ACCOUNTING FOR DERIVATIVES - SCHEDULE PRE-TAX GAINS (LOSSES) RECOGNIZED IN NET INCOME FOR DERIVATIVE INSTRUMENTS (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Derivative [Line Items]
Gains (losses) on derivatives not designated as hedging instruments	$ (17.5)	$ 27.9	$ (7.5)	$ 56.6
Net investment income (loss) from policyholder and other special-purpose portfolios | Fixed index call options
Derivative [Line Items]
Gains (losses) on derivatives not designated as hedging instruments	22.5	13.4	65.2	7.8
Net realized gains (losses) | Embedded derivative | Coinsurance agreements
Derivative [Line Items]
Gains (losses) on derivatives not designated as hedging instruments	2.6	(1.5)	4.9	(4.2)
Insurance policy benefits | Embedded derivative | Fixed index annuities
Derivative [Line Items]
Gains (losses) on derivatives not designated as hedging instruments	$ (42.6)	$ 16.0	$ (77.6)	$ 53.0