Investments - Gross Unrealized Losses for Fixed Maturities (Details) $ in Millions	Dec. 31, 2022 USD ($) security	Dec. 31, 2021 USD ($) security
Gross Unrealized Losses for Fixed Maturities
Fixed maturities, Less than twelve months, Fair value	$ 45,651.0	$ 14,561.3
Fixed maturities, Less than twelve months, Gross unrealized losses	6,183.1	227.1
Fixed maturities, Greater than or equal to twelve months, Fair value	8,850.9	3,042.6
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	1,695.2	179.3
Fixed maturities, Total, Fair value	54,501.9	17,603.9
Fixed maturities, Total, Gross unrealized losses	7,878.3	406.4
U.S. government and agencies
Gross Unrealized Losses for Fixed Maturities
Fixed maturities, Less than twelve months, Fair value	1,528.3	129.3
Fixed maturities, Less than twelve months, Gross unrealized losses	209.4	3.4
Fixed maturities, Greater than or equal to twelve months, Fair value	181.5	482.9
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	41.8	34.0
Fixed maturities, Total, Fair value	1,709.8	612.2
Fixed maturities, Total, Gross unrealized losses	251.2	37.4
Non-U.S. governments
Gross Unrealized Losses for Fixed Maturities
Fixed maturities, Less than twelve months, Fair value	407.5	57.8
Fixed maturities, Less than twelve months, Gross unrealized losses	57.7	2.0
Fixed maturities, Greater than or equal to twelve months, Fair value	19.9
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	7.1
Fixed maturities, Total, Fair value	427.4	57.8
Fixed maturities, Total, Gross unrealized losses	64.8	2.0
States and political subdivisions
Gross Unrealized Losses for Fixed Maturities
Fixed maturities, Less than twelve months, Fair value	5,303.5	690.2
Fixed maturities, Less than twelve months, Gross unrealized losses	1,008.9	10.5
Fixed maturities, Greater than or equal to twelve months, Fair value	391.9	102.3
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	127.8	6.1
Fixed maturities, Total, Fair value	5,695.4	792.5
Fixed maturities, Total, Gross unrealized losses	1,136.7	16.6
Corporate debt securities
Gross Unrealized Losses for Fixed Maturities
Fixed maturities, Less than twelve months, Fair value	27,309.5	5,281.6
Fixed maturities, Less than twelve months, Gross unrealized losses	3,944.6	121.2
Fixed maturities, Greater than or equal to twelve months, Fair value	2,944.1	1,327.5
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	698.0	101.5
Fixed maturities, Total, Fair value	30,253.6	6,609.1
Fixed maturities, Total, Gross unrealized losses	4,642.6	222.7
Residential mortgage-backed pass-through securities
Gross Unrealized Losses for Fixed Maturities
Fixed maturities, Less than twelve months, Fair value	1,201.7	1,562.6
Fixed maturities, Less than twelve months, Gross unrealized losses	97.5	22.2
Fixed maturities, Greater than or equal to twelve months, Fair value	574.8	194.9
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	105.7	6.3
Fixed maturities, Total, Fair value	1,776.5	1,757.5
Fixed maturities, Total, Gross unrealized losses	203.2	28.5
Commercial mortgage-backed securities
Gross Unrealized Losses for Fixed Maturities
Fixed maturities, Less than twelve months, Fair value	3,648.5	1,297.4
Fixed maturities, Less than twelve months, Gross unrealized losses	484.0	15.6
Fixed maturities, Greater than or equal to twelve months, Fair value	1,124.8	299.6
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	222.5	15.7
Fixed maturities, Total, Fair value	4,773.3	1,597.0
Fixed maturities, Total, Gross unrealized losses	706.5	31.3
Collateralized debt obligations
Gross Unrealized Losses for Fixed Maturities
Fixed maturities, Less than twelve months, Fair value	2,832.2	1,592.5
Fixed maturities, Less than twelve months, Gross unrealized losses	89.0	2.8
Fixed maturities, Greater than or equal to twelve months, Fair value	1,330.1	424.4
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	54.7	6.7
Fixed maturities, Total, Fair value	4,162.3	2,016.9
Fixed maturities, Total, Gross unrealized losses	143.7	9.5
Other debt obligations
Gross Unrealized Losses for Fixed Maturities
Fixed maturities, Less than twelve months, Fair value	3,419.8	3,949.9
Fixed maturities, Less than twelve months, Gross unrealized losses	292.0	49.4
Fixed maturities, Greater than or equal to twelve months, Fair value	2,283.8	211.0
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	437.6	9.0
Fixed maturities, Total, Fair value	5,703.6	4,160.9
Fixed maturities, Total, Gross unrealized losses	729.6	58.4
Principal Life Insurance Company
Gross Unrealized Losses for Fixed Maturities
Fixed maturities, Less than twelve months, Fair value	44,857.0	13,052.3
Fixed maturities, Less than twelve months, Gross unrealized losses	6,096.3	150.9
Fixed maturities, Greater than or equal to twelve months, Fair value	8,496.1	2,740.3
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	1,645.1	137.1
Fixed maturities, Total, Fair value	53,353.1	15,792.6
Fixed maturities, Total, Gross unrealized losses	$ 7,741.4	$ 288.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure
Available-for-sale Securities in Unrealized Loss Positions, Qualitative Disclosure, Percent Investment Grade (as a percent)	94.00%	91.00%
Available-for-sale Securities in Unrealized Loss Positions, Qualitative Disclosure, Average Price (percent of carrying value to amortized cost)	87.00%	98.00%
Available-for-sale Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less Than Twelve Months | security	7,589	1,805
Available-for-sale Securities in Unrealized Loss Positions, Average Price, Less Than Twelve Months (percent of carrying value to amortized cost)	88.00%	99.00%
Available-for-sale Securities in Unrealized Loss Positions, Percent Investment Grade, Less Than Twelve Months (as a percent)	95.00%	90.00%
Available-for-sale Securities in Unrealized Loss Position, Aggregate Losses On Investment Grade Investments, Less Than Twelve Months	$ 5,920.4	$ 138.9
Available-for-sale Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Twelve Months or Longer | security	1,654	459
Available-for-sale Securities in Unrealized Loss Positions, Average Price, Twelve Months or Longer (percent of carrying value to amortized cost)	84.00%	95.00%
Principal Life Insurance Company | U.S. government and agencies
Gross Unrealized Losses for Fixed Maturities
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses		$ 30.9
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure
Available-for-sale Securities in Unrealized Loss Positions, Average Price, Twelve Months or Longer (percent of carrying value to amortized cost)		93.00%
Principal Life Insurance Company | States and political subdivisions
Gross Unrealized Losses for Fixed Maturities
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	$ 126.8
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure
Available-for-sale Securities in Unrealized Loss Positions, Average Price, Twelve Months or Longer (percent of carrying value to amortized cost)	75.00%
Principal Life Insurance Company | Corporate debt securities
Gross Unrealized Losses for Fixed Maturities
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	$ 654.9	$ 67.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure
Available-for-sale Securities in Unrealized Loss Positions, Average Price, Twelve Months or Longer (percent of carrying value to amortized cost)	80.00%	95.00%
Principal Life Insurance Company | Commercial mortgage-backed securities
Gross Unrealized Losses for Fixed Maturities
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	$ 220.9	$ 15.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure
Available-for-sale Securities in Unrealized Loss Positions, Average Price, Twelve Months or Longer (percent of carrying value to amortized cost)	83.00%	95.00%
Principal Life Insurance Company | Collateralized mortgage obligation security
Gross Unrealized Losses for Fixed Maturities
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses	$ 320.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure
Available-for-sale Securities in Unrealized Loss Positions, Average Price, Twelve Months or Longer (percent of carrying value to amortized cost)	81.00%
Principal Life Insurance Company | Collateralized debt obligations
Gross Unrealized Losses for Fixed Maturities
Fixed maturities, Greater than or equal to twelve months, Gross unrealized losses		$ 6.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure
Available-for-sale Securities in Unrealized Loss Positions, Average Price, Twelve Months or Longer (percent of carrying value to amortized cost)		98.00%