Consolidated Statements of Financial Position (Parenthetical) - USD ($) shares in Millions, $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fixed maturities, available-for-sale	$ 70,106.2	$ 60,108.5
Equity securities	1,879.4	1,843.7
Real estate	1,714.8	1,729.7
Other investments	4,690.2	4,310.3
Other investments measured at fair value under fair value option	22.8	23.6
Separate account assets	165,468.0	144,987.9
Contractholder funds	41,367.5	39,699.7
Long-term debt	3,734.1	3,259.6
Separate account liabilities	165,468.0	144,987.9
Other liabilities	6,863.7	5,661.9
Redeemable noncontrolling interest	$ 264.9	$ 391.2
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)	479.3	476.7
Common stock, outstanding (in shares)	276.6	279.5
Treasury stock (in shares)	202.7	197.2
Aggregate consolidated variable interest entities
Fixed maturities, available-for-sale	$ 99.4	$ 94.5
Equity securities	810.9	774.8
Real estate	457.6	364.0
Other investments	263.7	457.9
Separate account assets	39,130.3	37,183.3
Contractholder funds	394.6	396.0
Long-term debt	64.2	58.4
Separate account liabilities	39,130.3	37,183.3
Other liabilities	124.4	104.9
Redeemable noncontrolling interest	$ 215.4	$ 325.7