Condensed Consolidated Statements of Financial Position (Parenthetical) - USD ($) shares in Millions, $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Fixed maturities, available-for-sale	$ 76,494.1	$ 70,106.2
Equity securities	1,862.7	1,879.4
Real estate	1,781.8	1,714.8
Other investments	4,676.0	4,690.2
Other investments measured at fair value under fair value option	27.0	22.8
Separate account assets	160,737.3	165,468.0
Contractholder funds	42,947.1	41,367.5
Long-term debt	4,279.0	3,734.1
Separate account liabilities	160,737.3	165,468.0
Other liabilities	7,316.1	6,863.7
Redeemable noncontrolling interest	$ 278.5	$ 264.9
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	2,500.0	2,500.0
Common stock, issued (in shares)	481.7	479.3
Common stock, outstanding (in shares)	274.5	276.6
Treasury stock (in shares)	207.2	202.7
Aggregate consolidated variable interest entities
Fixed maturities, available-for-sale		$ 99.4
Equity securities	$ 844.8	810.9
Real estate	454.2	457.6
Other investments	318.8	263.7
Separate account assets	36,267.2	39,130.3
Contractholder funds	393.9	394.6
Long-term debt		64.2
Separate account liabilities	36,267.2	39,130.3
Other liabilities	35.3	124.4
Redeemable noncontrolling interest	$ 210.5	$ 215.4