Indemnifications and Guarantees - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014 Financial_Institution Transactions	Jun. 30, 2013	Jun. 30, 2014 Financial_Institution Transactions	Jun. 30, 2013	Dec. 31, 2013 Transactions
Guarantor Obligations [Line Items]
Provision for losses at the time of sale	$ 50,000	$ 1,680,000	$ 2,680,000	$ 3,911,000
Number of unrelated financial institutions	3		3
Derivative transaction held for guarantee	104		104		101
Aggregate notional amount	451,400,000		451,400,000		423,900,000
Notional amount maturity period, minimum			1 year
Notional amount maturity period, maximum			11 years
Aggregate market value of swaps to customers	20,900,000		20,900,000		17,800,000
Reserve for swap guarantees	70,000		70,000		70,000
Secondary Market Loan Sales [Member]
Guarantor Obligations [Line Items]
Provision for losses at the time of sale			0
Repurchase of the loans			$ 354,000
Number of loans repurchased			2
Minimum [Member]
Guarantor Obligations [Line Items]
Term period of loan			15 years
Maximum [Member]
Guarantor Obligations [Line Items]
Term period of loan			30 years