Segment Information - Reconciliation of Segment Operating Revenues and Earnings to Consolidated (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Operating Revenue And Profit (Loss) From Segments To Consolidated
Revenues from exited business	$ (547.6)
Total revenues	2,819.0	$ 3,095.5
Pre-tax income (loss) from exited business	(608.3)
Income (loss) before income taxes	(212.5)	378.4
Retirement and Income Solutions
Operating Revenue And Profit (Loss) From Segments To Consolidated
Inter-segment revenues	94.8	97.4
Principal Asset Management
Operating Revenue And Profit (Loss) From Segments To Consolidated
Inter-segment revenues	70.7	76.5
Operating Segments
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	3,439.6	3,268.5
Pre-tax operating earnings (losses)	440.8	469.0
Operating Segments | Retirement and Income Solutions
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	1,616.1	1,263.0
Pre-tax operating earnings (losses)	249.8	294.2
Operating Segments | Principal Asset Management
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	692.5	755.9
Pre-tax operating earnings (losses)	187.8	211.0
Operating Segments | Principal Asset Management | Principal International
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	305.1	327.2
Operating Segments | Principal Asset Management | Principal Global Investors
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	392.7	435.3
Operating Segments | Principal Asset Management | Eliminations
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	(5.3)	(6.6)
Operating Segments | Benefits and Protection
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	1,103.4	1,243.3
Pre-tax operating earnings (losses)	99.3	92.8
Operating Segments | Benefits and Protection | Specialty Benefits
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	782.2	717.7
Operating Segments | Benefits and Protection | Life Insurance
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	321.4	525.7
Operating Segments | Benefits and Protection | Eliminations
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	(0.2)	(0.1)
Operating Segments | Corporate
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	27.6	6.3
Pre-tax operating earnings (losses)	(96.1)	(129.0)
Reconciling Items
Operating Revenue And Profit (Loss) From Segments To Consolidated
Net realized capital gains (losses), net of related revenue adjustments	(39.2)	(146.4)
Revenues from exited business	(547.6)
Adjustments related to equity method investments	(22.6)	(18.5)
Market risk benefit derivative settlements	(11.2)	(8.1)
Pre-tax net realized capital gains (losses), as adjusted	(24.3)	(87.9)
Pre-tax income (loss) from exited business	(608.3)
Earnings adjustments related to equity method investments and noncontrolling interest	$ (20.7)	$ (2.7)