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Cash based compensation award, expenses

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Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

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Period Of Service From Grant Date Stock Options Awarded Not Subject To Forfeiture

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Provisional compensation cash award approved for future grant by compensation committee, units

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Provisional Compensation Cash Award Approved for Future Grant by Compensation Committee, Value

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Share Based Compensation Arrangement By Share Based Payment Award Aggregate Fair Value

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- Definition

Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Date

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Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Option Nonvested Intrinsic Value

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Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Fair Value

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Value

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Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Fair Value

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Ultimate Award Value Multiples of Original Value of Units, Maximum

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Ultimate Award Value Multiples of Original Value of Units, Minimum

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- Definition

The noncash expense that represents the cost of restricted stock or unit distributed to employees as compensation.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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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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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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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Date the equity-based award expires, in CCYY-MM-DD format.

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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Number of options outstanding, including both vested and non-vested options.

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Description of pertinent provisions of equity-based compensation awards that have actual or potential impact upon the company's financial statements.

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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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Restricted Stock, Performance Share and Cash Awards - Additional Information (Detail)				3 Months Ended			12 Months Ended
	Mar. 15, 2018 USD ($) shares	Mar. 16, 2017 USD ($) shares	Mar. 17, 2016 USD ($) shares	Mar. 31, 2018 shares	Mar. 31, 2017 shares	Mar. 31, 2016 shares	Dec. 31, 2018 USD ($) Times shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares	Mar. 11, 2015 USD ($) shares
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Share-based compensation, shares outstanding \| shares							8,800,000	9,500,000	9,500,000
Shares granted in the period \| shares							439,100	476,350	479,167
Long Term Incentive Plan [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Share-based compensation, shares outstanding, Value							$ 4,000,000
Share-based compensation, shares outstanding \| shares							3,300,000
Shares granted in the period \| shares							3,300,000
Restricted Stock Units (RSUs) [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Shares granted in the period \| shares				420,200	477,500	466,600	439,100	476,350	479,167
Fair value of grants in period							$ 28,700,000	$ 26,800,000	$ 20,400,000
Share based payment award vesting date				Mar. 15, 2023	Mar. 19, 2022	Mar. 17, 2021
Restricted stock or unit expense							27,200,000	19,600,000	18,200,000
Unvested Restricted Stock [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Total intrinsic value							140,800,000	109,300,000
Equity awards with an aggregate fair value							23,600,000	23,300,000
Performance Shares [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Equity awards with an aggregate fair value							$ 3,700,000	3,300,000
Shares authorized \| shares	78,200	86,250	72,900
Performance unit awards approved, Fair value	$ 5,300,000	$ 4,900,000	$ 3,200,000
Provisional awards, terms							Granted units for the 2018 and 2017 provisional awards will fully vest based on continuous employment through March 16, 2021 and 2020, respectively, and will be settled in shares of our common stock on a one-for-one basis as soon as practicable thereafter.
Performance awards period, years							1 year
Vesting period, years							2 years
2018 Provisional Cash Awards [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Performance awards expiration date							Jan. 01, 2021
Provisional compensation cash award approved for future grant by compensation committee, units \| shares							190,000
Cash-based compensation awards, expenses							$ 0
2017 Performance Share Awards [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Provisional awards, terms							The 2018 and 2017 awards are subject to a three-year performance period that begins on January 1, 2018 and 2017, respectively, and vest on the three-year anniversary of the date of grant (March 15, 2021 and March 16, 2020)
Performance awards period, years							3 years
Vesting period, years							3 years
Performance awards expiration date							Mar. 15, 2021
2017 Provisional Cash Awards [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Performance awards expiration date							Jan. 01, 2020
Cash-based compensation awards, expenses							$ 8,700,000
2016 Provisional Cash Awards [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Performance awards expiration date					Jan. 01, 2019
Cash-based compensation awards, expenses							$ 11,700,000	10,600,000
2015 Provisional Cash Awards [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Performance awards expiration date						Jan. 01, 2018
Provisional compensation cash award approved for future grant by compensation committee, units \| shares							269,000
Cash-based compensation awards, expenses							$ 15,800,000	$ 9,300,000	$ 6,600,000
2014 Provisional Cash Awards [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Provisional compensation cash award approved for future grant by compensation committee, units \| shares								199,000
Grants vested in period fair value								$ 9,300,000
2013 Provisional Cash Awards [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Provisional compensation cash award approved for future grant by compensation committee, units \| shares									246,000
Grants vested in period fair value									$ 11,200,000
Minimum [Member] \| Restricted Stock Units (RSUs) [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Period of service from grant date stock options awarded not subject to forfeiture							2 years	2 years	2 years
Officer and Key Employees [Member] \| Cash Awards [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Provisional awards, terms							He ultimate award value will be equal to the trailing twelve-month price of our common stock on December 31, 2020, multiplied by the number of units subject to the award, but limited to between 0.5 and 1.5 times the original value of the units determined as of the grant date.
Performance awards period, years							1 year
Vesting period, years							2 years
Provisional compensation cash awards approved for future grant by compensation committee, value	$ 15,000,000	$ 14,300,000
Provisional compensation cash award approved for future grant by compensation committee, units \| shares	219,000	255,000		242,000
Ultimate award value, multiples of original value of the units, minimum \| Times							0.5
Ultimate award value, multiples of original value of the units, maximum \| Times							1.5
Officer and Key Employees [Member] \| 2016 Provisional Cash Awards [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Provisional compensation cash awards approved for future grant by compensation committee, value			$ 17,400,000
Provisional compensation cash award approved for future grant by compensation committee, units \| shares			397,000		385,000
Officer and Key Employees [Member] \| 2015 Provisional Cash Awards [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Provisional compensation cash awards approved for future grant by compensation committee, value										$ 14,600,000
Provisional compensation cash award approved for future grant by compensation committee, units \| shares						294,000				315,000
Executive Officer [Member] \| Minimum [Member] \| Restricted Stock Units (RSUs) [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Minimum age of employee with not subject to award forfeiture on condition compliance							55 years	55 years	55 years