Investment Securities - Realized Gains and Losses and OTTI Losses (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Securities gains and losses
Realized gains	$ 115,000,000	$ 9,000,000	$ 376,000,000	$ 79,000,000
Realized losses	(71,000,000)	(88,000,000)	(319,000,000)	(403,000,000)
OTTI losses	0	(1,000,000)	0	(1,000,000)
Net investment securities gains/(losses)	$ 44,000,000	$ (80,000,000)	57,000,000	(325,000,000)
Realized losses on securities that had previously been reported as an OTTI loss due to the intention to sell the securities				20,000,000
Credit-related losses recognized in income
Securities gains and losses
OTTI losses			$ 0	$ 0