Fair Value Measurements - Fair Value of Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Financial Assets
Estimated Fair Value	$ 522,212
Corporate
Financial Assets
Estimated Fair Value	213,964
U.S. Treasury
Financial Assets
Estimated Fair Value	109,561
States and municipalities
Financial Assets
Estimated Fair Value	39,929
Foreign
Financial Assets
Estimated Fair Value	18,634
Asset-backed securities
Financial Assets
Estimated Fair Value	25,767
Mortgage-backed securities
Financial Assets
Estimated Fair Value	114,357
Fair Value, Recurring
Financial Assets
Total	533,792	$ 18,706
Liabilities, Fair Value Disclosure [Abstract]
Total		34,018
Fair Value, Recurring \| Corporate
Financial Assets
Estimated Fair Value	213,964
Fair Value, Recurring \| U.S. Treasury
Financial Assets
Estimated Fair Value	109,561
Fair Value, Recurring \| States and municipalities
Financial Assets
Estimated Fair Value	39,929
Fair Value, Recurring \| Foreign
Financial Assets
Estimated Fair Value	18,634	16,472
Fair Value, Recurring \| Asset-backed securities
Financial Assets
Estimated Fair Value	25,767
Fair Value, Recurring \| Mortgage-backed securities
Financial Assets
Estimated Fair Value	114,357
Fair Value, Recurring \| Common stocks
Financial Assets
Estimated Fair Value	11,580
Fair Value, Recurring \| Public Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		9,488
Fair Value, Recurring \| Private Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		476
Fair Value, Recurring \| Underwriter Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		53
Fair Value, Recurring \| OTM Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		3,981
Fair Value, Recurring \| PIPE Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		20,020
Fair Value, Recurring \| Investments:
Financial Assets
Investments:		2,234
Fair Value, Recurring \| Level 1
Financial Assets
Total	11,580	0
Liabilities, Fair Value Disclosure [Abstract]
Total		9,488
Fair Value, Recurring \| Level 1 \| Corporate
Financial Assets
Estimated Fair Value	0
Fair Value, Recurring \| Level 1 \| U.S. Treasury
Financial Assets
Estimated Fair Value	0
Fair Value, Recurring \| Level 1 \| States and municipalities
Financial Assets
Estimated Fair Value	0
Fair Value, Recurring \| Level 1 \| Foreign
Financial Assets
Estimated Fair Value	0	0
Fair Value, Recurring \| Level 1 \| Asset-backed securities
Financial Assets
Estimated Fair Value	0
Fair Value, Recurring \| Level 1 \| Mortgage-backed securities
Financial Assets
Estimated Fair Value	0
Fair Value, Recurring \| Level 1 \| Common stocks
Financial Assets
Estimated Fair Value	11,580
Fair Value, Recurring \| Level 1 \| Public Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		9,488
Fair Value, Recurring \| Level 1 \| Private Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		0
Fair Value, Recurring \| Level 1 \| Underwriter Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		0
Fair Value, Recurring \| Level 1 \| OTM Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		0
Fair Value, Recurring \| Level 1 \| PIPE Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		0
Fair Value, Recurring \| Level 1 \| Investments:
Financial Assets
Investments:		0
Fair Value, Recurring \| Level 2
Financial Assets
Total	522,212	18,706
Liabilities, Fair Value Disclosure [Abstract]
Total		0
Fair Value, Recurring \| Level 2 \| Corporate
Financial Assets
Estimated Fair Value	213,964
Fair Value, Recurring \| Level 2 \| U.S. Treasury
Financial Assets
Estimated Fair Value	109,561
Fair Value, Recurring \| Level 2 \| States and municipalities
Financial Assets
Estimated Fair Value	39,929
Fair Value, Recurring \| Level 2 \| Foreign
Financial Assets
Estimated Fair Value	18,634	16,472
Fair Value, Recurring \| Level 2 \| Asset-backed securities
Financial Assets
Estimated Fair Value	25,767
Fair Value, Recurring \| Level 2 \| Mortgage-backed securities
Financial Assets
Estimated Fair Value	114,357
Fair Value, Recurring \| Level 2 \| Common stocks
Financial Assets
Estimated Fair Value	0
Fair Value, Recurring \| Level 2 \| Public Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		0
Fair Value, Recurring \| Level 2 \| Private Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		0
Fair Value, Recurring \| Level 2 \| Underwriter Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		0
Fair Value, Recurring \| Level 2 \| OTM Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		0
Fair Value, Recurring \| Level 2 \| PIPE Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		0
Fair Value, Recurring \| Level 2 \| Investments:
Financial Assets
Investments:		2,234
Fair Value, Recurring \| Level 3
Financial Assets
Total	0	0
Liabilities, Fair Value Disclosure [Abstract]
Total		24,530
Fair Value, Recurring \| Level 3 \| Corporate
Financial Assets
Estimated Fair Value	0
Fair Value, Recurring \| Level 3 \| U.S. Treasury
Financial Assets
Estimated Fair Value	0
Fair Value, Recurring \| Level 3 \| States and municipalities
Financial Assets
Estimated Fair Value	0
Fair Value, Recurring \| Level 3 \| Foreign
Financial Assets
Estimated Fair Value	0	0
Fair Value, Recurring \| Level 3 \| Asset-backed securities
Financial Assets
Estimated Fair Value	0
Fair Value, Recurring \| Level 3 \| Mortgage-backed securities
Financial Assets
Estimated Fair Value	0
Fair Value, Recurring \| Level 3 \| Common stocks
Financial Assets
Estimated Fair Value	$ 0
Fair Value, Recurring \| Level 3 \| Public Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		0
Fair Value, Recurring \| Level 3 \| Private Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		476
Fair Value, Recurring \| Level 3 \| Underwriter Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		53
Fair Value, Recurring \| Level 3 \| OTM Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		3,981
Fair Value, Recurring \| Level 3 \| PIPE Warrants
Liabilities, Fair Value Disclosure [Abstract]
Fair Value		20,020
Fair Value, Recurring \| Level 3 \| Investments:
Financial Assets
Investments:		$ 0