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Fair Value Disclosures - Assets and Liabilities Measured on Recurring Basis (Q2) (Details) - USD ($) | Jun. 30, 2018 | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | $ 156,577,182 | $ 151,944,567 | $ 129,421,914
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 0 | 0 |
Significant Other Observable Inputs (Level 2) [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 156,577,000 | 151,944,000 |
Significant Other Unobservable Inputs (Level 3) [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 0 | 0 |
U.S. Government-sponsored enterprises (GSEs) [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 28,128,000 | 25,776,000 |
U.S. Government-sponsored enterprises (GSEs) [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 0 | 0 |
U.S. Government-sponsored enterprises (GSEs) [Member] | Significant Other Observable Inputs (Level 2) [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 28,128,000 | 25,776,000 |
U.S. Government-sponsored enterprises (GSEs) [Member] | Significant Other Unobservable Inputs (Level 3) [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 0 | 0 |
Mortgage-backed securities [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 111,954,000 | 116,215,000 |
Mortgage-backed securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 0 | 0 |
Mortgage-backed securities [Member] | Significant Other Observable Inputs (Level 2) [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 111,954,000 | 116,215,000 |
Mortgage-backed securities [Member] | Significant Other Unobservable Inputs (Level 3) [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 0 | 0 |
Other debt securities [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 911,000 | 950,000 |
Other debt securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 0 | 0 |
Other debt securities [Member] | Significant Other Observable Inputs (Level 2) [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 911,000 | 950,000 |
Other debt securities [Member] | Significant Other Unobservable Inputs (Level 3) [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 0 | 0 |
Municipal securities [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 15,584,000 | 9,003,000 |
Municipal securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 0 | 0 |
Municipal securities [Member] | Significant Other Observable Inputs (Level 2) [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | 15,584,000 | 9,003,000 |
Municipal securities [Member] | Significant Other Unobservable Inputs (Level 3) [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities available-for-sale, at fair value | $ 0 | $ 0 |

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