Fair Value Measurements - Fair Value Inputs (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	$ 6,577,100,000		$ 6,577,100,000			$ 7,986,900,000
Equity securities	322,700,000		322,700,000			830,600,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	96,200,000	$ 14,600,000	119,800,000	$ 82,500,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	17,600,000	0	22,900,000	14,200,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	233,200,000	235,100,000	233,200,000	235,100,000	$ 191,300,000	251,400,000	$ 464,800,000	$ 449,200,000
Included in Condensed Consolidated Statement of Operations	(6,300,000)	1,200,000	(12,200,000)	1,200,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0	(211,700,000)	(5,700,000)	(212,300,000)
Included in Other Comprehensive Income (Loss)	(3,300,000)	4,600,000	(15,100,000)	5,000,000.0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0	0	0	(100,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(62,300,000)	(38,400,000)	(127,900,000)	(104,600,000)
Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	2,700,000	0	2,700,000	1,700,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0	0	1,700,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	2,500,000	1,100,000	2,500,000	1,100,000	1,700,000	1,500,000	3,400,000	0
Included in Condensed Consolidated Statement of Operations	0	300,000	0	300,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0		0	(2,600,000)
Included in Other Comprehensive Income (Loss)	0	0	200,000	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(1,900,000)	0	(1,900,000)	0
Collateralized Loan Obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		17,700,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		10,000,000.0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		0		0			27,800,000	0
Included in Condensed Consolidated Statement of Operations		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		(17,800,000)		(17,800,000)
Included in Other Comprehensive Income (Loss)		0		100,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		(10,000,000.0)		(10,000,000.0)
Redeemable Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0	2,000,000.0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	6,800,000	6,100,000	6,800,000	6,100,000	$ 6,900,000	6,100,000	$ 6,200,000	$ 6,200,000
Included in Condensed Consolidated Statement of Operations	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0	0	0
Included in Other Comprehensive Income (Loss)	(100,000)	(100,000)	(1,300,000)	(100,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0	$ 0	0	$ 0
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt at fair value	42,600,000		42,600,000			46,400,000
Total	7,044,400,000		7,044,400,000			8,863,900,000
Fair Value, Measurements, Recurring | Investments in Fixed Maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	6,679,100,000		6,679,100,000			7,986,900,000
Fair Value, Measurements, Recurring | U.S. Government and Government Agencies and Authorities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	526,800,000		526,800,000			637,400,000
Fair Value, Measurements, Recurring | States and Political Subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	1,552,100,000		1,552,100,000			1,890,100,000
Fair Value, Measurements, Recurring | Foreign Governments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	3,700,000		3,700,000			5,500,000
Fair Value, Measurements, Recurring | Bonds and Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	3,341,500,000		3,341,500,000			4,386,900,000
Fair Value, Measurements, Recurring | Redeemable Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	8,000,000.0		8,000,000.0			7,400,000
Fair Value, Measurements, Recurring | Collateralized Loan Obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	952,600,000		952,600,000			752,100,000
Fair Value, Measurements, Recurring | Other Mortgage- and Asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	294,400,000		294,400,000			307,500,000
Fair Value, Measurements, Recurring | Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	322,700,000		322,700,000			830,600,000
Fair Value, Measurements, Recurring | Exchange Traded Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	70,700,000		70,700,000			432,000,000.0
Fair Value, Measurements, Recurring | Limited Liability Companies and Limited Partnerships
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	208,500,000		208,500,000			325,000,000.0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt at fair value	0		0			0
Total	183,800,000		183,800,000			586,600,000
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Investments in Fixed Maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	112,000,000.0		112,000,000.0			132,800,000
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Government and Government Agencies and Authorities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	112,000,000.0		112,000,000.0			132,800,000
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | States and Political Subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0			0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign Governments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0			0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Bonds and Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0			0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Redeemable Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Redeemable Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value						0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Collateralized Loan Obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0			0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Mortgage- and Asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0			0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	71,800,000		71,800,000			453,800,000
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Exchange Traded Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	70,700,000		70,700,000			432,000,000.0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Limited Liability Companies and Limited Partnerships
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0		0			0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt at fair value	42,600,000		42,600,000			46,400,000
Total	6,418,900,000		6,418,900,000			7,700,900,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Investments in Fixed Maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	6,336,400,000		6,336,400,000			7,604,200,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. Government and Government Agencies and Authorities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	414,800,000		414,800,000			504,600,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | States and Political Subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	1,552,100,000		1,552,100,000			1,890,100,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Foreign Governments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	3,700,000		3,700,000			5,500,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Bonds and Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	3,122,800,000		3,122,800,000			4,150,100,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Redeemable Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	1,200,000		1,200,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Redeemable Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value						1,300,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Collateralized Loan Obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	952,600,000		952,600,000			752,100,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Other Mortgage- and Asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	289,200,000		289,200,000			300,500,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	39,900,000		39,900,000			50,300,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Exchange Traded Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0		0			0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Limited Liability Companies and Limited Partnerships
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0		0			0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt at fair value	0		0			0
Total	233,200,000		233,200,000			251,400,000
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Investments in Fixed Maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	230,700,000		230,700,000			249,900,000
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | U.S. Government and Government Agencies and Authorities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0			0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | States and Political Subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0			0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Foreign Governments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0			0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Bonds and Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	218,700,000		218,700,000			236,800,000
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Redeemable Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	6,800,000		6,800,000
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Redeemable Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value						6,100,000
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Collateralized Loan Obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0			0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Other Mortgage- and Asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	5,200,000		5,200,000			7,000,000.0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	2,500,000		2,500,000			1,500,000
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Exchange Traded Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0		0			0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Limited Liability Companies and Limited Partnerships
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0		0			0
Finance, Insurance and Real Estate | Fair Value, Measurements, Recurring | Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	29,800,000		29,800,000			34,200,000
Finance, Insurance and Real Estate | Fair Value, Measurements, Recurring | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	900,000		900,000			18,900,000
Finance, Insurance and Real Estate | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0		0			0
Finance, Insurance and Real Estate | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	900,000		900,000			18,900,000
Finance, Insurance and Real Estate | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	29,800,000		29,800,000			34,200,000
Finance, Insurance and Real Estate | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0		0			0
Finance, Insurance and Real Estate | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0		0			0
Finance, Insurance and Real Estate | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0		0			0
Other Industries | Fair Value, Measurements, Recurring | Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	11,700,000		11,700,000			17,600,000
Other Industries | Fair Value, Measurements, Recurring | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	1,100,000		1,100,000			2,900,000
Other Industries | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0		0			0
Other Industries | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	200,000		200,000			2,900,000
Other Industries | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	9,700,000		9,700,000			16,100,000
Other Industries | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	400,000		400,000			0
Other Industries | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	2,000,000.0		2,000,000.0			1,500,000
Other Industries | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	500,000		500,000			0
Measured at Net Asset Value | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt at fair value	0		0			0
Total	208,500,000		208,500,000			325,000,000.0
Measured at Net Asset Value | Fair Value, Measurements, Recurring | Investments in Fixed Maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0			0
Measured at Net Asset Value | Fair Value, Measurements, Recurring | U.S. Government and Government Agencies and Authorities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0			0
Measured at Net Asset Value | Fair Value, Measurements, Recurring | States and Political Subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0			0
Measured at Net Asset Value | Fair Value, Measurements, Recurring | Foreign Governments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0			0
Measured at Net Asset Value | Fair Value, Measurements, Recurring | Bonds and Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0			0
Measured at Net Asset Value | Fair Value, Measurements, Recurring | Redeemable Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0
Measured at Net Asset Value | Fair Value, Measurements, Recurring | Redeemable Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value						0
Measured at Net Asset Value | Fair Value, Measurements, Recurring | Collateralized Loan Obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0			0
Measured at Net Asset Value | Fair Value, Measurements, Recurring | Other Mortgage- and Asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities at fair value	0		0			0
Measured at Net Asset Value | Fair Value, Measurements, Recurring | Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	208,500,000		208,500,000			325,000,000.0
Measured at Net Asset Value | Fair Value, Measurements, Recurring | Exchange Traded Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0		0			0
Measured at Net Asset Value | Fair Value, Measurements, Recurring | Limited Liability Companies and Limited Partnerships
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	208,500,000		208,500,000			325,000,000.0
Measured at Net Asset Value | Finance, Insurance and Real Estate | Fair Value, Measurements, Recurring | Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0		0			0
Measured at Net Asset Value | Finance, Insurance and Real Estate | Fair Value, Measurements, Recurring | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0		0			0
Measured at Net Asset Value | Other Industries | Fair Value, Measurements, Recurring | Preferred Stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0		0			0
Measured at Net Asset Value | Other Industries | Fair Value, Measurements, Recurring | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	$ 0		$ 0			$ 0