Share-Based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation	$ 3,081,000	$ 3,918,000	$ 3,209,000
Proceeds from Stock Options Exercised	44,000	0	0
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	$ 247,000	275,000	383,000
Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period	12,155
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	4,600
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation	$ 3,081,000	3,918,000	3,209,000
Total income tax benefit recognized related to restricted stock awards	1,012,000	1,398,000	1,123,000
Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized	$ 4,600,000
Compensation cost recognition weighted average period	2 years 2 months 12 days
Award vesting period	7 years
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	$ 247,000	$ 275,000	$ 383,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized	$ 600,000
Compensation cost recognition weighted average period	1 year 10 months 24 days
Share-based compensation arrangement by share-based payment award, options, grants in period, weighted average grant date fair value	$ 15.24
Share based compensation arrangement by share based payment award options expiration term	10 years
Share based compensation arrangement by share based payment award options vesting period	3 years
Stock Options [Member] \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, shares authorized under stock option plans, exercise price range, upper range limit	$ 31.55
Stock Options [Member] \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, shares authorized under stock option plans, exercise price range, lower range limit	$ 24.26
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation	$ 734,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	46,530

Expiration term for options outstanding during the reporting period.

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- Definition

Share based compensation arrangement by share-based payment award options vesting period during the reporting period.

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Amount of increase in additional paid in capital (APIC) resulting from a tax benefit associated with share-based compensation plan other than an employee stock ownership plan (ESOP). Includes, but is not limited to, excess tax benefit.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 740
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6419406&loc=d3e23524-113945

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

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

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- Definition

The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

+ References

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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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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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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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- Definition

The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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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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- Definition

Number of share instruments newly issued under a share-based compensation plan.

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-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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