Reserve for Repurchased Loans and Loss Sharing Obligations - Additional Information (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2015 USD ($) SecurityLoan	Dec. 31, 2014 SecurityLoan	Sep. 30, 2014 USD ($)
Receivables [Abstract]
Reserve for repurchased loans and loss sharing obligations	$ 1,000,000		$ 1,100,000
Decrease in reserve for repurchased loans and loss sharing obligations	$ 388,000
Outstanding number of loan repurchase requests | SecurityLoan	0	0