Consolidated Statements of Earnings and Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenues
Net premiums earned	$ 1,209,188	$ 1,221,565
Net investment income	115,538	104,863
Net realized capital gains	59,651	35,893
Other than temporary impairment losses	(3,217)	(20,759)
Other revenue	151,292	137,388
Total revenues	1,532,452	1,478,950
Costs and Expenses
Net loss and loss adjustment expenses	699,305	664,644
Commissions, brokerage and other underwriting expenses	408,515	406,733
Other operating expenses	175,138	162,164
Corporate administration	16,885	9,734
Amortization of intangible assets	3,764	3,085
Interest expense	20,935	20,269
Total costs and expenses	1,324,542	1,266,629
Earnings (losses) before income taxes	207,910	212,321
Income taxes	58,550	57,668
Net earnings	149,360	154,653
Net earnings attributable to noncontrolling interest	184	148
Net earnings attributable to Alleghany stockholders	149,176	154,505
Net earnings	149,360	154,653
Other comprehensive income:
Change in unrealized gains (losses), net of deferred taxes of $67,270 and $54,981 for 2017 and 2016, respectively	124,929	102,107
Less: reclassification for net realized capital gains and other than temporary impairment losses, net of taxes of ($19,752) and ($5,297) for 2017 and 2016, respectively	(36,682)	(9,837)
Change in unrealized currency translation adjustment, net of deferred taxes of $2,719 and $11,077 for 2017 and 2016, respectively	5,049	20,571
Retirement plans	(395)	262
Comprehensive income	242,261	267,756
Comprehensive income attributable to noncontrolling interest	184	148
Comprehensive income attributable to Alleghany stockholders	$ 242,077	$ 267,608
Basic earnings per share attributable to Alleghany stockholders	$ 9.68	$ 10.00
Diluted earnings per share attributable to Alleghany stockholders	$ 9.67	$ 9.96