Schedule II - Condensed Financial Information of Registrant (Parent Company) - Balance Sheet Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Condensed Balance Sheet Statements Captions [Line Items]
Available-for-sale, amortized cost	$ 2,945,273	$ 2,346,267
Available-for-sale, allowance for credit losses	339	441	$ 397
Property and equipment, accumulated depreciation	$ 68,633	$ 75,236
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)	68,399,966	68,219,551
Common stock, shares outstanding (in shares)	45,469,752	45,289,337
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	$ 250,904	$ 84,823
Available-for-sale, allowance for credit losses	0	0
Property and equipment, accumulated depreciation	$ 1,340	$ 1,697
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)	68,399,966	68,219,551
Common stock, shares outstanding (in shares)	45,469,752	45,289,337
Treasury stock, shares (in shares)	22,930,214	22,930,214