Consolidated Statements of Earnings and Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues
Net premiums earned		$ 4,975,777	$ 4,230,286	$ 4,410,647
Net investment income		438,455	438,817	459,876
Net realized capital gains		63,205	213,897	247,058
Other than temporary impairment losses		(45,165)	(133,868)	(36,294)
Other revenue		698,747	250,346	150,522
Total revenues		6,131,019	4,999,478	5,231,809
Costs and Expenses
Net loss and loss adjustment expenses		2,917,166	2,339,790	2,494,565
Commissions, brokerage and other underwriting expenses	[1]	1,657,251	1,423,889	1,421,306
Other operating expenses		765,226	342,361	252,673
Corporate administration		42,960	46,503	47,054
Amortization of intangible assets		19,012	(2,211)	(5,750)
Interest expense		81,599	91,778	90,052
Total costs and expenses		5,483,214	4,242,110	4,299,900
Earnings (losses) before income taxes		647,805	757,368	931,909
Income taxes		187,141	195,173	251,777
Net earnings		460,664	562,195	680,132
Net earnings attributable to noncontrolling interest		3,743	1,880	893
Net earnings attributable to Alleghany stockholders		456,921	560,315	679,239
Net earnings		460,664	562,195	680,132
Other comprehensive income:
Change in unrealized gains (losses), net of deferred taxes of $36,468, ($83,332) and $193,881 for 2016, 2015 and 2014, respectively		67,726	(154,759)	360,065
Less: reclassification for net realized capital gains and other than temporary impairment losses, net of taxes of ($36,281), ($37,044) and ($77,042) for 2016, 2015 and 2014, respectively		(67,380)	(68,796)	(143,077)
Change in unrealized currency translation adjustment, net of deferred taxes of ($3,889), ($7,940) and ($21,464) for 2016, 2015 and 2014, respectively		(7,223)	(14,746)	(39,861)
Retirement plans		(112)	990	(10,473)
Comprehensive income (loss)		453,675	324,884	846,786
Comprehensive income attributable to noncontrolling interest		3,743	1,880	893
Comprehensive income attributable to Alleghany stockholders		$ 449,932	$ 323,004	$ 845,893
Basic earnings per share attributable to Alleghany stockholders		$ 29.60	$ 35.14	$ 41.40
Diluted earnings per share attributable to Alleghany stockholders		$ 29.59	$ 35.13	$ 41.40

[1] Includes amortization associated with deferred acquisition costs of $1,253.2 million, $1,024.5 million and $1,042.0 million for the years ended December 31, 2016, 2015 and 2014, respectively.