Consolidated Statements of Earnings and Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues
Net premiums earned		$ 4,230,286	$ 4,410,647	$ 4,239,216
Net investment income		438,817	459,876	465,664
Net realized capital gains		213,897	247,058	232,119
Other than temporary impairment losses		(133,868)	(36,294)	(44,047)
Other income		250,346	150,522	78,702
Total revenues		4,999,478	5,231,809	4,971,654
Costs and Expenses
Net loss and loss adjustment expenses		2,339,790	2,494,565	2,479,353
Commissions, brokerage and other underwriting expenses	[1]	1,423,889	1,421,306	1,339,191
Other operating expenses		342,361	252,673	164,859
Corporate administration		46,503	47,054	36,111
Amortization of intangible assets		(2,211)	(5,750)	10,164
Interest expense		91,778	90,052	86,740
Total costs and expenses		4,242,110	4,299,900	4,116,418
Earnings (losses) before income taxes		757,368	931,909	855,236
Income taxes		195,173	251,777	225,882
Net earnings		562,195	680,132	629,354
Net earnings attributable to noncontrolling interest		1,880	893	933
Net earnings attributable to Alleghany stockholders		560,315	679,239	628,421
Net earnings		562,195	680,132	629,354
Other comprehensive income:
Change in unrealized gains (losses), net of deferred taxes of ($83,332), $193,881 and $37,791 for 2015, 2014 and 2013, respectively		(154,759)	360,065	70,183
Less: reclassification for net realized capital gains and other than temporary impairment losses, net of taxes of ($37,044), ($77,042) and ($51,209) for 2015, 2014 and 2013, respectively		(68,796)	(143,077)	(95,102)
Change in unrealized currency translation adjustment, net of deferred taxes of ($7,940), ($21,464) and ($19,323) for 2015, 2014 and 2013, respectively		(14,746)	(39,861)	(35,886)
Retirement plans		990	(10,473)	(2,773)
Comprehensive income		324,884	846,786	565,776
Comprehensive income attributable to noncontrolling interest		1,880	893	933
Comprehensive income attributable to Alleghany stockholders		$ 323,004	$ 845,893	$ 564,843
Basic earnings per share attributable to Alleghany stockholders		$ 35.14	$ 41.40	$ 37.44
Diluted earnings per share attributable to Alleghany stockholders		$ 35.13	$ 41.40	$ 37.44

[1] Includes amortization associated with deferred acquisition costs of $1,024.5 million, $1,042.0 million and $973.5 million for the years ended December 31, 2015, 2014 and 2013, respectively.