Comprehensive Income and Shareholders' Equity (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Comprehensive Income		$ 2,858	$ 1,383	$ 1,263
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		21,540	21,350	20,548
Other comprehensive income (loss) before reclassifications		610
Amounts reclassified from accumulated other comprehensive items		23
Total other comprehensive items		633	(639)	(712)
Balance	$ 25,413	$ 25,413	21,540	21,350
Class of Stock Disclosures [Abstract]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)	30	30
Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		$ (2,343)
Other comprehensive income (loss) before reclassifications		588
Total other comprehensive items		588
Balance	$ (1,755)	(1,755)	(2,343)
Unrealized Gains on Available-for-Sale Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		1
Other comprehensive income (loss) before reclassifications		(1)
Amounts reclassified from accumulated other comprehensive items		(1)
Total other comprehensive items		(2)
Balance	(1)	(1)	1
Unrealized Losses on Hedging Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		(57)
Amounts reclassified from accumulated other comprehensive items		7
Total other comprehensive items		7
Balance	(50)	(50)	(57)
Pension and Other Postretirement Benefit Liability Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		(237)
Other comprehensive income (loss) before reclassifications		23
Amounts reclassified from accumulated other comprehensive items		17
Total other comprehensive items		40
Balance	(197)	(197)	(237)
Accumulated Other Comprehensive Items [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		(2,636)	(1,997)	(1,285)
Total other comprehensive items		633	(639)	(712)
Balance	(2,003)	$ (2,003)	$ (2,636)	$ (1,997)
Income Taxes on Net Investment Hedge [Member] | Restatement Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Comprehensive Income	$ 101