Goodwill and Mortgage Servicing Rights - Goodwill Changes During Period (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Goodwill [Roll Forward]
Balance at beginning of period	$ 49,243,000,000	$ 47,800,000,000	$ 49,248,000,000	$ 47,823,000,000	$ 47,823,000,000
Changes during the period from:
Other	13,000,000	11,000,000	8,000,000	(12,000,000)
Balance at end of period	$ 49,256,000,000	$ 47,811,000,000	49,256,000,000	$ 47,811,000,000	49,248,000,000
Goodwill impairment			$ 0		$ 0