DEBT AND CREDIT FACILITIES (Narrative) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Line of Credit Facility [Line Items]
Payments of Debt Issuance Costs			$ 8,500,000	$ 5,200,000
Gain (loss) on extinguishment/restructuring of debt	$ (4,900,000)	$ 3,600,000	(76,800,000)	$ 182,400,000
Debt redemption premiums paid	2,900,000		47,600,000
$500 Million 5.75% 2025 Senior Notes [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Par Value	$ 500,000,000		$ 500,000,000
Debt Instrument, Interest Rate, Effective Percentage	5.75%		5.75%
Note Redemption Price, Percent of Principal Amount to be Redeemed	100.00%		100.00%
Amount in aggregate that can be redeemed on or prior to March 1, 2020			0.3500
Repurchase price if triggering event occurs			1.01
Redemption Price of 35 percent or less of Outstanding			1.0575
In the Event of Default Amount that will Accelerate			0.25
Unamortized Debt Issuance Expense	$ 8,100,000		$ 8,100,000
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit facility, amount outstanding	0		0		$ 0
Line of Credit Facility, Maximum Borrowing Capacity	296,600,000		296,600,000		333,000,000
Debt Instrument, Par Value	550,000,000		550,000,000		550,000,000
Letters of credit outstanding	82,500,000		82,500,000		106,000,000
Credit facility remaining capacity	$ 214,100,000		$ 214,100,000		$ 227,000,000