Debt - Standby Letters of Credit (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Letters of credit, amount outstanding	$ 113	$ 86
JP Morgan Chase
Debt Instrument [Line Items]
Letters of credit, amount outstanding	20	20
Deutsche Bank
Debt Instrument [Line Items]
Letters of credit, amount outstanding	$ 93	$ 66