Market Risk Benefits - Asset and Liability Position and Reconciliation (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Market Risk Benefits
Market risk benefit asset	$ 173.1	$ 109.2
Market risk benefit liability	112.5	207.4
Net asset (liability)	60.6	(98.2)
Retirement and Income Solutions \| Individual variable annuities
Market Risk Benefits
Market risk benefit asset	173.1	109.2
Market risk benefit liability	90.8	181.4
Net asset (liability)	82.3	(72.2)	$ (494.7)	$ (591.3)
Principal Asset Management \| Principal International \| Guaranteed pension \| Asia
Market Risk Benefits
Market risk benefit liability	21.7	26.0
Net asset (liability)	$ (21.7)	$ (26.0)	$ (35.1)	$ (53.3)

Amount, before effect of reinsurance and after accumulated increase (decrease) in instrument-specific credit risk, of contract or contract feature in long-duration contract issued by insurance entity that both protects contract holder from other-than-nominal capital market risk and exposes insurance entity to other-than-nominal capital market risk.

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