Stockholders' Equity - AOCI and Noncontrolling Interest (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Change in accumulated other comprehensive income (loss) rollforward
Balances				$ 16,069.4
Purchase of subsidiary shares from noncontrolling interest	[1]	$ (1.4)	$ (1.1)	(8.1)	$ (18.1)
Adjustment for reinsurance				131.8
Balances		9,446.2		9,446.2
Change in redeemable noncontrolling interest rollforward
Redeemable noncontrolling interest, balance at beginning of period		268.5	330.6	332.5	255.6
Net income (loss) attributable to redeemable noncontrolling interest		(4.6)	2.7	(38.0)	9.5
Redeemable noncontrolling interest of deconsolidated entities		(2.8)	(37.4)	(2.8)	(37.4)
Contributions from redeemable noncontrolling interest		17.2	60.2	48.2	148.2
Distributions to redeemable noncontrolling interest		(22.7)	(11.7)	(84.1)	(34.8)
Purchase of subsidiary shares from redeemable noncontrolling interest		(1.1)	(0.7)	(1.1)	(6.1)
Change in redemption value of redeemable noncontrolling interest		(0.5)		(0.1)	8.6
Other comprehensive income (loss) attributable to redeemable noncontrolling interest		1.1	(0.4)	0.5	(0.3)
Redeemable noncontrolling interest, balance at end of period		255.1	343.3	255.1	343.3
Accumulated other comprehensive income (loss)
Change in accumulated other comprehensive income (loss) rollforward
Balances		(5,630.1)	1,803.8	1,610.9	2,383.1
Other comprehensive income (loss) during the period, net of adjustments		(2,504.8)	(188.4)	(9,879.3)	(778.4)
Amounts reclassified to accumulated other comprehensive income (loss)		64.3	3.8	66.0	14.5
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.		(2,440.5)	(184.6)	(9,813.3)	(763.9)
Adjustment for reinsurance				131.8
Balances		(8,070.6)	1,619.2	(8,070.6)	1,619.2
Net unrealized gains (losses) on available-for-sale securities
Change in accumulated other comprehensive income (loss) rollforward
Balances		(3,649.7)	3,555.8	3,467.4	4,138.3
Other comprehensive income (loss) during the period, net of adjustments		(2,531.7)	(21.2)	(9,775.3)	(602.5)
Amounts reclassified to accumulated other comprehensive income (loss)		60.7	(2.4)	62.8	(3.6)
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.		(2,471.0)	(23.6)	(9,712.5)	(606.1)
Adjustment for reinsurance				124.4
Balances		(6,120.7)	3,532.2	(6,120.7)	3,532.2
Net unrealized gains (losses) on available-for-sale debt securities with allowance for credit losses		0.9	(16.2)	0.9	(16.2)
Net unrealized gains (losses) on derivative instruments
Change in accumulated other comprehensive income (loss) rollforward
Balances		31.5	29.9	51.8	18.2
Other comprehensive income (loss) during the period, net of adjustments		81.8	23.8	67.9	42.7
Amounts reclassified to accumulated other comprehensive income (loss)		(3.4)	(3.1)	(17.2)	(10.3)
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.		78.4	20.7	50.7	32.4
Adjustment for reinsurance				7.4
Balances		109.9	50.6	109.9	50.6
Foreign currency translation adjustment
Change in accumulated other comprehensive income (loss) rollforward
Balances		(1,682.2)	(1,333.3)	(1,563.6)	(1,312.9)
Other comprehensive income (loss) during the period, net of adjustments		(54.9)	(191.0)	(173.5)	(211.4)
Amounts reclassified to accumulated other comprehensive income (loss)		0.0		0.0
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.		(54.9)	(191.0)	(173.5)	(211.4)
Balances		(1,737.1)	(1,524.3)	(1,737.1)	(1,524.3)
Unrecognized postretirement benefit obligations
Change in accumulated other comprehensive income (loss) rollforward
Balances		(329.7)	(448.6)	(344.7)	(460.5)
Other comprehensive income (loss) during the period, net of adjustments				1.6	(7.2)
Amounts reclassified to accumulated other comprehensive income (loss)		7.0	9.3	20.4	28.4
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.		7.0	9.3	22.0	21.2
Balances		$ (322.7)	$ (439.3)	$ (322.7)	$ (439.3)

[1] Excludes amounts attributable to redeemable noncontrolling interest. See Note 11, Stockholders’ Equity, for further details.