Derivative Instruments and Hedging Activities - Offsetting Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Derivative liabilities
Derivative liabilities, gross amount	$ 875	$ 1,201
Derivative liabilities, offsetting financial instruments	(265)	(205)
Derivative liabilities, offsetting cash collateral	(156)	(82)
Total derivative liabilities	454	914
Derivative liabilities, securities collateral not netted	0	0
Net exposure	454	914
Repurchase agreements
Gross amounts	335	352
Repurchase agreements, securities sold, offset	0	0
Repurchase agreements, cash collateral pledged, offset	0	0
Net amounts as recognized	335	352
Repurchase agreements, securities collateral not netted	(335)	(352)
Net exposure	0	0
Derivative, collateral, obligation to return cash	440	925
Derivative, collateral, obligation to return securities	1	1
Derivative, collateral, right to reclaim cash	695	633
Securities sold under repurchase agreements, fair value of collateral	$ 342	$ 359