Business Combination Business Combination - Capstone Merger (Details)	Nov. 01, 2017 USD ($) $ / shares
Business Combinations [Abstract]
Shares of SMBK common stock issued to Capstone shareholders as of November 1, 2017 (in shares)	$ 2,908,094
Market price of SMBK common stock on November 1, 2017 \| $ / shares	$ 23.49
Estimated fair value of SMBK common stock issued	$ 68,311,000
Estimated fair value of Capstone stock options	1,585,000
Cash consideration paid	15,826,000
Total consideration	85,722,000
Fair value of assets acquired and liabilities assumed:
Cash and cash equivalents	16,810,000
Investment securities available for sale	51,638,000
Restricted investments	1,049,000
Loans	413,023,000
Premises and equipment	8,668,000
Bank owned life insurance	10,031,000
Core deposit intangible	5,530,000
Other real estate owned	410,000
Prepaid and other assets	6,360,000
Deposits	(454,154,000)
FHLB advances and other borrowings	(4,887,000)
Payables and other liabilities	(6,803,000)
Total fair value of net assets acquired	47,675,000
Goodwill	$ 38,047,000

Purchase price of common stock shares outstanding value.

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The amount of Assets Acquired and Liabilities Assumed Core Deposit Intangible.

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The amount of assets acquired and liabilities assumed deposits liability.

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Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Investment Owned Restricted Cost

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The amount of assets acquired and liabilities assumed other real estate owned.

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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.

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Amount of tangible or intangible assets, including a business or subsidiary of the acquirer transferred by the entity to the former owners of the acquiree. Excludes cash.

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Amount of currency on hand as well as demand deposits with banks or financial institutions, acquired at the acquisition date. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of investments in debt and equity securities, including, but not limited to, held-to-maturity, trading and available-for-sale expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer, acquired at the acquisition date.

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Amount of asset related to consideration paid in advance for costs that provide economic benefits in future periods, and amount of other assets that are expected to be realized or consumed within one year or the normal operating cycle, if longer, acquired at the acquisition date.

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Amount due from customers or clients for goods or services, including trade receivables, that have been delivered or sold in the normal course of business, and amounts due from others, including related parties expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer, acquired at the acquisition date.

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Amount of liabilities incurred for goods and services received that are used in an entity's business and related party payables, assumed at the acquisition date.

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Amount of other liabilities due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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