Financial Instruments - Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Millions		Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		$ 1,213	$ 2,150
Total assets	[1]	167,838	171,797
Total liabilities		1,174	691
Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		18,866	24,937
Total liabilities		1,174	691
Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		1,213	2,150
Available-for-sale debt securities		11,256	15,362
Total short-term investments		12,469	17,512
Other Current Assets [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative assets		576	337
Other Current Assets [Member] | Recurring [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative assets		88	104
Other Current Assets [Member] | Recurring [Member] | Foreign exchange contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative assets		488	234
Long-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	[2]	1,563	1,440
Available-for-sale debt securities		3,742	5,090
Trading securities, debt		50	73
Trading funds and securities		1,612	1,514
Total long-term investments		5,354	6,603
Other Noncurrent Assets [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative assets		467	484
Other Noncurrent Assets [Member] | Recurring [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative assets		246	477
Other Noncurrent Assets [Member] | Recurring [Member] | Foreign exchange contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative assets		220	7
Other Current Liabilities [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative liabilities		89	201
Other Current Liabilities [Member] | Recurring [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative liabilities		9	1
Other Current Liabilities [Member] | Recurring [Member] | Foreign exchange contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative liabilities		80	201
Other Noncurrent Liabilities [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative liabilities		1,085	490
Other Noncurrent Liabilities [Member] | Recurring [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative liabilities		653	177
Other Noncurrent Liabilities [Member] | Recurring [Member] | Foreign exchange contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative liabilities		432	313
Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		1,594	1,523
Total liabilities		0	0
Level 1 [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		17	16
Available-for-sale debt securities		0	0
Total short-term investments		17	16
Level 1 [Member] | Other Current Assets [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative assets		0	0
Level 1 [Member] | Other Current Assets [Member] | Recurring [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative assets		0	0
Level 1 [Member] | Other Current Assets [Member] | Recurring [Member] | Foreign exchange contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative assets		0	0
Level 1 [Member] | Long-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	[2]	1,527	1,398
Available-for-sale debt securities		0	36
Trading securities, debt		50	73
Trading funds and securities		1,577	1,472
Total long-term investments		1,577	1,507
Level 1 [Member] | Other Noncurrent Assets [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative assets		0	0
Level 1 [Member] | Other Noncurrent Assets [Member] | Recurring [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative assets		0	0
Level 1 [Member] | Other Noncurrent Assets [Member] | Recurring [Member] | Foreign exchange contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative assets		0	0
Level 1 [Member] | Other Current Liabilities [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative liabilities		0	0
Level 1 [Member] | Other Current Liabilities [Member] | Recurring [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative liabilities		0	0
Level 1 [Member] | Other Current Liabilities [Member] | Recurring [Member] | Foreign exchange contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative liabilities		0	0
Level 1 [Member] | Other Noncurrent Liabilities [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative liabilities		0	0
Level 1 [Member] | Other Noncurrent Liabilities [Member] | Recurring [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative liabilities		0	0
Level 1 [Member] | Other Noncurrent Liabilities [Member] | Recurring [Member] | Foreign exchange contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative liabilities		0	0
Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		17,272	23,414
Total liabilities		1,174	691
Level 2 [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		1,196	2,134
Available-for-sale debt securities		11,256	15,362
Total short-term investments		12,452	17,496
Level 2 [Member] | Other Current Assets [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative assets		576	337
Level 2 [Member] | Other Current Assets [Member] | Recurring [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative assets		88	104
Level 2 [Member] | Other Current Assets [Member] | Recurring [Member] | Foreign exchange contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative assets		488	234
Level 2 [Member] | Long-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	[2]	36	42
Available-for-sale debt securities		3,742	5,054
Trading securities, debt		0	0
Trading funds and securities		36	42
Total long-term investments		3,778	5,096
Level 2 [Member] | Other Noncurrent Assets [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative assets		467	484
Level 2 [Member] | Other Noncurrent Assets [Member] | Recurring [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative assets		246	477
Level 2 [Member] | Other Noncurrent Assets [Member] | Recurring [Member] | Foreign exchange contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative assets		220	7
Level 2 [Member] | Other Current Liabilities [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative liabilities		89	201
Level 2 [Member] | Other Current Liabilities [Member] | Recurring [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative liabilities		9	1
Level 2 [Member] | Other Current Liabilities [Member] | Recurring [Member] | Foreign exchange contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current derivative liabilities		80	201
Level 2 [Member] | Other Noncurrent Liabilities [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative liabilities		1,085	490
Level 2 [Member] | Other Noncurrent Liabilities [Member] | Recurring [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative liabilities		653	177
Level 2 [Member] | Other Noncurrent Liabilities [Member] | Recurring [Member] | Foreign exchange contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent derivative liabilities		432	313
Money market funds [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		1,184	2,115
Money market funds [Member] | Level 1 [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		0	0
Money market funds [Member] | Level 2 [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		1,184	2,115
Equity [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	[2]	29	35
Equity [Member] | Level 1 [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	[2]	17	16
Equity [Member] | Level 2 [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	[2]	12	19
Government and agency - non U.S. [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		8,442	12,629
Government and agency - non U.S. [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		8,336	12,242
Government and agency - non U.S. [Member] | Long-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		106	387
Government and agency - non U.S. [Member] | Level 1 [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		0	0
Government and agency - non U.S. [Member] | Level 1 [Member] | Long-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		0	0
Government and agency - non U.S. [Member] | Level 2 [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		8,336	12,242
Government and agency - non U.S. [Member] | Level 2 [Member] | Long-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		106	387
Corporate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	[3]	6,100	6,938
Corporate [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		2,890	2,766
Corporate [Member] | Long-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		3,210	4,172
Corporate [Member] | Level 1 [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		0	0
Corporate [Member] | Level 1 [Member] | Long-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		0	36
Corporate [Member] | Level 2 [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		2,890	2,766
Corporate [Member] | Level 2 [Member] | Long-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		3,210	4,136
Government - U.S. [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		428	747
Government - U.S. [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		8	252
Government - U.S. [Member] | Long-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		421	495
Government - U.S. [Member] | Level 1 [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		0	0
Government - U.S. [Member] | Level 1 [Member] | Long-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		0	0
Government - U.S. [Member] | Level 2 [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		8	252
Government - U.S. [Member] | Level 2 [Member] | Long-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		421	495
Agency asset-backed - U.S. [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		18	24
Agency asset-backed - U.S. [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		17	23
Agency asset-backed - U.S. [Member] | Level 1 [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		0	0
Agency asset-backed - U.S. [Member] | Level 2 [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		17	23
Other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	[4]	9	114
Other asset-backed [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		5	79
Other asset-backed [Member] | Long-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		4	35
Other asset-backed [Member] | Level 1 [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		0	0
Other asset-backed [Member] | Level 1 [Member] | Long-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		0	0
Other asset-backed [Member] | Level 2 [Member] | Short-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		5	79
Other asset-backed [Member] | Level 2 [Member] | Long-term Investments [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities		$ 4	$ 35

[1] Amounts may not add due to rounding.

[2] As of September 30, 2018, short-term equity securities of $12 million and long-term equity securities of $35 million are held in trust for benefits attributable to the former Pharmacia Savings Plus Plan. As of December 31, 2017, short-term equity securities of $19 million and long-term equity securities of $42 million are held in trust for benefits attributable to the former Pharmacia Savings Plus Plan.

[3] Issued by a diverse group of corporations.

[4] Includes mortgage-backed, loan-backed and receivable-backed securities, all of which are in senior positions in the capital structure of the security. Mortgage-backed securities are collateralized by diversified pools of residential and commercial mortgages. Loan-backed securities are collateralized by senior secured obligations of a diverse pool of companies or student loans. Receivable-backed securities are collateralized by credit cards receivables.