Unaudited Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Revenues
Net premiums earned	$ 2,470,750	$ 1,929,337	$ 6,917,158	$ 5,998,668
Net investment income	128,640	88,195	315,468	298,664
Net realized gains (losses)	(183,673)	(25,040)	(742,666)	320,328
Other underwriting income	3,077	7,274	11,944	18,913
Equity in net income (loss) of investment funds accounted for using the equity method	(18,861)	105,398	75,505	299,270
Other income (loss)	(13,684)	(3,960)	(34,486)	1,151
Total revenues	2,386,249	2,101,204	6,542,923	6,936,994
Expenses
Losses and loss adjustment expenses	1,682,696	1,226,019	3,786,187	3,588,950
Acquisition expenses	447,587	306,015	1,239,065	945,639
Other operating expenses	274,747	230,832	842,082	736,808
Corporate expenses	17,710	19,672	77,662	61,007
Amortization of intangible assets	26,104	20,135	80,478	49,823
Interest expense	33,063	33,176	98,566	107,222
Net foreign exchange (gains) losses	(90,509)	(36,078)	(182,129)	(38,366)
Total expenses	2,391,398	1,799,771	5,941,911	5,451,083
Income (loss) before income taxes and income (loss) from operating affiliates	(5,149)	301,433	601,012	1,485,911
Income tax expense	14,900	(4,137)	(19,042)	(94,176)
Income (loss) from operating affiliates	8,507	124,119	37,665	224,052
Net income (loss)	18,258	421,415	619,635	1,615,787
Net (income) loss attributable to noncontrolling interests	(1,157)	(1,473)	(2,390)	(82,203)
Net income (loss) available to Arch	17,101	419,942	617,245	1,533,584
Preferred dividends	(10,184)	(16,090)	(30,552)	(38,159)
Loss on redemption of preferred shares	0	(15,101)	0	(15,101)
Net income (loss) available to Arch common shareholders	$ 6,917	$ 388,751	$ 586,693	$ 1,480,324
Net income per common share and common share equivalent
Basic (per share)	$ 0.02	$ 1.00	$ 1.59	$ 3.74
Diluted (per share)	$ 0.02	$ 0.98	$ 1.55	$ 3.66
Weighted average common shares and common share equivalents outstanding
Basic (shares)	365,190,527	389,274,220	369,525,348	395,899,591
Diluted (shares)	373,727,277	397,903,347	378,373,180	404,260,485