Presentation Prior period adjustment (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred income taxes	$ 570	$ 598
Other Liabilities and deferred revenue	43,577	40,886
Total equity	24,832	26,145	15,686	14,821
Adjustments for Change in Accounting Principle [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred income taxes		13,468	15,350
Other Liabilities and deferred revenue		40,886	48,727
Total equity		26,145	15,686
Scenario, Previously Reported [Member] | Adjustments for Change in Accounting Principle [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred income taxes		13,315	15,185
Other Liabilities and deferred revenue		40,462	48,259
Total equity		26,416	15,989
Scenario, Adjustment [Member] | Adjustments for Change in Accounting Principle [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred income taxes		153	165
Other Liabilities and deferred revenue		424	468
Total equity		$ (271)	$ (303)	$ (250)