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Securities - Amortized Cost and Fair Value of Available-for-sale Securities (Q2) (Details) - USD ($) | Jun. 30, 2018 | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |  |
Amortized Cost | $ 160,547,000 | $ 153,566,000 | $ 131,046,000
Gross Unrealized Gains | 179,000 | 165,000 |
Gross Unrealized Losses | (4,149,000) | (1,787,000) |
Fair Value | 156,577,182 | 151,944,567 | 129,421,914
U.S. Government-sponsored enterprises (GSEs) [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Amortized Cost | 29,137,000 | 26,207,000 | $ 18,279,000
Gross Unrealized Gains | 0 | 1,000 |
Gross Unrealized Losses | (1,009,000) | (432,000) |
Fair Value | 28,128,000 | 25,776,000 |
Municipal securities [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Amortized Cost | 15,896,000 | 9,122,000 |
Gross Unrealized Gains | 8,000 | 28,000 |
Gross Unrealized Losses | (320,000) | (147,000) |
Fair Value | 15,584,000 | 9,003,000 |
Other debt securities [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Amortized Cost | 976,000 | 974,000 |
Gross Unrealized Gains | 0 | 0 |
Gross Unrealized Losses | (65,000) | (24,000) |
Fair Value | 911,000 | 950,000 |
Mortgage-backed securities (GSEs) [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Amortized Cost | 114,538,000 | 117,263,000 |
Gross Unrealized Gains | 171,000 | 136,000 |
Gross Unrealized Losses | (2,755,000) | (1,184,000) |
Fair Value | $ 111,954,000 | $ 116,215,000 |

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- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
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- Definition Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
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- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
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