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Securities - Available-for-sale Securities in Continuous Loss Position (Q2) (Details) - USD ($) $ in Thousands | Jun. 30, 2018 | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |  |
Available-for-sale, fair value, less than 12 months | $ 85,205 | $ 67,058 |
Available-for-sale, gross unrealized losses, less than 12 months | (2,261) | (475) | $ (1,433)
Available-for-sale, fair value, 12 months or greater | 46,160 | 50,580 |
Available-for-sale, gross unrealized losses, 12 months or greater | (1,888) | (1,312) | (400)
Securities available for sale | 131,365 | 117,638 |
Available-for-sale, gross unrealized losses, total | (4,149) | (1,787) | (1,833)
U.S. Government-sponsored enterprises (GSEs) [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Available-for-sale, fair value, less than 12 months | 14,862 | 1,358 |
Available-for-sale, gross unrealized losses, less than 12 months | (425) | (1) | (564)
Available-for-sale, fair value, 12 months or greater | 13,266 | 13,420 |
Available-for-sale, gross unrealized losses, 12 months or greater | (584) | (431) | 0
Securities available for sale | 28,128 | 14,778 |
Available-for-sale, gross unrealized losses, total | (1,009) | (432) | (564)
Municipal securities [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Available-for-sale, fair value, less than 12 months | 11,966 | 3,418 |
Available-for-sale, gross unrealized losses, less than 12 months | (182) | (43) |
Available-for-sale, fair value, 12 months or greater | 2,072 | 2,112 |
Available-for-sale, gross unrealized losses, 12 months or greater | (138) | (104) |
Securities available for sale | 14,038 | 5,530 |
Available-for-sale, gross unrealized losses, total | (320) | (147) |
Other debt securities [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Available-for-sale, fair value, less than 12 months | 0 | 950 |
Available-for-sale, gross unrealized losses, less than 12 months | 0 | (24) |
Available-for-sale, fair value, 12 months or greater | 911 | 0 |
Available-for-sale, gross unrealized losses, 12 months or greater | (65) | 0 |
Securities available for sale | 911 | 950 |
Available-for-sale, gross unrealized losses, total | (65) | (24) |
Mortgage-backed securities (GSEs) [Member] |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Available-for-sale, fair value, less than 12 months | 58,377 | 61,332 |
Available-for-sale, gross unrealized losses, less than 12 months | (1,654) | (407) | (690)
Available-for-sale, fair value, 12 months or greater | 29,911 | 35,048 |
Available-for-sale, gross unrealized losses, 12 months or greater | (1,101) | (777) | (400)
Securities available for sale | 88,288 | 96,380 |
Available-for-sale, gross unrealized losses, total | $ (2,755) | $ (1,184) | $ (1,090)

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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563 + Details
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- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563 + Details
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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563 + Details
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