Fair value measurements (Details 3) (USD $) In Millions	Dec. 31, 2010
Fair value
Non-financial assets: [Line Item]
Intangible assets, net	$ 0
Total non-financial assets at fair value	0
Fair value measurements using quoted prices in active markets for identical financial instruments (Level 1)
Non-financial assets: [Line Item]
Intangible assets, net	0
Total non-financial assets at fair value	0
Fair value measurements using significant other observable inputs (Level 2)
Non-financial assets: [Line Item]
Intangible assets, net	0
Total non-financial assets at fair value	0
Fair value measurements using significant unobservable inputs (Level 3)
Non-financial assets: [Line Item]
Intangible assets, net	0
Total non-financial assets at fair value	0
Total Losses
Non-financial assets: [Line Item]
Intangible assets, net	326
Total non-financial assets at fair value	$ 326