Restructuring charges/other - Components of restructuring charges (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended						15 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Restructuring charges									$ 20	[1]	$ 126	[1]	$ 400	[1]
Gains on sales of assets									(75)		0		0
Gain on technology transfer									0		(315)		0
Gain on transfer of Japan substitutional pension									0		0		(144)
Other									4		0		8
Restructuring charges/other	(27)	(9)	(4)	(11)	62	16	(282)	15	(51)		(189)		264
2013 Actions
Restructuring Cost and Reserve [Line Items]
Severance and benefits cost									16	[1]	49	[1]	0	[1]
Other exit costs									10		0		0
Restructuring charges									26		49		0		75
Prior Actions
Restructuring Cost and Reserve [Line Items]
Severance and benefits cost									(6)	[1]	36	[1]	251	[1]
Other exit costs									(1)	[1]	30	[1]	128	[1]
Accelerated depreciation									1		11		21
Restructuring charges									$ (6)		$ 77		$ 400

[1] Includes changes in estimates.