stock issued to employees per share	$ 26.67