Goodwill and Other Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Unamortizable intangible assets:
Indefinite-Lived Intangible Assets, Net Carrying Value	$ 379.0	$ 372.0
Amortizable intangible assets:
Gross Carrying Amount	3,881.0	3,737.0
Accumulated Amortization	(2,178.9)	(1,915.7)
Gross Carrying Amount	379.0	372.0
Intangible Assets, Gross (Excluding Goodwill)	4,260.0	4,109.0
Gross Carrying Amount, Total intangible assets	4,260.0	4,109.0
Management contracts
Unamortizable intangible assets:
Indefinite-Lived Intangible Assets, Net Carrying Value	62.0	60.0
Amortizable intangible assets:
Gross Carrying Amount	62.0	60.0
Trademark
Unamortizable intangible assets:
Indefinite-Lived Intangible Assets, Net Carrying Value	317.0	312.0
Amortizable intangible assets:
Gross Carrying Amount	317.0	312.0
Customer relationships
Amortizable intangible assets:
Gross Carrying Amount	1,727.0	1,637.0
Accumulated Amortization	(893.0)	(774.0)
Mortgage servicing rights
Amortizable intangible assets:
Gross Carrying Amount	1,055.0	1,030.0
Accumulated Amortization	(556.0)	(469.0)
Trademarks/Trade names
Amortizable intangible assets:
Gross Carrying Amount	315.0	305.0
Accumulated Amortization	(147.0)	(129.0)
Management contracts
Amortizable intangible assets:
Gross Carrying Amount	122.0	149.0
Accumulated Amortization	(121.0)	(146.0)
Covenant not to compete
Amortizable intangible assets:
Gross Carrying Amount	4.0	4.0
Accumulated Amortization	(1.0)	(1.0)
Other
Amortizable intangible assets:
Gross Carrying Amount	658.0	612.0
Accumulated Amortization	$ (461.0)	$ (397.0)