Basis of Presentation and Summary of Significant Accounting Policies Assets Held for Sale (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Long Lived Assets Held-for-sale [Line Items]
Current assets held for sale	$ 11	$ 4
Property and equipment held for sale, net	588	634
Current liabilities held for sale	20	21
Accounts Receivable [Member]
Long Lived Assets Held-for-sale [Line Items]
Current assets held for sale	11	4
Current Assets Held for Sale [Member]
Long Lived Assets Held-for-sale [Line Items]
Current assets held for sale	11	4
Natural Gas Processing Plant [Member]
Long Lived Assets Held-for-sale [Line Items]
Property and equipment held for sale, net	330	352
Oilfield Services
Long Lived Assets Held-for-sale [Line Items]
Property and equipment held for sale, net	0	27
Property, Plant and Equipment, Other Types
Long Lived Assets Held-for-sale [Line Items]
Property and equipment held for sale, net	258	255
Property and equipment held for sale, net [Member]
Long Lived Assets Held-for-sale [Line Items]
Property and equipment held for sale, net	588	634
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	$ 20	$ 17