Derivative Financial Instruments and Off-balance sheet Financial Instruments - Gross and net amounts for OTC derivatives (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Asset derivatives
Asset derivatives gross amount	$ 124	$ 30
Asset derivatives, Gross liability	0	(2)
Total asset derivatives, Fair value, net	124	28
Liability derivatives
Liability derivatives gross amount	(492)	(228)
Liability derivatives, Gross asset	10	1
Derivative liabilities net amount on balance sheet	(482)	(227)
OTC derivatives
Asset derivatives
Asset derivatives gross amount	10	10
Asset derivatives, Gross liability	(10)	(3)
Derivative asset offsets under cash collateral received	0	(5)
Total asset derivatives, Fair value, net	0	2
Derivative assets pledged under securities collateral	0	0
Asset derivatives, net amount	0	2
Liability derivatives
Liability derivatives gross amount	(5)	(2)
Liability derivatives, Gross asset	10	3
Derivative liability offsets under cash collateral pledged	(7)	(1)
Derivative liabilities net amount on balance sheet	(2)	0
Derivative liabilities received under securities collateral	0	0
Liability derivatives, net amount	$ (2)	$ 0