Derivative Financial Instruments - Gross and net amounts for OTC derivatives (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Asset derivatives
Asset derivatives gross amount	$ 178	$ 218
Asset derivatives, gross liability	(2)	(12)
Derivative assets net amount on balance sheet	176	206
Liability derivatives
Liability derivatives gross amount	(580)	(657)
Liability derivatives, gross asset	24	2
Net amount on balance sheet	(556)	(655)
OTC derivatives
Asset derivatives
Asset derivatives gross amount	17	10
Asset derivatives, gross liability	(19)	(9)
Derivative, collateral, right to reclaim cash	2	0
Derivative assets net amount on balance sheet	0	1
Derivative assets received under securities collateral	0	0
Derivative asset, fair value, amount offset against collateral	0	1
Liability derivatives
Liability derivatives gross amount	(15)	(19)
Liability derivatives, gross asset	19	9
Derivative liability offsets under cash collateral pledged	(6)	9
Net amount on balance sheet	(2)	(1)
Derivative liabilities received under securities collateral	0	0
Derivative liability, fair value, amount offset against collateral	$ (2)	$ (1)