ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Performance Indicators for Nonperforming Assets (Details)	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans and leases as a percentage of total loans and leases	1.07%	1.18%
Nonperforming assets as a percentage of total assets	0.80%	0.86%
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans and leases as a percentage of total loans and leases	0.15%	0.18%
Nonperforming assets as a percentage of total assets	0.11%	0.13%
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans and leases as a percentage of total loans and leases	0.92%	1.00%
Nonperforming assets as a percentage of total assets	0.69%	0.73%