Deposits (Textual) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Time Deposits Maturity [Line Items]
Time deposits of 250,000 or more	$ 136,500	$ 165,100
Fair value adjustments to time deposits	206	759
Deposit liabilities reclassified as loans receivable	254	747
Related Party [Member]
Time Deposits Maturity [Line Items]
Related party deposit liabilities	$ 16,800	$ 24,300

Amount of fair value adjustments to time deposits as a result of the business combination.

No definition available.

Name:	smbk_FairValueAdjustmentsToTimeDepositsOnBusinessCombination
Namespace Prefix:	smbk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The aggregate amount of domestic and foreign time deposit liabilities (including certificates of deposits, individual retirement accounts and open accounts) in denominations of $250,000 or more.

+ References

No definition available.

+ Details

Name:	smbk_TimeDeposits250000OrMore
Namespace Prefix:	smbk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	smbk_TimeDepositsMaturityLineItems
Namespace Prefix:	smbk_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of deposits held by the entity that have been reclassified as loan balances receivable, for example, but not limited to, overdrafts receivable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 405
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=116652737&loc=d3e64164-112818

+ Details

Name:	us-gaap_DepositLiabilitiesReclassifiedAsLoansReceivable1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of deposits held by the entity for a related party (entity, shareholder, employee).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

Name:	us-gaap_RelatedPartyDepositLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=smbk_RelatedPartyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: