Consolidated Statements Of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 592	$ 469	$ 309
Other comprehensive income, net of tax:
Net unrealized holding losses on investment securities	(2)	(74)	(23)
Reclassification of HTM securities to AFS securities	0	0	11
Reclassification to earnings for realized securities losses	0	0	86
Net unrealized gains (losses) on other noninterest-bearing investments	3	2	(3)
Net unrealized holding gains (losses) on derivative instruments	(3)	5	7
Reclassification adjustment for increase in interest income recognized in earnings on derivative instruments	(2)	(7)	(6)
Pension and postretirement	(12)	(7)	(1)
Effect of new tax rates from Tax Cuts and Jobs Act of 2017	25	0	0
Other comprehensive income, net of tax	(17)	(67)	73
Comprehensive income	$ 575	$ 402	$ 382