Derivative Instruments and Hedging Activities - Offsetting Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Derivative liabilities
Derivative liabilities, gross amount	$ 1,265	$ 1,201
Derivative liabilities, offsetting financial instruments	(333)	(205)
Derivative liabilities, offsetting cash collateral	(45)	(82)
Total derivative liabilities	887	914
Derivative liabilities, securities collateral not netted	0	0
Net exposure	887	914
Repurchase agreements
Gross amounts	363	352
Repurchase agreements, securities sold, offset	0	0
Repurchase agreements, cash collateral pledged, offset	0	0
Net amounts as recognized	363	352
Repurchase agreements, securities collateral not netted	(363)	(352)
Net exposure	0	0
Derivative, collateral, obligation to return cash	891	925
Derivative, collateral, obligation to return securities	1	1
Derivative, collateral, right to reclaim cash	858	633
Securities sold under repurchase agreements, fair value of collateral	$ 371	$ 359