Mortgage Banking Activities - Valuation Allowance for Mortgage Servicing Rights (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Mortgage Banking [Abstract]
Balance, beginning of period	$ (39)	$ (58)
Impairment charges	(435)	(161)
Balance, end of period	$ (474)	$ (219)