Number of shares of common stock issued and outstanding over which shares can be repurchased under a repurchase plan.

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Total fair market value of annual grant of restricted stock awards per participant, under a restricted stock plan.

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Maximum adjustment factor allowed under the form of performance share award agreement.

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Minimum Adjustment Factor

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The minimum number of awards to be issued if minimum performance targets are not achieved.

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Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other Than Options, Number of Shares of Common Shares Awarded Upon Settlement

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No definition available.

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Unrecognized cost of unvested share-based compensation awards.

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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 obligations incurred for employer-related costs classified as other, payable within one year or the normal operating cycle, if longer.

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

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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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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 number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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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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Number of additional shares authorized for issuance under an established share-based compensation plan.

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No definition available.

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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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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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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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

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No definition available.

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Number of shares issued during the period as a result of an employee stock purchase plan.

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The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

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Shareholders' Equity - Additional Information (Detail) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended			48 Months Ended	187 Months Ended
	May 07, 2014 shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares	Apr. 30, 2016	Dec. 31, 2017 USD ($) shares	May 02, 2017 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in Period		593
Issuance of shares under stock purchase plan						10,896
Weighted average fair value of award granted during the period \| $ / shares		$ 54.11
Total intrinsic value of options exercised \| $		$ 55,000	$ 29,000	$ 31,000
Total unrecognized share-based compensation cost \| $		$ 69,000				$ 69,000
Unrecognized share-based compensation cost, weighted average period		1 year 10 months 24 days
2017 Omnibus Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for grant							2,500
Shares available for granting of awards		1,896				1,896
2017 Omnibus Incentive Plan \| Upper end
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		3 years
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock issued per unit based award upon vesting		1
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in Period		23
Maximum Adjustment Factor		2
Minimum Adjustment Factor		0.5
Minimum Shares Issued		0
Number of common stock issued per unit based award upon vesting		1
Employee Stock Option Plan \| Upper end
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years		5 years
Maximum contractual term		10 years
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for grant		12,305				12,305
Number of additional shares authorized	3,000
Purchase price percentage of fair market value		85.00%
Amount withheld employee stock purchase plan \| $		$ 16,400				$ 16,400
Weighted average fair value of award granted during the period \| $ / shares		$ 11.69	$ 10.99	$ 10.45
Directors' Restricted Stock Plan 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for grant		250				250
Grants in Period		38
Shares available for granting of awards		106				106
Fair value of annual grant per participant of restricted stock awards \| $		$ 200
Unvested restricted shares		0				0
Weighted average fair value of award granted during the period \| $ / shares		$ 52.75
Retirement-Eligible Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock or Unit Expense \| $		$ 4,000
Non-Discretionary Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for repurchase		40,000				40,000
Discretionary Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected common stock shares issued and outstanding		170,000				170,000