Additional Information about Impaired Loans (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance, Recorded Investment	$ 56,936,000	$ 52,169,000
Impaired loans with no related allowance, Unpaid Principal Balance	143,149,000	126,513,000
Impaired loans with no related allowance, Average Recorded Investment	54,393,000	63,146,000
Impaired loans with no related allowance, Interest Income Recognized	3,516,000	4,013,000
Impaired loans with an allowance recorded, Recorded Investment	1,445,000
Impaired loans with an allowance recorded, Unpaid Principal Balance	4,173,000
Impaired loans with an allowance recorded, Related Allowance	116,000
Impaired loans with an allowance recorded, Average Recorded Investment	4,111,000	20,000
Impaired loans with an allowance recorded, Interest Income Recognized	13,000
Total impaired loans, Recorded Investment	58,381,000	52,169,000
Total impaired loans, Unpaid Principal Balance	147,322	126,513,000
Total impaired loans, Related Allowance	116,000
Total impaired loans, Average Recorded Investment	58,504,000	63,166,000
Total impaired loans, Interest Income Recognized	3,529,000	4,013,000
Multi-Family
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance, Recorded Investment	3,577,000	4,220,000
Impaired loans with no related allowance, Unpaid Principal Balance	6,790,000	7,168,000
Impaired loans with no related allowance, Average Recorded Investment	4,336,000	6,114,000
Impaired loans with no related allowance, Interest Income Recognized	266,000	340,000
Total impaired loans, Recorded Investment	3,577,000	4,220,000
Total impaired loans, Unpaid Principal Balance	6,790	7,168,000
Total impaired loans, Average Recorded Investment	4,336,000	6,114,000
Total impaired loans, Interest Income Recognized	266,000	340,000
Commercial Real Estate
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance, Recorded Investment	14,717,000	2,256,000
Impaired loans with no related allowance, Unpaid Principal Balance	19,832,000	7,371,000
Impaired loans with no related allowance, Average Recorded Investment	6,140,000	3,234,000
Impaired loans with no related allowance, Interest Income Recognized	371,000
Total impaired loans, Recorded Investment	14,717,000	2,256,000
Total impaired loans, Unpaid Principal Balance	19,832	7,371,000
Total impaired loans, Average Recorded Investment	6,140,000	3,234,000
Total impaired loans, Interest Income Recognized	371,000
One-to-four family
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance, Recorded Investment	584,000	1,022,000
Impaired loans with no related allowance, Unpaid Principal Balance	602,000	1,076,000
Impaired loans with no related allowance, Average Recorded Investment	811,000	1,576,000
Impaired loans with no related allowance, Interest Income Recognized	21,000	26,000
Total impaired loans, Recorded Investment	584,000	1,022,000
Total impaired loans, Unpaid Principal Balance	602,000	1,076,000
Total impaired loans, Average Recorded Investment	811,000	1,576,000
Total impaired loans, Interest Income Recognized	21,000	26,000
Acquisition, development, and construction
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance, Recorded Investment	389,000	8,296,000
Impaired loans with no related allowance, Unpaid Principal Balance	1,289,000	9,197,000
Impaired loans with no related allowance, Average Recorded Investment	3,508,000	9,238,000
Impaired loans with no related allowance, Interest Income Recognized	364,000	590,000
Total impaired loans, Recorded Investment	389,000	8,296,000
Total impaired loans, Unpaid Principal Balance	1,289	9,197,000
Total impaired loans, Average Recorded Investment	3,508,000	9,238,000
Total impaired loans, Interest Income Recognized	364,000	590,000
Other
Financing Receivable, Impaired [Line Items]
Impaired loans with no related allowance, Recorded Investment	37,669,000	36,375,000
Impaired loans with no related allowance, Unpaid Principal Balance	114,636,000	101,701,000
Impaired loans with no related allowance, Average Recorded Investment	39,598,000	42,984,000
Impaired loans with no related allowance, Interest Income Recognized	2,494,000	3,057,000
Impaired loans with an allowance recorded, Recorded Investment	1,445,000
Impaired loans with an allowance recorded, Unpaid Principal Balance	4,173,000
Impaired loans with an allowance recorded, Related Allowance	116,000
Impaired loans with an allowance recorded, Average Recorded Investment	4,111,000	20,000
Impaired loans with an allowance recorded, Interest Income Recognized	13,000
Total impaired loans, Recorded Investment	39,114,000	36,375,000
Total impaired loans, Unpaid Principal Balance	118,809	101,701,000
Total impaired loans, Related Allowance	116,000
Total impaired loans, Average Recorded Investment	43,709,000	43,004,000
Total impaired loans, Interest Income Recognized	$ 2,507,000	$ 3,057,000