Goodwill and Mortgage Servicing Rights - Goodwill Changes During Period (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Mar. 31, 2023
Goodwill [Roll Forward]
Balance at beginning of period	$ 52,380,000,000	$ 50,697,000,000	$ 51,662,000,000	$ 50,315,000,000
Changes during the period from:
Business combinations	166,000,000	882,000,000	853,000,000	1,352,000,000
Other	(54,000,000)	(118,000,000)	(23,000,000)	(206,000,000)
Balance at end of period	$ 52,492,000,000	$ 51,461,000,000	52,492,000,000	51,461,000,000
Business Acquisition [Line Items]
Goodwill impairment			$ 0	$ 0
CIFM
Business Acquisition [Line Items]
Percentage interest acquired					51.00%