Segment Information - Income Tax Expense (Benefit) by Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Information: Income tax expense (benefit)
Income taxes (benefits)	$ 68.7	$ 1,189.5	$ 283.9
Operating Segments
Segment Information: Income tax expense (benefit)
Total segment income taxes from operating earnings	407.1	343.9	366.7
Reconciling Items
Segment Information: Income tax expense (benefit)
Tax benefit related to net realized capital losses, as adjusted	(22.0)	(56.6)	(35.7)
Tax expense (benefit) related to other after-tax adjustments	(238.1)	956.4
Certain adjustments related to equity method investments and noncontrolling interest	(78.3)	(54.2)	(47.1)
Retirement and Income Solutions | Operating Segments
Segment Information: Income tax expense (benefit)
Total segment income taxes from operating earnings	130.9	90.6	94.7
Principal Asset Management | Operating Segments
Segment Information: Income tax expense (benefit)
Total segment income taxes from operating earnings	220.7	213.3	272.2
Benefits and Protection | Operating Segments
Segment Information: Income tax expense (benefit)
Total segment income taxes from operating earnings	97.7	109.1	70.5
Corporate | Operating Segments
Segment Information: Income tax expense (benefit)
Total segment income taxes from operating earnings	$ (42.2)	$ (69.1)	$ (70.7)