Summary of Financial Effects of Troubled Debt Restructurings (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($) Investment	Dec. 31, 2017 USD ($) Investment	Dec. 31, 2016 USD ($) Investment
Financing Receivable, Modifications [Line Items]
Number of loans classified as a non-accrual TDRs \| Investment	22	71	13
Pre-Modification Recorded Investment	$ 8,663	$ 61,641	$ 14,937
Post-Modification Recorded Investment	6,355	36,047	13,100
Trouble debt restructuring, charge-off amount	$ 2,308	14,273	170
Capitalized interest		$ 12	$ 11
Multi-Family
Financing Receivable, Modifications [Line Items]
Number of loans classified as a non-accrual TDRs \| Investment			1
Pre-Modification Recorded Investment			$ 9,340
Post-Modification Recorded Investment			$ 8,129
Weighted Average Interest Rate, Pre-Modification			4.63%
Weighted Average Interest Rate, Post-Modification			4.00%
One-to-four family
Financing Receivable, Modifications [Line Items]
Number of loans classified as a non-accrual TDRs \| Investment		4	5
Pre-Modification Recorded Investment		$ 810	$ 900
Post-Modification Recorded Investment		$ 986	$ 1,036
Weighted Average Interest Rate, Pre-Modification		5.93%	4.26%
Weighted Average Interest Rate, Post-Modification		2.21%	2.65%
Capitalized interest		$ 12	$ 11
Commercial and Industrial
Financing Receivable, Modifications [Line Items]
Number of loans classified as a non-accrual TDRs \| Investment	21	65	7
Pre-Modification Recorded Investment	$ 7,763	$ 52,179	$ 4,697
Post-Modification Recorded Investment	$ 5,455	$ 26,409	$ 3,935
Weighted Average Interest Rate, Pre-Modification	3.25%	3.36%	3.22%
Weighted Average Interest Rate, Post-Modification	3.13%	3.29%	3.19%
Trouble debt restructuring, charge-off amount	$ 2,308	$ 14,273	$ 170
Acquisition, development, and construction
Financing Receivable, Modifications [Line Items]
Number of loans classified as a non-accrual TDRs \| Investment	1	2
Pre-Modification Recorded Investment	$ 900	$ 8,652
Post-Modification Recorded Investment	$ 900	$ 8,652
Weighted Average Interest Rate, Pre-Modification	4.50%	5.50%
Weighted Average Interest Rate, Post-Modification	4.50%	5.50%

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Weighted Average Interest Rate Pre Modification

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Number of financing receivables that have been modified by troubled debt restructurings.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
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Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

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Reflects the amount of the write-down related to a troubled debt restructuring.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18845-111554

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The gross interest income that would have been recorded in the period on troubled debt restructurings, if the loans had been current in accordance with their original terms and had been outstanding throughout the period or since origination, if held for part of the period.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 310
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