FAIR VALUE MEASUREMENTS - Carrying Values and Fair Values of Financial Assets Recorded at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2022		Dec. 31, 2021		Jun. 30, 2021	Dec. 31, 2020
Assets
Excess MSRs	$ 337,050		$ 344,947
Mortgage servicing rights, at fair value	8,626,409		6,858,803
Real estate and other securities	7,988,802		9,396,539
Residential mortgage loans, held-for-sale	5,410,989		11,347,845
Residential mortgage loans, held-for-sale, at fair value	5,293,936		11,214,924
Residential mortgage loans subject to repurchase	1,758,509	[1]	1,787,314	[1]	$ 1,308,242
Cash, cash equivalents and restricted cash	1,944,808		1,528,442		$ 1,194,743	$ 1,080,473
Derivative assets	194,507		138,173
Liabilities
Residential mortgage loan repurchase liability	1,800,000
Derivative liabilities	57,224		34,583
Recurring Basis
Assets
Excess MSRs, principal balance	73,121,546
MSRs and MSR financing receivables, principal balance	548,095,165
Servicer advance investments, principal balance	341,328
Real estate and other securities, principal balance	25,301,502
Residential mortgage loans, held-for-sale, principal balance	131,937
Residential mortgage loans, held-for-sale, at fair value, principal balance	5,388,033
Residential mortgage loans, held-for-investment, at fair value, principal balance	576,750
Residential mortgage loans, subject to repurchase, principal balance	1,758,509
Consumer loans, principal balance	380,603
Mortgage loans receivable, principal balance	1,756,079
Note receivable, principal balance	61,785
Loans receivable, principal balance	164,321
Cash, cash equivalents and restricted cash	1,944,808
Derivative assets, principal balance	34,903,771
Liabilities
Secured financing agreements, principal balance	13,969,519
Secured notes and bonds payable, principal amount	9,370,942
Unsecured senior notes, net of issuance costs, principal balance	544,167
Residential mortgage loan repurchase liability, principal balance	1,758,509
Derivative liabilities, principal amount	4,487,083
Recurring Basis | Mortgage Loans Receivable Securitization
Liabilities
Fair value, measurement with unobservable inputs reconciliation, recurring basis, asset value	40,000
Recurring Basis | Asset Backed Securities Issued
Liabilities
Fair value, measurement with unobservable inputs reconciliation, recurring basis, liability value	698,100
Recurring Basis | Level 3
Liabilities
Fair value, measurement with unobservable inputs reconciliation, recurring basis, asset value	13,442,718		13,425,847
Recurring Basis | Level 3 | Asset Backed Securities Issued
Liabilities
Fair value, measurement with unobservable inputs reconciliation, recurring basis, liability value	380,662		$ 511,107
Recurring Basis | Carrying Value
Assets
Excess MSRs	337,050
Mortgage servicing rights, at fair value	8,626,409
Servicer advance investments	379,901
Real estate and other securities	7,988,802
Residential mortgage loans, held-for-sale	117,053
Residential mortgage loans, held-for-sale, at fair value	5,293,937
Residential mortgage loans, held-for-investment, at fair value	510,744
Residential mortgage loans subject to repurchase	1,758,509
Consumer loans	423,735
Mortgage loans receivable	1,756,079
Notes receivable	52,692
Loans receivable	164,901
Cash, cash equivalents and restricted cash	1,944,808
Other assets	28,965
Derivative assets	194,507
Assets, fair value	29,578,092
Liabilities
Secured financing agreements	13,967,234
Secured notes and bonds payable	9,322,026
Notes Payable, Fair Value Disclosure	544,167
Residential mortgage loan repurchase liability	1,758,509
Derivative liabilities	57,224
Liabilities, fair value	25,649,160
Recurring Basis | Fair Value
Assets
Excess MSRs	337,050
Mortgage servicing rights, at fair value	8,626,409
Servicer advance investments	379,901
Real estate and other securities	7,988,802
Residential mortgage loans, held-for-sale	118,299
Residential mortgage loans, held-for-sale, at fair value	5,293,937
Residential mortgage loans, held-for-investment, at fair value	510,744
Residential mortgage loans subject to repurchase	1,758,509
Consumer loans	423,735
Mortgage loans receivable	1,756,079
Notes receivable	52,692
Loans receivable	164,901
Cash, cash equivalents and restricted cash	1,944,808
Other assets	28,965
Derivative assets	194,507
Assets, fair value	29,579,338
Liabilities
Secured financing agreements	13,967,234
Secured notes and bonds payable	9,521,247
Notes Payable, Fair Value Disclosure	478,841
Residential mortgage loan repurchase liability	1,758,509
Derivative liabilities	57,224
Liabilities, fair value	25,783,055
Recurring Basis | Fair Value | Level 1
Assets
Excess MSRs	0
Mortgage servicing rights, at fair value	0
Servicer advance investments	0
Real estate and other securities	0
Residential mortgage loans, held-for-sale	0
Residential mortgage loans, held-for-sale, at fair value	0
Residential mortgage loans, held-for-investment, at fair value	0
Residential mortgage loans subject to repurchase	0
Consumer loans	0
Mortgage loans receivable	0
Notes receivable	0
Loans receivable	0
Cash, cash equivalents and restricted cash	1,944,808
Other assets	1,754
Derivative assets	0
Assets, fair value	1,946,562
Liabilities
Secured financing agreements	0
Secured notes and bonds payable	0
Notes Payable, Fair Value Disclosure	0
Residential mortgage loan repurchase liability	0
Derivative liabilities	0
Liabilities, fair value	0
Recurring Basis | Fair Value | Level 2
Assets
Excess MSRs	0
Mortgage servicing rights, at fair value	0
Servicer advance investments	0
Real estate and other securities	7,064,068
Residential mortgage loans, held-for-sale	0
Residential mortgage loans, held-for-sale, at fair value	4,736,171
Residential mortgage loans, held-for-investment, at fair value	0
Residential mortgage loans subject to repurchase	1,758,509
Consumer loans	0
Mortgage loans receivable	352,867
Notes receivable	0
Loans receivable	0
Cash, cash equivalents and restricted cash	0
Other assets	0
Derivative assets	120,723
Assets, fair value	14,032,338
Liabilities
Secured financing agreements	13,967,234
Secured notes and bonds payable	1,074,062
Notes Payable, Fair Value Disclosure	0
Residential mortgage loan repurchase liability	1,758,509
Derivative liabilities	45,014
Liabilities, fair value	16,844,819
Recurring Basis | Fair Value | Level 3
Assets
Excess MSRs	337,050
Mortgage servicing rights, at fair value	8,626,409
Servicer advance investments	379,901
Real estate and other securities	924,734
Residential mortgage loans, held-for-sale	118,299
Residential mortgage loans, held-for-sale, at fair value	557,766
Residential mortgage loans, held-for-investment, at fair value	510,744
Residential mortgage loans subject to repurchase	0
Consumer loans	423,735
Mortgage loans receivable	1,403,212
Notes receivable	52,692
Loans receivable	164,901
Cash, cash equivalents and restricted cash	0
Other assets	27,211
Derivative assets	73,784
Assets, fair value	13,600,438
Liabilities
Secured financing agreements	0
Secured notes and bonds payable	8,447,185
Notes Payable, Fair Value Disclosure	478,841
Residential mortgage loan repurchase liability	0
Derivative liabilities	12,210
Liabilities, fair value	8,938,236
Recurring Basis | Fair Value | Fair Value Measured at Net Asset Value Per Share
Assets
Other assets	$ 28,500

[1] See Note 5 for details.