Loans Receivable - Average Recorded Investment of Impaired Loans (Details) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Related Specific Valuation Allowance	$ 2,143,000	$ 4,170,000
Average recorded investment of impaired loans	47,166,000	39,488,000	$ 32,751,000
Nonaccrual
Financing Receivable, Modifications [Line Items]
Interest income recognized	0	0	0
Restructured performing
Financing Receivable, Modifications [Line Items]
Interest income recognized	1,200,000	1,400,000	1,200,000
Commercial business
Financing Receivable, Modifications [Line Items]
Related Specific Valuation Allowance	1,944,000	3,955,000
Average recorded investment of impaired loans	45,667,000	37,550,000	28,873,000
Commercial business \| Commercial and industrial
Financing Receivable, Modifications [Line Items]
Related Specific Valuation Allowance	1,372,000	2,607,000
Average recorded investment of impaired loans	31,906,000	16,773,000	11,310,000
Commercial business \| Owner-occupied commercial real estate
Financing Receivable, Modifications [Line Items]
Related Specific Valuation Allowance	426,000	1,142,000
Average recorded investment of impaired loans	6,009,000	11,312,000	5,401,000
Commercial business \| Non-owner occupied commercial real estate
Financing Receivable, Modifications [Line Items]
Related Specific Valuation Allowance	146,000	206,000
Average recorded investment of impaired loans	7,752,000	9,465,000	12,162,000
One-to-four family residential
Financing Receivable, Modifications [Line Items]
Related Specific Valuation Allowance	56,000	76,000
Average recorded investment of impaired loans	243,000	290,000	309,000
Real estate construction and land development
Financing Receivable, Modifications [Line Items]
Related Specific Valuation Allowance	0	0
Average recorded investment of impaired loans	682,000	1,220,000	3,218,000
Real estate construction and land development \| One-to-four family residential
Financing Receivable, Modifications [Line Items]
Related Specific Valuation Allowance	0	0
Average recorded investment of impaired loans	682,000	1,091,000	2,315,000
Real estate construction and land development \| Five or more family residential and commercial properties
Financing Receivable, Modifications [Line Items]
Average recorded investment of impaired loans	0	129,000	903,000
Consumer
Financing Receivable, Modifications [Line Items]
Related Specific Valuation Allowance	143,000	139,000
Average recorded investment of impaired loans	$ 574,000	$ 428,000	$ 351,000

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- Definition

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5258-111524

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Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

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Amount of allowance for credit losses related to recorded investment.

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