Navigators (NAVG) 10-Q 5 May 17 2017 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2017	Apr. 28, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q1
Trading Symbol	NAVG
Entity Registrant Name	NAVIGATORS GROUP INC
Entity Central Index Key	793,547
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		29,466,253

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands		Mar. 31, 2017	Dec. 31, 2016
Investments:
Fixed maturities, available-for-sale, at fair value (amortized cost: 2017: $2,678,475; 2016: $2,628,225)		$ 2,695,277	$ 2,635,882
Equity securities, available-for-sale, at fair value (cost: 2017: $326,910; 2016: $327,911)		362,214	349,142
Other invested assets		1,776	1,960
Short-term investments, at fair value (amortized cost: 2017: $123,796; 2016: $143,451)		123,846	143,539
Total investments		3,183,113	3,130,523
Cash		63,462	64,643
Premiums receivable		379,787	306,686
Prepaid reinsurance premiums		224,562	213,377
Reinsurance recoverable on paid losses		76,876	82,582
Reinsurance recoverable on unpaid losses and loss adjustment expenses		794,576	779,276
Deferred policy acquisition costs		126,199	119,660
Accrued investment income		18,107	17,315
Goodwill and other intangible assets		6,442	6,451
Current income tax receivable, net		4,280	20,556
Deferred income tax, net		21,574	20,938
Other assets		58,365	52,030
Total assets		4,957,343	4,814,037
Liabilities:
Reserves for losses and loss adjustment expenses		2,331,392	2,289,727
Unearned premiums		949,483	887,344
Reinsurance balances payable		118,167	108,980
Senior notes		263,767	263,728
Payable for investments purchased		6,715	0
Accounts payable and other liabilities		81,683	86,070
Total liabilities		3,751,207	3,635,849
Stockholders' equity:
Preferred stock ($.10 par value per share, authorized 1,000 shares, none issued)	[1]	0	0
Common stock ($.10 par value per share, authorized 50,000 shares, issued 36,484 shares for 2017 and 36,147 shares for 2016)		3,645	3,612
Additional paid-in capital	[1]	367,311	373,983
Treasury stock, at cost (7,023 shares for 2017 and 2016)	[1]	(155,801)	(155,801)
Retained earnings	[1]	967,305	947,519
Accumulated other comprehensive income	[1]	23,676	8,875
Total stockholders' equity	[1]	1,206,136	1,178,188
Total liabilities and stockholders' equity		$ 4,957,343	$ 4,814,037
[1]	We completed a two-for-one stock split on January 20, 2017. All share and per share data prior to January 20, 2017 has been retroactively restated on a post-split basis.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) $ in Thousands	Mar. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares
Statement Of Financial Position [Abstract]
Fixed maturities, available-for-sale, amortized cost | $	$ 2,678,475	$ 2,628,225
Equity securities, available-for-sale, cost | $	326,910	327,911
Short-term investments, amortized cost | $	$ 123,796	$ 143,451
Preferred stock, par value | $ / shares	$ 0.10	$ 0.10
Preferred stock, authorized shares	1,000,000	1,000,000
Preferred stock, issued shares	0	0
Common stock, par value | $ / shares	$ 0.10	$ 0.10
Common stock, authorized shares	50,000,000	50,000,000
Common stock, issued shares	36,484,000	36,147,000
Treasury stock, shares	7,023,000	7,023,000

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Gross written premiums		$ 450,305	$ 413,877
Revenues:
Net written premiums		337,163	319,820
Change in unearned premiums		(51,032)	(55,462)
Net earned premiums		286,131	264,358
Net investment income		21,448	19,594
Total other-than-temporary impairment losses		(1,077)	(109)
Portion of loss recognized in other comprehensive income (before tax)		(16)	109
Net other-than-temporary impairment losses recognized in earnings		(1,093)	0
Net realized gains		1,049	1,597
Other income		1,068	2,549
Total revenues		308,603	288,098
Expenses:
Net losses and loss adjustment expenses		169,600	152,956
Commission expenses		47,844	37,554
Other operating expenses		58,538	60,809
Interest expense		3,861	3,858
Total expenses		279,843	255,177
Income before income taxes		28,760	32,921
Income tax expense		7,650	9,989
Net income		$ 21,110	$ 22,932
Net income per common share:
Basic	[1]	$ 0.72	$ 0.79
Diluted	[1]	$ 0.70	$ 0.77
Average common shares outstanding:
Basic	[1]	29,283	28,984
Diluted	[1]	30,000	29,783
Cash dividends declared per common share		$ 0.045	$ 0
[1]	We completed a two-for-one stock split on January 20, 2017. All share and per share data prior to January 20, 2017 has been retroactively restated on a post-split basis.

Consolidated Statements of Inc5

Consolidated Statements of Income (Parenthetical)	Jan. 20, 2017	Mar. 31, 2017
Income Statement [Abstract]
Stock split ratio	2
Stockholders equity, stock split		We completed a two-for-one stock split on January 20, 2017.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 21,110	$ 22,932
Change in net unrealized gains on investments:
Unrealized gains on investments arising during the period, net of deferred tax of $(7,771) and $(11,737) in 2017 and 2016, respectively	14,434	21,798
Reclassification adjustment for net realized losses included in net income net of deferred tax of $(114) and $(758) in 2017 and 2016, respectively	211	1,408
Change in net unrealized gains on investments	14,645	23,206
Change in other-than-temporary impairments:
Non credit other-than-temporary impairments arising during the period, net of deferred tax of $(6) and $38 in 2017 and 2016, respectively	10	(71)
Reclassification adjustment for other-than-temporary impairment credit losses recognized in net income net of deferred tax of $(222) and $0 in 2017 and 2016, respectively	412	0
Change in other-than-temporary impairments	422	(71)
Change in foreign currency translation losses, net of deferred tax of $143 and $183 in 2017 and 2016, respectively	(266)	(346)
Other comprehensive income	14,801	22,789
Comprehensive income	$ 35,911	$ 45,721

Consolidated Statements of Com7

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Unrealized gains on investments arising during the period, deferred tax	$ (7,771)	$ (11,737)
Reclassification adjustment for net realized losses included in net income, deferred tax	(114)	(758)
Non credit other-than-temporary impairments arising during the period, deferred tax	(6)	38
Reclassification adjustment for other-than-temporary impairment credit losses recognized in net income, deferred tax	(222)	0
Change in foreign currency translation losses, deferred tax	$ 143	$ 183

Consolidated Statement of Stock

Consolidated Statement of Stockholders' Equity - 3 months ended Mar. 31, 2017 - 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, 2016		$ 1,178,188	[1]	$ 3,612		$ 373,983	$ (155,801)		$ 947,519	$ 8,875
Beginning balance (in shares) at Dec. 31, 2016		36,147		36,147	[2]		7,023	[2]
Net income		$ 21,110							21,110
Dividends declared		(1,324)							(1,324)
Changes in comprehensive income:
Change in net unrealized gain on investments		14,645								14,645
Change in net non-credit other-than-temporary impairment losses		422								422
Change in foreign currency translation loss		(266)								(266)
Total comprehensive income		14,801								14,801
Shares issued	[3]	(11,106)		$ 33		(11,139)
Shares issued (in shares)	[2],[3]			337
Share-based compensation		4,467				4,467
Ending balance at Mar. 31, 2017		$ 1,206,136	[1]	$ 3,645		$ 367,311	$ (155,801)		$ 967,305	$ 23,676
Ending balance (in shares) at Mar. 31, 2017		36,484		36,484	[2]		7,023	[2]
[1]	We completed a two-for-one stock split on January 20, 2017. All share and per share data prior to January 20, 2017 has been retroactively restated on a post-split basis.
[2]	We completed a two-for-one stock split on January 20, 2017. All share data prior to January 20, 2017 has been retroactively restated on a post-split basis.
[3]	Includes shares issued under the Second Amended and Restated 2005 Stock Incentive Plan to Directors and the Employee Stock Purchase Plan.

Consolidated Statement of Stoc9

Consolidated Statement of Stockholders' Equity (Parenthetical)	Jan. 20, 2017	Mar. 31, 2017
Statement Of Stockholders Equity [Abstract]
Stock split ratio	2
Stockholders equity, stock split		We completed a two-for-one stock split on January 20, 2017.

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities:
Net income	$ 21,110	$ 22,932
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation & amortization	1,184	1,459
Share-based compensation	4,467	4,926
Deferred income taxes	(8,598)	191
Net realized gains	(1,049)	(1,597)
Net other-than-temporary impairments recognized in earnings	1,093	0
Changes in assets and liabilities:
Reinsurance recoverable on paid and unpaid losses and loss adjustment expenses	(9,593)	9,640
Reserves for losses and loss adjustment expenses	41,664	9,204
Prepaid reinsurance premiums	(11,186)	11,891
Unearned premiums	62,139	43,571
Premiums receivable	(74,566)	(72,300)
Deferred policy acquisition costs	(6,539)	(13,376)
Accrued investment income	(792)	(450)
Reinsurance balances payable	9,187	15,753
Current income tax payable, net	19,098	9,291
Other	(10,276)	1,717
Net cash provided by operating activities	37,343	42,852
Fixed maturities
Redemptions and maturities	86,049	44,996
Sales	34,973	98,680
Purchases	(175,679)	(177,719)
Equity securities
Sales	13,316	10,724
Purchases	(11,492)	(15,601)
Change in payable for securities	6,757	(1,472)
Net change in short-term investments	18,093	6,146
Purchase of property and equipment	(956)	(2,452)
Net cash used in investing activities	(28,939)	(36,698)
Financing activities:
Proceeds of stock issued from employee stock purchase plan	1,147	867
Payment of employee tax withholding on stock compensation	(10,295)	(4,304)
Dividends paid	(1,324)	0
Net cash used in financing activities	(10,472)	(3,437)
Effect of exchange rate on cash	887
Change in cash	(1,181)	2,717
Cash at beginning of year	64,643	69,901
Cash at end of period	63,462	72,618
Supplemental information:
Income taxes paid, net	136	40
Interest paid	0	0
Issuance of stock to directors	$ 578	$ 633

Organization and Summary of Sig

Organization and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2017
Accounting Policies [Abstract]
Organization and Summary of Significant Accounting Policies	NOTE 1. ORGANIZATION & SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES 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. 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 (“NMC”). NIC includes a branch in the United Kingdom (“U.K”). We also have operations domiciled in the U.K., Belgium, Hong Kong and throughout 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. Effective January 1, 2017, we sold our underwriting agency operations in Sweden and Denmark. The transaction represented a 100% disposition of our Sweden and Denmark corporations, NUAL AB and Navigators A/S, respectively. This transaction did not have a material impact on our financial statements. Basis of Presentation The Consolidated Balance Sheet at March 31, 2017 and the Consolidated Statements of Income, Comprehensive Income, Stockholders’ Equity and Cash Flows for the periods ended March 31, 2017 and 2016 are unaudited. The Balance Sheet at December 31, 2016 is derived from our audited Financial Statements. The accompanying Interim Consolidated Financial Statements reflect all adjustments, which, in the opinion of management, are necessary to fairly present the results of The Navigators Group, Inc. and its subsidiaries for the interim periods presented on the basis of United States generally accepted accounting principles (“GAAP” or “U.S. GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X as promulgated by the U.S. Securities and Exchange Commission. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. 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 and disclosures of contingent assets and liabilities at the date of the Financial Statements and the reported revenues and expenses during the reporting periods. The results of operations for any interim period are not necessarily indicative of results for the full year. The Interim Consolidated Financial Statements should be read in conjunction with our Annual Report on Form 10-K for the year ended December 31, 2016. Certain amounts for the prior period have been reclassified to conform with the current period presentation. Income Taxes The interim income tax provision has been computed based on our estimated annual Effective tax rate, which represents our best estimate on a year to date basis for the interim period. As a result, the tax provision for a given quarter equals the difference between the provision recorded cumulatively year to date less the amount recorded cumulatively as of the end of the prior interim period. Our Effective tax rate for the quarter and year to date differs from the federal tax rate of 35% primarily due to an excess tax benefit related to the vesting of stock compensation at fair market value, tax-exempt investment income and dividends received deduction. In the first quarter of 2017, excess tax benefits related to the vesting of stock compensation was recognized as a reduction to Income tax expense rather than as an increase to Additional paid-in capital as a result of the adoption of the Accounting Standards Update (“ASU”) 2016-09 (see section New Accounting Standards Adopted in 2017 Significant Accounting Policies There were no changes in our significant accounting policies subsequent to our Annual Report on Form 10-K for the year ended December 31, 2016. New Accounting Standards Adopted in 2017 Share-Based Compensation Accounting Effective January 1, 2017, our Company adopted ASU 2016-09, “Improvements to Employee Share-Based Payment Accounting” issued by the Financial Accounting Standards Board (the “FASB”). This guidance requires all income tax effects of awards to be recognized in the income statement when the awards vest or are settled, eliminates the requirement that excess tax benefits be realized before companies can recognize them, requires the presentation of excess tax benefits as an operating activity on the statement of cash flows, allows employers to increase the amounts withheld to cover income taxes on share-based compensation awards without requiring liability classification, requires the presentation of employee taxes paid as a financing activity on the statement of cash flows, and requires companies to elect whether they will account for award forfeitures by recognizing forfeitures only as they occur or by estimating the number of awards expected to be forfeited. The requirement to recognize all income tax effects of awards in the income statement when the awards vest or are settled was adopted on a prospective basis. Previously, these amounts were recorded in Additional paid-in capital. This change also prospectively impacts the calculation of potential common shares used to determine Diluted net income per common share under the treasury stock method. The new standard requires that assumed proceeds under the treasury stock method be modified to exclude the amount of excess tax benefits that previously would have been recognized in Additional paid-in capital. We elected to account for forfeitures of share-based payment awards by recognizing forfeitures of awards as they occur, and upon adoption of this guidance, the payment of employee taxes was retrospectively adjusted on the Consolidated Statements of Cash Flows to be classified as a financing activity. All other changes in the ASU did not result in cumulative-effect or retrospective adjustments. The adoption of this guidance did not materially impact our results of operations, financial condition or liquidity. Transition to Equity Method of Accounting Effective January 1, 2017, our Company adopted the ASU 2016-07, “Simplifying the Transition to the Equity Method of Accounting” issued by the FASB. This guidance eliminates the requirement to retrospectively apply equity method accounting when an investment that had been accounted for by another method initially qualifies for the equity method. Our Company did not have any investments transitioning to the equity method of accounting during the three months ended March 31, 2017. The adoption of this guidance did not impact our results of operations, financial condition or liquidity. Recently Issued Accounting Standards Not Yet Adopted Definition of a Business In January 2017, the FASB issued ASU 2017-01, “Clarifying the Definition of a Business” with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. This guidance is effective for annual periods beginning after December 15, 2017, and interim periods within those fiscal years with early adoption permitted. This guidance will be applied prospectively to any transactions occurring within the period of adoption. 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.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2017
Segment Reporting [Abstract]
Segment Information	NOTE 2. 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. 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 loss adjustment expenses (“LAE”), Commission expenses, Other operating expenses and Other underwriting income (expense). The Combined ratio is derived by dividing the sum of Net losses and LAE, Commission expenses, Other operating expenses and Other underwriting income (expense) by Net earned premiums. A Combined ratio of less than 100% indicates an underwriting profit and greater than 100% indicates an underwriting loss. Our underwriting performance is evaluated separately from the rest of our operations. The performance of our investment portfolios, our liquidity and capital resource needs, our foreign currency exposure and our tax planning strategies are evaluated on a consolidated basis within our Corporate segment. We do not allocate our assets by underwriting segment, with the exception of goodwill and other intangible assets, as we evaluate the underwriting results of these segments separately from the results of our investments portfolio. Financial data by segment for the three months ended March 31, 2017 and 2016 was as follows: Three Months Ended March 31, 2017 U.S. Int'l amounts in thousands Insurance Insurance GlobalRe Corporate (1) Total Net earned premiums $ 164,004 $ 84,086 $ 38,041 $ — $ 286,131 Net losses and LAE (98,826 ) (50,705 ) (20,069 ) — (169,600 ) Commission expenses (20,384 ) (19,233 ) (8,492 ) 265 (47,844 ) Other operating expenses (33,472 ) (19,793 ) (5,273 ) — (58,538 ) Other underwriting income (expense) 110 — 176 (265 ) 21 Underwriting profit (loss) $ 11,432 $ (5,645 ) $ 4,383 $ — $ 10,170 Net investment income 21,448 21,448 Net realized losses (44 ) (44 ) Interest expense (3,861 ) (3,861 ) Other income 1,047 1,047 Income (loss) before income taxes $ 11,432 $ (5,645 ) $ 4,383 $ 18,590 $ 28,760 Income tax expense (7,650 ) (7,650 ) Net income $ 21,110 Losses and LAE ratio 60.3 % 60.3 % 52.8 % 59.3 % Commission expense ratio 12.4 % 22.9 % 22.3 % 16.7 % Other operating expense ratio (2) 20.3 % 23.5 % 13.4 % 20.4 % Combined ratio 93.0 % 106.7 % 88.5 % 96.4 % Goodwill and other intangible assets $ 2,534 $ 3,908 $ — $ 6,442 (1) - Includes Corporate segment intercompany eliminations. (2) - Includes Other operating expenses and Other underwriting income (expense). Three Months Ended March 31, 2016 U.S. Int'l amounts in thousands Insurance Insurance GlobalRe Corporate (1) Total Net earned premiums $ 148,340 $ 78,008 $ 38,010 $ — $ 264,358 Net losses and LAE (91,512 ) (40,410 ) (21,034 ) — (152,956 ) Commission expenses (14,855 ) (15,355 ) (7,745 ) 401 (37,554 ) Other operating expenses (33,761 ) (21,771 ) (5,277 ) — (60,809 ) Other underwriting income (expense) 361 — 49 (401 ) 9 Underwriting profit $ 8,573 $ 472 $ 4,003 $ — $ 13,048 Net investment income 19,594 19,594 Net realized gains 1,597 1,597 Interest expense (3,858 ) (3,858 ) Other income 2,540 2,540 Income before income taxes $ 8,573 $ 472 $ 4,003 $ 19,873 $ 32,921 Income tax expense (9,989 ) (9,989 ) Net income $ 22,932 Losses and LAE ratio 61.7 % 51.8 % 55.3 % 57.9 % Commission expense ratio 10.0 % 19.7 % 20.4 % 14.2 % Other operating expense ratio (2) 22.5 % 27.9 % 13.8 % 23.0 % Combined ratio 94.2 % 99.4 % 89.5 % 95.1 % Goodwill and other intangible assets $ 2,534 $ 4,212 $ — $ 6,746 (1) - Includes Corporate segment intercompany eliminations. (2) - Includes Other operating expenses and Other underwriting income (expense). Revenue by operating segment for the three months ended March 31, 2017 and 2016 was as follows: Three Months Ended March 31, 2017 Three Months Ended March 31, 2016 % Change amounts in thousands Gross written premiums Ceded written premiums Net premiums Net earned premiums Gross written premiums Ceded written premiums Net written premiums Net earned premiums Gross written premiums Ceded written premiums Net written premiums Net earned premiums U.S. Insurance Marine $ 40,950 $ (17,520 ) $ 23,430 $ 22,694 $ 43,163 $ (17,647 ) $ 25,516 $ 23,250 (5.1 %) (0.7 %) (8.2 %) (2.4 %) P&C 170,634 (38,198 ) 132,436 119,123 141,278 (30,507 ) 110,771 109,159 20.8 % 25.2 % 19.6 % 9.1 % Professional 26,021 (5,769 ) 20,252 22,187 26,206 (6,343 ) 19,863 15,931 (0.7 %) (9.0 %) 2.0 % 39.3 % Total $ 237,605 $ (61,487 ) $ 176,118 $ 164,004 $ 210,647 $ (54,497 ) $ 156,150 $ 148,340 12.8 % 12.8 % 12.8 % 10.6 % Int'l Insurance Marine $ 68,833 $ (10,926 ) $ 57,907 $ 37,495 $ 71,948 $ (11,089 ) $ 60,859 $ 38,856 (4.3 %) (1.5 %) (4.9 %) (3.5 %) P&C 40,368 (29,646 ) 10,722 22,180 44,046 (17,229 ) 26,817 21,209 (8.4 %) 72.1 % (60.0 %) 4.6 % Professional Liability 32,659 (6,021 ) 26,638 24,411 28,149 (6,653 ) 21,496 17,943 16.0 % (9.5 %) 23.9 % 36.0 % Total $ 141,860 $ (46,593 ) $ 95,267 $ 84,086 $ 144,143 $ (34,971 ) $ 109,172 $ 78,008 (1.6 %) 33.2 % (12.7 %) 7.8 % GlobalRe $ 70,840 $ (5,062 ) $ 65,778 $ 38,041 $ 59,087 $ (4,589 ) $ 54,498 $ 38,010 19.9 % 10.3 % 20.7 % 0.1 % Total $ 450,305 $ (113,142 ) $ 337,163 $ 286,131 $ 413,877 $ (94,057 ) $ 319,820 $ 264,358 8.8 % 20.3 % 5.4 % 8.2 %

Investments

Investments	3 Months Ended
	Mar. 31, 2017
Investments Debt And Equity Securities [Abstract]
Investments	NOTE 3. INVESTMENTS The following tables set forth our Company’s available-for-sale investments as of March 31, 2017 and December 31, 2016 and include Other-than-temporary-impairment (“OTTI”) securities recognized within Accumulated other comprehensive income (“AOCI”): March 31, 2017 Gross Gross Cost or Fair Unrealized Unrealized Amortized amounts in thousands Value Gains (Losses) Cost Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 270,009 $ 2,110 $ (3,671 ) $ 271,570 States, municipalities and political subdivisions 604,912 13,772 (3,353 ) 594,493 Mortgage-backed and asset-backed securities: Agency mortgage-backed securities 468,255 3,858 (7,051 ) 471,448 Residential mortgage obligations 16,970 439 (37 ) 16,568 Asset-backed securities 331,567 1,470 (769 ) 330,866 Commercial mortgage-backed securities 147,353 2,670 (1,843 ) 146,526 Subtotal $ 964,145 $ 8,437 $ (9,700 ) $ 965,408 Corporate exposures 856,211 12,948 (3,741 ) 847,004 Total fixed maturities $ 2,695,277 $ 37,267 $ (20,465 ) $ 2,678,475 Equity securities: Common stocks $ 169,905 $ 29,474 $ (652 ) $ 141,083 Preferred stocks 192,309 7,702 (1,220 ) 185,827 Total Equity securities $ 362,214 $ 37,176 $ (1,872 ) $ 326,910 Short-term investments 123,846 50 — 123,796 Total investments $ 3,181,337 $ 74,493 $ (22,337 ) $ 3,129,181 December 31, 2016 Gross Gross Cost or Fair Unrealized Unrealized Amortized amounts in thousands Value Gains (Losses) Cost Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 273,776 $ 2,192 $ (5,128 ) $ 276,712 States, municipalities and political subdivisions 547,415 11,542 (4,036 ) 539,909 Mortgage-backed and asset-backed securities: Agency mortgage-backed securities 487,364 4,016 (6,585 ) 489,933 Residential mortgage obligations 20,530 453 (55 ) 20,132 Asset-backed securities 314,601 824 (1,178 ) 314,955 Commercial mortgage-backed securities 154,139 2,859 (1,904 ) 153,184 Subtotal $ 976,634 $ 8,152 $ (9,722 ) $ 978,204 Corporate exposures 838,057 10,185 (5,528 ) 833,400 Total fixed maturities $ 2,635,882 $ 32,071 $ (24,414 ) $ 2,628,225 Equity securities: Common stocks $ 164,087 $ 24,677 $ (964 ) $ 140,374 Preferred stocks 185,055 2,339 (4,821 ) 187,537 Total Equity securities $ 349,142 $ 27,016 $ (5,785 ) $ 327,911 Short-term investments 143,539 88 — 143,451 Total investments $ 3,128,563 $ 59,175 $ (30,199 ) $ 3,099,587 Corporate exposures consist of investments in corporate bonds, hybrid bonds and redeemable preferred stocks. During 2016, our Company made 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 investments. Our initial purchase price for these investments was $2.0 million with a current carrying value of $1.8 million at March 31, 2017 as reflected on our Consolidated Balance Sheet. As of March 31, 2017 and December 31, 2016, our Company did not have a concentration of greater than 5% of invested assets in a single non-government backed issuer. As of March 31, 2017 and December 31, 2016, Fixed maturities for which non-credit OTTI was previously recognized and included in AOCI were in a net unrealized gain position of $0.4 million in each period. The fair value of our Company’s investment portfolio may fluctuate significantly in response to various factors such as changes in interest rates, investment quality ratings, equity prices, foreign exchange rates and credit spreads. Our Company does not have the intent to sell nor is it more likely than not that it will have to sell Fixed maturities in unrealized loss positions that are not other-than-temporarily impaired before recovery. For structured securities, default probability and severity assumptions differ based on property type, vintage and the stress of the collateral. Our Company does not intend to sell, and it is more likely than not that our Company will not be required to sell, these securities before the recovery of the amortized cost basis. For Equity securities, our Company also considers our intent to hold securities as part of the process of evaluating whether a decline in fair value represents an other-than-temporary decline in value. Our Company may realize investment losses to the extent our liquidity needs require the disposition of Fixed maturity securities in unfavorable interest rate, liquidity or credit spread environments. Significant changes in the factors our Company considers when evaluating investments for impairment losses could result in a significant change in impairment losses reported in the Consolidated Financial Statements. The contractual maturity dates for Fixed maturities categorized by the number of years until maturity as of March 31, 2017 are shown in the following table: March 31, 2017 Fair Amortized amounts in thousands Value Cost Due in one year or less $ 173,505 $ 174,014 Due after one year through five years 732,625 730,523 Due after five years through ten years 321,037 315,580 Due after ten years 503,965 492,950 Mortgage-backed and asset-backed securities 964,145 965,408 Total $ 2,695,277 $ 2,678,475 Expected maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. Prepayment assumptions associated with the mortgage-backed and asset-backed securities are reviewed on a periodic basis. When changes in prepayment assumptions are deemed necessary as the result of actual prepayments differing from anticipated prepayments, securities are revalued based upon the new prepayment assumptions utilizing the retrospective accounting method. Due to the periodic repayment of principal, the mortgage-backed and asset-backed securities are estimated to have an effective maturity of approximately 4.8 years. The following tables summarize all securities in a gross unrealized loss position as of March 31, 2017 and December 31, 2016, 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: March 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 $ 153,332 $ (2,275 ) $ 11,844 $ (1,396 ) $ 165,176 $ (3,671 ) States, municipalities and political subdivisions 120,372 (2,534 ) 17,706 (819 ) 138,078 (3,353 ) Mortgage-backed and asset-backed securities: Agency mortgage-backed securities 347,179 (6,622 ) 11,810 (429 ) 358,989 (7,051 ) Residential mortgage obligations 486 (5 ) 1,204 (32 ) 1,690 (37 ) Asset-backed securities 68,847 (708 ) 17,944 (61 ) 86,791 (769 ) Commercial mortgage-backed securities 51,336 (1,024 ) 6,385 (819 ) 57,721 (1,843 ) Subtotal $ 467,848 $ (8,359 ) $ 37,343 $ (1,341 ) $ 505,191 $ (9,700 ) Corporate exposures 269,427 (3,571 ) 21,901 (170 ) 291,328 (3,741 ) Total fixed maturities $ 1,010,979 $ (16,739 ) $ 88,794 $ (3,726 ) $ 1,099,773 $ (20,465 ) Equity securities: Common Stocks $ 28,586 $ (652 ) $ — $ — $ 28,586 $ (652 ) Preferred Stocks 42,470 (1,128 ) 2,557 (92 ) 45,027 (1,220 ) Total Equity securities $ 71,056 $ (1,780 ) $ 2,557 $ (92 ) $ 73,613 $ (1,872 ) Total fixed maturities and equity securities $ 1,082,035 $ (18,519 ) $ 91,351 $ (3,818 ) $ 1,173,386 $ (22,337 ) December 31, 2016 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 $ 150,891 $ (2,570 ) $ 16,819 $ (2,558 ) $ 167,710 $ (5,128 ) States, municipalities and political subdivisions 137,731 (3,111 ) 13,255 (925 ) 150,986 (4,036 ) Mortgage-backed and asset-backed securities: Agency mortgage-backed securities 349,119 (6,155 ) 12,401 (430 ) 361,520 (6,585 ) Residential mortgage obligations 953 (18 ) 926 (37 ) 1,879 (55 ) Asset-backed securities 95,514 (970 ) 48,093 (208 ) 143,607 (1,178 ) Commercial mortgage-backed securities 51,932 (1,164 ) 7,910 (740 ) 59,842 (1,904 ) Subtotal $ 497,518 $ (8,307 ) $ 69,330 $ (1,415 ) $ 566,848 $ (9,722 ) Corporate exposures 325,733 (5,086 ) 26,005 (442 ) 351,738 (5,528 ) Total fixed maturities $ 1,111,873 $ (19,074 ) $ 125,409 $ (5,340 ) $ 1,237,282 $ (24,414 ) Equity securities: Common stocks $ 31,272 $ (634 ) $ 1,471 $ (330 ) $ 32,743 $ (964 ) Preferred stocks 113,742 (4,785 ) 523 (36 ) 114,265 (4,821 ) Total Equity securities $ 145,014 $ (5,419 ) $ 1,994 $ (366 ) $ 147,008 $ (5,785 ) Total fixed maturities and equity securities $ 1,256,887 $ (24,493 ) $ 127,403 $ (5,706 ) $ 1,384,290 $ (30,199 ) Our Company analyzes impaired securities quarterly to determine if any impairments are other-than-temporary. The above securities with unrealized losses are deemed to be temporarily impaired based on our evaluation. As of March 31, 2017, there were 398 Fixed maturities and 45 Equity securities in an unrealized loss position. As of December 31, 2016, there were 413 Fixed maturities and 75 Equity securities in an unrealized loss position. As of March 31, 2017 and December 31, 2016, the gross unrealized loss for the greater than 12 months category consists primarily of agency and foreign government bonds principally due to an unfavorable foreign exchange movement. To a lesser extent the gross unrealized loss for the greater than 12 months category is driven by unrealized losses on our longer dated municipal bonds and one commercial mortgage-backed security which were impacted by rising interest rates and widening credit spreads. The gross unrealized loss for the less than 12 months category for the period ended March 31, 2017 and December 31, 2016 consists primarily of agency mortgage-backed securities and corporate exposures due to an increase in interest rates since the time of purchase. As of March 31, 2017 and December 31, 2016, the largest unrealized loss by a non-government backed issuer in the investment portfolio was $1.1 million and $1.0 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. Our Company had two credit related OTTI losses of $1.1 million in the equity portfolio during the three months ended March 31, 2017. Our Company did not have any credit related losses during the three months ended March 31, 2016. As of March 31, 2017 and 2016, the cumulative amounts related to our Company’s credit loss portion of the OTTI losses on Fixed maturities was $2.4 million. There was no change to the cumulative amounts of our Company’s credit loss portion of OTTI for the three months ended March 31, 2017 and 2016. Our Company’s Net investment income was derived from the following sources: Three Months Ended March 31, amounts in thousands 2017 2016 Fixed maturities $ 18,341 $ 16,737 Equity securities 3,784 3,447 Short-term investments 212 210 Total investment income $ 22,337 $ 20,394 Investment expenses (889 ) (800 ) Net investment income $ 21,448 $ 19,594 Realized gains and losses, excluding net OTTI losses recognized in earnings, for the periods indicated, were as follows: Three Months Ended March 31, amounts in thousands 2017 2016 Fixed maturities: Gains $ 468 $ 2,548 Losses (1,256 ) (1,127 ) Fixed maturities, net $ (788 ) $ 1,421 Short-term: Gains $ 112 $ 268 Losses (191 ) (83 ) Short-term, net $ (79 ) $ 185 Equity securities: Gains $ 1,916 $ 609 Losses — (618 ) Equity securities, net $ 1,916 $ (9 ) Net realized gains $ 1,049 $ 1,597

Fair Value Measurement

Fair Value Measurement	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurement	NOTE 4. FAIR VALUE MEASUREMENT 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 common stocks 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 described above, 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 “Senior notes”) carried at amortized cost as of March 31, 2017 and December 31, 2016: March 31, 2017 amounts in thousands Level 1 Level 2 Level 3 Total Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 47,903 $ 222,106 $ — $ 270,009 States, municipalities and political subdivisions — 604,912 — 604,912 Mortgage-backed and asset-backed securities: Agency mortgage-backed securities — 468,255 — 468,255 Residential mortgage obligations — 16,970 — 16,970 Asset-backed securities — 331,567 — 331,567 Commercial mortgage-backed securities — 147,353 — 147,353 Subtotal $ — $ 964,145 $ — $ 964,145 Corporate exposures — 856,211 — 856,211 Total fixed maturities $ 47,903 $ 2,647,374 $ — $ 2,695,277 Equity securities: Common stocks $ 169,905 $ — $ — $ 169,905 Preferred stocks — 192,309 — 192,309 Total Equity securities $ 169,905 $ 192,309 $ — $ 362,214 Short-term investments 123,846 — — 123,846 Total assets measured at fair value $ 341,654 $ 2,839,683 $ — $ 3,181,337 Senior notes $ — $ 284,135 $ — $ 284,135 Total liabilities measured at fair value $ — $ 284,135 $ — $ 284,135 December 31, 2016 amounts in thousands Level 1 Level 2 Level 3 Total Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 47,704 $ 226,072 $ — $ 273,776 States, municipalities and political subdivisions — 547,415 — 547,415 Mortgage-backed and asset-backed securities: Agency mortgage-backed securities — 487,364 — 487,364 Residential mortgage obligations — 20,530 — 20,530 Asset-backed securities — 314,601 — 314,601 Commercial mortgage-backed securities — 154,139 — 154,139 Subtotal $ — $ 976,634 $ — $ 976,634 Corporate exposures — 838,057 — 838,057 Total fixed maturities $ 47,704 $ 2,588,178 $ — $ 2,635,882 Equity securities: Common stocks $ 164,087 $ — $ — $ 164,087 Preferred stocks — 185,055 — 185,055 Total Equity securities $ 164,087 $ 185,055 — $ 349,142 Short-term investments 143,539 — — 143,539 Total assets measured at fair value $ 355,330 $ 2,773,233 $ — $ 3,128,563 Senior notes $ — $ 280,316 $ — $ 280,316 Total liabilities measured at fair value $ — $ 280,316 $ — $ 280,316 All other financial assets and liabilities including Cash, Premium receivable, Reinsurance recoverable and Reinsurance balances payable are carried at cost, which approximates fair value. Our Company did not have any significant transfers between Level 1 and Level 2 classifications for the three months ended March 31, 2017. As of March 31, 2017, our Company did not have any Level 3 assets.

Loss Reserves

Loss Reserves	3 Months Ended
	Mar. 31, 2017
Insurance [Abstract]
Loss Reserves	NOTE 5. LOSS RESERVES 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 judgements may be revised as additional experience and other data become available and are reviewed, as new or improved methodologies are developed, or as laws change. Frequency/severity analyses are also performed for certain books of business. To the extent that reserves are found deficient or redundant, a strengthening or release is recognized as a charge or credit to earnings. The following table summarizes our Company’s Reserves for losses and LAE activity for the three months ended March 31, 2017 and 2016: For the Three Months Ended March 31, amounts in thousands 2017 2016 Net reserves for losses and LAE at beginning of year $ 1,510,451 $ 1,393,126 Provision for losses and LAE for claims occurring in the current year 162,515 154,790 Increase (decrease) in estimated losses and LAE for claims occurring in prior years 7,085 (1,834 ) Incurred losses and LAE $ 169,600 $ 152,956 Losses and LAE paid for claims occurring during: Current year (16,287 ) (15,325 ) Prior years (126,722 ) (112,084 ) Losses and LAE payments $ (143,009 ) $ (127,409 ) Foreign currency adjustment (226 ) (457 ) Net reserves for losses and LAE at end of period 1,536,816 1,418,216 Reinsurance recoverables on unpaid losses and LAE 794,576 793,632 Gross reserves for losses and LAE at end of period $ 2,331,392 $ 2,211,848 For the three months ended March 31, 2017, our Incurred losses and LAE increased $16.6 million as compared to the same period in 2016, primarily due to increases in Net earned premium resulting from growth in production, an $8.9 million increase in net prior accident year (“AY”) reserve strengthening, and $4.9 million of additional net current AY loss activity. During the three months ended March 31, 2017 we had Net prior AY reserve strengthening of $7.1 million compared to Net prior AY reserve releases of $1.8 million for the same period in 2016. This was mostly due to large loss activity in our Int’l Insurance and GlobalRe reporting segments, as well as a lower level of reserve releases within our U.S. Insurance reporting segment. Additional net current AY loss activity of $4.9 million increased $2.5 million as compared to the same period in 2016, primarily due to a large loss in our Int’l Insurance reporting segment and catastrophic loss activity mostly in our GlobalRe reporting segment.

Ceded Reinsurance

Ceded Reinsurance	3 Months Ended
	Mar. 31, 2017
Insurance [Abstract]
Ceded Reinsurance	NOTE 6. CEDED REINSURANCE As of March 31, 2017, the credit quality distribution of our Company’s Reinsurance recoverable of $1.1 billion for ceded paid losses, ceded unpaid losses and LAE, and ceded unearned premiums based on insurer financial strength ratings from A.M. Best or S&P was not significantly different from the credit quality distribution as of December 31, 2016. Our allowance for uncollectible reinsurance was $12.1 million as of March 31, 2017 and December 31, 2016. As of March 31, 2017, the list of our 10 largest reinsurers measured by the amount of Reinsurance recoverable for ceded losses and LAE and ceded unearned premium, together with the reinsurance recoverable and collateral, was comparable to the list as of December 31, 2016.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	NOTE 7. COMMITMENTS AND 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 March 31, 2017, our Company had received $9.0 million of the award ($7.0 million in loans and $2.0 million of the grant) and earned a loan forgiveness credit of $6.0 million with the State . 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”). The Guarantee will 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 will 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 will 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. 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.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	NOTE 8. STOCK-BASED COMPENSATION 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. Performance units generally cliff vest three years after they are granted. For the three months ended March 31, 2017, we granted 260,733 stock incentive units at a grant price between $55.55 and $58.88. Each performance unit and restricted stock unit represents a contingent right to receive one share of common stock as of the vesting date. Such common stock may be subject to forfeiture for the payment of any required tax withholding.

Stockholders Equity

Stockholders Equity	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
Stockholders' Equity	NOTE 9. STOCKHOLDERS’ EQUITY On March 29, 2017 our Company paid a dividend of $0.045 per share on The Navigators Group, Inc. Common stock to Stockholders of record on March 3, 2017. The declaration and amount of any future dividend will be at the discretion of the Board of Directors, and will depend upon many factors, including financial condition, results of operations, business requirements, regulatory, legal constraints and other factors the Board of Directors deems relevant.

Organization and Summary of S20

Organization and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2017
Accounting Policies [Abstract]
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 (“NMC”). NIC includes a branch in the United Kingdom (“U.K”). We also have operations domiciled in the U.K., Belgium, Hong Kong and throughout 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. Effective January 1, 2017, we sold our underwriting agency operations in Sweden and Denmark. The transaction represented a 100% disposition of our Sweden and Denmark corporations, NUAL AB and Navigators A/S, respectively. This transaction did not have a material impact on our financial statements.
Basis of Presentation	Basis of Presentation The Consolidated Balance Sheet at March 31, 2017 and the Consolidated Statements of Income, Comprehensive Income, Stockholders’ Equity and Cash Flows for the periods ended March 31, 2017 and 2016 are unaudited. The Balance Sheet at December 31, 2016 is derived from our audited Financial Statements. The accompanying Interim Consolidated Financial Statements reflect all adjustments, which, in the opinion of management, are necessary to fairly present the results of The Navigators Group, Inc. and its subsidiaries for the interim periods presented on the basis of United States generally accepted accounting principles (“GAAP” or “U.S. GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X as promulgated by the U.S. Securities and Exchange Commission. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. 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 and disclosures of contingent assets and liabilities at the date of the Financial Statements and the reported revenues and expenses during the reporting periods. The results of operations for any interim period are not necessarily indicative of results for the full year. The Interim Consolidated Financial Statements should be read in conjunction with our Annual Report on Form 10-K for the year ended December 31, 2016. Certain amounts for the prior period have been reclassified to conform with the current period presentation.
Reclassification	Certain amounts for the prior period have been reclassified to conform with the current period presentation.
Income Taxes	Income Taxes The interim income tax provision has been computed based on our estimated annual Effective tax rate, which represents our best estimate on a year to date basis for the interim period. As a result, the tax provision for a given quarter equals the difference between the provision recorded cumulatively year to date less the amount recorded cumulatively as of the end of the prior interim period. Our Effective tax rate for the quarter and year to date differs from the federal tax rate of 35% primarily due to an excess tax benefit related to the vesting of stock compensation at fair market value, tax-exempt investment income and dividends received deduction. In the first quarter of 2017, excess tax benefits related to the vesting of stock compensation was recognized as a reduction to Income tax expense rather than as an increase to Additional paid-in capital as a result of the adoption of the Accounting Standards Update (“ASU”) 2016-09 (see section New Accounting Standards Adopted in 2017
Significant Accounting Policies	Significant Accounting Policies There were no changes in our significant accounting policies subsequent to our Annual Report on Form 10-K for the year ended December 31, 2016.
New Accounting Standards Adopted in 2017	New Accounting Standards Adopted in 2017 Share-Based Compensation Accounting Effective January 1, 2017, our Company adopted ASU 2016-09, “Improvements to Employee Share-Based Payment Accounting” issued by the Financial Accounting Standards Board (the “FASB”). This guidance requires all income tax effects of awards to be recognized in the income statement when the awards vest or are settled, eliminates the requirement that excess tax benefits be realized before companies can recognize them, requires the presentation of excess tax benefits as an operating activity on the statement of cash flows, allows employers to increase the amounts withheld to cover income taxes on share-based compensation awards without requiring liability classification, requires the presentation of employee taxes paid as a financing activity on the statement of cash flows, and requires companies to elect whether they will account for award forfeitures by recognizing forfeitures only as they occur or by estimating the number of awards expected to be forfeited. The requirement to recognize all income tax effects of awards in the income statement when the awards vest or are settled was adopted on a prospective basis. Previously, these amounts were recorded in Additional paid-in capital. This change also prospectively impacts the calculation of potential common shares used to determine Diluted net income per common share under the treasury stock method. The new standard requires that assumed proceeds under the treasury stock method be modified to exclude the amount of excess tax benefits that previously would have been recognized in Additional paid-in capital. We elected to account for forfeitures of share-based payment awards by recognizing forfeitures of awards as they occur, and upon adoption of this guidance, the payment of employee taxes was retrospectively adjusted on the Consolidated Statements of Cash Flows to be classified as a financing activity. All other changes in the ASU did not result in cumulative-effect or retrospective adjustments. The adoption of this guidance did not materially impact our results of operations, financial condition or liquidity. Transition to Equity Method of Accounting Effective January 1, 2017, our Company adopted the ASU 2016-07, “Simplifying the Transition to the Equity Method of Accounting” issued by the FASB. This guidance eliminates the requirement to retrospectively apply equity method accounting when an investment that had been accounted for by another method initially qualifies for the equity method. Our Company did not have any investments transitioning to the equity method of accounting during the three months ended March 31, 2017. The adoption of this guidance did not impact our results of operations, financial condition or liquidity.
Recently Issued Accounting Standards Not Yet Adopted	Recently Issued Accounting Standards Not Yet Adopted Definition of a Business In January 2017, the FASB issued ASU 2017-01, “Clarifying the Definition of a Business” with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. This guidance is effective for annual periods beginning after December 15, 2017, and interim periods within those fiscal years with early adoption permitted. This guidance will be applied prospectively to any transactions occurring within the period of adoption. 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.

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2017
Segment Reporting [Abstract]
Financial Data by Segment	Financial data by segment for the three months ended March 31, 2017 and 2016 was as follows: Three Months Ended March 31, 2017 U.S. Int'l amounts in thousands Insurance Insurance GlobalRe Corporate (1) Total Net earned premiums $ 164,004 $ 84,086 $ 38,041 $ — $ 286,131 Net losses and LAE (98,826 ) (50,705 ) (20,069 ) — (169,600 ) Commission expenses (20,384 ) (19,233 ) (8,492 ) 265 (47,844 ) Other operating expenses (33,472 ) (19,793 ) (5,273 ) — (58,538 ) Other underwriting income (expense) 110 — 176 (265 ) 21 Underwriting profit (loss) $ 11,432 $ (5,645 ) $ 4,383 $ — $ 10,170 Net investment income 21,448 21,448 Net realized losses (44 ) (44 ) Interest expense (3,861 ) (3,861 ) Other income 1,047 1,047 Income (loss) before income taxes $ 11,432 $ (5,645 ) $ 4,383 $ 18,590 $ 28,760 Income tax expense (7,650 ) (7,650 ) Net income $ 21,110 Losses and LAE ratio 60.3 % 60.3 % 52.8 % 59.3 % Commission expense ratio 12.4 % 22.9 % 22.3 % 16.7 % Other operating expense ratio (2) 20.3 % 23.5 % 13.4 % 20.4 % Combined ratio 93.0 % 106.7 % 88.5 % 96.4 % Goodwill and other intangible assets $ 2,534 $ 3,908 $ — $ 6,442 (1) - Includes Corporate segment intercompany eliminations. (2) - Includes Other operating expenses and Other underwriting income (expense). Three Months Ended March 31, 2016 U.S. Int'l amounts in thousands Insurance Insurance GlobalRe Corporate (1) Total Net earned premiums $ 148,340 $ 78,008 $ 38,010 $ — $ 264,358 Net losses and LAE (91,512 ) (40,410 ) (21,034 ) — (152,956 ) Commission expenses (14,855 ) (15,355 ) (7,745 ) 401 (37,554 ) Other operating expenses (33,761 ) (21,771 ) (5,277 ) — (60,809 ) Other underwriting income (expense) 361 — 49 (401 ) 9 Underwriting profit $ 8,573 $ 472 $ 4,003 $ — $ 13,048 Net investment income 19,594 19,594 Net realized gains 1,597 1,597 Interest expense (3,858 ) (3,858 ) Other income 2,540 2,540 Income before income taxes $ 8,573 $ 472 $ 4,003 $ 19,873 $ 32,921 Income tax expense (9,989 ) (9,989 ) Net income $ 22,932 Losses and LAE ratio 61.7 % 51.8 % 55.3 % 57.9 % Commission expense ratio 10.0 % 19.7 % 20.4 % 14.2 % Other operating expense ratio (2) 22.5 % 27.9 % 13.8 % 23.0 % Combined ratio 94.2 % 99.4 % 89.5 % 95.1 % Goodwill and other intangible assets $ 2,534 $ 4,212 $ — $ 6,746 (1) - Includes Corporate segment intercompany eliminations. (2) - Includes Other operating expenses and Other underwriting income (expense).
Additional Financial Data by Segment	Revenue by operating segment for the three months ended March 31, 2017 and 2016 was as follows: Three Months Ended March 31, 2017 Three Months Ended March 31, 2016 % Change amounts in thousands Gross written premiums Ceded written premiums Net premiums Net earned premiums Gross written premiums Ceded written premiums Net written premiums Net earned premiums Gross written premiums Ceded written premiums Net written premiums Net earned premiums U.S. Insurance Marine $ 40,950 $ (17,520 ) $ 23,430 $ 22,694 $ 43,163 $ (17,647 ) $ 25,516 $ 23,250 (5.1 %) (0.7 %) (8.2 %) (2.4 %) P&C 170,634 (38,198 ) 132,436 119,123 141,278 (30,507 ) 110,771 109,159 20.8 % 25.2 % 19.6 % 9.1 % Professional 26,021 (5,769 ) 20,252 22,187 26,206 (6,343 ) 19,863 15,931 (0.7 %) (9.0 %) 2.0 % 39.3 % Total $ 237,605 $ (61,487 ) $ 176,118 $ 164,004 $ 210,647 $ (54,497 ) $ 156,150 $ 148,340 12.8 % 12.8 % 12.8 % 10.6 % Int'l Insurance Marine $ 68,833 $ (10,926 ) $ 57,907 $ 37,495 $ 71,948 $ (11,089 ) $ 60,859 $ 38,856 (4.3 %) (1.5 %) (4.9 %) (3.5 %) P&C 40,368 (29,646 ) 10,722 22,180 44,046 (17,229 ) 26,817 21,209 (8.4 %) 72.1 % (60.0 %) 4.6 % Professional Liability 32,659 (6,021 ) 26,638 24,411 28,149 (6,653 ) 21,496 17,943 16.0 % (9.5 %) 23.9 % 36.0 % Total $ 141,860 $ (46,593 ) $ 95,267 $ 84,086 $ 144,143 $ (34,971 ) $ 109,172 $ 78,008 (1.6 %) 33.2 % (12.7 %) 7.8 % GlobalRe $ 70,840 $ (5,062 ) $ 65,778 $ 38,041 $ 59,087 $ (4,589 ) $ 54,498 $ 38,010 19.9 % 10.3 % 20.7 % 0.1 % Total $ 450,305 $ (113,142 ) $ 337,163 $ 286,131 $ 413,877 $ (94,057 ) $ 319,820 $ 264,358 8.8 % 20.3 % 5.4 % 8.2 %

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2017
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 as of March 31, 2017 and December 31, 2016 and include Other-than-temporary-impairment (“OTTI”) securities recognized within Accumulated other comprehensive income (“AOCI”): March 31, 2017 Gross Gross Cost or Fair Unrealized Unrealized Amortized amounts in thousands Value Gains (Losses) Cost Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 270,009 $ 2,110 $ (3,671 ) $ 271,570 States, municipalities and political subdivisions 604,912 13,772 (3,353 ) 594,493 Mortgage-backed and asset-backed securities: Agency mortgage-backed securities 468,255 3,858 (7,051 ) 471,448 Residential mortgage obligations 16,970 439 (37 ) 16,568 Asset-backed securities 331,567 1,470 (769 ) 330,866 Commercial mortgage-backed securities 147,353 2,670 (1,843 ) 146,526 Subtotal $ 964,145 $ 8,437 $ (9,700 ) $ 965,408 Corporate exposures 856,211 12,948 (3,741 ) 847,004 Total fixed maturities $ 2,695,277 $ 37,267 $ (20,465 ) $ 2,678,475 Equity securities: Common stocks $ 169,905 $ 29,474 $ (652 ) $ 141,083 Preferred stocks 192,309 7,702 (1,220 ) 185,827 Total Equity securities $ 362,214 $ 37,176 $ (1,872 ) $ 326,910 Short-term investments 123,846 50 — 123,796 Total investments $ 3,181,337 $ 74,493 $ (22,337 ) $ 3,129,181 December 31, 2016 Gross Gross Cost or Fair Unrealized Unrealized Amortized amounts in thousands Value Gains (Losses) Cost Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 273,776 $ 2,192 $ (5,128 ) $ 276,712 States, municipalities and political subdivisions 547,415 11,542 (4,036 ) 539,909 Mortgage-backed and asset-backed securities: Agency mortgage-backed securities 487,364 4,016 (6,585 ) 489,933 Residential mortgage obligations 20,530 453 (55 ) 20,132 Asset-backed securities 314,601 824 (1,178 ) 314,955 Commercial mortgage-backed securities 154,139 2,859 (1,904 ) 153,184 Subtotal $ 976,634 $ 8,152 $ (9,722 ) $ 978,204 Corporate exposures 838,057 10,185 (5,528 ) 833,400 Total fixed maturities $ 2,635,882 $ 32,071 $ (24,414 ) $ 2,628,225 Equity securities: Common stocks $ 164,087 $ 24,677 $ (964 ) $ 140,374 Preferred stocks 185,055 2,339 (4,821 ) 187,537 Total Equity securities $ 349,142 $ 27,016 $ (5,785 ) $ 327,911 Short-term investments 143,539 88 — 143,451 Total investments $ 3,128,563 $ 59,175 $ (30,199 ) $ 3,099,587
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 March 31, 2017 are shown in the following table: March 31, 2017 Fair Amortized amounts in thousands Value Cost Due in one year or less $ 173,505 $ 174,014 Due after one year through five years 732,625 730,523 Due after five years through ten years 321,037 315,580 Due after ten years 503,965 492,950 Mortgage-backed and asset-backed securities 964,145 965,408 Total $ 2,695,277 $ 2,678,475
Summary of Aggregate Fair Value and Gross Unrealized Loss by Length of Time Securities had Continuously been in Gross Unrealized Loss Position	The following tables summarize all securities in a gross unrealized loss position as of March 31, 2017 and December 31, 2016, 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: March 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 $ 153,332 $ (2,275 ) $ 11,844 $ (1,396 ) $ 165,176 $ (3,671 ) States, municipalities and political subdivisions 120,372 (2,534 ) 17,706 (819 ) 138,078 (3,353 ) Mortgage-backed and asset-backed securities: Agency mortgage-backed securities 347,179 (6,622 ) 11,810 (429 ) 358,989 (7,051 ) Residential mortgage obligations 486 (5 ) 1,204 (32 ) 1,690 (37 ) Asset-backed securities 68,847 (708 ) 17,944 (61 ) 86,791 (769 ) Commercial mortgage-backed securities 51,336 (1,024 ) 6,385 (819 ) 57,721 (1,843 ) Subtotal $ 467,848 $ (8,359 ) $ 37,343 $ (1,341 ) $ 505,191 $ (9,700 ) Corporate exposures 269,427 (3,571 ) 21,901 (170 ) 291,328 (3,741 ) Total fixed maturities $ 1,010,979 $ (16,739 ) $ 88,794 $ (3,726 ) $ 1,099,773 $ (20,465 ) Equity securities: Common Stocks $ 28,586 $ (652 ) $ — $ — $ 28,586 $ (652 ) Preferred Stocks 42,470 (1,128 ) 2,557 (92 ) 45,027 (1,220 ) Total Equity securities $ 71,056 $ (1,780 ) $ 2,557 $ (92 ) $ 73,613 $ (1,872 ) Total fixed maturities and equity securities $ 1,082,035 $ (18,519 ) $ 91,351 $ (3,818 ) $ 1,173,386 $ (22,337 ) December 31, 2016 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 $ 150,891 $ (2,570 ) $ 16,819 $ (2,558 ) $ 167,710 $ (5,128 ) States, municipalities and political subdivisions 137,731 (3,111 ) 13,255 (925 ) 150,986 (4,036 ) Mortgage-backed and asset-backed securities: Agency mortgage-backed securities 349,119 (6,155 ) 12,401 (430 ) 361,520 (6,585 ) Residential mortgage obligations 953 (18 ) 926 (37 ) 1,879 (55 ) Asset-backed securities 95,514 (970 ) 48,093 (208 ) 143,607 (1,178 ) Commercial mortgage-backed securities 51,932 (1,164 ) 7,910 (740 ) 59,842 (1,904 ) Subtotal $ 497,518 $ (8,307 ) $ 69,330 $ (1,415 ) $ 566,848 $ (9,722 ) Corporate exposures 325,733 (5,086 ) 26,005 (442 ) 351,738 (5,528 ) Total fixed maturities $ 1,111,873 $ (19,074 ) $ 125,409 $ (5,340 ) $ 1,237,282 $ (24,414 ) Equity securities: Common stocks $ 31,272 $ (634 ) $ 1,471 $ (330 ) $ 32,743 $ (964 ) Preferred stocks 113,742 (4,785 ) 523 (36 ) 114,265 (4,821 ) Total Equity securities $ 145,014 $ (5,419 ) $ 1,994 $ (366 ) $ 147,008 $ (5,785 ) Total fixed maturities and equity securities $ 1,256,887 $ (24,493 ) $ 127,403 $ (5,706 ) $ 1,384,290 $ (30,199 )
Net Investment Income	Our Company’s Net investment income was derived from the following sources: Three Months Ended March 31, amounts in thousands 2017 2016 Fixed maturities $ 18,341 $ 16,737 Equity securities 3,784 3,447 Short-term investments 212 210 Total investment income $ 22,337 $ 20,394 Investment expenses (889 ) (800 ) Net investment income $ 21,448 $ 19,594
Realized Gains and Losses, Excluding Net Other-Than-Temporary Impairment Losses Recognized in Earnings	Realized gains and losses, excluding net OTTI losses recognized in earnings, for the periods indicated, were as follows: Three Months Ended March 31, amounts in thousands 2017 2016 Fixed maturities: Gains $ 468 $ 2,548 Losses (1,256 ) (1,127 ) Fixed maturities, net $ (788 ) $ 1,421 Short-term: Gains $ 112 $ 268 Losses (191 ) (83 ) Short-term, net $ (79 ) $ 185 Equity securities: Gains $ 1,916 $ 609 Losses — (618 ) Equity securities, net $ 1,916 $ (9 ) Net realized gains $ 1,049 $ 1,597

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	3 Months Ended
	Mar. 31, 2017
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 described above, 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 “Senior notes”) carried at amortized cost as of March 31, 2017 and December 31, 2016: March 31, 2017 amounts in thousands Level 1 Level 2 Level 3 Total Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 47,903 $ 222,106 $ — $ 270,009 States, municipalities and political subdivisions — 604,912 — 604,912 Mortgage-backed and asset-backed securities: Agency mortgage-backed securities — 468,255 — 468,255 Residential mortgage obligations — 16,970 — 16,970 Asset-backed securities — 331,567 — 331,567 Commercial mortgage-backed securities — 147,353 — 147,353 Subtotal $ — $ 964,145 $ — $ 964,145 Corporate exposures — 856,211 — 856,211 Total fixed maturities $ 47,903 $ 2,647,374 $ — $ 2,695,277 Equity securities: Common stocks $ 169,905 $ — $ — $ 169,905 Preferred stocks — 192,309 — 192,309 Total Equity securities $ 169,905 $ 192,309 $ — $ 362,214 Short-term investments 123,846 — — 123,846 Total assets measured at fair value $ 341,654 $ 2,839,683 $ — $ 3,181,337 Senior notes $ — $ 284,135 $ — $ 284,135 Total liabilities measured at fair value $ — $ 284,135 $ — $ 284,135 December 31, 2016 amounts in thousands Level 1 Level 2 Level 3 Total Fixed maturities: U.S. Treasury bonds, agency bonds and foreign government bonds $ 47,704 $ 226,072 $ — $ 273,776 States, municipalities and political subdivisions — 547,415 — 547,415 Mortgage-backed and asset-backed securities: Agency mortgage-backed securities — 487,364 — 487,364 Residential mortgage obligations — 20,530 — 20,530 Asset-backed securities — 314,601 — 314,601 Commercial mortgage-backed securities — 154,139 — 154,139 Subtotal $ — $ 976,634 $ — $ 976,634 Corporate exposures — 838,057 — 838,057 Total fixed maturities $ 47,704 $ 2,588,178 $ — $ 2,635,882 Equity securities: Common stocks $ 164,087 $ — $ — $ 164,087 Preferred stocks — 185,055 — 185,055 Total Equity securities $ 164,087 $ 185,055 — $ 349,142 Short-term investments 143,539 — — 143,539 Total assets measured at fair value $ 355,330 $ 2,773,233 $ — $ 3,128,563 Senior notes $ — $ 280,316 $ — $ 280,316 Total liabilities measured at fair value $ — $ 280,316 $ — $ 280,316

Loss Reserves (Tables)

Loss Reserves (Tables)	3 Months Ended
	Mar. 31, 2017
Insurance [Abstract]
Summary of Reserves for Losses and LAE Activity	The following table summarizes our Company’s Reserves for losses and LAE activity for the three months ended March 31, 2017 and 2016: For the Three Months Ended March 31, amounts in thousands 2017 2016 Net reserves for losses and LAE at beginning of year $ 1,510,451 $ 1,393,126 Provision for losses and LAE for claims occurring in the current year 162,515 154,790 Increase (decrease) in estimated losses and LAE for claims occurring in prior years 7,085 (1,834 ) Incurred losses and LAE $ 169,600 $ 152,956 Losses and LAE paid for claims occurring during: Current year (16,287 ) (15,325 ) Prior years (126,722 ) (112,084 ) Losses and LAE payments $ (143,009 ) $ (127,409 ) Foreign currency adjustment (226 ) (457 ) Net reserves for losses and LAE at end of period 1,536,816 1,418,216 Reinsurance recoverables on unpaid losses and LAE 794,576 793,632 Gross reserves for losses and LAE at end of period $ 2,331,392 $ 2,211,848

Organization and Summary of S25

Organization and Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2017USD ($)Insurance	Jan. 01, 2017
Organization And Summary Of Significant Accounting Policies [Line Items]
Number of insurance companies | Insurance	2
Percentage of ownership interest sold		100.00%
Effective Tax Rate	35.00%
Investments transitioning to equity method of accounting | $	$ 0
Syndicate 1,221
Organization And Summary Of Significant Accounting Policies [Line Items]
Percentage control of stamp capacity	100.00%

Segment Information - Additiona

Segment Information - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2017Segment
Segment Reporting Information [Line Items]
Number of underwriting Segments	3
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
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net earned premiums		$ 286,131	$ 264,358
Net losses and LAE		(169,600)	(152,956)
Commission expenses		(47,844)	(37,554)
Other operating expenses		(58,538)	(60,809)
Other underwriting income (expense)		21	9
Underwriting profit (loss)		10,170	13,048
Net investment income		21,448	19,594
Net realized gains (losses)		(44)	1,597
Interest expense		(3,861)	(3,858)
Other income		1,047	2,540
Income before income taxes		28,760	32,921
Income tax expense		(7,650)	(9,989)
Net income		$ 21,110	$ 22,932
Losses and LAE ratio		59.30%	57.90%
Commission expense ratio		16.70%	14.20%
Other operating expense ratio	[1]	20.40%	23.00%
Combined ratio		96.40%	95.10%
Goodwill and other intangible assets		$ 6,442	$ 6,746	$ 6,451
U.S.Insurance
Segment Reporting Information [Line Items]
Net earned premiums		164,004	148,340
Net losses and LAE		(98,826)	(91,512)
Commission expenses		(20,384)	(14,855)
Other operating expenses		(33,472)	(33,761)
Other underwriting income (expense)		110	361
Underwriting profit (loss)		11,432	8,573
Income before income taxes		$ 11,432	$ 8,573
Losses and LAE ratio		60.30%	61.70%
Commission expense ratio		12.40%	10.00%
Other operating expense ratio	[1]	20.30%	22.50%
Combined ratio		93.00%	94.20%
Goodwill and other intangible assets		$ 2,534	$ 2,534
International Insurance
Segment Reporting Information [Line Items]
Net earned premiums		84,086	78,008
Net losses and LAE		(50,705)	(40,410)
Commission expenses		(19,233)	(15,355)
Other operating expenses		(19,793)	(21,771)
Underwriting profit (loss)		(5,645)	472
Income before income taxes		$ (5,645)	$ 472
Losses and LAE ratio		60.30%	51.80%
Commission expense ratio		22.90%	19.70%
Other operating expense ratio	[1]	23.50%	27.90%
Combined ratio		106.70%	99.40%
Goodwill and other intangible assets		$ 3,908	$ 4,212
Global Reinsurance
Segment Reporting Information [Line Items]
Net earned premiums		38,041	38,010
Net losses and LAE		(20,069)	(21,034)
Commission expenses		(8,492)	(7,745)
Other operating expenses		(5,273)	(5,277)
Other underwriting income (expense)		176	49
Underwriting profit (loss)		4,383	4,003
Income before income taxes		$ 4,383	$ 4,003
Losses and LAE ratio		52.80%	55.30%
Commission expense ratio		22.30%	20.40%
Other operating expense ratio	[1]	13.40%	13.80%
Combined ratio		88.50%	89.50%
Corporate
Segment Reporting Information [Line Items]
Net investment income	[2]	$ 21,448	$ 19,594
Net realized gains (losses)	[2]	(44)	1,597
Interest expense	[2]	(3,861)	(3,858)
Other income	[2]	1,047	2,540
Income before income taxes	[2]	18,590	19,873
Income tax expense	[2]	(7,650)	(9,989)
Intersegment Elimination
Segment Reporting Information [Line Items]
Commission expenses	[2]	265	401
Other underwriting income (expense)	[2]	$ (265)	$ (401)
[1]	Includes Other operating expenses and Other underwriting income (expense).
[2]	Includes Corporate segment intercompany eliminations.

Additional Financial Data by Se

Additional Financial Data by Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Gross written premiums	$ 450,305	$ 413,877
Ceded written premiums	(113,142)	(94,057)
Net written premiums	337,163	319,820
Net earned premiums	$ 286,131	264,358
% Change Gross written premiums	8.80%
% Change Ceded written premiums	20.30%
% Change Net written premiums	5.40%
% Change Net earned premiums	8.20%
U.S.Insurance
Segment Reporting Information [Line Items]
Gross written premiums	$ 237,605	210,647
Ceded written premiums	(61,487)	(54,497)
Net written premiums	176,118	156,150
Net earned premiums	$ 164,004	148,340
% Change Gross written premiums	12.80%
% Change Ceded written premiums	12.80%
% Change Net written premiums	12.80%
% Change Net earned premiums	10.60%
U.S.Insurance | Marine
Segment Reporting Information [Line Items]
Gross written premiums	$ 40,950	43,163
Ceded written premiums	(17,520)	(17,647)
Net written premiums	23,430	25,516
Net earned premiums	$ 22,694	23,250
% Change Gross written premiums	(5.10%)
% Change Ceded written premiums	(0.70%)
% Change Net written premiums	(8.20%)
% Change Net earned premiums	(2.40%)
U.S.Insurance | Property Casualty
Segment Reporting Information [Line Items]
Gross written premiums	$ 170,634	141,278
Ceded written premiums	(38,198)	(30,507)
Net written premiums	132,436	110,771
Net earned premiums	$ 119,123	109,159
% Change Gross written premiums	20.80%
% Change Ceded written premiums	25.20%
% Change Net written premiums	19.60%
% Change Net earned premiums	9.10%
U.S.Insurance | Professional Liability
Segment Reporting Information [Line Items]
Gross written premiums	$ 26,021	26,206
Ceded written premiums	(5,769)	(6,343)
Net written premiums	20,252	19,863
Net earned premiums	$ 22,187	15,931
% Change Gross written premiums	(0.70%)
% Change Ceded written premiums	(9.00%)
% Change Net written premiums	2.00%
% Change Net earned premiums	39.30%
International Insurance
Segment Reporting Information [Line Items]
Gross written premiums	$ 141,860	144,143
Ceded written premiums	(46,593)	(34,971)
Net written premiums	95,267	109,172
Net earned premiums	$ 84,086	78,008
% Change Gross written premiums	(1.60%)
% Change Ceded written premiums	33.20%
% Change Net written premiums	(12.70%)
% Change Net earned premiums	7.80%
International Insurance | Marine
Segment Reporting Information [Line Items]
Gross written premiums	$ 68,833	71,948
Ceded written premiums	(10,926)	(11,089)
Net written premiums	57,907	60,859
Net earned premiums	$ 37,495	38,856
% Change Gross written premiums	(4.30%)
% Change Ceded written premiums	(1.50%)
% Change Net written premiums	(4.90%)
% Change Net earned premiums	(3.50%)
International Insurance | Property Casualty
Segment Reporting Information [Line Items]
Gross written premiums	$ 40,368	44,046
Ceded written premiums	(29,646)	(17,229)
Net written premiums	10,722	26,817
Net earned premiums	$ 22,180	21,209
% Change Gross written premiums	(8.40%)
% Change Ceded written premiums	72.10%
% Change Net written premiums	(60.00%)
% Change Net earned premiums	4.60%
International Insurance | Professional Liability
Segment Reporting Information [Line Items]
Gross written premiums	$ 32,659	28,149
Ceded written premiums	(6,021)	(6,653)
Net written premiums	26,638	21,496
Net earned premiums	$ 24,411	17,943
% Change Gross written premiums	16.00%
% Change Ceded written premiums	(9.50%)
% Change Net written premiums	23.90%
% Change Net earned premiums	36.00%
Global Reinsurance
Segment Reporting Information [Line Items]
Gross written premiums	$ 70,840	59,087
Ceded written premiums	(5,062)	(4,589)
Net written premiums	65,778	54,498
Net earned premiums	$ 38,041	$ 38,010
% Change Gross written premiums	19.90%
% Change Ceded written premiums	10.30%
% Change Net written premiums	20.70%
% Change Net earned premiums	0.10%

Available-for-Sale Investments

Available-for-Sale Investments Including Other-Than-Temporarily Impaired Securities Recognized within Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Gain (Loss) on Investments [Line Items]
Total investments	$ 3,181,337	$ 3,128,563
Gross Unrealized Gains	74,493	59,175
Gross Unrealized Losses	(22,337)	(30,199)
Amortized Cost	3,129,181	3,099,587
Fixed maturities
Gain (Loss) on Investments [Line Items]
Total investments	2,695,277	2,635,882
Gross Unrealized Gains	37,267	32,071
Gross Unrealized Losses	(20,465)	(24,414)
Amortized Cost	2,678,475	2,628,225
Fixed maturities | U.S. Treasury bonds, agency bonds, and foreign
Gain (Loss) on Investments [Line Items]
Total investments	270,009	273,776
Gross Unrealized Gains	2,110	2,192
Gross Unrealized Losses	(3,671)	(5,128)
Amortized Cost	271,570	276,712
Fixed maturities | States, municipalities and political subdivisions
Gain (Loss) on Investments [Line Items]
Total investments	604,912	547,415
Gross Unrealized Gains	13,772	11,542
Gross Unrealized Losses	(3,353)	(4,036)
Amortized Cost	594,493	539,909
Fixed maturities | Agency mortgage-backed securities
Gain (Loss) on Investments [Line Items]
Total investments	468,255	487,364
Gross Unrealized Gains	3,858	4,016
Gross Unrealized Losses	(7,051)	(6,585)
Amortized Cost	471,448	489,933
Fixed maturities | Residential Mortgage Backed Securities
Gain (Loss) on Investments [Line Items]
Total investments	16,970	20,530
Gross Unrealized Gains	439	453
Gross Unrealized Losses	(37)	(55)
Amortized Cost	16,568	20,132
Fixed maturities | Asset-backed securities
Gain (Loss) on Investments [Line Items]
Total investments	331,567	314,601
Gross Unrealized Gains	1,470	824
Gross Unrealized Losses	(769)	(1,178)
Amortized Cost	330,866	314,955
Fixed maturities | Commercial mortgage-backed securities
Gain (Loss) on Investments [Line Items]
Total investments	147,353	154,139
Gross Unrealized Gains	2,670	2,859
Gross Unrealized Losses	(1,843)	(1,904)
Amortized Cost	146,526	153,184
Fixed maturities | Mortgage-backed and asset-backed securities
Gain (Loss) on Investments [Line Items]
Total investments	964,145	976,634
Gross Unrealized Gains	8,437	8,152
Gross Unrealized Losses	(9,700)	(9,722)
Amortized Cost	965,408	978,204
Fixed maturities | Corporate exposures
Gain (Loss) on Investments [Line Items]
Total investments	856,211	838,057
Gross Unrealized Gains	12,948	10,185
Gross Unrealized Losses	(3,741)	(5,528)
Amortized Cost	847,004	833,400
Equity Securities
Gain (Loss) on Investments [Line Items]
Total investments	362,214	349,142
Gross Unrealized Gains	37,176	27,016
Gross Unrealized Losses	(1,872)	(5,785)
Amortized Cost	326,910	327,911
Equity Securities | Common stocks
Gain (Loss) on Investments [Line Items]
Total investments	169,905	164,087
Gross Unrealized Gains	29,474	24,677
Gross Unrealized Losses	(652)	(964)
Amortized Cost	141,083	140,374
Equity Securities | Preferred stocks
Gain (Loss) on Investments [Line Items]
Total investments	192,309	185,055
Gross Unrealized Gains	7,702	2,339
Gross Unrealized Losses	(1,220)	(4,821)
Amortized Cost	185,827	187,537
Short-term investments
Gain (Loss) on Investments [Line Items]
Total investments	123,846	143,539
Gross Unrealized Gains	50	88
Amortized Cost	$ 123,796	$ 143,451

Investments - Additional Inform

Investments - Additional Information (Detail)	3 Months Ended		12 Months Ended
	Mar. 31, 2017USD ($)Security	Mar. 31, 2016USD ($)	Dec. 31, 2016USD ($)Security
Schedule of Investments [Line Items]
Other invested assets	$ 1,776,000		$ 1,960,000
Non-credit OTTI on fixed maturities in a net unrealized gain position	400,000		400,000
Gross Unrealized Loss	22,337,000		$ 30,199,000
OTTI losses		$ 0
Change to cumulative amounts of credit loss portion of OTTI losses	$ 0	0
Equity Securities
Schedule of Investments [Line Items]
Number of securities in unrealized loss position | Security	45		75
Gross Unrealized Loss	$ 1,872,000		$ 5,785,000
Fixed maturities
Schedule of Investments [Line Items]
Number of securities in unrealized loss position | Security	398		413
Gross Unrealized Loss	$ 20,465,000		$ 24,414,000
OTTI losses	1,100,000
Cumulative amounts related to credit loss portion of OTTI losses	2,400,000	$ 2,400,000
Non-government-backed securities
Schedule of Investments [Line Items]
Gross Unrealized Loss	$ 1,100,000		$ 1,000,000
Non-government-backed securities | Maximum
Schedule of Investments [Line Items]
Percentage of investment	5.00%		5.00%
Mortgage-backed and asset-backed securities
Schedule of Investments [Line Items]
Securities, effective maturities	4 years 9 months 18 days
Mortgage-backed and asset-backed securities | Fixed maturities
Schedule of Investments [Line Items]
Gross Unrealized Loss	$ 9,700,000		$ 9,722,000

Scheduled Maturity Dates for Fi

Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value
Due in one year or less	$ 173,505
Due after one year through five years	732,625
Due after five years through ten years	321,037
Due after ten years	503,965
Mortgage-backed and asset-backed securities	964,145
Total	2,695,277	$ 2,635,882
Amortized Cost
Due in one year or less	174,014
Due after one year through five years	730,523
Due after five years through ten years	315,580
Due after ten years	492,950
Mortgage-backed and asset-backed securities	965,408
Total	$ 2,678,475	$ 2,628,225

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	Mar. 31, 2017	Dec. 31, 2016
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	$ 1,082,035	$ 1,256,887
Less than 12 months Gross Unrealized Losses	(18,519)	(24,493)
Greater than 12 months Fair Value	91,351	127,403
Greater than 12 months Gross Unrealized Losses	(3,818)	(5,706)
Fair Value	1,173,386	1,384,290
Gross Unrealized Losses	(22,337)	(30,199)
Fixed maturities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	1,010,979	1,111,873
Less than 12 months Gross Unrealized Losses	(16,739)	(19,074)
Greater than 12 months Fair Value	88,794	125,409
Greater than 12 months Gross Unrealized Losses	(3,726)	(5,340)
Fair Value	1,099,773	1,237,282
Gross Unrealized Losses	(20,465)	(24,414)
Fixed maturities | U.S. Treasury bonds, agency bonds, and foreign
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	153,332	150,891
Less than 12 months Gross Unrealized Losses	(2,275)	(2,570)
Greater than 12 months Fair Value	11,844	16,819
Greater than 12 months Gross Unrealized Losses	(1,396)	(2,558)
Fair Value	165,176	167,710
Gross Unrealized Losses	(3,671)	(5,128)
Fixed maturities | States, municipalities and political subdivisions
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	120,372	137,731
Less than 12 months Gross Unrealized Losses	(2,534)	(3,111)
Greater than 12 months Fair Value	17,706	13,255
Greater than 12 months Gross Unrealized Losses	(819)	(925)
Fair Value	138,078	150,986
Gross Unrealized Losses	(3,353)	(4,036)
Fixed maturities | Agency mortgage-backed securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	347,179	349,119
Less than 12 months Gross Unrealized Losses	(6,622)	(6,155)
Greater than 12 months Fair Value	11,810	12,401
Greater than 12 months Gross Unrealized Losses	(429)	(430)
Fair Value	358,989	361,520
Gross Unrealized Losses	(7,051)	(6,585)
Fixed maturities | Residential Mortgage Backed Securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	486	953
Less than 12 months Gross Unrealized Losses	(5)	(18)
Greater than 12 months Fair Value	1,204	926
Greater than 12 months Gross Unrealized Losses	(32)	(37)
Fair Value	1,690	1,879
Gross Unrealized Losses	(37)	(55)
Fixed maturities | Asset-backed securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	68,847	95,514
Less than 12 months Gross Unrealized Losses	(708)	(970)
Greater than 12 months Fair Value	17,944	48,093
Greater than 12 months Gross Unrealized Losses	(61)	(208)
Fair Value	86,791	143,607
Gross Unrealized Losses	(769)	(1,178)
Fixed maturities | Commercial mortgage-backed securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	51,336	51,932
Less than 12 months Gross Unrealized Losses	(1,024)	(1,164)
Greater than 12 months Fair Value	6,385	7,910
Greater than 12 months Gross Unrealized Losses	(819)	(740)
Fair Value	57,721	59,842
Gross Unrealized Losses	(1,843)	(1,904)
Fixed maturities | Mortgage-backed and asset-backed securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	467,848	497,518
Less than 12 months Gross Unrealized Losses	(8,359)	(8,307)
Greater than 12 months Fair Value	37,343	69,330
Greater than 12 months Gross Unrealized Losses	(1,341)	(1,415)
Fair Value	505,191	566,848
Gross Unrealized Losses	(9,700)	(9,722)
Fixed maturities | Corporate exposures
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	269,427	325,733
Less than 12 months Gross Unrealized Losses	(3,571)	(5,086)
Greater than 12 months Fair Value	21,901	26,005
Greater than 12 months Gross Unrealized Losses	(170)	(442)
Fair Value	291,328	351,738
Gross Unrealized Losses	(3,741)	(5,528)
Equity Securities
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	71,056	145,014
Less than 12 months Gross Unrealized Losses	(1,780)	(5,419)
Greater than 12 months Fair Value	2,557	1,994
Greater than 12 months Gross Unrealized Losses	(92)	(366)
Fair Value	73,613	147,008
Gross Unrealized Losses	(1,872)	(5,785)
Equity Securities | Common stocks
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	28,586	31,272
Less than 12 months Gross Unrealized Losses	(652)	(634)
Greater than 12 months Fair Value	0	1,471
Greater than 12 months Gross Unrealized Losses	0	(330)
Fair Value	28,586	32,743
Gross Unrealized Losses	(652)	(964)
Equity Securities | Preferred stocks
Gain (Loss) on Investments [Line Items]
Less than 12 months Fair Value	42,470	113,742
Less than 12 months Gross Unrealized Losses	(1,128)	(4,785)
Greater than 12 months Fair Value	2,557	523
Greater than 12 months Gross Unrealized Losses	(92)	(36)
Fair Value	45,027	114,265
Gross Unrealized Losses	$ (1,220)	$ (4,821)

Net Investment Income (Detail)

Net Investment Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Net Investment Income [Line Items]
Investment Income	$ 22,337	$ 20,394
Investment expenses	(889)	(800)
Net investment income	21,448	19,594
Fixed maturities
Net Investment Income [Line Items]
Investment Income	18,341	16,737
Equity Securities
Net Investment Income [Line Items]
Investment Income	3,784	3,447
Short-term investments
Net Investment Income [Line Items]
Investment Income	$ 212	$ 210

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
	Mar. 31, 2017	Mar. 31, 2016
Gain (Loss) on Investments [Line Items]
Net realized gains (losses)	$ 1,049	$ 1,597
Fixed maturities
Gain (Loss) on Investments [Line Items]
Gains	468	2,548
Losses	(1,256)	(1,127)
Net realized gains (losses)	(788)	1,421
Short-term investments
Gain (Loss) on Investments [Line Items]
Gains	112	268
Losses	(191)	(83)
Net realized gains (losses)	(79)	185
Equity Securities
Gain (Loss) on Investments [Line Items]
Gains	1,916	609
Losses	0	(618)
Net realized gains (losses)	$ 1,916	$ (9)

Fair Value Measurement - Additi

Fair Value Measurement - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2017USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Significant transfers between Level 1 and Level 2	$ 0
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Level 3 assets	$ 0
5.75% Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate stated on senior notes	5.75%
Senior notes due date	Oct. 15, 2023

Fixed Maturities and Equity Sec

Fixed Maturities and Equity Securities by Asset Class that are Measured at Fair Value (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	$ 3,181,337	$ 3,128,563
Total liabilities measured at fair value	284,135	280,316
Fixed maturities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	2,695,277	2,635,882
Fixed maturities | U.S. Treasury bonds, agency bonds, and foreign
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	270,009	273,776
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	604,912	547,415
Fixed maturities | Agency mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	468,255	487,364
Fixed maturities | Residential Mortgage Backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	16,970	20,530
Fixed maturities | Asset-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	331,567	314,601
Fixed maturities | Commercial mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	147,353	154,139
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	964,145	976,634
Fixed maturities | Corporate exposures
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	856,211	838,057
Equity Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	362,214	349,142
Equity Securities | Common stocks
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	169,905	164,087
Equity Securities | Preferred stocks
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	192,309	185,055
Short-term investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	123,846	143,539
Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes, at fair value	284,135	280,316
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	341,654	355,330
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	47,903	47,704
Level 1 | Fixed maturities | U.S. Treasury bonds, agency bonds, and foreign
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	47,903	47,704
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 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	169,905	164,087
Level 1 | Equity Securities | Common stocks
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	169,905	164,087
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	123,846	143,539
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]
Fixed maturities and equity securities, at fair Value	2,839,683	2,773,233
Total liabilities measured at fair value	284,135	280,316
Level 2 | Fixed maturities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	2,647,374	2,588,178
Level 2 | Fixed maturities | U.S. Treasury bonds, agency bonds, and foreign
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	222,106	226,072
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	604,912	547,415
Level 2 | Fixed maturities | Agency mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	468,255	487,364
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	16,970	20,530
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	331,567	314,601
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	147,353	154,139
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	964,145	976,634
Level 2 | Fixed maturities | Corporate exposures
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	856,211	838,057
Level 2 | Equity Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	192,309	185,055
Level 2 | 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 2 | Equity Securities | Preferred stocks
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	192,309	185,055
Level 2 | Short-term investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, at fair Value	0	0
Level 2 | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes, at fair value	284,135	280,316
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities and equity securities, 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
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 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

Summary of Reserves for Losses

Summary of Reserves for Losses and LAE Activity (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Insurance [Abstract]
Net reserves for losses and LAE at beginning of year	$ 1,510,451	$ 1,393,126
Provision for losses and LAE for claims occurring in the current year	162,515	154,790
Increase (decrease) in estimated losses and LAE for claims occurring in prior years	7,085	(1,834)
Incurred losses and LAE	169,600	152,956
Losses and LAE paid for claims occurring during:
Current year	(16,287)	(15,325)
Prior years	(126,722)	(112,084)
Losses and LAE payments	(143,009)	(127,409)
Foreign currency adjustment	(226)	(457)
Net reserves for losses and LAE at end of period	1,536,816	1,418,216
Reinsurance recoverables on unpaid losses and LAE	794,576	793,632	$ 779,276
Reserves for losses and loss adjustment expenses	$ 2,331,392	$ 2,211,848	$ 2,289,727

Loss Reserves - Additional Info

Loss Reserves - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Insurance [Abstract]
Increase in incurred losses and LAE	$ 16,600
Increase in net prior accident year reserve strengthening	8,900
Additional net current AY loss activity	4,900
Net prior AY reserve strengthening	7,085	$ (1,834)
Increase in additional net current AY loss activity	$ 2,500

Ceded Reinsurance - Additional

Ceded Reinsurance - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Insurance [Abstract]
Reinsurance recoverables	$ 1,100
Reserve for uncollectible reinsurance amount	$ 12.1	$ 12.1

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2013	Dec. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Incentive awarded to the company by the State of Connecticut, total	$ 9		$ 11.5
Incentive awarded to the company by the State of Connecticut, non-interest bearing loans	7		8
Incentive awarded to the company by the State of Connecticut, grants	$ 2		$ 3.5
Non-interest bearing incentive loan term	10 years
Forgiveness awarded to the company by the state of Connecticut	$ 6
Incentive awarded to the company by the State of Connecticut, revenue recognized	0.3	$ 0.4
Incentive awarded to the company by the State of Connecticut, deferred revenue	$ 4.6			$ 4.8

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2017$ / sharesshares
Non-Performance Based Grants | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based payment award, award vesting period	3 years
Non-Performance Based Grants | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based payment award, award vesting period	4 years
Performance Based Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based payment award, award vesting period	3 years
Stock incentive Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive units granted | shares	260,733
Stock incentive Units | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive unit, grant price	$ 55.55
Stock incentive Units | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive unit, grant price	$ 58.88

Stockholders Equity - Additiona

Stockholders Equity - Additional Information (Detail) - $ / shares	Mar. 29, 2017	Mar. 31, 2017
Equity [Abstract]
Common stock dividend paid per share	$ 0.045
Dividend payable record date		Mar. 3, 2017