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Loans - Additional Information (Detail)	3 Months Ended	12 Months Ended
	Mar. 31, 2018 USD ($) Investment	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) Investment
Financing Receivable, Recorded Investment [Line Items]
Outstanding loans to Executive officers, directors, principal shareholders, related interest and parties	$ 56,800,000	$ 56,800,000
Loans held for sale	31,402,000	31,402,000	$ 35,258,000
Delinquent loans selectively extended to certain borrowers, rate reductions, forbearance of arrears, and extension of maturity dates	$ 2,654,000		$ 5,084,000
Number of loans classified as a non-accrual TDRs | Investment	7		18
Freedom Mortgage Corporation
Financing Receivable, Recorded Investment [Line Items]
Loans held for sale	$ 31,400,000	31,400,000	$ 35,300,000
One-to-four family
Financing Receivable, Recorded Investment [Line Items]
Delinquent loans selectively extended to certain borrowers, rate reductions, forbearance of arrears, and extension of maturity dates			$ 339,000
Number of loans classified as a non-accrual TDRs | Investment			1
One-to-four family | Freedom Mortgage Corporation
Financing Receivable, Recorded Investment [Line Items]
Loans held for sale	21,900,000	21,900,000
Commercial Real Estate | Freedom Mortgage Corporation
Financing Receivable, Recorded Investment [Line Items]
Loans held for sale	9,500,000	9,500,000
Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Delinquent loans selectively extended to certain borrowers, rate reductions, forbearance of arrears, and extension of maturity dates	$ 1,754,000		$ 4,745,000
Number of loans classified as a non-accrual TDRs | Investment	6		17
Commercial and Industrial | Payment Default
Financing Receivable, Recorded Investment [Line Items]
Number of loans classified as a non-accrual TDRs	11
Loan classified as non accrual TDRs	$ 2,900,000	2,900,000
Principal shareholders
Financing Receivable, Recorded Investment [Line Items]
Outstanding loans to Executive officers, directors, principal shareholders, related interest and parties	$ 0	0
Financing Receivable Troubled Debt Restructurings Rate Reductions
Financing Receivable, Recorded Investment [Line Items]
Delinquent loans selectively extended to certain borrowers, rate reductions, forbearance of arrears, and extension of maturity dates		44,600,000
Financing Receivable Troubled Debt Restructurings Forbearance of Arrears
Financing Receivable, Recorded Investment [Line Items]
Delinquent loans selectively extended to certain borrowers, rate reductions, forbearance of arrears, and extension of maturity dates		$ 1,800,000

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- Definition

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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+ 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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Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5111-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k)(1))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.3)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Name Accounting Standards Codification
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