Mortgage Loan Losses Allowance - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Mortgage Loan Loss Allowance [Abstract]
Pre-tax charges for loan losses related to mortgage loans sold	$ 2,700	$ 2,400	$ 2,300
Mortgage loan loss allowance	$ 12,300	$ 10,000