Schedule II - Condensed Financial Information of Registrant (Parent Company) - Balance Sheet Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Condensed Balance Sheet Statements Captions [Line Items]
Available-for-sale, amortized cost	$ 3,054,391	$ 2,945,273
Available-for-sale, allowance for credit losses	306	339	$ 441
Property and equipment, accumulated depreciation	$ 74,279	$ 68,633
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	68,570,261	68,399,966
Common stock, shares outstanding (in shares)	45,640,047	45,469,752
Treasury stock, shares (in shares)	22,930,214	22,930,214
Parent Company
Condensed Balance Sheet Statements Captions [Line Items]
Available-for-sale, amortized cost	$ 78,431	$ 250,904
Available-for-sale, allowance for credit losses	0	0
Property and equipment, accumulated depreciation	$ 1,375	$ 1,340
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	68,570,261	68,399,966
Common stock, shares outstanding (in shares)	45,640,047	45,469,752
Treasury stock, shares (in shares)	22,930,214	22,930,214