Derivatives - Offsetting Derivative Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Asset Derivatives	$ 40	$ 31
Derivative assets	12	7
Gross Amounts of Recognized (Liabilities)	(106)	(92)
Derivative liabilities	(78)	(68)
Derivative Liabilities
Derivative [Line Items]
Derivative, Collateral, Obligation to Return Cash	(5)	(4)
Gross Amounts of Recognized (Liabilities)	(106)	(92)
Gross Amounts Offset in the Statement of Financial Position, liabilities	(23)	(20)
Derivative liabilities	(78)	(68)
Financial Collateral (Received)	(73)	(65)
Net amount, liabilities	(10)	(7)
Derivative Assets
Derivative [Line Items]
Asset Derivatives	40	31
Gross Amounts Offset in the Statement of Financial Position, assets	37	26
Derivative assets	12	7
Derivative, Collateral, Obligation to Return Cash	(9)	(2)
Financial Collateral Pledged	1	2
Net Amount, assets	$ 2	$ 3