INCOME TAXES - Open Tax Year (Details)	12 Months Ended
	Dec. 31, 2016
Federal [Member]
Income Tax Contingency [Line Items]
Open tax years that remain subject to examination	2016
Maximum [Member] | Connecticut [Member]
Income Tax Contingency [Line Items]
Open tax years that remain subject to examination	2016
Maximum [Member] | Massachusetts [Member]
Income Tax Contingency [Line Items]
Open tax years that remain subject to examination	2016
Maximum [Member] | New Hampshire [Member]
Income Tax Contingency [Line Items]
Open tax years that remain subject to examination	2016
Minimum [Member] | Connecticut [Member]
Income Tax Contingency [Line Items]
Open tax years that remain subject to examination	2013
Minimum [Member] | Massachusetts [Member]
Income Tax Contingency [Line Items]
Open tax years that remain subject to examination	2013
Minimum [Member] | New Hampshire [Member]
Income Tax Contingency [Line Items]
Open tax years that remain subject to examination	2014