Nature of Operations and Significant Accounting Policies - Retirement and Income Solutions and Principal Asset Management - Principal International (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement and Income Solutions | Pension risk transfer
Present value of expected future policy benefit payments
Balance at beginning of period, Present value of expected future policy benefit payments	$ 21,211.4	$ 25,365.8	$ 25,863.7
Effect of changes in discount rate assumptions at beginning of period	1,799.6	(3,386.5)	(4,827.9)
Balance at beginning of period at original discount rate	23,011.0	21,979.3	21,035.8
Effect of actual variances from expected experience	(9.8)	(3.2)	(2.4)
Adjusted beginning of period balance at original discount rate	22,947.8	21,968.2	21,033.4
Interest accrual	749.5	935.7	916.7
Benefit payments	(1,471.6)	(1,841.7)	(1,772.5)
Issuances	1,747.7	1,948.8	1,801.7
Balance at end of period at original discount rate	23,973.4	23,011.0	21,979.3
Effect of changes in discount rate assumptions at end of period	2,618.2	1,799.6	(3,386.5)
Balance at end of period, Present value of expected future policy benefit payments	21,355.2	21,211.4	25,365.8
Retirement and Income Solutions | Individual fixed income annuities
Present value of expected future policy benefit payments
Balance at beginning of period, Present value of expected future policy benefit payments	5,019.4	6,535.0	7,145.8
Effect of changes in discount rate assumptions at beginning of period	439.0	(812.6)	(1,213.5)
Balance at beginning of period at original discount rate	5,458.4	5,722.4	5,932.3
Effect of actual variances from expected experience	(0.7)		(1.3)
Adjusted beginning of period balance at original discount rate	5,456.4	5,719.4	5,931.0
Interest accrual	165.3	229.7	240.5
Benefit payments	(378.5)	(520.4)	(532.0)
Issuances	31.2	29.7	82.9
Balance at end of period at original discount rate	5,274.4	5,458.4	5,722.4
Effect of changes in discount rate assumptions at end of period	612.5	439.0	(812.6)
Balance at end of period, Present value of expected future policy benefit payments	4,661.9	5,019.4	6,535.0
Principal Asset Management | Principal International | Latin America | Individual fixed income annuities
Present value of expected future policy benefit payments
Balance at beginning of period, Present value of expected future policy benefit payments	5,042.3	4,336.8	6,561.5
Effect of changes in discount rate assumptions at beginning of period	(754.6)	(478.5)	(2,096.0)
Balance at beginning of period at original discount rate	4,287.7	3,858.3	4,465.5
Effect of actual variances from expected experience	(0.1)	(4.7)	(4.9)
Adjusted beginning of period balance at original discount rate	4,287.6	3,853.6	4,460.6
Interest accrual	276.4	662.0	444.3
Benefit payments	(271.0)	(325.8)	(436.0)
Issuances	18.8	86.4	141.3
Foreign currency translation adjustment	(201.9)	11.5	(751.9)
Balance at end of period at original discount rate	4,109.9	4,287.7	3,858.3
Effect of changes in discount rate assumptions at end of period	(115.2)	(754.6)	(478.5)
Balance at end of period, Present value of expected future policy benefit payments	$ 4,225.1	$ 5,042.3	$ 4,336.8