Consolidated Statements Of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income for the period	$ 66	$ 198	$ 80	$ 411
Other comprehensive income (loss), net of tax:
Net unrealized holding gains on investment securities	94	116	242	237
Net unrealized gains on other noninterest-bearing investments	(8)	0	(6)	(3)
Net unrealized holding gains on derivative instruments	7	30	76	39
Reclassification adjustment for (increase) decrease in interest income recognized in earnings on derivative instruments	(10)	1	(13)	2
Reclassification to earnings for termination of pension plan	13	0	13	0
Other comprehensive income	96	147	312	275
Comprehensive income	$ 162	$ 345	$ 392	$ 686