Regulatory Capital Matters - Actual and Statutory Required Capital Amounts and Ratios (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
United Community [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Total capital (to risk-weighted assets), Actual Amount	$ 306,946	$ 277,817
Tier 1 capital (to risk-weighted assets), Actual Amount	285,744	258,869
Common equity Tier 1 capital (to risk-weighted assets), Actual Amount	285,744	258,869
Tier 1 capital (to average assets), Actual Amount	$ 285,744	$ 258,869
Total capital (to risk-weighted assets), Actual Ratio	15.35%	18.38%
Tier 1 capital (to risk-weighted assets), Actual Ratio	14.29%	17.13%
Common equity Tier 1 capital (to risk-weighted assets), Actual Ratio	14.29%	17.13%
Tier 1 capital (to average assets), Actual Ratio	10.93%	11.98%
Total capital (to risk-weighted assets), Minimum Capital Requirements For Capital Adequacy Purposes Amount	$ 184,881	$ 130,369
Tier 1 capital (to risk-weighted assets), Minimum Capital Requirements For Capital Adequacy Purposes Amount	144,907	100,139
Common equity Tier 1 capital (to risk-weighted assets), Minimum Capital Requirements For Capital Adequacy Purposes Amount	114,926	77,466
Tier 1 capital (to average assets), Minimum Capital Requirements For Capital Adequacy Purposes Amount	$ 104,588	$ 86,425
Total capital (to risk-weighted assets), Minimum Capital Requirements For Capital Adequacy Purposes Ratio	9.25%	8.63%
Tier 1 capital (to risk-weighted assets), Minimum Capital Requirements For Capital Adequacy Purposes Ratio	7.25%	6.63%
Common equity Tier 1 capital (to risk-weighted assets), Minimum Capital Requirements For Capital Adequacy Purposes Ratio	5.75%	5.13%
Tier 1 capital (to average assets), Minimum Capital Requirements For Capital Adequacy Purposes Ratio	4.00%	4.00%
Total capital (to risk-weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 199,872	$ 151,153
Tier 1 capital (to risk-weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	159,897	120,922
Common equity Tier 1 capital (to risk-weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	119,923	98,249
Tier 1 capital (to average assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 130,735	$ 108,031
Total capital (to risk-weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	10.00%	10.00%
Tier 1 capital (to risk-weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	8.00%	8.00%
Common equity Tier 1 capital (to risk-weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	6.50%	6.50%
Tier 1 capital (to average assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	5.00%	5.00%
Home Savings [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Total capital (to risk-weighted assets), Actual Amount	$ 292,928	$ 248,861
Tier 1 capital (to risk-weighted assets), Actual Amount	271,777	229,938
Common equity Tier 1 capital (to risk-weighted assets), Actual Amount	271,777	229,938
Tier 1 capital (to average assets), Actual Amount	$ 271,777	$ 229,938
Total capital (to risk-weighted assets), Actual Ratio	14.70%	16.47%
Tier 1 capital (to risk-weighted assets), Actual Ratio	13.64%	15.22%
Common equity Tier 1 capital (to risk-weighted assets), Actual Ratio	13.64%	15.22%
Tier 1 capital (to average assets), Actual Ratio	10.42%	10.65%
Total capital (to risk-weighted assets), Minimum Capital Requirements For Capital Adequacy Purposes Amount	$ 184,235	$ 130,292
Tier 1 capital (to risk-weighted assets), Minimum Capital Requirements For Capital Adequacy Purposes Amount	144,400	100,079
Common equity Tier 1 capital (to risk-weighted assets), Minimum Capital Requirements For Capital Adequacy Purposes Amount	114,525	77,420
Tier 1 capital (to average assets), Minimum Capital Requirements For Capital Adequacy Purposes Amount	$ 104,308	$ 86,360
Total capital (to risk-weighted assets), Minimum Capital Requirements For Capital Adequacy Purposes Ratio	9.25%	8.63%
Tier 1 capital (to risk-weighted assets), Minimum Capital Requirements For Capital Adequacy Purposes Ratio	7.25%	6.63%
Common equity Tier 1 capital (to risk-weighted assets), Minimum Capital Requirements For Capital Adequacy Purposes Ratio	5.75%	5.13%
Tier 1 capital (to average assets), Minimum Capital Requirements For Capital Adequacy Purposes Ratio	4.00%	4.00%
Total capital (to risk-weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 199,173	$ 151,063
Tier 1 capital (to risk-weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	159,338	120,850
Common equity Tier 1 capital (to risk-weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	129,463	98,191
Tier 1 capital (to average assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 130,385	$ 107,950
Total capital (to risk-weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	10.00%	10.00%
Tier 1 capital (to risk-weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	8.00%	8.00%
Common equity Tier 1 capital (to risk-weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	6.50%	6.50%
Tier 1 capital (to average assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	5.00%	5.00%