Condensed Consolidating Financial Information of Guarantor Subsidiaries - CONDENSED CONSOLIDATING CASH FLOW INFORMATION (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	$ 2,123	$ 1,756
Net cash used in investing activities	(2,393)	(2,242)
Net cash (used in) provided by financing activities	(7)	477
Effect of foreign exchange rates	(10)	21
Net (decrease) increase in cash and cash equivalents	(287)	12
Cash and cash equivalents at beginning of period	352	312
Cash and cash equivalents at end of period	65	324
Eliminations
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	0	0
Net cash used in investing activities	0	0
Net cash (used in) provided by financing activities	0	0
Effect of foreign exchange rates	0	0
Net (decrease) increase in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	0	0
Parent \| Reportable Legal Entities
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	22	15
Net cash used in investing activities	(22)	(15)
Net cash (used in) provided by financing activities	0	0
Effect of foreign exchange rates	0	0
Net (decrease) increase in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	0	0
URNA \| Reportable Legal Entities
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	2,354	1,839
Net cash used in investing activities	(2,259)	(2,135)
Net cash (used in) provided by financing activities	(101)	298
Effect of foreign exchange rates	0	0
Net (decrease) increase in cash and cash equivalents	(6)	2
Cash and cash equivalents at beginning of period	23	21
Cash and cash equivalents at end of period	17	23
Guarantor Subsidiaries \| Reportable Legal Entities
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(1)	(2)
Net cash used in investing activities	0	0
Net cash (used in) provided by financing activities	1	2
Effect of foreign exchange rates	0	0
Net (decrease) increase in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	0	0
Non-Guarantor Subsidiaries - Foreign \| Reportable Legal Entities
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(50)	83
Net cash used in investing activities	(112)	(92)
Net cash (used in) provided by financing activities	(109)	(2)
Effect of foreign exchange rates	(10)	21
Net (decrease) increase in cash and cash equivalents	(281)	10
Cash and cash equivalents at beginning of period	329	291
Cash and cash equivalents at end of period	48	301
Non-Guarantor Subsidiaries - Domestic \| Reportable Legal Entities
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(202)	(179)
Net cash used in investing activities	0	0
Net cash (used in) provided by financing activities	202	179
Effect of foreign exchange rates	0	0
Net (decrease) increase in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	$ 0	$ 0

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (a)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Section 45
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Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

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