Debt, Principal Payments Due on Debt and Capital Lease Obligations (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Principal Payments Due on Debt
2012	$ 1,004
2013	484
2014	200
2015	475
2016	0
Thereafter	5,578
Net unamortized discount and fair value adjustments	(51)	(64)
Total debt	7,690	8,300
Future minimum rental on capital lease obligations
2012	11
2013	10
2014	9
2015	8
2016	8
Thereafter	37
Less interest expense	32
Total capital lease obligations	$ 51	$ 37

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 7

-Section 03

-Paragraph 16

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6455398&loc=d3e45280-112737