Derivative Instruments - Derivatives - Offsetting Derivative Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Asset Derivatives	$ 32	$ 40
Derivative assets	12	12
Gross Amounts of Recognized (Liabilities)	(92)	(106)
Derivative Liability	(72)	(78)
Other liabilities
Derivative [Line Items]
Derivative, Collateral, Obligation to Return Cash	16	5
Gross Amounts of Recognized (Liabilities)	(92)	(106)
Gross Amounts Offset in the Statement of Financial Position, liabilities	(4)	(23)
Derivative Liability	(72)	(78)
Derivative, Collateral, Obligation to Return Cash	(16)	(5)
Financial Collateral (Received)	(81)	(73)
Net amount, liabilities	(7)	(10)
Other investments
Derivative [Line Items]
Asset Derivatives	32	40
Gross Amounts Offset in the Statement of Financial Position, assets	9	37
Derivative assets	12	12
Derivative, Collateral, Obligation to Return Cash	(11)	9
Financial Collateral Pledged	1	1
Net Amount, assets	22	2
Derivative, Collateral, Obligation to Return Cash	$ 11	$ (9)