Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
CASH FROM OPERATING ACTIVITIES:
Net income to common stockholders	$ 1,381,359	$ 1,381,062	$ 1,022,490
Adjustments to reconcile net income to net cash from operating activities:
Net investment gains	(47,042)	(202,397)	(90,632)
Depreciation and (accretion) amortization	(20,861)	55,872	129,682
Noncontrolling interests	2,487	3,892	8,525
Investment funds	(16,743)	(145,099)	(220,015)
Stock incentive plans	51,000	49,411	46,680
Change in:
Arbitrage trading account	(54,213)	(53,291)	(268,649)
Premiums and fees receivable	(334,178)	(268,171)	(364,395)
Reinsurance accounts	(306,017)	(266,307)	(433,644)
Deferred policy acquisition costs	(99,387)	(88,844)	(121,663)
Current income taxes	52,451	(3,534)	(43,890)
Deferred income taxes	(26,691)	(64,712)	7,630
Reserves for losses and loss expenses	1,715,076	1,684,254	1,635,774
Unearned premiums	617,535	466,590	786,627
Other	14,462	19,878	89,467
Net cash from operating activities	2,929,238	2,568,604	2,183,987
CASH FLOWS USED IN INVESTING ACTIVITIES:
Proceeds from sale of fixed maturity securities	1,011,195	797,948	1,842,139
Proceeds from sale of equity securities	318,852	82,319	126,980
(Contributions to) distributions from investment funds	19,904	(24,623)	(101,050)
Proceeds from maturities and prepayments of fixed maturity securities	3,506,903	4,891,179	6,067,230
Purchase of fixed maturity securities	(6,664,763)	(8,036,680)	(10,716,748)
Purchase of equity securities	(80,454)	(340,482)	(464,645)
Real estate (purchased) sold	(2,074)	(45,920)	166,886
Change in loans receivable	(29,719)	(83,212)	(27,421)
Net additions to property, furniture and equipment	(53,080)	(52,684)	(66,634)
Change in balances due from security brokers	(33,929)	14,337	(17,983)
Cash received in connection with business disposition	96,567	906,789	0
Payment for business purchased, net of cash acquired	(11,558)	(49,572)	0
Net cash used in investing activities	(1,961,964)	(1,891,355)	(2,989,146)
CASH FLOWS (USED IN) FROM FINANCING ACTIVITIES:
Net (payments) proceeds from issuance of debt	(974)	(3,309)
Net (payments) proceeds from issuance of debt			1,034,107
Repayment of senior notes and other debt	0	(426,503)	(504,952)
Cash dividends to common stockholders	(501,456)	(235,192)	(355,736)
Purchase of common treasury shares	(537,163)	(94,140)	(122,426)
Other, net	(22,902)	(12,848)	(45,162)
Net cash (used in) from financing activities	(1,062,495)	(771,992)	5,831
Net impact on cash due to change in foreign exchange rates	9,070	(24,754)	(4,195)
Net decrease in cash and cash equivalents	(86,151)	(119,497)	(803,523)
Cash and cash equivalents at beginning of year	1,449,346	1,568,843	2,372,366
Cash and cash equivalents at end of year	$ 1,363,195	$ 1,449,346	$ 1,568,843