Lease Commitments (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Schedule of capitalized leased assets
Upstream	$ 585	$ 561
Downstream	316	316
All Other		169
Total	901	1,046
Less: Accumulated amortization	568	573
Net capitalized leased assets	333	473
Rental expenses incurred for operating leases
Minimum rentals	892	931	933
Contingent rentals	11	10	7
Total	903	941	940
Less: Sublease rental income	39	41	41
Net rental expense	864	900	899
Estimated future minimum lease payments (net of noncancelable sublease rentals) under operating and capital leases
Future minimum operating lease payments, Current	693
Future minimum capital lease payments, Current	70
Future minimum operating lease payments, due in two years	632
Future minimum capital lease payments, due in two years	47
Future minimum operating lease payments, due in three years	523
Future minimum capital lease payments, due in three years	32
Future minimum operating lease payments, due in four years	475
Future minimum capital lease payments, due in four years	21
Future minimum operating lease payments, due in five years	393
Future minimum capital lease payments, due in five years	13
Future minimum operating lease payments, due thereafter	793
Future minimum capital lease payments, due thereafter	68
Future minimum operating leases payments, total	3,509
Future minimum capital lease payments, total	251
Less: Amounts representing interest and executory costs	(55)
Net present values	196
Less: Capital lease obligations included in short-term debt	(68)
Long-term capital lease obligations	$ 128	$ 286
Lease Commitments (Textual)
Renewal term of leasing arrangement (in years)	Up to 25
Non-cancelable term of operating and capital leases (in years)	more than 1