Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2013

Fair Value Disclosures [Abstract]

Schedule of carrying amount and estimated fair values of our exchangeable notes as well as current and long-term debt

The following table presents carrying amounts and estimated fair values of our exchangeable notes and embedded derivative as well as current and long-term debt:

	Carrying amount at March 31, 2013		Estimated Fair Value Using Input Type
			Quoted prices in active markets		Observable		Unobservable		Total estimated fair value
	(in millions)
Exchangeable Notes	$	80	$	—	$	—	$	80	$	80
Current and long-term debt	$	23,733	$	17,399	$	5,352	$	4,048	$	26,799

	Carrying amount at December 31, 2012		Estimated Fair Value Using Input Type
			Quoted prices in active markets		Observable		Unobservable		Total estimated fair value
	(in millions)
Exchangeable Notes	$	—	$	—	$	—	$	—	$	—
Current and long-term debt	$	23,569	$	17,506	$	6,118	$	3,104	$	26,728