Business Combination - Additional Information (Detail) - USD ($)		3 Months Ended
	Jan. 31, 2017	Mar. 31, 2017
Business Acquisition [Line Items]
Business acquisition, related costs		$ 4,962,000
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
OLCB [Member] | Core Deposits [Member]
Business Acquisition [Line Items]
Fair value of intangible assets	$ 2,200,000