CONTINGENCIES AND COMMITMENTS (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Asset Retirement Obligation	$ 7,000,000
Surety Bond Outstanding	56,000,000
Loss Contingency, Damages Sought, Value	1,000,000,000
Standby letters of credit
Loss Contingencies [Line Items]
Letters of credit	47,200,000	$ 37,300,000
Financial Standby Letter of Credit [Member]
Loss Contingencies [Line Items]
Letters of credit	12,800,000	$ 14,700,000
Failure to Meet Contractual Obligations [Member]
Loss Contingencies [Line Items]
Loss Contingency, Damages Sought, Value	25,000,000
Minimum [Member] | Failure to Meet Contractual Obligations [Member]
Loss Contingencies [Line Items]
Loss Contingency, Range of Possible Loss, Minimum	0
Maximum [Member] | Failure to Meet Contractual Obligations [Member]
Loss Contingencies [Line Items]
Loss Contingency, Range of Possible Loss, Minimum	$ 55,500,000