Unaudited Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues
Net premiums written	$ 1,444,898	$ 1,298,896	$ 2,970,157	$ 2,711,440
Change in unearned premiums	18,829	37,867	(137,564)	(139,778)
Net premiums earned	1,463,727	1,336,763	2,832,593	2,571,662
Net investment income	155,038	135,668	311,987	262,392
Net realized gains (losses)	120,806	(76,611)	262,371	(187,609)
Other-than-temporary impairment losses	(49)	(470)	(1,358)	(632)
Less investment impairments recognized in other comprehensive income, before taxes	0	0	0	0
Net impairment losses recognized in earnings	(49)	(470)	(1,358)	(632)
Other underwriting income	5,953	3,874	14,778	9,223
Equity in net income of investment funds accounted for using the equity method	32,536	8,472	79,403	36,541
Other income	1,129	3,113	2,212	3,187
Total revenues	1,779,140	1,410,809	3,501,986	2,694,764
Expenses
Losses and loss adjustment expenses	767,543	726,153	1,486,075	1,363,013
Acquisition expenses	210,089	202,838	407,937	394,214
Other operating expenses	198,914	176,181	400,077	351,196
Corporate expenses	18,251	22,512	36,213	37,824
Amortization of intangible assets	19,794	26,472	40,211	53,208
Interest expense	29,280	30,344	58,345	60,980
Net foreign exchange (gains) losses	4,952	(53,706)	1,427	(33,985)
Total expenses	1,248,823	1,130,794	2,430,285	2,226,450
Income before income taxes	530,317	280,015	1,071,701	468,314
Income tax expense	(44,472)	(23,668)	(90,358)	(45,583)
Net income	485,845	256,347	981,343	422,731
Net (income) loss attributable to noncontrolling interests	(16,891)	(12,701)	(63,861)	(28,662)
Net income available to Arch	468,954	243,646	917,482	394,069
Preferred dividends	(10,403)	(10,403)	(20,806)	(20,840)
Loss on redemption of preferred shares	0	0	0	(2,710)
Net income available to Arch common shareholders	$ 458,551	$ 233,243	$ 896,676	$ 370,519
Net income per common share and common share equivalent
Basic (per share)	$ 1.14	$ 0.58	$ 2.24	$ 0.91
Diluted (per share)	$ 1.12	$ 0.56	$ 2.19	$ 0.89
Weighted average common shares and common share equivalents outstanding
Basic (shares)	401,482,784	404,800,421	400,837,181	406,162,508
Diluted (shares)	410,899,483	413,111,205	409,755,250	415,460,756