Indemnifications and Guarantees - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($) Transactions Financial_Institution	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) Transactions Financial_Institution	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) Transactions
Guarantor Obligations [Line Items]
Provision for losses at the time of sale	$ 1,254,000	$ 3,773,000	$ 2,034,000	$ 4,559,000
Number of unrelated financial institutions | Financial_Institution	4		4
Derivative transaction held for guarantee | Transactions	130		130		119
Aggregate notional amount	$ 504,700,000		$ 504,700,000		$ 481,600,000
Aggregate fair value of swaps to customers	31,100,000		31,100,000		$ 18,100,000
Reserves for swap guarantees	$ 0		$ 0
Minimum [Member]
Guarantor Obligations [Line Items]
Notional amount maturity period			1 month
Maximum [Member]
Guarantor Obligations [Line Items]
Notional amount maturity period			11 years
Secondary Market Loan Sales [Member]
Guarantor Obligations [Line Items]
Provision for losses at the time of sale			$ 0
Number of loans repurchased | Transactions			0