Loans - Presentation of Recorded Investment in Nonaccrual Loans and Loans Past Due Over 90 Days and Still on Accrual by Class of Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	$ 11,703	$ 12,439
Commercial Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	3,007	3,941
Commercial Loans [Member] | Multifamily [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	275
Commercial Loans [Member] | Nonresidential [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	1,218	3,546
Commercial Loans [Member] | Land [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	9	34
Commercial Loans [Member] | Secured [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	1,505	361
Residential Mortgage Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	6,076	6,084
Residential Mortgage Loans [Member] | One-to Four-Family [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	6,076	6,084
Consumer Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	2,620	2,414
Consumer Loans [Member] | Home Equity [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	2,074	1,936
Consumer Loans [Member] | Auto [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	155	31
Consumer Loans [Member] | Marine [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	181	267
Consumer Loans [Member] | Recreational Vehicle [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	208	178
Consumer Loans [Member] | Other [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	$ 2	$ 2