Schedule II. Condensed Financial Information of Registrant (Condensed Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Assets:
Short-term investments	$ 114,121	$ 69,145
Total investments	18,208,368	22,757,991
Cash	92,559	92,163
Other assets	760,066	782,625
Total assets	25,537,159	29,768,048
Liabilities:
Short-term debt	449,103	479,644
Long-term debt	1,627,952	1,546,494
Other liabilities	542,094	722,009
Total liabilities	20,641,298	21,125,242
Shareholders' equity:
Preferred stock	0	0
Common stock	105,218	109,218
Additional paid-in-capital	529,661	520,564
Accumulated other comprehensive income	(1,415,714)	2,677,583
Retained earnings	6,466,220	6,182,100
Treasury stock	(789,524)	(846,659)
Total shareholders' equity	4,895,861	8,642,806	$ 8,771,092	$ 7,294,307
Total liabilities and shareholders' equity	25,537,159	29,768,048
Parent Company
Assets:
Long-term investments	31,651	31,384
Short-term investments	15,001	0
Total investments	46,652	31,384
Cash	58	20,228
Investment in affiliates	6,886,870	10,618,826
Due from affiliates	131,353	170,983
Taxes receivable from affiliates	14,161	33,229
Other assets	173,044	185,143
Total assets	7,252,138	11,059,793
Liabilities:
Short-term debt	449,103	629,607
Long-term debt	1,777,490	1,546,494
Other liabilities	129,684	240,886
Total liabilities	2,356,277	2,416,987
Shareholders' equity:
Preferred stock	351	351
Common stock	105,218	109,218
Additional paid-in-capital	880,172	871,075
Accumulated other comprehensive income	(1,415,714)	2,677,583
Retained earnings	6,466,220	6,182,100
Treasury stock	(1,140,386)	(1,197,521)
Total shareholders' equity	4,895,861	8,642,806
Total liabilities and shareholders' equity	$ 7,252,138	$ 11,059,793