Amount of amortization expense attributable to debt issuance costs.

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Amount, after accumulated amortization, of debt premium.

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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, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Unamortized premium	$ 37
Interest Expense
Debt Instrument [Line Items]
Amortization of debt issuance fees	18	$ 8	$ 4
Other Assets
Debt Instrument [Line Items]
Amortization of debt issuance fees	5
Senior Notes
Debt Instrument [Line Items]
Unamortized premium	54
Interest income	$ 13	$ 3