Related Party Transactions Affiliated Balances (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Related party balances [Line Items]
Related party, accounts receivable, net of allowance	$ 15	$ 25
Related party assets held for sale	0	114
Related party, other current assets	5	14
Related Party Deferred Charges and Other Assets	48	48
Related party assets	68	201
Notes Payable, Related Parties, Current	5	5
Notes Payable, Related Parties, Noncurrent	172	173
Accounts Payable, Related Parties, Current	7	11
Long-term Debt, Current Maturities	2,876	2,401
Due to Related Parties, Current	184	189
EPB [Member] \| WYCO Development L.L.C. [Member]
Related party balances [Line Items]
Long-term Debt, Current Maturities	$ 5

Related party, accounts receivable, net of allowance

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Related party assets

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Related party assets held for sale

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Related Party Deferred Charges and Other Assets

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Related party, other current assets

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- Definition

Amount for accounts payable to related parties. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Carrying amount as of the balance sheet date of obligations due all related parties. For classified balance sheets, represents the current portion of such liabilities (due within one year or within the normal operating cycle if longer).

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Carrying amount of long-term debt, net of unamortized discount or premium, scheduled to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The amount for notes payable (written promise to pay), due to related parties. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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The amount for notes payable (written promise to pay), payable to related parties, which are due after one year (or one business cycle).

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