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Derivative Financial Instruments and Hedging Activities - Summary of Derivatives (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025
Derivative [Line Items]
Notional balance	$ 7,315.2		$ 7,315.2		$ 5,034.0
Derivatives, at fair value - See Note 15	41.4		41.4		28.1
Derivative liability, notional amount	3,562.0		3,562.0		4,186.6
Derivative liability, fair value	(10.4)		(10.4)		(9.1)
Gains (losses) on derivatives	(36.8)	$ (3.4)	(44.1)	$ 5.3
Forward Sales Of Reverse Loans
Derivative [Line Items]
Derivative liability, notional amount	0.0		0.0		30.0
Derivative liability, fair value	0.0		0.0		(0.2)
Gains (losses) on derivatives	0.0	0.1	0.2	(0.5)
Forward loans IRLCs
Derivative [Line Items]
Notional balance	2,305.9		2,305.9		2,461.9
Derivatives, at fair value - See Note 15	17.3		17.3		16.5
Gains (losses) on derivatives	13.1	8.9	0.8	17.8
Reverse loans IRLCs
Derivative [Line Items]
Notional balance	0.4		0.4		18.6
Derivatives, at fair value - See Note 15	0.0		0.0		0.8
Gains (losses) on derivatives	(0.8)	(0.2)	(0.8)	0.8
TBA forward MBS trades
Derivative [Line Items]
Notional balance	2,277.9		2,277.9		1,913.5
Derivatives, at fair value - See Note 15	8.8		8.8		8.4
Derivative liability, notional amount	3,240.5		3,240.5		2,171.6
Derivative liability, fair value	(9.8)		(9.8)		(6.6)
Interest Rate Swap
Derivative [Line Items]
Notional balance	2,331.0		2,331.0		590.0
Derivatives, at fair value - See Note 15	14.9		14.9		1.9
Derivative liability, notional amount	321.5		321.5		1,935.0
Derivative liability, fair value	(0.6)		(0.6)		(1.8)
TBA Forward Pipelines Trades
Derivative [Line Items]
Gains (losses) on derivatives			12.9	(25.4)
Interest Rate Swap Futures And TBA Forward MBS Trades
Derivative [Line Items]
Gains (losses) on derivatives	(34.0)	(5.5)	(62.0)	15.3
Forward LHFS Trades
Derivative [Line Items]
Gains (losses) on derivatives	0.0	(1.1)	0.0	(2.8)
Interest rate option contracts
Derivative [Line Items]
Notional balance	400.0		400.0		50.0
Derivatives, at fair value - See Note 15	0.4		0.4		0.5
Derivative liability, notional amount	0.0		0.0		50.0
Derivative liability, fair value	0.0		0.0		$ (0.5)
Future
Derivative [Line Items]
Gains (losses) on derivatives	2.4	0.0	$ 4.8	$ 0.0
TRA Trades And Interest Rate Futures
Derivative [Line Items]
Gains (losses) on derivatives	$ (17.5)	$ (5.6)