Name:	us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of unrealized (holding) gain (loss) which is included in the statement of income (or changes in net assets) related to those liabilities still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3).

Fair Value Measurement of Assets and Liabilities - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended					3 Months Ended						3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Minimum [Member]	Sep. 30, 2014 Maximum [Member]	Sep. 30, 2014 Significant Unobservable Inputs (Level 3) [Member]	Sep. 30, 2014 Available-for-sale Securities [Member]	Sep. 30, 2013 Available-for-sale Securities [Member]	Mar. 31, 2014 Available-for-sale Securities [Member]	Dec. 31, 2013 Available-for-sale Securities [Member]	Mar. 31, 2013 Available-for-sale Securities [Member]	Dec. 31, 2012 Available-for-sale Securities [Member]	Sep. 30, 2014 Non-Performing Loans [Member] Changes Measurement [Member]	Sep. 30, 2014 Non-Performing Loans [Member] Changes Measurement [Member]	Sep. 30, 2014 Non-Performing Loans [Member] Fair Value [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Changes in unrealized losses on Level 3 securities							$ 0	$ 0
Transfer of loans to loans held for sale		27,329,000	0										500,000	2,800,000	7,400,000
Discount rate on impaired loans						38.20%
Impaired trust preferred securities ,fair value							25,701,000	78,211,000	26,029,000	28,523,000	79,112,000	71,674,000
Impaired collateral dependent loans, charge-offs	495,000	3,700,000
Collateral dependent impaired loans, recorded investment	13,400,000	13,400,000
Specific valuation allowance allocations	1,500,000	1,500,000
Reported net carrying amount of impaired loans	11,900,000	11,900,000
Valuation of loan servicing rights, discount rate		8.00%
Valuation of loan servicing rights, prepayment rate				0.00%	25.00%
Net recoveries of impairment charges	131,000	273,000
Fair Value, Unobservable Inputs Quantitative Information For Assets Measured On Nonrecurring Basis, Foreclosed Assets, Discount Rate		4.80%
Foreclosed assets measured at fair value upon initial recognition	12,400,000	12,400,000
Allowance for loan losses, charge-offs	1,700,000	3,700,000
Loss due to re-measurement of repossessed assets	$ 799,000	$ 2,700,000