FINANCIAL INSTRUMENTS - Summary of Characteristics of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	$ 86,832,017	$ 81,850,712	[1]
Liabilities	74,922,984	70,481,286	[1]
Total securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	69,238,185	65,789,907
Agency mortgage-backed securities, recognized through comprehensive income
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	30,891,678	34,528,515
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	34,731,856	27,746,380
Residential credit risk transfer securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	1,085,384	997,557
Non-agency mortgage-backed securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	2,028,656	1,991,146
Commercial real estate debt investments - CMBS
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	482,780	508,406
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	17,831	17,903
Total loans, net
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	1,642,822	1,809,832
Residential mortgage loans
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	1,642,822	1,809,832
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	10,277,588	9,121,912
Residential mortgage loans
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Assets	10,277,588	9,121,912
Repurchase agreements
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Liabilities	60,993,018	59,512,597
Other secured financing
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Liabilities	250,000	250,000
Debt issued by securitization vehicles
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Liabilities	8,805,911	7,744,160
Participations issued
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Liabilities	$ 673,431	$ 800,849

[1] (1)Derived from the audited consolidated financial statements at December 31, 2022.