Derivative Financial Instruments (Schedule Of Oil Derivative Contracts Volume And Weighted Average Prices) (Details) $ in Millions		9 Months Ended
		Sep. 30, 2016 USD ($) bbl / d $ / bbl	Oct. 28, 2016 bbl / d $ / bbl
Oil contracts [Member] | Basis Swap Contracts for Year 2 [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | bbl / d		0
Oil contracts [Member] | Basis Swap Contracts for Fourth Quarter of Year One [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | bbl / d		6,630
Oil contracts [Member] | Collar Contracts With Short Puts for Year 2 - Converted [Member]
Derivative [Line Items]
Premium Paid on Derivative Contract | $		$ 24
Derivative, Nonmonetary Notional Amount | bbl / d	[1]	33,000
Oil contracts [Member] | Collar Contracts With Short Puts for Year 2 [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | bbl / d	[1]	94,973
Oil contracts [Member] | Collar Contracts for Year 2 [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | bbl / d		6,000
Oil contracts [Member] | Collar Contracts With Short Puts For Fourth Quarter of Year One [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | bbl / d		112,000
Oil contracts, price per bbl [Member] | Basis Swap Contracts for Year 2 [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price		0
Oil contracts, price per bbl [Member] | Basis Swap Contracts for Fourth Quarter of Year One [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price		(1)
Oil contracts, price per bbl [Member] | Collar Contracts With Short Puts for Year 2 - Converted [Member]
Derivative [Line Items]
Derivative, Average Cap Price		60.76
Derivative, Average Floor Price		45.00
Derivative, Notional Amount, Price Per Unit		40.00
Oil contracts, price per bbl [Member] | Collar Contracts With Short Puts for Year 2 [Member]
Derivative [Line Items]
Derivative, Average Cap Price		62.36
Derivative, Average Floor Price		49.07
Derivative, Notional Amount, Price Per Unit		41.30
Oil contracts, price per bbl [Member] | Collar Contracts for Year 2 [Member]
Derivative [Line Items]
Derivative, Average Cap Price		70.40
Derivative, Average Floor Price		50.00
Oil contracts, price per bbl [Member] | Collar Contracts With Short Puts For Fourth Quarter of Year One [Member]
Derivative [Line Items]
Derivative, Average Cap Price		75.94
Derivative, Average Floor Price		65.41
Derivative, Notional Amount, Price Per Unit		47.03
Subsequent Event [Member] | Oil contracts [Member] | Collar Contracts With Short Puts for January to June Year 2 [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | bbl / d			20,000
Subsequent Event [Member] | Oil contracts [Member] | Collar Contracts With Short Puts for July to December Year 2 [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | bbl / d			32,000
Subsequent Event [Member] | Oil contracts [Member] | Collar Contracts With Short Puts for Year 3 [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | bbl / d			20,000
Subsequent Event [Member] | Oil contracts, price per bbl [Member] | Collar Contracts With Short Puts for January to June Year 2 [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount			39.00
Derivative, Average Cap Price			58.99
Derivative, Average Floor Price			48.50
Subsequent Event [Member] | Oil contracts, price per bbl [Member] | Collar Contracts With Short Puts for July to December Year 2 [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount			40.00
Derivative, Average Cap Price			60.77
Derivative, Average Floor Price			50.00
Subsequent Event [Member] | Oil contracts, price per bbl [Member] | Collar Contracts With Short Puts for Year 3 [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount			40.00
Derivative, Average Cap Price			65.14
Derivative, Average Floor Price			50.00

[1] During the nine months ended September 30, 2016, the Company paid $24 million to convert 33,000 Bbls per day of 2017 collar contracts with short puts into new 2017 collar contracts with short puts with a ceiling price of $60.76 per Bbl, a floor price of $45.00 per Bbl and a short put price of $40.00 per Bbl. During the period from October 1, 2016 through October 28, 2016, the Company entered into additional oil collar contracts with short puts for (i) 20,000 Bbls per day of January through June 2017 production with a ceiling price of $58.99 per Bbl, a floor price of $48.50 per Bbl and a short put price of $39.00 per Bbl, (ii) 32,000 Bbls per day of July through December 2017 production with a ceiling price of $60.77 per Bbl, a floor price of $50.00 per Bbl and a short put price of $40.00 per Bbl and (iii) 20,000 Bbls per day of 2018 production with a ceiling price of $65.14 per Bbl, a floor price of $50.00 per Bbl and a short put price of $40.00 per Bbl.