Derivative Instruments and Hedging Activities (Basis Adjustments for Hedged Items) (Details) - Fair Value Hedging - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Par value of hedged liabilities	$ (500,000,000)	$ (500,000,000)
Carrying amount of hedged liabilities	(514,000,000)	(537,000,000)
Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged liabilities	(14,000,000)	(37,000,000)
Par value of hedged assets	383,000,000	383,000,000
Carrying amount of hedged assets	339,000,000	362,000,000
Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged assets	$ (44,000,000)	$ (21,000,000)