Consolidated Statements Of Income (Loss) And Comprehensive Income (Loss) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
OPERATING REVENUES
Earned premiums		$ 4,712,060		$ 4,247,978		$ 3,865,870
Net investment income		434,215		405,709		373,230
Net investment gains (losses):
Other-than-temporary impairment losses recognized in net income		0		(7,589)		(18,355)
Net realized investment gains (losses), excluding other-than-temporary impairment losses		(11,974)		47,174		66,711
Change in fair value of equity securities	[1]	(425,622)		(44,888)		16,791
Net investment gains (losses)		(437,596)	[2]	(5,303)	[3]	65,147	[4]
Products Revenues		1,497,523		951,012		885,473
Services and other revenues		635,083		462,263		422,306
Total Operating Revenues		6,841,285		6,061,659		5,612,026
OPERATING EXPENSES
Losses and loss adjustment expenses		2,820,715		2,865,761		2,050,744
Underwriting, acquisition and insurance expenses		1,777,511		1,589,464		1,497,125
Products expenses		1,413,248	[5]	850,449	[6]	755,591	[7]
Services and other expenses		474,924	[5]	458,621	[6]	416,141	[7]
Amortization of intangible assets		115,930	[8]	80,758	[9]	68,533	[10]
Impairment of Goodwill and Intangible Assets		199,198		0		18,723
Total Operating Expenses		6,801,526		5,845,053		4,806,857
Operating Income		39,759		216,606		805,169
Interest expense		154,212		132,451		129,896
Net foreign exchange losses (gains)		(106,598)		(3,140)		1,253
Loss on early extinguishment of debt		0		0		44,100
Income (Loss) Before Income Taxes		(7,855)		87,295		629,920
Income tax expense (benefit)		122,498		(313,463)		169,477
Net Income (loss)		(130,353)		400,758		460,443
Net income (loss) attributable to noncontrolling interests		(2,173)		5,489		4,754
Net Income (Loss) to Shareholders	[11]	(128,180)		395,269		455,689
OTHER COMPREHENSIVE INCOME (LOSS)
Net holding gains (losses) arising during the period		(241,325)		787,339		275,661
Change in unrealized other-than-temporary impairment losses on fixed maturities arising during the period		0		0		35
Reclassification adjustments for net gains (losses) included in net income		7,849		(24,296)		(33,528)
Change in net unrealized gains on available-for-sale investments, net of taxes		(233,476)		763,043		242,168
Change in foreign currency translation adjustments, net of taxes		(16,495)		10,449		(11,704)
Change in net actuarial pension loss, net of taxes		2,341		6,259		(19,100)
Total Other Comprehensive Income (Loss)		(247,630)		779,751		211,364
Comprehensive Income (Loss)		(377,983)		1,180,509		671,807
Comprehensive income (loss) attributable to noncontrolling interests		(2,213)		5,535		4,760
Comprehensive Income (Loss) to Shareholders		$ (375,770)		$ 1,174,974		$ 667,047
NET INCOME (LOSS) PER SHARE
Basic (dollars per share)		$ (9.55)		$ 25.89		$ 31.41
Diluted (dollars per share)	[12]	$ (9.55)		$ 25.81		$ 31.27

[1] Effective January 1, 2018, the Company adopted ASU No. 2016-01. As a result, equity securities are no longer classified as available-for-sale with unrealized gains and losses recognized in other comprehensive income; rather, all changes in the fair value of equity securities are now recognized in net income. Prior periods have not been restated to conform to the current presentation. See note 1. Prior to adopting ASU No. 2016-01, the Company recorded certain investments in equity securities at estimated fair value with changes in fair value recorded in net income.

[2] Effective January 1, 2018, the Company adopted ASU No. 2016-01. As a result, the change in fair value of equity securities is no longer recognized in other comprehensive income; rather, all changes in the fair value of equity securities are now recognized in net investment losses within net income. Prior periods have not been restated to conform to the current presentation. See note 1.

[3] Effective January 1, 2018, the Company adopted ASU No. 2016-01. As a result, the change in fair value of equity securities is no longer recognized in other comprehensive income; rather, all changes in the fair value of equity securities are now recognized in net investment losses within net income. Prior periods have not been restated to conform to the current presentation. See note 1.

[4] Effective January 1, 2018, the Company adopted ASU No. 2016-01. As a result, the change in fair value of equity securities is no longer recognized in other comprehensive income; rather, all changes in the fair value of equity securities are now recognized in net investment gains within net income. Prior periods have not been restated to conform to the current presentation. See note 1.

[5] Products expenses and services and other expenses for the Markel Ventures segment include depreciation expense of $52.2 million for the year ended December 31, 2018.

[6] Products expenses and services and other expenses for the Markel Ventures segment include depreciation expense of $41.7 million for the year ended December 31, 2017.

[7] Products expenses and services and other expenses for the Markel Ventures segment include depreciation expense of $35.5 million for the year ended December 31, 2016.

[8] Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to any other reportable segments.

[9] Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to any other reportable segments.

[10] Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to any other reportable segments.

[11] Effective January 1, 2018, the Company adopted ASU No. 2016-01 and equity securities are no longer classified as available-for-sale with unrealized gains and losses recognized in other comprehensive income, rather, changes in the fair value of equity securities are now recognized in net income. Prior periods have not been restated to conform to the current presentation. See note 1.

[12] The impact of restricted stock units and restricted stock of 25 thousand shares was excluded from the computation of diluted earnings per share for the year ended December 31, 2018 because the effect would have been anti-dilutive.