Consolidated Statements of Earnings and Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues
Net premiums earned	$ 1,297,309	$ 1,207,856
Net investment income	123,049	124,126
Change in the fair value of equity securities	392,353	(42,649)
Net realized capital gains	4,442	44,505
Other than temporary impairment losses	(10,020)	(511)
Noninsurance revenue	514,123	251,627
Total revenues	2,321,256	1,584,954
Costs and Expenses
Net loss and loss adjustment expenses	792,498	670,578
Commissions, brokerage and other underwriting expenses	420,126	406,295
Other operating expenses	502,418	264,897
Corporate administration	19,369	7,785
Amortization of intangible assets	6,900	5,264
Interest expense	23,531	21,531
Total costs and expenses	1,764,842	1,376,350
Earnings before income taxes	556,414	208,604
Income taxes	108,512	37,422
Net earnings	447,902	171,182
Net earnings attributable to noncontrolling interest	7,675	(393)
Net earnings attributable to Alleghany stockholders	440,227	171,575
Net earnings	447,902	171,182
Other comprehensive income (loss):
Change in unrealized gains (losses), net of deferred taxes	183,387	(146,358)
Less: reclassification for net realized capital gains and other than temporary impairments, net of taxes	4,407	1,379
Change in unrealized currency translation adjustment, net of deferred taxes	(885)	5,100
Retirement plans	937	(1,322)
Comprehensive income	635,748	29,981
Comprehensive income attributable to noncontrolling interests	7,675	(393)
Comprehensive income attributable to Alleghany stockholders	$ 628,073	$ 30,374
Basic earnings per share attributable to Alleghany stockholders	$ 30.40	$ 11.15
Diluted earnings per share attributable to Alleghany stockholders	$ 30.39	$ 11.04