Unaudited Condensed Quarterly Financial Information (Tables)

12 Months Ended

Dec. 31, 2014

Quarterly Financial Information Disclosure [Abstract]

Summary of condensed quarterly financial information

The following table summarizes the Company’s 2014 and 2013 unaudited condensed quarterly financial information (including the results of the ‘other’ segment):

	Fourth Quarter			Third Quarter			Second Quarter			First Quarter
Year Ended December 31, 2014
Net premiums written	$	895,481		$	959,539		$	971,928		$	1,064,990
Net premiums earned	923,165			903,651			907,152			859,780
Net investment income	82,496			80,105			72,990			66,994
Net realized gains	10,561			18,515			54,144			19,697
Net impairment losses recognized in earnings	(3,837		)	(8,593		)	(14,749		)	(2,971		)
Underwriting income	113,464			101,087			124,091			132,456
Net income	207,134			223,264			211,717			179,145
Preferred dividends	(5,485		)	(5,484		)	(5,485		)	(5,484		)
Net income available to Arch common shareholders	209,679			223,191			202,531			177,016
Net income per common share -- basic	$	1.65		$	1.69		$	1.53		$	1.34
Net income per common share -- diluted	$	1.60		$	1.64		$	1.48		$	1.30
Year Ended December 31, 2013
Net premiums written	$	748,921		$	839,135		$	810,535		$	952,776
Net premiums earned	839,366			795,000			758,816			752,770
Net investment income	67,095			66,083			68,369			65,672
Net realized gains (losses)	9,048			(6,022		)	12,652			58,340
Net impairment losses recognized in earnings	(88		)	(728		)	(724		)	(2,246		)
Underwriting income	128,318			110,992			96,029			116,398
Net income	161,490			114,825			176,940			256,476
Preferred dividends	(5,485		)	(5,484		)	(5,485		)	(5,484		)
Net income available to Arch common shareholders	156,005			109,341			171,455			250,992
Net income per common share -- basic	$	1.19		$	0.83		$	1.31		$	1.92
Net income per common share -- diluted	$	1.14		$	0.80		$	1.26		$	1.85