Investment Securities - Realized Gains and Losses and OTTI Losses (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Securities gains and losses
Realized gains	$ 78,000,000	$ 58,000,000	$ 454,000,000	$ 137,000,000
Realized losses	0	(103,000,000)	(319,000,000)	(507,000,000)
OTTI losses	0	(1,000,000)	0	(1,000,000)
Net investment securities gains/(losses)	$ 78,000,000	$ (46,000,000)	135,000,000	(371,000,000)
Realized losses on securities that had previously been reported as an OTTI loss due to the intention to sell the securities				21,000,000
Credit-related losses recognized in income
Securities gains and losses
OTTI losses			$ 0	$ 0