Derivatives - Offsetting Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Offsetting of Financial Liabilities under Master Netting Agreements with Derivative Counterparties
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	$ 14	$ 53
Net Amount of Derivative Liabilities	5	15
Derivatives subject to master netting agreements
Offsetting of Financial Liabilities under Master Netting Agreements with Derivative Counterparties
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	14	53
Gross Amount of Eligible Offsetting Recognized Derivative Assets	9	38
Net Amount of Derivative Liabilities	$ 5	$ 15