Separate Account Balances - Principal Asset Management - Principal International (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Changes in separate account liabilities
Balance at beginning of period	$ 167,605.6
Balance at end of period	171,788.2	$ 167,605.6
Principal Asset Management | Principal International
Changes in separate account liabilities
Balance at beginning of period	34,724.8
Balance at end of period	32,550.6	34,724.8
Principal Asset Management | Principal International | Pension | Latin America
Changes in separate account liabilities
Balance at beginning of period	34,580.6	33,316.7
Premiums and deposits	798.1	3,628.6
Policy charges	(4.0)	(17.8)
Surrenders, withdrawals and benefit payments	(879.6)	(4,191.7)
Investment performance	1,733.5	2,733.7
Other	3.0	7.6
Foreign currency translation adjustment	(3,820.9)	(896.5)
Balance at end of period	32,410.7	34,580.6
Cash surrender value	32,410.7	34,580.6
Principal Asset Management | Principal International | Guaranteed pension | Asia
Changes in separate account liabilities
Balance at beginning of period	144.2	915.0
Premiums and deposits	4.0	217.2
Policy charges	(0.7)	(16.9)
Surrenders, withdrawals and benefit payments	(9.3)	(1,006.8)
Investment performance	2.1	37.7
Other	(0.1)	(0.3)
Foreign currency translation adjustment	(0.3)	(1.7)
Balance at end of period	139.9	144.2
Cash surrender value	$ 139.9	$ 144.2