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Retirement Plans - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2014 RetirementPlans	Mar. 31, 2013	Dec. 31, 2008
Disclosure Retirement Plans [Abstract]
Number of supplemental non-qualified retirement plans sponsored by the Corporation	2
Consecutive calendar years used to calculate BRP benefits			5 years
Term of employment for consideration of BRP			10 years
Annuity equivalent of contribution to defined contribution plan deducted from monthly benefit of basic retirement plan	3.00%
Percent of employer match	100.00%
Employee contribution percentage	4.00%
Additional automatic contribution increase, percentage	3.00%
Additional discretionary contribution, performance goals, percentage	2.00%
Contribution expense of the Corporation	$ 2,570	$ 2,335

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- Definition

Annuity equivalent of contribution to defined contribution plan deducted from monthly benefit of basic retirement plan.

+ References

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- Definition

Defined benefit plan assumptions consecutive period of highest average compensation.

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- Definition

Defined benefit plan assumptions consecutive term of employment.

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- Definition

Employees additional eligible automatic contribution.

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- Definition

Number of supplemental non-qualified retirement plans sponsored by the entity.

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- Definition

Original annuity equivalent of contribution to defined contribution plan deducted from monthly benefit of basic retirement plan.

+ References

No definition available.

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- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

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- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

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- Definition

Percentage employer matches of the employee's percentage contribution matched.

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