Mortgage Servicing Rights - Summary of Mortgage Servicing Rights (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Mortgage Servicing Rights Activity
Balance at beginning of period	$ 20,685	$ 23,041
Additions	2,952	1,442
Amortization	(4,010)	(3,798)
Balance at end of period - before valuation allowance	19,627	20,685
Valuation allowance	(685)	(1,281)
Balance at end of period	18,942	19,404
Fair value at the end of the period	$ 19,252	$ 19,590
Key assumptions:
Weighted average discount rate	11.35%	11.45%
Weighted average prepayment speed	11.31%	10.01%