Debt, Principal Payments Due on Debt and Capital Lease Obligations (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Principal Payments Due on Debt
2014	$ 300
2015	475
2016	0
2017	950
2018	0
Thereafter	4,824
Net unamortized discount and fair value adjustments	(24)	(29)
Total debt	6,525	7,000
Future Minimum Rental on Capital Lease Obligations
2014	8
2015	8
2016	7
2017	7
2018	6
Thereafter	27
Capital lease, net unamortized fair value adjustment	1
Less interest expense	(25)
Total capital lease obligations	$ 39	$ 49

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.

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- Details

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