Stockholders' Equity - AOCI and Noncontrolling Interest (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Change in accumulated other comprehensive income (loss) rollforward
Balances			$ 9,976.7
Adjustment for reinsurance				$ 114.6
Balances	$ 10,671.6		10,671.6
Change in redeemable noncontrolling interest rollforward
Redeemable noncontrolling interest, balance at beginning of period	266.7	$ 268.5	262.0	332.5
Net income (loss) attributable to redeemable noncontrolling interest	(2.8)	(4.6)	5.3	(38.0)
Redeemable noncontrolling interest of deconsolidated entities		(2.8)	(3.0)	(2.8)
Contributions from redeemable noncontrolling interest	8.3	17.2	31.6	48.2
Distributions to redeemable noncontrolling interest	(11.6)	(22.7)	(34.4)	(84.1)
Purchase of subsidiary shares from redeemable noncontrolling interest		(1.1)	(1.6)	(1.1)
Change in redemption value of redeemable noncontrolling interest	(0.8)	(0.5)	(0.7)	(0.1)
Stock-based compensation attributable to redeemable noncontrolling interest	0.1		0.1
Other comprehensive income (loss) attributable to redeemable noncontrolling interest	(0.4)	1.1	0.2	0.5
Redeemable noncontrolling interest, balance at end of period	259.5	255.1	259.5	255.1
Accumulated other comprehensive income (loss)
Change in accumulated other comprehensive income (loss) rollforward
Balances	(6,245.2)	(6,106.2)	(6,879.0)	(2,084.1)
Other comprehensive income (loss) during the period, net of adjustments	(623.0)	(1,339.3)	(139.1)	(5,477.7)
Amounts reclassified to accumulated other comprehensive income (loss)	27.3	64.3	177.2	66.0
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	(595.7)	(1,275.0)	38.1	(5,411.7)
Adjustment for reinsurance				114.6
Balances	(6,840.9)	(7,381.2)	(6,840.9)	(7,381.2)
Net unrealized gains (losses) on available-for-sale securities
Change in accumulated other comprehensive income (loss) rollforward
Balances	(5,322.2)	(3,984.2)	(5,857.9)	3,880.4
Other comprehensive income (loss) during the period, net of adjustments	(1,833.5)	(2,875.5)	(1,443.0)	(10,850.6)
Amounts reclassified to accumulated other comprehensive income (loss)	24.1	60.7	169.3	62.8
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	(1,809.4)	(2,814.8)	(1,273.7)	(10,787.8)
Adjustment for reinsurance				108.4
Balances	(7,131.6)	(6,799.0)	(7,131.6)	(6,799.0)
Net unrealized gains (losses) on available-for-sale debt securities with allowance for credit losses	(3.8)	0.9	(3.8)	0.9
Net unrealized gains (losses) on derivative instruments
Change in accumulated other comprehensive income (loss) rollforward
Balances	33.9	33.1	39.7	56.6
Other comprehensive income (loss) during the period, net of adjustments	(13.9)	82.6	(15.8)	66.7
Amounts reclassified to accumulated other comprehensive income (loss)	(1.0)	(3.4)	(4.9)	(17.2)
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	(14.9)	79.2	(20.7)	49.5
Adjustment for reinsurance				6.2
Balances	19.0	112.3	19.0	112.3
Liability for future policy benefits discount rate remeasurement gain (loss)
Change in accumulated other comprehensive income (loss) rollforward
Balances	709.2	(209.2)	740.9	(4,037.6)
Other comprehensive income (loss) during the period, net of adjustments	1,373.6	1,511.6	1,341.9	5,340.0
Amounts reclassified to accumulated other comprehensive income (loss)	0.0		0.0
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	1,373.6	1,511.6	1,341.9	5,340.0
Balances	2,082.8	1,302.4	2,082.8	1,302.4
Market risk benefit nonperformance risk gain (loss)
Change in accumulated other comprehensive income (loss) rollforward
Balances	24.4	43.8	24.0	(90.1)
Other comprehensive income (loss) during the period, net of adjustments	(17.9)	(2.9)	(17.5)	131.0
Amounts reclassified to accumulated other comprehensive income (loss)	0.0		0.0
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	(17.9)	(2.9)	(17.5)	131.0
Balances	6.5	40.9	6.5	40.9
Foreign currency translation adjustment
Change in accumulated other comprehensive income (loss) rollforward
Balances	(1,431.1)	(1,660.0)	(1,571.6)	(1,548.7)
Other comprehensive income (loss) during the period, net of adjustments	(131.4)	(55.1)	8.8	(166.4)
Amounts reclassified to accumulated other comprehensive income (loss)	0.1		0.4
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	(131.3)	(55.1)	9.2	(166.4)
Balances	(1,562.4)	(1,715.1)	(1,562.4)	(1,715.1)
Unrecognized postretirement benefit obligations
Change in accumulated other comprehensive income (loss) rollforward
Balances	(259.4)	(329.7)	(254.1)	(344.7)
Other comprehensive income (loss) during the period, net of adjustments	0.1		(13.5)	1.6
Amounts reclassified to accumulated other comprehensive income (loss)	4.1	7.0	12.4	20.4
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	4.2	7.0	(1.1)	22.0
Balances	$ (255.2)	$ (322.7)	$ (255.2)	$ (322.7)