Derivative Instruments and Hedging Activities - Offsetting Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Derivative liabilities
Derivative liabilities, gross amount	$ 1,518	$ 1,197
Derivative liabilities, offsetting financial instruments	(383)	(347)
Derivative liabilities, offsetting cash collateral	(356)	(176)
Total derivative liabilities	779	674
Derivative liabilities, securities collateral not netted	0	0
Net exposure	779	674
Repurchase agreements
Gross amounts	668	314
Repurchase agreements, securities sold, offset	0	0
Repurchase agreements, cash collateral pledged, offset	0	0
Net amounts as recognized	668	314
Repurchase agreements, securities collateral not netted	(668)	(314)
Net exposure	0	0
Derivative, collateral, obligation to return cash	862	347
Derivative, collateral, obligation to return securities	1	1
Derivative, collateral, right to reclaim cash	1,500	954
Securities sold under repurchase agreements, fair value of collateral	$ 682	$ 320