Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net earnings	$ 1,130,778	$ 126,883	$ 890,201
Adjustments to reconcile net earnings to net cash provided by (used in) operating activities:
Depreciation and amortization	178,031	160,002	119,513
Change in the fair value of equity securities	(506,769)	110,459	(709,695)
Net realized capital (gains) losses	(67,493)	(3,098)	6,551
Change in allowance for credit losses on available for sale securities	(2,077)	8,029
Change in allowance for credit losses on available for sale securities			19,660
(Increase) decrease in reinsurance recoverables, net of reinsurance payable	(300,361)	(79,149)	259,048
(Increase) decrease in premium balances receivable	(313,338)	(197,331)	(105,368)
(Increase) decrease in ceded unearned premiums	(151,514)	(63,745)	(26,921)
(Increase) decrease in deferred acquisition costs	8,364	(72,540)	(58,031)
(Increase) decrease in funds held under reinsurance agreements	160,271	(38,938)	(11,458)
Increase (decrease) in unearned premiums	195,453	417,890	299,092
Increase (decrease) in loss and loss adjustment expenses	1,387,009	1,042,267	(321,935)
Change in unrealized foreign currency exchange rate losses (gains)	85,778	(99,134)	(18,033)
Other, net	56,101	(274,761)	371,781
Net adjustments	729,455	909,951	(175,796)
Net cash provided by (used in) operating activities	1,860,233	1,036,834	714,405
Cash flows from investing activities
Purchases of debt securities	(6,737,728)	(6,721,073)	(6,726,809)
Purchases of equity securities	(1,092,926)	(1,974,625)	(520,961)
Sales of debt securities	3,582,319	4,042,915	3,645,307
Maturities and redemptions of debt securities	2,240,302	1,664,285	1,166,841
Sales of equity securities	633,111	1,659,234	2,296,371
Net (purchases) sales of short-term investments	(432,422)	208,263	(21,564)
Net (purchases) sales and maturities of commercial mortgage loans	194,379	15,967	(9,674)
(Purchases) sales of property and equipment	(59,651)	(37,519)	(47,572)
Purchases of affiliates and subsidiaries, net of cash acquired	(303,475)	(128,921)	(218,260)
Other, net	(33,039)	(12,973)	(40,218)
Net cash provided by (used in) investing activities	(2,009,130)	(1,284,447)	(476,539)
Cash flows from financing activities
Repayment of senior notes	0	(307,095)	0
Treasury stock acquisitions	(290,521)	(194,762)	(144,422)
Proceeds from issuance of senior notes	493,195	499,335	0
Debt issue costs paid	(5,675)	(4,550)	0
Increase (decrease) in other debt	189,749	85,989	81,738
Cash dividends paid	0	(215,013)	0
Other, net	(82,178)	(27,912)	(40,530)
Net cash provided by (used in) financing activities	304,570	(164,008)	(103,214)
Effect of foreign exchange rate changes on cash	(19,149)	23,965	5,683
Net (decrease) increase in cash	136,524	(387,656)	140,335
Cash at beginning of period	791,442	1,179,098	1,038,763
Cash at end of period	927,966	791,442	1,179,098
Supplemental disclosures of cash flow information
Interest paid	94,540	91,832	97,016
Income taxes paid (refund received)	$ 162,336	$ 90,828	$ 61,786