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Business Combinations - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands |  | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Oct. 01, 2018 | Dec. 31, 2018 | Dec. 31, 2017 | Jun. 30, 2019 | Sep. 30, 2018
Business Acquisition [Line Items] |  |  |  |  |
Business combination, number of shares transferred (shares) |  | 904,826 |  |  |
Goodwill acquired |  | $ 8,970 |  |  |
South Sound Merger |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Business combination, number of shares transferred (shares) | 904,826 |  |  |  |
Issued, value assigned | $ 28,270 |  |  |  |
Business combination, share price (dollars per share) | $ 31.24 |  |  |  |
Cash paid | $ 6,900 |  |  |  |
Total merger consideration | 35,170 |  |  |  |
Goodwill acquired | 8,970 |  |  |  |
Acquisition related costs | $ 64 | $ 64 | $ 41 |  | $ 616
Timberland Bank | South Sound Merger |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Shares issued (in dollars per share) | $ 0.746 |  |  |  |
South Sound Bank | South Sound Merger |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Shares issued (in dollars per share) | $ 5.68825 |  |  |  |
Acquisition related costs |  |  | $ 2 |  |
Forecast | South Sound Merger |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Acquisition related costs |  |  |  | $ 580 |

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- Definition Value of equity interests (such as common shares, preferred shares, or partnership interest) issued or issuable to acquire the entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b)(4) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479 + Details
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- Definition Number of shares of equity interests issued or issuable to acquire entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b)(4) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479 + Details
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