Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
OPERATING ACTIVITIES
Net income	$ 2,285,974	$ 1,306,997
Adjustments to reconcile net income to net cash provided by operating activities	(185,913)	657,280
Net Cash Provided By Operating Activities	2,100,061	1,964,277
INVESTING ACTIVITIES
Proceeds from sales, maturities, calls and prepayments of fixed maturity securities	1,623,112	1,359,948
Cost of fixed maturity securities purchased	(2,923,357)	(2,661,587)
Proceeds from sales of equity securities	117,006	179,665
Cost of equity securities purchased	(434,996)	(448,388)
Net change in short-term investments	305,207	487,839
Cost of other investments purchased	(204,338)	(159,591)
Additions to property and equipment	(181,040)	(155,088)
Acquisitions, net of cash acquired	207,231	3,584
Proceeds from sales of subsidiaries, net	0	(41,302)
Other	21,276	16,851
Net Cash Used By Investing Activities	(1,884,361)	(1,342,633)
FINANCING ACTIVITIES
Additions to senior long-term debt and other debt	1,278,485	475,964
Repayment of senior long-term debt and other debt	(716,543)	(811,857)
Repurchases of common stock	(389,089)	(269,593)
Dividends paid on preferred stock	(18,000)	(18,000)
Redemption of Markel CATCo Re noncontrolling interests	0	(88,997)
Purchase of noncontrolling interests	(46,492)	(54,371)
Other	(42,629)	(32,434)
Net Cash Provided (Used) By Financing Activities	65,732	(799,288)
Effect of foreign currency rate changes on cash, cash equivalents, restricted cash and restricted cash equivalents	13,051	993
Increase (decrease) in cash, cash equivalents, restricted cash and restricted cash equivalents	294,483	(176,651)
Cash, cash equivalents, restricted cash and restricted cash equivalents at beginning of period	4,332,034	5,221,513
CASH, CASH EQUIVALENTS, RESTRICTED CASH AND RESTRICTED CASH EQUIVALENTS AT END OF PERIOD	$ 4,626,517	$ 5,044,862