Unaudited Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenues
Net premiums written	$ 1,248,695	$ 1,023,563	$ 2,524,955	$ 2,144,798
Change in unearned premiums	(7,821)	(17,578)	(167,064)	(187,234)
Net premiums earned	1,240,874	1,005,985	2,357,891	1,957,564
Net investment income	111,124	88,338	228,998	182,073
Net realized gains (losses)	21,735	68,218	55,888	105,542
Other-than-temporary impairment losses	(1,730)	(5,395)	(3,537)	(13,132)
Less investment impairments recognized in other comprehensive income, before taxes	0	52	0	150
Net impairment losses recognized in earnings	(1,730)	(5,343)	(3,537)	(12,982)
Other underwriting income	4,822	25,224	9,455	30,271
Equity in net income (loss) of investment funds accounted for using the equity method	32,706	8,737	80,794	15,392
Other income (loss)	(1,994)	(7)	(2,776)	(32)
Total revenues	1,407,537	1,191,152	2,726,713	2,277,828
Expenses
Losses and loss adjustment expenses	689,860	584,592	1,242,430	1,107,541
Acquisition expenses	190,436	172,677	372,725	340,515
Other operating expenses	169,981	157,314	344,700	307,462
Corporate expenses	24,876	17,200	52,668	26,583
Amortization of intangible assets	30,824	4,880	62,118	9,628
Interest expense	28,749	15,663	57,425	31,770
Net foreign exchange losses (gains)	39,543	(24,662)	58,947	(1,096)
Total expenses	1,174,269	927,664	2,191,013	1,822,403
Income before income taxes	233,268	263,488	535,700	455,425
Income tax expense	(34,169)	(14,131)	(62,566)	(30,441)
Net income	199,099	249,357	473,134	424,984
Net (income) loss attributable to noncontrolling interests	(13,932)	(38,302)	(34,840)	(59,131)
Net income available to Arch	185,167	211,055	438,294	365,853
Preferred dividends	(11,349)	(5,485)	(22,567)	(10,969)
Net income available to Arch common shareholders	$ 173,818	$ 205,570	$ 415,727	$ 354,884
Net income per common share
Basic (per share)	$ 1.29	$ 1.70	$ 3.10	$ 2.94
Diluted (per share)	$ 1.25	$ 1.65	$ 2.99	$ 2.85
Weighted average common shares and common share equivalents outstanding
Basic (shares)	134,486,664	120,599,060	134,262,043	120,513,620
Diluted (shares)	139,244,646	124,365,596	139,140,632	124,425,126