Regulatory Matters (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jun. 30, 2017
The Bank of Greene County [Member]
Compliance with Regulatory Capital [Abstract]
Total risk-based capital, actual amount	$ 102,549	$ 87,719
Total risk-based capital, actual ratio	15.50%	15.80%
Total risk-based capital for capital adequacy purposes, amount	$ 53,024	$ 44,433
Total risk-based capital for capital adequacy purposes, ratio	8.00%	8.00%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount	$ 66,280	$ 55,542
Total risk-based capital to be well capitalized under prompt corrective action provisions, ratio	10.00%	10.00%
Total risk-based capital for capital conservation buffer, actual	7.472%	7.794%
Total risk-based capital for capital conservation buffer, required	1.875%	1.25%
Tier 1 risk-based capital, actual amount	$ 94,148	$ 80,671
Tier 1 risk-based capital, actual ratio	14.20%	14.50%
Tier 1 risk-based capital for capital adequacy purposes, amount	$ 39,768	$ 33,325
Tier 1 risk-based capital for capital adequacy purposes, ratio	6.00%	6.00%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount	$ 53,024	$ 44,433
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio	8.00%	8.00%
Tier 1 risk-based capital for capital conservation buffer, actual	8.205%	8.525%
Tier 1 risk-based capital for capital conservation buffer, required	1.875%	1.25%
Common equity tier 1 capital, actual amount	$ 94,148	$ 80,671
Common equity tier 1 capital, actual ratio	14.20%	14.50%
Common equity tier 1 capital for capital adequacy purposes, amount	$ 29,826	$ 24,994
Common equity tier 1 capital for capital adequacy purposes, ratio	4.50%	4.50%
Common equity tier 1 capital to be well capitalized under prompt corrective action provisions, amount	$ 43,082	$ 36,102
Common equity tier 1 capital to be well capitalized under prompt corrective action provisions, ratio	6.50%	6.50%
Common equity tier 1 capital for capital conservation buffer, actual	9.705%	10.024%
Common equity tier 1 capital for capital conservation buffer, required	1.875%	1.25%
Tier 1 leverage ratio, actual amount	$ 94,148	$ 80,671
Tier 1 leverage ratio, actual ratio	8.20%	8.50%
Tier 1 leverage ratio for capital adequacy purposes, amount	$ 45,789	$ 38,056
Tier 1 leverage ratio for capital adequacy purposes, ratio	4.00%	4.00%
Tier 1 leverage ratio to be well capitalized under prompt corrective action provisions, amount	$ 57,236	$ 47,571
Tier 1 leverage ratio to be well capitalized under prompt corrective action provisions, ratio	5.00%	5.00%
Tier 1 leverage ratio for capital conservation buffer, actual	4.225%	4.479%
Tier 1 leverage ratio for capital conservation buffer, required	1.875%	1.25%
Greene County Commercial Bank [Member]
Compliance with Regulatory Capital [Abstract]
Total risk-based capital, actual amount	$ 40,286	$ 30,095
Total risk-based capital, actual ratio	47.10%	40.10%
Total risk-based capital for capital adequacy purposes, amount	$ 6,837	$ 6,011
Total risk-based capital for capital adequacy purposes, ratio	8.00%	8.00%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount	$ 8,546	$ 7,514
Total risk-based capital to be well capitalized under prompt corrective action provisions, ratio	10.00%	10.00%
Total risk-based capital for capital conservation buffer, actual	39.139%	32.053%
Total risk-based capital for capital conservation buffer, required	1.875%	1.25%
Tier 1 risk-based capital, actual amount	$ 40,286	$ 30,095
Tier 1 risk-based capital, actual ratio	47.10%	40.10%
Tier 1 risk-based capital for capital adequacy purposes, amount	$ 5,128	$ 4,508
Tier 1 risk-based capital for capital adequacy purposes, ratio	6.00%	6.00%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount	$ 6,837	$ 6,011
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio	8.00%	8.00%
Tier 1 risk-based capital for capital conservation buffer, actual	41.139%	34.053%
Tier 1 risk-based capital for capital conservation buffer, required	1.875%	1.25%
Common equity tier 1 capital, actual amount	$ 40,286	$ 30,095
Common equity tier 1 capital, actual ratio	47.10%	40.10%
Common equity tier 1 capital for capital adequacy purposes, amount	$ 3,846	$ 3,381
Common equity tier 1 capital for capital adequacy purposes, ratio	4.50%	4.50%
Common equity tier 1 capital to be well capitalized under prompt corrective action provisions, amount	$ 5,555	$ 4,884
Common equity tier 1 capital to be well capitalized under prompt corrective action provisions, ratio	6.50%	6.50%
Common equity tier 1 capital for capital conservation buffer, actual	42.639%	35.55%
Common equity tier 1 capital for capital conservation buffer, required	1.875%	1.25%
Tier 1 leverage ratio, actual amount	$ 40,286	$ 30,095
Tier 1 leverage ratio, actual ratio	9.10%	9.60%
Tier 1 leverage ratio for capital adequacy purposes, amount	$ 17,747	$ 12,508
Tier 1 leverage ratio for capital adequacy purposes, ratio	4.00%	4.00%
Tier 1 leverage ratio to be well capitalized under prompt corrective action provisions, amount	$ 22,184	$ 15,635
Tier 1 leverage ratio to be well capitalized under prompt corrective action provisions, ratio	5.00%	5.00%
Tier 1 leverage ratio for capital conservation buffer, actual	5.08%	5.624%
Tier 1 leverage ratio for capital conservation buffer, required	1.875%	1.25%