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Securities (FY) (Details) - USD ($) | Jun. 30, 2018 | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | --- | ---
Debt securities available-for-sale: |  |  |
Amortized Cost | $ 160,547,000 | $ 153,566,000 | $ 131,046,000
Gross Unrealized Gains |  | 165,000 | 209,000
Gross Unrealized Losses |  | (1,787,000) | (1,833,000)
Fair Value |  | 151,944,000 | 129,422,000
U.S. Government-sponsored enterprises (GSEs) [Member] |  |  |
Debt securities available-for-sale: |  |  |
Amortized Cost | 29,137,000 | 26,207,000 | 18,279,000
Gross Unrealized Gains |  | 1,000 | 8,000
Gross Unrealized Losses |  | (432,000) | (564,000)
Fair Value |  | 25,776,000 | 17,723,000
Muncipal Securities [Member] |  |  |
Debt securities available-for-sale: |  |  |
Amortized Cost |  | 9,122,000 | 8,182,000
Gross Unrealized Gains |  | 28,000 | 16,000
Gross Unrealized Losses |  | (147,000) | (179,000)
Fair Value |  | 9,003,000 | 8,019,000
Other Debt Securities [Member] |  |  |
Debt securities available-for-sale: |  |  |
Amortized Cost | $ 976,000 | 974,000 |
Gross Unrealized Gains |  | 0 |
Gross Unrealized Losses |  | (24,000) |
Fair Value |  | 950,000 |
Mortgage Backed Securities [Member] |  |  |
Debt securities available-for-sale: |  |  |
Amortized Cost |  | 117,263,000 | 104,585,000
Gross Unrealized Gains |  | 136,000 | 185,000
Gross Unrealized Losses |  | (1,184,000) | (1,090,000)
Fair Value |  | $ 116,215,000 | $ 103,680,000

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