Derivatives - Fair Value Hedges (Details) - Fair value hedges - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2018
Derivatives in Fair Value Hedging Relationships
Gain (Loss) on Derivative Recognized in Income	$ (1)	$ (12)
Gain (Loss) on Hedged Item Recognized in Income	1	12
Interest rate swap contracts \| Interest expense.
Derivatives in Fair Value Hedging Relationships
Gain (Loss) on Derivative Recognized in Income	(1)	(12)
Gain (Loss) on Hedged Item Recognized in Income	$ 1	$ 12

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
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+ References

No definition available.

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The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4D
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