Amount of amortization expense attributable to debt issuance costs.

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Amount, after accumulated amortization, of debt premium.

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-SubTopic 30
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Amount of operating interest income, including, but not limited to, amortization and accretion of premiums and discounts on securities.

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Debt and Other Financing Arrangements - Interest Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Debt Instrument, Unamortized Premium	$ 49
Interest Expense
Debt Instrument [Line Items]
Amortization of debt issuance fees	8	$ 4	$ 4
Prepayments and other current assets
Debt Instrument [Line Items]
Amortization of debt issuance fees	9
Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Unamortized Premium	54
Interest income	$ 3