Number of business days prior to closing date considered for average closing price.

No definition available.

Name:	smbk_BusinessCombinationBusinessDaysPriorToClosingDate
Namespace Prefix:	smbk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of consecutive trading days of common stock reported on NASDAQ considered for average closing price.

+ References

No definition available.

+ Details

Name:	smbk_BusinessCombinationConsecutiveTradingDaysForAverageClosingPrice
Namespace Prefix:	smbk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Business Combination, Consideration Transferred, Equity Interests Issued And Issuable, Cash Paid Per Acquiree Share

+ References

No definition available.

+ Details

Name:	smbk_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuableCashPaidPerAcquireeShare
Namespace Prefix:	smbk_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Business Combination, Consideration Transferred, Equity Interests Issued And Issuable, Entity Shares Issued Per Acquiree Share

+ References

No definition available.

+ Details

Name:	smbk_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuableEntitySharesIssuedPerAcquireeShare
Namespace Prefix:	smbk_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares owned by each shareholder.

+ References

No definition available.

+ Details

Name:	smbk_BusinessCombinationNumberOfSharesOwnedByHolder
Namespace Prefix:	smbk_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of stock holders considered for stock consideration price determination.

+ References

No definition available.

+ Details

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

- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6613-128477

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6578-128477

+ Details

Name:	us-gaap_BusinessCombinationConsiderationTransferred1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of liability recognized arising from contingent consideration in a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 35
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=116859824&loc=d3e6819-128478

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476

+ Details

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

- Definition

Amount of liabilities assumed at the acquisition date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=116869197&loc=d3e4845-128472

+ Details

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

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

+ Details

Name:	us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Price of a single share of a number of saleable stocks of a company.

+ References

No definition available.

+ Details

Name:	us-gaap_SharePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

Name:	us-gaap_SubsequentEventLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=smbk_SevierCountyBancsharesIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=smbk_FountainLeasingLlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Subsequent Events (Details) - Subsequent Event [Member] - USD ($)	May 03, 2021	Apr. 14, 2021	Apr. 13, 2021
Sevier County Bancshares Inc [Member]
Subsequent Event [Line Items]
Common shares to be converted (in shares)		0.4116
Number of consecutive trading days		10 days
Number of business days prior to closing date		5 days
Market price of SMBK common stock			$ 21.25
Cash to be paid upon conversion (in dollars per share)		$ 8.75
Total consideration		$ 38,200,000
Sevier County Bancshares Inc [Member] \| Minimum [Member]
Subsequent Event [Line Items]
Number of shares owned by each shareholder (in shares)		20,000
Stockholder's equity		$ 30,326,000
Sevier County Bancshares Inc [Member] \| Maximum [Member]
Subsequent Event [Line Items]
Number of shares owned by each shareholder (in shares)		20,000
Stockholder's equity		$ 30,326,000
Fountain Leasing LLC [Member]
Subsequent Event [Line Items]
Cash consideration paid	$ 14,000,000
Liabilities amount repaid	45,000,000
Fountain Leasing LLC [Member] \| Maximum [Member]
Subsequent Event [Line Items]
Future cash payments of performance-based earnout	$ 6,000,000