Financial Instruments: (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Financial assets and financial liabilities measured at fair value on a recurring basis:
Debt securities - noncurrent	$ 8	$ 8
Available-for-sale equity investments	59	83
Potential reduction in net position of total derivative liabilities	230	324
Recurring | Prepaid expenses and other current assets
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	451	546
Recurring | Investments and other sundry assets
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	728	754
Recurring | Other accrued expenses and liabilities
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative liabilities	223	365
Recurring | Other liabilities.
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative liabilities	96	166
Level 1 | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	1,171	1,886
Debt securities - noncurrent	1	1
Available-for-sale equity investments	27	69
Total Assets	1,199	1,956
Level 1 | Money market funds | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	1,171	1,886
Level 2 | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	7,275	6,600
Debt securities - current	500
Debt securities - noncurrent	7	7
Available-for-sale equity investments	32	14
Derivative assets	1,179	1,300
Total Assets	8,993	7,921
Total Liabilities	319	531
Level 2 | Interest rate contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	756	783
Level 2 | Foreign exchange contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	393	510
Derivative liabilities	315	523
Level 2 | Equity contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	30	7
Derivative liabilities	4	8
Level 2 | Time deposits and certificates of deposit | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	1,604	2,082
Level 2 | Commercial paper | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	1,016	777
Level 2 | U.S. government securities | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	3,200	2,750
Level 2 | Canada government securities | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	1,454	983
Level 2 | Other securities | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	1	8
Total fair value | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	8,446	8,486
Debt securities - current	500
Debt securities - noncurrent	8	8
Available-for-sale equity investments	59	83
Derivative assets	1,179	1,300
Total Assets	10,192	9,877
Total Liabilities	319	531
Potential reduction in net position of total derivative assets	230	324
Potential reduction in net position of total derivative liabilities	230	324
Total fair value | Interest rate contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	756	783
Total fair value | Foreign exchange contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	393	510
Derivative liabilities	315	523
Total fair value | Equity contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	30	7
Derivative liabilities	4	8
Total fair value | Time deposits and certificates of deposit | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	1,604	2,082
Total fair value | Commercial paper | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	1,016	777
Total fair value | Money market funds | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	1,171	1,886
Total fair value | U.S. government securities | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	3,200	2,750
Total fair value | Canada government securities | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	1,454	983
Total fair value | Other securities | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	$ 1	$ 8