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Federal Home Loan Bank Advances - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Federal Home Loan Bank Advances [Line Items]
Federal home loan bank advances, acquisition accounting adjustments	$ 19,000	$ 228,000
Federal home loan bank, required investment conversion ratio	0.05
Additional borrowing capacity from FHLB	$ 795,000,000	647,900,000
Federal home loan bank advances maximum borrowing capacity as percentage of total assets	35.00%
Federal home loan bank, advances, putable option	$ 361,506,000	$ 313,715,000
Ridgestone
Federal Home Loan Bank Advances [Line Items]
Federal home loan bank, advances, putable option	$ 1,500,000
Minimum
Federal Home Loan Bank Advances [Line Items]
Federal home loan bank advances, Fixed interest rate	1.32%
Federal home loan bank fixed rate advances, maturity date	2018-01
Maximum
Federal Home Loan Bank Advances [Line Items]
Federal home loan bank advances, Fixed interest rate	3.22%
Federal home loan bank fixed rate advances, maturity date	2018-03

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Federal home loan bank advances acquisition accounting adjustments.

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

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

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Federal home loan bank fixed rate advances maturity date.

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

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Amount of Federal Home Loan Bank (FHLBank) advances to member financial institutions.

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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

Reference 2: 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 (b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: 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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