Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
CASH FROM OPERATING ACTIVITIES:
Net income to common stockholders	$ 1,756,115	$ 1,381,359	$ 1,381,062
Adjustments to reconcile net income to net cash from operating activities:
Net investment gains	(117,708)	(47,042)	(202,397)
Depreciation and (accretion) amortization	(170,638)	(20,861)	55,872
Noncontrolling interests	(1,538)	2,487	3,892
Investment funds	11,491	(16,743)	(145,099)
Stock incentive plans	54,381	51,000	49,411
Change in:
Arbitrage trading account	122,738	(54,213)	(53,291)
Premiums and fees receivable	(184,431)	(334,178)	(268,171)
Reinsurance accounts	(31,738)	(306,017)	(266,307)
Deferred policy acquisition costs	(91,150)	(99,387)	(88,844)
Current income taxes	(28,526)	52,451	(3,534)
Deferred income taxes	95,311	(26,691)	(64,712)
Reserves for losses and loss expenses	1,707,722	1,715,076	1,684,254
Unearned premiums	485,488	617,535	466,590
Other	70,851	14,462	19,878
Net cash from operating activities	3,678,368	2,929,238	2,568,604
CASH FLOWS USED IN INVESTING ACTIVITIES:
Proceeds from sale of fixed maturity securities	2,310,746	1,011,195	797,948
Proceeds from sale of equity securities	331,291	318,852	82,319
Proceeds From (Payments To) Equity Method Investments	134,853	(19,904)	24,623
Proceeds from maturities and prepayments of fixed maturity securities	4,890,572	3,506,903	4,891,179
Purchase of fixed maturity securities	(9,368,703)	(6,664,763)	(8,036,680)
Purchase of equity securities	(207,457)	(80,454)	(340,482)
Real estate purchased	(66,632)	(2,074)	(45,920)
Change in loans receivable	(210,816)	(29,719)	(83,212)
Net additions to property, furniture and equipment	(105,623)	(53,080)	(52,684)
Change in balances due from security brokers	107,280	(33,929)	14,337
Cash received in connection with business disposition	0	96,567	906,789
Payment for business purchased, net of cash acquired	0	(11,558)	(49,572)
Net cash used in investing activities	(2,184,489)	(1,961,964)	(1,891,355)
CASH FLOWS USED IN FINANCING ACTIVITIES:
Net proceeds from issuance of debt	3,105	980	0
Repayment of senior notes and other debt	0	(1,954)	(429,812)
Cash dividends to common stockholders	(531,953)	(501,456)	(235,192)
Purchase of common treasury shares	(303,655)	(537,163)	(94,140)
Other, net	(19,984)	(22,902)	(12,848)
Net cash used in financing activities	(852,487)	(1,062,495)	(771,992)
Net impact on cash due to change in foreign exchange rates	(29,840)	9,070	(24,754)
Net increase (decrease) in cash and cash equivalents	611,552	(86,151)	(119,497)
Cash and cash equivalents at beginning of year	1,363,195	1,449,346	1,568,843
Cash and cash equivalents at end of year	$ 1,974,747	$ 1,363,195	$ 1,449,346