Mortgage Banking Activities - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Mortgage Loan Activity [Line Items]
Mortgage loans serviced for others	$ 1,200,000	$ 1,200,000
Fair value of mortgage servicing rights	10,300	10,200
Private Investor [Member]
Mortgage Loan Activity [Line Items]
Mortgage loans serviced for others	27,917
Private Investor [Member] | Adjustable Rate Residential Mortgages [Member] | One-to Four-Family [Member]
Mortgage Loan Activity [Line Items]
Mortgage loans serviced for others	$ 27,900
Percentage of mortgage service release premium as part of gain recognized on sale	0.45%
FHLMC, FNMA and Private Investor [Member]
Mortgage Loan Activity [Line Items]
Customer escrow balances	$ 12,100	$ 14,300