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	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	$ 9,061	$ 11,703
Commercial Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	2,865	3,007
Commercial Loans [Member] | Multifamily [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	275	275
Commercial Loans [Member] | Nonresidential [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	1,101	1,218
Commercial Loans [Member] | Land [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual		9
Commercial Loans [Member] | Secured [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	1,489	1,505
Residential Mortgage Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	4,426	6,076
Residential Mortgage Loans [Member] | One-to Four-Family [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	4,426	6,076
Consumer Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	1,770	2,620
Consumer Loans [Member] | Home Equity [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	1,431	2,074
Consumer Loans [Member] | Auto [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	42	155
Consumer Loans [Member] | Marine [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	181	181
Consumer Loans [Member] | Recreational Vehicle [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	98	208
Consumer Loans [Member] | Other [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, recorded investment, Nonaccrual	$ 18	$ 2