Derivatives - Offsetting Liabilities (Details) - USD ($) $ in Millions	Jun. 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	$ 85	$ 53
Net Amount of Derivative Liabilities	43	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	85	53
Gross Amount of Eligible Offsetting Recognized Derivative Assets	42	38
Net Amount of Derivative Liabilities	$ 43	$ 15