ALLOWANCE FOR RISK-SHARING OBLIGATIONS AND GUARANTY OBLIGATION - CECL Provision Impact (Details) $ in Millions	3 Months Ended												12 Months Ended
	Dec. 31, 2025 USD ($)	Sep. 30, 2025 USD ($)	Jun. 30, 2025 USD ($)	Mar. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)	Sep. 30, 2024 USD ($)	Jun. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Forecast-period loss rate	0.021	0.021	0.021	0.021	0.021	0.021	0.023	0.023	0.024	0.023	0.023	0.023
Reversion-period loss rate	0.012	0.012	0.012	0.012	0.012	0.012	0.013	0.013	0.015	0.015	0.015	0.015
Historical loss rate	0.003	0.003	0.003	0.003	0.003	0.003	0.003	0.003	0.006	0.006	0.006	0.006
CECL allowance	$ 25.0	$ 24.8	$ 24.6	$ 24.4	$ 24.2	$ 23.4	$ 24.9	$ 25.0	$ 31.6	$ 31.0	$ 28.9	$ 28.7
Provision (benefit) for CECL allowance	0.2	0.1	0.2	0.2	0.8	(1.5)	(0.1)	(6.6)	0.6	0.5	0.2	(11.0)	$ 0.7	$ (7.4)	$ (9.7)
Fannie Mae DUS Program
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
At-risk Fannie Mae servicing portfolio UPB	$ 67,500.0	$ 66,000.0	$ 64,700.0	$ 63,600.0	$ 62,900.0	$ 60,600.0	$ 59,500.0	$ 59,200.0	$ 58,500.0	$ 57,400.0	$ 55,700.0	$ 54,500.0