Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues
Net premiums earned	$ 12,440	$ 9,679	$ 8,082
Net investment income	1,023	496	389
Net realized gains (losses)	(165)	(663)	380
Other underwriting income	31	13	21
Equity in net income of investments accounted for using the equity method	278	115	366
Other income (loss)	27	(27)	10
Total revenues	13,634	9,613	9,248
Expenses
Losses and loss adjustment expenses	6,246	5,028	4,585
Acquisition expenses	2,312	1,740	1,303
Other operating expenses	1,301	1,128	999
Corporate expenses	102	95	78
Amortization of intangible assets	95	106	82
Interest expense	133	131	139
Net foreign exchange losses (gains)	60	(102)	(41)
Total expenses	10,249	8,126	7,145
Income before income taxes and income (loss) from operating affiliates	3,385	1,487	2,103
Income taxes:
Current tax expense (benefit)	288	201	295
Deferred tax expense (benefit)	(1,161)	(121)	(167)
Income tax expense (benefit)	(873)	80	128
Income (loss) from operating affiliates	184	75	264
Net income	4,442	1,482	2,239
Net (income) loss attributable to noncontrolling interests	1	(6)	(82)
Net income available to Arch	4,443	1,476	2,157
Preferred share dividends	(40)	(40)	(48)
Loss on redemption of preferred shares	0	0	(15)
Net income available to Arch common shareholders	$ 4,403	$ 1,436	$ 2,094
Net income per common share and common share equivalent
Basic (per share)	$ 11.94	$ 3.90	$ 5.35
Diluted (per share)	$ 11.62	$ 3.80	$ 5.23
Weighted average common shares and common share equivalents outstanding
Basic (shares)	368.7	368.6	391.7
Diluted (shares)	378.8	377.6	400.3