Loans and Allowance for Loan Losses - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014 SecurityLoan	Mar. 31, 2013	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	$ 2,605,000	$ 0	$ 2,707,000
Contractual balance	3,844,000	0	3,970,000
Loans held for sale	10,429,000	10,122,000	5,163,000
Average recorded investment in impaired loans	26,770,000	23,163,000	31,293,000
Non-accrual loans still accruing, past due 90 days, restructured loans and foreclosed assets	27,553,000	25,718,000	31,128,000
Non-accrual loans	24,710,000	22,509,000	27,926,000
Interest income recognized on impaired loans	0	0	685,000
Allowance for purchased credit impaired loans	0		0
Default for purposes of this disclosure is a troubled debt restructured loan	90 days
Number of loans modified	11
Loans held by subsidiaries subject to blanket liens	1,565,974,000
Letters of credit outstanding, amount	40,100,000
Short-term borrowings outstanding	$ 76,092,000