Segment and Other Operating Information - Premiums and Other Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Reporting [Abstract]
Premiums and contract revenues	$ 58,352	$ 55,462	$ 115,285	$ 114,400
Net investment income (loss)	122,514	55,474	212,423	125,198
Other revenues	5,285	5,578	10,990	11,375
Net realized investment gains	26	1,766	93	5,560
Total revenues	$ 186,177	$ 118,280	$ 338,791	$ 256,533