Business Combination - Additional Information (Detail) - USD ($)			6 Months Ended
	Feb. 28, 2017	Jan. 31, 2017	Jun. 30, 2017
Business Acquisition [Line Items]
Business acquisition, related costs			$ 4,962,000
HSB Insurance, LLC [Member]
Business Acquisition [Line Items]
Acquisition date			Feb. 28, 2017
Business acquisition, cash	$ 107,000
Business acquisition, remaining amount to be paid	$ 428,000
Business acquisition, equal installments	four equal installments
Business acquisition, total consideration	$ 535,000
Customer list intangible [Member] | HSB Insurance, LLC [Member]
Business Acquisition [Line Items]
Business acquisition, total assets purchase	$ 535,000
United Community [Member]
Business Acquisition [Line Items]
Business acquisition, related costs			$ 4,100,000
OLCB [Member]
Business Acquisition [Line Items]
Acquisition date			Jan. 31, 2017
Common stock conversion		Each OLCB common share was converted into the right to receive either $18.00 in cash or 2.736 United Community common shares, subject to certain allocation procedures set forth in the Merger Agreement that ensured that 50% of OLCB’s common shares outstanding were converted into United Community common shares and 50% of OLCB’s common shares outstanding were exchanged for the cash consideration.
Business acquisition, per share price		$ 18.00
Business acquisition, common stock issuable per each acquired share		2.736
Business acquisition, shares consideration		50.00%
Business acquisition, cash consideration		50.00%
Business acquisition, common shares issued		3,033,604
Business acquisition, cash		$ 20,379,000
Business acquisition, related costs			$ 368,000
Gross value of acquired receivables		2,600,000
Fair value of acquired receivables		2,500,000
Deductible goodwill for income tax purposes		0
Business acquisition, total consideration		46,195,000
OLCB [Member] | Core Deposits [Member]
Business Acquisition [Line Items]
Fair value of intangible assets		$ 2,200,000