Derivative Financial Instruments - Gross and net amounts for OTC derivatives (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Asset derivatives
Asset derivatives gross amount	$ 155	$ 130
Asset derivatives, gross liability	(5)	(6)
Derivative assets net amount on balance sheet	150	124
Liability derivatives
Liability derivatives gross amount	(509)	(281)
Liability derivatives, gross asset	32	12
Derivative liabilities net amount on balance sheet	(477)	(269)
OTC derivatives
Asset derivatives
Asset derivatives gross amount	55	25
Asset derivatives, gross liability	(37)	(18)
Derivative, collateral, right to reclaim cash	(15)	(5)
Derivative assets net amount on balance sheet	3	2
Derivative assets received under securities collateral	0	0
Derivative asset, fair value, amount offset against collateral	3	2
Liability derivatives
Liability derivatives gross amount	(7)	(12)
Liability derivatives, gross asset	37	18
Derivative liability offsets under cash collateral pledged	(32)	(12)
Derivative liabilities net amount on balance sheet	(2)	(6)
Derivative liabilities received under securities collateral	0	0
Derivative liability, fair value, amount offset against collateral	$ (2)	$ (6)