Derivative Financial Instruments (Textuals) (Details)
$ in Millions

3 Months Ended

Mar. 31, 2017

USD ($)

MMBTU

$ / bbl

$ / MMBTU

MBbls

Mar. 31, 2016

USD ($)

Derivative [Line Items]

Schedule of Derivative Instruments [Table Text Block]

At March 31, 2017, we had outstanding derivative positions as set forth in the tables below.

Crude Oil

		NYMEX Contract Price Per Bbl
								Collars				Estimated Fair Value Asset (Liability)
Period and Type of Instrument	Volume in MBbls	Swaps (Weighted Average)		Purchased Calls (Weighted Average)(2)		Sold Puts (Weighted Average)(1)		Floors (Weighted Average)		Ceilings (Weighted Average)
												(In millions)
2017:
Fixed-price swaps	4,675	$	45.43	$	—	$	—	$	—	$	—	$	(29	)
Fixed-price swaps with sold puts:	3,118
Fixed-price swaps		87.99		—		—		—		—		112
Sold puts		—		—		73.09		—		—		(68		)
Collars with sold puts:	910
Collars		—		—		—		90.00		95.69		36
Sold puts		—		—		75.00		—		—		(22		)
Purchased calls	4,028	—		73.52		—		—		—		1
Total												$	30

_________________

(1) For the volumes with sold puts, if the market prices remain below our sold puts at contract settlement, we will receive the market price plus the following:

• the difference between our floors and our sold puts for collars with sold puts; or

• the difference between our swaps and our sold puts for fixed-price swaps with sold puts.

We have effectively locked in the spreads noted above (less the deferred call premium) for all of the volumes with sold puts using purchased calls.

(2) We deferred the premiums related to the purchased calls until contract settlement. At March 31, 2017, the deferred premiums totaled $7 million.

Natural Gas

		NYMEX Contract Price Per MMBtu
				Collars				Estimated Fair Value Asset (Liability)
Period and Type of Instrument	Volume in MMMBtus	Swaps (Weighted Average)		Floors (Weighted Average)		Ceilings (Weighted Average)
								(In millions)
2017:
Fixed-price swaps	20,625	$	2.73	$	—	$	—	$	(12	)
Collars	41,260	—		2.82		3.23		(10		)
2018:
Fixed-price swaps	10,950	3.01		—		—		—
Collars	18,150	—		3.00		3.55		—
Total								$	(22	)

Realized Gain Loss On Derivatives

$ 20

$ 82

Unrealized Gain (Loss) on Derivatives

33

(99)

Deferred Premium

7

Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net

$ 53

(17)

ConcentrationOfCounterpartiesUnderCreditFacility

83.00%

Total Derivative Counterparties

15

Primary Derivative Counterparties

10

Percent of future hedged production with primary counterparties

84.00%

Percentage of contracted volumes held by the largest counterparty.

13.00%

Natural gas contracts [Member]

Derivative [Line Items]

Realized Gain Loss On Derivatives

$ (6)

11

Unrealized Gain (Loss) on Derivatives

32

(16)

Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value

(22)

Oil contracts [Member]

Derivative [Line Items]

Realized Gain Loss On Derivatives

26

71

Unrealized Gain (Loss) on Derivatives

1

$ (83)

Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value

$ 30

Year 2017 [Member] | Natural gas contracts [Member] | Swap [Member]

Derivative [Line Items]

Derivative, Swap Type, Average Fixed Price | $ / MMBTU

2.73

Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value

$ (12)

Volume In Mmbtus | MMBTU

20,625,000

Year 2017 [Member] | Natural gas contracts [Member] | Collars [Member]

Derivative [Line Items]

Derivative, Weighted Average Floor Price | $ / MMBTU

2.82

Derivative, Weighted Average Ceiling Price | $ / MMBTU

3.23

Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value

$ (10)

Volume In Mmbtus | MMBTU

41,260,000

Year 2017 [Member] | Oil contracts [Member] | Swap [Member]

Derivative [Line Items]

Volume in MBbls | MBbls

4,675

Derivative, Swap Type, Average Fixed Price | $ / bbl

45.43

Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value

$ (29)

Year 2017 [Member] | Oil contracts [Member] | Fixed Price Swaps With Sold Puts [Member]

Derivative [Line Items]

Volume in MBbls | MBbls

3,118

Year 2017 [Member] | Oil contracts [Member] | Fixed Price Swaps with Sold Puts - Sold Put [Member]

Derivative [Line Items]

Derivative Average Additional Put Price | $ / bbl

73.09

Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value

$ (68)

Year 2017 [Member] | Oil contracts [Member] | Fixed Price Swaps with Sold Puts - Swap [Member]

Derivative [Line Items]

Derivative, Swap Type, Average Fixed Price | $ / bbl

87.99

Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value

$ 112

Year 2017 [Member] | Oil contracts [Member] | Collars With Sold Puts [Member]

Derivative [Line Items]

Volume in MBbls | MBbls

910

Year 2017 [Member] | Oil contracts [Member] | Collars with Sold Puts - Collar [Member]

Derivative [Line Items]

Derivative, Weighted Average Floor Price | $ / bbl

90

Derivative, Weighted Average Ceiling Price | $ / bbl

95.69

Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value

$ 36

Year 2017 [Member] | Oil contracts [Member] | Collars with Sold Puts - Sold Put [Member]

Derivative [Line Items]

Derivative Average Additional Put Price | $ / bbl

75

Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value

$ (22)

Year 2017 [Member] | Oil contracts [Member] | Call Option [Member]

Derivative [Line Items]

Volume in MBbls | MBbls

4,028

Derivative, Weighted Average Ceiling Price | $ / bbl

73.52

Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value

$ 1

Year 2018 [Member] | Natural gas contracts [Member] | Swap [Member]

Derivative [Line Items]

Derivative, Swap Type, Average Fixed Price | $ / MMBTU

3.01

Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value

$ 0

Volume In Mmbtus | MMBTU

10,950,000

Year 2018 [Member] | Natural gas contracts [Member] | Collars [Member]

Derivative [Line Items]

Derivative, Weighted Average Floor Price | $ / MMBTU

3

Derivative, Weighted Average Ceiling Price | $ / MMBTU

3.55

Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value

$ 0

Volume In Mmbtus | MMBTU

18,150,000