Stockholders' Equity - AOCI and Noncontrolling Interest (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Change in accumulated other comprehensive income (loss) rollforward
Balances	$ 9,976.7
Adjustment for reinsurance		$ 114.5
Balances	10,916.0	9,976.7
Change in redeemable noncontrolling interest rollforward
Redeemable noncontrolling interest, balance at beginning of period	262.0	332.5	$ 255.6
Net income (loss) attributable to redeemable noncontrolling interest	23.7	(25.8)	17.5
Redeemable noncontrolling interest of deconsolidated entities	(3.0)	(2.8)	(37.4)
Contributions from redeemable noncontrolling interest	43.3	67.3	166.8
Distributions to redeemable noncontrolling interest	(75.0)	(108.9)	(66.8)
Purchase of subsidiary shares from redeemable noncontrolling interest	(1.6)	(1.1)	(6.1)
Change in redemption value of redeemable noncontrolling interest	(1.1)	(0.2)	3.1
Stock-based compensation attributable to redeemable noncontrolling interest	0.1	0.1
Other comprehensive income (loss) attributable to redeemable noncontrolling interest	0.5	0.9	(0.2)
Redeemable noncontrolling interest, balance at end of period	248.9	262.0	332.5
Accumulated other comprehensive income (loss)
Change in accumulated other comprehensive income (loss) rollforward
Balances	(6,879.0)	(2,084.1)	2,383.1
Other comprehensive income (loss) during the period, net of adjustments	1,244.8	(5,225.6)	609.5
Amounts reclassified to accumulated other comprehensive income (loss)	288.9	316.2	51.3
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	1,533.7	(4,909.4)	660.8
Adjustment for reinsurance		114.5
Balances	(5,345.3)	(6,879.0)	(2,084.1)
Accumulated other comprehensive income (loss) | ASU 2016-13 - CECL | Effects of implementation of accounting change
Change in accumulated other comprehensive income (loss) rollforward
Balances		(5,128.0)
Balances			(5,128.0)
Net unrealized gains (losses) on available-for-sale securities
Change in accumulated other comprehensive income (loss) rollforward
Balances	(5,857.9)	3,880.4	4,138.3
Other comprehensive income (loss) during the period, net of adjustments	1,565.5	(10,157.9)	(2,099.6)
Amounts reclassified to accumulated other comprehensive income (loss)	277.6	311.3	14.3
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	1,843.1	(9,846.6)	(2,085.3)
Adjustment for reinsurance		108.3
Balances	(4,014.8)	(5,857.9)	3,880.4
Net unrealized gains (losses) on available-for-sale debt securities with allowance for credit losses	(4.3)	0.3	(2.1)
Net unrealized gains (losses) on available-for-sale securities | ASU 2016-13 - CECL | Effects of implementation of accounting change
Change in accumulated other comprehensive income (loss) rollforward
Balances		1,827.4
Balances			1,827.4
Net unrealized gains (losses) on derivative instruments
Change in accumulated other comprehensive income (loss) rollforward
Balances	39.7	56.6	18.2
Other comprehensive income (loss) during the period, net of adjustments	(36.0)	(0.9)	53.5
Amounts reclassified to accumulated other comprehensive income (loss)	(5.8)	(22.2)	(20.1)
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	(41.8)	(23.1)	33.4
Adjustment for reinsurance		6.2
Balances	(2.1)	39.7	56.6
Net unrealized gains (losses) on derivative instruments | ASU 2016-13 - CECL | Effects of implementation of accounting change
Change in accumulated other comprehensive income (loss) rollforward
Balances		5.0
Balances			5.0
Liability for future policy benefits discount rate remeasurement gain (loss)
Change in accumulated other comprehensive income (loss) rollforward
Balances	740.9	(4,037.6)
Other comprehensive income (loss) during the period, net of adjustments	(312.7)	4,778.5	2,839.7
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	(312.7)	4,778.5	2,839.7
Balances	428.2	740.9	(4,037.6)
Liability for future policy benefits discount rate remeasurement gain (loss) | ASU 2016-13 - CECL | Effects of implementation of accounting change
Change in accumulated other comprehensive income (loss) rollforward
Balances		(6,877.3)
Balances			(6,877.3)
Market risk benefit nonperformance risk gain (loss)
Change in accumulated other comprehensive income (loss) rollforward
Balances	24.0	(90.1)
Other comprehensive income (loss) during the period, net of adjustments	(30.9)	114.1	(0.4)
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	(30.9)	114.1	(0.4)
Balances	(6.9)	24.0	(90.1)
Market risk benefit nonperformance risk gain (loss) | ASU 2016-13 - CECL | Effects of implementation of accounting change
Change in accumulated other comprehensive income (loss) rollforward
Balances		(89.7)
Balances			(89.7)
Foreign currency translation adjustment
Change in accumulated other comprehensive income (loss) rollforward
Balances	(1,571.6)	(1,548.7)	(1,312.9)
Other comprehensive income (loss) during the period, net of adjustments	73.0	(22.9)	(261.7)
Amounts reclassified to accumulated other comprehensive income (loss)	0.6		19.3
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	73.6	(22.9)	(242.4)
Balances	(1,498.0)	(1,571.6)	(1,548.7)
Foreign currency translation adjustment | ASU 2016-13 - CECL | Effects of implementation of accounting change
Change in accumulated other comprehensive income (loss) rollforward
Balances		6.6
Balances			6.6
Unrecognized postretirement benefit obligations
Change in accumulated other comprehensive income (loss) rollforward
Balances	(254.1)	(344.7)	(460.5)
Other comprehensive income (loss) during the period, net of adjustments	(14.1)	63.5	78.0
Amounts reclassified to accumulated other comprehensive income (loss)	16.5	27.1	37.8
Other comprehensive income (loss) attributable to Principal Financial Group, Inc.	2.4	90.6	115.8
Balances	$ (251.7)	$ (254.1)	$ (344.7)