Goodwill and Mortgage Servicing Rights - Changes During Period (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Goodwill [Roll Forward]
Balance at beginning of period	$ 47,474	$ 47,499	$ 47,471	$ 47,507
Changes during the period from:
Other	3	(11)	6	(19)
Balance at end of period	$ 47,477	$ 47,488	$ 47,477	$ 47,488