Navigators (NAVG) 10-K 28 Feb 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Feb. 21, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
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	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		29,818,468
Entity Public Float			$ 1,320,453,310
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Investments:
Available-for-sale, at fair value	$ 3,093,156
Equity Securities, at fair value (cost: 2018: $361,418; 2017: $224,159)	339,892
Equity Securities, at fair value (cost: 2018: $361,418; 2017: $224,159)		$ 235,981
Other Invested Assets	48,406	30,488
Total Investments	3,481,454	3,330,003
Cash and Cash Equivalents	155,834	102,735
Restricted Cash and Cash Equivalents	66,320	56,229
Premiums Receivable	380,576	351,393
Prepaid Reinsurance Premiums	226,723	228,569
Reinsurance Recoverable on Paid Losses	118,259	72,494
Reinsurance Recoverable on Unpaid Losses and Loss Adjustment Expenses	820,189	809,765
Deferred Policy Acquisition Costs	158,080	135,249
Accrued Investment Income	22,168	19,480
Goodwill and Other Intangible Assets	27,146	6,596
Current Income Tax Receivable, Net	0	16,667
Deferred Income Tax Asset	49,893	22,271
Other Assets	96,807	73,171
Total Assets	5,603,449	5,224,622
Liabilities:
Reserves for Losses and Loss Adjustment Expenses	2,743,973	2,515,145
Unearned Premiums	1,102,735	987,681
Reinsurance Balances Payable	145,027	136,192
Senior Notes	264,052	263,885
Current Income Tax Payable, Net	1,594	0
Deferred Income Tax Liability	7,596	0
Accounts Payable and Other Liabilities	151,622	95,754
Total Liabilities	4,416,599	3,998,657
Stockholders' Equity:
Preferred Stock, ($.10 par value, authorized 1,000 shares, none issued)	0	0
Common Stock, ($.10 par value, authorized 50,000 shares, issued 36,805 shares for 2018 and 36,530 shares for 2017)	3,678	3,650
Additional Paid-In Capital	378,274	376,868
Treasury Stock, at cost (7,023 shares for 2018 and 2017)	(155,801)	(155,801)
Retained Earnings	1,012,220	981,380
Accumulated Other Comprehensive Income (Loss)	(51,521)	19,868
Total Stockholders' Equity	1,186,850	1,225,965
Total Liabilities and Stockholders' Equity	5,603,449	5,224,622
Fixed Maturities
Investments:
Available-for-sale, at fair value	3,082,923	3,057,054
Short-Term Investments
Investments:
Available-for-sale, at fair value	$ 10,233	$ 6,480

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) $ in Thousands	Dec. 31, 2017USD ($)$ / sharesshares
Equity Securities, cost | $	$ 224,159
Preferred Stock, par value | $ / shares	$ 0.10
Preferred Stock, authorized shares	1,000,000
Preferred Stock, issued shares	0
Common Stock, par value | $ / shares	$ 0.10
Common Stock, authorized shares	50,000,000
Common Stock, issued shares	36,530,000
Treasury Stock, shares	7,023,000
Fixed Maturities
Amortized cost | $	$ 3,027,408
Short-Term Investments
Amortized cost | $	$ 6,477

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Gross Written Premiums	$ 1,912,961	$ 1,713,265	$ 1,568,911
Revenues:
Net Written Premiums	1,471,085	1,271,330	1,186,224
Change in Net Unearned Premiums	(107,862)	(84,910)	(85,879)
Net Earned Premiums	1,363,223	1,186,420	1,100,345
Net Investment Income	103,113	89,293	79,451
Net Realized and Unrealized Gains (Losses):
Total Other-Than-Temporary Impairment Losses	(118)	(2,002)	(227)
Portion of Loss Recognized in Other Comprehensive Income	118	(62)	77
Net Other-Than-Temporary Impairment Losses Recognized in Earnings	0	(2,064)	(150)
Net Realized Gains on Investments Sold	2,989	45,073	9,186
Net Unrealized Losses on Equity Securities	(33,337)	0	0
Total Net Realized and Unrealized Gains (Losses)	(30,348)	43,009	9,036
Other Income (Loss)	7,169	(4,243)	8,701
Total Revenues	1,443,157	1,314,479	1,197,533
Expenses:
Net Losses and Loss Adjustment Expenses	893,779	806,265	665,448
Commission Expenses	220,144	184,731	165,045
Other Operating Expenses	261,224	233,230	234,096
Merger Transaction Costs	3,950	0	0
Interest Expense	15,485	15,447	15,435
Total Expenses	1,394,582	1,239,673	1,080,024
Income Before Income Taxes	48,575	74,806	117,509
Income Tax Expense	14,336	34,312	34,783
Net Income	$ 34,239	$ 40,494	$ 82,726
Net Income Per Common Share:
Basic	$ 1.15	$ 1.38	$ 2.85
Diluted	$ 1.13	$ 1.35	$ 2.75
Average Common Shares Outstanding:
Basic	29,720	29,441	29,074
Diluted	30,193	30,071	30,032

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net Income	$ 34,239	$ 40,494	$ 82,726
Change in Net Unrealized Gains (Losses) on Available-for-Sale Investments:
Unrealized Gains (Losses) on Investments arising during the period, net of Deferred Tax of $14,380, $(8,748) and $3,730 in 2018, 2017 and 2016, respectively	(53,770)	23,123	(6,927)
Reclassification adjustment for Net Realized Gains (Losses) included in Net Income, net of Deferred Tax of $1,029, $5,335 and $(846) in 2018, 2017 and 2016, respectively	(2,835)	(14,100)	1,572
Change in Net Unrealized Gains (Losses) on Available-for-Sale Investments	(56,605)	9,023	(5,355)
Change in Other-Than-Temporary Impairments
Non Credit Other-Than-Temporary Impairments arising during the period, net of Deferred Tax of $34, $(16) and $27 in 2018, 2017 and 2016, respectively	(93)	40	(50)
Reclassification Adjustment for Other-Than-Temporary Impairment Credit Losses Recognized in Net Income net of Deferred Tax of $0 in 2018, 2017 and 2016, respectively	0	0	0
Change in Other-Than-Temporary Impairments	(93)	40	(50)
Change in Foreign Currency Translation Gains (Losses), net of Deferred Tax of $2,069, $(2,874) and $5,017 in 2018, 2017 and 2016, respectively	(9,567)	1,930	(9,324)
Change in Benefit Plans' Obligations, net of Deferred Tax of $68 in 2018	(204)	0	0
Other Comprehensive Income (Loss)	(66,469)	10,993	(14,729)
Comprehensive Income (Loss)	$ (32,230)	$ 51,487	$ 67,997

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Unrealized Gains (Losses) on Investments arising during the period, Deferred Tax	$ 14,380	$ (8,748)	$ 3,730
Reclassification adjustment for Net Realized (Gains) Losses included in Net Income, Deferred Tax	1,029	5,335	(846)
Non Credit Other-Than-Temporary Impairments arising during the period, Deferred Tax	34	(16)	27
Reclassification Adjustment for Other-Than-Temporary Impairment Credit Losses Recognized in Net Income, Deferred Tax	0	0	0
Change in Foreign Currency Translation Gains (Losses), Deferred Tax	2,069	$ (2,874)	$ 5,017
Change in Benefit Plans' Obligations, Deferred Tax	$ 68

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands		Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2015		$ 1,096,148	$ 3,586	$ 356,036	$ (155,801)	$ 868,723	$ 23,604
Beginning Balance (in shares) at Dec. 31, 2015			35,885		7,023
Net Income		82,726				82,726
Dividends Declared	[1]	(3,930)				(3,930)
Changes in Comprehensive Income (Loss):
Change in Net Unrealized Loss on Investments		(5,355)					(5,355)
Change in Net Non-Credit Other-Than- Temporary Impairment Losses		(50)					(50)
Change in Foreign Currency Translation Loss		(9,324)					(9,324)
Change in Benefit Plans' Obligations		0
Other Comprehensive Income (Loss)		(14,729)					(14,729)
Shares Issued	[2]	349	$ 26	323
Shares Issued (in shares)	[2]		262
Share-Based Compensation		17,624		17,624
Ending Balance at Dec. 31, 2016		1,178,188	$ 3,612	373,983	$ (155,801)	947,519	8,875
Ending Balance (in shares) at Dec. 31, 2016			36,147		7,023
Net Income		40,494				40,494
Dividends Declared	[1]	(6,633)				(6,633)
Changes in Comprehensive Income (Loss):
Change in Net Unrealized Loss on Investments		9,023					9,023
Change in Net Non-Credit Other-Than- Temporary Impairment Losses		40					40
Change in Foreign Currency Translation Loss		1,930					1,930
Change in Benefit Plans' Obligations		0
Other Comprehensive Income (Loss)		10,993					10,993
Shares Issued	[2]	(10,906)	$ 38	(10,944)
Shares Issued (in shares)	[2]		383
Share-Based Compensation		13,829		13,829
Ending Balance at Dec. 31, 2017		$ 1,225,965	$ 3,650	376,868	$ (155,801)	981,380	19,868
Ending Balance (in shares) at Dec. 31, 2017		36,530	36,530		7,023
Net Income		$ 34,239				34,239
Dividends Declared	[1]	(8,319)				(8,319)
Changes in Comprehensive Income (Loss):
Change in Net Unrealized Loss on Investments		(56,605)					(56,605)
Change in Net Non-Credit Other-Than- Temporary Impairment Losses		(93)					(93)
Change in Foreign Currency Translation Loss		(9,567)					(9,567)
Change in Benefit Plans' Obligations		(204)					(204)
Other Comprehensive Income (Loss)		(66,469)					(66,469)
Cumulative Effect of Adoption of ASU at January 1st, Net of Tax | ASU 2016-01						7,748	(7,748)
Cumulative Effect of Adoption of ASU at January 1st, Net of Tax | Accounting Standards Update 2018-02						(2,828)	2,828
Shares Issued	[2]	(5,352)	$ 28	(5,380)
Shares Issued (in shares)	[2]		275
Share-Based Compensation		6,786		6,786
Ending Balance at Dec. 31, 2018		$ 1,186,850	$ 3,678	$ 378,274	$ (155,801)	$ 1,012,220	$ (51,521)
Ending Balance (in shares) at Dec. 31, 2018		36,805	36,805		7,023
[1]	Dividends Declared were $0.28 per share, $0.225 per share and $0.135 per share for the years ended December 31, 2018, 2017 and 2016, respectively.
[2]	Includes shares issued under the Second Amended and Restated 2005 Stock Incentive Plan, to directors and the Employees Stock Purchase Plan.

Consolidated Statement of Stock

Consolidated Statement of Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Stockholders Equity [Abstract]
Dividends declared	$ 0.28	$ 0.225	$ 0.135

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Activities:
Net Income	$ 34,239	$ 40,494	$ 82,726
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Depreciation & Amortization	3,675	3,645	5,429
Amortization of Finite-Lived Intangible Assets	657	0	0
Share-Based Compensation	6,786	13,829	17,624
Deferred Income Taxes	(14,366)	(8,879)	(5,755)
Total Net Realized and Unrealized (Gains) Losses	30,348	(43,009)	(9,036)
Changes in Assets And Liabilities:
Reinsurance Recoverable on Paid and Unpaid Losses and Loss Adjustment Expenses	(39,224)	(20,399)	(2,835)
Reserves for Losses and Loss Adjustment Expenses	198,818	225,132	87,083
Prepaid Reinsurance Premiums	4,346	(15,168)	19,211
Unearned Premiums	104,781	100,160	66,668
Premiums Receivable	(31,308)	(45,035)	(30,070)
Deferred Policy Acquisition Costs	(22,969)	(15,552)	(27,677)
Accrued Investment Income	(2,712)	(2,139)	(1,314)
Reinsurance Balances Payable	8,875	27,362	1,568
Current Income Tax Receivable/Payable, Net	17,674	3,966	(1,988)
Other	42,718	936	27,791
Net Cash Provided by Operating Activities	342,338	265,343	229,425
Fixed Maturities
Redemptions and Maturities	418,367	373,380	275,706
Sales	358,309	225,962	446,666
Purchases	(887,996)	(1,008,537)	(962,419)
Equity Securities
Sales		207,838	54,798
Sales	34,617
Purchases		(62,887)	(92,329)
Purchases	(126,746)
Net Sales and Purchases of Other Invested Assets	(19,097)	(933)	(7,519)
Net Sales, Maturities and Purchases of Short-Term Investments	(4,179)	2,487	88,349
Net Change in Unsettled Security Transactions	(2,194)	2,135	(1,517)
Purchase of Subsidiaries, Net of Acquired Cash	(22,383)	0	0
Net Purchase of Property and Equipment	(8,845)	(3,474)	(3,918)
Net Cash Used in Investing Activities	(260,147)	(264,029)	(202,183)
Financing Activities:
Proceeds from Employee Stock Purchase Plan	2,008	2,076	1,840
Payment of Employee Tax Withholding on Stock Compensation	(8,456)	(13,887)	(5,198)
Dividends Paid	(8,319)	(6,633)	(3,930)
Net Cash Used in Financing Activities	(14,767)	(18,444)	(7,288)
Effect of Exchange Rate on Unrestricted and Restricted Cash and Cash Equivalents	(4,234)	3,248	(15,963)
Change in Unrestricted and Restricted Cash and Cash Equivalents	63,190	(13,882)	3,991
Unrestricted and Restricted Cash and Cash Equivalents at Beginning of Year	158,964	172,846	168,855
Unrestricted and Restricted Cash and Cash Equivalents at End of Period	222,154	158,964	172,846
Supplemental Information:
Income Taxes Paid, Net	21,422	39,689	34,830
Interest Paid	15,238	15,238	15,238
Issuance of Stock to Directors	$ 783	$ 578	$ 633

Organization and Summary of Sig

Organization and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Organization and Summary of Significant Accounting Policies	NOTE 1. ORGANIZATION & SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of 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 term “Parent Company” is used to mean The Navigators Group, Inc. without its subsidiaries. The accompanying consolidated financial statements of our Company have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP” or “U.S. GAAP”) and the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”). 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. Organization We are an international insurance company with a long-standing area of specialization in Marine insurance. We also offer Property and Casualty (“P&C”) insurance, primarily 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, as well as assumed reinsurance products. We operate through various wholly-owned insurance and service companies. Our subsidiaries domiciled in the United States (“U.S.”) include two insurance companies, Navigators Insurance Company (“NIC”) and Navigators Specialty Insurance Company (“NSIC”), as well as our U.S. underwriting agency, Navigators Management Company, Inc. (“NMC”). NIC includes a branch in the United Kingdom (“U.K.”). We also have operations domiciled in the U.K., Hong Kong and Europe. Navigators International Insurance Company Ltd. (“NIIC”), Navigators Management (U.K.) Ltd. (“NMUK”) and Navigators Underwriting Ltd. (“NUL”) are domiciled in the U.K. and NUL includes European branches. Navigators Underwriting Agency Ltd. (“NUAL”), a Lloyd’s of London (“Lloyd’s”) underwriting agency, manages and provides the capital, through Navigators Corporate Underwriters Ltd. (“NCUL”), for our Lloyd’s Syndicate 1221 (the “Syndicate”), and is also domiciled in the U.K. We control 100% of the Syndicate’s stamp capacity. On June 7, 2018, we acquired 100% ownership interest in Bracht, Deckers & Mackelbert NV, an insurance underwriting agency organized under the laws of Belgium (“BDM”) and Assurances Continentales – Continentale Verzekeringen NV, an insurance company licensed under the laws of Belgium (“ASCO”). The acquisition was accounted for in accordance with Accounting Standards Codification (“ASC”) 805, “Business Combinations.” Refer to Note 2 Merger and Business Combinations Goodwill and Intangible Assets On August 22, 2018, our Company entered into an Agreement and Plan of Merger (the “Merger Agreement”) with The Hartford Financial Services Group, Inc. (“The Hartford”). The Merger Agreement provides that, subject to the terms and conditions set forth therein, our Company will merge with an existing subsidiary of The Hartford, with our Company surviving as a wholly owned subsidiary of The Hartford (the “Merger”). Refer to Note 2 Merger and Business Combinations Immaterial Error Corrections Cash and overseas deposits that were misclassified within Short-Term Investments were reclassified representing an immaterial correction. Cash of $20.5 million as of December 31, 2017 was reclassified from Short-Term Investments to Cash and Cash Equivalents. Overseas deposits of $28.8 million as of December 31, 2017 were reclassified from Short-Term Investments to Other Invested Assets. The reclassification of cash within Short-Term Investments to Cash and Cash Equivalents impacted the Statement of Cash Flows for the years ended December 31, 2017 and 2016 by increasing Net Cash Used in Investing Activities by $1.9 million and decreasing Net Cash Used in Investing Activities by $6.0 million, respectively. During the year ended December 31, 2018, a full review of foreign taxes paid and refunds received was performed resulting in an increase in our Income Tax Expense of $7.0 million, inclusive of interest. Refer to Note 11 Income Taxes Additionally, during the year ended December 31, 2018, various adjustments increasing Net Income by $5.1 million were recorded relating to items dating back as far as 2005. These various adjustments were identified as part of a finance transformation initiative and were not material, individually or in the aggregate in the current year or any prior year. In total all adjustments resulted in a combined impact to Net Income for the year ended December 31, 2018 of $0.3 million. The controls related to the adjustments were also evaluated and none were deemed to represent a material weakness in our internal control over financial reporting. Significant Accounting Policies Cash Cash includes cash on hand and demand deposits with banks. Cash Equivalents include highly liquid investments with original maturities of three months or less including money-market funds. Restricted Cash and Cash Equivalents primarily relates to funds that are held to support regulatory and contractual obligations. Investments Fixed Maturities held by our Company were carried at fair value and classified as available-for-sale. Available-for-sale securities are debt 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 Maturities include bonds, mortgage-backed and asset-backed securities, and redeemable preferred stocks. Upon adoption of ASU 2016-01 on January 1, 2018, Equity Securities held by our Company were carried at fair value with any changes in fair value recognized in Net Income through the Net Unrealized Gains (Losses) on Equity Securities account. Prior to the adoption of ASU 2016-01, Equity Securities were carried at fair value and classified as available-for-sale. Equity Securities consist of common stock, exchange traded funds, mutual funds and preferred stock. Other Invested Assets consist of investments our Company made in certain strategic companies which are accounted for using the equity method of accounting and overseas deposits which are carried at fair value. For our investments applying the equity method, these investments are initially recorded at cost and are subsequently adjusted based on our Company’s proportionate share of the net income or loss of the companies. Changes in the carrying value of such investments are recorded in Other Income. In applying the equity method, we use the most recently available financial information provided by the companies which is generally three months prior to the end of the reporting period. Overseas deposits include private funds held by the Syndicate and invested according to local regulatory requirements. The compositions of the overseas deposits vary and the deposits are based on the portfolio level reporting that is provided by Lloyd’s. The fair values of these overseas deposits were measured using the net asset value practical expedient and therefore have not been categorized within the fair value hierarchy. Changes in the fair value of the overseas deposits are recorded in Net Investment Income. Short-Term Investments are carried at fair value. Short-Term Investments have maturities greater than three months but less than 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 Maturities 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 Maturities portfolio to evaluate the necessity of recording impairment losses for other-than-temporary declines in the fair value of securities. Our Company reviews the magnitude of a security’s unrealized loss compared to its cost/amortized cost and the length of time that the security has been impaired to determine if an unrealized loss is other-than-temporary. If warranted as a result of conditions relating to a particular security, our Company will also review securities with declines in fair value resulting from a headline news event involving the issuer, a headline news event involving the asset class, the advice of our external asset managers, or economic events that may impact the issuer to determine if an unrealized loss is other-than-temporary. The depth of analysis performed is dependent upon the nature and magnitude of the indicators of other-than-temporary impairment present in regards to each impaired security. Our Company assesses the underlying fundamentals of each issuer to determine if there is a change in the amount or timing of expected cash flows. Management compares the amortized cost basis to the present value of the revised cash flows using the historical book yield to determine the credit loss portion of impairment which is recognized in earnings. All non-credit losses where we have the intent and ability to hold the security until recovery are recognized as changes in Other than Temporary Impairment (“OTTI”) losses within AOCI. Specifically, for structured Fixed Maturities, our Company analyzes 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. For securities in which a tranche loss is present and the net present value of loss adjusted cash flows is less than book value, credit impairment is recognized in earnings. 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 are actual delinquency rates, default probability, severity and prepayment assumptions. Projected losses are a function of both loss severity and probability of default, which differ based on property type, vintage and the stress of the collateral. 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 Other Income (Loss) in the Consolidated Statements of Income, with the exception of those related to foreign-denominated available-for-sale investments and equity securities. For the available-for-sale investments, exchange rate fluctuations represent an unrealized appreciation/depreciation in the value of the securities and are included in the related component of AOCI. For the equity securities, exchange rate fluctuations are included in the related component of Total Net Realized and Unrealized Gains (Losses). Functional currency assets and liabilities of foreign operations 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. 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 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 net of 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 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, Loss Adjustment Expense (“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 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 reserves for losses and LAE are calculated by our actuaries using several standard actuarial methodologies, including the paid and incurred loss development and the paid and incurred Bornhuetter-Ferguson loss methods. Frequency/severity analyses are performed for certain books of business. The Reserve for Losses and LAE has been established to cover the estimated unpaid cost of claims incurred. Such estimates are regularly compared to indicated reserves 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 stock grants were fully vested. Share-Based Compensation Our Company applies a fair value based measurement method in accounting for its share-based payment arrangements with eligible employees and directors. The associated expense is estimated based on the fair value of the award at the grant date and is recognized in Net Income over the requisite service period with a corresponding increase in Shareholder’s Equity. Forfeitures of share-based payment awards are recognized as they occur. 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 the cost of acquiring a business enterprise over the fair value of the net assets acquired. Our Company’s recorded indefinite lived intangible assets represent acquired stamp capacity in the Syndicate and ASCO’s European insurance licenses. Our Company’s recorded definite lived intangible assets represent customer relationships, the value of business acquired (“VOBA”), broker networks, and a trade name. 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. Finite-lived intangibles are amortized over the estimated useful life of the asset and are reviewed for impairment when indicators of impairment are present. Our Company did not recognize an impairment of goodwill or intangible assets for any of the years ended December 31, 2018, 2017 and 2016. As of December 31, 2018, the carrying value of goodwill and intangible assets was $27.1 million, which is $20.5 million more than the carrying value of $6.6 million as of December 31, 2017. Changes in the carrying value of the goodwill and intangible assets were due to the acquisition of BDM and ASCO, as well as fluctuations in currency exchange rates. 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. Income Taxes. New Accounting Standards Adopted in 2018 Revenue From Contracts With Customers Effective January 1, 2018, our Company adopted ASU 2014-09, “Revenue from Contracts with Customers (Topic 606)”. This guidance affects any contracts with customers to transfer goods or services or for the transfer of nonfinancial assets unless those contracts are within the scope of other standards (for example, insurance contracts are not in scope of the new guidance). The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. Our Company generates an insignificant amount of fee income that is within the scope of this guidance and was not materially impacted by the adoption of this guidance. The adoption of this guidance did not have a material impact on our results of operations, financial condition or liquidity. Classification and Measurement of Financial Instruments Effective January 1, 2018, our Company adopted ASU 2016-01 “Financial Instruments – Overall (Subtopic 825-10) – Recognition and Measurement of Financial Assets and Financial Liabilities”. This guidance requires equity investments (except those accounted for under the equity method of accounting, investments that are consolidated or those that meet a practicability exception) to be measured at fair value with changes in fair value recognized in net income, simplifies the impairment assessment of equity investments without readily determinable values by requiring a qualitative assessment to identify impairment, eliminates the requirement to disclose the methods and significant assumptions used to estimate the fair value for financial instruments measured at amortized cost, requires the use of the exit price notion when measuring the fair value of financial instruments for disclosure purposes, requires separate presentation in other comprehensive income of the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the organization has elected to measure the liabilities in accordance with the fair value option, requires the separate presentation of financial assets and financial liabilities by measurement category and form of financial asset on the balance sheet or the accompanying notes to the financial statements and clarifies that the reporting organization should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the organization’s other deferred tax assets. As of January 1, 2018, the adoption of this guidance resulted in a $7.7 million net after-tax increase to Retained Earnings with a corresponding decrease to Accumulated Other Comprehensive Income (Loss), resulting in no change to our Total Stockholders’ Equity. This adjustment reflects the cumulative effect adjustment to reclassify Net Unrealized Gain on Investments in Accumulated Other Comprehensive Income (Loss) for available-for-sale Equity Securities to Retained Earnings upon adoption. Upon the adoption of this guidance, Equity Securities have been measured at fair value with changes in fair value recognized in Net Income through Net Unrealized Gains (Losses) on Equity Securities. The other aspects of this guidance only impacted disclosure or did not apply to our Company and therefore did not impact our results of operations, financial condition or liquidity. Cash Flows Effective January 1, 2018, our Company adopted ASU 2016-15, “Statement of Cash Flows (Topic 230) – Classification of Certain Cash Receipts and Cash Payments” which addresses diversity in practice in how eight specific cash receipts and cash payments should be presented and classified on the statement of cash flows. The adoption of this guidance did not impact our results of operations, financial condition or liquidity. Effective January 1, 2018, our Company adopted ASU 2016-18, “Statement of Cash Flows (Topic 230) – Restricted Cash” which addresses diversity in practice in the classification and presentation of changes in restricted cash on the statement of cash flows. This guidance requires a statement of cash flows to explain the change during the period in the total of cash, cash equivalents, restricted cash and restricted cash equivalents. Transfers between cash and cash equivalents and restricted cash and restricted cash equivalents will no longer be presented on the statement of cash flows. To assist in meeting the requirements of this guidance to provide a reconciliation from the Statement of Cash Flows to the Balance Sheet, upon adoption of this guidance our Company added new accounts titled “Cash and Cash Equivalents” and “Restricted Cash and Cash Equivalents” and reclassified amounts previously held in Short-Term Investments to these accounts for all periods presented. This resulted in the reclassification of $71.3 million of restricted and unrestricted cash and cash equivalent balances as of December 31, 2017. This guidance was adopted on a retrospective basis. Prior to the adoption of this guidance, restricted and unrestricted cash and cash equivalent balances included in the Short-Term Investments account had been presented as a cash flow provided by (used in) investing activities. Consequently, the Statement of Cash Flows for the years ended December 31, 2017 and 2016 include a revision to increase “Net Cash Used in Investing Activities” by $14.4 million and a revision to decrease “Net Cash Used in Investing Activities” by $3.3 million, respectively. Income Taxes Effective January 1, 2018, our Company adopted ASU 2016-16, “Income Taxes (Topic 740) – Intra-Entity Transfers of Assets Other than Inventory” that requires companies to account for the income tax effects of intercompany transfers of assets other than inventory when the transfer occurs. The adoption of this guidance did not impact our results of operations, financial condition or liquidity. Definition of a Business Effective January 1, 2018, our Company adopted ASU 2017-01, “Clarifying the Definition of a Business” that provides guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. This guidance will be applied to transactions prospectively. The adoption of this guidance did not impact our results of operations, financial condition or liquidity. Tax Reform Reclassification from Other Comprehensive Income Effective January 1, 2018, our Company early adopted ASU 2018-02, “Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income” that permits entities to reclassify tax effects stranded in accumulated other comprehensive income as a result of tax reform to retained earnings. The total impact of the remeasurement and other adjustments was reflected in 2017 income from continuing operations, regardless of where deferred taxes were originally recorded. As of January 1, 2018, the adoption of this guidance resulted in a one-time reclassification of $2.8 million, decreasing Retained Earnings and increasing Accumulated Other Comprehensive Income (Loss) primarily from the remeasurement of deferred tax assets and liabilities associated with unrealized gains and losses on investments and currency translation adjustments using the 21% corporate tax rate. Recently Issued Accounting Standards Not Yet Adopted Leases In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842)” which provides a new comprehensive model for lease accounting. Topic 842 was subsequently amended by ASU 2018-10, Codification Improvements to Topic 842, Leases and ASU 2018-11, Targeted Improvements. The new standard requires a lessee to recognize a liability to make lease payments (the lease liability) and a right-of-use (“ROU”) asset representing its right to use the underlying asset for the lease term. Leases will be classified as finance or operating, with classification affecting the pattern and classification of expense recognition in the income statement. The new standard is effective for us on January 1, 2019, with early adoption permitted. A modified retrospective transition approach is required, applying the new standard to all leases existing at the date of initial application. An entity may choose to use either (1) its effective date or (2) the beginning of the earliest comparative period presented in the financial statements as its date of initial application. We expect to adopt the new standard on January 1, 2019 and use the effective date as our date of initial application. Consequently, financial information will not be updated and the disclosures required under the new standard will not be provided for dates and periods before January 1, 2019. The new st

Merger And Business Combination

Merger And Business Combinations	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Merger And Business Combinations	NOTE 2. MERGER AND BUSINESS COMBINATIONS The Hartford On August 22, 2018, our Company entered into the Merger Agreement with The Hartford, where subject to the terms and conditions set forth therein, our Company will merge with an existing subsidiary of The Hartford, with our Company surviving as a wholly owned subsidiary of The Hartford. Pursuant to the Merger Agreement, at the effective time of the Merger, holders of the Company’s common shares will be entitled to receive consideration of $70.00 in cash per common share (the “Merger Consideration”). At a special meeting of stockholders of the Company held on November 16, 2018, the Company’s stockholders approved by the requisite vote a proposal to adopt the Merger Agreement. The Merger is expected to close in the first half of 2019, but remains subject to the receipt of regulatory approvals and other customary closing conditions. The Merger Agreement contains various covenants of our Company and The Hartford. These covenants include interim operating covenants that, subject to certain exceptions, (i) require the Company to (1) conduct its business in all material respects in the ordinary course of business consistent with past practice, (2) use reasonable best efforts to preserve substantially intact, consistent with past practice, the Company’s business organization and (3) preserve, consistent with past practice, existing relations and goodwill with customers, producers, reinsurance providers, governmental authorities and other persons with whom the Company or its subsidiaries have significant business relationships, and (ii) restrict the Company’s ability to take certain actions prior to the effective time of the Merger without The Hartford’s consent (such consent, in certain cases, not to be unreasonably withheld, conditioned or delayed), which include, subject to certain exceptions, issuing additional common shares, incurring additional indebtedness, selling or purchasing material assets, making unbudgeted capital expenditures, making loans or investments (or disposing of investments) not permitted by the Company’s investment guidelines, increasing compensation other than in ordinary course, making material changes to accounting, underwriting, or reserving practices, making material tax elections, settling material litigation, or entering into, modifying or terminating material contracts. BDM and ASCO During the second quarter of 2018, our Company established a wholly owned subsidiary, Navigators Holdings (Europe) NV, which on June 7, 2018 (the “acquisition date”), acquired a 100% ownership interest in BDM, ASCO, and a wholly-owned subsidiary of ASCO, Canal Re S.A., a reinsurance company licensed under the laws of the Grand Duchy of Luxembourg (“Canal Re”). The acquisition of all three of these entities will be referred to as the “Acquisition” and the group of companies will be referred to as the Navigators Insurance Company Europe Group (the “NICE Group”). The Acquisition was undertaken as part of our Company’s strategy of expanding to more brokers and insureds across Europe and reinforces our Company’s presence in the European Union’s single market. We anticipate that this will enable our Company to better serve its European clients after Brexit, and will also provide an opportunity to reach a wider European audience. Our Company paid a purchase price of EUR 35.0 million in cash at the acquisition date (which was approximately $40.5 million based on the exchange rate as of the acquisition date). Additionally, our Company will be reimbursed up to EUR 5.0 million (which was approximately $5.8 million based on the exchange rate as of the acquisition date) in the event of adverse development of claims incurred prior to December 31, 2016 as measured on December 31, 2019. This reimbursement was valued at $nil as of the acquisition date and December 31, 2018. The purchase price was allocated to the assets acquired and liabilities assumed of the NICE Group, based on estimated fair values as of the acquisition date and our Company recognized goodwill of $12.7 million. Our Company identified finite lived intangible assets of $6.5 million, including customer relationships, the value of business acquired (“VOBA”), broker networks, and a trade name. These finite lived intangible assets will be amortized over a weighted average period of 9 years. Our Company identified indefinite lived intangible assets of $2.5 million, related to ASCO’s European licenses. The fair value of the assets acquired and liabilities assumed and the allocation of the purchase price on the acquisition date are summarized in the table below: amounts in thousands Consideration paid $ 40,492 Assets Investments 45,182 Cash and Cash Equivalents 18,109 Prepaid Reinsurance Premiums 2,701 Reinsurance Recoverables on Paid Losses 1,311 Reinsurance Recoverables on Unpaid Losses and LAE 15,769 Other Assets 19,943 Fair Value of Identifiable Intangible Assets 9,000 Total Assets Acquired $ 112,015 Liabilities Reserves for Losses and LAE 31,928 Unearned Premiums 11,139 Deferred Income Tax 8,947 Accounts Payable and Other Liabilities 32,212 Total Liabilities Assumed $ 84,226 Goodwill $ 12,703 Significant Fair Value Adjustments were as follows: • Fair Value of Finite and Indefinite-Lived Intangibles – To establish the fair value of identifiable intangible assets related to customer relationships, licenses, value of business acquired, broker networks, and trade name. • Fair Value of Property – To adjust the carrying value of real estate property to reflect fair value. • Fair Value of Software – To establish the fair value of internal use software systems. • Deferred Income Tax – To reflect the deferred tax impact on the fair value adjustments. • Goodwill – To establish the value of goodwill related to the Acquisition. As part of our business combination accounting within the measurement period, the Company recorded an adjustment to the fair value of the customer relationships intangible asset. As a result, the Fair Value of Identifiable Intangible Assets decreased by $1.4 million and Goodwill increased by $1.4 million from the amounts initially recorded at June 30, 2018. Refer to Note 6 Goodwill and Intangible Assets for further information. The business combination accounting is subject to change if additional information that existed as of the balance sheet date, but was not available, later becomes available within the measurement period, which cannot exceed twelve months from the acquisition date. The acquisition date fair values of the assets acquired and liabilities assumed, including Reserves for Losses and LAE, Deferred Income Tax and Identifiable Intangible Assets, as well as the related estimated useful lives, are provisional and may be subject to adjustments, which may impact the amounts recorded for assets acquired and liabilities assumed as well as the goodwill. Since the acquisition date, total NICE Group Revenues and Net Income (Loss) of $11.1 million and $(0.3) million, respectively, have been included in our Company’s Consolidated Statements of Income.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Segment Information	NOTE 3. SEGMENT INFORMATION We report our results of operations consistent with the manner in which our Chief Operating Decision Maker reviews the business to assess performance through our reporting segments: U.S. Insurance, International Insurance (“Int’l Insurance”), Global Reinsurance (“GlobalRe”) and Corporate. We classify our business into three underwriting segments: U.S. Insurance, Int’l Insurance and GlobalRe. Both the U.S. Insurance and Int’l Insurance reporting segments are each comprised of three operating segments: Marine, P&C and Professional Liability. The underwriting results of the acquired business from the NICE Group are included in the Int’l Insurance reporting segment, with no new operating segments resulting from the acquisition. 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 measures of underwriting profitability. Underwriting Profit (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. We evaluate our written premiums on a gross, ceded, and net basis. Additionally, we evaluate the retention ratio related to our written premiums, which represents the amount of written premium retained by the Company after ceding to reinsurers and is derived by dividing Net Written Premiums by Gross Written Premiums. 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. We do not allocate our assets by underwriting segment as we evaluate the underwriting results of these segments separately from the results of our investments portfolio. The following tables set forth the financial data by segment for the years ended December 31, 2018, 2017 and 2016: Year Ended December 31, 2018 U.S. Int'l amounts in thousands Insurance Insurance GlobalRe Corporate (1) Total Gross written premiums $ 1,083,116 $ 530,710 $ 299,135 $ — $ 1,912,961 Ceded written premiums (283,025 ) (147,402 ) (11,449 ) — (441,876 ) Net written premiums 800,091 383,308 287,686 — 1,471,085 Retention Ratio 73.9 % 72.2 % 96.2 % — 76.9 % Net Earned Premiums $ 737,646 $ 380,503 $ 245,074 $ — $ 1,363,223 Net Losses and LAE (485,960 ) (252,268 ) (155,551 ) — (893,779 ) Commission Expenses (85,127 ) (80,526 ) (55,056 ) 565 (220,144 ) Other Operating Expenses (142,333 ) (93,882 ) (25,009 ) — (261,224 ) Other Underwriting Income (Expense) 354 2,206 316 (565 ) 2,311 Underwriting Profit (Loss) $ 24,580 $ (43,967 ) $ 9,774 $ — $ (9,613 ) Net Investment Income 103,113 103,113 Total Net Realized and Unrealized Losses (30,348 ) (30,348 ) Interest Expense (15,485 ) (15,485 ) Other Income 4,858 4,858 Merger Transaction Costs (3,950 ) (3,950 ) Income (Loss) Before Income Taxes $ 24,580 $ (43,967 ) $ 9,774 $ 58,188 $ 48,575 Income Tax Expense (14,336 ) (14,336 ) Net Income $ 34,239 Losses and LAE ratio 65.9 % 66.3 % 63.5 % 65.6 % Commission Expense Ratio 11.5 % 21.2 % 22.5 % 16.1 % Other Operating Expense Ratio (2) 19.3 % 24.1 % 10.0 % 19.0 % Combined Ratio 96.7 % 111.6 % 96.0 % 100.7 % (1) - Includes Corporate segment intercompany eliminations. (2) - Includes Other Operating Expenses and Other Underwriting Income. Year Ended December 31, 2017 U.S. Int'l amounts in thousands Insurance Insurance GlobalRe Corporate (1) Total Gross written premiums $ 988,293 $ 501,130 $ 223,842 $ — $ 1,713,265 Ceded written premiums (266,993 ) (165,278 ) (9,664 ) — (441,935 ) Net written premiums 721,300 335,852 214,178 — 1,271,330 Retention Ratio 73.0 % 67.0 % 95.7 % — 74.2 % Net Earned Premiums $ 674,665 $ 333,792 $ 177,963 $ — $ 1,186,420 Net Losses and LAE (443,353 ) (229,601 ) (133,311 ) — (806,265 ) Commission Expenses (77,729 ) (68,824 ) (39,136 ) 958 (184,731 ) Other Operating Expenses (128,905 ) (83,464 ) (20,861 ) — (233,230 ) Other Underwriting Income (Expense) 461 — 565 (958 ) 68 Underwriting Profit (Loss) $ 25,139 $ (48,097 ) $ (14,780 ) $ — $ (37,738 ) Net Investment Income 89,293 89,293 Total Net Realized and Unrealized Gains 43,009 43,009 Interest Expense (15,447 ) (15,447 ) Other Loss (4,311 ) (4,311 ) Income (Loss) Before Income Taxes $ 25,139 $ (48,097 ) $ (14,780 ) $ 112,544 $ 74,806 Income Tax Expense (34,312 ) (34,312 ) Net Income $ 40,494 Losses and LAE ratio 65.7 % 68.8 % 74.9 % 68.0 % Commission Expense Ratio 11.5 % 20.6 % 22.0 % 15.6 % Other Operating Expense Ratio (2) 19.1 % 25.0 % 11.4 % 19.6 % Combined Ratio 96.3 % 114.4 % 108.3 % 103.2 % (1) - Includes Corporate segment intercompany eliminations. (2) - Includes Other Operating Expenses and Other Underwriting Income. Year Ended December 31, 2016 U.S. Int'l amounts in thousands Insurance Insurance GlobalRe Corporate (1) Total Gross written premiums $ 919,395 $ 484,471 $ 165,045 $ — $ 1,568,911 Ceded written premiums (235,827 ) (138,504 ) (8,356 ) — (382,687 ) Net written premiums 683,568 345,967 156,689 — 1,186,224 Retention Ratio 74.3 % 71.4 % 94.9 % — 75.6 % Net Earned Premiums $ 629,308 $ 307,416 $ 163,621 $ — $ 1,100,345 Net Losses and LAE (397,860 ) (178,284 ) (89,304 ) — (665,448 ) Commission Expenses (70,812 ) (61,703 ) (34,008 ) 1,478 (165,045 ) Other Operating Expenses (128,108 ) (86,395 ) (19,593 ) — (234,096 ) Other Underwriting Income (Expense) 1,092 — 522 (1,478 ) 136 Underwriting Profit (Loss) $ 33,620 $ (18,966 ) $ 21,238 $ — $ 35,892 Net Investment Income 79,451 79,451 Total Net Realized and Unrealized Gains 9,036 9,036 Interest Expense (15,435 ) (15,435 ) Other Income 8,565 8,565 Income (Loss) Before Income Taxes $ 33,620 $ (18,966 ) $ 21,238 $ 81,617 $ 117,509 Income Tax Expense (34,783 ) (34,783 ) Net Income $ 82,726 Losses and LAE ratio 63.2 % 58.0 % 54.6 % 60.5 % Commission Expense Ratio 11.3 % 20.1 % 20.8 % 15.0 % Other Operating Expense Ratio (2) 20.2 % 28.1 % 11.6 % 21.2 % Combined Ratio 94.7 % 106.2 % 87.0 % 96.7 % (1) - Includes Corporate segment intercompany eliminations. (2) - Includes Other Operating Expenses and Other Underwriting Income. The following tables provide additional financial data by operating segment for the years ended December 31, 2018, 2017 and 2016: Year Ended December 31, 2018 amounts in thousands Gross written premiums Ceded premiums Net written premiums Net earned premiums U.S. Insurance Marine $ 148,485 $ (64,097 ) $ 84,388 $ 84,774 P&C 803,759 (199,307 ) 604,452 549,136 Professional Liability 130,872 (19,621 ) 111,251 103,736 Total $ 1,083,116 $ (283,025 ) $ 800,091 $ 737,646 Int'l Insurance Marine $ 181,053 $ (44,356 ) $ 136,697 $ 151,296 P&C 171,502 (64,176 ) 107,326 105,144 Professional Liability 178,155 (38,870 ) 139,285 124,063 Total $ 530,710 $ (147,402 ) $ 383,308 $ 380,503 GlobalRe $ 299,135 $ (11,449 ) $ 287,686 $ 245,074 Total $ 1,912,961 $ (441,876 ) $ 1,471,085 $ 1,363,223 Year Ended December 31, 2017 amounts in thousands Gross written premiums Ceded written premiums Net written premiums Net earned premiums U.S. Insurance Marine $ 156,171 $ (72,431 ) $ 83,740 $ 86,605 P&C 713,539 (173,501 ) 540,038 495,260 Professional Liability 118,583 (21,061 ) 97,522 92,800 Total $ 988,293 $ (266,993 ) $ 721,300 $ 674,665 Int'l Insurance Marine $ 198,241 $ (42,018 ) $ 156,223 $ 152,396 P&C 159,123 (85,298 ) 73,825 88,517 Professional Liability 143,766 (37,962 ) 105,804 92,879 Total $ 501,130 $ (165,278 ) $ 335,852 $ 333,792 GlobalRe $ 223,842 $ (9,664 ) $ 214,178 $ 177,963 Total $ 1,713,265 $ (441,935 ) $ 1,271,330 $ 1,186,420 Year Ended December 31, 2016 amounts in thousands Gross written premiums Ceded written premiums Net written premiums Net earned premiums U.S. Insurance Marine $ 169,405 $ (70,858 ) $ 98,547 $ 100,132 P&C 631,562 (135,888 ) 495,674 453,673 Professional Liability 118,428 (29,081 ) 89,347 75,503 Total $ 919,395 $ (235,827 ) $ 683,568 $ 629,308 Int'l Insurance Marine $ 183,228 $ (40,092 ) $ 143,136 $ 141,593 P&C 181,094 (69,606 ) 111,488 89,455 Professional Liability 120,149 (28,806 ) 91,343 76,368 Total $ 484,471 $ (138,504 ) $ 345,967 $ 307,416 GlobalRe $ 165,045 $ (8,356 ) $ 156,689 $ 163,621 Total $ 1,568,911 $ (382,687 ) $ 1,186,224 $ 1,100,345 The following is a summary of our Company's Gross Written Premiums allocated based on the location of the insured's head office: Years Ended December 31, amounts in thousands 2018 2017 2016 United States $ 1,373,346 $ 1,203,695 $ 1,101,337 Worldwide (Excluding the United States) 539,615 509,570 467,574 Total $ 1,912,961 $ 1,713,265 $ 1,568,911 Our Company distributes our insurance products through international, national, regional and retail insurance brokers. For the year ended December 31, 2018, business produced within our U.S. Insurance, Int’l Insurance and GlobalRe reporting segments through the broker Marsh & McLennan Companies Inc. represented just over 10% of consolidated gross premiums written. The assets of our Company are reviewed in total by management for purposes of decision making.

Investments

Investments	12 Months Ended
	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Investments	NOTE 4. INVESTMENTS The following tables set forth our Company’s available-for-sale investments and Equity Securities as of December 31, 2018 and 2017 and include OTTI securities recognized within AOCI: December 31, 2018 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 $ 239,776 $ 901 $ (3,957 ) $ 242,832 States, Municipalities and Political Subdivisions 646,551 10,734 (3,448 ) 639,265 Mortgage-Backed and Asset-Backed Securities: Agency Residential Mortgage-Backed Securities 335,542 843 (13,118 ) 347,817 Residential Mortgage Obligations 138,373 604 (530 ) 138,299 Asset-Backed Securities 531,991 1,018 (8,040 ) 539,013 Commercial Mortgage-Backed Securities 188,201 858 (2,816 ) 190,159 Subtotal $ 1,194,107 $ 3,323 $ (24,504 ) $ 1,215,288 Corporate Exposures (1) 1,002,489 3,101 (28,640 ) 1,028,028 Total Fixed Maturities $ 3,082,923 $ 18,059 $ (60,549 ) $ 3,125,413 Short-Term Investments 10,233 — (1 ) 10,234 Total Available-For-Sale Investments $ 3,093,156 $ 18,059 $ (60,550 ) $ 3,135,647 (1) - Corporate Exposures consist of investments in corporate bonds, hybrid bonds and redeemable preferred stocks. As of December 31, 2018 Gross Gross Fair Unrealized Unrealized amounts in thousands Value Gains (Losses) Cost Equity Securities: Common Stocks $ 166,353 $ 4,738 $ (15,984 ) $ 177,599 Preferred Stocks 173,539 511 (10,791 ) 183,819 Total Equity Securities $ 339,892 $ 5,249 $ (26,775 ) $ 361,418 December 31, 2017 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 $ 393,563 $ 2,081 $ (2,014 ) $ 393,496 States, Municipalities and Political Subdivisions 814,632 20,136 (1,423 ) 795,919 Mortgage-Backed and Asset-Backed Securities: Agency Residential Mortgage-Backed Securities 407,619 2,352 (5,414 ) 410,681 Residential Mortgage Obligations 54,104 606 (79 ) 53,577 Asset-Backed Securities 328,753 2,138 (663 ) 327,278 Commercial Mortgage-Backed Securities 160,904 2,354 (1,182 ) 159,732 Subtotal $ 951,380 $ 7,450 $ (7,338 ) $ 951,268 Corporate Exposures (1) 897,479 14,491 (3,737 ) 886,725 Total Fixed Maturities $ 3,057,054 $ 44,158 $ (14,512 ) $ 3,027,408 Equity Securities: Common Stocks $ 52,439 $ 7,423 $ (112 ) $ 45,128 Preferred Stocks 183,542 6,071 (1,560 ) 179,031 Total Equity Securities $ 235,981 $ 13,494 $ (1,672 ) $ 224,159 Short-Term Investments (2) 6,480 3 — 6,477 Total Available-For-Sale Investments $ 3,299,515 $ 57,655 $ (16,184 ) $ 3,258,044 (1) - Corporate Exposures consist of investments in corporate bonds, hybrid bonds and redeemable preferred stocks. (2) - Cash and overseas deposits that were misclassified within Short-Term Investments prior to 2018 were reclassified, representing an immaterial correction. Refer to Note 1 Organization & Summary of Significant Accounting Policies Our Company made strategic investments in certain companies which are reported as Other Invested Assets on the Consolidated Balance Sheet and accounted for using the equity method. In applying the equity method, these investments are initially recorded at cost and are subsequently adjusted based on our Company’s proportionate share of the net income or loss of the companies. Our initial purchase price of $2.0 million had a current carrying value of $1.9 million and $1.7 million at December 31, 2018 and 2017, respectively. Other Invested Assets also includes overseas deposits with a fair value of $46.5 million at December 31, 2018 and $28.8 million at December 31, 2017. The overseas deposits consist of investments in private funds which are managed centrally by The Corporation of Lloyd’s in support of all Lloyd’s market participants. The funds consist of fixed income securities, bank deposits, and cash invested in local markets which are intended to fulfill regulatory deposit requirements in worldwide jurisdictions. Our Company’s ability to withdraw from the funds is restricted by an annual and quarterly funding and release process managed by Lloyd’s in conjunction with Syndicate 1221’s capital requirements in various jurisdictions. As of December 31, 2018 and 2017, 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, 2018 and 2017, Fixed Maturities for which non-credit OTTI was previously recognized and included in AOCI are now in a net unrealized net gains position of $0.3 million and $0.5 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. 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, 2018 are shown in the following table: December 31, 2018 Amortized amounts in thousands Fair Value Cost Due in One Year or Less $ 183,390 $ 184,761 Due after One Year Through Five Years 793,254 801,841 Due After Five Years Through Ten Years 370,056 368,933 Due After Ten Years 542,116 554,592 Mortgage-Backed and Asset-Backed Securities 1,194,107 1,215,286 Total $ 3,082,923 $ 3,125,413 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 5.2 years. The following tables summarize all securities available-for-sale in a gross unrealized loss position as of December 31, 2018 and 2017, 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, 2018 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 $ 101,395 $ (2,486 ) $ 112,195 $ (1,471 ) $ 213,590 $ (3,957 ) States, Municipalities and Political Subdivisions 123,479 (1,274 ) 105,405 (2,174 ) 228,884 (3,448 ) Mortgage-Backed and Asset-Backed Securities: Agency Residential Mortgage-Backed Securities 34,819 (814 ) 270,997 (12,304 ) 305,816 (13,118 ) Residential Mortgage Obligations 70,965 (249 ) 10,110 (281 ) 81,075 (530 ) Asset-Backed Securities 345,437 (6,950 ) 77,362 (1,090 ) 422,799 (8,040 ) Commercial Mortgage-Backed Securities 58,877 (282 ) 41,477 (2,534 ) 100,354 (2,816 ) Subtotal $ 510,098 $ (8,295 ) $ 399,946 $ (16,209 ) $ 910,044 $ (24,504 ) Corporate Exposures (1) 481,057 (15,456 ) 300,113 (13,184 ) 781,170 (28,640 ) Total Fixed Maturities $ 1,216,029 $ (27,511 ) $ 917,659 $ (33,038 ) $ 2,133,688 $ (60,549 ) (1) - Corporate Exposures consist of investments in corporate bonds, hybrid bonds and redeemable preferred stocks. December 31, 2017 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 $ 273,672 $ (1,502 ) $ 54,484 $ (512 ) $ 328,156 $ (2,014 ) States, Municipalities and Political Subdivisions 74,097 (503 ) 45,085 (920 ) 119,182 (1,423 ) Mortgage-Backed and Asset-Backed Securities: Agency Residential Mortgage-Backed Securities 87,496 (346 ) 236,745 (5,068 ) 324,241 (5,414 ) Residential Mortgage Obligations 12,418 (62 ) 546 (17 ) 12,964 (79 ) Asset-Backed Securities 85,877 (468 ) 24,733 (195 ) 110,610 (663 ) Commercial Mortgage-Backed Securities 20,482 (95 ) 22,903 (1,087 ) 43,385 (1,182 ) Subtotal $ 206,273 $ (971 ) $ 284,927 $ (6,367 ) $ 491,200 $ (7,338 ) Corporate Exposures (1) 295,433 (1,690 ) 121,410 (2,047 ) 416,843 (3,737 ) Total Fixed Maturities $ 849,475 $ (4,666 ) $ 505,906 $ (9,846 ) $ 1,355,381 $ (14,512 ) Equity Securities: Common Stocks $ 11,245 $ (81 ) $ 1,770 $ (31 ) $ 13,015 $ (112 ) Preferred Stocks 50,861 (1,524 ) 662 (36 ) 51,523 (1,560 ) Total Equity Securities $ 62,106 $ (1,605 ) $ 2,432 $ (67 ) $ 64,538 $ (1,672 ) Total Fixed Maturities and Equity Securities $ 911,581 $ (6,271 ) $ 508,338 $ (9,913 ) $ 1,419,919 $ (16,184 ) (1) - Corporate Exposures consist of investments in corporate bonds, hybrid bonds and redeemable preferred stocks. Our Company analyzes impaired securities quarterly to determine if any impairments are other-than-temporary. The above securities with unrealized losses have been determined to be temporarily impaired based on our evaluation. At December 31, 2018, there were 808 Fixed Maturities in an unrealized loss position. In the above table, the gross unrealized loss for the greater than 12 months category consists primarily of Agency Residential Mortgage-Backed Securities and Hybrid bonds and Redeemable Preferred stocks, which are reported in Corporate Exposures, and is mostly due to an increase in interest rates and spread widening. The gross unrealized loss for the less than 12 months category consists primarily of Hybrid bonds and Redeemable Preferred stocks, which are reported in Corporate Exposures, and Asset Backed Securities mainly due to spread widening. At December 31, 2017, there were 454 Fixed Maturities and 22 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 Residential Mortgage-backed Securities and Corporate Exposures and is mostly due to an increase in interest rates at the time of purchase. The gross unrealized loss for the less than 12 months category consists primarily of Corporate Bonds and Preferred Stocks, which are reported in Equity Securities, due to an increase in interest rates since time of purchase, as well as Foreign Government Bonds due to an unfavorable exchange rate movement in our Canadian portfolio. As of December 31, 2018 and 2017, the largest unrealized loss by a non-government backed issuer in the investment portfolio was $3.7 million and $0.7 million, respectively. 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. Upon adoption of ASU 2016-01 as of January 1, 2018, changes in the fair value of Equity Securities are recognized through Net Income. Our Company had no credit related OTTI losses during the year ended December 31, 2018. Our Company had four credit related OTTI losses totaling $2.1 million during the year ended December 31, 2017 from our Equity Securities portfolio. Our Company had one credit related OTTI loss totaling $0.2 million from our Fixed Maturities portfolio during the year ended December 31, 2016. 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, 2018, 2017 and 2016. Years Ended December 31, amounts in thousands 2018 2017 2016 Beginning Balance $ 2,361 $ 2,361 $ 2,361 Additions for Credit Loss Impairments recognized in the current period on securities not previously impaired — — 150 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 (17 ) — (150 ) Ending Balance $ 2,344 $ 2,361 $ 2,361 Our Company’s Net Investment Income was derived from the following sources: Years Ended December 31, amounts in thousands 2018 2017 2016 Fixed Maturities $ 90,101 $ 76,784 $ 67,772 Equity Securities 13,807 15,108 14,271 Short-Term Investments, Cash and Cash Equivalents (1) 1,676 428 317 Other Invested Assets (1) 666 636 410 Total Investment Income $ 106,250 $ 92,956 $ 82,770 Investment Expenses (3,137 ) (3,663 ) (3,319 ) Net Investment Income $ 103,113 $ 89,293 $ 79,451 (1) - Cash and overseas deposits that were misclassified within Short-Term Investments prior to 2018 were reclassified, representing an immaterial correction. Refer to Note 1 Organization & Summary of Significant Accounting Policies 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 2018 2017 2016 Fixed Maturities: Gains $ 3,775 $ 4,041 $ 5,681 Losses (1,306 ) (3,249 ) (4,271 ) Fixed Maturities, Net $ 2,469 $ 792 $ 1,410 Short-Term Investments, Cash and Cash Equivalents: (1) Gains $ 208 $ 1,575 $ 871 Losses (319 ) (243 ) (1,444 ) Short-Term, Net $ (111 ) $ 1,332 $ (573 ) Other Invested Assets: (1) Gains $ 92 $ 56 $ 19 Losses (213 ) (369 ) (108 ) Other Invested Assets, Net $ (121 ) $ (313 ) $ (89 ) Equity Securities: Gains $ 1,102 $ 44,783 $ 9,096 Losses (350 ) (1,521 ) (658 ) Equity Securities, Net $ 752 $ 43,262 $ 8,438 Net Realized Gains on Investments Sold $ 2,989 $ 45,073 $ 9,186 (1) - Cash and overseas deposits that were misclassified within Short-Term Investments prior to 2018 were reclassified, representing an immaterial correction. Refer to Note 1 Organization & Summary of Significant Accounting Policies The following table presents the portion of Net Unrealized Losses recognized during the year that relates to Equity Securities held as of December 31, 2018: amounts in thousands Year Ended December 31, 2018 Equity Securities: Total Net Realized and Unrealized Losses recognized $ (32,585 ) Less: Net Realized Gains on Investments Sold 752 Net Unrealized Losses recognized $ (33,337 )

Fair Value Measurement

Fair Value Measurement	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurement	NOTE 5. FAIR VALUE MEASUREMENT 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. 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 count 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.18 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. 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, 2018 and 2017: December 31, 2018 amounts in thousands Level 1 Level 2 Level 3 Total Fixed Maturities: U.S. Treasury Bonds, Agency Bonds and Foreign Government Bonds $ 35,537 $ 204,239 $ — $ 239,776 States, Municipalities and Political Subdivisions — 646,551 — 646,551 Mortgage-Backed and Asset-Backed Securities: Agency Residential Mortgage-Backed Securities — 335,542 — 335,542 Residential Mortgage Obligations — 138,373 — 138,373 Asset-Backed Securities — 531,991 — 531,991 Commercial Mortgage-Backed Securities — 188,201 — 188,201 Subtotal $ — $ 1,194,107 $ — $ 1,194,107 Corporate Exposures — 1,002,489 — 1,002,489 Total Fixed Maturities $ 35,537 $ 3,047,386 $ — $ 3,082,923 Equity Securities: Common Stocks 35,029 131,324 — 166,353 Preferred Stocks — 173,539 — 173,539 Total Equity Securities $ 35,029 $ 304,863 $ — $ 339,892 Short-Term Investments — 10,233 — 10,233 Total Assets Measured at Fair Value $ 70,566 $ 3,362,482 $ — $ 3,433,048 Senior Notes $ — $ 278,150 $ — $ 278,150 Total Liabilities Measured at Fair Value $ — $ 278,150 $ — $ 278,150 December 31, 2017 amounts in thousands Level 1 Level 2 Level 3 Total Fixed Maturities: U.S. Treasury Bonds, Agency Bonds and Foreign Government Bonds $ 178,251 $ 215,312 $ — $ 393,563 States, Municipalities and Political Subdivisions — 814,632 — 814,632 Mortgage-Backed and Asset-Backed Securities: Agency Residential Mortgage-Backed Securities — 407,619 — 407,619 Residential Mortgage Obligations — 54,104 — 54,104 Asset-Backed Securities — 328,753 — 328,753 Commercial Mortgage-Backed Securities — 160,904 — 160,904 Subtotal $ — $ 951,380 $ — $ 951,380 Corporate Exposures — 897,479 — 897,479 Total Fixed Maturities $ 178,251 $ 2,878,803 $ — $ 3,057,054 Equity Securities: Common Stocks 52,439 — — 52,439 Preferred Stocks — 183,542 — 183,542 Total Equity Securities $ 52,439 $ 183,542 $ — $ 235,981 Short-Term Investments (1) 6,480 — — 6,480 Total Assets Measured at Fair Value $ 237,170 $ 3,062,345 $ — $ 3,299,515 Senior Notes $ — $ 277,951 $ — $ 277,951 Total Liabilities Measured at Fair Value $ — $ 277,951 $ — $ 277,951 (1) - Cash and overseas deposits that were misclassified within Short-Term Investments prior to 2018 were reclassified, representing an immaterial correction. Refer to Note 1 Organization & Summary of Significant Accounting Policies 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 has overseas deposits in Other Invested Assets of $46.5 million and $28.8 million at December 31 2018 and December 2017, respectively, which is measured at fair value using the net asset value (“NAV”) as a practical expedient. Our Company did not have any significant transfers between the Level 1 and Level 2 classifications for the years ended December 31, 2018 and 2017. As of December 31, 2018 and 2017, our Company did not have any Level 3 assets.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	NOTE 6. GOODWILL AND INTANGIBLE ASSETS Goodwill The following table shows an analysis of goodwill by reporting segment: Year Ended December 31, 2018 U.S. Int'l amounts in thousands Insurance Insurance Total Goodwill at Beginning of the Year $ 1,978 $ 2,482 $ 4,460 Goodwill Acquired — 12,703 12,703 Foreign Currency Translation Adjustment — (345 ) (345 ) Goodwill at End of the Year $ 1,978 $ 14,840 $ 16,818 The Goodwill Acquired primarily relates to expected synergies from combining operations of the NICE Group and is not expected to be deductible for tax purposes. Included in the Goodwill Acquired is an increase of $1.4 million from the amount initially recorded at June 30, 2018, as a result of a measurement period adjustment to the fair value of the ASCO customer relationships intangible asset. See the “Intangibles” section below for further information. Intangibles The gross carrying value and weighted average amortization period of intangible assets by type at December 31, 2018 was as follows: As of December 31, 2018 amounts in thousands Gross Carrying Amount Accumulated Amortization Weighted Average Amortization Period Finite-Lived Assets ASCO Customer Relationships $ 3,289 $ (164 ) 10 years ASCO VOBA 1,663 (208 ) 4 years BDM Broker Networks 984 (33 ) 15 years BDM Trade Name 484 (242 ) 1 year Total $ 6,420 $ (647 ) Indefinite-Lived Assets ASCO European Licenses $ 2,419 indefinite NUAL Lloyd's Syndicate Capacity $ 2,136 indefinite Total $ 4,555 As part of our business combination accounting within the measurement period, the Company recorded an adjustment to the fair value of the ASCO customer relationships intangible asset. The adjustment resulted from additional analysis of the duration of customer contracts, which decreased the useful life of the intangible asset from 15 to 10 years. As a result, the fair value of the intangible asset decreased by $1.4 million from the amount initially recorded at June 30, 2018. The amortization of the Finite-Lived Assets was recognized within Other Operating Expenses on our Consolidated Statements of Income (Loss) with the exception of the amortization of the VOBA asset, which was recognized within Commission Expenses. The estimated remaining amortization expense for the finite-lived intangible assets is as follows: amounts in thousands Total 2019 $ 1,052 2020 810 2021 810 2022 602 2023 394 2024 and thereafter 2,105 Total $ 5,773

Reserves for Losses and LAE

Reserves for Losses and LAE	12 Months Ended
	Dec. 31, 2018
Insurance [Abstract]
Reserves for Losses and LAE	NOTE 7. 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 activity for our Company’s Reserves for Losses and LAE for the years ended December 31, 2018, 2017 and 2016: Years Ended December 31, amounts in thousands 2018 2017 2016 Net Reserves for Losses and LAE at Beginning of Year $ 1,705,380 $ 1,510,451 $ 1,393,126 Acquired Net Reserves 16,159 — — Provision for Losses and LAE for Claims Occurring in the Current Year 817,537 771,955 693,976 Increase (Decrease) in Estimated Losses and LAE for Claims Occurring in Prior Years 76,242 34,310 (28,528 ) Incurred Losses and LAE $ 893,779 $ 806,265 $ 665,448 Losses and LAE Paid for Claims Occurring During: Current Year (124,754 ) (144,095 ) (119,485 ) Prior Years (554,733 ) (478,979 ) (412,544 ) Losses and LAE Payments $ (679,487 ) $ (623,074 ) $ (532,029 ) Foreign Currency Adjustment (12,047 ) 11,738 (16,094 ) Net Reserves for Losses and LAE at End of Period 1,923,784 1,705,380 1,510,451 Reinsurance Recoverables on Unpaid Losses and LAE 820,189 809,765 779,276 Gross Reserves for Losses and LAE at End of Period $ 2,743,973 $ 2,515,145 $ 2,289,727 For the year ended December 31, 2018, our Incurred Losses and LAE increased $87.5 million as compared to the same period in 2017 and for the year ended December 31, 2017, our Incurred Losses and LAE increased $140.8 million as compared to the same period in 2016. The increases for both years were the result of increased current and prior year Incurred Losses and LAE. Current Accident Year Losses and LAE For the year ended December 31, 2018, the Provision for Losses and LAE for Claims Occurring in the Current Year increased primarily due to growth in Net Earned Premium over the prior year. This increase was partially offset by a decrease in additional net current accident year (“AY”) loss activity related to a lower level of catastrophe (“CAT”) losses incurred in the year, including Typhoon Jebi ($13.9 million), Hurricane Michael ($4.8 million), Hurricane Florence ($3.5 million), the California Camp Fire ($3.2 million), Typhoon Trami ($3.0 million), and other CAT events ($0.3 million), as compared to $84.8 million for the same period in 2017. The following is a discussion of CAT losses incurred of $28.7 million for the year ended December 31, 2018: • Our U.S. Insurance reporting segment incurred $1.8 million of CAT losses, including $0.9 million and $0.9 million in our P&C and Marine operating segments, respectively, primarily due to Hurricanes Michael and Florence, the California Camp Fire, and Typhoon Jebi. • Our Int’l Insurance reporting segment incurred $3.5 million of CAT losses, including $1.9 million and $1.6 million within our P&C and Marine operating segments, primarily due to Hurricanes Florence and Michael. • Our GlobalRe reporting segment incurred $23.4 million of CAT losses primarily due to Typhoon Jebi, Hurricanes Michael and Florence, the California Camp Fire, and Typhoon Trami. For the year ended December 31, 2017, the Provision for Losses and LAE for Claims Occurring in the Current Year increased primarily due to additional net current AY loss activity related to a higher level of CAT losses incurred during the year, including Hurricanes Irma ($28.3 million), Maria ($23.4 million) and Harvey ($15.8 million), Typhoon Hato ($4.2 million), the Puebla, Mexico Earthquake ($3.5 million), and other CAT events ($9.6 million), as compared to the same period in 2016 which primarily consisted of the Alberta Wildfires ($11.7 million), Hurricane Matthew ($7.1 million), the Ecuador Earthquake ($3.8 million) and the Taiwan Earthquake ($3.3 million). Additionally, growth in Net Earned Premium over the prior year added to the increase in Provision for Losses and LAE for Claims Occurring in the Current Year. The following is a discussion of CAT losses incurred of $84.8 million for the year ended December 31, 2017: • Our U.S. Insurance reporting segment incurred $8.2 million of CAT losses, including $6.6 million and $1.6 million in our P&C and Marine operating segments, respectively, primarily due to Hurricanes Harvey, Irma and Maria. • Our Int’l Insurance reporting segment incurred $32.9 million of CAT losses, including $16.9 million and $16.0 million within our P&C and Marine operating segments, primarily due to Hurricanes Irma, Maria and Harvey, Typhoon Hato, and to a lesser extent, the California Wildfires and Puebla, Mexico Earthquake. • Our GlobalRe reporting segment incurred $43.7 million of CAT losses primarily due to Hurricanes Irma, Maria and Harvey, and the Puebla, Mexico Earthquake. Our December 31, 2018 Net Reserves for Losses and LAE include $14.2 million of net incurred but not reported (“IBNR”) claims activities for numerous catastrophe events. We caution that the magnitude and complexity of losses arising from these events inherently increases the level of uncertainty and therefore the level of management judgement involved in arriving at our estimated Net Reserves for Losses and LAE. As a result, our actual losses for these events may ultimately differ materially from our current estimates. Prior Year Incurred Losses and LAE The reporting and operating segments breakdowns of prior period net reserve strengthening (releases) for the years ended December 31, 2018, 2017 and 2016 are as follows: Years Ended December 31, amounts in thousands 2018 2017 2016 U.S. Insurance Marine $ (789 ) $ 1,696 $ (10,122 ) P&C 10,310 1,613 2,790 Professional Liability 9,387 13,405 5,984 Total $ 18,908 $ 16,714 $ (1,348 ) Int'l Insurance Marine $ 21,788 $ 6,518 $ (22,068 ) P&C (4,913 ) 3,118 (7,051 ) Professional Liability 14,478 5,198 4,100 Total $ 31,353 $ 14,834 $ (25,019 ) GlobalRe $ 25,981 $ 2,762 $ (2,161 ) Total Strengthening (Releases) $ 76,242 $ 34,310 $ (28,528 ) The following is a discussion of the relevant factors related to the prior period net reserve strengthening of $76.2 million recorded for the year ended December 31, 2018: Our U.S. Insurance reporting segment recorded prior period net reserve strengthening of $18.9 million. The drivers are as follows: • Our Marine operating segment recorded prior period net reserve releases of $0.8 million driven by favorable loss emergence in our Cargo, Inland Marine, Marine Liability and Hull product lines, as well as, prior period CAT reserve release mostly within our Cargo product line, partially offset by large loss activity in our Craft and Fishing Vessels products. • Our P&C operating segment recorded prior period net reserve strengthening of $10.3 million driven by large loss activity within our Primary Casualty division, partially offset by ongoing favorable performance within our Excess Casualty, Environmental and Other P&C divisions. • Our Professional Liability operating segment recorded prior period net reserve strengthening of $9.4 million driven by unfavorable loss emergence within our D&O division, and to a lesser extent, our E&O division. Our Int’l Insurance reporting segment recorded prior period net reserve strengthening of $31.4 million. The drivers are as follows: • Our Marine operating segment recorded prior period net reserve strengthening of $21.8 million due to large loss activity in our Hull and Cargo product lines, unfavorable loss development within our Transport and Specie product lines, and prior period CAT development on our Cargo product line. This was partially offset by favorable loss emergence on our Energy Liability and Marine Liability product lines. • Our P&C operating segment recorded prior period net reserve releases of $4.9 million resulting from net catastrophe loss release primarily related to the 2017 Hurricane events and the Puebla, Mexico Earthquake and favorable loss emergence in our PV&T division, partially offset by unfavorable loss development in our Energy and Engineering division. • Our Professional Liability operating segment recorded prior period net reserve strengthening of $14.5 million primarily due to large loss development within our D&O division and worse than expected loss emergence within our E&O division, partially offset by favorable loss emergence in our Other Professional Liability division. Our GlobalRe reporting segment recorded prior period net reserve strengthening of $26.0 million primarily driven by significant unfavorable loss emergence in our Accident & Health (“A&H”) product line, and to a lesser extent our P&C product line, partially offset by favorable loss emergence in our Surety product. The following is a discussion of the relevant factors related to the prior period net reserve strengthening of $34.3 million recorded for the year ended December 31, 2017: Our U.S. Insurance reporting segment recorded prior period net reserve strengthening of $16.7 million. The drivers are as follows: • Our Marine operating segment recorded prior period net reserve strengthening of $1.7 million driven by large loss activity within our Cargo product line. • Our P&C operating segment recorded prior period net reserve strengthening of $1.6 million driven by large loss activity within our Primary Casualty division, partially offset by ongoing favorable performance within our Excess Casualty, Environmental and Other P&C divisions. • Our Professional Liability operating segment recorded prior period net reserve strengthening of $13.4 million driven by large loss activity within our D&O division. Our Int’l Insurance reporting segment recorded prior period net reserve strengthening of $14.8 million. The drivers are as follows: • Our Marine operating segment recorded prior period net reserve strengthening of $6.5 million due to unfavorable loss development predominately from our Cargo, Specie and P&I products. • Our P&C operating segment recorded prior period net reserve strengthening of $3.1 million primarily due to unfavorable loss development within our Property division, partially offset by favorable loss emergence in our Energy & Engineering division. • Our Professional Liability operating segment recorded prior period net reserve strengthening of $5.2 million primarily due to large loss development within our E&O and D&O divisions. Our GlobalRe reporting segment recorded prior period net reserve strengthening of $2.8 million primarily driven by the settlement of a large claim in our A&H product, and unfavorable loss emergence within our P&C product. This strengthening was partially offset by reserve releases in our Agriculture and Marine products due to favorable loss emergence. The following is a discussion of the relevant factors related to the prior period net reserve releases of $28.5 million recorded for the year ended December 31, 2016: Our U.S. Insurance reporting segment recorded prior period net reserve releases of $1.3 million. The drivers are as follows: • Our Marine operating segment recorded prior period net reserve releases of $10.1 million driven by favorable claims development in the Craft, Marine Liability, Customs Bonds and Inland Marine products. • Our P&C operating segment recorded prior period net reserve strengthening of $2.8 million driven by large loss activity within our Primary Casualty division, partially offset by ongoing favorable performance within our Excess Casualty, Environmental and Other P&C divisions. • Our Professional Liability operating segment recorded prior period net reserve strengthening of $6.0 million driven by unfavorable development on a few large D&O claims. Our Int’l Insurance reporting segment recorded prior period net reserve releases of $25.0 million. The drivers are as follows: • Our Marine operating segment recorded prior period net reserve releases of $22.1 million due to favorable claims development predominately from our Marine Liability product. • Our P&C operating segment recorded prior period net reserve releases of $7.1 million primarily due to favorable claims development in our Energy & Engineering division, partially offset by large loss activity within our Property division. • Our Professional Liability operating segment recorded prior period net reserve strengthening of $4.1 million primarily due to a decline in expected recoveries from a large reinsurer resulting in an increase in bad debt reserve within our D&O division. Our GlobalRe reporting segment recorded prior period net reserve releases of $2.2 million primarily driven by favorable loss development in our A&H, P&C and Professional Liability products, partially offset by large loss activity in our Marine product. Losses and LAE Payments For the year ended December 31, 2018, our Losses and LAE Payments increased $56.4 million as compared to the same period in 2017, primarily due to increased claim payments associated with growth in our business and the catastrophe activity occurring in 2017. For the year ended December 31, 2017, our Losses and LAE Payments increased $91.0 million as compared to the same period in 2016, primarily due to increased claim payments in our Int’l Insurance reporting segment. Supplemental tables related to Short Duration Contracts Effectively all property and casualty insurance contracts are described as “Short Duration Contracts” as opposed to life insurance, by the Securities and Exchange Commission. Our Company only issues short duration contracts. Below are two tables with reserve data for each operating segment. These tables are presented net of reinsurance. The first table reflects incurred claims development as of December 31, 2018, as well as the cumulative claims frequency and the total of Incurred But Not Reported (“IBNR”) liabilities and expected development on reported claims included within the net incurred claims amounts. The second table reflects the cumulative paid claims development as of December 31, 2018. The conversion of all non USD currencies amounts, for all accident years, is in USD as of December 31, 2018. The information provided in our supplemental tables related to short duration contracts includes estimates. Beginning in the 2016 calendar year, the Company implemented a process for the business underwritten through Syndicate 1221 that captures and retains more detailed incurred claim data to enable it to assign AY information as accurately and completely as possible using the data available. Prior to the 2016 calendar year, records for Syndicate 1221 were not available by individual AY, which impacts the presentation of our Int’l Insurance and, to a limited extent, our Global Re supplemental tables for 2015 and prior reporting years. For these years, the Company developed a process to allocate the Syndicate 1221 incurred claims to individual prior accident years using only data known as of the end of the calendar year allowing for the development tables to reflect information on the variability of loss emergence from period to period. Due to the limitations of the data available for our Syndicate 1221 business, the supplemental tables below for our Int’l Insurance and GlobalRe reporting segments begin with the 2012 reporting year and will increase by one year until ten years are presented. The reserves related to the acquisition of ASCO during the year have been excluded from the development tables below due to data limitations and the overall insignificance of this category to total reserves. The reserve balance for this category has been included in the reconciliation table below. Claims frequency is based on claims posted in our Company’s data system as reported. Generally, for most direct insurance and excess-of-loss assumed reinsurance, one claim count is posted for each claim. For assumed bordereau business and business written on binders, one claim count is posted for each bordereau received, which could account for multiple claims. Additionally, if the insured is covered for multiple years, a claim may be initially established in all potentially impacted policy years until the appropriate policy year is determined. The information about incurred claims development and cumulative paid claims and Allocated Loss Adjustment Expense (“ALAE”), net of reinsurance, for the years ended December 31, 2009 through 2017, is presented as unaudited supplementary information. Note that asbestos reserves are included in the U.S. Marine operating segment in years prior to 2009. IBNR values shown in the following tables are the difference between the case reserves for reported losses and the estimated future payments for claims arising from the specific accident period. Our Company has always applied prudent claim reserving practices. For a number of segments, this has resulted in case reserves for more mature accident years exceeding the future payments consistently. IBNR estimates will be negative where our history indicates such favorable future emergence is the best estimate. U.S. Marine Loss and ALAE, Net of Reinsurance amounts in thousands except # of reported claims For the Years Ended December 31, As of December 31, 2018 AY 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Total IBNR # of Reported Claims 2009 $ 62,044 $ 58,500 $ 55,277 $ 49,650 $ 47,204 $ 48,488 $ 50,694 $ 49,870 $ 50,545 $ 50,625 $ 105 2,334 2010 64,212 63,221 59,219 53,684 51,791 55,974 55,478 55,316 55,687 67 2,011 2011 69,652 68,967 66,900 62,464 61,258 59,709 59,151 58,237 (95 ) 1,916 2012 84,927 87,253 71,941 68,546 70,057 70,573 72,896 1,774 1,863 2013 60,887 57,598 51,464 53,987 55,886 54,033 (882 ) 1,818 2014 58,009 41,454 40,211 44,985 49,366 603 1,951 2015 59,296 50,837 49,341 48,027 338 2,257 2016 51,289 47,254 46,817 2,187 2,534 2017 52,135 49,961 10,634 2,389 2018 49,188 28,204 1,735 Total $ 534,837 U.S. Marine Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance amounts in thousands For the Years Ended December 31, AY 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2009 $ 12,857 $ 28,714 $ 34,769 $ 40,763 $ 42,528 $ 45,106 $ 45,952 $ 48,634 $ 49,252 $ 49,543 2010 16,258 31,769 39,081 42,017 47,173 50,963 54,163 54,321 54,612 2011 14,925 39,707 48,443 51,897 56,405 57,350 57,992 57,879 2012 27,254 46,215 54,470 60,486 66,950 68,750 69,007 2013 17,789 35,350 41,281 46,782 51,041 51,245 2014 10,677 23,162 34,453 40,487 44,852 2015 16,801 30,565 39,927 43,897 2016 11,587 24,566 38,163 2017 18,861 32,341 2018 11,010 Total $ 452,549 Net reserves < 2009 7,740 Total Net reserves $ 90,028 U.S. Marine Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 7 8 9 10 U.S. Marine 29.2 % 29.9 % 16.7 % 8.9 % 7.7 % 3.3 % 2.2 % 1.8 % 0.9 % 0.6 % U.S. P&C Loss and ALAE, Net of Reinsurance amounts in thousands except # of reported claims For the Years Ended December 31, As of December 31, 2018 AY 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Total IBNR # of Reported Claims 2009 $ 127,749 $ 130,391 $ 131,636 $ 136,835 $ 142,348 $ 147,405 $ 148,126 $ 151,298 $ 150,614 $ 152,609 $ 4,699 8,603 2010 97,426 97,037 95,133 101,134 104,094 105,989 108,894 111,136 110,940 5,939 7,981 2011 80,399 78,420 87,297 90,301 91,267 98,857 101,061 102,403 9,172 6,623 2012 103,437 90,111 91,780 99,502 107,526 111,459 118,647 14,122 4,664 2013 139,986 126,220 129,385 137,692 149,841 156,793 14,770 4,040 2014 192,897 160,828 149,462 156,149 167,782 36,292 4,154 2015 246,404 220,278 215,822 235,390 39,530 4,115 2016 273,693 245,905 242,986 133,717 3,772 2017 298,195 259,919 183,018 3,851 2018 335,885 301,480 3,514 Total $ 1,883,354 U.S. P&C Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance amounts in thousands For the Years Ended December 31, AY 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2009 $ 11,335 $ 33,601 $ 56,453 $ 87,622 $ 111,571 $ 124,908 $ 130,402 $ 137,576 $ 139,768 $ 144,224 2010 12,310 27,036 47,222 65,972 78,243 86,665 91,559 98,053 100,698 2011 3,660 14,694 30,766 47,150 59,038 71,065 80,248 85,885 2012 4,761 17,404 27,717 47,253 67,772 83,215 91,557 2013 7,188 21,035 48,923 84,874 118,932 136,446 2014 5,269 13,569 44,999 75,618 113,585 2015 3,719 24,579 79,639 142,655 2016 5,885 30,124 65,439 2017 13,014 40,012 2018 16,752 Total $ 937,253 Net reserves < 2009 31,867 Total Net reserves $ 977,968 U.S. P&C Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 7 8 9 10 U.S. P&C 4.8 % 10.3 % 16.5 % 19.7 % 16.7 % 10.5 % 6.0 % 5.4 % 1.9 % 2.9 % U.S. Professional Liability Loss and ALAE, Net of Reinsurance amounts in thousands except # of reported claims For the Years Ended December 31, As of December 31, 2018 AY 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Total IBNR # of Reported Claims 2009 $ 47,473 $ 53,273 $ 61,023 $ 58,600 $ 60,789 $ 58,487 $ 58,660 $ 58,143 $ 61,083 $ 60,067 $ 716 1,370 2010 52,302 64,020 68,375 75,619 74,535 86,787 85,348 86,164 87,687 477 1,430 2011 58,116 62,087 70,240 73,028 79,181 79,136 82,558 82,754 715 1,726 2012 61,196 54,480 57,097 55,917 58,344 58,563 58,040 1,657 2,175 2013 60,899 54,982 49,104 48,298 54,228 58,855 3,230 1,984 2014 49,899 35,749 39,699 41,936 43,585 4,590 2,016 2015 31,375 30,486 30,802 35,186 4,712 1,680 2016 41,053 36,036 41,299 5,266 1,813 2017 50,825 44,346 22,367 1,980 2018 54,629 46,916 2,017 Total $ 566,448 U.S. Professional Liability Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance amounts in thousands For the Years Ended December 31, AY 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2009 $ 3,837 $ 21,742 $ 41,675 $ 51,642 $ 55,378 $ 53,859 $ 57,744 $ 58,095 $ 58,150 $ 58,161 2010 2,981 23,147 46,868 54,019 59,765 82,013 84,511 84,529 85,158 2011 3,204 23,878 43,551 59,576 65,710 75,641 78,258 78,382 2012 3,855 22,635 35,681 44,028 49,675 54,728 55,215 2013 4,677 22,167 32,904 38,876 47,062 50,909 2014 2,304 14,319 29,309 35,008 37,780 2015 2,256 11,173 18,303 23,321 2016 2,351 18,283 31,563 2017 2,613 16,246 2018 2,719 Total $ 439,454 Net reserves < 2009 1,327 Total Net reserves $ 128,321 U.S. Professional Liability Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 7 8 9 10 U.S. Professional Liability 5.7 % 29.1 % 26.4 % 13.7 % 8.4 % 10.0 % 3.3 % 0.3 % 0.4 % 0.0 % Int'l Marine Loss and ALAE, Net of Reinsurance amounts in thousands except # of reported claims For the Years Ended December 31, As of December 31, 2018 AY 2012 2013 2014 2015 2016 2017 2018 Total IBNR # of Reported Claims 2009 $ 95,612 $ 90,880 $ 89,667 $ 82,730 $ 81,296 $ 80,930 $ 82,896 $ 2,065 4,908 2010 130,924 128,878 118,028 113,877 111,165 107,400 107,443 330 5,231 2011 99,374 84,959 81,617 77,099 73,181 73,508 72,008 107 4,855 2012 109,784 131,234 106,553 98,960 91,991 91,844 93,931 272 5,368 2013 87,215 93,736 81,807 81,072 83,094 79,832 669 5,052 2014 104,464 117,228 115,909 118,195 112,498 (6,412 ) 5,125 2015 98,245 94,055 95,449 99,103 (1,843 ) 7,664 2016 87,690 94,464 89,992 1,561 10,085 2017 107,151 135,759 15,783 12,028 2018 94,251 16,778 7,603 Total $ 967,713 Int'l Marine Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance amounts in thousands For the Years Ended December 31, AY 2012 2013 2014 2015 2016 2017 2018 2009 $ 65,715 $ 69,853 $ 72,605 $ 76,050 $ 76,752 $ 78,007 $ 78,044 2010 77,626 89,896 95,906 99,875 102,161 102,597 102,841 2011 45,400 58,695 63,084 67,988 68,951 69,287 69,962 2012 23,088 54,300 69,811 77,847 80,449 82,370 84,744 2013 23,455 45,992 57,973 64,075 66,900 68,443 2014 29,625 56,964 80,943 89,506 104,801 2015 22,651 53,995 75,185 80,684 2016 23,357 54,708 66,912 2017 28,774 77,451 2018 25,404 Total $ 759,286 Net reserves < 2009 6,028 Total Net reserves $ 214,455 Int'l Marine Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 7 8 9 10 Int'l Marine 24.7 % 34.1 % 18.8 % 6.9 % 6.6 % 1.8 % 1.7 % 0.7 % 0.9 % 0.0 % Int'l P&C Loss and ALAE, Net of Reinsurance amounts in thousands except # of reported claims For the Years Ended December 31, As of December 31, 2018 AY 2012 2013 2014 2015 2016 2017 2018 Total IBNR # of Reported Claims 2009 $ 38,479 $ 40,687 $ 40,776 $ 40,488 $ 34,049 $ 34,305 $ 34,679 $ (100 ) 1,038 2010 42,807 42,234 41,628 41,911 42,528 42,285 40,594 (240 ) 1,026 2011 71,160 61,290 59,128 59,237 59,238 54,798 59,050 (215 ) 1,030 2012 45,287 37,168 36,167 32,242 32,376 32,830 32,069 (251 ) 921 2013 35,862 37,182 36,307 34,221 35,185 34,656 154 1,298 2014 26,741 22,200 20,417 16,363 17,517 (497 ) 1,273 2015 34,678 36,391 33,703 32,566 (86 ) 2,045 2016 78,827 91,431 74,382 987 3,800 2017 56,376 70,448 15,782 3,209 2018 46,487 15,981 1,053 Total $ 442,448 Int'l P&C Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance amounts in thousands For the Years Ended December 31, AY 2012 2013 2014 2015 2016 2017 2018 2009 $ 28,790 $ 33,079 $ 33,538 $ 33,180 $ 33,276 $ 33,359 $ 34,711 2010 34,935 40,576 43,112 40,818 40,935 41,405 41,505 2011 38,362 47,594 50,480 53,034 53,963 51,940 58,422 2012 13,171 21,436 26,904 29,937 31,136 31,389 32,041 2013 7,093 18,294 25,649 28,484 30,067 32,715 2014 3,864 8,948 13,150 16,709 17,626 2015 6,780 18,293 29,420 30,659 2016 25,971 55,287 66,743 2017 14,875 35,628 2018 9,580 Total $ 359,630 Net reserves < 2009 4,550 Total Net reserves $ 87,368 Int'l P&C Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 7 8 9 10 Int'l P&C 25.5 % 34.7 % 24.5 % 10.8 % 4.5 % 3.3 % -0.4 % 4.1 % 0.2 % 3.9 % Int'l Professional Liability Loss and ALAE, Net of Reinsurance amounts in thousands except # of reported claims For the Years Ended December 31, As of December 31, 2018 AY 2012 2013 2014 2015 2016 2017 2018 Total IBNR # of Reported Claims 2009 $ 16,528 $ 17,061 $ 17,143 $ 16,785 $ 15,752 $ 15,711 $ 14,496 $ 118 624 2010 14,388 13,935 14,076 14,066 15,611 14,376 16,245 13 746 2011 15,310 17,971 19,213 8,817 6,872 12,622 10,704 3 666 2012 6,810 11,433 12,665 13,302 16,970 17,886 21,691 2 1,107 2013 10,250 4,232 14,469 15,546 16,575 15,529 0 1,181 2014 20,607 24,419 23,663 21,438 25,411 6,564 1,775 2015 28,132 30,322 35,144 40,182 5,923 2,483 2016 36,103 34,074 35,873 15,285 3,212 2017 47,610 45,128 32,642 3,642 2018 66,823 55,207 2,031 Total $ 292,082 Int'l Professional Liability Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance amounts in thousands For the Years Ended December 31, AY 2012 2013 2014 2015 2016 2017 2018 2009 $ 8,879 $ 10,804 $ 12,857 $ 13,842 $ 14,136 $ 14,674 $ 14,842 2010 5,861 7,256 10,556 12,688 13,412 13,419 13,566 2011 1,211 2,020 2,965 4,038 4,613 16,367 16,430 2012 2,123 3,207 4,251 5,533 7,423 6,818 7,675 2013 726 2,263 3,042 9,349 13,676 14,334 2014 1,373 2,464 5,158 8,799 20,192 2015 3,417 5,864 17,242 21,128 2016 2,051 6,857 10,931 2017 1,992 5,881 2018 4,768 Total $ 129,747 Net reserves < 2009 265 Total Net reserves $ 162,600 Int'l Professional Liability Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 7 8 9 10 Int'l Professional Liability 5.8 % 9.4 % 16.8 % 21.5 % 27.1 % 2.3 % 39.4 % 0.9 % 2.3 % 1.2 % GlobalRe Loss and ALAE, Net of Reinsurance amounts in thousands except # of reported claims For the Years Ended December 31, As of December 31, 2018 AY 2012 2013 2014 2015 2016 2017 2018 Total IBNR # of Reported Claims 2009 $ 11,158 $ 11,290 $ 11,171 $ 10,426 $ 10,466 $ 10,307 $ 10,610 $ 338 201 2010 13,036 12,997 14,012 11,796 12,476 13,012 13,073 21 202 2011 53,778 76,261 76,054 73,528 72,782 73,428 73,474 (586 ) 740 2012 107,134 99,019 92,584 88,203 114,856 119,565 118,477 (1,218 ) 1,395 2013 114,785 118,688 102,514 105,049 102,323 101,705 (561 ) 1,271 2014 119,351 141,968 121,591 118,131 114,981 860 1,172 2015 101,626 91,526 94,187 93,693 5,777 1,033 2016 88,401 90,567 97,921 5,781 1,022 2017 129,001 153,017 19,356 1,018 2018 128,284 83,977 435 Total $ 905,235 GlobalRe Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance amounts in thousands For the Years Ended December 31, AY 2012 2013 2014 2015 2016 2017 2018 2009 $ 8,635 $ 8,865 $ 8,992 $ 9,939 $ 10,049 $ 10,049 $ 10,118 2010 9,927 10,263 10,439 11,058 11,105 11,170 11,203 2011 43,412 71,086 71,754 72,038 72,177 72,345 72,743 2012 37,709 77,147 83,287 84,668 111,816 117,631 118,006 2013 53,445 82,641 90,649 98,393 99,965 100,981 2014 66,271 119,195 105,574 108,693 111,712 2015 41,623 64,425 76,837 82,942 2016 36,312 66,141 84,245 2017 43,639 115,743 2018 25,017 Total $ 732,710 Net reserves < 2009 1,870 Total Net reserves $ 174,395 GlobalRe Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 7 8 9 10 GlobalRe 28.4 % 34.0 % 6.6 % 5.6 % 9.0 % 2.0 % 0.3 % 0.7 % 0.1 % 0.7 % The reconciliation of the net incurred and paid claims development tables to the Reserve for losses and LAE in the consolidated statement of financial position is as follows: Carried Reserves Reconciliation amounts in thousands As of December 31, 2018 Total Net Reserves Reinsurance Recoverables on Unpaid Claims Total Gross Reserves U.S. Marine $ 90,028 $ 88,783 $ 178,811 U.S. P&C 977,968 387,081 1,365,049 U.S. Professional Liability 128,321 54,052 182,373 Int'l Marine 214,455 68,117 282,572 Int'l P&C 87,368 106,879 194,247 Int'l Professional Liability 162,600 86,970 249,570 GlobalRe 174,395 12,751 187,146 Liabilities for Unpaid Claims and Claim Adjustment Expenses $ 1,835,135 $ 804,633 $ 2,639,768 Unallocated Claims Adjustment Expenses 72,099 ASCO Reserves 31,834 Other 272 Total Gross Liability for Unpaid Claims and Claim Adjustment Expense $ 2,743,973

Ceded Reinsurance

Ceded Reinsurance	12 Months Ended
	Dec. 31, 2018
Insurance [Abstract]
Ceded Reinsurance	NOTE 8. 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 of our Board of Directors, 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, 2018, and the reinsurers’ ratings from A.M. Best and S&P: Reinsurance Recoverables Unearned Paid/Unpaid Collateral amounts in thousands Premium Losses (1) Total Held A.M. Best S&P Everest Reinsurance Company $ 34,809 $ 106,334 $ 141,143 $ 1,547 A+ A+ Swiss Reinsurance America Corporation 13,514 64,457 77,971 4,223 A+ AA- National Indemnity Company 5,338 61,540 66,878 8,320 A++ AA+ Transatlantic Reinsurance Company 7,597 48,328 55,925 2,541 A+ A+ Munich Reinsurance America Inc. 10,932 41,369 52,301 6,054 A+ AA- Employers Mutual Casualty Company 16,491 34,445 50,936 18,120 A NR Aspen Insurance UK Ltd. 11,801 31,508 43,309 6,446 A A Allied World Reinsurance 7,303 30,439 37,742 1,757 A A- XL Reinsurance America Inc. 7,240 21,250 28,490 2,761 A+ AA- Ace Property & Casualty Insurance Company 1,591 24,148 25,739 63 A++ AA Top 10 Reinsurers $ 116,616 $ 463,818 $ 580,434 $ 51,832 Others 110,107 474,630 584,737 154,085 Total $ 226,723 $ 938,448 $ 1,165,171 $ 205,917 (1) - Net of reserve for uncollectible reinsurance of approximately $13.4 million. Our Company holds reserves for uncollectible reinsurance in the amounts of $13.4 million and $12.6 million as of December 31, 2018 and 2017, 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. The increase in our reserves for uncollectible reinsurance as compared to 2017 is driven primarily by one of our reinsurers having been placed in liquidation by the State of California. We continue to monitor the liquidation process and assess our potential exposure. Our Company holds collateral of $205.9 million, which consists of $145.0 million in ceded balances payable, $41.2 million in letters of credit and $19.7 million of funds held as 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 2018 2017 2016 Direct $ 1,613,825 $ 1,489,422 $ 1,403,865 Assumed 299,136 223,843 165,046 Ceded (441,876 ) (441,935 ) (382,687 ) Net Written Premiums $ 1,471,085 $ 1,271,330 $ 1,186,224 The following table summarizes the components of Net Earned Premium: Years Ended December 31, amounts in thousands 2018 2017 2016 Direct $ 1,553,852 $ 1,425,582 $ 1,330,265 Assumed 256,509 187,609 171,978 Ceded (447,138 ) (426,771 ) (401,898 ) Net Earned Premiums $ 1,363,223 $ 1,186,420 $ 1,100,345 The following table summarizes the components of Net Losses and LAE Incurred: Years Ended December 31, amounts in thousands 2018 2017 2016 Direct $ 1,002,358 $ 938,640 $ 795,414 Assumed 159,989 148,606 87,995 Ceded (268,568 ) (280,981 ) (217,961 ) Net Losses and LAE $ 893,779 $ 806,265 $ 665,448

Debt

Debt	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Debt	NOTE 9. DEBT Credit Facilities On November 4, 2016, NUAL entered into an Australian Dollar credit facility, which was subsequently amended on October 30, 2017, with Barclays Bank PLC. Letter of Credit commissions are payable under this facility at a rate of 1.55% per annum. 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 Funds at Lloyd’s. As of December 31, 2018, letters of credit with an aggregate face amount of 24.0 million Australian Dollars were outstanding under the credit facility, and our Company was in compliance with all covenants. On November 7, 2018, we entered into a credit facility agreement with ING Bank N.V., London Branch, individually and as Administrative Agent for a syndicate of lenders (the “Club Facility”), which is secured by all the common stock of NIC and requires us to maintain at least forty percent of the outstanding amounts under such facility as Funds at Lloyd’s. The Club Facility has two tranches with one tranche extending a $165.0 million commitment and the other tranche extending a £60.0 million commitment. In addition, in order to support the increased underwriting capacity of the Syndicate for the 2019 UWY, we amended the $25.0 million credit facility with ING Bank N.V., London Branch, dated November 20, 2015, on November 7, 2016 and again on January 23, 2019, to extend the term for an additional two years (the “Bilateral Facility”). Both of these facilities, as well as the November 4, 2016 facility, are used to fund underwriting obligations at Lloyd’s for the 2019 UWY, as well as open prior UWYs. The Bilateral 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 Club 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 then-current financial strength ratings issued by S&P and A.M. Best and the amount of our own collateral utilized to fund our participation in the Syndicate. If any letters of credit remain outstanding under these facilities after December 31, 2020, we would be required to post additional collateral to secure the remaining letters of credit. As of December 31, 2018, letters of credit with an aggregate face amount of $165.0 million and £60.0 million were outstanding under the Club Facility and we had an aggregate of $1.2 million of cash collateral posted. As of December 31, 2018 there were letters of credit with a face amount of $8.0 million outstanding under the Bilateral Facility. The Bilateral and Club Facilities contain 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 and our subsidiaries, the occurrence of certain material judgments, or a change in control of our Company. During the first quarter of 2018, the Company reclassified certain overseas deposits from Short-Term Investments to Other Invested Assets. Refer to Note 1 Organization & Summary of Significant Accounting Policies 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 due on October 15, 2023 and received net proceeds of $263.3 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, 2018 and 2017 was $0.9 million and $1.1 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, 2018, our Company was in compliance with all such covenants.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	NOTE 10. COMMITMENT AND CONTINGENCIES Rental Commitments Future minimum annual rental commitments as of December 31, 2018 under various non-cancellable operating leases for our office facilities, which expire at various dates through 2032, are as follows: Rental Commitments for Years Ended December 31, amounts in thousands 2019 $ 12,907 2020 12,470 2021 11,542 2022 10,354 2023 9,379 2024-2032 28,268 Total Minimum Operating Lease Payments $ 84,920 We are also liable for additional payments to the landlords for certain annual cost increases. Rent expense for the years ended December 31, 2018, 2017 and 2016 was $12.2 million, $13.2 million and $13.2 million, respectively. Legal Contingencies 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. Guarantees On February 16, 2017, our Company entered into a Guarantee, pursuant to which it guaranteed all of the liabilities and obligations of NIIC (the “Guarantee”), to facilitate the issuance of a financial strength rating to NIIC by A.M. Best. The Guarantee would remain effective until all of such liabilities and obligations are discharged, and in the event that our Company does not meet its obligations under the Guarantee, any person who is covered by an insurance policy, certificate of coverage or reinsurance contract issued by NIIC would be a third party beneficiary under the Guarantee. Our Company’s obligations under the Guarantee may be terminated by providing twelve months prior written notice to NIIC. However, the obligations of our Company under the Guarantee terminate immediately in the event that (i) the majority of the outstanding voting capital stock in NIIC is sold to any non-affiliated entity; (ii) A.M. Best confirms that NIIC would receive the same financial strength rating as NIC or NSIC, without the benefit of the Guarantee; or (iii) NIIC withdraws its request to be rated by A.M. Best, provided that NIIC has not been downgraded within the prior twelve months. State Loan and Grant Contingencies 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. As of December 31, 2018, our Company has received all of the award and earned a loan forgiveness credit of $7.0 million with the State. Our Company is recognizing the amount of loan and grants received over the period in which offsetting expenses are recognized. Our Company recognized $1.3 million, $1.3 million and $1.4 million for the years ended December 31, 2018, 2017 and 2016. As of December 31, 2018 and December 31, 2017, our Company had deferred revenue of $4.7 million and $4.4 million, respectively, which is included in other liabilities on the Consolidated Balance Sheets. Merger Agreement On August 22, 2018, our Company entered into a Merger Agreement with The Hartford. In accordance with the terms of the Merger Agreement, our Company would be obligated to pay The Hartford a $68.25 million termination fee if the Merger Agreement is terminated for certain reasons outlined in the Merger Agreement.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 11. 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 including 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 21% 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 21% 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. Our Company’s undistributed foreign earnings are intended to be permanently reinvested. As a result of the Tax Act’s one-time Transition Tax on the earnings of foreign subsidiaries, our Company determined the unrecognized deferred tax liability attributable to indefinitely reinvested earnings to be immaterial as of December 31, 2018. On December 22, 2017, the Tax Act was enacted into law and the new legislation contained several key tax provisions that affect us, including the Transition Tax on accumulated foreign earnings and a reduction of the corporate income tax rate to 21% effective January 1, 2018, among others. Due to the timing and significance of the Tax Act, in December 2017 the SEC staff issued SAB 118, Income Tax Accounting Implications of the Tax Act, which allowed us to record provisional amounts during a measurement period not to extend beyond one year of the enactment date. During the fourth quarter of 2017, we made a reasonable estimate of the Tax Act effects on our deferred tax balances and recognized provisional tax amounts of $2.6 million related to the Transition Tax. The final determination of the Transition Tax and the remeasurement of our net deferred tax assets was completed by the fourth quarter of 2018, in accordance with SAB 118. This resulted in a reduction of $1.3 million of Transition Tax, which was calculated and recognized in the third quarter of 2018 and confirmed under final review in the fourth quarter. Additionally, a tax benefit of $0.5 million related to the remeasurement of net deferred tax assets was recognized in the fourth quarter of 2018. The components of current and deferred income tax expense (benefit) are as follows: Years Ended December 31, amounts in thousands 2018 2017 2016 Current Income Tax Expense (Benefit): Federal and Foreign $ 27,768 $ 42,427 $ 39,900 State and Local 934 764 638 Subtotal $ 28,702 $ 43,191 $ 40,538 Deferred Income Tax Expense (Benefit): Federal and Foreign $ (14,366 ) $ (8,879 ) $ (5,755 ) State and local — — — Subtotal $ (14,366 ) $ (8,879 ) $ (5,755 ) Total Income Tax Expense (Benefit) $ 14,336 $ 34,312 $ 34,783 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 2018 2017 2016 Computed Expected Tax Expense $ 10,201 21.0 % $ 26,182 35.0 % $ 41,128 35.0 % Tax-Exempt Interest (3,356 ) (6.9 %) (5,394 ) (7.2 %) (4,559 ) (3.9 %) Dividends Received Deduction (2,041 ) (4.2 %) (4,689 ) (6.3 %) (3,812 ) (3.2 %) Proration of DRD and Tax-Exempt Interest 1,330 2.7 % 1,512 2.0 % 1,256 1.1 % State and Local Income Taxes, Net of Federal Income Tax Deduction 738 1.5 % 497 0.7 % 415 0.4 % Stock Compensation Fair Market Value (1,711 ) (3.5 %) (5,027 ) (6.7 %) N/A N/A Change in Valuation Allowance (774 ) (1.6 %) 1,182 1.6 % — — Deferred Tax Expense due to Tax Law Changes (506 ) (1.0 %) 17,107 22.9 % N/A N/A Transition Tax (1,314 ) (2.7 %) 2,587 3.5 % N/A N/A Uncertain Tax Position - FTC IRS Audit 7,029 14.5 % — — — — Non-Deductible Expenses 1,197 2.5 % 405 0.5 % 406 0.2 % Return to Provision 2,326 4.8 % (158 ) (0.2 %) 1 0.0 % Other 1,217 2.4 % 108 0.1 % (52 ) 0.0 % Actual Tax Expense and Rate $ 14,336 29.5 % $ 34,312 45.9 % $ 34,783 29.6 % N/A - Not applicable 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 2018 2017 Deferred Tax Assets: Loss Reserve Discount $ 26,468 $ 20,425 Unearned Premiums 29,500 24,352 Compensation Related 9,433 8,462 Lloyd's Year of Account Deferral 12,623 9,400 State and Local 3,551 616 Net Currency Translation Adjustments 299 2,084 Net Unrealized Losses on Securities 11,553 — Other 3,598 152 Total Gross Deferred Tax Assets $ 97,025 $ 65,491 Less: Valuation Allowance (4,367 ) (1,798 ) Total Deferred Tax Assets $ 92,658 $ 63,693 Deferred Tax Liabilities: Loss Reserve Discount - Transition Rule $ (7,570 ) $ (5,066 ) Net Unrealized Gains on Securities — (8,708 ) Deferred Acquisition Costs (25,109 ) (20,670 ) Claims Equalization Reserve (7,913 ) — Net Unrealized Foreign Exchange (3,769 ) (3,782 ) Intangibles (3,438 ) — Other (2,562 ) (3,196 ) Total Deferred Tax Liabilities $ (50,361 ) $ (41,422 ) Net Deferred Income Tax Asset $ 42,297 $ 22,271 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. As of December 31, 2018, management believes it is more likely than not that our Company will realize the benefits of its deferred tax assets, net of any valuation allowance. Our Company had state and local deferred tax assets of $3.6 million and $0.6 million as of December 31, 2018 and 2017, 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 also recorded a net valuation allowance decrease of $0.8 million related to our foreign operations, of which a decrease of $1.2 million relates to the U.K. Based upon a review of the Company’s anticipated future taxable income, and also including all other available evidence, both positive and negative, particularly around strategic shifts in business written, the Company’s management concluded that it is more likely than not that the U.K deferred tax asset will be realized. The Company is currently under examination by the IRS for tax years 2014, 2015, and 2016 with tax years prior to 2014 being closed. In addition, our Company is generally subject to state, local or foreign tax examinations by tax authorities for open tax years in the respective jurisdictions. In the U.K, the Company is no longer subject to income tax examinations for years prior to 2016. Unrecognized tax benefits are differences between tax positions taken in the tax returns and tax benefits or expenses recognized in the financial statements. In connection with the IRS audit, the Company conducted a comprehensive review of all foreign taxes supporting tax return positions, and has estimated $6.4 million of unrecognized tax benefits and $0.9 million of related interest ($0.6 million net of tax) and no penalties for the year ended December 31, 2018. December 31, amounts in thousands 2018 Balance at January 1, $ — Additions for Tax Positions of Prior Years 6,350 Reductions for Tax Positions of Prior Years — Additions for Tax Positions of Current Year — Reductions for Tax Positions of Current Year — Settlements with Tax Authorities — Lapse of Statute of Limitations — Balance at December 31, $ 6,350 Unrecognized Tax Benefits that, if Recognized, would Impact the Effective Rate $ 6,350 It is reasonable to expect the IRS audit to be concluded within the next twelve months, which may result in a change in unrecognized tax benefits. We do not expect future audit adjustments or changes in unrecognized tax benefits to have a significant impact on our financial statements. Our Company policy is to recognize interest and penalties related to unrecognized tax benefits as income tax expense. Gross interest was accrued and reported as follows: December 31, amounts in thousands 2018 Interest Recognized on the Consolidated Statements of Operations $ 860 Interest Included in Other Liabilities on the Consolidated Balance Sheets $ 860

Stockholders Equity

Stockholders Equity	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Stockholders' Equity	NOTE 12. STOCKHOLDERS’ EQUITY Our authorized share capital consists of 50 million common shares with a par value of $0.10 per share and 1 million preferred shares with a par value of $0.10 per share. Our Company has not issued any preferred shares as of December 31, 2018. 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 2018 2017 2016 Beginning Balance 29,507 29,124 28,862 Net Vested Stock Grants 230 343 220 Employee Stock Purchase Plan 45 40 42 Ending Balance 29,782 29,507 29,124 On December 6, 2016, our Board of Directors declared a two-for-one stock split of The Navigators Group, Inc. Common stock, to be effected in the form of a stock dividend. Stockholders of record at the close of business on December 30, 2016 received one additional share of Common stock for every share of Common stock held. All disclosures of shares and per share data have been retroactively adjusted to reflect the stock split for all periods presented. For the years ended December 31, 2018, 2017 and 2016, our Company paid total dividends of $0.28, $0.225 and $0.135 per share, respectively, to stockholders of record of our Company’s Common Stock. . The declaration and amount of any future dividend will be at the discretion of the Board of Directors, and will depend upon our Company’s financial condition, results of operations, business requirements, regulatory and legal constraints and any other factors the Board of Directors deems relevant. Refer to Note 18 Subsequent Events. 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, 2018, the maximum amount available for the payment of dividends by NIC without prior regulatory approval is $5.2 million. NIC paid a dividend to our Parent Company of $97.0 million and $19.0 million in 2018 and 2017, respectively. The statutory calculation for dividends without prior regulatory approval uses a rolling twelve-month basis and as of December 31, 2018 this calculation was temporarily impacted by the dividends used to acquire the NICE Group during the first half of 2018. This calculation also excludes consideration for the Company’s ability to request extraordinary dividends. 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 2018, NCUL posted all of the available undistributed profits on closed years of $235.8 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 Company in the form of a dividend. As of December 31, 2018, NCUL does not have the ability to pay dividends to the Parent Company. NIIC may pay dividends to our Parent Company out of its statutory profits subject to the restrictions imposed under UK Company law and European Insurance regulation (Solvency II). As of December 31, 2018, the maximum amount available for the payment of dividends by NIIC without prior regulatory approval is $20.3 million. In addition, NIIC must provide at least 14 days’ notice to the Prudential Regulatory Authority prior to agreeing to make any material dividend payment to any of its affiliated entities that are domiciled outside of the European Economic Area. ASCO may only pay a dividend if at the end of its last fiscal year the total amount of its assets, as reduced by its provisions and debts, are in excess of certain minimum capital thresholds calculated under Belgian law. As of December 31, 2018, ASCO may not declare a dividend. In accordance with the Merger Agreement, the Company’s quarterly cash dividend payments are not to exceed $0.07 per share. The amount and nature of net assets that are restricted from payment of dividends as of December 31, 2018 and 2017 are presented in the following table: As of December 31, amounts in thousands 2018 2017 Restricted Net Assets: NIC and NSIC: Fixed Maturities at Fair Value (Amortized Cost: 2018, $9,890; 2017, $9,856) $ 10,441 $ 10,655 Cash (1) 6,074 3,118 Total NIC and NSIC (2) $ 16,515 $ 13,773 NHUK: Fixed Maturities at Fair Value (Amortized Cost: 2018, $481,501; 2017, $472,701) $ 474,128 $ 471,831 Other Invested Assets (1) 46,528 28,767 Cash (1) 60,233 53,111 Total NHUK (3) $ 580,889 $ 553,709 All other Entities: Cash $ 13 $ — Total All other Entities $ 13 $ — Total Restricted Net Assets $ 597,417 $ 567,482 (1) - Cash and overseas deposits that were misclassified within Short-Term Investments prior to 2018 were reclassified, representing an immaterial correction. Refer to Note 1 Organization & Summary of Significant Accounting Policies (2) - 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, 2018 and 2017, as presented in the table above, is held in various collateral accounts to support underwriting activities. (3) - The restricted net assets for NHUK consists of fixed maturities and cash held in trust for the benefit of syndicate policyholders and other invested assets 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, 2018
Earnings Per Share [Abstract]
Earnings Per Share	NOTE 13. EARNINGS PER SHARE The following is a reconciliation of the basic and diluted EPS computations for the years ended December 31, 2018, 2017 and 2016: Years Ended December 31, amounts in thousands, except per share amounts 2018 2017 2016 Net Income $ 34,239 $ 40,494 $ 82,726 Basic Weighted Average Shares 29,720 29,441 29,074 Effect of Common Stock Equivalents: Assumed Vesting of Stock 473 630 958 Diluted Weighted Average Shares 30,193 30,071 30,032 Net Income per Common Share: Basic $ 1.15 $ 1.38 $ 2.85 Diluted $ 1.13 $ 1.35 $ 2.75

Statutory Financial Information

Statutory Financial Information	12 Months Ended
	Dec. 31, 2018
Text Block [Abstract]
Statutory Financial Information	NOTE 14. 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 2018 2017 2016 NIC & NSIC: Statutory Net Income $ 75.0 $ 79.3 $ 84.2 Statutory Capital and Surplus $ 1,005.4 $ 1,056.6 $ 1,027.3 The Syndicate: Syndicate's Net Income $ 6.8 $ (23.4 ) $ 46.3 Syndicate's Capital and Surplus $ 165.3 $ 168.7 $ 180.7 NIIC: Statutory Net Income $ (14.7 ) $ (8.4 ) $ 0.4 Statutory Capital and Surplus $ 43.3 $ 62.9 $ 70.7 As of December 31, 2018, 2017, and 2016, 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. 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. United States 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 Unrealized gains/losses on Equities Recognized in Surplus Recognized in Income Deferred tax assets Certain temporary differences are not recognized All temporary differences recognized Receivables over 90 days outstanding and other intangible assets Not recognized Generally recognized (subject to valuation allowances) Provision for Reinsurance Recorded through a charge to surplus Recorded through income when deemed uncollectible Unearned premiums and loss reserves Net of ceded amounts Gross of ceded amounts United Kingdom 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 on Fixed Maturities 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. NIIC is subject to oversight and regulation by the PRA and the FCA. The following table represents some of the significant differences between U.K. GAAP and U.S. GAAP as they relate to our NIIC operations: Differences U.K. GAAP U.S. GAAP Unrealized gains/losses on Fixed Maturities Recognized in income Recognized in AOCI Foreign exchange gains/losses on translation Recognized in income Recognized in AOCI Europe During the second quarter of 2018, our Company acquired ASCO, an insurance subsidiary subject to the oversight and regulation of the National Bank of Belgium (the “NBB”). Canal Re, a wholly owned subsidiary of ASCO, is subject to the oversight and regulation of the Commissariat Aux Assurances (the “CAA”). ASCO and Canal Re are subject to statutory capital requirements as determined by the NBB and the CAA. Additionally for Solvency II, ASCO and Canal Re are required to maintain the minimum capital requirement. As of December 31, 2018, ASCO and Canal Re individually exceed the minimum required statutory capital and surplus requirements.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	NOTE 15. STOCK-BASED COMPENSATION In May 2005 our shareholders approved the 2005 Stock Incentive Plan authorizing the issuance in aggregate of 1,000,000 incentive stock options, non-incentive stock options, restricted shares and stock appreciation rights for our common stock. In April 2009, the stockholders approved an amendment to the 2005 Stock Incentive Plan increasing the available number of awards from 1,000,000 to 1,500,000. In April 2013, the stockholders further amended and restated the 2005 Stock Incentive Plan increasing the available number of awards from 1,500,000 to 2,000,000 in the Second Amended and Restated 2005 Stock Incentive Plan. The stock split that occurred on January 20, 2017 doubled the number of awards from 2,000,000 to 4,000,000. As of December 31, 2018, 3,192,376 of such awards were issued leaving 807,624 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. Non-performance based grants generally vest equally over a three or four year period. Our Company’s performance based share grants generally consist of three types of awards. The performance units issued in 2018, 2017 and 2016 will cliff vest on the third anniversary of the date of the grant in an amount as determined by 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. During 2018, 2017 and 2016, the total compensation cost for share-based payment arrangements recognized in the income statement was $6.8 million, $13.8 million and $17.6 million, and the recorded tax benefits related to share-based awards were $1.4 million, $2.9 million and $6.2 million, respectively. As of December 31, 2018 and 2017, the total unrecognized compensation expense related to nonvested stock awards was $11.8 million and $18.0 million, respectively, which is expected to be recognized as expense over weighted average periods of 1.8 years and 1.9 years, respectively. The aggregate fair value of all unvested restricted stock units as of December 31, 2018 and 2017 was $44.6 million and $49.9 million, respectively. Restricted Stock Units The activity related to our Company’s restricted stock unit awards was as follows: Year Ended December 31, 2018 Number of Awards Weighted Average Grant Date Fair Value (1) Nonvested at the beginning of the year 159,539 $ 41.60 Granted 24,593 50.01 Vested (2) (90,543 ) 36.66 Forfeited (7,000 ) 38.00 Nonvested at the end of the year 86,589 $ 49.45 ( 1) Fair value is based on the closing price of our common shares on the NASDAQ on the grant date. (2) This amount represents the gross number of shares vested before any share forfeiture to pay required tax withholdings. For the year ended December 31, 2018 share awards of 34,430 were withheld for tax payments at a weighted average vest date fair value of $58.44. During 2018, 2017 and 2016, we granted 24,593, 35,297 and 84,000 restricted stock units, respectively, with weighted average grant-date fair values per share of $50.01, $56.05 and $44.52, respectively. During 2018, 2017 and 2016, the total fair value of restricted stock units vested was $5.3 million, $3.3 million and $2.5 million, respectively. Performance-based Equity Awards The activity related to our Company’s performance-based equity awards was as follows: Year Ended December 31, 2018 Number of Awards Weighted Average Grant Date Fair Value (1) Nonvested at the beginning of the year 966,361 $ 43.39 Granted 247,554 54.15 Performance Adjustment (59,833 ) 37.25 Vested (2) (274,299 ) 37.25 Forfeited (34,250 ) 46.00 Nonvested at the end of the year 845,533 $ 48.86 ( 1) Fair value is based on the closing price of our common shares on the NASDAQ on the grant date. (2) This amount represents the gross number of shares vested before any share forfeiture to pay required tax withholdings. For the year ended December 31, 2018 share awards of 117,005 were withheld for tax payments at a weighted average vest date fair value of $55.65. During 2018, 2017 and 2016, we granted 247,554, 253,333 and 404,946 performance-based equity awards, respectively, with weighted average grant-date fair values per share of $54.15, $55.70 and $40.77, respectively. During 2018, 2017 and 2016, the total fair value of performance-based equity awards vested was $15.3 million, $29.0 million and $11.5 million, respectively. Awards that remain outstanding at the time of the Merger will be treated as follows in accordance with the Merger Agreement: Each performance unit award granted prior to January 1, 2017, and each tranche of a restricted stock unit award that vests prior to January 1, 2020, that was granted prior to January 1, 2019, and that is payable in shares (together, the “2019 Vesting Company Awards”) will be converted into the right to receive an amount in cash equal to the product of (x) the Merger Consideration multiplied by (y) the number of restricted stock units in the applicable tranche or, in the case of performance unit awards, the target number of shares, in each case subject to the 2019 Vesting Company Award immediately prior to the Merger. Each performance unit award granted on or after January 1, 2017 and prior to January 1, 2019, and each tranche of a restricted stock unit award that vests on or after January 1, 2020, that was granted prior to January 1, 2019, and that is payable in shares (together, the “2020 Vesting Company Awards”) will be canceled and converted into the right to receive a cash payment equal to the product of (x) the Merger Consideration multiplied by (y) the number of restricted stock units in the applicable tranche or, in the case of performance units, the target number of shares, in each case subject to the 2020 Vesting Company Award immediately prior to the Merger; provided that the right to a cash payment with respect to a 2020 Vesting Company Award shall be subject to the same vesting and payment schedules as the 2020 Vesting Company Award it replaces (other than performance-based vesting conditions). Employee Stock Purchase Plan 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 45,008 shares purchased in 2018 from funds withheld during the July 1, 2017 to December 31, 2017 and January 1, 2018 to June 30, 2018 offering periods. There were 40,488 shares purchased in 2017 in the aggregate from funds withheld during the offering periods of July 1, 2016 to December 31, 2016 and January 1, 2017 to June 30, 2017. 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. In accordance with the Merger Agreement, the Company’s ESPP will be terminated at the time of the Merger. There will be no more offering periods under the Company’s ESPP after December 31, 2018.

Retirement Plans

Retirement Plans	12 Months Ended
	Dec. 31, 2018
Compensation And Retirement Disclosure [Abstract]
Retirement Plans	NOTE 16. 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, 2018 was $8.3 million, consisting of $5.1 million for the retirement savings contributions and $3.2 million for the non-discretionary matching contributions. The expense recorded for all contributions to the 401(k) Plan for the year ended December 31, 2017 was $7.5 million, consisting of $4.9 million for the retirement savings contributions and $2.6 million for the non-discretionary matching contributions. The expense recorded for all contributions to the 401(k) Plan for the year ended December 31, 2016 was $7.4 million, consisting of $4.2 million for the retirement savings contributions and $3.2 million for the non-discretionary matching contributions. 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 $2.5 million, $2.6 million and $2.9 million for the years ended December 31, 2018, 2017 and 2016, 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% and 26.0% of each eligible employee’s gross base salary. The expense recorded for the other European offices defined contribution plans was $0.5 million, $0.3 million and $0.5 million for the years ended December 31, 2018, 2017 and 2016, respectively. Such expenses are included in Other operating expenses. BDM and ASCO maintain defined benefit pension plans that provide retirement capital and death coverage in service for employees. These plans are closed to new employees. The funded status of the plans for the year ended December 31, 2018, was $(0.7) million, which consists of a benefit obligation of $2.1 million and the fair value of the pension plan assets of $1.4 million.

Condensed Quarterly Financial D

Condensed Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Condensed Quarterly Financial Data (Unaudited)	NOTE 17. CONDENSED 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 2018 2018 2018 2018 Gross Written Premiums $ 495,224 $ 497,236 $ 455,943 $ 464,558 Revenues: Net Written Premiums $ 393,262 $ 379,292 $ 352,412 $ 346,119 Change in Unearned Premiums (70,635 ) (48,277 ) (5,374 ) 16,424 Net Earned Premiums $ 322,627 $ 331,015 $ 347,038 $ 362,543 Net Investment Income 23,702 24,601 25,651 29,159 Net Realized and Unrealized Gains (Losses): Total Other-Than-Temporary Impairment Losses (37 ) (18 ) (15 ) (48 ) Portion of Loss Recognized in Other Comprehensive Income 37 18 15 48 Net Other-Than-Temporary Impairment Losses Recognized in Earnings — — — — Net Realized Gains (Losses) on Investments Sold 1,169 1,787 253 (220 ) Net Unrealized Gains (Losses) on Equity Securities (3,181 ) 1,329 2,310 (33,795 ) Total Net Realized and Unrealized Gains (Losses) (2,012 ) 3,116 2,563 (34,015 ) Other Income (Loss) (117 ) 2,628 1,724 2,934 Total Revenues $ 344,200 $ 361,360 $ 376,976 $ 360,621 Expenses: Net Losses and LAE $ 186,145 $ 196,333 $ 240,900 $ 270,401 Commission Expenses 54,152 53,193 57,999 54,800 Other Operating Expenses 62,926 68,182 67,584 62,532 Merger Transaction Costs — — 2,439 1,511 Interest Expense 3,864 3,864 3,891 3,866 Total Expenses $ 307,087 $ 321,572 $ 372,813 $ 393,110 Income (Loss) Before Income Taxes 37,113 39,788 4,163 (32,489 ) Income Tax Expense (Benefit) $ 6,235 $ 7,684 $ (462 ) $ 879 Net Income (Loss) $ 30,878 $ 32,104 $ 4,625 $ (33,368 ) Comprehensive Income (Loss) $ (2,962 ) $ 15,373 $ (2,681 ) $ (41,960 ) Combined Ratio 94.0 % 96.0 % 105.3 % 106.6 % Net Income (Loss) per Share: Basic $ 1.04 $ 1.08 $ 0.16 $ (1.12 ) Diluted $ 1.02 $ 1.07 $ 0.15 $ (1.12 ) March 31, June 30, September 30, December 31, amounts in thousands, except per share amounts 2017 2017 2017 2017 Gross Written Premiums $ 450,305 $ 452,179 $ 402,038 $ 408,743 Revenues: Net Written Premiums $ 337,163 $ 333,282 $ 296,016 $ 304,869 Change in Unearned Premiums (51,032 ) (39,447 ) 5,339 230 Net Earned Premiums $ 286,131 $ 293,835 $ 301,355 $ 305,099 Net Investment Income 21,448 22,265 22,598 22,982 Total Other-Than-Temporary Impairment Losses (1,077 ) 29 (957 ) 3 Portion of Loss Recognized in Other Comprehensive Income (16 ) (29 ) (15 ) (3 ) Net Other-Than-Temporary Impairment Losses Recognized in Earnings (1,093 ) — (972 ) — Net Realized Gains 1,049 1,694 5,190 37,141 Other Income (Loss) 1,068 (411 ) (1,699 ) (3,201 ) Total Revenues $ 308,603 $ 317,383 $ 326,472 $ 362,021 Expenses: Net Losses and LAE $ 169,600 $ 177,110 $ 276,171 $ 183,384 Commission Expenses 47,844 48,173 45,509 43,205 Other Operating Expenses 58,538 60,766 45,773 68,153 Interest Expense 3,861 3,861 3,862 3,863 Total Expenses $ 279,843 $ 289,910 $ 371,315 $ 298,605 Income (Loss) Before Income Taxes 28,760 27,473 (44,843 ) 63,416 Income Tax Expense (Benefit) $ 7,650 $ 6,971 $ (16,864 ) $ 36,555 Net Income (Loss) $ 21,110 $ 20,502 $ (27,979 ) $ 26,861 Comprehensive Income (Loss) $ 35,911 $ 35,699 $ (18,311 ) $ (1,812 ) Combined Ratio 96.4 % 97.3 % 121.9 % 96.6 % Net Income (Loss) per Share: Basic $ 0.72 $ 0.70 $ (0.95 ) $ 0.91 Diluted $ 0.70 $ 0.69 $ (0.95 ) $ 0.89

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	NOTE 18. SUBSEQUENT EVENTS On February 14, 2019, our Board of Directors declared a cash dividend on our Company’s Common Stock of $0.07 per share, payable on March 11, 2019 to stockholders of record on February 25, 2019.

Summary of Consolidated Investm

Summary of Consolidated Investments-Other Than Investments in Related Parties	12 Months Ended
	Dec. 31, 2018
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 Other than Investments in Related Parties December 31, 2018 Amount At Amortized Which Shown amounts in thousands Fair Value (1) Cost / Cost on Balance Sheet Fixed Maturities: U.S. Treasury Bonds, Agency Bonds and Foreign Government Bonds $ 239,776 $ 242,832 $ 239,776 States, Municipalities and Political Subdivisions 646,551 639,265 646,551 Mortgage-Backed and Asset-Backed Securities: Agency Mortgage-Backed Securities 335,542 347,817 335,542 Residential Mortgage Obligations 138,373 138,299 138,373 Asset-Backed Securities 531,991 539,013 531,991 Commercial Mortgage-Backed Securities 188,201 190,159 188,201 Subtotal $ 1,194,107 $ 1,215,288 $ 1,194,107 Corporate Exposures (2) 1,002,489 1,028,028 1,002,489 Total Fixed Maturities $ 3,082,923 $ 3,125,413 $ 3,082,923 Other Invested Assets 48,406 48,549 48,406 Equity Securities: Common Stocks 166,353 177,599 166,353 Preferred Stocks 173,539 183,819 173,539 Total Equity Securities $ 339,892 $ 361,418 $ 339,892 Short-Term Investments 10,233 10,234 10,233 Total Investments $ 3,481,454 $ 3,545,614 $ 3,481,454 (1) Other invested assets are accounted for using the equity method of accounting. All other investments are shown at fair value. (2) Corporate Exposures consist of investments in corporate bonds, hybrid bonds and redeemable preferred stocks.

Condensed Financial Information

Condensed Financial Information of Registrant	12 Months Ended
	Dec. 31, 2018
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]
Condensed Financial Information of Registrant	THE NAVIGATORS GROUP, INC. AND SUBSIDIARIES The Navigators Group, Inc. Balance Sheets (Parent Company) December 31, amounts in thousands, except per share amounts 2018 2017 ASSETS Cash $ 6,414 $ 9,235 Investments in Subsidiaries 1,391,620 1,423,843 Goodwill and Other Intangible Assets 2,534 2,534 Current Income Tax Receivable, Net 35,553 30,573 Other Assets 19,686 28,063 Total Assets $ 1,455,807 $ 1,494,248 LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities: Senior Notes $ 264,052 $ 263,885 Accounts Payable and Other Liabilities 1,731 1,224 Accrued Interest Payable 3,174 3,174 Total Liabilities $ 268,957 $ 268,283 Stockholders' Equity: Preferred Stock, ($.10 par value, authorized 1,000 shares, none issued) $ — $ — Common Stock, ($.10 par value, authorized 50,000 shares, issued 36,805 shares for 2018 and 36,530 shares for 2017) 3,678 3,650 Additional Paid-In Capital 378,274 376,868 Treasury Stock, at cost (7,023 shares for 2018 and 2017) (155,801 ) (155,801 ) Retained Earnings 1,012,220 981,380 Accumulated Other Comprehensive Income: Net Unrealized Gains (Losses) on Securities Available-for-Sale, Net of Tax (51,513 ) 19,874 Foreign Currency Translation Adjustment, Net of Tax (8 ) (6 ) Total Stockholders' Equity $ 1,186,850 $ 1,225,965 Total Liabilities and Stockholders' Equity $ 1,455,807 $ 1,494,248 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 2018 2017 2016 Revenues: Net Investment Income $ 18 $ 7 $ 53 Total Revenues $ 18 $ 7 $ 53 Expenses: Interest Expense 15,460 15,447 15,435 Other (Income) Expense 2,563 (28 ) 22 Total Expenses $ 18,023 $ 15,419 $ 15,457 Loss Before Income Tax Benefit $ (18,005 ) $ (15,412 ) $ (15,404 ) Income Tax Expense (Benefit) 2,919 (5,709 ) (8,009 ) Loss Before Equity in Undistributed Net Income of Wholly Owned Subsidiaries $ (20,924 ) $ (9,703 ) $ (7,395 ) Equity in Undistributed Net Income of Wholly-Owned Subsidiaries 55,163 50,197 90,121 Net Income $ 34,239 $ 40,494 $ 82,726 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 2018 2017 2016 Operating Activities: Net Income $ 34,239 $ 40,494 $ 82,726 Adjustments to Reconcile Net Income to Net Cash Provided By (Used in) Operations: Equity in Undistributed Net Income of Wholly-Owned Subsidiaries (55,163 ) (50,197 ) (90,121 ) Dividends Received from Subsidiaries 97,000 19,000 5,000 Other 9,757 5,841 5,737 Net Cash Provided By (Used in) Operating Activities $ 85,833 $ 15,138 $ 3,342 Investing Activities: Net (Increase) Decrease in Short-Term Investments — — 89,576 Net Cash Provided By (Used in) Investing Activities $ — $ — $ 89,576 Financing Activities: Capital Contribution to Subsidiary $ (76,083 ) $ (1 ) $ (79,250 ) Proceeds of Stock Issued from Employee Stock Purchase Plan 2,036 1,846 1,840 Dividends Paid (8,319 ) (6,633 ) (3,930 ) Payment of Employee Tax Withholding on Stock Compensation (6,288 ) (13,778 ) (5,358 ) Net cash Provided By (Used in) Financing Activities $ (88,654 ) $ (18,566 ) $ (86,698 ) Increase (Decrease) in Cash $ (2,821 ) $ (3,428 ) $ 6,220 Cash at Beginning of Year 9,235 12,663 6,443 Cash at End of Year $ 6,414 $ 9,235 $ 12,663

Supplementary Insurance Informa

Supplementary Insurance Information	12 Months Ended
	Dec. 31, 2018
Supplementary Insurance Information [Abstract]
Supplementary Insurance Information	SCHEDULE III THE NAVIGATORS GROUP, INC. AND SUBSIDIARIES 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 Expenses Premiums Year ended December 31, 2018 U.S. Insurance $ 63,903 $ 1,784,339 $ 642,725 $ — $ 737,646 $ — $ 485,960 $ 85,127 $ 142,333 $ 800,091 Int'l Insurance 39,472 768,301 265,753 — 380,503 — 252,268 80,526 93,882 383,308 GlobalRe 54,705 191,333 194,257 — 245,074 — 155,551 55,056 25,009 287,686 Corporate — — — — — 103,113 — (565 ) — — $ 158,080 $ 2,743,973 $ 1,102,735 $ — $ 1,363,223 $ 103,113 $ 893,779 $ 220,144 $ 261,224 $ 1,471,085 Year ended December 31, 2017 U.S. Insurance $ 54,674 $ 1,629,015 $ 575,068 $ — $ 674,665 $ — $ 443,353 $ 77,729 $ 128,905 $ 721,300 Int'l Insurance 38,988 716,352 260,982 — 333,792 — 229,601 68,824 83,464 335,852 GlobalRe 41,587 169,778 151,631 — 177,963 — 133,311 39,136 20,861 214,178 Corporate — — — — — 89,293 — (958 ) — — $ 135,249 $ 2,515,145 $ 987,681 $ — $ 1,186,420 $ 89,293 $ 806,265 $ 184,731 $ 233,230 $ 1,271,330 Year ended December 31, 2016 U.S. Insurance $ 50,028 $ 1,564,524 $ 519,505 $ — $ 629,308 $ — $ 397,860 $ 70,812 $ 128,108 $ 683,568 Int'l Insurance 37,385 605,105 252,442 — 307,416 — 178,284 61,703 86,395 345,967 GlobalRe 32,247 120,098 115,397 — 163,621 — 89,304 34,008 19,593 156,689 Corporate — — — — — 79,451 — (1,478 ) — — $ 119,660 $ 2,289,727 $ 887,344 $ — $ 1,100,345 $ 79,451 $ 665,448 $ 165,045 $ 234,096 $ 1,186,224 (1) As we evaluate the underwriting results of each of our reportable segments separately from the results of our investment portfolio, we do not allocate net investment income to our reportable segments.

Reinsurance - Written Premium

Reinsurance - Written Premium	12 Months Ended
	Dec. 31, 2018
Supplemental Schedule Of Reinsurance Premiums For Insurance Companies [Abstract]
Reinsurance - Written Premium	SCHEDULE IV THE NAVIGATORS GROUP, INC. AND SUBSIDIARIES Ceded to Assumed Percentage Direct Other from Other Net of Amount amounts in thousands Amount Companies Companies Amount Assumed Year ended December 31, 2018 Accident & Health $ — $ — $ 139,692 $ 139,692 100.0 % Property & Liability 1,613,825 441,876 159,444 1,331,393 12.0 % Total $ 1,613,825 $ 441,876 $ 299,136 $ 1,471,085 20.3 % Year ended December 31, 2017 Accident & Health $ — $ — $ 80,605 $ 80,605 100.0 % Property & Liability 1,489,422 441,935 143,238 1,190,725 12.0 % Total $ 1,489,422 $ 441,935 $ 223,843 $ 1,271,330 17.6 % Year ended December 31, 2016 Accident & Health $ — $ — $ 53,814 $ 53,814 100.0 % Property & Liability 1,403,865 382,687 111,232 1,132,410 9.8 % Total $ 1,403,865 $ 382,687 $ 165,046 $ 1,186,224 13.9 %

Valuation and Qualifying Accoun

Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2018
Valuation And Qualifying Accounts [Abstract]
Valuation and Qualifying Accounts	SCHEDULE V THE NAVIGATORS GROUP, INC. AND SUBSIDIARIES Balance at Charged (Credited) to Charged to Balance at amounts in thousands January 1 Costs and Expenses Other Accounts Deductions (1) December 31 Year ended December 31, 2018 Allowance for Uncollectable Reinsurance $ 12,597 $ 770 $ — $ — $ 13,367 Valuation Allowance in Deferred Taxes $ 1,798 $ 3,897 $ — $ (1,328 ) $ 4,367 Year ended December 31, 2017 Allowance for Uncollectable Reinsurance $ 12,078 $ 519 $ — $ — $ 12,597 Valuation Allowance in Deferred Taxes $ 699 $ 1,099 $ — $ — $ 1,798 Year ended December 31, 2016 Allowance for Uncollectable Reinsurance $ 6,921 $ 5,157 $ — $ — $ 12,078 Valuation Allowance in Deferred Taxes $ 721 $ (22 ) $ — $ — $ 699 (1) Management has concluded that it is more likely than not that the deferred tax assets related to the U.K. net operating loss will be realized.

Supplementary Information Conce

Supplementary Information Concerning Property-Casualty Insurance Operations	12 Months Ended
	Dec. 31, 2018
Supplemental Information For Property Casualty Insurance Underwriters [Abstract]
Supplementary Information Concerning Property-Casualty Insurance Operations	SCHEDULE VI THE NAVIGATORS GROUP, INC. AND SUBSIDIARIES 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 Year Years Costs Expenses Premiums Consolidated Subsidiaries: Year ended December 31, $ 158,080 $ 2,743,973 $ 1,102,735 $ 1,363,223 $ 103,113 $ 817,537 $ 76,242 $ 220,144 $ 261,224 $ 1,471,085 Year ended December 31, 2017 $ 135,249 $ 2,515,145 $ 987,681 $ 1,186,420 $ 89,293 $ 771,955 $ 34,310 $ 184,731 $ 233,230 $ 1,271,330 Year ended December 31, 2016 $ 119,660 $ 2,289,727 $ 887,344 $ 1,100,345 $ 79,451 $ 693,976 $ (28,528 ) $ 165,045 $ 234,096 $ 1,186,224

Organization and Summary of S_2

Organization and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of 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 term “Parent Company” is used to mean The Navigators Group, Inc. without its subsidiaries. The accompanying consolidated financial statements of our Company have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP” or “U.S. GAAP”) and the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”). 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.
Organization	Organization We are an international insurance company with a long-standing area of specialization in Marine insurance. We also offer Property and Casualty (“P&C”) insurance, primarily 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, as well as assumed reinsurance products. We operate through various wholly-owned insurance and service companies. Our subsidiaries domiciled in the United States (“U.S.”) include two insurance companies, Navigators Insurance Company (“NIC”) and Navigators Specialty Insurance Company (“NSIC”), as well as our U.S. underwriting agency, Navigators Management Company, Inc. (“NMC”). NIC includes a branch in the United Kingdom (“U.K.”). We also have operations domiciled in the U.K., Hong Kong and Europe. Navigators International Insurance Company Ltd. (“NIIC”), Navigators Management (U.K.) Ltd. (“NMUK”) and Navigators Underwriting Ltd. (“NUL”) are domiciled in the U.K. and NUL includes European branches. Navigators Underwriting Agency Ltd. (“NUAL”), a Lloyd’s of London (“Lloyd’s”) underwriting agency, manages and provides the capital, through Navigators Corporate Underwriters Ltd. (“NCUL”), for our Lloyd’s Syndicate 1221 (the “Syndicate”), and is also domiciled in the U.K. We control 100% of the Syndicate’s stamp capacity. On June 7, 2018, we acquired 100% ownership interest in Bracht, Deckers & Mackelbert NV, an insurance underwriting agency organized under the laws of Belgium (“BDM”) and Assurances Continentales – Continentale Verzekeringen NV, an insurance company licensed under the laws of Belgium (“ASCO”). The acquisition was accounted for in accordance with Accounting Standards Codification (“ASC”) 805, “Business Combinations.” Refer to Note 2 Merger and Business Combinations Goodwill and Intangible Assets On August 22, 2018, our Company entered into an Agreement and Plan of Merger (the “Merger Agreement”) with The Hartford Financial Services Group, Inc. (“The Hartford”). The Merger Agreement provides that, subject to the terms and conditions set forth therein, our Company will merge with an existing subsidiary of The Hartford, with our Company surviving as a wholly owned subsidiary of The Hartford (the “Merger”). Refer to Note 2 Merger and Business Combinations
Immaterial Error Corrections	Immaterial Error Corrections Cash and overseas deposits that were misclassified within Short-Term Investments were reclassified representing an immaterial correction. Cash of $20.5 million as of December 31, 2017 was reclassified from Short-Term Investments to Cash and Cash Equivalents. Overseas deposits of $28.8 million as of December 31, 2017 were reclassified from Short-Term Investments to Other Invested Assets. The reclassification of cash within Short-Term Investments to Cash and Cash Equivalents impacted the Statement of Cash Flows for the years ended December 31, 2017 and 2016 by increasing Net Cash Used in Investing Activities by $1.9 million and decreasing Net Cash Used in Investing Activities by $6.0 million, respectively. During the year ended December 31, 2018, a full review of foreign taxes paid and refunds received was performed resulting in an increase in our Income Tax Expense of $7.0 million, inclusive of interest. Refer to Note 11 Income Taxes Additionally, during the year ended December 31, 2018, various adjustments increasing Net Income by $5.1 million were recorded relating to items dating back as far as 2005. These various adjustments were identified as part of a finance transformation initiative and were not material, individually or in the aggregate in the current year or any prior year. In total all adjustments resulted in a combined impact to Net Income for the year ended December 31, 2018 of $0.3 million. The controls related to the adjustments were also evaluated and none were deemed to represent a material weakness in our internal control over financial reporting.
Cash and Cash Equivalents and Restricted Cash and Cash Equivalents	Cash Cash includes cash on hand and demand deposits with banks. Cash Equivalents include highly liquid investments with original maturities of three months or less including money-market funds. Restricted Cash and Cash Equivalents primarily relates to funds that are held to support regulatory and contractual obligations.
Investments	Investments Fixed Maturities held by our Company were carried at fair value and classified as available-for-sale. Available-for-sale securities are debt 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 Maturities include bonds, mortgage-backed and asset-backed securities, and redeemable preferred stocks. Upon adoption of ASU 2016-01 on January 1, 2018, Equity Securities held by our Company were carried at fair value with any changes in fair value recognized in Net Income through the Net Unrealized Gains (Losses) on Equity Securities account. Prior to the adoption of ASU 2016-01, Equity Securities were carried at fair value and classified as available-for-sale. Equity Securities consist of common stock, exchange traded funds, mutual funds and preferred stock. Other Invested Assets consist of investments our Company made in certain strategic companies which are accounted for using the equity method of accounting and overseas deposits which are carried at fair value. For our investments applying the equity method, these investments are initially recorded at cost and are subsequently adjusted based on our Company’s proportionate share of the net income or loss of the companies. Changes in the carrying value of such investments are recorded in Other Income. In applying the equity method, we use the most recently available financial information provided by the companies which is generally three months prior to the end of the reporting period. Overseas deposits include private funds held by the Syndicate and invested according to local regulatory requirements. The compositions of the overseas deposits vary and the deposits are based on the portfolio level reporting that is provided by Lloyd’s. The fair values of these overseas deposits were measured using the net asset value practical expedient and therefore have not been categorized within the fair value hierarchy. Changes in the fair value of the overseas deposits are recorded in Net Investment Income. Short-Term Investments are carried at fair value. Short-Term Investments have maturities greater than three months but less than 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 Maturities 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 Maturities portfolio to evaluate the necessity of recording impairment losses for other-than-temporary declines in the fair value of securities. Our Company reviews the magnitude of a security’s unrealized loss compared to its cost/amortized cost and the length of time that the security has been impaired to determine if an unrealized loss is other-than-temporary. If warranted as a result of conditions relating to a particular security, our Company will also review securities with declines in fair value resulting from a headline news event involving the issuer, a headline news event involving the asset class, the advice of our external asset managers, or economic events that may impact the issuer to determine if an unrealized loss is other-than-temporary. The depth of analysis performed is dependent upon the nature and magnitude of the indicators of other-than-temporary impairment present in regards to each impaired security. Our Company assesses the underlying fundamentals of each issuer to determine if there is a change in the amount or timing of expected cash flows. Management compares the amortized cost basis to the present value of the revised cash flows using the historical book yield to determine the credit loss portion of impairment which is recognized in earnings. All non-credit losses where we have the intent and ability to hold the security until recovery are recognized as changes in Other than Temporary Impairment (“OTTI”) losses within AOCI. Specifically, for structured Fixed Maturities, our Company analyzes 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. For securities in which a tranche loss is present and the net present value of loss adjusted cash flows is less than book value, credit impairment is recognized in earnings. 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 are actual delinquency rates, default probability, severity and prepayment assumptions. Projected losses are a function of both loss severity and probability of default, which differ based on property type, vintage and the stress of the collateral.
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 Other Income (Loss) in the Consolidated Statements of Income, with the exception of those related to foreign-denominated available-for-sale investments and equity securities. For the available-for-sale investments, exchange rate fluctuations represent an unrealized appreciation/depreciation in the value of the securities and are included in the related component of AOCI. For the equity securities, exchange rate fluctuations are included in the related component of Total Net Realized and Unrealized Gains (Losses). Functional currency assets and liabilities of foreign operations 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.
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 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 net of 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 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, Loss Adjustment Expense (“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 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 reserves for losses and LAE are calculated by our actuaries using several standard actuarial methodologies, including the paid and incurred loss development and the paid and incurred Bornhuetter-Ferguson loss methods. Frequency/severity analyses are performed for certain books of business. The Reserve for Losses and LAE has been established to cover the estimated unpaid cost of claims incurred. Such estimates are regularly compared to indicated reserves 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 stock grants were fully vested.
Share-Based Compensation	Share-Based Compensation Our Company applies a fair value based measurement method in accounting for its share-based payment arrangements with eligible employees and directors. The associated expense is estimated based on the fair value of the award at the grant date and is recognized in Net Income over the requisite service period with a corresponding increase in Shareholder’s Equity. Forfeitures of share-based payment awards are recognized as they occur.
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 the cost of acquiring a business enterprise over the fair value of the net assets acquired. Our Company’s recorded indefinite lived intangible assets represent acquired stamp capacity in the Syndicate and ASCO’s European insurance licenses. Our Company’s recorded definite lived intangible assets represent customer relationships, the value of business acquired (“VOBA”), broker networks, and a trade name. 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. Finite-lived intangibles are amortized over the estimated useful life of the asset and are reviewed for impairment when indicators of impairment are present. Our Company did not recognize an impairment of goodwill or intangible assets for any of the years ended December 31, 2018, 2017 and 2016. As of December 31, 2018, the carrying value of goodwill and intangible assets was $27.1 million, which is $20.5 million more than the carrying value of $6.6 million as of December 31, 2017. Changes in the carrying value of the goodwill and intangible assets were due to the acquisition of BDM and ASCO, as well as fluctuations in currency exchange rates.
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. Income Taxes.
New Accounting Standards Adopted in 2018	New Accounting Standards Adopted in 2018 Revenue From Contracts With Customers Effective January 1, 2018, our Company adopted ASU 2014-09, “Revenue from Contracts with Customers (Topic 606)”. This guidance affects any contracts with customers to transfer goods or services or for the transfer of nonfinancial assets unless those contracts are within the scope of other standards (for example, insurance contracts are not in scope of the new guidance). The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. Our Company generates an insignificant amount of fee income that is within the scope of this guidance and was not materially impacted by the adoption of this guidance. The adoption of this guidance did not have a material impact on our results of operations, financial condition or liquidity. Classification and Measurement of Financial Instruments Effective January 1, 2018, our Company adopted ASU 2016-01 “Financial Instruments – Overall (Subtopic 825-10) – Recognition and Measurement of Financial Assets and Financial Liabilities”. This guidance requires equity investments (except those accounted for under the equity method of accounting, investments that are consolidated or those that meet a practicability exception) to be measured at fair value with changes in fair value recognized in net income, simplifies the impairment assessment of equity investments without readily determinable values by requiring a qualitative assessment to identify impairment, eliminates the requirement to disclose the methods and significant assumptions used to estimate the fair value for financial instruments measured at amortized cost, requires the use of the exit price notion when measuring the fair value of financial instruments for disclosure purposes, requires separate presentation in other comprehensive income of the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the organization has elected to measure the liabilities in accordance with the fair value option, requires the separate presentation of financial assets and financial liabilities by measurement category and form of financial asset on the balance sheet or the accompanying notes to the financial statements and clarifies that the reporting organization should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the organization’s other deferred tax assets. As of January 1, 2018, the adoption of this guidance resulted in a $7.7 million net after-tax increase to Retained Earnings with a corresponding decrease to Accumulated Other Comprehensive Income (Loss), resulting in no change to our Total Stockholders’ Equity. This adjustment reflects the cumulative effect adjustment to reclassify Net Unrealized Gain on Investments in Accumulated Other Comprehensive Income (Loss) for available-for-sale Equity Securities to Retained Earnings upon adoption. Upon the adoption of this guidance, Equity Securities have been measured at fair value with changes in fair value recognized in Net Income through Net Unrealized Gains (Losses) on Equity Securities. The other aspects of this guidance only impacted disclosure or did not apply to our Company and therefore did not impact our results of operations, financial condition or liquidity. Cash Flows Effective January 1, 2018, our Company adopted ASU 2016-15, “Statement of Cash Flows (Topic 230) – Classification of Certain Cash Receipts and Cash Payments” which addresses diversity in practice in how eight specific cash receipts and cash payments should be presented and classified on the statement of cash flows. The adoption of this guidance did not impact our results of operations, financial condition or liquidity. Effective January 1, 2018, our Company adopted ASU 2016-18, “Statement of Cash Flows (Topic 230) – Restricted Cash” which addresses diversity in practice in the classification and presentation of changes in restricted cash on the statement of cash flows. This guidance requires a statement of cash flows to explain the change during the period in the total of cash, cash equivalents, restricted cash and restricted cash equivalents. Transfers between cash and cash equivalents and restricted cash and restricted cash equivalents will no longer be presented on the statement of cash flows. To assist in meeting the requirements of this guidance to provide a reconciliation from the Statement of Cash Flows to the Balance Sheet, upon adoption of this guidance our Company added new accounts titled “Cash and Cash Equivalents” and “Restricted Cash and Cash Equivalents” and reclassified amounts previously held in Short-Term Investments to these accounts for all periods presented. This resulted in the reclassification of $71.3 million of restricted and unrestricted cash and cash equivalent balances as of December 31, 2017. This guidance was adopted on a retrospective basis. Prior to the adoption of this guidance, restricted and unrestricted cash and cash equivalent balances included in the Short-Term Investments account had been presented as a cash flow provided by (used in) investing activities. Consequently, the Statement of Cash Flows for the years ended December 31, 2017 and 2016 include a revision to increase “Net Cash Used in Investing Activities” by $14.4 million and a revision to decrease “Net Cash Used in Investing Activities” by $3.3 million, respectively. Income Taxes Effective January 1, 2018, our Company adopted ASU 2016-16, “Income Taxes (Topic 740) – Intra-Entity Transfers of Assets Other than Inventory” that requires companies to account for the income tax effects of intercompany transfers of assets other than inventory when the transfer occurs. The adoption of this guidance did not impact our results of operations, financial condition or liquidity. Definition of a Business Effective January 1, 2018, our Company adopted ASU 2017-01, “Clarifying the Definition of a Business” that provides guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. This guidance will be applied to transactions prospectively. The adoption of this guidance did not impact our results of operations, financial condition or liquidity. Tax Reform Reclassification from Other Comprehensive Income Effective January 1, 2018, our Company early adopted ASU 2018-02, “Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income” that permits entities to reclassify tax effects stranded in accumulated other comprehensive income as a result of tax reform to retained earnings. The total impact of the remeasurement and other adjustments was reflected in 2017 income from continuing operations, regardless of where deferred taxes were originally recorded. As of January 1, 2018, the adoption of this guidance resulted in a one-time reclassification of $2.8 million, decreasing Retained Earnings and increasing Accumulated Other Comprehensive Income (Loss) primarily from the remeasurement of deferred tax assets and liabilities associated with unrealized gains and losses on investments and currency translation adjustments using the 21% corporate tax rate.
Recently Issued Accounting Standards Not Yet Adopted	Recently Issued Accounting Standards Not Yet Adopted Leases In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842)” which provides a new comprehensive model for lease accounting. Topic 842 was subsequently amended by ASU 2018-10, Codification Improvements to Topic 842, Leases and ASU 2018-11, Targeted Improvements. The new standard requires a lessee to recognize a liability to make lease payments (the lease liability) and a right-of-use (“ROU”) asset representing its right to use the underlying asset for the lease term. Leases will be classified as finance or operating, with classification affecting the pattern and classification of expense recognition in the income statement. The new standard is effective for us on January 1, 2019, with early adoption permitted. A modified retrospective transition approach is required, applying the new standard to all leases existing at the date of initial application. An entity may choose to use either (1) its effective date or (2) the beginning of the earliest comparative period presented in the financial statements as its date of initial application. We expect to adopt the new standard on January 1, 2019 and use the effective date as our date of initial application. Consequently, financial information will not be updated and the disclosures required under the new standard will not be provided for dates and periods before January 1, 2019. The new standard provides a number of optional practical expedients in transition. We expect to elect the ‘package of practical expedients’, which permits us not to reassess under the new standard our prior conclusions about lease identification, lease classification and initial direct costs. We do not expect to elect the use-of-hindsight or the practical expedient pertaining to land easements; the latter not being applicable to us. The new standard also provides practical expedients for an entity’s ongoing accounting. We currently do not have any leases with a term shorter than 12 months. We also currently expect to elect the practical expedient to not separate lease and non-lease components for certain classes of leases. Adoption of this guidance will impact our Company’s consolidated balance sheet, but is not expected to have a material impact on our Company’s results of operations, financial condition and liquidity. While we continue to assess all of the effects of adoption, we currently believe the most significant effects relate to (1) the recognition of new ROU assets and lease liabilities on our balance sheet for our office and equipment operating leases; (2) the derecognition of the deferred rent liability on our balance sheet; and (3) providing significant new disclosures about our leasing activities. We do not expect a significant change in our leasing activities between now and adoption On adoption, we currently expect to recognize additional operating liabilities ranging from $45.0 million to $55.0 million with corresponding ROU assets ranging from $35.0 million to $45.0 million, with the difference between the lease liability and ROU asset being the derecognition of existing deferred rent liabilities and policy changes due to the adoption of the guidance. Credit Losses In June 2016, the FASB issued ASU 2016-13, “Financial Instruments – Credit Losses (Topic 326) – Measurement of Credit Losses on Financial Instruments” which replaces the “incurred loss” impairment methodology with an approach based on “expected losses” to estimate credit losses on certain types of financial instruments and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. The guidance requires financial assets measured at amortized cost to be presented at the net amount expected to be collected. The allowance for credit losses is a valuation account that is deducted from the amortized cost of the financial asset to present the net carrying value at the amount expected to be collected on the financial asset. Credit losses relating to available-for-sale debt securities will be recorded through an allowance for credit losses. The guidance also provides for a simplified accounting model for purchased financial assets with credit deterioration since their origination. This guidance is effective for interim and annual periods beginning after December 15, 2019. Early adoption is permitted for interim and annual periods beginning after December 15, 2018. The application of this guidance is not expected to significantly impact our Company’s available-for-sale debt investment portfolio, but will impact our Company’s other financial assets, including our reinsurance recoverables and premium receivable. Upon adoption of this guidance, any impairment losses on our available-for-sale debt securities will be recorded as an allowance, subject to reversal, rather than as a reduction in amortized cost. Our Company is currently evaluating the impact of this guidance on our results of operations, financial condition and liquidity. Goodwill Impairment In January 2017, the FASB issued ASU 2017-04, “Simplifying the Test for Goodwill Impairment” that eliminates the requirement to calculate the implied fair value of goodwill (i.e., Step 2 of the current goodwill impairment test) to measure a goodwill impairment charge. Instead, an impairment charge will be based on the excess of a reporting unit’s carrying amount over its fair value (i.e., measure the charge based on Step 1 of the current goodwill impairment test). This guidance is effective for annual and interim impairment tests performed in periods beginning after December 15, 2019, with early adoption permitted for annual and interim goodwill impairment testing dates after January 1, 2017. This guidance will be adopted on a prospective basis. Callable Debt Securities In March 2017, the FASB issued ASU 2017-08, “Premium Amortization on Purchased Callable Debt Securities” that shortens the amortization period for the premium on certain purchased callable debt securities to the earliest call date. This guidance is effective for annual periods beginning after December 15, 2018, and interim periods within those fiscal years with early adoption permitted. This guidance will be adopted using a modified retrospective transition approach. The adoption of this guidance is not expected to materially impact our results of operations, financial condition or liquidity. Fair Value Measurement Disclosure In August 2018, the FASB issued ASU 2018-13, “Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement”, which eliminates, adds, and modifies certain disclosure requirements for fair value measurements. The guidance eliminates the requirement to disclose the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, the policy for the timing of transfers between levels of the fair value hierarchy, and the valuation processes for Level 3 fair value measurements. The guidance adds the requirement to disclose changes in unrealized gains and losses included in other comprehensive income for the period and to disclose the range and weighted average used to develop significant unobservable inputs for Level 3 fair value measurements. The guidance modifies disclosures around the use of the practical expedient to measure the fair value of certain investments at their net asset values and modifies the requirement to disclose information as of the reporting date about the measurement uncertainty of Level 3 fair value measurement. This guidance is effective for interim and annual reporting periods beginning after December 15, 2019, with early adoption permitted for the entire standard or only the provisions that eliminate or modify requirements. This guidance will be adopted on a prospective and retrospective basis, where applicable and as required. As this new guidance is disclosure-related only, adoption will not impact our results of operations, financial condition or liquidity. Implementation Costs in a Cloud Computing Arrangement In August 2018, the FASB issued ASU 2018-15, “Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract”, which requires companies to follow the internal-use software guidance in ASC 350-40 (Intangibles - Goodwill and Other - Internal-Use Software) to determine which implementation costs to capitalize as an asset and which costs to expense. Capitalized implementation costs will be amortized over the term of the service arrangement, beginning when the service arrangement or a component of the arrangement is ready for its intended use. This guidance is effective for interim and annual reporting periods beginning after December 15, 2019, with early adoption permitted. This guidance will be applied prospectively. The adoption of this guidance is not expected to materially impact our results of operations, financial condition or liquidity.

Merger And Business Combinati_2

Merger And Business Combinations (Tables)	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The fair value of the assets acquired and liabilities assumed and the allocation of the purchase price on the acquisition date are summarized in the table below: amounts in thousands Consideration paid $ 40,492 Assets Investments 45,182 Cash and Cash Equivalents 18,109 Prepaid Reinsurance Premiums 2,701 Reinsurance Recoverables on Paid Losses 1,311 Reinsurance Recoverables on Unpaid Losses and LAE 15,769 Other Assets 19,943 Fair Value of Identifiable Intangible Assets 9,000 Total Assets Acquired $ 112,015 Liabilities Reserves for Losses and LAE 31,928 Unearned Premiums 11,139 Deferred Income Tax 8,947 Accounts Payable and Other Liabilities 32,212 Total Liabilities Assumed $ 84,226 Goodwill $ 12,703

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Financial Data by Segment	The following tables set forth the financial data by segment for the years ended December 31, 2018, 2017 and 2016: Year Ended December 31, 2018 U.S. Int'l amounts in thousands Insurance Insurance GlobalRe Corporate (1) Total Gross written premiums $ 1,083,116 $ 530,710 $ 299,135 $ — $ 1,912,961 Ceded written premiums (283,025 ) (147,402 ) (11,449 ) — (441,876 ) Net written premiums 800,091 383,308 287,686 — 1,471,085 Retention Ratio 73.9 % 72.2 % 96.2 % — 76.9 % Net Earned Premiums $ 737,646 $ 380,503 $ 245,074 $ — $ 1,363,223 Net Losses and LAE (485,960 ) (252,268 ) (155,551 ) — (893,779 ) Commission Expenses (85,127 ) (80,526 ) (55,056 ) 565 (220,144 ) Other Operating Expenses (142,333 ) (93,882 ) (25,009 ) — (261,224 ) Other Underwriting Income (Expense) 354 2,206 316 (565 ) 2,311 Underwriting Profit (Loss) $ 24,580 $ (43,967 ) $ 9,774 $ — $ (9,613 ) Net Investment Income 103,113 103,113 Total Net Realized and Unrealized Losses (30,348 ) (30,348 ) Interest Expense (15,485 ) (15,485 ) Other Income 4,858 4,858 Merger Transaction Costs (3,950 ) (3,950 ) Income (Loss) Before Income Taxes $ 24,580 $ (43,967 ) $ 9,774 $ 58,188 $ 48,575 Income Tax Expense (14,336 ) (14,336 ) Net Income $ 34,239 Losses and LAE ratio 65.9 % 66.3 % 63.5 % 65.6 % Commission Expense Ratio 11.5 % 21.2 % 22.5 % 16.1 % Other Operating Expense Ratio (2) 19.3 % 24.1 % 10.0 % 19.0 % Combined Ratio 96.7 % 111.6 % 96.0 % 100.7 % (1) - Includes Corporate segment intercompany eliminations. (2) - Includes Other Operating Expenses and Other Underwriting Income. Year Ended December 31, 2017 U.S. Int'l amounts in thousands Insurance Insurance GlobalRe Corporate (1) Total Gross written premiums $ 988,293 $ 501,130 $ 223,842 $ — $ 1,713,265 Ceded written premiums (266,993 ) (165,278 ) (9,664 ) — (441,935 ) Net written premiums 721,300 335,852 214,178 — 1,271,330 Retention Ratio 73.0 % 67.0 % 95.7 % — 74.2 % Net Earned Premiums $ 674,665 $ 333,792 $ 177,963 $ — $ 1,186,420 Net Losses and LAE (443,353 ) (229,601 ) (133,311 ) — (806,265 ) Commission Expenses (77,729 ) (68,824 ) (39,136 ) 958 (184,731 ) Other Operating Expenses (128,905 ) (83,464 ) (20,861 ) — (233,230 ) Other Underwriting Income (Expense) 461 — 565 (958 ) 68 Underwriting Profit (Loss) $ 25,139 $ (48,097 ) $ (14,780 ) $ — $ (37,738 ) Net Investment Income 89,293 89,293 Total Net Realized and Unrealized Gains 43,009 43,009 Interest Expense (15,447 ) (15,447 ) Other Loss (4,311 ) (4,311 ) Income (Loss) Before Income Taxes $ 25,139 $ (48,097 ) $ (14,780 ) $ 112,544 $ 74,806 Income Tax Expense (34,312 ) (34,312 ) Net Income $ 40,494 Losses and LAE ratio 65.7 % 68.8 % 74.9 % 68.0 % Commission Expense Ratio 11.5 % 20.6 % 22.0 % 15.6 % Other Operating Expense Ratio (2) 19.1 % 25.0 % 11.4 % 19.6 % Combined Ratio 96.3 % 114.4 % 108.3 % 103.2 % (1) - Includes Corporate segment intercompany eliminations. (2) - Includes Other Operating Expenses and Other Underwriting Income. Year Ended December 31, 2016 U.S. Int'l amounts in thousands Insurance Insurance GlobalRe Corporate (1) Total Gross written premiums $ 919,395 $ 484,471 $ 165,045 $ — $ 1,568,911 Ceded written premiums (235,827 ) (138,504 ) (8,356 ) — (382,687 ) Net written premiums 683,568 345,967 156,689 — 1,186,224 Retention Ratio 74.3 % 71.4 % 94.9 % — 75.6 % Net Earned Premiums $ 629,308 $ 307,416 $ 163,621 $ — $ 1,100,345 Net Losses and LAE (397,860 ) (178,284 ) (89,304 ) — (665,448 ) Commission Expenses (70,812 ) (61,703 ) (34,008 ) 1,478 (165,045 ) Other Operating Expenses (128,108 ) (86,395 ) (19,593 ) — (234,096 ) Other Underwriting Income (Expense) 1,092 — 522 (1,478 ) 136 Underwriting Profit (Loss) $ 33,620 $ (18,966 ) $ 21,238 $ — $ 35,892 Net Investment Income 79,451 79,451 Total Net Realized and Unrealized Gains 9,036 9,036 Interest Expense (15,435 ) (15,435 ) Other Income 8,565 8,565 Income (Loss) Before Income Taxes $ 33,620 $ (18,966 ) $ 21,238 $ 81,617 $ 117,509 Income Tax Expense (34,783 ) (34,783 ) Net Income $ 82,726 Losses and LAE ratio 63.2 % 58.0 % 54.6 % 60.5 % Commission Expense Ratio 11.3 % 20.1 % 20.8 % 15.0 % Other Operating Expense Ratio (2) 20.2 % 28.1 % 11.6 % 21.2 % Combined Ratio 94.7 % 106.2 % 87.0 % 96.7 % (1) - Includes Corporate segment intercompany eliminations. (2) - Includes Other Operating Expenses and Other Underwriting Income.
Additional Financial Data by Segment	The following tables provide additional financial data by operating segment for the years ended December 31, 2018, 2017 and 2016: Year Ended December 31, 2018 amounts in thousands Gross written premiums Ceded premiums Net written premiums Net earned premiums U.S. Insurance Marine $ 148,485 $ (64,097 ) $ 84,388 $ 84,774 P&C 803,759 (199,307 ) 604,452 549,136 Professional Liability 130,872 (19,621 ) 111,251 103,736 Total $ 1,083,116 $ (283,025 ) $ 800,091 $ 737,646 Int'l Insurance Marine $ 181,053 $ (44,356 ) $ 136,697 $ 151,296 P&C 171,502 (64,176 ) 107,326 105,144 Professional Liability 178,155 (38,870 ) 139,285 124,063 Total $ 530,710 $ (147,402 ) $ 383,308 $ 380,503 GlobalRe $ 299,135 $ (11,449 ) $ 287,686 $ 245,074 Total $ 1,912,961 $ (441,876 ) $ 1,471,085 $ 1,363,223 Year Ended December 31, 2017 amounts in thousands Gross written premiums Ceded written premiums Net written premiums Net earned premiums U.S. Insurance Marine $ 156,171 $ (72,431 ) $ 83,740 $ 86,605 P&C 713,539 (173,501 ) 540,038 495,260 Professional Liability 118,583 (21,061 ) 97,522 92,800 Total $ 988,293 $ (266,993 ) $ 721,300 $ 674,665 Int'l Insurance Marine $ 198,241 $ (42,018 ) $ 156,223 $ 152,396 P&C 159,123 (85,298 ) 73,825 88,517 Professional Liability 143,766 (37,962 ) 105,804 92,879 Total $ 501,130 $ (165,278 ) $ 335,852 $ 333,792 GlobalRe $ 223,842 $ (9,664 ) $ 214,178 $ 177,963 Total $ 1,713,265 $ (441,935 ) $ 1,271,330 $ 1,186,420 Year Ended December 31, 2016 amounts in thousands Gross written premiums Ceded written premiums Net written premiums Net earned premiums U.S. Insurance Marine $ 169,405 $ (70,858 ) $ 98,547 $ 100,132 P&C 631,562 (135,888 ) 495,674 453,673 Professional Liability 118,428 (29,081 ) 89,347 75,503 Total $ 919,395 $ (235,827 ) $ 683,568 $ 629,308 Int'l Insurance Marine $ 183,228 $ (40,092 ) $ 143,136 $ 141,593 P&C 181,094 (69,606 ) 111,488 89,455 Professional Liability 120,149 (28,806 ) 91,343 76,368 Total $ 484,471 $ (138,504 ) $ 345,967 $ 307,416 GlobalRe $ 165,045 $ (8,356 ) $ 156,689 $ 163,621 Total $ 1,568,911 $ (382,687 ) $ 1,186,224 $ 1,100,345
Summary of Gross Written Premiums Allocated Based on Location of Insured's Head Office	The following is a summary of our Company's Gross Written Premiums allocated based on the location of the insured's head office: Years Ended December 31, amounts in thousands 2018 2017 2016 United States $ 1,373,346 $ 1,203,695 $ 1,101,337 Worldwide (Excluding the United States) 539,615 509,570 467,574 Total $ 1,912,961 $ 1,713,265 $ 1,568,911

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Available-for-Sale Investments Including Other-Than-Temporarily Impaired Securities Recognized within Accumulated Other Comprehensive Income	The following tables set forth our Company’s available-for-sale investments and Equity Securities as of December 31, 2018 and 2017 and include OTTI securities recognized within AOCI: December 31, 2018 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 $ 239,776 $ 901 $ (3,957 ) $ 242,832 States, Municipalities and Political Subdivisions 646,551 10,734 (3,448 ) 639,265 Mortgage-Backed and Asset-Backed Securities: Agency Residential Mortgage-Backed Securities 335,542 843 (13,118 ) 347,817 Residential Mortgage Obligations 138,373 604 (530 ) 138,299 Asset-Backed Securities 531,991 1,018 (8,040 ) 539,013 Commercial Mortgage-Backed Securities 188,201 858 (2,816 ) 190,159 Subtotal $ 1,194,107 $ 3,323 $ (24,504 ) $ 1,215,288 Corporate Exposures (1) 1,002,489 3,101 (28,640 ) 1,028,028 Total Fixed Maturities $ 3,082,923 $ 18,059 $ (60,549 ) $ 3,125,413 Short-Term Investments 10,233 — (1 ) 10,234 Total Available-For-Sale Investments $ 3,093,156 $ 18,059 $ (60,550 ) $ 3,135,647 (1) - Corporate Exposures consist of investments in corporate bonds, hybrid bonds and redeemable preferred stocks. December 31, 2017 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 $ 393,563 $ 2,081 $ (2,014 ) $ 393,496 States, Municipalities and Political Subdivisions 814,632 20,136 (1,423 ) 795,919 Mortgage-Backed and Asset-Backed Securities: Agency Residential Mortgage-Backed Securities 407,619 2,352 (5,414 ) 410,681 Residential Mortgage Obligations 54,104 606 (79 ) 53,577 Asset-Backed Securities 328,753 2,138 (663 ) 327,278 Commercial Mortgage-Backed Securities 160,904 2,354 (1,182 ) 159,732 Subtotal $ 951,380 $ 7,450 $ (7,338 ) $ 951,268 Corporate Exposures (1) 897,479 14,491 (3,737 ) 886,725 Total Fixed Maturities $ 3,057,054 $ 44,158 $ (14,512 ) $ 3,027,408 Equity Securities: Common Stocks $ 52,439 $ 7,423 $ (112 ) $ 45,128 Preferred Stocks 183,542 6,071 (1,560 ) 179,031 Total Equity Securities $ 235,981 $ 13,494 $ (1,672 ) $ 224,159 Short-Term Investments (2) 6,480 3 — 6,477 Total Available-For-Sale Investments $ 3,299,515 $ 57,655 $ (16,184 ) $ 3,258,044 (1) - Corporate Exposures consist of investments in corporate bonds, hybrid bonds and redeemable preferred stocks. (2) - Cash and overseas deposits that were misclassified within Short-Term Investments prior to 2018 were reclassified, representing an immaterial correction. Refer to Note 1 Organization & Summary of Significant Accounting Policies
Equity Securities At Fair Value [Table Text Block]	As of December 31, 2018 Gross Gross Fair Unrealized Unrealized amounts in thousands Value Gains (Losses) Cost Equity Securities: Common Stocks $ 166,353 $ 4,738 $ (15,984 ) $ 177,599 Preferred Stocks 173,539 511 (10,791 ) 183,819 Total Equity Securities $ 339,892 $ 5,249 $ (26,775 ) $ 361,418
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, 2018 are shown in the following table: December 31, 2018 Amortized amounts in thousands Fair Value Cost Due in One Year or Less $ 183,390 $ 184,761 Due after One Year Through Five Years 793,254 801,841 Due After Five Years Through Ten Years 370,056 368,933 Due After Ten Years 542,116 554,592 Mortgage-Backed and Asset-Backed Securities 1,194,107 1,215,286 Total $ 3,082,923 $ 3,125,413
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 available-for-sale in a gross unrealized loss position as of December 31, 2018 and 2017, 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, 2018 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 $ 101,395 $ (2,486 ) $ 112,195 $ (1,471 ) $ 213,590 $ (3,957 ) States, Municipalities and Political Subdivisions 123,479 (1,274 ) 105,405 (2,174 ) 228,884 (3,448 ) Mortgage-Backed and Asset-Backed Securities: Agency Residential Mortgage-Backed Securities 34,819 (814 ) 270,997 (12,304 ) 305,816 (13,118 ) Residential Mortgage Obligations 70,965 (249 ) 10,110 (281 ) 81,075 (530 ) Asset-Backed Securities 345,437 (6,950 ) 77,362 (1,090 ) 422,799 (8,040 ) Commercial Mortgage-Backed Securities 58,877 (282 ) 41,477 (2,534 ) 100,354 (2,816 ) Subtotal $ 510,098 $ (8,295 ) $ 399,946 $ (16,209 ) $ 910,044 $ (24,504 ) Corporate Exposures (1) 481,057 (15,456 ) 300,113 (13,184 ) 781,170 (28,640 ) Total Fixed Maturities $ 1,216,029 $ (27,511 ) $ 917,659 $ (33,038 ) $ 2,133,688 $ (60,549 ) (1) - Corporate Exposures consist of investments in corporate bonds, hybrid bonds and redeemable preferred stocks. December 31, 2017 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 $ 273,672 $ (1,502 ) $ 54,484 $ (512 ) $ 328,156 $ (2,014 ) States, Municipalities and Political Subdivisions 74,097 (503 ) 45,085 (920 ) 119,182 (1,423 ) Mortgage-Backed and Asset-Backed Securities: Agency Residential Mortgage-Backed Securities 87,496 (346 ) 236,745 (5,068 ) 324,241 (5,414 ) Residential Mortgage Obligations 12,418 (62 ) 546 (17 ) 12,964 (79 ) Asset-Backed Securities 85,877 (468 ) 24,733 (195 ) 110,610 (663 ) Commercial Mortgage-Backed Securities 20,482 (95 ) 22,903 (1,087 ) 43,385 (1,182 ) Subtotal $ 206,273 $ (971 ) $ 284,927 $ (6,367 ) $ 491,200 $ (7,338 ) Corporate Exposures (1) 295,433 (1,690 ) 121,410 (2,047 ) 416,843 (3,737 ) Total Fixed Maturities $ 849,475 $ (4,666 ) $ 505,906 $ (9,846 ) $ 1,355,381 $ (14,512 ) Equity Securities: Common Stocks $ 11,245 $ (81 ) $ 1,770 $ (31 ) $ 13,015 $ (112 ) Preferred Stocks 50,861 (1,524 ) 662 (36 ) 51,523 (1,560 ) Total Equity Securities $ 62,106 $ (1,605 ) $ 2,432 $ (67 ) $ 64,538 $ (1,672 ) Total Fixed Maturities and Equity Securities $ 911,581 $ (6,271 ) $ 508,338 $ (9,913 ) $ 1,419,919 $ (16,184 ) (1) - Corporate Exposures consist of investments in corporate bonds, hybrid bonds and redeemable preferred stocks.
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, 2018, 2017 and 2016. Years Ended December 31, amounts in thousands 2018 2017 2016 Beginning Balance $ 2,361 $ 2,361 $ 2,361 Additions for Credit Loss Impairments recognized in the current period on securities not previously impaired — — 150 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 (17 ) — (150 ) Ending Balance $ 2,344 $ 2,361 $ 2,361
Net Investment Income	Our Company’s Net Investment Income was derived from the following sources: Years Ended December 31, amounts in thousands 2018 2017 2016 Fixed Maturities $ 90,101 $ 76,784 $ 67,772 Equity Securities 13,807 15,108 14,271 Short-Term Investments, Cash and Cash Equivalents (1) 1,676 428 317 Other Invested Assets (1) 666 636 410 Total Investment Income $ 106,250 $ 92,956 $ 82,770 Investment Expenses (3,137 ) (3,663 ) (3,319 ) Net Investment Income $ 103,113 $ 89,293 $ 79,451 (1) - Cash and overseas deposits that were misclassified within Short-Term Investments prior to 2018 were reclassified, representing an immaterial correction. Refer to Note 1 Organization & Summary of Significant Accounting Policies
Realized Gains and Losses on Investments Sold, 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 2018 2017 2016 Fixed Maturities: Gains $ 3,775 $ 4,041 $ 5,681 Losses (1,306 ) (3,249 ) (4,271 ) Fixed Maturities, Net $ 2,469 $ 792 $ 1,410 Short-Term Investments, Cash and Cash Equivalents: (1) Gains $ 208 $ 1,575 $ 871 Losses (319 ) (243 ) (1,444 ) Short-Term, Net $ (111 ) $ 1,332 $ (573 ) Other Invested Assets: (1) Gains $ 92 $ 56 $ 19 Losses (213 ) (369 ) (108 ) Other Invested Assets, Net $ (121 ) $ (313 ) $ (89 ) Equity Securities: Gains $ 1,102 $ 44,783 $ 9,096 Losses (350 ) (1,521 ) (658 ) Equity Securities, Net $ 752 $ 43,262 $ 8,438 Net Realized Gains on Investments Sold $ 2,989 $ 45,073 $ 9,186 (1) - Cash and overseas deposits that were misclassified within Short-Term Investments prior to 2018 were reclassified, representing an immaterial correction. Refer to Note 1 Organization & Summary of Significant Accounting Policies
Portion of Net Unrealized Losses Recognized to Equity Securities	The following table presents the portion of Net Unrealized Losses recognized during the year that relates to Equity Securities held as of December 31, 2018: amounts in thousands Year Ended December 31, 2018 Equity Securities: Total Net Realized and Unrealized Losses recognized $ (32,585 ) Less: Net Realized Gains on Investments Sold 752 Net Unrealized Losses recognized $ (33,337 )

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	12 Months Ended
	Dec. 31, 2018
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, 2018 and 2017: December 31, 2018 amounts in thousands Level 1 Level 2 Level 3 Total Fixed Maturities: U.S. Treasury Bonds, Agency Bonds and Foreign Government Bonds $ 35,537 $ 204,239 $ — $ 239,776 States, Municipalities and Political Subdivisions — 646,551 — 646,551 Mortgage-Backed and Asset-Backed Securities: Agency Residential Mortgage-Backed Securities — 335,542 — 335,542 Residential Mortgage Obligations — 138,373 — 138,373 Asset-Backed Securities — 531,991 — 531,991 Commercial Mortgage-Backed Securities — 188,201 — 188,201 Subtotal $ — $ 1,194,107 $ — $ 1,194,107 Corporate Exposures — 1,002,489 — 1,002,489 Total Fixed Maturities $ 35,537 $ 3,047,386 $ — $ 3,082,923 Equity Securities: Common Stocks 35,029 131,324 — 166,353 Preferred Stocks — 173,539 — 173,539 Total Equity Securities $ 35,029 $ 304,863 $ — $ 339,892 Short-Term Investments — 10,233 — 10,233 Total Assets Measured at Fair Value $ 70,566 $ 3,362,482 $ — $ 3,433,048 Senior Notes $ — $ 278,150 $ — $ 278,150 Total Liabilities Measured at Fair Value $ — $ 278,150 $ — $ 278,150 December 31, 2017 amounts in thousands Level 1 Level 2 Level 3 Total Fixed Maturities: U.S. Treasury Bonds, Agency Bonds and Foreign Government Bonds $ 178,251 $ 215,312 $ — $ 393,563 States, Municipalities and Political Subdivisions — 814,632 — 814,632 Mortgage-Backed and Asset-Backed Securities: Agency Residential Mortgage-Backed Securities — 407,619 — 407,619 Residential Mortgage Obligations — 54,104 — 54,104 Asset-Backed Securities — 328,753 — 328,753 Commercial Mortgage-Backed Securities — 160,904 — 160,904 Subtotal $ — $ 951,380 $ — $ 951,380 Corporate Exposures — 897,479 — 897,479 Total Fixed Maturities $ 178,251 $ 2,878,803 $ — $ 3,057,054 Equity Securities: Common Stocks 52,439 — — 52,439 Preferred Stocks — 183,542 — 183,542 Total Equity Securities $ 52,439 $ 183,542 $ — $ 235,981 Short-Term Investments (1) 6,480 — — 6,480 Total Assets Measured at Fair Value $ 237,170 $ 3,062,345 $ — $ 3,299,515 Senior Notes $ — $ 277,951 $ — $ 277,951 Total Liabilities Measured at Fair Value $ — $ 277,951 $ — $ 277,951 (1) - Cash and overseas deposits that were misclassified within Short-Term Investments prior to 2018 were reclassified, representing an immaterial correction. Refer to Note 1 Organization & Summary of Significant Accounting Policies

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Summary of Analysis of Goodwill by Reporting Segment	The following table shows an analysis of goodwill by reporting segment: Year Ended December 31, 2018 U.S. Int'l amounts in thousands Insurance Insurance Total Goodwill at Beginning of the Year $ 1,978 $ 2,482 $ 4,460 Goodwill Acquired — 12,703 12,703 Foreign Currency Translation Adjustment — (345 ) (345 ) Goodwill at End of the Year $ 1,978 $ 14,840 $ 16,818
Summary of Gross Carrying Value and Weighted Average Amortization Period of Intangible Assets by Type	The gross carrying value and weighted average amortization period of intangible assets by type at December 31, 2018 was as follows: As of December 31, 2018 amounts in thousands Gross Carrying Amount Accumulated Amortization Weighted Average Amortization Period Finite-Lived Assets ASCO Customer Relationships $ 3,289 $ (164 ) 10 years ASCO VOBA 1,663 (208 ) 4 years BDM Broker Networks 984 (33 ) 15 years BDM Trade Name 484 (242 ) 1 year Total $ 6,420 $ (647 ) Indefinite-Lived Assets ASCO European Licenses $ 2,419 indefinite NUAL Lloyd's Syndicate Capacity $ 2,136 indefinite Total $ 4,555
Summary of Estimated Remaining Amortization Expense for Finite-Lived Intangible Assets	The estimated remaining amortization expense for the finite-lived intangible assets is as follows: amounts in thousands Total 2019 $ 1,052 2020 810 2021 810 2022 602 2023 394 2024 and thereafter 2,105 Total $ 5,773

Reserves for Losses and LAE (Ta

Reserves for Losses and LAE (Tables)	12 Months Ended
	Dec. 31, 2018
Summary of Activity in Reserve for Losses and LAE	The following table summarizes activity for our Company’s Reserves for Losses and LAE for the years ended December 31, 2018, 2017 and 2016: Years Ended December 31, amounts in thousands 2018 2017 2016 Net Reserves for Losses and LAE at Beginning of Year $ 1,705,380 $ 1,510,451 $ 1,393,126 Acquired Net Reserves 16,159 — — Provision for Losses and LAE for Claims Occurring in the Current Year 817,537 771,955 693,976 Increase (Decrease) in Estimated Losses and LAE for Claims Occurring in Prior Years 76,242 34,310 (28,528 ) Incurred Losses and LAE $ 893,779 $ 806,265 $ 665,448 Losses and LAE Paid for Claims Occurring During: Current Year (124,754 ) (144,095 ) (119,485 ) Prior Years (554,733 ) (478,979 ) (412,544 ) Losses and LAE Payments $ (679,487 ) $ (623,074 ) $ (532,029 ) Foreign Currency Adjustment (12,047 ) 11,738 (16,094 ) Net Reserves for Losses and LAE at End of Period 1,923,784 1,705,380 1,510,451 Reinsurance Recoverables on Unpaid Losses and LAE 820,189 809,765 779,276 Gross Reserves for Losses and LAE at End of Period $ 2,743,973 $ 2,515,145 $ 2,289,727
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, 2018, 2017 and 2016 are as follows: Years Ended December 31, amounts in thousands 2018 2017 2016 U.S. Insurance Marine $ (789 ) $ 1,696 $ (10,122 ) P&C 10,310 1,613 2,790 Professional Liability 9,387 13,405 5,984 Total $ 18,908 $ 16,714 $ (1,348 ) Int'l Insurance Marine $ 21,788 $ 6,518 $ (22,068 ) P&C (4,913 ) 3,118 (7,051 ) Professional Liability 14,478 5,198 4,100 Total $ 31,353 $ 14,834 $ (25,019 ) GlobalRe $ 25,981 $ 2,762 $ (2,161 ) Total Strengthening (Releases) $ 76,242 $ 34,310 $ (28,528 )
Summary of Reconciliation of Net Incurred and Paid Claims Development to the Reserve for Losses and LAE	The reconciliation of the net incurred and paid claims development tables to the Reserve for losses and LAE in the consolidated statement of financial position is as follows: Carried Reserves Reconciliation amounts in thousands As of December 31, 2018 Total Net Reserves Reinsurance Recoverables on Unpaid Claims Total Gross Reserves U.S. Marine $ 90,028 $ 88,783 $ 178,811 U.S. P&C 977,968 387,081 1,365,049 U.S. Professional Liability 128,321 54,052 182,373 Int'l Marine 214,455 68,117 282,572 Int'l P&C 87,368 106,879 194,247 Int'l Professional Liability 162,600 86,970 249,570 GlobalRe 174,395 12,751 187,146 Liabilities for Unpaid Claims and Claim Adjustment Expenses $ 1,835,135 $ 804,633 $ 2,639,768 Unallocated Claims Adjustment Expenses 72,099 ASCO Reserves 31,834 Other 272 Total Gross Liability for Unpaid Claims and Claim Adjustment Expense $ 2,743,973
U.S.Insurance | Professional Liability
Summary of Information about Incurred Claims Development and Cumulative Paid Claims and Allocated Loss Adjustment Expense (ALAE), Net of Reinsurance	U.S. Professional Liability Loss and ALAE, Net of Reinsurance amounts in thousands except # of reported claims For the Years Ended December 31, As of December 31, 2018 AY 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Total IBNR # of Reported Claims 2009 $ 47,473 $ 53,273 $ 61,023 $ 58,600 $ 60,789 $ 58,487 $ 58,660 $ 58,143 $ 61,083 $ 60,067 $ 716 1,370 2010 52,302 64,020 68,375 75,619 74,535 86,787 85,348 86,164 87,687 477 1,430 2011 58,116 62,087 70,240 73,028 79,181 79,136 82,558 82,754 715 1,726 2012 61,196 54,480 57,097 55,917 58,344 58,563 58,040 1,657 2,175 2013 60,899 54,982 49,104 48,298 54,228 58,855 3,230 1,984 2014 49,899 35,749 39,699 41,936 43,585 4,590 2,016 2015 31,375 30,486 30,802 35,186 4,712 1,680 2016 41,053 36,036 41,299 5,266 1,813 2017 50,825 44,346 22,367 1,980 2018 54,629 46,916 2,017 Total $ 566,448 U.S. Professional Liability Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance amounts in thousands For the Years Ended December 31, AY 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2009 $ 3,837 $ 21,742 $ 41,675 $ 51,642 $ 55,378 $ 53,859 $ 57,744 $ 58,095 $ 58,150 $ 58,161 2010 2,981 23,147 46,868 54,019 59,765 82,013 84,511 84,529 85,158 2011 3,204 23,878 43,551 59,576 65,710 75,641 78,258 78,382 2012 3,855 22,635 35,681 44,028 49,675 54,728 55,215 2013 4,677 22,167 32,904 38,876 47,062 50,909 2014 2,304 14,319 29,309 35,008 37,780 2015 2,256 11,173 18,303 23,321 2016 2,351 18,283 31,563 2017 2,613 16,246 2018 2,719 Total $ 439,454 Net reserves < 2009 1,327 Total Net reserves $ 128,321
Summary of Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance	U.S. Professional Liability Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 7 8 9 10 U.S. Professional Liability 5.7 % 29.1 % 26.4 % 13.7 % 8.4 % 10.0 % 3.3 % 0.3 % 0.4 % 0.0 %
U.S.Insurance | Marine
Summary of Information about Incurred Claims Development and Cumulative Paid Claims and Allocated Loss Adjustment Expense (ALAE), Net of Reinsurance	U.S. Marine Loss and ALAE, Net of Reinsurance amounts in thousands except # of reported claims For the Years Ended December 31, As of December 31, 2018 AY 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Total IBNR # of Reported Claims 2009 $ 62,044 $ 58,500 $ 55,277 $ 49,650 $ 47,204 $ 48,488 $ 50,694 $ 49,870 $ 50,545 $ 50,625 $ 105 2,334 2010 64,212 63,221 59,219 53,684 51,791 55,974 55,478 55,316 55,687 67 2,011 2011 69,652 68,967 66,900 62,464 61,258 59,709 59,151 58,237 (95 ) 1,916 2012 84,927 87,253 71,941 68,546 70,057 70,573 72,896 1,774 1,863 2013 60,887 57,598 51,464 53,987 55,886 54,033 (882 ) 1,818 2014 58,009 41,454 40,211 44,985 49,366 603 1,951 2015 59,296 50,837 49,341 48,027 338 2,257 2016 51,289 47,254 46,817 2,187 2,534 2017 52,135 49,961 10,634 2,389 2018 49,188 28,204 1,735 Total $ 534,837 U.S. Marine Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance amounts in thousands For the Years Ended December 31, AY 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2009 $ 12,857 $ 28,714 $ 34,769 $ 40,763 $ 42,528 $ 45,106 $ 45,952 $ 48,634 $ 49,252 $ 49,543 2010 16,258 31,769 39,081 42,017 47,173 50,963 54,163 54,321 54,612 2011 14,925 39,707 48,443 51,897 56,405 57,350 57,992 57,879 2012 27,254 46,215 54,470 60,486 66,950 68,750 69,007 2013 17,789 35,350 41,281 46,782 51,041 51,245 2014 10,677 23,162 34,453 40,487 44,852 2015 16,801 30,565 39,927 43,897 2016 11,587 24,566 38,163 2017 18,861 32,341 2018 11,010 Total $ 452,549 Net reserves < 2009 7,740 Total Net reserves $ 90,028
Summary of Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance	U.S. Marine Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 7 8 9 10 U.S. Marine 29.2 % 29.9 % 16.7 % 8.9 % 7.7 % 3.3 % 2.2 % 1.8 % 0.9 % 0.6 %
U.S.Insurance | Property Casualty
Summary of Information about Incurred Claims Development and Cumulative Paid Claims and Allocated Loss Adjustment Expense (ALAE), Net of Reinsurance	U.S. P&C Loss and ALAE, Net of Reinsurance amounts in thousands except # of reported claims For the Years Ended December 31, As of December 31, 2018 AY 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Total IBNR # of Reported Claims 2009 $ 127,749 $ 130,391 $ 131,636 $ 136,835 $ 142,348 $ 147,405 $ 148,126 $ 151,298 $ 150,614 $ 152,609 $ 4,699 8,603 2010 97,426 97,037 95,133 101,134 104,094 105,989 108,894 111,136 110,940 5,939 7,981 2011 80,399 78,420 87,297 90,301 91,267 98,857 101,061 102,403 9,172 6,623 2012 103,437 90,111 91,780 99,502 107,526 111,459 118,647 14,122 4,664 2013 139,986 126,220 129,385 137,692 149,841 156,793 14,770 4,040 2014 192,897 160,828 149,462 156,149 167,782 36,292 4,154 2015 246,404 220,278 215,822 235,390 39,530 4,115 2016 273,693 245,905 242,986 133,717 3,772 2017 298,195 259,919 183,018 3,851 2018 335,885 301,480 3,514 Total $ 1,883,354 U.S. P&C Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance amounts in thousands For the Years Ended December 31, AY 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2009 $ 11,335 $ 33,601 $ 56,453 $ 87,622 $ 111,571 $ 124,908 $ 130,402 $ 137,576 $ 139,768 $ 144,224 2010 12,310 27,036 47,222 65,972 78,243 86,665 91,559 98,053 100,698 2011 3,660 14,694 30,766 47,150 59,038 71,065 80,248 85,885 2012 4,761 17,404 27,717 47,253 67,772 83,215 91,557 2013 7,188 21,035 48,923 84,874 118,932 136,446 2014 5,269 13,569 44,999 75,618 113,585 2015 3,719 24,579 79,639 142,655 2016 5,885 30,124 65,439 2017 13,014 40,012 2018 16,752 Total $ 937,253 Net reserves < 2009 31,867 Total Net reserves $ 977,968
Summary of Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance	U.S. P&C Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 7 8 9 10 U.S. P&C 4.8 % 10.3 % 16.5 % 19.7 % 16.7 % 10.5 % 6.0 % 5.4 % 1.9 % 2.9 %
International Insurance | Professional Liability
Summary of Information about Incurred Claims Development and Cumulative Paid Claims and Allocated Loss Adjustment Expense (ALAE), Net of Reinsurance	Int'l Professional Liability Loss and ALAE, Net of Reinsurance amounts in thousands except # of reported claims For the Years Ended December 31, As of December 31, 2018 AY 2012 2013 2014 2015 2016 2017 2018 Total IBNR # of Reported Claims 2009 $ 16,528 $ 17,061 $ 17,143 $ 16,785 $ 15,752 $ 15,711 $ 14,496 $ 118 624 2010 14,388 13,935 14,076 14,066 15,611 14,376 16,245 13 746 2011 15,310 17,971 19,213 8,817 6,872 12,622 10,704 3 666 2012 6,810 11,433 12,665 13,302 16,970 17,886 21,691 2 1,107 2013 10,250 4,232 14,469 15,546 16,575 15,529 0 1,181 2014 20,607 24,419 23,663 21,438 25,411 6,564 1,775 2015 28,132 30,322 35,144 40,182 5,923 2,483 2016 36,103 34,074 35,873 15,285 3,212 2017 47,610 45,128 32,642 3,642 2018 66,823 55,207 2,031 Total $ 292,082 Int'l Professional Liability Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance amounts in thousands For the Years Ended December 31, AY 2012 2013 2014 2015 2016 2017 2018 2009 $ 8,879 $ 10,804 $ 12,857 $ 13,842 $ 14,136 $ 14,674 $ 14,842 2010 5,861 7,256 10,556 12,688 13,412 13,419 13,566 2011 1,211 2,020 2,965 4,038 4,613 16,367 16,430 2012 2,123 3,207 4,251 5,533 7,423 6,818 7,675 2013 726 2,263 3,042 9,349 13,676 14,334 2014 1,373 2,464 5,158 8,799 20,192 2015 3,417 5,864 17,242 21,128 2016 2,051 6,857 10,931 2017 1,992 5,881 2018 4,768 Total $ 129,747 Net reserves < 2009 265 Total Net reserves $ 162,600
Summary of Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance	Int'l Professional Liability Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 7 8 9 10 Int'l Professional Liability 5.8 % 9.4 % 16.8 % 21.5 % 27.1 % 2.3 % 39.4 % 0.9 % 2.3 % 1.2 %
International Insurance | Marine
Summary of Information about Incurred Claims Development and Cumulative Paid Claims and Allocated Loss Adjustment Expense (ALAE), Net of Reinsurance	Int'l Marine Loss and ALAE, Net of Reinsurance amounts in thousands except # of reported claims For the Years Ended December 31, As of December 31, 2018 AY 2012 2013 2014 2015 2016 2017 2018 Total IBNR # of Reported Claims 2009 $ 95,612 $ 90,880 $ 89,667 $ 82,730 $ 81,296 $ 80,930 $ 82,896 $ 2,065 4,908 2010 130,924 128,878 118,028 113,877 111,165 107,400 107,443 330 5,231 2011 99,374 84,959 81,617 77,099 73,181 73,508 72,008 107 4,855 2012 109,784 131,234 106,553 98,960 91,991 91,844 93,931 272 5,368 2013 87,215 93,736 81,807 81,072 83,094 79,832 669 5,052 2014 104,464 117,228 115,909 118,195 112,498 (6,412 ) 5,125 2015 98,245 94,055 95,449 99,103 (1,843 ) 7,664 2016 87,690 94,464 89,992 1,561 10,085 2017 107,151 135,759 15,783 12,028 2018 94,251 16,778 7,603 Total $ 967,713 Int'l Marine Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance amounts in thousands For the Years Ended December 31, AY 2012 2013 2014 2015 2016 2017 2018 2009 $ 65,715 $ 69,853 $ 72,605 $ 76,050 $ 76,752 $ 78,007 $ 78,044 2010 77,626 89,896 95,906 99,875 102,161 102,597 102,841 2011 45,400 58,695 63,084 67,988 68,951 69,287 69,962 2012 23,088 54,300 69,811 77,847 80,449 82,370 84,744 2013 23,455 45,992 57,973 64,075 66,900 68,443 2014 29,625 56,964 80,943 89,506 104,801 2015 22,651 53,995 75,185 80,684 2016 23,357 54,708 66,912 2017 28,774 77,451 2018 25,404 Total $ 759,286 Net reserves < 2009 6,028 Total Net reserves $ 214,455
Summary of Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance	Int'l Marine Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 7 8 9 10 Int'l Marine 24.7 % 34.1 % 18.8 % 6.9 % 6.6 % 1.8 % 1.7 % 0.7 % 0.9 % 0.0 %
International Insurance | Property Casualty
Summary of Information about Incurred Claims Development and Cumulative Paid Claims and Allocated Loss Adjustment Expense (ALAE), Net of Reinsurance	Int'l P&C Loss and ALAE, Net of Reinsurance amounts in thousands except # of reported claims For the Years Ended December 31, As of December 31, 2018 AY 2012 2013 2014 2015 2016 2017 2018 Total IBNR # of Reported Claims 2009 $ 38,479 $ 40,687 $ 40,776 $ 40,488 $ 34,049 $ 34,305 $ 34,679 $ (100 ) 1,038 2010 42,807 42,234 41,628 41,911 42,528 42,285 40,594 (240 ) 1,026 2011 71,160 61,290 59,128 59,237 59,238 54,798 59,050 (215 ) 1,030 2012 45,287 37,168 36,167 32,242 32,376 32,830 32,069 (251 ) 921 2013 35,862 37,182 36,307 34,221 35,185 34,656 154 1,298 2014 26,741 22,200 20,417 16,363 17,517 (497 ) 1,273 2015 34,678 36,391 33,703 32,566 (86 ) 2,045 2016 78,827 91,431 74,382 987 3,800 2017 56,376 70,448 15,782 3,209 2018 46,487 15,981 1,053 Total $ 442,448 Int'l P&C Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance amounts in thousands For the Years Ended December 31, AY 2012 2013 2014 2015 2016 2017 2018 2009 $ 28,790 $ 33,079 $ 33,538 $ 33,180 $ 33,276 $ 33,359 $ 34,711 2010 34,935 40,576 43,112 40,818 40,935 41,405 41,505 2011 38,362 47,594 50,480 53,034 53,963 51,940 58,422 2012 13,171 21,436 26,904 29,937 31,136 31,389 32,041 2013 7,093 18,294 25,649 28,484 30,067 32,715 2014 3,864 8,948 13,150 16,709 17,626 2015 6,780 18,293 29,420 30,659 2016 25,971 55,287 66,743 2017 14,875 35,628 2018 9,580 Total $ 359,630 Net reserves < 2009 4,550 Total Net reserves $ 87,368
Summary of Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance	Int'l P&C Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 7 8 9 10 Int'l P&C 25.5 % 34.7 % 24.5 % 10.8 % 4.5 % 3.3 % -0.4 % 4.1 % 0.2 % 3.9 %
Global Reinsurance
Summary of Information about Incurred Claims Development and Cumulative Paid Claims and Allocated Loss Adjustment Expense (ALAE), Net of Reinsurance	GlobalRe Loss and ALAE, Net of Reinsurance amounts in thousands except # of reported claims For the Years Ended December 31, As of December 31, 2018 AY 2012 2013 2014 2015 2016 2017 2018 Total IBNR # of Reported Claims 2009 $ 11,158 $ 11,290 $ 11,171 $ 10,426 $ 10,466 $ 10,307 $ 10,610 $ 338 201 2010 13,036 12,997 14,012 11,796 12,476 13,012 13,073 21 202 2011 53,778 76,261 76,054 73,528 72,782 73,428 73,474 (586 ) 740 2012 107,134 99,019 92,584 88,203 114,856 119,565 118,477 (1,218 ) 1,395 2013 114,785 118,688 102,514 105,049 102,323 101,705 (561 ) 1,271 2014 119,351 141,968 121,591 118,131 114,981 860 1,172 2015 101,626 91,526 94,187 93,693 5,777 1,033 2016 88,401 90,567 97,921 5,781 1,022 2017 129,001 153,017 19,356 1,018 2018 128,284 83,977 435 Total $ 905,235 GlobalRe Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance amounts in thousands For the Years Ended December 31, AY 2012 2013 2014 2015 2016 2017 2018 2009 $ 8,635 $ 8,865 $ 8,992 $ 9,939 $ 10,049 $ 10,049 $ 10,118 2010 9,927 10,263 10,439 11,058 11,105 11,170 11,203 2011 43,412 71,086 71,754 72,038 72,177 72,345 72,743 2012 37,709 77,147 83,287 84,668 111,816 117,631 118,006 2013 53,445 82,641 90,649 98,393 99,965 100,981 2014 66,271 119,195 105,574 108,693 111,712 2015 41,623 64,425 76,837 82,942 2016 36,312 66,141 84,245 2017 43,639 115,743 2018 25,017 Total $ 732,710 Net reserves < 2009 1,870 Total Net reserves $ 174,395
Summary of Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance	GlobalRe Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 7 8 9 10 GlobalRe 28.4 % 34.0 % 6.6 % 5.6 % 9.0 % 2.0 % 0.3 % 0.7 % 0.1 % 0.7 %

Ceded Reinsurance (Tables)

Ceded Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2018
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, 2018, and the reinsurers’ ratings from A.M. Best and S&P: Reinsurance Recoverables Unearned Paid/Unpaid Collateral amounts in thousands Premium Losses (1) Total Held A.M. Best S&P Everest Reinsurance Company $ 34,809 $ 106,334 $ 141,143 $ 1,547 A+ A+ Swiss Reinsurance America Corporation 13,514 64,457 77,971 4,223 A+ AA- National Indemnity Company 5,338 61,540 66,878 8,320 A++ AA+ Transatlantic Reinsurance Company 7,597 48,328 55,925 2,541 A+ A+ Munich Reinsurance America Inc. 10,932 41,369 52,301 6,054 A+ AA- Employers Mutual Casualty Company 16,491 34,445 50,936 18,120 A NR Aspen Insurance UK Ltd. 11,801 31,508 43,309 6,446 A A Allied World Reinsurance 7,303 30,439 37,742 1,757 A A- XL Reinsurance America Inc. 7,240 21,250 28,490 2,761 A+ AA- Ace Property & Casualty Insurance Company 1,591 24,148 25,739 63 A++ AA Top 10 Reinsurers $ 116,616 $ 463,818 $ 580,434 $ 51,832 Others 110,107 474,630 584,737 154,085 Total $ 226,723 $ 938,448 $ 1,165,171 $ 205,917 (1) - Net of reserve for uncollectible reinsurance of approximately $13.4 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 2018 2017 2016 Direct $ 1,613,825 $ 1,489,422 $ 1,403,865 Assumed 299,136 223,843 165,046 Ceded (441,876 ) (441,935 ) (382,687 ) Net Written Premiums $ 1,471,085 $ 1,271,330 $ 1,186,224
Summary of Components of Net Earned Premium	The following table summarizes the components of Net Earned Premium: Years Ended December 31, amounts in thousands 2018 2017 2016 Direct $ 1,553,852 $ 1,425,582 $ 1,330,265 Assumed 256,509 187,609 171,978 Ceded (447,138 ) (426,771 ) (401,898 ) Net Earned Premiums $ 1,363,223 $ 1,186,420 $ 1,100,345
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 2018 2017 2016 Direct $ 1,002,358 $ 938,640 $ 795,414 Assumed 159,989 148,606 87,995 Ceded (268,568 ) (280,981 ) (217,961 ) Net Losses and LAE $ 893,779 $ 806,265 $ 665,448

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Annual Rental Commitments under Various Non-cancellable Operating Leases	Rental Commitments Future minimum annual rental commitments as of December 31, 2018 under various non-cancellable operating leases for our office facilities, which expire at various dates through 2032, are as follows: Rental Commitments for Years Ended December 31, amounts in thousands 2019 $ 12,907 2020 12,470 2021 11,542 2022 10,354 2023 9,379 2024-2032 28,268 Total Minimum Operating Lease Payments $ 84,920

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
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 2018 2017 2016 Current Income Tax Expense (Benefit): Federal and Foreign $ 27,768 $ 42,427 $ 39,900 State and Local 934 764 638 Subtotal $ 28,702 $ 43,191 $ 40,538 Deferred Income Tax Expense (Benefit): Federal and Foreign $ (14,366 ) $ (8,879 ) $ (5,755 ) State and local — — — Subtotal $ (14,366 ) $ (8,879 ) $ (5,755 ) Total Income Tax Expense (Benefit) $ 14,336 $ 34,312 $ 34,783
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 2018 2017 2016 Computed Expected Tax Expense $ 10,201 21.0 % $ 26,182 35.0 % $ 41,128 35.0 % Tax-Exempt Interest (3,356 ) (6.9 %) (5,394 ) (7.2 %) (4,559 ) (3.9 %) Dividends Received Deduction (2,041 ) (4.2 %) (4,689 ) (6.3 %) (3,812 ) (3.2 %) Proration of DRD and Tax-Exempt Interest 1,330 2.7 % 1,512 2.0 % 1,256 1.1 % State and Local Income Taxes, Net of Federal Income Tax Deduction 738 1.5 % 497 0.7 % 415 0.4 % Stock Compensation Fair Market Value (1,711 ) (3.5 %) (5,027 ) (6.7 %) N/A N/A Change in Valuation Allowance (774 ) (1.6 %) 1,182 1.6 % — — Deferred Tax Expense due to Tax Law Changes (506 ) (1.0 %) 17,107 22.9 % N/A N/A Transition Tax (1,314 ) (2.7 %) 2,587 3.5 % N/A N/A Uncertain Tax Position - FTC IRS Audit 7,029 14.5 % — — — — Non-Deductible Expenses 1,197 2.5 % 405 0.5 % 406 0.2 % Return to Provision 2,326 4.8 % (158 ) (0.2 %) 1 0.0 % Other 1,217 2.4 % 108 0.1 % (52 ) 0.0 % Actual Tax Expense and Rate $ 14,336 29.5 % $ 34,312 45.9 % $ 34,783 29.6 % N/A - Not applicable
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 2018 2017 Deferred Tax Assets: Loss Reserve Discount $ 26,468 $ 20,425 Unearned Premiums 29,500 24,352 Compensation Related 9,433 8,462 Lloyd's Year of Account Deferral 12,623 9,400 State and Local 3,551 616 Net Currency Translation Adjustments 299 2,084 Net Unrealized Losses on Securities 11,553 — Other 3,598 152 Total Gross Deferred Tax Assets $ 97,025 $ 65,491 Less: Valuation Allowance (4,367 ) (1,798 ) Total Deferred Tax Assets $ 92,658 $ 63,693 Deferred Tax Liabilities: Loss Reserve Discount - Transition Rule $ (7,570 ) $ (5,066 ) Net Unrealized Gains on Securities — (8,708 ) Deferred Acquisition Costs (25,109 ) (20,670 ) Claims Equalization Reserve (7,913 ) — Net Unrealized Foreign Exchange (3,769 ) (3,782 ) Intangibles (3,438 ) — Other (2,562 ) (3,196 ) Total Deferred Tax Liabilities $ (50,361 ) $ (41,422 ) Net Deferred Income Tax Asset $ 42,297 $ 22,271
Summary of Income Tax Contingencies	December 31, amounts in thousands 2018 Balance at January 1, $ — Additions for Tax Positions of Prior Years 6,350 Reductions for Tax Positions of Prior Years — Additions for Tax Positions of Current Year — Reductions for Tax Positions of Current Year — Settlements with Tax Authorities — Lapse of Statute of Limitations — Balance at December 31, $ 6,350 Unrecognized Tax Benefits that, if Recognized, would Impact the Effective Rate $ 6,350
Accrued Interest and Penalties on Unrecognized Tax Benefits	Our Company policy is to recognize interest and penalties related to unrecognized tax benefits as income tax expense. Gross interest was accrued and reported as follows: December 31, amounts in thousands 2018 Interest Recognized on the Consolidated Statements of Operations $ 860 Interest Included in Other Liabilities on the Consolidated Balance Sheets $ 860

Stockholders Equity (Tables)

Stockholders Equity (Tables)	12 Months Ended
	Dec. 31, 2018
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 2018 2017 2016 Beginning Balance 29,507 29,124 28,862 Net Vested Stock Grants 230 343 220 Employee Stock Purchase Plan 45 40 42 Ending Balance 29,782 29,507 29,124
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, 2018 and 2017 are presented in the following table: As of December 31, amounts in thousands 2018 2017 Restricted Net Assets: NIC and NSIC: Fixed Maturities at Fair Value (Amortized Cost: 2018, $9,890; 2017, $9,856) $ 10,441 $ 10,655 Cash (1) 6,074 3,118 Total NIC and NSIC (2) $ 16,515 $ 13,773 NHUK: Fixed Maturities at Fair Value (Amortized Cost: 2018, $481,501; 2017, $472,701) $ 474,128 $ 471,831 Other Invested Assets (1) 46,528 28,767 Cash (1) 60,233 53,111 Total NHUK (3) $ 580,889 $ 553,709 All other Entities: Cash $ 13 $ — Total All other Entities $ 13 $ — Total Restricted Net Assets $ 597,417 $ 567,482 (1) - Cash and overseas deposits that were misclassified within Short-Term Investments prior to 2018 were reclassified, representing an immaterial correction. Refer to Note 1 Organization & Summary of Significant Accounting Policies (2) - 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, 2018 and 2017, as presented in the table above, is held in various collateral accounts to support underwriting activities. (3) - The restricted net assets for NHUK consists of fixed maturities and cash held in trust for the benefit of syndicate policyholders and other invested assets 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, 2018
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, 2018, 2017 and 2016: Years Ended December 31, amounts in thousands, except per share amounts 2018 2017 2016 Net Income $ 34,239 $ 40,494 $ 82,726 Basic Weighted Average Shares 29,720 29,441 29,074 Effect of Common Stock Equivalents: Assumed Vesting of Stock 473 630 958 Diluted Weighted Average Shares 30,193 30,071 30,032 Net Income per Common Share: Basic $ 1.15 $ 1.38 $ 2.85 Diluted $ 1.13 $ 1.35 $ 2.75

Statutory Financial Informati_2

Statutory Financial Information (Tables)	12 Months Ended
	Dec. 31, 2018
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 2018 2017 2016 NIC & NSIC: Statutory Net Income $ 75.0 $ 79.3 $ 84.2 Statutory Capital and Surplus $ 1,005.4 $ 1,056.6 $ 1,027.3 The Syndicate: Syndicate's Net Income $ 6.8 $ (23.4 ) $ 46.3 Syndicate's Capital and Surplus $ 165.3 $ 168.7 $ 180.7 NIIC: Statutory Net Income $ (14.7 ) $ (8.4 ) $ 0.4 Statutory Capital and Surplus $ 43.3 $ 62.9 $ 70.7

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Restricted Stock Unit Awards	The activity related to our Company’s restricted stock unit awards was as follows: Year Ended December 31, 2018 Number of Awards Weighted Average Grant Date Fair Value (1) Nonvested at the beginning of the year 159,539 $ 41.60 Granted 24,593 50.01 Vested (2) (90,543 ) 36.66 Forfeited (7,000 ) 38.00 Nonvested at the end of the year 86,589 $ 49.45 ( 1) Fair value is based on the closing price of our common shares on the NASDAQ on the grant date. (2) This amount represents the gross number of shares vested before any share forfeiture to pay required tax withholdings. For the year ended December 31, 2018 share awards of 34,430 were withheld for tax payments at a weighted average vest date fair value of $58.44.
Performance-based Equity Awards	The activity related to our Company’s performance-based equity awards was as follows: Year Ended December 31, 2018 Number of Awards Weighted Average Grant Date Fair Value (1) Nonvested at the beginning of the year 966,361 $ 43.39 Granted 247,554 54.15 Performance Adjustment (59,833 ) 37.25 Vested (2) (274,299 ) 37.25 Forfeited (34,250 ) 46.00 Nonvested at the end of the year 845,533 $ 48.86 ( 1) Fair value is based on the closing price of our common shares on the NASDAQ on the grant date. (2) This amount represents the gross number of shares vested before any share forfeiture to pay required tax withholdings. For the year ended December 31, 2018 share awards of 117,005 were withheld for tax payments at a weighted average vest date fair value of $55.65.

Condensed Quarterly Financial_2

Condensed Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Summary of Condensed 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 2018 2018 2018 2018 Gross Written Premiums $ 495,224 $ 497,236 $ 455,943 $ 464,558 Revenues: Net Written Premiums $ 393,262 $ 379,292 $ 352,412 $ 346,119 Change in Unearned Premiums (70,635 ) (48,277 ) (5,374 ) 16,424 Net Earned Premiums $ 322,627 $ 331,015 $ 347,038 $ 362,543 Net Investment Income 23,702 24,601 25,651 29,159 Net Realized and Unrealized Gains (Losses): Total Other-Than-Temporary Impairment Losses (37 ) (18 ) (15 ) (48 ) Portion of Loss Recognized in Other Comprehensive Income 37 18 15 48 Net Other-Than-Temporary Impairment Losses Recognized in Earnings — — — — Net Realized Gains (Losses) on Investments Sold 1,169 1,787 253 (220 ) Net Unrealized Gains (Losses) on Equity Securities (3,181 ) 1,329 2,310 (33,795 ) Total Net Realized and Unrealized Gains (Losses) (2,012 ) 3,116 2,563 (34,015 ) Other Income (Loss) (117 ) 2,628 1,724 2,934 Total Revenues $ 344,200 $ 361,360 $ 376,976 $ 360,621 Expenses: Net Losses and LAE $ 186,145 $ 196,333 $ 240,900 $ 270,401 Commission Expenses 54,152 53,193 57,999 54,800 Other Operating Expenses 62,926 68,182 67,584 62,532 Merger Transaction Costs — — 2,439 1,511 Interest Expense 3,864 3,864 3,891 3,866 Total Expenses $ 307,087 $ 321,572 $ 372,813 $ 393,110 Income (Loss) Before Income Taxes 37,113 39,788 4,163 (32,489 ) Income Tax Expense (Benefit) $ 6,235 $ 7,684 $ (462 ) $ 879 Net Income (Loss) $ 30,878 $ 32,104 $ 4,625 $ (33,368 ) Comprehensive Income (Loss) $ (2,962 ) $ 15,373 $ (2,681 ) $ (41,960 ) Combined Ratio 94.0 % 96.0 % 105.3 % 106.6 % Net Income (Loss) per Share: Basic $ 1.04 $ 1.08 $ 0.16 $ (1.12 ) Diluted $ 1.02 $ 1.07 $ 0.15 $ (1.12 ) March 31, June 30, September 30, December 31, amounts in thousands, except per share amounts 2017 2017 2017 2017 Gross Written Premiums $ 450,305 $ 452,179 $ 402,038 $ 408,743 Revenues: Net Written Premiums $ 337,163 $ 333,282 $ 296,016 $ 304,869 Change in Unearned Premiums (51,032 ) (39,447 ) 5,339 230 Net Earned Premiums $ 286,131 $ 293,835 $ 301,355 $ 305,099 Net Investment Income 21,448 22,265 22,598 22,982 Total Other-Than-Temporary Impairment Losses (1,077 ) 29 (957 ) 3 Portion of Loss Recognized in Other Comprehensive Income (16 ) (29 ) (15 ) (3 ) Net Other-Than-Temporary Impairment Losses Recognized in Earnings (1,093 ) — (972 ) — Net Realized Gains 1,049 1,694 5,190 37,141 Other Income (Loss) 1,068 (411 ) (1,699 ) (3,201 ) Total Revenues $ 308,603 $ 317,383 $ 326,472 $ 362,021 Expenses: Net Losses and LAE $ 169,600 $ 177,110 $ 276,171 $ 183,384 Commission Expenses 47,844 48,173 45,509 43,205 Other Operating Expenses 58,538 60,766 45,773 68,153 Interest Expense 3,861 3,861 3,862 3,863 Total Expenses $ 279,843 $ 289,910 $ 371,315 $ 298,605 Income (Loss) Before Income Taxes 28,760 27,473 (44,843 ) 63,416 Income Tax Expense (Benefit) $ 7,650 $ 6,971 $ (16,864 ) $ 36,555 Net Income (Loss) $ 21,110 $ 20,502 $ (27,979 ) $ 26,861 Comprehensive Income (Loss) $ 35,911 $ 35,699 $ (18,311 ) $ (1,812 ) Combined Ratio 96.4 % 97.3 % 121.9 % 96.6 % Net Income (Loss) per Share: Basic $ 0.72 $ 0.70 $ (0.95 ) $ 0.91 Diluted $ 0.70 $ 0.69 $ (0.95 ) $ 0.89

Organization and Summary of S_3

Organization and Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		12 Months Ended
	Dec. 31, 2018USD ($)Insurance	Dec. 31, 2017USD ($)	Dec. 31, 2018USD ($)Insurance	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Jan. 01, 2019USD ($)	Jun. 07, 2018	Jan. 01, 2018USD ($)
Organization And Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in net cash used in investing activities			$ (260,147,000)	$ (264,029,000)	$ (202,183,000)
Impairment of goodwill and intangible assets			0	0	$ 0
Goodwill and intangible assets	$ 27,146,000	$ 6,596,000	27,146,000	$ 6,596,000
Changes in carrying value of goodwill and intangible assets			$ 20,500,000
Corporate income tax rate			21.00%	35.00%	35.00%
Transition tax		2,600,000		$ 2,600,000
Tax benefit (expense) related to transition tax			$ 1,300,000
Tax benefit (expense) related to remeasurement of net deferred tax assets	$ 500,000
Accounting Standards Update 2016-01
Organization And Summary Of Significant Accounting Policies [Line Items]
Cumulative-effect adjustment from adoption								$ 0
Accounting Standards Update 2016-01 | Retained Earnings
Organization And Summary Of Significant Accounting Policies [Line Items]
Cumulative-effect adjustment from adoption								7,700,000
Accounting Standards Update 2016-01 | Accumulated Other Comprehensive Income (Loss)
Organization And Summary Of Significant Accounting Policies [Line Items]
Cumulative-effect adjustment from adoption								(7,700,000)
Accounting Standards Update 2016-18
Organization And Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in net cash used in investing activities				14,400,000	$ (3,300,000)
Reclassification of restricted and unrestricted cash and cash equivalent		71,300,000		71,300,000
Accounting Standards Update 2018-02 | Retained Earnings
Organization And Summary Of Significant Accounting Policies [Line Items]
Cumulative-effect adjustment from adoption								(2,800,000)
Accounting Standards Update 2018-02 | Accumulated Other Comprehensive Income (Loss)
Organization And Summary Of Significant Accounting Policies [Line Items]
Cumulative-effect adjustment from adoption								$ 2,800,000
Minimum
Organization And Summary Of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life			3 years
Minimum | Accounting Standards Update 2016-02 | Subsequent Event
Organization And Summary Of Significant Accounting Policies [Line Items]
Additional operating liabilities						$ 45,000,000
Operating lease, Right-of-use asset						35,000,000
Maximum
Organization And Summary Of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life			7 years
Maximum | Accounting Standards Update 2016-02 | Subsequent Event
Organization And Summary Of Significant Accounting Policies [Line Items]
Additional operating liabilities						55,000,000
Operating lease, Right-of-use asset						$ 45,000,000
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
Immaterial Error Correction
Organization And Summary Of Significant Accounting Policies [Line Items]
Cash reclassified from short- term investment to cash and cash equivalent		20,500,000		20,500,000
Overseas deposits reclassified from short-term investments to other invested assets		$ 28,800,000		28,800,000
Increase (decrease) in net cash used in investing activities				$ 1,900,000	$ (6,000,000)
Increase in income tax expense			$ 7,000,000
Quantifying misstatement in current year financial statements, amount			300,000
Immaterial Error Correction | Impacting Income Tax Expense Line Item
Organization And Summary Of Significant Accounting Policies [Line Items]
Quantifying misstatement in current year financial statements, amount			5,400,000
Immaterial Error Correction | Impacting Various Line Items
Organization And Summary Of Significant Accounting Policies [Line Items]
Quantifying misstatement in current year financial statements, amount			$ 5,100,000
Bracht, Deckers & Mackelbert NV and Assurances Continentales - Continentale Verzekeringen NV
Organization And Summary Of Significant Accounting Policies [Line Items]
Business acquisition, percentage of ownership interest acquired							100.00%
United States
Organization And Summary Of Significant Accounting Policies [Line Items]
Number of insurance companies | Insurance	2		2
Syndicate 1,221
Organization And Summary Of Significant Accounting Policies [Line Items]
Percentage control of stamp capacity	100.00%		100.00%

Merger And Business Combinati_3

Merger And Business Combinations - Additional Information (Detail) $ / shares in Units, € in Millions	Jun. 30, 2018USD ($)	Jun. 07, 2018USD ($)	Jun. 07, 2018EUR (€)	Dec. 31, 2018USD ($)	Dec. 31, 2018USD ($)	Aug. 22, 2018$ / shares	Jun. 07, 2018EUR (€)	Dec. 31, 2017USD ($)
Business Acquisition [Line Items]
Goodwill recognized at date of acquisition				$ 16,818,000	$ 16,818,000			$ 4,460,000
Finite-Lived Intangible Assets
Business Acquisition [Line Items]
Increase (decrease) in fair value of identifiable intangible assets and goodwill	$ (1,400,000)
Goodwill
Business Acquisition [Line Items]
Increase (decrease) in fair value of identifiable intangible assets and goodwill	$ 1,400,000
The Hartford
Business Acquisition [Line Items]
Merger Consideration | $ / shares						$ 70
Bracht, Deckers & Mackelbert NV and Assurances Continentales - Continentale Verzekeringen NV
Business Acquisition [Line Items]
Acquisition date		Jun. 7, 2018	Jun. 7, 2018
Business acquisition, name of acquired entity					BDM, ASCO, and a wholly-owned subsidiary of ASCO, Canal Re S.A.
Business acquisition, percentage of ownership interest acquired		100.00%					100.00%
Business acquisition, purchase price		$ 40,492,000	€ 35
Additional reimbursement amount receivable		5,800,000					€ 5
Business combination, fair value of acquisition reimbursement amount		0		0	$ 0
Goodwill recognized at date of acquisition		12,703,000
Business combination, identified finite lived intangible assets		$ 6,500,000
Business combination, finite lived intangible assets weighted average amortization period		9 years	9 years
Business combination, indefinite intangible assets		$ 2,500,000
Revenues				11,100,000
Net Income (Loss)				$ (300,000)

Merger And Business Combinati_4

Merger And Business Combinations - Schedule of Recognized Identified Assets Acquired and Liabilities Assumed (Details) $ in Thousands, € in Millions	Jun. 07, 2018USD ($)	Jun. 07, 2018EUR (€)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Liabilities
Goodwill			$ 16,818	$ 4,460
Bracht, Deckers & Mackelbert NV and Assurances Continentales - Continentale Verzekeringen NV
Business Acquisition [Line Items]
Consideration paid	$ 40,492	€ 35
Assets
Investments	45,182
Cash and Cash Equivalents	18,109
Prepaid Reinsurance Premiums	2,701
Reinsurance Recoverables on Paid Losses	1,311
Reinsurance Recoverables on Unpaid Losses and LAE	15,769
Other Assets	19,943
Fair Value of Identifiable Intangible Assets	9,000
Total Assets Acquired	112,015
Liabilities
Reserves for Losses and LAE	31,928
Unearned Premiums	11,139
Deferred Income Tax	8,947
Accounts Payable and Other Liabilities	32,212
Total Liabilities Assumed	84,226
Goodwill	$ 12,703

Segment Information - Additiona

Segment Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018Segment
Segment Reporting Information [Line Items]
Number of underwriting Segments	3
Marsh & McLennan Companies Inc. | Gross Premiums Written
Segment Reporting Information [Line Items]
Concentration percentage of gross premiums written	10.00%
U.S.Insurance
Segment Reporting Information [Line Items]
Number of Operating Segments	3
International Insurance
Segment Reporting Information [Line Items]
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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Gross Written Premiums		$ 464,558	$ 455,943	$ 497,236	$ 495,224	$ 408,743	$ 402,038	$ 452,179	$ 450,305	$ 1,912,961	$ 1,713,265	$ 1,568,911
Ceded written premiums										(441,876)	(441,935)	(382,687)
Net written premiums		346,119	352,412	379,292	393,262	304,869	296,016	333,282	337,163	$ 1,471,085	$ 1,271,330	$ 1,186,224
Retention Ratio										76.90%	74.20%	75.60%
Net Earned Premiums		362,543	347,038	331,015	322,627	305,099	301,355	293,835	286,131	$ 1,363,223	$ 1,186,420	$ 1,100,345
Net Losses and LAE		(270,401)	(240,900)	(196,333)	(186,145)	(183,384)	(276,171)	(177,110)	(169,600)	(893,779)	(806,265)	(665,448)
Commission Expenses		(54,800)	(57,999)	(53,193)	(54,152)	(43,205)	(45,509)	(48,173)	(47,844)	(220,144)	(184,731)	(165,045)
Other Operating Expenses		(62,532)	(67,584)	(68,182)	(62,926)	(68,153)	(45,773)	(60,766)	(58,538)	(261,224)	(233,230)	(234,096)
Other Underwriting Income (Expense)										2,311	68	136
Underwriting Profit (Loss)										(9,613)	(37,738)	35,892
Net Investment Income		29,159	25,651	24,601	23,702	22,982	22,598	22,265	21,448	103,113	89,293	79,451
Total Net Realized and Unrealized Losses		(34,015)	2,563	3,116	(2,012)					(30,348)	43,009	9,036
Interest Expense		(3,866)	(3,891)	(3,864)	(3,864)	(3,863)	(3,862)	(3,861)	(3,861)	(15,485)	(15,447)	(15,435)
Other Income										4,858	(4,311)	8,565
Merger Transaction Costs		(1,511)	(2,439)							(3,950)	0	0
Income Before Income Taxes		(32,489)	4,163	39,788	37,113	63,416	(44,843)	27,473	28,760	48,575	74,806	117,509
Income Tax Expense		(879)	462	(7,684)	(6,235)	(36,555)	16,864	(6,971)	(7,650)	(14,336)	(34,312)	(34,783)
Net Income		$ (33,368)	$ 4,625	$ 32,104	$ 30,878	$ 26,861	$ (27,979)	$ 20,502	$ 21,110	$ 34,239	$ 40,494	$ 82,726
Losses and LAE ratio										65.60%	68.00%	60.50%
Commission Expense Ratio										16.10%	15.60%	15.00%
Other Operating Expense Ratio	[1]									19.00%	19.60%	21.20%
Combined Ratio		106.60%	105.30%	96.00%	94.00%	96.60%	121.90%	97.30%	96.40%	100.70%	103.20%	96.70%
U.S.Insurance
Segment Reporting Information [Line Items]
Gross Written Premiums										$ 1,083,116	$ 988,293	$ 919,395
Ceded written premiums										(283,025)	(266,993)	(235,827)
Net written premiums										$ 800,091	$ 721,300	$ 683,568
Retention Ratio										73.90%	73.00%	74.30%
Net Earned Premiums										$ 737,646	$ 674,665	$ 629,308
Net Losses and LAE										(485,960)	(443,353)	(397,860)
Commission Expenses										(85,127)	(77,729)	(70,812)
Other Operating Expenses										(142,333)	(128,905)	(128,108)
Other Underwriting Income (Expense)										354	461	1,092
Underwriting Profit (Loss)										24,580	25,139	33,620
Income Before Income Taxes										$ 24,580	$ 25,139	$ 33,620
Losses and LAE ratio										65.90%	65.70%	63.20%
Commission Expense Ratio										11.50%	11.50%	11.30%
Other Operating Expense Ratio	[1]									19.30%	19.10%	20.20%
Combined Ratio										96.70%	96.30%	94.70%
International Insurance
Segment Reporting Information [Line Items]
Gross Written Premiums										$ 530,710	$ 501,130	$ 484,471
Ceded written premiums										(147,402)	(165,278)	(138,504)
Net written premiums										$ 383,308	$ 335,852	$ 345,967
Retention Ratio										72.20%	67.00%	71.40%
Net Earned Premiums										$ 380,503	$ 333,792	$ 307,416
Net Losses and LAE										(252,268)	(229,601)	(178,284)
Commission Expenses										(80,526)	(68,824)	(61,703)
Other Operating Expenses										(93,882)	(83,464)	(86,395)
Other Underwriting Income (Expense)										2,206	0	0
Underwriting Profit (Loss)										(43,967)	(48,097)	(18,966)
Income Before Income Taxes										$ (43,967)	$ (48,097)	$ (18,966)
Losses and LAE ratio										66.30%	68.80%	58.00%
Commission Expense Ratio										21.20%	20.60%	20.10%
Other Operating Expense Ratio	[1]									24.10%	25.00%	28.10%
Combined Ratio										111.60%	114.40%	106.20%
Global Reinsurance
Segment Reporting Information [Line Items]
Gross Written Premiums										$ 299,135	$ 223,842	$ 165,045
Ceded written premiums										(11,449)	(9,664)	(8,356)
Net written premiums										$ 287,686	$ 214,178	$ 156,689
Retention Ratio										96.20%	95.70%	94.90%
Net Earned Premiums										$ 245,074	$ 177,963	$ 163,621
Net Losses and LAE										(155,551)	(133,311)	(89,304)
Commission Expenses										(55,056)	(39,136)	(34,008)
Other Operating Expenses										(25,009)	(20,861)	(19,593)
Other Underwriting Income (Expense)										316	565	522
Underwriting Profit (Loss)										9,774	(14,780)	21,238
Income Before Income Taxes										$ 9,774	$ (14,780)	$ 21,238
Losses and LAE ratio										63.50%	74.90%	54.60%
Commission Expense Ratio										22.50%	22.00%	20.80%
Other Operating Expense Ratio	[1]									10.00%	11.40%	11.60%
Combined Ratio										96.00%	108.30%	87.00%
Corporate
Segment Reporting Information [Line Items]
Net Investment Income	[2]									$ 103,113	$ 89,293	$ 79,451
Total Net Realized and Unrealized Losses	[2]									(30,348)	43,009	9,036
Interest Expense	[2]									(15,485)	(15,447)	(15,435)
Other Income	[2]									4,858	(4,311)	8,565
Merger Transaction Costs	[2]									(3,950)
Income Before Income Taxes	[2]									58,188	112,544	81,617
Income Tax Expense	[2]									(14,336)	(34,312)	(34,783)
Intersegment Elimination
Segment Reporting Information [Line Items]
Commission Expenses	[2]									565	958	1,478
Other Underwriting Income (Expense)	[2]									$ (565)	$ (958)	$ (1,478)
[1]	Includes Other Operating Expenses and Other Underwriting Income.
[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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Gross written premiums	$ 464,558	$ 455,943	$ 497,236	$ 495,224	$ 408,743	$ 402,038	$ 452,179	$ 450,305	$ 1,912,961	$ 1,713,265	$ 1,568,911
Ceded written premiums									(441,876)	(441,935)	(382,687)
Net written premiums	346,119	352,412	379,292	393,262	304,869	296,016	333,282	337,163	1,471,085	1,271,330	1,186,224
Net earned premiums	$ 362,543	$ 347,038	$ 331,015	$ 322,627	$ 305,099	$ 301,355	$ 293,835	$ 286,131	1,363,223	1,186,420	1,100,345
U.S.Insurance
Segment Reporting Information [Line Items]
Gross written premiums									1,083,116	988,293	919,395
Ceded written premiums									(283,025)	(266,993)	(235,827)
Net written premiums									800,091	721,300	683,568
Net earned premiums									737,646	674,665	629,308
U.S.Insurance | Professional Liability
Segment Reporting Information [Line Items]
Gross written premiums									130,872	118,583	118,428
Ceded written premiums									(19,621)	(21,061)	(29,081)
Net written premiums									111,251	97,522	89,347
Net earned premiums									103,736	92,800	75,503
U.S.Insurance | Marine
Segment Reporting Information [Line Items]
Gross written premiums									148,485	156,171	169,405
Ceded written premiums									(64,097)	(72,431)	(70,858)
Net written premiums									84,388	83,740	98,547
Net earned premiums									84,774	86,605	100,132
U.S.Insurance | Property Casualty
Segment Reporting Information [Line Items]
Gross written premiums									803,759	713,539	631,562
Ceded written premiums									(199,307)	(173,501)	(135,888)
Net written premiums									604,452	540,038	495,674
Net earned premiums									549,136	495,260	453,673
International Insurance
Segment Reporting Information [Line Items]
Gross written premiums									530,710	501,130	484,471
Ceded written premiums									(147,402)	(165,278)	(138,504)
Net written premiums									383,308	335,852	345,967
Net earned premiums									380,503	333,792	307,416
International Insurance | Professional Liability
Segment Reporting Information [Line Items]
Gross written premiums									178,155	143,766	120,149
Ceded written premiums									(38,870)	(37,962)	(28,806)
Net written premiums									139,285	105,804	91,343
Net earned premiums									124,063	92,879	76,368
International Insurance | Marine
Segment Reporting Information [Line Items]
Gross written premiums									181,053	198,241	183,228
Ceded written premiums									(44,356)	(42,018)	(40,092)
Net written premiums									136,697	156,223	143,136
Net earned premiums									151,296	152,396	141,593
International Insurance | Property Casualty
Segment Reporting Information [Line Items]
Gross written premiums									171,502	159,123	181,094
Ceded written premiums									(64,176)	(85,298)	(69,606)
Net written premiums									107,326	73,825	111,488
Net earned premiums									105,144	88,517	89,455
Global Reinsurance
Segment Reporting Information [Line Items]
Gross written premiums									299,135	223,842	165,045
Ceded written premiums									(11,449)	(9,664)	(8,356)
Net written premiums									287,686	214,178	156,689
Net earned premiums									$ 245,074	$ 177,963	$ 163,621

Summary of Gross Written Premiu

Summary of Gross Written Premiums Allocated Based on Location of Insured's Head Office (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Gross Written Premiums	$ 464,558	$ 455,943	$ 497,236	$ 495,224	$ 408,743	$ 402,038	$ 452,179	$ 450,305	$ 1,912,961	$ 1,713,265	$ 1,568,911
United States
Segment Reporting Information [Line Items]
Gross Written Premiums									1,373,346	1,203,695	1,101,337
Worldwide (Excluding the United States)
Segment Reporting Information [Line Items]
Gross Written Premiums									$ 539,615	$ 509,570	$ 467,574

Available-for-Sale Investments

Available-for-Sale Investments and Equity Securities Including Other-Than-Temporarily Impaired Securities Recognized within Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Gain (Loss) on Investments [Line Items]
Total available for sale investments		$ 3,093,156
Gross Unrealized Gains		18,059
Gross Unrealized Losses		(60,550)
Amortized Cost		3,135,647
Total available for sale investments			$ 3,299,515
Gross Unrealized Gains			57,655
Gross Unrealized Losses			(16,184)
Amortized Cost			3,258,044
Fixed Maturities
Gain (Loss) on Investments [Line Items]
Total available for sale investments		3,082,923	3,057,054
Gross Unrealized Gains		18,059	44,158
Gross Unrealized Losses		(60,549)	(14,512)
Amortized Cost		3,125,413	3,027,408
Fixed Maturities | U.S. Treasury Bonds, Agency Bonds and Foreign Government Bonds
Gain (Loss) on Investments [Line Items]
Total available for sale investments		239,776	393,563
Gross Unrealized Gains		901	2,081
Gross Unrealized Losses		(3,957)	(2,014)
Amortized Cost		242,832	393,496
Fixed Maturities | States, Municipalities and Political Subdivisions
Gain (Loss) on Investments [Line Items]
Total available for sale investments		646,551	814,632
Gross Unrealized Gains		10,734	20,136
Gross Unrealized Losses		(3,448)	(1,423)
Amortized Cost		639,265	795,919
Fixed Maturities | Agency Residential Mortgage-Backed Securities
Gain (Loss) on Investments [Line Items]
Total available for sale investments		335,542	407,619
Gross Unrealized Gains		843	2,352
Gross Unrealized Losses		(13,118)	(5,414)
Amortized Cost		347,817	410,681
Fixed Maturities | Residential Mortgage Backed Securities
Gain (Loss) on Investments [Line Items]
Total available for sale investments		138,373	54,104
Gross Unrealized Gains		604	606
Gross Unrealized Losses		(530)	(79)
Amortized Cost		138,299	53,577
Fixed Maturities | Asset-Backed Securities
Gain (Loss) on Investments [Line Items]
Total available for sale investments		531,991	328,753
Gross Unrealized Gains		1,018	2,138
Gross Unrealized Losses		(8,040)	(663)
Amortized Cost		539,013	327,278
Fixed Maturities | Commercial Mortgage-Backed Securities
Gain (Loss) on Investments [Line Items]
Total available for sale investments		188,201	160,904
Gross Unrealized Gains		858	2,354
Gross Unrealized Losses		(2,816)	(1,182)
Amortized Cost		190,159	159,732
Fixed Maturities | Mortgage-Backed and Asset-Backed Securities
Gain (Loss) on Investments [Line Items]
Total available for sale investments		1,194,107	951,380
Gross Unrealized Gains		3,323	7,450
Gross Unrealized Losses		(24,504)	(7,338)
Amortized Cost		1,215,288	951,268
Fixed Maturities | Corporate Exposures
Gain (Loss) on Investments [Line Items]
Total available for sale investments	[1]	1,002,489	897,479
Gross Unrealized Gains	[1]	3,101	14,491
Gross Unrealized Losses	[1]	(28,640)	(3,737)
Amortized Cost	[1]	1,028,028	886,725
Short-Term Investments
Gain (Loss) on Investments [Line Items]
Total available for sale investments		10,233	6,480
Gross Unrealized Gains		0	3
Gross Unrealized Losses		(1)	0
Amortized Cost		$ 10,234	6,477
Equity Securities
Gain (Loss) on Investments [Line Items]
Total available for sale investments			235,981
Gross Unrealized Gains			13,494
Gross Unrealized Losses			(1,672)
Amortized Cost			224,159
Equity Securities | Common Stocks
Gain (Loss) on Investments [Line Items]
Total available for sale investments			52,439
Gross Unrealized Gains			7,423
Gross Unrealized Losses			(112)
Amortized Cost			45,128
Equity Securities | Preferred Stocks
Gain (Loss) on Investments [Line Items]
Total available for sale investments			183,542
Gross Unrealized Gains			6,071
Gross Unrealized Losses			(1,560)
Amortized Cost			$ 179,031
[1]	Corporate Exposures consist of investments in corporate bonds, hybrid bonds and redeemable preferred stocks.

Equity Securities at Fair Value

Equity Securities at Fair Value (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Gain (Loss) on Investments [Line Items]
Fair Value	$ 339,892
Gross Unrealized Gains	5,249
Gross Unrealized (Losses)	(26,775)
Cost	361,418
Common Stocks
Gain (Loss) on Investments [Line Items]
Fair Value	166,353
Gross Unrealized Gains	4,738
Gross Unrealized (Losses)	(15,984)
Cost	177,599
Preferred Stocks
Gain (Loss) on Investments [Line Items]
Fair Value	173,539
Gross Unrealized Gains	511
Gross Unrealized (Losses)	(10,791)
Cost	$ 183,819

Investments - Additional Inform

Investments - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)Security	Dec. 31, 2017USD ($)Security	Dec. 31, 2016USD ($)
Schedule of Investments [Line Items]
Non-credit OTTI on fixed maturities in a net unrealized gain position	$ 300	$ 500
Fixed Maturities
Schedule of Investments [Line Items]
Number of securities in unrealized loss position | Security	808	454
Gross Unrealized Loss	$ 60,549	$ 14,512
OTTI losses			$ 200
Equity Securities
Schedule of Investments [Line Items]
Number of securities in unrealized loss position | Security		22
OTTI losses		$ 2,100
Mortgage-Backed and Asset-Backed Securities
Schedule of Investments [Line Items]
Securities, effective maturities	5 years 2 months 12 days
Mortgage-Backed and Asset-Backed Securities | Fixed Maturities
Schedule of Investments [Line Items]
Gross Unrealized Loss	$ 24,504	$ 7,338
Maximum | Non-government-backed securities
Schedule of Investments [Line Items]
Percentage of investment	5.00%	5.00%
Gross Unrealized Loss	$ 3,700	$ 700
Other Invested Assets
Schedule of Investments [Line Items]
Equity method investments, cost	2,000
Equity method investments, carrying Value	1,900	1,700
Fair value of overseas deposits	$ 46,500	$ 28,800

Scheduled Maturity Dates for Fi

Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value
Total	$ 3,093,156
Amortized Cost
Amortized Cost	3,135,647
Fixed Maturities
Fair Value
Due in One Year or Less	183,390
Due after One Year Through Five Years	793,254
Due After Five Years Through Ten Years	370,056
Due After Ten Years	542,116
Mortgage-Backed and Asset-Backed Securities	1,194,107
Total	3,082,923	$ 3,057,054
Amortized Cost
Due in One Year or Less	184,761
Due after One Year Through Five Years	801,841
Due After Five Years Through Ten Years	368,933
Due After Ten Years	554,592
Mortgage-Backed and Asset-Backed Securities	1,215,286
Amortized Cost	$ 3,125,413	$ 3,027,408

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, 2018	Dec. 31, 2017
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value			$ 911,581
Less than 12 months Gross Unrealized Losses			(6,271)
Greater than 12 months Fair Value			508,338
Greater than 12 months Gross Unrealized Losses			(9,913)
Fair Value			1,419,919
Gross Unrealized Losses			(16,184)
Fixed Maturities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value		$ 1,216,029	849,475
Less than 12 months Gross Unrealized Losses		(27,511)	(4,666)
Greater than 12 months Fair Value		917,659	505,906
Greater than 12 months Gross Unrealized Losses		(33,038)	(9,846)
Fair Value		2,133,688	1,355,381
Gross Unrealized Losses		(60,549)	(14,512)
Fixed Maturities | U.S. Treasury Bonds, Agency Bonds and Foreign Government Bonds
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value		101,395	273,672
Less than 12 months Gross Unrealized Losses		(2,486)	(1,502)
Greater than 12 months Fair Value		112,195	54,484
Greater than 12 months Gross Unrealized Losses		(1,471)	(512)
Fair Value		213,590	328,156
Gross Unrealized Losses		(3,957)	(2,014)
Fixed Maturities | States, Municipalities and Political Subdivisions
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value		123,479	74,097
Less than 12 months Gross Unrealized Losses		(1,274)	(503)
Greater than 12 months Fair Value		105,405	45,085
Greater than 12 months Gross Unrealized Losses		(2,174)	(920)
Fair Value		228,884	119,182
Gross Unrealized Losses		(3,448)	(1,423)
Fixed Maturities | Agency Residential Mortgage-Backed Securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value		34,819	87,496
Less than 12 months Gross Unrealized Losses		(814)	(346)
Greater than 12 months Fair Value		270,997	236,745
Greater than 12 months Gross Unrealized Losses		(12,304)	(5,068)
Fair Value		305,816	324,241
Gross Unrealized Losses		(13,118)	(5,414)
Fixed Maturities | Residential Mortgage Backed Securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value		70,965	12,418
Less than 12 months Gross Unrealized Losses		(249)	(62)
Greater than 12 months Fair Value		10,110	546
Greater than 12 months Gross Unrealized Losses		(281)	(17)
Fair Value		81,075	12,964
Gross Unrealized Losses		(530)	(79)
Fixed Maturities | Asset-Backed Securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value		345,437	85,877
Less than 12 months Gross Unrealized Losses		(6,950)	(468)
Greater than 12 months Fair Value		77,362	24,733
Greater than 12 months Gross Unrealized Losses		(1,090)	(195)
Fair Value		422,799	110,610
Gross Unrealized Losses		(8,040)	(663)
Fixed Maturities | Commercial Mortgage-Backed Securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value		58,877	20,482
Less than 12 months Gross Unrealized Losses		(282)	(95)
Greater than 12 months Fair Value		41,477	22,903
Greater than 12 months Gross Unrealized Losses		(2,534)	(1,087)
Fair Value		100,354	43,385
Gross Unrealized Losses		(2,816)	(1,182)
Fixed Maturities | Mortgage-Backed and Asset-Backed Securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value		510,098	206,273
Less than 12 months Gross Unrealized Losses		(8,295)	(971)
Greater than 12 months Fair Value		399,946	284,927
Greater than 12 months Gross Unrealized Losses		(16,209)	(6,367)
Fair Value		910,044	491,200
Gross Unrealized Losses		(24,504)	(7,338)
Fixed Maturities | Corporate Exposures
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	[1]	481,057	295,433
Less than 12 months Gross Unrealized Losses	[1]	(15,456)	(1,690)
Greater than 12 months Fair Value	[1]	300,113	121,410
Greater than 12 months Gross Unrealized Losses	[1]	(13,184)	(2,047)
Fair Value	[1]	781,170	416,843
Gross Unrealized Losses	[1]	$ (28,640)	(3,737)
Equity Securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value			62,106
Less than 12 months Gross Unrealized Losses			(1,605)
Greater than 12 months Fair Value			2,432
Greater than 12 months Gross Unrealized Losses			(67)
Fair Value			64,538
Gross Unrealized Losses			(1,672)
Equity Securities | Common Stocks
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value			11,245
Less than 12 months Gross Unrealized Losses			(81)
Greater than 12 months Fair Value			1,770
Greater than 12 months Gross Unrealized Losses			(31)
Fair Value			13,015
Gross Unrealized Losses			(112)
Equity Securities | Preferred Stocks
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value			50,861
Less than 12 months Gross Unrealized Losses			(1,524)
Greater than 12 months Fair Value			662
Greater than 12 months Gross Unrealized Losses			(36)
Fair Value			51,523
Gross Unrealized Losses			$ (1,560)
[1]	Corporate Exposures consist of investments in corporate bonds, hybrid bonds and redeemable preferred stocks.

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, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments Debt And Equity Securities [Abstract]
Beginning Balance	$ 2,361	$ 2,361	$ 2,361
Additions for Credit Loss Impairments recognized in the current period on securities not previously impaired	0	0	150
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	(17)	0	(150)
Ending Balance	$ 2,344	$ 2,361	$ 2,361

Net Investment Income (Detail)

Net Investment Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net Investment Income [Line Items]
Investment Income									$ 106,250	$ 92,956	$ 82,770
Investment Expenses									(3,137)	(3,663)	(3,319)
Net Investment Income	$ 29,159	$ 25,651	$ 24,601	$ 23,702	$ 22,982	$ 22,598	$ 22,265	$ 21,448	103,113	89,293	79,451
Fixed Maturities
Net Investment Income [Line Items]
Investment Income									90,101	76,784	67,772
Equity Securities
Net Investment Income [Line Items]
Investment Income									13,807	15,108	14,271
Short-Term Investments, Cash & Cash Equivalents
Net Investment Income [Line Items]
Investment Income									1,676	428	317
Other Invested Assets
Net Investment Income [Line Items]
Investment Income									$ 666	$ 636	$ 410

Realized Gains and Losses, Excl

Realized Gains and Losses, Excluding Net Other-Than-Temporary Impairment Losses Recognized in Earnings (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Gain (Loss) on Investments [Line Items]
Net Realized Gains (Losses) on Investments Sold	$ (220)	$ 253	$ 1,787	$ 1,169					$ 2,989	$ 45,073	$ 9,186
Net Realized Gains (Losses) on Investments Sold					$ 37,141	$ 5,190	$ 1,694	$ 1,049
Fixed Maturities
Gain (Loss) on Investments [Line Items]
Gains									3,775	4,041	5,681
Losses									(1,306)	(3,249)	(4,271)
Net Realized Gains (Losses) on Investments Sold									2,469	792	1,410
Short-Term Investments, Cash & Cash Equivalents
Gain (Loss) on Investments [Line Items]
Gains									208	1,575	871
Losses									(319)	(243)	(1,444)
Net Realized Gains (Losses) on Investments Sold									(111)	1,332	(573)
Other Invested Assets
Gain (Loss) on Investments [Line Items]
Gains									92	56	19
Losses									(213)	(369)	(108)
Net Realized Gains (Losses) on Investments Sold									(121)	(313)	(89)
Equity Securities
Gain (Loss) on Investments [Line Items]
Gains									1,102
Gains										44,783	9,096
Losses									(350)
Losses										(1,521)	(658)
Net Realized Gains (Losses) on Investments Sold									$ 752
Net Realized Gains (Losses) on Investments Sold										$ 43,262	$ 8,438

Portion of Net Unrealized Losse

Portion of Net Unrealized Losses Recognized to Equity Securities (Detail) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Gain (Loss) on Investments [Line Items]
Net Unrealized Losses on Equity Securities	$ (33,795)	$ 2,310	$ 1,329	$ (3,181)	$ (33,337)	$ 0	$ 0
Equity Securities
Gain (Loss) on Investments [Line Items]
Total Net Realized and Unrealized Losses recognized					(32,585)
Less: Net Realized Gains on Investments Sold					752
Net Unrealized Losses on Equity Securities					$ (33,337)

Fair Value Measurement - Additi

Fair Value Measurement - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Significant transfers between Level 1 and Level 2	$ 0	$ 0
Level 3 assets	0	0
Foreign
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets at fair value	$ 46,500,000	$ 28,800,000
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, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Assets Measured at Fair Value	$ 3,433,048	$ 3,299,515
Total Liabilities Measured at Fair Value	278,150	277,951
Fixed Maturities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	3,082,923	3,057,054
Fixed Maturities | U.S. Treasury Bonds, Agency Bonds and Foreign Government Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	239,776	393,563
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	646,551	814,632
Fixed Maturities | Agency Residential Mortgage-Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	335,542	407,619
Fixed Maturities | Residential Mortgage Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	138,373	54,104
Fixed Maturities | Asset-Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	531,991	328,753
Fixed Maturities | Commercial Mortgage-Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	188,201	160,904
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	1,194,107	951,380
Fixed Maturities | Corporate Exposures
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	1,002,489	897,479
Equity Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	339,892	235,981
Equity Securities | Common Stocks
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	166,353	52,439
Equity Securities | Preferred Stocks
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	173,539	183,542
Short-Term Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	10,233	6,480
Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, at Fair Value	278,150	277,951
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Assets Measured at Fair Value	70,566	237,170
Total Liabilities Measured at Fair Value	0	0
Level 1 | Fixed Maturities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	35,537	178,251
Level 1 | Fixed Maturities | U.S. Treasury Bonds, Agency Bonds and Foreign Government Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	35,537	178,251
Level 1 | 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	0	0
Level 1 | Fixed Maturities | Agency Residential Mortgage-Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	0
Level 1 | Fixed Maturities | Residential Mortgage Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	0
Level 1 | Fixed Maturities | Asset-Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	0
Level 1 | Fixed Maturities | Commercial Mortgage-Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	0
Level 1 | 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	0	0
Level 1 | Fixed Maturities | Corporate Exposures
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	0
Level 1 | Equity Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	35,029	52,439
Level 1 | Equity Securities | Common Stocks
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	35,029	52,439
Level 1 | Equity Securities | Preferred Stocks
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	0
Level 1 | Short-Term Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	6,480
Level 1 | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, at Fair Value	0	0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Assets Measured at Fair Value	3,362,482	3,062,345
Total Liabilities Measured at Fair Value	278,150	277,951
Level 2 | Fixed Maturities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	3,047,386	2,878,803
Level 2 | Fixed Maturities | U.S. Treasury Bonds, Agency Bonds and Foreign Government Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	204,239	215,312
Level 2 | 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	646,551	814,632
Level 2 | Fixed Maturities | Agency Residential Mortgage-Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	335,542	407,619
Level 2 | Fixed Maturities | Residential Mortgage Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	138,373	54,104
Level 2 | Fixed Maturities | Asset-Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	531,991	328,753
Level 2 | Fixed Maturities | Commercial Mortgage-Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	188,201	160,904
Level 2 | 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	1,194,107	951,380
Level 2 | Fixed Maturities | Corporate Exposures
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	1,002,489	897,479
Level 2 | Equity Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	304,863	183,542
Level 2 | Equity Securities | Common Stocks
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	131,324	0
Level 2 | Equity Securities | Preferred Stocks
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	173,539	183,542
Level 2 | Short-Term Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	10,233	0
Level 2 | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, at Fair Value	278,150	277,951
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Assets Measured at Fair Value	0	0
Total Liabilities Measured at Fair Value	0	0
Level 3 | Fixed Maturities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	0
Level 3 | Fixed Maturities | U.S. Treasury Bonds, Agency Bonds and Foreign Government Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	0
Level 3 | 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	0	0
Level 3 | Fixed Maturities | Agency Residential Mortgage-Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	0
Level 3 | Fixed Maturities | Residential Mortgage Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	0
Level 3 | Fixed Maturities | Asset-Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	0
Level 3 | Fixed Maturities | Commercial Mortgage-Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	0
Level 3 | 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	0	0
Level 3 | Fixed Maturities | Corporate Exposures
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	0
Level 3 | Equity Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	0
Level 3 | Equity Securities | Common Stocks
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	0
Level 3 | Equity Securities | Preferred Stocks
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	0
Level 3 | Short-Term Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed Maturities and Equity Securities, at Fair Value	0	0
Level 3 | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, at Fair Value	$ 0	$ 0

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Summary of Analysis of Goodwill by Reporting Segment (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Goodwill [Line Items]
Goodwill at Beginning of the Year	$ 4,460
Goodwill Acquired	12,703
Foreign Currency Translation Adjustment	(345)
Goodwill at End of the Year	16,818
U.S.Insurance
Goodwill [Line Items]
Goodwill at Beginning of the Year	1,978
Goodwill at End of the Year	1,978
International Insurance
Goodwill [Line Items]
Goodwill at Beginning of the Year	2,482
Goodwill Acquired	12,703
Foreign Currency Translation Adjustment	(345)
Goodwill at End of the Year	$ 14,840

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Additional Information (Details) - USD ($) $ in Millions	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2018
ASCO Customer Relationships
Goodwill And Intangible Assets [Line Items]
Finite-Lived Assets, Weighted Average Amortization Period		15 years	10 years
Goodwill
Goodwill And Intangible Assets [Line Items]
Increase (decrease) in fair value of identifiable intangible assets and goodwill	$ 1.4
Finite-Lived Intangible Assets
Goodwill And Intangible Assets [Line Items]
Increase (decrease) in fair value of identifiable intangible assets and goodwill	$ (1.4)

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Summary of Gross Carrying Value and Weighted Average Amortization Period of Intangible Assets by Type (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2018
Intangible Assets [Line Items]
Finite-Lived Assets, Gross Carrying Amount		$ 6,420
Finite-Lived Assets, Accumulated Amortization		(647)
Indefinite-Lived Assets, Gross Carrying Amount		4,555
ASCO Customer Relationships
Intangible Assets [Line Items]
Finite-Lived Assets, Gross Carrying Amount		3,289
Finite-Lived Assets, Accumulated Amortization		$ (164)
Finite-Lived Assets, Weighted Average Amortization Period	15 years	10 years
ASCO VOBA
Intangible Assets [Line Items]
Finite-Lived Assets, Gross Carrying Amount		$ 1,663
Finite-Lived Assets, Accumulated Amortization		$ (208)
Finite-Lived Assets, Weighted Average Amortization Period		4 years
BDM Broker Networks
Intangible Assets [Line Items]
Finite-Lived Assets, Gross Carrying Amount		$ 984
Finite-Lived Assets, Accumulated Amortization		$ (33)
Finite-Lived Assets, Weighted Average Amortization Period		15 years
BDM Trade Name
Intangible Assets [Line Items]
Finite-Lived Assets, Gross Carrying Amount		$ 484
Finite-Lived Assets, Accumulated Amortization		$ (242)
Finite-Lived Assets, Weighted Average Amortization Period		1 year
ASCO European Licenses
Intangible Assets [Line Items]
Indefinite-Lived Assets, Gross Carrying Amount		$ 2,419
NUAL Lloyd's Syndicate Capacity
Intangible Assets [Line Items]
Indefinite-Lived Assets, Gross Carrying Amount		$ 2,136

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Summary of Estimated Remaining Amortization Expense for Finite-Lived Intangible Assets (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Finite Lived Intangible Assets Future Amortization Expense Current And Five Succeeding Fiscal Years [Abstract]
2,019	$ 1,052
2,020	810
2,021	810
2,022	602
2,023	394
2024 and thereafter	2,105
Total	$ 5,773

Summary of Activity in Reserve

Summary of Activity in Reserve for Losses and LAE (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Insurance [Abstract]
Net Reserves for Losses and LAE at Beginning of Year	$ 1,705,380	$ 1,510,451	$ 1,393,126
Acquired Net Reserves	16,159
Provision for Losses and LAE for Claims Occurring in the Current Year	817,537	771,955	693,976
Increase (Decrease) in Estimated Losses and LAE for Claims Occurring in Prior Years	76,242	34,310	(28,528)
Incurred Losses and LAE	893,779	806,265	665,448
Losses and LAE Paid for Claims Occurring During:
Current Year	(124,754)	(144,095)	(119,485)
Prior Years	(554,733)	(478,979)	(412,544)
Losses and LAE Payments	(679,487)	(623,074)	(532,029)
Foreign Currency Adjustment	(12,047)	11,738	(16,094)
Net Reserves for Losses and LAE at End of Period	1,923,784	1,705,380	1,510,451
Reinsurance Recoverables on Unpaid Losses and LAE	820,189	809,765	779,276
Gross Reserves for Losses and LAE at End of Period	$ 2,743,973	$ 2,515,145	$ 2,289,727

Reserves for Losses and LAE - A

Reserves for Losses and LAE - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Increase in incurred losses and LAE	$ 87,500	$ 140,800
Provision for Losses and LAE for Claims Occurring in the Current Year	817,537	771,955	$ 693,976
Net reserve deficiencies (redundancies) in prior years	76,242	34,310	(28,528)
Increase in losses and LAE payments	56,400	91,000
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	18,908	16,714	(1,348)
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	9,387	13,405	5,984
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	10,310	1,613	2,790
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	(789)	1,696	(10,122)
International Insurance
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	31,353	14,834	(25,019)
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	14,478	5,198	4,100
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	(4,913)	3,118	(7,051)
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	21,788	6,518	(22,068)
Global Reinsurance
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	25,981	2,762	(2,161)
Typhoon Jebi
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year	13,900
Hurricane Michael
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year	4,800
Hurricane Florence
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year	3,500
California Camp Fire
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year	3,200
Typhoon Trami
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year	3,000
Other CAT Events
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year	300	9,600
Catastrophe
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year	28,700	84,800
Short-duration Insurance Contracts Incurred But Not Reported IBNR Claims And Recoveries In Excess Of Loss	14,200
Catastrophe | U.S.Insurance
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year	1,800	8,200
Catastrophe | U.S.Insurance | Property Casualty
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year	900	6,600
Catastrophe | U.S.Insurance | Marine
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year	900	1,600
Catastrophe | International Insurance
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year	3,500	32,900
Catastrophe | International Insurance | Property Casualty
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year	1,900	16,900
Catastrophe | International Insurance | Marine
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year	1,600	16,000
Catastrophe | Global Reinsurance
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year	$ 23,400	43,700
Irma
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year		28,300
Maria
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year		23,400
Harvey
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year		15,800
Typhoon Hato
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year		4,200
Puebla, Mexico Earthquake
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year		$ 3,500
Alberta Wildfires
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year			11,700
Hurricane Matthew
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year			7,100
Ecuador Earthquake
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year			3,800
Taiwan Earthquake
Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Provision for Losses and LAE for Claims Occurring in the Current Year			$ 3,300

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, 2018	Dec. 31, 2017	Dec. 31, 2016
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	$ 76,242	$ 34,310	$ (28,528)
U.S.Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	18,908	16,714	(1,348)
U.S.Insurance | Professional Liability
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	9,387	13,405	5,984
U.S.Insurance | Marine
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(789)	1,696	(10,122)
U.S.Insurance | Property Casualty
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	10,310	1,613	2,790
International Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	31,353	14,834	(25,019)
International Insurance | Professional Liability
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	14,478	5,198	4,100
International Insurance | Marine
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	21,788	6,518	(22,068)
International Insurance | Property Casualty
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	(4,913)	3,118	(7,051)
Global Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Net reserve deficiencies (redundancies) in prior years	$ 25,981	$ 2,762	$ (2,161)

Summary of Information about In

Summary of Information about Incurred Claims Development and Cumulative Paid Claims and Allocated Loss Adjustment Expense (ALAE), Net of Reinsurance (Detail) $ in Thousands	Dec. 31, 2018USD ($)Claim	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2012USD ($)	Dec. 31, 2011USD ($)	Dec. 31, 2010USD ($)	Dec. 31, 2009USD ($)
Claims Development [Line Items]
Total Net reserves	$ 1,835,135
U.S.Insurance | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	566,448
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	439,454
Net reserves lesser than 2009	1,327
Total Net reserves	$ 128,321
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 1	5.70%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 2	29.10%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 3	26.40%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 4	13.70%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 5	8.40%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 6	10.00%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 7	3.30%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 8	0.30%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 9	0.40%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 10	0.00%
U.S.Insurance | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	$ 534,837
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	452,549
Net reserves lesser than 2009	7,740
Total Net reserves	$ 90,028
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 1	29.20%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 2	29.90%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 3	16.70%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 4	8.90%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 5	7.70%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 6	3.30%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 7	2.20%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 8	1.80%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 9	0.90%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 10	0.60%
U.S.Insurance | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	$ 1,883,354
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	937,253
Net reserves lesser than 2009	31,867
Total Net reserves	$ 977,968
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 1	4.80%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 2	10.30%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 3	16.50%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 4	19.70%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 5	16.70%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 6	10.50%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 7	6.00%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 8	5.40%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 9	1.90%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 10	2.90%
U.S.Insurance | 2009 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	$ 60,067	$ 61,083	$ 58,143	$ 58,660	$ 58,487	$ 60,789	$ 58,600	$ 61,023	$ 53,273	$ 47,473
Total IBNR	$ 716
Number of Reported Claims | Claim	1,370
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 58,161	58,150	58,095	57,744	53,859	55,378	51,642	41,675	21,742	3,837
U.S.Insurance | 2009 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	50,625	50,545	49,870	50,694	48,488	47,204	49,650	55,277	58,500	62,044
Total IBNR	$ 105
Number of Reported Claims | Claim	2,334
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 49,543	49,252	48,634	45,952	45,106	42,528	40,763	34,769	28,714	12,857
U.S.Insurance | 2009 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	152,609	150,614	151,298	148,126	147,405	142,348	136,835	131,636	130,391	127,749
Total IBNR	$ 4,699
Number of Reported Claims | Claim	8,603
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 144,224	139,768	137,576	130,402	124,908	111,571	87,622	56,453	33,601	$ 11,335
U.S.Insurance | 2010 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	87,687	86,164	85,348	86,787	74,535	75,619	68,375	64,020	52,302
Total IBNR	$ 477
Number of Reported Claims | Claim	1,430
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 85,158	84,529	84,511	82,013	59,765	54,019	46,868	23,147	2,981
U.S.Insurance | 2010 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	55,687	55,316	55,478	55,974	51,791	53,684	59,219	63,221	64,212
Total IBNR	$ 67
Number of Reported Claims | Claim	2,011
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 54,612	54,321	54,163	50,963	47,173	42,017	39,081	31,769	16,258
U.S.Insurance | 2010 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	110,940	111,136	108,894	105,989	104,094	101,134	95,133	97,037	97,426
Total IBNR	$ 5,939
Number of Reported Claims | Claim	7,981
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 100,698	98,053	91,559	86,665	78,243	65,972	47,222	27,036	$ 12,310
U.S.Insurance | 2011 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	82,754	82,558	79,136	79,181	73,028	70,240	62,087	58,116
Total IBNR	$ 715
Number of Reported Claims | Claim	1,726
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 78,382	78,258	75,641	65,710	59,576	43,551	23,878	3,204
U.S.Insurance | 2011 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	58,237	59,151	59,709	61,258	62,464	66,900	68,967	69,652
Total IBNR	$ (95)
Number of Reported Claims | Claim	1,916
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 57,879	57,992	57,350	56,405	51,897	48,443	39,707	14,925
U.S.Insurance | 2011 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	102,403	101,061	98,857	91,267	90,301	87,297	78,420	80,399
Total IBNR	$ 9,172
Number of Reported Claims | Claim	6,623
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 85,885	80,248	71,065	59,038	47,150	30,766	14,694	$ 3,660
U.S.Insurance | 2012 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	58,040	58,563	58,344	55,917	57,097	54,480	61,196
Total IBNR	$ 1,657
Number of Reported Claims | Claim	2,175
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 55,215	54,728	49,675	44,028	35,681	22,635	3,855
U.S.Insurance | 2012 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	72,896	70,573	70,057	68,546	71,941	87,253	84,927
Total IBNR	$ 1,774
Number of Reported Claims | Claim	1,863
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 69,007	68,750	66,950	60,486	54,470	46,215	27,254
U.S.Insurance | 2012 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	118,647	111,459	107,526	99,502	91,780	90,111	103,437
Total IBNR	$ 14,122
Number of Reported Claims | Claim	4,664
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 91,557	83,215	67,772	47,253	27,717	17,404	4,761
U.S.Insurance | 2013 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	58,855	54,228	48,298	49,104	54,982	60,899
Total IBNR	$ 3,230
Number of Reported Claims | Claim	1,984
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 50,909	47,062	38,876	32,904	22,167	4,677
U.S.Insurance | 2013 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	54,033	55,886	53,987	51,464	57,598	60,887
Total IBNR	$ (882)
Number of Reported Claims | Claim	1,818
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 51,245	51,041	46,782	41,281	35,350	17,789
U.S.Insurance | 2013 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	156,793	149,841	137,692	129,385	126,220	139,986
Total IBNR	$ 14,770
Number of Reported Claims | Claim	4,040
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 136,446	118,932	84,874	48,923	21,035	7,188
U.S.Insurance | 2014 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	43,585	41,936	39,699	35,749	49,899
Total IBNR	$ 4,590
Number of Reported Claims | Claim	2,016
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 37,780	35,008	29,309	14,319	2,304
U.S.Insurance | 2014 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	49,366	44,985	40,211	41,454	58,009
Total IBNR	$ 603
Number of Reported Claims | Claim	1,951
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 44,852	40,487	34,453	23,162	10,677
U.S.Insurance | 2014 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	167,782	156,149	149,462	160,828	192,897
Total IBNR	$ 36,292
Number of Reported Claims | Claim	4,154
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 113,585	75,618	44,999	13,569	5,269
U.S.Insurance | 2015 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	35,186	30,802	30,486	31,375
Total IBNR	$ 4,712
Number of Reported Claims | Claim	1,680
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 23,321	18,303	11,173	2,256
U.S.Insurance | 2015 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	48,027	49,341	50,837	59,296
Total IBNR	$ 338
Number of Reported Claims | Claim	2,257
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 43,897	39,927	30,565	16,801
U.S.Insurance | 2015 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	235,390	215,822	220,278	246,404
Total IBNR	$ 39,530
Number of Reported Claims | Claim	4,115
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 142,655	79,639	24,579	3,719
U.S.Insurance | 2016 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	41,299	36,036	41,053
Total IBNR	$ 5,266
Number of Reported Claims | Claim	1,813
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 31,563	18,283	2,351
U.S.Insurance | 2016 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	46,817	47,254	51,289
Total IBNR	$ 2,187
Number of Reported Claims | Claim	2,534
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 38,163	24,566	11,587
U.S.Insurance | 2016 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	242,986	245,905	273,693
Total IBNR	$ 133,717
Number of Reported Claims | Claim	3,772
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 65,439	30,124	5,885
U.S.Insurance | 2017 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	44,346	50,825
Total IBNR	$ 22,367
Number of Reported Claims | Claim	1,980
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 16,246	2,613
U.S.Insurance | 2017 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	49,961	52,135
Total IBNR	$ 10,634
Number of Reported Claims | Claim	2,389
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 32,341	18,861
U.S.Insurance | 2017 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	259,919	298,195
Total IBNR	$ 183,018
Number of Reported Claims | Claim	3,851
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 40,012	13,014
U.S.Insurance | 2018 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	54,629
Total IBNR	$ 46,916
Number of Reported Claims | Claim	2,017
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 2,719
U.S.Insurance | 2018 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	49,188
Total IBNR	$ 28,204
Number of Reported Claims | Claim	1,735
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 11,010
U.S.Insurance | 2018 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	335,885
Total IBNR	$ 301,480
Number of Reported Claims | Claim	3,514
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 16,752
International Insurance | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	292,082
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	129,747
Net reserves lesser than 2009	265
Total Net reserves	$ 162,600
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 1	5.80%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 2	9.40%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 3	16.80%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 4	21.50%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 5	27.10%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 6	2.30%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 7	39.40%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 8	0.90%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 9	2.30%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 10	1.20%
International Insurance | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	$ 967,713
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	759,286
Net reserves lesser than 2009	6,028
Total Net reserves	$ 214,455
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 1	24.70%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 2	34.10%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 3	18.80%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 4	6.90%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 5	6.60%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 6	1.80%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 7	1.70%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 8	0.70%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 9	0.90%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 10	0.00%
International Insurance | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	$ 442,448
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	359,630
Net reserves lesser than 2009	4,550
Total Net reserves	$ 87,368
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 1	25.50%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 2	34.70%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 3	24.50%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 4	10.80%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 5	4.50%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 6	3.30%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 7	(0.40%)
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 8	4.10%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 9	0.20%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 10	3.90%
International Insurance | 2009 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	$ 14,496	15,711	15,752	16,785	17,143	17,061	16,528
Total IBNR	$ 118
Number of Reported Claims | Claim	624
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 14,842	14,674	14,136	13,842	12,857	10,804	8,879
International Insurance | 2009 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	82,896	80,930	81,296	82,730	89,667	90,880	95,612
Total IBNR	$ 2,065
Number of Reported Claims | Claim	4,908
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 78,044	78,007	76,752	76,050	72,605	69,853	65,715
International Insurance | 2009 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	34,679	34,305	34,049	40,488	40,776	40,687	38,479
Total IBNR	$ (100)
Number of Reported Claims | Claim	1,038
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 34,711	33,359	33,276	33,180	33,538	33,079	28,790
International Insurance | 2010 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	16,245	14,376	15,611	14,066	14,076	13,935	14,388
Total IBNR	$ 13
Number of Reported Claims | Claim	746
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 13,566	13,419	13,412	12,688	10,556	7,256	5,861
International Insurance | 2010 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	107,443	107,400	111,165	113,877	118,028	128,878	130,924
Total IBNR	$ 330
Number of Reported Claims | Claim	5,231
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 102,841	102,597	102,161	99,875	95,906	89,896	77,626
International Insurance | 2010 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	40,594	42,285	42,528	41,911	41,628	42,234	42,807
Total IBNR	$ (240)
Number of Reported Claims | Claim	1,026
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 41,505	41,405	40,935	40,818	43,112	40,576	34,935
International Insurance | 2011 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	10,704	12,622	6,872	8,817	19,213	17,971	15,310
Total IBNR	$ 3
Number of Reported Claims | Claim	666
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 16,430	16,367	4,613	4,038	2,965	2,020	1,211
International Insurance | 2011 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	72,008	73,508	73,181	77,099	81,617	84,959	99,374
Total IBNR	$ 107
Number of Reported Claims | Claim	4,855
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 69,962	69,287	68,951	67,988	63,084	58,695	45,400
International Insurance | 2011 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	59,050	54,798	59,238	59,237	59,128	61,290	71,160
Total IBNR	$ (215)
Number of Reported Claims | Claim	1,030
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 58,422	51,940	53,963	53,034	50,480	47,594	38,362
International Insurance | 2012 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	21,691	17,886	16,970	13,302	12,665	11,433	6,810
Total IBNR	$ 2
Number of Reported Claims | Claim	1,107
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 7,675	6,818	7,423	5,533	4,251	3,207	2,123
International Insurance | 2012 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	93,931	91,844	91,991	98,960	106,553	131,234	109,784
Total IBNR	$ 272
Number of Reported Claims | Claim	5,368
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 84,744	82,370	80,449	77,847	69,811	54,300	23,088
International Insurance | 2012 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	32,069	32,830	32,376	32,242	36,167	37,168	45,287
Total IBNR	$ (251)
Number of Reported Claims | Claim	921
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 32,041	31,389	31,136	29,937	26,904	21,436	13,171
International Insurance | 2013 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	15,529	16,575	15,546	14,469	4,232	10,250
Total IBNR	$ 0
Number of Reported Claims | Claim	1,181
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 14,334	13,676	9,349	3,042	2,263	726
International Insurance | 2013 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	79,832	83,094	81,072	81,807	93,736	87,215
Total IBNR	$ 669
Number of Reported Claims | Claim	5,052
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 68,443	66,900	64,075	57,973	45,992	23,455
International Insurance | 2013 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	34,656	35,185	34,221	36,307	37,182	35,862
Total IBNR	$ 154
Number of Reported Claims | Claim	1,298
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 32,715	30,067	28,484	25,649	18,294	7,093
International Insurance | 2014 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	25,411	21,438	23,663	24,419	20,607
Total IBNR	$ 6,564
Number of Reported Claims | Claim	1,775
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 20,192	8,799	5,158	2,464	1,373
International Insurance | 2014 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	112,498	118,195	115,909	117,228	104,464
Total IBNR	$ (6,412)
Number of Reported Claims | Claim	5,125
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 104,801	89,506	80,943	56,964	29,625
International Insurance | 2014 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	17,517	16,363	20,417	22,200	26,741
Total IBNR	$ (497)
Number of Reported Claims | Claim	1,273
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 17,626	16,709	13,150	8,948	3,864
International Insurance | 2015 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	40,182	35,144	30,322	28,132
Total IBNR	$ 5,923
Number of Reported Claims | Claim	2,483
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 21,128	17,242	5,864	3,417
International Insurance | 2015 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	99,103	95,449	94,055	98,245
Total IBNR	$ (1,843)
Number of Reported Claims | Claim	7,664
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 80,684	75,185	53,995	22,651
International Insurance | 2015 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	32,566	33,703	36,391	34,678
Total IBNR	$ (86)
Number of Reported Claims | Claim	2,045
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 30,659	29,420	18,293	6,780
International Insurance | 2016 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	35,873	34,074	36,103
Total IBNR	$ 15,285
Number of Reported Claims | Claim	3,212
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 10,931	6,857	2,051
International Insurance | 2016 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	89,992	94,464	87,690
Total IBNR	$ 1,561
Number of Reported Claims | Claim	10,085
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 66,912	54,708	23,357
International Insurance | 2016 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	74,382	91,431	78,827
Total IBNR	$ 987
Number of Reported Claims | Claim	3,800
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 66,743	55,287	25,971
International Insurance | 2017 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	45,128	47,610
Total IBNR	$ 32,642
Number of Reported Claims | Claim	3,642
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 5,881	1,992
International Insurance | 2017 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	135,759	107,151
Total IBNR	$ 15,783
Number of Reported Claims | Claim	12,028
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 77,451	28,774
International Insurance | 2017 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	70,448	56,376
Total IBNR	$ 15,782
Number of Reported Claims | Claim	3,209
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 35,628	14,875
International Insurance | 2018 | Professional Liability
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	66,823
Total IBNR	$ 55,207
Number of Reported Claims | Claim	2,031
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 4,768
International Insurance | 2018 | Marine
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	94,251
Total IBNR	$ 16,778
Number of Reported Claims | Claim	7,603
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 25,404
International Insurance | 2018 | Property Casualty
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	46,487
Total IBNR	$ 15,981
Number of Reported Claims | Claim	1,053
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 9,580
Global Reinsurance
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	905,235
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	732,710
Net reserves lesser than 2009	1,870
Total Net reserves	$ 174,395
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 1	28.40%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 2	34.00%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 3	6.60%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 4	5.60%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 5	9.00%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 6	2.00%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 7	0.30%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 8	0.70%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 9	0.10%
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance 10	0.70%
Global Reinsurance | 2009
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	$ 10,610	10,307	10,466	10,426	11,171	11,290	11,158
Total IBNR	$ 338
Number of Reported Claims | Claim	201
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 10,118	10,049	10,049	9,939	8,992	8,865	8,635
Global Reinsurance | 2010
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	13,073	13,012	12,476	11,796	14,012	12,997	13,036
Total IBNR	$ 21
Number of Reported Claims | Claim	202
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 11,203	11,170	11,105	11,058	10,439	10,263	9,927
Global Reinsurance | 2011
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	73,474	73,428	72,782	73,528	76,054	76,261	53,778
Total IBNR	$ (586)
Number of Reported Claims | Claim	740
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 72,743	72,345	72,177	72,038	71,754	71,086	43,412
Global Reinsurance | 2012
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	118,477	119,565	114,856	88,203	92,584	99,019	107,134
Total IBNR	$ (1,218)
Number of Reported Claims | Claim	1,395
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 118,006	117,631	111,816	84,668	83,287	77,147	$ 37,709
Global Reinsurance | 2013
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	101,705	102,323	105,049	102,514	118,688	114,785
Total IBNR	$ (561)
Number of Reported Claims | Claim	1,271
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 100,981	99,965	98,393	90,649	82,641	$ 53,445
Global Reinsurance | 2014
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	114,981	118,131	121,591	141,968	119,351
Total IBNR	$ 860
Number of Reported Claims | Claim	1,172
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 111,712	108,693	105,574	119,195	$ 66,271
Global Reinsurance | 2015
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	93,693	94,187	91,526	101,626
Total IBNR	$ 5,777
Number of Reported Claims | Claim	1,033
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 82,942	76,837	64,425	$ 41,623
Global Reinsurance | 2016
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	97,921	90,567	88,401
Total IBNR	$ 5,781
Number of Reported Claims | Claim	1,022
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 84,245	66,141	$ 36,312
Global Reinsurance | 2017
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	153,017	129,001
Total IBNR	$ 19,356
Number of Reported Claims | Claim	1,018
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 115,743	$ 43,639
Global Reinsurance | 2018
Claims Development [Line Items]
Loss and ALAE, Net of Reinsurance	128,284
Total IBNR	$ 83,977
Number of Reported Claims | Claim	435
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 25,017

Summary of Reconciliation of Ne

Summary of Reconciliation of Net Incurred and Paid Claims Development to the Reserve for Losses and LAE (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Shortduration Insurance Contracts Reconciliation Of Claims Development To Liability [Line Items]
Total Net Reserves	$ 1,835,135
Reinsurance Recoverables on Unpaid Claims	804,633
Total Gross Reserves	2,639,768
Unallocated Claims Adjustment Expenses	72,099
ASCO Reserves	31,834
Other	272
Total Gross Liability for Unpaid Claims and Claim Adjustment Expense	2,743,973	$ 2,515,145	$ 2,289,727
U.S.Insurance | Professional Liability
Shortduration Insurance Contracts Reconciliation Of Claims Development To Liability [Line Items]
Total Net Reserves	128,321
Reinsurance Recoverables on Unpaid Claims	54,052
Total Gross Reserves	182,373
U.S.Insurance | Marine
Shortduration Insurance Contracts Reconciliation Of Claims Development To Liability [Line Items]
Total Net Reserves	90,028
Reinsurance Recoverables on Unpaid Claims	88,783
Total Gross Reserves	178,811
U.S.Insurance | Property Casualty
Shortduration Insurance Contracts Reconciliation Of Claims Development To Liability [Line Items]
Total Net Reserves	977,968
Reinsurance Recoverables on Unpaid Claims	387,081
Total Gross Reserves	1,365,049
International Insurance | Professional Liability
Shortduration Insurance Contracts Reconciliation Of Claims Development To Liability [Line Items]
Total Net Reserves	162,600
Reinsurance Recoverables on Unpaid Claims	86,970
Total Gross Reserves	249,570
International Insurance | Marine
Shortduration Insurance Contracts Reconciliation Of Claims Development To Liability [Line Items]
Total Net Reserves	214,455
Reinsurance Recoverables on Unpaid Claims	68,117
Total Gross Reserves	282,572
International Insurance | Property Casualty
Shortduration Insurance Contracts Reconciliation Of Claims Development To Liability [Line Items]
Total Net Reserves	87,368
Reinsurance Recoverables on Unpaid Claims	106,879
Total Gross Reserves	194,247
Global Reinsurance
Shortduration Insurance Contracts Reconciliation Of Claims Development To Liability [Line Items]
Total Net Reserves	174,395
Reinsurance Recoverables on Unpaid Claims	12,751
Total Gross Reserves	$ 187,146

Ceded Reinsurance - Additional

Ceded Reinsurance - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Effects of Reinsurance [Line Items]
Minimum amount of policyholders' surplus for reinsurance	$ 500,000,000
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	$ 13,400,000	$ 12,600,000
Collateral held	205,917,000
Ceded Balances Payable
Effects of Reinsurance [Line Items]
Collateral held	145,000,000
Letter of Credit
Effects of Reinsurance [Line Items]
Collateral held	41,200,000
Trust Account Balances
Effects of Reinsurance [Line Items]
Collateral held	$ 19,700,000

Lists of 10 Largest Reinsurers

Lists of 10 Largest Reinsurers Measured by Reinsurance Recoverable (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		$ 226,723	$ 228,569
Reinsurance Recoverables Paid/Unpaid Losses	[1]	938,448
Reinsurance Recoverables Total		1,165,171
Collateral Held		205,917
National Indemnity Company | AM Best, A++ Rating | Standard & Poor's, AA+ Rating
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		5,338
Reinsurance Recoverables Paid/Unpaid Losses	[1]	61,540
Reinsurance Recoverables Total		66,878
Collateral Held		$ 8,320
National Indemnity Company | AM Best, A++ Rating | AM Best | Standard & Poor's, AA+ Rating
Ceded Credit Risk [Line Items]
Rating		A++
National Indemnity Company | AM Best, A++ Rating | Standard & Poor's | 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		$ 34,809
Reinsurance Recoverables Paid/Unpaid Losses	[1]	106,334
Reinsurance Recoverables Total		141,143
Collateral Held		$ 1,547
Everest Reinsurance Company | AM Best, A+ Rating | AM Best | Standard & Poor's, A+ Rating
Ceded Credit Risk [Line Items]
Rating		A+
Everest Reinsurance Company | AM Best, A+ Rating | Standard & Poor's | 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		$ 13,514
Reinsurance Recoverables Paid/Unpaid Losses	[1]	64,457
Reinsurance Recoverables Total		77,971
Collateral Held		$ 4,223
Swiss Reinsurance America Corporation | AM Best, A+ Rating | AM Best | Standard & Poor's, AA- Rating
Ceded Credit Risk [Line Items]
Rating		A+
Swiss Reinsurance America Corporation | AM Best, A+ Rating | Standard & Poor's | 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		$ 7,597
Reinsurance Recoverables Paid/Unpaid Losses	[1]	48,328
Reinsurance Recoverables Total		55,925
Collateral Held		$ 2,541
Transatlantic Reinsurance Company | AM Best, A+ Rating | AM Best | Standard & Poor's, A+ Rating
Ceded Credit Risk [Line Items]
Rating		A+
Transatlantic Reinsurance Company | AM Best, A+ Rating | Standard & Poor's | 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		$ 10,932
Reinsurance Recoverables Paid/Unpaid Losses	[1]	41,369
Reinsurance Recoverables Total		52,301
Collateral Held		$ 6,054
Munich Reinsurance America Inc | AM Best, A+ Rating | AM Best | Standard & Poor's, AA- Rating
Ceded Credit Risk [Line Items]
Rating		A+
Munich Reinsurance America Inc | AM Best, A+ Rating | Standard & Poor's | 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		$ 7,303
Reinsurance Recoverables Paid/Unpaid Losses	[1]	30,439
Reinsurance Recoverables Total		37,742
Collateral Held		$ 1,757
Allied World Reinsurance | AM Best, A Rating | AM Best | Standard & Poor's, A- Rating
Ceded Credit Risk [Line Items]
Rating		A
Allied World Reinsurance | AM Best, A Rating | Standard & Poor's | 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		$ 16,491
Reinsurance Recoverables Paid/Unpaid Losses	[1]	34,445
Reinsurance Recoverables Total		50,936
Collateral Held		$ 18,120
Employers Mutual Casualty Company | AM Best, A Rating | AM Best | Standard & Poor's, Not Rated
Ceded Credit Risk [Line Items]
Rating		A
Employers Mutual Casualty Company | AM Best, A Rating | Standard & Poor's | Standard & Poor's, Not Rated
Ceded Credit Risk [Line Items]
Rating		NR
Aspen Insurance UK Ltd. | AM Best, A Rating | Standard & Poor's, A Rating
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		$ 11,801
Reinsurance Recoverables Paid/Unpaid Losses	[1]	31,508
Reinsurance Recoverables Total		43,309
Collateral Held		$ 6,446
Aspen Insurance UK Ltd. | AM Best, A Rating | AM Best | Standard & Poor's, A Rating
Ceded Credit Risk [Line Items]
Rating		A
Aspen Insurance UK Ltd. | AM Best, A Rating | Standard & Poor's | Standard & Poor's, A Rating
Ceded Credit Risk [Line Items]
Rating		A
XL Reinsurance America Inc. | AM Best, A+ Rating | Standard & Poor's, AA- Rating
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		$ 7,240
Reinsurance Recoverables Paid/Unpaid Losses	[1]	21,250
Reinsurance Recoverables Total		28,490
Collateral Held		$ 2,761
XL Reinsurance America Inc. | AM Best, A+ Rating | AM Best | Standard & Poor's, AA- Rating
Ceded Credit Risk [Line Items]
Rating		A+
XL Reinsurance America Inc. | AM Best, A+ Rating | Standard & Poor's | Standard & Poor's, AA- Rating
Ceded Credit Risk [Line Items]
Rating		AA-
Ace Property & Casualty Insurance Company | AM Best, A++ Rating | Standard & Poor's, AA Rating
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		$ 1,591
Reinsurance Recoverables Paid/Unpaid Losses	[1]	24,148
Reinsurance Recoverables Total		25,739
Collateral Held		$ 63
Ace Property & Casualty Insurance Company | AM Best, A++ Rating | AM Best | Standard & Poor's, AA Rating
Ceded Credit Risk [Line Items]
Rating		A++
Ace Property & Casualty Insurance Company | AM Best, A++ Rating | Standard & Poor's | Standard & Poor's, AA Rating
Ceded Credit Risk [Line Items]
Rating		AA
Insurance Companies
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		$ 116,616
Reinsurance Recoverables Paid/Unpaid Losses	[1]	463,818
Reinsurance Recoverables Total		580,434
Collateral Held		51,832
All Others
Ceded Credit Risk [Line Items]
Reinsurance Recoverables Unearned Premium		110,107
Reinsurance Recoverables Paid/Unpaid Losses	[1]	474,630
Reinsurance Recoverables Total		584,737
Collateral Held		$ 154,085
[1]	Net of reserve for uncollectible reinsurance of approximately $13.4 million.

Lists of 10 Largest Reinsurer_2

Lists of 10 Largest Reinsurers Measured by Reinsurance Recoverable (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Insurance [Abstract]
Reserve for uncollectible reinsurance amount	$ 13.4	$ 12.6

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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Insurance [Abstract]
Direct									$ 1,613,825	$ 1,489,422	$ 1,403,865
Assumed									299,136	223,843	165,046
Ceded written premiums									(441,876)	(441,935)	(382,687)
Net written premiums	$ 346,119	$ 352,412	$ 379,292	$ 393,262	$ 304,869	$ 296,016	$ 333,282	$ 337,163	$ 1,471,085	$ 1,271,330	$ 1,186,224

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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Insurance [Abstract]
Direct									$ 1,553,852	$ 1,425,582	$ 1,330,265
Assumed									256,509	187,609	171,978
Ceded									(447,138)	(426,771)	(401,898)
Net Earned Premiums	$ 362,543	$ 347,038	$ 331,015	$ 322,627	$ 305,099	$ 301,355	$ 293,835	$ 286,131	$ 1,363,223	$ 1,186,420	$ 1,100,345

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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Insurance [Abstract]
Direct									$ 1,002,358	$ 938,640	$ 795,414
Assumed									159,989	148,606	87,995
Ceded									(268,568)	(280,981)	(217,961)
Net Losses and LAE	$ 270,401	$ 240,900	$ 196,333	$ 186,145	$ 183,384	$ 276,171	$ 177,110	$ 169,600	$ 893,779	$ 806,265	$ 665,448

Debt - Additional Information (

Debt - Additional Information (Detail) £ in Millions, $ in Millions	Nov. 07, 2018USD ($)Tranche	Nov. 07, 2016	Nov. 04, 2016GBP (£)	Oct. 04, 2013USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2018GBP (£)	Dec. 31, 2018AUD ($)	Nov. 07, 2018GBP (£)Tranche	Dec. 31, 2017USD ($)
Line of Credit Facility [Line Items]
Issuance of new letters of credit, expiry date					Dec. 31, 2020
Line of credit facility, covenant terms					The Bilateral and Club Facilities contain 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 and our subsidiaries, the occurrence of certain material judgments, or a change in control of our Company. During the first quarter of 2018, the Company reclassified certain overseas deposits from Short-Term Investments to Other Invested Assets. Refer to Note 1 Organization & Summary of Significant Accounting Policies. Although the nature of the investments did not change, this reclassification caused the Company to exceed a covenant of our Club Facility that sets a limitation on other investments as a percentage of total investments. During the second quarter of 2018, our Company received a waiver of compliance with respect to this covenant, which was subsequently amended to increase the percentage of other investments permitted. As of December 31, 2018, our Company was in compliance with all covenants.
Senior Notes
Line of Credit Facility [Line Items]
Unamortized discount					$ 900,000				$ 1,100,000
5.75% Senior Notes
Line of Credit Facility [Line Items]
Interest rate stated on senior notes					5.75%	5.75%	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				$ 265,000,000
Interest rate stated on senior notes				5.75%
Net proceeds from issuance of senior notes				$ 263,300,000
Debt instrument, covenant compliance					As of December 31, 2018, 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%	7.00%	7.00%
Senior notes due date					May 1, 2016
Call premium on redemption of Senior notes					$ 17,900,000
Club Facility
Line of Credit Facility [Line Items]
Number of tranches | Tranche	2							2
Club Facility | Minimum
Line of Credit Facility [Line Items]
Credit facility fee rate	0.95%
Club Facility | Maximum
Line of Credit Facility [Line Items]
Credit facility fee rate	1.60%
Club Facility | Tranche One Extending
Line of Credit Facility [Line Items]
Line of credit, commitment	$ 165,000,000
Club Facility | Tranche Two Extending
Line of Credit Facility [Line Items]
Line of credit, commitment | £								£ 60
Bilateral Facility
Line of Credit Facility [Line Items]
Line of credit facility	$ 25,000,000
Additional extended term		2 years
Bilateral Facility | Minimum
Line of Credit Facility [Line Items]
Credit facility fee rate	0.85%
Bilateral Facility | Maximum
Line of Credit Facility [Line Items]
Credit facility fee rate	1.20%
Syndicate 1,221
Line of Credit Facility [Line Items]
Aggregate face amount of letters of credit outstanding							$ 24
Line of credit facility, covenant compliance					As of December 31, 2018, our Company was in compliance with all covenants.
Syndicate 1221 | Line of Credit
Line of Credit Facility [Line Items]
Line of credit facility, interest rate			1.55%
Lloyd's | Syndicate 1221
Line of Credit Facility [Line Items]
Line of credit facility, underwriting reserve required | £			£ 75
Lloyd's | Syndicate 1221 | Club Facility
Line of Credit Facility [Line Items]
Aggregate face amount of letters of credit outstanding					$ 165,000,000	£ 60
Cash collateral posted					1,200,000
Lloyd's | Syndicate 1221 | Bilateral Facility
Line of Credit Facility [Line Items]
Aggregate face amount of letters of credit outstanding					$ 8,000,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Aug. 22, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2013
Loss Contingencies [Line Items]
Rent expense			$ 12,200	$ 13,200	$ 13,200
Incentive awarded to the company by the State of Connecticut, total						$ 11,500
Incentive awarded to the company by the State of Connecticut, non-interest bearing loans						8,000
Incentive awarded to the company by the State of Connecticut, grants						$ 3,500
Non-interest bearing incentive loan term			10 years
Forgiveness awarded to the company by the state of Connecticut	$ 7,000
Incentive awarded to the company by the State of Connecticut, other revenue recognized			$ 1,300	1,300	$ 1,400
Incentive awarded to the company by the State of Connecticut, deferred revenue included in other liabilities	$ 4,700		$ 4,700	$ 4,400
The Hartford
Loss Contingencies [Line Items]
Merger Termination Fee		$ 68,250
Maximum
Loss Contingencies [Line Items]
Non-cancellable operating leases expiration year			2,032

Future Minimum Annual Rental Co

Future Minimum Annual Rental Commitments Under Various Non-cancellable Operating Leases (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Leases [Abstract]
2,019	$ 12,907
2,020	12,470
2,021	11,542
2,022	10,354
2,023	9,379
2024-2032	28,268
Total Minimum Operating Lease Payments	$ 84,920

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Corporate income tax rate			21.00%	35.00%	35.00%
Transition tax		$ 2,600		$ 2,600
Tax benefit (expense) related to transition tax			$ 1,300
Tax benefit (expense) related to remeasurement of net deferred tax assets	$ 500
Deferred Tax Assets: State and Local	3,551	616	3,551	616
Decrease in net valuation allowance			800
Unrecognized tax benefits	$ 6,350	$ 0	6,350	$ 0
Interest related to unrecognized tax benefits			860
Interest related to unrecognized tax benefits, net of tax			600
Penalties			$ 0
United Kingdom
Income Taxes [Line Items]
Foreign effective income tax rate			21.00%
Decrease in net valuation allowance			$ 1,200
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			21.00%

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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current Income Tax Expense (Benefit):
Federal and Foreign									$ 27,768	$ 42,427	$ 39,900
State and Local									934	764	638
Subtotal									28,702	43,191	40,538
Deferred Income Tax Expense (Benefit):
Federal and Foreign									(14,366)	(8,879)	(5,755)
State and local									0	0	0
Subtotal									(14,366)	(8,879)	(5,755)
Actual Tax Expense and Rate	$ 879	$ (462)	$ 7,684	$ 6,235	$ 36,555	$ (16,864)	$ 6,971	$ 7,650	$ 14,336	$ 34,312	$ 34,783

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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation
Computed Expected Tax Expense									$ 10,201	$ 26,182	$ 41,128
Tax-Exempt Interest									(3,356)	(5,394)	(4,559)
Dividends Received Deduction									(2,041)	(4,689)	(3,812)
Proration of DRD and Tax-Exempt Interest									1,330	1,512	1,256
State and Local Income Taxes, Net of Federal Income Tax Deduction									738	497	415
Stock Compensation Fair Market Value									(1,711)	(5,027)
Change in Valuation Allowance									(774)	1,182
Deferred Tax Expense due to Tax Law Changes									(506)	17,107
Transition Tax									(1,314)	2,587
Uncertain Tax Position - FTC IRS Audit									7,029
Non-Deductible Expenses									1,197	405	406
Return to Provision									2,326	(158)	1
Other									1,217	108	(52)
Actual Tax Expense and Rate	$ 879	$ (462)	$ 7,684	$ 6,235	$ 36,555	$ (16,864)	$ 6,971	$ 7,650	$ 14,336	$ 34,312	$ 34,783
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation
Computed Expected Tax Expense									21.00%	35.00%	35.00%
Tax-Exempt Interest									(6.90%)	(7.20%)	(3.90%)
Dividends Received Deduction									(4.20%)	(6.30%)	(3.20%)
Proration of DRD and Tax-Exempt Interest									2.70%	2.00%	1.10%
State and Local Income Taxes, Net of Federal Income Tax Deduction									1.50%	0.70%	0.40%
Stock Compensation Fair Market Value									(3.50%)	(6.70%)
Change in Valuation Allowance									(1.60%)	1.60%
Deferred Tax Expense due to Tax Law Changes									(1.00%)	22.90%
Transition Tax									(2.70%)	3.50%
Uncertain Tax Position - FTC IRS Audit									14.50%
Non-Deductible Expenses									2.50%	0.50%	0.20%
Return to Provision									4.80%	(0.20%)	0.00%
Other									2.40%	0.10%	0.00%
Actual Tax Expense and Rate									29.50%	45.90%	29.60%

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, 2018	Dec. 31, 2017
Deferred Tax Assets:
Loss Reserve Discount	$ 26,468	$ 20,425
Unearned Premiums	29,500	24,352
Compensation Related	9,433	8,462
State and Local	3,551	616
Net Currency Translation Adjustments	299	2,084
Net Unrealized Losses on Securities	11,553
Other	3,598	152
Total Gross Deferred Tax Assets	97,025	65,491
Less: Valuation Allowance	(4,367)	(1,798)
Total Deferred Tax Assets	92,658	63,693
Deferred Tax Liabilities:
Loss Reserve Discount - Transition Rule	(7,570)	(5,066)
Net Unrealized Gains on Securities		(8,708)
Deferred Acquisition Costs	(25,109)	(20,670)
Claims Equalization Reserve	(7,913)
Net Unrealized Foreign Exchange	(3,769)	(3,782)
Intangibles	(3,438)
Other	(2,562)	(3,196)
Total Deferred Tax Liabilities	50,361	41,422
Net Deferred Income Tax Asset	42,297	22,271
Lloyd's
Deferred Tax Assets:
Lloyd's Year of Account Deferral	$ 12,623	$ 9,400

Summary of Income Tax Contingen

Summary of Income Tax Contingencies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits, Balance	$ 0
Additions for Tax Positions of Prior Years	6,350
Reductions for Tax Positions of Prior Years	0
Additions for Tax Positions of Current Year	0
Reductions for Tax Positions of Current Year	0
Settlements with Tax Authorities	0
Lapse of Statute of Limitations	0
Unrecognized Tax Benefits, Balance	6,350
Unrecognized Tax Benefits that, if Recognized, would Impact the Effective Rate	$ 6,350

Accrued Interest and Penalties

Accrued Interest and Penalties on Unrecognized Tax Benefits (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Income Tax Disclosure [Abstract]
Interest related to unrecognized tax benefits	$ 860
Interest Included in Other Liabilities on the Consolidated Balance Sheets	$ 860

Stockholders Equity - Additiona

Stockholders Equity - Additional Information (Detail) $ / shares in Units, $ in Millions	Dec. 30, 2016shares	Dec. 06, 2016	Nov. 30, 2018USD ($)	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016$ / shares
Stockholders Equity [Line Items]
Common stock, authorized shares | shares				50,000,000	50,000,000	50,000,000
Common stock, par value | $ / shares				$ 0.10	$ 0.10	$ 0.10
Preferred stock, authorized shares | shares				1,000,000	1,000,000	1,000,000
Preferred stock, par value | $ / shares				$ 0.10	$ 0.10	$ 0.10
Stock split ratio		2
Stockholders equity, stock split					On December 6, 2016, our Board of Directors declared a two-for-one stock split of The Navigators Group, Inc. Common stock, to be effected in the form of a stock dividend.
Number of additional shares for every share held | shares	1
Common stock dividend paid per share | $ / shares					$ 0.28	$ 0.225	$ 0.135
Maximum
Stockholders Equity [Line Items]
Quarterly cash dividend payments restricted per share | $ / shares				$ 0.07
NCUL
Stockholders Equity [Line Items]
Undistributed Profit | $			$ 235.8
NIIC
Stockholders Equity [Line Items]
Maximum amount available for payment of dividends without prior regulatory approval | $				$ 20.3	$ 20.3
Navigators Insurance Company
Stockholders Equity [Line Items]
Maximum amount available for payment of dividends without prior regulatory approval | $				$ 5.2	5.2
Dividend paid | $					$ 97	$ 19

Changes in Issued and Outstandi

Changes in Issued and Outstanding Common Shares (Detail) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Equity [Abstract]
Beginning Balance	29,507,000	29,124,000	28,862,000
Net Vested Stock Grants	230,000	343,000	220,000
Employee Stock Purchase Plan	45,000	40,000	42,000
Ending Balance	29,782,000	29,507,000	29,124,000

Amount and Nature of Net Assets

Amount and Nature of Net Assets Restricted from Payment of Dividends (Detail) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets		$ 597,417	$ 567,482
NIC and NSIC
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets	[1]	16,515	13,773
NIC and NSIC | Fixed Maturities
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets		10,441	10,655
NIC and NSIC | Cash
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets	[2]	6,074	3,118
NHUK
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets	[3]	580,889	553,709
NHUK | Fixed Maturities
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets		474,128	471,831
NHUK | Cash
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets	[2]	60,233	53,111
NHUK | Other Invested Assets
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets	[2]	46,528	$ 28,767
All other Entities
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets		13
All other Entities | Cash
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Total Restricted Net Assets		$ 13
[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, 2018 and 2017, as presented in the table above, is held in various collateral accounts to support underwriting activities.
[2]	Cash and overseas deposits that were misclassified within Short-Term Investments prior to 2018 were reclassified, representing an immaterial correction. Refer to Note 1 Organization & Summary of Significant Accounting Policies for further information.
[3]	- The restricted net assets for NHUK consists of fixed maturities and cash held in trust for the benefit of syndicate policyholders and other invested assets primarily consisting of overseas deposits in various countries with Lloyd's to support underwriting activities in those countries

Amount and Nature of Net Asse_2

Amount and Nature of Net Assets Restricted from Payment of Dividends (Parenthetical) (Detail) - Fixed Maturities - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
NIC and NSIC
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Restricted net assets, amortized cost	$ 9,890	$ 9,856
NHUK
Restricted Assets And Liabilities Relating To Securitization [Line Items]
Restricted net assets, amortized cost	$ 481,501	$ 472,701

Reconciliation of Basic and Dil

Reconciliation of Basic and Diluted Earnings per Share Computations (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earning Per Share Basic And Diluted [Abstract]
Net Income	$ (33,368)	$ 4,625	$ 32,104	$ 30,878	$ 26,861	$ (27,979)	$ 20,502	$ 21,110	$ 34,239	$ 40,494	$ 82,726
Basic weighted average shares									29,720	29,441	29,074
Effect of Common Stock Equivalents:
Assumed Vesting of Stock Grants									473	630	958
Diluted Weighted Average Shares									30,193	30,071	30,032
Net Income Per Common Share:
Basic	$ (1.12)	$ 0.16	$ 1.08	$ 1.04	$ 0.91	$ (0.95)	$ 0.70	$ 0.72	$ 1.15	$ 1.38	$ 2.85
Diluted	$ (1.12)	$ 0.15	$ 1.07	$ 1.02	$ 0.89	$ (0.95)	$ 0.69	$ 0.70	$ 1.13	$ 1.35	$ 2.75

Summary of Statutory Net Income

Summary of Statutory Net Income (Loss) and Capital and Surplus (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
NIC and NSIC
Statutory Accounting Practices [Line Items]
Net Income	$ 75	$ 79.3	$ 84.2
Capital and Surplus	1,005.4	1,056.6	1,027.3
Syndicate
Statutory Accounting Practices [Line Items]
Net Income	6.8	(23.4)	46.3
Capital and Surplus	165.3	168.7	180.7
NIIC
Statutory Accounting Practices [Line Items]
Net Income	(14.7)	(8.4)	0.4
Capital and Surplus	$ 43.3	$ 62.9	$ 70.7

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 20, 2017	Apr. 30, 2013	Apr. 30, 2009	May 31, 2005
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock split effective date									Jan. 20, 2017
Stockholders equity, stock split									On December 6, 2016, our Board of Directors declared a two-for-one stock split of The Navigators Group, Inc. Common stock, to be effected in the form of a stock dividend.
Total compensation cost for share-based payment arrangements recognized in income statement									$ 6,800,000	$ 13,800,000	$ 17,600,000
Income tax benefits	$ 879,000	$ (462,000)	$ 7,684,000	$ 6,235,000	$ 36,555,000	$ (16,864,000)	$ 6,971,000	$ 7,650,000	14,336,000	34,312,000	$ 34,783,000
Unrecognized compensation expense	11,800,000				18,000,000				$ 11,800,000	$ 18,000,000
Weighted Average Periods									1 year 9 months 18 days	1 year 10 months 25 days
Aggregate fair value of all unvested RSU	$ 44,600,000				$ 49,900,000				$ 44,600,000	$ 49,900,000
Employee Stock Purchase Plan, shares purchased by employees									45,000	40,000	42,000
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%
Percentage of employees base compensation that can be invested for the purchase of common stock, maximum	10.00%								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									45,008	40,488
Discount on employee stock purchase plan									10.00%
Share-based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Income tax benefits									$ (1,400,000)	$ (2,900,000)	$ (6,200,000)
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of awards, granted									24,593	35,297	84,000
Weighted average grant-date fair values per share									$ 50.01	$ 56.05	$ 44.52
Total fair value of shares vested									$ 5,300,000	$ 3,300,000	$ 2,500,000
Performance-based Equity Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of awards, granted									247,554	253,333	404,946
Weighted average grant-date fair values per share									$ 54.15	$ 55.70	$ 40.77
Total fair value of shares vested									$ 15,300,000	$ 29,000,000	$ 11,500,000
Minimum | Non-Performance Based Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based payment award, award vesting period									3 years
Minimum | Performance Based Shares Issued in 2017, 2016 and 2015 | 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%
Maximum | Non-Performance Based Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based payment award, award vesting period									4 years
Maximum | Performance Based Shares Issued in 2017, 2016 and 2015 | 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%
2005 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock authorized for issuance															1,000,000
Second Amended and Restated 2005 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock authorized for issuance												4,000,000	2,000,000
Stockholders equity, stock split									The stock split that occurred on January 20, 2017 doubled the number of awards from 2,000,000 to 4,000,000.
Stock issued during period under incentive plan									3,192,376
Number of stock available to be issued	807,624								807,624
First Amended and Restated 2005 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock authorized for issuance														1,500,000

Restricted Stock Unit Awards (D

Restricted Stock Unit Awards (Detail) - Restricted Stock Units (RSUs) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Awards
Nonvested at the beginning of the year	159,539
Granted	24,593	35,297	84,000
Vested	(90,543)
Forfeited	(7,000)
Nonvested at the end of the year	86,589	159,539
Weighted Average Grant Date Fair Value
Nonvested at the beginning of the year	$ 41.60
Granted	50.01	$ 56.05	$ 44.52
Vested	36.66
Forfeited	38
Nonvested at the end of the year	$ 49.45	$ 41.60

Restricted Stock Unit Awards (P

Restricted Stock Unit Awards (Parenthetical) (Detail) - Restricted Stock Units (RSUs)	12 Months Ended
	Dec. 31, 2018$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share awards withheld for tax payments | shares	34,430
Weighted average vest date fair value, withheld for tax payments | $ / shares	$ 58.44

Performance-based Equity Awards

Performance-based Equity Awards (Detail) - Performance-based Equity Awards - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Awards
Nonvested at the beginning of the year	966,361
Granted	247,554	253,333	404,946
Performance Adjustment	(59,833)
Vested	(274,299)
Forfeited	(34,250)
Nonvested at the end of the year	845,533	966,361
Weighted Average Grant Date Fair Value
Nonvested at the beginning of the year	$ 43.39
Granted	54.15	$ 55.70	$ 40.77
Performance Adjustment	37.25
Vested	37.25
Forfeited	46
Nonvested at the end of the year	$ 48.86	$ 43.39

Performance-based Equity Awar_2

Performance-based Equity Awards (Parenthetical) (Detail) - Performance-based Equity Awards	12 Months Ended
	Dec. 31, 2018$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share awards withheld for tax payments | shares	117,005
Weighted average vest date fair value, withheld for tax payments | $ / shares	$ 55.65

Retirement Plans - Additional I

Retirement Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Funded status of plan	$ (0.7)
Defined benefit plan, benefit obligation	2.1
Fair value of pension plan assets	1.4
United States
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan	8.3	$ 7.5	$ 7.4
United Kingdom
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan	$ 2.5	2.6	2.9
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, Outside of U.K.
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan	$ 0.5	0.3	0.5
European, Outside of U.K. | Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	2.10%
European, Outside of U.K. | Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	26.00%
Retirement Savings Contributions | United States
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan	$ 5.1	4.9	4.2
Non Discretionary Matching Contributions | United States
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan	$ 3.2	$ 2.6	$ 3.2

Summary of Condensed Quarterly

Summary of Condensed Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Gross Written Premiums	$ 464,558	$ 455,943	$ 497,236	$ 495,224	$ 408,743	$ 402,038	$ 452,179	$ 450,305	$ 1,912,961	$ 1,713,265	$ 1,568,911
Revenues:
Net Written Premiums	346,119	352,412	379,292	393,262	304,869	296,016	333,282	337,163	1,471,085	1,271,330	1,186,224
Change in Net Unearned Premiums	16,424	(5,374)	(48,277)	(70,635)	230	5,339	(39,447)	(51,032)	(107,862)	(84,910)	(85,879)
Net Earned Premiums	362,543	347,038	331,015	322,627	305,099	301,355	293,835	286,131	1,363,223	1,186,420	1,100,345
Net Investment Income	29,159	25,651	24,601	23,702	22,982	22,598	22,265	21,448	103,113	89,293	79,451
Net Realized and Unrealized Gains (Losses):
Total Other-Than-Temporary Impairment Losses	(48)	(15)	(18)	(37)	3	(957)	29	(1,077)
Portion of Loss Recognized in Other Comprehensive Income	48	15	18	37	(3)	(15)	(29)	(16)	118	(62)	77
Net Other-Than-Temporary Impairment Losses Recognized in Earnings						(972)		(1,093)	0	(2,064)	(150)
Net Realized Gains on Investments Sold	(220)	253	1,787	1,169					2,989	45,073	9,186
Net Unrealized Gains (Losses) on Equity Securities	(33,795)	2,310	1,329	(3,181)					(33,337)	0	0
Total Net Realized and Unrealized Gains (Losses)	(34,015)	2,563	3,116	(2,012)					(30,348)	43,009	9,036
Net Realized Gains					37,141	5,190	1,694	1,049
Other Income (Loss)	2,934	1,724	2,628	(117)	(3,201)	(1,699)	(411)	1,068	7,169	(4,243)	8,701
Total Revenues	360,621	376,976	361,360	344,200	362,021	326,472	317,383	308,603	1,443,157	1,314,479	1,197,533
Expenses:
Net Losses and LAE	270,401	240,900	196,333	186,145	183,384	276,171	177,110	169,600	893,779	806,265	665,448
Commission Expenses	54,800	57,999	53,193	54,152	43,205	45,509	48,173	47,844	220,144	184,731	165,045
Other Operating Expenses	62,532	67,584	68,182	62,926	68,153	45,773	60,766	58,538	261,224	233,230	234,096
Merger Transaction Costs	1,511	2,439							3,950	0	0
Interest Expense	3,866	3,891	3,864	3,864	3,863	3,862	3,861	3,861	15,485	15,447	15,435
Total Expenses	393,110	372,813	321,572	307,087	298,605	371,315	289,910	279,843	1,394,582	1,239,673	1,080,024
Income Before Income Taxes	(32,489)	4,163	39,788	37,113	63,416	(44,843)	27,473	28,760	48,575	74,806	117,509
Income Tax Expense	879	(462)	7,684	6,235	36,555	(16,864)	6,971	7,650	14,336	34,312	34,783
Net Income	(33,368)	4,625	32,104	30,878	26,861	(27,979)	20,502	21,110	34,239	40,494	82,726
Comprehensive Income (Loss)	$ (41,960)	$ (2,681)	$ 15,373	$ (2,962)	$ (1,812)	$ (18,311)	$ 35,699	$ 35,911	$ (32,230)	$ 51,487	$ 67,997
Combined Ratio	106.60%	105.30%	96.00%	94.00%	96.60%	121.90%	97.30%	96.40%	100.70%	103.20%	96.70%
Basic	$ (1.12)	$ 0.16	$ 1.08	$ 1.04	$ 0.91	$ (0.95)	$ 0.70	$ 0.72	$ 1.15	$ 1.38	$ 2.85
Diluted	$ (1.12)	$ 0.15	$ 1.07	$ 1.02	$ 0.89	$ (0.95)	$ 0.69	$ 0.70	$ 1.13	$ 1.35	$ 2.75

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - $ / shares	Feb. 14, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Subsequent Event [Line Items]
Common stock dividends per share declared		$ 0.28	$ 0.225	$ 0.135
Subsequent Event
Subsequent Event [Line Items]
Dividends payable, date declared	Feb. 14, 2019
Common stock dividends per share declared	$ 0.07
Dividend payable, date paid	Mar. 11, 2019
Dividends payable record date	Feb. 25, 2019

Summary of Consolidated Inves_2

Summary of Consolidated Investments-Other Than Investments in Related Parties (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Fixed Maturities
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fair Value	$ 3,082,923	[1]
Amortized Cost	3,125,413
Amount At Which Shown on Balance Sheet	3,082,923
Fixed Maturities | U.S. Treasury Bonds, Agency Bonds and Foreign Government Bonds
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fair Value	239,776	[1]
Amortized Cost	242,832
Amount At Which Shown on Balance Sheet	239,776
Fixed Maturities | States, Municipalities and Political Subdivisions
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fair Value	646,551	[1]
Amortized Cost	639,265
Amount At Which Shown on Balance Sheet	646,551
Fixed Maturities | Agency Residential Mortgage-Backed Securities
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fair Value	335,542	[1]
Amortized Cost	347,817
Amount At Which Shown on Balance Sheet	335,542
Fixed Maturities | Residential Mortgage Backed Securities
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fair Value	138,373	[1]
Amortized Cost	138,299
Amount At Which Shown on Balance Sheet	138,373
Fixed Maturities | Asset-Backed Securities
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fair Value	531,991	[1]
Amortized Cost	539,013
Amount At Which Shown on Balance Sheet	531,991
Fixed Maturities | Commercial Mortgage-Backed Securities
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fair Value	188,201	[1]
Amortized Cost	190,159
Amount At Which Shown on Balance Sheet	188,201
Fixed Maturities | Mortgage-Backed and Asset-Backed Securities
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fair Value	1,194,107	[1]
Amortized Cost	1,215,288
Amount At Which Shown on Balance Sheet	1,194,107
Fixed Maturities | Corporate Exposures
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fair Value	1,002,489	[1],[2]
Amortized Cost	1,028,028	[2]
Amount At Which Shown on Balance Sheet	1,002,489	[2]
Short-Term Investments
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fair Value	10,233	[1]
Amortized Cost	10,234
Amount At Which Shown on Balance Sheet	10,233
Equity Securities
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fair Value	339,892	[1]
Amortized Cost	361,418
Amount At Which Shown on Balance Sheet	339,892
Equity Securities | Common Stock
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fair Value	166,353	[1]
Amortized Cost	177,599
Amount At Which Shown on Balance Sheet	166,353
Equity Securities | Preferred Stocks
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fair Value	173,539	[1]
Amortized Cost	183,819
Amount At Which Shown on Balance Sheet	173,539
Investment Including Other Invested Assets
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fair Value	3,481,454	[1]
Amortized Cost	3,545,614
Amount At Which Shown on Balance Sheet	3,481,454
Other Invested Assets
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fair Value	48,406	[1]
Amortized Cost	48,549
Amount At Which Shown on Balance Sheet	$ 48,406
[1]	Other invested assets are accounted for using the equity method of accounting. All other investments are shown at fair value.
[2]	Corporate Exposures consist of investments in corporate bonds, hybrid bonds and redeemable preferred stocks.

Condensed Financial Informati_2

Condensed Financial Information - Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
ASSETS
Goodwill and Other Intangible Assets	$ 27,146	$ 6,596
Current Income Tax Receivable, Net	0	16,667
Other Assets	96,807	73,171
Total Assets	5,603,449	5,224,622
Liabilities:
Reserves for Losses and Loss Adjustment Expenses	2,743,973	2,515,145	$ 2,289,727
Unearned Premiums	1,102,735	987,681
Reinsurance Balances Payable	145,027	136,192
Senior Notes	264,052	263,885
Accounts Payable and Other Liabilities	151,622	95,754
Total Liabilities	4,416,599	3,998,657
Stockholders' Equity:
Preferred Stock, ($.10 par value, authorized 1,000 shares, none issued)	0	0
Common Stock, ($.10 par value, authorized 50,000 shares, issued 36,805 shares for 2018 and 36,530 shares for 2017)	3,678	3,650
Additional Paid-In Capital	378,274	376,868
Treasury Stock, at cost (7,023 shares for 2018 and 2017)	(155,801)	(155,801)
Retained Earnings	1,012,220	981,380
Accumulated Other Comprehensive Income:
Total Stockholders' Equity	1,186,850	1,225,965	1,178,188	$ 1,096,148
Total Liabilities and Stockholders' Equity	5,603,449	5,224,622
Parent Company
ASSETS
Cash	6,414	9,235	$ 12,663	$ 6,443
Investments in Subsidiaries	1,391,620	1,423,843
Goodwill and Other Intangible Assets	2,534	2,534
Current Income Tax Receivable, Net	35,553	30,573
Other Assets	19,686	28,063
Total Assets	1,455,807	1,494,248
Liabilities:
Senior Notes	264,052	263,885
Accounts Payable and Other Liabilities	1,731	1,224
Accrued Interest Payable	3,174	3,174
Total Liabilities	268,957	268,283
Stockholders' Equity:
Preferred Stock, ($.10 par value, authorized 1,000 shares, none issued)
Common Stock, ($.10 par value, authorized 50,000 shares, issued 36,805 shares for 2018 and 36,530 shares for 2017)	3,678	3,650
Additional Paid-In Capital	378,274	376,868
Treasury Stock, at cost (7,023 shares for 2018 and 2017)	(155,801)	(155,801)
Retained Earnings	1,012,220	981,380
Accumulated Other Comprehensive Income:
Net Unrealized Gains (Losses) on Securities Available-for-Sale, Net of Tax	(51,513)	19,874
Foreign Currency Translation Adjustment, Net of Tax	(8)	(6)
Total Stockholders' Equity	1,186,850	1,225,965
Total Liabilities and Stockholders' Equity	$ 1,455,807	$ 1,494,248

Condensed Financial Informati_3

Condensed Financial Information - Balance Sheets (Parenthetical) (Detail) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
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	36,805,000	36,530,000
Treasury Stock, shares	7,023,000	7,023,000
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	36,805,000	36,530,000
Treasury Stock, shares	7,023,000	7,023,000

Condensed Financial Informati_4

Condensed Financial Information - Statement of Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Net Investment Income	$ 29,159	$ 25,651	$ 24,601	$ 23,702	$ 22,982	$ 22,598	$ 22,265	$ 21,448	$ 103,113	$ 89,293	$ 79,451
Total Revenues	360,621	376,976	361,360	344,200	362,021	326,472	317,383	308,603	1,443,157	1,314,479	1,197,533
Expenses:
Interest Expense	3,866	3,891	3,864	3,864	3,863	3,862	3,861	3,861	15,485	15,447	15,435
Other (Income) Expense	(2,934)	(1,724)	(2,628)	117	3,201	1,699	411	(1,068)	(7,169)	4,243	(8,701)
Total Expenses	393,110	372,813	321,572	307,087	298,605	371,315	289,910	279,843	1,394,582	1,239,673	1,080,024
Loss Before Income Tax Benefit	(32,489)	4,163	39,788	37,113	63,416	(44,843)	27,473	28,760	48,575	74,806	117,509
Income Tax Expense	879	(462)	7,684	6,235	36,555	(16,864)	6,971	7,650	14,336	34,312	34,783
Net Income	$ (33,368)	$ 4,625	$ 32,104	$ 30,878	$ 26,861	$ (27,979)	$ 20,502	$ 21,110	34,239	40,494	82,726
Parent Company
Revenues:
Net Investment Income									18	7	53
Total Revenues									18	7	53
Expenses:
Interest Expense									15,460	15,447	15,435
Other (Income) Expense									2,563	(28)	22
Total Expenses									18,023	15,419	15,457
Loss Before Income Tax Benefit									(18,005)	(15,412)	(15,404)
Income Tax Expense									2,919	(5,709)	(8,009)
Loss Before Equity in Undistributed Net Income of Wholly Owned Subsidiaries									(20,924)	(9,703)	(7,395)
Equity in Undistributed Net Income of Wholly-Owned Subsidiaries									55,163	50,197	90,121
Net Income									$ 34,239	$ 40,494	$ 82,726

Condensed Financial Informati_5

Condensed Financial Information - Statement of Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Activities:
Net Income	$ (33,368)	$ 4,625	$ 32,104	$ 30,878	$ 26,861	$ (27,979)	$ 20,502	$ 21,110	$ 34,239	$ 40,494	$ 82,726
Adjustments to Reconcile Net Income to Net Cash Provided By (Used in) Operations:
Other									42,718	936	27,791
Net Cash Provided by Operating Activities									342,338	265,343	229,425
Investing Activities:
Sales									34,617
Purchases									(126,746)
Net Cash Used in Investing Activities									(260,147)	(264,029)	(202,183)
Financing Activities:
Proceeds from Employee Stock Purchase Plan									2,008	2,076	1,840
Dividends Paid									(8,319)	(6,633)	(3,930)
Payment of Employee Tax Withholding on Stock Compensation									(8,456)	(13,887)	(5,198)
Net Cash Used in Financing Activities									(14,767)	(18,444)	(7,288)
Parent Company
Operating Activities:
Net Income									34,239	40,494	82,726
Adjustments to Reconcile Net Income to Net Cash Provided By (Used in) Operations:
Equity in Undistributed Net Income of Wholly-Owned Subsidiaries									(55,163)	(50,197)	(90,121)
Dividends Received from Subsidiaries									97,000	19,000	5,000
Other									9,757	5,841	5,737
Net Cash Provided by Operating Activities									85,833	15,138	3,342
Investing Activities:
Net (Increase) Decrease in Short-Term Investments											89,576
Net Cash Used in Investing Activities											89,576
Financing Activities:
Capital Contribution to Subsidiary									(76,083)	(1)	(79,250)
Proceeds from Employee Stock Purchase Plan									2,036	1,846	1,840
Dividends Paid									(8,319)	(6,633)	(3,930)
Payment of Employee Tax Withholding on Stock Compensation									(6,288)	(13,778)	(5,358)
Net Cash Used in Financing Activities									(88,654)	(18,566)	(86,698)
Increase (Decrease) in Cash									(2,821)	(3,428)	6,220
Cash at Beginning of Year				$ 9,235				$ 12,663	9,235	12,663	6,443
Cash at End of Year	$ 6,414				$ 9,235				$ 6,414	$ 9,235	$ 12,663

Supplementary Insurance Infor_2

Supplementary Insurance Information (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs		$ 158,080	$ 135,249	$ 119,660
Reserve for Losses and LAE		2,743,973	2,515,145	2,289,727
Unearned Premiums		1,102,735	987,681	887,344
Net Earned Premiums		1,363,223	1,186,420	1,100,345
Net Investment Income	[1]	103,113	89,293	79,451
Losses and LAE Incurred		893,779	806,265	665,448
Amortization of Deferred Policy Acquisition Costs		220,144	184,731	165,045
Other Operating Expenses		261,224	233,230	234,096
Net Written Premiums		1,471,085	1,271,330	1,186,224
U.S.Insurance
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs		63,903	54,674	50,028
Reserve for Losses and LAE		1,784,339	1,629,015	1,564,524
Unearned Premiums		642,725	575,068	519,505
Net Earned Premiums		737,646	674,665	629,308
Losses and LAE Incurred		485,960	443,353	397,860
Amortization of Deferred Policy Acquisition Costs		85,127	77,729	70,812
Other Operating Expenses		142,333	128,905	128,108
Net Written Premiums		800,091	721,300	683,568
International Insurance
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs		39,472	38,988	37,385
Reserve for Losses and LAE		768,301	716,352	605,105
Unearned Premiums		265,753	260,982	252,442
Net Earned Premiums		380,503	333,792	307,416
Losses and LAE Incurred		252,268	229,601	178,284
Amortization of Deferred Policy Acquisition Costs		80,526	68,824	61,703
Other Operating Expenses		93,882	83,464	86,395
Net Written Premiums		383,308	335,852	345,967
Global Reinsurance
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs		54,705	41,587	32,247
Reserve for Losses and LAE		191,333	169,778	120,098
Unearned Premiums		194,257	151,631	115,397
Net Earned Premiums		245,074	177,963	163,621
Losses and LAE Incurred		155,551	133,311	89,304
Amortization of Deferred Policy Acquisition Costs		55,056	39,136	34,008
Other Operating Expenses		25,009	20,861	19,593
Net Written Premiums		287,686	214,178	156,689
Corporate
Supplementary Insurance Information, by Segment [Line Items]
Net Investment Income	[1]	103,113	89,293	79,451
Amortization of Deferred Policy Acquisition Costs		$ (565)	$ (958)	$ (1,478)
[1]	As we evaluate the underwriting results of each of our reportable segments separately from the results of our investment portfolio, we do not allocate net investment income to our reportable segments.

Reinsurance Written Premium (De

Reinsurance Written Premium (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplementary Insurance Information, by Segment [Line Items]
Direct Amount									$ 1,613,825	$ 1,489,422	$ 1,403,865
Ceded to Other Companies									441,876	441,935	382,687
Assumed from Other Companies									299,136	223,843	165,046
Net written premiums	$ 346,119	$ 352,412	$ 379,292	$ 393,262	$ 304,869	$ 296,016	$ 333,282	$ 337,163	$ 1,471,085	$ 1,271,330	$ 1,186,224
Percentage of Amount Assumed to Net									20.30%	17.60%	13.90%
Accident & Health
Supplementary Insurance Information, by Segment [Line Items]
Assumed from Other Companies									$ 139,692	$ 80,605	$ 53,814
Net written premiums									$ 139,692	$ 80,605	$ 53,814
Percentage of Amount Assumed to Net									100.00%	100.00%	100.00%
Property Casualty
Supplementary Insurance Information, by Segment [Line Items]
Direct Amount									$ 1,613,825	$ 1,489,422	$ 1,403,865
Ceded to Other Companies									441,876	441,935	382,687
Assumed from Other Companies									159,444	143,238	111,232
Net written premiums									$ 1,331,393	$ 1,190,725	$ 1,132,410
Percentage of Amount Assumed to Net									12.00%	12.00%	9.80%

Valuation and Qualifying Acco_2

Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for Uncollectable Reinsurance
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 12,597	$ 12,078	$ 6,921
Charged (Credited) to Costs and Expenses	770	519	5,157
Charged to Other Accounts	0	0	0
Deductions (Describe)	0	0	0
Ending Balance	13,367	12,597	12,078
Valuation Allowance in Deferred Taxes
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	1,798	699	721
Charged (Credited) to Costs and Expenses	3,897	1,099	(22)
Charged to Other Accounts	0	0	0
Deductions (Describe)	(1,328)	0	0
Ending Balance	$ 4,367	$ 1,798	$ 699

Supplementary Information Con_2

Supplementary Information Concerning P&C Insurance Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Information For Property Casualty Insurance Underwriters [Abstract]
Deferred Policy Acquisition Costs	$ 158,080	$ 135,249	$ 119,660
Reserve for Losses and LAE	2,743,973	2,515,145	2,289,727
Unearned Premiums	1,102,735	987,681	887,344
Net Earned Premiums	1,363,223	1,186,420	1,100,345
Net Investment Income	103,113	89,293	79,451
Losses and LAE Expenses Incurred Related to Current Year	817,537	771,955	693,976
Losses and LAE Expenses Incurred Related to Prior Years	76,242	34,310	(28,528)
Amortization of Deferred Policy Acquisition Costs	220,144	184,731	165,045
Other Operating Expenses	261,224	233,230	234,096
Net Written Premiums	$ 1,471,085	$ 1,271,330	$ 1,186,224