Basis of Presentation and Summary of Significant Accounting Policies Assets Held for Sale Table (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Long Lived Assets Held-for-sale [Line Items]
Current assets held for sale	$ 0	$ 4
Property and equipment held for sale, net	597	634
Current liabilities held for sale	0	21
Compressor [Member]
Long Lived Assets Held-for-sale [Line Items]
Property and equipment held for sale, net	242	0
Accounts Receivable [Member]
Long Lived Assets Held-for-sale [Line Items]
Current assets held for sale	0	4
Natural Gas Processing Plant [Member]
Long Lived Assets Held-for-sale [Line Items]
Property and equipment held for sale, net	10	352
Exploration and Production Equipment [Member]
Long Lived Assets Held-for-sale [Line Items]
Property and equipment held for sale, net	26	27
Property, Plant and Equipment, Other Types
Long Lived Assets Held-for-sale [Line Items]
Property and equipment held for sale, net	319	255
Accounts Payable [Member]
Long Lived Assets Held-for-sale [Line Items]
Current liabilities held for sale	0	4
Accrued Liabilities [Member]
Long Lived Assets Held-for-sale [Line Items]
Current liabilities held for sale	$ 0	$ 17