Fair Value Measurements (Assets And Liabilities Accounted For At Fair Value On Recurring Basis) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash collateral	$ 32		$ 39
Liabilities, current	159
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets	0	[1]	0	[1]
Other assets	2	[1]	2	[1]
Total assets at fair value	2	[1]	2	[1]
Commodity derivative instruments, liabilities	0	[1]	0	[1]
Contingent consideration, liability	625	[1],[2]
Total liabilities at fair value	625	[1]
Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets	21		49
Other assets	2		2
Total assets at fair value	23		51
Commodity derivative instruments, liabilities	53		88
Contingent consideration, liability	0
Total liabilities at fair value	53
Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets	0		0
Other assets	0		0
Total assets at fair value	0		0
Commodity derivative instruments, liabilities	0		0
Contingent consideration, liability	0
Total liabilities at fair value	0
Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets	0		0
Other assets	0		0
Total assets at fair value	0		0
Commodity derivative instruments, liabilities	0		0
Contingent consideration, liability	625	[2]
Total liabilities at fair value	625
Collateral [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets	(21)	[3]	(49)	[3]
Total assets at fair value	(21)	[3]	(49)	[3]
Commodity derivative instruments, liabilities	(53)	[3]	(88)	[3]
Total liabilities at fair value	(53)	[3]
Collateral Pledged Not Offset [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets	61		45
Other assets	0		0
Total assets at fair value	61		45
Commodity derivative instruments, liabilities	0		0
Contingent consideration, liability	0
Total liabilities at fair value	$ 0

[1] We have no derivative contracts that are subject to master netting arrangements that are reflected gross on the balance sheet.

[2] Includes $159 million classified as current.

[3] Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of December 31, 2013 and 2012, cash collateral of $32 million and $39 million, respectively, was netted with mark-to-market derivative liabilities.