Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Statement of Financial Position [Abstract]
Trade accounts receivable, allowance	$ 1	$ 1
Other, accumulated amortization of debt issuance costs	17	10
Intangible assets, accumulated amortization	74	45
Series A convertible redeemable preferred units, redemption amount	$ 85	$ 85
Common units, authorized	174,574,175	161,233,046
Common units, issued	170,951,457	157,437,608
Common units, outstanding	170,951,457	157,437,608

The number of limited partner units authorized to be issued.

The number of limited partner units issued.

The number of limited partner units outstanding.

The aggregate amount to be paid by the entity upon redemption of the security that is classified as temporary equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

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