Summary of Significant Accounting Policies - Deferred Policy Acquisition Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Recorded asset at beginning of year	$ 104,225
Recorded asset at end of year	126,532	$ 104,225
Property and casualty business
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Recorded asset at beginning of year	104,225	91,446	$ 87,094
Underwriting costs deferred	267,298	225,854	207,784
Amortization of deferred policy acquisition costs	(244,991)	(213,075)	(203,432)
Recorded asset at end of year	$ 126,532	$ 104,225	$ 91,446