Retirement Plans - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2014 RetirementPlans	Jun. 30, 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	$ 4,962	$ 4,535