Loans and Allowance for Loan Losses - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2014 SecurityLoan	Jun. 30, 2013 SecurityLoan	Jun. 30, 2014 SecurityLoan	Jun. 30, 2013 SecurityLoan	Dec. 31, 2013
Receivables [Abstract]
Minimum number of days to consider the loans as non-accrual			Greater than 90 days
Carrying amount of purchased credit impaired loans			$ 2,519,000	$ 3,497,000	$ 2,707,000
Contractual balance	3,754,000	4,848,000	3,754,000	4,848,000	3,970,000
Loans held for sale	13,570,000	17,993,000	13,570,000	17,993,000	5,163,000
Average recorded investment in impaired loans	25,004,000		26,522,000	22,693,000	31,293,000
Non-accrual loans still accruing, past due 90 days, restructured loans and foreclosed assets	26,030,000	31,073,000	26,030,000	31,073,000	31,128,000
Additional funds advanced in connection with impaired loans	0		0
Interest income recognized on impaired loans			0		685,000
Allowance for purchased credit impaired loans	0		0		0
Number of loans modified	1	1	1	5
Default for purposes of this disclosure is a troubled debt restructured loan			90 days
Commitments to lend additional funds to borrowers with loan that have been modified as TDRs	0		0
Loans held by subsidiaries subject to blanket liens	1,585,000,000		1,585,000,000
Letters of credit outstanding, amount	7,000,000		7,000,000
Short-term borrowings outstanding	$ 111,065,000		$ 111,065,000