Supplemental financial information - Other income (expense), net (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Supplemental Financial Information [Abstract]
Interest income	$ 7		$ 10		$ 8
Tax interest income (expense)	6		(10)		32
Net gains on investments	5		18		18
Other	3	[1]	(1)	[1]	(11)	[1]
Total	21		17		47
Lease income	15		15		15
Aggregate amount of non-cancellable future lease payments	$ 51

[1] Includes lease income of approximately $15 million per year, primarily from the purchaser of a former business. As of December 31, 2014, the aggregate amount of non-cancellable future lease payments to be received from these leases is $51 million. These leases contain renewal options. Other also includes miscellaneous non-operational items such as losses related to former businesses, including settlements in 2012; gains and losses from currency exchange rate changes; and gains and losses from our derivative financial instruments, primarily forward foreign currency exchange contracts.