Components of Loss on Extinguishment of Debt (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Components of Loss on Extinguishment of Debt [Line Items]
Loss on extinguishment of debt	$ 3		$ 1		$ 15
Additional Paid-in Capital [Member]
Components of Loss on Extinguishment of Debt [Line Items]
Adjustments to Additional Paid in Capital, Other					8
Credit Facility [Member]
Components of Loss on Extinguishment of Debt [Line Items]
Loss on extinguishment of debt	(2)	[1]	0	[1]	0	[1]
Project Debt Type [Member]
Components of Loss on Extinguishment of Debt [Line Items]
Loss on extinguishment of debt	(1)	[2]	0	[2]	0	[2]
1.00% Senior Convertible Debentures due 2027 [Member]
Components of Loss on Extinguishment of Debt [Line Items]
Loss on extinguishment of debt	$ 0	[3]	$ (1)	[3]	$ (15)	[3]

[1] (1) Comprised of the write-off of deferred financing costs in connection with previously existing financing arrangements. See 2012 Credit Facilities discussion above.

[2] (2) Comprised of the write-off of financing costs in connection with the new tax-exempt bonds, offset by the write-off of unamortized premiums on the previously existing financing arrangements. See Tax-Exempt Bonds discussion above.

[3] (3) Comprised of the difference between the fair value and carrying value of the liability component of the Debentures tendered, a write-off of deferred financing costs and fees incurred in conjunction with the tender offer.