Long-Term Debt (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	May 31, 2016
Debt Instrument [Line Items]
Long-term debt, excluding current maturities	[1]	$ 35,193	$ 33,542
Long-term debt instruments		32,490	27,071
Unamortized discounts and debt issuance costs		44	43
Debt due within one year		(6,256)	(1,487)
Unamortized discounts and debt issuance costs, due within one year		(3)	(1)
Reclassified from short-term debt		9,000	8,000
Total long-term debt		35,234	33,584
Unamortized discounts and debt issuance costs, excluding current maturities		41	42
Long-term debt maturing 2017		6,256
Long-term debt maturing 2018		6,722
Long-term debt maturing 2019		4,000
Long-term debt maturing 2020		4,054
Long-term debt maturing 2021		2,054
Long-term debt maturing after 2021		9,404
Notes Payable [Member] | 3.191% notes due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		2,250	2,250
Unamortized discounts and debt issuance costs		$ 4	4
Interest rate		3.191%
Notes Payable [Member] | 2.954% notes due 2026 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 2,250	0
Unamortized discounts and debt issuance costs		$ 6	0
Interest rate		2.954%
Notes Payable [Member] | Floating rate notes due 2017 (1.091%) [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 2,050	2,050
Unamortized discounts and debt issuance costs		$ 1	2
Interest rate		1.091%
Notes Payable [Member] | 1.104% notes due 2017 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 2,000	2,000
Unamortized discounts and debt issuance costs		$ 1	2
Interest rate		1.104%
Notes Payable [Member] | 1.718% notes due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 2,000	2,000
Unamortized discounts and debt issuance costs		$ 1	2
Interest rate		1.718%
Notes Payable [Member] | 2.355% notes due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 2,000	2,000
Unamortized discounts and debt issuance costs		$ 5	5
Interest rate		2.355%
Notes Payable [Member] | 1.365% notes due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 1,750	1,750
Unamortized discounts and debt issuance costs		$ 1	2
Interest rate		1.365%
Notes Payable [Member] | 1.961% notes due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 1,750	1,750
Unamortized discounts and debt issuance costs		$ 2	2
Interest rate		1.961%
Notes Payable [Member] | Floating Rate Notes due 2018 (1.310%) [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 1,650	800
Unamortized discounts and debt issuance costs		$ 2	1
Interest rate		1.31%
Notes Payable [Member] | 4.95% notes due 2019 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 1,500	1,500
Unamortized discounts and debt issuance costs		$ 2	2
Interest rate		4.95%
Notes Payable [Member] | 1.561% notes due 2019 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 1,350	0
Unamortized discounts and debt issuance costs		$ 2	0
Interest rate		1.561%
Notes Payable [Member] | 2.100% notes due 2021 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 1,350	0
Unamortized discounts and debt issuance costs		$ 2	0
Interest rate		2.10%
Notes Payable [Member] | 1.790% notes due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 1,250	1,250
Unamortized discounts and debt issuance costs		$ 1	2
Interest rate		1.79%
Notes Payable [Member] | 2.419% notes due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 1,250	1,250
Unamortized discounts and debt issuance costs		$ 2	2
Interest rate		2.419%
Notes Payable [Member] | 1.345% notes due 2017 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 1,100	1,100
Unamortized discounts and debt issuance costs		$ 0	2
Interest rate		1.345%
Notes Payable [Member] | 1.344% notes due 2017 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 1,000	1,000
Unamortized discounts and debt issuance costs		$ 1	1
Interest rate		1.344%
Notes Payable [Member] | 2.427% notes due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 1,000	1,000
Unamortized discounts and debt issuance costs		$ 1	2
Interest rate		2.427%
Notes Payable [Member] | 2.193% notes due 2019 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 750	750
Unamortized discounts and debt issuance costs		$ 1	1
Interest rate		2.193%
Notes Payable [Member] | 2.566% notes due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 750	0
Unamortized discounts and debt issuance costs		$ 1	0
Interest rate		2.566%
Notes Payable [Member] | 3.326% notes due 2025 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 750	750
Unamortized discounts and debt issuance costs		$ 2	2
Interest rate		3.326%
Notes Payable [Member] | 2.411% notes due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 700	700
Unamortized discounts and debt issuance costs		$ 1	1
Interest rate		2.411%
Notes Payable [Member] | Floating Rate Notes due 2021 (1.599%) [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 650	400
Unamortized discounts and debt issuance costs		$ 1	1
Interest rate		1.599%
Notes Payable [Member] | Floating rate notes due 2019 (1.316%) [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 400	400
Unamortized discounts and debt issuance costs		$ 1	2
Interest rate		1.316%
Notes Payable [Member] | Floating rate notes due 2022 (1.472%) [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 350	350
Unamortized discounts and debt issuance costs		$ 0	1
Interest rate		1.472%
Notes Payable [Member] | 0.889% notes due 2016 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 0	750
Unamortized discounts and debt issuance costs		$ 0	0
Interest rate		0.889%
Notes Payable [Member] | Floating rate notes due 2016 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 0	700
Unamortized discounts and debt issuance costs		0	1
Debentures [Member] | Amortizing Bank Loan due 2018 (1.527%) [Member]
Debt Instrument [Line Items]
Long-term debt instruments		178	110
Unamortized discounts and debt issuance costs		$ 0	0
Interest rate		1.527%
Debentures [Member] | 8.625% debentures due 2032 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 147	147
Unamortized discounts and debt issuance costs		$ 1	1
Interest rate		8.625%
Debentures [Member] | 8.625 % debentures due 2031 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 108	108
Unamortized discounts and debt issuance costs		$ 1	1
Interest rate		8.625%
Debentures [Member] | 8 % debentures due 2032 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 75	74
Unamortized discounts and debt issuance costs		$ 1	1
Interest rate		8.00%
Debentures [Member] | 9.75 % debentures due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 54	54
Unamortized discounts and debt issuance costs		$ 0	0
Interest rate		9.75%
Debentures [Member] | 8.875 % debentures due 2021 [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 40	40
Unamortized discounts and debt issuance costs		$ 0	0
Interest rate		8.875%
Medium-term Notes [Member] | Medium-term notes, maturing from 2021 to 2038 (6.133%) [Member]
Debt Instrument [Line Items]
Long-term debt instruments		$ 38	38
Unamortized discounts and debt issuance costs		$ 0	$ 0
Interest rate		6.133%
Corporate Bond Securities [Member]
Debt Instrument [Line Items]
Debt issued				$ 6,800

[1] 2015 adjusted to conform to ASU 2015-03. Refer to Note 5, "New Accounting Standards" beginning on page FS-32.