Loans Receivable and Allowance for Loan Losses - Summary of Allowance for Loan Losses by Portfolio Segment and Impairment Classification (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	$ 5,067	$ 1,165
Collectively evaluated for impairment	50,458	54,397
Total	55,525	55,562	$ 60,195	$ 61,883
Mortgage Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	1,580	1,026
Collectively evaluated for impairment	23,931	26,652
Total	25,511	27,678	28,052
Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	3,462	92
Collectively evaluated for impairment	24,801	25,601
Total	28,263	25,693	29,814
Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	25	47
Collectively evaluated for impairment	1,726	2,144
Total	$ 1,751	$ 2,191	$ 2,329