Note Borrowings (Notes payable) (Parenthetical) (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2018 USD ($)
Maximum
Debt Instrument [Line Items]
Advances with the FHLB, interest rate	2.02%
Minimum
Debt Instrument [Line Items]
Advances with the FHLB, interest rate	1.63%
Advances due 2018 To 2029 with fixed Rates 0.84% to 4.19%
Debt Instrument [Line Items]
Advances with the FHLB, earliest maturity	2018
Advances with the FHLB, latest maturity	2029
Advances due 2018 To 2029 with fixed Rates 0.84% to 4.19% \| Maximum
Debt Instrument [Line Items]
Advances with the FHLB, interest rate	4.19%
Advances due 2018 To 2029 with fixed Rates 0.84% to 4.19% \| Minimum
Debt Instrument [Line Items]
Advances with the FHLB, interest rate	0.84%
Floating Rate from 0.22% to 0.34% over the 1 month LIBOR with maturities ranging from 2018 to 2019
Debt Instrument [Line Items]
Advances with the FHLB, earliest maturity	2018
Advances with the FHLB, latest maturity	2019
Floating Rate from 0.22% to 0.34% over the 1 month LIBOR with maturities ranging from 2018 to 2019 \| Maximum
Debt Instrument [Line Items]
Advances with the FHLB, interest rate	0.34%
Floating Rate from 0.22% to 0.34% over the 1 month LIBOR with maturities ranging from 2018 to 2019 \| Minimum
Debt Instrument [Line Items]
Advances with the FHLB, interest rate	0.22%
Floating Rate from 0.09% to 0.24% over the 3 month LIBOR with maturities ranging from 2018 to 2019)
Debt Instrument [Line Items]
Advances with the FHLB, earliest maturity	2018
Advances with the FHLB, latest maturity	2019
Floating Rate from 0.09% to 0.24% over the 3 month LIBOR with maturities ranging from 2018 to 2019) \| Maximum
Debt Instrument [Line Items]
Advances with the FHLB, interest rate	0.24%
Floating Rate from 0.09% to 0.24% over the 3 month LIBOR with maturities ranging from 2018 to 2019) \| Minimum
Debt Instrument [Line Items]
Advances with the FHLB, interest rate	0.09%
Fixed Rate 7.00% Percent Notes Due July 2019 paying interest semiannually, net of debt issuance costs of $2,606
Debt Instrument [Line Items]
Interest Rate Percentage	7.00%
Senior Debt Maturity Year	2019
Debt issuance costs line of credit arrangements net	$ 2,606
Fixed Rate 6.125% to 8.327% Junior Subordinated Deferrable Interest Debentures Due 2027 to 2034, net of debt issuance costs of $443
Debt Instrument [Line Items]
Notes Payable Maturity Year Range Start	2027
Notes Payable Maturity Year Range End	2034
Debt issuance costs line of credit arrangements net	$ 443
Fixed Rate 6.125% to 8.327% Junior Subordinated Deferrable Interest Debentures Due 2027 to 2034, net of debt issuance costs of $443 \| Maximum
Debt Instrument [Line Items]
Interest Rate Percentage	8.327%
Fixed Rate 6.125% to 8.327% Junior Subordinated Deferrable Interest Debentures Due 2027 to 2034, net of debt issuance costs of $443 \| Minimum
Debt Instrument [Line Items]
Interest Rate Percentage	6.125%

Latest year the outstanding debt instruments are required to be repaid.

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Earliest year the outstanding debt instruments are required to be repaid.

+ References

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Maturity year the outstanding debt instruments are required to be repaid.

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Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount, after accumulated amortization, of debt issuance costs related to line of credit arrangements. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section S45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=68176171&loc=SL68176184-208336

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- Definition

The earliest year of maturity for the advances from the Federal Home Loan Bank as of the Balance Sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

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The last year of maturity for the advances from the Federal Home Loan Bank as of the Balance Sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
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States the interest rate applicable to Federal Home Loan Bank advances outstanding as of the Balance Sheet date.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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