Consolidated Statements of Changes in Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Contributed Capital	Accumulated Other Comprehensive Income	Treasury Stock	Retained Earnings	Total Stockholders' Equity attributable to Alleghany Shareholders	Non controlling Interest
Beginning balance at Dec. 31, 2010	$ 2,908,868	$ 9,118	$ 928,816	$ 170,262	$ (99,686)	$ 1,900,358	$ 2,908,868
Net earnings	143,251					143,251	143,251
Other comprehensive income (loss), net of tax:
Retirement plans	(3,407)			(3,407)			(3,407)
Change in unrealized appreciation of investments, net	(11,324)			(11,324)			(11,324)
Comprehensive income	128,520			(14,731)		143,251	128,520
Dividends paid	(547)		8,408		49,405	(58,360)	(547)
Treasury stock repurchase	(120,325)				(120,325)		(120,325)
Other, net	9,161		813	1	3,287	5,060	9,161
Ending balance at Dec. 31, 2011	2,925,677	9,118	938,037	155,532	(167,319)	1,990,309	2,925,677
Net earnings	702,244					702,244	702,244
Other comprehensive income (loss), net of tax:
Retirement plans	520			520			520
Change in unrealized appreciation of investments, net	107,828			107,828			107,828
Change in unrealized currency translation adjustment, net	(13,371)			(13,371)			(13,371)
Comprehensive income	797,221			94,977		702,244	797,221
Treasury stock repurchase	(17,768)				(17,768)		(17,768)
Stock issuance in connection with acquisitions	2,696,409	8,361	2,688,048				2,696,409
Other, net	2,248		(6,173)	(1)	9,269	(847)	2,248
Ending balance at Dec. 31, 2012	6,403,787	17,479	3,619,912	250,508	(175,818)	2,691,706	6,403,787
Net earnings	629,354					628,421	628,421	933
Other comprehensive income (loss), net of tax:
Retirement plans	(2,773)			(2,773)			(2,773)
Change in unrealized appreciation of investments, net	(24,919)			(24,919)			(24,919)
Change in unrealized currency translation adjustment, net	(35,886)			(35,886)			(35,886)
Comprehensive income	565,776			(63,578)		628,421	564,843	933
Treasury stock repurchase	(40,389)				(40,389)		(40,389)
Other, net	18,347	(19)	(6,761)		2,296		(4,484)	22,831
Ending balance at Dec. 31, 2013	$ 6,947,521	$ 17,460	$ 3,613,151	$ 186,930	$ (213,911)	$ 3,320,127	$ 6,923,757	$ 23,764