Condensed Consolidating Financial Information of Guarantor Subsidiaries - CONDENSED CONSOLIDATING CASH FLOW INFORMATION (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	$ 1,649	$ 1,329
Net cash used in investing activities	(1,005)	(1,684)
Net cash (used in) provided by financing activities	(870)	370
Effect of foreign exchange rates	(9)	11
Net (decrease) increase in cash and cash equivalents	(235)	26
Cash and cash equivalents at beginning of period	352	312
Cash and cash equivalents at end of period	117	338
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	12	10
Net cash used in investing activities	(12)	(10)
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	1,714	1,297
Net cash used in investing activities	(920)	(1,624)
Net cash (used in) provided by financing activities	(773)	315
Effect of foreign exchange rates	0	0
Net (decrease) increase in cash and cash equivalents	21	(12)
Cash and cash equivalents at beginning of period	23	21
Cash and cash equivalents at end of period	44	9
Guarantor Subsidiaries \| Reportable Legal Entities
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(1)	(1)
Net cash used in investing activities	0	0
Net cash (used in) provided by financing activities	1	1
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	(66)	78
Net cash used in investing activities	(73)	(50)
Net cash (used in) provided by financing activities	(108)	(1)
Effect of foreign exchange rates	(9)	11
Net (decrease) increase in cash and cash equivalents	(256)	38
Cash and cash equivalents at beginning of period	329	291
Cash and cash equivalents at end of period	73	329
Non-Guarantor Subsidiaries - SPV \| Reportable Legal Entities
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(10)	(55)
Net cash used in investing activities	0	0
Net cash (used in) provided by financing activities	10	55
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)
-URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6676-107765

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
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-Name Accounting Standards Codification
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Amount of increase (decrease) in cash and cash equivalents. Cash and cash equivalents are the 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. Includes effect from exchange rate changes.

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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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Amount of cash inflow (outflow) from investing activities, including discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.

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