Schedule I - Condensed Financial Information of Parent (Statement of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	$ (2,755)	$ (2,466)	$ (2,343)
Investing Activities:
Sale of short-term investments	627	666	1,302
Net cash used in investing activities	(2,295)	(2,721)	(505)
Financing Activities:
Common stock dividends paid	(381)	(362)	(344)
Payments for deferred financing costs	(107)	(126)	(39)
Proceeds from (Payments for) Other Financing Activities	(52)	9	49
Net cash used in financing activities	(78)	(86)	(1,643)
Effect of exchange rate changes on cash	(24)	(18)	(54)
Cash and cash equivalents, beginning	1,029
Cash and cash equivalents, ending	1,089	1,029
SUPPLEMENTAL DISCLOSURES:
Cash payments for interest, net of amounts capitalized	(908)	(946)	(1,003)
Cash payments for income taxes, net of refunds	(333)	(363)	(370)
Parent Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	(434)	(583)	409
Investing Activities:
Proceeds from the sale of business interests, net of expenses	412	196	1,222
Investment in and net advances to subsidiaries	(652)	(596)	(216)
Return of capital	346	411	242
Additions to property, plant and equipment	(8)	(8)	(13)
Sale of short-term investments	(1)	0	0
Net cash used in investing activities	97	3	1,235
Financing Activities:
(Repayments) Borrowings under the revolver, net	(110)	180	(207)
Borrowings of notes payable and other coupon bearing securities	3,397	0	1,000
Repayments of notes payable and other coupon bearing securities	(3,366)	(450)	(1,933)
Loans from (Repayments to) subsidiaries	25	40	(143)
Proceeds from issuance of common stock	4	6	7
Common stock dividends paid	(381)	(362)	(344)
Payments for deferred financing costs	(38)	(3)	(11)
Proceeds from (Payments for) Other Financing Activities	(3)	(4)	(5)
Net cash used in financing activities	(472)	(593)	(1,636)
Effect of exchange rate changes on cash	0	(1)	1
Total increase (decrease) in cash, cash equivalents and restricted cash	59	(8)	9
Cash and cash equivalents, beginning	11	19
Cash and cash equivalents, ending	70	11	19
SUPPLEMENTAL DISCLOSURES:
Cash payments for interest, net of amounts capitalized	156	192	232
Cash payments for income taxes, net of refunds	$ (8)	$ (5)	$ 10