FINANCIAL INSTRUMENTS - Summary of Characteristics of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	$ 81,850,712	$ 76,764,064
Liabilities	70,481,286	63,568,739
Agency mortgage-backed securities, recognized through other comprehensive income
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	34,528,515	59,939,383
Agency mortgage-backed securities, recognized through earnings
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	27,746,380	586,222
Residential credit risk transfer securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	997,557	936,228
Non-agency mortgage-backed securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	1,991,146	1,663,336
Commercial real estate debt investments - CMBS
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	508,406	521,440
Commercial real estate debt investments - credit risk transfer securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	17,903	9,065
Total loans, net
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	1,809,832	4,242,043
Residential mortgage loans
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	1,809,832	2,272,072
Residential mortgage loan warehouse facility
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	0	980
Corporate debt, held for investment
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	0	1,968,991
Total assets transferred or pledged to securitization vehicles
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	9,121,912	6,086,308
Interest in net servicing cash flows
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	0	69,316
Agency mortgage-backed securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	0	589,873
Residential mortgage loans
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	9,121,912	5,496,435
Repurchase agreements
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Liabilities	59,512,597	54,769,643
Other secured financing
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Liabilities	250,000	903,255
Debt issued by securitization vehicles
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Liabilities	7,744,160	5,155,633
Participations issued
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Liabilities	800,849	1,049,066
Available-For-Sale Securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	$ 65,789,907	$ 63,655,674