Federal Home Loan Bank Advances - Additional Information (Details) - USD ($)	9 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Federal Home Loan Bank Advances [Line Items]
Federal home loan bank, total fixed-rate advances	$ 250,000,000
Federal home loan bank, total variable rate advances	$ 175,000,000
Federal home loan bank advances, Variable interest rate	2.22%
Federal home loan bank, required investment conversion ratio	0.045
Additional borrowing capacity from FHLB	$ 1,200,000,000	$ 795,000,000
Federal home loan bank advances maximum borrowing capacity as percentage of total assets	35.00%
2.36% Fixed-Rate Advances
Federal Home Loan Bank Advances [Line Items]
Federal home loan bank advances, Fixed interest rate	2.36%
Federal home loan bank fixed rate advances, maturity date	2018-12
Minimum
Federal Home Loan Bank Advances [Line Items]
Federal home loan bank variable rate advances, maturity date	2018-10
Maximum
Federal Home Loan Bank Advances [Line Items]
Federal home loan bank variable rate advances, maturity date	2018-12

Fixed interest rate of advances made and reported by Federal Home Loan Bank (FHLBank).

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Federal home loan bank advances floating interest rate.

+ References

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- Definition

Federal home loan bank advances maximum borrowing capacity as percentage of total assets.

+ References

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Federal home loan bank fixed rate advances maturity date.

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Federal home loan bank floating rate advances maturity date.

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- Definition

Ratio applied to the conversion of required investment in Federal Home Loan Bank (FHL Bank) $1 for every $ 20.

+ References

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- Definition

Par amount of advances made and reported by Federal Home Loan Bank (FHLBank) with fixed interest rate.

+ References

No definition available.

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- Definition

Par amount of advances made and reported by Federal Home Loan Bank (FHLBank) with floating interest rate.

+ References

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- Definition

Amount of advances or credit lines available from the Federal Home Loan Bank (FHLB).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22 (b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13(3)(a))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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-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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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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