Derivative Instruments and Hedging Activities - Offsetting Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Derivative liabilities
Derivative liabilities, gross amount	$ 1,651	$ 1,518
Derivative liabilities, offsetting financial instruments	(369)	(383)
Derivative liabilities, offsetting cash collateral	(310)	(356)
Total derivative liabilities	972	779
Derivative liabilities, securities collateral not netted	0	0
Net exposure	972	779
Repurchase agreements
Gross amounts	842	668
Repurchase agreements, securities sold, offset	0	0
Repurchase agreements, cash collateral pledged, offset	0	0
Net amounts as recognized	842	668
Repurchase agreements, securities collateral not netted	(842)	(668)
Net exposure	0	0
Derivative, collateral, obligation to return cash	562	862
Derivative, collateral, obligation to return securities	1	1
Derivative, collateral, right to reclaim cash	1,700	1,500
Securities sold under repurchase agreements, fair value of collateral	$ 859	$ 682