COMMITMENTS AND CONTINGENCIES Additional information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loss Contingencies [Line Items]
Operating Lease Expense	$ 10.2	$ 9.8	$ 7.0
Gas Marketing Segment
Loss Contingencies [Line Items]
Allowance for Doubtful Accounts Receivable	$ 1.3	$ 0.5