Retirement Plans - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Employee service period under ESOP	1 year		1 year
Contribution and paid out as benefits	$ 376,000	$ 155,000	$ 752,000	$ 260,000
Deferred compensation obligations	7,213,000		7,213,000		7,357,000
Earnings credits on deferred balances included in noninterest expense	138,000	147,000	290,000	294,000
401(k) Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Minimum age for employees			21 years
Minimum period for employees to participate			90 days
Supplemental Retirement Plans [Member] | December 31, 2014 [Member]
Defined Benefit Plan Disclosure [Line Items]
Contribution and paid out as benefits			$ 569,000