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Summary of Financial Effects of Troubled Debt Restructurings (Detail) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018 USD ($) Investment	Dec. 31, 2017 USD ($) Investment
Financing Receivable, Modifications [Line Items]
Number of loans classified as a non-accrual TDRs | Investment	7	18
Pre-Modification Recorded Investment	$ 4,066	$ 8,262
Post-Modification Recorded Investment	2,654	5,084
Trouble debt restructuring, charge-off amount	$ 1,318	3,280
Capitalized interest		$ 5
Acquisition, Development and Construction
Financing Receivable, Modifications [Line Items]
Number of loans classified as a non-accrual TDRs | Investment	1
Pre-Modification Recorded Investment	$ 900
Post-Modification Recorded Investment	$ 900
Weighted Average Interest Rate, Pre-Modification	4.50%
Weighted Average Interest Rate, Post-Modification	4.50%
Commercial and Industrial
Financing Receivable, Modifications [Line Items]
Number of loans classified as a non-accrual TDRs | Investment	6	17
Pre-Modification Recorded Investment	$ 3,166	$ 7,998
Post-Modification Recorded Investment	$ 1,754	$ 4,745
Weighted Average Interest Rate, Pre-Modification	3.28%	3.30%
Weighted Average Interest Rate, Post-Modification	3.21%	3.46%
Trouble debt restructuring, charge-off amount	$ 1,318	$ 3,280
One-to-four family
Financing Receivable, Modifications [Line Items]
Number of loans classified as a non-accrual TDRs | Investment		1
Pre-Modification Recorded Investment		$ 264
Post-Modification Recorded Investment		$ 339
Weighted Average Interest Rate, Pre-Modification		6.00%
Weighted Average Interest Rate, Post-Modification		2.63%
Capitalized interest		$ 5

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

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Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

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

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-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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-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18794-111554

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