REGULATORY MATTERS (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Tier 1 Leverage ratio [Abstract]
Tier 1 Leverage ratio, actual amount	$ 858,347	$ 788,717
Tier 1 Leverage ratio, actual ratio	10.55%	10.32%
Tier 1 leverage ratio for capital adequacy purposes, amount	$ 325,438	$ 305,761
Tier 1 leverage ratio for capital adequacy purposes, ratio	4.00%	4.00%
Tier 1 leverage capital to be well-capitalized under prompt corrective action, amount	$ 406,798	$ 382,201
Tier 1 leverage capital to be well-capitalized under prompt corrective action, ratio	5.00%	5.00%
Tier 1 risk-based capital [Abstract]
Tier 1 risk-based capital, actual amount	$ 858,347	$ 788,717
Tier 1 risk-based capital, actual ratio	18.10%	17.09%
Tier 1 risk-based capital for capital adequacy purposes, amount	$ 284,583	$ 276,886
Tier 1 risk-based capital for capital adequacy purposes, ratio	6.00%	6.00%
Tier 1 risk-based capital for capital adequacy purposes plus capital conservation buffer, amount	$ 314,228
Tier 1 risk-based capital for capital adequacy purposes plus capital conservation buffer, ratio	6.625%
Tier 1 risk based capital to be well-capitalized under prompt corrective action, amount	$ 379,445	$ 369,181
Tier 1 risk-based capital to be well-capitalized under prompt corrective action, ratio	8.00%	8.00%
Total risk-based capital [Abstract]
Total risk-based capital, actual amount	$ 905,996	$ 834,539
Total risk-based capital, actual ratio	19.10%	18.08%
Total risk-based capital for capital adequacy purposes, amount	$ 379,445	$ 369,181
Total risk-based capita for capital adequacy purposes, ratio	8.00%	8.00%
Total risk-based capital for capital adequacy purposes plus capital conservation buffer, amount	$ 409,089
Total risk-based capita for capital adequacy purposes plus capital conservation buffer, ratio	8.625%
Total risk based capital to be well-capitalized under prompt corrective action, amount	$ 474,306	$ 461,477
Total risk based capital to be well-capitalized under prompt corrective action, ratio	10.00%	10.00%
Common equity Tier 1 capital [Abstract]
Common equity Tier 1 capital, actual amount	$ 759,199	$ 689,528
Common equity Tier 1 capital, actual ratio	16.01%	14.94%
Common equity Tier 1 capital for capital adequacy purposes, amount	$ 213,438	$ 207,664
Common equity Tier 1 capital for capital adequacy purposes, ratio	4.50%	4.50%
Common equity Tier 1 capital for capital adequacy purposes plus capital conservation buffer, amount	$ 243,082
Common equity Tier 1 capital for capital adequacy purposes plus capital conservation buffer, ratio	5.125%
Common equity Tier 1 capital to be well-capitalized under prompt corrective action, amount	$ 308,299	$ 299,960
Common equity Tier 1 capital to be well-capitalized under prompt corrective action, ratio	6.50%	6.50%
Community Bank, N.A. [Member]
Tier 1 Leverage ratio [Abstract]
Tier 1 Leverage ratio, actual amount	$ 672,633	$ 673,443
Tier 1 Leverage ratio, actual ratio	8.30%	8.88%
Tier 1 leverage ratio for capital adequacy purposes, amount	$ 324,080	$ 303,256
Tier 1 leverage ratio for capital adequacy purposes, ratio	4.00%	4.00%
Tier 1 leverage capital to be well-capitalized under prompt corrective action, amount	$ 405,099	$ 379,070
Tier 1 leverage capital to be well-capitalized under prompt corrective action, ratio	5.00%	5.00%
Tier 1 risk-based capital [Abstract]
Tier 1 risk-based capital, actual amount	$ 672,633	$ 673,443
Tier 1 risk-based capital, actual ratio	14.28%	14.65%
Tier 1 risk-based capital for capital adequacy purposes, amount	$ 282,662	$ 275,739
Tier 1 risk-based capital for capital adequacy purposes, ratio	6.00%	6.00%
Tier 1 risk-based capital for capital adequacy purposes plus capital conservation buffer, amount	$ 312,106
Tier 1 risk-based capital for capital adequacy purposes plus capital conservation buffer, ratio	6.625%
Tier 1 risk based capital to be well-capitalized under prompt corrective action, amount	$ 376,883	$ 367,652
Tier 1 risk-based capital to be well-capitalized under prompt corrective action, ratio	8.00%	8.00%
Total risk-based capital [Abstract]
Total risk-based capital, actual amount	$ 720,282	$ 719,265
Total risk-based capital, actual ratio	15.29%	15.65%
Total risk-based capital for capital adequacy purposes, amount	$ 376,883	$ 367,652
Total risk-based capita for capital adequacy purposes, ratio	8.00%	8.00%
Total risk-based capital for capital adequacy purposes plus capital conservation buffer, amount	$ 406,327
Total risk-based capita for capital adequacy purposes plus capital conservation buffer, ratio	8.625%
Total risk based capital to be well-capitalized under prompt corrective action, amount	$ 471,104	$ 459,565
Total risk based capital to be well-capitalized under prompt corrective action, ratio	10.00%	10.00%
Common equity Tier 1 capital [Abstract]
Common equity Tier 1 capital, actual amount	$ 672,578	$ 673,326
Common equity Tier 1 capital, actual ratio	14.28%	14.65%
Common equity Tier 1 capital for capital adequacy purposes, amount	$ 211,997	$ 206,804
Common equity Tier 1 capital for capital adequacy purposes, ratio	4.50%	4.50%
Common equity Tier 1 capital for capital adequacy purposes plus capital conservation buffer, amount	$ 241,441
Common equity Tier 1 capital for capital adequacy purposes plus capital conservation buffer, ratio	5.125%
Common equity Tier 1 capital to be well-capitalized under prompt corrective action, amount	$ 306,217	$ 298,717
Common equity Tier 1 capital to be well-capitalized under prompt corrective action, ratio	6.50%	6.50%