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Business - Additional Information (Detail) $ in Millions	Mar. 10, 2017 USD ($) Branch	Feb. 29, 2016 USD ($) Branch	Dec. 31, 2018 Subsidiary Location	Aug. 10, 2018 USD ($)
Schedule Of Description Of Company [Line Items]
Number of inactive subsidiaries \| Subsidiary			1
Bank operated banking centers \| Location			68
Bank operated trust office locations, number \| Location			3
Valley Commerce Bancorp [Member]
Schedule Of Description Of Company [Line Items]
Total assets	$ 400
Number of bank branches acquired \| Branch	4
County Commerce Bank [Member]
Schedule Of Description Of Company [Line Items]
Total assets		$ 253
Number of bank branches acquired \| Branch		4
Community Bank [Member]
Schedule Of Description Of Company [Line Items]
Bank operated banking centers				16
Total assets				$ 4,090