Markel (MKL) 10-K 26 Feb 16 2015 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 08, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Entity Registrant Name	MARKEL CORP
Entity Central Index Key	1,096,343
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		13,961,293
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 10,847,000,000

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
ASSETS
Fixed maturities (amortized cost of $9,038,158 in 2015 and $9,929,137 in 2014)	$ 9,394,468	$ 10,422,882
Equity securities (cost of $2,208,834 in 2015 and $1,951,658 in 2014)	4,074,475	4,137,576
Short-term investments (estimated fair value approximates cost)	1,642,261	1,594,849
Total Investments	15,111,204	16,155,307
Cash and cash equivalents	2,630,009	1,960,169
Restricted cash and cash equivalents	440,132	522,225
Receivables	1,113,703	1,135,217
Reinsurance recoverable on unpaid losses	2,016,665	1,868,669
Reinsurance recoverable on paid losses	50,123	102,206
Deferred policy acquisition costs	352,756	353,410
Prepaid reinsurance premiums	322,362	365,458
Goodwill	1,167,844	1,049,115
Intangible assets	792,372	702,747
Other assets	944,101	985,834
Total Assets	24,941,271	25,200,357
LIABILITIES AND EQUITY
Unpaid losses and loss adjustment expenses	10,251,953	10,404,152
Life and annuity benefits	1,123,275	1,305,818
Unearned premiums	2,166,105	2,245,690
Payables to insurance and reinsurance companies	224,921	276,122
Senior long-term debt and other debt (estimated fair value of $2,403,000 in 2015 and $2,493,000 in 2014)	2,241,427	2,253,594
Other liabilities	1,030,023	1,051,931
Total Liabilities	17,037,704	17,537,307
Redeemable noncontrolling interests	$ 62,958	$ 61,048
Commitments and contingencies
Shareholders' equity:
Common stock	$ 3,342,357	$ 3,308,395
Retained earnings	3,137,285	2,581,866
Accumulated other comprehensive income	1,354,508	1,704,557
Total Shareholders' Equity	7,834,150	7,594,818
Noncontrolling interests	6,459	7,184
Total Equity	7,840,609	7,602,002
Total Liabilities and Equity	$ 24,941,271	$ 25,200,357

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Fixed maturities, amortized cost	$ 9,038,158	$ 9,929,137
Equity securities, cost	2,208,834	1,951,658
Senior long-term debt and other debt, estimated fair value	$ 2,403,000	$ 2,493,000

Consolidated Statements Of Inco

Consolidated Statements Of Income And Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
OPERATING REVENUES
Earned premiums	$ 3,823,532	$ 3,840,912	$ 3,231,616
Net investment income	353,213	363,230	317,373
Net realized investment gains:
Other-than-temporary impairment losses	(44,481)	(4,784)	(4,706)
Net realized investment gains, excluding other-than-temporary impairment losses	150,961	50,784	67,858
Net realized investment gains	106,480	46,000	63,152
Other revenues	1,086,758	883,525	710,942
Total Operating Revenues	5,369,983	5,133,667	4,323,083
OPERATING EXPENSES
Losses and loss adjustment expenses	1,938,745	2,202,467	1,816,273
Underwriting, acquisition and insurance expenses	1,455,080	1,460,882	1,312,312
Amortization of intangible assets	68,947	57,627	55,223
Other expenses	1,046,805	854,871	663,528
Total Operating Expenses	4,509,577	4,575,847	3,847,336
Operating Income	860,406	557,820	475,747
Interest expense	118,301	117,442	114,004
Income Before Income Taxes	742,105	440,378	361,743
Income tax expense	152,963	116,690	77,898
Net Income	589,142	323,688	283,845
Net income attributable to noncontrolling interests	6,370	2,506	2,824
Net Income to Shareholders	582,772	321,182	281,021
OTHER COMPREHENSIVE INCOME (LOSS)
Net holding gains (losses) arising during the period	(240,170)	687,735	225,545
Change in unrealized other-than-temporary impairment losses on fixed maturities arising during the period	160	173	(141)
Reclassification adjustments for net gains included in net income	(80,482)	(26,161)	(40,830)
Change in net unrealized gains on investments, net of taxes	(320,492)	661,747	184,574
Change in foreign currency translation adjustments, net of taxes	(29,278)	(32,241)	(10,143)
Change in net actuarial pension loss, net of taxes	(352)	(14,750)	4,065
Total Other Comprehensive Income (Loss)	(350,122)	614,756	178,496
Comprehensive Income	239,020	938,444	462,341
Comprehensive income attributable to noncontrolling interests	6,297	2,510	2,852
Comprehensive Income to Shareholders	$ 232,723	$ 935,934	$ 459,489
NET INCOME PER SHARE
Basic (dollars per share)	$ 41.99	$ 22.38	$ 22.57
Diluted (dollars per share)	$ 41.74	$ 22.27	$ 22.48

Consolidated Statements Of Chan

Consolidated Statements Of Changes In Equity - USD ($) shares in Thousands, $ in Thousands	Total	Total Equity [Member]	Total Shareholders' Equity [Member]	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Noncontrolling Interests [Member]	Redeemable Noncontrolling Interests [Member]
Balance at Dec. 31, 2012		$ 3,889,017	$ 3,888,657	$ 908,980	$ 2,068,340	$ 911,337	$ 360
Balance, shares at Dec. 31, 2012				9,629
Balance, redeemable noncontrolling interests at Dec. 31, 2012								$ 86,225
Net income (loss)	$ 283,845	280,063	281,021		281,021	0	(958)	3,782
Other comprehensive income (loss)	178,496	178,468	178,468		0	178,468	0	28
Comprehensive Income	462,341	458,531	459,489				(958)	3,810
Issuance of common stock		24,518	24,518	$ 24,518	0	0	0	0
Issuance of common stock, shares				71
Repurchase of common stock		(57,388)	(57,388)	$ 0	(57,388)	0	0	0
Repurchase of common stock, shares				(109)
Restricted stock awards expensed		25,239	25,239	$ 25,239	0	0	0	0
Restricted stock awards expensed, shares				(3)
Acquisition of Alterra		2,330,199	2,330,199	$ 2,330,199	0	0	0	0
Acquisition of Alterra, shares				4,398
Adjustment of redeemable noncontrolling interests		1,963	1,963	$ 0	1,963	0	0	(1,963)
Adjustment of redeemable noncontrolling interests, shares				0
Purchase of noncontrolling interest		(136)	(136)	$ (136)	0	0	0	(11,716)
Purchase of noncontrolling interest, shares				0
Other		6,067	1,036	$ 63	973	0	5,031	(4,173)
Other, shares				0
Balance at Dec. 31, 2013		6,678,010	6,673,577	$ 3,288,863	2,294,909	1,089,805	4,433
Balance, shares at Dec. 31, 2013				13,986
Balance, redeemable noncontrolling interests at Dec. 31, 2013								72,183
Net income (loss)	323,688	319,201	321,182		321,182	0	(1,981)	4,487
Other comprehensive income (loss)	614,756	614,752	614,752		0	614,752	0	4
Comprehensive Income	938,444	933,953	935,934				(1,981)	4,491
Issuance of common stock		5,691	5,691	$ 5,691	0	0	0	0
Issuance of common stock, shares				19
Repurchase of common stock		(26,053)	(26,053)	$ 0	(26,053)	0	0	0
Repurchase of common stock, shares				(43)
Restricted stock awards expensed		22,935	22,935	$ 22,935	0	0	0	0
Restricted stock awards expensed, shares				0
Adjustment of redeemable noncontrolling interests		(8,186)	(8,186)	$ 0	(8,186)	0	0	8,186
Adjustment of redeemable noncontrolling interests, shares				0
Purchase of noncontrolling interest		(9,352)	(10,257)	$ (10,257)	0	0	905	(18,566)
Purchase of noncontrolling interest, shares				0
Other		5,004	1,177	$ 1,163	14	0	3,827	(5,246)
Other, shares				0
Balance at Dec. 31, 2014	7,602,002	7,602,002	7,594,818	$ 3,308,395	2,581,866	1,704,557	7,184
Balance, shares at Dec. 31, 2014				13,962
Balance, redeemable noncontrolling interests at Dec. 31, 2014	61,048							61,048
Net income (loss)	589,142	581,784	582,772		582,772	0	(988)	7,358
Other comprehensive income (loss)	(350,122)	(350,049)	(350,049)		0	(350,049)	0	(73)
Comprehensive Income	239,020	231,735	232,723				(988)	7,285
Issuance of common stock		4,752	4,752	$ 4,752	0	0	0	0
Issuance of common stock, shares				34
Repurchase of common stock		(31,491)	(31,491)	$ 0	(31,491)	0	0	0
Repurchase of common stock, shares				(37)
Restricted stock awards expensed		24,129	24,129	$ 24,129	0	0	0	0
Restricted stock awards expensed, shares				0
Acquisition of CapTech		0	0	$ 0	0	0	0	13,817
Acquisition of CapTech, shares				0
Adjustment of redeemable noncontrolling interests		4,144	4,144	$ 0	4,144	0	0	(4,144)
Adjustment of redeemable noncontrolling interests, shares				0
Purchase of noncontrolling interest		(1,447)	(1,447)	$ (1,447)	0	0	0	(8,224)
Purchase of noncontrolling interest, shares				0
Other		6,785	6,522	$ 6,528	(6)	0	263	(6,824)
Other, shares				0
Balance at Dec. 31, 2015	7,840,609	$ 7,840,609	$ 7,834,150	$ 3,342,357	$ 3,137,285	$ 1,354,508	$ 6,459
Balance, shares at Dec. 31, 2015				13,959
Balance, redeemable noncontrolling interests at Dec. 31, 2015	$ 62,958							$ 62,958

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
OPERATING ACTIVITIES
Net income	$ 589,142	$ 323,688	$ 283,845
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income tax expense (benefit)	(9,678)	84,543	4,050
Depreciation and amortization	200,987	203,580	190,066
Net realized investment gains	(106,480)	(46,000)	(63,152)
Decrease in receivables	5,604	21,148	142,065
Increase in deferred policy acquisition costs	(7,360)	(99,387)	(103,704)
Increase (decrease) in unpaid losses and loss adjustment expenses, net	(91,960)	249,873	290,130
Decrease in life and annuity benefits	(85,257)	(62,883)	(40,235)
Increase (decrease) in unearned premiums, net	(4,522)	147,840	97,249
Decrease in payables to insurance and reinsurance companies	(31,829)	(45,204)	(150,764)
Increase (decrease) in income taxes payable	27,817	(46,576)	81,995
Increase in accrued expenses	97,273	56,042	19,144
Other	67,414	(69,872)	(5,168)
Net Cash Provided By Operating Activities	651,151	716,792	745,521
INVESTING ACTIVITIES
Proceeds from sales of fixed maturities and equity securities	538,978	1,286,871	879,564
Proceeds from maturities, calls and prepayments of fixed maturities	1,503,616	1,420,817	1,475,938
Cost of fixed maturities and equity securities purchased	(1,576,254)	(3,153,055)	(1,651,397)
Net change in short-term investments	(62,124)	(129,164)	(470,423)
Proceeds from sales of equity method investments	23,155	107,292	313,557
Cost of equity method investments	(21,849)	(16,081)	(38,018)
Change in restricted cash and cash equivalents	62,324	264,701	(263,014)
Additions to property and equipment	(79,755)	(82,132)	(47,725)
Acquisitions, net of cash acquired	(261,521)	(319,086)	(12,198)
Other	(797)	(2,368)	1,103
Net Cash Provided (Used) By Investing Activities	125,773	(622,205)	187,387
FINANCING ACTIVITIES
Additions to senior long-term debt and other debt	69,797	89,480	547,214
Repayment and retirement of senior long-term debt and other debt	(88,020)	(83,722)	(321,978)
Repurchases of common stock	(31,491)	(26,053)	(57,388)
Issuance of common stock	4,752	5,691	24,518
Purchase of redeemable noncontrolling interests	(12,474)	(25,918)	(11,852)
Distributions to noncontrolling interests	(6,287)	(5,245)	(5,124)
Other	(10,488)	(21,357)	(23)
Net Cash Provided (Used) By Financing Activities	(74,211)	(67,124)	175,367
Effect of foreign currency rate changes on cash and cash equivalents	(32,873)	(45,820)	6,485
Increase (decrease) in cash and cash equivalents	669,840	(18,357)	1,114,760
Cash and cash equivalents at beginning of year	1,960,169	1,978,526	863,766
CASH AND CASH EQUIVALENTS AT END OF YEAR	$ 2,630,009	$ 1,960,169	$ 1,978,526

Summary Of Significant Accounti

Summary Of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Summary Of Significant Accounting Policies	Summary of Significant Accounting Policies Markel Corporation is a diverse financial holding company serving a variety of niche markets. Markel Corporation's principal business markets and underwrites specialty insurance products. Through its wholly-owned subsidiary, Markel Ventures, Inc. (Markel Ventures), Markel Corporation also owns interests in various industrial and service businesses that operate outside of the specialty insurance marketplace. On May 1, 2013 (the Acquisition Date), Markel Corporation completed the acquisition of 100% of the issued and outstanding common stock of Alterra Capital Holdings Limited (Alterra). a) Basis of Presentation. The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (U.S. GAAP) and include the accounts of Markel Corporation and its consolidated subsidiaries (the Company). All significant intercompany balances and transactions have been eliminated in consolidation. The consolidated financial statements include the results of operations and cash flows of Alterra from the Acquisition Date to December 31, 2015 and not in any prior periods, except with respect to the Supplemental Pro Forma Information included in note 2 . The Company consolidates the results of its Markel Ventures subsidiaries on a one-month lag. Certain prior year amounts have been reclassified to conform to the current presentation. b) Use of Estimates. The preparation of financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities. Management periodically reviews its estimates and assumptions. Quarterly reviews include evaluating the adequacy of reserves for unpaid losses and loss adjustment expenses, life and annuity reinsurance benefit reserves, litigation contingencies, the reinsurance allowance for doubtful accounts and income tax liabilities, as well as analyzing the recoverability of deferred tax assets, estimating reinsurance premiums written and earned and evaluating the investment portfolio for other-than-temporary declines in estimated fair value. Estimates and assumptions for goodwill and intangible assets are reviewed in conjunction with an acquisition, and goodwill and indefinite-lived intangible assets are reassessed at least annually for impairment. Actual results may differ materially from the estimates and assumptions used in preparing the consolidated financial statements. c) Investments. Available-for-sale investments are recorded at estimated fair value. Unrealized gains and losses on investments, net of deferred income taxes, are included in accumulated other comprehensive income in shareholders' equity. The Company completes a detailed analysis each quarter to assess whether the decline in the fair value of any investment below its cost basis is deemed other-than-temporary. Premiums and discounts are amortized or accreted over the lives of the related fixed maturities as an adjustment to the yield using the effective interest method. Dividend and interest income are recognized when earned. Realized investment gains or losses are included in earnings. Realized gains or losses from sales of investments are derived using the first-in, first-out method. Investments accounted for under the equity method of accounting are recorded at cost within other assets on the consolidated balance sheets and subsequently increased or decreased by the Company's proportionate share of the net income or loss of the investee. The Company records its proportionate share of net income or loss of the investee in net investment income. The Company records its proportionate share of other comprehensive income or loss of the investee as a component of other comprehensive income (loss). Dividends or other equity distributions are recorded as a reduction of the investment. The Company reviews equity method investments for impairment when events or circumstances indicate that a decline in the fair value of the investment below its carrying value is other-than-temporary. d) Cash and Cash Equivalents. The Company considers all investments with original maturities of 90 days or less to be cash equivalents. The carrying value of the Company's cash and cash equivalents and restricted cash and cash equivalents approximates fair value. e) Receivables. Receivables include amounts receivable from agents, brokers and insureds, which represent premiums that are both currently due and amounts not yet due on insurance and reinsurance policies. Premiums for insurance policies are generally due at inception. Premiums for reinsurance policies generally become due over the period of coverage based on the policy terms. The Company monitors the credit risk associated with premiums receivable, taking into consideration the fact that in certain instances credit risk may be reduced by the Company's right to offset loss obligations or unearned premiums against premiums receivable. Amounts deemed uncollectible are charged to net income in the period they are determined. Changes in the estimate of reinsurance premiums written will result in an adjustment to premiums receivable in the period they are determined. f) Reinsurance Recoverables. Amounts recoverable from reinsurers are estimated in a manner consistent with the claim liability associated with the reinsured business. Allowances are established for amounts deemed uncollectible and reinsurance recoverables are recorded net of these allowances. The Company evaluates the financial condition of its reinsurers and monitors concentration risk to minimize its exposure to significant losses from individual reinsurers. g) Deferred Policy Acquisition Costs. Costs directly related to the acquisition of insurance premiums are deferred and amortized over the related policy period, generally one year . The Company only defers acquisition costs incurred that are related directly to the successful acquisition of new or renewal insurance contracts, including commissions to agents and brokers and premium taxes. Commissions received related to reinsurance premiums ceded are netted against broker commissions in determining acquisition costs eligible for deferral. To the extent that future policy revenues on existing policies are not adequate to cover related costs and expenses, deferred policy acquisition costs are charged to earnings. The Company does not consider anticipated investment income in determining whether a premium deficiency exists. h) Goodwill and Intangible Assets. Goodwill and intangible assets are recorded as a result of business acquisitions. Goodwill represents the excess of the amount paid to acquire a business over the net fair value of assets acquired and liabilities assumed at the date of acquisition. Indefinite-lived and other intangible assets are recorded at fair value as of the acquisition date. The determination of the fair value of certain assets acquired and liabilities assumed involves significant judgment and the use of valuation models and other estimates, which require assumptions that are inherently subjective. Goodwill and indefinite-lived intangible assets are tested for impairment at least annually. The Company completes an annual test during the fourth quarter of each year based upon the results of operations through September 30. Intangible assets with definite lives are amortized using the straight-line method over their estimated useful lives, generally five to 20 years , and are reviewed for impairment when events or circumstances indicate that their carrying value may not be recoverable. i) Property and Equipment. Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization of property and equipment are calculated using the straight-line method over the estimated useful lives (generally, the life of the lease for leasehold improvements, ten to 40 years for buildings, seven to 40 years for land improvements, three to ten years for furniture and equipment and three to 25 years for other property and equipment). j) Redeemable Noncontrolling Interests. The Company owns controlling interests in various companies through its Markel Ventures operations. In some cases, the Company has the option to acquire the remaining equity interests, and the remaining equity interests have the option to sell their interests to the Company, in the future. The redemption value of the remaining equity interests is generally based on the respective company's earnings in specified periods preceding the redemption date. The redeemable noncontrolling interests generally become redeemable through 2020. The Company recognizes changes in the redemption value that exceed the carrying value of redeemable noncontrolling interests to retained earnings as if the balance sheet date were also the redemption date. Changes in the redemption value also result in an adjustment to net income to shareholders in the calculation of basic and diluted net income per share. The change in the redemption value of redeemable noncontrolling interests in 2015 , 2014 and 2013 resulted in an adjustment to retained earnings of an increase of $4.1 million , a decrease of $8.2 million , and an increase of $2.0 million , respectively. k) Income Taxes. The Company records deferred income taxes to reflect the net tax effect of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and their tax bases. Deferred tax assets are reduced by a valuation allowance when management believes it is more likely than not that some, or all, of the deferred tax assets will not be realized. The Company recognizes the tax benefit from an uncertain tax position taken or expected to be taken in income tax returns only if it is more likely than not that the tax position will be sustained upon examination by tax authorities, based on the technical merits of the position. Tax positions that meet the more likely than not threshold are then measured using a probability weighted approach, whereby the largest amount of tax benefit that is greater than 50% likely of being realized upon ultimate settlement is recognized. The Company recognizes interest and penalties related to uncertain tax positions in income tax expense. l) Unpaid Losses and Loss Adjustment Expenses. Unpaid losses and loss adjustment expenses on our property and casualty insurance business are based on evaluations of reported claims and estimates for losses and loss adjustment expenses incurred but not reported. Estimates for losses and loss adjustment expenses incurred but not reported are based on reserve development studies, among other things. The Company does not discount reserves for losses and loss adjustment expenses to reflect estimated present value, except for reserves assumed in connection with an acquisition, which are recorded at fair value at the acquisition date. Recorded reserves are estimates, and the ultimate liability may be greater or less than the estimates. m) Life and Annuity Benefits. The Company previously acquired a block of long duration reinsurance contracts for life and annuity benefits which subject the Company to mortality, longevity and morbidity risks. The assumptions used to determine policy benefit reserves are generally locked-in for the life of the contract unless an unlocking event occurs. To the extent existing policy reserves, together with the present value of future gross premiums and expected investment income earned thereon, are not adequate to cover the present value of future benefits, settlement and maintenance costs, the locked-in assumptions are revised to current best estimate assumptions and a charge to earnings for life and annuity benefits is recognized at that time. Because of the assumptions and estimates used in establishing reserves for life and annuity benefit obligations and the long-term nature of these reinsurance contracts, the ultimate liability may be greater or less than the estimates. Results attributable to the run-off of life and annuity reinsurance business are included in other revenues and other expenses in the Company's consolidated statements of income and comprehensive income and as part of the Company's Other Insurance (Discontinued Lines) segment. n) Revenue Recognition. Property and Casualty Premiums Insurance premiums are generally earned on a pro rata basis over the policy period, typically one year . The cost of reinsurance ceded is initially recorded as prepaid reinsurance premiums and is amortized over the reinsurance contract period in proportion to the amount of insurance protection provided. Premiums ceded are netted against premiums written. Assumed reinsurance premiums are recorded at the inception of each contract based upon contract terms and information received from cedents and brokers and are earned on a pro rata basis over the coverage period, or for multi-year contracts, in proportion with the underlying risk exposure to the extent there is variability in the exposure through the coverage period. Changes in reinsurance premium estimates are expected and may result in significant adjustments in any period. These estimates change over time as additional information regarding changes in underlying exposures is obtained. Any subsequent differences arising on such estimates are recorded as premiums written in the period they are determined and are earned on a pro rata basis over the coverage period. The Company uses the periodic method to account for assumed reinsurance from foreign reinsurers. The Company's foreign reinsurers provide sufficient information to record foreign assumed business in the same manner as the Company records assumed business from United States reinsurers. Certain contracts that the Company writes provide for reinstatement of coverage. Reinstatement premiums are the premiums for the restoration of the insurance or reinsurance limit of a contract to its full amount after a loss occurrence by the insured or reinsured. The Company accrues for reinstatement premiums resulting from losses recorded. Such accruals are based upon contractual terms and management judgment is involved with respect to the amount of losses recorded. Changes in estimates of losses recorded on contracts with reinstatement premium features will result in changes in reinstatement premiums based on contractual terms. Reinstatement premiums are recognized at the time losses are recorded and are earned on a pro-rata basis over the coverage period. Other Revenues Other revenues primarily relate to the Company's Markel Ventures operations and consist of revenues from the sale of manufactured products and service revenues. Revenues from manufactured products are generally recognized at the time title transfers to the customer, which typically occurs at the point of shipment or delivery to the customer, depending on the terms of the sales arrangement. Revenues from services are generally recognized as the services are performed. Services provided pursuant to a contract are recognized either over the contract period or upon completion of the elements specified in the contract, depending on the terms of the contract. o) Stock-based Compensation. Stock-based compensation expense is generally recognized as part of underwriting, acquisition and insurance expenses over the requisite service period. Stock-based compensation expense, net of taxes, was $16.3 million in 2015 , $18.7 million in 2014 and $18.4 million in 2013 . See note 12 . p) Foreign Currency Translation. The functional currencies of the Company's foreign operations are the currencies in which the majority of their business is transacted. Assets and liabilities of foreign operations are translated into the United States Dollar using the exchange rates in effect at the balance sheet date. Revenues and expenses of foreign operations are translated using the average exchange rate for the period. Gains or losses from translating the financial statements of foreign operations denominated in a functional currency are included, net of taxes, in shareholders' equity as a component of accumulated other comprehensive income. Gains and losses arising from transactions denominated in a foreign currency, other than a functional currency, are included in net income. The Company manages its exposure to foreign currency risk primarily by matching assets, other than goodwill and intangible assets, and liabilities denominated in the same currency. To the extent that assets and liabilities in foreign currencies are not matched, the Company is exposed to foreign currency risk. For functional currencies, the related exchange rate fluctuations are reflected in other comprehensive income (loss). The cumulative foreign currency translation adjustment, net of taxes, was a loss of $72.7 million and $43.5 million at December 31, 2015 and 2014 , respectively. q) Derivative Financial Instruments. Derivative instruments, including derivative instruments resulting from hedging activities, are measured at fair value and recognized as either assets or liabilities on the consolidated balance sheets. The changes in fair value of derivatives are recognized in earnings unless the derivative is designated as a hedge and qualifies for hedge accounting. The Company's foreign currency forward contracts are generally designated and qualify as hedges of a net investment in a foreign operation. The effective portion of the change in fair value resulting from these hedges is reported in currency translation adjustments as part of other comprehensive income (loss). The ineffective portion of the change in fair value is recognized in earnings. r) Comprehensive Income. Comprehensive income represents all changes in equity that result from recognized transactions and other economic events during the period. Other comprehensive income (loss) refers to revenues, expenses, gains and losses that under U.S. GAAP are included in comprehensive income but excluded from net income, such as unrealized gains or losses on investments, foreign currency translation adjustments and changes in net actuarial pension loss. s) Net Income Per Share. Basic net income per share is computed by dividing adjusted net income to shareholders by the weighted average number of common shares outstanding during the year. Diluted net income per share is computed by dividing adjusted net income to shareholders by the weighted average number of common shares and dilutive potential common shares outstanding during the year. See note 12 (b). t) Recent Accounting Pronouncements. In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606) , which creates a new comprehensive revenue recognition standard that will serve as a single source of revenue guidance for all companies in all industries. The guidance applies to all companies that either enter into contracts with customers to transfer goods or services or enter into contracts for the transfer of nonfinancial assets, unless those contracts are within the scope of other standards, such as insurance contracts. ASU No. 2014-09's core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under the current guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers (Topic 606), Deferral of the Effective Date , which deferred the original effective date of ASU No. 2014-09 by one year. As a result, ASU No. 2014-09 becomes effective for the Company during the first quarter of 2018 and may be applied retrospectively or under a modified retrospective method where the cumulative effect is recognized at the date of initial application. Early application is permitted, but not before the first quarter of 2017. The Company is currently evaluating ASU No. 2014-09 to determine the potential impact that adopting this standard will have on its consolidated financial statements. Adoption of this ASU is not expected to have a material impact on the Company's insurance operations, but may have a material impact on the Company's non-insurance operations. In February 2015, the FASB issued ASU No. 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis , which changes the way reporting enterprises evaluate whether (a) they should consolidate limited partnerships and similar entities, (b) fees paid to a decision maker or service provider are variable interests in a variable interest entity (VIE), and (c) variable interests in a VIE held by related parties of the reporting enterprise require the reporting enterprise to consolidate the VIE. It also eliminates the VIE consolidation model based on majority exposure to variability that applied to certain investment companies and similar entities. The ASU also significantly changes how to evaluate voting rights for entities that are not similar to limited partnerships when determining whether the entity is a VIE, which may affect entities for which the decision making rights are conveyed through a contractual arrangement. ASU No. 2015-02 becomes effective for the Company during the first quarter of 2016 and may be applied retrospectively or under a modified retrospective method where the cumulative-effect adjustment to retained earnings is recognized as of the beginning of the fiscal year of adoption. Reporting enterprises may also restate previously issued financial statements for one or more years with a cumulative-effect adjustment to retained earnings as of the beginning of the first year restated. The adoption of this ASU is not expected to have a material impact on the Company's financial position, results of operations or cash flows. In April 2015, the FASB issued ASU No. 2015-03, Interest-Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs . The ASU requires that debt issuance costs related to a recognized debt liability be presented on the balance sheet as a direct deduction from the debt liability, similar to the presentation of debt discounts. The cost of issuing debt will no longer be recorded as a separate asset on the balance sheet. The amortization of debt issuance costs will continue to be included in interest expense. ASU No. 2015-03 becomes effective for the Company during the first quarter of 2016 and will be applied retrospectively to all prior periods presented. The adoption of this ASU is not expected to have a material impact on the Company's financial position, results of operations or cash flows. In April 2015, the FASB issued ASU No. 2015-05, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer's Accounting for Fees Paid in a Cloud Computing Arrangement , which clarifies that software licenses contained in a cloud computing arrangement should be capitalized if the customer has the right to take possession of the software and the ability to run the software outside of the cloud computing arrangement. ASU No. 2015-05 becomes effective for the Company during the first quarter of 2016 and may be applied prospectively or retrospectively. The adoption of this ASU is not expected to have a material impact on the Company's financial position, results of operations or cash flows. In May 2015, the FASB issued ASU No. 2015-09, Financial Services-Insurance (Topic 944): Disclosures about Short-Duration Contracts . The ASU requires significant new disclosures for insurers relating to short-duration insurance contract claims and the unpaid claims liability rollforward for long and short-duration contracts. The guidance requires annual tabular disclosure, on a disaggregated basis, of undiscounted incurred and paid claim and allocated claim adjustment expense development by accident year, on a net basis after reinsurance, for up to 10 years. Tables must also include the total incurred but not reported claims liabilities, plus expected development on reported claims, and claims frequency for each accident year. A description of estimation methodologies and any significant changes in methodologies and assumptions used to calculate the liability and frequency is also required. Based on the disaggregated claims information in the tables, disclosure of historical average annual percentage payout of incurred claims is also required. Interim period disclosures must include a tabular rollforward and related qualitative information for the liability for unpaid losses and loss adjustment expenses for both long-duration and short-duration contracts. ASU No. 2015-09 becomes effective for the Company during 2016, with interim disclosures required beginning in the first quarter of 2017. The ASU must be applied retrospectively by providing comparative disclosures for each period presented. Early application is permitted. The adoption of this ASU is not expected to have a material impact on the Company's financial position, results of operations or cash flows, but will expand the nature and extent of its insurance contract disclosures, as described above. In July 2015, the FASB issued ASU No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory . The ASU changes the measurement principle for inventory from the lower of cost or market to lower of cost and net realizable value and eliminates the requirement to consider replacement cost or net realizable value less an approximately normal profit margin when measuring inventory. ASU 2015-11 becomes effective for the Company during the first quarter of 2017 and will be applied prospectively. The Company is currently evaluating ASU 2015-11 but does not expect adoption of this ASU to have a material impact on the Company's financial position, results of operations or cash flows. In September 2015, the FASB issued ASU No. 2015-16, Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments . The ASU eliminates the requirement to retrospectively adjust the financial statements for measurement-period adjustments that occur in periods after a business combination is consummated. ASU 2015-16 becomes effective for the Company during the first quarter of 2016 and will be applied prospectively. The adoption of this ASU is not expected to have a material impact on the Company's financial position, results of operations or cash flows. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments (Topic 825): Recognition and Measurement of Financial Assets and Financial Liabilities . The ASU significantly changes the income statement impact of equity investments and the recognition of changes in fair value of financial liabilities attributable to an entities own credit risk when the fair value option is elected. The ASU requires equity instruments that do not result in consolidation and are not accounted for under the equity method to be measured at fair value and to recognize any changes in fair value in net income rather than other comprehensive income. ASU 2016-01 becomes effective for the Company during the first quarter of 2018 and will be applied using a cumulative-effect adjustment to retained earnings as of the beginning of the fiscal year of adoption. The provisions related to equity investments without a readily determinable fair value will be applied prospectively to equity investments as of the adoption date. Early adoption is permitted for certain provisions of the ASU. The Company is currently evaluating ASU No. 2016-01 to determine the potential impact that adopting this standard will have on the consolidated financial statements. Adoption of this ASU is not expected to have a material impact on the Company's financial position, cash flows, or total comprehensive income, but will have a significant impact on the Company's results of operations as changes in fair value will be presented in net income rather than other comprehensive income.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2015
Acquisitions [Abstract]
Acquisitions	Acquisitions CATCo Investment Management Acquisition On December 8, 2015, the Company completed the acquisition of substantially all of the assets of CATCo Investment Management Ltd. (CATCo IM) and CATCo-Re Ltd. CATCo IM was a leading insurance-linked securities investment fund manager and reinsurance manager headquartered in Bermuda focused on building and managing highly diversified, collateralized retrocession and reinsurance portfolios covering global property catastrophe risks. Results attributable to Markel CATCo Investment Management Ltd. (Markel CATCo IM), the wholly-owned subsidiary formed in conjunction with this transaction, are included with the Company's non-insurance operations, which are not included in a reportable segment. Total consideration for the acquisition was $205.7 million , all of which was cash. The purchase price was allocated to the acquired assets and liabilities based on estimated fair values on December 8, 2015. The Company recognized goodwill of $91.9 million , all of which is expected to be deductible for income tax purposes. The goodwill is primarily attributable to the Company's ability to achieve continued capital growth in excess of that which can be expected for the investment funds previously managed by CATCo IM. The Company also recognized other intangible assets of $113.0 million , primarily related to its investment management agreements. These intangible assets are expected to be amortized over a weighted average period of 14 years . In connection with the acquisition, the Company instituted performance incentive and retention arrangements for former CATCo employees, whom are now employed by Markel CATCo IM. Pursuant to these agreements, the Company committed to the payment of performance bonuses derived from the results of the business through 2018 and retention bonuses that will be paid annually over the three year period following the acquisition. The total amount of these payments is currently estimated to be $100 million , all of which will be recognized in the consolidated financial statements as post-acquisition compensation expense over the performance period and as services are provided. Markel Ventures Acquisitions In December 2015, the Company acquired 80% of the outstanding shares of CapTech Ventures, Inc. (CapTech), a privately held company headquartered in Richmond, Virginia. CapTech is a leading management and IT consulting firm, providing services and solutions to a wide array of customers. Under the terms of the acquisition agreement for CapTech, the Company has the option to acquire the remaining equity interests and the remaining equity interests have the option to sell their interests to the Company in the future. The redemption value of the remaining equity interests is generally based on CapTech’s earnings in specified periods preceding the redemption date. Total consideration for the CapTech acquisition was $60.6 million . Total consideration included the estimated fair value of contingent consideration we expect to pay based on CapTech's earnings, as defined in the stock purchase agreement, through 2018. The purchase price was allocated to the acquired assets and liabilities based on the estimated fair values at the acquisition date. The Company has preliminarily recognized goodwill of $48.5 million related to this acquisition, none of which is expected to be deductible for income tax purposes. The Company has also preliminarily recognized other intangible assets of $49.2 million , primarily related to customer relationships, and redeemable noncontrolling interest of $13.8 million . These intangible assets are expected to be amortized over a weighted average period of 14 years . Results attributable to this acquisition are included with the Company's non-insurance operations, which are not included in a reportable segment. Due to the one month lag in consolidating the results of the Company's Markel Ventures operations, the financial results for CapTech will be included in our consolidated statements of income and comprehensive income beginning in January 2016. The Company has not completed the process of determining the fair value of the assets and liabilities acquired with CapTech. These valuations will be completed within the measurement period, which cannot exceed 12 months from the acquisition date. As a result, the fair value amounts recorded for these items are provisional estimates subject to adjustment. Once completed, any adjustments resulting from the valuations may impact the individual amounts recorded for assets acquired and liabilities assumed, the residual goodwill, and the fair value attributable to the noncontrolling equity interest holders. In July 2014, the Company acquired 100% of the outstanding shares of Cottrell, Inc. (Cottrell), a privately held company headquartered in Gainesville, Georgia. Cottrell is a leading manufacturer of over-the-road car hauler equipment and related car hauler parts. In June and August 2014, ParkLand Ventures, Inc. (ParkLand) also completed the acquisition of several manufactured housing communities. Total consideration for these acquisitions was $187.0 million , which primarily consisted of cash consideration. Total consideration included the estimated fair value of contingent consideration we expected to pay based on Cottrell's earnings, as defined in the stock purchase agreement, in 2014 and 2015. The Company recognized goodwill of $38.7 million related to these acquisitions, the majority of which we expect to amortize for income tax purposes. The Company also recognized other intangible assets of $78.7 million , including $53.7 million of customer relationships and $13.0 million of trade names, which are expected to be amortized over a weighted average period of 17 years and 10 years , respectively. Results attributable to these acquisitions are included with the Company's non-insurance operations, which are not included in a reportable segment. Acquisition of Alterra a) Overview. On May 1, 2013, the Company completed the acquisition of 100% of the the issued and outstanding common stock of Alterra pursuant to an agreement dated December 18, 2012 (the Merger Agreement) which provided for the merger of Alterra with one of the Company's subsidiaries. Alterra was a Bermuda-headquartered global enterprise providing diversified specialty property and casualty insurance and reinsurance products to corporations, public entities and other property and casualty insurers. Results attributable to Alterra's property and casualty insurance and reinsurance business are included in each of the Company's underwriting segments. Previously, Alterra also offered life and annuity reinsurance products. In 2010, Alterra ceased writing life and annuity reinsurance contracts and placed this business into run-off. Results attributable to the run-off of Alterra's life and annuity reinsurance business are included in the Company's Other Insurance (Discontinued Lines) segment. See note 19 for further discussion of the Company's reportable segments. Pursuant to the terms of the Merger Agreement, on the Acquisition Date, equity holders of Alterra received, in exchange for each share of Alterra common stock held (other than restricted shares that did not vest in connection with the transaction), (1) 0.04315 shares of the Company's common stock and (2) $10.00 in cash. Equity holders of Alterra received total consideration of $3.3 billion , consisting of cash consideration of $964.3 million and stock consideration of 4.3 million shares of the Company's common stock. b) Purchase Price. The Company's total purchase price for Alterra as of the Acquisition Date was calculated as follows: (in thousands, except per share amounts) Shares of Alterra common stock outstanding as of the Acquisition Date 96,433 Exchange ratio per the Merger Agreement 0.04315 Markel share issuance to Alterra shareholders 4,161 Shares of Alterra restricted stock outstanding as of the Acquisition Date 2,239 Incentive award ratio per the Merger Agreement 0.06252 Markel restricted stock issuance to Alterra restricted stock holders 140 Multiplied by Markel's weighted average stock price on April 30, 2013 (1) $ 529.59 Markel share and restricted stock issuance consideration, net of taxes $ 2,267,648 Alterra common shares outstanding as of the Acquisition Date that received cash consideration 96,433 Multiplied by cash price per share component per the Merger Agreement $ 10.00 Markel cash consideration $ 964,330 Fair value of Markel warrant issuance to Alterra warrant holders as of the Acquisition Date $ 73,685 Fair value of Markel stock option issuance to Alterra stock option holders as of the Acquisition Date, net of taxes $ 12,335 Fair value of partially vested Markel restricted stock unit issuance as of the Acquisition Date, net of taxes $ 6,867 Unrecognized compensation on unvested restricted stock and restricted stock units $ (20,572 ) Total acquisition consideration $ 3,304,293 (1) The fair value of the shares issued by the Company was calculated as the weighted average price of the Company's stock on April 30, 2013, the day preceding the Acquisition Date. As part of the consideration, the Company issued replacement warrants, options and restricted stock awards to holders of Alterra warrants, options and restricted stock awards. The acquisition consideration related to the options, restricted stock and restricted stock units issued was net of income taxes of $1.9 million , $10.1 million and $0.7 million , respectively. See note 12 for additional information about the equity awards issued in connection with the acquisition. c) Fair Value of Net Assets Acquired and Liabilities Assumed. The purchase price was allocated to the acquired assets and liabilities of Alterra based on estimated fair values at the Acquisition Date. The Company recognized goodwill of $295.7 million , of which $107.8 million was allocated to the U.S. Insurance segment, $65.2 million was allocated to the International Insurance segment and $122.7 million was allocated to the Reinsurance segment. The goodwill is primarily attributable to Alterra's assembled workforce and synergies that are expected to result upon integration of Alterra into the Company's insurance operations and investing activities. None of the goodwill that was recorded is deductible for income tax purposes. The Company also recognized indefinite lived intangible assets of $37.5 million and other intangible assets of $170.0 million , which will be amortized over a weighted average period of 17 years . The following table summarizes the fair values of the assets acquired and liabilities assumed at the Acquisition Date. (dollars in thousands) ASSETS Investments $ 6,407,841 Cash and cash equivalents 1,036,274 Restricted cash and cash equivalents 414,497 Receivables 866,388 Reinsurance recoverable on unpaid losses 1,169,084 Reinsurance recoverable on paid losses 80,672 Prepaid reinsurance premiums 317,445 Other assets 859,884 LIABILITIES Unpaid losses and loss adjustment expenses 4,719,461 Life and annuity benefits 1,477,482 Unearned premiums 1,075,610 Payables to insurance and reinsurance companies 342,858 Senior long-term debt 512,463 Other liabilities 223,108 Net assets 2,801,103 Goodwill 295,690 Intangible assets 207,500 Acquisition date fair value $ 3,304,293 An explanation of the significant adjustments for fair value and the related impact on amortization is as follows: • Investments - Fixed maturity investments acquired include a net increase of $223.1 million to adjust the historical carrying amount of Alterra's investments to their estimated fair value as of the Acquisition Date. The difference in the historical amortized cost of the fixed maturity investments acquired and their estimated fair value as of the Acquisition Date, $495.5 million , represents incremental premium that will be amortized to net investment income over the term of the underlying securities. The amount of the unamortized incremental premium as of December 31, 2015 and 2014 was $198.3 million and $281.1 million , respectively. The decrease in the unamortized incremental premium is due to amortization expense of $39.6 million , $59.3 million and $58.3 million for the years ended December 31, 2015 , 2014 and 2013 , respectively, and sales of securities. • Intangible assets - Establish the estimated fair value of intangible assets related to Alterra (see below for further detail). • Unearned Premiums - Unearned premiums acquired include a decrease of $176.3 million to adjust the carrying value of Alterra's historical unearned premiums to fair value as of the Acquisition Date. The adjustment consists of the present value of the expected underwriting profit within the unearned premiums liability less costs to service the related policies and a risk premium. This adjustment was amortized to underwriting, acquisition and insurance expenses over a weighted average period of approximately one year , as the contracts for business in-force as of the Acquisition Date expired. As of December 31, 2014, this adjustment was fully amortized. • Unpaid losses and loss adjustment expenses - Unpaid losses and loss adjustment expenses acquired include an increase of $120.8 million to adjust the carrying value of Alterra's historical unpaid losses and loss adjustment expenses, net of related reinsurance recoverable, to fair value as of the Acquisition Date. The estimated fair value consists of the present value of the expected net loss and loss adjustment expense payments plus a risk premium. This adjustment, plus the $26.5 million unamortized fair value adjustment included in Alterra's historical unpaid losses and loss adjustment expenses, will be amortized to losses and loss adjustment expenses over a weighted average period of approximately five years , based on the estimated payout pattern of net reserves as of the Acquisition Date. The amount of the unamortized fair value adjustment included in unpaid losses and loss adjustment expenses as of December 31, 2015 and 2014 was $91.0 million and $114.6 million , respectively. • Life and Annuity Benefits - Life and annuity benefits acquired include an increase of $329.6 million to adjust the carrying value of Alterra's historical life and annuity benefits to fair value as of the Acquisition Date. The estimated fair value consists of the present value of the expected net life and annuity benefit payments plus a risk premium. See note 10 for detail regarding accounting for life and annuity benefits. • Senior long-term debt - Senior long-term debt acquired includes an increase of $71.9 million to adjust the carrying value of Alterra's senior long-term debt to its estimated fair value based on prevailing interest rates and other factors as of the Acquisition Date. This adjustment will be amortized to interest expense over the term of the notes. See note 11 . The amount of the unamortized premium on the acquired senior long-term debt as of December 31, 2015 and 2014 was $46.3 million and $56.7 million , respectively. The following table summarizes the intangible assets recorded in connection with the acquisition. (dollars in thousands) Amount Economic Useful Life Customer relationships $ 132,000 18 years Broker relationships 19,000 18 years Technology 18,000 Ten years Trade names 1,000 One year Lloyd's syndicate capacity 12,000 Indefinite Insurance licenses 25,500 Indefinite Intangible assets as of the Acquisition Date $ 207,500 Customer relationships represent policyholder relationships and the network of insurance companies through which Alterra conducted its operations. The fair value of customer relationships and broker relationships was estimated using the income approach. Critical inputs into the valuation model for customer relationships and broker relationships include estimates of expected premium and attrition rates, and discounting at a weighted average cost of capital. Technology represents the intangible asset related to Alterra's internally developed software and was valued using the income approach. The fair value of Lloyd's syndicate capacity and insurance licenses was estimated using the market approach. Lloyd's syndicate capacity represents Alterra's authorized premium income limit to write insurance business in the Lloyd's of London (Lloyd's) insurance market. The Lloyd's capacity is renewed annually at no cost to the Company or may be freely purchased or sold, subject to Lloyd's approval. The ability to write insurance business within the syndicate capacity is indefinite with the premium income limit being set annually by the Company, subject to Lloyd's approval. d) Income Taxes. As a result of the acquisition, Alterra and its non-U.S. subsidiaries became controlled foreign corporations subject to U.S. income tax at a statutory rate of 35% . The acquisition was taxable to U.S. shareholders of Alterra, and Markel has elected to treat it as an asset acquisition under section 338(g) of the U.S. Internal Revenue Code of 1986 (IRC), as amended. Effective May 1, 2013, the Company made an IRC section 953(d) election with respect to Markel Bermuda Limited (Markel Bermuda, formerly known as Alterra Bermuda Limited), a wholly-owned subsidiary of Alterra. As a result of the 953(d) election, Markel Bermuda is treated as a domestic corporation for U.S. tax purposes and, accordingly, is required to record deferred taxes at the 35% statutory U.S. rate. As part of the allocation of the purchase price, the Company recorded net deferred tax assets of $310.1 million . Of this amount, $343.9 million represents deferred tax assets related to accrued losses and loss adjustment expenses and life and annuity benefits, which were partially offset by deferred tax liabilities of $64.6 million related to the estimated fair value of the intangible assets recorded. Other net deferred tax assets recorded primarily relate to differences between financial reporting and tax bases of the acquired assets and liabilities as of the Acquisition Date. As of the Acquisition Date, earnings of Alterra's foreign subsidiaries were considered reinvested indefinitely, consistent with the Company's other foreign subsidiaries, and no provision for deferred U.S. income tax was recorded. e) Transaction and Acquisition-Related Costs. The following table summarizes transaction and acquisition-related costs incurred by the Company in connection with the acquisition, all of which were included in underwriting, acquisition and insurance expenses in the consolidated statements of income and comprehensive income. (dollars in thousands) Year Ended December 31, 2013 Transaction costs $ 15,981 Acquisition-related costs: Severance costs 31,734 Stay bonuses 14,804 Acceleration of Alterra long-term incentive compensation awards and restricted stock awards 12,621 Total transaction and acquisition-related costs $ 75,140 Transaction costs primarily consist of due diligence, legal and investment banking costs. Per the terms of the Merger Agreement, transaction costs attributable to Alterra were recorded and paid by Alterra prior to the Acquisition Date ( $23.0 million ) and are not included within the Company's consolidated statements of income and comprehensive income. In connection with the acquisition, Alterra instituted a retention plan for certain employees under which Alterra committed to the payment of stay bonuses to such employees one year from the Acquisition Date, provided they remain employed with the Company through that date. Payments may have been accelerated for certain qualifying employment terminations. Prior to its acquisition by the Company, Alterra granted long term incentive awards to certain employees to be paid in the form of cash on March 1, 2016, provided they remain employed with the Company on that date. Payments may be accelerated prior to March 1, 2016 for certain qualifying employment terminations. Additionally, as part of the purchase consideration, the Company issued replacement restricted stock awards to holders of Alterra restricted stock awards. As a result of separations made in connection with the acquisition, the Company recognized expense totaling $12.6 million related to the acceleration of certain of these awards during the year ended December 31, 2013. f) Financial Results. The following table summarizes the results of Alterra from the Acquisition Date through December 31, 2013 that have been included within the Company's consolidated statements of income and comprehensive income. (dollars in thousands) Year Ended December 31, 2013 Operating revenues $ 912,387 Net loss to shareholders $ (93,074 ) g) Supplemental Pro Forma Information (unaudited). Alterra's results have been included in the Company's Consolidated Financial Statements from the Acquisition Date to December 31, 2015. The following table presents unaudited pro forma consolidated information for the year ended December 31, 2013 and assumes the Company's acquisition of Alterra occurred on January 1, 2012. The pro forma financial information is presented for informational purposes only and does not necessarily reflect the results that would have occurred had the acquisition taken place on January 1, 2012, nor is it necessarily indicative of future results. Significant adjustments used to determine pro forma results include amortization of intangible assets and amortization of fair value adjustments discussed in c) above, and the corresponding income tax effects. The Company also excluded certain charges from the pro forma results, including transaction costs incurred by the Company ( $16.0 million ) and Alterra ( $23.0 million ) totaling $39.0 million for the year ended December 31, 2013, severance costs attributable to the acquisition totaling $31.7 million for the year ended December 31, 2013, and stay bonuses of $14.8 million for the year ended December 31, 2013. The acceleration of compensation expense during the year ended December 31, 2013 related to Alterra's long-term incentive compensation awards and restricted stock awards was attributable to the acquisition; however, the incremental expense recognized during the period only represents a timing difference in the recognition of expense. Therefore, it was not excluded from the pro forma underwriting results. Unaudited Consolidated Pro Forma (in thousands, except per share amounts) Year Ended December 31, 2013 Earned premiums $ 3,680,220 Operating revenues 4,899,628 Net income to shareholders 422,829 U.S. GAAP combined ratio (1) 95 % Basic net income per share $ 30.33 Diluted net income per share $ 30.19 Weighted average common shares outstanding: Basic 14,007 Diluted 14,069 (1) The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums. Acquisition of Abbey Protection On January 17, 2014, the Company completed its acquisition of 100% of the share capital of Abbey Protection plc (Abbey), an integrated specialty insurance and consultancy group headquartered in London. Abbey's business is focused on the underwriting and sale of insurance products to small and medium-sized enterprises and affinity groups in the United Kingdom providing protection against legal expenses and professional fees incurred as a result of legal actions or investigations by tax authorities, as well as providing a range of complementary legal and professional consulting services. Results attributable to Abbey's insurance operations are included in the International Insurance segment. Results attributable to Abbey's consultancy operations are reported with the Company's non-insurance operations, which are not included in a reportable segment. Total consideration for this acquisition was $190.7 million , all of which was cash consideration. The purchase price was allocated to the acquired assets and liabilities based on estimated fair values on January 17, 2014. The Company recognized goodwill of $65.8 million , of which $43.0 million was allocated to the International Insurance segment and $22.8 million was allocated to the Company's non-insurance operations. None of the goodwill recognized is expected to be deductible for income tax purposes. The goodwill is primarily attributable to Abbey's assembled workforce and synergies that are expected to result upon integration of Abbey into the Company's insurance operations. The Company also recognized other intangible assets of $113.4 million , including $103.5 million of customer relationships and $9.9 million of trade names. These intangible assets are expected to be amortized over 20 years and 14 years , respectively. Acquisition of Essentia Effective January 1, 2013, the Company completed its acquisition of 100% of the outstanding shares of Essentia Insurance Company, a company that underwrites insurance exclusively for Hagerty Insurance Agency and Hagerty Classic Marine Insurance Agency (collectively, Hagerty) throughout the United States. Hagerty offers insurance for classic cars, vintage boats, motorcycles and related automotive collectibles. The Company recognized intangible assets of $35.4 million associated with this acquisition, which includes $25.0 million of customer relationships to be amortized over a weighted average period of six years . Results attributable to this acquisition are included in the U.S. Insurance segment. Effective January 1, 2014, Hagerty exercised its option to purchase 9.9% of the outstanding shares of Essentia, which reduced the Company's ownership interest in Essentia to 90.1% .

Investments

Investments	12 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Investments	Investments a) The following tables summarize the Company's available-for-sale investments. December 31, 2015 (dollars in thousands) Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Unrealized Other- Than-Temporary Impairment Losses Estimated Fair Value Fixed maturities: U.S. Treasury securities and obligations of U.S. government agencies $ 695,652 $ 9,836 $ (4,781 ) $ — $ 700,707 Obligations of states, municipalities and political subdivisions 3,817,136 204,302 (8,225 ) — 4,013,213 Foreign governments 1,302,329 115,809 (1,681 ) — 1,416,457 Commercial mortgage-backed securities 657,670 6,867 (4,999 ) — 659,538 Residential mortgage-backed securities 837,964 22,563 (4,022 ) (2,258 ) 854,247 Asset-backed securities 36,462 15 (406 ) — 36,071 Corporate bonds 1,690,945 41,123 (16,209 ) (1,624 ) 1,714,235 Total fixed maturities 9,038,158 400,515 (40,323 ) (3,882 ) 9,394,468 Equity securities: Insurance, banks and other financial institutions 651,002 690,271 (6,551 ) — 1,334,722 Industrial, consumer and all other 1,557,832 1,227,052 (45,131 ) — 2,739,753 Total equity securities 2,208,834 1,917,323 (51,682 ) — 4,074,475 Short-term investments 1,642,103 167 (9 ) — 1,642,261 Investments, available-for-sale $ 12,889,095 $ 2,318,005 $ (92,014 ) $ (3,882 ) $ 15,111,204 December 31, 2014 (dollars in thousands) Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Unrealized Other- Than-Temporary Impairment Losses Estimated Fair Value Fixed maturities: U.S. Treasury securities and obligations of U.S. government agencies $ 662,462 $ 12,963 $ (2,163 ) $ — $ 673,262 Obligations of states, municipalities and political subdivisions 4,075,748 245,158 (3,359 ) — 4,317,547 Foreign governments 1,458,255 154,707 (1,041 ) — 1,611,921 Commercial mortgage-backed securities 427,904 5,325 (2,602 ) — 430,627 Residential mortgage-backed securities 954,263 34,324 (3,482 ) (2,258 ) 982,847 Asset-backed securities 100,073 99 (682 ) — 99,490 Corporate bonds 2,250,432 69,016 (10,441 ) (1,819 ) 2,307,188 Total fixed maturities 9,929,137 521,592 (23,770 ) (4,077 ) 10,422,882 Equity securities: Insurance, banks and other financial institutions 523,739 789,717 (1,531 ) — 1,311,925 Industrial, consumer and all other 1,427,919 1,403,566 (5,834 ) — 2,825,651 Total equity securities 1,951,658 2,193,283 (7,365 ) — 4,137,576 Short-term investments 1,594,819 36 (6 ) — 1,594,849 Investments, available-for-sale $ 13,475,614 $ 2,714,911 $ (31,141 ) $ (4,077 ) $ 16,155,307 b) The following tables summarize gross unrealized investment losses by the length of time that securities have continuously been in an unrealized loss position. December 31, 2015 Less than 12 months 12 months or longer Total (dollars in thousands) Estimated Fair Value Gross Unrealized Holding and Other-Than- Temporary Impairment Losses Estimated Fair Value Gross Unrealized Holding and Other-Than- Temporary Impairment Losses Estimated Fair Value Gross Unrealized Holding and Other-Than- Temporary Impairment Losses Fixed maturities: U.S. Treasury securities and obligations of U.S. government agencies $ 427,003 $ (3,648 ) $ 92,552 $ (1,133 ) $ 519,555 $ (4,781 ) Obligations of states, municipalities and political subdivisions 169,362 (4,864 ) 70,101 (3,361 ) 239,463 (8,225 ) Foreign governments 51,328 (249 ) 40,345 (1,432 ) 91,673 (1,681 ) Commercial mortgage-backed securities 289,058 (3,600 ) 95,843 (1,399 ) 384,901 (4,999 ) Residential mortgage-backed securities 78,814 (2,858 ) 137,100 (3,422 ) 215,914 (6,280 ) Asset-backed securities 6,228 (54 ) 24,315 (352 ) 30,543 (406 ) Corporate bonds 470,694 (9,509 ) 343,737 (8,324 ) 814,431 (17,833 ) Total fixed maturities 1,492,487 (24,782 ) 803,993 (19,423 ) 2,296,480 (44,205 ) Equity securities: Insurance, banks and other financial institutions 63,873 (6,384 ) 6,247 (167 ) 70,120 (6,551 ) Industrial, consumer and all other 344,857 (44,879 ) 2,907 (252 ) 347,764 (45,131 ) Total equity securities 408,730 (51,263 ) 9,154 (419 ) 417,884 (51,682 ) Short-term investments 129,473 (9 ) — — 129,473 (9 ) Total $ 2,030,690 $ (76,054 ) $ 813,147 $ (19,842 ) $ 2,843,837 $ (95,896 ) At December 31, 2015 , the Company held 659 securities with a total estimated fair value of $2.8 billion and gross unrealized losses of $95.9 million . Of these 659 securities, 271 securities had been in a continuous unrealized loss position for one year or longer and had a total estimated fair value of $813.1 million and gross unrealized losses of $19.8 million . Of these securities, 264 securities were fixed maturities and seven were equity securities. The Company does not intend to sell or believe it will be required to sell these fixed maturities before recovery of their amortized cost. The Company has the ability and intent to hold these equity securities for a period of time sufficient to allow for the anticipated recovery of their fair value. December 31, 2014 Less than 12 months 12 months or longer Total (dollars in thousands) Estimated Fair Value Gross Unrealized Holding and Other-Than- Temporary Impairment Losses Estimated Fair Value Gross Unrealized Holding and Other-Than- Temporary Impairment Losses Estimated Fair Value Gross Unrealized Holding and Other-Than- Temporary Impairment Losses Fixed maturities: U.S. Treasury securities and obligations of U.S. government agencies $ 108,250 $ (62 ) $ 163,359 $ (2,101 ) $ 271,609 $ (2,163 ) Obligations of states, municipalities and political subdivisions 58,583 (542 ) 92,441 (2,817 ) 151,024 (3,359 ) Foreign governments 18,856 (386 ) 56,217 (655 ) 75,073 (1,041 ) Commercial mortgage-backed securities 45,931 (210 ) 147,558 (2,392 ) 193,489 (2,602 ) Residential mortgage-backed securities 9,613 (2,285 ) 207,374 (3,455 ) 216,987 (5,740 ) Asset-backed securities 30,448 (20 ) 45,160 (662 ) 75,608 (682 ) Corporate bonds 141,176 (2,263 ) 621,821 (9,997 ) 762,997 (12,260 ) Total fixed maturities 412,857 (5,768 ) 1,333,930 (22,079 ) 1,746,787 (27,847 ) Equity securities: Insurance, banks and other financial institutions 16,219 (1,531 ) — — 16,219 (1,531 ) Industrial, consumer and all other 86,062 (5,834 ) — — 86,062 (5,834 ) Total equity securities 102,281 (7,365 ) — — 102,281 (7,365 ) Short-term investments 181,964 (6 ) — — 181,964 (6 ) Total $ 697,102 $ (13,139 ) $ 1,333,930 $ (22,079 ) $ 2,031,032 $ (35,218 ) At December 31, 2014 , the Company held 552 securities with a total estimated fair value of $2.0 billion and gross unrealized losses of $35.2 million . Of these 552 securities, 396 securities had been in a continuous unrealized loss position for one year or longer and had a total estimated fair value of $1.3 billion and gross unrealized losses of $22.1 million . All 396 securities were fixed maturities. The Company completes a detailed analysis each quarter to assess whether the decline in the fair value of any investment below its cost basis is deemed other-than-temporary. All securities with unrealized losses are reviewed. The Company considers many factors in completing its quarterly review of securities with unrealized losses for other-than-temporary impairment, including the length of time and the extent to which fair value has been below cost and the financial condition and near-term prospects of the issuer. For equity securities, the ability and intent to hold the security for a period of time sufficient to allow for anticipated recovery is considered. For fixed maturities, the Company considers whether it intends to sell the security or if it is more likely than not that it will be required to sell the security before recovery, the implied yield-to-maturity, the credit quality of the issuer and the ability to recover all amounts outstanding when contractually due. For equity securities, a decline in fair value that is considered to be other-than-temporary is recognized in net income based on the fair value of the security at the time of assessment, resulting in a new cost basis for the security. For fixed maturities where the Company intends to sell the security or it is more likely than not that the Company will be required to sell the security before recovery of its amortized cost, a decline in fair value is considered to be other-than-temporary and is recognized in net income based on the fair value of the security at the time of assessment, resulting in a new cost basis for the security. If the decline in fair value of a fixed maturity below its amortized cost is considered to be other-than-temporary based upon other considerations, the Company compares the estimated present value of the cash flows expected to be collected to the amortized cost of the security. The extent to which the estimated present value of the cash flows expected to be collected is less than the amortized cost of the security represents the credit-related portion of the other-than-temporary impairment, which is recognized in net income, resulting in a new cost basis for the security. Any remaining decline in fair value represents the non-credit portion of the other-than-temporary impairment, which is recognized in other comprehensive income (loss). The discount rate used to calculate the estimated present value of the cash flows expected to be collected is the effective interest rate implicit for the security at the date of purchase. When assessing whether it intends to sell a fixed maturity or if it is likely to be required to sell a fixed maturity before recovery of its amortized cost, the Company evaluates facts and circumstances including decisions to reposition the investment portfolio, potential sales of investments to meet cash flow needs and, ultimately, current market prices. c) The amortized cost and estimated fair value of fixed maturities at December 31, 2015 are shown below by contractual maturity. (dollars in thousands) Amortized Cost Estimated Fair Value Due in one year or less $ 482,284 $ 485,605 Due after one year through five years 1,820,680 1,857,267 Due after five years through ten years 1,576,656 1,663,076 Due after ten years 3,626,442 3,838,664 7,506,062 7,844,612 Commercial mortgage-backed securities 657,670 659,538 Residential mortgage-backed securities 837,964 854,247 Asset-backed securities 36,462 36,071 Total fixed maturities $ 9,038,158 $ 9,394,468 Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties, and the lenders may have the right to put the securities back to the borrower. Based on expected maturities, the estimated average duration of fixed maturities at December 31, 2015 was 5.9 years. d) The following table presents the components of net investment income. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Interest: Municipal bonds (tax-exempt) $ 93,580 $ 98,262 $ 82,308 Municipal bonds (taxable) 57,550 49,345 28,041 Other taxable bonds 138,763 152,789 134,377 Short-term investments, including overnight deposits 5,223 5,959 3,573 Dividends on equity securities 74,705 65,031 48,641 Change in fair value of credit default swap — 2,230 10,460 Income (loss) from equity method investments (262 ) 4,766 21,898 Other 651 108 355 370,210 378,490 329,653 Investment expenses (16,997 ) (15,260 ) (12,280 ) Net investment income $ 353,213 $ 363,230 $ 317,373 e) Cumulative credit losses recognized in net income on fixed maturities where other-than-temporary impairment was identified and a portion of the other-than-temporary impairment was included in other comprehensive income (loss) were $10.7 million at December 31, 2015 and $12.7 million at December 31, 2014 and 2013 . f) The following table presents net realized investment gains and the change in net unrealized gains on investments. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Realized gains: Sales of fixed maturities $ 3,073 $ 8,417 $ 13,772 Sales of equity securities 156,987 51,356 73,592 Other 8,103 15,205 5,940 Total realized gains 168,163 74,978 93,304 Realized losses: Sales of fixed maturities (4,598 ) (18,136 ) (25,168 ) Sales of equity securities (1,232 ) (802 ) (278 ) Other-than-temporary impairments (44,481 ) (4,784 ) (4,706 ) Other (11,372 ) (5,256 ) — Total realized losses (61,683 ) (28,978 ) (30,152 ) Net realized investment gains $ 106,480 $ 46,000 $ 63,152 Change in net unrealized gains on investments: Fixed maturities $ (137,435 ) $ 480,350 $ (403,610 ) Equity securities (320,277 ) 500,673 665,599 Short-term investments 128 12 6 Net increase (decrease) $ (457,584 ) $ 981,035 $ 261,995 g) The following table presents other-than-temporary impairment losses recognized in net income and included in net realized investment gains by investment type. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Fixed maturities: Obligations of states, municipalities and political subdivisions $ — $ — $ (1,242 ) Commercial mortgage-backed securities — (61 ) — Residential mortgage-backed securities — — (640 ) Asset-backed securities — (197 ) — Corporate bonds — (46 ) — Total fixed maturities — (304 ) (1,882 ) Equity securities: Insurance, banks and other financial institutions (9,835 ) (341 ) — Industrial, consumer and all other (34,646 ) (4,139 ) (2,824 ) Total equity securities (44,481 ) (4,480 ) (2,824 ) Total $ (44,481 ) $ (4,784 ) $ (4,706 ) h) The following table presents the components of restricted assets. December 31, (dollars in thousands) 2015 2014 Restricted assets held in trust or on deposit to support underwriting activities $ 4,037,458 $ 4,961,061 Investments and cash and cash equivalents pledged as security for letters of credit 745,744 635,340 Total $ 4,783,202 $ 5,596,401 Total restricted assets are included on the Company's consolidated balance sheets as follows. December 31, (dollars in thousands) 2015 2014 Investments, available-for-sale $ 4,343,070 $ 5,040,413 Restricted cash and cash equivalents 440,132 522,225 Other assets — 33,763 Total $ 4,783,202 $ 5,596,401 i) At December 31, 2015 and December 31, 2014 , investments in U.S. Treasury securities and obligations of U.S. government agencies were the only investments in any one issuer that exceeded 10% of shareholders' equity. At December 31, 2015 , the Company's ten largest equity holdings represented $1.8 billion , or 44% , of the equity portfolio. Investments in the property and casualty insurance industry represented $690.0 million , or 17% , of the equity portfolio at December 31, 2015 . Investments in the property and casualty insurance industry included a $414.1 million investment in the common stock of Berkshire Hathaway Inc.

Receivables

Receivables	12 Months Ended
	Dec. 31, 2015
Receivables [Abstract]
Receivables	Receivables The following table presents the components of receivables. December 31, (dollars in thousands) 2015 2014 Amounts receivable from agents, brokers and insureds $ 1,009,115 $ 1,031,519 Trade accounts receivable 93,953 97,225 Employee stock loans receivable (see note 12(c)) 16,900 15,044 Other 6,165 8,601 1,126,133 1,152,389 Allowance for doubtful receivables (12,430 ) (17,172 ) Receivables $ 1,113,703 $ 1,135,217

Deferred Policy Acquisition Cos

Deferred Policy Acquisition Costs	12 Months Ended
	Dec. 31, 2015
Deferred Policy Acquisition Costs Disclosures [Abstract]
Deferred Policy Acquisition Costs	Deferred Policy Acquisition Costs The following table presents the amounts of policy acquisition costs deferred and amortized. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Balance, beginning of year $ 353,410 $ 260,967 $ 157,465 Policy acquisition costs deferred 752,324 754,303 577,620 Amortization of policy acquisition costs (744,964 ) (654,916 ) (471,915 ) Foreign currency movements (8,014 ) (6,944 ) (2,203 ) Deferred policy acquisition costs $ 352,756 $ 353,410 $ 260,967 The following table presents the components of underwriting, acquisition and insurance expenses. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Amortization of policy acquisition costs 744,964 654,916 471,915 Transaction costs and other acquisition-related expenses (1) — — 75,140 Other operating expenses 710,116 805,966 765,257 Underwriting, acquisition and insurance expenses $ 1,455,080 $ 1,460,882 $ 1,312,312 (1) In connection with the acquisition of Alterra, the Company incurred transaction costs of $16.0 million for the year ended December 31, 2013, which primarily consist of due diligence, legal and investment banking costs. Additionally, the Company incurred severance costs of $31.7 million , stay bonuses of $14.8 million and other compensation costs totaling $12.6 million related to the acceleration of certain long-term incentive compensation awards and restricted stock awards that were granted by Alterra prior to the acquisition.

Property And Equipment

Property And Equipment	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property And Equipment	Property and Equipment The following table presents the components of property and equipment, which are included in other assets on the consolidated balance sheets. December 31, (dollars in thousands) 2015 2014 Land $ 56,408 $ 56,848 Buildings 77,488 78,786 Leasehold improvements 104,003 98,098 Land improvements 71,585 70,596 Furniture and equipment 291,736 255,566 Other 134,939 116,884 736,159 676,778 Accumulated depreciation and amortization (305,324 ) (255,388 ) Property and equipment $ 430,835 $ 421,390 Depreciation and amortization expense of property and equipment was $64.2 million , $51.2 million and $51.5 million for the years ended December 31, 2015 , 2014 and 2013 , respectively. The Company does not own any material properties. The Company leases substantially all of the facilities used by its insurance operations and certain furniture and equipment under operating leases. The Company leases offices for the U.S. Insurance segment in Glen Allen, Virginia and in 23 other locations; the Company leases offices for the International Insurance segment in London, England, Hamilton, Bermuda and 29 other locations; and the Company leases offices for the Reinsurance segment primarily in Summit, New Jersey and Hamilton, Bermuda. The Company's Markel Ventures operations own certain of their office, clinic, manufacturing, warehouse and distribution facilities and lease others. The Company believes these facilities are suitable and adequate for the Company's insurance and non-insurance operations.

Goodwill And Intangible Assets

Goodwill And Intangible Assets	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill And Intangible Assets	Goodwill and Intangible Assets The following table presents the components of goodwill by reportable segment. (dollars in thousands) U.S. Insurance International Insurance Reinsurance Other (1) Total January 1, 2014 $ 280,579 $ 372,764 $ 122,745 $ 191,629 $ 967,717 Acquisitions (see note 2) — 42,989 — 61,539 104,528 Impairment loss — — — (13,737 ) (13,737 ) Foreign currency movements and other adjustments — (7,570 ) — (1,823 ) (9,393 ) December 31, 2014 (2) $ 280,579 $ 408,183 $ 122,745 $ 237,608 $ 1,049,115 Acquisitions (see note 2) — — — 146,659 146,659 Impairment loss — — — (14,880 ) (14,880 ) Foreign currency movements and other adjustments — (10,190 ) — (2,860 ) (13,050 ) December 31, 2015 (2) $ 280,579 $ 397,993 $ 122,745 $ 366,527 $ 1,167,844 (1) Amounts included in Other above are related to the Company's non-insurance operations, which are not included in a reportable segment. (2) Goodwill is net of accumulated impairment losses of $28.6 million and $13.7 million , as of December 31, 2015 and 2014, respectively, included in Other. Goodwill and indefinite-lived intangible assets are tested for impairment at least annually. The Company completes an annual test during the fourth quarter of each year based upon the results of operations through September 30. As part of our annual impairment test, during the fourth quarters of 2015 and 2014, the Company recorded a goodwill impairment charge of $14.9 million and $13.7 million , respectively, to other expenses, to reduce the carrying value of the Diamond Healthcare reporting unit's goodwill to its implied fair value. Diamond Healthcare's operations consist of the planning, development and operation of behavioral health services in partnership with healthcare organizations, and are reported in our non-insurance operations. In both periods, the Company determined the goodwill for the reporting unit was impaired as a result of lower than expected earnings and lower estimated future earnings. To determine the value of the impairment loss, the Company estimated the fair value of the reporting unit primarily using an income approach based on a discounted cash flow model. Following the impairment charge in 2015, the carrying value of the Diamond Healthcare goodwill is zero . There were no impairment losses recognized during 2013 . The following table presents the components of intangible assets with a net carrying amount. December 31, 2015 2014 (dollars in thousands) Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Customer relationships $ 481,547 $ (97,892 ) $ 452,157 $ (69,483 ) Broker relationships 182,626 (45,135 ) 175,681 (34,827 ) Trade names 103,681 (23,821 ) 94,795 (17,673 ) Investment management agreements 98,000 — — — Technology 54,241 (22,288 ) 62,288 (22,671 ) Insurance licenses 30,185 — 39,985 — Lloyd's syndicate capacity 12,000 — 12,000 — Other 30,496 (11,268 ) 18,903 (8,408 ) Total $ 992,776 $ (200,404 ) $ 855,809 $ (153,062 ) Amortization of intangible assets was $68.9 million , $57.6 million and $55.2 million for the years ended December 31, 2015 , 2014 and 2013 , respectively. Amortization of intangible assets is estimated to be $69.7 million for 2016 , $67.6 million for 2017 , $65.8 million for 2018 , $56.6 million for 2019 and $51.5 million for 2020 . Indefinite-lived intangible assets were $48.2 million at December 31, 2015 and $58.0 million at December 31, 2014 . In 2015 , the Company acquired $166.9 million of intangible assets. The definite-lived intangible assets acquired are expected to be amortized over a weighted average period of 14 years. The definite-lived intangible assets acquired during 2015 primarily include customer relationships and investment management agreements, which are expected to be amortized over a weighted average period of 17 and 14 years, respectively

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income before income taxes includes the following components. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Domestic operations $ 323,954 $ 240,279 $ 325,133 Foreign operations 418,151 200,099 36,610 Income before income taxes $ 742,105 $ 440,378 $ 361,743 Income tax expense includes the following components. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Current: Domestic $ 44,406 $ 7,573 $ 50,683 Foreign 118,235 24,574 23,165 Total current tax expense 162,641 32,147 73,848 Deferred: Domestic 9,415 43,673 23,906 Foreign (19,093 ) 40,870 (19,856 ) Total deferred tax expense (benefit) (9,678 ) 84,543 4,050 Income tax expense $ 152,963 $ 116,690 $ 77,898 Foreign income tax expense includes United States tax expense on foreign operations. State income tax expense is not material to the consolidated financial statements. The Company made income tax payments of $132.5 million , $89.5 million and $35.7 million in 2015 , 2014 and 2013 , respectively. Current income taxes payable were $63.5 million and $37.6 million at December 31, 2015 and 2014 , respectively, and were included in other liabilities on the consolidated balance sheets. Reconciliations of the United States corporate income tax rate to the effective tax rate on income before income taxes are presented in the following table. Years Ended December 31, 2015 2014 2013 United States corporate tax rate 35 % 35 % 35 % Tax credits (8 ) (1 ) — Tax-exempt investment income (5 ) (9 ) (9 ) Foreign operations (1 ) — (4 ) Other — 1 — Effective tax rate 21 % 26 % 22 % The 2015 effective tax rate included an 8% income tax benefit related to tax credits for foreign taxes paid. In previous periods, these foreign taxes paid were not available for use as tax credits against the Company's United States provision for income taxes. Based on the Company's earnings from foreign operations in 2015, significant foreign taxes paid, both in the current period and prior periods, have been used as credits against its United States provision for income taxes in 2015. The following table presents the components of domestic and foreign deferred tax assets and liabilities. December 31, (dollars in thousands) 2015 2014 Assets: Unpaid losses and loss adjustment expenses $ 212,012 $ 239,588 Life and annuity benefits 156,950 143,102 Unearned premiums recognized for income tax purposes 102,076 108,960 Investments, including other-than-temporary impairments 65,641 28,106 Accrued incentive compensation 53,586 37,329 Stock-based compensation 21,948 31,314 Net operating loss carryforwards 18,771 36,359 Tax credit carryforwards 18,158 32,525 Other differences between financial reporting and tax bases 40,497 64,235 Total gross deferred tax assets 689,639 721,518 Less valuation allowance (5,131 ) (4,801 ) Total gross deferred tax assets, net of allowance 684,508 716,717 Liabilities: Net unrealized gains on investments 626,776 759,212 Amortization of goodwill and other intangible assets 107,271 106,927 Deferred policy acquisition costs 88,036 101,766 Other differences between financial reporting and tax bases 38,613 59,359 Total gross deferred tax liabilities 860,696 1,027,264 Net deferred tax liability $ 176,188 $ 310,547 The net deferred tax liability at December 31, 2015 and 2014 was included in other liabilities on the consolidated balance sheets. At December 31, 2015 , the Company had tax credit carryforwards of $18.2 million . The earliest any of these credits will expire is 2025 . At December 31, 2015 , the Company had net operating losses of $39.2 million that can be used to offset future income that is taxable in the United States from Markel Capital Limited, a wholly owned United Kingdom subsidiary. The Company's ability to use these losses in the United States expires between the years 2023 and 2033 . At December 31, 2015 , the Company had net operating losses of $19.0 million that can be used to offset future income that is taxable in the United States. The Company's ability to use these losses in the United States expires between the years 2028 and 2030 . The Company believes that it is more likely than not that it will realize $684.5 million of gross deferred tax assets, including net operating losses, recorded at December 31, 2015 , through generating taxable income or the reversal of existing temporary differences attributable to the gross deferred tax liabilities. The Company has a valuation allowance that offsets the deferred tax asset on losses incurred primarily in our Brazilian subsidiary. At December 31, 2015 , the Company had unrecognized tax benefits of $15.3 million . If recognized, $14.7 million of these tax benefits would decrease the annual effective tax rate. The Company does not currently anticipate any changes in unrecognized tax benefits during 2016 that would have a material impact on the Company's income tax provision. The following table presents a reconciliation of unrecognized tax benefits. Years Ended December 31, (dollars in thousands) 2015 2014 Unrecognized tax benefits, beginning of year $ 17,700 $ 18,219 Increases for tax positions taken in prior years — 3 Decreases for tax positions taken in prior years (146 ) — Lapse of statute of limitations (606 ) (522 ) Settlement with taxing authorities (1,624 ) — Unrecognized tax benefits, end of year $ 15,324 $ 17,700 At December 31, 2015 , earnings of the Company's foreign subsidiaries, with the exception of certain of our Bermuda subsidiaries, are considered reinvested indefinitely and no provision for deferred United States income taxes has been recorded. If the Company's intentions with respect to reinvestment were to change, and earnings were to be repatriated to the United States, these foreign subsidiaries would be subject to tax in the United States less applicable foreign tax credits. As of December 31, 2015, cumulative earnings of our foreign subsidiaries that are considered reinvested indefinitely and have not previously been subject to tax in the United States totaled approximately $650 million . The Company is subject to income tax in the United States and in foreign jurisdictions. With few exceptions, the Company is no longer subject to income tax examination by tax authorities for years ended before January 1, 2012. The Internal Revenue Service is currently examining the Company's 2012 federal income tax return. The Company believes its income tax liabilities are adequate as of December 31, 2015, however, these liabilities could be adjusted as a result of this examination.

Unpaid Losses And Loss Adjustme

Unpaid Losses And Loss Adjustment Expenses	12 Months Ended
	Dec. 31, 2015
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Unpaid Losses And Loss Adjustment Expenses	Unpaid Losses and Loss Adjustment Expenses a) The following table presents a reconciliation of consolidated beginning and ending reserves for losses and loss adjustment expenses. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Net reserves for losses and loss adjustment expenses, beginning of year $ 8,535,483 $ 8,407,642 $ 4,592,652 Foreign currency movements, commutations and other (134,173 ) (137,385 ) (780 ) Adjusted net reserves for losses and loss adjustment expenses, beginning of year 8,401,310 8,270,257 4,591,872 Incurred losses and loss adjustment expenses: Current year 2,566,545 2,638,012 2,227,402 Prior years (627,800 ) (435,545 ) (411,129 ) Total incurred losses and loss adjustment expenses 1,938,745 2,202,467 1,816,273 Payments: Current year 486,551 502,107 670,928 Prior years 1,423,286 1,436,851 906,302 Total payments 1,909,837 1,938,958 1,577,230 Effect of foreign currency rate changes (17,281 ) (19,476 ) (7,915 ) Net reserves for losses and loss adjustment expenses of acquired insurance companies — 21,193 3,584,642 Reinsurance recoverable on retroactive reinsurance transactions (177,649 ) — — Net reserves for losses and loss adjustment expenses, end of year 8,235,288 8,535,483 8,407,642 Reinsurance recoverable on unpaid losses 2,016,665 1,868,669 1,854,414 Gross reserves for losses and loss adjustment expenses, end of year $ 10,251,953 $ 10,404,152 $ 10,262,056 Beginning of year net reserves for losses and loss adjustment expenses are adjusted, when applicable, for the impact of changes in foreign currency rates, commutations and other items. In 2015 , beginning of year net reserves for losses and loss adjustment expenses were decreased by a movement of $134.8 million in foreign currency rates of exchange. In 2014 , beginning of year net reserves for losses and loss adjustment expenses were decreased by a movement of $127.7 million in foreign currency rates of exchange. In 2013 , beginning of year net reserves for losses and loss adjustment expenses were increased by a movement of $0.7 million in foreign currency rates of exchange, which was more than offset by commutations. On March 9, 2015, the Company completed a retroactive reinsurance transaction to cede a portfolio of policies primarily comprised of liabilities arising from asbestos and environmental (A&E) exposures that originated before 1992 in exchange for payments totaling $89.0 million , which included cash paid at closing of $69.9 million . At the time of the transaction, reserves for unpaid losses and loss adjustment expenses on the policies ceded totaled $94.1 million , resulting in a deferred gain of $5.1 million which will be recognized in earnings in proportion to actual reinsurance recoveries received pursuant to the transaction. The ceded reserves attributable to A&E exposures represented approximately 30% of the Company's net asbestos and environmental reserves for losses and loss adjustment expenses as of December 31, 2014. On October 30, 2015, the Company completed a second retroactive reinsurance transaction to cede a portfolio of policies primarily comprised of liabilities arising from A&E exposures that originated before 1987 in exchange for cash payments totaling $86.5 million . The transaction provides up to $300 million of coverage for losses in excess of a $97.0 million retention on the ceded policies and 50% coverage on an additional $100 million of losses. The transaction is effective as of January 1, 2015, at which time reserves for unpaid losses and loss adjustment expenses on the policies ceded totaled $173.4 million . After considering the Company's retention on the ceded policies, ceded reserves for unpaid losses and loss adjustment expenses totaled $76.4 million , resulting in an underwriting loss of $10.1 million on the transaction. The ceded reserves attributable to A&E exposures represented approximately 25% of the Company's net asbestos and environmental reserves for losses and loss adjustment expenses as of December 31, 2014. In 2015, incurred losses and loss adjustment expenses included $627.8 million of favorable development on prior years' loss reserves, which was due in part to $375.8 million of loss reserve redundancies on our general liability, workers' compensation, inland marine and brokerage property product lines within the U.S. Insurance segment and on our general liability, professional liability and marine and energy product lines within the International Insurance segment, as actual claims reporting patterns on prior accident years have been more favorable than the Company's actuarial analyses initially anticipated. In 2015, incurred losses and loss adjustment expenses also included $82.7 million of favorable development on prior years' loss reserves attributable to a decrease in the estimated volatility of our consolidated net reserves for unpaid losses and loss adjustment expenses as a result of ceding a significant portion of the Company's A&E exposures to a third party during 2015, as described above. As a result of this decrease in estimated volatility, the level of confidence in the Company's net reserves for unpaid losses and loss adjustment expenses increased. Therefore, management reduced prior years' loss reserves by $82.7 million in order to maintain a consolidated confidence level in a range consistent with the Company's historic levels. This reduction in prior years' loss reserves occurred across all three of the Company's ongoing underwriting segments. The favorable development on prior years' loss reserves in 2015 was partially offset by $25.4 million of adverse development in prior years' loss reserves on asbestos and environmental (A&E) exposures, of which $7.1 million is attributable to the underwriting loss on the retroactive reinsurance transaction described above. Following the October 2015 retroactive reinsurance transaction, the Company's actuaries increased their estimate of the ultimate losses on the remaining A&E claims and management increased prior years’ loss reserves by $15.0 million . Without the diversification of a larger portfolio of loss reserves, there is greater uncertainty around the potential outcomes of the remaining claims, and management strengthened reserves accordingly. Once a year, generally during the third quarter, the Company completes an in-depth, actuarial review of its A&E exposures. During the annual review for both 2014 and 2013, the Company increased its expectation of the severity of the outcome of certain claims subject to litigation. As the ultimate outcome of known claims increases, the Company's expected ultimate closure value on unreported claims also increases. As a result, prior years' loss reserves for A&E exposures were increased by $27.2 million in 2014 and $28.4 million in 2013 . During the 2015 annual review, which was performed during the third quarter, the Company determined that no adjustment to loss reserves was required. In 2014, the Company recorded net reserves for losses and loss adjustment expenses of $21.2 million as a result of the acquisition of Abbey. These reserves were recorded at fair value as part of the Company's purchase accounting. In 2014, incurred losses and loss adjustment expenses included $435.5 million of favorable development on prior years' loss reserves, which was due in part to $250.4 million of loss reserve redundancies on our long-tail casualty and professional liability lines within the U.S. Insurance segment and on our professional liability and marine and energy product lines within the International Insurance segment, as actual claims reporting patterns on prior accident years have been more favorable than the Company's actuarial analyses initially anticipated. The favorable development on prior years' loss reserves in 2014 was partially offset by $32.8 million of adverse development in prior years' loss reserves on A&E exposures. In 2013, the Company recorded net reserves for losses and loss adjustment expenses of $3.6 billion as a result of the acquisition of Alterra. These reserves were recorded at fair value as part of the Company's purchase accounting. See note 2 for a discussion of the Company's acquisition of Alterra. In 2013, incurred losses and loss adjustment expenses included $411.1 million of favorable development on prior years' loss reserves, which was due in part to $255.2 million of loss reserve redundancies on our long-tail casualty and professional liability product lines within the U.S. Insurance segment and on our professional liability and marine and energy product lines within the International Insurance segment, as actual claims reporting patterns on prior accident years have been more favorable than the Company's actuarial analyses initially anticipated. The favorable development on prior years' loss reserves in 2013 was partially offset by $30.1 million of adverse development in prior years' loss reserves on A&E exposures. Inherent in the Company's reserving practices is the desire to establish loss reserves that are more likely redundant than deficient. As such, the Company seeks to establish loss reserves that will ultimately prove to be adequate. As part of the Company's acquisition of insurance operations, to the extent the reserving philosophy of the acquired business differs from the Company's reserving philosophy, the post-acquisition loss reserves will be built until total loss reserves are consistent with the Company's target level of confidence. Furthermore, the Company's philosophy is to price its insurance products to make an underwriting profit. Management continually attempts to improve its loss estimation process by refining its ability to analyze loss development patterns, claim payments and other information, but uncertainty remains regarding the potential for adverse development of estimated ultimate liabilities. The Company uses a variety of techniques to establish the liabilities for unpaid losses and loss adjustment expenses, all of which involve significant judgments and assumptions. These techniques include detailed statistical analysis of past claim reporting, settlement activity, claim frequency and severity, policyholder loss experience, industry loss experience and changes in market conditions, policy forms and exposures. Greater judgment may be required when new product lines are introduced or when there have been changes in claims handling practices, as the statistical data available may be insufficient. The Company's estimates reflect implicit and explicit assumptions regarding the potential effects of external factors, including economic and social inflation, judicial decisions, changes in law, general economic conditions and recent trends in these factors. In some of the Company's markets, and where the Company acts as a reinsurer, the timing and amount of information reported about underlying claims are in the control of third parties. There is often a time lag between cedents establishing case reserves and re-estimating their reserves, and notifying the Company of the new or revised case reserves. This can also affect estimates and require re-estimation as new information becomes available. The Company believes the process of evaluating past experience, adjusted for the effects of current developments and anticipated trends, is an appropriate basis for predicting future events. Management currently believes the Company's gross and net reserves, including the reserves for A&E exposures, are adequate. However, there is no precise method for evaluating the impact of any significant factor on the adequacy of reserves, and actual results will differ from original estimates. b) The Company's exposure to A&E claims results from policies written by acquired insurance operations before their acquisitions by the Company. The Company's exposure to A&E claims originated from umbrella, excess and commercial general liability (CGL) insurance policies and assumed reinsurance contracts that were written on an occurrence basis from the 1970s to mid-1980s. Exposure also originated from claims-made policies that were designed to cover environmental risks provided that all other terms and conditions of the policy were met. A&E claims include property damage and clean-up costs related to pollution, as well as personal injury allegedly arising from exposure to hazardous materials. After 1986, the Company began underwriting CGL coverage with pollution exclusions, and in some lines of business the Company began using a claims-made form. These changes significantly reduced the Company's exposure to future A&E claims on post-1986 business. The following table provides a reconciliation of beginning and ending A&E reserves for losses and loss adjustment expenses, which are a component of consolidated unpaid losses and loss adjustment expenses. Amounts included in the following table are presented before consideration of reinsurance allowances. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Net reserves for A&E losses and loss adjustment expenses, beginning of year $ 287,723 $ 272,194 $ 260,791 Commutations and other — 115 (5,067 ) Adjusted net reserves for A&E losses and loss adjustment expenses, beginning of year 287,723 272,309 255,724 Incurred losses and loss adjustment expenses 25,415 32,840 30,128 Payments (20,628 ) (17,426 ) (13,658 ) Reinsurance recoverable on retroactive reinsurance transactions (159,641 ) — — Net reserves for A&E losses and loss adjustment expenses, end of year 132,869 287,723 272,194 Reinsurance recoverable on unpaid losses 253,756 102,719 100,784 Gross reserves for A&E losses and loss adjustment expenses, end of year $ 386,625 $ 390,442 $ 372,978 At December 31, 2015 , asbestos-related reserves were $291.5 million and $93.1 million on a gross and net basis, respectively. Net reserves for reported claims for A&E exposures were $129.0 million at December 31, 2015 . Net incurred but not reported reserves for A&E exposures were $3.9 million at December 31, 2015 . Inception-to-date net paid losses and loss adjustment expenses for A&E related exposures totaled $595.9 million at December 31, 2015 , which includes $159.6 million of payments for two retroactive reinsurance transactions and $90.6 million of litigation-related expense. As previously described, during 2015, the Company completed two retroactive reinsurance transactions to cede two portfolios of policies primarily comprised of liabilities arising from A&E exposures. The reinsurance recoverable for the retroactive reinsurance coverage totaled $177.6 million , of which $159.6 million was attributable to A&E exposures. The Company's reserves for losses and loss adjustment expenses related to A&E exposures represent management's best estimate of ultimate settlement values. A&E reserves are monitored by management, and the Company's statistical analysis of these reserves is reviewed by the Company's independent actuaries. A&E exposures are subject to significant uncertainty due to potential loss severity and frequency resulting from the uncertain and unfavorable legal climate. A&E reserves could be subject to increases in the future; however, management believes the Company's gross and net A&E reserves at December 31, 2015 are adequate.

Life And Annuity Benefits

Life And Annuity Benefits	12 Months Ended
	Dec. 31, 2015
Liability for Future Policy Benefits [Abstract]
Life And Annuity Benefits	Life and Annuity Benefits The following table presents life and annuity benefits. December 31, (dollars in thousands) 2015 2014 Life $ 142,068 $ 182,604 Annuities 901,218 1,031,946 Accident and health 79,989 91,268 Total $ 1,123,275 $ 1,305,818 Life and annuity benefits are compiled on a reinsurance contract-by-contract basis and are discounted using standard actuarial techniques and cash flow models. Since the development of the life and annuity reinsurance reserves is based upon cash flow projection models, the Company must make estimates and assumptions based on cedent experience, industry mortality tables, and expense and investment experience, including a provision for adverse deviation. The assumptions used to determine policy benefit reserves are generally locked-in for the life of the contract unless an unlocking event occurs. To the extent existing policy reserves, together with the present value of future gross premiums and expected investment income earned thereon, are not adequate to cover the present value of future benefits, settlement and maintenance costs, the locked-in assumptions are revised to current best estimate assumptions and a charge to earnings for life and annuity benefits is recognized at that time. Because of the assumptions and estimates used in establishing the Company's reserves for life and annuity benefit obligations and the long-term nature of these reinsurance contracts, the ultimate liability may be greater or less than the estimates. The average discount rate for the life and annuity benefit reserves was 2.3% as of December 31, 2015 . As of December 31, 2015 , the largest life and annuity benefits reserve for a single contract was 33.2% of the total. No annuities included in life and annuity benefits in the consolidated balance sheet are subject to discretionary withdrawal. On April 24, 2015, the Company completed a novation that transferred its obligations under a reinsurance contract for life and annuity benefit policies to a third party in exchange for cash payments totaling $29.0 million , net of commissions. At the time of the transaction, reserves for life and annuity benefits on the novated reinsurance contract totaled $32.6 million , resulting in a gain of $3.6 million that was recorded as an offset to other expenses.

Senior Long-Term Debt And Other

Senior Long-Term Debt And Other Debt	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Senior Long-Term Debt And Other Debt	Senior Long-Term Debt and Other Debt The following table summarizes the Company's senior long-term debt and other debt. December 31, (dollars in thousands) 2015 2014 7.20% unsecured senior notes, due April 14, 2017, interest payable semi-annually, net of unamortized premium of $1,808 in 2015 and $3,526 in 2014 $ 92,436 $ 94,155 7.125% unsecured senior notes, due September 30, 2019, interest payable semi-annually, net of unamortized discount of $1,060 in 2015 and $1,343 in 2014 346,940 348,657 6.25% unsecured senior notes, due September 30, 2020, interest payable semi-annually, net of unamortized premium of $44,519 in 2015 and $53,172 in 2014 394,517 403,172 5.35% unsecured senior notes, due June 1, 2021, interest payable semi-annually, net of unamortized discount of $1,119 in 2015 and $1,325 in 2014 248,881 248,675 4.90% unsecured senior notes, due July 1, 2022, interest payable semi-annually, net of unamortized discount of $1,815 in 2015 and $2,095 in 2014 348,185 347,905 3.625% unsecured senior notes, due March 30, 2023, interest payable semi-annually, net of unamortized discount of $1,458 in 2015 and $1,659 in 2014 248,542 248,341 7.35% unsecured senior notes, due August 15, 2034, interest payable semi-annually, net of unamortized discount of $1,972 in 2015 and $2,078 in 2014 198,028 197,922 5.0% unsecured senior notes, due March 30, 2043, interest payable semi-annually, net of unamortized discount of $6,103 in 2015 and $6,327 in 2014 243,897 243,673 Subsidiary debt, at various interest rates ranging from 1.9% to 6.5% 120,001 121,094 Senior long-term debt and other debt $ 2,241,427 $ 2,253,594 On April 16, 2007, Alterra USA Holdings Limited (Alterra USA), a wholly-owned indirect subsidiary of Alterra, privately issued $100 million of 7.20% unsecured senior notes due April 14, 2017 (the 7.20% unsecured senior notes). The 7.20% unsecured senior notes are Alterra USA's senior unsecured obligations and rank equally in right of payment with all existing and future senior unsecured indebtedness of Alterra USA. The 7.20% unsecured senior notes are fully and unconditionally guaranteed by Alterra. The principal amount of the 7.20% unsecured senior notes outstanding as of the Acquisition Date was $90.6 million . As of the Acquisition Date, the 7.20% unsecured senior notes were recorded at their estimated fair value of $95.8 million . On September 27, 2010, Alterra Finance LLC, a wholly-owned indirect subsidiary of Alterra, issued $350 million of 6.25% unsecured senior notes due September 30, 2020 (the 6.25% unsecured senior notes). The 6.25% unsecured senior notes are Alterra Finance LLC's senior unsecured obligations and rank equally in right of payment with all of Alterra Finance LLC's future unsecured and unsubordinated indebtedness and rank senior to all of Alterra Finance LLC's future subordinated indebtedness. The 6.25% unsecured senior notes are fully and unconditionally guaranteed by Alterra on a senior unsecured basis. The guarantee ranks equally with all of Alterra's existing and future unsecured and unsubordinated indebtedness and ranks senior to all of Alterra's future subordinated indebtedness. As of the Acquisition Date, the 6.25% unsecured senior notes were recorded at their estimated fair value of $416.6 million . Alterra Finance LLC is a finance subsidiary and has no independent activities, assets or operations other than in connection with the 6.25% unsecured senior notes. On June 30, 2014, Markel Corporation entered into agreements guaranteeing the 7.20% unsecured senior notes and 6.25% unsecured senior notes. These guarantee agreements were issued pursuant to supplemental indentures entered into by the Company on June 30, 2014 and are in addition to the existing guarantees provided by Alterra. Effective August 1, 2014, both Alterra Finance and Alterra USA provided guarantees for the Company's revolving credit facility. As a result, the Company's revolving credit facility ranks equally with the 6.25% unsecured senior notes and the 7.20% unsecured senior notes. The Company's 7.35% unsecured senior notes due August 15, 2034 are not redeemable. The Company's other unsecured senior notes are redeemable by the Company at any time, subject to payment of a make-whole premium to the noteholders. None of the Company's senior long-term debt is subject to any sinking fund requirements. The Company's other debt is primarily associated with its Markel Ventures operations and is non-recourse to the holding company. The debt of the Company's Markel Ventures subsidiaries generally is secured by the assets of those subsidiaries. ParkLand, a subsidiary of the Company, has formed subsidiaries for the purpose of acquiring and financing real estate (the real estate subsidiaries). The assets of the real estate subsidiaries, which are not material to the Company, are consolidated in accordance with U.S. GAAP but are not available to satisfy the debt and other obligations of the Company or any affiliates other than the real estate subsidiaries. The estimated fair value based on quoted market prices of the Company's senior long-term debt and other debt was $2.4 billion and $2.5 billion at December 31, 2015 and 2014 , respectively. The following table summarizes the future principal payments due at maturity on senior long-term debt and other debt as of December 31, 2015 . Years Ending December 31, (dollars in thousands) 2016 $ 30,267 2017 120,268 2018 4,845 2019 352,843 2020 359,128 2021 and thereafter 1,341,276 Total principal payments $ 2,208,627 Net unamortized premium 32,800 Senior long-term debt and other debt $ 2,241,427 On August 1, 2014, the Company entered into a credit agreement for a revolving credit facility, which provides $300 million of capacity for future acquisitions, investments, repurchases of capital stock of the Company and for general corporate purposes. At the Company's discretion, $200 million of the total capacity may be used for secured letters of credit. The Company may increase the capacity of the facility to $500 million subject to certain terms and conditions. The Company pays interest on balances outstanding under the facility and a utilization fee for letters of credit issued under the facility. The Company also pays a commitment fee ( 0.225% at December 31, 2015 ) on the unused portion of the facility based on the Company's debt to equity leverage ratio as calculated under the credit agreement. Markel Corporation, along with Alterra Finance and Alterra USA, guaranteed the Company's obligations under the facility. At December 31, 2015 and 2014 , the Company had no borrowings outstanding under this revolving credit facility. This facility replaced the Company's previous $300 million revolving credit facility and expires in August 2019. Alterra and Markel Bermuda were party to a secured credit facility (the senior credit facility), which expired on December 15, 2015. At December 31, 2015 , $10.6 million of letters of credit were issued and outstanding under the senior credit facility. The last outstanding letter of credit under the senior credit facility expired on January 31, 2016. At December 31, 2015 and 2014 , the Company had no borrowings outstanding under the senior credit facility. At December 31, 2015 , the Company was in compliance with all covenants contained in its revolving credit facility and senior credit facility. To the extent that the Company is not in compliance with its covenants, the Company's access to the revolving credit facility could be restricted. The Company paid $127.0 million , $125.8 million and $114.5 million in interest on its senior long-term debt and other debt during the years ended December 31, 2015 , 2014 and 2013 , respectively.

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2015
Stockholders' Equity Note [Abstract]
Shareholders' Equity	Shareholders' Equity a) The Company had 50,000,000 shares of no par value common stock authorized of which 13,959,018 shares and 13,961,675 shares were issued and outstanding at December 31, 2015 and 2014 , respectively. The Company also has 10,000,000 shares of no par value preferred stock authorized, none of which was issued or outstanding at December 31, 2015 or 2014 . The Company's Board of Directors has approved the repurchase of up to $300 million of common stock under a share repurchase program (the Program). Under the Program, the Company may repurchase outstanding shares of common stock from time to time, primarily through open-market transactions. The Program has no expiration date but may be terminated by the Board of Directors at any time. As of December 31, 2015 , the Company had repurchased 56,455 shares of common stock at a cost of $37.1 million under the Program. b) Net income per share was determined by dividing adjusted net income to shareholders by the applicable weighted average shares outstanding. Diluted net income per share is computed by dividing adjusted net income to shareholders by the weighted average number of common shares and dilutive potential common shares outstanding during the year. Average closing common stock market prices are used to calculate the dilutive effect attributable to restricted stock. Years Ended December 31, (in thousands, except per share amounts) 2015 2014 2013 Net income to shareholders $ 582,772 $ 321,182 $ 281,021 Adjustment of redeemable noncontrolling interests 4,144 (8,186 ) 1,963 Adjusted net income to shareholders $ 586,916 $ 312,996 $ 282,984 Basic common shares outstanding 13,978 13,984 12,538 Dilutive potential common shares from conversion of options 9 11 12 Dilutive potential common shares from conversion of restricted stock 74 62 36 Diluted shares outstanding 14,061 14,057 12,586 Basic net income per share $ 41.99 $ 22.38 $ 22.57 Diluted net income per share $ 41.74 $ 22.27 $ 22.48 c) The Company's Employee Stock Purchase and Bonus Plan provides a method for employees and directors to purchase shares of the Company's common stock on the open market. The plan encourages share ownership by providing for the award of bonus shares to participants equal to 10% of the net increase in the number of shares owned under the plan in a given year, excluding shares acquired through the plan's loan program component. Under the loan program, the Company offers subsidized unsecured loans so participants may purchase shares and awards bonus shares equal to 5% of the shares purchased with a loan. The Company has authorized 100,000 shares for purchase under this plan, of which 9,458 and 20,740 shares were available for purchase at December 31, 2015 and 2014 , respectively. At December 31, 2015 and 2014 , loans outstanding under the plan, which are included in receivables on the consolidated balance sheets, totaled $16.9 million and $15.0 million , respectively. d) In April 2012, the Company adopted the 2012 Equity Incentive Compensation Plan (2012 Compensation Plan), which replaced the Markel Corporation Omnibus Incentive Plan (Omnibus Incentive Plan). The 2012 Compensation Plan provides for grants and awards of restricted stock, restricted stock units, performance grants, and other stock based awards to employees and directors and is administered by the Compensation Committee of the Company's Board of Directors (Compensation Committee). At December 31, 2015 , there were 143,139 shares reserved for issuance under the 2012 Compensation Plan. Restricted stock units are awarded to certain associates and executive officers based upon meeting performance conditions determined by the Compensation Committee. These awards generally vest at the end of the third year following the year for which the Compensation Committee determines performance conditions have been met. At the end of the vesting period, recipients are entitled to receive one share of the Company's common stock for each vested restricted stock unit. During 2015 , the Company awarded 21,122 restricted stock units to associates and executive officers based on performance conditions being met. Restricted stock units also are awarded to associates and executive officers to assist the Company in securing or retaining the services of key employees. During 2015 , the Company awarded 567 restricted stock units to associates and executive officers as a hiring or retention incentive. The restricted stock units had a grant-date fair value of $0.4 million . These awards generally vest over a three -year period and entitle the recipient to receive one share of the Company's common stock for each vested restricted stock unit. During 2015 , the Company awarded 1,324 shares of restricted stock to its non-employee directors. The shares awarded to non-employee directors will vest in 2016 . The following table summarizes nonvested share-based awards. Number of Awards Weighted Average Grant-Date Fair Value Nonvested awards at January 1, 2015 118,132 $ 479.11 Granted 23,013 740.80 Vested (37,262 ) 424.51 Nonvested awards at December 31, 2015 103,883 $ 556.66 The fair value of the Company's share-based awards issued under the Omnibus Incentive Plan was determined based on the average price of the Company's common shares on the grant date. The fair value of the Company's share-based awards granted under the 2012 Compensation Plan is determined based on the closing price of the Company's common shares on the grant date. The weighted average grant-date fair value of the Company's share-based awards granted in 2015 , 2014 and 2013 was $740.80 , $583.74 and $517.24 , respectively. As of December 31, 2015 , unrecognized compensation cost related to nonvested share-based awards issued under the Omnibus Incentive Plan and 2012 Compensation plan was $16.4 million , which is expected to be recognized over a weighted average period of 1.9 years . The fair value of the Company's share-based awards that vested during 2015 , 2014 and 2013 was $15.8 million , $4.2 million and $2.5 million , respectively. e) In May 2013, in connection with the acquisition of Alterra, the Company issued 101,875 replacement options and 154,103 restricted stock awards to holders of Alterra options and restricted stock awards. The replacement options and restricted stock awards were issued under the terms and conditions of the Alterra Capital Holdings Limited 2008 Stock Incentive Plan, the Alterra Capital Holdings Limited 2006 Equity Incentive Plan and the Alterra Capital Holdings Limited 2000 Stock Incentive Plan (collectively, the Alterra Equity Award Plans). No further options or restricted stock awards are available for issuance under the Alterra Equity Award Plans. The replacement options issued were fully vested and exercisable as of the Acquisition Date and had a weighted average exercise price of $398.96 and a grant-date fair value of $140.08 , which was included in the acquisition consideration. The fair value of the options was estimated on the grant date using the Black-Scholes option pricing model. Assumptions used in the pricing model included an expected annual volatility of 19.04% , a risk-free rate of approximately 0.20% and an expected term of approximately two years . The expected annual volatility was based on the historical volatility of the Company's stock and other factors. The risk-free rate was based on the U.S. Treasury yield curve, with a remaining term equal to the expected term assumption at the grant date. The expected term of the options granted represents the period of time that the options were expected to be outstanding at the grant date. The following table summarizes additional information with respect to these options. Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (years) Intrinsic Value (in millions) Outstanding and exercisable, January 1, 2015 22,305 $ 411.98 Exercised 10,787 $ 418.41 Outstanding and exercisable, December 31, 2015 11,518 $ 405.97 0.9 $ 5.5 During 2015 , 10,787 options were exercised under the Alterra Equity Award Plans, resulting in cash proceeds of $4.5 million and a current tax benefit of $1.4 million . The intrinsic value of options exercised in 2015 was $4.1 million . During 2014, 13,636 options were exercised under the Alterra Equity Award Plans, resulting in cash proceeds of $5.6 million and a current tax benefit of $0.8 million . The intrinsic value of options exercised in 2014 was $2.5 million . From the Acquisition Date through December 31, 2013 , 65,934 options were exercised under the Alterra Equity Award Plans, resulting in cash proceeds of $24.3 million and a current tax benefit of $0.8 million . The intrinsic value of options exercised in 2013 was $9.4 million . The replacement restricted stock awards issued by the Company had a grant date fair value of $81.6 million , or $529.59 per share. The awards were partially vested as of the Acquisition Date and had a weighted average remaining service period of approximately one year . As a result, $61.0 million was recognized as part of the Acquisition Consideration and $20.6 million was recognized as compensation expense over the remaining service period of the awards. The fair value of the replacement restricted stock awards was determined based on the weighted average price of the Company's stock on April 30, 2013, the day preceding the Acquisition Date. The following table summarizes activity related to these nonvested restricted stock awards. Number of Awards Weighted Average Grant-Date Fair Value Nonvested awards at January 1, 2015 33,915 $ 529.59 Vested (33,915 ) 529.59 Nonvested awards at December 31, 2015 — $ — The Company recognized compensation expense totaling $0.5 million , $3.9 million and $12.7 million for the years ended December 31, 2015 , 2014 and 2013 , respectively, related to these restricted stock awards. As of December 31, 2015 , there was no unrecognized compensation cost related to the nonvested restricted stock awards. The fair value of the restricted stock awards that vested during 2015 , 2014 and 2013 was $18.0 million , $18.1 million and $41.3 million , respectively.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2015
Other Comprehensive Income (Loss), Tax [Abstract]
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) Other comprehensive income (loss) includes net holding gains (losses) arising during the period, changes in unrealized other-than-temporary impairment losses on fixed maturities arising during the period and reclassification adjustments for net gains included in net income. Other comprehensive income (loss) also includes changes in foreign currency translation adjustments and changes in net actuarial pension loss. The following table presents the change in accumulated other comprehensive income by component, net of taxes and noncontrolling interests. (dollars in thousands) Unrealized Holding Gains on Available-for- Sale Securities Foreign Currency Net Actuarial Pension Loss Total December 31, 2012 $ 946,933 $ (1,075 ) $ (34,521 ) $ 911,337 Other comprehensive income (loss) before reclassifications 225,404 (10,171 ) 2,517 217,750 Amounts reclassified from accumulated other comprehensive income (40,830 ) — 1,548 (39,282 ) Total other comprehensive income (loss) 184,574 (10,171 ) 4,065 178,468 December 31, 2013 $ 1,131,507 $ (11,246 ) $ (30,456 ) $ 1,089,805 Other comprehensive income (loss) before reclassifications 687,908 (32,245 ) (16,516 ) 639,147 Amounts reclassified from accumulated other comprehensive income (26,161 ) — 1,766 (24,395 ) Total other comprehensive income (loss) 661,747 (32,245 ) (14,750 ) 614,752 December 31, 2014 $ 1,793,254 $ (43,491 ) $ (45,206 ) $ 1,704,557 Other comprehensive loss before reclassifications (240,010 ) (29,205 ) (2,482 ) (271,697 ) Amounts reclassified from accumulated other comprehensive income (80,482 ) — 2,130 (78,352 ) Total other comprehensive loss (320,492 ) (29,205 ) (352 ) (350,049 ) December 31, 2015 $ 1,472,762 $ (72,696 ) $ (45,558 ) $ 1,354,508 The following table summarizes the tax expense (benefit) associated with each component of other comprehensive income (loss). Years Ended December 31, (dollars in thousands) 2015 2014 2013 Change in net unrealized gains on investments: Net holding gains (losses) arising during the period $ (107,860 ) $ 328,564 $ 93,837 Change in unrealized other-than-temporary impairment losses on fixed maturities arising during the period 35 614 (34 ) Reclassification adjustments for net gains included in net income (29,267 ) (9,890 ) (16,382 ) Change in net unrealized gains on investments (137,092 ) 319,288 77,421 Change in foreign currency translation adjustments 408 1,918 (1,619 ) Change in net actuarial pension loss (88 ) (3,687 ) 1,015 Total $ (136,772 ) $ 317,519 $ 76,817 The following table presents the details of amounts reclassified from accumulated other comprehensive income into income, by component. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Unrealized holding gains on available-for-sale securities: Other-than-temporary impairment losses $ (44,481 ) $ (4,784 ) $ (4,706 ) Net realized investment gains, excluding other-than-temporary impairment losses 154,230 40,835 61,918 Total before taxes 109,749 36,051 57,212 Income taxes (29,267 ) (9,890 ) (16,382 ) Reclassification of unrealized holding gains, net of taxes $ 80,482 $ 26,161 $ 40,830 Net actuarial pension loss: Underwriting, acquisition and insurance expenses $ (2,662 ) $ (2,084 ) $ (1,934 ) Income taxes 532 318 386 Reclassification of net actuarial pension loss, net of taxes $ (2,130 ) $ (1,766 ) $ (1,548 )

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements FASB ASC 820-10, Fair Value Measurements and Disclosures, establishes a three-level hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). If the inputs used to measure the assets or liabilities fall within different levels of the hierarchy, the classification is based on the lowest level input that is significant to the fair value measurement of the asset or liability. Classification of assets and liabilities within the hierarchy considers the markets in which the assets and liabilities are traded and the reliability and transparency of the assumptions used to determine fair value. The hierarchy requires the use of observable market data when available. The levels of the hierarchy are defined as follows: Level 1 - Inputs to the valuation methodology are quoted prices (unadjusted) for identical assets or liabilities traded in active markets. Level 2 - Inputs to the valuation methodology include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability and market-corroborated inputs. Level 3 - Inputs to the valuation methodology are unobservable for the asset or liability and are significant to the fair value measurement. In accordance with FASB ASC 820, the Company determines fair value based on the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. In determining fair value, the Company uses various methods, including the market, income and cost approaches. The Company uses valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs. The following section describes the valuation methodologies used by the Company to measure assets and liabilities at fair value, including an indication of the level within the fair value hierarchy in which each asset or liability is generally classified. Investments available-for-sale. Investments available-for-sale are recorded at fair value on a recurring basis and include fixed maturities, equity securities and short-term investments. Short-term investments include certificates of deposit, commercial paper, discount notes and treasury bills with original maturities of one year or less. Fair value for investments available-for-sale is determined by the Company after considering various sources of information, including information provided by a third party pricing service. The pricing service provides prices for substantially all of the Company's fixed maturities and equity securities. In determining fair value, the Company generally does not adjust the prices obtained from the pricing service. The Company obtains an understanding of the pricing service's valuation methodologies and related inputs, which include, but are not limited to, reported trades, benchmark yields, issuer spreads, bids, offers, duration, credit ratings, estimated cash flows and prepayment speeds. The Company validates prices provided by the pricing service by reviewing prices from other pricing sources and analyzing pricing data in certain instances. The Company has evaluated the various types of securities in its investment portfolio to determine an appropriate fair value hierarchy level based upon trading activity and the observability of market inputs. Level 1 investments include those traded on an active exchange, such as the New York Stock Exchange. Level 2 investments include U.S. Treasury securities and obligations of U.S. government agencies, municipal bonds, foreign government bonds, commercial mortgage-backed securities, residential mortgage-backed securities, asset-backed securities and corporate debt securities. Fair value for investments available-for-sale is measured based upon quoted prices in active markets, if available. Due to variations in trading volumes and the lack of quoted market prices, fixed maturities are classified as Level 2 investments. The fair value of fixed maturities is normally derived through recent reported trades for identical or similar securities, making adjustments through the reporting date based upon available market observable data described above. If there are no recent reported trades, the fair value of fixed maturities may be derived through the use of matrix pricing or model processes, where future cash flow expectations are developed based upon collateral performance and discounted at an estimated market rate. Significant inputs used to determine the fair value of obligations of states, municipalities and political subdivisions, corporate bonds and obligations of foreign governments include reported trades, benchmark yields, issuer spreads, bids, offers, credit information and estimated cash flows. Significant inputs used to determine the fair value of commercial mortgage-backed securities, residential mortgage-backed securities and asset-backed securities include the type of underlying assets, benchmark yields, prepayment speeds, collateral information, tranche type and volatility, estimated cash flows, credit information, default rates, recovery rates, issuer spreads and the year of issue. Senior long-term debt and other debt. Senior long-term debt and other debt is carried at amortized cost with the estimated fair value disclosed on the consolidated balance sheets. Senior long-term debt and other debt is classified as Level 2 within the fair value hierarchy due to variations in trading volumes and the lack of quoted market prices. Fair value for senior long-term debt and other debt is generally derived through recent reported trades for identical securities, making adjustments through the reporting date, if necessary, based upon available market observable data including U.S. Treasury securities and implied credit spreads. Significant inputs used to determine the fair value of senior long-term debt and other debt include reported trades, benchmark yields, issuer spreads, bids and offers. The following tables present the balances of assets measured at fair value on a recurring basis by level within the fair value hierarchy. December 31, 2015 (dollars in thousands) Level 1 Level 2 Level 3 Total Assets: Investments available-for-sale: Fixed maturities: U.S. Treasury securities and obligations of U.S. government agencies $ — $ 700,707 $ — $ 700,707 Obligations of states, municipalities and political subdivisions — 4,013,213 — 4,013,213 Foreign governments — 1,416,457 — 1,416,457 Commercial mortgage-backed securities — 659,538 — 659,538 Residential mortgage-backed securities — 854,247 — 854,247 Asset-backed securities — 36,071 — 36,071 Corporate bonds — 1,714,235 — 1,714,235 Total fixed maturities — 9,394,468 — 9,394,468 Equity securities: Insurance, banks and other financial institutions 1,334,722 — — 1,334,722 Industrial, consumer and all other 2,739,753 — — 2,739,753 Total equity securities 4,074,475 — — 4,074,475 Short-term investments 1,529,924 112,337 — 1,642,261 Total investments available-for-sale $ 5,604,399 $ 9,506,805 $ — $ 15,111,204 December 31, 2014 (dollars in thousands) Level 1 Level 2 Level 3 Total Assets: Investments available-for-sale: Fixed maturities: U.S. Treasury securities and obligations of U.S. government agencies $ — $ 673,262 $ — $ 673,262 Obligations of states, municipalities and political subdivisions — 4,317,547 — 4,317,547 Foreign governments — 1,611,921 — 1,611,921 Commercial mortgage-backed securities — 430,627 — 430,627 Residential mortgage-backed securities — 982,847 — 982,847 Asset-backed securities — 99,490 — 99,490 Corporate bonds — 2,307,188 — 2,307,188 Total fixed maturities — 10,422,882 — 10,422,882 Equity securities: Insurance, banks and other financial institutions 1,311,925 — — 1,311,925 Industrial, consumer and all other 2,825,651 — — 2,825,651 Total equity securities 4,137,576 — — 4,137,576 Short-term investments 1,469,975 124,874 — 1,594,849 Total investments available-for-sale $ 5,607,551 $ 10,547,756 $ — $ 16,155,307 There were no transfers into or out of Level 1 and Level 2 during 2015 or 2014 . Other than the acquisitions disclosed in note 2, the Company did not have any assets or liabilities measured at fair value on a non-recurring basis during the years ended December 31, 2015 and 2014 .

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2015
Reinsurance Disclosures [Abstract]
Reinsurance	Reinsurance The Company uses reinsurance and retrocessional reinsurance to manage its net retention on individual risks and overall exposure to losses while providing it with the ability to offer policies with sufficient limits to meet policyholder needs. Historically, the Company's products were written with limits that did not require significant reinsurance. Following the acquisition of Alterra, the Company has certain insurance and reinsurance products that use higher levels of reinsurance. In a reinsurance transaction, an insurance company transfers, or cedes, all or part of its exposure in return for a portion of the premium. In a retrocessional reinsurance transaction, a reinsurance company transfers, or cedes, all or part of its exposure in return for a portion of the premium. The ceding of insurance does not legally discharge the Company from its primary liability for the full amount of the policies, and the Company will be required to pay the loss and bear collection risk if the reinsurer fails to meet its obligations under the reinsurance or retrocessional agreement. A credit risk exists with ceded reinsurance to the extent that any reinsurer is unable to meet the obligations assumed under the reinsurance or retrocessional contracts. Allowances are established for amounts deemed uncollectible. The Company evaluates the financial condition of its reinsurers and monitors concentration of credit risk arising from its exposure to individual reinsurers. At December 31, 2015 and 2014 , balances recoverable from the Company's ten largest reinsurers, by group, represented approximately 68% and 63% , respectively, of the reinsurance recoverable on paid and unpaid losses, before considering reinsurance allowances. At December 31, 2015 , the Company's largest reinsurance balance was due from the Fairfax Financial Group and represented 17% of the reinsurance recoverable on paid and unpaid losses, before considering reinsurance allowances. To further reduce credit exposure to reinsurance recoverable balances, the Company has received collateral, including letters of credit and trust accounts, from certain reinsurers. Collateral related to these reinsurance agreements is available, without restriction, when the Company pays losses covered by the reinsurance agreements. The following table summarizes the Company's reinsurance allowance for doubtful accounts. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Reinsurance allowance, beginning of year $ 59,813 $ 76,210 $ 71,148 Additions 5,897 10,316 13,621 Deductions (6,360 ) (26,713 ) (8,559 ) Reinsurance allowance, end of year $ 59,350 $ 59,813 $ 76,210 Management believes the Company's reinsurance allowance for doubtful accounts is adequate at December 31, 2015 ; however, the deterioration in the credit quality of existing reinsurers or disputes over reinsurance and retrocessional contracts could result in additional charges. The following table summarizes the effect of reinsurance and retrocessional reinsurance on premiums written and earned. Years Ended December 31, 2015 2014 2013 (dollars in thousands) Written Earned Written Earned Written Earned Direct $ 3,474,510 $ 3,480,297 $ 3,478,273 $ 3,443,912 $ 3,143,957 $ 2,947,812 Assumed 1,158,402 1,194,772 1,327,240 1,298,371 776,269 1,016,853 Ceded (813,619 ) (851,537 ) (888,498 ) (901,371 ) (683,543 ) (733,049 ) Net premiums $ 3,819,293 $ 3,823,532 $ 3,917,015 $ 3,840,912 $ 3,236,683 $ 3,231,616 Incurred losses and loss adjustment expenses were net of reinsurance recoverables (ceded incurred losses and loss adjustment expenses) of $330.7 million , $423.1 million and $269.4 million for the years ended December 31, 2015 , 2014 and 2013 , respectively. The percentage of ceded earned premiums to gross earned premiums was 18% , 19% and 18% for the years ended December 31, 2015 , 2014 and 2013 , respectively. The percentage of assumed earned premiums to net earned premiums was 31% , 34% and 31% for the years ended December 31, 2015 , 2014 and 2013 , respectively. See note 9 of the notes to consolidated financial statements for information regarding two retroactive reinsurance transactions completed during 2015 to cede portfolios of policies primarily comprised of liabilities arising from A&E exposures.

Commitments And Contingencies

Commitments And Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingencies	Commitments and Contingencies a) The Company leases substantially all of its facilities and certain furniture and equipment under noncancelable operating leases with remaining terms up to 19 years. The following table summarizes the Company's minimum annual rental commitments, excluding taxes, insurance and other operating costs payable directly by the Company, for noncancelable operating leases at December 31, 2015 . Years Ending December 31, (dollars in thousands) 2016 $ 29,664 2017 34,083 2018 30,708 2019 27,947 2020 21,597 2021 and thereafter 130,844 Total $ 274,843 Rental expense was $44.3 million , $42.7 million and $35.3 million for the years ended December 31, 2015 , 2014 and 2013 , respectively. b) Contingencies arise in the normal course of the Company's operations and are not expected to have a material impact on the Company's financial condition or results of operations.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2015
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions The Company engages in certain related party transactions in the normal course of business. These transactions are at arm's length and are not material to the Company's consolidated financial statements.

Statutory Financial Information

Statutory Financial Information	12 Months Ended
	Dec. 31, 2015
Statutory Financial Information [Abstract]
Statutory Financial Information	Statutory Financial Information a) Statutory capital and surplus and statutory net income (loss) for the Company's wholly-owned insurance subsidiaries as of December 31, 2015 and 2014 and for the years ended December 31, 2015 , 2014 and 2013 , respectively, is summarized below. Statutory Capital and Surplus (dollars in thousands) 2015 2014 United States $ 2,569,928 $ 2,619,001 United Kingdom $ 608,342 $ 608,001 Bermuda $ 1,966,021 $ 1,890,218 Other $ 17,305 $ 177,824 As of December 31, 2015 , the amount of statutory capital and surplus necessary to satisfy regulatory requirements is not significant in relation to actual statutory capital and surplus. Statutory Net Income (Loss) Years Ended December 31, (dollars in thousands) 2015 2014 2013 United States $ 291,783 $ 212,909 $ 235,009 United Kingdom $ 63,583 $ 73,697 $ 109,983 Bermuda $ 189,800 $ 110,401 $ 249,772 Other $ (3,181 ) $ 1,367 $ (12,617 ) United States The laws of the domicile states of the Company's U.S. insurance subsidiaries govern the amount of dividends that may be paid to the Company. Generally, statutes in the domicile states of the Company's U.S. insurance subsidiaries require prior approval for payment of extraordinary, as opposed to ordinary, dividends. At December 31, 2015 , the Company's U.S. insurance subsidiaries could pay up to $354.0 million during the following 12 months under the ordinary dividend regulations. In converting from U.S. statutory accounting principles to U.S. GAAP, typical adjustments include deferral of policy acquisition costs, differences in the calculation of deferred income taxes and the inclusion of net unrealized gains or losses relating to fixed maturities in shareholders' equity. The Company does not use any permitted statutory accounting practices that are different from prescribed statutory accounting practices which impact statutory capital and surplus. United Kingdom The Company's United Kingdom insurance subsidiary and its Lloyd's managing agent are authorized by the Prudential Regulation Authority (PRA) and regulated by both the PRA and the Financial Conduct Authority (FCA). The PRA oversees compliance with established periodic auditing and reporting requirements, minimum solvency margins and individual capital assessment requirements under the Solvency II Directive and imposes dividend restrictions, while both the PRA and the FCA oversee compliance with risk assessment reviews and various other requirements. Markel International Insurance Company Limited (MIICL) is required to give advance notice to the PRA for any dividends from MIICL and any transaction or proposed transaction with a connected or related person. Markel Syndicate Management Limited, the managing agent of the Company's syndicate at Lloyd's, is required to satisfy the solvency requirements of Lloyd's. In addition, the Company's United Kingdom subsidiaries must comply with the United Kingdom Companies Act of 2006, which provides that dividends may only be paid out of profits available for that purpose. As of December 31, 2015 , earnings of the Company's United Kingdom subsidiaries are considered reinvested indefinitely for U.S. income tax purposes and will not be made available for distributions to the holding company. Bermuda Markel Bermuda is subject to enhanced capital requirements in addition to minimum solvency and liquidity requirements. The enhanced capital requirement is determined by reference to a risk-based capital model that determines a control threshold for statutory capital and surplus by taking into account the risk characteristics of different aspects of the insurer's business. At December 31, 2015 , Markel Bermuda satisfied both the enhanced capital requirements and the minimum solvency and liquidity requirements. Under the Bermuda Insurance Act, Markel Bermuda is prohibited from paying or declaring dividends during a fiscal year if it is in breach of its enhanced capital requirement, solvency margin or minimum liquidity ratio or if the declaration or payment of the dividend would cause a breach. If an insurer fails to meet its solvency margin or minimum liquidity ratio on the last day of any financial year, it is prohibited from declaring or paying any dividends during the next financial year without the approval of the Bermuda Monetary Authority (BMA). Further, Markel Bermuda is prohibited from declaring or paying, in any financial year, dividends of more than 25% of its total statutory capital and surplus as set forth in its previous year's statutory balance sheet unless at least seven days before payment of those dividends it files with the BMA an affidavit stating that it will continue to meet its solvency margin and minimum liquidity ratio. Markel Bermuda must obtain the BMA's prior approval for a reduction by 15% or more of the total statutory capital as set forth in its previous year's financial statements. In addition, as a long-term insurer, Markel Bermuda may not declare or pay a dividend to any person other than a policyholder unless the value of the assets in its long-term business fund, as certified by Markel Bermuda's approved actuary, exceeds the liabilities of its long-term business by the amount of the dividend and at least the prescribed minimum solvency margin. As of December 31, 2015 , Markel Bermuda could pay up to $491.5 million during the following 12 months without making any additional filings with the BMA. Other Jurisdictions The Company's other foreign subsidiaries are subject to capital and solvency requirements in their respective jurisdictions of domicile that govern their ability to declare and pay dividends. As of December 31, 2015 , earnings of our foreign subsidiaries are considered reinvested indefinitely for U.S. income tax purposes and will not be made available for distributions to the holding company. b) Lloyd's sets the corporate members' required capital annually based on each syndicates' business plans, rating environment, reserving environment and input arising from Lloyd's discussions with, inter alia, regulatory and rating agencies. Such required capital is referred to as Funds at Lloyd's (FAL), and comprises cash and investments. The amount of cash and investments held as FAL as of December 31, 2015 was $827.9 million . The amount which the Company provides as FAL is not available for distribution to the holding company. The Company's corporate members may also be required to maintain funds under the control of Lloyd's in excess of their capital requirements and such funds also may not be available for distribution to the holding company.

Segment Reporting Disclosures

Segment Reporting Disclosures	12 Months Ended
	Dec. 31, 2015
Segment Reporting, Disclosure of Entity's Reportable Segments [Abstract]
Segment Reporting Disclosures	Segment Reporting Disclosures The Company monitors and reports its ongoing underwriting operations in the following three segments: U.S. Insurance, International Insurance and Reinsurance. In determining how to aggregate and monitor its underwriting results, the Company considers many factors, including the geographic location and regulatory environment of the insurance entity underwriting the risk, the nature of the insurance product sold, the type of account written and the type of customer served. The U.S. Insurance segment includes all direct business and facultative placements written by the Company's insurance subsidiaries domiciled in the United States. The International Insurance segment includes all direct business and facultative placements written by the Company's insurance subsidiaries domiciled outside of the United States, including the Company's syndicate at Lloyd's. The Reinsurance segment includes all treaty reinsurance written across the Company. Results for lines of business discontinued prior to, or in conjunction with, acquisitions, including the results attributable to the run-off of life and annuity reinsurance business, are reported in the Other Insurance (Discontinued Lines) segment. All investing activities related to the Company's insurance operations are included in the Investing segment. The Company's non-insurance operations include its Markel Ventures operations, which primarily consist of controlling interests in various industrial and service businesses. The Company's non-insurance operations also include the results of the Company's legal and professional consulting services, and effective December 8, 2015, the results attributable to Markel CATCo IM. For purposes of segment reporting, the Company's non-insurance operations are not considered to be a reportable segment. The following table summarizes the Company's gross written premiums by country. Gross written premiums are attributed to individual countries based upon location of risk. Years Ended December 31, (dollars in thousands) 2015 % of Total 2014 % of Total 2013 % of Total United States $ 3,519,487 76 % $ 3,523,239 73 % $ 2,934,868 75 % United Kingdom 414,941 9 441,669 9 245,143 6 Canada 115,191 2 125,617 3 128,420 3 Other countries 583,293 13 714,988 15 611,795 16 Total $ 4,632,912 100 % $ 4,805,513 100 % $ 3,920,226 100 % Most of the Company's gross written premiums are placed through insurance and reinsurance brokers. During the years ended December 31, 2015 , 2014 and 2013 , the top three independent brokers accounted for approximately 27% , 28% and 24% of consolidated gross premiums written. During the years ended December 31, 2015 , 2014 and 2013 , the top three independent brokers accounted for approximately and 42% , 41% and 42% , respectively, of gross premiums written in the International Insurance segment, and 68% of gross premiums written in the Reinsurance segment each year. Segment profit for the Investing segment is measured by net investment income and net realized investment gains or losses. Segment profit or loss for each of the Company's underwriting segments is measured by underwriting profit or loss. The property and casualty insurance industry commonly defines underwriting profit or loss as earned premiums net of losses and loss adjustment expenses and underwriting, acquisition and insurance expenses. Underwriting profit or loss does not replace operating income or net income computed in accordance with U.S. GAAP as a measure of profitability. Underwriting profit or loss provides a basis for management to evaluate the Company's underwriting performance. Segment profit or loss for the Company's underwriting segments also includes other revenues and other expenses, primarily related to the run-off of managing general agent operations that were discontinued in conjunction with acquisitions. Other revenues and other expenses in the Other Insurance (Discontinued Lines) segment are comprised of the results attributable to the run-off of life and annuity reinsurance business. For management reporting purposes, the Company allocates assets to its underwriting, investing and non-insurance operations. Underwriting assets are all assets not specifically allocated to the Investing segment or to the Company's non-insurance operations. Underwriting and investing assets are not allocated to the U.S. Insurance, International Insurance, Reinsurance or Other Insurance (Discontinued Lines) segments since the Company does not manage its assets by underwriting segment. The Company does not allocate capital expenditures for long-lived assets to any of its underwriting segments for management reporting purposes. a) The following tables summarize the Company's segment disclosures. Year Ended December 31, 2015 (dollars in thousands) U.S. Insurance International Insurance Reinsurance Other Insurance (Discontinued Lines) Investing Consolidated Gross premium volume $ 2,504,096 $ 1,164,866 $ 965,374 $ (1,424 ) $ — $ 4,632,912 Net written premiums 2,106,490 888,214 824,324 265 — 3,819,293 Earned premiums 2,105,212 879,426 838,543 351 — 3,823,532 Losses and loss adjustment expenses: Current accident year (1,367,159 ) (638,144 ) (561,242 ) — — (2,566,545 ) Prior accident years 298,967 248,834 97,860 (17,861 ) — 627,800 Amortization of policy acquisition costs (420,289 ) (142,657 ) (182,018 ) — — (744,964 ) Other operating expenses (378,563 ) (221,758 ) (106,863 ) (2,932 ) — (710,116 ) Underwriting profit (loss) 238,168 125,701 86,280 (20,442 ) — 429,707 Net investment income — — — — 353,213 353,213 Net realized investment gains — — — — 106,480 106,480 Other revenues (insurance) 3,331 7,790 593 617 — 12,331 Other expenses (insurance) (3,902 ) (5,717 ) (1,419 ) (29,057 ) — (40,095 ) Segment profit (loss) $ 237,597 $ 127,774 $ 85,454 $ (48,882 ) $ 459,693 $ 861,636 Other revenues (non-insurance) 1,074,427 Other expenses (non-insurance) (1,006,710 ) Amortization of intangible assets (68,947 ) Interest expense (118,301 ) Income before income taxes $ 742,105 U.S. GAAP combined ratio (1) 89 % 86 % 90 % NM (2) 89 % (1) The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums. (2) NM — Ratio is not meaningful. Year Ended December 31, 2014 (dollars in thousands) U.S. Insurance International Insurance Reinsurance Other Insurance (Discontinued Lines) Investing Consolidated Gross premium volume $ 2,493,823 $ 1,200,403 $ 1,112,728 $ (1,441 ) $ — $ 4,805,513 Net written premiums 2,071,466 889,336 956,584 (371 ) — 3,917,015 Earned premiums 2,022,860 909,679 908,385 (12 ) — 3,840,912 Losses and loss adjustment expenses: Current accident year (1,340,129 ) (660,409 ) (637,474 ) — — (2,638,012 ) Prior accident years 216,557 166,615 79,951 (27,578 ) — 435,545 Amortization of policy acquisition costs (403,233 ) (141,394 ) (110,289 ) — — (654,916 ) Other operating expenses (396,737 ) (207,175 ) (201,673 ) (381 ) — (805,966 ) Underwriting profit (loss) 99,318 67,316 38,900 (27,971 ) — 177,563 Net investment income — — — — 363,230 363,230 Net realized investment gains — — — — 46,000 46,000 Other revenues (insurance) 2,478 21,827 2,696 1,631 — 28,632 Other expenses (insurance) (5,149 ) (18,706 ) (1,847 ) (37,132 ) — (62,834 ) Segment profit (loss) $ 96,647 $ 70,437 $ 39,749 $ (63,472 ) $ 409,230 $ 552,591 Other revenues (non-insurance) 854,893 Other expenses (non-insurance) (792,037 ) Amortization of intangible assets (57,627 ) Interest expense (117,442 ) Income before income taxes $ 440,378 U.S. GAAP combined ratio (1) 95 % 93 % 96 % NM (2) 95 % (1) The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums. (2) NM — Ratio is not meaningful. Year Ended December 31, 2013 (dollars in thousands) U.S. Insurance International Insurance Reinsurance Other Insurance (Discontinued Lines) Investing Consolidated Gross premium volume $ 2,252,739 $ 1,101,099 $ 566,348 $ 40 $ — $ 3,920,226 Net written premiums 1,915,770 840,050 480,822 41 — 3,236,683 Earned premiums 1,727,766 833,984 669,826 40 — 3,231,616 Losses and loss adjustment expenses: Current accident year (1,173,258 ) (588,759 ) (465,385 ) — — (2,227,402 ) Prior accident years 298,113 130,660 12,938 (30,582 ) — 411,129 Transaction costs and other acquisition-related expenses (1) (12,724 ) (13,366 ) (49,050 ) — — (75,140 ) Amortization of policy acquisition costs (287,795 ) (138,626 ) (45,494 ) — — (471,915 ) Other operating expenses (409,886 ) (171,666 ) (183,817 ) 112 — (765,257 ) Underwriting profit (loss) 142,216 52,227 (60,982 ) (30,430 ) — 103,031 Net investment income — — — — 317,373 317,373 Net realized investment gains — — — — 63,152 63,152 Other revenues (insurance) 13,648 4,284 5,432 1,130 — 24,494 Other expenses (insurance) (17,087 ) (5,065 ) — (28,126 ) — (50,278 ) Segment profit (loss) $ 138,777 $ 51,446 $ (55,550 ) $ (57,426 ) $ 380,525 $ 457,772 Other revenues (non-insurance) 686,448 Other expenses (non-insurance) (613,250 ) Amortization of intangible assets (55,223 ) Interest expense (114,004 ) Income before income taxes $ 361,743 U.S. GAAP combined ratio (2) 92 % 94 % 109 % NM (3) 97 % (1) In connection with the acquisition of Alterra, the Company incurred transaction costs of $16.0 million for the year ended December 31, 2013, which primarily consist of due diligence, legal and investment banking costs. Additionally, the Company incurred severance costs of $31.7 million , stay bonuses of $14.8 million and other compensation costs totaling $12.6 million related to the acceleration of certain long-term incentive compensation awards and restricted stock awards that were granted by Alterra prior to the acquisition. (2) The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums. (3) NM — Ratio is not meaningful. b) The following table summarizes deferred policy acquisition costs, unearned premiums and unpaid losses and loss adjustment expenses by segment. (dollars in thousands) Deferred Policy Acquisition Costs Unearned Premiums Unpaid Losses and Loss Adjustment Expenses December 31, 2015 U.S. Insurance $ 162,289 $ 1,105,456 $ 3,720,429 International Insurance 48,913 467,158 3,140,000 Reinsurance 141,554 593,491 2,750,258 Other Insurance (Discontinued Lines) — — 641,266 Total $ 352,756 $ 2,166,105 $ 10,251,953 December 31, 2014 U.S. Insurance $ 165,333 $ 1,110,910 $ 3,577,166 International Insurance 47,618 491,708 3,353,417 Reinsurance 140,459 643,072 2,818,792 Other Insurance (Discontinued Lines) — — 654,777 Total $ 353,410 $ 2,245,690 $ 10,404,152 c) The following table summarizes segment earned premiums by major product grouping. Years Ended December 31, (dollars in thousands) 2015 2014 2013 U.S. Insurance: General liability $ 522,358 $ 491,645 $ 431,798 Professional liability 324,230 321,005 268,203 Property 264,232 266,019 190,530 Personal lines 325,811 299,442 185,935 Programs 277,829 244,216 205,004 Workers compensation 281,954 263,164 250,790 Other 108,798 137,369 195,506 Total U.S. Insurance 2,105,212 2,022,860 1,727,766 International Insurance: General liability 124,198 146,178 128,171 Professional liability 268,637 285,300 252,816 Property 85,152 76,691 91,497 Marine and energy 262,307 287,263 287,745 Other 139,132 114,247 73,755 Total International Insurance 879,426 909,679 833,984 Reinsurance: Property 265,373 270,461 227,394 Casualty 315,027 323,390 244,981 Auto 102,227 152,645 84,042 Other 155,916 161,889 113,409 Total Reinsurance 838,543 908,385 669,826 Other Insurance (Discontinued Lines) 351 (12 ) 40 Total earned premiums $ 3,823,532 $ 3,840,912 $ 3,231,616 The Company does not manage products at this level of aggregation. The Company offers a diverse portfolio of products and manages these products in logical groupings within each operating segment. d) The following table reconciles segment assets to the Company's consolidated balance sheets. December 31, (dollars in thousands) 2015 2014 2013 Segment assets: Investing $ 18,056,947 $ 18,531,150 $ 17,550,332 Underwriting 5,386,710 5,422,445 5,468,731 Total segment assets 23,443,657 23,953,595 23,019,063 Non-insurance operations 1,497,614 1,246,762 936,448 Total assets $ 24,941,271 $ 25,200,357 $ 23,955,511

Other Revenues And Other Expens

Other Revenues And Other Expenses	12 Months Ended
	Dec. 31, 2015
Other Income and Expenses [Abstract]
Other Revenues And Other Expenses	Other Revenues and Other Expenses The following table summarizes the components of other revenues and other expenses. Years Ended December 31, 2015 2014 2013 (dollars in thousands) Other Revenues Other Expenses Other Revenues Other Expenses Other Revenues Other Expenses Insurance: Managing general agent operations $ 10,202 $ 9,619 $ 23,324 $ 22,527 $ 17,399 $ 20,382 Life and annuity 617 29,057 1,631 37,132 1,130 28,126 Other 1,512 1,419 3,677 3,175 5,965 1,770 12,331 40,095 28,632 62,834 24,494 50,278 Non-Insurance: Markel Ventures: Manufacturing 755,802 677,054 575,353 513,668 495,138 437,712 Markel Ventures: Non-Manufacturing 291,714 301,004 262,767 261,551 191,310 175,538 Other 26,911 28,652 16,773 16,818 — — 1,074,427 1,006,710 854,893 792,037 686,448 613,250 Total $ 1,086,758 $ 1,046,805 $ 883,525 $ 854,871 $ 710,942 $ 663,528 The Company's Markel Ventures operations primarily consist of controlling interests in various industrial and service businesses and are viewed by management as separate and distinct from the Company's insurance operations. While each of the businesses is operated independently from one another, management aggregates financial results into two industry groups: manufacturing and non-manufacturing.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2015
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Employee Benefit Plans	Employee Benefit Plans a) The Company maintains defined contribution plans for employees of its United States insurance operations in accordance with Section 401(k) of the IRC. Employees of the Company's Markel Ventures subsidiaries are provided post-retirement benefits under separate plans. The Company also provides various defined contribution plans for employees of its international insurance and non-insurance operations, which are in line with local market terms and conditions of employment. Expenses relating to the Company's defined contribution plans, including the defined contribution plans of Alterra effective May 1, 2013, were $27.7 million , $27.2 million and $24.3 million in 2015 , 2014 and 2013 , respectively. b) The Terra Nova Pension Plan is a defined benefit plan which covers certain employees in our international insurance operations who meet the eligibility conditions set out in the plan. The plan has been closed to new participants since 2001. The cost of providing pensions for employees is charged to earnings over the average working life of employees according to actuarial recommendations. Final benefits are based on the employee's years of credited service and the higher of pensionable compensation received in the calendar year preceding retirement or the best average pensionable compensation received in any three consecutive years in the ten years preceding retirement. Effective April 1, 2012, employees are no longer accruing benefits for future service in the Terra Nova Pension Plan. The Company uses December 31 as the measurement date for the Terra Nova Pension Plan. The following table summarizes the funded status of the Terra Nova Pension Plan and the amounts recognized on the accompanying consolidated balance sheets of the Company. Years Ended December 31, (dollars in thousands) 2015 2014 Change in projected benefit obligation: Projected benefit obligation at beginning of period $ 185,556 $ 163,010 Interest cost 6,645 7,572 Plan amendments — 495 Plan settlements (2,863 ) — Benefits paid (3,970 ) (4,424 ) Actuarial loss (gain) (6,051 ) 29,609 Effect of foreign currency rate changes (9,312 ) (10,706 ) Projected benefit obligation at end of year $ 170,005 $ 185,556 Change in plan assets: Fair value of plan assets at beginning of period $ 201,399 $ 189,437 Actual gain on plan assets 2,246 22,395 Employer contributions — 5,610 Plan settlements (2,766 ) — Benefits paid (3,970 ) (4,424 ) Effect of foreign currency rate changes (10,182 ) (11,619 ) Fair value of plan assets at end of year $ 186,727 $ 201,399 Funded status of the plan $ 16,722 $ 15,843 Net actuarial pension loss 61,818 61,378 Total $ 78,540 $ 77,221 Net actuarial pension loss is recognized as a component of accumulated other comprehensive income, net of taxes. The asset for pension benefits, also referred to as the funded status of the plan, at December 31, 2015 and December 31, 2014 was included in other assets on the consolidated balance sheets. The following table presents the changes in plan assets and projected benefit obligation recognized in accumulated other comprehensive income. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Net actuarial gain (loss) $ (3,102 ) $ (20,521 ) $ 3,146 Settlement loss recognized 343 — — Amortization of: Net actuarial loss 2,319 1,589 1,934 Prior service costs — 495 — Tax benefit (expense) 88 3,687 (1,015 ) Total other comprehensive income (loss) $ (352 ) $ (14,750 ) $ 4,065 The following table summarizes the components of net periodic benefit income and the weighted average assumptions for the Terra Nova Pension Plan. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Components of net periodic benefit income: Interest cost $ 6,645 $ 7,572 $ 6,533 Expected return on plan assets (11,496 ) (12,812 ) (10,825 ) Amortization of prior service cost — 495 — Amortization of net actuarial pension loss 2,319 1,589 1,934 Settlement loss recognized 343 — — Net periodic benefit income $ (2,189 ) $ (3,156 ) $ (2,358 ) Weighted average assumptions as of December 31: Discount rate 4.0 % 3.8 % 4.7 % Expected return on plan assets 5.4 % 6.0 % 6.6 % Rate of compensation increase 2.9 % 2.9 % 3.2 % The projected benefit obligation and the net periodic benefit income are determined by independent actuaries using assumptions provided by the Company. In determining the discount rate, the Company uses the current yield on high-quality, fixed-income investments that have maturities corresponding to the anticipated timing of estimated defined benefit payments. The expected return on plan assets is estimated based upon the anticipated average yield on plan assets using asset return assumptions for each asset class, and the cross-correlations between the asset classes, over a specified projection horizon. The rate of compensation increase is based upon historical experience and management's expectation of future compensation. Management's discount rate and rate of compensation increase assumptions at December 31, 2015 were used to calculate the Company's projected benefit obligation. Management's discount rate, expected return on plan assets and rate of compensation increase assumptions at December 31, 2014 were used to calculate the net periodic benefit income for 2015 . The Company estimates that net periodic benefit income in 2016 will include an expense of $2.3 million resulting from the amortization of the net actuarial pension loss included as a component of accumulated other comprehensive income at December 31, 2015 . The fair values of each of the plan's assets are measured using quoted prices in active markets for identical assets, which represent Level 1 inputs within the fair value hierarchy established in FASB ASC 820-10. The following table summarizes the fair value of plan assets as of December 31, 2015 and 2014 . December 31, (dollars in thousands) 2015 2014 Plan assets: Fixed maturity index funds $ 107,033 $ 114,243 Equity security index funds 79,686 87,148 Cash and cash equivalents 8 8 Total $ 186,727 $ 201,399 During 2014, the Company revised the target asset allocation and adjusted the investment balances to reduce risk while maintaining long-term return objectives. The Company's target asset allocation for the plan is 47% equity securities and 53% fixed maturities. At December 31, 2015 and 2014 , the actual allocation of assets in the plan was 43% equity securities and 57% fixed maturities. Investments are managed by a third party investment manager. Equity securities are invested in an index fund where 30% is indexed to United Kingdom equities and 70% is indexed to other markets. Assets are also invested in a mutual fund with a diversified global portfolio of equities, investment grade debt, property and cash. The primary objective of investing in these funds is to earn rates of return that are consistently in excess of inflation. Investing in equity securities, historically, has provided rates of return that are higher than investments in fixed maturities. Fixed maturity investments are allocated between five mutual funds; two index funds that include United Kingdom government securities, one index fund that includes securities issued by other foreign governments, one mutual fund that includes investment grade corporate bonds from the United Kingdom and foreign markets and one index fund that includes United Kingdom corporate securities. The assets in these funds are invested to meet the Company's obligations for current pensioners and those individuals nearing retirement. The plan does not invest in the Company's common shares. At December 31, 2015 and 2014 , the fair value of plan assets exceeded the plan's accumulated benefit obligation of $164.8 million and $166.9 million , respectively. The Company does not expect to have any required contributions or make any voluntary plan contributions in 2016 . The benefits expected to be paid in each year from 2016 to 2020 are $3.1 million , $3.2 million , $3.3 million , $3.3 million and $3.4 million , respectively. The aggregate benefits expected to be paid in the five years from 2021 to 2025 are $18.3 million . The expected benefits to be paid are based on the same assumptions used to measure the Company's projected benefit obligation at December 31, 2015 and include estimated future employee service.

Markel Corporation (Parent Comp

Markel Corporation (Parent Company Only) Financial Information	12 Months Ended
	Dec. 31, 2015
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Markel Corporation (Parent Company Only) Financial Information	Markel Corporation (Parent Company Only) Financial Information The following parent company only condensed financial information reflects the financial position, results of operations and cash flows of Markel Corporation. CONDENSED BALANCE SHEETS December 31, 2015 2014 (dollars in thousands) ASSETS Investments, available-for-sale, at estimated fair value: Fixed maturities (amortized cost of $35,475 in 2015 and $47,346 in 2014) $ 36,618 $ 48,807 Equity securities (cost of $204,289 in 2015 and $193,864 in 2014) 311,405 434,714 Short-term investments (estimated fair value approximates cost) 755,619 764,953 Total Investments 1,103,642 1,248,474 Cash and cash equivalents 460,271 243,702 Restricted cash and cash equivalents 670 959 Receivables 17,200 16,110 Investments in consolidated subsidiaries 7,961,315 7,560,862 Notes receivable from subsidiaries 212,636 212,631 Income taxes receivable — 10,951 Other assets 91,151 93,434 Total Assets $ 9,846,885 $ 9,387,123 LIABILITIES AND SHAREHOLDERS' EQUITY Senior long-term debt $ 1,634,472 $ 1,635,173 Notes payable to subsidiaries 300,000 15,000 Income taxes payable 4,262 — Net deferred tax liability 7,498 74,534 Other liabilities 66,503 67,598 Total Liabilities 2,012,735 1,792,305 Total Shareholders' Equity 7,834,150 7,594,818 Total Liabilities and Shareholders' Equity $ 9,846,885 $ 9,387,123 CONDENSED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME Years Ended December 31, 2015 2014 2013 (dollars in thousands) REVENUES Net investment income $ 2,565 $ 5,354 $ 21,946 Dividends on common stock of consolidated subsidiaries 187,496 217,121 806,233 Net realized investment gains: Other-than-temporary impairment losses (3,455 ) (120 ) (15 ) Net realized investment gains, excluding other-than-temporary impairment losses 75,000 3,873 67,232 Net realized investment gains 71,545 3,753 67,217 Other — — 1 Total Revenues 261,606 226,228 895,397 EXPENSES Interest expense 95,620 94,097 92,743 Other expenses 11,287 2,685 2,617 Total Expenses 106,907 96,782 95,360 Income Before Equity in Undistributed Earnings of Consolidated Subsidiaries and Income Taxes 154,699 129,446 800,037 Equity in undistributed earnings of consolidated subsidiaries 407,489 163,341 (520,323 ) Income tax benefit (20,584 ) (28,395 ) (1,307 ) Net Income to Shareholders $ 582,772 $ 321,182 $ 281,021 OTHER COMPREHENSIVE INCOME (LOSS) TO SHAREHOLDERS Change in net unrealized gains on investments, net of taxes: Net holding gains (losses) arising during the period $ (41,861 ) $ 32,118 $ 66,623 Consolidated subsidiaries' net holding gains (losses) arising during the period (198,309 ) 655,617 158,922 Consolidated subsidiaries' change in unrealized other-than-temporary impairment losses on fixed maturities arising during the period 160 173 (141 ) Reclassification adjustments for net losses included in net income to shareholders (45,273 ) (1,874 ) (43,220 ) Consolidated subsidiaries' reclassification adjustments for net gains (losses) included in net income to shareholders (35,209 ) (24,287 ) 2,390 Change in net unrealized gains on investments, net of taxes (320,492 ) 661,747 184,574 Change in foreign currency translation adjustments, net of taxes 2,970 1,949 (2,670 ) Consolidated subsidiaries' change in foreign currency translation adjustments, net of taxes (32,175 ) (34,194 ) (7,501 ) Consolidated subsidiaries' change in net actuarial pension loss, net of taxes (352 ) (14,750 ) 4,065 Total Other Comprehensive Income (Loss) to Shareholders (350,049 ) 614,752 178,468 Comprehensive Income to Shareholders $ 232,723 $ 935,934 $ 459,489 CONDENSED STATEMENTS OF CASH FLOWS Years Ended December 31, 2015 2014 2013 (dollars in thousands) OPERATING ACTIVITIES Net income to shareholders $ 582,772 $ 321,182 $ 281,021 Adjustments to reconcile net income to shareholders to net cash provided by operating activities (464,193 ) (218,396 ) 186,574 Net Cash Provided By Operating Activities 118,579 102,786 467,595 INVESTING ACTIVITIES Proceeds from sales of fixed maturities and equity securities 100,633 9,306 142,259 Proceeds from maturities, calls and prepayments of fixed maturities 24,945 15,710 2,819 Cost of fixed maturities and equity securities purchased (55,656 ) (687 ) (23,412 ) Net change in short-term investments 9,956 (109,728 ) 10,251 Securities received from subsidiaries as dividends or repayment of notes receivable — 89,996 249,996 Decrease in notes receivable due from subsidiaries — 28,506 5,302 Capital contributions to subsidiaries (228,578 ) (74,788 ) (67,878 ) Acquisitions — — (1,017,988 ) Cost of equity method investments (13,164 ) — (5,291 ) Change in restricted cash and cash equivalents 289 51 (348 ) Additions to property and equipment (305 ) (342 ) (3,653 ) Other (376 ) (2,150 ) 3,207 Net Cash Used By Investing Activities (162,256 ) (44,126 ) (704,736 ) FINANCING ACTIVITIES Additions to senior long-term debt — — 491,235 Increase in notes payable to subsidiaries 285,000 — — Repayment and retirement of senior long-term debt (2,000 ) — (246,665 ) Repurchases of common stock (31,491 ) (26,053 ) (57,388 ) Issuance of common stock 4,752 5,691 24,518 Other 3,985 (1,948 ) (5,023 ) Net Cash Provided (Used) By Financing Activities 260,246 (22,310 ) 206,677 Increase (decrease) in cash and cash equivalents 216,569 36,350 (30,464 ) Cash and cash equivalents at beginning of year 243,702 207,352 237,816 CASH AND CASH EQUIVALENTS AT END OF YEAR $ 460,271 $ 243,702 $ 207,352

Quarterly Financial Information

Quarterly Financial Information	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	Quarterly Financial Information (unaudited) The following table presents the unaudited quarterly results of consolidated operations for 2015 , 2014 and 2013 . Quarters Ended (dollars in thousands, except per share amounts) Mar. 31 June 30 Sept. 30 Dec. 31 2015 Operating revenues $ 1,302,154 $ 1,304,605 $ 1,342,764 $ 1,420,460 Net income 194,006 92,453 104,410 198,273 Net income to shareholders 190,992 91,369 102,519 197,892 Comprehensive income (loss) to shareholders 281,807 (132,925 ) (51,143 ) 134,984 Net income per share: Basic $ 13.57 $ 6.76 $ 7.43 $ 14.23 Diluted 13.49 6.72 7.39 14.14 Common stock price ranges: High $ 783.50 $ 821.00 $ 898.08 $ 937.91 Low 660.05 736.96 775.00 791.97 2014 Operating revenues $ 1,239,655 $ 1,258,971 $ 1,299,286 $ 1,335,755 Net income 87,501 41,141 76,824 118,222 Net income to shareholders 87,716 40,068 75,803 117,595 Comprehensive income to shareholders 230,273 250,588 36,502 418,571 Net income per share: Basic $ 6.28 $ 2.67 $ 5.33 $ 8.10 Diluted 6.25 2.66 5.30 8.05 Common stock price ranges: High $ 596.87 $ 655.75 $ 666.00 $ 707.36 Low 527.17 593.76 623.90 632.65 2013 Operating revenues $ 819,864 $ 1,031,769 $ 1,191,665 $ 1,279,785 Net income 89,263 28,676 66,967 98,939 Net income to shareholders 88,902 27,756 65,599 98,764 Comprehensive income (loss) to shareholders 257,684 (149,054 ) 144,409 206,450 Net income per share: Basic $ 9.53 $ 2.24 $ 4.69 $ 6.98 Diluted 9.50 2.24 4.67 6.95 Common stock price ranges: High $ 510.05 $ 546.94 $ 549.09 $ 582.59 Low 434.98 501.76 506.64 511.06

Summary Of Significant Accoun30

Summary Of Significant Accounting Policies (Policy)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation. The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (U.S. GAAP) and include the accounts of Markel Corporation and its consolidated subsidiaries (the Company). All significant intercompany balances and transactions have been eliminated in consolidation. The consolidated financial statements include the results of operations and cash flows of Alterra from the Acquisition Date to December 31, 2015 and not in any prior periods, except with respect to the Supplemental Pro Forma Information included in note 2 . The Company consolidates the results of its Markel Ventures subsidiaries on a one-month lag. Certain prior year amounts have been reclassified to conform to the current presentation.
Use of Estimates	Use of Estimates. The preparation of financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities. Management periodically reviews its estimates and assumptions. Quarterly reviews include evaluating the adequacy of reserves for unpaid losses and loss adjustment expenses, life and annuity reinsurance benefit reserves, litigation contingencies, the reinsurance allowance for doubtful accounts and income tax liabilities, as well as analyzing the recoverability of deferred tax assets, estimating reinsurance premiums written and earned and evaluating the investment portfolio for other-than-temporary declines in estimated fair value. Estimates and assumptions for goodwill and intangible assets are reviewed in conjunction with an acquisition, and goodwill and indefinite-lived intangible assets are reassessed at least annually for impairment. Actual results may differ materially from the estimates and assumptions used in preparing the consolidated financial statements.
Investments	Investments. Available-for-sale investments are recorded at estimated fair value. Unrealized gains and losses on investments, net of deferred income taxes, are included in accumulated other comprehensive income in shareholders' equity. The Company completes a detailed analysis each quarter to assess whether the decline in the fair value of any investment below its cost basis is deemed other-than-temporary. Premiums and discounts are amortized or accreted over the lives of the related fixed maturities as an adjustment to the yield using the effective interest method. Dividend and interest income are recognized when earned. Realized investment gains or losses are included in earnings. Realized gains or losses from sales of investments are derived using the first-in, first-out method. Investments accounted for under the equity method of accounting are recorded at cost within other assets on the consolidated balance sheets and subsequently increased or decreased by the Company's proportionate share of the net income or loss of the investee. The Company records its proportionate share of net income or loss of the investee in net investment income. The Company records its proportionate share of other comprehensive income or loss of the investee as a component of other comprehensive income (loss). Dividends or other equity distributions are recorded as a reduction of the investment. The Company reviews equity method investments for impairment when events or circumstances indicate that a decline in the fair value of the investment below its carrying value is other-than-temporary.
Cash and Cash Equivalents	Cash and Cash Equivalents. The Company considers all investments with original maturities of 90 days or less to be cash equivalents. The carrying value of the Company's cash and cash equivalents and restricted cash and cash equivalents approximates fair value.
Receivables	Receivables. Receivables include amounts receivable from agents, brokers and insureds, which represent premiums that are both currently due and amounts not yet due on insurance and reinsurance policies. Premiums for insurance policies are generally due at inception. Premiums for reinsurance policies generally become due over the period of coverage based on the policy terms. The Company monitors the credit risk associated with premiums receivable, taking into consideration the fact that in certain instances credit risk may be reduced by the Company's right to offset loss obligations or unearned premiums against premiums receivable. Amounts deemed uncollectible are charged to net income in the period they are determined. Changes in the estimate of reinsurance premiums written will result in an adjustment to premiums receivable in the period they are determined.
Reinsurance Recoverables	Reinsurance Recoverables. Amounts recoverable from reinsurers are estimated in a manner consistent with the claim liability associated with the reinsured business. Allowances are established for amounts deemed uncollectible and reinsurance recoverables are recorded net of these allowances. The Company evaluates the financial condition of its reinsurers and monitors concentration risk to minimize its exposure to significant losses from individual reinsurers.
Deferred Policy Acquisition Costs	Deferred Policy Acquisition Costs. Costs directly related to the acquisition of insurance premiums are deferred and amortized over the related policy period, generally one year . The Company only defers acquisition costs incurred that are related directly to the successful acquisition of new or renewal insurance contracts, including commissions to agents and brokers and premium taxes. Commissions received related to reinsurance premiums ceded are netted against broker commissions in determining acquisition costs eligible for deferral. To the extent that future policy revenues on existing policies are not adequate to cover related costs and expenses, deferred policy acquisition costs are charged to earnings. The Company does not consider anticipated investment income in determining whether a premium deficiency exists.
Goodwill and Intangible Assets	Goodwill and Intangible Assets. Goodwill and intangible assets are recorded as a result of business acquisitions. Goodwill represents the excess of the amount paid to acquire a business over the net fair value of assets acquired and liabilities assumed at the date of acquisition. Indefinite-lived and other intangible assets are recorded at fair value as of the acquisition date. The determination of the fair value of certain assets acquired and liabilities assumed involves significant judgment and the use of valuation models and other estimates, which require assumptions that are inherently subjective. Goodwill and indefinite-lived intangible assets are tested for impairment at least annually. The Company completes an annual test during the fourth quarter of each year based upon the results of operations through September 30. Intangible assets with definite lives are amortized using the straight-line method over their estimated useful lives, generally five to 20 years , and are reviewed for impairment when events or circumstances indicate that their carrying value may not be recoverable.
Property and Equipment	Property and Equipment. Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization of property and equipment are calculated using the straight-line method over the estimated useful lives (generally, the life of the lease for leasehold improvements, ten to 40 years for buildings, seven to 40 years for land improvements, three to ten years for furniture and equipment and three to 25 years for other property and equipment).
Redeemable Noncontrolling Interests	Redeemable Noncontrolling Interests. The Company owns controlling interests in various companies through its Markel Ventures operations. In some cases, the Company has the option to acquire the remaining equity interests, and the remaining equity interests have the option to sell their interests to the Company, in the future. The redemption value of the remaining equity interests is generally based on the respective company's earnings in specified periods preceding the redemption date. The redeemable noncontrolling interests generally become redeemable through 2020. The Company recognizes changes in the redemption value that exceed the carrying value of redeemable noncontrolling interests to retained earnings as if the balance sheet date were also the redemption date. Changes in the redemption value also result in an adjustment to net income to shareholders in the calculation of basic and diluted net income per share. The change in the redemption value of redeemable noncontrolling interests in 2015 , 2014 and 2013 resulted in an adjustment to retained earnings of an increase of $4.1 million , a decrease of $8.2 million , and an increase of $2.0 million , respectively.
Income Taxes	Income Taxes. The Company records deferred income taxes to reflect the net tax effect of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and their tax bases. Deferred tax assets are reduced by a valuation allowance when management believes it is more likely than not that some, or all, of the deferred tax assets will not be realized. The Company recognizes the tax benefit from an uncertain tax position taken or expected to be taken in income tax returns only if it is more likely than not that the tax position will be sustained upon examination by tax authorities, based on the technical merits of the position. Tax positions that meet the more likely than not threshold are then measured using a probability weighted approach, whereby the largest amount of tax benefit that is greater than 50% likely of being realized upon ultimate settlement is recognized. The Company recognizes interest and penalties related to uncertain tax positions in income tax expense.
Unpaid Losses and Loss Adjustment Expenses	Unpaid Losses and Loss Adjustment Expenses. Unpaid losses and loss adjustment expenses on our property and casualty insurance business are based on evaluations of reported claims and estimates for losses and loss adjustment expenses incurred but not reported. Estimates for losses and loss adjustment expenses incurred but not reported are based on reserve development studies, among other things. The Company does not discount reserves for losses and loss adjustment expenses to reflect estimated present value, except for reserves assumed in connection with an acquisition, which are recorded at fair value at the acquisition date. Recorded reserves are estimates, and the ultimate liability may be greater or less than the estimates.
Life and Annuity Benefits	Life and Annuity Benefits. The Company previously acquired a block of long duration reinsurance contracts for life and annuity benefits which subject the Company to mortality, longevity and morbidity risks. The assumptions used to determine policy benefit reserves are generally locked-in for the life of the contract unless an unlocking event occurs. To the extent existing policy reserves, together with the present value of future gross premiums and expected investment income earned thereon, are not adequate to cover the present value of future benefits, settlement and maintenance costs, the locked-in assumptions are revised to current best estimate assumptions and a charge to earnings for life and annuity benefits is recognized at that time. Because of the assumptions and estimates used in establishing reserves for life and annuity benefit obligations and the long-term nature of these reinsurance contracts, the ultimate liability may be greater or less than the estimates. Results attributable to the run-off of life and annuity reinsurance business are included in other revenues and other expenses in the Company's consolidated statements of income and comprehensive income and as part of the Company's Other Insurance (Discontinued Lines) segment.
Revenue Recognition	Revenue Recognition. Property and Casualty Premiums Insurance premiums are generally earned on a pro rata basis over the policy period, typically one year . The cost of reinsurance ceded is initially recorded as prepaid reinsurance premiums and is amortized over the reinsurance contract period in proportion to the amount of insurance protection provided. Premiums ceded are netted against premiums written. Assumed reinsurance premiums are recorded at the inception of each contract based upon contract terms and information received from cedents and brokers and are earned on a pro rata basis over the coverage period, or for multi-year contracts, in proportion with the underlying risk exposure to the extent there is variability in the exposure through the coverage period. Changes in reinsurance premium estimates are expected and may result in significant adjustments in any period. These estimates change over time as additional information regarding changes in underlying exposures is obtained. Any subsequent differences arising on such estimates are recorded as premiums written in the period they are determined and are earned on a pro rata basis over the coverage period. The Company uses the periodic method to account for assumed reinsurance from foreign reinsurers. The Company's foreign reinsurers provide sufficient information to record foreign assumed business in the same manner as the Company records assumed business from United States reinsurers. Certain contracts that the Company writes provide for reinstatement of coverage. Reinstatement premiums are the premiums for the restoration of the insurance or reinsurance limit of a contract to its full amount after a loss occurrence by the insured or reinsured. The Company accrues for reinstatement premiums resulting from losses recorded. Such accruals are based upon contractual terms and management judgment is involved with respect to the amount of losses recorded. Changes in estimates of losses recorded on contracts with reinstatement premium features will result in changes in reinstatement premiums based on contractual terms. Reinstatement premiums are recognized at the time losses are recorded and are earned on a pro-rata basis over the coverage period. Other Revenues Other revenues primarily relate to the Company's Markel Ventures operations and consist of revenues from the sale of manufactured products and service revenues. Revenues from manufactured products are generally recognized at the time title transfers to the customer, which typically occurs at the point of shipment or delivery to the customer, depending on the terms of the sales arrangement. Revenues from services are generally recognized as the services are performed. Services provided pursuant to a contract are recognized either over the contract period or upon completion of the elements specified in the contract, depending on the terms of the contract.
Stock-based Compensation	Stock-based Compensation. Stock-based compensation expense is generally recognized as part of underwriting, acquisition and insurance expenses over the requisite service period. Stock-based compensation expense, net of taxes, was $16.3 million in 2015 , $18.7 million in 2014 and $18.4 million in 2013 . See note 12 .
Foreign Currency Translation	Foreign Currency Translation. The functional currencies of the Company's foreign operations are the currencies in which the majority of their business is transacted. Assets and liabilities of foreign operations are translated into the United States Dollar using the exchange rates in effect at the balance sheet date. Revenues and expenses of foreign operations are translated using the average exchange rate for the period. Gains or losses from translating the financial statements of foreign operations denominated in a functional currency are included, net of taxes, in shareholders' equity as a component of accumulated other comprehensive income. Gains and losses arising from transactions denominated in a foreign currency, other than a functional currency, are included in net income. The Company manages its exposure to foreign currency risk primarily by matching assets, other than goodwill and intangible assets, and liabilities denominated in the same currency. To the extent that assets and liabilities in foreign currencies are not matched, the Company is exposed to foreign currency risk. For functional currencies, the related exchange rate fluctuations are reflected in other comprehensive income (loss). The cumulative foreign currency translation adjustment, net of taxes, was a loss of $72.7 million and $43.5 million at December 31, 2015 and 2014 , respectively.
Derivative Financial Instruments	Derivative Financial Instruments. Derivative instruments, including derivative instruments resulting from hedging activities, are measured at fair value and recognized as either assets or liabilities on the consolidated balance sheets. The changes in fair value of derivatives are recognized in earnings unless the derivative is designated as a hedge and qualifies for hedge accounting. The Company's foreign currency forward contracts are generally designated and qualify as hedges of a net investment in a foreign operation. The effective portion of the change in fair value resulting from these hedges is reported in currency translation adjustments as part of other comprehensive income (loss). The ineffective portion of the change in fair value is recognized in earnings.
Comprehensive Income	Comprehensive Income. Comprehensive income represents all changes in equity that result from recognized transactions and other economic events during the period. Other comprehensive income (loss) refers to revenues, expenses, gains and losses that under U.S. GAAP are included in comprehensive income but excluded from net income, such as unrealized gains or losses on investments, foreign currency translation adjustments and changes in net actuarial pension loss.
Net Income Per Share	Net Income Per Share. Basic net income per share is computed by dividing adjusted net income to shareholders by the weighted average number of common shares outstanding during the year. Diluted net income per share is computed by dividing adjusted net income to shareholders by the weighted average number of common shares and dilutive potential common shares outstanding during the year. See note 12 (b).
Recent Accounting Pronouncements	Recent Accounting Pronouncements. In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606) , which creates a new comprehensive revenue recognition standard that will serve as a single source of revenue guidance for all companies in all industries. The guidance applies to all companies that either enter into contracts with customers to transfer goods or services or enter into contracts for the transfer of nonfinancial assets, unless those contracts are within the scope of other standards, such as insurance contracts. ASU No. 2014-09's core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under the current guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers (Topic 606), Deferral of the Effective Date , which deferred the original effective date of ASU No. 2014-09 by one year. As a result, ASU No. 2014-09 becomes effective for the Company during the first quarter of 2018 and may be applied retrospectively or under a modified retrospective method where the cumulative effect is recognized at the date of initial application. Early application is permitted, but not before the first quarter of 2017. The Company is currently evaluating ASU No. 2014-09 to determine the potential impact that adopting this standard will have on its consolidated financial statements. Adoption of this ASU is not expected to have a material impact on the Company's insurance operations, but may have a material impact on the Company's non-insurance operations. In February 2015, the FASB issued ASU No. 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis , which changes the way reporting enterprises evaluate whether (a) they should consolidate limited partnerships and similar entities, (b) fees paid to a decision maker or service provider are variable interests in a variable interest entity (VIE), and (c) variable interests in a VIE held by related parties of the reporting enterprise require the reporting enterprise to consolidate the VIE. It also eliminates the VIE consolidation model based on majority exposure to variability that applied to certain investment companies and similar entities. The ASU also significantly changes how to evaluate voting rights for entities that are not similar to limited partnerships when determining whether the entity is a VIE, which may affect entities for which the decision making rights are conveyed through a contractual arrangement. ASU No. 2015-02 becomes effective for the Company during the first quarter of 2016 and may be applied retrospectively or under a modified retrospective method where the cumulative-effect adjustment to retained earnings is recognized as of the beginning of the fiscal year of adoption. Reporting enterprises may also restate previously issued financial statements for one or more years with a cumulative-effect adjustment to retained earnings as of the beginning of the first year restated. The adoption of this ASU is not expected to have a material impact on the Company's financial position, results of operations or cash flows. In April 2015, the FASB issued ASU No. 2015-03, Interest-Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs . The ASU requires that debt issuance costs related to a recognized debt liability be presented on the balance sheet as a direct deduction from the debt liability, similar to the presentation of debt discounts. The cost of issuing debt will no longer be recorded as a separate asset on the balance sheet. The amortization of debt issuance costs will continue to be included in interest expense. ASU No. 2015-03 becomes effective for the Company during the first quarter of 2016 and will be applied retrospectively to all prior periods presented. The adoption of this ASU is not expected to have a material impact on the Company's financial position, results of operations or cash flows. In April 2015, the FASB issued ASU No. 2015-05, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer's Accounting for Fees Paid in a Cloud Computing Arrangement , which clarifies that software licenses contained in a cloud computing arrangement should be capitalized if the customer has the right to take possession of the software and the ability to run the software outside of the cloud computing arrangement. ASU No. 2015-05 becomes effective for the Company during the first quarter of 2016 and may be applied prospectively or retrospectively. The adoption of this ASU is not expected to have a material impact on the Company's financial position, results of operations or cash flows. In May 2015, the FASB issued ASU No. 2015-09, Financial Services-Insurance (Topic 944): Disclosures about Short-Duration Contracts . The ASU requires significant new disclosures for insurers relating to short-duration insurance contract claims and the unpaid claims liability rollforward for long and short-duration contracts. The guidance requires annual tabular disclosure, on a disaggregated basis, of undiscounted incurred and paid claim and allocated claim adjustment expense development by accident year, on a net basis after reinsurance, for up to 10 years. Tables must also include the total incurred but not reported claims liabilities, plus expected development on reported claims, and claims frequency for each accident year. A description of estimation methodologies and any significant changes in methodologies and assumptions used to calculate the liability and frequency is also required. Based on the disaggregated claims information in the tables, disclosure of historical average annual percentage payout of incurred claims is also required. Interim period disclosures must include a tabular rollforward and related qualitative information for the liability for unpaid losses and loss adjustment expenses for both long-duration and short-duration contracts. ASU No. 2015-09 becomes effective for the Company during 2016, with interim disclosures required beginning in the first quarter of 2017. The ASU must be applied retrospectively by providing comparative disclosures for each period presented. Early application is permitted. The adoption of this ASU is not expected to have a material impact on the Company's financial position, results of operations or cash flows, but will expand the nature and extent of its insurance contract disclosures, as described above. In July 2015, the FASB issued ASU No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory . The ASU changes the measurement principle for inventory from the lower of cost or market to lower of cost and net realizable value and eliminates the requirement to consider replacement cost or net realizable value less an approximately normal profit margin when measuring inventory. ASU 2015-11 becomes effective for the Company during the first quarter of 2017 and will be applied prospectively. The Company is currently evaluating ASU 2015-11 but does not expect adoption of this ASU to have a material impact on the Company's financial position, results of operations or cash flows. In September 2015, the FASB issued ASU No. 2015-16, Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments . The ASU eliminates the requirement to retrospectively adjust the financial statements for measurement-period adjustments that occur in periods after a business combination is consummated. ASU 2015-16 becomes effective for the Company during the first quarter of 2016 and will be applied prospectively. The adoption of this ASU is not expected to have a material impact on the Company's financial position, results of operations or cash flows. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments (Topic 825): Recognition and Measurement of Financial Assets and Financial Liabilities . The ASU significantly changes the income statement impact of equity investments and the recognition of changes in fair value of financial liabilities attributable to an entities own credit risk when the fair value option is elected. The ASU requires equity instruments that do not result in consolidation and are not accounted for under the equity method to be measured at fair value and to recognize any changes in fair value in net income rather than other comprehensive income. ASU 2016-01 becomes effective for the Company during the first quarter of 2018 and will be applied using a cumulative-effect adjustment to retained earnings as of the beginning of the fiscal year of adoption. The provisions related to equity investments without a readily determinable fair value will be applied prospectively to equity investments as of the adoption date. Early adoption is permitted for certain provisions of the ASU. The Company is currently evaluating ASU No. 2016-01 to determine the potential impact that adopting this standard will have on the consolidated financial statements. Adoption of this ASU is not expected to have a material impact on the Company's financial position, cash flows, or total comprehensive income, but will have a significant impact on the Company's results of operations as changes in fair value will be presented in net income rather than other comprehensive income.

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2015
Acquisitions [Abstract]
Calculation Of Total Purchase Price	The Company's total purchase price for Alterra as of the Acquisition Date was calculated as follows: (in thousands, except per share amounts) Shares of Alterra common stock outstanding as of the Acquisition Date 96,433 Exchange ratio per the Merger Agreement 0.04315 Markel share issuance to Alterra shareholders 4,161 Shares of Alterra restricted stock outstanding as of the Acquisition Date 2,239 Incentive award ratio per the Merger Agreement 0.06252 Markel restricted stock issuance to Alterra restricted stock holders 140 Multiplied by Markel's weighted average stock price on April 30, 2013 (1) $ 529.59 Markel share and restricted stock issuance consideration, net of taxes $ 2,267,648 Alterra common shares outstanding as of the Acquisition Date that received cash consideration 96,433 Multiplied by cash price per share component per the Merger Agreement $ 10.00 Markel cash consideration $ 964,330 Fair value of Markel warrant issuance to Alterra warrant holders as of the Acquisition Date $ 73,685 Fair value of Markel stock option issuance to Alterra stock option holders as of the Acquisition Date, net of taxes $ 12,335 Fair value of partially vested Markel restricted stock unit issuance as of the Acquisition Date, net of taxes $ 6,867 Unrecognized compensation on unvested restricted stock and restricted stock units $ (20,572 ) Total acquisition consideration $ 3,304,293 (1) The fair value of the shares issued by the Company was calculated as the weighted average price of the Company's stock on April 30, 2013, the day preceding the Acquisition Date.
Summary Of Fair Value Of Assets Acquired And Liabilities Assumed	The following table summarizes the fair values of the assets acquired and liabilities assumed at the Acquisition Date. (dollars in thousands) ASSETS Investments $ 6,407,841 Cash and cash equivalents 1,036,274 Restricted cash and cash equivalents 414,497 Receivables 866,388 Reinsurance recoverable on unpaid losses 1,169,084 Reinsurance recoverable on paid losses 80,672 Prepaid reinsurance premiums 317,445 Other assets 859,884 LIABILITIES Unpaid losses and loss adjustment expenses 4,719,461 Life and annuity benefits 1,477,482 Unearned premiums 1,075,610 Payables to insurance and reinsurance companies 342,858 Senior long-term debt 512,463 Other liabilities 223,108 Net assets 2,801,103 Goodwill 295,690 Intangible assets 207,500 Acquisition date fair value $ 3,304,293
Summary Of Intangible Assets Acquired	The following table summarizes the intangible assets recorded in connection with the acquisition. (dollars in thousands) Amount Economic Useful Life Customer relationships $ 132,000 18 years Broker relationships 19,000 18 years Technology 18,000 Ten years Trade names 1,000 One year Lloyd's syndicate capacity 12,000 Indefinite Insurance licenses 25,500 Indefinite Intangible assets as of the Acquisition Date $ 207,500
Summary Of Transaction And Acquisition-Related Costs	The following table summarizes transaction and acquisition-related costs incurred by the Company in connection with the acquisition, all of which were included in underwriting, acquisition and insurance expenses in the consolidated statements of income and comprehensive income. (dollars in thousands) Year Ended December 31, 2013 Transaction costs $ 15,981 Acquisition-related costs: Severance costs 31,734 Stay bonuses 14,804 Acceleration of Alterra long-term incentive compensation awards and restricted stock awards 12,621 Total transaction and acquisition-related costs $ 75,140
Summary Of Results Of Operations	The following table summarizes the results of Alterra from the Acquisition Date through December 31, 2013 that have been included within the Company's consolidated statements of income and comprehensive income. (dollars in thousands) Year Ended December 31, 2013 Operating revenues $ 912,387 Net loss to shareholders $ (93,074 )
Unaudited Pro Forma Consolidated Financial Information	The following table presents unaudited pro forma consolidated information for the year ended December 31, 2013 and assumes the Company's acquisition of Alterra occurred on January 1, 2012. The pro forma financial information is presented for informational purposes only and does not necessarily reflect the results that would have occurred had the acquisition taken place on January 1, 2012, nor is it necessarily indicative of future results. Significant adjustments used to determine pro forma results include amortization of intangible assets and amortization of fair value adjustments discussed in c) above, and the corresponding income tax effects. The Company also excluded certain charges from the pro forma results, including transaction costs incurred by the Company ( $16.0 million ) and Alterra ( $23.0 million ) totaling $39.0 million for the year ended December 31, 2013, severance costs attributable to the acquisition totaling $31.7 million for the year ended December 31, 2013, and stay bonuses of $14.8 million for the year ended December 31, 2013. The acceleration of compensation expense during the year ended December 31, 2013 related to Alterra's long-term incentive compensation awards and restricted stock awards was attributable to the acquisition; however, the incremental expense recognized during the period only represents a timing difference in the recognition of expense. Therefore, it was not excluded from the pro forma underwriting results. Unaudited Consolidated Pro Forma (in thousands, except per share amounts) Year Ended December 31, 2013 Earned premiums $ 3,680,220 Operating revenues 4,899,628 Net income to shareholders 422,829 U.S. GAAP combined ratio (1) 95 % Basic net income per share $ 30.33 Diluted net income per share $ 30.19 Weighted average common shares outstanding: Basic 14,007 Diluted 14,069 (1) The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums.

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Available-For-Sale Investments	The following tables summarize the Company's available-for-sale investments. December 31, 2015 (dollars in thousands) Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Unrealized Other- Than-Temporary Impairment Losses Estimated Fair Value Fixed maturities: U.S. Treasury securities and obligations of U.S. government agencies $ 695,652 $ 9,836 $ (4,781 ) $ — $ 700,707 Obligations of states, municipalities and political subdivisions 3,817,136 204,302 (8,225 ) — 4,013,213 Foreign governments 1,302,329 115,809 (1,681 ) — 1,416,457 Commercial mortgage-backed securities 657,670 6,867 (4,999 ) — 659,538 Residential mortgage-backed securities 837,964 22,563 (4,022 ) (2,258 ) 854,247 Asset-backed securities 36,462 15 (406 ) — 36,071 Corporate bonds 1,690,945 41,123 (16,209 ) (1,624 ) 1,714,235 Total fixed maturities 9,038,158 400,515 (40,323 ) (3,882 ) 9,394,468 Equity securities: Insurance, banks and other financial institutions 651,002 690,271 (6,551 ) — 1,334,722 Industrial, consumer and all other 1,557,832 1,227,052 (45,131 ) — 2,739,753 Total equity securities 2,208,834 1,917,323 (51,682 ) — 4,074,475 Short-term investments 1,642,103 167 (9 ) — 1,642,261 Investments, available-for-sale $ 12,889,095 $ 2,318,005 $ (92,014 ) $ (3,882 ) $ 15,111,204 December 31, 2014 (dollars in thousands) Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Unrealized Other- Than-Temporary Impairment Losses Estimated Fair Value Fixed maturities: U.S. Treasury securities and obligations of U.S. government agencies $ 662,462 $ 12,963 $ (2,163 ) $ — $ 673,262 Obligations of states, municipalities and political subdivisions 4,075,748 245,158 (3,359 ) — 4,317,547 Foreign governments 1,458,255 154,707 (1,041 ) — 1,611,921 Commercial mortgage-backed securities 427,904 5,325 (2,602 ) — 430,627 Residential mortgage-backed securities 954,263 34,324 (3,482 ) (2,258 ) 982,847 Asset-backed securities 100,073 99 (682 ) — 99,490 Corporate bonds 2,250,432 69,016 (10,441 ) (1,819 ) 2,307,188 Total fixed maturities 9,929,137 521,592 (23,770 ) (4,077 ) 10,422,882 Equity securities: Insurance, banks and other financial institutions 523,739 789,717 (1,531 ) — 1,311,925 Industrial, consumer and all other 1,427,919 1,403,566 (5,834 ) — 2,825,651 Total equity securities 1,951,658 2,193,283 (7,365 ) — 4,137,576 Short-term investments 1,594,819 36 (6 ) — 1,594,849 Investments, available-for-sale $ 13,475,614 $ 2,714,911 $ (31,141 ) $ (4,077 ) $ 16,155,307
Summary Of Gross Unrealized Investment Losses By Length Of Time That Securities Have Continuously Been In An Unrealized Loss Position	The following tables summarize gross unrealized investment losses by the length of time that securities have continuously been in an unrealized loss position. December 31, 2015 Less than 12 months 12 months or longer Total (dollars in thousands) Estimated Fair Value Gross Unrealized Holding and Other-Than- Temporary Impairment Losses Estimated Fair Value Gross Unrealized Holding and Other-Than- Temporary Impairment Losses Estimated Fair Value Gross Unrealized Holding and Other-Than- Temporary Impairment Losses Fixed maturities: U.S. Treasury securities and obligations of U.S. government agencies $ 427,003 $ (3,648 ) $ 92,552 $ (1,133 ) $ 519,555 $ (4,781 ) Obligations of states, municipalities and political subdivisions 169,362 (4,864 ) 70,101 (3,361 ) 239,463 (8,225 ) Foreign governments 51,328 (249 ) 40,345 (1,432 ) 91,673 (1,681 ) Commercial mortgage-backed securities 289,058 (3,600 ) 95,843 (1,399 ) 384,901 (4,999 ) Residential mortgage-backed securities 78,814 (2,858 ) 137,100 (3,422 ) 215,914 (6,280 ) Asset-backed securities 6,228 (54 ) 24,315 (352 ) 30,543 (406 ) Corporate bonds 470,694 (9,509 ) 343,737 (8,324 ) 814,431 (17,833 ) Total fixed maturities 1,492,487 (24,782 ) 803,993 (19,423 ) 2,296,480 (44,205 ) Equity securities: Insurance, banks and other financial institutions 63,873 (6,384 ) 6,247 (167 ) 70,120 (6,551 ) Industrial, consumer and all other 344,857 (44,879 ) 2,907 (252 ) 347,764 (45,131 ) Total equity securities 408,730 (51,263 ) 9,154 (419 ) 417,884 (51,682 ) Short-term investments 129,473 (9 ) — — 129,473 (9 ) Total $ 2,030,690 $ (76,054 ) $ 813,147 $ (19,842 ) $ 2,843,837 $ (95,896 ) December 31, 2014 Less than 12 months 12 months or longer Total (dollars in thousands) Estimated Fair Value Gross Unrealized Holding and Other-Than- Temporary Impairment Losses Estimated Fair Value Gross Unrealized Holding and Other-Than- Temporary Impairment Losses Estimated Fair Value Gross Unrealized Holding and Other-Than- Temporary Impairment Losses Fixed maturities: U.S. Treasury securities and obligations of U.S. government agencies $ 108,250 $ (62 ) $ 163,359 $ (2,101 ) $ 271,609 $ (2,163 ) Obligations of states, municipalities and political subdivisions 58,583 (542 ) 92,441 (2,817 ) 151,024 (3,359 ) Foreign governments 18,856 (386 ) 56,217 (655 ) 75,073 (1,041 ) Commercial mortgage-backed securities 45,931 (210 ) 147,558 (2,392 ) 193,489 (2,602 ) Residential mortgage-backed securities 9,613 (2,285 ) 207,374 (3,455 ) 216,987 (5,740 ) Asset-backed securities 30,448 (20 ) 45,160 (662 ) 75,608 (682 ) Corporate bonds 141,176 (2,263 ) 621,821 (9,997 ) 762,997 (12,260 ) Total fixed maturities 412,857 (5,768 ) 1,333,930 (22,079 ) 1,746,787 (27,847 ) Equity securities: Insurance, banks and other financial institutions 16,219 (1,531 ) — — 16,219 (1,531 ) Industrial, consumer and all other 86,062 (5,834 ) — — 86,062 (5,834 ) Total equity securities 102,281 (7,365 ) — — 102,281 (7,365 ) Short-term investments 181,964 (6 ) — — 181,964 (6 ) Total $ 697,102 $ (13,139 ) $ 1,333,930 $ (22,079 ) $ 2,031,032 $ (35,218 )
Schedule Of Amortized Cost And Estimated Fair Value Of Fixed Maturities By Contractual Maturity	The amortized cost and estimated fair value of fixed maturities at December 31, 2015 are shown below by contractual maturity. (dollars in thousands) Amortized Cost Estimated Fair Value Due in one year or less $ 482,284 $ 485,605 Due after one year through five years 1,820,680 1,857,267 Due after five years through ten years 1,576,656 1,663,076 Due after ten years 3,626,442 3,838,664 7,506,062 7,844,612 Commercial mortgage-backed securities 657,670 659,538 Residential mortgage-backed securities 837,964 854,247 Asset-backed securities 36,462 36,071 Total fixed maturities $ 9,038,158 $ 9,394,468
Components Of Net Investment Income	The following table presents the components of net investment income. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Interest: Municipal bonds (tax-exempt) $ 93,580 $ 98,262 $ 82,308 Municipal bonds (taxable) 57,550 49,345 28,041 Other taxable bonds 138,763 152,789 134,377 Short-term investments, including overnight deposits 5,223 5,959 3,573 Dividends on equity securities 74,705 65,031 48,641 Change in fair value of credit default swap — 2,230 10,460 Income (loss) from equity method investments (262 ) 4,766 21,898 Other 651 108 355 370,210 378,490 329,653 Investment expenses (16,997 ) (15,260 ) (12,280 ) Net investment income $ 353,213 $ 363,230 $ 317,373
Summary Of Net Realized Investment Gains And The Change In Net Unrealized Gains On Investments	The following table presents net realized investment gains and the change in net unrealized gains on investments. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Realized gains: Sales of fixed maturities $ 3,073 $ 8,417 $ 13,772 Sales of equity securities 156,987 51,356 73,592 Other 8,103 15,205 5,940 Total realized gains 168,163 74,978 93,304 Realized losses: Sales of fixed maturities (4,598 ) (18,136 ) (25,168 ) Sales of equity securities (1,232 ) (802 ) (278 ) Other-than-temporary impairments (44,481 ) (4,784 ) (4,706 ) Other (11,372 ) (5,256 ) — Total realized losses (61,683 ) (28,978 ) (30,152 ) Net realized investment gains $ 106,480 $ 46,000 $ 63,152 Change in net unrealized gains on investments: Fixed maturities $ (137,435 ) $ 480,350 $ (403,610 ) Equity securities (320,277 ) 500,673 665,599 Short-term investments 128 12 6 Net increase (decrease) $ (457,584 ) $ 981,035 $ 261,995
Summary of Other-Than-Temporary Impairment Losses Recognized In Net Income And In Net Realized Investment Gains By Investment Type	The following table presents other-than-temporary impairment losses recognized in net income and included in net realized investment gains by investment type. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Fixed maturities: Obligations of states, municipalities and political subdivisions $ — $ — $ (1,242 ) Commercial mortgage-backed securities — (61 ) — Residential mortgage-backed securities — — (640 ) Asset-backed securities — (197 ) — Corporate bonds — (46 ) — Total fixed maturities — (304 ) (1,882 ) Equity securities: Insurance, banks and other financial institutions (9,835 ) (341 ) — Industrial, consumer and all other (34,646 ) (4,139 ) (2,824 ) Total equity securities (44,481 ) (4,480 ) (2,824 ) Total $ (44,481 ) $ (4,784 ) $ (4,706 )
Components Of Restricted Assets	The following table presents the components of restricted assets. December 31, (dollars in thousands) 2015 2014 Restricted assets held in trust or on deposit to support underwriting activities $ 4,037,458 $ 4,961,061 Investments and cash and cash equivalents pledged as security for letters of credit 745,744 635,340 Total $ 4,783,202 $ 5,596,401
Schedule Of Restricted Assets	Total restricted assets are included on the Company's consolidated balance sheets as follows. December 31, (dollars in thousands) 2015 2014 Investments, available-for-sale $ 4,343,070 $ 5,040,413 Restricted cash and cash equivalents 440,132 522,225 Other assets — 33,763 Total $ 4,783,202 $ 5,596,401

Receivables (Tables)

Receivables (Tables)	12 Months Ended
	Dec. 31, 2015
Receivables [Abstract]
Components Of Receivables	The following table presents the components of receivables. December 31, (dollars in thousands) 2015 2014 Amounts receivable from agents, brokers and insureds $ 1,009,115 $ 1,031,519 Trade accounts receivable 93,953 97,225 Employee stock loans receivable (see note 12(c)) 16,900 15,044 Other 6,165 8,601 1,126,133 1,152,389 Allowance for doubtful receivables (12,430 ) (17,172 ) Receivables $ 1,113,703 $ 1,135,217

Deferred Policy Acquisition C34

Deferred Policy Acquisition Costs (Tables)	12 Months Ended
	Dec. 31, 2015
Deferred Policy Acquisition Costs Disclosures [Abstract]
Amounts Of Policy Acquisition Costs Acquired, Deferred And Amortized	The following table presents the amounts of policy acquisition costs deferred and amortized. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Balance, beginning of year $ 353,410 $ 260,967 $ 157,465 Policy acquisition costs deferred 752,324 754,303 577,620 Amortization of policy acquisition costs (744,964 ) (654,916 ) (471,915 ) Foreign currency movements (8,014 ) (6,944 ) (2,203 ) Deferred policy acquisition costs $ 352,756 $ 353,410 $ 260,967
Components Of Underwriting, Acquisition And Insurance Expenses	The following table presents the components of underwriting, acquisition and insurance expenses. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Amortization of policy acquisition costs 744,964 654,916 471,915 Transaction costs and other acquisition-related expenses (1) — — 75,140 Other operating expenses 710,116 805,966 765,257 Underwriting, acquisition and insurance expenses $ 1,455,080 $ 1,460,882 $ 1,312,312 (1) In connection with the acquisition of Alterra, the Company incurred transaction costs of $16.0 million for the year ended December 31, 2013, which primarily consist of due diligence, legal and investment banking costs. Additionally, the Company incurred severance costs of $31.7 million , stay bonuses of $14.8 million and other compensation costs totaling $12.6 million related to the acceleration of certain long-term incentive compensation awards and restricted stock awards that were granted by Alterra prior to the acquisition.

Property And Equipment (Tables)

Property And Equipment (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Components Of Property And Equipment	The following table presents the components of property and equipment, which are included in other assets on the consolidated balance sheets. December 31, (dollars in thousands) 2015 2014 Land $ 56,408 $ 56,848 Buildings 77,488 78,786 Leasehold improvements 104,003 98,098 Land improvements 71,585 70,596 Furniture and equipment 291,736 255,566 Other 134,939 116,884 736,159 676,778 Accumulated depreciation and amortization (305,324 ) (255,388 ) Property and equipment $ 430,835 $ 421,390

Goodwill And Intangible Assets

Goodwill And Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Components Of Goodwill	The following table presents the components of goodwill by reportable segment. (dollars in thousands) U.S. Insurance International Insurance Reinsurance Other (1) Total January 1, 2014 $ 280,579 $ 372,764 $ 122,745 $ 191,629 $ 967,717 Acquisitions (see note 2) — 42,989 — 61,539 104,528 Impairment loss — — — (13,737 ) (13,737 ) Foreign currency movements and other adjustments — (7,570 ) — (1,823 ) (9,393 ) December 31, 2014 (2) $ 280,579 $ 408,183 $ 122,745 $ 237,608 $ 1,049,115 Acquisitions (see note 2) — — — 146,659 146,659 Impairment loss — — — (14,880 ) (14,880 ) Foreign currency movements and other adjustments — (10,190 ) — (2,860 ) (13,050 ) December 31, 2015 (2) $ 280,579 $ 397,993 $ 122,745 $ 366,527 $ 1,167,844 (1) Amounts included in Other above are related to the Company's non-insurance operations, which are not included in a reportable segment. (2) Goodwill is net of accumulated impairment losses of $28.6 million and $13.7 million , as of December 31, 2015 and 2014, respectively, included in Other.
Components Of Intangible Assets	The following table presents the components of intangible assets with a net carrying amount. December 31, 2015 2014 (dollars in thousands) Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Customer relationships $ 481,547 $ (97,892 ) $ 452,157 $ (69,483 ) Broker relationships 182,626 (45,135 ) 175,681 (34,827 ) Trade names 103,681 (23,821 ) 94,795 (17,673 ) Investment management agreements 98,000 — — — Technology 54,241 (22,288 ) 62,288 (22,671 ) Insurance licenses 30,185 — 39,985 — Lloyd's syndicate capacity 12,000 — 12,000 — Other 30,496 (11,268 ) 18,903 (8,408 ) Total $ 992,776 $ (200,404 ) $ 855,809 $ (153,062 )

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Components Of Income Before Income Taxes	Income before income taxes includes the following components. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Domestic operations $ 323,954 $ 240,279 $ 325,133 Foreign operations 418,151 200,099 36,610 Income before income taxes $ 742,105 $ 440,378 $ 361,743
Components Of Income Tax Expense	Income tax expense includes the following components. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Current: Domestic $ 44,406 $ 7,573 $ 50,683 Foreign 118,235 24,574 23,165 Total current tax expense 162,641 32,147 73,848 Deferred: Domestic 9,415 43,673 23,906 Foreign (19,093 ) 40,870 (19,856 ) Total deferred tax expense (benefit) (9,678 ) 84,543 4,050 Income tax expense $ 152,963 $ 116,690 $ 77,898
Reconciliations Of United States Corporate Income Tax Rate To Effective Tax Rate On Income Before Income Taxes	Reconciliations of the United States corporate income tax rate to the effective tax rate on income before income taxes are presented in the following table. Years Ended December 31, 2015 2014 2013 United States corporate tax rate 35 % 35 % 35 % Tax credits (8 ) (1 ) — Tax-exempt investment income (5 ) (9 ) (9 ) Foreign operations (1 ) — (4 ) Other — 1 — Effective tax rate 21 % 26 % 22 %
Components Of Domestic And Foreign Deferred Tax Assets And Liabilities	The following table presents the components of domestic and foreign deferred tax assets and liabilities. December 31, (dollars in thousands) 2015 2014 Assets: Unpaid losses and loss adjustment expenses $ 212,012 $ 239,588 Life and annuity benefits 156,950 143,102 Unearned premiums recognized for income tax purposes 102,076 108,960 Investments, including other-than-temporary impairments 65,641 28,106 Accrued incentive compensation 53,586 37,329 Stock-based compensation 21,948 31,314 Net operating loss carryforwards 18,771 36,359 Tax credit carryforwards 18,158 32,525 Other differences between financial reporting and tax bases 40,497 64,235 Total gross deferred tax assets 689,639 721,518 Less valuation allowance (5,131 ) (4,801 ) Total gross deferred tax assets, net of allowance 684,508 716,717 Liabilities: Net unrealized gains on investments 626,776 759,212 Amortization of goodwill and other intangible assets 107,271 106,927 Deferred policy acquisition costs 88,036 101,766 Other differences between financial reporting and tax bases 38,613 59,359 Total gross deferred tax liabilities 860,696 1,027,264 Net deferred tax liability $ 176,188 $ 310,547
Reconciliation Of Beginning And Ending Unrecognized Tax Benefits	The following table presents a reconciliation of unrecognized tax benefits. Years Ended December 31, (dollars in thousands) 2015 2014 Unrecognized tax benefits, beginning of year $ 17,700 $ 18,219 Increases for tax positions taken in prior years — 3 Decreases for tax positions taken in prior years (146 ) — Lapse of statute of limitations (606 ) (522 ) Settlement with taxing authorities (1,624 ) — Unrecognized tax benefits, end of year $ 15,324 $ 17,700

Unpaid Losses And Loss Adjust38

Unpaid Losses And Loss Adjustment Expenses (Tables)	12 Months Ended
	Dec. 31, 2015
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Reconciliation Of Consolidated Reserves For Losses And Loss Adjustment Expenses	The following table presents a reconciliation of consolidated beginning and ending reserves for losses and loss adjustment expenses. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Net reserves for losses and loss adjustment expenses, beginning of year $ 8,535,483 $ 8,407,642 $ 4,592,652 Foreign currency movements, commutations and other (134,173 ) (137,385 ) (780 ) Adjusted net reserves for losses and loss adjustment expenses, beginning of year 8,401,310 8,270,257 4,591,872 Incurred losses and loss adjustment expenses: Current year 2,566,545 2,638,012 2,227,402 Prior years (627,800 ) (435,545 ) (411,129 ) Total incurred losses and loss adjustment expenses 1,938,745 2,202,467 1,816,273 Payments: Current year 486,551 502,107 670,928 Prior years 1,423,286 1,436,851 906,302 Total payments 1,909,837 1,938,958 1,577,230 Effect of foreign currency rate changes (17,281 ) (19,476 ) (7,915 ) Net reserves for losses and loss adjustment expenses of acquired insurance companies — 21,193 3,584,642 Reinsurance recoverable on retroactive reinsurance transactions (177,649 ) — — Net reserves for losses and loss adjustment expenses, end of year 8,235,288 8,535,483 8,407,642 Reinsurance recoverable on unpaid losses 2,016,665 1,868,669 1,854,414 Gross reserves for losses and loss adjustment expenses, end of year $ 10,251,953 $ 10,404,152 $ 10,262,056
Reconciliation Of Asbestos And Environmental Reserves For Losses And Loss Adjustment Expenses	The following table provides a reconciliation of beginning and ending A&E reserves for losses and loss adjustment expenses, which are a component of consolidated unpaid losses and loss adjustment expenses. Amounts included in the following table are presented before consideration of reinsurance allowances. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Net reserves for A&E losses and loss adjustment expenses, beginning of year $ 287,723 $ 272,194 $ 260,791 Commutations and other — 115 (5,067 ) Adjusted net reserves for A&E losses and loss adjustment expenses, beginning of year 287,723 272,309 255,724 Incurred losses and loss adjustment expenses 25,415 32,840 30,128 Payments (20,628 ) (17,426 ) (13,658 ) Reinsurance recoverable on retroactive reinsurance transactions (159,641 ) — — Net reserves for A&E losses and loss adjustment expenses, end of year 132,869 287,723 272,194 Reinsurance recoverable on unpaid losses 253,756 102,719 100,784 Gross reserves for A&E losses and loss adjustment expenses, end of year $ 386,625 $ 390,442 $ 372,978

Life And Annuity Benefits (Tabl

Life And Annuity Benefits (Tables)	12 Months Ended
	Dec. 31, 2015
Liability for Future Policy Benefits [Abstract]
Schedule Of Life And Annuity Benefits	The following table presents life and annuity benefits. December 31, (dollars in thousands) 2015 2014 Life $ 142,068 $ 182,604 Annuities 901,218 1,031,946 Accident and health 79,989 91,268 Total $ 1,123,275 $ 1,305,818

Senior Long-Term Debt And Oth40

Senior Long-Term Debt And Other Debt (Tables)	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Summary Of Senior Long-Term Debt And Other Debt	The following table summarizes the Company's senior long-term debt and other debt. December 31, (dollars in thousands) 2015 2014 7.20% unsecured senior notes, due April 14, 2017, interest payable semi-annually, net of unamortized premium of $1,808 in 2015 and $3,526 in 2014 $ 92,436 $ 94,155 7.125% unsecured senior notes, due September 30, 2019, interest payable semi-annually, net of unamortized discount of $1,060 in 2015 and $1,343 in 2014 346,940 348,657 6.25% unsecured senior notes, due September 30, 2020, interest payable semi-annually, net of unamortized premium of $44,519 in 2015 and $53,172 in 2014 394,517 403,172 5.35% unsecured senior notes, due June 1, 2021, interest payable semi-annually, net of unamortized discount of $1,119 in 2015 and $1,325 in 2014 248,881 248,675 4.90% unsecured senior notes, due July 1, 2022, interest payable semi-annually, net of unamortized discount of $1,815 in 2015 and $2,095 in 2014 348,185 347,905 3.625% unsecured senior notes, due March 30, 2023, interest payable semi-annually, net of unamortized discount of $1,458 in 2015 and $1,659 in 2014 248,542 248,341 7.35% unsecured senior notes, due August 15, 2034, interest payable semi-annually, net of unamortized discount of $1,972 in 2015 and $2,078 in 2014 198,028 197,922 5.0% unsecured senior notes, due March 30, 2043, interest payable semi-annually, net of unamortized discount of $6,103 in 2015 and $6,327 in 2014 243,897 243,673 Subsidiary debt, at various interest rates ranging from 1.9% to 6.5% 120,001 121,094 Senior long-term debt and other debt $ 2,241,427 $ 2,253,594
Summary Of Future Principal Payments Due At Maturity On Senior Long-Term Debt And Other Debt	The following table summarizes the future principal payments due at maturity on senior long-term debt and other debt as of December 31, 2015 . Years Ending December 31, (dollars in thousands) 2016 $ 30,267 2017 120,268 2018 4,845 2019 352,843 2020 359,128 2021 and thereafter 1,341,276 Total principal payments $ 2,208,627 Net unamortized premium 32,800 Senior long-term debt and other debt $ 2,241,427

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule Of Net Income Per Share	Net income per share was determined by dividing adjusted net income to shareholders by the applicable weighted average shares outstanding. Diluted net income per share is computed by dividing adjusted net income to shareholders by the weighted average number of common shares and dilutive potential common shares outstanding during the year. Average closing common stock market prices are used to calculate the dilutive effect attributable to restricted stock. Years Ended December 31, (in thousands, except per share amounts) 2015 2014 2013 Net income to shareholders $ 582,772 $ 321,182 $ 281,021 Adjustment of redeemable noncontrolling interests 4,144 (8,186 ) 1,963 Adjusted net income to shareholders $ 586,916 $ 312,996 $ 282,984 Basic common shares outstanding 13,978 13,984 12,538 Dilutive potential common shares from conversion of options 9 11 12 Dilutive potential common shares from conversion of restricted stock 74 62 36 Diluted shares outstanding 14,061 14,057 12,586 Basic net income per share $ 41.99 $ 22.38 $ 22.57 Diluted net income per share $ 41.74 $ 22.27 $ 22.48
Summary Of Options	The following table summarizes additional information with respect to these options. Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (years) Intrinsic Value (in millions) Outstanding and exercisable, January 1, 2015 22,305 $ 411.98 Exercised 10,787 $ 418.41 Outstanding and exercisable, December 31, 2015 11,518 $ 405.97 0.9 $ 5.5
2012 Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary Of Nonvested Share-Based Awards	The following table summarizes nonvested share-based awards. Number of Awards Weighted Average Grant-Date Fair Value Nonvested awards at January 1, 2015 118,132 $ 479.11 Granted 23,013 740.80 Vested (37,262 ) 424.51 Nonvested awards at December 31, 2015 103,883 $ 556.66
Alterra Equity Award Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary Of Nonvested Share-Based Awards	The following table summarizes activity related to these nonvested restricted stock awards. Number of Awards Weighted Average Grant-Date Fair Value Nonvested awards at January 1, 2015 33,915 $ 529.59 Vested (33,915 ) 529.59 Nonvested awards at December 31, 2015 — $ —

Other Comprehensive Income (L42

Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2015
Other Comprehensive Income (Loss), Tax [Abstract]
Change In Accumulated Other Comprehensive Income By Component, Net Of Taxes And Noncontrolling Interests	The following table presents the change in accumulated other comprehensive income by component, net of taxes and noncontrolling interests. (dollars in thousands) Unrealized Holding Gains on Available-for- Sale Securities Foreign Currency Net Actuarial Pension Loss Total December 31, 2012 $ 946,933 $ (1,075 ) $ (34,521 ) $ 911,337 Other comprehensive income (loss) before reclassifications 225,404 (10,171 ) 2,517 217,750 Amounts reclassified from accumulated other comprehensive income (40,830 ) — 1,548 (39,282 ) Total other comprehensive income (loss) 184,574 (10,171 ) 4,065 178,468 December 31, 2013 $ 1,131,507 $ (11,246 ) $ (30,456 ) $ 1,089,805 Other comprehensive income (loss) before reclassifications 687,908 (32,245 ) (16,516 ) 639,147 Amounts reclassified from accumulated other comprehensive income (26,161 ) — 1,766 (24,395 ) Total other comprehensive income (loss) 661,747 (32,245 ) (14,750 ) 614,752 December 31, 2014 $ 1,793,254 $ (43,491 ) $ (45,206 ) $ 1,704,557 Other comprehensive loss before reclassifications (240,010 ) (29,205 ) (2,482 ) (271,697 ) Amounts reclassified from accumulated other comprehensive income (80,482 ) — 2,130 (78,352 ) Total other comprehensive loss (320,492 ) (29,205 ) (352 ) (350,049 ) December 31, 2015 $ 1,472,762 $ (72,696 ) $ (45,558 ) $ 1,354,508
Summary Of Tax Expense (Benefit) Of Other Comprehensive Income (Loss)	The following table summarizes the tax expense (benefit) associated with each component of other comprehensive income (loss). Years Ended December 31, (dollars in thousands) 2015 2014 2013 Change in net unrealized gains on investments: Net holding gains (losses) arising during the period $ (107,860 ) $ 328,564 $ 93,837 Change in unrealized other-than-temporary impairment losses on fixed maturities arising during the period 35 614 (34 ) Reclassification adjustments for net gains included in net income (29,267 ) (9,890 ) (16,382 ) Change in net unrealized gains on investments (137,092 ) 319,288 77,421 Change in foreign currency translation adjustments 408 1,918 (1,619 ) Change in net actuarial pension loss (88 ) (3,687 ) 1,015 Total $ (136,772 ) $ 317,519 $ 76,817
Reclassifications From Accumulated Other Comprehensive Income Into Income, By Component	The following table presents the details of amounts reclassified from accumulated other comprehensive income into income, by component. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Unrealized holding gains on available-for-sale securities: Other-than-temporary impairment losses $ (44,481 ) $ (4,784 ) $ (4,706 ) Net realized investment gains, excluding other-than-temporary impairment losses 154,230 40,835 61,918 Total before taxes 109,749 36,051 57,212 Income taxes (29,267 ) (9,890 ) (16,382 ) Reclassification of unrealized holding gains, net of taxes $ 80,482 $ 26,161 $ 40,830 Net actuarial pension loss: Underwriting, acquisition and insurance expenses $ (2,662 ) $ (2,084 ) $ (1,934 ) Income taxes 532 318 386 Reclassification of net actuarial pension loss, net of taxes $ (2,130 ) $ (1,766 ) $ (1,548 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Balances Of Assets And Liabilities Measured At Fair Value On A Recurring Basis	The following tables present the balances of assets measured at fair value on a recurring basis by level within the fair value hierarchy. December 31, 2015 (dollars in thousands) Level 1 Level 2 Level 3 Total Assets: Investments available-for-sale: Fixed maturities: U.S. Treasury securities and obligations of U.S. government agencies $ — $ 700,707 $ — $ 700,707 Obligations of states, municipalities and political subdivisions — 4,013,213 — 4,013,213 Foreign governments — 1,416,457 — 1,416,457 Commercial mortgage-backed securities — 659,538 — 659,538 Residential mortgage-backed securities — 854,247 — 854,247 Asset-backed securities — 36,071 — 36,071 Corporate bonds — 1,714,235 — 1,714,235 Total fixed maturities — 9,394,468 — 9,394,468 Equity securities: Insurance, banks and other financial institutions 1,334,722 — — 1,334,722 Industrial, consumer and all other 2,739,753 — — 2,739,753 Total equity securities 4,074,475 — — 4,074,475 Short-term investments 1,529,924 112,337 — 1,642,261 Total investments available-for-sale $ 5,604,399 $ 9,506,805 $ — $ 15,111,204 December 31, 2014 (dollars in thousands) Level 1 Level 2 Level 3 Total Assets: Investments available-for-sale: Fixed maturities: U.S. Treasury securities and obligations of U.S. government agencies $ — $ 673,262 $ — $ 673,262 Obligations of states, municipalities and political subdivisions — 4,317,547 — 4,317,547 Foreign governments — 1,611,921 — 1,611,921 Commercial mortgage-backed securities — 430,627 — 430,627 Residential mortgage-backed securities — 982,847 — 982,847 Asset-backed securities — 99,490 — 99,490 Corporate bonds — 2,307,188 — 2,307,188 Total fixed maturities — 10,422,882 — 10,422,882 Equity securities: Insurance, banks and other financial institutions 1,311,925 — — 1,311,925 Industrial, consumer and all other 2,825,651 — — 2,825,651 Total equity securities 4,137,576 — — 4,137,576 Short-term investments 1,469,975 124,874 — 1,594,849 Total investments available-for-sale $ 5,607,551 $ 10,547,756 $ — $ 16,155,307

Reinsurance (Tables)

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2015
Reinsurance Disclosures [Abstract]
Reinsurance Allowance For Doubtful Accounts	The following table summarizes the Company's reinsurance allowance for doubtful accounts. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Reinsurance allowance, beginning of year $ 59,813 $ 76,210 $ 71,148 Additions 5,897 10,316 13,621 Deductions (6,360 ) (26,713 ) (8,559 ) Reinsurance allowance, end of year $ 59,350 $ 59,813 $ 76,210
Effect Of Reinsurance On Premiums Written And Earned	The following table summarizes the effect of reinsurance and retrocessional reinsurance on premiums written and earned. Years Ended December 31, 2015 2014 2013 (dollars in thousands) Written Earned Written Earned Written Earned Direct $ 3,474,510 $ 3,480,297 $ 3,478,273 $ 3,443,912 $ 3,143,957 $ 2,947,812 Assumed 1,158,402 1,194,772 1,327,240 1,298,371 776,269 1,016,853 Ceded (813,619 ) (851,537 ) (888,498 ) (901,371 ) (683,543 ) (733,049 ) Net premiums $ 3,819,293 $ 3,823,532 $ 3,917,015 $ 3,840,912 $ 3,236,683 $ 3,231,616

Commitments And Contingencies (

Commitments And Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Minimum Annual Rental Commitments	The following table summarizes the Company's minimum annual rental commitments, excluding taxes, insurance and other operating costs payable directly by the Company, for noncancelable operating leases at December 31, 2015 . Years Ending December 31, (dollars in thousands) 2016 $ 29,664 2017 34,083 2018 30,708 2019 27,947 2020 21,597 2021 and thereafter 130,844 Total $ 274,843

Statutory Financial Informati46

Statutory Financial Information (Tables)	12 Months Ended
	Dec. 31, 2015
Statutory Financial Information [Abstract]
Actual Statutory Capital And Surplus	Statutory capital and surplus and statutory net income (loss) for the Company's wholly-owned insurance subsidiaries as of December 31, 2015 and 2014 and for the years ended December 31, 2015 , 2014 and 2013 , respectively, is summarized below. Statutory Capital and Surplus (dollars in thousands) 2015 2014 United States $ 2,569,928 $ 2,619,001 United Kingdom $ 608,342 $ 608,001 Bermuda $ 1,966,021 $ 1,890,218 Other $ 17,305 $ 177,824
Statutory Net Income (Loss)	Statutory Net Income (Loss) Years Ended December 31, (dollars in thousands) 2015 2014 2013 United States $ 291,783 $ 212,909 $ 235,009 United Kingdom $ 63,583 $ 73,697 $ 109,983 Bermuda $ 189,800 $ 110,401 $ 249,772 Other $ (3,181 ) $ 1,367 $ (12,617 )

Segment Reporting Disclosures (

Segment Reporting Disclosures (Tables)	12 Months Ended
	Dec. 31, 2015
Segment Reporting, Disclosure of Entity's Reportable Segments [Abstract]
Summary Of Gross Written Premiums By Country	The following table summarizes the Company's gross written premiums by country. Gross written premiums are attributed to individual countries based upon location of risk. Years Ended December 31, (dollars in thousands) 2015 % of Total 2014 % of Total 2013 % of Total United States $ 3,519,487 76 % $ 3,523,239 73 % $ 2,934,868 75 % United Kingdom 414,941 9 441,669 9 245,143 6 Canada 115,191 2 125,617 3 128,420 3 Other countries 583,293 13 714,988 15 611,795 16 Total $ 4,632,912 100 % $ 4,805,513 100 % $ 3,920,226 100 %
Company's Segment Disclosures	The following tables summarize the Company's segment disclosures. Year Ended December 31, 2015 (dollars in thousands) U.S. Insurance International Insurance Reinsurance Other Insurance (Discontinued Lines) Investing Consolidated Gross premium volume $ 2,504,096 $ 1,164,866 $ 965,374 $ (1,424 ) $ — $ 4,632,912 Net written premiums 2,106,490 888,214 824,324 265 — 3,819,293 Earned premiums 2,105,212 879,426 838,543 351 — 3,823,532 Losses and loss adjustment expenses: Current accident year (1,367,159 ) (638,144 ) (561,242 ) — — (2,566,545 ) Prior accident years 298,967 248,834 97,860 (17,861 ) — 627,800 Amortization of policy acquisition costs (420,289 ) (142,657 ) (182,018 ) — — (744,964 ) Other operating expenses (378,563 ) (221,758 ) (106,863 ) (2,932 ) — (710,116 ) Underwriting profit (loss) 238,168 125,701 86,280 (20,442 ) — 429,707 Net investment income — — — — 353,213 353,213 Net realized investment gains — — — — 106,480 106,480 Other revenues (insurance) 3,331 7,790 593 617 — 12,331 Other expenses (insurance) (3,902 ) (5,717 ) (1,419 ) (29,057 ) — (40,095 ) Segment profit (loss) $ 237,597 $ 127,774 $ 85,454 $ (48,882 ) $ 459,693 $ 861,636 Other revenues (non-insurance) 1,074,427 Other expenses (non-insurance) (1,006,710 ) Amortization of intangible assets (68,947 ) Interest expense (118,301 ) Income before income taxes $ 742,105 U.S. GAAP combined ratio (1) 89 % 86 % 90 % NM (2) 89 % (1) The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums. (2) NM — Ratio is not meaningful. Year Ended December 31, 2014 (dollars in thousands) U.S. Insurance International Insurance Reinsurance Other Insurance (Discontinued Lines) Investing Consolidated Gross premium volume $ 2,493,823 $ 1,200,403 $ 1,112,728 $ (1,441 ) $ — $ 4,805,513 Net written premiums 2,071,466 889,336 956,584 (371 ) — 3,917,015 Earned premiums 2,022,860 909,679 908,385 (12 ) — 3,840,912 Losses and loss adjustment expenses: Current accident year (1,340,129 ) (660,409 ) (637,474 ) — — (2,638,012 ) Prior accident years 216,557 166,615 79,951 (27,578 ) — 435,545 Amortization of policy acquisition costs (403,233 ) (141,394 ) (110,289 ) — — (654,916 ) Other operating expenses (396,737 ) (207,175 ) (201,673 ) (381 ) — (805,966 ) Underwriting profit (loss) 99,318 67,316 38,900 (27,971 ) — 177,563 Net investment income — — — — 363,230 363,230 Net realized investment gains — — — — 46,000 46,000 Other revenues (insurance) 2,478 21,827 2,696 1,631 — 28,632 Other expenses (insurance) (5,149 ) (18,706 ) (1,847 ) (37,132 ) — (62,834 ) Segment profit (loss) $ 96,647 $ 70,437 $ 39,749 $ (63,472 ) $ 409,230 $ 552,591 Other revenues (non-insurance) 854,893 Other expenses (non-insurance) (792,037 ) Amortization of intangible assets (57,627 ) Interest expense (117,442 ) Income before income taxes $ 440,378 U.S. GAAP combined ratio (1) 95 % 93 % 96 % NM (2) 95 % (1) The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums. (2) NM — Ratio is not meaningful. Year Ended December 31, 2013 (dollars in thousands) U.S. Insurance International Insurance Reinsurance Other Insurance (Discontinued Lines) Investing Consolidated Gross premium volume $ 2,252,739 $ 1,101,099 $ 566,348 $ 40 $ — $ 3,920,226 Net written premiums 1,915,770 840,050 480,822 41 — 3,236,683 Earned premiums 1,727,766 833,984 669,826 40 — 3,231,616 Losses and loss adjustment expenses: Current accident year (1,173,258 ) (588,759 ) (465,385 ) — — (2,227,402 ) Prior accident years 298,113 130,660 12,938 (30,582 ) — 411,129 Transaction costs and other acquisition-related expenses (1) (12,724 ) (13,366 ) (49,050 ) — — (75,140 ) Amortization of policy acquisition costs (287,795 ) (138,626 ) (45,494 ) — — (471,915 ) Other operating expenses (409,886 ) (171,666 ) (183,817 ) 112 — (765,257 ) Underwriting profit (loss) 142,216 52,227 (60,982 ) (30,430 ) — 103,031 Net investment income — — — — 317,373 317,373 Net realized investment gains — — — — 63,152 63,152 Other revenues (insurance) 13,648 4,284 5,432 1,130 — 24,494 Other expenses (insurance) (17,087 ) (5,065 ) — (28,126 ) — (50,278 ) Segment profit (loss) $ 138,777 $ 51,446 $ (55,550 ) $ (57,426 ) $ 380,525 $ 457,772 Other revenues (non-insurance) 686,448 Other expenses (non-insurance) (613,250 ) Amortization of intangible assets (55,223 ) Interest expense (114,004 ) Income before income taxes $ 361,743 U.S. GAAP combined ratio (2) 92 % 94 % 109 % NM (3) 97 % (1) In connection with the acquisition of Alterra, the Company incurred transaction costs of $16.0 million for the year ended December 31, 2013, which primarily consist of due diligence, legal and investment banking costs. Additionally, the Company incurred severance costs of $31.7 million , stay bonuses of $14.8 million and other compensation costs totaling $12.6 million related to the acceleration of certain long-term incentive compensation awards and restricted stock awards that were granted by Alterra prior to the acquisition. (2) The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums. (3) NM — Ratio is not meaningful.
Summary Of Deferred Policy Acquisition Costs, Unearned Premiums And Unpaid Losses And Loss Adjustment Expenses	The following table summarizes deferred policy acquisition costs, unearned premiums and unpaid losses and loss adjustment expenses by segment. (dollars in thousands) Deferred Policy Acquisition Costs Unearned Premiums Unpaid Losses and Loss Adjustment Expenses December 31, 2015 U.S. Insurance $ 162,289 $ 1,105,456 $ 3,720,429 International Insurance 48,913 467,158 3,140,000 Reinsurance 141,554 593,491 2,750,258 Other Insurance (Discontinued Lines) — — 641,266 Total $ 352,756 $ 2,166,105 $ 10,251,953 December 31, 2014 U.S. Insurance $ 165,333 $ 1,110,910 $ 3,577,166 International Insurance 47,618 491,708 3,353,417 Reinsurance 140,459 643,072 2,818,792 Other Insurance (Discontinued Lines) — — 654,777 Total $ 353,410 $ 2,245,690 $ 10,404,152
Summary Of Segment Earned Premiums By Product	The following table summarizes segment earned premiums by major product grouping. Years Ended December 31, (dollars in thousands) 2015 2014 2013 U.S. Insurance: General liability $ 522,358 $ 491,645 $ 431,798 Professional liability 324,230 321,005 268,203 Property 264,232 266,019 190,530 Personal lines 325,811 299,442 185,935 Programs 277,829 244,216 205,004 Workers compensation 281,954 263,164 250,790 Other 108,798 137,369 195,506 Total U.S. Insurance 2,105,212 2,022,860 1,727,766 International Insurance: General liability 124,198 146,178 128,171 Professional liability 268,637 285,300 252,816 Property 85,152 76,691 91,497 Marine and energy 262,307 287,263 287,745 Other 139,132 114,247 73,755 Total International Insurance 879,426 909,679 833,984 Reinsurance: Property 265,373 270,461 227,394 Casualty 315,027 323,390 244,981 Auto 102,227 152,645 84,042 Other 155,916 161,889 113,409 Total Reinsurance 838,543 908,385 669,826 Other Insurance (Discontinued Lines) 351 (12 ) 40 Total earned premiums $ 3,823,532 $ 3,840,912 $ 3,231,616
Reconciliation Of Segment Assets To The Company's Consolidated Balance Sheets	The following table reconciles segment assets to the Company's consolidated balance sheets. December 31, (dollars in thousands) 2015 2014 2013 Segment assets: Investing $ 18,056,947 $ 18,531,150 $ 17,550,332 Underwriting 5,386,710 5,422,445 5,468,731 Total segment assets 23,443,657 23,953,595 23,019,063 Non-insurance operations 1,497,614 1,246,762 936,448 Total assets $ 24,941,271 $ 25,200,357 $ 23,955,511

Other Revenues And Other Expe48

Other Revenues And Other Expenses (Tables)	12 Months Ended
	Dec. 31, 2015
Other Income and Expenses [Abstract]
Summary Of Other Revenues And Other Expenses By Component	The following table summarizes the components of other revenues and other expenses. Years Ended December 31, 2015 2014 2013 (dollars in thousands) Other Revenues Other Expenses Other Revenues Other Expenses Other Revenues Other Expenses Insurance: Managing general agent operations $ 10,202 $ 9,619 $ 23,324 $ 22,527 $ 17,399 $ 20,382 Life and annuity 617 29,057 1,631 37,132 1,130 28,126 Other 1,512 1,419 3,677 3,175 5,965 1,770 12,331 40,095 28,632 62,834 24,494 50,278 Non-Insurance: Markel Ventures: Manufacturing 755,802 677,054 575,353 513,668 495,138 437,712 Markel Ventures: Non-Manufacturing 291,714 301,004 262,767 261,551 191,310 175,538 Other 26,911 28,652 16,773 16,818 — — 1,074,427 1,006,710 854,893 792,037 686,448 613,250 Total $ 1,086,758 $ 1,046,805 $ 883,525 $ 854,871 $ 710,942 $ 663,528

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2015
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Funded Status Of The Terra Nova Pension Plan	The following table summarizes the funded status of the Terra Nova Pension Plan and the amounts recognized on the accompanying consolidated balance sheets of the Company. Years Ended December 31, (dollars in thousands) 2015 2014 Change in projected benefit obligation: Projected benefit obligation at beginning of period $ 185,556 $ 163,010 Interest cost 6,645 7,572 Plan amendments — 495 Plan settlements (2,863 ) — Benefits paid (3,970 ) (4,424 ) Actuarial loss (gain) (6,051 ) 29,609 Effect of foreign currency rate changes (9,312 ) (10,706 ) Projected benefit obligation at end of year $ 170,005 $ 185,556 Change in plan assets: Fair value of plan assets at beginning of period $ 201,399 $ 189,437 Actual gain on plan assets 2,246 22,395 Employer contributions — 5,610 Plan settlements (2,766 ) — Benefits paid (3,970 ) (4,424 ) Effect of foreign currency rate changes (10,182 ) (11,619 ) Fair value of plan assets at end of year $ 186,727 $ 201,399 Funded status of the plan $ 16,722 $ 15,843 Net actuarial pension loss 61,818 61,378 Total $ 78,540 $ 77,221
Schedule of Defined Benefit Plan Amounts Recognized in Accumulated Other Comprehensive Income	The following table presents the changes in plan assets and projected benefit obligation recognized in accumulated other comprehensive income. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Net actuarial gain (loss) $ (3,102 ) $ (20,521 ) $ 3,146 Settlement loss recognized 343 — — Amortization of: Net actuarial loss 2,319 1,589 1,934 Prior service costs — 495 — Tax benefit (expense) 88 3,687 (1,015 ) Total other comprehensive income (loss) $ (352 ) $ (14,750 ) $ 4,065
Schedule Of Net Periodic Benefit Income And Weighted Average Assumptions	The following table summarizes the components of net periodic benefit income and the weighted average assumptions for the Terra Nova Pension Plan. Years Ended December 31, (dollars in thousands) 2015 2014 2013 Components of net periodic benefit income: Interest cost $ 6,645 $ 7,572 $ 6,533 Expected return on plan assets (11,496 ) (12,812 ) (10,825 ) Amortization of prior service cost — 495 — Amortization of net actuarial pension loss 2,319 1,589 1,934 Settlement loss recognized 343 — — Net periodic benefit income $ (2,189 ) $ (3,156 ) $ (2,358 ) Weighted average assumptions as of December 31: Discount rate 4.0 % 3.8 % 4.7 % Expected return on plan assets 5.4 % 6.0 % 6.6 % Rate of compensation increase 2.9 % 2.9 % 3.2 %
Summary Of Fair Value Of Plan Assets	The following table summarizes the fair value of plan assets as of December 31, 2015 and 2014 . December 31, (dollars in thousands) 2015 2014 Plan assets: Fixed maturity index funds $ 107,033 $ 114,243 Equity security index funds 79,686 87,148 Cash and cash equivalents 8 8 Total $ 186,727 $ 201,399

Markel Corporation (Parent Co50

Markel Corporation (Parent Company Only) Financial Information (Tables)	12 Months Ended
	Dec. 31, 2015
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Schedule Of Condensed Balance Sheets	CONDENSED BALANCE SHEETS December 31, 2015 2014 (dollars in thousands) ASSETS Investments, available-for-sale, at estimated fair value: Fixed maturities (amortized cost of $35,475 in 2015 and $47,346 in 2014) $ 36,618 $ 48,807 Equity securities (cost of $204,289 in 2015 and $193,864 in 2014) 311,405 434,714 Short-term investments (estimated fair value approximates cost) 755,619 764,953 Total Investments 1,103,642 1,248,474 Cash and cash equivalents 460,271 243,702 Restricted cash and cash equivalents 670 959 Receivables 17,200 16,110 Investments in consolidated subsidiaries 7,961,315 7,560,862 Notes receivable from subsidiaries 212,636 212,631 Income taxes receivable — 10,951 Other assets 91,151 93,434 Total Assets $ 9,846,885 $ 9,387,123 LIABILITIES AND SHAREHOLDERS' EQUITY Senior long-term debt $ 1,634,472 $ 1,635,173 Notes payable to subsidiaries 300,000 15,000 Income taxes payable 4,262 — Net deferred tax liability 7,498 74,534 Other liabilities 66,503 67,598 Total Liabilities 2,012,735 1,792,305 Total Shareholders' Equity 7,834,150 7,594,818 Total Liabilities and Shareholders' Equity $ 9,846,885 $ 9,387,123
Schedule Of Condensed Statements Of Income And Comprehensive Income	CONDENSED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME Years Ended December 31, 2015 2014 2013 (dollars in thousands) REVENUES Net investment income $ 2,565 $ 5,354 $ 21,946 Dividends on common stock of consolidated subsidiaries 187,496 217,121 806,233 Net realized investment gains: Other-than-temporary impairment losses (3,455 ) (120 ) (15 ) Net realized investment gains, excluding other-than-temporary impairment losses 75,000 3,873 67,232 Net realized investment gains 71,545 3,753 67,217 Other — — 1 Total Revenues 261,606 226,228 895,397 EXPENSES Interest expense 95,620 94,097 92,743 Other expenses 11,287 2,685 2,617 Total Expenses 106,907 96,782 95,360 Income Before Equity in Undistributed Earnings of Consolidated Subsidiaries and Income Taxes 154,699 129,446 800,037 Equity in undistributed earnings of consolidated subsidiaries 407,489 163,341 (520,323 ) Income tax benefit (20,584 ) (28,395 ) (1,307 ) Net Income to Shareholders $ 582,772 $ 321,182 $ 281,021 OTHER COMPREHENSIVE INCOME (LOSS) TO SHAREHOLDERS Change in net unrealized gains on investments, net of taxes: Net holding gains (losses) arising during the period $ (41,861 ) $ 32,118 $ 66,623 Consolidated subsidiaries' net holding gains (losses) arising during the period (198,309 ) 655,617 158,922 Consolidated subsidiaries' change in unrealized other-than-temporary impairment losses on fixed maturities arising during the period 160 173 (141 ) Reclassification adjustments for net losses included in net income to shareholders (45,273 ) (1,874 ) (43,220 ) Consolidated subsidiaries' reclassification adjustments for net gains (losses) included in net income to shareholders (35,209 ) (24,287 ) 2,390 Change in net unrealized gains on investments, net of taxes (320,492 ) 661,747 184,574 Change in foreign currency translation adjustments, net of taxes 2,970 1,949 (2,670 ) Consolidated subsidiaries' change in foreign currency translation adjustments, net of taxes (32,175 ) (34,194 ) (7,501 ) Consolidated subsidiaries' change in net actuarial pension loss, net of taxes (352 ) (14,750 ) 4,065 Total Other Comprehensive Income (Loss) to Shareholders (350,049 ) 614,752 178,468 Comprehensive Income to Shareholders $ 232,723 $ 935,934 $ 459,489
Schedule Of Condensed Statements Of Cash Flows	CONDENSED STATEMENTS OF CASH FLOWS Years Ended December 31, 2015 2014 2013 (dollars in thousands) OPERATING ACTIVITIES Net income to shareholders $ 582,772 $ 321,182 $ 281,021 Adjustments to reconcile net income to shareholders to net cash provided by operating activities (464,193 ) (218,396 ) 186,574 Net Cash Provided By Operating Activities 118,579 102,786 467,595 INVESTING ACTIVITIES Proceeds from sales of fixed maturities and equity securities 100,633 9,306 142,259 Proceeds from maturities, calls and prepayments of fixed maturities 24,945 15,710 2,819 Cost of fixed maturities and equity securities purchased (55,656 ) (687 ) (23,412 ) Net change in short-term investments 9,956 (109,728 ) 10,251 Securities received from subsidiaries as dividends or repayment of notes receivable — 89,996 249,996 Decrease in notes receivable due from subsidiaries — 28,506 5,302 Capital contributions to subsidiaries (228,578 ) (74,788 ) (67,878 ) Acquisitions — — (1,017,988 ) Cost of equity method investments (13,164 ) — (5,291 ) Change in restricted cash and cash equivalents 289 51 (348 ) Additions to property and equipment (305 ) (342 ) (3,653 ) Other (376 ) (2,150 ) 3,207 Net Cash Used By Investing Activities (162,256 ) (44,126 ) (704,736 ) FINANCING ACTIVITIES Additions to senior long-term debt — — 491,235 Increase in notes payable to subsidiaries 285,000 — — Repayment and retirement of senior long-term debt (2,000 ) — (246,665 ) Repurchases of common stock (31,491 ) (26,053 ) (57,388 ) Issuance of common stock 4,752 5,691 24,518 Other 3,985 (1,948 ) (5,023 ) Net Cash Provided (Used) By Financing Activities 260,246 (22,310 ) 206,677 Increase (decrease) in cash and cash equivalents 216,569 36,350 (30,464 ) Cash and cash equivalents at beginning of year 243,702 207,352 237,816 CASH AND CASH EQUIVALENTS AT END OF YEAR $ 460,271 $ 243,702 $ 207,352

Quarterly Financial Informati51

Quarterly Financial Information (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results Of Consolidated Operations	The following table presents the unaudited quarterly results of consolidated operations for 2015 , 2014 and 2013 . Quarters Ended (dollars in thousands, except per share amounts) Mar. 31 June 30 Sept. 30 Dec. 31 2015 Operating revenues $ 1,302,154 $ 1,304,605 $ 1,342,764 $ 1,420,460 Net income 194,006 92,453 104,410 198,273 Net income to shareholders 190,992 91,369 102,519 197,892 Comprehensive income (loss) to shareholders 281,807 (132,925 ) (51,143 ) 134,984 Net income per share: Basic $ 13.57 $ 6.76 $ 7.43 $ 14.23 Diluted 13.49 6.72 7.39 14.14 Common stock price ranges: High $ 783.50 $ 821.00 $ 898.08 $ 937.91 Low 660.05 736.96 775.00 791.97 2014 Operating revenues $ 1,239,655 $ 1,258,971 $ 1,299,286 $ 1,335,755 Net income 87,501 41,141 76,824 118,222 Net income to shareholders 87,716 40,068 75,803 117,595 Comprehensive income to shareholders 230,273 250,588 36,502 418,571 Net income per share: Basic $ 6.28 $ 2.67 $ 5.33 $ 8.10 Diluted 6.25 2.66 5.30 8.05 Common stock price ranges: High $ 596.87 $ 655.75 $ 666.00 $ 707.36 Low 527.17 593.76 623.90 632.65 2013 Operating revenues $ 819,864 $ 1,031,769 $ 1,191,665 $ 1,279,785 Net income 89,263 28,676 66,967 98,939 Net income to shareholders 88,902 27,756 65,599 98,764 Comprehensive income (loss) to shareholders 257,684 (149,054 ) 144,409 206,450 Net income per share: Basic $ 9.53 $ 2.24 $ 4.69 $ 6.98 Diluted 9.50 2.24 4.67 6.95 Common stock price ranges: High $ 510.05 $ 546.94 $ 549.09 $ 582.59 Low 434.98 501.76 506.64 511.06

Summary Of Significant Accoun52

Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	May. 01, 2013
Summary of Significant Accounting Policies [Line Items]
Deferred policy acquisition cost amortization period	1 year
Adjustment of redeemable noncontrolling interests	$ 4,144	$ (8,186)	$ 1,963
Tax benefit greater than 50%	50.00%
Insurance premiums revenue recognition period	1 year
Stock-based compensation expense, net of taxes	$ 16,300	18,700	$ 18,400
Cumulative foreign currency translation loss	$ (72,700)	$ (43,500)
Alterra Capital Holdings [Member]
Summary of Significant Accounting Policies [Line Items]
Percentage of issued and outstanding common stock acquired				100.00%

Summary of Significant Accoun53

Summary of Significant Accounting Policies (Cash and Cash Equivalents) (Details)	12 Months Ended
	Dec. 31, 2015
Maximum [Member] | Cash And Cash Equivalents [Member]
Cash and Cash Equivalents [Line Items]
Investment maturity period	90 days

Summary of Significant Accoun54

Summary of Significant Accounting Policies (Goodwill and Intangible Assets) (Details)	12 Months Ended
	Dec. 31, 2015
Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, estimated useful life	5 years
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, estimated useful life	20 years

Summary of Significant Accoun55

Summary of Significant Accounting Policies (Property and Equipment) (Details)	12 Months Ended
	Dec. 31, 2015
Building [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	10 years
Building [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	40 years
Land Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	7 years
Land Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	40 years
Furniture and Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	3 years
Furniture and Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	10 years
Other Property And Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	3 years
Other Property And Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	25 years

Acquisitions (Narrative) (Detai

Acquisitions (Narrative) (Details) - USD ($)		Jan. 17, 2014	May. 01, 2013	Jan. 01, 2013	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jul. 31, 2014	Jan. 01, 2014
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Definite-lived intangible assets, weighted-average amortization period							14 years
United States corporate tax rate							35.00%	35.00%	35.00%
Provision for United States income taxes on earnings of the Company's foreign subsidiaries					$ 0	$ 0	$ 0
Acceleration of Alterra long-term incentive compensation awards and restricted stock awards	[1],[2]								$ 12,621,000
Transaction costs	[1],[2]								15,981,000
Pro forma transaction costs, total									39,000,000
Other acquisition related costs, severance costs	[1],[2]								31,734,000
Other acquisition related costs, stay bonuses	[1],[2]								14,804,000
Customer Relationships [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Definite-lived intangible assets, weighted-average amortization period							17 years
Markel CATCo IM [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Total purchase consideration					205,700,000
Cash consideration					205,700,000
Goodwill recognized					91,900,000	91,900,000	$ 91,900,000
Goodwill, tax deductible					91,900,000	91,900,000	91,900,000
Finite-lived intangible assets					$ 113,000,000	113,000,000	113,000,000
Definite-lived intangible assets, weighted-average amortization period					14 years
Estimated amount of performance and retention bonus payments					$ 100,000,000
Essentia Insurance Company [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Percentage of outstanding shares acquired				100.00%
Other intangible assets recognized, asset acquisition				$ 35,400,000
Percentage of outstanding shares of Essentia purchased by Hagerty due to the exercise of options											9.90%
Company's ownership interest in Essentia											90.10%
Essentia Insurance Company [Member] | Customer Relationships [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Definite-lived intangible assets, weighted-average amortization period				6 years
Other intangible assets recognized, asset acquisition				$ 25,000,000
CapTech Ventures Inc [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Total purchase consideration						60,600,000
Goodwill recognized					48,500,000	48,500,000	48,500,000
Goodwill, tax deductible					0	0	0
Finite-lived intangible assets					$ 49,200,000	$ 49,200,000	$ 49,200,000
Definite-lived intangible assets, weighted-average amortization period						14 years
Percentage acquired					80.00%	80.00%	80.00%
Redeemable noncontrolling interest					$ 13,800,000	$ 13,800,000	$ 13,800,000
Cottrell Inc [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Percentage acquired										100.00%
Non-Insurance Acquisitions [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Total purchase consideration								$ 187,000,000
Goodwill recognized								38,700,000
Finite-lived intangible assets								78,700,000
Non-Insurance Acquisitions [Member] | Customer Relationships [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Finite-lived intangible assets								$ 53,700,000
Definite-lived intangible assets, weighted-average amortization period								17 years
Non-Insurance Acquisitions [Member] | Trade Names [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Finite-lived intangible assets								$ 13,000,000
Definite-lived intangible assets, weighted-average amortization period								10 years
Alterra Capital Holdings [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Total purchase consideration			$ 3,304,293,000
Cash consideration			964,330,000
Goodwill recognized			295,690,000
Goodwill, tax deductible			0
Finite-lived intangible assets			$ 170,000,000
Definite-lived intangible assets, weighted-average amortization period			17 years
Percentage acquired			100.00%
Number of Markel Corporation shares issued for each outstanding share of Alterra common stock			0.04315
Cash paid for each oustanding share of Alterra common stock			$ 10
Stock consideration, shares			4,300,000
Options issued, taxes			$ 1,900,000
Restricted stock issued, taxes			10,100,000
Restricted stock units issued, taxes			700,000
Indefinite-lived intangible assets			37,500,000
Investments acquired, adjustment to fair value			223,100,000
Investments acquired, incremental premium to be amortized to net investment income			495,500,000
Investments, unamortized incremental premium					198,300,000	198,300,000	198,300,000	$ 281,100,000
Investments, amortization expense on incremental premium							39,600,000	59,300,000	58,300,000
Unearned premiums acquired, adjustment to fair value			$ (176,300,000)
Unearned premiums, weighted average amortization period, years			1 year
Unpaid losses and loss adjustment expenses acquired, adjustment to fair value			$ 120,800,000
Unpaid losses and loss adjustment expenses acquired pre acquisition adjustment, unamortized balance			$ 26,500,000
Unpaid losses and loss adjustment expenses, weighted average amortization period, years			5 years
Unpaid losses and loss adjustment expenses, unamortized fair value adjustment					91,000,000	91,000,000	91,000,000	114,600,000
Life and annuity benefits acquired, adjustment to fair value			$ 329,600,000
Senior long-term debt acquired, adjustment to fair value			$ 71,900,000
Senior long-term debt acquired, unamortized premium					$ 46,300,000	$ 46,300,000	$ 46,300,000	$ 56,700,000
United States corporate tax rate			35.00%
Net deferred tax assets recognized			$ 310,100,000
Deferred tax assets recognized, accrued losses and loss adjustment expenses and life and annuity benefits			343,900,000
Deferred tax liabilities recognized, intangible assets			64,600,000
Provision for United States income taxes on earnings of the Company's foreign subsidiaries			0
Pro forma transaction costs, Alterra									$ 23,000,000
Alterra Capital Holdings [Member] | Customer Relationships [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Finite-lived intangible assets			$ 132,000,000
Definite-lived intangible assets, weighted-average amortization period			18 years
Alterra Capital Holdings [Member] | Trade Names [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Finite-lived intangible assets			$ 1,000,000
Definite-lived intangible assets, weighted-average amortization period			1 year
Alterra Capital Holdings [Member] | U.S. Insurance [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Goodwill recognized			$ 107,800,000
Alterra Capital Holdings [Member] | International Insurance [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Goodwill recognized			65,200,000
Alterra Capital Holdings [Member] | Reinsurance [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Goodwill recognized			$ 122,700,000
Abbey Protection plc [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Total purchase consideration		$ 190,700,000
Cash consideration		190,700,000
Goodwill recognized		65,800,000
Goodwill, tax deductible		0
Finite-lived intangible assets		$ 113,400,000
Percentage acquired		100.00%
Abbey Protection plc [Member] | Customer Relationships [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Finite-lived intangible assets		$ 103,500,000
Definite-lived intangible assets, weighted-average amortization period		20 years
Abbey Protection plc [Member] | Trade Names [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Finite-lived intangible assets		$ 9,900,000
Definite-lived intangible assets, weighted-average amortization period		14 years
Abbey Protection plc [Member] | International Insurance [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Goodwill recognized		$ 43,000,000
Abbey Protection plc [Member] | Non-Insurance Operations [Member]
Schedule of Asset and Business Acquisitions, by Acquisition [Line Items]
Goodwill recognized		$ 22,800,000
[1]	In connection with the acquisition of Alterra, the Company incurred transaction costs of $16.0 million for the year ended December 31, 2013, which primarily consist of due diligence, legal and investment banking costs. Additionally, the Company incurred severance costs of $31.7 million, stay bonuses of $14.8 million and other compensation costs totaling $12.6 million related to the acceleration of certain long-term incentive compensation awards and restricted stock awards that were granted by Alterra prior to the acquisition.
[2]	In connection with the acquisition of Alterra, the Company incurred transaction costs of $16.0 million for the year ended December 31, 2013, which primarily consist of due diligence, legal and investment banking costs. Additionally, the Company incurred severance costs of $31.7 million, stay bonuses of $14.8 million and other compensation costs totaling $12.6 million related to the acceleration of certain long-term incentive compensation awards and restricted stock awards that were granted by Alterra prior to the acquisition.

Acquisitions (Calculation Of To

Acquisitions (Calculation Of Total Purchase Price) (Details) - Alterra Capital Holdings [Member] $ / shares in Units, $ in Thousands	May. 01, 2013USD ($)$ / sharesshares
Business Acquisition [Line Items]
Exchange ratio per the Merger Agreement	0.04315
Markel share issuance to Alterra shareholders	4,300,000
Incentive award ratio per the Merger Agreement	0.06252
Multiplied by Markel's weighted average stock price on April 30, 2013 | $ / shares	$ 529.59	[1]
Markel share and restricted stock issuance consideration, net of taxes | $	$ 2,267,648
Alterra common shares outstanding as of the Acquisition Date that received cash consideration	96,433,000
Multiplied by cash price per share component per the Merger Agreement | $ / shares	$ 10
Markel cash consideration | $	$ 964,330
Fair value of Markel warrant issuance to Alterra warrant holders as of the Acquisition Date | $	73,685
Fair value of Markel stock option issuance to Alterra stock option holders as of the Acquisition Date, net of taxes | $	12,335
Fair value of partially vested Markel restricted stock unit issuance as of the Acquisition Date, net of taxes | $	6,867
Unrecognized compensation on unvested restricted stock and restricted stock units | $	(20,572)
Total acquisition consideration | $	$ 3,304,293
Common Stock [Member]
Business Acquisition [Line Items]
Shares of Alterra stock outstanding as of the Acquisition Date	96,433,000
Markel share issuance to Alterra shareholders	4,161,000
Restricted Stock [Member]
Business Acquisition [Line Items]
Shares of Alterra stock outstanding as of the Acquisition Date	2,239,000
Markel share issuance to Alterra shareholders	140,000
[1]	The fair value of the shares issued by the Company was calculated as the weighted average price of the Company's stock on April 30, 2013, the day preceding the Acquisition Date.

Acquisitions (Summary Of Fair V

Acquisitions (Summary Of Fair Value Of Assets Acquired And Liabilities Assumed) (Details) - Alterra Capital Holdings [Member] $ in Thousands	May. 01, 2013USD ($)
ASSETS
Investments	$ 6,407,841
Cash and cash equivalents	1,036,274
Restricted cash and cash equivalents	414,497
Receivables	866,388
Reinsurance recoverable on unpaid losses	1,169,084
Reinsurance recoverable on paid losses	80,672
Prepaid reinsurance premiums	317,445
Other assets	859,884
LIABILITIES
Unpaid losses and loss adjustment expenses	4,719,461
Life and annuity benefits	1,477,482
Unearned premiums	1,075,610
Payables to insurance and reinsurance companies	342,858
Senior long-term debt	512,463
Other liabilities	223,108
Net assets	2,801,103
Goodwill	295,690
Intangible assets	207,500
Acquisition date fair value	$ 3,304,293

Acquisitions (Summary Of Intang

Acquisitions (Summary Of Intangible Assets Acquired) (Details) - USD ($) $ in Thousands	May. 01, 2013	Dec. 31, 2015
Schedule of Intangible Assets [Line Items]
Economic useful lives of finite-lived intangible assets, years		14 years
Customer Relationships [Member]
Schedule of Intangible Assets [Line Items]
Economic useful lives of finite-lived intangible assets, years		17 years
Alterra Capital Holdings [Member]
Schedule of Intangible Assets [Line Items]
Finite-lived intangible assets	$ 170,000
Indefinite-lived intangible assets	$ 37,500
Economic useful lives of finite-lived intangible assets, years	17 years
Intangible assets as of the Acquisition Date	$ 207,500
Alterra Capital Holdings [Member] | Lloyd's Syndicate Capacity [Member]
Schedule of Intangible Assets [Line Items]
Indefinite-lived intangible assets	$ 12,000
Economic useful lives of indefinite-lived intangible assets, years	Indefinite
Alterra Capital Holdings [Member] | Insurance Licenses [Member]
Schedule of Intangible Assets [Line Items]
Indefinite-lived intangible assets	$ 25,500
Economic useful lives of indefinite-lived intangible assets, years	Indefinite
Alterra Capital Holdings [Member] | Customer Relationships [Member]
Schedule of Intangible Assets [Line Items]
Finite-lived intangible assets	$ 132,000
Economic useful lives of finite-lived intangible assets, years	18 years
Alterra Capital Holdings [Member] | Broker Relationships [Member]
Schedule of Intangible Assets [Line Items]
Finite-lived intangible assets	$ 19,000
Economic useful lives of finite-lived intangible assets, years	18 years
Alterra Capital Holdings [Member] | Technology [Member]
Schedule of Intangible Assets [Line Items]
Finite-lived intangible assets	$ 18,000
Economic useful lives of finite-lived intangible assets, years	10 years
Alterra Capital Holdings [Member] | Trade Names [Member]
Schedule of Intangible Assets [Line Items]
Finite-lived intangible assets	$ 1,000
Economic useful lives of finite-lived intangible assets, years	1 year

Acquisitions (Summary Of Transa

Acquisitions (Summary Of Transaction And Acquisition-Related Costs) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Acquisitions [Abstract]
Transaction costs	[1],[2]			$ 15,981
Severance costs	[1],[2]			31,734
Stay bonuses	[1],[2]			14,804
Acceleration of Alterra long-term incentive compensation awards and restricted stock awards	[1],[2]			12,621
Total transaction and acquisition-related costs	[1]	$ 0	$ 0	$ 75,140	[2]
[1]	In connection with the acquisition of Alterra, the Company incurred transaction costs of $16.0 million for the year ended December 31, 2013, which primarily consist of due diligence, legal and investment banking costs. Additionally, the Company incurred severance costs of $31.7 million, stay bonuses of $14.8 million and other compensation costs totaling $12.6 million related to the acceleration of certain long-term incentive compensation awards and restricted stock awards that were granted by Alterra prior to the acquisition.
[2]	In connection with the acquisition of Alterra, the Company incurred transaction costs of $16.0 million for the year ended December 31, 2013, which primarily consist of due diligence, legal and investment banking costs. Additionally, the Company incurred severance costs of $31.7 million, stay bonuses of $14.8 million and other compensation costs totaling $12.6 million related to the acceleration of certain long-term incentive compensation awards and restricted stock awards that were granted by Alterra prior to the acquisition.

Acquisitions (Summary Of Result

Acquisitions (Summary Of Results Of Operations) (Details) - Alterra Capital Holdings [Member] $ in Thousands	8 Months Ended
	Dec. 31, 2013USD ($)
Business Acquisition [Line Items]
Operating revenues	$ 912,387
Net loss to shareholders	$ (93,074)

Acquisitions (Unaudited Pro For

Acquisitions (Unaudited Pro Forma Consolidated Financial Information) (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2013USD ($)$ / sharesshares
Acquisitions [Abstract]
Earned premiums	$ 3,680,220
Operating revenues	4,899,628
Net income to shareholders	$ 422,829
U.S. GAAP combined ratio	95.00%	[1]
Basic net income per share | $ / shares	$ 30.33
Diluted net income per share | $ / shares	$ 30.19
Weighted average common shares outstanding, basic | shares	14,007
Weighted average common shares outstanding, diluted | shares	14,069
[1]	The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums.

Investments (Narrative) (Detail

Investments (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)securities	Dec. 31, 2014USD ($)securities	Dec. 31, 2013USD ($)
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities in unrealized loss position, number of positions | securities	659	552
Available-for-sale securities, estimated fair value	$ 2,843,837	$ 2,031,032
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	$ (95,896)	$ (35,218)
Number of available-for-sale securities positions in a continuous unrealized loss position for one year or longer at period end | securities	271	396
Available-for-sale securities, estimated fair value, 12 months or longer	$ 813,147	$ 1,333,930
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	$ (19,842)	(22,079)
Estimated average duration of the fixed maturities	5 years 10 months 22 days
Cumulative credit loss recognized in income	$ 10,700	$ 12,700	$ 12,700
Percentage threshold of shareholders' equity used to define concentration of investments	10.00%	10.00%
Ten largest equity holdings	$ 1,800,000
Ten largest equity holdings, percentage of equity portfolio	44.00%
Investments in property and casualty	$ 690,000
Investments in property and casualty, percentage of equity portfolio	17.00%
Berkshire Hathaway Inc. [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments in property and casualty	$ 414,100
Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value	2,296,480	$ 1,746,787
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	$ (44,205)	$ (27,847)
Number of available-for-sale securities positions in a continuous unrealized loss position for one year or longer at period end | securities	264	396
Available-for-sale securities, estimated fair value, 12 months or longer	$ 803,993	$ 1,333,930
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(19,423)	(22,079)
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value	417,884	102,281
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	$ (51,682)	(7,365)
Number of available-for-sale securities positions in a continuous unrealized loss position for one year or longer at period end | securities	7
Available-for-sale securities, estimated fair value, 12 months or longer	$ 9,154	0
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	$ (419)	$ 0

Investments (Available-For-Sale

Investments (Available-For-Sale Investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale investments, amortized cost	$ 12,889,095	$ 13,475,614
Available-for-sale investments, gross unrealized holding gains	2,318,005	2,714,911
Available-for-sale investments, gross unrealized holding losses	(92,014)	(31,141)
Available-for-sale investments, unrealized other-than-temporary impairment losses	(3,882)	(4,077)
Available-for-sale investments, estimated fair value	15,111,204	16,155,307
U.S. Treasury Securities And Obligations Of U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale investments, amortized cost	695,652	662,462
Available-for-sale investments, gross unrealized holding gains	9,836	12,963
Available-for-sale investments, gross unrealized holding losses	(4,781)	(2,163)
Available-for-sale investments, unrealized other-than-temporary impairment losses	0	0
Available-for-sale investments, estimated fair value	700,707	673,262
Obligations Of States, Municipalities And Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale investments, amortized cost	3,817,136	4,075,748
Available-for-sale investments, gross unrealized holding gains	204,302	245,158
Available-for-sale investments, gross unrealized holding losses	(8,225)	(3,359)
Available-for-sale investments, unrealized other-than-temporary impairment losses	0	0
Available-for-sale investments, estimated fair value	4,013,213	4,317,547
Foreign Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale investments, amortized cost	1,302,329	1,458,255
Available-for-sale investments, gross unrealized holding gains	115,809	154,707
Available-for-sale investments, gross unrealized holding losses	(1,681)	(1,041)
Available-for-sale investments, unrealized other-than-temporary impairment losses	0	0
Available-for-sale investments, estimated fair value	1,416,457	1,611,921
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale investments, amortized cost	657,670	427,904
Available-for-sale investments, gross unrealized holding gains	6,867	5,325
Available-for-sale investments, gross unrealized holding losses	(4,999)	(2,602)
Available-for-sale investments, unrealized other-than-temporary impairment losses	0	0
Available-for-sale investments, estimated fair value	659,538	430,627
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale investments, amortized cost	837,964	954,263
Available-for-sale investments, gross unrealized holding gains	22,563	34,324
Available-for-sale investments, gross unrealized holding losses	(4,022)	(3,482)
Available-for-sale investments, unrealized other-than-temporary impairment losses	(2,258)	(2,258)
Available-for-sale investments, estimated fair value	854,247	982,847
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale investments, amortized cost	36,462	100,073
Available-for-sale investments, gross unrealized holding gains	15	99
Available-for-sale investments, gross unrealized holding losses	(406)	(682)
Available-for-sale investments, unrealized other-than-temporary impairment losses	0	0
Available-for-sale investments, estimated fair value	36,071	99,490
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale investments, amortized cost	1,690,945	2,250,432
Available-for-sale investments, gross unrealized holding gains	41,123	69,016
Available-for-sale investments, gross unrealized holding losses	(16,209)	(10,441)
Available-for-sale investments, unrealized other-than-temporary impairment losses	(1,624)	(1,819)
Available-for-sale investments, estimated fair value	1,714,235	2,307,188
Total Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale investments, amortized cost	9,038,158	9,929,137
Available-for-sale investments, gross unrealized holding gains	400,515	521,592
Available-for-sale investments, gross unrealized holding losses	(40,323)	(23,770)
Available-for-sale investments, unrealized other-than-temporary impairment losses	(3,882)	(4,077)
Available-for-sale investments, estimated fair value	9,394,468	10,422,882
Insurance, Banks And Other Financial Institutions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale investments, amortized cost	651,002	523,739
Available-for-sale investments, gross unrealized holding gains	690,271	789,717
Available-for-sale investments, gross unrealized holding losses	(6,551)	(1,531)
Available-for-sale investments, unrealized other-than-temporary impairment losses	0	0
Available-for-sale investments, estimated fair value	1,334,722	1,311,925
Industrial, Consumer And All Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale investments, amortized cost	1,557,832	1,427,919
Available-for-sale investments, gross unrealized holding gains	1,227,052	1,403,566
Available-for-sale investments, gross unrealized holding losses	(45,131)	(5,834)
Available-for-sale investments, unrealized other-than-temporary impairment losses	0	0
Available-for-sale investments, estimated fair value	2,739,753	2,825,651
Total Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale investments, amortized cost	2,208,834	1,951,658
Available-for-sale investments, gross unrealized holding gains	1,917,323	2,193,283
Available-for-sale investments, gross unrealized holding losses	(51,682)	(7,365)
Available-for-sale investments, unrealized other-than-temporary impairment losses	0	0
Available-for-sale investments, estimated fair value	4,074,475	4,137,576
Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale investments, amortized cost	1,642,103	1,594,819
Available-for-sale investments, gross unrealized holding gains	167	36
Available-for-sale investments, gross unrealized holding losses	(9)	(6)
Available-for-sale investments, unrealized other-than-temporary impairment losses	0	0
Available-for-sale investments, estimated fair value	$ 1,642,261	$ 1,594,849

Investments (Summary Of Gross U

Investments (Summary Of Gross Unrealized Investment Losses By Length Of Time That Securities Have Continuously Been In An Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	$ 2,030,690	$ 697,102
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(76,054)	(13,139)
Available-for-sale securities, estimated fair value, 12 months or longer	813,147	1,333,930
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(19,842)	(22,079)
Available-for-sale securities, estimated fair value	2,843,837	2,031,032
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(95,896)	(35,218)
U.S. Treasury Securities And Obligations Of U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	427,003	108,250
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(3,648)	(62)
Available-for-sale securities, estimated fair value, 12 months or longer	92,552	163,359
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(1,133)	(2,101)
Available-for-sale securities, estimated fair value	519,555	271,609
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(4,781)	(2,163)
Obligations Of States, Municipalities And Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	169,362	58,583
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(4,864)	(542)
Available-for-sale securities, estimated fair value, 12 months or longer	70,101	92,441
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(3,361)	(2,817)
Available-for-sale securities, estimated fair value	239,463	151,024
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(8,225)	(3,359)
Foreign Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	51,328	18,856
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(249)	(386)
Available-for-sale securities, estimated fair value, 12 months or longer	40,345	56,217
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(1,432)	(655)
Available-for-sale securities, estimated fair value	91,673	75,073
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(1,681)	(1,041)
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	289,058	45,931
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(3,600)	(210)
Available-for-sale securities, estimated fair value, 12 months or longer	95,843	147,558
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(1,399)	(2,392)
Available-for-sale securities, estimated fair value	384,901	193,489
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(4,999)	(2,602)
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	78,814	9,613
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(2,858)	(2,285)
Available-for-sale securities, estimated fair value, 12 months or longer	137,100	207,374
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(3,422)	(3,455)
Available-for-sale securities, estimated fair value	215,914	216,987
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(6,280)	(5,740)
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	6,228	30,448
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(54)	(20)
Available-for-sale securities, estimated fair value, 12 months or longer	24,315	45,160
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(352)	(662)
Available-for-sale securities, estimated fair value	30,543	75,608
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(406)	(682)
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	470,694	141,176
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(9,509)	(2,263)
Available-for-sale securities, estimated fair value, 12 months or longer	343,737	621,821
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(8,324)	(9,997)
Available-for-sale securities, estimated fair value	814,431	762,997
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(17,833)	(12,260)
Total Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	1,492,487	412,857
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(24,782)	(5,768)
Available-for-sale securities, estimated fair value, 12 months or longer	803,993	1,333,930
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(19,423)	(22,079)
Available-for-sale securities, estimated fair value	2,296,480	1,746,787
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(44,205)	(27,847)
Insurance, Banks And Other Financial Institutions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	63,873	16,219
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(6,384)	(1,531)
Available-for-sale securities, estimated fair value, 12 months or longer	6,247	0
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(167)	0
Available-for-sale securities, estimated fair value	70,120	16,219
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(6,551)	(1,531)
Industrial, Consumer And All Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	344,857	86,062
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(44,879)	(5,834)
Available-for-sale securities, estimated fair value, 12 months or longer	2,907	0
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(252)	0
Available-for-sale securities, estimated fair value	347,764	86,062
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(45,131)	(5,834)
Total Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	408,730	102,281
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(51,263)	(7,365)
Available-for-sale securities, estimated fair value, 12 months or longer	9,154	0
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(419)	0
Available-for-sale securities, estimated fair value	417,884	102,281
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(51,682)	(7,365)
Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	129,473	181,964
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(9)	(6)
Available-for-sale securities, estimated fair value, 12 months or longer	0	0
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	0	0
Available-for-sale securities, estimated fair value	129,473	181,964
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	$ (9)	$ (6)

Investments (Schedule Of Amorti

Investments (Schedule Of Amortized Cost And Estimated Fair Value Of Fixed Maturities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Due in one year or less, amortized cost	$ 482,284
Due after one year through five years, amortized cost	1,820,680
Due after five years through ten years, amortized cost	1,576,656
Due after ten years, amortized cost	3,626,442
Amortized cost, sub-total	7,506,062
Fixed maturities, amortized cost	9,038,158	$ 9,929,137
Due in one year or less, estimated fair value	485,605
Due after one year through five years, estimated fair value	1,857,267
Due after five years through ten years, estimated fair value	1,663,076
Due after ten years, estimated fair value	3,838,664
Estimated fair value, sub-total	7,844,612
Fixed maturities, estimated fair value	9,394,468	$ 10,422,882
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	657,670
Estimated fair value	659,538
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	837,964
Estimated fair value	854,247
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	36,462
Estimated fair value	$ 36,071

Investments (Components Of Net

Investments (Components Of Net Investment Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Municipal bonds (tax-exempt)	$ 93,580	$ 98,262	$ 82,308
Short-term investments, including overnight deposits	5,223	5,959	3,573
Dividends on equity securities	74,705	65,031	48,641
Change in fair value of credit default swap	0	2,230	10,460
Income (loss) from equity method investments	(262)	4,766	21,898
Other	651	108	355
Total investment income	370,210	378,490	329,653
Investment expenses	(16,997)	(15,260)	(12,280)
Net investment income	353,213	363,230	317,373
Taxable Municipal Bonds [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Taxable bonds	57,550	49,345	28,041
Other Taxable Bonds [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Taxable bonds	$ 138,763	$ 152,789	$ 134,377

Investments (Summary Of Net Rea

Investments (Summary Of Net Realized Investment Gains And The Change In Net Unrealized Gains On Investments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Gain (Loss) on Investments [Line Items]
Realized gains	$ 168,163	$ 74,978	$ 93,304
Realized losses	(61,683)	(28,978)	(30,152)
Other-than-temporary impairment losses recognized in net income	(44,481)	(4,784)	(4,706)
Net realized investment gains	106,480	46,000	63,152
Change in net unrealized gains on investments	(457,584)	981,035	261,995
Sales Of Fixed Maturities [Member]
Gain (Loss) on Investments [Line Items]
Realized gains	3,073	8,417	13,772
Realized losses	(4,598)	(18,136)	(25,168)
Sales Of Equity Securities [Member]
Gain (Loss) on Investments [Line Items]
Realized gains	156,987	51,356	73,592
Realized losses	(1,232)	(802)	(278)
Other [Member]
Gain (Loss) on Investments [Line Items]
Realized gains	8,103	15,205	5,940
Realized losses	(11,372)	(5,256)	0
Fixed Maturities [Member]
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairment losses recognized in net income	0	(304)	(1,882)
Change in net unrealized gains on investments	(137,435)	480,350	(403,610)
Equity Securities [Member]
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairment losses recognized in net income	(44,481)	(4,480)	(2,824)
Change in net unrealized gains on investments	(320,277)	500,673	665,599
Short-Term Investments [Member]
Gain (Loss) on Investments [Line Items]
Change in net unrealized gains on investments	$ 128	$ 12	$ 6

Investments (Summary Of Other-T

Investments (Summary Of Other-Than-Temporary Impairment Losses Recognized In Net Income And In Net Realized Investment Gains By Investment Type) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Other-than-temporary impairment losses recognized in net income	$ (44,481)	$ (4,784)	$ (4,706)
Obligations Of States, Municipalities And Political Subdivisions [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Other-than-temporary impairment losses recognized in net income	0	0	(1,242)
Commercial Mortgage-Backed Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Other-than-temporary impairment losses recognized in net income	0	(61)	0
Residential Mortgage-Backed Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Other-than-temporary impairment losses recognized in net income	0	0	(640)
Asset-Backed Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Other-than-temporary impairment losses recognized in net income	0	(197)	0
Corporate Bonds [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Other-than-temporary impairment losses recognized in net income	0	(46)	0
Fixed Maturities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Other-than-temporary impairment losses recognized in net income	0	(304)	(1,882)
Insurance, Banks And Other Financial Institutions [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Other-than-temporary impairment losses recognized in net income	(9,835)	(341)	0
Industrial, Consumer And All Other [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Other-than-temporary impairment losses recognized in net income	(34,646)	(4,139)	(2,824)
Equity Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Other-than-temporary impairment losses recognized in net income	$ (44,481)	$ (4,480)	$ (2,824)

Investments Investments (Compon

Investments Investments (Components Of Restricted Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Components Of Restricted Assets [Line Items]
Restricted assets	$ 4,783,202	$ 5,596,401
Held In Trust Or On Deposit [Member]
Components Of Restricted Assets [Line Items]
Restricted assets	4,037,458	4,961,061
Cash And Cash Equivalents And Securities Pledged As Collateral [Member]
Components Of Restricted Assets [Line Items]
Restricted assets	$ 745,744	$ 635,340

Investments (Schedule Of Restri

Investments (Schedule Of Restricted Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Investments, available-for-sale	$ 4,343,070	$ 5,040,413
Restricted cash and cash equivalents	440,132	522,225
Other assets	0	33,763
Total	$ 4,783,202	$ 5,596,401

Receivables (Components Of Rece

Receivables (Components Of Receivables) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Receivables [Abstract]
Amounts receivable from agents, brokers and insureds	$ 1,009,115	$ 1,031,519
Trade accounts receivable	93,953	97,225
Employee stock loans receivable (see note 12(c))	16,900	15,044
Other	6,165	8,601
Receivables, gross	1,126,133	1,152,389
Allowance for doubtful receivables	(12,430)	(17,172)
Receivables	$ 1,113,703	$ 1,135,217

Deferred Policy Acquisition C73

Deferred Policy Acquisition Costs (Amounts Of Policy Acquisition Costs Acquired, Deferred And Amortized) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of year	$ 353,410	$ 260,967	$ 157,465
Policy acquisition costs deferred	752,324	754,303	577,620
Amortization of policy acquisition costs	(744,964)	(654,916)	(471,915)
Foreign currency movements	(8,014)	(6,944)	(2,203)
Deferred policy acquisition costs	$ 352,756	$ 353,410	$ 260,967

Deferred Policy Acquisition C74

Deferred Policy Acquisition Costs (Components Of Underwriting, Acquisition And Insurance Expenses) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deferred Policy Acquisition Costs Disclosures [Abstract]
Amortization of policy acquisition costs		$ 744,964	$ 654,916	$ 471,915
Transaction costs and other acquisition-related expenses	[1]	0	0	75,140	[2]
Transaction costs	[1],[2]			15,981
Other acquisition related costs, severance costs	[1],[2]			31,734
Other acquisition related costs, stay bonuses	[1],[2]			14,804
Other acquisition related costs, other compensation costs	[1],[2]			12,621
Other operating expenses		710,116	805,966	765,257
Underwriting, acquisition and insurance expenses		$ 1,455,080	$ 1,460,882	$ 1,312,312
[1]	In connection with the acquisition of Alterra, the Company incurred transaction costs of $16.0 million for the year ended December 31, 2013, which primarily consist of due diligence, legal and investment banking costs. Additionally, the Company incurred severance costs of $31.7 million, stay bonuses of $14.8 million and other compensation costs totaling $12.6 million related to the acceleration of certain long-term incentive compensation awards and restricted stock awards that were granted by Alterra prior to the acquisition.
[2]	In connection with the acquisition of Alterra, the Company incurred transaction costs of $16.0 million for the year ended December 31, 2013, which primarily consist of due diligence, legal and investment banking costs. Additionally, the Company incurred severance costs of $31.7 million, stay bonuses of $14.8 million and other compensation costs totaling $12.6 million related to the acceleration of certain long-term incentive compensation awards and restricted stock awards that were granted by Alterra prior to the acquisition.

Property And Equipment (Compone

Property And Equipment (Components Of Property And Equipment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Abstract]
Land	$ 56,408	$ 56,848
Buildings	77,488	78,786
Leasehold improvements	104,003	98,098
Land improvements	71,585	70,596
Furniture and equipment	291,736	255,566
Other	134,939	116,884
Property and equipment, gross	736,159	676,778
Accumulated depreciation and amortization	(305,324)	(255,388)
Property and equipment	430,835	421,390
Depreciation and amortization expense of property and equipment	$ 64,200	$ 51,200	$ 51,500

Goodwill And Intangible Asset76

Goodwill And Intangible Assets (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill And Intangible Assets [Line Items]
Goodwill impairment	$ (14,880,000)	$ (13,737,000)	$ 0
Carrying value following 2015 impairment charge	1,167,844,000	1,049,115,000	967,717,000
Amortization of intangible assets	68,947,000	57,627,000	$ 55,223,000
Estimated amortization of intangible assets for 2016	69,700,000
Estimated amortization of intangible assets for 2017	67,600,000
Estimated amortization of intangible assets for 2018	65,800,000
Estimated amortization of intangible assets for 2019	56,600,000
Estimated amortization of intangible assets for 2020	51,500,000
Indefinite-lived intangible assets	48,200,000	$ 58,000,000
Intangible assets acquired during period	$ 166,900,000
Definite-lived intangible assets, weighted-average amortization period	14 years
Customer Relationships [Member]
Goodwill And Intangible Assets [Line Items]
Definite-lived intangible assets, weighted-average amortization period	17 years
Investment Management Agreements [Member]
Goodwill And Intangible Assets [Line Items]
Definite-lived intangible assets, weighted-average amortization period	14 years
Diamond Healthcare [Member]
Goodwill And Intangible Assets [Line Items]
Carrying value following 2015 impairment charge	$ 0

Goodwill And Intangible Asset77

Goodwill And Intangible Assets (Components Of Goodwill) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Goodwill [Line Items]
Goodwill, beginning balance		$ 1,049,115,000		$ 967,717,000
Acquisitions (see note 2)		146,659,000		104,528,000
Impairment loss		(14,880,000)		(13,737,000)		$ 0
Foreign currency movements and other adjustments		(13,050,000)		(9,393,000)
Goodwill, ending balance		1,167,844,000		1,049,115,000		967,717,000
U.S. Insurance [Member]
Goodwill [Line Items]
Goodwill, beginning balance		280,579,000		280,579,000
Acquisitions (see note 2)		0		0
Impairment loss		0		0
Foreign currency movements and other adjustments		0		0
Goodwill, ending balance		280,579,000		280,579,000		280,579,000
International Insurance [Member]
Goodwill [Line Items]
Goodwill, beginning balance		408,183,000		372,764,000
Acquisitions (see note 2)		0		42,989,000
Impairment loss		0		0
Foreign currency movements and other adjustments		(10,190,000)		(7,570,000)
Goodwill, ending balance		397,993,000		408,183,000		372,764,000
Reinsurance [Member]
Goodwill [Line Items]
Goodwill, beginning balance		122,745,000		122,745,000
Acquisitions (see note 2)		0		0
Impairment loss		0		0
Foreign currency movements and other adjustments		0		0
Goodwill, ending balance		122,745,000		122,745,000		122,745,000
Other [Member]
Goodwill [Line Items]
Goodwill, beginning balance	[1]	237,608,000	[2]	191,629,000
Acquisitions (see note 2)	[1]	146,659,000		61,539,000
Impairment loss	[1]	(14,880,000)		(13,737,000)
Foreign currency movements and other adjustments	[1]	(2,860,000)		(1,823,000)
Accumulated impairment losses	[2]	28,600,000		13,700,000
Goodwill, ending balance	[1]	$ 366,527,000	[2]	$ 237,608,000	[2]	$ 191,629,000
[1]	Amounts included in Other above are related to the Company's non-insurance operations, which are not included in a reportable segment.
[2]	Goodwill is net of accumulated impairment losses of $28.6 million and $13.7 million, as of December 31, 2015 and 2014, respectively, included in Other.

Goodwill And Intangible Asset78

Goodwill And Intangible Assets (Components Of Intangible Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	$ 992,776	$ 855,809
Intangible assets, accumulated amortization	(200,404)	(153,062)
Customer Relationships [Member]
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	481,547	452,157
Intangible assets, accumulated amortization	(97,892)	(69,483)
Broker Relationships [Member]
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	182,626	175,681
Intangible assets, accumulated amortization	(45,135)	(34,827)
Trade Names [Member]
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	103,681	94,795
Intangible assets, accumulated amortization	(23,821)	(17,673)
Investment Management Agreements [Member]
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	98,000	0
Intangible assets, accumulated amortization	0	0
Technology [Member]
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	54,241	62,288
Intangible assets, accumulated amortization	(22,288)	(22,671)
Insurance Licenses [Member]
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	30,185	39,985
Intangible assets, accumulated amortization	0	0
Lloyd's Syndicate Capacity [Member]
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	12,000	12,000
Intangible assets, accumulated amortization	0	0
Other [Member]
Schedule of Indefinite-Lived And Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	30,496	18,903
Intangible assets, accumulated amortization	$ (11,268)	$ (8,408)

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Line Items]
Income tax payments	$ 132,500,000	$ 89,500,000	$ 35,700,000
Income taxes payable	$ 63,500,000	$ 37,600,000
Income tax benefit related to tax credits for foreign taxes paid	(8.00%)	(1.00%)	0.00%
Tax credit carryforwards	$ 18,158,000	$ 32,525,000
Tax credit, expiration date	Dec. 31, 2025
Net operating loss carryforwards	$ 19,000,000
Estimated gross deferred tax assets including net operating losses realized through reversal of existing temporary differences attributable to gross deferred tax liabilities	684,500,000
Unrecognized tax benefits	15,324,000	$ 17,700,000	$ 18,219,000
Unrecognized tax benefits decrease on effective tax rate	14,700,000
Provision for United States income taxes on earnings of the Company's foreign subsidiaries	0
Undistributed earnings of foreign subsidiaries	$ 650,000,000
Earliest Tax Year [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards, expiration date	Dec. 31, 2028
Latest Tax Year [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards, expiration date	Dec. 31, 2030
Markel Capital Limited [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 39,200,000
Markel Capital Limited [Member] | Earliest Tax Year [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards, expiration date	Dec. 31, 2023
Markel Capital Limited [Member] | Latest Tax Year [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards, expiration date	Dec. 31, 2033

Income Taxes (Components Of Inc

Income Taxes (Components Of Income Before Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Domestic operations	$ 323,954	$ 240,279	$ 325,133
Foreign operations	418,151	200,099	36,610
Income Before Income Taxes	$ 742,105	$ 440,378	$ 361,743

Income Taxes (Components Of I81

Income Taxes (Components Of Income Tax Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Domestic, current	$ 44,406	$ 7,573	$ 50,683
Foreign, current	118,235	24,574	23,165
Total current tax expense	162,641	32,147	73,848
Domestic, deferred	9,415	43,673	23,906
Foreign, deferred	(19,093)	40,870	(19,856)
Total deferred tax expense (benefit)	(9,678)	84,543	4,050
Income tax expense	$ 152,963	$ 116,690	$ 77,898

Income Taxes (Reconciliations O

Income Taxes (Reconciliations Of United States Corporate Income Tax Rate To Effective Tax Rate On Income Before Income Taxes) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
United States corporate tax rate	35.00%	35.00%	35.00%
Tax credits	(8.00%)	(1.00%)	0.00%
Tax-exempt investment income	(5.00%)	(9.00%)	(9.00%)
Foreign operations	(1.00%)	0.00%	(4.00%)
Other	0.00%	1.00%	0.00%
Effective tax rate	21.00%	26.00%	22.00%

Income Taxes (Components Of Dom

Income Taxes (Components Of Domestic And Foreign Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Unpaid losses and loss adjustment expenses	$ 212,012	$ 239,588
Life and annuity benefits	156,950	143,102
Unearned premiums recognized for income tax purposes	102,076	108,960
Investments, including other-than-temporary impairments	65,641	28,106
Accrued incentive compensation	53,586	37,329
Stock-based compensation	21,948	31,314
Net operating loss carryforwards	18,771	36,359
Tax credit carryforwards	18,158	32,525
Other differences between financial reporting and tax bases	40,497	64,235
Total gross deferred tax assets	689,639	721,518
Less valuation allowance	(5,131)	(4,801)
Total gross deferred tax assets, net of allowance	684,508	716,717
Net unrealized gains on investments	626,776	759,212
Amortization of goodwill and other intangible assets	107,271	106,927
Deferred policy acquisition costs	88,036	101,766
Other differences between financial reporting and tax bases	38,613	59,359
Total gross deferred tax liabilities	860,696	1,027,264
Net deferred tax liability	$ 176,188	$ 310,547

Income Taxes (Reconciliation Of

Income Taxes (Reconciliation Of Beginning And Ending Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Unrecognized tax benefits, beginning of year	$ 17,700	$ 18,219
Increases for tax positions taken in prior years	0	3
Decreases for tax positions taken in prior years	(146)	0
Lapse of statute of limitations	(606)	(522)
Settlement with taxing authorities	(1,624)	0
Unrecognized tax benefits, end of year	$ 15,324	$ 17,700

Unpaid Losses And Loss Adjust85

Unpaid Losses And Loss Adjustment Expenses (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Oct. 30, 2015	Mar. 09, 2015	Dec. 31, 2012
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Increase (decrease) in reserves for losses and loss adjustment expenses due to movement in foreign currency rates of exchange	$ (134,800)	$ (127,700)	$ 700
Favorable development on prior years' loss reserves	(627,800)	(435,545)	(411,129)
Prior years' development on asbestos and environmental exposures	25,415	32,840	30,128
Loss on retrospective reinsurance transaction recognized in losses and loss adjustment expenses	7,100
Increase in asbestos and environmental prior years’ loss reserves following the retroactive reinsurance transaction	15,000
Liability for asbestos and environmental claims net incurred loss annual claim review	0	27,200	28,400
Net reserves for losses and loss adjustment expenses of acquired insurance companies	0	21,193	3,584,642
Asbestos-related reserves, gross loss incurred	386,625	390,442	372,978
Asbestos-related reserves, net loss incurred	132,869	287,723	272,194			$ 260,791
Asbestos and environmental net reserves for reported claims	129,000
Asbestos and environmental reserves incurred but not reported, net	3,900
Liability for asbestos and environmental claims, net claims paid since inception	595,900
Reinsurance recoverable on retroactive reinsurance transactions attributable to A&E exposures	159,641	0	0
Liability for asbestos and environmental claims, net litigation paid since inception	90,600
Reinsurance recoverable on retroactive reinsurance transactions	177,649	0	0
Impact Of Retroactive Reinsurance Transactions On Reserve Volatility [Member]
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Favorable development on prior years' loss reserves	(82,700)
Asbestos [Member]
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Asbestos-related reserves, gross loss incurred	291,500
Asbestos-related reserves, net loss incurred	93,100
Asbestos And Environmental [Member]
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Total payment under retrospective reinsurance transaction on ceded asbestos and environmental policies	159,600
General Liability Workers Compensation Inland Marine And Brokerage Property Within U.S. Insurance Segment And General Liability Professional Liability And Marine And Energy Within International Segment [Member]
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Favorable development on prior years' loss reserves	$ (375,800)
Long-Tail Casualty And Professional Liability Witihin U.S. Insurance Segment And Professional Liability And Marine And Energy International Segment [Member]
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Favorable development on prior years' loss reserves		$ (250,400)	$ (255,200)
March 9, 2015 [Member]
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Total payment under retrospective reinsurance transaction on ceded asbestos and environmental policies					$ 89,000
Cash paid at closing under retrospective reinsurance transaction on ceded asbestos and environmental policies					69,900
Cumulative amount of reserves for losses and loss adjustment expenses on ceded asbestos and environmental policies					94,100
Deferred gain under retrospective reinsurance transaction on ceded asbestos and environmental policies					$ 5,100
Approximate percentage of ceded reserves under retrospective reinsurance transaction to net asbestos and environmental reserves for losses and loss adjustment expenses		30.00%
October 30, 2015 [Member]
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Total payment under retrospective reinsurance transaction on ceded asbestos and environmental policies				$ 86,500
Cumulative amount of reserves for losses and loss adjustment expenses on ceded asbestos and environmental policies				173,400
Approximate percentage of ceded reserves under retrospective reinsurance transaction to net asbestos and environmental reserves for losses and loss adjustment expenses		25.00%
Cumulative reserves for losses and loss adjustment expenses on ceded asbestos and environmental policies, net of retention				76,400
Loss on retrospective reinsurance transaction				$ 10,100

Unpaid Losses And Loss Adjust86

Unpaid Losses And Loss Adjustment Expenses (Reconciliation Of Consolidated Reserves For Losses And Loss Adjustment Expenses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Net reserves for losses and loss adjustment expenses, beginning of year	$ 8,535,483	$ 8,407,642	$ 4,592,652
Foreign currency movements, commutations and other	(134,173)	(137,385)	(780)
Adjusted net reserves for losses and loss adjustment expenses, beginning of year	8,401,310	8,270,257	4,591,872
Incurred losses and loss adjustment expenses, current year	2,566,545	2,638,012	2,227,402
Incurred losses and loss adjustment expenses, prior years	(627,800)	(435,545)	(411,129)
Total incurred losses and loss adjustment expenses	1,938,745	2,202,467	1,816,273
Payments, current year	486,551	502,107	670,928
Payments, prior years	1,423,286	1,436,851	906,302
Total payments	1,909,837	1,938,958	1,577,230
Effect of foreign currency rate changes	(17,281)	(19,476)	(7,915)
Net reserves for losses and loss adjustment expenses of acquired insurance companies	0	21,193	3,584,642
Reinsurance recoverable on retroactive reinsurance transactions	(177,649)	0	0
Net reserves for losses and loss adjustment expenses, end of year	8,235,288	8,535,483	8,407,642
Reinsurance recoverable on unpaid losses	2,016,665	1,868,669	1,854,414
Gross reserves for losses and loss adjustment expenses, end of year	$ 10,251,953	$ 10,404,152	$ 10,262,056

Unpaid Losses And Loss Adjust87

Unpaid Losses And Loss Adjustment Expenses (Reconciliation Of Consolidated A&E Reserves For Losses And Loss Adjustment Expenses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Net reserves for A&E losses and loss adjustment expenses, beginning of year	$ 287,723	$ 272,194	$ 260,791
Commutations and other	0	115	(5,067)
Adjusted net reserves for A&E losses and loss adjustment expenses, beginning of year	287,723	272,309	255,724
Incurred losses and loss adjustment expenses	25,415	32,840	30,128
Payments	(20,628)	(17,426)	(13,658)
Reinsurance recoverable on retroactive reinsurance transactions	(159,641)	0	0
Net reserves for A&E losses and loss adjustment expenses, end of year	132,869	287,723	272,194
Reinsurance recoverable on unpaid losses	253,756	102,719	100,784
Gross reserves for A&E losses and loss adjustment expenses, end of year	$ 386,625	$ 390,442	$ 372,978

Life And Annuity Benefits (Narr

Life And Annuity Benefits (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Apr. 24, 2015
Liability for Future Policy Benefits [Abstract]
Average reserve valuation rate	2.30%
Life and annuity benefits reserve single contract concentration	33.20%
Annuities included in life and annuity benefits subject to discretionary withdrawal	$ 0
Cash payments for life and annuity benefit policies transferred under novated reinsurance contract		$ 29,000
Reserves on novated life and annuity benefit reinsurance contract		32,600
Gain on novated life and annuity benefit reinsurance contract		$ 3,600

Life And Annuity Benefits (Sche

Life And Annuity Benefits (Schedule Of Life And Annuity Benefits) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Liability for Future Policy Benefits [Abstract]
Life	$ 142,068	$ 182,604
Annuities	901,218	1,031,946
Accident and health	79,989	91,268
Total life and annuity benefits	$ 1,123,275	$ 1,305,818

Senior Long-Term Debt And Oth90

Senior Long-Term Debt And Other Debt (Narrative) (Details) - USD ($) $ in Thousands	Aug. 01, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	May. 01, 2013	Sep. 27, 2010	Apr. 16, 2007
Debt Instrument [Line Items]
Senior long-term debt and other debt, estimated fair value		$ 2,403,000	$ 2,493,000
Interest on senior long-term debt and other debt		$ 127,000	125,800	$ 114,500
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, capacity available	$ 300,000
Line of credit facility, potential increased maximum capacity	500,000
Line of credit facility, unused capacity, commitment fee, percent		0.225%
Borrowings outstanding under the facility		$ 0	0
Previous line of credit facility, borrowing capacity	300,000
Senior Credit Facility [Member]
Debt Instrument [Line Items]
Borrowings outstanding under the facility		0	$ 0
Credit facility, letters of credit issued and outstanding		$ 10,600
Secured Letters Of Credit [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, capacity available	$ 200,000
Unsecured Senior Notes [Member] | 7.20% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, face amount							$ 100,000
Debt instrument, interest rate		7.20%	7.20%
Debt instrument, principal amount outstanding					$ 90,600
Debt instrument, estimated fair value					95,800
Unsecured Senior Notes [Member] | 6.25% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, face amount						$ 350,000
Debt instrument, interest rate		6.25%	6.25%
Debt instrument, estimated fair value					$ 416,600
Unsecured Senior Notes [Member] | 7.35% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate		7.35%	7.35%

Senior Long-Term Debt And Oth91

Senior Long-Term Debt And Other Debt (Summary Of Senior Long-Term Debt And Other Debt) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Senior long-term debt and other debt	$ 2,241,427	$ 2,253,594
Unsecured Senior Notes [Member] | 7.20% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes	$ 92,436	$ 94,155
Debt instrument, interest rate	7.20%	7.20%
Debt Instrument, unamortized premium	$ 1,808	$ 3,526
Unsecured Senior Notes [Member] | 7.125% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes	$ 346,940	$ 348,657
Debt instrument, interest rate	7.125%	7.125%
Debt instrument, unamortized discount	$ 1,060	$ 1,343
Unsecured Senior Notes [Member] | 6.25% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes	$ 394,517	$ 403,172
Debt instrument, interest rate	6.25%	6.25%
Debt Instrument, unamortized premium	$ 44,519	$ 53,172
Unsecured Senior Notes [Member] | 5.35% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes	$ 248,881	$ 248,675
Debt instrument, interest rate	5.35%	5.35%
Debt instrument, unamortized discount	$ 1,119	$ 1,325
Unsecured Senior Notes [Member] | 4.90% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes	$ 348,185	$ 347,905
Debt instrument, interest rate	4.90%	4.90%
Debt instrument, unamortized discount	$ 1,815	$ 2,095
Unsecured Senior Notes [Member] | 3.625% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes	$ 248,542	$ 248,341
Debt instrument, interest rate	3.625%	3.625%
Debt instrument, unamortized discount	$ 1,458	$ 1,659
Unsecured Senior Notes [Member] | 7.35% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes	$ 198,028	$ 197,922
Debt instrument, interest rate	7.35%	7.35%
Debt instrument, unamortized discount	$ 1,972	$ 2,078
Unsecured Senior Notes [Member] | 5.0% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes	$ 243,897	$ 243,673
Debt instrument, interest rate	5.00%	5.00%
Debt instrument, unamortized discount	$ 6,103	$ 6,327
Subsidiary And Other Debt [Member]
Debt Instrument [Line Items]
Senior long-term debt and other debt	$ 120,001	$ 121,094
Debt instrument, interest rate, percentage rate range, minimum	1.90%
Debt instrument, interest rate, percentage rate range, maximum	6.50%

Senior Long-Term Debt And Oth92

Senior Long-Term Debt And Other Debt (Summary Of Future Principal Payments Due At Maturity On Senior Long-Term Debt And Other Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
2,016	$ 30,267
2,017	120,268
2,018	4,845
2,019	352,843
2,020	359,128
2021 and thereafter	1,341,276
Total principal payments	2,208,627
Net unamortized premium	32,800
Senior long-term debt and other debt	$ 2,241,427	$ 2,253,594

Shareholders' Equity (Narrative

Shareholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	May. 01, 2013	May. 31, 2013	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized				50,000,000	50,000,000
Common stock, par value				$ 0	$ 0
Common stock, shares issued				13,959,018	13,961,675
Common stock, shares outstanding				13,959,018	13,961,675
Preferred stock, shares authorized				10,000,000	10,000,000
Preferred stock, par value				$ 0	$ 0
Preferred stock, shares issued				0	0
Preferred stock, shares outstanding				0	0
November 2013 Share Repurchase Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Board of Directors approved the repurchase of common stock under a share repurchase program, maximum				$ 300
Cumulative number of common stock shares repurchased				56,455
Cumulative stock repurchased value				$ 37.1
Employee Stock Purchase And Bonus Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Bonus calculation percentage based on the value of stocks acquired by employees				10.00%
Percentage of bonus shares award to loan program participants				5.00%
Shares authorized under Employee Stock Purchase and Bonus Plan				100,000
Shares available for purchase				9,458	20,740
Loans outstanding under Employee Stock Purchase and Bonus Plan				$ 16.9	$ 15
2012 Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance				143,139
2012 Compensation Plan [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of restricted stock units awarded				23,013
Weighted average grant-date fair value, share-based awards				$ 740.80	$ 583.74	$ 517.24
Unrecognized compensation cost related to nonvested share-based awards				$ 16.4
Weighted average remaining service period of share-based awards				1 year 11 months
Fair value of the vested share-based awards				$ 15.8	$ 4.2	$ 2.5
2012 Compensation Plan [Member] | Restricted Stock Units (RSUs) [Member] | Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of restricted stock units awarded				1,324
Restricted stock awards, year awards vest				2,016
2012 Compensation Plan [Member] | Restricted Stock Units (RSUs) [Member] | Performance Based [Member] | Associates And Executive Officers [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock issuable for each vested restricted stock unit				1
Number of restricted stock units awarded				21,122
Restricted stock awards, vesting period				3 years
2012 Compensation Plan [Member] | Restricted Stock Units (RSUs) [Member] | Retention And Hiring [Member] | Associates And Executive Officers [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock issuable for each vested restricted stock unit				1
Number of restricted stock units awarded				567
Restricted stock units, grant date fair value				$ 0.4
Restricted stock awards, vesting period				3 years
Alterra Equity Award Plans [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units, grant date fair value	$ 81.6
Weighted average grant-date fair value, share-based awards	$ 529.59
Weighted average remaining service period of share-based awards	1 year
Fair value of the vested share-based awards				$ 18	18.1	41.3
Number of awards issued in connection with acquisition		154,103
Recognized compensation expense related to vested restricted stock awards as of the acquisition date	$ (61)
Unrecognized compensation on unvested restricted stock and restricted stock units				(20.6)
Recognized compensation expense related to restricted stock awards				0.5	$ 3.9	$ 12.7
Unrecognized compensation cost related to nonvested restricted stock awards				$ 0
Alterra Equity Award Plans [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of awards issued in connection with acquisition		101,875
Weighted average exercise price of options issued	$ 398.96
Weighted average grant-date fair value of options	$ 140.08
Expected annual volatility, assumption used in pricing model	19.04%
Risk-free rate, assumption used in pricing model	0.20%
Expected term, assumption used in pricing model	2 years
Number of options exercised under option plans			65,934	10,787	13,636
Cash proceeds resulting from exercise of stock options			$ 24.3	$ 4.5	$ 5.6
Current tax benefits resulting from exercise of stock options			0.8	1.4	0.8
Intrinsic value of options exercised			$ 9.4	$ 4.1	$ 2.5

Shareholders' Equity (Schedule

Shareholders' Equity (Schedule Of Net Income Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Line Items]
Net income to shareholders	$ 197,892	$ 102,519	$ 91,369	$ 190,992	$ 117,595	$ 75,803	$ 40,068	$ 87,716	$ 98,764	$ 65,599	$ 27,756	$ 88,902	$ 582,772	$ 321,182	$ 281,021
Adjustment of redeemable noncontrolling interests													4,144	(8,186)	1,963
Adjusted net income to shareholders													$ 586,916	$ 312,996	$ 282,984
Basic common shares outstanding													13,978	13,984	12,538
Diluted shares outstanding													14,061	14,057	12,586
Basic net income per share (dollars per share)	$ 14.23	$ 7.43	$ 6.76	$ 13.57	$ 8.10	$ 5.33	$ 2.67	$ 6.28	$ 6.98	$ 4.69	$ 2.24	$ 9.53	$ 41.99	$ 22.38	$ 22.57
Diluted net income per share (dollars per share)	$ 14.14	$ 7.39	$ 6.72	$ 13.49	$ 8.05	$ 5.30	$ 2.66	$ 6.25	$ 6.95	$ 4.67	$ 2.24	$ 9.50	$ 41.74	$ 22.27	$ 22.48
Stock Options [Member]
Earnings Per Share [Line Items]
Dilutive potential common shares													9	11	12
Restricted Stock Units (RSUs) [Member]
Earnings Per Share [Line Items]
Dilutive potential common shares													74	62	36

Shareholders' Equity (Summary O

Shareholders' Equity (Summary Of Nonvested Share-Based Awards) (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares	May. 01, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
2012 Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of awards, nonvested awards, beginning balance		118,132
Number of awards, granted		23,013
Number of awards, vested		(37,262)
Number of awards, nonvested awards, ending balance		103,883	118,132
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted average grant-date fair value, nonvested awards, beginning balance		$ 479.11
Weighted average grant-date fair value, granted		740.80	$ 583.74	$ 517.24
Weighted average grant-date fair value, vested		424.51
Weighted average grant-date fair value, nonvested awards, ending balance		$ 556.66	$ 479.11
Alterra Equity Award Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of awards, nonvested awards, beginning balance		33,915
Number of awards, vested		(33,915)
Number of awards, nonvested awards, ending balance		0	33,915
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted average grant-date fair value, nonvested awards, beginning balance		$ 529.59
Weighted average grant-date fair value, granted	$ 529.59
Weighted average grant-date fair value, vested		529.59
Weighted average grant-date fair value, nonvested awards, ending balance		$ 0	$ 529.59

Shareholders' Equity (Summary96

Shareholders' Equity (Summary Of Options) (Details) - Alterra Equity Award Plans [Member] - Stock Options [Member] - USD ($) $ / shares in Units, $ in Millions	8 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding and exercisable, beginning balance, number of shares		22,305
Exercised, number of shares	65,934	10,787	13,636
Outstanding and exercisable, ending balance, number of shares		11,518	22,305
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding and exercisable, January 1, 2015, weighted average exercise price (dollars per share)		$ 411.98
Exercised, weighted average exercise price (dollars per share)		418.41
Outstanding and exercisable, December 31, 2015, weighted average exercise price (dollars per share)		$ 405.97	$ 411.98
Outstanding and exercisable, December 31, 2015, weighted average remaining contractual term		11 months
Outstanding and exercisable, December 31, 2015, intrinsic value		$ 5.5

Other Comprehensive Income (L97

Other Comprehensive Income (Loss) (Change In Accumulated Other Comprehensive Income By Component, Net Of Taxes And Noncontrolling Interests) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income, beginning balance	$ 1,704,557	$ 1,089,805	$ 911,337
Other comprehensive income (loss) before reclassifications	(271,697)	639,147	217,750
Amounts reclassified from accumulated other comprehensive income	(78,352)	(24,395)	(39,282)
Total other comprehensive income (loss)	(350,049)	614,752	178,468
Accumulated other comprehensive income, ending balance	1,354,508	1,704,557	1,089,805
Unrealized Holding Gains On Available-For-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income, beginning balance	1,793,254	1,131,507	946,933
Other comprehensive income (loss) before reclassifications	(240,010)	687,908	225,404
Amounts reclassified from accumulated other comprehensive income	(80,482)	(26,161)	(40,830)
Total other comprehensive income (loss)	(320,492)	661,747	184,574
Accumulated other comprehensive income, ending balance	1,472,762	1,793,254	1,131,507
Foreign Currency [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income, beginning balance	(43,491)	(11,246)	(1,075)
Other comprehensive income (loss) before reclassifications	(29,205)	(32,245)	(10,171)
Amounts reclassified from accumulated other comprehensive income	0	0	0
Total other comprehensive income (loss)	(29,205)	(32,245)	(10,171)
Accumulated other comprehensive income, ending balance	(72,696)	(43,491)	(11,246)
Net Actuarial Pension Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income, beginning balance	(45,206)	(30,456)	(34,521)
Other comprehensive income (loss) before reclassifications	(2,482)	(16,516)	2,517
Amounts reclassified from accumulated other comprehensive income	2,130	1,766	1,548
Total other comprehensive income (loss)	(352)	(14,750)	4,065
Accumulated other comprehensive income, ending balance	$ (45,558)	$ (45,206)	$ (30,456)

Other Comprehensive Income (L98

Other Comprehensive Income (Loss) (Schedule Of Tax Expense (Benefit) Of Other Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Comprehensive Income (Loss), Tax [Abstract]
Net holding gains (losses) arising during the period	$ (107,860)	$ 328,564	$ 93,837
Change in unrealized other-than-temporary impairment losses on fixed maturities arising during the period	35	614	(34)
Reclassification adjustments for net gains included in net income	(29,267)	(9,890)	(16,382)
Change in net unrealized gains on investments	(137,092)	319,288	77,421
Change in foreign currency translation adjustments	408	1,918	(1,619)
Change in net actuarial pension loss	(88)	(3,687)	1,015
Total	$ (136,772)	$ 317,519	$ 76,817

Other Comprehensive Income (L99

Other Comprehensive Income (Loss) (Amounts Reclassified From Accumulated Other Comprehensive Income Into Income, By Component) (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reclassification Out Of Accumulated Other Comprehensive Income [Line Items]
Other-than-temporary impairment losses recognized in net income													$ (44,481)	$ (4,784)	$ (4,706)
Net realized investment gains, excluding other-than-temporary impairment losses													150,961	50,784	67,858
Income Before Income Taxes													742,105	440,378	361,743
Underwriting, acquisition and insurance expenses													(1,455,080)	(1,460,882)	(1,312,312)
Income Taxes													(152,963)	(116,690)	(77,898)
Net Income	$ 198,273	$ 104,410	$ 92,453	$ 194,006	$ 118,222	$ 76,824	$ 41,141	$ 87,501	$ 98,939	$ 66,967	$ 28,676	$ 89,263	589,142	323,688	283,845
Reclassification Out Of Accumulated Other Comprehensive Income [Member] | Unrealized Holding Gains On Available-For-Sale Securities [Member]
Reclassification Out Of Accumulated Other Comprehensive Income [Line Items]
Other-than-temporary impairment losses recognized in net income													(44,481)	(4,784)	(4,706)
Net realized investment gains, excluding other-than-temporary impairment losses													154,230	40,835	61,918
Income Before Income Taxes													109,749	36,051	57,212
Income Taxes													(29,267)	(9,890)	(16,382)
Net Income													80,482	26,161	40,830
Reclassification Out Of Accumulated Other Comprehensive Income [Member] | Net Actuarial Pension Loss [Member]
Reclassification Out Of Accumulated Other Comprehensive Income [Line Items]
Underwriting, acquisition and insurance expenses													(2,662)	(2,084)	(1,934)
Income Taxes													532	318	386
Net Income													$ (2,130)	$ (1,766)	$ (1,548)

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, level 1 to level 2 transfers, amount	$ 0	$ 0
Fair value, level 2 to level 1 transfers, amount	0	0
Assets measured at fair value on a non-recurring basis	0	0
Liabilities measured at fair value on a non-recurring basis	$ 0	$ 0
Short-Term Investments [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment maturity period	1 year

Fair Value Measurements (Balanc

Fair Value Measurements (Balances Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	$ 9,394,468	$ 10,422,882
Equity securities	4,074,475	4,137,576
Short-term investments	1,642,261	1,594,849
Total investments available-for-sale	15,111,204	16,155,307
Fixed Maturities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	9,394,468	10,422,882
U.S. Treasury Securities And Obligations Of U.S. Government Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	700,707	673,262
Obligations Of States, Municipalities And Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	4,013,213	4,317,547
Foreign Governments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	1,416,457	1,611,921
Commercial Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	659,538	430,627
Residential Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	854,247	982,847
Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	36,071	99,490
Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	1,714,235	2,307,188
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	4,074,475	4,137,576
Insurance, Banks And Other Financial Institutions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	1,334,722	1,311,925
Industrial, Consumer And All Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments available-for-sale	2,739,753	2,825,651
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	9,394,468	10,422,882
Equity securities	4,074,475	4,137,576
Short-term investments	1,642,261	1,594,849
Total investments available-for-sale	15,111,204	16,155,307
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	0	0
Equity securities	4,074,475	4,137,576
Short-term investments	1,529,924	1,469,975
Total investments available-for-sale	5,604,399	5,607,551
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	9,394,468	10,422,882
Equity securities	0	0
Short-term investments	112,337	124,874
Total investments available-for-sale	9,506,805	10,547,756
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	0	0
Equity securities	0	0
Short-term investments	0	0
Total investments available-for-sale	0	0
Fair Value, Measurements, Recurring [Member] | U.S. Treasury Securities And Obligations Of U.S. Government Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	700,707	673,262
Fair Value, Measurements, Recurring [Member] | U.S. Treasury Securities And Obligations Of U.S. Government Agencies [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	0	0
Fair Value, Measurements, Recurring [Member] | U.S. Treasury Securities And Obligations Of U.S. Government Agencies [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	700,707	673,262
Fair Value, Measurements, Recurring [Member] | U.S. Treasury Securities And Obligations Of U.S. Government Agencies [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	0	0
Fair Value, Measurements, Recurring [Member] | Obligations Of States, Municipalities And Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	4,013,213	4,317,547
Fair Value, Measurements, Recurring [Member] | Obligations Of States, Municipalities And Political Subdivisions [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	0	0
Fair Value, Measurements, Recurring [Member] | Obligations Of States, Municipalities And Political Subdivisions [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	4,013,213	4,317,547
Fair Value, Measurements, Recurring [Member] | Obligations Of States, Municipalities And Political Subdivisions [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	0	0
Fair Value, Measurements, Recurring [Member] | Foreign Governments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	1,416,457	1,611,921
Fair Value, Measurements, Recurring [Member] | Foreign Governments [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	0	0
Fair Value, Measurements, Recurring [Member] | Foreign Governments [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	1,416,457	1,611,921
Fair Value, Measurements, Recurring [Member] | Foreign Governments [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	0	0
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	659,538	430,627
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	0	0
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	659,538	430,627
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	0	0
Fair Value, Measurements, Recurring [Member] | Residential Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	854,247	982,847
Fair Value, Measurements, Recurring [Member] | Residential Mortgage-Backed Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	0	0
Fair Value, Measurements, Recurring [Member] | Residential Mortgage-Backed Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	854,247	982,847
Fair Value, Measurements, Recurring [Member] | Residential Mortgage-Backed Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	0	0
Fair Value, Measurements, Recurring [Member] | Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	36,071	99,490
Fair Value, Measurements, Recurring [Member] | Asset-Backed Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	0	0
Fair Value, Measurements, Recurring [Member] | Asset-Backed Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	36,071	99,490
Fair Value, Measurements, Recurring [Member] | Asset-Backed Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	0	0
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	1,714,235	2,307,188
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	0	0
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	1,714,235	2,307,188
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, estimated fair value	0	0
Fair Value, Measurements, Recurring [Member] | Insurance, Banks And Other Financial Institutions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	1,334,722	1,311,925
Fair Value, Measurements, Recurring [Member] | Insurance, Banks And Other Financial Institutions [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	1,334,722	1,311,925
Fair Value, Measurements, Recurring [Member] | Insurance, Banks And Other Financial Institutions [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0	0
Fair Value, Measurements, Recurring [Member] | Insurance, Banks And Other Financial Institutions [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0	0
Fair Value, Measurements, Recurring [Member] | Industrial, Consumer And All Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	2,739,753	2,825,651
Fair Value, Measurements, Recurring [Member] | Industrial, Consumer And All Other [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	2,739,753	2,825,651
Fair Value, Measurements, Recurring [Member] | Industrial, Consumer And All Other [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0	0
Fair Value, Measurements, Recurring [Member] | Industrial, Consumer And All Other [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	$ 0	$ 0

Reinsurance (Narrative) (Detail

Reinsurance (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)reinsurer	Dec. 31, 2014USD ($)reinsurer	Dec. 31, 2013USD ($)
Reinsurance Disclosures [Line Items]
Number of largest company reinsurers | reinsurer	10	10
Reinsurance recoverables | $	$ 330.7	$ 423.1	$ 269.4
Percentage of ceded earned premiums to gross earned premiums	18.00%	19.00%	18.00%
Percentage of assumed earned premiums to net earned premiums	31.00%	34.00%	31.00%
Ten Largest Reinsurers [Member]
Reinsurance Disclosures [Line Items]
Recoverable balances as a percentage of the total balance	68.00%	63.00%
Fairfax Financial Group [Member]
Reinsurance Disclosures [Line Items]
Recoverable balances as a percentage of the total balance	17.00%

Reinsurance (Reinsurance Allowa

Reinsurance (Reinsurance Allowance For Doubtful Accounts) (Details) - Allowance For Reinsurance Recoverable [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Valuation and Qualifying Accounts Disclosure [Line Items]
Reinsurance allowance, beginning of year	$ 59,813	$ 76,210	$ 71,148
Additions	5,897	10,316	13,621
Deductions	(6,360)	(26,713)	(8,559)
Reinsurance allowance, end of year	$ 59,350	$ 59,813	$ 76,210

Reinsurance (Effect Of Reinsura

Reinsurance (Effect Of Reinsurance On Premiums Written And Earned) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reinsurance Disclosures [Abstract]
Direct premiums written	$ 3,474,510	$ 3,478,273	$ 3,143,957
Direct premiums earned	3,480,297	3,443,912	2,947,812
Assumed premiums written	1,158,402	1,327,240	776,269
Assumed premiums earned	1,194,772	1,298,371	1,016,853
Ceded premiums written	(813,619)	(888,498)	(683,543)
Ceded premiums earned	(851,537)	(901,371)	(733,049)
Net premiums written	3,819,293	3,917,015	3,236,683
Net premiums earned	$ 3,823,532	$ 3,840,912	$ 3,231,616

Commitments And Contingencie105

Commitments And Contingencies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]
Maximum remaining term of noncancelable operating leases	19 years
Rental expense	$ 44.3	$ 42.7	$ 35.3

Commitments And Contingencie106

Commitments And Contingencies (Minimum Annual Rental Commitments) (Details) $ in Thousands	Dec. 31, 2015USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,016	$ 29,664
2,017	34,083
2,018	30,708
2,019	27,947
2,020	21,597
2021 and thereafter	130,844
Total	$ 274,843

Statutory Financial Informat107

Statutory Financial Information (Narrative) (Details) $ in Millions	Dec. 31, 2015USD ($)
Statutory Accounting Practices [Line Items]
Amount of cash and investments held as funds at Lloyd's	$ 827.9
United States [Member]
Statutory Accounting Practices [Line Items]
Amount available for dividend payment	354
Bermuda [Member]
Statutory Accounting Practices [Line Items]
Amount available for dividend payment	$ 491.5

Statutory Financial Informat108

Statutory Financial Information (Actual Statutory Capital And Surplus) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
United States [Member]
Statutory Accounting Practices [Line Items]
Actual statutory capital and surplus	$ 2,569,928	$ 2,619,001
United Kingdom [Member]
Statutory Accounting Practices [Line Items]
Actual statutory capital and surplus	608,342	608,001
Bermuda [Member]
Statutory Accounting Practices [Line Items]
Actual statutory capital and surplus	1,966,021	1,890,218
Other Countries [Member]
Statutory Accounting Practices [Line Items]
Actual statutory capital and surplus	$ 17,305	$ 177,824

Statutory Financial Informat109

Statutory Financial Information (Statutory Net Income (Loss)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
United States [Member]
Statutory Accounting Practices [Line Items]
Statutory net income (loss)	$ 291,783	$ 212,909	$ 235,009
United Kingdom [Member]
Statutory Accounting Practices [Line Items]
Statutory net income (loss)	63,583	73,697	109,983
Bermuda [Member]
Statutory Accounting Practices [Line Items]
Statutory net income (loss)	189,800	110,401	249,772
Other Countries [Member]
Statutory Accounting Practices [Line Items]
Statutory net income (loss)	$ (3,181)	$ 1,367	$ (12,617)

Segment Reporting Disclosure110

Segment Reporting Disclosures (Narrative) (Details) - segment	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue, Major Customer [Line Items]
Number of reportable ongoing underwriting segments	3
Percentage of gross premiums written	100.00%	100.00%	100.00%
Top Three Independent Brokers [Member]
Revenue, Major Customer [Line Items]
Percentage of gross premiums written	27.00%	28.00%	24.00%
Top Three Independent Brokers [Member] | Reinsurance [Member]
Revenue, Major Customer [Line Items]
Percentage of gross premiums written	68.00%	68.00%	68.00%
Top Three Independent Brokers [Member] | International Insurance [Member]
Revenue, Major Customer [Line Items]
Percentage of gross premiums written	42.00%	41.00%	42.00%

Segment Reporting Disclosure111

Segment Reporting Disclosures (Summary Of Gross Written Premiums By Country) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Gross written premiums	$ 4,632,912	$ 4,805,513	$ 3,920,226
Percentage of gross premiums written	100.00%	100.00%	100.00%
United States [Member]
Segment Reporting Information [Line Items]
Gross written premiums	$ 3,519,487	$ 3,523,239	$ 2,934,868
Percentage of gross premiums written	76.00%	73.00%	75.00%
United Kingdom [Member]
Segment Reporting Information [Line Items]
Gross written premiums	$ 414,941	$ 441,669	$ 245,143
Percentage of gross premiums written	9.00%	9.00%	6.00%
Canada [Member]
Segment Reporting Information [Line Items]
Gross written premiums	$ 115,191	$ 125,617	$ 128,420
Percentage of gross premiums written	2.00%	3.00%	3.00%
Other Countries [Member]
Segment Reporting Information [Line Items]
Gross written premiums	$ 583,293	$ 714,988	$ 611,795
Percentage of gross premiums written	13.00%	15.00%	16.00%

Segment Reporting Disclosure112

Segment Reporting Disclosures (Company's Segment Disclosures) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Segment Reporting Information [Line Items]
Percentage of gross premiums written		100.00%		100.00%		100.00%
Gross premium volume		$ 4,632,912		$ 4,805,513		$ 3,920,226
Net written premiums		3,819,293		3,917,015		3,236,683
Earned premiums		3,823,532		3,840,912		3,231,616
Losses and loss adjustment expenses, current accident year		(2,566,545)		(2,638,012)		(2,227,402)
Losses and loss adjustment expenses, prior accident years		627,800		435,545		411,129
Transaction costs and other acquisition-related expenses	[1]	0		0		(75,140)	[2]
Transaction costs	[1],[2]					(15,981)
Other acquisition related costs, severance costs	[1],[2]					(31,734)
Other acquisition related costs, stay bonuses	[1],[2]					(14,804)
Other acquisition related costs, other compensation costs	[1],[2]					(12,621)
Amortization of policy acquisition costs		(744,964)		(654,916)		(471,915)
Other operating expenses		(710,116)		(805,966)		(765,257)
Underwriting profit (loss)		429,707		177,563		103,031
Net investment income		353,213		363,230		317,373
Net realized investment gains		106,480		46,000		63,152
Other revenues (insurance)		12,331		28,632		24,494
Other expenses (insurance)		(40,095)		(62,834)		(50,278)
Segment profit (loss)		861,636		552,591		457,772
Other revenues (non-insurance)		1,074,427		854,893		686,448
Other expenses (non-insurance)		(1,006,710)		(792,037)		(613,250)
Amortization of intangible assets		(68,947)		(57,627)		(55,223)
Interest expense		(118,301)		(117,442)		(114,004)
Income Before Income Taxes		$ 742,105		$ 440,378		$ 361,743
U.S. GAAP combined ratio		89.00%	[3]	95.00%	[4]	97.00%	[5]
U.S. Insurance [Member]
Segment Reporting Information [Line Items]
Gross premium volume		$ 2,504,096		$ 2,493,823		$ 2,252,739
Net written premiums		2,106,490		2,071,466		1,915,770
Earned premiums		2,105,212		2,022,860		1,727,766
Losses and loss adjustment expenses, current accident year		(1,367,159)		(1,340,129)		(1,173,258)
Losses and loss adjustment expenses, prior accident years		298,967		216,557		298,113
Transaction costs and other acquisition-related expenses	[2]					(12,724)
Amortization of policy acquisition costs		(420,289)		(403,233)		(287,795)
Other operating expenses		(378,563)		(396,737)		(409,886)
Underwriting profit (loss)		238,168		99,318		142,216
Net investment income		0		0		0
Net realized investment gains		0		0		0
Other revenues (insurance)		3,331		2,478		13,648
Other expenses (insurance)		(3,902)		(5,149)		(17,087)
Segment profit (loss)		$ 237,597		$ 96,647		$ 138,777
U.S. GAAP combined ratio		89.00%	[3]	95.00%	[4]	92.00%	[5]
International Insurance [Member]
Segment Reporting Information [Line Items]
Gross premium volume		$ 1,164,866		$ 1,200,403		$ 1,101,099
Net written premiums		888,214		889,336		840,050
Earned premiums		879,426		909,679		833,984
Losses and loss adjustment expenses, current accident year		(638,144)		(660,409)		(588,759)
Losses and loss adjustment expenses, prior accident years		248,834		166,615		130,660
Transaction costs and other acquisition-related expenses	[2]					(13,366)
Amortization of policy acquisition costs		(142,657)		(141,394)		(138,626)
Other operating expenses		(221,758)		(207,175)		(171,666)
Underwriting profit (loss)		125,701		67,316		52,227
Net investment income		0		0		0
Net realized investment gains		0		0		0
Other revenues (insurance)		7,790		21,827		4,284
Other expenses (insurance)		(5,717)		(18,706)		(5,065)
Segment profit (loss)		$ 127,774		$ 70,437		$ 51,446
U.S. GAAP combined ratio		86.00%	[3]	93.00%	[4]	94.00%	[5]
Reinsurance [Member]
Segment Reporting Information [Line Items]
Gross premium volume		$ 965,374		$ 1,112,728		$ 566,348
Net written premiums		824,324		956,584		480,822
Earned premiums		838,543		908,385		669,826
Losses and loss adjustment expenses, current accident year		(561,242)		(637,474)		(465,385)
Losses and loss adjustment expenses, prior accident years		97,860		79,951		12,938
Transaction costs and other acquisition-related expenses	[2]					(49,050)
Amortization of policy acquisition costs		(182,018)		(110,289)		(45,494)
Other operating expenses		(106,863)		(201,673)		(183,817)
Underwriting profit (loss)		86,280		38,900		(60,982)
Net investment income		0		0		0
Net realized investment gains		0		0		0
Other revenues (insurance)		593		2,696		5,432
Other expenses (insurance)		(1,419)		(1,847)		0
Segment profit (loss)		$ 85,454		$ 39,749		$ (55,550)
U.S. GAAP combined ratio		90.00%	[3]	96.00%	[4]	109.00%	[5]
Other Insurance (Discontinued Lines) [Member]
Segment Reporting Information [Line Items]
Gross premium volume		$ (1,424)		$ (1,441)		$ 40
Net written premiums		265		(371)		41
Earned premiums		351		(12)		40
Losses and loss adjustment expenses, current accident year		0		0		0
Losses and loss adjustment expenses, prior accident years		(17,861)		(27,578)		(30,582)
Transaction costs and other acquisition-related expenses	[2]					0
Amortization of policy acquisition costs		0		0		0
Other operating expenses		(2,932)		(381)		112
Underwriting profit (loss)		(20,442)		(27,971)		(30,430)
Net investment income		0		0		0
Net realized investment gains		0		0		0
Other revenues (insurance)		617		1,631		1,130
Other expenses (insurance)		(29,057)		(37,132)		(28,126)
Segment profit (loss)		$ (48,882)		$ (63,472)		$ (57,426)
U.S. GAAP combined ratio - not meaniningful		NM	[3],[6]	NM	[4],[7]	NM	[5],[8]
Investing [Member]
Segment Reporting Information [Line Items]
Gross premium volume		$ 0		$ 0		$ 0
Net written premiums		0		0		0
Earned premiums		0		0		0
Losses and loss adjustment expenses, current accident year		0		0		0
Losses and loss adjustment expenses, prior accident years		0		0		0
Transaction costs and other acquisition-related expenses	[2]					0
Amortization of policy acquisition costs		0		0		0
Other operating expenses		0		0		0
Underwriting profit (loss)		0		0		0
Net investment income		353,213		363,230		317,373
Net realized investment gains		106,480		46,000		63,152
Other revenues (insurance)		0		0		0
Other expenses (insurance)		0		0		0
Segment profit (loss)		$ 459,693		$ 409,230		$ 380,525
Top Three Independent Brokers [Member]
Segment Reporting Information [Line Items]
Percentage of gross premiums written		27.00%		28.00%		24.00%
Top Three Independent Brokers [Member] | International Insurance [Member]
Segment Reporting Information [Line Items]
Percentage of gross premiums written		42.00%		41.00%		42.00%
Top Three Independent Brokers [Member] | Reinsurance [Member]
Segment Reporting Information [Line Items]
Percentage of gross premiums written		68.00%		68.00%		68.00%
[1]	In connection with the acquisition of Alterra, the Company incurred transaction costs of $16.0 million for the year ended December 31, 2013, which primarily consist of due diligence, legal and investment banking costs. Additionally, the Company incurred severance costs of $31.7 million, stay bonuses of $14.8 million and other compensation costs totaling $12.6 million related to the acceleration of certain long-term incentive compensation awards and restricted stock awards that were granted by Alterra prior to the acquisition.
[2]	In connection with the acquisition of Alterra, the Company incurred transaction costs of $16.0 million for the year ended December 31, 2013, which primarily consist of due diligence, legal and investment banking costs. Additionally, the Company incurred severance costs of $31.7 million, stay bonuses of $14.8 million and other compensation costs totaling $12.6 million related to the acceleration of certain long-term incentive compensation awards and restricted stock awards that were granted by Alterra prior to the acquisition.
[3]	The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums.
[4]	The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums.
[5]	The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums.
[6]	NM — Ratio is not meaningful
[7]	NM — Ratio is not meaningful.
[8]	NM — Ratio is not meaningful.

Segment Reporting Disclosure113

Segment Reporting Disclosures (Summary Of Deferred Policy Acquisition Costs, Unearned Premiums And Unpaid Losses And Loss Adjustment Expenses) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Deferred policy acquisition costs	$ 352,756	$ 353,410	$ 260,967	$ 157,465
Unearned premiums	2,166,105	2,245,690
Unpaid losses and loss adjustment expenses	10,251,953	10,404,152	$ 10,262,056
U.S. Insurance [Member]
Segment Reporting Information [Line Items]
Deferred policy acquisition costs	162,289	165,333
Unearned premiums	1,105,456	1,110,910
Unpaid losses and loss adjustment expenses	3,720,429	3,577,166
International Insurance [Member]
Segment Reporting Information [Line Items]
Deferred policy acquisition costs	48,913	47,618
Unearned premiums	467,158	491,708
Unpaid losses and loss adjustment expenses	3,140,000	3,353,417
Reinsurance [Member]
Segment Reporting Information [Line Items]
Deferred policy acquisition costs	141,554	140,459
Unearned premiums	593,491	643,072
Unpaid losses and loss adjustment expenses	2,750,258	2,818,792
Other Insurance (Discontinued Lines) [Member]
Segment Reporting Information [Line Items]
Deferred policy acquisition costs	0	0
Unearned premiums	0	0
Unpaid losses and loss adjustment expenses	$ 641,266	$ 654,777

Segment Reporting Disclosure114

Segment Reporting Disclosures (Summary Of Segment Earned Premiums By Product) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Earned premiums	$ 3,823,532	$ 3,840,912	$ 3,231,616
U.S. Insurance [Member]
Segment Reporting Information [Line Items]
Earned premiums	2,105,212	2,022,860	1,727,766
U.S. Insurance [Member] | General Liability [Member]
Segment Reporting Information [Line Items]
Earned premiums	522,358	491,645	431,798
U.S. Insurance [Member] | Professional Liability [Member]
Segment Reporting Information [Line Items]
Earned premiums	324,230	321,005	268,203
U.S. Insurance [Member] | Property [Member]
Segment Reporting Information [Line Items]
Earned premiums	264,232	266,019	190,530
U.S. Insurance [Member] | Personal Lines [Member]
Segment Reporting Information [Line Items]
Earned premiums	325,811	299,442	185,935
U.S. Insurance [Member] | Programs [Member]
Segment Reporting Information [Line Items]
Earned premiums	277,829	244,216	205,004
U.S. Insurance [Member] | Workers' Compensation [Member]
Segment Reporting Information [Line Items]
Earned premiums	281,954	263,164	250,790
U.S. Insurance [Member] | Other Products [Member]
Segment Reporting Information [Line Items]
Earned premiums	108,798	137,369	195,506
International Insurance [Member]
Segment Reporting Information [Line Items]
Earned premiums	879,426	909,679	833,984
International Insurance [Member] | General Liability [Member]
Segment Reporting Information [Line Items]
Earned premiums	124,198	146,178	128,171
International Insurance [Member] | Professional Liability [Member]
Segment Reporting Information [Line Items]
Earned premiums	268,637	285,300	252,816
International Insurance [Member] | Property [Member]
Segment Reporting Information [Line Items]
Earned premiums	85,152	76,691	91,497
International Insurance [Member] | Marine And Energy [Member]
Segment Reporting Information [Line Items]
Earned premiums	262,307	287,263	287,745
International Insurance [Member] | Other Products [Member]
Segment Reporting Information [Line Items]
Earned premiums	139,132	114,247	73,755
Reinsurance [Member]
Segment Reporting Information [Line Items]
Earned premiums	838,543	908,385	669,826
Reinsurance [Member] | Property [Member]
Segment Reporting Information [Line Items]
Earned premiums	265,373	270,461	227,394
Reinsurance [Member] | Casualty [Member]
Segment Reporting Information [Line Items]
Earned premiums	315,027	323,390	244,981
Reinsurance [Member] | Auto [Member]
Segment Reporting Information [Line Items]
Earned premiums	102,227	152,645	84,042
Reinsurance [Member] | Other Products [Member]
Segment Reporting Information [Line Items]
Earned premiums	155,916	161,889	113,409
Other Insurance (Discontinued Lines) [Member]
Segment Reporting Information [Line Items]
Earned premiums	$ 351	$ (12)	$ 40

Segment Reporting Disclosure115

Segment Reporting Disclosures (Reconciliation Of Segment Assets To The Company's Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Assets	$ 24,941,271	$ 25,200,357	$ 23,955,511
Non-Insurance Operations [Member]
Segment Reporting Information [Line Items]
Assets	1,497,614	1,246,762	936,448
Segment Assets [Member]
Segment Reporting Information [Line Items]
Assets	23,443,657	23,953,595	23,019,063
Segment Assets [Member] | Investing [Member]
Segment Reporting Information [Line Items]
Assets	18,056,947	18,531,150	17,550,332
Segment Assets [Member] | Underwriting [Member]
Segment Reporting Information [Line Items]
Assets	$ 5,386,710	$ 5,422,445	$ 5,468,731

Other Revenues And Other Exp116

Other Revenues And Other Expenses (Summary Of Other Revenues And Other Expenses By Component) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Revenues and Other Expenses [Line Items]
Other revenues	$ 1,086,758	$ 883,525	$ 710,942
Other expenses	1,046,805	854,871	663,528
Insurance Operations [Member]
Other Revenues and Other Expenses [Line Items]
Other revenues	12,331	28,632	24,494
Other expenses	40,095	62,834	50,278
Non-Insurance Operations [Member]
Other Revenues and Other Expenses [Line Items]
Other revenues	1,074,427	854,893	686,448
Other expenses	1,006,710	792,037	613,250
Managing General Agent Operations [Member] | Insurance Operations [Member]
Other Revenues and Other Expenses [Line Items]
Other revenues	10,202	23,324	17,399
Other expenses	9,619	22,527	20,382
Life And Annuity [Member] | Insurance Operations [Member]
Other Revenues and Other Expenses [Line Items]
Other revenues	617	1,631	1,130
Other expenses	29,057	37,132	28,126
Other Insurance [Member] | Insurance Operations [Member]
Other Revenues and Other Expenses [Line Items]
Other revenues	1,512	3,677	5,965
Other expenses	1,419	3,175	1,770
Manufacturing [Member] | Non-Insurance Operations [Member] | Markel Ventures Operations [Member]
Other Revenues and Other Expenses [Line Items]
Other revenues	755,802	575,353	495,138
Other expenses	677,054	513,668	437,712
Non-Manufacturing [Member] | Non-Insurance Operations [Member] | Markel Ventures Operations [Member]
Other Revenues and Other Expenses [Line Items]
Other revenues	291,714	262,767	191,310
Other expenses	301,004	261,551	175,538
Other Non-Insurance [Member] | Non-Insurance Operations [Member]
Other Revenues and Other Expenses [Line Items]
Other revenues	26,911	16,773	0
Other expenses	$ 28,652	$ 16,818	$ 0

Employee Benefit Plans (Narrati

Employee Benefit Plans (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)fundsfund	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Defined Benefit Plan Disclosure [Line Items]
Expenses relating to defined contribution plans	$ 27,700	$ 27,200	$ 24,300
Consecutive number of years	3 years
Number of years preceding retirement	10 years
Amortization of the net actuarial pension loss included as a component of accumulated other comprehensive income	$ 2,300
Percentage of equity securities invested in UK companies	30.00%
Percentage of equity securities invested in other markets	70.00%
Number of fixed maturity mutual funds | funds	5
Accumulated benefit obligation	$ 164,800	$ 166,900
Expected plan contributions in 2016	0
Expected benefits to be paid in 2016	3,100
Expected benefits to be paid in 2017	3,200
Expected benefits to be paid in 2018	3,300
Expected benefits to be paid in 2019	3,300
Expected benefits to be paid in 2020	3,400
Aggregate benefits expected to be paid from 2021 to 2025	$ 18,300
United Kingdom [Member] | Foreign Governments [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of fixed maturity mutual funds | funds	2
United Kingdom [Member] | Corporate Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of fixed maturity mutual funds | funds	1
Other Foreign Governments [Member] | Foreign Governments [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of fixed maturity mutual funds | funds	1
United Kingdom And Other Foreign Governments [Member] | Corporate Bond Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of fixed maturity mutual funds | fund	1
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percent	47.00%
Actual asset allocation, percent	43.00%	43.00%
Fixed Maturities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percent	53.00%
Actual asset allocation, percent	57.00%	57.00%

Employee Benefit Plans (Schedul

Employee Benefit Plans (Schedule Of Amounts Recognized On The Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of period	$ 185,556	$ 163,010
Interest cost	6,645	7,572	$ 6,533
Plan amendments	0	495
Plan settlements	(2,863)	0
Benefits paid	(3,970)	(4,424)
Actuarial loss (gain)	(6,051)	29,609
Effect of foreign currency rate changes	(9,312)	(10,706)
Projected benefit obligation at end of year	170,005	185,556	163,010
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of period	201,399	189,437
Actual gain on plan assets	2,246	22,395
Employer contributions	0	5,610
Plan settlements	(2,766)	0
Benefits paid	(3,970)	(4,424)
Effect of foreign currency rate changes	(10,182)	(11,619)
Fair value of plan assets at end of year	186,727	201,399	$ 189,437
Funded status of the plan	16,722	15,843
Net actuarial pension loss	61,818	61,378
Total	$ 78,540	$ 77,221

Employee Benefit Plans (Sche119

Employee Benefit Plans (Schedule of Defined Benefit Plan Amounts Recognized in Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Tax benefit (expense)	$ 88	$ 3,687	$ (1,015)
Total other comprehensive income (loss)	(350,049)	614,752	178,468
Net Actuarial Pension Loss [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial gain (loss)	(3,102)	(20,521)	3,146
Settlement loss recognized	343	0	0
Amortization of net actuarial loss	2,319	1,589	1,934
Amortization of prior service costs	0	495	0
Tax benefit (expense)	88	3,687	(1,015)
Total other comprehensive income (loss)	$ (352)	$ (14,750)	$ 4,065

Employee Benefit Plans (Sche120

Employee Benefit Plans (Schedule Of Net Periodic Benefit Income And Weighted Average Assumptions) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Interest cost	$ 6,645	$ 7,572	$ 6,533
Expected return on plan assets	(11,496)	(12,812)	(10,825)
Amortization of prior service cost	0	495	0
Amortization of net actuarial pension loss	2,319	1,589	1,934
Settlement loss recognized	343	0	0
Net periodic benefit income	$ (2,189)	$ (3,156)	$ (2,358)
Discount rate	4.00%	3.80%	4.70%
Expected return on plan assets, percent	5.40%	6.00%	6.60%
Rate of compensation increase	2.90%	2.90%	3.20%

Employee Benefit Plans (Summary

Employee Benefit Plans (Summary Of Fair Value Of Plan Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 186,727	$ 201,399	$ 189,437
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	186,727	201,399
Level 1 [Member] | Fixed Maturities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	107,033	114,243
Level 1 [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	79,686	87,148
Level 1 [Member] | Cash And Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 8	$ 8

Markel Corporation (Parent C122

Markel Corporation (Parent Company Only) Financial Information (Schedule Of Condensed Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Fixed maturities	$ 9,394,468	$ 10,422,882
Equity securities	4,074,475	4,137,576
Short-term investments (estimated fair value approximates cost)	1,642,261	1,594,849
Total Investments	15,111,204	16,155,307
Cash and cash equivalents	2,630,009	1,960,169	$ 1,978,526	$ 863,766
Restricted cash and cash equivalents	440,132	522,225
Other assets	944,101	985,834
Total Assets	24,941,271	25,200,357	23,955,511
Net deferred tax liability	176,188	310,547
Other liabilities	1,030,023	1,051,931
Total Liabilities	17,037,704	17,537,307
Total Shareholders' Equity	7,834,150	7,594,818
Total Liabilities and Equity	24,941,271	25,200,357
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Fixed maturities	36,618	48,807
Equity securities	311,405	434,714
Short-term investments (estimated fair value approximates cost)	755,619	764,953
Total Investments	1,103,642	1,248,474
Cash and cash equivalents	460,271	243,702	$ 207,352	$ 237,816
Restricted cash and cash equivalents	670	959
Receivables	17,200	16,110
Investments in consolidated subsidiaries	7,961,315	7,560,862
Notes receivable from subsidiaries	212,636	212,631
Income taxes receivable	0	10,951
Other assets	91,151	93,434
Total Assets	9,846,885	9,387,123
Senior long-term debt	1,634,472	1,635,173
Notes payable to subsidiaries	300,000	15,000
Income taxes payable	4,262	0
Net deferred tax liability	7,498	74,534
Other liabilities	66,503	67,598
Total Liabilities	2,012,735	1,792,305
Total Shareholders' Equity	7,834,150	7,594,818
Total Liabilities and Equity	$ 9,846,885	$ 9,387,123

Markel Corporation (Parent C123

Markel Corporation (Parent Company Only) Financial Information (Schedule of Condensed Balance Sheets - Parenthetical) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Fixed maturities, amortized cost	$ 9,038,158	$ 9,929,137
Equity securities, cost	2,208,834	1,951,658
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Fixed maturities, amortized cost	35,475	47,346
Equity securities, cost	$ 204,289	$ 193,864

Markel Corporation (Parent C124

Markel Corporation (Parent Company Only) Financial Information (Schedule Of Condensed Statements Of Income And Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Net investment income													$ 353,213	$ 363,230	$ 317,373
Other-than-temporary impairment losses													(44,481)	(4,784)	(4,706)
Net realized investment gains, excluding other-than-temporary impairment losses													150,961	50,784	67,858
Net realized investment gains													106,480	46,000	63,152
Other													1,086,758	883,525	710,942
Total Operating Revenues	$ 1,420,460	$ 1,342,764	$ 1,304,605	$ 1,302,154	$ 1,335,755	$ 1,299,286	$ 1,258,971	$ 1,239,655	$ 1,279,785	$ 1,191,665	$ 1,031,769	$ 819,864	5,369,983	5,133,667	4,323,083
Interest expense													118,301	117,442	114,004
Other expenses													1,046,805	854,871	663,528
Total Operating Expenses													4,509,577	4,575,847	3,847,336
Income tax benefit													152,963	116,690	77,898
Net Income to Shareholders	197,892	102,519	91,369	190,992	117,595	75,803	40,068	87,716	98,764	65,599	27,756	88,902	582,772	321,182	281,021
Net holding gains (losses) arising during the period													(240,170)	687,735	225,545
Reclassification adjustments for net losses included in net income to shareholders													(80,482)	(26,161)	(40,830)
Change in net unrealized gains on investments, net of taxes													(320,492)	661,747	184,574
Change in foreign currency translation adjustments, net of taxes													(29,278)	(32,241)	(10,143)
Total Other Comprehensive Income (Loss)													(350,122)	614,756	178,496
Comprehensive Income to Shareholders	$ 134,984	$ (51,143)	$ (132,925)	$ 281,807	$ 418,571	$ 36,502	$ 250,588	$ 230,273	$ 206,450	$ 144,409	$ (149,054)	$ 257,684	232,723	935,934	459,489
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net investment income													2,565	5,354	21,946
Dividends on common stock of consolidated subsidiaries													187,496	217,121	806,233
Other-than-temporary impairment losses													(3,455)	(120)	(15)
Net realized investment gains, excluding other-than-temporary impairment losses													75,000	3,873	67,232
Net realized investment gains													71,545	3,753	67,217
Other													0	0	1
Total Operating Revenues													261,606	226,228	895,397
Interest expense													95,620	94,097	92,743
Other expenses													11,287	2,685	2,617
Total Operating Expenses													106,907	96,782	95,360
Income Before Equity in Undistributed Earnings of Consolidated Subsidiaries and Income Taxes													154,699	129,446	800,037
Equity in undistributed earnings of consolidated subsidiaries													407,489	163,341	(520,323)
Income tax benefit													(20,584)	(28,395)	(1,307)
Net Income to Shareholders													582,772	321,182	281,021
Net holding gains (losses) arising during the period													(41,861)	32,118	66,623
Consolidated subsidiaries' net holding gains (losses) arising during the period													(198,309)	655,617	158,922
Consolidated subsidiaries' change in unrealized other-than-temporary impairment losses on fixed maturities arising during the period													160	173	(141)
Reclassification adjustments for net losses included in net income to shareholders													(45,273)	(1,874)	(43,220)
Consolidated subsidiaries' reclassification adjustments for net gains (losses) included in net income to shareholders													(35,209)	(24,287)	2,390
Change in net unrealized gains on investments, net of taxes													(320,492)	661,747	184,574
Change in foreign currency translation adjustments, net of taxes													2,970	1,949	(2,670)
Consolidated subsidiaries' change in foreign currency translation adjustments, net of taxes													(32,175)	(34,194)	(7,501)
Consolidated subsidiaries' change in net actuarial pension loss, net of taxes													(352)	(14,750)	4,065
Total Other Comprehensive Income (Loss)													(350,049)	614,752	178,468
Comprehensive Income to Shareholders													$ 232,723	$ 935,934	$ 459,489

Markel Corporation (Parent C125

Markel Corporation (Parent Company Only) Financial Information (Schedule Of Condensed Statements Of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Net income to shareholders	$ 197,892	$ 102,519	$ 91,369	$ 190,992	$ 117,595	$ 75,803	$ 40,068	$ 87,716	$ 98,764	$ 65,599	$ 27,756	$ 88,902	$ 582,772	$ 321,182	$ 281,021
Net Cash Provided By Operating Activities													651,151	716,792	745,521
Proceeds from sales of fixed maturities and equity securities													538,978	1,286,871	879,564
Proceeds from maturities, calls and prepayments of fixed maturities													1,503,616	1,420,817	1,475,938
Cost of fixed maturities and equity securities purchased													(1,576,254)	(3,153,055)	(1,651,397)
Net change in short-term investments													(62,124)	(129,164)	(470,423)
Cost of equity method investments													(21,849)	(16,081)	(38,018)
Change in restricted cash and cash equivalents													62,324	264,701	(263,014)
Additions to property and equipment													(79,755)	(82,132)	(47,725)
Other													(797)	(2,368)	1,103
Net Cash Provided (Used) By Investing Activities													125,773	(622,205)	187,387
Additions to senior long-term debt													69,797	89,480	547,214
Repurchases of common stock													(31,491)	(26,053)	(57,388)
Issuance of common stock													4,752	5,691	24,518
Other													(10,488)	(21,357)	(23)
Net Cash Provided (Used) By Financing Activities													(74,211)	(67,124)	175,367
Increase (decrease) in cash and cash equivalents													669,840	(18,357)	1,114,760
Cash and cash equivalents at beginning of year				1,960,169				1,978,526				863,766	1,960,169	1,978,526	863,766
CASH AND CASH EQUIVALENTS AT END OF YEAR	2,630,009				1,960,169				1,978,526				2,630,009	1,960,169	1,978,526
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net income to shareholders													582,772	321,182	281,021
Adjustments to reconcile net income to shareholders to net cash provided by operating activities													(464,193)	(218,396)	186,574
Net Cash Provided By Operating Activities													118,579	102,786	467,595
Proceeds from sales of fixed maturities and equity securities													100,633	9,306	142,259
Proceeds from maturities, calls and prepayments of fixed maturities													24,945	15,710	2,819
Cost of fixed maturities and equity securities purchased													(55,656)	(687)	(23,412)
Net change in short-term investments													9,956	(109,728)	10,251
Securities received from subsidiaries as dividends or repayment of notes receivable													0	89,996	249,996
Decrease in notes receivable due from subsidiaries													0	28,506	5,302
Capital contributions to subsidiaries													(228,578)	(74,788)	(67,878)
Acquisitions													0	0	(1,017,988)
Cost of equity method investments													(13,164)	0	(5,291)
Change in restricted cash and cash equivalents													289	51	(348)
Additions to property and equipment													(305)	(342)	(3,653)
Other													(376)	(2,150)	3,207
Net Cash Provided (Used) By Investing Activities													(162,256)	(44,126)	(704,736)
Additions to senior long-term debt													0	0	491,235
Increase in notes payable to subsidiaries													285,000	0	0
Repayment and retirement of senior long-term debt													(2,000)	0	(246,665)
Repurchases of common stock													(31,491)	(26,053)	(57,388)
Issuance of common stock													4,752	5,691	24,518
Other													3,985	(1,948)	(5,023)
Net Cash Provided (Used) By Financing Activities													260,246	(22,310)	206,677
Increase (decrease) in cash and cash equivalents													216,569	36,350	(30,464)
Cash and cash equivalents at beginning of year				$ 243,702				$ 207,352				$ 237,816	243,702	207,352	237,816
CASH AND CASH EQUIVALENTS AT END OF YEAR	$ 460,271				$ 243,702				$ 207,352				$ 460,271	$ 243,702	$ 207,352

Quarterly Financial Informat126

Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Operating revenues	$ 1,420,460	$ 1,342,764	$ 1,304,605	$ 1,302,154	$ 1,335,755	$ 1,299,286	$ 1,258,971	$ 1,239,655	$ 1,279,785	$ 1,191,665	$ 1,031,769	$ 819,864	$ 5,369,983	$ 5,133,667	$ 4,323,083
Net income	198,273	104,410	92,453	194,006	118,222	76,824	41,141	87,501	98,939	66,967	28,676	89,263	589,142	323,688	283,845
Net income to shareholders	197,892	102,519	91,369	190,992	117,595	75,803	40,068	87,716	98,764	65,599	27,756	88,902	582,772	321,182	281,021
Comprehensive income (loss) to shareholders	$ 134,984	$ (51,143)	$ (132,925)	$ 281,807	$ 418,571	$ 36,502	$ 250,588	$ 230,273	$ 206,450	$ 144,409	$ (149,054)	$ 257,684	$ 232,723	$ 935,934	$ 459,489
Basic net income per share (dollars per share)	$ 14.23	$ 7.43	$ 6.76	$ 13.57	$ 8.10	$ 5.33	$ 2.67	$ 6.28	$ 6.98	$ 4.69	$ 2.24	$ 9.53	$ 41.99	$ 22.38	$ 22.57
Diluted net income per share (dollars per share)	14.14	7.39	6.72	13.49	8.05	5.30	2.66	6.25	6.95	4.67	2.24	9.50	$ 41.74	$ 22.27	$ 22.48
Common stock price, high (dollars per share)	937.91	898.08	821	783.50	707.36	666	655.75	596.87	582.59	549.09	546.94	510.05
Common stock price, low (dollars per share)	$ 791.97	$ 775	$ 736.96	$ 660.05	$ 632.65	$ 623.90	$ 593.76	$ 527.17	$ 511.06	$ 506.64	$ 501.76	$ 434.98