Financial Instruments: (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Financial assets and financial liabilities measured at fair value on a recurring basis:
Debt securities - noncurrent	$ 9	$ 8
Available-for-sale equity investments	53	83
Potential reduction in net position of total derivative liabilities	245	324
Recurring | Prepaid expenses and other current assets
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	418	546
Recurring | Investments and other sundry assets
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	810	754
Recurring | Other accrued expenses and liabilities
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative liabilities	324	365
Recurring | Other liabilities.
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative liabilities	75	166
Level 1 | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	1,313	1,886
Debt securities - noncurrent	2	1
Available-for-sale equity investments	53	69
Total Assets	1,368	1,956
Level 1 | Money market funds | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	1,313	1,886
Level 2 | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	7,822	6,600
Debt securities - current	345
Debt securities - noncurrent	7	7
Available-for-sale equity investments	0	14
Derivative assets	1,228	1,300
Total Assets	9,402	7,921
Total Liabilities	399	531
Level 2 | Interest rate contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	826	783
Level 2 | Foreign exchange contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	391	510
Derivative liabilities	388	523
Level 2 | Equity contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	11	7
Derivative liabilities	11	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	2,487	2,082
Level 2 | Commercial paper | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	3,574	777
Level 2 | U.S. government securities | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	1,450	2,750
Level 2 | Canada government securities | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	254	983
Level 2 | Other securities | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	57	8
Total fair value | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	9,135	8,486
Debt securities - current	345
Debt securities - noncurrent	9	8
Available-for-sale equity investments	53	83
Derivative assets	1,228	1,300
Total Assets	10,770	9,877
Total Liabilities	399	531
Potential reduction in net position of total derivative assets	245	324
Potential reduction in net position of total derivative liabilities	245	324
Total fair value | Interest rate contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	826	783
Total fair value | Foreign exchange contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	391	510
Derivative liabilities	388	523
Total fair value | Equity contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	11	7
Derivative liabilities	11	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	2,487	2,082
Total fair value | Commercial paper | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	3,574	777
Total fair value | Money market funds | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	1,313	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	1,450	2,750
Total fair value | Canada government securities | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	254	983
Total fair value | Other securities | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	$ 57	$ 8