XML 46 R34.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Securities - Narrative (Details) | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2018 USD ($) investment | Jun. 30, 2017 USD ($) | Jun. 30, 2018 USD ($) investment | Jun. 30, 2017 USD ($) | Dec. 31, 2017 USD ($)
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Proceeds from sale of available-for-sale securities | $ | $ 0 | $ 0 | $ 0 | $ 0 |
Loss from redemption of securities | $ | 1,200 |  | 1,200 | $ 0 |
Collateral Pledged [Member] |  |  |  |  |
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Restricted securities | $ | $ 113,500,000 |  | $ 113,500,000 |  | $ 97,200,000
Mortgage-backed securities [Member] |  |  |  |  |
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Number of positions | 65 |  | 65 |  |
US Government-sponsored Enterprises Debt Securities [Member] |  |  |  |  |
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Number of positions | 8 |  | 8 |  |
Municipal securities [Member] |  |  |  |  |
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Number of positions | 21 |  | 21 |  |
Other debt securities [Member] |  |  |  |  |
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Number of positions | 1 |  | 1 |  |

X
- Definition Amount of unrealized and realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References No definition available. + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleGainLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of realized loss 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://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleRealizedLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of restricted 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 860 -SubTopic 30 -Section 50 -Paragraph 1A -Subparagraph (b)(1)(i) -URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleRestricted
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_LoansAndLeasesReceivableDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_CollateralAxis=us-gaap_CollateralPledgedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ResidentialMortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=smbk_MunicipalSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_OtherDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |