Goodwill and Mortgage Servicing Rights - Changes During Period (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Goodwill [Roll Forward]
Balance at beginning of period	$ 47,477	$ 47,488	$ 47,471	$ 47,507
Changes during the period from:
Business combinations	348	0	348	0
Other	(7)	(5)	(1)	(24)
Balance at end of period	$ 47,818	$ 47,483	$ 47,818	$ 47,483