Short-term Borrowings and Long-term Debt (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended
	Apr. 01, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Short-term Borrowings and Long-term Debt [Line Items]
Interest Paid, Including Capitalized Interest, Operating and Investing Activities					$ 243	$ 253
Revolving credit facilities, three months or less, net					575	157
Capital lease obligations		$ 71			71		$ 77
Long-term debt and capital less obligations, including current maturities and debt issuance costs		11,780			11,780		10,648
Less Debt Issuance Costs, Noncurrent, Net		(84)			(84)		(80)
Less current maturities of long-term debt		(444)			(444)		(437)
Other Short-term Borrowings		0			0		4
Short-term Debt, excluding debt issuance costs		444			444		441
Long-term debt		11,252			11,252		10,131
Short-term borrowings		434			434		431
Less current portion of debt issuance costs and discounts		(10)			(10)		(10)
Interest Income (Expense), Net		(132)		$ (119)	(250)	$ (234)
Unsecured Debt [Member] | Unsecured Notes Due April 2025 [Member]
Short-term Borrowings and Long-term Debt [Line Items]
Proceeds from Issuance of Debt	$ 600
Debt Instrument, Interest Rate Terms	7.75%
Debt Instrument, Frequency of Periodic Payment	semi-annually
Debt Instrument, Debt Default, Description of Violation or Event of Default	The indenture governing the 2025 Notes contains covenants and events of default that are customary for debt securities of this type, including cross-default provisions whereby the acceleration of the maturity of any of our indebtedness in a principal amount of $100 million or more or the failure to pay the principal of such indebtedness at its stated maturity will constitute an event of default under the 2025 Notes unless such indebtedness is discharged, or the acceleration of the maturity of that indebtedness is annulled, within 30 days after notice.
Unsecured Debt [Member] | Subsidiary Senior Unsecured Notes [Member]
Short-term Borrowings and Long-term Debt [Line Items]
Senior Notes		2,850			2,850		2,850
Secured Debt [Member]
Short-term Borrowings and Long-term Debt [Line Items]
Senior Notes		2,883			2,883		2,898
Secured Debt [Member] | Term Loan A Facility [Member]
Short-term Borrowings and Long-term Debt [Line Items]
Long-term Debt		450			450		463
Secured Debt [Member] | Revolving Credit Facility [Member]
Short-term Borrowings and Long-term Debt [Line Items]
Long-term Line of Credit		575	$ 950		575		0
Secured Debt [Member] | Term Loan B Facility [Member]
Short-term Borrowings and Long-term Debt [Line Items]
Long-term Debt		1,926			$ 1,926		$ 1,935
Revolving Facility Borrowing 3/24 [Member] | Secured Debt [Member] | Revolving Credit Facility [Member]
Short-term Borrowings and Long-term Debt [Line Items]
Revolving credit facilities, three months or less, net			525
Revolving Facility Borrowing 3/18 [Member] | Secured Debt [Member] | Revolving Credit Facility [Member]
Short-term Borrowings and Long-term Debt [Line Items]
Revolving credit facilities, three months or less, net			$ 425
Revolving Credit Facility [Member] | Secured Debt [Member] | Revolving Credit Facility [Member]
Short-term Borrowings and Long-term Debt [Line Items]
Revolving credit facilities, three months or less, net		$ 375