STATEMENT OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Change in Net Unrealized Gain on Securities Before Adjustment, Tax Expense (Benefit)	$ (436.5)	$ 326.8
Change in Adjustment to Deferred Acquisition Costs and Reserves for Future Policy and Contract Benefits, Net of Reinsurance, Tax Expense (Benefit)	380.8	(245.5)
Change in Net Gain on Hedges, Tax Expense (Benefit)	6.6	(5.8)
Change in Foreign Currency Translation Adjustment, Tax Expense (Benefit)	(2.1)	(0.3)
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense	$ 1.9	$ 0.7