COMMERCIAL MORTGAGE LOANS - Schedule of Commercial Mortgage Loans Amortized Cost Basis by Origination Year (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Total Commercial Loans
Total commercial mortgage loans	$ 10,005,562	$ 9,379,401
Commercial Mortgage Loans
Amortized Cost
2020	1,462,919
2019	2,442,361
2018	1,576,927
2017	1,343,889
2016	943,491
Prior	2,458,139
Amortized cost	10,227,726	$ 9,384,284
Allowance for Credit Loss
2020	(20,903)
2019	(46,664)
2018	(54,999)
2017	(36,737)
2016	(25,105)
Prior	(37,756)
Allowance for credit losses	(222,164)
Total Commercial Loans
2020	1,442,016
2019	2,395,697
2018	1,521,928
2017	1,307,152
2016	918,386
Prior	2,420,383
Total commercial mortgage loans	10,005,562
Performing | Commercial Mortgage Loans
Amortized Cost
2020	1,462,919
2019	2,442,361
2018	1,576,927
2017	1,343,889
2016	943,491
Prior	2,457,291
Amortized cost	10,226,878
Non-performing | Commercial Mortgage Loans
Amortized Cost
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	848
Amortized cost	$ 848