Loans Receivable and Allowance for Loan Losses (Summary of Allowance for Loan Losses by Portfolio Segment and Impairment Classification) (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	$ 1,749	$ 1,165
Collectively evaluated for impairment	53,604	54,397
Total	55,353	55,562	$ 62,521	$ 60,195
Mortgage Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	897	1,026
Collectively evaluated for impairment	26,029	26,652
Total	26,926	27,678	28,001	28,052
Commercial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	806	92
Collectively evaluated for impairment	25,545	25,601
Total	26,351	25,693	32,326	29,814
Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	46	47
Collectively evaluated for impairment	2,030	2,144
Total	$ 2,076	$ 2,191	$ 2,194	$ 2,329