INVESTMENTS IN VARIABLE INTEREST ENTITIES - SCHEDULE OF VIEs (Details) - USD ($) $ in Millions	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019	Jan. 01, 2019
Amortized cost
Due in one year or less	$ 329.8		$ 282.2
Due after one year through five years	1,086.6		1,082.2
Due after five years through ten years	1,456.3		1,376.6
Due after ten years	11,189.8		10,908.6
Amortized cost	19,641.6		19,179.5
Estimated fair value
Due in one year or less	336.1		286.0
Due after one year through five years	1,133.9		1,130.8
Due after five years through ten years	1,561.1		1,481.7
Due after ten years	13,411.7		12,583.7
Total fixed maturities, available for sale	22,167.9	$ 21,293.1	$ 21,295.2	$ 18,443.7
Variable Interest Entity, Primary Beneficiary
Amortized cost
Due in one year or less	1.0
Due after one year through five years	771.5
Due after five years through ten years	447.2
Due after ten years	4.0
Amortized cost	1,223.7
Estimated fair value
Due in one year or less	0.4
Due after one year through five years	709.8
Due after five years through ten years	423.5
Due after ten years	3.7
Total fixed maturities, available for sale	$ 1,137.4