Consolidating Financial Information - Condensed Consolidating Statement of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended			63 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
Cash Flows from Operating Activities:
Total Cash Flows from Operating Activities	$ 916	$ 1,158	$ 1,557
Cash Flows from Investing Activities:
Capital Expenditures	(811)	(881)	(996)
Asset Dispositions	2	12	35
Short Term Securities Acquired	(68)	(83)	(72)
Short Term Securities Redeemed	68	83	60
Capital Contributions Received and Loans Incurred	0	0	0
Capital Redemptions and Loans Paid	0	0	0
Notes Receivable	(55)	0	0
Other Transactions	(3)	(10)	(6)
Total Cash Flows from Investing Activities	(867)	(879)	(979)
Cash Flows from Financing Activities:
Short Term Debt and Overdrafts Incurred	1,944	1,054	417
Short Term Debt and Overdrafts Paid	(1,795)	(1,046)	(228)
Long Term Debt Incurred	6,455	6,463	4,988
Long Term Debt Paid	(6,469)	(6,342)	(5,433)
Common Stock Issued	4	14	13
Common Stock Repurchased	(220)	(400)	(500)	$ (1,534)
Common Stock Dividends Paid	(138)	(110)	(82)
Capital Contributions Received and Loans Incurred	0	0	0
Capital Redemptions and Loans Paid	0	0	0
Intercompany Dividends Paid	0	0	0
Transactions with Minority Interests in Subsidiaries	(31)	(7)	(11)
Debt Related Costs and Other Transactions	7	(41)	(40)
Total Cash Flows from Financing Activities	(243)	(415)	(876)
Effect of Exchange Rate Changes on Cash, Cash Equivalents and Restricted Cash	(43)	57	(15)
Net Change in Cash, Cash Equivalents and Restricted Cash	(237)	(79)	(313)
Cash, Cash Equivalents and Restricted Cash at Beginning of the Year	1,110	1,189	1,502
Cash, Cash Equivalents and Restricted Cash at End of the Year	873	1,110	1,189	873
Reportable Legal Entities | Parent Company
Cash Flows from Operating Activities:
Total Cash Flows from Operating Activities	1,771	1,192	609
Cash Flows from Investing Activities:
Capital Expenditures	(307)	(305)	(370)
Asset Dispositions	0	1	11
Short Term Securities Acquired	0	0	0
Short Term Securities Redeemed	0	0	0
Capital Contributions Received and Loans Incurred	(1,205)	(79)	(257)
Capital Redemptions and Loans Paid	282	76	163
Notes Receivable	(55)
Other Transactions	1	(3)	0
Total Cash Flows from Investing Activities	(1,284)	(310)	(453)
Cash Flows from Financing Activities:
Short Term Debt and Overdrafts Incurred	965	420	0
Short Term Debt and Overdrafts Paid	(940)	(420)	0
Long Term Debt Incurred	3,200	3,062	2,896
Long Term Debt Paid	(3,260)	(3,151)	(3,016)
Common Stock Issued	4	14	13
Common Stock Repurchased	(220)	(400)	(500)
Common Stock Dividends Paid	(138)	(110)	(82)
Capital Contributions Received and Loans Incurred	283	292	576
Capital Redemptions and Loans Paid	(430)	(563)	(148)
Intercompany Dividends Paid	0	0	0
Transactions with Minority Interests in Subsidiaries	0	0	0
Debt Related Costs and Other Transactions	16	(35)	(46)
Total Cash Flows from Financing Activities	(520)	(891)	(307)
Effect of Exchange Rate Changes on Cash, Cash Equivalents and Restricted Cash	0	0	0
Net Change in Cash, Cash Equivalents and Restricted Cash	(33)	(9)	(151)
Cash, Cash Equivalents and Restricted Cash at Beginning of the Year	201	210	361
Cash, Cash Equivalents and Restricted Cash at End of the Year	168	201	210	168
Reportable Legal Entities | Guarantor Subsidiaries
Cash Flows from Operating Activities:
Total Cash Flows from Operating Activities	32	67	135
Cash Flows from Investing Activities:
Capital Expenditures	(61)	(136)	(107)
Asset Dispositions	2	1	0
Short Term Securities Acquired	0	0	0
Short Term Securities Redeemed	0	0	0
Capital Contributions Received and Loans Incurred	0	0	0
Capital Redemptions and Loans Paid	88	0	0
Notes Receivable	0
Other Transactions	0	0	0
Total Cash Flows from Investing Activities	29	(135)	(107)
Cash Flows from Financing Activities:
Short Term Debt and Overdrafts Incurred	0	0	0
Short Term Debt and Overdrafts Paid	0	0	0
Long Term Debt Incurred	15	204	0
Long Term Debt Paid	0	(52)	0
Common Stock Issued	0	0	0
Common Stock Repurchased	0	0	0
Common Stock Dividends Paid	0	0	0
Capital Contributions Received and Loans Incurred	67	66	59
Capital Redemptions and Loans Paid	(77)	(48)	(80)
Intercompany Dividends Paid	(65)	(128)	(19)
Transactions with Minority Interests in Subsidiaries	0	0	0
Debt Related Costs and Other Transactions	0	0	0
Total Cash Flows from Financing Activities	(60)	42	(40)
Effect of Exchange Rate Changes on Cash, Cash Equivalents and Restricted Cash	(3)	3	0
Net Change in Cash, Cash Equivalents and Restricted Cash	(2)	(23)	(12)
Cash, Cash Equivalents and Restricted Cash at Beginning of the Year	32	55	67
Cash, Cash Equivalents and Restricted Cash at End of the Year	30	32	55	30
Reportable Legal Entities | Non-Guarantor Subsidiaries
Cash Flows from Operating Activities:
Total Cash Flows from Operating Activities	(279)	577	885
Cash Flows from Investing Activities:
Capital Expenditures	(443)	(442)	(525)
Asset Dispositions	0	10	24
Short Term Securities Acquired	(68)	(83)	(72)
Short Term Securities Redeemed	68	83	60
Capital Contributions Received and Loans Incurred	(283)	(292)	(576)
Capital Redemptions and Loans Paid	430	563	148
Notes Receivable	0
Other Transactions	(4)	(7)	(6)
Total Cash Flows from Investing Activities	(300)	(168)	(947)
Cash Flows from Financing Activities:
Short Term Debt and Overdrafts Incurred	979	634	417
Short Term Debt and Overdrafts Paid	(855)	(626)	(228)
Long Term Debt Incurred	3,240	3,197	2,092
Long Term Debt Paid	(3,209)	(3,139)	(2,417)
Common Stock Issued	0	0	0
Common Stock Repurchased	0	0	0
Common Stock Dividends Paid	0	0	0
Capital Contributions Received and Loans Incurred	1,138	13	198
Capital Redemptions and Loans Paid	(293)	(28)	(83)
Intercompany Dividends Paid	(543)	(548)	(47)
Transactions with Minority Interests in Subsidiaries	(31)	(7)	(11)
Debt Related Costs and Other Transactions	(9)	(6)	6
Total Cash Flows from Financing Activities	417	(510)	(73)
Effect of Exchange Rate Changes on Cash, Cash Equivalents and Restricted Cash	(40)	54	(15)
Net Change in Cash, Cash Equivalents and Restricted Cash	(202)	(47)	(150)
Cash, Cash Equivalents and Restricted Cash at Beginning of the Year	877	924	1,074
Cash, Cash Equivalents and Restricted Cash at End of the Year	675	877	924	675
Consolidating Entries and Eliminations
Cash Flows from Operating Activities:
Total Cash Flows from Operating Activities	(608)	(678)	(72)
Cash Flows from Investing Activities:
Capital Expenditures	0	2	6
Asset Dispositions	0	0	0
Short Term Securities Acquired	0	0	0
Short Term Securities Redeemed	0	0	0
Capital Contributions Received and Loans Incurred	1,488	371	833
Capital Redemptions and Loans Paid	(800)	(639)	(311)
Notes Receivable	0
Other Transactions	0	0	0
Total Cash Flows from Investing Activities	688	(266)	528
Cash Flows from Financing Activities:
Short Term Debt and Overdrafts Incurred	0	0	0
Short Term Debt and Overdrafts Paid	0	0	0
Long Term Debt Incurred	0	0	0
Long Term Debt Paid	0	0	0
Common Stock Issued	0	0	0
Common Stock Repurchased	0	0	0
Common Stock Dividends Paid	0	0	0
Capital Contributions Received and Loans Incurred	(1,488)	(371)	(833)
Capital Redemptions and Loans Paid	800	639	311
Intercompany Dividends Paid	608	676	66
Transactions with Minority Interests in Subsidiaries	0	0	0
Debt Related Costs and Other Transactions	0	0	0
Total Cash Flows from Financing Activities	(80)	944	(456)
Effect of Exchange Rate Changes on Cash, Cash Equivalents and Restricted Cash	0	0	0
Net Change in Cash, Cash Equivalents and Restricted Cash	0	0	0
Cash, Cash Equivalents and Restricted Cash at Beginning of the Year	0	0	0
Cash, Cash Equivalents and Restricted Cash at End of the Year	$ 0	$ 0	$ 0	$ 0