Derivative Instruments and Hedging Activities (Long-term debt hedged items) (Details) - Fair Value Hedging - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Par value of hedged liabilities	$ (500,000,000)	$ (1,500,000,000)
Carrying amount of hedged liabilities	(537,000,000)	(1,510,000,000)
Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged liabilities	(37,000,000)	(10,000,000)
Par value of hedged assets	383,000,000	0
Carrying amount of hedged assets	362,000,000	0
Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged assets	$ (21,000,000)	$ 0