Segment Information - Reconciliation of Segment Operating Revenues and Earnings to Consolidated (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating Revenue And Profit (Loss) From Segments To Consolidated
Net realized capital gains (losses), net of related revenue adjustments	$ (381.5)	$ (164.0)	$ 195.3
Revenues from exited business	4,447.2
Total revenues	17,491.6	14,262.7	14,741.7
Pre-tax net realized capital gains (losses), as adjusted	(286.7)	(179.8)	63.6
Pre-tax income (loss) from exited business	4,260.5
Income (loss) before income taxes	6,060.1	2,083.6	1,693.5
Retirement and Income Solutions
Operating Revenue And Profit (Loss) From Segments To Consolidated
Inter-segment revenues	364.4	413.1	342.6
Principal Global Investors
Operating Revenue And Profit (Loss) From Segments To Consolidated
Inter-segment revenues	323.4	308.9	273.8
Operating Segments
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	13,475.0	14,458.2	14,579.9
Pre-tax operating earnings (losses)	2,065.3	2,261.4	1,636.9
Pre-tax income (loss) from exited business	4,260.5
Operating Segments | Retirement and Income Solutions
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	5,975.2	6,510.0	7,503.5
Pre-tax operating earnings (losses)	1,090.4	1,141.2	966.9
Operating Segments | Retirement and Income Solutions | Retirement and Income Solutions - Fee
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	2,253.9	2,322.7	2,149.8
Operating Segments | Retirement and Income Solutions | Retirement and Income Solutions - Spread
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	3,721.3	4,187.3	5,353.7
Operating Segments | Principal Global Investors
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	1,715.5	1,828.0	1,539.1
Pre-tax operating earnings (losses)	604.0	708.4	512.9
Operating Segments | Principal International
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	1,475.9	1,351.8	1,096.8
Pre-tax operating earnings (losses)	308.6	309.0	243.6
Operating Segments | U.S. Insurance Solutions
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	4,314.9	4,766.6	4,480.2
Pre-tax operating earnings (losses)	531.7	470.8	239.9
Operating Segments | U.S. Insurance Solutions | Specialty Benefits insurance
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	2,984.6	2,709.6	2,525.4
Operating Segments | U.S. Insurance Solutions | Individual Life insurance
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	1,330.9	2,057.2	1,955.0
Operating Segments | U.S. Insurance Solutions | Eliminations
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	(0.6)	(0.2)	(0.2)
Operating Segments | Corporate
Operating Revenue And Profit (Loss) From Segments To Consolidated
Operating revenues	(6.5)	1.8	(39.7)
Pre-tax operating earnings (losses)	(469.4)	(368.0)	(326.4)
Reconciling Items
Operating Revenue And Profit (Loss) From Segments To Consolidated
Net realized capital gains (losses), net of related revenue adjustments	(381.5)	(164.0)	195.3
Adjustments related to equity method investments	(49.1)	(31.5)	(33.5)
Pre-tax net realized capital gains (losses), as adjusted	(286.7)	(179.8)	63.6
Pre-tax income (loss) from exited business	956.5
Earnings adjustments related to equity method investments and noncontrolling interest	$ 21.0	$ 2.0	$ (7.0)