Navigators (NAVG) 10-K 12 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Jan. 28, 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
Trading Symbol	NAVG
Entity Registrant Name	NAVIGATORS GROUP INC
Entity Central Index Key	793,547
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		14,441,411
Entity Public Float			$ 843,496,877

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Investments:
Fixed maturities, available-for-sale, at fair value (amortized cost: 2015: $2,400,245; 2014: $2,323,959)	$ 2,414,210	$ 2,365,934
Equity securities, available-for-sale, at fair value (cost: 2015: $281,943; 2014: $154,843)	305,271	184,295
Short-term investments, at fair value (amortized cost: 2015: $217,743; 2014: $179,527)	217,745	179,506
Total investments	2,937,226	2,729,735
Cash	69,901	90,751
Premiums receivable	276,616	342,479
Prepaid reinsurance premiums	232,588	237,851
Reinsurance recoverable on paid losses	49,506	51,347
Reinsurance recoverable on unpaid losses and loss adjustment expenses	809,518	851,498
Deferred policy acquisition costs	91,983	79,452
Accrued investment income	16,001	14,791
Goodwill and other intangible assets	6,807	7,013
Current income tax receivable, net	22,323	14,549
Deferred income tax, net	3,900
Other assets	67,643	56,719
Total assets	4,584,012	4,476,185
Liabilities:
Reserves for losses and loss adjustment expenses	2,202,644	2,159,634
Unearned premiums	820,676	766,167
Reinsurance balances payable	107,411	152,774
Senior notes	263,580	263,440
Deferred income tax, net		1,467
Payable for investments purchased	1,495	134
Accounts payable and other liabilities	92,058	105,345
Total liabilities	$ 3,487,864	$ 3,448,961
Stockholders' equity:
Preferred stock, $.10 par value, authorized 1,000,000 shares, none issued
Common stock, $.10 par value, authorized 50,000,000 shares, issued 17,942,269 shares for 2015 and 17,792,846 shares for 2014	$ 1,793	$ 1,778
Additional paid-in capital	357,829	347,022
Treasury stock, at cost (3,511,380 shares for 2015 and 2014)	(155,801)	(155,801)
Retained earnings	868,723	787,666
Accumulated other comprehensive income	23,604	46,559
Total stockholders' equity	1,096,148	1,027,224
Total liabilities and stockholders' equity	$ 4,584,012	$ 4,476,185

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Fixed maturities, available-for-sale, amortized cost	$ 2,400,245	$ 2,323,959
Equity securities, available-for-sale, cost	281,943	154,843
Short-term investments, amortized cost	$ 217,743	$ 179,527
Preferred stock, par value	$ 0.10	$ 0.10
Preferred stock, authorized shares	1,000,000	1,000,000
Preferred stock, issued shares	0	0
Common stock, par value	$ 0.10	$ 0.10
Common stock, authorized shares	50,000,000	50,000,000
Common stock, issued shares	17,942,269	17,792,846
Treasury stock, shares	3,511,380	3,511,380

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Gross written premiums	$ 1,453,502	$ 1,432,353	$ 1,370,517
Revenues:
Net written premiums	1,043,860	1,000,138	887,922
Change in unearned premiums	(59,773)	(64,243)	(45,983)
Net earned premiums	984,087	935,895	841,939
Net investment income	68,718	64,168	56,251
Total other-than-temporary impairment losses	(1,870)	137	(2,393)
Portion of loss recognized in other comprehensive income (before tax)	172	(137)
Net other-than-temporary impairment losses recognized in earnings	(1,698)	0	(2,393)
Net realized gains (losses)	8,373	12,812	22,939
Other income (expense)	(491)	10,656	(1,172)
Total revenues	1,058,989	1,023,531	917,564
Expenses:
Net losses and loss adjustment expenses	572,598	545,229	518,961
Commission expenses	129,977	125,528	113,494
Other operating expenses	223,516	196,825	164,434
Call premium on Senior notes			17,895
Interest expense	15,424	15,413	10,507
Total expenses	941,515	882,995	825,291
Income before income taxes	117,474	140,536	92,273
Income tax expense (benefit)	36,417	45,207	28,807
Net income	$ 81,057	$ 95,329	$ 63,466
Net income per common share:
Basic	$ 5.63	$ 6.69	$ 4.49
Diluted	$ 5.47	$ 6.51	$ 4.42
Average common shares outstanding:
Basic	14,392,522	14,259,768	14,133,925
Diluted	14,825,745	14,646,369	14,345,553

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 81,057	$ 95,329	$ 63,466
Change in net unrealized gains (losses) on investments:
Unrealized gains (losses) on investments arising during the period, net of deferred tax of $2,534, $14,925 and $17,521 in 2015, 2014 and 2013 respectively	(5,331)	28,252	(32,546)
Reclassification adjustment for net realized (gains) losses included in net income net of deferred tax of $9,185, $2,776 and $6,218 in 2015, 2014 and 2013 respectively	(17,058)	(5,156)	(11,548)
Change in net unrealized gains (losses on investments)	(22,389)	23,096	(44,094)
Change in other-than-temporary impairments:
Non credit other-than-temporary impairments arising during the period, net of deferred tax of $60, $48 and $174 in 2015, 2014 and 2013 respectively	(112)	89	320
Reclassification adjustment for non credit other-than-temporary impairment losses recognized in net income net of deferred tax of $0 in 2015, 2014 and 2013 respectively	168
Change in other-than-temporary impairments	56	89	320
Change in foreign currency translation gains (losses), net of deferred tax of $351, $2,800, and $1,650 in 2015, 2014 and 2013 respectively	(622)	(4,986)	(3,074)
Other comprehensive income (loss)	(22,955)	18,199	(46,848)
Comprehensive income (loss)	$ 58,102	$ 113,528	$ 16,618

Consolidated Statements of Com6

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Unrealized gains (losses) on investments arising during the period, deferred tax	$ 2,624	$ (14,925)	$ 17,521
Reclassification adjustment for net realized (gains) losses included in net income, deferred tax	9,185	2,776	6,218
Non credit other-than-temporary impairments arising during the period, deferred tax	60	(48)	(174)
Reclassification adjustment for non credit other-than-temporary impairment losses recognized in net income, deferred tax	(90)	0	0
Change in foreign currency translation gains (losses), deferred tax	$ 351	$ 2,800	$ 1,650

Consolidated Statement of Stock

Consolidated Statement of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2012		17,558,046		3,511,380
Beginning balance at Dec. 31, 2012	$ 879,485	$ 1,755	$ 329,452	$ (155,801)	$ 628,871	$ 75,208
Net income	63,466				63,466
Changes in comprehensive income:
Change in net unrealized gain (loss) on investments	(44,094)					(44,094)
Change in net non-credit other-than-temporary impairment losses	320					320
Change in foreign currency translation gain (loss)	(3,074)					(3,074)
Other comprehensive income (loss)	(46,848)					(46,848)
Shares issued under stock plan (in shares)		151,830
Shares issued under stock plan	2,740	$ 15	2,725
Share-based compensation	3,369		3,369
Ending balance (in shares) at Dec. 31, 2013		17,709,876		3,511,380
Ending balance at Dec. 31, 2013	902,212	$ 1,770	335,546	$ (155,801)	692,337	28,360
Net income	95,329				95,329
Changes in comprehensive income:
Change in net unrealized gain (loss) on investments	23,096					23,096
Change in net non-credit other-than-temporary impairment losses	89					89
Change in foreign currency translation gain (loss)	(4,986)					(4,986)
Other comprehensive income (loss)	18,199					18,199
Shares issued under stock plan (in shares)		82,970
Shares issued under stock plan	(23)	$ 8	(31)
Share-based compensation	$ 11,507		11,507
Ending balance (in shares) at Dec. 31, 2014	17,792,846	17,792,846		3,511,380
Ending balance at Dec. 31, 2014	$ 1,027,224	$ 1,778	347,022	$ (155,801)	787,666	46,559
Net income	81,057				81,057
Changes in comprehensive income:
Change in net unrealized gain (loss) on investments	(22,389)					(22,389)
Change in net non-credit other-than-temporary impairment losses	56					56
Change in foreign currency translation gain (loss)	(622)					(622)
Other comprehensive income (loss)	(22,955)					(22,955)
Shares issued under stock plan (in shares)		149,423
Shares issued under stock plan	(4,175)	$ 15	(4,190)
Share-based compensation	$ 14,997		14,997
Ending balance (in shares) at Dec. 31, 2015	17,942,269	17,942,269		3,511,380
Ending balance at Dec. 31, 2015	$ 1,096,148	$ 1,793	$ 357,829	$ (155,801)	$ 868,723	$ 23,604

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	$ 81,057	$ 95,329	$ 63,466
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation & amortization	5,386	4,915	4,518
Deferred income taxes	7,004	16,881	4,658
Net realized (gains) losses	(8,373)	(12,812)	(22,939)
Net other-than-temporary losses recognized in earnings	1,698	0	2,393
Call premium on redemption of Senior notes			17,895
Changes in assets and liabilities:
Reinsurance recoverable on paid and unpaid losses and loss adjustment expenses	43,822	(42,024)	68,599
Reserves for losses and loss adjustment expenses	43,010	114,563	(51,977)
Prepaid reinsurance premiums	5,264	10,344	(26,807)
Unearned premiums	54,509	52,380	72,199
Premiums receivable	65,863	(17,455)	(4,843)
Deferred policy acquisition costs	(12,531)	(12,445)	(6,002)
Accrued investment income	(1,210)	(925)	(1,279)
Reinsurance balances payable	(45,124)	(14,716)	1,439
Current income taxes	(8,072)	(582)	(16,432)
Other	(4,679)	29,039	31,987
Net cash provided by (used in) operating activities	227,624	222,492	136,875
Fixed maturities
Redemptions and maturities	180,876	210,674	237,627
Sales	376,522	362,136	648,335
Purchases	(648,059)	(864,902)	(899,930)
Equity securities
Sales	96,405	54,900	72,113
Purchases	(215,405)	(83,845)	(89,288)
Change in payable for securities	1,851	(7,814)	(46,414)
Net change in short-term investments	(38,468)	117,740	(142,214)
Purchase of property and equipment	(3,577)	(8,359)	(10,088)
Net cash provided by (used in) investing activities	(249,855)	(219,470)	(229,859)
Financing activities:
Net proceeds from debt offering			263,278
Redemption of 7.0% Senior notes due May 1, 2016			(132,437)
Proceeds of stock issued from employee stock purchase plan	1,352	1,067	821
Proceeds of stock issued from exercise of stock options	29	153	2,495
Net cash provided by (used in) financing activities	1,381	1,220	134,157
Increase (decrease) in cash	(20,850)	4,242	41,173
Cash at beginning of year	90,751	86,509	45,336
Cash at end of period	69,901	90,751	86,509
Supplemental cash information:
Income taxes paid, net	35,447	27,066	41,094
Interest paid	15,238	15,703	8,050
Issuance of stock to directors	$ 563	$ 438	$ 400

Consolidated Statements of Cas9

Consolidated Statements of Cash Flows (Parenthetical)	12 Months Ended
	Dec. 31, 2015
Statement Of Cash Flows [Abstract]
Interest rate stated on senior notes	7.00%
Senior notes due date	May 1, 2016

Organization and Summary of Sig

Organization and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Organization and Summary of Significant Accounting Policies	NOTE 1. ORGANIZATION & SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying consolidated financial statements of The Navigators Group, Inc. and its subsidiaries have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP” or “U.S. GAAP”). All significant intercompany transactions and balances have been eliminated in consolidation. The preparation of these financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and the reported revenues and expenses during the reporting periods. Certain amounts for the prior year have been reclassified to conform with the current period presentation. Unless the context requires otherwise, the terms “we,” “us,” “our,” or “our Company” are used to mean The Navigators Group, Inc., a Delaware holding company established in 1982, and its subsidiaries. The terms “Parent” or “Parent Company” are used to mean The Navigators Group, Inc. without its subsidiaries. Organization We are an international insurance company with a long-standing area of specialization in Marine insurance. Our Property and Casualty (“P&C”) insurance business primarily offers general liability coverage and umbrella & excess liability coverage to commercial enterprises through our Primary and Excess Casualty divisions. We have also developed niches in Professional Liability insurance, through our Directors & Officers (“D&O”) and Errors & Omissions (“E&O”) divisions. Beginning in 2010, we added reinsurance products through our Global Reinsurance (“GlobalRe”) business. We operate through various wholly-owned subsidiaries, including Navigators Insurance Company (“NIC”), inclusive of its United Kingdom Branch (“U.K. Branch”), and Navigators Specialty Insurance Company (“NSIC”), both of which are U.S. insurance companies, and Navigators Underwriting Agency Ltd. (“NUAL”), a Lloyd’s of London (“Lloyd’s”) underwriting agency that manages Lloyd’s Syndicate 1221 (“the Syndicate”) in the U.K. and is the underwriting company of Navigators Holdings (U.K.) Ltd. (“NHUK”), the holding company for our non U.S. domiciled entities. Our Company controls 100% of the Syndicate’s stamp capacity. Significant Accounting Policies Cash Cash includes cash on hand and demand deposits with banks, excluding such amounts held by the Syndicate included as Funds at Lloyd’s (“FAL”), which are classified as short term investments. Investments As of December 31, 2015 and 2014, all fixed maturity and equity securities held by our Company were carried at fair value and classified as available-for-sale. Available-for-sale securities are debt and equity securities not classified as either held-to-maturity securities or trading securities and are reported at fair value, with unrealized gains and losses excluded from earnings and reported in accumulated other comprehensive income (“AOCI”) as a separate component of stockholders’ equity. Fixed maturity securities include bonds, mortgage-backed and asset-backed securities. Equity securities consist of common stock, exchange traded funds and preferred stock. Short-term investments are carried at fair value. Short-term investments mature within one year from the purchase date. All prices for our fixed maturities, equity securities and short-term investments are classified as Level 1, Level 2 or Level 3 under the fair value hierarchy, as defined in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification 820 (“ASC 820”). Premiums and discounts on fixed maturity securities are amortized into interest income over the life of the security using the interest method. For mortgage-backed and asset-backed securities, anticipated prepayments and expected maturities are utilized in applying the interest rate method. An effective yield is calculated based on projected principal cash flows at the time of original purchase. The effective yield is used to amortize the purchase price of the security over the security’s expected life. Book values are adjusted to reflect the amortization of premium or accretion of discount on a monthly basis. The projected principal cash flows are based on certain prepayment assumptions, which are generated using a prepayment model. The prepayment model uses a number of factors to estimate prepayment activity including the current levels of interest rates (refinancing incentive), time of year (seasonality), economic activity (including housing turnover) and term and age of the underlying collateral (burnout, seasoning). Prepayment assumptions associated with the mortgage-backed and asset-backed securities are reviewed on a periodic basis. When changes in prepayment assumptions are deemed necessary as the result of actual prepayments differing from anticipated prepayments, securities are revalued based upon the new prepayment assumptions utilizing the retrospective adjustment method, whereby the effective yield is recalculated to reflect actual payments to date and anticipated future payments. The investment in such securities is adjusted to the amount that would have existed had the new effective yield been applied since the acquisition of the security. Such adjustments, if any, are included in Net investment income for the current period. Realized gains and losses on sales of investments are recognized when the related trades are executed and are determined on the basis of the specific identification method. Impairment of Invested Assets Management regularly reviews our fixed maturity and equity securities portfolios to evaluate the necessity of recording impairment losses for other-than-temporary declines in the fair value of securities. For fixed maturity securities, we consider our intent to sell a security and whether it is more likely than not that, we will be required to sell a security before the anticipated recovery as part of the process of evaluating whether a security’s unrealized loss represents an other-than-temporary decline. For fixed maturity securities that have a fair value below amortized cost and that we intend to sell or for which it is more likely than not that we would be required to sell, an other than temporary impairment (“OTTI”) loss is recognized in earnings by writing such security down to fair value. For fixed maturity securities which we do not intend to sell or for which it is more likely than not that our Company would not be required to sell, a decline in value below amortized cost is only recognized to the extent the present value of future cash flows expected to be collected is less than the amortized cost of the security. Such shortfall in the present value of future cash flows is considered the credit loss and is recognized as an OTTI loss in earnings, with the non-credit portion of the impairment (i.e., the difference between the present value of future cash flows and fair value of the security) recognized as OTTI losses in AOCI. In evaluating OTTI of equity securities, we consider our intent to hold the securities as part of the process of evaluating whether a decline in fair value below cost represents an other than temporary decline in value. For equity securities in an unrealized loss position that we do not intend to hold or that we do not expect to recover their value within a reasonable period of time, a net OTTI loss is recognized in earnings by writing such security down to the fair value. Foreign Currency Remeasurement and Translation The functional currency of each of our operations is generally the currency of the local operating environment, except for our Lloyd’s business which is United States Dollar (“USD”). Transactions in currencies other than an operation’s functional currency are remeasured into the functional currency and the resulting foreign exchange gains and losses are reflected in net Other income (expense) in the Consolidated Statements of Income. Functional currency assets and liabilities are translated into USD using period end rates of exchange and the related translation adjustments are recorded as a separate component of AOCI. Consolidated Statements of Income amounts expressed in functional currencies are translated using average exchange rates. During the first quarter of 2014, the Syndicate revised its foreign exchange accounting methodology from reporting its financial position and results using three functional currencies (British pound sterling (“GBP”), U.S.dollars (“USD”) and Canadian dollars (“CAD”)) to one functional currency (USD). The USD was chosen as the single functional currency as the majority of the Syndicate’s insurance business has been and continues to be transacted in USD. This cumulative change in remeasurement resulted in a 2014 immaterial correction of $10.0 million ($6.6 million after-tax) in AOCI, on the Consolidated Balance Sheets, offset by a gain in Other income in the Consolidated Statements of Income. Premium Revenues Written premium is based on the insurance policies that have been reported to us and the policies that have been written by agents but not yet reported to us. We estimate the amount of written premium not yet reported based on judgments relative to current and historical trends of the business being written. Such estimates are regularly reviewed and updated and any resulting adjustments are included in the current year’s results. An Unearned premium reserve is established to reflect the unexpired portion of each policy at the financial reporting date. Substantially all of our business is placed through agents and brokers. We record estimates for both unreported direct and assumed premiums. We also record the ceded portion of the estimated Gross written premiums and related acquisition costs. These estimates are mostly for our Marine and Energy & Engineering products written by our International Insurance (“Int’l Insurance”) reporting segment as well as our Accident & Health (“A&H”) and Latin American (“LatAm”) business within our P&C and Surety products written by our GlobalRe reporting segment. Such premium estimates are generally based on submission data received from brokers and agents and recorded when the insurance policy or reinsurance contract is written or bound. The earned gross, ceded and net premiums are calculated based on our earning methodology, which is generally pro-rata over the policy period or over the period of risk if the period of risk differs significantly from the contract period. Reinsurance Ceded In the normal course of business, we purchase reinsurance from insurers or reinsurers to reduce the amount of loss arising from claims. Management analyzes the reinsurance agreements to determine whether the reinsurance should be classified as prospective or retroactive based upon the terms of the reinsurance agreement and whether the reinsurer has assumed significant insurance risk to the extent that the reinsurer may realize a significant loss from the transaction. Prospective reinsurance is reinsurance in which an assuming company agrees to reimburse the ceding company for losses that may be incurred as a result of future insurable events covered under contracts subject to the reinsurance. Retroactive reinsurance is reinsurance in which an assuming company agrees to reimburse a ceding company for liabilities incurred as a result of past insurable events covered under contracts subject to the reinsurance. Ceded reinsurance premiums and any related ceding commissions and ceded losses are reflected as reductions of the respective income or expense accounts over the terms of the reinsurance contracts. Prepaid reinsurance premiums represent the portion of premiums ceded to reinsurers applicable to the unexpired terms of the reinsurance contracts in force. Reinsurance reinstatement premiums (“RRPs”) are recognized in the same period as the loss event that gave rise to the reinstatement premiums. Amounts recoverable from reinsurers are estimated in a manner consistent with the claim liability associated with the reinsured policy. Ceded Unearned premiums and estimates of amounts recoverable from reinsurers on paid and unpaid losses are reflected as assets. Provisions are made for estimated unrecoverable reinsurance. Deferred Policy Acquisition Costs Costs of acquiring business are deferred and amortized ratably over the period that the related premiums are recognized as revenue. Such costs (e.g., Commission expenses, Other underwriting expenses and premium taxes) are limited to the incremental direct costs related to the successful acquisition of new or renewal business. The method of computing deferred policy acquisition costs limits the deferral to their estimated net realizable value based on the related Unearned premiums and takes into account anticipated losses and LAE, commission expenses and operating expenses based on historical and current experience, as well as anticipated investment income. Reserves for Losses and Loss Adjustment Expenses Unpaid losses and loss adjustment expenses (“LAE”) are determined on: (a) individual claims reported on direct business for insureds, (b) from reports received from ceding insurers for assumed business and (c) on estimates based on Company and industry experience for incurred but not reported (“IBNR”) claims and LAE. Indicated IBNR loss reserves are calculated by our actuaries using several standard actuarial methodologies, including the paid and incurred loss development and the paid and incurred Bornheutter-Ferguson loss methods. Frequency/severity analyses are performed for certain books of business. The provision for unpaid losses and LAE has been established to cover the estimated unpaid cost of claims incurred. Such estimates are regularly reviewed and updated and any resulting adjustments are included in the current year’s results. Management believes that the liability recognized for unpaid losses and LAE is a reasonable estimate of the ultimate unpaid claims incurred, however, no representation is made that the ultimate liability will not differ materially from the amounts recorded in the accompanying Consolidated Financial Statements. Losses and LAE are recorded on an undiscounted basis. Earnings per Share Basic earnings per share (“EPS”) is computed by dividing Net income by the weighted average number of common shares outstanding for the period. Diluted EPS reflects the basic EPS adjusted for the potential dilution that would occur if all issued stock options were exercised and all stock grants were fully vested. Depreciation and Amortization Depreciation of furniture and fixtures, electronic data processing equipment and computer software is provided over the estimated useful lives of the respective assets, ranging from three to seven years, using the straight-line method. Amortization of leasehold improvements are provided over the shorter of the useful lives of those improvements or the contractual terms of the leases, ranging from five to ten years, using the straight-line method. Goodwill and Other Intangible Assets Goodwill represents the excess of cost of acquiring a business enterprise over the fair value of the net assets acquired. Our Company has also recorded indefinite lived intangible assets related to the acquisition of the remaining non-controlled stamp capacity of the Syndicate. Goodwill and indefinite lived intangible assets are reported at carrying value and are tested for impairment at least annually, and when permitted by the applicable accounting guidance, qualitative factors are assessed to determine whether it is necessary to calculate an asset’s fair value when testing an asset with an indefinite life for impairment. Goodwill and indefinite lived intangible assets are considered impaired if the estimated fair value is less than its carrying value and any impairment loss is measured as the difference between the implied fair value and the carrying value. Our Company did not recognize an impairment of goodwill or the indefinite lived intangible assets for any of the years ended December 31, 2015, 2014 and 2013. As of December 31, 2015, the carrying value of goodwill and indefinite lived intangible assets was $6.8 million, which is $0.2 million less than the carrying value as of December 31, 2014, $7.0 million. Changes in the carrying value of the goodwill and indefinite lived intangible assets are due to amortization and fluctuations in currency exchange rates between the USD and the GBP. Income Taxes We recognize deferred tax assets and liabilities based on the differences between the financial statement carrying amounts and the tax bases of assets and liabilities. Deferred tax assets are reduced by a valuation allowance if, based on the weight of available evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. All available evidence, both positive and negative, is considered to determine whether, based on the weight of that evidence, a valuation allowance is needed. Future realization of the tax benefit of an existing deferred tax asset ultimately depends on the existence of sufficient taxable income of the appropriate character within the carryback/carryforward period available under the tax law. In determining whether a valuation allowance is needed, management considers the timing of the reversal of each deferred tax asset as well as expected future levels of taxable income, amounts of taxable income in carryback years, and tax planning strategies. Additional information regarding our deferred tax assets can be found in Note 9, Income Taxes. Current and Pending Accounting Pronouncements In 2015, we did not adopt any new accounting pronouncements. We are currently assessing the future impact to our Consolidated Financial Statements of the following 2015 pronouncements issued by the FASB. · Accounting Standards Update 2015-03 – Interest – Imputation of Interest (Subtopic 835-30) – Simplifying the Presentation of Debt Issuance Costs, which will be effective for fiscal years beginning after December 15, 2015. The new pronouncement was issued to simplify presentation of debt issuance costs. · Accounting Standards Update 2015-05 – Intangibles – Goodwill and Other – Internal Use Software (Subtopic 350-40) Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement, which will be effective for fiscal years beginning after December 15, 2015. The new pronouncement was issued to provide guidance to customers about whether a cloud computing arrangement includes a software license. · Accounting Standards Update 2015-07 – Fair Value Measurement – (Topic 820) Disclosures for Investments in Certain Entities that Calculate Net Asset Value per Share (or its equivalent) (a consensus of the Emerging Issues Task Force), which will be effective for fiscal years beginning after December 15, 2015. The new pronouncement was issued to ensure that all investments categorized in the fair value hierarchy are classified using a consistent approach. · Accounting Standards Update 2015-09 – Financial Services Insurance – (Topic 944) Disclosures about Short-Duration Contracts, effective for annual periods beginning after December 15, 2015. The new pronouncement was issued to (1) increase the usefulness of the information about a reporting entity’s insurance liabilities, including the nature, amount, timing, and uncertainty of cash flows related to those liabilities and the effect of those cash flows on the Statements of Comprehensive Income and (2) improve comparability between reporting entities, regardless of the type of entity issuing the contract. · Accounting Standards Update 2015-12 – Plan Accounting: Defined Benefit Pension Plans, Defined Contribution Pension Plans, Health and Welfare Plans, effective for annual periods beginning after December 15, 2015. This update was issued to reduce complexity in employee benefit plan accounting. This update designates contract value as the only required measure for fully benefit-responsive investment contracts, which maintains the relevant information while reducing the cost and complexity of reporting for fully benefit-responsive investment contracts. · Accounting Standards Update 2015-14 – Revenue from Contracts with Customers (Topic 606) – Deferral of the Effective Date, effective for annual periods beginning after December 15, 2017. In response to stakeholders’ request to defer the effective date of the guidance in Update 2014-09 and in consideration of feedback received through extensive outreach with preparers, practitioners, and users of financial statements, the Board issued this proposed update. The amendments in this update defer the effective date of Update 2014-09 for all entities by one year. · Accounting Standards Update 2015-15 – Interest – Imputation of Interest (Subtopic 835-30) – Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements, effective for annual periods beginning after December 15, 2015. This update changed the wording in Subtopic 835-30 for the imputation of interest. Given the absence of authoritative guidance within Update 2015-03 for debt issuance costs related to line-of-credit arrangements, the Security and Exchange Commission (“SEC”) staff would not object to an entity deferring and presenting debt issuance costs as an asset and subsequently amortizing the deferred debt issuance costs ratably over the term of the line-of-credit arrangement, regardless of whether there are any outstanding borrowings on the line-of-credit arrangements. There were no additional 2015 accounting pronouncements that are expected to have a significant impact on our Consolidated Financial Statements upon adoption.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Segment Information	NOTE 2. SEGMENT INFORMATION During the first quarter of 2015, we realigned our reporting segments from Insurance Companies, Lloyd’s Operations and Corporate to U.S. Insurance, Int’l Insurance, GlobalRe and Corporate. The new segment presentation reflects an increase in the level of importance that the Chief Operating Decision Maker now places on the results of the underlying operating segments when aggregated and reported in alignment with the products and services offered to the marketplace versus when aggregated and reported in alignment with our legal entity structure. Over the past few years, we have been monitoring the growth and stability of our reinsurance business and in 2015 determined that reinsurance has become a stable and significant component of our Company. We are also increasing our focus on additional international insurance markets by establishing underwriting offices in Continental Europe. The offices were fully operational during our January 2015 renewal season. We considered these changes in conjunction with operating and reportable segments. Our previously reported segments were consistent with our legal entity structure; however, our new reporting segments are now primarily reflective of where our business is written. We reclassified our international business from our previously reported Lloyd’s Operations segment to the Int’l Insurance segment. We also reclassified our non-Lloyd’s business written internationally (primarily business written by the U.K. Branch) into this segment and have excluded Assumed Reinsurance. Our new GlobalRe segment was previously reported within our U.S. Insurance and Lloyd’s Operations segments as Assumed Reinsurance. Our U.S. Insurance segment now excludes the U.K. Branch and Assumed Reinsurance. Our Corporate segment now includes Net investment income, Net realized gains (losses), Interest expense, Other income (loss) primarily consisting of foreign exchange gain (loss) and Income tax (expense) benefit, which are not allocated to the U.S. Insurance, Int’l Insurance and GlobalRe segments (together, “underwriting segments”). We do not allocate assets under the new reporting segments, as it is impracticable to do so. As noted above, we classify our business into three underwriting segments (U.S. Insurance, Int’l Insurance and GlobalRe) and a Corporate Segment. Both the U.S. Insurance and Int’l Insurance reporting segments are each comprised of three operating segments: Marine, P&C and Professional Liability. We evaluate the performance of each of the underwriting segments based on underwriting results. Underwriting results are measured based on Underwriting profit or loss and the related Combined ratio, which are both non-GAAP measures of underwriting profitability. Underwriting profit or loss is calculated from Net earned premiums less the sum of Net losses and LAE, Commission expenses, Other operating expenses and Other underwriting income (expense). The Combined ratio is derived by dividing the sum of Net losses and LAE, Commission expenses, Other operating expenses and Other underwriting income (expense) by Net earned premiums. A Combined ratio of less than 100% indicates an underwriting profit and greater than 100% indicates an underwriting loss. Our underwriting performance is evaluated separately from the rest of our operations. The performance of our investment portfolios, our liquidity and capital resource needs, our foreign currency exposure and our tax planning strategies are evaluated on a consolidated basis within our Corporate segment. The following tables set forth the financial data by segment for the years ended December 31, 2015, 2014 and 2013: Year Ended December 31, 2015 U.S. Int'l amounts in thousands Insurance Insurance GlobalRe Corporate (1) Total Net earned premiums $ 555,836 $ 259,960 $ 168,291 $ — $ 984,087 Net losses and LAE (343,497 ) (134,702 ) (94,399 ) — (572,598 ) Commission expenses (56,319 ) (43,676 ) (32,240 ) 2,258 (129,977 ) Other operating expenses (131,407 ) (75,867 ) (16,242 ) — (223,516 ) Other underwriting income (expense) 1,690 — 690 (2,258 ) 122 Underwriting profit (loss) $ 26,303 $ 5,715 $ 26,100 $ — $ 58,118 Net investment income 68,718 68,718 Net realized gains (losses) 6,675 6,675 Interest expense (15,424 ) (15,424 ) Other income (loss) (613 ) (613 ) Income before income taxes $ 26,303 $ 5,715 $ 26,100 $ 59,356 $ 117,474 Income tax (expense) benefit (36,417 ) (36,417 ) Net income (loss) $ 81,057 Losses and LAE ratio 61.8 % 51.8 % 56.1 % 58.2 % Commission expense ratio 10.1 % 16.8 % 19.2 % 13.2 % Other operating expense ratio (2) 23.4 % 29.2 % 9.2 % 22.7 % Combined ratio 95.3 % 97.8 % 84.5 % 94.1 % ( 1) - Includes Corporate segment intercompany eliminations. (2) - Includes Other operating expenses and Other underwriting income (expense). Year Ended December 31, 2014 U.S. Int'l amounts in thousands Insurance Insurance GlobalRe Corporate (1) Total Net earned premiums $ 504,289 $ 243,485 $ 188,121 $ — $ 935,895 Net losses and LAE (311,839 ) (115,079 ) (118,311 ) — (545,229 ) Commission expenses (49,840 ) (44,426 ) (33,429 ) 2,167 (125,528 ) Other operating expenses (115,817 ) (65,275 ) (15,733 ) — (196,825 ) Other underwriting income (expense) 2,241 32 489 (2,167 ) 595 Underwriting profit (loss) $ 29,034 $ 18,737 $ 21,137 $ — $ 68,908 Net investment income 64,168 64,168 Net realized gains (losses) 12,812 12,812 Interest expense (15,413 ) (15,413 ) Other income (loss) 10,061 10,061 Income before income taxes $ 29,034 $ 18,737 $ 21,137 $ 71,628 $ 140,536 Income tax (expense) benefit (45,207 ) (45,207 ) Net income (loss) $ 95,329 Losses and LAE ratio 61.8 % 47.3 % 62.9 % 58.3 % Commission expense ratio 9.9 % 18.2 % 17.8 % 13.4 % Other operating expense ratio (2) 22.5 % 26.8 % 8.1 % 20.9 % Combined ratio 94.2 % 92.3 % 88.8 % 92.6 % (1) - Includes Corporate segment intercompany eliminations. (2) - Includes Other operating expenses and Other underwriting income (expense ). Year Ended December 31, 2013 U.S. Int'l amounts in thousands Insurance Insurance GlobalRe Corporate (1) Total Net earned premiums $ 437,737 $ 232,962 $ 171,240 $ — $ 841,939 Net losses and LAE (283,694 ) (103,853 ) (131,414 ) — (518,961 ) Commission expenses (43,409 ) (42,977 ) (29,456 ) 2,348 (113,494 ) Other operating expenses (99,013 ) (54,062 ) (11,359 ) — (164,434 ) Other underwriting income (expense) 2,924 (1,867 ) 119 (2,348 ) (1,172 ) Underwriting profit (loss) $ 14,545 $ 30,203 $ (870 ) $ — $ 43,878 Net investment income 56,251 56,251 Net realized gains (losses) 20,546 20,546 Interest expense (10,507 ) (10,507 ) Call premium on Senior notes (17,895 ) (17,895 ) Other income (loss) — — Income (loss) before income taxes $ 14,545 $ 30,203 $ (870 ) $ 48,395 $ 92,273 Income tax (expense) benefit (28,807 ) (28,807 ) Net income (loss) $ 63,466 Losses and LAE ratio 64.8 % 44.6 % 76.7 % 61.6 % Commission expense ratio 9.9 % 18.4 % 17.2 % 13.5 % Other operating expense ratio (2) 22.0 % 24.0 % 6.6 % 19.7 % Combined ratio 96.7 % 87.0 % 100.5 % 94.8 % (1) - Includes Corporate segment intercompany eliminations. (2) - Includes Other operating expenses and Other underwriting income (expense ). The following tables provide additional financial data by operating segment for the years ended December 31, 2015, 2014 and 2013: Year Ended December 31, 2015 amounts in thousands Gross written premiums Ceded premiums Net written premiums Net earned premiums U.S. Insurance Marine $ 158,124 $ (61,916 ) $ 96,208 $ 96,082 P&C 596,673 (152,168 ) 444,505 401,408 Professional Liability 110,984 (54,691 ) 56,293 58,346 Total $ 865,781 $ (268,775 ) $ 597,006 $ 555,836 Int'l Insurance Marine $ 183,707 $ (36,515 ) $ 147,192 $ 149,256 P&C 130,729 (67,722 ) 63,007 55,320 Professional Liability 97,511 (29,768 ) 67,743 55,384 Total $ 411,947 $ (134,005 ) $ 277,942 $ 259,960 GlobalRe $ 175,774 $ (6,862 ) $ 168,912 $ 168,291 Total $ 1,453,502 $ (409,642 ) $ 1,043,860 $ 984,087 Year Ended December 31, 2014 amounts in thousands Gross written premiums Ceded written premiums Net written premiums Net earned premiums U.S. Insurance Marine $ 154,233 $ (46,685 ) $ 107,548 $ 105,650 P&C 543,045 (169,953 ) 373,092 314,833 Professional Liability 109,830 (38,345 ) 71,485 83,806 Total $ 807,108 $ (254,983 ) $ 552,125 $ 504,289 Int'l Insurance Marine $ 190,787 $ (47,805 ) $ 142,982 $ 141,097 P&C 158,139 (98,087 ) 60,052 62,520 Professional Liability 75,978 (26,029 ) 49,949 39,868 Total $ 424,904 $ (171,921 ) $ 252,983 $ 243,485 GlobalRe $ 200,341 $ (5,311 ) $ 195,030 $ 188,121 Total $ 1,432,353 $ (432,215 ) $ 1,000,138 $ 935,895 Year Ended December 31, 2013 amounts in thousands Gross written premiums Ceded written premiums Net written premiums Net earned premiums U.S. Insurance Marine $ 143,867 $ (44,359 ) $ 99,508 $ 106,150 P&C 472,049 (202,430 ) 269,619 231,186 Professional Liability 130,079 (32,980 ) 97,099 100,401 Total $ 745,995 $ (279,769 ) $ 466,226 $ 437,737 Int'l Insurance Marine $ 192,870 $ (50,887 ) $ 141,983 $ 150,784 P&C 180,657 (120,068 ) 60,589 55,809 Professional Liability 57,961 (26,877 ) 31,084 26,369 Total $ 431,488 $ (197,832 ) $ 233,656 $ 232,962 GlobalRe $ 193,034 $ (4,994 ) $ 188,040 $ 171,240 Total $ 1,370,517 $ (482,595 ) $ 887,922 $ 841,939 The following table presents identifiable assets by legal entity as we do not allocate assets under the new reporting segments: Years ended December 31, amounts in thousands 2015 2014 Identifiable assets: NIC, NSIC and Navigators Management Company, Inc. $ 3,455,586 $ 3,356,093 NHUK 996,242 957,795 Parent Company (1) 132,184 162,297 Total identifiable assets $ 4,584,012 $ 4,476,185 (1) - Includes Corporate segment intercompany eliminations.

Investments

Investments	12 Months Ended
	Dec. 31, 2015
Investments Debt And Equity Securities [Abstract]
Investments	NOTE 3. INVESTMENTS The following tables set forth our Company’s investments as of December 31, 2015 and 2014 and include OTTI securities recognized within AOCI: December 31, 2015 Gross Gross Unrealized Unrealized Amortized amounts in thousands Fair Value Gains Losses Cost Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 252,882 $ 2,273 $ (9,214 ) $ 259,823 States, municipalities and political subdivisions 576,859 21,233 (781 ) 556,407 Mortgage-backed and asset-backed securities: Agency mortgage-backed securities 379,269 5,573 (2,082 ) 375,778 Residential mortgage obligations 30,465 694 (82 ) 29,853 Asset-backed securities 225,012 85 (1,624 ) 226,551 Commercial mortgage-backed securities 189,713 3,119 (1,864 ) 188,458 Subtotal $ 824,459 $ 9,471 $ (5,652 ) $ 820,640 Corporate bonds 760,010 7,373 (10,738 ) 763,375 Total fixed maturities $ 2,414,210 $ 40,350 $ (26,385 ) $ 2,400,245 Equity securities 305,271 26,341 (3,013 ) 281,943 Short-term investments 217,745 2 — 217,743 Total investments $ 2,937,226 $ 66,693 $ (29,398 ) $ 2,899,931 December 31, 2014 Gross Gross Unrealized Unrealized Amortized amounts in thousands Fair Value Gains Losses Cost Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 397,923 $ 3,431 $ (5,965 ) $ 400,457 States, municipalities and political subdivisions 541,007 19,204 (558 ) 522,361 Mortgage-backed and asset-backed securities: Agency mortgage-backed securities 364,622 8,476 (998 ) 357,144 Residential mortgage obligations 34,087 1,153 (138 ) 33,072 Asset-backed securities 206,413 380 (964 ) 206,997 Commercial mortgage-backed securities 206,318 6,630 (98 ) 199,786 Subtotal $ 811,440 $ 16,639 $ (2,198 ) $ 796,999 Corporate bonds 615,564 13,048 (1,626 ) 604,142 Total fixed maturities $ 2,365,934 $ 52,322 $ (10,347 ) $ 2,323,959 Equity securities 184,295 30,756 (1,304 ) 154,843 Short-term investments 179,506 — (21 ) 179,527 Total investments $ 2,729,735 $ 83,078 $ (11,672 ) $ 2,658,329 As of December 31, 2015 and 2014, our Company did not have a concentration of greater than 5% of invested assets in a single non-U.S. government-backed issuer. As of December 31, 2015 and 2014, fixed maturities for which non-credit OTTI was previously recognized and included in AOCI are now in an unrealized gains position of $0.5 million and $0.7 million, respectively. The fair value of our Company’s investment portfolio may fluctuate significantly in response to various factors such as changes in interest rates, investment quality ratings, equity prices, foreign exchange rates and credit spreads. Our Company does not have the intent to sell nor is it more likely than not that it will have to sell fixed maturities in unrealized loss positions that are not other-than-temporarily impaired before recovery. For structured securities, default probability and severity assumptions differ based on property type, vintage and the stress of the collateral. Our Company does not intend to sell, and it is more likely than not that our Company will not be required to sell, these securities before the recovery of the amortized cost basis. For equity securities, our Company also considers our intent to hold securities as part of the process of evaluating whether a decline in fair value represents an other-than-temporary decline in value. Our Company may realize investment losses to the extent our liquidity needs require the disposition of fixed maturity securities in unfavorable interest rate, liquidity or credit spread environments. Significant changes in the factors our Company considers when evaluating investments for impairment losses could result in a significant change in impairment losses reported in the Consolidated Financial Statements. The contractual maturity dates for fixed maturities categorized by the number of years until maturity as of December 31, 2015 are shown in the following table: December 31, 2015 Amortized amounts in thousands Fair Value Cost Due in one year or less $ 79,279 $ 81,819 Due after one year through five years 766,001 767,634 Due after five years through ten years 323,003 320,503 Due after ten years 421,468 409,648 Mortgage-backed and asset-backed securities 824,459 820,641 Total $ 2,414,210 $ 2,400,245 Expected maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. Prepayment assumptions associated with the mortgage-backed and asset-backed securities are reviewed on a periodic basis. When changes in prepayment assumptions are deemed necessary as the result of actual prepayments differing from anticipated prepayments, securities are revalued based upon the new prepayment assumptions utilizing the retrospective accounting method. Due to the periodic repayment of principal, the mortgage-backed and asset-backed securities are estimated to have an effective maturity of approximately 4.6 years. The following tables summarize all securities in a gross unrealized loss position as of December 31, 2015 and 2014, showing the aggregate fair value and gross unrealized loss by the length of time those securities have continuously been in a gross unrealized loss position: December 31, 2015 Less than 12 months Greater than 12 months Total Gross Gross Gross Fair Unrealized Fair Unrealized Fair Unrealized amounts in thousands Value (Losses) Value (Losses) Value (Losses) Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 142,233 $ (3,032 ) $ 22,230 $ (6,182 ) $ 164,463 $ (9,214 ) States, municipalities and political subdivisions 50,577 (549 ) 4,808 (232 ) 55,385 (781 ) Mortgage-backed and asset-backed securities: Agency mortgage-backed securities 164,817 (1,315 ) 29,862 (767 ) 194,679 (2,082 ) Residential mortgage obligations 3,910 (5 ) 1,684 (77 ) 5,594 (82 ) Asset-backed securities 112,479 (663 ) 81,477 (961 ) 193,956 (1,624 ) Commercial mortgage-backed securities 83,024 (1,826 ) 3,065 (38 ) 86,089 (1,864 ) Subtotal $ 364,230 $ (3,809 ) $ 116,088 $ (1,843 ) $ 480,318 $ (5,652 ) Corporate bonds 395,399 (10,114 ) 13,849 (624 ) 409,248 (10,738 ) Total fixed maturities $ 952,439 $ (17,504 ) $ 156,975 $ (8,881 ) $ 1,109,414 $ (26,385 ) Equity securities 58,531 (3,013 ) — — 58,531 (3,013 ) Total fixed maturities and equity securities $ 1,010,970 $ (20,517 ) $ 156,975 $ (8,881 ) $ 1,167,945 $ (29,398 ) December 31, 2014 Less than 12 months Greater than 12 months Total Gross Gross Gross Fair Unrealized Fair Unrealized Fair Unrealized amounts in thousands Value (Losses) Value (Losses) Value (Losses) Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 87,915 $ (1,061 ) $ 117,683 $ (4,904 ) $ 205,598 $ (5,965 ) States, municipalities and political subdivisions 16,349 (60 ) 37,340 (498 ) 53,689 (558 ) Mortgage-backed and asset-backed securities: Agency mortgage-backed securities 18,881 (80 ) 58,301 (918 ) 77,182 (998 ) Residential mortgage obligations 5,625 (50 ) 1,728 (88 ) 7,353 (138 ) Asset-backed securities 110,275 (539 ) 34,530 (425 ) 144,805 (964 ) Commercial mortgage-backed securities 19,741 (71 ) 1,391 (27 ) 21,132 (98 ) Subtotal $ 154,522 $ (740 ) $ 95,950 $ (1,458 ) $ 250,472 $ (2,198 ) Corporate bonds 190,461 (871 ) 31,126 (755 ) 221,587 (1,626 ) Total fixed maturities $ 449,247 $ (2,732 ) $ 282,099 $ (7,615 ) $ 731,346 $ (10,347 ) Equity securities 19,690 (1,297 ) 238 (7 ) 19,928 (1,304 ) Total fixed maturities and equity securities $ 468,937 $ (4,029 ) $ 282,337 $ (7,622 ) $ 751,274 $ (11,651 ) At December 31, 2015, there were 368 fixed maturities in an unrealized loss position, and there were 57 equity securities in an unrealized loss position. In the above table, the gross unrealized loss for the greater than 12 months category consists primarily of agency and foreign government bonds mostly due to an unfavorable foreign exchange movement in our Canadian portfolio. The gross unrealized loss for the less than 12 months category consists primarily of corporate bonds in the energy sector which have been impacted by recent declines in the oil market. To a lesser extent, losses on equity securities in the less than 12 month category have been impacted by recent volatility in the equity markets coupled with the timing of the purchases of certain equity securities. At December 31, 2014, there were 259 fixed maturities in an unrealized loss position, and there were 15 equity securities in an unrealized loss position. The gross unrealized loss for the greater than 12 months category consists primarily of Treasury and agency bonds, due to an increase in interest rates and unfavorable foreign exchange movement. As of December 31, 2015 and 2014, the largest unrealized loss by a non-government backed issuer in the investment portfolio was $2.6 million and $0.5 million, respectively. Our Company analyzes impaired securities quarterly to determine if any are other-than-temporary. The above securities with unrealized losses have been determined to be temporarily impaired based on our evaluation. For fixed maturities, when assessing whether the amortized cost basis of the security will be recovered, our Company compares the present value of cash flows expected to be collected in relation to the current book value. Any shortfalls of the present value of the cash flows expected to be collected to the amortized cost basis is considered the credit loss portion of OTTI losses and is recognized in earnings. All non-credit losses are recognized as changes in OTTI losses within AOCI. To determine whether the unrealized loss on structured securities is other-than-temporary, our Company analyzes the projections provided by our investment managers with respect to an expected principal loss under a range of scenarios and utilizes the most likely outcomes. The analysis relies on actual collateral performance measures such as default rate, prepayment rate and loss severity. These assumptions are applied throughout the remaining term of the deal, incorporating the transaction structure and priority of payments, to generate loss adjusted cash flows. Results of the analysis will indicate whether the security is expected ultimately to incur a loss or whether there is a material impact on yield due to either a projected loss or a change in cash flow timing. A break-even default rate is also calculated. A comparison of the break-even default rate to the actual default rate provides an indication of the level of cushion or coverage to the first dollar principal loss. The analysis applies the stated assumptions throughout the remaining term of the transaction to forecast cash flows, which are then applied through the transaction structure to determine whether there is a loss to the security. For securities in which a tranche loss is present and the net present value of loss adjusted cash flows is less than book value, impairment is recognized. The output data also includes a number of additional metrics such as average life remaining, original and current credit support, over 60 day delinquency and security rating. The significant inputs used to measure the amount of credit loss recognized in earnings were actual delinquency rates, default probability assumptions, severity assumptions and prepayment assumptions. Projected losses are a function of both loss severity and probability of default. Default probability and severity assumptions differ based on property type, vintage and the stress of the collateral. Our Company does not intend to sell, and it is more likely than not that it will not be required to sell, these securities before the recovery of the amortized cost basis. For equity securities, in general, our Company focuses our attention on those securities with a fair value less than 80% of their cost for six or more consecutive months. If warranted as the result of conditions relating to a particular security, our Company will focus on a significant decline in fair value regardless of the time period involved. Factors considered in evaluating potential impairment include, but are not limited to, the current fair value as compared to cost of the security, the length of time the investment has been below cost and by how much the investment is below cost. If an equity security is deemed to be other-than-temporarily impaired, the cost is written down to fair value with the loss recognized in earnings. Our Company’s ability to hold securities is supported by sufficient cash flow from our operations and from maturities within our investment portfolio in order to meet our claims payments and other disbursement obligations arising from our underwriting operations without selling such investments. With respect to securities where the decline in value is determined to be temporary and the security's value is not written down, a subsequent decision may be made to sell that security and realize a loss. Subsequent decisions on security sales are made within the context of overall risk monitoring, changing information and market conditions. Our Company had three credit related OTTI losses totalling $1.7 million during the year ended December 31, 2015 from our equity portfolio. Our Company did not have any credit related OTTI losses during the year ended December 31, 2014. During the year ended December 31, 2013, we recognized OTTI credit related losses of $2.4 million related to three equity securities and one municipal bond. The following table summarizes the cumulative amounts related to our Company’s credit loss portion of the OTTI losses on fixed maturities for the years ended December 31, 2015, 2014 and 2013. Our Company does not intend to sell, and it is more likely than not that we will not be required to sell, the securities prior to recovery of the amortized cost basis and for which the non-credit loss portion is included in AOCI. Years Ended December 31, amounts in thousands 2015 2014 2013 Beginning balance $ 2,361 $ 5,154 $ 3,332 Additions for credit loss impairments recognized in the current period on securities not previously impaired — — 1,822 Additions for credit loss impairments recognized in the current period on securities previously impaired — — — Reductions for credit loss impairments previously recognized on securities sold during the period — (2,793 ) — Ending balance $ 2,361 $ 2,361 $ 5,154 Our Company’s Net investment income was derived from the following sources: Years Ended December 31, amounts in thousands 2015 2014 2013 Fixed maturities $ 61,572 $ 57,219 $ 53,898 Equity securities 9,813 9,036 4,835 Short-term investments 683 911 774 Total investment income $ 72,068 $ 67,166 $ 59,507 Investment expenses (3,350 ) (2,998 ) (3,256 ) Net investment income $ 68,718 $ 64,168 $ 56,251 Realized gains and losses, excluding net OTTI losses recognized in earnings, for the periods indicated, were as follows: Years Ended December 31, amounts in thousands 2015 2014 2013 Fixed maturities: Gains $ 4,756 $ 8,326 $ 8,539 Losses (5,926 ) (2,610 ) (2,797 ) Fixed maturities, net $ (1,170 ) $ 5,716 $ 5,742 Short-term: Gains $ 130 $ — $ — Losses (383 ) — — Short-term, net $ (253 ) $ — $ — Equity securities: Gains $ 14,331 $ 9,447 $ 17,955 Losses (4,535 ) (2,351 ) (758 ) Equity securities, net $ 9,796 $ 7,096 $ 17,197 Net realized gains (losses) $ 8,373 $ 12,812 $ 22,939

Fair Value Measurement

Fair Value Measurement	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurement	NOTE 4. FAIR VALUE MEASUREMENT We obtain values for the majority of our investment securities from pricing services, however, it is ultimately our responsibility to determine whether the values obtained from these service providers are representative of fair value. To validate the techniques or models used by pricing sources, our review process includes, but is not limited to: (i) A review of the validity of the fair market valuation of individual securities deemed as outliers (i.e., vendor price differed significantly from other vendor prices), securities with significant price movements from previous months, securities with stale prices and securities with negative yields. (ii) A comparison of the tally of securities priced by certain vendors for significant movements in vendor CUSIP counts. (iii) A review of the results of back-testing, including the comparison of executed prices to the historical fair value estimates from the pricing service and documentation to support trades above certain variance thresholds. (iv) A review of the Statement on Standards for Attestation Engagements (“SSAE”) No.16 report of our outside investment managers for any exceptions. (v) Management also periodically independently prices the portfolio using alternative pricing vendors and investigates variances outside of the established thresholds. The fair value of our financial instruments is determined based on the following fair value hierarchy: Level 1 – Quoted prices for identical instruments in active markets. Examples are listed equity and fixed income securities traded on an exchange. U.S. Treasury securities are reported as Level 1 and are valued based on unadjusted quoted prices for identical assets in active markets that our Company can access. Level 2 – Quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs and significant value drivers are observable in active markets. Examples are asset-backed and mortgage-backed securities that are similar to other asset-backed or mortgage-backed securities observed in the market. U.S. government agency securities are reported as Level 2 and are valued using yields and spreads that are observable in active markets. Level 3 – Valuations derived from valuation techniques in which one or more significant inputs or significant value drivers are unobservable. An example would be a private placement with minimal liquidity. Fair value measurements are received from independent pricing service vendors, utilized by our outside investment manager whom we employ to assist us with investment accounting services. This manager utilizes a pricing committee, which oversees the use of one or more independent pricing service vendors. The pricing committee consists of five or more members of the investment management firm, one from senior management and one from the accounting group, with the remainder representing asset class specialists and client strategists. The pricing source for each security is determined in accordance with the pricing source procedures approved by the pricing committee. The investment manager receives supporting documentation from the independent pricing service vendor detailing the inputs, models and processes used in the vendors’ evaluation process to determine the appropriate fair value hierarchy. Any pricing where the input is believed to be unobservable is deemed to be a Level 3 price. Management has reviewed this process by which the manager determines the prices and has obtained alternative pricing to validate a sample of the prices and assess their reasonableness. The following tables present, for each of the fair value hierarchy levels as defined by the accounting guidance for fair value measurements and described below, our Company’s fixed maturities and equity securities by asset class that are measured at fair value on a recurring basis, as well as the fair value of the 5.75% Senior notes due October 15, 2023 (the “5.75% Senior notes”) carried at amortized cost as of December 31, 2015 and 2014: December 31, 2015 amounts in thousands Level 1 Level 2 Level 3 Total Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 67,394 $ 185,488 $ — $ 252,882 States, municipalities and political subdivisions — 576,859 — 576,859 Mortgage-backed and asset-backed securities: Agency mortgage-backed securities — 379,269 — 379,269 Residential mortgage obligations — 30,465 — 30,465 Asset-backed securities — 225,012 — 225,012 Commercial mortgage-backed securities — 189,713 — 189,713 Subtotal $ — $ 824,459 $ — $ 824,459 Corporate bonds — 760,010 — 760,010 Total fixed maturities $ 67,394 $ 2,346,816 $ — $ 2,414,210 Equity securities 126,455 178,816 — 305,271 Short-term investments 217,745 — — 217,745 Total assets measured at fair value $ 411,594 $ 2,525,632 $ — $ 2,937,226 Senior notes $ — $ 282,486 $ — $ 282,486 Total liabilities measured at fair value $ — $ 282,486 $ — $ 282,486 December 31, 2014 amounts in thousands Level 1 Level 2 Level 3 Total Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 146,904 $ 251,019 $ — $ 397,923 States, municipalities and political subdivisions — 541,007 — 541,007 Mortgage-backed and asset-backed securities: Agency mortgage-backed securities — 364,622 — 364,622 Residential mortgage obligations — 34,087 — 34,087 Asset-backed securities — 206,413 — 206,413 Commercial mortgage-backed securities — 206,318 — 206,318 Subtotal $ — $ 811,440 $ — $ 811,440 Corporate bonds — 615,564 — 615,564 Total fixed maturities $ 146,904 $ 2,219,030 $ — $ 2,365,934 Equity securities 127,183 57,112 — 184,295 Short-term investments 179,506 — — 179,506 Total assets measured at fair value $ 453,593 $ 2,276,142 $ — $ 2,729,735 Senior notes $ — $ 285,710 $ — $ 285,710 Total liabilities measured at fair value $ — $ 285,710 $ — $ 285,710 All other financial assets and liabilities including cash, premium receivables, reinsurance recoverables and reinsurance balance payables are carried at cost, which approximates fair value. Our Company did not have any significant transfers between the Level 1 and Level 2 classifications for the years ended December 31, 2015 and 2014. As of December 31, 2015 and 2014, our Company did not have any Level 3 assets. During 2014, one security was transferred from Level 3 to Level 2 as our Company was able to obtain a valuation in which all significant inputs to the model were observable in active markets.

Reserves for Losses and LAE

Reserves for Losses and LAE	12 Months Ended
	Dec. 31, 2015
Insurance [Abstract]
Reserves for Losses and LAE	NOTE 5. RESERVES FOR LOSSES AND LAE We establish reserves for the estimated unpaid ultimate liability for losses and LAE under the terms of our policies and agreements. The determination of reserves for losses and LAE is partially dependent upon the receipt of information from agents and brokers. Reserves include estimates for both claims that have been reported and for IBNR, and include estimates of expenses associated with processing and settling these claims. Reserves are recorded in Reserves for losses and LAE in the Consolidated Balance Sheets. Our estimates and judgments may be revised as additional experience and other data become available and are reviewed, as new or improved methodologies are developed, or as laws change. Frequency/severity analyses, are also performed for certain books of business. To the extent that reserves are found deficient or redundant, a strengthening or release is recognized as a charge or credit to earnings. The following table summarizes our Company’s Reserves for losses and LAE activity for the years ended December 31, 2015, 2014 and 2013: Years Ended December 31, amounts in thousands 2015 2014 2013 Net reserves for losses and LAE at beginning of year $ 1,308,136 $ 1,222,633 $ 1,216,909 Provision for losses and LAE for claims occurring in the current year 637,267 601,041 520,227 Increase (decrease) in estimated losses and LAE for claims occurring in prior years (64,669 ) (55,812 ) (1,266 ) Incurred losses and LAE $ 572,598 $ 545,229 $ 518,961 Losses and LAE paid for claims occurring during: Current year (159,802 ) (158,806 ) (147,864 ) Prior years (320,863 ) (295,527 ) (365,479 ) Losses and LAE payments $ (480,665 ) $ (454,333 ) $ (513,343 ) Foreign Currency Adjustment (6,943 ) (5,393 ) 106 Net reserves for losses and LAE at end of year 1,393,126 1,308,136 1,222,633 Reinsurance recoverables on unpaid losses and LAE 809,518 851,498 822,438 Gross reserves for losses and LAE at end of year $ 2,202,644 $ 2,159,634 $ 2,045,071 The reporting and operating segments breakdowns of prior period net reserve strengthening (releases) for the years ended December 31, 2015, 2014 and 2013 are as follows: Years Ended December 31, amounts in thousands 2015 2014 2013 U.S. Insurance Marine $ (24,825 ) $ (29,047 ) $ (13,679 ) P&C (706 ) 17,081 12,938 Professional Liability (3,788 ) (3,454 ) 11,777 Total $ (29,319 ) $ (15,420 ) $ 11,036 Int'l Insurance Marine (21,914 ) (31,677 ) (6,361 ) P&C (8,458 ) (3,829 ) (22,263 ) Professional Liability 4,156 (2,746 ) 1,289 Total $ (26,216 ) $ (38,252 ) $ (27,335 ) GlobalRe $ (9,134 ) $ (2,140 ) $ 15,033 Total strengthening (releases) $ (64,669 ) $ (55,812 ) $ (1,266 ) The following is a discussion of the relevant factors related to the prior period net reserve releases of $64.7 million recorded for the year ended December 31, 2015: U.S. Insurance reporting segment recorded prior period net reserve releases of $29.3 million. The drivers are as follows: · U.S. Marine operating segment recorded prior period net reserve releases of $24.8 million driven by favorable claims development in the Marine Liability, Inland Marine and Cargo products. · U.S. P&C operating segment recorded prior period net reserve releases of $0.7 million driven by ongoing favorable performance within our Excess Casualty, Environmental and Other P&C divisions, mostly offset by large loss activity within our Primary Casualty division. · U.S. Professional Liability operating segment recorded prior period net reserve releases of $3.8 million driven by favorable emergence in our E&O division, partially offset by unfavorable development in several large D&O claims Int’l Insurance reporting segment recorded prior period net reserve releases of $26.2 million. The drivers are as follows: · Int’l Marine operating segment recorded prior period net reserve releases of $21.9 million driven primarily due to favorable claims development on the Marine Liability, Protection and Indemnity and Specie products. · Int’l P&C operating segment recorded prior period net reserve releases of $8.5 million due to favorable claims development on the Offshore Energy product within the Energy & Engineering division. · Int’l Professional Liability operating segment recorded prior period net reserve strengthening of $4.2 million driven by adverse development in our D&O division related to two large losses, partially offset by favorable claims development on our E&O division. GlobalRe reporting segment recorded prior period net reserve releases of $9.1 million primarily driven by favorable loss development in our Marine, P&C and A&H products. The following is a discussion of relevant factors related to the prior period net reserve releases of $55.8 million recorded for the year ended December 31, 2014: U.S. Insurance reporting segment recorded prior period net reserve releases of $15.4 million. The drivers of these prior period net reserve releases by operating segment are as follows. · U.S. Marine operating segment recorded prior period net reserve releases of $29.0 million driven by favorable claims development on our Marine Liability, Craft, Fishing Vessels, Inland Marine, Hull and Cargo products. · U.S. P&C operating segment recorded prior period net reserve strengthening of $17.1 million driven by unfavorable activity on pre-2010 California construction defect liability claims in our Primary Casualty division, partially offset by reserve releases due to favorable loss emergence from our Excess Casualty division. · U.S. Professional Liability operating segment recorded prior period net reserve releases of $3.5 million driven primarily by favorable loss emergence from our D&O division due to a cash settlement of a contract dispute with a former third party administrator. Int’l Insurance reporting segment recorded prior period net reserve releases of $38.3 million. The drivers are as follows: · Int’l Marine operating segment recorded prior period net reserve releases of $31.7 million driven by favorable loss emergence across various products. · Int’l P&C operating segment recorded prior period net reserve releases of $3.8 million driven primarily by favorable claims development in our Energy & Engineering division. · Int’l Professional Liability operating segment recorded prior period net reserve releases of $2.7 million due to favorable loss emergence in our E&O and D&O divisions. GlobalRe reporting segment recorded prior period net reserve releases of $2.1 million driven by favorable claim development in our Marine product. The following is a discussion of relevant factors related to the prior period net reserve releases of $1.3 million recorded for the year ended December 31, 2013: U.S. Insurance reporting segment recorded prior period net reserve strengthening of $11.0 million. The drivers are as follows: · U.S. Marine operating segment recorded prior period net reserve releases of $13.7 million driven by favorable claims development on our Marine Liability product for underwriting years (“UWYs”) 2012 and prior. · U.S. P&C operating segment recorded prior period net reserve strengthening of $12.9 million primarily from our Primary Casualty division due to unfavorable claims activity. · U.S. Professional Liability operating segment recorded prior period net reserve strengthening of $11.8 million from our D&O division related to specific large claims for UWYs 2010 and prior, and additional reserve strengthening in our E&O division related to specific large claims from our Miscellaneous Professional Liability and Other E&O products from UWYs 2011 and prior. Int’l Insurance reporting segment recorded prior period net reserve releases of $27.3 million. The drivers are as follows: · Int’l Marine operating segment recorded prior period net reserve releases of $6.4 million driven primarily by favorable loss emergence in International Marine Liability. · Int’l P&C operating segment recorded prior period net reserve releases of $22.3 million driven primarily by favorable emergence on our Marine Liability product. · Int’l Professional Liability operating segment recorded prior period net reserve strengthening of $1.3 million from our E&O division, partially offset by reserve releases related to favorable activity in our D&O division. GlobalRe reporting segment recorded prior period net reserve strengthening of $15.0 million primarily due to worse than expected results within our A&H product in connection with UWYs 2012 and 2011 and to a lesser extent unfavorable loss emergence in our Marine product.

Ceded Reinsurance

Ceded Reinsurance	12 Months Ended
	Dec. 31, 2015
Insurance [Abstract]
Ceded Reinsurance	NOTE 6. CEDED REINSURANCE We utilize reinsurance principally to reduce our exposure on individual risks, to protect against catastrophic losses and to stabilize loss ratios and net underwriting results. Reinsurers are liable to us to the extent the risk is transferred or ceded to them. However, ceded reinsurance arrangements do not eliminate our obligation to pay claims to our policyholders. Accordingly, we bear credit risk with respect to our reinsurers. We are protected by various treaty and facultative reinsurance agreements. Our exposure to credit risk from any one reinsurer is managed through diversification of reinsurers, principally in the U.S. and European reinsurance markets. A reinsurer generally must have a rating from A.M. Best and/or S&P of “A” or better, or an equivalent financial strength if not rated, plus at least $500 million in policyholders’ surplus to meet our standards of acceptability. Our Reinsurance Security Committee, which is part of our Enterprise Risk Management Finance and Credit Sub-Committee, monitors the financial strength of our reinsurers and the related reinsurance recoverables and periodically reviews the list of acceptable reinsurers. The following table lists our Company’s 10 largest reinsurers measured by the amount of total reinsurance recoverables as of December 31, 2015, and the reinsurers’ ratings from A.M. Best and S&P: Reinsurance Recoverables Unearned Paid/Unpaid Collateral amounts in thousands Premium Losses Total (1) Held A.M. Best S&P National Indemnity Company $ 14,854 $ 118,337 $ 133,191 $ 7,198 A++ AA+ Everest Reinsurance Company 21,097 77,702 98,799 3,933 A+ A+ Swiss Reinsurance America Corporation 25,564 63,081 88,645 7,814 A+ AA- Transatlantic Reinsurance Company 9,267 62,402 71,669 1,783 A A+ Munich Reinsurance America Inc. 9,051 51,795 60,846 1,577 A+ AA- Allied World Reinsurance 7,177 38,343 45,520 1,012 A A Employers Mutual Casualty Company 10,775 28,321 39,096 4,015 A NR Ace Property and Casualty Insurance Company 12,577 21,470 34,047 3,284 A++ AA Partner Reinsurance Europe 11,231 21,728 32,959 17,619 A A+ National Union Fire Ins. 7,478 22,288 29,766 5,717 A A+ Top 10 $ 129,071 $ 505,467 $ 634,538 $ 53,952 Others 103,517 353,557 457,074 105,618 Total $ 232,588 $ 859,024 $ 1,091,612 $ 159,570 (1) - Net of reserve for uncollectible reinsurance of approximately $6.9 million. We have established reserves for uncollectible reinsurance in the amounts of $6.9 million and $11.3 million as of December 31, 2015 and 2014, respectively. This reserve is determined by reinsurer specific default risk as indicated by their financial strength ratings as well as additional default risk for asbestos and environmental related recoverables. Actual uncollectible reinsurance could exceed or be less than our reserve balance. Our Company holds collateral of $159.6 million, which consists of $107.4 million in ceded balances payable, $45.8 million in letters of credit and $6.4 million of funds held and trust account balances. NIC and NSIC are required to collateralize reinsurance obligations due to us from reinsurers not authorized by their respective states of domicile. The following table summarizes the components of Net written premium: Years Ended December 31, amounts in thousands 2015 2014 2013 Direct $ 1,277,728 $ 1,232,012 $ 1,177,483 Assumed 175,774 200,341 193,034 Ceded (409,642 ) (432,215 ) (482,595 ) Net written premiums $ 1,043,860 $ 1,000,138 $ 887,922 The following table summarizes the components of Net earned premium: Years Ended December 31, amounts in thousands 2015 2014 2013 Direct $ 1,223,840 $ 1,183,120 $ 1,121,198 Assumed 175,153 193,431 176,726 Ceded (414,906 ) (440,656 ) (455,985 ) Net earned premiums $ 984,087 $ 935,895 $ 841,939 The following table summarizes the components of Net losses and LAE incurred: Years Ended December 31, amounts in thousands 2015 2014 2013 Direct $ 703,361 $ 657,059 $ 574,020 Assumed 97,947 118,352 133,674 Ceded (228,710 ) (230,182 ) (188,733 ) Net losses and LAE $ 572,598 $ 545,229 $ 518,961

Debt

Debt	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Debt	NOTE 7. DEBT Credit Facilities On November 6, 2014, NUAL entered into a credit facility for 8.0 million Australian Dollars with Barclays Bank PLC. Interest is payable under this facility at a rate of 2.0% per annum above a floating rate tied to the average mid-rate for Australian bills of exchange administered by the Australian Financial Markets Association. The facility may be cancelled by either party after providing written notice. This credit facility contains customary covenants for facilities of this type, including a restriction on future encumbrances that are outside the ordinary course of business, and a requirement to maintain at least £75.0 million of FAL. As of December 31, 2015, letters of credit with an aggregate face amount of 8.0 million Australian Dollars were outstanding under the credit facility, and our Company was in compliance with all covenants. On November 24, 2014, our Company entered into a $175.0 million credit facility agreement with ING Bank N.V., London Branch, individually and as Administrative Agent and a syndicate of lenders, which is secured by all the common stock of NIC and requires our Company to maintain at least 40.0% of the outstanding amounts under such facility as FAL. In addition, in order to support the increased underwriting capacity of the Syndicate for the 2016 UWY, our Company entered into a $25.0 million credit facility with ING Bank N.V., London Branch on November 20, 2015. Both of these facilities, as well as the November 6, 2014 facility, are used to fund underwriting obligations at Lloyd’s for the 2016 UWY, as well as open prior UWYs. The November 20, 2015 credit facility is a non-committed facility which has an applicable fee rate ranging from 0.85% to 1.20% per annum based upon our Company’s S&P rating. For the November 24, 2014 credit facility the applicable fee rate payable ranges from 0.95% to 1.60% per annum based on a tiered schedule that is based on our Company’s then-current financial strength ratings issued by S&P and A.M. Best and the amount of our Company’s own collateral utilized to fund its participation in the Syndicate. The letters of credit issued under both of these facilities can be denominated in GBP and their aggregate face amount will fluctuate based on exchange rates. If any letters of credit remain outstanding under these facilities after December 31, 2016, our Company would be required to post additional collateral to secure the remaining letters of credit. As of December 31, 2015, letters of credit with an aggregate face amount of $20.0 million and $175.0 million were outstanding under the November 20, 2015 and November 24, 2014 credit facilities, respectively, and our Company had an aggregate of $3.3 million of cash collateral posted. Each of the November 20, 2015 and November 24, 2014 credit facilities contains customary covenants for facilities of this type, including restrictions on indebtedness and liens, limitations on mergers, dividends and the sale of assets, and requirements as to maintaining certain consolidated tangible net worth, statutory surplus and other financial ratios. These credit facilities also provide for customary events of default, including failure to pay principal, interest or fees when due, failure to comply with covenants, any representation or warranty made by our Company being false in any material respect, default under certain other indebtedness, certain insolvency or receivership events affecting our Company, the occurrence of certain material judgments, or a change in control of our Company. As of December 31, 2015, our Company was in compliance with all covenants. Senior notes On October 4, 2013, our Company completed a public debt offering of $265.0 million principal amount of the 5.75% Senior notes and received net proceeds of $263.0 million. Our Company used a portion of the proceeds for the redemption of the 7.0% Senior notes due May 1, 2016 (“7.0% Senior notes”), as well as a $17.9 million call premium in connection with the redemption of the 7.0% Senior notes. The unamortized discount as of December 31, 2015 and 2014 was $1.4 million and $1.6 million, respectively. The interest rate payable on the 5.75% Senior notes is subject to a tiered adjustment based on defined changes in our Company’s debt ratings. Our Company may redeem the 5.75% Senior notes in whole at any time or in part from time to time at a make-whole redemption price. The 5.75% Senior notes are our Company’s only senior unsecured obligation and will rank equally with future senior unsecured indebtedness. The terms of the 5.75% Senior notes contain various restrictive business and financial covenants, including a restriction on indebtedness, and other restrictions typical for debt obligations of this type, including limitations on mergers, liens and dispositions of the Common stock of certain subsidiaries. As of December 31, 2015, our Company was in compliance with all such covenants.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	NOTE 8. COMMITMENT AND CONTINGENCIES Future minimum annual rental commitments as of December 31, 2015 under various non-cancellable operating leases for our office facilities, which expire at various dates through 2030, are as follows: Rental Commitments for Years Ended December 31, amounts in thousands 2016 $ 12,769 2017 12,213 2018 10,327 2019 8,482 2020 8,313 2021-2030 42,173 Total minimum operating lease payments $ 94,277 We are also liable for additional payments to the landlords for certain annual cost increases. Rent expense for the years ended December 31, 2015, 2014 and 2013 was $12.9 million, $13.2 million and $11.5 million, respectively. In 2013, the State of Connecticut (“the State”) awarded our Company up to $11.5 million ($8.0 million in loans and $3.5 million in grants) to move our corporate headquarters to Stamford, Connecticut. The loan is non-interest bearing, has a term of 10 years and is subject to forgiveness based on our compliance with certain conditions set forth in the agreement with the State. The amount of the loan to be received is dependent on our Company reaching certain milestones for creation of new jobs over a five-year period, and the funds are to be used to offset certain equipment purchases, facility costs, training of employees and other eligible project-related costs. Our Company completed the move to Stamford in September 2013 and received $7.5 million of the award, which is comprised of $6.0 million of the loan and $1.5 million of the grant for reaching the first job milestone. Under the terms of the agreement with the State, if our Company maintains an average of 100 full-time employees in Connecticut over a 12-month period, the State will forgive the initial $6.0 million of the loan. In addition, as soon as our Company achieves a total of 150 full-time employees in Connecticut, we are eligible to receive an additional $1.0 million of the loan and $0.5 million of the grant. On October 20, 2015, our Company received a letter from the State determining that we had achieved both of these milestones for the period starting September 30, 2013 through July 31, 2015. As a result, our Company earned a loan forgiveness credit of $6.0 million with the State and received the additional $1.0 million of the loan and $0.5 million of the grant. Earning of the remaining portions of the grant and forgiveness of any outstanding amounts of the loan is subject to certain conditions, including maintaining the required jobs for an extended period of time. The length of time commitment for forgiveness of the additional $1.0 million of the October 20, 2015 loan has not been met. However, our Company expects to meet all the conditions for the State to forgive the loan. Accordingly, our Company is recognizing the amount of loan and grants received over the period in which offsetting expenses are recognized. Our Company recognized $1.4 million, $1.1 million and $0.3 million for the years ended December 31, 2015, 2014 and 2013. As of December 31, 2015 and December 31, 2014, our Company has deferred revenue of $6.3 million and $6.1 million, respectively, which is included in other liabilities and accounts payable on the Consolidated Balance Sheets. In the ordinary course of conducting business, our Parent Company’s subsidiaries are involved in various legal proceedings. Most of these proceedings consist of claims litigation involving our Parent Company’s subsidiaries as either: (a) liability insurers defending or providing indemnity for third party claims brought against insureds or (b) insurers defending first party coverage claims brought against them. In general, our Company believes we have valid defenses to these cases. Our Company’s management believes that the ultimate liability, if any, with respect to these legal proceedings, after consideration of provisions made for potential losses and cost of defense, will not be material to our Company’s Consolidated Balance Sheets, Statements of Income and Statements of Cash Flows.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 9. INCOME TAXES Our Company is subject to the tax laws and regulations of the U.S. and the foreign countries in which it operates. Our Company files a consolidated U.S. Federal tax return, which includes all domestic subsidiaries and the U.K. Branch. The income from the foreign operations is designated as either U.S. connected income or non-U.S. connected income. Lloyd’s is required to pay U.S. income tax on U.S. connected income written by Lloyd’s syndicates. Lloyd’s and the Internal Revenue Service (“IRS”) have entered into an agreement whereby the amount of tax due on U.S. connected income is calculated by Lloyd’s and remitted directly to the IRS. These amounts are then charged to the corporate member in proportion to its participation in the relevant syndicates. Our Company’s corporate member is subject to this agreement and receives U.K. tax credits in the U.K. for any U.S. income tax incurred up to the U.K. income tax charged on the U.S. connected income. The non-U.S. connected insurance income would generally constitute taxable income under the Subpart F income section of the U.S. Internal Revenue Code (“Subpart F”) since less than 50% of the Syndicate’s premiums are derived within the U.K. and would therefore be subject to U.S. taxation when the Lloyd’s year of account closes. Taxes are accrued at a 35% rate on our Company’s foreign source insurance income and foreign tax credits, where available, are utilized to offset U.S. tax as permitted. Our Company’s effective tax rate for the Syndicate taxable income could substantially exceed 35% to the extent our Company is unable to offset U.S. taxes paid under Subpart F tax regulations with U.K. tax credits on future underwriting year distributions. U.S. taxes are not accrued on the earnings of our Company’s foreign agencies as these earnings are subject to the active financing exception and are not includable as Subpart F income. The components of current and deferred income tax expense (benefit) are as follows: Years Ended December 31, amounts in thousands 2015 2014 2013 Current income tax expense (benefit): Federal and foreign $ 27,937 $ 27,290 $ 23,703 State and local 1,476 1,036 446 Subtotal $ 29,413 $ 28,326 $ 24,149 Deferred income tax expense (benefit): Federal and foreign 7,004 16,881 4,658 State and local — — — Subtotal $ 7,004 $ 16,881 $ 4,658 Total income tax expense (benefit) $ 36,417 $ 45,207 $ 28,807 A reconciliation of total income taxes applicable to pre‑tax operating income and the amounts computed by applying the federal statutory income tax rate to the pre‑tax operating income were as follows: Years Ended December 31, amounts in thousands 2015 2014 2013 Computed expected tax expense $ 41,116 35.0 % $ 49,187 35.0 % $ 32,299 35.0 % Tax-exempt interest (4,987 ) -4.2 % (4,771 ) -3.4 % (3,839 ) -4.2 % Dividends received deduction (2,086 ) -1.8 % (1,257 ) -0.9 % (897 ) -1.0 % Proration of DRD and Tax-exempt interest 1,061 0.9 % 904 0.6 % 710 0.8 % Current state and local income taxes, net of federal income tax deduction 959 0.8 % 674 0.5 % 290 0.3 % Other 354 0.3 % 470 0.4 % 244 0.3 % Actual tax expense and rate $ 36,417 31.0 % $ 45,207 32.2 % $ 28,807 31.2 % The tax effects of cumulative temporary differences that give rise to federal, foreign, state and local deferred tax assets and deferred tax liabilities were as follows: December 31, amounts in thousands 2015 2014 Deferred tax assets: Loss reserve discount $ 25,353 $ 24,820 Unearned premiums 31,486 29,080 Compensation related 11,175 10,586 State and local net deferred tax assets 721 777 Other 4,315 3,732 Total gross deferred tax assets 73,050 68,995 Less: Valuation allowance (721 ) (777 ) Total deferred tax assets $ 72,329 $ 68,218 Deferred tax liabilities: Net unrealized gains/ losses on securities (13,053 ) (26,730 ) Deferred acquisition costs (24,037 ) (22,120 ) Lloyd's year of account deferral (24,466 ) (13,578 ) Net unrealized foreign exchange (4,164 ) (4,470 ) Other (2,709 ) (2,787 ) Total deferred tax liabilities $ (68,429 ) $ (69,685 ) Net deferred income tax asset (liability) $ 3,900 $ (1,467 ) Our Company has not provided for U.S. income taxes on approximately $21.5 million of undistributed earnings of our non-U.S. subsidiaries since it is intended that those earnings will be reinvested indefinitely in those subsidiaries. If a future determination is made that those earnings no longer are intended to be reinvested indefinitely in those subsidiaries, U.S. income taxes of approximately $2.5 million, assuming all foreign tax credits are realized, would be included in the tax provision at that time and would be payable if those earnings were distributed to our Company. Unrecognized tax benefits are differences between tax positions taken in the tax returns and benefits recognized in the financial statements. Our Company has no unrecognized tax benefits as of December 31, 2015, 2014 and 2013. Our Company did not incur any interest or penalties related to unrecognized tax benefits for the years ended December 31, 2015, 2014 and 2013. Our Company currently is under examination by the IRS for taxable years 2010, 2011 and 2012 and generally is subject to U.S. Federal, state or local or foreign tax examinations by tax authorities for 2009 and subsequent years. Our Company recorded income tax expense of $36.4 million for the year ended December 31, 2015 compared to $45.2 million and $28.8 million for the same periods in 2014 and 2013, respectively; resulting in an effective tax rate of 31.0%, 32.2% and 31.2% for the years ended December 31, 2015, 2014 and 2013, respectively. Our Company had state and local deferred tax assets amounting to potential future tax benefits of $0.7 million and $0.8 million as of December 31, 2015 and 2014, respectively. Included in the deferred tax assets are minimal state and local net operating loss carry-forwards. A valuation allowance was established for the full amount of these potential future tax benefits due to the uncertainty associated with their realization. Our Company’s state and local tax carry-forwards as of December 31, 2015 expire from 2025 to 2033. In assessing the realization of deferred tax assets, management considers whether it is more likely than not that, the deferred tax assets will be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considers the scheduled reversal of deferred tax liabilities, tax planning strategies and anticipated future taxable income in making this assessment and believes it is more likely than not that our Company will realize the benefits of its deductible differences as of December 31, 2015, net of any valuation allowance.

Stockholders Equity

Stockholders Equity	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
STOCKHOLDERS’ EQUITY	NOTE 10. STOCKHOLDERS’ EQUITY Our authorized share capital consists of 50,000,000 common shares with a par value of $0.10 per share and 1,000,000 preferred shares with a par value of $0.10 per share. Our Company has not issued any preferred shares as of December 31, 2015. The following table represents changes in our Company’s issued and outstanding common shares for the periods indicated: Years Ended December 31, amounts in thousands 2015 2014 2013 Beginning balance 14,281 14,198 14,047 Vested stock grants 127 59 50 Employee stock purchase plan 21 19 17 Stock options exercised 2 5 84 Treasury shares purchased — — — Ending balance 14,431 14,281 14,198 Our Parent Company has not paid or declared any cash dividends on Common stock. Declarations of cash dividends are at the discretion of our Board of Directors. The amounts of such dividends will be dependent upon factors such as, our results of operations and cash flow, financial condition and business needs, restrictive covenants under our credit facility and senior notes that require us to maintain certain consolidated tangible net worth, the capital and surplus requirements of our subsidiaries, and applicable insurance regulations that limit the amount of dividends that may be paid by our regulated insurance subsidiaries. NIC may pay dividends to our Parent Company out of its statutory earned surplus pursuant to statutory restrictions imposed under the New York insurance law. As of December 31, 2015, the maximum amount available for the payment of dividends by NIC without prior regulatory approval is $94.9 million. NIC did not pay any dividends to our Parent Company in 2015 or 2014. NCUL may pay dividends to our Parent Company up to the extent of available profits that have been distributed from the Syndicate. The Syndicate’s capital and surplus as filed with Lloyd’s consists of undistributed profits on closed and open UWYs. In connection with the business plan approved in November 2015, NCUL posted all of the available undistributed profits on closed years of $156.7 million to support a portion of the FAL requirement and therefore that amount is not available for distribution to NCUL, which ultimately is not available to our Parent in the form of a dividend. As of December 31, 2015, NCUL has the ability to pay dividends of up to $1.1 million, consisting of undistributed profits on closed and open UWYs from the Syndicate, to the Parent in the form of dividends. The amount and nature of net assets that are restricted from payment of dividends as of December 31, 2015 and 2014 are presented in the following table: As of December 31, amounts in thousands 2015 2014 Restricted net assets: NIC and NSIC: Fixed maturities at fair value (amortized cost: 2015, $9,950; 2014, $10,086) $ 11,277 $ 11,732 Short term investments, at fair value 290 290 Cash 6,208 1,212 Total NIC and NSIC (1) $ 17,775 $ 13,234 NHUK: Fixed maturities at fair value (amortized cost: 2015, $458,558; 2014, $445,504) $ 448,666 $ 447,679 Short term investments, at fair value 71,320 61,549 Cash 3,262 963 Total NHUK (2) $ 523,248 $ 510,191 Total Restricted Net Assets $ 541,023 $ 523,425 (1) - The restricted net assets for NIC and NSIC primarily consist of fixed maturities on deposit with various state insurance departments. The cash as of December 31, 2015 and 2014, as presented in the table above, was on deposit with a U.K. bank to comply with the regulatory requirements of the Prudential Regulation Authority for the underwriting activities of the U.K. Branch. (2) - The restricted net assets for NHUK consists of fixed maturities and cash held in trust for the benefit of syndicate policyholders and short term investments primarily consisting of overseas deposits in various countries with Lloyd's to support underwriting activities in those countries.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Earnings Per Share	NOTE 11. EARNINGS PER SHARE The following is a reconciliation of the basic and diluted EPS computations for the years ended December 31, 2015, 2014 and 2013: Years Ended December 31, amounts in thousands, except share and per share amounts 2015 2014 2013 Net income $ 81,057 $ 95,329 $ 63,466 Basic weighted average shares 14,392,522 14,259,768 14,133,925 Effect of common stock equivalents: Assumed exercise of stock options and vesting of stock 433,223 386,601 211,628 Diluted weighted average shares 14,825,745 14,646,369 14,345,553 Net income per common share: Basic $ 5.63 $ 6.69 $ 4.49 Diluted $ 5.47 $ 6.51 $ 4.42

Statutory Financial Information

Statutory Financial Information	12 Months Ended
	Dec. 31, 2015
Text Block [Abstract]
Statutory Financial Information	NOTE 12. STATUTORY FINANCIAL INFORMATION The following table presents statutory Net income and capital and surplus in accordance with statutory accounting practices: Years Ended December 31, amounts in millions 2015 2014 2013 NIC & NSIC: Statutory net income $ 60.8 $ 75.7 $ 59.4 Statutory capital and surplus $ 949.1 $ 893.9 $ 804.1 The Syndicate: Syndicate's net income $ 41.0 $ 33.8 $ 21.0 Syndicate's capital and surplus $ 177.5 $ 140.1 $ 124.2 Our insurance subsidiaries file financial statements prepared in accordance with statutory accounting practices prescribed or permitted by domestic and foreign insurance regulatory authorities. The differences between statutory financial statements and financial statements prepared in accordance with U.S. GAAP vary between domestic and foreign jurisdictions. For NIC and NSIC, the National Association of Insurance Commissioners (“NAIC”) has codified Statutory Accounting Practices and Procedures (“SAP”) for insurance enterprises. We prepare our statutory basis financial statements in accordance with the most recently updated NAIC SAP manual subject to any deviations prescribed or permitted by the New York Insurance Commissioner. The following table represents some of the significant differences between SAP and U.S. GAAP as they relate to our operations: Differences SAP U.S. GAAP Acquisition and Commission Costs Expensed when incurred Costs are generally deferred Bonds Generally stated at amortized cost Stated at fair value Deferred tax assets Certain temporary differences are not admitted All temporary differences recognized Receivables over 90 days outstanding and other intangible assets Not recognized Generally recognized (subject to valuation allowances) Unearned premiums and loss reserves Net of ceded amounts Gross of ceded amounts The Syndicate is subject to oversight by the Council of Lloyd’s. Lloyd’s as a whole is authorized and regulated by the PRA. Our other international businesses are also regulated by the PRA. The following table represents some of the significant differences between U.K. GAAP and U.S. GAAP as they relate to our operations: Differences U.K. GAAP U.S. GAAP Unrealized gains/losses Recognized in income Recognized in AOCI Foreign exchange gains/losses on translation Recognized in income Recognized in AOCI Lloyd’s membership costs Expensed when incurred Amortized over each UWY Refer to Note 1, Organization and Summary of Significant Accounting Policies For NIC and NSIC, aggregate minimum required statutory capital and surplus is based on the greater of the risk-based capital level that would trigger regulatory action or minimum requirements per state insurance regulation. Capital and surplus requirements of our foreign subsidiaries differ from those prescribed in the U.S. and vary by jurisdiction. The capital requirement of the Syndicate, known as FAL, is currently calculated using the internal Lloyd’s risk-based capital model. The FAL may be comprised of cash, investments and undrawn letters of credit provided by various banks. Lloyd’s sets the corporate member’s required capital annually based on the Syndicate business plans, rating environment, reserving environment and input arising from Lloyd’s discussions with regulatory and rating agencies. As of December 31, 2015 and 2014, all insurance subsidiaries individually exceed the minimum required statutory capital and surplus requirements and all U.S. domestic insurance subsidiaries individually exceeded risk-based capital minimum requirements.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	NOTE 13. STOCK-BASED COMPENSATION In April 2013, the stockholders further amended and restated the 2005 Stock Incentive Plan increasing the available number of restricted shares from 1,500,000 to 2,000,000. As of December 31, 2015, 1,435,308 of such awards were issued leaving 564,692 awards available to be issued in subsequent periods. Stock-based compensation granted under our Company’s stock plans is expensed in tranches over the vesting period. Options and non-performance based grants generally vest equally over a three or four year period and the options have a maximum term of ten years. Our Company’s performance based share grants generally consist of three types of awards. The performance units issued in 2015 and 2014 will cliff vest on the third anniversary of the date of the grant with 100% dependence on the rate of cumulative annual growth in tangible book value for the three years immediately prior to the vesting date, with actual shares that vest ranging between 150% to 50% of that portion of the original award. The performance units issued between 2011 - 2013 will have cliff vested on the third anniversary of the date of grant, with 50% vesting in full, and 50% dependent on the rate of compound annual growth in book value per share for the three years immediately prior to the vesting date, with actual shares that vest ranging between 150% to 0% of that portion of the original award. Unvested restricted stock units and performance units outstanding as of December 31, 2015, 2014 and 2013, and changes during the years ended on those dates, are presented in the following table: December 31, 2015 2014 2013 Beginning balance 718,892 626,812 587,629 Granted - Performance 185,050 228,607 114,463 Granted - Non Performance 32,158 59,523 155,463 Total Granted 217,208 288,130 269,926 Vested - Performance Earned — — (15,714 ) Vested - Performance Unearned (68,080 ) (93,453 ) (57,585 ) Vested - Non Performance (135,600 ) (90,263 ) (60,183 ) Total Vested (203,680 ) (183,716 ) (133,482 ) Forfeited (35,905 ) (12,334 ) (97,261 ) Ending balance 696,515 718,892 626,812 As of December 31, 2015 and 2014, the total unrecognized compensation expense, net of estimated forfeitures, related to unvested stock units was $17.3 million and $16.3 million, respectively, which is expected to be recognized as expense over weighted average periods of 2.0 years and 2.3 years, respectively. The aggregate fair value of all unvested restricted stock units as of December 31, 2015 and 2014 was $55.2 million and $46.1 million, respectively. Stock options outstanding as of December 31, 2015, 2014 and 2013 are as follows: December 31, 2015 2014 2013 Average Average Average # of Shares Exercise Price # of Shares Exercise Price # of Shares Exercise Price Beginning balance 1,500 $ 36.03 6,750 $ 30.65 90,250 $ 29.94 Granted — — — — — — Exercised (1,500 ) $ 36.03 (5,250 ) $ 29.11 (83,500 ) $ 29.88 Expired or forfeited — — — — — — Ending balance — $ — 1,500 $ 36.03 6,750 $ 30.65 Number of options exercisable — $ — 1,500 $ 36.03 6,750 $ 30.65 We offer an Employee Stock Purchase Plan (the “ESPP”) to all of our eligible employees. Employees are offered the opportunity to purchase our Company’s Common stock at 90% of fair market value at the lower of the price at the beginning or the end of each six month offering period. Each employee can invest up to 10% of their base compensation subject to the lesser of 1,000 common stock shares or total market value of $25,000. There were 20,857 shares purchased in 2015 from funds withheld during the July 1, 2014 to December 31, 2014 and January 1, 2015 to June 30, 2015 offering periods. There were 19,386 shares purchased in 2014 in the aggregate from funds withheld during the offering periods of July 1, 2013 to December 31, 2013 and January 1, 2014 to June 30, 2014. We expense both the value of the 10% discount and the “look-back” option, which provides for the more favorable price at either the beginning or end of the offering period.

Retirement Plans

Retirement Plans	12 Months Ended
	Dec. 31, 2015
Compensation And Retirement Disclosure [Abstract]
Retirement Plans	NOTE 14. RETIREMENT PLANS We have a 401(k) Plan for all U.S. eligible employees. Each eligible employee can contribute a portion of their salary, limited by certain Federal regulations. The expense recorded for all contributions to the 401(k) Plan for the year ended December 31, 2015 was $6.3 million, consisting of $3.8 million for the retirement savings contributions and $2.5 million for the non-discretionary matching contributions. The expense recorded for all contributions to the 401(k) Plan for the year ended December 31, 2014 was $7.5 million, consisting of $3.8 million for the retirement savings contributions, $2.1 million for the non-discretionary matching contributions and $1.6 million for the discretionary matching contribution. The expense recorded for all contributions to the 401(k) Plan for the year ended December 31, 2013 was $5.1 million, consisting of $2.7 million for the retirement savings contributions, $1.6 million for the non-discretionary matching contributions and $0.8 million for the discretionary matching contribution. Our Company sponsors a defined contribution plan for all of our Company’s U.K. employees under U.K. regulations. Contributions, which are fully vested when made, are equal to 15.0% of each eligible employee’s gross base salary for all U.K. employees hired prior to November 2014 and 12.0% for all employees hired after November 2014. The expense recorded for the U.K. defined contribution plan was $2.9 million, $2.6 million and $2.2 million for the years ended December 31, 2015, 2014 and 2013, respectively. Our Company sponsors defined contribution plans for employees in several of our other European offices, outside of the U.K., under each countries’ regulations. Contributions, which are fully vested when made, range by European office between 2.1 26.0 0.5 0.2 0.3 Such expenses are included in Other operating expenses.

Quarterly Financial Data (Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data (Unaudited)	NOTE 15. QUARTERLY FINANCIAL DATA (Unaudited) The following is a summary of quarterly financial data for the periods indicated: March 31, June 30, September December 31, amounts in thousands, except per share amounts 2015 2015 2015 2015 Gross written premiums $ 396,460 $ 379,471 $ 354,062 $ 323,509 Revenues: Net written premiums $ 288,958 $ 258,244 $ 251,939 $ 244,719 Change in unearned premiums (52,826 ) (15,916 ) 2,143 6,826 Net earned premiums $ 236,132 $ 242,328 $ 254,082 $ 251,545 Net investment income 16,253 16,595 17,371 18,499 Total other-than-temporary impairment losses — (423 ) (1,298 ) (123 ) Portion of loss recognized in other comprehensive income (before tax) — — 23 123 Net other-than-temporary impairment losses recognized in earnings — (423 ) (1,275 ) — Net realized gains (losses) 5,596 4,339 518 (2,080 ) Other income (expense) 2,242 (4,362 ) (2,518 ) 4,147 Total revenues $ 260,223 $ 258,477 $ 268,178 $ 272,111 Expenses: Net losses and LAE $ 130,198 $ 141,973 $ 146,546 $ 153,881 Commission expenses 32,905 31,480 34,253 31,339 Other operating expenses 54,909 52,789 56,599 59,219 Interest expense 3,855 3,856 3,856 3,857 Total expenses $ 221,867 $ 230,098 $ 241,254 $ 248,296 Income before income taxes 38,356 28,379 26,924 23,815 Income tax expense $ 12,427 $ 9,195 $ 8,723 $ 6,072 Net income $ 25,929 $ 19,184 $ 18,201 $ 17,743 Comprehensive income (loss) $ 27,052 $ (3,789 ) $ 18,849 $ 15,990 Combined ratio 92.3 % 93.4 % 93.4 % 97.2 % Net income per share: Basic $ 1.81 $ 1.33 $ 1.26 $ 1.23 Diluted $ 1.77 $ 1.30 $ 1.23 $ 1.19 March 31, June 30, September 30, December 31, amounts in thousands, except per share amounts 2014 2014 2014 2014 Gross written premiums $ 422,790 $ 348,795 $ 327,469 $ 333,299 Revenues: Net written premiums $ 311,850 $ 231,864 $ 228,417 $ 228,007 Change in unearned premiums (86,578 ) (780 ) 16,950 6,165 Net earned premiums $ 225,272 $ 231,084 $ 245,367 $ 234,172 Net investment income 16,610 15,648 15,839 16,071 Total other-than-temporary impairment losses — — 158 (21 ) Portion of loss recognized in other comprehensive income (before tax) — — (158 ) 21 Net other-than-temporary impairment losses recognized in earnings — — — — Net realized gains 833 4,473 6,718 788 Other income (expense) 10,399 (1,665 ) 1,336 586 Total revenues $ 253,114 $ 249,540 $ 269,260 $ 251,617 Expenses: Net losses and LAE $ 135,067 $ 140,220 $ 135,284 $ 134,658 Commission expenses 25,727 32,150 33,943 33,708 Other operating expenses 47,146 47,992 50,388 51,299 Interest expense 3,852 4,319 3,388 3,854 Total expenses $ 211,792 $ 224,681 $ 223,003 $ 223,519 Income before income taxes 41,322 24,859 46,257 28,098 Income tax expense $ 13,354 $ 7,998 $ 15,032 $ 8,823 Net income $ 27,968 $ 16,861 $ 31,225 $ 19,275 Comprehensive income $ 32,920 $ 32,965 $ 20,628 $ 27,015 Combined ratio 92.2 % 95.3 % 89.5 % 93.8 % Net income per share: Basic $ 1.96 $ 1.18 $ 2.19 $ 1.35 Diluted $ 1.94 $ 1.17 $ 2.14 $ 1.31

Summary of Consolidated Investm

Summary of Consolidated Investments-Other Than Investments in Related Parties	12 Months Ended
	Dec. 31, 2015
Summary Of Investments Other Than Investments In Related Parties [Abstract]
Summary of Consolidated Investments-Other Than Investments in Related Parties	THE NAVIGATORS GROUP, INC. AND SUBSIDIARIES Summary of Consolidated Investments - Other than Investments in Related Parties December 31, 2015 Gross Gross Unrealized Unrealized Amortized amounts in thousands Fair Value Gains Losses Cost Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 252,882 $ 2,273 $ (9,214 ) $ 259,823 States, municipalities and political subdivisions 576,859 21,233 (781 ) 556,407 Mortgage-backed and asset-backed securities: Agency mortgage-backed securities 379,269 5,573 (2,082 ) 375,778 Residential mortgage obligations 30,465 694 (82 ) 29,853 Asset-backed securities 225,012 85 (1,624 ) 226,551 Commercial mortgage-backed securities 189,713 3,119 (1,864 ) 188,458 Subtotal $ 824,459 $ 9,471 $ (5,652 ) $ 820,640 Corporate bonds 760,010 7,373 (10,738 ) 763,375 Total fixed maturities $ 2,414,210 $ 40,350 $ (26,385 ) $ 2,400,245 Equity securities 305,271 26,341 (3,013 ) 281,943 Short-term investments 217,745 2 — 217,743 Total investments $ 2,937,226 $ 66,693 $ (29,398 ) $ 2,899,931

Condensed Financial Information

Condensed Financial Information of Registrant	12 Months Ended
	Dec. 31, 2015
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]
Condensed Financial Information of Registrant	THE NAVIGATORS GROUP, INC. AND SUBSIDIARIES Condensed Financial Information of Registrant The Navigators Group, Inc. Balance Sheets (Parent Company) December 31, amounts in thousands except share amounts 2015 2014 ASSETS Investments $ 89,586 $ 94,732 Cash 6,417 6,300 Investments in subsidiaries 1,232,012 1,163,822 Goodwill and other intangible assets 2,534 2,534 Other assets 33,647 27,531 Total assets $ 1,364,196 $ 1,294,919 LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities: Senior notes $ 263,580 $ 263,440 Accounts payable and other liabilities 1,294 1,081 Accrued interest payable 3,174 3,174 Total liabilities $ 268,048 $ 267,695 Stockholders' Equity: Preferred stock, $.10 par value, authorized 1,000,000 shares, none issued $ — $ — Common stock, $.10 par value, authorized 50,000,000 shares, issued 17,942,269 shares for 2015 and 17,792,846 shares for 2014 1,793 1,778 Additional paid-in capital 357,829 347,022 Treasury stock, at cost (3,511,380 shares for 2015 and 2014) (155,801 ) (155,801 ) Retained earnings 868,723 787,666 Accumulated other comprehensive income: Net unrealized gains (losses) on securities available-for-sale, net of tax 23,611 46,573 Foreign currency translation adjustment, net of tax (7 ) (14 ) Total stockholders' equity $ 1,096,148 $ 1,027,224 Total liabilities and stockholders' equity $ 1,364,196 $ 1,294,919 SCHEDULE II THE NAVIGATORS GROUP, INC. AND SUBSIDIARIES Condensed Financial Information of Registrant (Continued) The Navigators Group, Inc. Statements of Income (Parent Company) Years Ended December 31, amounts in thousands 2015 2014 2013 Revenues: Net investment income $ 147 $ 76 $ 13 Total revenues $ 147 $ 76 $ 13 Expenses: Call premium on Senior notes $ — $ — $ 17,895 Interest expense 15,424 15,413 10,507 Other (income) expense — — 2 Total expenses $ 15,424 $ 15,413 $ 28,404 Income (loss) before income tax benefit $ (15,277 ) $ (15,337 ) $ (28,391 ) Income tax benefit (5,472 ) (5,287 ) (9,886 ) Income (loss) before equity in undistributed net income of wholly owned subsidiaries $ (9,805 ) $ (10,050 ) $ (18,505 ) Equity in undistributed net income of wholly-owned subsidiaries 90,862 105,379 81,971 Net income $ 81,057 $ 95,329 $ 63,466 SCHEDULE II THE NAVIGATORS GROUP, INC. AND SUBSIDIARIES Condensed Financial Information of Registrant (Continued) The Navigators Group, Inc. Statements of Cash Flows (Parent Company) Years Ended December 31, amounts in thousands 2015 2014 2013 Operating activities: Net income $ 81,057 $ 95,329 $ 63,466 Adjustments to reconcile net income to net cash provided by (used in) operations: Equity in undistributed net income of wholly-owned subsidiaries (90,862 ) (105,379 ) (81,971 ) Dividends received from subsidiaries — — — Call premium on redemption of Senior notes — — 17,895 Other 3,373 9,211 2,098 Net cash provided by (used in) operating activities $ (6,432 ) $ (839 ) $ 1,488 Investing activities: Fixed maturities, available-for-sale Sales $ 1,250 $ 3,200 $ 8,754 Purchases — — (1,249 ) Equity securities Sales — — — Purchases — — — Net increase in short-term investments 3,918 (3,424 ) (89,988 ) Net cash provided by (used in) investing activities $ 5,168 $ (224 ) $ (82,483 ) Financing activities: Capital contribution to subsidiary $ — $ — $ (50,000 ) Net proceeds from debt offering — — 263,278 Redemption of 7.0% Senior notes — — (132,437 ) Proceeds of stock issued from employee stock purchase plan 1,352 1,067 821 Proceeds of stock issued from exercise of stock options 29 153 2,495 Net cash provided by (used in) financing activities $ 1,381 $ 1,220 $ 84,157 Increase (decrease) in cash $ 117 $ 157 $ 3,162 Cash at beginning of year 6,300 6,143 2,981 Cash at end of year $ 6,417 $ 6,300 $ 6,143

Supplementary Insurance Informa

Supplementary Insurance Information	12 Months Ended
	Dec. 31, 2015
Supplementary Insurance Information [Abstract]
Supplementary Insurance Information	SCHEDULE III THE NAVIGATORS GROUP, INC. AND SUBSIDIARIES Supplementary Insurance Information Amortization Deferred Other policy of deferred policy Reserve claims and Net Net Losses policy Other Net acquisition for losses Unearned benefits earned investment and LAE acquisition operating written amounts in thousands costs and LAE premiums payable premiums income (1) incurred costs (2) expenses (1) premiums Year ended December 31, 2015 NIC, NSIC and Navigators Management Company, Inc. $ 67,144 $ 1,692,886 $ 607,062 $ — $ 722,749 $ 61,863 $ 451,296 $ 88,597 $ 153,194 $ 757,117 NHUK 24,839 509,758 213,614 — 261,338 6,708 121,302 41,380 67,449 286,743 $ 91,983 $ 2,202,644 $ 820,676 $ — $ 984,087 $ 68,571 $ 572,598 $ 129,977 $ 220,643 $ 1,043,860 Year ended December 31, 2014 NIC, NSIC and Navigators Management Company, Inc. $ 63,200 $ 1,645,984 $ 579,331 $ — $ 704,574 $ 56,714 $ 434,396 $ 85,137 $ 138,675 $ 752,773 NHUK 16,252 513,650 186,836 — 231,321 7,378 110,833 42,558 58,150 247,365 $ 79,452 $ 2,159,634 $ 766,167 $ — $ 935,895 $ 64,092 $ 545,229 $ 127,695 $ 196,825 $ 1,000,138 Year ended December 31, 2013 NIC, NSIC and Navigators Management Company, Inc. $ 54,984 $ 1,523,175 $ 536,303 $ — $ 639,338 $ 49,083 $ 415,413 $ 81,132 $ 119,920 $ 680,008 NHUK 12,023 521,896 178,303 — 202,601 7,160 103,548 34,710 44,514 207,914 $ 67,007 $ 2,045,071 $ 714,606 $ — $ 841,939 $ 56,243 $ 518,961 $ 115,842 $ 164,434 $ 887,922 (1) - Net investment income and Other operating expenses reflect only such amounts attributable to our Company's insurance operations. (2) - Amortization of deferred policy acquisition costs reflects only such amounts attributable to our Company's insurance operations. A portion of these costs is eliminated in consolidation.

Reinsurance - Written Premium

Reinsurance - Written Premium	12 Months Ended
	Dec. 31, 2015
Supplemental Schedule Of Reinsurance Premiums For Insurance Companies [Abstract]
Reinsurance - Written Premium	SCHEDULE IV THE NAVIGATORS GROUP, INC. AND SUBSIDIARIES Reinsurance - Written Premium Ceded to Assumed Percentage Direct other from other Net of amount amounts in thousands Amount companies companies amount assumed Year ended December 31, 2015 P&C $ 1,277,728 $ 409,642 $ 175,774 $ 1,043,860 17 % Year ended December 31, 2014 P&C $ 1,232,012 $ 432,215 $ 200,341 $ 1,000,138 20 % Year ended December 31, 2013 P&C $ 1,177,483 $ 482,595 $ 193,034 $ 887,922 22 %

Valuation and Qualifying Accoun

Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2015
Valuation And Qualifying Accounts [Abstract]
Valuation and Qualifying Accounts	SCHEDULE V THE NAVIGATORS GROUP, INC. AND SUBSIDIARIES Valuation and Qualifying Accounts Balance at Charged (Credited) to Charged to Deductions Balance at amounts in thousands January 1 Costs and Expenses Other Accounts (Describe) December 31 Year ended December 31, 2015 Allowance for uncollectable reinsurance $ 11,332 $ (4,411 ) $ — $ — $ 6,921 Valuation allowance in deferred taxes $ 776 $ (55 ) $ — $ — $ 721 Year ended December 31, 2014 Allowance for uncollectable reinsurance $ 11,332 $ — $ — $ — $ 11,332 Valuation allowance in deferred taxes $ 554 $ 222 $ — $ — $ 776 Year ended December 31, 2013 Allowance for uncollectable reinsurance $ 11,520 $ (188 ) $ — $ — $ 11,332 Valuation allowance in deferred taxes $ 499 $ 55 $ — $ — $ 554

Supplementary Information Conce

Supplementary Information Concerning Property-Casualty Insurance Operations	12 Months Ended
	Dec. 31, 2015
Supplemental Information For Property Casualty Insurance Underwriters [Abstract]
Supplementary Information Concerning Property-Casualty Insurance Operations	SCHEDULE VI THE NAVIGATORS GROUP, INC. AND SUBSIDIARIES Supplementary Information Concerning P&C Insurance Operations Losses and LAE Amortization Deferred policy Reserve Net Net expenses incurred related to of deferred policy Other Net amounts in thousands acquisition for losses Unearned earned investment Current Prior acquisition operating written Affiliation with Registrant costs and LAE premiums premiums income (1) year years costs (2) expenses (1) premiums Consolidated Subsidiaries: Year ended December 31, $ 91,983 $ 2,202,644 $ 820,676 $ 984,087 $ 68,571 $ 637,267 $ (64,669 ) $ 129,977 $ 220,643 $ 1,043,860 Year ended December 31, 2014 $ 79,452 $ 2,159,634 $ 766,167 $ 935,895 $ 64,092 $ 601,041 $ (55,812 ) $ 127,695 $ 196,825 $ 1,000,138 Year ended December 31, 2013 $ 67,007 $ 2,045,071 $ 714,606 $ 841,939 $ 56,243 $ 520,227 $ (1,266 ) $ 115,842 $ 164,434 $ 887,922 (1) - Net investment income and Other operating expenses reflect only such amounts attributable to our Company's insurance operations. (2) - Amortization of deferred policy acquisition costs reflects only such amounts attributable to our Company's insurance operations. A portion of these costs is eliminated in consolidation.

Organization & Summary of Signi

Organization & Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements of The Navigators Group, Inc. and its subsidiaries have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP” or “U.S. GAAP”). All significant intercompany transactions and balances have been eliminated in consolidation. The preparation of these financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and the reported revenues and expenses during the reporting periods. Certain amounts for the prior year have been reclassified to conform with the current period presentation. Unless the context requires otherwise, the terms “we,” “us,” “our,” or “our Company” are used to mean The Navigators Group, Inc., a Delaware holding company established in 1982, and its subsidiaries. The terms “Parent” or “Parent Company” are used to mean The Navigators Group, Inc. without its subsidiaries.
Organization	Organization We are an international insurance company with a long-standing area of specialization in Marine insurance. Our Property and Casualty (“P&C”) insurance business primarily offers general liability coverage and umbrella & excess liability coverage to commercial enterprises through our Primary and Excess Casualty divisions. We have also developed niches in Professional Liability insurance, through our Directors & Officers (“D&O”) and Errors & Omissions (“E&O”) divisions. Beginning in 2010, we added reinsurance products through our Global Reinsurance (“GlobalRe”) business. We operate through various wholly-owned subsidiaries, including Navigators Insurance Company (“NIC”), inclusive of its United Kingdom Branch (“U.K. Branch”), and Navigators Specialty Insurance Company (“NSIC”), both of which are U.S. insurance companies, and Navigators Underwriting Agency Ltd. (“NUAL”), a Lloyd’s of London (“Lloyd’s”) underwriting agency that manages Lloyd’s Syndicate 1221 (“the Syndicate”) in the U.K. and is the underwriting company of Navigators Holdings (U.K.) Ltd. (“NHUK”), the holding company for our non U.S. domiciled entities. Our Company controls 100% of the Syndicate’s stamp capacity.
Cash	Cash Cash includes cash on hand and demand deposits with banks, excluding such amounts held by the Syndicate included as Funds at Lloyd’s (“FAL”), which are classified as short term investments.
Investments	Investments As of December 31, 2015 and 2014, all fixed maturity and equity securities held by our Company were carried at fair value and classified as available-for-sale. Available-for-sale securities are debt and equity securities not classified as either held-to-maturity securities or trading securities and are reported at fair value, with unrealized gains and losses excluded from earnings and reported in accumulated other comprehensive income (“AOCI”) as a separate component of stockholders’ equity. Fixed maturity securities include bonds, mortgage-backed and asset-backed securities. Equity securities consist of common stock, exchange traded funds and preferred stock. Short-term investments are carried at fair value. Short-term investments mature within one year from the purchase date. All prices for our fixed maturities, equity securities and short-term investments are classified as Level 1, Level 2 or Level 3 under the fair value hierarchy, as defined in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification 820 (“ASC 820”). Premiums and discounts on fixed maturity securities are amortized into interest income over the life of the security using the interest method. For mortgage-backed and asset-backed securities, anticipated prepayments and expected maturities are utilized in applying the interest rate method. An effective yield is calculated based on projected principal cash flows at the time of original purchase. The effective yield is used to amortize the purchase price of the security over the security’s expected life. Book values are adjusted to reflect the amortization of premium or accretion of discount on a monthly basis. The projected principal cash flows are based on certain prepayment assumptions, which are generated using a prepayment model. The prepayment model uses a number of factors to estimate prepayment activity including the current levels of interest rates (refinancing incentive), time of year (seasonality), economic activity (including housing turnover) and term and age of the underlying collateral (burnout, seasoning). Prepayment assumptions associated with the mortgage-backed and asset-backed securities are reviewed on a periodic basis. When changes in prepayment assumptions are deemed necessary as the result of actual prepayments differing from anticipated prepayments, securities are revalued based upon the new prepayment assumptions utilizing the retrospective adjustment method, whereby the effective yield is recalculated to reflect actual payments to date and anticipated future payments. The investment in such securities is adjusted to the amount that would have existed had the new effective yield been applied since the acquisition of the security. Such adjustments, if any, are included in Net investment income for the current period. Realized gains and losses on sales of investments are recognized when the related trades are executed and are determined on the basis of the specific identification method.
Impairment of Invested Assets	Impairment of Invested Assets Management regularly reviews our fixed maturity and equity securities portfolios to evaluate the necessity of recording impairment losses for other-than-temporary declines in the fair value of securities. For fixed maturity securities, we consider our intent to sell a security and whether it is more likely than not that, we will be required to sell a security before the anticipated recovery as part of the process of evaluating whether a security’s unrealized loss represents an other-than-temporary decline. For fixed maturity securities that have a fair value below amortized cost and that we intend to sell or for which it is more likely than not that we would be required to sell, an other than temporary impairment (“OTTI”) loss is recognized in earnings by writing such security down to fair value. For fixed maturity securities which we do not intend to sell or for which it is more likely than not that our Company would not be required to sell, a decline in value below amortized cost is only recognized to the extent the present value of future cash flows expected to be collected is less than the amortized cost of the security. Such shortfall in the present value of future cash flows is considered the credit loss and is recognized as an OTTI loss in earnings, with the non-credit portion of the impairment (i.e., the difference between the present value of future cash flows and fair value of the security) recognized as OTTI losses in AOCI. In evaluating OTTI of equity securities, we consider our intent to hold the securities as part of the process of evaluating whether a decline in fair value below cost represents an other than temporary decline in value. For equity securities in an unrealized loss position that we do not intend to hold or that we do not expect to recover their value within a reasonable period of time, a net OTTI loss is recognized in earnings by writing such security down to the fair value.
Foreign Currency Remeasurement and Translation	Foreign Currency Remeasurement and Translation The functional currency of each of our operations is generally the currency of the local operating environment, except for our Lloyd’s business which is United States Dollar (“USD”). Transactions in currencies other than an operation’s functional currency are remeasured into the functional currency and the resulting foreign exchange gains and losses are reflected in net Other income (expense) in the Consolidated Statements of Income. Functional currency assets and liabilities are translated into USD using period end rates of exchange and the related translation adjustments are recorded as a separate component of AOCI. Consolidated Statements of Income amounts expressed in functional currencies are translated using average exchange rates. During the first quarter of 2014, the Syndicate revised its foreign exchange accounting methodology from reporting its financial position and results using three functional currencies (British pound sterling (“GBP”), U.S.dollars (“USD”) and Canadian dollars (“CAD”)) to one functional currency (USD). The USD was chosen as the single functional currency as the majority of the Syndicate’s insurance business has been and continues to be transacted in USD. This cumulative change in remeasurement resulted in a 2014 immaterial correction of $10.0 million ($6.6 million after-tax) in AOCI, on the Consolidated Balance Sheets, offset by a gain in Other income in the Consolidated Statements of Income.
Premium Revenues	Premium Revenues Written premium is based on the insurance policies that have been reported to us and the policies that have been written by agents but not yet reported to us. We estimate the amount of written premium not yet reported based on judgments relative to current and historical trends of the business being written. Such estimates are regularly reviewed and updated and any resulting adjustments are included in the current year’s results. An Unearned premium reserve is established to reflect the unexpired portion of each policy at the financial reporting date. Substantially all of our business is placed through agents and brokers. We record estimates for both unreported direct and assumed premiums. We also record the ceded portion of the estimated Gross written premiums and related acquisition costs. These estimates are mostly for our Marine and Energy & Engineering products written by our International Insurance (“Int’l Insurance”) reporting segment as well as our Accident & Health (“A&H”) and Latin American (“LatAm”) business within our P&C and Surety products written by our GlobalRe reporting segment. Such premium estimates are generally based on submission data received from brokers and agents and recorded when the insurance policy or reinsurance contract is written or bound. The earned gross, ceded and net premiums are calculated based on our earning methodology, which is generally pro-rata over the policy period or over the period of risk if the period of risk differs significantly from the contract period.
Reinsurance Ceded	Reinsurance Ceded In the normal course of business, we purchase reinsurance from insurers or reinsurers to reduce the amount of loss arising from claims. Management analyzes the reinsurance agreements to determine whether the reinsurance should be classified as prospective or retroactive based upon the terms of the reinsurance agreement and whether the reinsurer has assumed significant insurance risk to the extent that the reinsurer may realize a significant loss from the transaction. Prospective reinsurance is reinsurance in which an assuming company agrees to reimburse the ceding company for losses that may be incurred as a result of future insurable events covered under contracts subject to the reinsurance. Retroactive reinsurance is reinsurance in which an assuming company agrees to reimburse a ceding company for liabilities incurred as a result of past insurable events covered under contracts subject to the reinsurance. Ceded reinsurance premiums and any related ceding commissions and ceded losses are reflected as reductions of the respective income or expense accounts over the terms of the reinsurance contracts. Prepaid reinsurance premiums represent the portion of premiums ceded to reinsurers applicable to the unexpired terms of the reinsurance contracts in force. Reinsurance reinstatement premiums (“RRPs”) are recognized in the same period as the loss event that gave rise to the reinstatement premiums. Amounts recoverable from reinsurers are estimated in a manner consistent with the claim liability associated with the reinsured policy. Ceded Unearned premiums and estimates of amounts recoverable from reinsurers on paid and unpaid losses are reflected as assets. Provisions are made for estimated unrecoverable reinsurance.
Deferred Policy Acquisition Costs	Deferred Policy Acquisition Costs Costs of acquiring business are deferred and amortized ratably over the period that the related premiums are recognized as revenue. Such costs (e.g., Commission expenses, Other underwriting expenses and premium taxes) are limited to the incremental direct costs related to the successful acquisition of new or renewal business. The method of computing deferred policy acquisition costs limits the deferral to their estimated net realizable value based on the related Unearned premiums and takes into account anticipated losses and LAE, commission expenses and operating expenses based on historical and current experience, as well as anticipated investment income.
Reserves for Losses and Loss Adjustment Expenses	Reserves for Losses and Loss Adjustment Expenses Unpaid losses and loss adjustment expenses (“LAE”) are determined on: (a) individual claims reported on direct business for insureds, (b) from reports received from ceding insurers for assumed business and (c) on estimates based on Company and industry experience for incurred but not reported (“IBNR”) claims and LAE. Indicated IBNR loss reserves are calculated by our actuaries using several standard actuarial methodologies, including the paid and incurred loss development and the paid and incurred Bornheutter-Ferguson loss methods. Frequency/severity analyses are performed for certain books of business. The provision for unpaid losses and LAE has been established to cover the estimated unpaid cost of claims incurred. Such estimates are regularly reviewed and updated and any resulting adjustments are included in the current year’s results. Management believes that the liability recognized for unpaid losses and LAE is a reasonable estimate of the ultimate unpaid claims incurred, however, no representation is made that the ultimate liability will not differ materially from the amounts recorded in the accompanying Consolidated Financial Statements. Losses and LAE are recorded on an undiscounted basis.
Earnings per Share	Earnings per Share Basic earnings per share (“EPS”) is computed by dividing Net income by the weighted average number of common shares outstanding for the period. Diluted EPS reflects the basic EPS adjusted for the potential dilution that would occur if all issued stock options were exercised and all stock grants were fully vested.
Depreciation and Amortization	Depreciation and Amortization Depreciation of furniture and fixtures, electronic data processing equipment and computer software is provided over the estimated useful lives of the respective assets, ranging from three to seven years, using the straight-line method. Amortization of leasehold improvements are provided over the shorter of the useful lives of those improvements or the contractual terms of the leases, ranging from five to ten years, using the straight-line method.
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets Goodwill represents the excess of cost of acquiring a business enterprise over the fair value of the net assets acquired. Our Company has also recorded indefinite lived intangible assets related to the acquisition of the remaining non-controlled stamp capacity of the Syndicate. Goodwill and indefinite lived intangible assets are reported at carrying value and are tested for impairment at least annually, and when permitted by the applicable accounting guidance, qualitative factors are assessed to determine whether it is necessary to calculate an asset’s fair value when testing an asset with an indefinite life for impairment. Goodwill and indefinite lived intangible assets are considered impaired if the estimated fair value is less than its carrying value and any impairment loss is measured as the difference between the implied fair value and the carrying value. Our Company did not recognize an impairment of goodwill or the indefinite lived intangible assets for any of the years ended December 31, 2015, 2014 and 2013. As of December 31, 2015, the carrying value of goodwill and indefinite lived intangible assets was $6.8 million, which is $0.2 million less than the carrying value as of December 31, 2014, $7.0 million. Changes in the carrying value of the goodwill and indefinite lived intangible assets are due to amortization and fluctuations in currency exchange rates between the USD and the GBP.
Income Taxes	Income Taxes We recognize deferred tax assets and liabilities based on the differences between the financial statement carrying amounts and the tax bases of assets and liabilities. Deferred tax assets are reduced by a valuation allowance if, based on the weight of available evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. All available evidence, both positive and negative, is considered to determine whether, based on the weight of that evidence, a valuation allowance is needed. Future realization of the tax benefit of an existing deferred tax asset ultimately depends on the existence of sufficient taxable income of the appropriate character within the carryback/carryforward period available under the tax law. In determining whether a valuation allowance is needed, management considers the timing of the reversal of each deferred tax asset as well as expected future levels of taxable income, amounts of taxable income in carryback years, and tax planning strategies. Additional information regarding our deferred tax assets can be found in Note 9, Income Taxes.
Current and Pending Accounting Pronouncements	Current and Pending Accounting Pronouncements In 2015, we did not adopt any new accounting pronouncements. We are currently assessing the future impact to our Consolidated Financial Statements of the following 2015 pronouncements issued by the FASB. · Accounting Standards Update 2015-03 – Interest – Imputation of Interest (Subtopic 835-30) – Simplifying the Presentation of Debt Issuance Costs, which will be effective for fiscal years beginning after December 15, 2015. The new pronouncement was issued to simplify presentation of debt issuance costs. · Accounting Standards Update 2015-05 – Intangibles – Goodwill and Other – Internal Use Software (Subtopic 350-40) Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement, which will be effective for fiscal years beginning after December 15, 2015. The new pronouncement was issued to provide guidance to customers about whether a cloud computing arrangement includes a software license. · Accounting Standards Update 2015-07 – Fair Value Measurement – (Topic 820) Disclosures for Investments in Certain Entities that Calculate Net Asset Value per Share (or its equivalent) (a consensus of the Emerging Issues Task Force), which will be effective for fiscal years beginning after December 15, 2015. The new pronouncement was issued to ensure that all investments categorized in the fair value hierarchy are classified using a consistent approach. · Accounting Standards Update 2015-09 – Financial Services Insurance – (Topic 944) Disclosures about Short-Duration Contracts, effective for annual periods beginning after December 15, 2015. The new pronouncement was issued to (1) increase the usefulness of the information about a reporting entity’s insurance liabilities, including the nature, amount, timing, and uncertainty of cash flows related to those liabilities and the effect of those cash flows on the Statements of Comprehensive Income and (2) improve comparability between reporting entities, regardless of the type of entity issuing the contract. · Accounting Standards Update 2015-12 – Plan Accounting: Defined Benefit Pension Plans, Defined Contribution Pension Plans, Health and Welfare Plans, effective for annual periods beginning after December 15, 2015. This update was issued to reduce complexity in employee benefit plan accounting. This update designates contract value as the only required measure for fully benefit-responsive investment contracts, which maintains the relevant information while reducing the cost and complexity of reporting for fully benefit-responsive investment contracts. · Accounting Standards Update 2015-14 – Revenue from Contracts with Customers (Topic 606) – Deferral of the Effective Date, effective for annual periods beginning after December 15, 2017. In response to stakeholders’ request to defer the effective date of the guidance in Update 2014-09 and in consideration of feedback received through extensive outreach with preparers, practitioners, and users of financial statements, the Board issued this proposed update. The amendments in this update defer the effective date of Update 2014-09 for all entities by one year. · Accounting Standards Update 2015-15 – Interest – Imputation of Interest (Subtopic 835-30) – Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements, effective for annual periods beginning after December 15, 2015. This update changed the wording in Subtopic 835-30 for the imputation of interest. Given the absence of authoritative guidance within Update 2015-03 for debt issuance costs related to line-of-credit arrangements, the Security and Exchange Commission (“SEC”) staff would not object to an entity deferring and presenting debt issuance costs as an asset and subsequently amortizing the deferred debt issuance costs ratably over the term of the line-of-credit arrangement, regardless of whether there are any outstanding borrowings on the line-of-credit arrangements. There were no additional 2015 accounting pronouncements that are expected to have a significant impact on our Consolidated Financial Statements upon adoption.

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Financial Data by Segment	The following tables set forth the financial data by segment for the years ended December 31, 2015, 2014 and 2013: Year Ended December 31, 2015 U.S. Int'l amounts in thousands Insurance Insurance GlobalRe Corporate (1) Total Net earned premiums $ 555,836 $ 259,960 $ 168,291 $ — $ 984,087 Net losses and LAE (343,497 ) (134,702 ) (94,399 ) — (572,598 ) Commission expenses (56,319 ) (43,676 ) (32,240 ) 2,258 (129,977 ) Other operating expenses (131,407 ) (75,867 ) (16,242 ) — (223,516 ) Other underwriting income (expense) 1,690 — 690 (2,258 ) 122 Underwriting profit (loss) $ 26,303 $ 5,715 $ 26,100 $ — $ 58,118 Net investment income 68,718 68,718 Net realized gains (losses) 6,675 6,675 Interest expense (15,424 ) (15,424 ) Other income (loss) (613 ) (613 ) Income before income taxes $ 26,303 $ 5,715 $ 26,100 $ 59,356 $ 117,474 Income tax (expense) benefit (36,417 ) (36,417 ) Net income (loss) $ 81,057 Losses and LAE ratio 61.8 % 51.8 % 56.1 % 58.2 % Commission expense ratio 10.1 % 16.8 % 19.2 % 13.2 % Other operating expense ratio (2) 23.4 % 29.2 % 9.2 % 22.7 % Combined ratio 95.3 % 97.8 % 84.5 % 94.1 % ( 1) - Includes Corporate segment intercompany eliminations. (2) - Includes Other operating expenses and Other underwriting income (expense). Year Ended December 31, 2014 U.S. Int'l amounts in thousands Insurance Insurance GlobalRe Corporate (1) Total Net earned premiums $ 504,289 $ 243,485 $ 188,121 $ — $ 935,895 Net losses and LAE (311,839 ) (115,079 ) (118,311 ) — (545,229 ) Commission expenses (49,840 ) (44,426 ) (33,429 ) 2,167 (125,528 ) Other operating expenses (115,817 ) (65,275 ) (15,733 ) — (196,825 ) Other underwriting income (expense) 2,241 32 489 (2,167 ) 595 Underwriting profit (loss) $ 29,034 $ 18,737 $ 21,137 $ — $ 68,908 Net investment income 64,168 64,168 Net realized gains (losses) 12,812 12,812 Interest expense (15,413 ) (15,413 ) Other income (loss) 10,061 10,061 Income before income taxes $ 29,034 $ 18,737 $ 21,137 $ 71,628 $ 140,536 Income tax (expense) benefit (45,207 ) (45,207 ) Net income (loss) $ 95,329 Losses and LAE ratio 61.8 % 47.3 % 62.9 % 58.3 % Commission expense ratio 9.9 % 18.2 % 17.8 % 13.4 % Other operating expense ratio (2) 22.5 % 26.8 % 8.1 % 20.9 % Combined ratio 94.2 % 92.3 % 88.8 % 92.6 % (1) - Includes Corporate segment intercompany eliminations. (2) - Includes Other operating expenses and Other underwriting income (expense ). Year Ended December 31, 2013 U.S. Int'l amounts in thousands Insurance Insurance GlobalRe Corporate (1) Total Net earned premiums $ 437,737 $ 232,962 $ 171,240 $ — $ 841,939 Net losses and LAE (283,694 ) (103,853 ) (131,414 ) — (518,961 ) Commission expenses (43,409 ) (42,977 ) (29,456 ) 2,348 (113,494 ) Other operating expenses (99,013 ) (54,062 ) (11,359 ) — (164,434 ) Other underwriting income (expense) 2,924 (1,867 ) 119 (2,348 ) (1,172 ) Underwriting profit (loss) $ 14,545 $ 30,203 $ (870 ) $ — $ 43,878 Net investment income 56,251 56,251 Net realized gains (losses) 20,546 20,546 Interest expense (10,507 ) (10,507 ) Call premium on Senior notes (17,895 ) (17,895 ) Other income (loss) — — Income (loss) before income taxes $ 14,545 $ 30,203 $ (870 ) $ 48,395 $ 92,273 Income tax (expense) benefit (28,807 ) (28,807 ) Net income (loss) $ 63,466 Losses and LAE ratio 64.8 % 44.6 % 76.7 % 61.6 % Commission expense ratio 9.9 % 18.4 % 17.2 % 13.5 % Other operating expense ratio (2) 22.0 % 24.0 % 6.6 % 19.7 % Combined ratio 96.7 % 87.0 % 100.5 % 94.8 % (1) - Includes Corporate segment intercompany eliminations. (2) - Includes Other operating expenses and Other underwriting income (expense ).
Additional Financial Data by Segment	The following tables provide additional financial data by operating segment for the years ended December 31, 2015, 2014 and 2013: Year Ended December 31, 2015 amounts in thousands Gross written premiums Ceded premiums Net written premiums Net earned premiums U.S. Insurance Marine $ 158,124 $ (61,916 ) $ 96,208 $ 96,082 P&C 596,673 (152,168 ) 444,505 401,408 Professional Liability 110,984 (54,691 ) 56,293 58,346 Total $ 865,781 $ (268,775 ) $ 597,006 $ 555,836 Int'l Insurance Marine $ 183,707 $ (36,515 ) $ 147,192 $ 149,256 P&C 130,729 (67,722 ) 63,007 55,320 Professional Liability 97,511 (29,768 ) 67,743 55,384 Total $ 411,947 $ (134,005 ) $ 277,942 $ 259,960 GlobalRe $ 175,774 $ (6,862 ) $ 168,912 $ 168,291 Total $ 1,453,502 $ (409,642 ) $ 1,043,860 $ 984,087 Year Ended December 31, 2014 amounts in thousands Gross written premiums Ceded written premiums Net written premiums Net earned premiums U.S. Insurance Marine $ 154,233 $ (46,685 ) $ 107,548 $ 105,650 P&C 543,045 (169,953 ) 373,092 314,833 Professional Liability 109,830 (38,345 ) 71,485 83,806 Total $ 807,108 $ (254,983 ) $ 552,125 $ 504,289 Int'l Insurance Marine $ 190,787 $ (47,805 ) $ 142,982 $ 141,097 P&C 158,139 (98,087 ) 60,052 62,520 Professional Liability 75,978 (26,029 ) 49,949 39,868 Total $ 424,904 $ (171,921 ) $ 252,983 $ 243,485 GlobalRe $ 200,341 $ (5,311 ) $ 195,030 $ 188,121 Total $ 1,432,353 $ (432,215 ) $ 1,000,138 $ 935,895 Year Ended December 31, 2013 amounts in thousands Gross written premiums Ceded written premiums Net written premiums Net earned premiums U.S. Insurance Marine $ 143,867 $ (44,359 ) $ 99,508 $ 106,150 P&C 472,049 (202,430 ) 269,619 231,186 Professional Liability 130,079 (32,980 ) 97,099 100,401 Total $ 745,995 $ (279,769 ) $ 466,226 $ 437,737 Int'l Insurance Marine $ 192,870 $ (50,887 ) $ 141,983 $ 150,784 P&C 180,657 (120,068 ) 60,589 55,809 Professional Liability 57,961 (26,877 ) 31,084 26,369 Total $ 431,488 $ (197,832 ) $ 233,656 $ 232,962 GlobalRe $ 193,034 $ (4,994 ) $ 188,040 $ 171,240 Total $ 1,370,517 $ (482,595 ) $ 887,922 $ 841,939
Identifiable Assets by Legal Entity	The following table presents identifiable assets by legal entity as we do not allocate assets under the new reporting segments: Years ended December 31, amounts in thousands 2015 2014 Identifiable assets: NIC, NSIC and Navigators Management Company, Inc. $ 3,455,586 $ 3,356,093 NHUK 996,242 957,795 Parent Company (1) 132,184 162,297 Total identifiable assets $ 4,584,012 $ 4,476,185 (1) - Includes Corporate segment intercompany eliminations.

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2015
Investments Debt And Equity Securities [Abstract]
Investments Including OTTI Securities Recognized within AOCI	The following tables set forth our Company’s investments as of December 31, 2015 and 2014 and include OTTI securities recognized within AOCI: December 31, 2015 Gross Gross Unrealized Unrealized Amortized amounts in thousands Fair Value Gains Losses Cost Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 252,882 $ 2,273 $ (9,214 ) $ 259,823 States, municipalities and political subdivisions 576,859 21,233 (781 ) 556,407 Mortgage-backed and asset-backed securities: Agency mortgage-backed securities 379,269 5,573 (2,082 ) 375,778 Residential mortgage obligations 30,465 694 (82 ) 29,853 Asset-backed securities 225,012 85 (1,624 ) 226,551 Commercial mortgage-backed securities 189,713 3,119 (1,864 ) 188,458 Subtotal $ 824,459 $ 9,471 $ (5,652 ) $ 820,640 Corporate bonds 760,010 7,373 (10,738 ) 763,375 Total fixed maturities $ 2,414,210 $ 40,350 $ (26,385 ) $ 2,400,245 Equity securities 305,271 26,341 (3,013 ) 281,943 Short-term investments 217,745 2 — 217,743 Total investments $ 2,937,226 $ 66,693 $ (29,398 ) $ 2,899,931 December 31, 2014 Gross Gross Unrealized Unrealized Amortized amounts in thousands Fair Value Gains Losses Cost Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 397,923 $ 3,431 $ (5,965 ) $ 400,457 States, municipalities and political subdivisions 541,007 19,204 (558 ) 522,361 Mortgage-backed and asset-backed securities: Agency mortgage-backed securities 364,622 8,476 (998 ) 357,144 Residential mortgage obligations 34,087 1,153 (138 ) 33,072 Asset-backed securities 206,413 380 (964 ) 206,997 Commercial mortgage-backed securities 206,318 6,630 (98 ) 199,786 Subtotal $ 811,440 $ 16,639 $ (2,198 ) $ 796,999 Corporate bonds 615,564 13,048 (1,626 ) 604,142 Total fixed maturities $ 2,365,934 $ 52,322 $ (10,347 ) $ 2,323,959 Equity securities 184,295 30,756 (1,304 ) 154,843 Short-term investments 179,506 — (21 ) 179,527 Total investments $ 2,729,735 $ 83,078 $ (11,672 ) $ 2,658,329
Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity	The contractual maturity dates for fixed maturities categorized by the number of years until maturity as of December 31, 2015 are shown in the following table: December 31, 2015 Amortized amounts in thousands Fair Value Cost Due in one year or less $ 79,279 $ 81,819 Due after one year through five years 766,001 767,634 Due after five years through ten years 323,003 320,503 Due after ten years 421,468 409,648 Mortgage-backed and asset-backed securities 824,459 820,641 Total $ 2,414,210 $ 2,400,245
Summary of Aggregate Fair Value and Gross Unrealized Loss by Length of Time Securities had Continuously been in Gross Unrealized Loss Position	The following tables summarize all securities in a gross unrealized loss position as of December 31, 2015 and 2014, showing the aggregate fair value and gross unrealized loss by the length of time those securities have continuously been in a gross unrealized loss position: December 31, 2015 Less than 12 months Greater than 12 months Total Gross Gross Gross Fair Unrealized Fair Unrealized Fair Unrealized amounts in thousands Value (Losses) Value (Losses) Value (Losses) Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 142,233 $ (3,032 ) $ 22,230 $ (6,182 ) $ 164,463 $ (9,214 ) States, municipalities and political subdivisions 50,577 (549 ) 4,808 (232 ) 55,385 (781 ) Mortgage-backed and asset-backed securities: Agency mortgage-backed securities 164,817 (1,315 ) 29,862 (767 ) 194,679 (2,082 ) Residential mortgage obligations 3,910 (5 ) 1,684 (77 ) 5,594 (82 ) Asset-backed securities 112,479 (663 ) 81,477 (961 ) 193,956 (1,624 ) Commercial mortgage-backed securities 83,024 (1,826 ) 3,065 (38 ) 86,089 (1,864 ) Subtotal $ 364,230 $ (3,809 ) $ 116,088 $ (1,843 ) $ 480,318 $ (5,652 ) Corporate bonds 395,399 (10,114 ) 13,849 (624 ) 409,248 (10,738 ) Total fixed maturities $ 952,439 $ (17,504 ) $ 156,975 $ (8,881 ) $ 1,109,414 $ (26,385 ) Equity securities 58,531 (3,013 ) — — 58,531 (3,013 ) Total fixed maturities and equity securities $ 1,010,970 $ (20,517 ) $ 156,975 $ (8,881 ) $ 1,167,945 $ (29,398 ) December 31, 2014 Less than 12 months Greater than 12 months Total Gross Gross Gross Fair Unrealized Fair Unrealized Fair Unrealized amounts in thousands Value (Losses) Value (Losses) Value (Losses) Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 87,915 $ (1,061 ) $ 117,683 $ (4,904 ) $ 205,598 $ (5,965 ) States, municipalities and political subdivisions 16,349 (60 ) 37,340 (498 ) 53,689 (558 ) Mortgage-backed and asset-backed securities: Agency mortgage-backed securities 18,881 (80 ) 58,301 (918 ) 77,182 (998 ) Residential mortgage obligations 5,625 (50 ) 1,728 (88 ) 7,353 (138 ) Asset-backed securities 110,275 (539 ) 34,530 (425 ) 144,805 (964 ) Commercial mortgage-backed securities 19,741 (71 ) 1,391 (27 ) 21,132 (98 ) Subtotal $ 154,522 $ (740 ) $ 95,950 $ (1,458 ) $ 250,472 $ (2,198 ) Corporate bonds 190,461 (871 ) 31,126 (755 ) 221,587 (1,626 ) Total fixed maturities $ 449,247 $ (2,732 ) $ 282,099 $ (7,615 ) $ 731,346 $ (10,347 ) Equity securities 19,690 (1,297 ) 238 (7 ) 19,928 (1,304 ) Total fixed maturities and equity securities $ 468,937 $ (4,029 ) $ 282,337 $ (7,622 ) $ 751,274 $ (11,651 )
Summary of Cumulative Amounts Related to Credit Loss Portion of Other-Than-Temporary Impairment Losses on Debt Securities	The following table summarizes the cumulative amounts related to our Company’s credit loss portion of the OTTI losses on fixed maturities for the years ended December 31, 2015, 2014 and 2013. Our Company does not intend to sell, and it is more likely than not that we will not be required to sell, the securities prior to recovery of the amortized cost basis and for which the non-credit loss portion is included in AOCI. Years Ended December 31, amounts in thousands 2015 2014 2013 Beginning balance $ 2,361 $ 5,154 $ 3,332 Additions for credit loss impairments recognized in the current period on securities not previously impaired — — 1,822 Additions for credit loss impairments recognized in the current period on securities previously impaired — — — Reductions for credit loss impairments previously recognized on securities sold during the period — (2,793 ) — Ending balance $ 2,361 $ 2,361 $ 5,154
Net Investment Income	Our Company’s Net investment income was derived from the following sources: Years Ended December 31, amounts in thousands 2015 2014 2013 Fixed maturities $ 61,572 $ 57,219 $ 53,898 Equity securities 9,813 9,036 4,835 Short-term investments 683 911 774 Total investment income $ 72,068 $ 67,166 $ 59,507 Investment expenses (3,350 ) (2,998 ) (3,256 ) Net investment income $ 68,718 $ 64,168 $ 56,251
Realized Gains and Losses, Excluding Net Other-Than-Temporary Impairment Losses Recognized in Earnings	Realized gains and losses, excluding net OTTI losses recognized in earnings, for the periods indicated, were as follows: Years Ended December 31, amounts in thousands 2015 2014 2013 Fixed maturities: Gains $ 4,756 $ 8,326 $ 8,539 Losses (5,926 ) (2,610 ) (2,797 ) Fixed maturities, net $ (1,170 ) $ 5,716 $ 5,742 Short-term: Gains $ 130 $ — $ — Losses (383 ) — — Short-term, net $ (253 ) $ — $ — Equity securities: Gains $ 14,331 $ 9,447 $ 17,955 Losses (4,535 ) (2,351 ) (758 ) Equity securities, net $ 9,796 $ 7,096 $ 17,197 Net realized gains (losses) $ 8,373 $ 12,812 $ 22,939

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fixed Maturities and Equity Securities by Asset Class that are Measured at Fair Value	The following tables present, for each of the fair value hierarchy levels as defined by the accounting guidance for fair value measurements and described below, our Company’s fixed maturities and equity securities by asset class that are measured at fair value on a recurring basis, as well as the fair value of the 5.75% Senior notes due October 15, 2023 (the “5.75% Senior notes”) carried at amortized cost as of December 31, 2015 and 2014: December 31, 2015 amounts in thousands Level 1 Level 2 Level 3 Total Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 67,394 $ 185,488 $ — $ 252,882 States, municipalities and political subdivisions — 576,859 — 576,859 Mortgage-backed and asset-backed securities: Agency mortgage-backed securities — 379,269 — 379,269 Residential mortgage obligations — 30,465 — 30,465 Asset-backed securities — 225,012 — 225,012 Commercial mortgage-backed securities — 189,713 — 189,713 Subtotal $ — $ 824,459 $ — $ 824,459 Corporate bonds — 760,010 — 760,010 Total fixed maturities $ 67,394 $ 2,346,816 $ — $ 2,414,210 Equity securities 126,455 178,816 — 305,271 Short-term investments 217,745 — — 217,745 Total assets measured at fair value $ 411,594 $ 2,525,632 $ — $ 2,937,226 Senior notes $ — $ 282,486 $ — $ 282,486 Total liabilities measured at fair value $ — $ 282,486 $ — $ 282,486 December 31, 2014 amounts in thousands Level 1 Level 2 Level 3 Total Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 146,904 $ 251,019 $ — $ 397,923 States, municipalities and political subdivisions — 541,007 — 541,007 Mortgage-backed and asset-backed securities: Agency mortgage-backed securities — 364,622 — 364,622 Residential mortgage obligations — 34,087 — 34,087 Asset-backed securities — 206,413 — 206,413 Commercial mortgage-backed securities — 206,318 — 206,318 Subtotal $ — $ 811,440 $ — $ 811,440 Corporate bonds — 615,564 — 615,564 Total fixed maturities $ 146,904 $ 2,219,030 $ — $ 2,365,934 Equity securities 127,183 57,112 — 184,295 Short-term investments 179,506 — — 179,506 Total assets measured at fair value $ 453,593 $ 2,276,142 $ — $ 2,729,735 Senior notes $ — $ 285,710 $ — $ 285,710 Total liabilities measured at fair value $ — $ 285,710 $ — $ 285,710

Reserves for Losses and LAE (Ta

Reserves for Losses and LAE (Tables)	12 Months Ended
	Dec. 31, 2015
Insurance [Abstract]
Summary of Activity in Reserve for Losses and LAE	The following table summarizes our Company’s Reserves for losses and LAE activity for the years ended December 31, 2015, 2014 and 2013: Years Ended December 31, amounts in thousands 2015 2014 2013 Net reserves for losses and LAE at beginning of year $ 1,308,136 $ 1,222,633 $ 1,216,909 Provision for losses and LAE for claims occurring in the current year 637,267 601,041 520,227 Increase (decrease) in estimated losses and LAE for claims occurring in prior years (64,669 ) (55,812 ) (1,266 ) Incurred losses and LAE $ 572,598 $ 545,229 $ 518,961 Losses and LAE paid for claims occurring during: Current year (159,802 ) (158,806 ) (147,864 ) Prior years (320,863 ) (295,527 ) (365,479 ) Losses and LAE payments $ (480,665 ) $ (454,333 ) $ (513,343 ) Foreign Currency Adjustment (6,943 ) (5,393 ) 106 Net reserves for losses and LAE at end of year 1,393,126 1,308,136 1,222,633 Reinsurance recoverables on unpaid losses and LAE 809,518 851,498 822,438 Gross reserves for losses and LAE at end of year $ 2,202,644 $ 2,159,634 $ 2,045,071
Reporting and Operating Segments Break Down of Prior Years' Net Reserve Deficiency (Redundancy)	The reporting and operating segments breakdowns of prior period net reserve strengthening (releases) for the years ended December 31, 2015, 2014 and 2013 are as follows: Years Ended December 31, amounts in thousands 2015 2014 2013 U.S. Insurance Marine $ (24,825 ) $ (29,047 ) $ (13,679 ) P&C (706 ) 17,081 12,938 Professional Liability (3,788 ) (3,454 ) 11,777 Total $ (29,319 ) $ (15,420 ) $ 11,036 Int'l Insurance Marine (21,914 ) (31,677 ) (6,361 ) P&C (8,458 ) (3,829 ) (22,263 ) Professional Liability 4,156 (2,746 ) 1,289 Total $ (26,216 ) $ (38,252 ) $ (27,335 ) GlobalRe $ (9,134 ) $ (2,140 ) $ 15,033 Total strengthening (releases) $ (64,669 ) $ (55,812 ) $ (1,266 )

Ceded Reinsurance (Tables)

Ceded Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2015
Insurance [Abstract]
Lists of 10 Largest Reinsurers Measured by Reinsurance Recoverable	The following table lists our Company’s 10 largest reinsurers measured by the amount of total reinsurance recoverables as of December 31, 2015, and the reinsurers’ ratings from A.M. Best and S&P: Reinsurance Recoverables Unearned Paid/Unpaid Collateral amounts in thousands Premium Losses Total (1) Held A.M. Best S&P National Indemnity Company $ 14,854 $ 118,337 $ 133,191 $ 7,198 A++ AA+ Everest Reinsurance Company 21,097 77,702 98,799 3,933 A+ A+ Swiss Reinsurance America Corporation 25,564 63,081 88,645 7,814 A+ AA- Transatlantic Reinsurance Company 9,267 62,402 71,669 1,783 A A+ Munich Reinsurance America Inc. 9,051 51,795 60,846 1,577 A+ AA- Allied World Reinsurance 7,177 38,343 45,520 1,012 A A Employers Mutual Casualty Company 10,775 28,321 39,096 4,015 A NR Ace Property and Casualty Insurance Company 12,577 21,470 34,047 3,284 A++ AA Partner Reinsurance Europe 11,231 21,728 32,959 17,619 A A+ National Union Fire Ins. 7,478 22,288 29,766 5,717 A A+ Top 10 $ 129,071 $ 505,467 $ 634,538 $ 53,952 Others 103,517 353,557 457,074 105,618 Total $ 232,588 $ 859,024 $ 1,091,612 $ 159,570 (1) - Net of reserve for uncollectible reinsurance of approximately $6.9 million.
Summary of Components of Net Written Premium	The following table summarizes the components of Net written premium: Years Ended December 31, amounts in thousands 2015 2014 2013 Direct $ 1,277,728 $ 1,232,012 $ 1,177,483 Assumed 175,774 200,341 193,034 Ceded (409,642 ) (432,215 ) (482,595 ) Net written premiums $ 1,043,860 $ 1,000,138 $ 887,922
Summary of Components of Net Earned Premium	The following table summarizes the components of Net earned premium: Years Ended December 31, amounts in thousands 2015 2014 2013 Direct $ 1,223,840 $ 1,183,120 $ 1,121,198 Assumed 175,153 193,431 176,726 Ceded (414,906 ) (440,656 ) (455,985 ) Net earned premiums $ 984,087 $ 935,895 $ 841,939
Summary of Components of Net Losses and Loss Adjustment Expenses Incurred	The following table summarizes the components of Net losses and LAE incurred: Years Ended December 31, amounts in thousands 2015 2014 2013 Direct $ 703,361 $ 657,059 $ 574,020 Assumed 97,947 118,352 133,674 Ceded (228,710 ) (230,182 ) (188,733 ) Net losses and LAE $ 572,598 $ 545,229 $ 518,961

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Annual Rental Commitments under Various Non-cancellable Operating Leases	Future minimum annual rental commitments as of December 31, 2015 under various non-cancellable operating leases for our office facilities, which expire at various dates through 2030, are as follows: Rental Commitments for Years Ended December 31, amounts in thousands 2016 $ 12,769 2017 12,213 2018 10,327 2019 8,482 2020 8,313 2021-2030 42,173 Total minimum operating lease payments $ 94,277

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Components of Current and Deferred Income Tax Expense (Benefit)	The components of current and deferred income tax expense (benefit) are as follows: Years Ended December 31, amounts in thousands 2015 2014 2013 Current income tax expense (benefit): Federal and foreign $ 27,937 $ 27,290 $ 23,703 State and local 1,476 1,036 446 Subtotal $ 29,413 $ 28,326 $ 24,149 Deferred income tax expense (benefit): Federal and foreign 7,004 16,881 4,658 State and local — — — Subtotal $ 7,004 $ 16,881 $ 4,658 Total income tax expense (benefit) $ 36,417 $ 45,207 $ 28,807
Reconciliation of Total Income Taxes Applicable to Pre-Tax Operating Income and Amounts Computed by Applying Federal Statutory Income Tax Rate to Pre-Tax Operating Income	A reconciliation of total income taxes applicable to pre‑tax operating income and the amounts computed by applying the federal statutory income tax rate to the pre‑tax operating income were as follows: Years Ended December 31, amounts in thousands 2015 2014 2013 Computed expected tax expense $ 41,116 35.0 % $ 49,187 35.0 % $ 32,299 35.0 % Tax-exempt interest (4,987 ) -4.2 % (4,771 ) -3.4 % (3,839 ) -4.2 % Dividends received deduction (2,086 ) -1.8 % (1,257 ) -0.9 % (897 ) -1.0 % Proration of DRD and Tax-exempt interest 1,061 0.9 % 904 0.6 % 710 0.8 % Current state and local income taxes, net of federal income tax deduction 959 0.8 % 674 0.5 % 290 0.3 % Other 354 0.3 % 470 0.4 % 244 0.3 % Actual tax expense and rate $ 36,417 31.0 % $ 45,207 32.2 % $ 28,807 31.2 %
Tax Effects of Temporary Differences That Give Rise to Federal, Foreign, State and Local Deferred Tax Assets and Deferred Tax Liabilities	The tax effects of cumulative temporary differences that give rise to federal, foreign, state and local deferred tax assets and deferred tax liabilities were as follows: December 31, amounts in thousands 2015 2014 Deferred tax assets: Loss reserve discount $ 25,353 $ 24,820 Unearned premiums 31,486 29,080 Compensation related 11,175 10,586 State and local net deferred tax assets 721 777 Other 4,315 3,732 Total gross deferred tax assets 73,050 68,995 Less: Valuation allowance (721 ) (777 ) Total deferred tax assets $ 72,329 $ 68,218 Deferred tax liabilities: Net unrealized gains/ losses on securities (13,053 ) (26,730 ) Deferred acquisition costs (24,037 ) (22,120 ) Lloyd's year of account deferral (24,466 ) (13,578 ) Net unrealized foreign exchange (4,164 ) (4,470 ) Other (2,709 ) (2,787 ) Total deferred tax liabilities $ (68,429 ) $ (69,685 ) Net deferred income tax asset (liability) $ 3,900 $ (1,467 )

Stockholders Equity (Tables)

Stockholders Equity (Tables)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Changes in Company's Issued and Outstanding Common Shares	The following table represents changes in our Company’s issued and outstanding common shares for the periods indicated: Years Ended December 31, amounts in thousands 2015 2014 2013 Beginning balance 14,281 14,198 14,047 Vested stock grants 127 59 50 Employee stock purchase plan 21 19 17 Stock options exercised 2 5 84 Treasury shares purchased — — — Ending balance 14,431 14,281 14,198
Amount and Nature of Net Assets Restricted from Payment of Dividends	The amount and nature of net assets that are restricted from payment of dividends as of December 31, 2015 and 2014 are presented in the following table: As of December 31, amounts in thousands 2015 2014 Restricted net assets: NIC and NSIC: Fixed maturities at fair value (amortized cost: 2015, $9,950; 2014, $10,086) $ 11,277 $ 11,732 Short term investments, at fair value 290 290 Cash 6,208 1,212 Total NIC and NSIC (1) $ 17,775 $ 13,234 NHUK: Fixed maturities at fair value (amortized cost: 2015, $458,558; 2014, $445,504) $ 448,666 $ 447,679 Short term investments, at fair value 71,320 61,549 Cash 3,262 963 Total NHUK (2) $ 523,248 $ 510,191 Total Restricted Net Assets $ 541,023 $ 523,425 (1) - The restricted net assets for NIC and NSIC primarily consist of fixed maturities on deposit with various state insurance departments. The cash as of December 31, 2015 and 2014, as presented in the table above, was on deposit with a U.K. bank to comply with the regulatory requirements of the Prudential Regulation Authority for the underwriting activities of the U.K. Branch. (2) - The restricted net assets for NHUK consists of fixed maturities and cash held in trust for the benefit of syndicate policyholders and short term investments primarily consisting of overseas deposits in various countries with Lloyd's to support underwriting activities in those countries.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Reconciliation of Basic and Diluted Earnings per Share Computations	The following is a reconciliation of the basic and diluted EPS computations for the years ended December 31, 2015, 2014 and 2013: Years Ended December 31, amounts in thousands, except share and per share amounts 2015 2014 2013 Net income $ 81,057 $ 95,329 $ 63,466 Basic weighted average shares 14,392,522 14,259,768 14,133,925 Effect of common stock equivalents: Assumed exercise of stock options and vesting of stock 433,223 386,601 211,628 Diluted weighted average shares 14,825,745 14,646,369 14,345,553 Net income per common share: Basic $ 5.63 $ 6.69 $ 4.49 Diluted $ 5.47 $ 6.51 $ 4.42

Statutory Financial Informati41

Statutory Financial Information (Tables)	12 Months Ended
	Dec. 31, 2015
Insurance [Abstract]
Summary of Statutory Net Income (Loss) and Capital and Surplus	The following table presents statutory Net income and capital and surplus in accordance with statutory accounting practices: Years Ended December 31, amounts in millions 2015 2014 2013 NIC & NSIC: Statutory net income $ 60.8 $ 75.7 $ 59.4 Statutory capital and surplus $ 949.1 $ 893.9 $ 804.1 The Syndicate: Syndicate's net income $ 41.0 $ 33.8 $ 21.0 Syndicate's capital and surplus $ 177.5 $ 140.1 $ 124.2

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Unvested Restricted Stock Units and Performance Units Grants Outstanding	Unvested restricted stock units and performance units outstanding as of December 31, 2015, 2014 and 2013, and changes during the years ended on those dates, are presented in the following table: December 31, 2015 2014 2013 Beginning balance 718,892 626,812 587,629 Granted - Performance 185,050 228,607 114,463 Granted - Non Performance 32,158 59,523 155,463 Total Granted 217,208 288,130 269,926 Vested - Performance Earned — — (15,714 ) Vested - Performance Unearned (68,080 ) (93,453 ) (57,585 ) Vested - Non Performance (135,600 ) (90,263 ) (60,183 ) Total Vested (203,680 ) (183,716 ) (133,482 ) Forfeited (35,905 ) (12,334 ) (97,261 ) Ending balance 696,515 718,892 626,812
Stock Options Outstanding	Stock options outstanding as of December 31, 2015, 2014 and 2013 are as follows: December 31, 2015 2014 2013 Average Average Average # of Shares Exercise Price # of Shares Exercise Price # of Shares Exercise Price Beginning balance 1,500 $ 36.03 6,750 $ 30.65 90,250 $ 29.94 Granted — — — — — — Exercised (1,500 ) $ 36.03 (5,250 ) $ 29.11 (83,500 ) $ 29.88 Expired or forfeited — — — — — — Ending balance — $ — 1,500 $ 36.03 6,750 $ 30.65 Number of options exercisable — $ — 1,500 $ 36.03 6,750 $ 30.65

Quarterly Financial Data (Una43

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Financial Data	The following is a summary of quarterly financial data for the periods indicated: March 31, June 30, September December 31, amounts in thousands, except per share amounts 2015 2015 2015 2015 Gross written premiums $ 396,460 $ 379,471 $ 354,062 $ 323,509 Revenues: Net written premiums $ 288,958 $ 258,244 $ 251,939 $ 244,719 Change in unearned premiums (52,826 ) (15,916 ) 2,143 6,826 Net earned premiums $ 236,132 $ 242,328 $ 254,082 $ 251,545 Net investment income 16,253 16,595 17,371 18,499 Total other-than-temporary impairment losses — (423 ) (1,298 ) (123 ) Portion of loss recognized in other comprehensive income (before tax) — — 23 123 Net other-than-temporary impairment losses recognized in earnings — (423 ) (1,275 ) — Net realized gains (losses) 5,596 4,339 518 (2,080 ) Other income (expense) 2,242 (4,362 ) (2,518 ) 4,147 Total revenues $ 260,223 $ 258,477 $ 268,178 $ 272,111 Expenses: Net losses and LAE $ 130,198 $ 141,973 $ 146,546 $ 153,881 Commission expenses 32,905 31,480 34,253 31,339 Other operating expenses 54,909 52,789 56,599 59,219 Interest expense 3,855 3,856 3,856 3,857 Total expenses $ 221,867 $ 230,098 $ 241,254 $ 248,296 Income before income taxes 38,356 28,379 26,924 23,815 Income tax expense $ 12,427 $ 9,195 $ 8,723 $ 6,072 Net income $ 25,929 $ 19,184 $ 18,201 $ 17,743 Comprehensive income (loss) $ 27,052 $ (3,789 ) $ 18,849 $ 15,990 Combined ratio 92.3 % 93.4 % 93.4 % 97.2 % Net income per share: Basic $ 1.81 $ 1.33 $ 1.26 $ 1.23 Diluted $ 1.77 $ 1.30 $ 1.23 $ 1.19 March 31, June 30, September 30, December 31, amounts in thousands, except per share amounts 2014 2014 2014 2014 Gross written premiums $ 422,790 $ 348,795 $ 327,469 $ 333,299 Revenues: Net written premiums $ 311,850 $ 231,864 $ 228,417 $ 228,007 Change in unearned premiums (86,578 ) (780 ) 16,950 6,165 Net earned premiums $ 225,272 $ 231,084 $ 245,367 $ 234,172 Net investment income 16,610 15,648 15,839 16,071 Total other-than-temporary impairment losses — — 158 (21 ) Portion of loss recognized in other comprehensive income (before tax) — — (158 ) 21 Net other-than-temporary impairment losses recognized in earnings — — — — Net realized gains 833 4,473 6,718 788 Other income (expense) 10,399 (1,665 ) 1,336 586 Total revenues $ 253,114 $ 249,540 $ 269,260 $ 251,617 Expenses: Net losses and LAE $ 135,067 $ 140,220 $ 135,284 $ 134,658 Commission expenses 25,727 32,150 33,943 33,708 Other operating expenses 47,146 47,992 50,388 51,299 Interest expense 3,852 4,319 3,388 3,854 Total expenses $ 211,792 $ 224,681 $ 223,003 $ 223,519 Income before income taxes 41,322 24,859 46,257 28,098 Income tax expense $ 13,354 $ 7,998 $ 15,032 $ 8,823 Net income $ 27,968 $ 16,861 $ 31,225 $ 19,275 Comprehensive income $ 32,920 $ 32,965 $ 20,628 $ 27,015 Combined ratio 92.2 % 95.3 % 89.5 % 93.8 % Net income per share: Basic $ 1.96 $ 1.18 $ 2.19 $ 1.35 Diluted $ 1.94 $ 1.17 $ 2.14 $ 1.31

Organization and Summary of S44

Organization and Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Organization And Summary Of Significant Accounting Policies [Line Items]
Remeasurement of Foreign Currency		$ 10,000,000
Remeasurement of Foreign currency, After tax		6,600,000
Impairment of goodwill and indefinite lived intangible assets	$ 0	0	$ 0
Goodwill and other intangible assets	6,807,000	$ 7,013,000
Changes in the carrying value of the goodwill and indefinite lived intangible assets	$ 200,000
Minimum
Organization And Summary Of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Maximum
Organization And Summary Of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	7 years
Leasehold Improvements | Minimum
Organization And Summary Of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Leasehold Improvements | Maximum
Organization And Summary Of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Syndicate 1,221
Organization And Summary Of Significant Accounting Policies [Line Items]
Percentage control of stamp capacity	100.00%

Segment Information - Additiona

Segment Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015Segment
Segment Reporting [Abstract]
Number of underwriting Segments	3
Number of Operating Segments	3

Financial Data by Segment (Deta

Financial Data by Segment (Detail) - 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, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Net earned premiums		$ 251,545	$ 254,082	$ 242,328	$ 236,132	$ 234,172	$ 245,367	$ 231,084	$ 225,272	$ 984,087	$ 935,895	$ 841,939
Net losses and LAE		(153,881)	(146,546)	(141,973)	(130,198)	(134,658)	(135,284)	(140,220)	(135,067)	(572,598)	(545,229)	(518,961)
Commission expenses		(31,339)	(34,253)	(31,480)	(32,905)	(33,708)	(33,943)	(32,150)	(25,727)	(129,977)	(125,528)	(113,494)
Other operating expenses										(223,516)	(196,825)	(164,434)
Other underwriting income (expense)										122	595	(1,172)
Underwriting profit (loss)										58,118	68,908	43,878
Net investment income		18,499	17,371	16,595	16,253	16,071	15,839	15,648	16,610	68,718	64,168	56,251
Net realized gains (losses)										6,675	12,812	20,546
Interest expense		(3,857)	(3,856)	(3,856)	(3,855)	(3,854)	(3,388)	(4,319)	(3,852)	(15,424)	(15,413)	(10,507)
Call premium on Senior notes												(17,895)
Other income (loss)										(613)	10,061
Income before income taxes		23,815	26,924	28,379	38,356	28,098	46,257	24,859	41,322	117,474	140,536	92,273
Income tax (expense) benefit		(6,072)	(8,723)	(9,195)	(12,427)	(8,823)	(15,032)	(7,998)	(13,354)	(36,417)	(45,207)	(28,807)
Net income		$ 17,743	$ 18,201	$ 19,184	$ 25,929	$ 19,275	$ 31,225	$ 16,861	$ 27,968	$ 81,057	$ 95,329	$ 63,466
Losses and LAE ratio										58.20%	58.30%	61.60%
Commission expense ratio										13.20%	13.40%	13.50%
Other operating expense ratio	[1]									22.70%	20.90%	19.70%
Combined ratio		97.20%	93.40%	93.40%	92.30%	93.80%	89.50%	95.30%	92.20%	94.10%	92.60%	94.80%
U.S.Insurance
Segment Reporting Information [Line Items]
Net earned premiums										$ 555,836	$ 504,289	$ 437,737
Net losses and LAE										(343,497)	(311,839)	(283,694)
Commission expenses										(56,319)	(49,840)	(43,409)
Other operating expenses										(131,407)	(115,817)	(99,013)
Other underwriting income (expense)										1,690	2,241	2,924
Underwriting profit (loss)										26,303	29,034	14,545
Income before income taxes										$ 26,303	$ 29,034	$ 14,545
Losses and LAE ratio										61.80%	61.80%	64.80%
Commission expense ratio										10.10%	9.90%	9.90%
Other operating expense ratio	[1]									23.40%	22.50%	22.00%
Combined ratio										95.30%	94.20%	96.70%
International Insurance
Segment Reporting Information [Line Items]
Net earned premiums										$ 259,960	$ 243,485	$ 232,962
Net losses and LAE										(134,702)	(115,079)	(103,853)
Commission expenses										(43,676)	(44,426)	(42,977)
Other operating expenses										(75,867)	(65,275)	(54,062)
Other underwriting income (expense)											32	(1,867)
Underwriting profit (loss)										5,715	18,737	30,203
Income before income taxes										$ 5,715	$ 18,737	$ 30,203
Losses and LAE ratio										51.80%	47.30%	44.60%
Commission expense ratio										16.80%	18.20%	18.40%
Other operating expense ratio	[1]									29.20%	26.80%	24.00%
Combined ratio										97.80%	92.30%	87.00%
Global Reinsurance
Segment Reporting Information [Line Items]
Net earned premiums										$ 168,291	$ 188,121	$ 171,240
Net losses and LAE										(94,399)	(118,311)	(131,414)
Commission expenses										(32,240)	(33,429)	(29,456)
Other operating expenses										(16,242)	(15,733)	(11,359)
Other underwriting income (expense)										690	489	119
Underwriting profit (loss)										26,100	21,137	(870)
Income before income taxes										$ 26,100	$ 21,137	$ (870)
Losses and LAE ratio										56.10%	62.90%	76.70%
Commission expense ratio										19.20%	17.80%	17.20%
Other operating expense ratio	[1]									9.20%	8.10%	6.60%
Combined ratio										84.50%	88.80%	100.50%
Corporate
Segment Reporting Information [Line Items]
Commission expenses	[2]									$ 2,258	$ 2,167	$ 2,348
Other underwriting income (expense)	[2]									(2,258)	(2,167)	(2,348)
Net investment income	[2]									68,718	64,168	56,251
Net realized gains (losses)	[2]									6,675	12,812	20,546
Interest expense	[2]									(15,424)	(15,413)	(10,507)
Call premium on Senior notes	[2]											(17,895)
Other income (loss)	[2]									(613)	10,061
Income before income taxes	[2]									59,356	71,628	48,395
Income tax (expense) benefit	[2]									$ (36,417)	$ (45,207)	$ (28,807)
[1]	Includes Other operating expenses and Other underwriting income (expense).
[2]	Includes Corporate segment intercompany eliminations.

Additional Financial Data by Se

Additional Financial Data by Segment (Detail) - 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, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Gross written premiums	$ 323,509	$ 354,062	$ 379,471	$ 396,460	$ 333,299	$ 327,469	$ 348,795	$ 422,790	$ 1,453,502	$ 1,432,353	$ 1,370,517
Ceded written premiums									(409,642)	(432,215)	(482,595)
Net written premiums	244,719	251,939	258,244	288,958	228,007	228,417	231,864	311,850	1,043,860	1,000,138	887,922
Net earned premiums	$ 251,545	$ 254,082	$ 242,328	$ 236,132	$ 234,172	$ 245,367	$ 231,084	$ 225,272	984,087	935,895	841,939
U.S.Insurance
Segment Reporting Information [Line Items]
Gross written premiums									865,781	807,108	745,995
Ceded written premiums									(268,775)	(254,983)	(279,769)
Net written premiums									597,006	552,125	466,226
Net earned premiums									555,836	504,289	437,737
U.S.Insurance | Marine
Segment Reporting Information [Line Items]
Gross written premiums									158,124	154,233	143,867
Ceded written premiums									(61,916)	(46,685)	(44,359)
Net written premiums									96,208	107,548	99,508
Net earned premiums									96,082	105,650	106,150
U.S.Insurance | Property Casualty
Segment Reporting Information [Line Items]
Gross written premiums									596,673	543,045	472,049
Ceded written premiums									(152,168)	(169,953)	(202,430)
Net written premiums									444,505	373,092	269,619
Net earned premiums									401,408	314,833	231,186
U.S.Insurance | Professional Liability
Segment Reporting Information [Line Items]
Gross written premiums									110,984	109,830	130,079
Ceded written premiums									(54,691)	(38,345)	(32,980)
Net written premiums									56,293	71,485	97,099
Net earned premiums									58,346	83,806	100,401
International Insurance
Segment Reporting Information [Line Items]
Gross written premiums									411,947	424,904	431,488
Ceded written premiums									(134,005)	(171,921)	(197,832)
Net written premiums									277,942	252,983	233,656
Net earned premiums									259,960	243,485	232,962
International Insurance | Marine
Segment Reporting Information [Line Items]
Gross written premiums									183,707	190,787	192,870
Ceded written premiums									(36,515)	(47,805)	(50,887)
Net written premiums									147,192	142,982	141,983
Net earned premiums									149,256	141,097	150,784
International Insurance | Property Casualty
Segment Reporting Information [Line Items]
Gross written premiums									130,729	158,139	180,657
Ceded written premiums									(67,722)	(98,087)	(120,068)
Net written premiums									63,007	60,052	60,589
Net earned premiums									55,320	62,520	55,809
International Insurance | Professional Liability
Segment Reporting Information [Line Items]
Gross written premiums									97,511	75,978	57,961
Ceded written premiums									(29,768)	(26,029)	(26,877)
Net written premiums									67,743	49,949	31,084
Net earned premiums									55,384	39,868	26,369
Global Reinsurance
Segment Reporting Information [Line Items]
Gross written premiums									175,774	200,341	193,034
Ceded written premiums									(6,862)	(5,311)	(4,994)
Net written premiums									168,912	195,030	188,040
Net earned premiums									$ 168,291	$ 188,121	$ 171,240

Identifiable Assets by Legal En

Identifiable Assets by Legal Entity (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Identifiable assets:
Total identifiable assets	$ 4,584,012	$ 4,476,185
NIC, NSIC and Navigators Management Company, Inc
Identifiable assets:
Total identifiable assets	3,455,586	3,356,093
NHUK
Identifiable assets:
Total identifiable assets	996,242	957,795
Parent Company
Identifiable assets:
Total identifiable assets	$ 132,184	$ 162,297

Investments Including OTTI Secu

Investments Including OTTI Securities Recognized within AOCI (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Gain (Loss) on Investments [Line Items]
Total investments	$ 2,937,226	$ 2,729,735
Gross Unrealized Gains	66,693	83,078
Gross Unrealized Losses	(29,398)	(11,672)
Amortized Cost	2,899,931	2,658,329
Fixed maturities
Gain (Loss) on Investments [Line Items]
Total investments	2,414,210	2,365,934
Gross Unrealized Gains	40,350	52,322
Gross Unrealized Losses	(26,385)	(10,347)
Amortized Cost	2,400,245	2,323,959
Fixed maturities | U.S. Treasury bonds, agency bonds, and foreign
Gain (Loss) on Investments [Line Items]
Total investments	252,882	397,923
Gross Unrealized Gains	2,273	3,431
Gross Unrealized Losses	(9,214)	(5,965)
Amortized Cost	259,823	400,457
Fixed maturities | States, municipalities and political subdivisions
Gain (Loss) on Investments [Line Items]
Total investments	576,859	541,007
Gross Unrealized Gains	21,233	19,204
Gross Unrealized Losses	(781)	(558)
Amortized Cost	556,407	522,361
Fixed maturities | Agency mortgage-backed securities
Gain (Loss) on Investments [Line Items]
Total investments	379,269	364,622
Gross Unrealized Gains	5,573	8,476
Gross Unrealized Losses	(2,082)	(998)
Amortized Cost	375,778	357,144
Fixed maturities | Residential Mortgage Backed Securities
Gain (Loss) on Investments [Line Items]
Total investments	30,465	34,087
Gross Unrealized Gains	694	1,153
Gross Unrealized Losses	(82)	(138)
Amortized Cost	29,853	33,072
Fixed maturities | Asset-backed securities
Gain (Loss) on Investments [Line Items]
Total investments	225,012	206,413
Gross Unrealized Gains	85	380
Gross Unrealized Losses	(1,624)	(964)
Amortized Cost	226,551	206,997
Fixed maturities | Commercial mortgage-backed securities
Gain (Loss) on Investments [Line Items]
Total investments	189,713	206,318
Gross Unrealized Gains	3,119	6,630
Gross Unrealized Losses	(1,864)	(98)
Amortized Cost	188,458	199,786
Fixed maturities | Mortgage-backed and asset-backed securities
Gain (Loss) on Investments [Line Items]
Total investments	824,459	811,440
Gross Unrealized Gains	9,471	16,639
Gross Unrealized Losses	(5,652)	(2,198)
Amortized Cost	820,640	796,999
Fixed maturities | Corporate bonds
Gain (Loss) on Investments [Line Items]
Total investments	760,010	615,564
Gross Unrealized Gains	7,373	13,048
Gross Unrealized Losses	(10,738)	(1,626)
Amortized Cost	763,375	604,142
Equity Securities
Gain (Loss) on Investments [Line Items]
Total investments	305,271	184,295
Gross Unrealized Gains	26,341	30,756
Gross Unrealized Losses	(3,013)	(1,304)
Amortized Cost	281,943	154,843
Short-term investments
Gain (Loss) on Investments [Line Items]
Total investments	217,745	179,506
Gross Unrealized Gains	2
Gross Unrealized Losses		(21)
Amortized Cost	$ 217,743	$ 179,527

Investments - Additional Inform

Investments - Additional Information (Detail) $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2015USD ($)	Jun. 30, 2015USD ($)	Dec. 31, 2015USD ($)Security	Dec. 31, 2014USD ($)Security	Dec. 31, 2013USD ($)
Schedule of Investments [Line Items]
Non-credit OTTI on fixed maturities in an unrealized gain position			$ 500	$ 700
Gross Unrealized Loss			29,398	11,651
OTTI losses	$ 1,275	$ 423	$ 1,698	$ 0	$ 2,393
Equity Securities And Municipal Bond
Schedule of Investments [Line Items]
OTTI losses					$ 2,400
Equity Securities
Schedule of Investments [Line Items]
Number of securities in unrealized loss position | Security			57	15
Gross Unrealized Loss			$ 3,013	$ 1,304
Fixed maturities
Schedule of Investments [Line Items]
Number of securities in unrealized loss position | Security			368	259
Gross Unrealized Loss			$ 26,385	$ 10,347
Maximum | Equity Securities
Schedule of Investments [Line Items]
Percentage of fair value under carrying value			80.00%
Non-government-backed securities
Schedule of Investments [Line Items]
Gross Unrealized Loss			$ 2,600	$ 500
Non-government-backed securities | Maximum
Schedule of Investments [Line Items]
Percentage of investment			5.00%	5.00%
Mortgage-backed and asset-backed securities
Schedule of Investments [Line Items]
Securities, effective maturities			4 years 7 months 6 days
Mortgage-backed and asset-backed securities | Fixed maturities
Schedule of Investments [Line Items]
Gross Unrealized Loss			$ 5,652	$ 2,198

Scheduled Maturity Dates for Fi

Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value
Due in one year or less	$ 79,279
Due after one year through five years	766,001
Due after five years through ten years	323,003
Due after ten years	421,468
Mortgage-backed and asset-backed securities	824,459
Total	2,414,210	$ 2,365,934
Amortized Cost
Due in one year or less	81,819
Due after one year through five years	767,634
Due after five years through ten years	320,503
Due after ten years	409,648
Mortgage-backed and asset-backed securities	820,641
Total	$ 2,400,245	$ 2,323,959

Summary of Aggregate Fair Value

Summary of Aggregate Fair Value and Gross Unrealized Loss by Length of Time Securities had Continuously been in Gross Unrealized Loss Position as Well as Number of Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	$ 1,010,970	$ 468,937
Less than 12 months Gross Unrealized Losses	(20,517)	(4,029)
Greater than 12 months Fair Value	156,975	282,337
Greater than 12 months Gross Unrealized Losses	(8,881)	(7,622)
Fair Value	1,167,945	751,274
Gross Unrealized Losses	(29,398)	(11,651)
Fixed maturities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	952,439	449,247
Less than 12 months Gross Unrealized Losses	(17,504)	(2,732)
Greater than 12 months Fair Value	156,975	282,099
Greater than 12 months Gross Unrealized Losses	(8,881)	(7,615)
Fair Value	1,109,414	731,346
Gross Unrealized Losses	(26,385)	(10,347)
Fixed maturities | U.S. Treasury bonds, agency bonds, and foreign
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	142,233	87,915
Less than 12 months Gross Unrealized Losses	(3,032)	(1,061)
Greater than 12 months Fair Value	22,230	117,683
Greater than 12 months Gross Unrealized Losses	(6,182)	(4,904)
Fair Value	164,463	205,598
Gross Unrealized Losses	(9,214)	(5,965)
Fixed maturities | States, municipalities and political subdivisions
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	50,577	16,349
Less than 12 months Gross Unrealized Losses	(549)	(60)
Greater than 12 months Fair Value	4,808	37,340
Greater than 12 months Gross Unrealized Losses	(232)	(498)
Fair Value	55,385	53,689
Gross Unrealized Losses	(781)	(558)
Fixed maturities | Agency mortgage-backed securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	164,817	18,881
Less than 12 months Gross Unrealized Losses	(1,315)	(80)
Greater than 12 months Fair Value	29,862	58,301
Greater than 12 months Gross Unrealized Losses	(767)	(918)
Fair Value	194,679	77,182
Gross Unrealized Losses	(2,082)	(998)
Fixed maturities | Residential Mortgage Backed Securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	3,910	5,625
Less than 12 months Gross Unrealized Losses	(5)	(50)
Greater than 12 months Fair Value	1,684	1,728
Greater than 12 months Gross Unrealized Losses	(77)	(88)
Fair Value	5,594	7,353
Gross Unrealized Losses	(82)	(138)
Fixed maturities | Asset-backed securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	112,479	110,275
Less than 12 months Gross Unrealized Losses	(663)	(539)
Greater than 12 months Fair Value	81,477	34,530
Greater than 12 months Gross Unrealized Losses	(961)	(425)
Fair Value	193,956	144,805
Gross Unrealized Losses	(1,624)	(964)
Fixed maturities | Commercial mortgage-backed securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	83,024	19,741
Less than 12 months Gross Unrealized Losses	(1,826)	(71)
Greater than 12 months Fair Value	3,065	1,391
Greater than 12 months Gross Unrealized Losses	(38)	(27)
Fair Value	86,089	21,132
Gross Unrealized Losses	(1,864)	(98)
Fixed maturities | Mortgage-backed and asset-backed securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	364,230	154,522
Less than 12 months Gross Unrealized Losses	(3,809)	(740)
Greater than 12 months Fair Value	116,088	95,950
Greater than 12 months Gross Unrealized Losses	(1,843)	(1,458)
Fair Value	480,318	250,472
Gross Unrealized Losses	(5,652)	(2,198)
Fixed maturities | Corporate bonds
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	395,399	190,461
Less than 12 months Gross Unrealized Losses	(10,114)	(871)
Greater than 12 months Fair Value	13,849	31,126
Greater than 12 months Gross Unrealized Losses	(624)	(755)
Fair Value	409,248	221,587
Gross Unrealized Losses	(10,738)	(1,626)
Equity Securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	58,531	19,690
Less than 12 months Gross Unrealized Losses	(3,013)	(1,297)
Greater than 12 months Fair Value		238
Greater than 12 months Gross Unrealized Losses		(7)
Fair Value	58,531	19,928
Gross Unrealized Losses	$ (3,013)	$ (1,304)

Summary of Cumulative Amounts R

Summary of Cumulative Amounts Related to Credit Loss Portion of Other-Than-Temporary Impairment Losses on Debt Securities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Investments Debt And Equity Securities [Abstract]
Beginning balance	$ 2,361	$ 5,154	$ 3,332
Additions for credit loss impairments recognized in the current period on securities not previously impaired	0	0	1,822
Additions for credit loss impairments recognized in the current period on securities previously impaired	0	0	0
Reductions for credit loss impairments previously recognized on securities sold during the period	0	(2,793)	0
Ending balance	$ 2,361	$ 2,361	$ 5,154

Net Investment Income (Detail)

Net Investment Income (Detail) - 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, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Investment Income [Line Items]
Investment Income									$ 72,068	$ 67,166	$ 59,507
Investment expenses									(3,350)	(2,998)	(3,256)
Net investment income	$ 18,499	$ 17,371	$ 16,595	$ 16,253	$ 16,071	$ 15,839	$ 15,648	$ 16,610	68,718	64,168	56,251
Fixed maturities
Net Investment Income [Line Items]
Investment Income									61,572	57,219	53,898
Equity Securities
Net Investment Income [Line Items]
Investment Income									9,813	9,036	4,835
Short-term investments
Net Investment Income [Line Items]
Investment Income									$ 683	$ 911	$ 774

Realized Gains and Losses, Excl

Realized Gains and Losses, Excluding Net Other-Than-Temporary Impairment Losses Recognized in Earnings (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Gain (Loss) on Investments [Line Items]
Net realized gains (losses)	$ 8,373	$ 12,812	$ 22,939
Fixed maturities
Gain (Loss) on Investments [Line Items]
Gains	4,756	8,326	8,539
Losses	(5,926)	(2,610)	(2,797)
Net realized gains (losses)	(1,170)	5,716	5,742
Short-term investments
Gain (Loss) on Investments [Line Items]
Gains	130
Losses	(383)
Net realized gains (losses)	(253)
Equity Securities
Gain (Loss) on Investments [Line Items]
Gains	14,331	9,447	17,955
Losses	(4,535)	(2,351)	(758)
Net realized gains (losses)	$ 9,796	$ 7,096	$ 17,197

Fair Value Measurement - Additi

Fair Value Measurement - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate stated on senior notes	7.00%
Senior notes due date	May 1, 2016
Significant transfers between Level 1 and Level 2	$ 0	$ 0
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Level 3 assets	$ 0	$ 0
5.75% Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate stated on senior notes	5.75%
Senior notes due date	Oct. 15, 2023

Fixed Maturities and Equity Sec

Fixed Maturities and Equity Securities by Asset Class that are Measured at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	$ 2,937,226	$ 2,729,735
Total liabilities measured at fair value	282,486	285,710
Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes, at fair value	282,486	285,710
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	411,594	453,593
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	2,525,632	2,276,142
Total liabilities measured at fair value	282,486	285,710
Level 2 | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes, at fair value	282,486	285,710
Fixed maturities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	2,414,210	2,365,934
Fixed maturities | U.S. Treasury bonds, agency bonds, and foreign
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	252,882	397,923
Fixed maturities | States, municipalities and political subdivisions
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	576,859	541,007
Fixed maturities | Agency mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	379,269	364,622
Fixed maturities | Residential Mortgage Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	30,465	34,087
Fixed maturities | Asset-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	225,012	206,413
Fixed maturities | Commercial mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	189,713	206,318
Fixed maturities | Mortgage-backed and asset-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	824,459	811,440
Fixed maturities | Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	760,010	615,564
Fixed maturities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	67,394	146,904
Fixed maturities | Level 1 | U.S. Treasury bonds, agency bonds, and foreign
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	67,394	146,904
Fixed maturities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	2,346,816	2,219,030
Fixed maturities | Level 2 | U.S. Treasury bonds, agency bonds, and foreign
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	185,488	251,019
Fixed maturities | Level 2 | States, municipalities and political subdivisions
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	576,859	541,007
Fixed maturities | Level 2 | Agency mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	379,269	364,622
Fixed maturities | Level 2 | Residential Mortgage Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	30,465	34,087
Fixed maturities | Level 2 | Asset-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	225,012	206,413
Fixed maturities | Level 2 | Commercial mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	189,713	206,318
Fixed maturities | Level 2 | Mortgage-backed and asset-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	824,459	811,440
Fixed maturities | Level 2 | Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	760,010	615,564
Equity Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	305,271	184,295
Equity Securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	126,455	127,183
Equity Securities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	178,816	57,112
Short-term investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	217,745	179,506
Short-term investments | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	$ 217,745	$ 179,506

Summary of Activity in Reserve

Summary of Activity in Reserve for Losses and LAE (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Insurance [Abstract]
Net reserves for losses and LAE at beginning of year	$ 1,308,136	$ 1,222,633	$ 1,216,909
Provision for losses and LAE for claims occurring in the current year	637,267	601,041	520,227
Increase (decrease) in estimated losses and LAE for claims occurring in prior years	(64,669)	(55,812)	(1,266)
Incurred losses and LAE	572,598	545,229	518,961
Losses and LAE paid for claims occurring during:
Current year	(159,802)	(158,806)	(147,864)
Prior years	(320,863)	(295,527)	(365,479)
Losses and LAE payments	(480,665)	(454,333)	(513,343)
Foreign Currency Adjustment	(6,943)	(5,393)	106
Net reserves for losses and LAE at end of year	1,393,126	1,308,136	1,222,633
Reinsurance recoverables on unpaid losses and LAE	809,518	851,498	822,438
Gross reserves for losses and LAE at end of year	$ 2,202,644	$ 2,159,634	$ 2,045,071

Reporting and Operating Segment

Reporting and Operating Segments Breakdowns of Prior Period Net Reserve Deficiency (Redundancy) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	$ (64,669)	$ (55,812)	$ (1,266)
U.S.Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(29,319)	(15,420)	11,036
U.S.Insurance | Marine
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(24,825)	(29,047)	(13,679)
U.S.Insurance | Property Casualty
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(706)	17,081	12,938
U.S.Insurance | Professional Liability
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(3,788)	(3,454)	11,777
International Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(26,216)	(38,252)	(27,335)
International Insurance | Marine
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(21,914)	(31,677)	(6,361)
International Insurance | Property Casualty
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(8,458)	(3,829)	(22,263)
International Insurance | Professional Liability
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	4,156	(2,746)	1,289
Global Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	$ (9,134)	(2,140)	15,033
Global Reinsurance | Marine
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years		$ (2,140)	$ 15,000

Reserves for Losses and LAE - A

Reserves for Losses and LAE - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	$ (64,669)	$ (55,812)	$ (1,266)
U.S.Insurance
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(29,319)	(15,420)	11,036
U.S.Insurance | Marine
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(24,825)	(29,047)	(13,679)
U.S.Insurance | Marine | Marine Liability Business
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years			(13,700)
U.S.Insurance | Property Casualty
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(706)	17,081	12,938
U.S.Insurance | Professional Liability
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(3,788)	(3,454)	11,777
U.S.Insurance | Professional Liability | Errors and Omissions
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(3,788)
U.S.Insurance | Professional Liability | Directors and Officers
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years		(3,500)	11,800
International Insurance
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(26,216)	(38,252)	(27,335)
International Insurance | Marine
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(21,914)	(31,677)	(6,361)
International Insurance | Marine | Marine Liability Business
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years			(6,400)
International Insurance | Property Casualty
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(8,458)	(3,829)	(22,263)
International Insurance | Property Casualty | Marine Liability Business
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years			(22,300)
International Insurance | Professional Liability
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	4,156	(2,746)	1,289
International Insurance | Professional Liability | Errors and Omissions
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years			1,300
International Insurance | Professional Liability | Directors and Officers
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	4,200
International Insurance | Professional Liability | Errors And Omissions And Management Liability
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years		(2,700)
Global Reinsurance
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(9,134)	(2,140)	15,033
Global Reinsurance | Marine
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years		$ (2,140)	$ 15,000
Global Reinsurance | Marine Property And Casualty And Accident And Health
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	$ (9,134)

Ceded Reinsurance - Additional

Ceded Reinsurance - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Effects of Reinsurance [Line Items]
Policyholders' surplus for reinsurance	$ 500,000
Reinsurance rating description	A reinsurer generally must have a rating from A.M. Best and/or S&P of “A” or better, or an equivalent financial strength if not rated, plus at least $500 million in policyholders’ surplus to meet our standards of acceptability.
Reserve for uncollectible reinsurance amount	$ 6,900	$ 11,300
Collateral Held	159,570
Ceded Balances Payable
Effects of Reinsurance [Line Items]
Collateral Held	107,400
Letter of Credit
Effects of Reinsurance [Line Items]
Collateral Held	45,800
All Other
Effects of Reinsurance [Line Items]
Collateral Held	$ 6,400

Lists of 10 Largest Reinsurers

Lists of 10 Largest Reinsurers Measured by Reinsurance Recoverable (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		$ 232,588	$ 237,851
Reinsurance Recoverables Paid/Unpaid Losses		859,024
Reinsurance Recoverables Total	[1]	1,091,612
Collateral Held		159,570
National Indemnity Company | AM Best, A++ Rating | Standard & Poor's, AA+ Rating
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		14,854
Reinsurance Recoverables Paid/Unpaid Losses		118,337
Reinsurance Recoverables Total	[1]	133,191
Collateral Held		$ 7,198
National Indemnity Company | AM Best | AM Best, A++ Rating | Standard & Poor's, AA+ Rating
Ceded Credit Risk [Line Items]
Rating		A++
National Indemnity Company | Standard & Poor's | AM Best, A++ Rating | Standard & Poor's, AA+ Rating
Ceded Credit Risk [Line Items]
Rating		AA+
Everest Reinsurance Company | AM Best, A+ Rating | Standard & Poor's, A+ Rating
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		$ 21,097
Reinsurance Recoverables Paid/Unpaid Losses		77,702
Reinsurance Recoverables Total	[1]	98,799
Collateral Held		$ 3,933
Everest Reinsurance Company | AM Best | AM Best, A+ Rating | Standard & Poor's, A+ Rating
Ceded Credit Risk [Line Items]
Rating		A+
Everest Reinsurance Company | Standard & Poor's | AM Best, A+ Rating | Standard & Poor's, A+ Rating
Ceded Credit Risk [Line Items]
Rating		A+
Swiss Reinsurance America Corporation | AM Best, A+ Rating | Standard & Poor's, AA- Rating
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		$ 25,564
Reinsurance Recoverables Paid/Unpaid Losses		63,081
Reinsurance Recoverables Total	[1]	88,645
Collateral Held		$ 7,814
Swiss Reinsurance America Corporation | AM Best | AM Best, A+ Rating | Standard & Poor's, AA- Rating
Ceded Credit Risk [Line Items]
Rating		A+
Swiss Reinsurance America Corporation | Standard & Poor's | AM Best, A+ Rating | Standard & Poor's, AA- Rating
Ceded Credit Risk [Line Items]
Rating		AA-
Transatlantic Reinsurance Company | AM Best, A Rating | Standard & Poor's, A+ Rating
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		$ 9,267
Reinsurance Recoverables Paid/Unpaid Losses		62,402
Reinsurance Recoverables Total	[1]	71,669
Collateral Held		$ 1,783
Transatlantic Reinsurance Company | AM Best | AM Best, A Rating | Standard & Poor's, A+ Rating
Ceded Credit Risk [Line Items]
Rating		A
Transatlantic Reinsurance Company | Standard & Poor's | AM Best, A Rating | Standard & Poor's, A+ Rating
Ceded Credit Risk [Line Items]
Rating		A+
Munich Reinsurance America Inc | AM Best, A+ Rating | Standard & Poor's, AA- Rating
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		$ 9,051
Reinsurance Recoverables Paid/Unpaid Losses		51,795
Reinsurance Recoverables Total	[1]	60,846
Collateral Held		$ 1,577
Munich Reinsurance America Inc | AM Best | AM Best, A+ Rating | Standard & Poor's, AA- Rating
Ceded Credit Risk [Line Items]
Rating		A+
Munich Reinsurance America Inc | Standard & Poor's | AM Best, A+ Rating | Standard & Poor's, AA- Rating
Ceded Credit Risk [Line Items]
Rating		AA-
Allied World Reinsurance | AM Best, A Rating | Standard & Poor's, A Rating
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		$ 7,177
Reinsurance Recoverables Paid/Unpaid Losses		38,343
Reinsurance Recoverables Total	[1]	45,520
Collateral Held		$ 1,012
Allied World Reinsurance | AM Best | AM Best, A Rating | Standard & Poor's, A Rating
Ceded Credit Risk [Line Items]
Rating		A
Allied World Reinsurance | Standard & Poor's | AM Best, A Rating | Standard & Poor's, A Rating
Ceded Credit Risk [Line Items]
Rating		A
Employers Mutual Casualty Company | AM Best, A Rating | Standard & Poor's, Not Rated
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		$ 10,775
Reinsurance Recoverables Paid/Unpaid Losses		28,321
Reinsurance Recoverables Total	[1]	39,096
Collateral Held		$ 4,015
Employers Mutual Casualty Company | AM Best | AM Best, A Rating | Standard & Poor's, Not Rated
Ceded Credit Risk [Line Items]
Rating		A
Employers Mutual Casualty Company | Standard & Poor's | AM Best, A Rating | Standard & Poor's, Not Rated
Ceded Credit Risk [Line Items]
Rating		NR
Ace Property and Casualty Insurance Company | AM Best, A++ Rating | Standard & Poor's, AA Rating
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		$ 12,577
Reinsurance Recoverables Paid/Unpaid Losses		21,470
Reinsurance Recoverables Total	[1]	34,047
Collateral Held		$ 3,284
Ace Property and Casualty Insurance Company | AM Best | AM Best, A++ Rating | Standard & Poor's, AA Rating
Ceded Credit Risk [Line Items]
Rating		A++
Ace Property and Casualty Insurance Company | Standard & Poor's | AM Best, A++ Rating | Standard & Poor's, AA Rating
Ceded Credit Risk [Line Items]
Rating		AA
Partner Reinsurance Europe | AM Best, A Rating | Standard & Poor's, A+ Rating
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		$ 11,231
Reinsurance Recoverables Paid/Unpaid Losses		21,728
Reinsurance Recoverables Total	[1]	32,959
Collateral Held		$ 17,619
Partner Reinsurance Europe | AM Best | AM Best, A Rating | Standard & Poor's, A+ Rating
Ceded Credit Risk [Line Items]
Rating		A
Partner Reinsurance Europe | Standard & Poor's | AM Best, A Rating | Standard & Poor's, A+ Rating
Ceded Credit Risk [Line Items]
Rating		A+
National Union Fire Ins | AM Best, A Rating | Standard & Poor's, A+ Rating
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		$ 7,478
Reinsurance Recoverables Paid/Unpaid Losses		22,288
Reinsurance Recoverables Total	[1]	29,766
Collateral Held		$ 5,717
National Union Fire Ins | AM Best | AM Best, A Rating | Standard & Poor's, A+ Rating
Ceded Credit Risk [Line Items]
Rating		A
National Union Fire Ins | Standard & Poor's | AM Best, A Rating | Standard & Poor's, A+ Rating
Ceded Credit Risk [Line Items]
Rating		A+
Insurance Companies
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		$ 129,071
Reinsurance Recoverables Paid/Unpaid Losses		505,467
Reinsurance Recoverables Total	[1]	634,538
Collateral Held		53,952
All Other
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		103,517
Reinsurance Recoverables Paid/Unpaid Losses		353,557
Reinsurance Recoverables Total	[1]	457,074
Collateral Held		$ 105,618
[1]	Net of reserve for uncollectible reinsurance of approximately $6.9 million.

Lists of 10 Largest Reinsurer63

Lists of 10 Largest Reinsurers Measured by Reinsurance Recoverable (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Insurance [Abstract]
Reserve for uncollectible reinsurance amount	$ 6.9	$ 11.3

Summary of Components of Net Wr

Summary of Components of Net Written Premium (Detail) - 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, 2015	Dec. 31, 2014	Dec. 31, 2013
Insurance [Abstract]
Direct									$ 1,277,728	$ 1,232,012	$ 1,177,483
Assumed									175,774	200,341	193,034
Ceded written premiums									(409,642)	(432,215)	(482,595)
Net written premiums	$ 244,719	$ 251,939	$ 258,244	$ 288,958	$ 228,007	$ 228,417	$ 231,864	$ 311,850	$ 1,043,860	$ 1,000,138	$ 887,922

Summary of Components of Net Ea

Summary of Components of Net Earned Premium (Detail) - 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, 2015	Dec. 31, 2014	Dec. 31, 2013
Insurance [Abstract]
Direct									$ 1,223,840	$ 1,183,120	$ 1,121,198
Assumed									175,153	193,431	176,726
Ceded									(414,906)	(440,656)	(455,985)
Net earned premiums	$ 251,545	$ 254,082	$ 242,328	$ 236,132	$ 234,172	$ 245,367	$ 231,084	$ 225,272	$ 984,087	$ 935,895	$ 841,939

Summary of Components of Net Lo

Summary of Components of Net Losses and Loss Adjustment Expenses Incurred (Detail) - 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, 2015	Dec. 31, 2014	Dec. 31, 2013
Insurance [Abstract]
Direct									$ 703,361	$ 657,059	$ 574,020
Assumed									97,947	118,352	133,674
Ceded									(228,710)	(230,182)	(188,733)
Net losses and LAE	$ 153,881	$ 146,546	$ 141,973	$ 130,198	$ 134,658	$ 135,284	$ 140,220	$ 135,067	$ 572,598	$ 545,229	$ 518,961

Debt - Additional Information (

Debt - Additional Information (Detail) $ in Thousands, £ in Millions	Nov. 20, 2015USD ($)	Nov. 24, 2014USD ($)	Nov. 06, 2014AUD	Oct. 04, 2013USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2014USD ($)	Nov. 06, 2014GBP (£)
Line of Credit Facility [Line Items]
Issuance of new letters of credit, expiry date	Dec. 31, 2016
Line of credit facility, covenant terms					Each of the November 20, 2015 and November 24, 2014 credit facilities contains customary covenants for facilities of this type, including restrictions on indebtedness and liens, limitations on mergers, dividends and the sale of assets, and requirements as to maintaining certain consolidated tangible net worth, statutory surplus and other financial ratios. These credit facilities also provide for customary events of default, including failure to pay principal, interest or fees when due, failure to comply with covenants, any representation or warranty made by our Company being false in any material respect, default under certain other indebtedness, certain insolvency or receivership events affecting our Company, the occurrence of certain material judgments, or a change in control of our Company
Interest rate stated on senior notes					7.00%
Senior notes due date					May 1, 2016
Call premium on redemption of Senior notes						$ 17,895
Senior Notes
Line of Credit Facility [Line Items]
Unamortized discount					$ 1,400		$ 1,600
Minimum
Line of Credit Facility [Line Items]
Credit facility fee rate	0.85%	0.95%
Maximum
Line of Credit Facility [Line Items]
Credit facility fee rate	1.20%	1.60%
Syndicate 1,221
Line of Credit Facility [Line Items]
Aggregate face amount of letters of credit outstanding					$ 8,000
Line of credit facility, covenant compliance					As of December 31, 2015, our Company was in compliance with all covenants.
Syndicate 1221 | Above Floating Rate | Line of Credit
Line of Credit Facility [Line Items]
Line of credit facility, interest rate			2.00%
Lloyd's | Syndicate 1221
Line of Credit Facility [Line Items]
Line of credit facility, underwriting reserve required | £								£ 75
Aggregate face amount of letters of credit outstanding	$ 20,000	$ 175,000
Cash collateral posted					$ 3,300
Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility	$ 25,000	$ 175,000
Credit Facility | Syndicate 1221
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing amount | AUD			AUD 8,000,000
5.75% Senior Notes
Line of Credit Facility [Line Items]
Interest rate stated on senior notes					5.75%
Senior notes due date					Oct. 15, 2023
5.75% Senior Notes | Senior Notes
Line of Credit Facility [Line Items]
Principal amount of senior notes				$ 265,000
Interest rate stated on senior notes				5.75%
Net proceeds from issuance of senior notes				$ 263,000
Debt instrument, covenant compliance					As of December 31, 2015, our Company was in compliance with all such covenants
7.0% Senior Notes | Senior Notes
Line of Credit Facility [Line Items]
Interest rate stated on senior notes					7.00%
Senior notes due date					May 1, 2016
Call premium on redemption of Senior notes					$ 17,900

Commitments, Contingencies & Gu

Commitments, Contingencies & Guarantees - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended			22 Months Ended
	Sep. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jul. 31, 2015
Loss Contingencies [Line Items]
Rent expense		$ 12.9	$ 13.2	$ 11.5
Incentive awarded to the company by the State of Connecticut, total		11.5
Incentive awarded to the company by the State of Connecticut, non-interest bearing loans	$ 6	8
Incentive awarded to the company by the State of Connecticut, grants	1.5	$ 3.5
Non-interest bearing incentive loan term		10 years
Incentive awarded to the company by the State of Connecticut, deferred revenue	$ 7.5	$ 6.3	6.1
Forgiveness awarded to the company by the state of Connecticut		6			$ 6
Additional forgiveness awarded to the company by the state of Connecticut		1			1
Forgiveness awarded to the company by the State of Connecticut, grants		0.5			$ 0.5
Incentive awarded to the company by the State of Connecticut, revenue recognized		$ 1.4	$ 1.1	$ 0.3
Maximum
Loss Contingencies [Line Items]
Non-cancellable operating leases expiration year		2,030

Future Minimum Annual Rental Co

Future Minimum Annual Rental Commitments Under Various Noncancellable Operating Leases (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Leases [Abstract]
2,016	$ 12,769
2,017	12,213
2,018	10,327
2,019	8,482
2,020	8,313
2021-2030	42,173
Total minimum operating lease payments	$ 94,277

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	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, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Line Items]
Undistributed earnings of non-U.S. subsidiaries	$ 21,500,000								$ 21,500,000
Taxes payable on undistributed earnings	2,500,000								2,500,000
Unrecognized tax benefits	0				$ 0				0	$ 0	$ 0
Interest or penalties related to unrecognized tax benefits									0	0	0
Income tax (benefit) expense	6,072,000	$ 8,723,000	$ 9,195,000	$ 12,427,000	8,823,000	$ 15,032,000	$ 7,998,000	$ 13,354,000	$ 36,417,000	$ 45,207,000	$ 28,807,000
Effective income tax rate									31.00%	32.20%	31.20%
Deferred Tax Assets: State and Local	$ 721,000				$ 777,000				$ 721,000	$ 777,000
United Kingdom
Income Taxes [Line Items]
Foreign effective income tax rate									35.00%
United Kingdom | Syndicate 1221 | Maximum
Income Taxes [Line Items]
Percentage of premiums	50.00%								50.00%
United Kingdom | Syndicate 1221 | Minimum
Income Taxes [Line Items]
Foreign effective income tax rate									35.00%
State and Local Jurisdiction | Maximum
Income Taxes [Line Items]
State and local tax carry-forwards expiration year										2,033
State and Local Jurisdiction | Minimum
Income Taxes [Line Items]
State and local tax carry-forwards expiration year										2,025

Components of Current and Defer

Components of Current and Deferred Income Tax Expense (Benefit) (Detail) - 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, 2015	Dec. 31, 2014	Dec. 31, 2013
Current income tax expense (benefit):
Federal and foreign									$ 27,937	$ 27,290	$ 23,703
State and local									1,476	1,036	446
Subtotal									29,413	28,326	24,149
Deferred income tax expense (benefit):
Federal and foreign									7,004	16,881	4,658
State and local									0	0	0
Subtotal									7,004	16,881	4,658
Actual tax expense and rate	$ 6,072	$ 8,723	$ 9,195	$ 12,427	$ 8,823	$ 15,032	$ 7,998	$ 13,354	$ 36,417	$ 45,207	$ 28,807

Reconciliation of Total Income

Reconciliation of Total Income Taxes Applicable to Pre-Tax Operating Income and Amounts Computed by Applying Federal Statutory Income Tax Rate to Pre-Tax Operating Income (Detail) - 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, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation
Computed expected tax expense									$ 41,116	$ 49,187	$ 32,299
Tax-exempt interest									(4,987)	(4,771)	(3,839)
Dividends received deduction									(2,086)	(1,257)	(897)
Proration of DRD and Tax-exempt interest									1,061	904	710
Current state and local income taxes, net of federal income tax deduction									959	674	290
Other									354	470	244
Actual tax expense and rate	$ 6,072	$ 8,723	$ 9,195	$ 12,427	$ 8,823	$ 15,032	$ 7,998	$ 13,354	$ 36,417	$ 45,207	$ 28,807
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation
Computed expected tax expense									35.00%	35.00%	35.00%
Tax-exempt interest									(4.20%)	(3.40%)	(4.20%)
Dividends received deduction									(1.80%)	(0.90%)	(1.00%)
Proration of DRD and Tax-exempt interest									0.90%	0.60%	0.80%
Current state and local income taxes, net of federal income tax deduction									0.80%	0.50%	0.30%
Other									0.30%	0.40%	0.30%
Actual tax expense and rate									31.00%	32.20%	31.20%

Tax Effects of Temporary Differ

Tax Effects of Temporary Differences That Give Rise to Federal, Foreign, State and Local Deferred Tax Assets and Deferred Tax Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Loss reserve discount	$ 25,353	$ 24,820
Unearned premiums	31,486	29,080
Compensation related	11,175	10,586
State and local net deferred tax assets	721	777
Other	4,315	3,732
Total gross deferred tax assets	73,050	68,995
Less: Valuation allowance	(721)	(777)
Total deferred tax assets	72,329	68,218
Deferred tax liabilities:
Net unrealized gains/ losses on securities	(13,053)	(26,730)
Deferred acquisition costs	(24,037)	(22,120)
Net unrealized foreign exchange	(4,164)	(4,470)
Other	(2,709)	(2,787)
Total deferred tax liabilities	(68,429)	(69,685)
Net deferred income tax asset	3,900
Net deferred income tax (liability)		(1,467)
Lloyd's
Deferred tax liabilities:
Lloyd's year of account deferral	$ (24,466)	$ (13,578)

Stockholders Equity - Additiona

Stockholders Equity - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Nov. 30, 2014	Dec. 31, 2015	Dec. 31, 2014
Stockholders Equity [Line Items]
Common stock, authorized shares		50,000,000	50,000,000
Common stock, par value		$ 0.10	$ 0.10
Preferred stock, authorized shares		1,000,000	1,000,000
Preferred stock, par value		$ 0.10	$ 0.10
Undistributed Profit	$ 156,700,000
Dividend Capacity		$ 1,100,000
Navigators Insurance Company
Stockholders Equity [Line Items]
Maximum amount available for payment of dividends without prior regulatory approval		94,900,000
Payment of dividends		$ 0	$ 0

Changes in Issued and Outstandi

Changes in Issued and Outstanding Common Shares (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity [Abstract]
Beginning balance	14,281,000	14,198,000	14,047,000
Vested stock grants	127,000	59,000	50,000
Employee stock purchase plan	21,000	19,386	17,000
Stock options exercised	1,500	5,250	83,500
Ending balance	14,431,000	14,281,000	14,198,000

Amount and Nature of Net Assets

Amount and Nature of Net Assets Restricted from Payment of Dividends (Detail) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets		$ 541,023	$ 523,425
NIC and NSIC
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets	[1]	17,775	13,234
NIC and NSIC | Fixed maturities
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets		11,277	11,732
NIC and NSIC | Short-term investments
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets		290	290
NIC and NSIC | Cash
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets		6,208	1,212
NHUK
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets	[2]	523,248	510,191
NHUK | Fixed maturities
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets		448,666	447,679
NHUK | Short-term investments
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets		71,320	61,549
NHUK | Cash
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets		$ 3,262	$ 963
[1]	The restricted net assets for NIC and NSIC primarily consist of fixed maturities on deposit with various state insurance departments. The cash as of December 31, 2015 and 2014, as presented in the table above, was on deposit with a U.K. bank to comply with the regulatory requirements of the Prudential Regulation Authority for the underwriting activities of the U.K. Branch.
[2]	The restricted net assets for NHUK consists of fixed maturities and cash held in trust for the benefit of syndicate policyholders and short term investments primarily consisting of overseas deposits in various countries with Lloyd's to support underwriting activities in those countries.

Amount and Nature of Net Asse77

Amount and Nature of Net Assets Restricted from Payment of Dividends (Parenthetical) (Detail) - Fixed maturities - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
NIC and NSIC
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Restricted net assets, amortized cost	$ 9,950	$ 10,086
NHUK
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Restricted net assets, amortized cost	$ 458,558	$ 445,504

Reconciliation of Basic and Dil

Reconciliation of Basic and Diluted Earnings per Share Computations (Detail) - 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, 2015	Dec. 31, 2014	Dec. 31, 2013
Earning Per Share Basic And Diluted [Abstract]
Net income	$ 17,743	$ 18,201	$ 19,184	$ 25,929	$ 19,275	$ 31,225	$ 16,861	$ 27,968	$ 81,057	$ 95,329	$ 63,466
Basic weighted average shares									14,392,522	14,259,768	14,133,925
Effect of common stock equivalents:
Assumed exercise of stock options and vesting of stock grants									433,223	386,601	211,628
Diluted weighted average shares									14,825,745	14,646,369	14,345,553
Net income per common share:
Basic	$ 1.23	$ 1.26	$ 1.33	$ 1.81	$ 1.35	$ 2.19	$ 1.18	$ 1.96	$ 5.63	$ 6.69	$ 4.49
Diluted	$ 1.19	$ 1.23	$ 1.30	$ 1.77	$ 1.31	$ 2.14	$ 1.17	$ 1.94	$ 5.47	$ 6.51	$ 4.42

Summary of Statutory Net Income

Summary of Statutory Net Income (Loss) and Capital and Surplus (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
NIC and NSIC
Statutory Accounting Practices [Line Items]
Net income	$ 60.8	$ 75.7	$ 59.4
Capital and surplus	949.1	893.9	804.1
Syndicate
Statutory Accounting Practices [Line Items]
Net income	41	33.8	21
Capital and surplus	$ 177.5	$ 140.1	$ 124.2

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Apr. 30, 2013	Apr. 30, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of employees base compensation that can be invested for the purchase of common stock, maximum	10.00%
Number of shares which can be acquired by employee, maximum	1,000
Total market value of shares that can be acquired by employee	$ 25,000
Employee Stock Purchase Plan, shares purchased by employees	20,857
Employee Stock Purchase Plan, shares purchased by employees	21,000	19,386	17,000
Discount on employee stock purchase plan	10.00%
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price as percentage of fair market value	90.00%
Options and Non Performance Based Grants | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based payment award, award vesting period	3 years
Options and Non Performance Based Grants | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based payment award, award vesting period	4 years
Options expiration term (in years)	10 years
Performance Based Shares Issued in 2014 and 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of remaining shares vesting over the period dependent on compound annual growth book value per share immediately prior to vesting date	100.00%
Performance Based Shares Issued in 2014 and 2015 | Minimum | Third Anniversary of Grant Date
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares vesting over the period	50.00%
Performance Based Shares Issued in 2014 and 2015 | Maximum | Third Anniversary of Grant Date
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares vesting over the period	150.00%
Performance Based Shares Issued Between 2011-2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of remaining shares vesting over the period dependent on compound annual growth book value per share immediately prior to vesting date	50.00%
Performance Based Shares Issued Between 2011-2013 | Third Anniversary of Grant Date
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares vesting over the period	50.00%
Performance Based Shares Issued Between 2011-2013 | Minimum | Third Anniversary of Grant Date
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares vesting over the period	0.00%
Performance Based Shares Issued Between 2011-2013 | Maximum | Third Anniversary of Grant Date
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares vesting over the period	150.00%
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense, net of estimated forfeitures	$ 17,300,000	$ 16,300,000
Weighted Average Periods	2 years	2 years 3 months 18 days
Aggregate fair value of all unvested RSU	$ 55,200,000	$ 46,100,000
Amended And Restated 2005 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock authorized for issuance				2,000,000	1,500,000
Stock issued during period under incentive plan	1,435,308
Number of stock available to be issued	564,692

Unvested Restricted Stock Units

Unvested Restricted Stock Units and Performance Units Grants Outstanding (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance	718,892	626,812	587,629
Granted	217,208	288,130	269,926
Vested	(203,680)	(183,716)	(133,482)
Forfeited	(35,905)	(12,334)	(97,261)
Ending balance	696,515	718,892	626,812
Performance Based Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	185,050	228,607	114,463
Performance Based Shares | Earned
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested			(15,714)
Performance Based Shares | Unearned
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested	(68,080)	(93,453)	(57,585)
Non Performance Based Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	32,158	59,523	155,463
Vested	(135,600)	(90,263)	(60,183)

Stock Options Outstanding (Deta

Stock Options Outstanding (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Number of Shares
Beginning balance	1,500	6,750	90,250
Granted	0	0	0
Exercised	(1,500)	(5,250)	(83,500)
Expired or forfeited	0	0	0
Ending balance		1,500	6,750
Number of options exercisable		1,500	6,750
Average Exercise Price
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Beginning of Period	$ 36.03	$ 30.65	$ 29.94
Granted	0	0	0
Exercised	36.03	29.11	29.88
Expired or forfeited	$ 0	0	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, End of Period		36.03	30.65
Number of options exercisable		$ 36.03	$ 30.65

Retirement Plans - Additional I

Retirement Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
401(k) plan expense	$ 6.3	$ 7.5	$ 5.1
Defined Contribution Plan, employer discretionary matching contribution amount		1.6	0.8
United Kingdom
Defined Benefit Plan Disclosure [Line Items]
401(k) plan expense	$ 2.9	2.6	2.2
United Kingdom | Employees hired prior to November 2014
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	15.00%
United Kingdom | Employees hired after November 2014
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	12.00%
European Offices
Defined Benefit Plan Disclosure [Line Items]
401(k) plan expense	$ 0.5	0.2	0.3
European Offices | Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	2.10%
European Offices | Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	26.00%
Retirement Savings Contributions
Defined Benefit Plan Disclosure [Line Items]
401(k) plan expense	$ 3.8	3.8	2.7
Non Discretionary Matching Contributions
Defined Benefit Plan Disclosure [Line Items]
401(k) plan expense	$ 2.5	$ 2.1	$ 1.6

Summary of Quarterly Financial

Summary of Quarterly Financial Data (Detail) - 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, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Gross written premiums	$ 323,509	$ 354,062	$ 379,471	$ 396,460	$ 333,299	$ 327,469	$ 348,795	$ 422,790	$ 1,453,502	$ 1,432,353	$ 1,370,517
Revenues:
Net written premiums	244,719	251,939	258,244	288,958	228,007	228,417	231,864	311,850	1,043,860	1,000,138	887,922
Change in unearned premiums	6,826	2,143	(15,916)	(52,826)	6,165	16,950	(780)	(86,578)	(59,773)	(64,243)	(45,983)
Net earned premiums	251,545	254,082	242,328	236,132	234,172	245,367	231,084	225,272	984,087	935,895	841,939
Net investment income	18,499	17,371	16,595	16,253	16,071	15,839	15,648	16,610	68,718	64,168	56,251
Total other-than-temporary impairment losses	(123)	(1,298)	(423)		(21)	158			(1,870)	137	(2,393)
Portion of loss recognized in other comprehensive income (before tax)	123	23			21	(158)			172	(137)
Net other-than-temporary impairment losses recognized in earnings		(1,275)	(423)						(1,698)	0	(2,393)
Net realized gains (losses)	(2,080)	518	4,339	5,596	788	6,718	4,473	833
Other income (expense)	4,147	(2,518)	(4,362)	2,242	586	1,336	(1,665)	10,399	(491)	10,656	(1,172)
Total revenues	272,111	268,178	258,477	260,223	251,617	269,260	249,540	253,114	1,058,989	1,023,531	917,564
Expenses:
Net losses and LAE	153,881	146,546	141,973	130,198	134,658	135,284	140,220	135,067	572,598	545,229	518,961
Commission expenses	31,339	34,253	31,480	32,905	33,708	33,943	32,150	25,727	129,977	125,528	113,494
Other operating expenses	59,219	56,599	52,789	54,909	51,299	50,388	47,992	47,146
Interest expense	3,857	3,856	3,856	3,855	3,854	3,388	4,319	3,852	15,424	15,413	10,507
Total expenses	248,296	241,254	230,098	221,867	223,519	223,003	224,681	211,792	941,515	882,995	825,291
Income before income taxes	23,815	26,924	28,379	38,356	28,098	46,257	24,859	41,322	117,474	140,536	92,273
Income tax expense	6,072	8,723	9,195	12,427	8,823	15,032	7,998	13,354	36,417	45,207	28,807
Net income	17,743	18,201	19,184	25,929	19,275	31,225	16,861	27,968	81,057	95,329	63,466
Comprehensive income (loss)	$ 15,990	$ 18,849	$ (3,789)	$ 27,052	$ 27,015	$ 20,628	$ 32,965	$ 32,920	$ 58,102	$ 113,528	$ 16,618
Combined ratio	97.20%	93.40%	93.40%	92.30%	93.80%	89.50%	95.30%	92.20%	94.10%	92.60%	94.80%
Net income per share:
Basic	$ 1.23	$ 1.26	$ 1.33	$ 1.81	$ 1.35	$ 2.19	$ 1.18	$ 1.96	$ 5.63	$ 6.69	$ 4.49
Diluted	$ 1.19	$ 1.23	$ 1.30	$ 1.77	$ 1.31	$ 2.14	$ 1.17	$ 1.94	$ 5.47	$ 6.51	$ 4.42

Summary of Consolidated Inves85

Summary of Consolidated Investments-Other Than Investments in Related Parties (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total investments	$ 2,937,226	$ 2,729,735
Gross Unrealized Gains	66,693	83,078
Gross Unrealized Losses	(29,398)	(11,672)
Amortized Cost	2,899,931	2,658,329
Fixed maturities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total investments	2,414,210	2,365,934
Gross Unrealized Gains	40,350	52,322
Gross Unrealized Losses	(26,385)	(10,347)
Amortized Cost	2,400,245	2,323,959
Fixed maturities | U.S. Treasury bonds, agency bonds, and foreign
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total investments	252,882	397,923
Gross Unrealized Gains	2,273	3,431
Gross Unrealized Losses	(9,214)	(5,965)
Amortized Cost	259,823	400,457
Fixed maturities | States, municipalities and political subdivisions
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total investments	576,859	541,007
Gross Unrealized Gains	21,233	19,204
Gross Unrealized Losses	(781)	(558)
Amortized Cost	556,407	522,361
Fixed maturities | Agency mortgage-backed securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total investments	379,269	364,622
Gross Unrealized Gains	5,573	8,476
Gross Unrealized Losses	(2,082)	(998)
Amortized Cost	375,778	357,144
Fixed maturities | Residential Mortgage Backed Securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total investments	30,465	34,087
Gross Unrealized Gains	694	1,153
Gross Unrealized Losses	(82)	(138)
Amortized Cost	29,853	33,072
Fixed maturities | Asset-backed securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total investments	225,012	206,413
Gross Unrealized Gains	85	380
Gross Unrealized Losses	(1,624)	(964)
Amortized Cost	226,551	206,997
Fixed maturities | Commercial mortgage-backed securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total investments	189,713	206,318
Gross Unrealized Gains	3,119	6,630
Gross Unrealized Losses	(1,864)	(98)
Amortized Cost	188,458	199,786
Fixed maturities | Mortgage-backed and asset-backed securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total investments	824,459	811,440
Gross Unrealized Gains	9,471	16,639
Gross Unrealized Losses	(5,652)	(2,198)
Amortized Cost	820,640	796,999
Fixed maturities | Corporate bonds
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total investments	760,010
Gross Unrealized Gains	7,373
Gross Unrealized Losses	(10,738)
Amortized Cost	763,375
Equity Securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total investments	305,271	184,295
Gross Unrealized Gains	26,341	30,756
Gross Unrealized Losses	(3,013)	(1,304)
Amortized Cost	281,943	154,843
Short-term investments
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Total investments	217,745	179,506
Gross Unrealized Gains	2
Gross Unrealized Losses		(21)
Amortized Cost	$ 217,743	$ 179,527

Condensed Financial Informati86

Condensed Financial Information - Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
ASSETS
Investments	$ 2,937,226	$ 2,729,735
Cash	69,901	90,751	$ 86,509	$ 45,336
Goodwill and other intangible assets	6,807	7,013
Other assets	67,643	56,719
Total assets	4,584,012	4,476,185
Liabilities:
Reserves for losses and loss adjustment expenses	2,202,644	2,159,634	2,045,071
Unearned premiums	820,676	766,167
Reinsurance balances payable	107,411	152,774
Senior notes	263,580	263,440
Accounts payable and other liabilities	92,058	105,345
Total liabilities	$ 3,487,864	$ 3,448,961
Stockholders' equity:
Preferred stock, $.10 par value, authorized 1,000,000 shares, none issued
Common stock, $.10 par value, authorized 50,000,000 shares, issued 17,942,269 shares for 2015 and 17,792,846 shares for 2014	$ 1,793	$ 1,778
Additional paid-in capital	357,829	347,022
Treasury stock, at cost (3,511,380 shares for 2015 and 2014)	(155,801)	(155,801)
Retained earnings	868,723	787,666
Accumulated other comprehensive income:
Total stockholders' equity	1,096,148	1,027,224	902,212	879,485
Total liabilities and stockholders' equity	4,584,012	4,476,185
Parent Company
ASSETS
Investments	89,586	94,732
Cash	6,417	6,300	$ 6,143	$ 2,981
Investments in subsidiaries	1,232,012	1,163,822
Goodwill and other intangible assets	2,534	2,534
Other assets	33,647	27,531
Total assets	1,364,196	1,294,919
Liabilities:
Senior notes	263,580	263,440
Accounts payable and other liabilities	1,294	1,081
Accrued interest payable	3,174	3,174
Total liabilities	$ 268,048	$ 267,695
Stockholders' equity:
Preferred stock, $.10 par value, authorized 1,000,000 shares, none issued
Common stock, $.10 par value, authorized 50,000,000 shares, issued 17,942,269 shares for 2015 and 17,792,846 shares for 2014	$ 1,793	$ 1,778
Additional paid-in capital	357,829	347,022
Treasury stock, at cost (3,511,380 shares for 2015 and 2014)	(155,801)	(155,801)
Retained earnings	868,723	787,666
Accumulated other comprehensive income:
Net unrealized gains (losses) on securities available-for-sale, net of tax	23,611	46,573
Foreign currency translation adjustment, net of tax	(7)	(14)
Total stockholders' equity	1,096,148	1,027,224
Total liabilities and stockholders' equity	$ 1,364,196	$ 1,294,919

Condensed Financial Informati87

Condensed Financial Information - Balance Sheets (Parenthetical) (Detail) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements Captions [Line Items]
Preferred stock, par value	$ 0.10	$ 0.10
Preferred stock, authorized shares	1,000,000	1,000,000
Preferred stock, issued shares	0	0
Common stock, par value	$ 0.10	$ 0.10
Common stock, authorized shares	50,000,000	50,000,000
Common stock, issued shares	17,942,269	17,792,846
Treasury stock, shares	3,511,380	3,511,380
Parent Company
Condensed Financial Statements Captions [Line Items]
Preferred stock, par value	$ 0.10	$ 0.10
Preferred stock, authorized shares	1,000,000	1,000,000
Preferred stock, issued shares	0	0
Common stock, par value	$ 0.10	$ 0.10
Common stock, authorized shares	50,000,000	50,000,000
Common stock, issued shares	17,942,269	17,792,846
Treasury stock, shares	3,511,380	3,511,380

Condensed Financial Informati88

Condensed Financial Information - Statement of Income (Detail) - 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, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Net investment income	$ 18,499	$ 17,371	$ 16,595	$ 16,253	$ 16,071	$ 15,839	$ 15,648	$ 16,610	$ 68,718	$ 64,168	$ 56,251
Total revenues	272,111	268,178	258,477	260,223	251,617	269,260	249,540	253,114	1,058,989	1,023,531	917,564
Expenses:
Call premium on Senior notes											17,895
Interest expense	3,857	3,856	3,856	3,855	3,854	3,388	4,319	3,852	15,424	15,413	10,507
Other (income) expense	(4,147)	2,518	4,362	(2,242)	(586)	(1,336)	1,665	(10,399)	491	(10,656)	1,172
Total expenses	248,296	241,254	230,098	221,867	223,519	223,003	224,681	211,792	941,515	882,995	825,291
Income before income taxes	23,815	26,924	28,379	38,356	28,098	46,257	24,859	41,322	117,474	140,536	92,273
Income tax (benefit) expense	6,072	8,723	9,195	12,427	8,823	15,032	7,998	13,354	36,417	45,207	28,807
Net income	$ 17,743	$ 18,201	$ 19,184	$ 25,929	$ 19,275	$ 31,225	$ 16,861	$ 27,968	81,057	95,329	63,466
Parent Company
Revenues:
Net investment income									147	76	13
Total revenues									147	76	13
Expenses:
Call premium on Senior notes											17,895
Interest expense									15,424	15,413	10,507
Other (income) expense											2
Total expenses									15,424	15,413	28,404
Income before income taxes									(15,277)	(15,337)	(28,391)
Income tax (benefit) expense									(5,472)	(5,287)	(9,886)
Income (loss) before equity in undistributed net income of wholly owned subsidiaries									(9,805)	(10,050)	(18,505)
Equity in undistributed net income of wholly-owned subsidiaries									90,862	105,379	81,971
Net income									$ 81,057	$ 95,329	$ 63,466

Condensed Financial Informati89

Condensed Financial Information - Statement of Cash Flows (Detail) - 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, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities:
Net income	$ 17,743	$ 18,201	$ 19,184	$ 25,929	$ 19,275	$ 31,225	$ 16,861	$ 27,968	$ 81,057	$ 95,329	$ 63,466
Adjustments to reconcile net income to net cash provided by (used in) operations:
Call premium on redemption of Senior notes											17,895
Other									(4,679)	29,039	31,987
Net cash provided by (used in) operating activities									227,624	222,492	136,875
Fixed maturities, available-for-sale
Sales									376,522	362,136	648,335
Purchases									(648,059)	(864,902)	(899,930)
Equity securities
Sales									96,405	54,900	72,113
Purchases									(215,405)	(83,845)	(89,288)
Net increase in short-term investments									(38,468)	117,740	(142,214)
Net cash provided by (used in) investing activities									(249,855)	(219,470)	(229,859)
Financing activities:
Net proceeds from debt offering											263,278
Redemption of 7.0% Senior notes due May 1, 2016											(132,437)
Proceeds of stock issued from employee stock purchase plan									1,352	1,067	821
Proceeds of stock issued from exercise of stock options									29	153	2,495
Net cash provided by (used in) financing activities									1,381	1,220	134,157
Increase (decrease) in cash									(20,850)	4,242	41,173
Cash at beginning of year				90,751				86,509	90,751	86,509	45,336
Cash at end of period	69,901				90,751				69,901	90,751	86,509
Parent Company
Operating activities:
Net income									81,057	95,329	63,466
Adjustments to reconcile net income to net cash provided by (used in) operations:
Equity in undistributed net income of wholly-owned subsidiaries									(90,862)	(105,379)	(81,971)
Call premium on redemption of Senior notes											17,895
Other									3,373	9,211	2,098
Net cash provided by (used in) operating activities									(6,432)	(839)	1,488
Fixed maturities, available-for-sale
Sales									1,250	3,200	8,754
Purchases											(1,249)
Equity securities
Sales									0	0	0
Purchases									0	0	0
Net increase in short-term investments									3,918	(3,424)	(89,988)
Net cash provided by (used in) investing activities									5,168	(224)	(82,483)
Financing activities:
Capital contribution to subsidiary											(50,000)
Net proceeds from debt offering											263,278
Redemption of 7.0% Senior notes due May 1, 2016											(132,437)
Proceeds of stock issued from employee stock purchase plan									1,352	1,067	821
Proceeds of stock issued from exercise of stock options									29	153	2,495
Net cash provided by (used in) financing activities									1,381	1,220	84,157
Increase (decrease) in cash									117	157	3,162
Cash at beginning of year				$ 6,300				$ 6,143	6,300	6,143	2,981
Cash at end of period	$ 6,417				$ 6,300				$ 6,417	$ 6,300	$ 6,143

Condensed Financial Informati90

Condensed Financial Information - Statement of Cash Flows (Parenthetical) (Detail)	Dec. 31, 2015
Condensed Financial Statements Captions [Line Items]
Interest rate stated on senior notes	7.00%
Parent Company
Condensed Financial Statements Captions [Line Items]
Interest rate stated on senior notes	7.00%

Supplementary Insurance Infor91

Supplementary Insurance Information (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs		$ 91,983	$ 79,452	$ 67,007
Reserve for losses and LAE		2,202,644	2,159,634	2,045,071
Unearned premiums		820,676	766,167	714,606
Net earned premiums		984,087	935,895	841,939
Net investment income	[1]	68,571	64,092	56,243
Losses and LAE incurred		572,598	545,229	518,961
Amortization of deferred policy acquisition costs	[2]	129,977	127,695	115,842
Other operating expenses	[3]	220,643	196,825	164,434
Net written premiums		1,043,860	1,000,138	887,922
NIC, NSIC and Navigators Management Company, Inc.
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs		67,144	63,200	54,984
Reserve for losses and LAE		1,692,886	1,645,984	1,523,175
Unearned premiums		607,062	579,331	536,303
Net earned premiums		722,749	704,574	639,338
Net investment income	[1]	61,863	56,714	49,083
Losses and LAE incurred		451,296	434,396	415,413
Amortization of deferred policy acquisition costs	[2]	88,597	85,137	81,132
Other operating expenses	[3]	153,194	138,675	119,920
Net written premiums		757,117	752,773	680,008
NHUK
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs		24,839	16,252	12,023
Reserve for losses and LAE		509,758	513,650	521,896
Unearned premiums		213,614	186,836	178,303
Net earned premiums		261,338	231,321	202,601
Net investment income	[1]	6,708	7,378	7,160
Losses and LAE incurred		121,302	110,833	103,548
Amortization of deferred policy acquisition costs	[2]	41,380	42,558	34,710
Other operating expenses	[3]	67,449	58,150	44,514
Net written premiums		$ 286,743	$ 247,365	$ 207,914
[1]	- Net investment income and Other operating expenses reflect only such amounts attributable to our Company's insurance operations.
[2]	Amortization of deferred policy acquisition costs reflects only such amounts attributable to our Company's insurance operations. A portion of these costs is eliminated in consolidation.
[3]	Net investment income and Other operating expenses reflect only such amounts attributable to our Company's insurance operations.

Reinsurance Written Premium (De

Reinsurance Written Premium (Detail) - 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, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplementary Insurance Information, by Segment [Line Items]
Direct Amount									$ 1,223,840	$ 1,183,120	$ 1,121,198
Ceded to other companies									414,906	440,656	455,985
Assumed from other companies									175,153	193,431	176,726
Net earned premiums	$ 251,545	$ 254,082	$ 242,328	$ 236,132	$ 234,172	$ 245,367	$ 231,084	$ 225,272	984,087	935,895	841,939
Property Casualty
Supplementary Insurance Information, by Segment [Line Items]
Direct Amount									1,277,728	1,232,012	1,177,483
Ceded to other companies									409,642	432,215	482,595
Assumed from other companies									175,774	200,341	193,034
Net earned premiums									$ 1,043,860	$ 1,000,138	$ 887,922
Percentage of amount assumed to net									17.00%	20.00%	22.00%

Valuation and Qualifying Acco93

Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for uncollectable reinsurance
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 11,332	$ 11,332	$ 11,520
Charged (Credited) to Costs and Expenses	(4,411)		(188)
Charged to Other Accounts	0	0	0
Deductions (Describe)	0	0	0
Ending Balance	6,921	11,332	11,332
Valuation allowance in deferred taxes
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	776	554	499
Charged (Credited) to Costs and Expenses	(55)	222	55
Charged to Other Accounts	0	0	0
Deductions (Describe)	0	0	0
Ending Balance	$ 721	$ 776	$ 554

Supplementary Information Con94

Supplementary Information Concerning P&C Insurance Operations (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplemental Information For Property Casualty Insurance Underwriters [Abstract]
Deferred policy acquisition costs		$ 91,983	$ 79,452	$ 67,007
Reserve for losses and LAE		2,202,644	2,159,634	2,045,071
Unearned premiums		820,676	766,167	714,606
Net earned premiums		984,087	935,895	841,939
Net investment income	[1]	68,571	64,092	56,243
Losses and LAE expenses incurred related to Current year		637,267	601,041	520,227
Losses and LAE expenses incurred related to Prior years		(64,669)	(55,812)	(1,266)
Amortization of deferred policy acquisition costs	[2]	129,977	127,695	115,842
Other operating expenses	[1]	220,643	196,825	164,434
Net written premiums		$ 1,043,860	$ 1,000,138	$ 887,922
[1]	Net investment income and Other operating expenses reflect only such amounts attributable to our Company's insurance operations.
[2]	Amortization of deferred policy acquisition costs reflects only such amounts attributable to our Company's insurance operations. A portion of these costs is eliminated in consolidation.