Stockholders' Equity - AOCI and Noncontrolling Interest (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Change in accumulated other comprehensive income (loss) rollforward
Balances	$ 10,916.0
Balances	11,185.5
Change in redeemable noncontrolling interest rollforward
Redeemable noncontrolling interest, balance at beginning of period	248.9	$ 262.0
Net income (loss) attributable to redeemable noncontrolling interest	(2.0)	4.5
Redeemable noncontrolling interest of deconsolidated entities	(90.0)	(2.4)
Contributions from redeemable noncontrolling interest	226.2	19.0
Distributions to redeemable noncontrolling interest	(14.2)	(8.4)
Purchase of subsidiary shares from redeemable noncontrolling interest		(1.6)
Change in redemption value of redeemable noncontrolling interest	2.1	(0.6)
Other comprehensive income (loss) attributable to redeemable noncontrolling interest	(0.2)	0.2
Redeemable noncontrolling interest, balance at end of period	370.8	272.7
Accumulated other comprehensive income (loss)
Change in accumulated other comprehensive income (loss) rollforward
Balances	(5,345.3)	(6,879.0)
Other comprehensive income (loss) during the period, net of adjustments	51.9	614.7
Amounts reclassified to accumulated other comprehensive income (loss)	37.3	63.0
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	89.2	677.7
Balances	(5,256.1)	(6,201.3)
Net unrealized gains (losses) on available-for-sale securities
Change in accumulated other comprehensive income (loss) rollforward
Balances	(4,014.8)	(5,857.9)
Other comprehensive income (loss) during the period, net of adjustments	(393.1)	1,016.0
Amounts reclassified to accumulated other comprehensive income (loss)	34.5	62.1
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	(358.6)	1,078.1
Balances	(4,373.4)	(4,779.8)
Net unrealized gains (losses) on available-for-sale debt securities with allowance for credit losses	(2.5)	0.6
Net unrealized gains (losses) on derivative instruments
Change in accumulated other comprehensive income (loss) rollforward
Balances	(2.1)	39.7
Other comprehensive income (loss) during the period, net of adjustments	18.2	2.9
Amounts reclassified to accumulated other comprehensive income (loss)	(0.7)	(2.9)
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	17.5
Balances	15.4	39.7
Liability for future policy benefits discount rate remeasurement gain (loss)
Change in accumulated other comprehensive income (loss) rollforward
Balances	428.2	740.9
Other comprehensive income (loss) during the period, net of adjustments	554.7	(540.9)
Amounts reclassified to accumulated other comprehensive income (loss)	0.0
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	554.7	(540.9)
Balances	982.9	200.0
Market risk benefit nonperformance risk remeasurement gain (loss)
Change in accumulated other comprehensive income (loss) rollforward
Balances	(6.9)	24.0
Other comprehensive income (loss) during the period, net of adjustments	(8.7)	6.0
Amounts reclassified to accumulated other comprehensive income (loss)	0.0
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	(8.7)	6.0
Balances	(15.6)	30.0
Foreign currency translation adjustment
Change in accumulated other comprehensive income (loss) rollforward
Balances	(1,498.0)	(1,571.6)
Other comprehensive income (loss) during the period, net of adjustments	(119.2)	130.7
Amounts reclassified to accumulated other comprehensive income (loss)	0.0
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	(119.2)	130.7
Balances	(1,617.2)	(1,440.9)
Unrecognized postretirement benefit obligations
Change in accumulated other comprehensive income (loss) rollforward
Balances	(251.7)	(254.1)
Other comprehensive income (loss) during the period, net of adjustments	0.0
Amounts reclassified to accumulated other comprehensive income (loss)	3.5	3.8
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	3.5	3.8
Balances	$ (248.2)	$ (250.3)