Schedule I - Condensed Financial Information of Parent (Statement of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	$ 2,343	$ 2,504	$ 2,897
Investing Activities:
Purchase of short term investments, net	(66)	(609)	(52)
Net cash used in investing activities	(505)	(2,599)	(2,136)
Financing Activities:
(Repayments) Borrowings under the revolver, net	1,865	2,156	1,465
Purchase of treasury stock	0	0	(79)
Common stock dividends paid	(344)	(317)	(290)
Payments for deferred financing costs	(39)	(100)	(105)
Payments to Noncontrolling Interests	(340)	(424)	(476)
Proceeds from (Payments for) Other Financing Activities	101	(52)	(44)
Net cash provided by (used in) financing activities	(1,643)	43	(747)
Effect of exchange rate changes on cash	(54)	8	37
Cash and cash equivalents, beginning	949
Cash and cash equivalents, ending	1,166	949
SUPPLEMENTAL DISCLOSURES:
Cash payments for interest, net of amounts capitalized	(1,003)	(1,196)	(1,273)
Cash payments for income taxes, net of refunds	(370)	(377)	(487)
Parent Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	409	148	818
Investing Activities:
Expenses related to asset sales, net of proceeds	1,222	0	0
Investment in and net advances to subsidiaries	(216)	(339)	(650)
Return of capital	242	243	247
Additions to property, plant and equipment	(13)	(13)	(12)
Net cash used in investing activities	1,235	(109)	(415)
Financing Activities:
(Repayments) Borrowings under the revolver, net	(207)	207	0
Borrowings of notes payable and other coupon bearing securities	1,000	1,025	500
Repayments of notes payable and other coupon bearing securities	(1,933)	(1,353)	(808)
Loans from (Repayments to) subsidiaries	(143)	309	183
Purchase of treasury stock	0	0	(79)
Proceeds from issuance of common stock	7	1	1
Common stock dividends paid	(344)	(317)	(290)
Payments for deferred financing costs	(11)	(12)	(12)
Payments to Noncontrolling Interests	0	0	(2)
Proceeds from (Payments for) Other Financing Activities	(5)	(7)	(3)
Net cash provided by (used in) financing activities	(1,636)	(147)	(510)
Effect of exchange rate changes on cash	1	6	1
Total increase (decrease) in cash, cash equivalents and restricted cash	9	(102)	(106)
Cash and cash equivalents, beginning	10	112	218
Cash and cash equivalents, ending	19	10	112
SUPPLEMENTAL DISCLOSURES:
Cash payments for interest, net of amounts capitalized	232	282	296
Cash payments for income taxes, net of refunds	$ 10	$ 2	$ 6