Consolidating Financial Information - Condensed Consolidating Statement of Cash Flows (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash Flows from Operating Activities:
Total Cash Flows from Operating Activities	$ (84)	$ (185)
Cash Flows from Investing Activities:
Capital Expenditures	(442)	(497)
Asset Dispositions	2	2
Short Term Securities Acquired	(30)	(43)
Short Term Securities Redeemed	38	43
Capital Contributions and Loans Incurred	0	0
Capital Redemptions and Loans Paid	0	0
Other Transactions	(38)	(3)
Total Cash Flows from Investing Activities	(470)	(498)
Cash Flows from Financing Activities:
Short Term Debt and Overdrafts Incurred	1,012	290
Short Term Debt and Overdrafts Paid	(920)	(303)
Long Term Debt Incurred	3,544	3,456
Long Term Debt Paid	(2,933)	(2,905)
Common Stock Issued	3	11
Common Stock Repurchased	(100)	(30)
Common Stock Dividends Paid	(67)	(50)
Capital Contributions and Loans Incurred	0	0
Capital Redemptions and Loans Paid	0	0
Intercompany Dividends Paid	0	0
Transactions with Minority Interests in Subsidiaries	(26)	(5)
Debt Related Costs and Other Transactions	6	(38)
Total Cash Flows from Financing Activities	519	426
Effect of Exchange Rate Changes on Cash, Cash Equivalents and Restricted Cash	(25)	37
Net Change in Cash, Cash Equivalents and Restricted Cash	(60)	(220)
Cash, Cash Equivalents and Restricted Cash at Beginning of the Period	1,110	1,189
Cash, Cash Equivalents and Restricted Cash at End of the Period	1,050	969
Reportable Legal Entities | Parent Company
Cash Flows from Operating Activities:
Total Cash Flows from Operating Activities	457	(49)
Cash Flows from Investing Activities:
Capital Expenditures	(180)	(190)
Asset Dispositions	0	1
Short Term Securities Acquired	0	0
Short Term Securities Redeemed	0	0
Capital Contributions and Loans Incurred	(306)	(62)
Capital Redemptions and Loans Paid	69	0
Other Transactions	(38)	0
Total Cash Flows from Investing Activities	(455)	(251)
Cash Flows from Financing Activities:
Short Term Debt and Overdrafts Incurred	575	40
Short Term Debt and Overdrafts Paid	(575)	(40)
Long Term Debt Incurred	1,605	2,090
Long Term Debt Paid	(1,267)	(1,759)
Common Stock Issued	3	11
Common Stock Repurchased	(100)	(30)
Common Stock Dividends Paid	(67)	(50)
Capital Contributions and Loans Incurred	213	30
Capital Redemptions and Loans Paid	(430)	(61)
Intercompany Dividends Paid	0	0
Transactions with Minority Interests in Subsidiaries	0	0
Debt Related Costs and Other Transactions	7	(26)
Total Cash Flows from Financing Activities	(36)	205
Effect of Exchange Rate Changes on Cash, Cash Equivalents and Restricted Cash	0	0
Net Change in Cash, Cash Equivalents and Restricted Cash	(34)	(95)
Cash, Cash Equivalents and Restricted Cash at Beginning of the Period	201	210
Cash, Cash Equivalents and Restricted Cash at End of the Period	167	115
Reportable Legal Entities | Guarantor Subsidiaries
Cash Flows from Operating Activities:
Total Cash Flows from Operating Activities	(9)	(30)
Cash Flows from Investing Activities:
Capital Expenditures	(41)	(86)
Asset Dispositions	2	0
Short Term Securities Acquired	0	0
Short Term Securities Redeemed	0	0
Capital Contributions and Loans Incurred	0	0
Capital Redemptions and Loans Paid	0	0
Other Transactions	0	0
Total Cash Flows from Investing Activities	(39)	(86)
Cash Flows from Financing Activities:
Short Term Debt and Overdrafts Incurred	0	0
Short Term Debt and Overdrafts Paid	0	0
Long Term Debt Incurred	15	52
Long Term Debt Paid	0	0
Common Stock Issued	0	0
Common Stock Repurchased	0	0
Common Stock Dividends Paid	0	0
Capital Contributions and Loans Incurred	52	62
Capital Redemptions and Loans Paid	0	0
Intercompany Dividends Paid	0	0
Transactions with Minority Interests in Subsidiaries	0	0
Debt Related Costs and Other Transactions	0	0
Total Cash Flows from Financing Activities	67	114
Effect of Exchange Rate Changes on Cash, Cash Equivalents and Restricted Cash	(2)	2
Net Change in Cash, Cash Equivalents and Restricted Cash	17	0
Cash, Cash Equivalents and Restricted Cash at Beginning of the Period	32	55
Cash, Cash Equivalents and Restricted Cash at End of the Period	49	55
Reportable Legal Entities | Non-Guarantor Subsidiaries
Cash Flows from Operating Activities:
Total Cash Flows from Operating Activities	(336)	(90)
Cash Flows from Investing Activities:
Capital Expenditures	(220)	(224)
Asset Dispositions	0	1
Short Term Securities Acquired	(30)	(43)
Short Term Securities Redeemed	38	43
Capital Contributions and Loans Incurred	(213)	(30)
Capital Redemptions and Loans Paid	430	61
Other Transactions	0	(3)
Total Cash Flows from Investing Activities	5	(195)
Cash Flows from Financing Activities:
Short Term Debt and Overdrafts Incurred	437	250
Short Term Debt and Overdrafts Paid	(345)	(263)
Long Term Debt Incurred	1,924	1,314
Long Term Debt Paid	(1,666)	(1,146)
Common Stock Issued	0	0
Common Stock Repurchased	0	0
Common Stock Dividends Paid	0	0
Capital Contributions and Loans Incurred	254	0
Capital Redemptions and Loans Paid	(69)	0
Intercompany Dividends Paid	(197)	(13)
Transactions with Minority Interests in Subsidiaries	(26)	(5)
Debt Related Costs and Other Transactions	(1)	(12)
Total Cash Flows from Financing Activities	311	125
Effect of Exchange Rate Changes on Cash, Cash Equivalents and Restricted Cash	(23)	35
Net Change in Cash, Cash Equivalents and Restricted Cash	(43)	(125)
Cash, Cash Equivalents and Restricted Cash at Beginning of the Period	877	924
Cash, Cash Equivalents and Restricted Cash at End of the Period	834	799
Consolidating Entries and Eliminations
Cash Flows from Operating Activities:
Total Cash Flows from Operating Activities	(196)	(16)
Cash Flows from Investing Activities:
Capital Expenditures	(1)	3
Asset Dispositions	0	0
Short Term Securities Acquired	0	0
Short Term Securities Redeemed	0	0
Capital Contributions and Loans Incurred	519	92
Capital Redemptions and Loans Paid	(499)	(61)
Other Transactions	0	0
Total Cash Flows from Investing Activities	19	34
Cash Flows from Financing Activities:
Short Term Debt and Overdrafts Incurred	0	0
Short Term Debt and Overdrafts Paid	0	0
Long Term Debt Incurred	0	0
Long Term Debt Paid	0	0
Common Stock Issued	0	0
Common Stock Repurchased	0	0
Common Stock Dividends Paid	0	0
Capital Contributions and Loans Incurred	(519)	(92)
Capital Redemptions and Loans Paid	499	61
Intercompany Dividends Paid	197	13
Transactions with Minority Interests in Subsidiaries	0	0
Debt Related Costs and Other Transactions	0	0
Total Cash Flows from Financing Activities	177	(18)
Effect of Exchange Rate Changes on Cash, Cash Equivalents and Restricted Cash	0	0
Net Change in Cash, Cash Equivalents and Restricted Cash	0	0
Cash, Cash Equivalents and Restricted Cash at Beginning of the Period	0	0
Cash, Cash Equivalents and Restricted Cash at End of the Period	$ 0	$ 0