Schedule II. Condensed Financial Information of Registrant (Condensed Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Assets:
Short-term investments	$ 85,035	$ 81,740
Total investments	19,571,563	19,724,043
Cash	165,325	103,156
Other receivables	691,907	630,223
Goodwill	490,446	481,791
Other assets	1,391,560	832,413
Total assets	29,076,181	28,051,499
Liabilities:
Short-term debt	415,401	486,113
Long-term debt	2,324,251	1,629,559
Other liabilities	583,424	487,632
Total liabilities	23,770,661	23,564,696
Shareholders' equity:
Preferred stock	0	0
Common stock	97,218	102,218
Additional paid-in-capital	527,795	532,474
Accumulated other comprehensive income	(2,029,720)	(2,772,419)
Retained earnings	8,002,521	7,478,813
Total shareholders' equity	5,305,520	4,486,803	$ 3,949,577	$ 2,003,808
Total liabilities and shareholders' equity	29,076,181	28,051,499
Parent Company
Assets:
Long-term investments	39,404	42,360
Short-term investments	29,005	1,005
Total investments	68,409	43,365
Cash	66,770	1,003
Investment in affiliates	7,740,073	6,539,183
Taxes receivable from affiliates	15,202	14,163
Total assets	8,362,118	6,884,436
Liabilities:
Short-term debt	415,401	486,113
Long-term debt	2,473,874	1,779,137
Total liabilities	3,056,598	2,397,633
Shareholders' equity:
Preferred stock	351	351
Common stock	97,218	102,218
Additional paid-in-capital	878,306	882,985
Accumulated other comprehensive income	(2,029,720)	(2,772,419)
Retained earnings	8,002,521	7,478,813
Treasury stock	(1,643,156)	(1,205,145)
Total shareholders' equity	5,305,520	4,486,803
Total liabilities and shareholders' equity	8,362,118	6,884,436
Parent Company | Related Party
Assets:
Other receivables	278,301	105,279
Liabilities:
Other liabilities	52,568	0
Parent Company | Nonrelated Party
Assets:
Other assets	193,363	181,443
Liabilities:
Other liabilities	$ 114,755	$ 132,383