Accumulated Other Comprehensive (Loss) Income - Schedule of Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pretax	$ (1,164)	$ (967)
Income Taxes	284	232
Net of Income Taxes	(880)	(735)
Unrealized loss on securities available for sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pretax	(1,175)	(972)
Income Taxes	286	233
Net of Income Taxes	(889)	(739)
Unrealized loss on securities available for sale transferred to held to maturity
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pretax	(7)	(8)
Income Taxes	2	2
Net of Income Taxes	(5)	(6)
Defined benefit pension items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pretax	18	13
Income Taxes	(4)	(3)
Net of Income Taxes	$ 14	$ 10