Consolidated Statements of Financial Position (Parenthetical) - USD ($) shares in Millions, $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Fixed maturities, available-for-sale	$ 65,268.1	$ 60,108.5
Equity securities	1,895.2	1,843.7
Real estate	1,740.4	1,729.7
Other investments	4,667.0	4,310.3
Other investments measured at fair value under fair value option	24.5	23.6
Separate account assets	162,848.6	144,987.9
Contractholder funds	39,658.8	39,699.7
Long-term debt	3,762.4	3,259.6
Separate account liabilities	162,848.6	144,987.9
Other liabilities	5,981.9	5,661.9
Redeemable noncontrolling interest	$ 304.5	$ 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)	478.9	476.7
Common stock, outstanding (in shares)	278.6	279.5
Treasury stock (in shares)	200.3	197.2
Aggregate consolidated variable interest entities
Fixed maturities, available-for-sale	$ 97.9	$ 94.5
Equity securities	831.7	774.8
Real estate	384.8	364.0
Other investments	288.8	457.9
Separate account assets	40,957.2	37,183.3
Contractholder funds	397.1	396.0
Long-term debt	64.2	58.4
Separate account liabilities	40,957.2	37,183.3
Other liabilities	113.1	104.9
Redeemable noncontrolling interest	$ 194.9	$ 325.7