CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
		Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Cash flows from operating activities:
Net income		$ 223,358	$ 211,964	$ 417,427	$ 607,425
Adjustments to reconcile net income to net cash provided by operating activities:
Net investment (gains) losses	[1]			(12,370)	62,687
Net realized and unrealized gains on other investments				(39,951)	(18,869)
Amortization of fixed maturities				(20,058)	(18,390)
Interest in income of equity method investments		705	(7,900)	(1,586)	(9,069)
Other amortization and depreciation				27,271	27,893
Share-based compensation expense				23,089	23,275
Changes in:
Accrued interest receivable				5,641	(12,294)
Reinsurance recoverable on unpaid losses and loss expenses				(2,247,316)	(278,507)
Reinsurance recoverable on paid losses and loss expenses				(124,418)	80,018
Deferred acquisition costs				(130,457)	(143,481)
Prepaid reinsurance premiums				(286,888)	(197,903)
Reserve for losses and loss expenses				645,415	326,820
Unearned premiums				942,072	936,026
Insurance and reinsurance balances, net				(517,574)	(272,528)
Other items				(25,436)	(210,864)
Net cash provided by (used in) operating activities				(1,345,139)	902,239
Purchases of:
Fixed maturities, available for sale				(4,836,342)	(4,534,094)
Fixed maturities, held to maturity				(43,923)	(77,033)
Equity securities				(81,146)	(78,131)
Mortgage loans				(10,225)	(2,385)
Other investments				(41,377)	(38,059)
Equity method investments				(7,340)	(10,002)
Short-term investments				(234,067)	(104,190)
Proceeds from the sale of:
Fixed maturities, available for sale				4,200,006	3,341,151
Equity securities				101,326	97,430
Other investments				72,684	69,701
Short-term investments				290,531	24,488
Proceeds from redemption of fixed maturities, available for sale				706,891	829,963
Proceeds from redemption of fixed maturities, held to maturity				82,290	125,552
Proceeds from redemption of short-term investments				118,319	40,411
Proceeds from the repayment of mortgage loans				73,655	53,524
Proceeds from the purchase of other asset, net				(19,342)	(8,932)
Loan advances made				(94,161)	(139,585)
Net cash provided by (used in) investing activities				277,779	(410,191)
Cash flows from financing activities:
Repurchase of common shares				(489,981)	(99,968)
Taxes paid on withholding shares				(25,614)	(14,556)
Dividends paid - common shares				(74,362)	(77,509)
Dividends paid - preferred shares				(15,125)	(15,125)
Net cash used in financing activities				(605,082)	(207,158)
Effect of exchange rate changes on foreign currency cash, cash equivalents and restricted cash				18,022	(13,812)
Increase (decrease) in cash, cash equivalents and restricted cash				(1,654,420)	271,078
Cash, cash equivalents and restricted cash - beginning of period				3,063,621	1,383,985	$ 1,383,985
Cash, cash equivalents and restricted cash - end of period		$ 1,409,201	$ 1,655,063	1,409,201	1,655,063	$ 3,063,621
Supplemental disclosures of cash flow information:
Income taxes paid				71,984	24,853
Interest paid				$ 31,293	$ 32,148

[1] In 2025, net investment losses in the consolidated statement of cash flows included net realized gains on overseas deposits of $1 million that are included in net investment gains (losses) in the consolidated statement of operations.