DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES (Fair Values of Expected Cash Flows of Commodity Based Swaps and Physical Contracts) (Details) $ in Millions		12 Months Ended
		Dec. 31, 2016 USD ($) Boe $ / Barrel-bbl bbl	Dec. 31, 2015 USD ($)
Fair Value
Asset		$ 47.3	$ 163.6
Liability		$ (221.0)	(221.5)
Swaps - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Fixed - Natural Gas [Member]
Derivative [Line Items]
Notional (MMBtu) | Boe	[1]	5,145,880
Fair Value
Asset	[2]	$ 2.6	0.0
Liability	[2]	$ 0.0	0.0
Swaps - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Fixed - Natural Gas [Member] | Receive [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	3.51
Swaps - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Fixed - Natural Gas [Member] | Pay [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	3.00
Swaps - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Fixed - NGL [Member]
Derivative [Line Items]
Notional (Bbl) | bbl	[1]	4,356,500
Fair Value
Asset	[2]	$ 21.4	0.0
Liability	[2]	$ 0.0	(4.5)
Swaps - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Fixed - NGL [Member] | Receive [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	29.43
Swaps - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Fixed - NGL [Member] | Pay [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	24.51
Swaps - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Fixed - Crude Oil [Member]
Derivative [Line Items]
Notional (Bbl) | bbl	[1]	736,750
Fair Value
Asset	[2]	$ 0.9	0.0
Liability	[2]	$ (5.6)	(10.9)
Swaps - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Fixed - Crude Oil [Member] | Receive [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	56.00
Swaps - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Fixed - Crude Oil [Member] | Pay [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	62.53
Swaps - Portion of Contracts Maturing in 2017 - Receive Fixed/Pay Variable - NGL [Member]
Derivative [Line Items]
Notional (Bbl) | bbl	[1]	6,006,000
Fair Value
Asset	[2]	$ 0.0	3.3
Liability	[2]	$ (27.5)	(0.1)
Swaps - Portion of Contracts Maturing in 2017 - Receive Fixed/Pay Variable - NGL [Member] | Receive [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	25.74
Swaps - Portion of Contracts Maturing in 2017 - Receive Fixed/Pay Variable - NGL [Member] | Pay [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	30.32
Swaps - Portion of Contracts Maturing in 2017 - Receive Fixed/Pay Variable - Crude Oil [Member]
Derivative [Line Items]
Notional (Bbl) | bbl	[1]	1,095,510
Fair Value
Asset	[2]	$ 5.7	10.9
Liability	[2]	$ (3.8)	0.0
Swaps - Portion of Contracts Maturing in 2017 - Receive Fixed/Pay Variable - Crude Oil [Member] | Receive [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	57.55
Swaps - Portion of Contracts Maturing in 2017 - Receive Fixed/Pay Variable - Crude Oil [Member] | Pay [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	55.82
Swaps - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Variable - Natural Gas [Member]
Derivative [Line Items]
Notional (MMBtu) | Boe	[1]	22,230,000
Fair Value
Asset	[2]	$ 2.5	0.5
Liability	[2]	$ (0.4)	(0.2)
Swaps - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Variable - Natural Gas [Member] | Receive [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	3.59
Swaps - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Variable - Natural Gas [Member] | Pay [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	3.49
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Fixed -Natural Gas [Member]
Derivative [Line Items]
Notional (MMBtu) | Boe	[1]	32,400
Fair Value
Asset	[2]	$ 0.0	0.0
Liability	[2]	$ 0.0	0.0
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Fixed -Natural Gas [Member] | Receive [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	3.68
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Fixed -Natural Gas [Member] | Pay [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	3.49
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Fixed - NGL [Member]
Derivative [Line Items]
Notional (Bbl) | bbl	[1]	412,090
Fair Value
Asset	[2]	$ 0.9	0.0
Liability	[2]	$ 0.0	0.0
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Fixed - NGL [Member] | Receive [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	23.61
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Fixed - NGL [Member] | Pay [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	21.56
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Fixed/Pay Variable - Natural Gas [Member]
Derivative [Line Items]
Notional (MMBtu) | Boe	[1]	69,600
Fair Value
Asset	[2]	$ 0.0	0.0
Liability	[2]	$ 0.0	0.0
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Fixed/Pay Variable - Natural Gas [Member] | Receive [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	3.56
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Fixed/Pay Variable - Natural Gas [Member] | Pay [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	3.67
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Fixed/Pay Variable - NGL [Member]
Derivative [Line Items]
Notional (Bbl) | bbl	[1]	264,380
Fair Value
Asset	[2]	$ 0.0	0.0
Liability	[2]	$ (1.2)	0.0
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Fixed/Pay Variable - NGL [Member] | Receive [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	33.22
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Fixed/Pay Variable - NGL [Member] | Pay [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	37.21
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Variable - Natural Gas [Member]
Derivative [Line Items]
Notional (Bbl) | bbl		49,299,457
Notional (MMBtu) | Boe	[1]	49,294,457
Fair Value
Asset	[2]	$ 0.6	0.1
Liability	[2]	$ 0.0	0.0
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Variable - Natural Gas [Member] | Receive [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	3.54
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Variable - Natural Gas [Member] | Pay [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	3.52
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Variable - NGL [Member]
Derivative [Line Items]
Notional (Bbl) | bbl	[1]	8,269,007
Fair Value
Asset	[2]	$ 2.6	0.0
Liability	[2]	$ (0.6)	0.0
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Variable - NGL [Member] | Receive [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	21.85
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Variable - NGL [Member] | Pay [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	21.61
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Variable - Crude oil [Member]
Derivative [Line Items]
Notional (Bbl) | bbl	[1]	453,392
Fair Value
Asset	[2]	$ 0.7	0.0
Liability	[2]	$ (2.0)	0.0
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Variable - Crude oil [Member] | Receive [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	50.34
Physical Contracts - Portion of Contracts Maturing in 2017 - Receive Variable/Pay Variable - Crude oil [Member] | Pay [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	52.85
Physical Contracts - Portion of Contracts Maturing in 2018 - Receive Variable/Pay Variable - Natural Gas [Member]
Derivative [Line Items]
Notional (MMBtu) | Boe	[1]	2,193,804
Fair Value
Asset	[2]	$ 0.1	0.1
Liability	[2]	$ 0.0	0.0
Physical Contracts - Portion of Contracts Maturing in 2018 - Receive Variable/Pay Variable - Natural Gas [Member] | Receive [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	3.16
Physical Contracts - Portion of Contracts Maturing in 2018 - Receive Variable/Pay Variable - Natural Gas [Member] | Pay [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	3.13
Physical Contracts - Portion of Contracts Maturing in 2018 - Receive Variable/Pay Variable - NGL [Member]
Derivative [Line Items]
Notional (Bbl) | bbl	[1]	6,756,250
Fair Value
Asset	[2]	$ 1.4	0.0
Liability	[2]	$ 0.0	0.0
Physical Contracts - Portion of Contracts Maturing in 2018 - Receive Variable/Pay Variable - NGL [Member] | Receive [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	19.36
Physical Contracts - Portion of Contracts Maturing in 2018 - Receive Variable/Pay Variable - NGL [Member] | Pay [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	19.15
Physical Contracts - Portion of Contracts Maturing in 2019 - Receive Variable/Pay Variable - Natural Gas [Member]
Derivative [Line Items]
Notional (MMBtu) | Boe	[1]	2,199,798
Fair Value
Asset	[2]	$ 0.1	0.1
Liability	[2]	$ 0.0	0.0
Physical Contracts - Portion of Contracts Maturing in 2019 - Receive Variable/Pay Variable - Natural Gas [Member] | Receive [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	2.92
Physical Contracts - Portion of Contracts Maturing in 2019 - Receive Variable/Pay Variable - Natural Gas [Member] | Pay [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	2.90
Physical Contracts - Portion of Contracts Maturing in 2020 - Receive Variable/Pay Variable - Natural Gas [Member]
Derivative [Line Items]
Notional (MMBtu) | Boe	[1]	365,634
Fair Value
Asset	[2]	$ 0.0	0.0
Liability	[2]	$ 0.0	0.0
Physical Contracts - Portion of Contracts Maturing in 2020 - Receive Variable/Pay Variable - Natural Gas [Member] | Receive [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	3.13
Physical Contracts - Portion of Contracts Maturing in 2020 - Receive Variable/Pay Variable - Natural Gas [Member] | Pay [Member]
Derivative [Line Items]
Wtd. Average Price | $ / Barrel-bbl	[3]	3.10
Swap [Member]
Fair Value
Credit Valuation Adjustments			$ 0.5

[1] Volumes of natural gas are measured in MMBtu, whereas volumes of NGL and crude oil are measured in Bbl.

[2] The fair value is determined based on quoted market prices at December 31, 2016 and 2015, respectively, discounted using the swap rate for the respective periods to consider the time value of money. Fair values exclude credit valuation adjustment gains of approximately $0.5 million at December 31, 2015, as well as cash collateral received.

[3] Weighted average prices received and paid are in $/MMBtu for natural gas and $/Bbl for NGL and crude oil.