Contingencies and commitments (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Minimum future rental commitments under non-cancelable operating leases
2012	$ 116
2013	104
2014	85
2015	76
2016	65
Thereafter	328
Total minimum operating lease commitments	$ 774

The total of future contractually required payments on leases defined as operating.

+ References+ Details

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within one year of the balance sheet date relating to leases defined as operating.

+ References+ Details

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the fifth year of the balance sheet date relating to leases defined as operating.

+ References+ Details

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the fourth year of the balance sheet date relating to leases defined as operating.

+ References+ Details

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the third year of the balance sheet date relating to leases defined as operating.

+ References+ Details

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the second year of the balance sheet date relating to leases defined as operating.

+ References+ Details

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due after the fifth year from the balance sheet date on leases defined as operating.

+ References+ Details