Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 1,235	$ 743	$ 477
Net unrealized holding losses arising during the period	(69)	(81)	(70)
Less reclassification adjustment for net securities losses included in net income	(20)	0	0
Less net losses realized as a yield adjustment in interest on investment securities	0	(3)	(3)
Change in net unrealized losses before income taxes	(49)	(78)	(67)
Actuarial gain (loss) arising during the period	(191)	72	(134)
Prior service credit arising during the period	0	0	234
Amortization of actuarial net loss	61	51	46
Amortization of prior service (credit) cost	(27)	(27)	(7)
Change in defined benefit pension and other postretirement plans adjustment before income taxes	(157)	96	139
Total other comprehensive income (loss) before income taxes	(206)	18	72
(Benefit) provision for income taxes	(47)	(1)	26
Total other comprehensive (loss) income, net of tax	(159)	19	46
Comprehensive Income	$ 1,076	$ 762	$ 523