BUSINESS ACQUISITIONS - Schedule of Purchase Price Allocation (Details) - USD ($) $ in Millions					9 Months Ended	12 Months Ended
	Dec. 20, 2021	Aug. 23, 2021	Oct. 01, 2019	Sep. 03, 2019	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2019
Business Acquisition [Line Items]
Total Consideration							$ 1,239.7
Assets
Mortgage servicing rights, at fair value							387.2
Residential mortgage loans, held-for-sale, at fair value							627.4
Mortgage loans receivable, at fair value							0.0
Residential mortgage loans subject to repurchase							0.0
Cash and cash equivalents							1.8
Restricted cash							0.0
Servicer advance receivable							238.0
Intangible assets							22.2
Other assets							71.4
Total Assets Acquired							1,348.0
Liabilities
Secured financing agreements							0.0
Secured notes and bonds payable							0.0
Residential mortgage loans repurchase liability							0.0
Accrued expenses and other liabilities							63.9
Total Liabilities Assumed							63.9
Net Assets							1,284.1
Bargain purchase gain						$ 49.7	(44.4)
Trademarks/trade names | Maximum
Liabilities
Estimated Useful Life						5 years
Total Acquisitions
Business Acquisition [Line Items]
Total Consideration						$ 2,953.1
Assets
Mortgage servicing rights, at fair value						1,507.5
Residential mortgage loans, held-for-sale, at fair value						7,685.7
Mortgage loans receivable, at fair value						1,505.6
Residential mortgage loans subject to repurchase						666.8
Cash and cash equivalents						489.1
Restricted cash						30.6
Servicer advance receivable						108.3
Intangible assets						97.8
Other assets						624.2
Total Assets Acquired						12,715.6
Liabilities
Secured financing agreements						7,090.6
Secured notes and bonds payable						1,121.8
Residential mortgage loans repurchase liability						666.8
Accrued expenses and other liabilities						933.0
Total Liabilities Assumed						9,812.2
Net Assets						2,903.4
Caliber Home Loans Inc
Business Acquisition [Line Items]
Total Consideration					$ 1,318.5	1,318.5
Assets
Mortgage servicing rights, at fair value					1,507.5	1,507.5
Residential mortgage loans, held-for-sale, at fair value					7,685.7	7,685.7
Mortgage loans receivable, at fair value						0.0
Residential mortgage loans subject to repurchase					666.8	666.8
Cash and cash equivalents					472.7	472.7
Restricted cash					30.6	30.6
Servicer advance receivable					108.3	108.3
Intangible assets					41.0	41.0
Other assets					605.4	609.7
Total Assets Acquired					11,118.0	11,122.3
Liabilities
Secured financing agreements					7,090.6	7,090.6
Secured notes and bonds payable					1,121.8	1,121.8
Residential mortgage loans repurchase liability					666.8	666.8
Accrued expenses and other liabilities					917.0	918.6
Total Liabilities Assumed					9,796.2	9,797.8
Net Assets					$ 1,321.8	1,324.5
Bargain purchase gain						(6.0)
Finite-lived intangible assets, useful life		4 years 9 months 18 days
Caliber Home Loans Inc | Maximum
Liabilities
Finite-lived intangible assets, useful life		5 years
Caliber Home Loans Inc | Purchased technology
Liabilities
Estimated Useful Life		5 years
Caliber Home Loans Inc | Trademarks/trade names
Liabilities
Estimated Useful Life		1 year
Genesis
Business Acquisition [Line Items]
Total Consideration						1,634.6
Assets
Mortgage servicing rights, at fair value						0.0
Residential mortgage loans, held-for-sale, at fair value						0.0
Mortgage loans receivable, at fair value						1,505.6
Residential mortgage loans subject to repurchase						0.0
Cash and cash equivalents						16.4
Restricted cash						0.0
Servicer advance receivable						0.0
Intangible assets						56.8
Other assets						14.5
Total Assets Acquired						1,593.3
Liabilities
Secured financing agreements						0.0
Secured notes and bonds payable						0.0
Residential mortgage loans repurchase liability						0.0
Accrued expenses and other liabilities						14.4
Total Liabilities Assumed						14.4
Net Assets						1,578.9
Bargain purchase gain						$ 55.7
Finite-lived intangible assets, useful life	8 years 6 months
Genesis | Purchased technology
Liabilities
Estimated Useful Life	9 years
Genesis | Trademarks/trade names
Liabilities
Estimated Useful Life	5 years
Ditech
Business Acquisition [Line Items]
Total Consideration			$ 1,218.2				1,218.2
Assets
Mortgage servicing rights, at fair value							387.2
Residential mortgage loans, held-for-sale, at fair value							627.4
Mortgage loans receivable, at fair value							0.0
Residential mortgage loans subject to repurchase							0.0
Cash and cash equivalents							0.0
Restricted cash							0.0
Servicer advance receivable							238.0
Intangible assets							10.5
Other assets							64.8
Total Assets Acquired							1,327.9
Liabilities
Secured financing agreements							0.0
Secured notes and bonds payable							0.0
Residential mortgage loans repurchase liability							0.0
Accrued expenses and other liabilities							60.2
Total Liabilities Assumed							60.2
Net Assets							1,267.7
Bargain purchase gain							(49.5)
Ditech | Customer relationships and servicing contracts
Liabilities
Finite-lived intangible assets, useful life						3 years
Guardian
Business Acquisition [Line Items]
Total Consideration				$ 21.5			21.5
Assets
Mortgage servicing rights, at fair value							0.0
Residential mortgage loans, held-for-sale, at fair value							0.0
Mortgage loans receivable, at fair value							0.0
Residential mortgage loans subject to repurchase							0.0
Cash and cash equivalents							1.8
Restricted cash							0.0
Servicer advance receivable							0.0
Intangible assets							11.7
Other assets							6.6
Total Assets Acquired							20.1
Liabilities
Secured financing agreements							0.0
Secured notes and bonds payable							0.0
Residential mortgage loans repurchase liability							0.0
Accrued expenses and other liabilities							3.7
Total Liabilities Assumed							3.7
Net Assets							16.4
Bargain purchase gain							$ 5.1
Guardian | Customer relationships and trade names
Liabilities
Finite-lived intangible assets, useful life						7 years