Navigators (NAVG) 10-Q 8 Nov 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2013	Oct. 25, 2013
Document Information [Line Items]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-13	'
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'
Trading Symbol	'NAVG	'
Entity Registrant Name	'NAVIGATORS GROUP INC	'
Entity Central Index Key	'0000793547	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	14,147,820

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Investments and cash:	'	'
Fixed maturities, available-for-sale, at fair value (amortized cost: 2013, $1,958,434; 2012, $2,034,765)	$1,981,731	$2,121,833
Equity securities, available-for-sale, at fair value (cost: 2013, $131,046; 2012, $85,004)	158,890	101,297
Short-term investments, at cost which approximates fair value	152,987	153,788
Cash	130,513	45,336
Total investments and cash	2,424,121	2,422,254
Premiums receivable	355,578	320,182
Prepaid reinsurance premiums	253,435	221,015
Reinsurance recoverable on paid losses	44,955	49,282
Reinsurance recoverable on unpaid losses and loss adjustment expenses	796,289	880,139
Deferred policy acquisition costs	63,171	61,005
Accrued investment income	13,746	12,587
Goodwill and other intangible assets	7,065	7,093
Deferred income tax, net	22,639	3,216
Receivable for investments sold	59,453	4,310
Other assets	34,124	26,587
Total assets	4,074,576	4,007,670
Liabilities:	'	'
Reserves for losses and loss adjustment expenses	2,050,720	2,097,048
Unearned premiums	716,236	642,407
Reinsurance balances payable	180,563	165,813
Senior Notes	114,542	114,424
Current income tax payable, net	5,449	2,133
Payable for investments purchased	48,855	58,345
Accounts payable and other liabilities	58,329	48,015
Total liabilities	3,174,694	3,128,185
Stockholders' equity:	'	'
Preferred stock, $.10 par value, authorized 1,000,000 shares, none issued	'	'
Common stock, $.10 par value, authorized 50,000,000 shares, issued 17,658,292 shares for 2013 and 17,558,046 shares for 2012	1,765	1,755
Additional paid-in capital	334,421	329,452
Treasury stock, at cost (3,511,380 shares for 2013 and 2012)	-155,801	-155,801
Retained earnings	678,004	628,871
Accumulated other comprehensive income	41,493	75,208
Total stockholders' equity	899,882	879,485
Total liabilities and stockholders' equity	$4,074,576	$4,007,670

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
Fixed maturities, available-for-sale, amortized cost	$1,958,434	$2,034,765
Equity securities, available-for-sale, cost	$131,046	$85,004
Preferred stock, par value	$0.10	$0.10
Preferred stock, authorized shares	1,000,000	1,000,000
Preferred stock, issued shares	'	'
Common stock, par value	$0.10	$0.10
Common stock, authorized shares	50,000,000	50,000,000
Common stock, issued shares	17,658,292	17,558,046
Treasury stock, shares	3,511,380	3,511,380

Consolidated_Statements_of_Inc

Consolidated Statements of Income (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Gross written premiums	$312,076	$298,742	$1,037,426	$964,878
Revenues:	'	'	'	'
Net written premiums	196,556	188,046	664,477	621,343
Change in unearned premiums	17,339	13,216	-42,440	-40,945
Net earned premiums	213,895	201,262	622,037	580,398
Net investment income	14,094	13,597	41,997	40,632
Total other-than-temporary impairment losses	-1,821	'	-1,863	-693
Portion of loss recognized in other comprehensive income (before tax)	'	'	'	43
Net other-than-temporary impairment losses recognized in earnings	-1,821	'	-1,863	-650
Net realized gains (losses)	-988	4,761	7,171	10,820
Other income (expense)	-210	789	-507	2,087
Total revenues	224,970	220,409	668,835	633,287
Expenses:	'	'	'	'
Net losses and loss adjustment expenses	125,086	128,850	387,576	370,242
Commission expenses	27,685	31,258	82,631	90,211
Other operating expenses	39,056	40,112	120,608	116,238
Interest expense	2,053	2,049	6,156	6,147
Total expenses	193,880	202,269	596,971	582,838
Income (loss) before income taxes	31,090	18,140	71,864	50,449
Income tax expense (benefit)	9,804	5,225	22,731	14,731
Net income (loss)	$21,286	$12,915	$49,133	$35,718
Net income per common share:	'	'	'	'
Basic	$1.50	$0.92	$3.48	$2.55
Diluted	$1.48	$0.90	$3.42	$2.51
Average common shares outstanding:	'	'	'	'
Basic	14,144,478	14,026,855	14,120,788	14,004,302
Diluted	14,408,413	14,272,477	14,379,943	14,255,301

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net income (loss)	$21,286	$12,915	$49,133	$35,718
Change in net unrealized gains (losses) on investments:	'	'	'	'
Unrealized gains (losses) on investments arising during the period, net of deferred tax of $2,676 and $8,845 for 3 months ended September 30, 2013 and September 30, 2012 and $14,988 and $16,564 for 9 months ended September 30, 2013 and September 30, 2012, respectively	5,003	16,471	-27,780	32,881
Reclassification adjustment for net realized (gains) losses included in net income net of deferred tax of $322 and $1,152 for 3 months ended September 30, 2013 and September 30, 2012, $3,442 and $1,353 for 9 months ended September 30, 2013 and September 30, 2012, respectively	598	-2,139	-6,392	-2,513
Change in net unrealized gains (losses) on investments	5,601	14,332	-34,172	30,368
Change in other-than-temporary impairments:	'	'	'	'
Non credit other-than-temporary impairments arising during the period, net of deferred tax of $30 and $213 for 3 months ended September 30, 2013 and September 30, 2012 and $134 and $476 for 9 months ended September 30, 2013 and September 30, 2012, respectively	-55	395	248	884
Reclassification adjustment for non credit other-than-temporary impairment losses recognized in net income net of deferred tax of $0 for 3 months ended September 30, 2013 and September 30, 2012,and $15 for 9 months ended September 30, 2012, respectively	'	'	'	28
Change in other-than-temporary impairments	-55	395	248	912
Change in foreign currency translation gains (losses), net of deferred tax of $867 and $1,679 for 3 months ended September 30, 2013 and September 30, 2012,and $108 and $172 for 9 months ended September 30, 2013 and September 30, 2012, respectively	-1,370	3,118	209	-694
Other comprehensive income (loss)	4,176	17,845	-33,715	30,586
Comprehensive income (loss)	$25,462	$30,760	$15,418	$66,304

Consolidated_Statements_of_Com1

Consolidated Statements of Comprehensive Income (Parenthetical) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Unrealized gains (losses) on investments arising during the period, deferred tax	$2,676	$8,845	$14,988	$16,564
Reclassification adjustment for net realized (gains) losses included in net income, deferred tax	322	1,152	3,442	1,353
Non credit other-than-temporary impairments arising during the period, deferred tax	30	213	134	476
Reclassification adjustment for non credit other-than-temporary impairment losses recognized in net income, deferred tax	0	0	'	15
Change in foreign currency translation gains (losses), deferred tax	$867	$1,679	$108	$172

Consolidated_Statements_of_Sto

Consolidated Statements of Stockholders' Equity (USD $)	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
In Thousands, except Share data, unless otherwise specified
Balance at Dec. 31, 2012	$879,485	$1,755	$329,452	($155,801)	$628,871	$75,208
Balance (in shares) at Dec. 31, 2012	'	17,558,046	'	3,511,380	'	'
Net income	49,133	'	'	'	49,133	'
Changes in other comprehensive income:	'	'	'	'	'	'
Change in net unrealized gain (loss) on investments	-34,172	'	'	'	'	-34,172
Change in net non-credit other-than-temporary impairment losses	248	'	'	'	'	248
Change in foreign currency translation gain (loss)	209	'	'	'	'	209
Other comprehensive income (loss)	-33,715	'	'	'	'	-33,715
Shares issued under stock plan (in shares)	'	100,246	'	'	'	'
Shares issued under stock plan	1,488	10	1,478	'	'	'
Share-based compensation	3,491	'	3,491	'	'	'
Balance at Sep. 30, 2013	$899,882	$1,765	$334,421	($155,801)	$678,004	$41,493
Balance (in shares) at Sep. 30, 2013	'	17,658,292	'	3,511,380	'	'

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Operating activities:	'	'
Net income (loss)	$49,133	$35,718
Adjustments to reconcile net income to net cash provided by (used in) operating activities:	'	'
Depreciation & amortization	3,076	3,635
Deferred income taxes	-1,256	-9,313
Net realized (gains) losses	-7,171	-10,820
Net other-than-temporary losses recognized in earnings	1,863	650
Changes in assets and liabilities:	'	'
Reinsurance recoverable on paid and unpaid losses and loss adjustment expenses	88,177	12,813
Reserves for losses and loss adjustment expenses	-46,328	-2,723
Prepaid reinsurance premiums	-32,420	-60,689
Unearned premiums	73,829	102,613
Premiums receivable	-35,396	-95,335
Deferred policy acquisition costs	-2,166	2,703
Accrued investment income	-1,159	317
Reinsurance balances payable	14,750	60,841
Current income tax payable, net	3,316	5,066
Other	21,748	23,647
Net cash provided by (used in) operating activities	129,996	69,123
Fixed maturities	'	'
Redemptions and maturities	143,591	134,050
Sales	637,176	905,450
Purchases	-713,450	-1,196,729
Equity securities	'	'
Sales	11,439	4,346
Purchases	-53,919	-5,553
Change in payable for securities	-64,633	65,299
Net change in short-term investments	801	-65,225
Purchase of property and equipment	-7,771	-2,872
Net cash provided by (used in) investing activities	-46,766	-161,234
Financing activities:	'	'
Proceeds of stock issued from employee stock purchase plan	821	672
Proceeds of stock issued from exercise of stock options	1,126	331
Net cash provided by (used in) financing activities	1,947	1,003
Increase (decrease) in cash	85,177	-91,108
Cash at beginning of year	45,336	127,360
Cash at end of period	130,513	36,252
Supplemental cash information:	'	'
Income taxes paid, net	20,425	16,734
Interest paid	4,025	4,025
Issuance of stock to directors	$400	$242

Accounting_Policies

Accounting Policies	9 Months Ended
	Sep. 30, 2013
Accounting Policies	'
	Note 1. Accounting Policies
	The accompanying interim consolidated financial statements are unaudited and 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”). All such adjustments are of a normal recurring nature. All significant intercompany transactions and balances have been eliminated. 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 term “the Company” as used herein is used to mean The Navigators Group, Inc. and its subsidiaries, unless the context otherwise requires. The terms “Parent” or “Parent Company” are used to mean The Navigators Group, Inc. without its subsidiaries. These financial statements should be read in conjunction with the consolidated financial statements and notes contained in the Company’s 2012 Annual Report on Form 10-K.

Recent_Accounting_Pronouncemen

Recent Accounting Pronouncements	9 Months Ended
	Sep. 30, 2013
Recent Accounting Pronouncements	'
	Note 2. Recent Accounting Pronouncements
	Recently Adopted Accounting Pronouncements
	In February 2013, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2013 -02 amending Codification topic 220 – Comprehensive Income. The amendments do not change the current requirements for reporting net income or other comprehensive income in the financial statements. The guidance requires an entity to present information about significant items reclassified out of Accumulated Other Comprehensive Income (“AOCI”) by component and for items reclassified out of AOCI and into net income, the entity must disclose the effect of such items on the affected net income line item. The Company adopted this standard effective January 1, 2013, and presents this information on the consolidated statements of comprehensive income. Adoption of this standard did not have any impact on the Company’s consolidated balance sheets, results of operations or cash flows.
	In July 2012, the FASB issued ASU 2012-02 amending Codification topic 350 – Intangibles – Goodwill and Other. The amendment is intended to reduce cost and complexity, in addition to enhancing consistency of impairment testing guidance among long-lived asset categories by permitting entities to assess qualitative factors to determine whether it is necessary to calculate an asset’s fair value when testing an indefinite-lived asset for impairment. The amendment is effective for fiscal years beginning after September 15, 2012. The Company adopted this standard effective January 1, 2013. Adoption of this standard did not have any impact on the Company’s consolidated financial position, results of operating or cash flows.

Segment_Information

Segment Information	9 Months Ended
	Sep. 30, 2013
Segment Information	'
	Note 3. Segment Information
	The Company classifies its business into two underwriting segments consisting of the Insurance Companies segment (“Insurance Companies”) and the Lloyd’s Operations segment (“Lloyd’s Operations”), which are separately managed, and a Corporate segment (“Corporate”). Segment data for each of the two underwriting segments include allocations of the operating expenses of the wholly-owned underwriting management companies and the Parent Company’s operating expenses and related income tax amounts. The Corporate segment consists of the Parent Company’s investment income, interest expense and the related tax effect.
	The Company evaluates the performance of each underwriting segment based on its underwriting and GAAP results. The Insurance Companies and the Lloyd’s Operations results are measured by taking into account net earned premiums, net losses and loss adjustment expenses (“LAE”), commission expenses, other operating expenses and other income (expense). Each segment maintains its own investments on which it earns income and realizes capital gains or losses. The Company’s underwriting performance is evaluated separately from the performance of its investment portfolios.
	The Insurance Companies segment consists of Navigators Insurance Company, which includes a United Kingdom Branch (the “U.K. Branch”), and Navigators Specialty Insurance Company, which underwrites specialty and professional liability insurance on an excess and surplus lines basis. All of the insurance business written by Navigators Specialty Insurance Company is fully reinsured by Navigators Insurance Company pursuant to a 100% quota share reinsurance agreement. The insurance and reinsurance business written by our Insurance Companies is underwritten through our wholly-owned underwriting management Companies, Navigators Management Company, Inc. (“NMC”) and Navigators Management (UK) Ltd. (“NMUK”).
	Our Lloyd’s Operations segment includes Navigators Underwriting Agency Ltd. (“NUAL”), a Lloyd’s of London (“Lloyd’s”) underwriting agency which manages Lloyd’s Syndicate 1221 (“Syndicate 1221”). Our Lloyd’s Operations primarily underwrite marine and related lines of business along with offshore energy, construction coverages for onshore energy business and professional liability insurance at Lloyd’s through Syndicate 1221. We control 100% of Syndicate 1221’s stamp capacity through our wholly-owned subsidiary, Navigators Corporate Underwriters Ltd. (“NCUL”), which is referred to as a corporate name in the Lloyd’s market.
	The Insurance Companies and the Lloyd’s Operations underwriting results are measured based on underwriting profit or loss and the related combined ratio, which are both non-GAAP measures of underwriting profitability. Underwriting profit or loss is calculated from net earned premiums, less the sum of net losses and LAE, commission expenses, other operating expenses and other income (expense). The combined ratio is derived by dividing the sum of net losses and LAE, commission expenses, other operating expenses and other 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.
	Financial data by segment for the three and nine months ended September 30, 2013 and 2012 were as follows:
			Three Month Ended September 30, 2013
			Insurance			Lloyd’s
	In thousands		Companies			Operations			Corporate(1)			Total
	Gross written premiums		$	227,609		$	84,467		$	—		$	312,076
	Net written premiums			149,290			47,266			—			196,556
	Net earned premiums			162,962			50,933			—			213,895
	Net losses and loss adjustment expenses			(95,315	)		(29,771	)		—			(125,086	)
	Commission expenses			(20,039	)		(8,289	)		643			(27,685	)
	Other operating expenses			(28,510	)		(10,546	)		—			(39,056	)
	Other income (expense)			955			(522	)		(643	)		(210	)
	Underwriting profit (loss)		$	20,053		$	1,805		$	—		$	21,858
	Net investment income			12,285			1,807			2			14,094
	Net realized gains (losses)			(1,890	)		(919	)		—			(2,809	)
	Interest expense			—			—			(2,053	)		(2,053	)
	Income (loss) before income taxes		$	30,448		$	2,693		$	(2,051	)	$	31,090
	Income tax expense (benefit)			9,355			878			(429	)		9,804
	Net income (loss)		$	21,093		$	1,815		$	(1,622	)	$	21,286
	Identifiable assets		$	3,018,100		$	983,382		$	73,094		$	4,074,576
	Losses and loss adjustment expenses ratio			58.5	%		58.5	%					58.5	%
	Commission expense ratio			12.3	%		16.3	%					12.9	%
	Other operating expense ratio (2)			16.9	%		21.7	%					18.4	%
	Combined ratio			87.7	%		96.5	%					89.8	%
	-1	-  Includes Corporate segment intercompany eliminations.
	-2	-  Includes Other operating expenses and Other income.
			Three Month Ended September 30, 2012
			Insurance			Lloyd’s
	In thousands		Companies			Operations			Corporate(1)			Total
	Gross written premiums		$	218,361		$	80,381		$	—		$	298,742
	Net written premiums			142,148			45,898			—			188,046
	Net earned premiums			149,090			52,172			—			201,262
	Net losses and loss adjustment expenses			(113,303	)		(15,547	)		—			(128,850	)
	Commission expenses			(20,827	)		(10,911	)		480			(31,258	)
	Other operating expenses			(29,387	)		(10,725	)		—			(40,112	)
	Other income (expense)			1,229			40			(480	)		789
	Underwriting profit (loss)		$	(13,198	)	$	15,029		$	—		$	1,831
	Net investment income			12,004			1,552			41			13,597
	Net realized gains (losses)			2,609			2,152			—			4,761
	Interest expense			—			—			(2,049	)		(2,049	)
	Income (loss) before income taxes		$	1,415		$	18,733		$	(2,008	)	$	18,140
	Income tax expense (benefit)			(377	)		6,525			(923	)		5,225
	Net income (loss)		$	1,792		$	12,208		$	(1,085	)	$	12,915
	Identifiable assets		$	2,995,530		$	958,238		$	40,929		$	3,994,697
	Losses and loss adjustment expenses ratio			76	%		29.8	%					64	%
	Commission expense ratio			14	%		20.9	%					15.5	%
	Other operating expense ratio (2)			18.9	%		20.5	%					19.6	%
	Combined ratio			108.9	%		71.2	%					99.1	%
	-1	-  Includes Corporate segment intercompany eliminations.
	-2	-  Includes Other operating expenses and Other income.
			Nine Month Ended September 30, 2013
			Insurance			Lloyd’s
	In thousands		Companies			Operations			Corporate(1)			Total
	Gross written premiums		$	757,802		$	279,624		$	—		$	1,037,426
	Net written premiums			508,989			155,488			—			664,477
	Net earned premiums			473,840			148,197			—			622,037
	Net losses and loss adjustment expenses			(308,968	)		(78,608	)		—			(387,576	)
	Commission expenses			(59,129	)		(25,245	)		1,743			(82,631	)
Other operating expenses			(87,682	)		(32,926	)		—			(120,608	)
Other income (expense)			2,303			(1,067	)		(1,743	)		(507	)
Underwriting profit (loss)		$	20,364		$	10,351		$	—		$	30,715
Net investment income			36,751			5,237			9			41,997
Net realized gains (losses)			6,001			(697	)		4			5,308
Interest expense			—			—			(6,156	)		(6,156	)
Income (loss) before income taxes		$	63,116		$	14,891		$	(6,143	)	$	71,864
Income tax expense (benefit)			19,554			5,120			(1,943	)		22,731
Net income (loss)		$	43,562		$	9,771		$	(4,200	)	$	49,133
Identifiable assets		$	3,018,100		$	983,382		$	73,094		$	4,074,576
Losses and loss adjustment expenses ratio			65.2	%		53	%					62.3	%
Commission expense ratio			12.5	%		17	%					13.3	%
Other operating expense ratio (2)			18	%		23	%					19.5	%
Combined ratio			95.7	%		93	%					95.1	%
-1	-  Includes Corporate segment intercompany eliminations.
-2	-  Includes Other operating expenses and Other income.
		Nine Month Ended September 30, 2012
		Insurance			Lloyd’s
In thousands		Companies			Operations			Corporate(1)			Total
Gross written premiums		$	680,763		$	284,115		$	—		$	964,878
Net written premiums			457,463			163,880			—			621,343
Net earned premiums			422,215			158,183			—			580,398
Net losses and loss adjustment expenses			(304,483	)		(65,759	)		—			(370,242	)
Commission expenses			(61,245	)		(30,735	)		1,769			(90,211	)
Other operating expenses			(83,646	)		(32,592	)		—			(116,238	)
Other income (expense)			3,750			106			(1,769	)		2,087
Underwriting profit (loss)		$	(23,409	)	$	29,203		$	—		$	5,794
Net investment income			34,225			6,289			118			40,632
Net realized gains (losses)			6,809			3,361			—			10,170
Interest expense			—			—			(6,147	)		(6,147	)
Income (loss) before income taxes		$	17,625		$	38,853		$	(6,029	)	$	50,449
Income tax expense (benefit)			3,603			13,458			(2,330	)		14,731
Net income (loss)		$	14,022		$	25,395		$	(3,699	)	$	35,718
Identifiable assets		$	2,995,530		$	958,238		$	40,929		$	3,994,697
Losses and loss adjustment expenses ratio			72.1	%		41.6	%					63.8	%
Commission expense ratio			14.5	%		19.4	%					15.5	%
Other operating expense ratio (2)			18.9	%		20.5	%					19.7	%
Combined ratio			105.5	%		81.5	%					99	%
-1	-  Includes Corporate segment intercompany eliminations.
-2	-  Includes Other operating expenses and Other income.
The following tables provide additional financial data by segment for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended September 30, 2013
		Insurance			Lloyd’s
In thousands		Companies			Operations			Total
Gross written premiums:
Marine		$	38,912		$	36,009		$	74,921
Property casualty			156,228			35,869			192,097
Professional liability			32,469			12,589			45,058
Total		$	227,609		$	84,467		$	312,076
Net written premiums:
Marine		$	26,437		$	26,795		$	53,232
Property casualty			97,553			13,761			111,314
Professional liability			25,300			6,710			32,010
Total		$	149,290		$	47,266		$	196,556
Net earned premiums:
Marine		$	31,490		$	34,264		$	65,754
Property casualty			105,759			10,472			116,231
Professional liability			25,713			6,197			31,910
Total		$	162,962		$	50,933		$	213,895
		Three Months Ended September 30, 2012
		Insurance			Lloyd’s
In thousands		Companies			Operations			Total
Gross written premiums:
Marine		$	44,879		$	37,716		$	82,595
Property casualty			139,948			32,789			172,737
Professional liability			33,534			9,876			43,410
Total		$	218,361		$	80,381		$	298,742
Net written premiums:
Marine		$	32,615		$	27,939		$	60,554
Property casualty			83,449			11,633			95,082
Professional liability			26,084			6,326			32,410
Total		$	142,148		$	45,898		$	188,046
Net earned premiums:
Marine		$	40,592		$	34,002		$	74,594
Property casualty			83,993			11,870			95,863
Professional liability			24,505			6,300			30,805
Total		$	149,090		$	52,172		$	201,262
		Nine Months Ended September 30, 2013
		Insurance			Lloyd’s
In thousands		Companies			Operations			Total
Gross written premiums:
Marine		$	132,836		$	135,546		$	268,382
Property casualty			527,287			102,144			629,431
Professional liability			97,679			41,934			139,613
Total		$	757,802		$	279,624		$	1,037,426
Net written premiums:
Marine		$	94,944		$	100,413		$	195,357
Property casualty			338,215			33,254			371,469
Professional liability			75,830			21,821			97,651
Total		$	508,989		$	155,488		$	664,477
Net earned premiums:
Marine		$	100,013		$	102,932		$	202,945
Property casualty			297,954			26,913			324,867
Professional liability			75,873			18,352			94,225
Total		$	473,840		$	148,197		$	622,037
		Nine Months Ended September 30, 2012
		Insurance			Lloyd’s
In thousands		Companies			Operations			Total
Gross written premiums:
Marine		$	156,640		$	146,528		$	303,168
Property casualty			426,494			106,063			532,557
Professional liability			97,629			31,524			129,153
Total		$	680,763		$	284,115		$	964,878
Net written premiums:
Marine		$	107,266		$	109,489		$	216,755
Property casualty			274,823			36,693			311,516
Professional liability			75,374			17,698			93,072
Total		$	457,463		$	163,880		$	621,343
Net earned premiums:
Marine		$	111,402		$	101,538		$	212,940
Property casualty			240,536			41,644			282,180
Professional liability			70,277			15,001			85,278
Total		$	422,215		$	158,183		$	580,398
The Insurance Companies net earned premiums include $13.9 million and $16.9 million of net earned premiums from the U.K. Branch for the three months ended September 30, 2013 and 2012, respectively, and $36.7 million and $56.0 million of net earned premiums from the U.K. Branch for the nine months ended September 30, 2013 and 2012, respectively.

Reinsurance_Ceded

Reinsurance Ceded	9 Months Ended
	Sep. 30, 2013
Reinsurance Ceded	'
	Note 4. Reinsurance Ceded
	The Company’s ceded earned premiums were $114.2 million and $97.4 million for the three months ended September 30, 2013 and 2012 and $340.5 million and $283.4 million for the nine months ended September 30, 2013 and 2012, respectively.
	The Company’s ceded incurred losses were $(37.0) million and $31.2 million, respectively, for the three months ended September 30, 2013 and 2012, and were $94.1 million and $154.4 million for the nine months ended September 30, 2013 and 2012, respectively.
	The following table lists the Company’s 20 largest reinsurers measured by the amount of reinsurance recoverable for ceded losses and loss adjustment expenses (“LAE”) and ceded unearned premium (constituting 76.3% of the total recoverable), together with the reinsurance recoverable and collateral as of September 30, 2013, and the reinsurers’ ratings from A.M. Best Company (“A.M. Best”) and Standard & Poor’s (“S&P”):
			Reinsurance Recoverables
	In thousands		Unearned		Paid/Unpaid		Total (1)		Collateral		A.M. Best		S&P
			Premium		Losses				Held (2)
	National Indemnity Company		$	56,161	$	73,815	$	129,976	$	37,385		A++		AA+
	Transatlantic Reinsurance Company			21,964		70,838		92,802		10,052		A		A+
	Everest Reinsurance Company			22,082		64,313		86,395		9,115		A+		A+
	Swiss Reinsurance America Corporation			6,094		76,895		82,989		8,638		A+		AA-
	Munich Reinsurance America Inc.			6,307		70,676		76,983		4,440		A+		AA-
	Partner Reinsurance Europe			11,141		40,623		51,764		18,715		A+		A+
	Lloyd’s Syndicate #2003			8,493		37,427		45,920		10,568		A		A+
	Allied World Reinsurance			14,006		28,718		42,724		4,724		A		A
	Scor Global P&C SE			12,212		25,127		37,339		11,826		A		A+
	Tower Insurance Company			13,271		16,002		29,273		8,305		B++		NR
	Validus Reinsurance Ltd.			2,576		21,140		23,716		12,756		A		A
	Employers Mutual Casualty Company			11,257		6,746		18,003		11,050		A		NR
	Atlantic Specialty Insurance			8,626		8,406		17,032		2,560		A		A-
	QBE Reinsurance Corp			6,959		9,559		16,518		2,416		A		A+
	Scor Holding (Switzerland) AG			675		14,050		14,725		4,927		A		A+
	Berkley Insurance Company			1,787		12,797		14,584		519		A+		A+
	Lloyd’s Syndicate #4000			345		13,930		14,275		305		A		A+
	AXIS Re Europe			4,750		9,511		14,261		4,486		A+		A+
	Lloyd’s Syndicate #1955			2,459		10,931		13,390		2,397		A		A+
	Platinum Underwriters Re			259		12,700		12,959		1,692		A		A-
	Top 20 Reinsurers		$	211,424	$	624,204	$	835,628	$	166,876
	Others			42,011		217,040		259,051		73,700
	Total		$	253,435	$	841,244	$	1,094,679	$	240,576
	(1) -	Net of reserve for uncollectible reinsurance of approximately $11.3 million.
	(2) -	Collateral of $240.6 million consists of $180.6 million in ceded balances payable, $57.2 million in letters of credit, and $2.8 million of other balances held by the Company’s Insurance Companies and Lloyd’s Operations.

StockBased_Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2013
Stock-Based Compensation	'
	Note 5. Stock-Based Compensation
	Stock-based compensation granted under the Company’s stock plans is expensed in tranches over the vesting period. Options and non-performance based grants generally vest equally over a three or four year period and the options have a maximum term of ten years. Certain non-performance based grants vest over five years with one-third vesting in each of the third, fourth and fifth years. The Company’s performance based share grants generally consist of two types of awards. The restricted stock units issued in 2011 and after will cliff vest on the third anniversary of the date of grant, with 50% vesting in full, and 50% dependent on the rate of compound annual growth in book value per share for the three years immediately prior to the vesting date, with actual shares that vest ranging between 150% to 0% of that portion of the original award. Those performance based restricted stock units issued prior to 2011 generally vest over five years with one-third vesting in each of the third, fourth and fifth years, dependent on the rolling three-year average return on equity based on the three years prior to the year in which the vesting occurs, with actual shares that vest ranging between 150% to 0% of the original award.
	The amounts charged to expense for stock-based compensation for the three and nine months ended September 30, 2013 and 2012 are presented in the following table:
			Three Months Ended				Nine Months Ended
			September 30,				September 30,
	In thousands		2013		2012		2013		2012
	Restricted stock units		$	17	$	1,818	$	3,491	$	5,004
	Directors restricted stock grants(1)			103		170		309		290
	Employee stock purchase plan			55		27		102		42
	Total stock based compensation		$	175	$	2,015	$	3,902	$	5,336
	(1)  -	Relates to non-employee directors serving on the Parent Company’s Board of Directors, all of whom have been elected by the Company’s stockholders, as well as non-employee directors serving on NUAL’s Board of Directors.

Lloyds_Syndicate_1221

Lloyd's Syndicate 1221	9 Months Ended
	Sep. 30, 2013
Lloyd's Syndicate 1221	'
	Note 6. Lloyd’s Syndicate 1221
	The Company’s Lloyd’s Operations included in the consolidated financial statements represents its participation in Syndicate 1221. Syndicate 1221’s stamp capacity is £195 million ($316 million) for the 2013 underwriting year compared to £184 million ($300 million) for the 2012 underwriting year. Stamp capacity is a measure of the amount of premiums a Lloyd’s syndicate is authorized to write based on a business plan approved by the Council of Lloyd’s. Syndicate 1221’s stamp capacity is expressed net of commission (as is standard at Lloyd’s). The Syndicate 1221 premiums recorded in the Company’s financial statements are gross of commission. The Company controlled 100% of Syndicate 1221’s stamp capacity for the 2013 and 2012 underwriting years through its wholly-owned Lloyd’s corporate member.
	The Company provides letters of credit and posts cash to Lloyd’s to support its participation in Syndicate 1221’s stamp capacity. As of September 30, 2013, the Company had provided letters of credit of $143.0 million and has $1.0 million of cash collateral posted. If Syndicate 1221 increases its stamp capacity and the Company participates in the additional stamp capacity, or if Lloyd’s changes the capital requirements, the Company may be required to supply additional collateral acceptable to Lloyd’s. If the Company is unwilling or unable to provide additional acceptable collateral, the Company will be required to reduce its participation in the stamp capacity of Syndicate 1221. The letters of credit are provided through a credit facility with a consortium of banks which provides the Company with the ability to have letters of credit issued to support Syndicate 1221’s stamp capacity at Lloyd’s for the 2013 and 2014 underwriting years, as well as open prior years. If any letters of credit remain outstanding under the facility after December 31, 2014, we would be required to post additional collateral to secure the remaining letters of credit. If the credit facility is not renewed prior to December 31, 2014, the Company will need to find internal and/or external sources to provide either letters of credit or other collateral in order to continue to participate in Syndicate 1221. The credit facility is collateralized by all of the common stock of Navigators Insurance Company. Refer to Note 11, Credit Facility, for additional information.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2013
Income Taxes	'
	Note 7. Income Taxes
	The Company is subject to the tax laws and regulations of the United States (“U.S.”) and the foreign countries in which it operates. The Company files a consolidated U.S. Federal tax return, which includes all domestic subsidiaries and the U.K. Branch. The income from the foreign operations is designated as either U.S. connected income or non-U.S. connected income. Lloyd’s is required to pay U.S. income tax on U.S. connected income written by Lloyd’s syndicates. Lloyd’s and the U.S. Internal Revenue Service (“IRS”) have entered into an agreement whereby the amount of tax due on U.S. connected income is calculated by Lloyd’s and remitted directly to the IRS. These amounts are then charged to the corporate member in proportion to its participation in the relevant syndicates. The Company’s corporate member is subject to this agreement and will receive United Kingdom (“U.K.”) tax credits in the U.K. for any U.S. income tax incurred up to the U.K. income tax charged on the U.S. connected income. The non-U.S. connected insurance income would generally constitute taxable income under the Subpart F income section of the U.S. Internal Revenue Code (“Subpart F”) since less than 50% of Syndicate 1221’s premiums are derived within the U.K. and would therefore be subject to U.S. taxation when the Lloyd’s year of account closes. Taxes are accrued at a 35% rate on the Company’s foreign source insurance income and foreign tax credits, where available, are utilized to offset U.S. tax as permitted. The Company’s effective tax rate for Syndicate 1221 taxable income could substantially exceed 35% to the extent the Company is unable to offset U.S. taxes paid under Subpart F tax regulations with U.K. tax credits on future underwriting year distributions. U.S. taxes are not accrued on the earnings of the Company’s foreign agencies as these earnings are not includable as Subpart F income in the current year. These earnings were subject to taxes under U.K. tax regulations at a 26% rate through March 31, 2012. A finance bill was enacted in the U.K. that reduced the U.K. corporate tax rate from 26% to 24% effective April 2012 and from 24% to 23% effective April 2013. The effect of such tax rate change was not material.
	The Company has not provided for U.S. income taxes on approximately $18.9 million of undistributed earnings of its non-U.S. subsidiaries since it is intended that those earnings will be reinvested indefinitely in those subsidiaries. If a future determination is made that those earnings no longer are intended to be reinvested indefinitely in those subsidiaries, U.S. income taxes of approximately $2.0 million, assuming all foreign tax credits are realized, would be included in the tax provision at that time and would be payable if those earnings were distributed to the Company.
	Unrecognized tax benefits are differences between tax positions taken in the tax returns and benefits recognized in the financial statements. The Company has no unrecognized tax benefits as of September 30, 2013 and 2012. The Company did not incur any interest or penalties related to unrecognized tax benefits for the three and nine months ended September 30, 2013 and 2012. The Company currently is under examination by the Internal Revenue Service for taxable years 2010 and 2011, and generally is subject to U.S. Federal, state or local, or foreign tax examinations by tax authorities for 2009 and subsequent years.
	The Company recorded income tax expense of $9.8 million and $22.7 million for the three and nine months ended September 30, 2013 compared to $5.2 million and $14.7 million for the same period in 2012, resulting in an effective tax rate of 31.5% and 31.6% for the three and nine months ended September 30, 2013 and 28.8% and 29.2% for the comparable periods in 2012.
	The Company had state and local deferred tax assets amounting to potential future tax benefits of $0.5 million as of both September 30, 2013 and December 31, 2012, respectively. Included in the deferred tax assets are state and local net operating loss carry-forwards of $0.1 million and $0.2 million for September 30, 2013 and December 31, 2012. A valuation allowance was established for the full amount of these potential future tax benefits due to the uncertainty associated with their realization. The Company’s state and local tax carry-forwards as of September 30, 2013 expire from 2023 to 2031.

Senior_Notes_due_May_1_2016

Senior Notes due May 1, 2016	9 Months Ended
	Sep. 30, 2013
Senior Notes due May 1, 2016	'
	Note 8. Senior Notes due May 1, 2016
	On April 17, 2006, we completed a public debt offering of $125 million principal amount of 7% senior unsecured notes (the “Senior Notes”) and received net proceeds of $123.5 million. The principal amount of the Senior Notes is payable in a single installment on May 1, 2016. In April 2009, the Company repurchased $10.0 million aggregate principal amount of the Senior Notes from an unaffiliated note holder on the open market for $7.0 million, which generated a $3.0 million pre-tax gain that was reflected in Other income. The Senior Notes liability as of September 30, 2013 was $114.5 million. The unamortized discount at September 30, 2013 was $0.5 million. The aggregate principal amount of the Senior Notes that will be repaid on May 1, 2016, as a result of these transactions, is $115.0 million.
	The fair value of the Senior Notes was $125.2 million and $123.2 million as of September 30, 2013 and December 31, 2012, respectively. The fair value was determined using quoted prices for similar instruments in active markets and is classified as Level 2 within the fair value hierarchy as defined by the accounting guidance for fair value measurements.
	Interest is payable on the Senior Notes each May 1 and November 1. The effective interest rate related to the Senior Notes, based on the proceeds net of discount and all issuance costs, approximates 7.17%. Interest expense on the Senior Notes for the three and nine months ended each of September 30, 2013 and 2012 was approximately $2.1 million and $6.1 million, respectively.
	The Senior Notes, the Company’s only senior unsecured obligation, will rank equally with any future senior unsecured indebtedness. The Company may redeem the Senior Notes at any time and from time to time, in whole or in part, at a “make-whole” redemption price. The terms of the Senior Notes contain various restrictive business and financial covenants typical for debt obligations of this type, including limitations on mergers, liens and dispositions of the common stock of certain subsidiaries. As of September 30, 2013, the Company was in compliance with all such covenants.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies	'
	Note 9. Commitments and Contingencies
	In the ordinary course of conducting business, the Company’s subsidiaries are involved in various legal proceedings, either indirectly as insurers for parties or directly as defendants. Most of these proceedings consist of claims litigation involving the 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. The Company accounts for such activity through the establishment of unpaid loss and loss adjustment reserves. The Company’s management believes that the ultimate liability, if any, with respect to such ordinary-course claims litigation, after consideration of provisions made for potential losses and cost of defense, will not be material to the Company’s consolidated financial condition, results of operations, or cash flows.
	The Company’s subsidiaries are also from time to time involved with other legal actions, some of which assert claims for substantial amounts. These actions include claims asserting extra contractual obligations, such as claims involving allegations of bad faith in the handling of claims or the underwriting of policies. In general, the Company believes it has valid defenses to these cases. The Company’s management expects that the ultimate liability, if any, with respect to future extra-contractual matters will not be material to its consolidated financial position. Nonetheless, given the large or indeterminate amounts sought in certain of these matters, and the inherent unpredictability of litigation, an adverse outcome in such matters could, from time to time, have a material adverse outcome on the Company’s consolidated results of operations or cash flows in a particular fiscal quarter or year.

Investments

Investments	9 Months Ended
	Sep. 30, 2013
Investments	'
	Note 10. Investments
	The following tables set forth the Company’s cash and investments as of September 30, 2013 and December 31, 2012. The table below includes other-than-temporarily impaired (“OTTI”) securities recognized within other comprehensive income (“OCI”).
		September 30, 2013
						Gross				Gross			Cost or
		Fair				Unrealized				Unrealized			Amortized
	In thousands	Value				Gains				(Losses)			Cost
	Fixed maturities:
	U.S. Treasury bonds, agency bonds and foreign government bonds	$	445,969			$	3,683			$	(5,694	)	$	447,980
	States, municipalities and political subdivisions		445,281				9,752				(12,240	)		447,769
	Mortgage-backed and asset-backed securities:
	Agency mortgage-backed securities		300,347				7,966				(3,925	)		296,306
	Residential mortgage obligations		35,277				1,107				(224	)		34,394
	Asset-backed securities		88,714				795				(190	)		88,109
	Commercial mortgage-backed securities		173,069				8,386				(365	)		165,048
	Subtotal	$	597,407			$	18,254			$	(4,704	)	$	583,857
	Corporate bonds		493,074				17,104				(2,858	)		478,828
	Total fixed maturities	$	1,981,731			$	48,793			$	(25,496	)	$	1,958,434
	Equity securities—common stocks		158,890				29,548				(1,704	)		131,046
	Short-term investments		152,987				—				—			152,987
	Cash		130,513				—				—			130,513
	Total	$	2,424,121			$	78,341			$	(27,200	)	$	2,372,980
		December 31, 2012
						Gross				Gross			Cost or
		Fair				Unrealized				Unrealized			Amortized
	In thousands	Value				Gains				(Losses)			Cost
	Fixed maturities:
	U.S. Treasury bonds, agency bonds and foreign government bonds	$	649,692			$	8,654			$	(36	)	$	641,074
	States, municipalities and political subdivisions		322,947				18,712				(380	)		304,615
	Mortgage-backed and asset-backed securities:
	Agency mortgage-backed securities		384,445				13,652				(204	)		370,997
	Residential mortgage obligations		38,692				1,053				(549	)		38,188
	Asset-backed securities		50,382				1,133				(49	)		49,298
	Commercial mortgage-backed securities		204,821				17,996				(18	)		186,843
	Subtotal	$	678,340			$	33,834			$	(820	)	$	645,326
	Corporate bonds		470,854				27,129				(25	)		443,750
	Total fixed maturities	$	2,121,833			$	88,329			$	(1,261	)	$	2,034,765
	Equity securities—common stocks		101,297				16,919				(626	)		85,004
	Short-term investments		153,788				—				—			153,788
	Cash		45,336				—				—			45,336
	Total	$	2,422,254			$	105,248			$	(1,887	)	$	2,318,893
	As of September 30, 2013 and December 31, 2012, debt securities for which non-credit OTTI was previously recognized and included in other comprehensive income are now in an unrealized gains position of $0.4 million and $20 thousand, respectively.
	The fair value of the 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. The Company does not have the intent to sell nor is it more likely than not that it will have to sell debt securities 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. We do not intend to sell any of these securities and it is more likely than not that we will not be required to sell these securities before the recovery of the amortized cost basis. For equity securities, the Company also considers its 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. The Company may realize investment losses to the extent its liquidity needs require the disposition of fixed maturity securities in unfavorable interest rate, liquidity or credit spread environments. Significant changes in the factors the 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 maturity securities categorized by the number of years until maturity as of September 30, 2013 are shown in the following table:
		September 30, 2013
		Fair				Amortized
	In thousands	Value				Cost
	Due in one year or less	$	79,192			$	78,621
	Due after one year through five years		616,576				603,165
	Due after five years through ten years		458,136				455,826
	Due after ten years		230,420				236,965
	Mortgage- and asset-backed securities		597,407				583,857
	Total	$	1,981,731			$	1,958,434
	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. Due to the periodic repayment of principal, the mortgage-backed and asset-backed securities are estimated to have an effective maturity of approximately 4.6 years.
	The following table shows the amount and percentage of the Company’s fixed maturities as of September 30, 2013 by S&P credit rating or, if an S&P rating is not available, the equivalent Moody’s Investor Services (“Moody’s”) rating. The table includes fixed maturities at fair value, and the total rating is the weighted average quality rating.
		September 30, 2013
				Fair				Percent
	In thousands	Rating		Value				of Total
	Rating description:
	Extremely strong	AAA		$	305,979				15	%
	Very strong	AA			1,051,156				54	%
	Strong	A			440,063				22	%
	Adequate	BBB			163,614				8	%
	Speculative	BB & Below			11,722				1	%
Not rated	NR			9,197				0	%
Total	AA		$	1,981,731				100	%
The following table summarizes all securities in a gross unrealized loss position as of September 30, 2013 and December 31, 2012, showing the aggregate fair value and gross unrealized loss by the length of time those securities had continuously been in a gross unrealized loss position as well as the relevant number of securities.
	September 30, 2013											December 31, 2012
									Gross									Gross
	Number of				Fair				Unrealized			Number of			Fair			Unrealized
In thousands, except # of securities	Securities				Value				Loss			Securities			Value			Loss
Fixed maturities:
U.S. Treasury bonds, agency bonds, and foreign government bonds
0-6 months		42			$	196,851			$	5,688			8		$	23,760		$	22
7-12 months		1				928				6			3			14,118			11
> 12 months		—				—				—			1			4,652			3
Subtotal		43			$	197,779			$	5,694			12		$	42,530		$	36
States, municipalities and political subdivisions
0-6 months		100			$	196,987			$	9,485			10		$	21,299		$	325
7-12 months		17				37,989				2,755			—			—			—
> 12 months		1				303				—			4			2,908			55
Subtotal		118			$	235,279			$	12,240			14		$	24,207		$	380
Agency mortgage-backed securities
0-6 months		71			$	90,215			$	2,472			10		$	62,516		$	174
7-12 months		9				18,667				1,354			2			1,671			30
> 12 months		2				5,130				99			—			—			—
Subtotal		82			$	114,012			$	3,925			12		$	64,187		$	204
Residential mortgage obligations
0-6 months		12			$	2,016			$	43			6		$	1,825		$	22
7-12 months		—				—				—			—			—			—
> 12 months		17				2,955				181			35			7,252			527
Subtotal		29			$	4,971			$	224			41		$	9,077		$	549
Asset-backed securities
0-6 months		3			$	32,019			$	189			—		$	—		$	—
7-12 months		1				339				1			—			—			—
> 12 months		—				—				—			2			2,369			49
Subtotal		4			$	32,358			$	190			2		$	2,369		$	49
Commercial mortgage-backed securities
0-6 months		6			$	19,891			$	341			7		$	2,639		$	7
7-12 months		—				—				—			—			—			—
> 12 months		5				889				24			5			845			11
Subtotal		11			$	20,780			$	365			12		$	3,484		$	18
Corporate bonds
0-6 months		37			$	123,673			$	2,856			2		$	3,528		$	6
7-12 months		2				2,315				2			—			—			—
> 12 months		—				—				—			4			6,689			19
Subtotal		39			$	125,988			$	2,858			6		$	10,217		$	25
Total fixed maturities		326			$	731,167			$	25,496			99		$	156,071		$	1,261
Equity securities—common stocks
0-6 months		13			$	33,429			$	1,340			13		$	23,345		$	522
7-12 months		1				1,904				364			1			1,943			104
> 12 months		—				—				—			—			—			—
Total equity securities		14			$	35,333			$	1,704			14		$	25,288		$	626
As of September 30, 2013 and December 31, 2012, the largest single unrealized loss by a non-government backed issuer in the investment portfolio was $1.0 million and $0.2 million, respectively.
The Company analyzes the unrealized losses quarterly to determine if any are other-than-temporary. The above unrealized losses have been determined to be temporary based on our policies.
For debt securities, when assessing whether the amortized cost basis of the security will be recovered, the Company compares the present value of cash flows expected to be collected in relation to the current book value. Any shortfalls of the present value of the cash flows expected to be collected to the amortized cost basis is considered the credit loss portion of OTTI losses and is recognized in earnings. All non-credit losses are recognized as changes in OTTI losses within OCI.
To determine whether the unrealized loss on structured securities is other-than-temporary, the Company analyzes the projections provided by its investment managers with respect to an expected principal loss under a range of scenarios and utilizes the most likely outcomes. The analysis relies on actual collateral performance measures such as default rate, prepayment rate and loss severity. These assumptions are applied throughout the remaining term of the deal, incorporating the transaction structure and priority of payments, to generate loss adjusted cash flows. Results of the analysis will indicate whether the security is expected ultimately to incur a loss or whether there is a material impact on yield due to either a projected loss or a change in cash flow timing. A break even default rate is also calculated. A comparison of the break even default rate to the actual default rate provides an indication of the level of cushion or coverage to the first dollar principal loss. The analysis applies the stated assumptions throughout the remaining term of the transaction to forecast cash flows, which are then applied through the transaction structure to determine whether there is a loss to the security. For securities in which a tranche loss is present, and the net present value of loss adjusted cash flows is less than book value, impairment is recognized. The output data also includes a number of additional metrics such as average life remaining, original and current credit support, over 60 day delinquency and security rating.
The significant inputs used to measure the amount of credit loss recognized in earnings were actual delinquency rates, default probability assumptions, severity assumptions and prepayment assumptions. Projected losses are a function of both loss severity and probability of default. Default probability and severity assumptions differ based on property type, vintage and the stress of the collateral. The Company does not intend to sell any of these securities and it is more likely than not that it will not be required to sell these securities before the recovery of the amortized cost basis.
For equity securities, in general, the Company focuses its attention on those securities with a fair value less than 80% of their cost for six or more consecutive months. If warranted as the result of conditions relating to a particular security, the Company will focus on a significant decline in fair value regardless of the time period involved. Factors considered in evaluating potential impairment include, but are not limited to, the current fair value as compared to cost of the security, the length of time the investment has been below cost and by how much the investment is below cost. If an equity security is deemed to be other-than-temporarily impaired, the cost is written down to fair value with the loss recognized in earnings.
For equity securities, the Company also considers its 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. For fixed maturity securities, the Company considers its intent to sell a security and whether it is more likely than not that the Company will be required to sell a security before the anticipated recovery as part of the process of evaluating whether a security’s unrealized loss represents an other-than-temporary decline. The Company’s ability to hold such securities is supported by sufficient cash flow from its operations and from maturities within its investment portfolio in order to meet its claims payment and other disbursement obligations arising from its 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.
As of September 30, 2013, there were no investments with a fair value that was less than 80% of amortized cost.
The table below summarizes the Company’s activity related to OTTI losses for the periods indicated:
	Three Months Ended September 30,														Nine Months Ended September 30,
	2013								2012						2013					2012
	Number of								Number of						Number of					Number of
In thousands, except # of securities	Securities				Amount				Securities			Amount			Securities			Amount		Securities		Amount
Total OTTI losses:
Corporate and other bonds		1			$	1,821				—		$	—			1		$	1,821		—	$	—
Commercial mortgage-backed securities		—				—				—			—			—			—		—		—
Residential mortgage-backed securities		—				—				—			—			—			—		1		54
Asset-backed securities		—				—				—			—			—			—		—		—
Equities		—				—				—			—			2			42		3		639
Total		1			$	1,821				—		$	—			3		$	1,863		4	$	693
Less: Portion of loss in accumulated other comprehensive income (loss):
Corporate and other bonds					$	—						$	—					$	—			$	—
Commercial mortgage-backed securities						—							—						—				—
Residential mortgage-backed securities						—							—						—				43
Asset-backed securities						—							—						—				—
Equities						—							—						—				—
Total					$	—						$	—					$	—			$	43
Impairment losses recognized in earnings:
Corporate and other bonds					$	1,821						$	—					$	1,821			$	—
Commercial mortgage-backed securities						—							—						—				—
Residential mortgage-backed securities						—							—						—				11
Asset-backed securities						—							—						—				—
Equities						—							—						42				639
Total					$	1,821						$	—					$	1,863			$	650
The following table summarizes the cumulative amounts related to the Company’s credit loss portion of the OTTI losses on debt securities for the three and nine months ended September 30, 2013 and 2012. The Company does not intend to sell and it is more likely than not that it will not be required to sell the securities prior to recovery of the amortized cost basis and for which the non-credit loss portion is included in OCI.
	Three Months Ended September 30,								Nine Months Ended September 30,
In thousands	2013				2012				2013			2012
Beginning balance	$	3,332			$	3,322			$	3,332		$	3,321
Additions for credit loss impairments recognized in the current period on securities not previously impaired		1,821				—				1,821			—
Additions for credit loss impairments recognized in the current period on securities previously impaired		—				—				—			11
Reductions for credit loss impairments previously recognized on securities sold during the period		—				—				—			—
Ending balance	$	5,153			$	3,332			$	5,153		$	3,332
The contractual maturity dates for fixed maturity securities categorized by the number of years until maturity, with a gross unrealized loss as of September 30, 2013 is presented in the following table:
	September 30, 2013
	Gross Unrealized Losses								Fair Value
					Percent							Percent
In thousands	Amount				of Total				Amount			of Total
Due in one year or less	$	1				0	%		$	1,716			0	%
Due after one year through five years		1,119				4	%			144,849			20	%
Due after five years through ten years		9,803				38	%			250,290			34	%
Due after ten years		9,869				40	%			162,191			22	%
Mortgage- and asset-backed securities		4,704				18	%			172,121			24	%
Total	$	25,496				100	%		$	731,167			100	%
The Company’s net investment income was derived from the following sources:
	Three Months Ended September 30,								Nine Months Ended September 30,
In thousands	2013				2012				2013			2012
Fixed maturities	$	13,399			$	14,364			$	40,142		$	44,779
Equity securities		1,315				989				3,603			2,930
Short-term investments		187				437				575			1,452
Total investment income	$	14,901			$	15,790			$	44,320		$	49,161
Investment expenses		(807	)			(2,193	)			(2,323	)		(8,529	)
Net investment income	$	14,094			$	13,597			$	41,997		$	40,632
Investment expense for the nine months ended September 30, 2012 included $4.5 million of interest expense related to a total $9.2 million settlement of a dispute with Equitas over foregone interest on amounts that were due on certain reinsurance contracts.
The portfolio duration was 3.9 years and 3.8 years for the nine months ended September 30, 2013 and 2012, respectively.
The change in net unrealized gains and losses, inclusive of the change in the non credit portion of other-than-temporary impairment losses, consisted of:
	Nine Months Ended September 30,
In thousands	2013				2012
Fixed maturities	$	(63,771	)		$	38,165
Equity securities		11,551				8,817
Gross unrealized gains (losses)	$	(52,220	)		$	46,982
Deferred income tax		(18,296	)			15,702
Change in net unrealized gains (losses), net	$	(33,924	)		$	31,280
Realized gains and losses, excluding net OTTI losses recognized in earnings, for the periods indicated were as follows:
	Three Months Ended September 30,								Nine Months Ended September 30,
In thousands	2013				2012				2013			2012
Fixed maturities:
Gains	$	1,099			$	4,011			$	6,035		$	11,868
Losses		(2,087	)			(216	)			(2,470	)		(1,746	)
Fixed maturities, net	$	(988	)		$	3,795			$	3,565		$	10,122
Equity securities:
Gains	$	—			$	966			$	3,733		$	1,171
Losses		—				—				(127	)		(473	)
Equity securities, net	$	—			$	966			$	3,606		$	698
Net realized gains (losses)	$	(988	)		$	4,761			$	7,171		$	10,820
Net realized gains and losses are generated as part of the normal ongoing management of our investment portfolio. Net realized losses of $1.0 million and net realized gains of $7.2 million for the three and nine months ended September 30, 2013 are primarily due to the sale of Treasury bonds, commercial mortgage-backed securities, municipal bonds and equity securities. Net realized gains of $4.8 million and $10.8 million for the three and nine months ended September 30, 2012 were due to the sale of corporate bonds and Treasury bonds.
The following tables present, for each of the fair value hierarchy levels as defined by the accounting guidance for fair value measurements, the Company’s fixed maturities and equity securities by asset class that are measured at fair value on a recurring basis as of September 30, 2013 and December 31, 2012:
	September 30, 2013
In thousands	Level 1				Level 2				Level 3			Total
Fixed maturities:
U.S. Treasury bonds, agency bonds and foreign government bonds	$	256,500			$	189,469			$	—		$	445,969
States, municipalities and political subdivisions		—				445,281				—			445,281
Mortgage-backed and asset-backed securities:													—
Agency mortgage-backed securities		—				300,347				—			300,347
Residential mortgage obligations		—				35,277				—			35,277
Asset-backed securities		—				88,714				—			88,714
Commercial mortgage-backed securities		—				173,069				—			173,069
Subtotal	$	—			$	597,407			$	—		$	597,407
Corporate bonds		—				488,512				4,562			493,074
Total fixed maturities	$	256,500			$	1,720,669			$	4,562		$	1,981,731
Equity securities—common stocks		158,890				—				—			158,890
Total	$	415,390			$	1,720,669			$	4,562		$	2,140,621
	December 31, 2012
In thousands	Level 1				Level 2				Level 3			Total
Fixed maturities:
U.S. Treasury bonds, agency bonds and foreign government bonds	$	414,502			$	235,190			$	—		$	649,692
States, municipalities and political subdivisions		—				322,947				—			322,947
Mortgage-backed and asset-backed securities:													—
Agency mortgage-backed securities		—				384,445				—			384,445
Residential mortgage obligations		—				38,692				—			38,692
Asset-backed securities		—				50,382				—			50,382
Commercial mortgage-backed securities		—				204,821				—			204,821
Subtotal	$	—			$	678,340			$	—		$	678,340
Corporate bonds		—				470,854				—			470,854
Total fixed maturities	$	414,502			$	1,707,331			$	—		$	2,121,833
Equity securities—common stocks		101,297				—				—			101,297
Total	$	515,799			$	1,707,331			$	—		$	2,223,130
The fair value of financial instruments is determined based on the following fair value hierarchy:
Level 1 – Quoted prices for identical instruments in active markets. Examples are listed equity and fixed income securities traded on an exchange. U.S. Treasury securities are reported as level 1 and are valued based on unadjusted quoted prices for identical assets in active markets that the 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 Company did not have any significant transfers between Level 1 and 2 for the three and nine months ended September 30, 2013.
The following tables present a reconciliation of the beginning and ending balances of all investments measured at fair value using Level 3 inputs during the three and nine months ended September 30, 2013.
	Three Months Ended September 30, 2013
In thousands	Beginning				Realized				Unrealized			Purchases			Sales			Settlements		Transfers		Transfers		Ending
	Balance				Gains				Gains											into Level 3		out of Level 3		Balance
					(Losses)				(Losses)
Assets:
Corporate Bonds	$	—			$	—			$	(15	)	$	4,661		$	(84	)	$	—	$	—	$	—	$	4,562
Total assets	$	—			$	—			$	(15	)	$	4,661		$	(84	)	$	—	$	—	$	—	$	4,562
	Nine Months Ended September 30, 2013
In thousands	Beginning				Realized				Unrealized			Purchases			Sales			Settlements		Transfers		Transfers		Ending
	Balance				Gains				Gains											into Level 3		out of Level 3		Balance
					(Losses)				(Losses)
Assets:
Corporate Bonds	$	—			$	—			$	(15	)	$	4,661		$	(84	)	$	—	$	—	$	—	$	4,562
Total assets	$	—			$	—			$	(15	)	$	4,661		$	(84	)	$	—	$	—	$	—	$	4,562
The Level 3 security is valued using unobservable inputs based on a proxy of a security of similar duration in which market quotations are available. As of September 30, 2012, the Company did not have any Level 3 assets, and there were no changes in Level 3 assets for the three and nine months ended September 30, 2012.
As of September 30, 2013 and December 31, 2012, the Company did not have a concentration of greater than 5% of invested assets in a single non-U.S. government-backed issuer.

Credit_Facility

Credit Facility	9 Months Ended
	Sep. 30, 2013
Credit Facility	'
	Note 11. Credit Facility
	On November 22, 2012, we entered into a $165 million credit facility agreement with ING Bank N.V., London Branch, individually and as Administrative Agent, and a syndicate of lenders. The new credit facility amended and restated a $165 million letter of credit facility entered into by the parties on March 28, 2011. The credit facility, which is denominated in U.S. dollars, is utilized to fund our participation in Syndicate 1221 through letters of credit for the 2013 and 2014 underwriting years, as well as open prior years. The letters of credit issued under the facility are denominated in British pounds and their aggregate face amount will fluctuate based on exchange rates. If any letters of credit remain outstanding under the facility after December 31, 2014, we would be required to post additional collateral to secure the remaining letters of credit. As of September 30, 2013, letters of credit with an aggregate face amount of $143.0 million were outstanding under the credit facility and we have $1.0 million of cash collateral posted.
	This credit facility contains customary covenants for facilities of this type, including restrictions on indebtedness and liens, limitations on mergers, dividends and the sale of assets, and requirements as to maintaining certain consolidated tangible net worth, statutory surplus and other financial ratios. The credit facility also provides for customary events of default, including failure to pay principal, interest or fees when due, failure to comply with covenants, any representation or warranty made by the Company being false in any material respect, default under certain other indebtedness, certain insolvency or receivership events affecting the Company and its subsidiaries, the occurrence of certain material judgments, or a change in control of the Company. The letter of credit facility is secured by a pledge of the stock of certain insurance subsidiaries of the Company. To the extent the aggregate face amount issued under the credit facility exceeds the commitment amount, the Company is required to post collateral with the lead bank of the consortium. The Company was in compliance with all covenants under the credit facility as of September 30, 2013.
	The applicable margin and applicable fee rate payable under the credit facility are based on a tiered schedule that is based on the Company’s then-current ratings issued by S&P and Moody’s with respect to the Company’s Senior Notes without third-party credit enhancement, and the amount of the Company’s own collateral utilized to fund its participation in Syndicate 1221.

Subsequent_Events

Subsequent Events	9 Months Ended
	Sep. 30, 2013
Subsequent Events	'
	Note 12. Subsequent Events
	On October 4, 2013, the Company completed a public debt offering of $265 million principal amount of 5.75% Senior Notes due October 15, 2023 (“5.75% Senior Notes”) and received net proceeds of $263 million. The Company used a portion of the proceeds of the 5.75% Senior Notes for the purpose of redeeming the $115 million aggregate principal amount of our 7% Senior Notes due May 1, 2016. The Company incurred a charge of $17.9 million for the payment of call premium in connection with the redemption of the 7.0% Senior Notes due 2016. The effective interest rate related to the net proceeds received from the 5.75% Senior Notes is approximately 5.84%. Interest will be paid on the 5.75% Senior Notes each April 15 and October 15 with the first payment due on April 15, 2014.
	The Company may redeem the 5.75% Senior Notes in whole at any time or in part from time to time at a make-whole redemption price. The 5.75% Senior Notes are the Company’s only senior unsecured obligation and will rank equally with future senior unsecured indebtedness.

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2013
Financial Data by Segment	'
	Financial data by segment for the three and nine months ended September 30, 2013 and 2012 were as follows:
			Three Month Ended September 30, 2013
			Insurance			Lloyd’s
	In thousands		Companies			Operations			Corporate(1)			Total
	Gross written premiums		$	227,609		$	84,467		$	—		$	312,076
	Net written premiums			149,290			47,266			—			196,556
	Net earned premiums			162,962			50,933			—			213,895
	Net losses and loss adjustment expenses			(95,315	)		(29,771	)		—			(125,086	)
	Commission expenses			(20,039	)		(8,289	)		643			(27,685	)
	Other operating expenses			(28,510	)		(10,546	)		—			(39,056	)
	Other income (expense)			955			(522	)		(643	)		(210	)
	Underwriting profit (loss)		$	20,053		$	1,805		$	—		$	21,858
	Net investment income			12,285			1,807			2			14,094
	Net realized gains (losses)			(1,890	)		(919	)		—			(2,809	)
	Interest expense			—			—			(2,053	)		(2,053	)
	Income (loss) before income taxes		$	30,448		$	2,693		$	(2,051	)	$	31,090
	Income tax expense (benefit)			9,355			878			(429	)		9,804
	Net income (loss)		$	21,093		$	1,815		$	(1,622	)	$	21,286
	Identifiable assets		$	3,018,100		$	983,382		$	73,094		$	4,074,576
	Losses and loss adjustment expenses ratio			58.5	%		58.5	%					58.5	%
	Commission expense ratio			12.3	%		16.3	%					12.9	%
	Other operating expense ratio (2)			16.9	%		21.7	%					18.4	%
	Combined ratio			87.7	%		96.5	%					89.8	%
	-1	-  Includes Corporate segment intercompany eliminations.
	-2	-  Includes Other operating expenses and Other income.
			Three Month Ended September 30, 2012
			Insurance			Lloyd’s
	In thousands		Companies			Operations			Corporate(1)			Total
	Gross written premiums		$	218,361		$	80,381		$	—		$	298,742
	Net written premiums			142,148			45,898			—			188,046
	Net earned premiums			149,090			52,172			—			201,262
	Net losses and loss adjustment expenses			(113,303	)		(15,547	)		—			(128,850	)
	Commission expenses			(20,827	)		(10,911	)		480			(31,258	)
	Other operating expenses			(29,387	)		(10,725	)		—			(40,112	)
	Other income (expense)			1,229			40			(480	)		789
	Underwriting profit (loss)		$	(13,198	)	$	15,029		$	—		$	1,831
	Net investment income			12,004			1,552			41			13,597
	Net realized gains (losses)			2,609			2,152			—			4,761
	Interest expense			—			—			(2,049	)		(2,049	)
	Income (loss) before income taxes		$	1,415		$	18,733		$	(2,008	)	$	18,140
	Income tax expense (benefit)			(377	)		6,525			(923	)		5,225
	Net income (loss)		$	1,792		$	12,208		$	(1,085	)	$	12,915
	Identifiable assets		$	2,995,530		$	958,238		$	40,929		$	3,994,697
	Losses and loss adjustment expenses ratio			76	%		29.8	%					64	%
	Commission expense ratio			14	%		20.9	%					15.5	%
	Other operating expense ratio (2)			18.9	%		20.5	%					19.6	%
	Combined ratio			108.9	%		71.2	%					99.1	%
	-1	-  Includes Corporate segment intercompany eliminations.
	-2	-  Includes Other operating expenses and Other income.
			Nine Month Ended September 30, 2013
			Insurance			Lloyd’s
	In thousands		Companies			Operations			Corporate(1)			Total
	Gross written premiums		$	757,802		$	279,624		$	—		$	1,037,426
	Net written premiums			508,989			155,488			—			664,477
	Net earned premiums			473,840			148,197			—			622,037
	Net losses and loss adjustment expenses			(308,968	)		(78,608	)		—			(387,576	)
	Commission expenses			(59,129	)		(25,245	)		1,743			(82,631	)
	Other operating expenses			(87,682	)		(32,926	)		—			(120,608	)
	Other income (expense)			2,303			(1,067	)		(1,743	)		(507	)
	Underwriting profit (loss)		$	20,364		$	10,351		$	—		$	30,715
	Net investment income			36,751			5,237			9			41,997
	Net realized gains (losses)			6,001			(697	)		4			5,308
	Interest expense			—			—			(6,156	)		(6,156	)
Income (loss) before income taxes		$	63,116		$	14,891		$	(6,143	)	$	71,864
Income tax expense (benefit)			19,554			5,120			(1,943	)		22,731
Net income (loss)		$	43,562		$	9,771		$	(4,200	)	$	49,133
Identifiable assets		$	3,018,100		$	983,382		$	73,094		$	4,074,576
Losses and loss adjustment expenses ratio			65.2	%		53	%					62.3	%
Commission expense ratio			12.5	%		17	%					13.3	%
Other operating expense ratio (2)			18	%		23	%					19.5	%
Combined ratio			95.7	%		93	%					95.1	%
-1	-  Includes Corporate segment intercompany eliminations.
-2	-  Includes Other operating expenses and Other income.
		Nine Month Ended September 30, 2012
		Insurance			Lloyd’s
In thousands		Companies			Operations			Corporate(1)			Total
Gross written premiums		$	680,763		$	284,115		$	—		$	964,878
Net written premiums			457,463			163,880			—			621,343
Net earned premiums			422,215			158,183			—			580,398
Net losses and loss adjustment expenses			(304,483	)		(65,759	)		—			(370,242	)
Commission expenses			(61,245	)		(30,735	)		1,769			(90,211	)
Other operating expenses			(83,646	)		(32,592	)		—			(116,238	)
Other income (expense)			3,750			106			(1,769	)		2,087
Underwriting profit (loss)		$	(23,409	)	$	29,203		$	—		$	5,794
Net investment income			34,225			6,289			118			40,632
Net realized gains (losses)			6,809			3,361			—			10,170
Interest expense			—			—			(6,147	)		(6,147	)
Income (loss) before income taxes		$	17,625		$	38,853		$	(6,029	)	$	50,449
Income tax expense (benefit)			3,603			13,458			(2,330	)		14,731
Net income (loss)		$	14,022		$	25,395		$	(3,699	)	$	35,718
Identifiable assets		$	2,995,530		$	958,238		$	40,929		$	3,994,697
Losses and loss adjustment expenses ratio			72.1	%		41.6	%					63.8	%
Commission expense ratio			14.5	%		19.4	%					15.5	%
Other operating expense ratio (2)			18.9	%		20.5	%					19.7	%
Combined ratio			105.5	%		81.5	%					99	%
-1	-  Includes Corporate segment intercompany eliminations.
-2	-  Includes Other operating expenses and Other income.
Additional Financial Data by Segment	'
	The following tables provide additional financial data by segment for the three and nine months ended September 30, 2013 and 2012:
			Three Months Ended September 30, 2013
			Insurance			Lloyd’s
	In thousands		Companies			Operations			Total
	Gross written premiums:
	Marine		$	38,912		$	36,009		$	74,921
	Property casualty			156,228			35,869			192,097
	Professional liability			32,469			12,589			45,058
	Total		$	227,609		$	84,467		$	312,076
	Net written premiums:
	Marine		$	26,437		$	26,795		$	53,232
	Property casualty			97,553			13,761			111,314
	Professional liability			25,300			6,710			32,010
	Total		$	149,290		$	47,266		$	196,556
	Net earned premiums:
	Marine		$	31,490		$	34,264		$	65,754
	Property casualty			105,759			10,472			116,231
	Professional liability			25,713			6,197			31,910
	Total		$	162,962		$	50,933		$	213,895
			Three Months Ended September 30, 2012
			Insurance			Lloyd’s
	In thousands		Companies			Operations			Total
	Gross written premiums:
	Marine		$	44,879		$	37,716		$	82,595
	Property casualty			139,948			32,789			172,737
	Professional liability			33,534			9,876			43,410
	Total		$	218,361		$	80,381		$	298,742
	Net written premiums:
	Marine		$	32,615		$	27,939		$	60,554
	Property casualty			83,449			11,633			95,082
	Professional liability			26,084			6,326			32,410
	Total		$	142,148		$	45,898		$	188,046
	Net earned premiums:
	Marine		$	40,592		$	34,002		$	74,594
	Property casualty			83,993			11,870			95,863
	Professional liability			24,505			6,300			30,805
	Total		$	149,090		$	52,172		$	201,262
			Nine Months Ended September 30, 2013
			Insurance			Lloyd’s
	In thousands		Companies			Operations			Total
	Gross written premiums:
	Marine		$	132,836		$	135,546		$	268,382
	Property casualty			527,287			102,144			629,431
	Professional liability			97,679			41,934			139,613
	Total		$	757,802		$	279,624		$	1,037,426
	Net written premiums:
	Marine		$	94,944		$	100,413		$	195,357
	Property casualty			338,215			33,254			371,469
	Professional liability			75,830			21,821			97,651
	Total		$	508,989		$	155,488		$	664,477
	Net earned premiums:
	Marine		$	100,013		$	102,932		$	202,945
	Property casualty			297,954			26,913			324,867
	Professional liability			75,873			18,352			94,225
	Total		$	473,840		$	148,197		$	622,037
			Nine Months Ended September 30, 2012
			Insurance			Lloyd’s
	In thousands		Companies			Operations			Total
	Gross written premiums:
	Marine		$	156,640		$	146,528		$	303,168
	Property casualty			426,494			106,063			532,557
	Professional liability			97,629			31,524			129,153
	Total		$	680,763		$	284,115		$	964,878
Net written premiums:
Marine		$	107,266		$	109,489		$	216,755
Property casualty			274,823			36,693			311,516
Professional liability			75,374			17,698			93,072
Total		$	457,463		$	163,880		$	621,343
Net earned premiums:
Marine		$	111,402		$	101,538		$	212,940
Property casualty			240,536			41,644			282,180
Professional liability			70,277			15,001			85,278
Total		$	422,215		$	158,183		$	580,398

Reinsurance_Ceded_Tables

Reinsurance Ceded (Tables)	9 Months Ended
	Sep. 30, 2013
Lists of 20 Largest Reinsurers Measured by Reinsurance Recoverable	'
	The following table lists the Company’s 20 largest reinsurers measured by the amount of reinsurance recoverable for ceded losses and loss adjustment expenses (“LAE”) and ceded unearned premium (constituting 76.3% of the total recoverable), together with the reinsurance recoverable and collateral as of September 30, 2013, and the reinsurers’ ratings from A.M. Best Company (“A.M. Best”) and Standard & Poor’s (“S&P”):
			Reinsurance Recoverables
	In thousands		Unearned		Paid/Unpaid		Total (1)		Collateral		A.M. Best		S&P
			Premium		Losses				Held (2)
	National Indemnity Company		$	56,161	$	73,815	$	129,976	$	37,385		A++		AA+
	Transatlantic Reinsurance Company			21,964		70,838		92,802		10,052		A		A+
	Everest Reinsurance Company			22,082		64,313		86,395		9,115		A+		A+
	Swiss Reinsurance America Corporation			6,094		76,895		82,989		8,638		A+		AA-
	Munich Reinsurance America Inc.			6,307		70,676		76,983		4,440		A+		AA-
	Partner Reinsurance Europe			11,141		40,623		51,764		18,715		A+		A+
	Lloyd’s Syndicate #2003			8,493		37,427		45,920		10,568		A		A+
	Allied World Reinsurance			14,006		28,718		42,724		4,724		A		A
	Scor Global P&C SE			12,212		25,127		37,339		11,826		A		A+
	Tower Insurance Company			13,271		16,002		29,273		8,305		B++		NR
	Validus Reinsurance Ltd.			2,576		21,140		23,716		12,756		A		A
	Employers Mutual Casualty Company			11,257		6,746		18,003		11,050		A		NR
	Atlantic Specialty Insurance			8,626		8,406		17,032		2,560		A		A-
	QBE Reinsurance Corp			6,959		9,559		16,518		2,416		A		A+
	Scor Holding (Switzerland) AG			675		14,050		14,725		4,927		A		A+
	Berkley Insurance Company			1,787		12,797		14,584		519		A+		A+
	Lloyd’s Syndicate #4000			345		13,930		14,275		305		A		A+
	AXIS Re Europe			4,750		9,511		14,261		4,486		A+		A+
	Lloyd’s Syndicate #1955			2,459		10,931		13,390		2,397		A		A+
	Platinum Underwriters Re			259		12,700		12,959		1,692		A		A-
	Top 20 Reinsurers		$	211,424	$	624,204	$	835,628	$	166,876
	Others			42,011		217,040		259,051		73,700
	Total		$	253,435	$	841,244	$	1,094,679	$	240,576
	(1)  -	Net of reserve for uncollectible reinsurance of approximately $11.3 million.
	(2)  -	Collateral of $240.6 million consists of $180.6 million in ceded balances payable, $57.2 million in letters of credit, and $2.8 million of other balances held by the Company’s Insurance Companies and Lloyd’s Operations.

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2013
Amounts Charged to Expense for Stock-based Compensation	'
	The amounts charged to expense for stock-based compensation for the three and nine months ended September 30, 2013 and 2012 are presented in the following table:
			Three Months Ended				Nine Months Ended
			September 30,				September 30,
	In thousands		2013		2012		2013		2012
	Restricted stock units		$	17	$	1,818	$	3,491	$	5,004
	Directors restricted stock grants(1)			103		170		309		290
	Employee stock purchase plan			55		27		102		42
	Total stock based compensation		$	175	$	2,015	$	3,902	$	5,336
	(1)  -	Relates to non-employee directors serving on the Parent Company’s Board of Directors, all of whom have been elected by the Company’s stockholders, as well as non-employee directors serving on NUAL’s Board of Directors.

Investments_Tables

Investments (Tables)	9 Months Ended
	Sep. 30, 2013
Cash and Investments Including Other-Than-Temporarily Impaired Securities Recognized within Other Comprehensive Income	'
	The following tables set forth the Company’s cash and investments as of September 30, 2013 and December 31, 2012. The table below includes other-than-temporarily impaired (“OTTI”) securities recognized within other comprehensive income (“OCI”).
		September 30, 2013
						Gross				Gross			Cost or
		Fair				Unrealized				Unrealized			Amortized
	In thousands	Value				Gains				(Losses)			Cost
	Fixed maturities:
	U.S. Treasury bonds, agency bonds and foreign government bonds	$	445,969			$	3,683			$	(5,694	)	$	447,980
	States, municipalities and political subdivisions		445,281				9,752				(12,240	)		447,769
	Mortgage-backed and asset-backed securities:
	Agency mortgage-backed securities		300,347				7,966				(3,925	)		296,306
	Residential mortgage obligations		35,277				1,107				(224	)		34,394
	Asset-backed securities		88,714				795				(190	)		88,109
	Commercial mortgage-backed securities		173,069				8,386				(365	)		165,048
	Subtotal	$	597,407			$	18,254			$	(4,704	)	$	583,857
	Corporate bonds		493,074				17,104				(2,858	)		478,828
	Total fixed maturities	$	1,981,731			$	48,793			$	(25,496	)	$	1,958,434
	Equity securities—common stocks		158,890				29,548				(1,704	)		131,046
	Short-term investments		152,987				—				—			152,987
	Cash		130,513				—				—			130,513
	Total	$	2,424,121			$	78,341			$	(27,200	)	$	2,372,980
		December 31, 2012
						Gross				Gross			Cost or
		Fair				Unrealized				Unrealized			Amortized
	In thousands	Value				Gains				(Losses)			Cost
	Fixed maturities:
	U.S. Treasury bonds, agency bonds and foreign government bonds	$	649,692			$	8,654			$	(36	)	$	641,074
	States, municipalities and political subdivisions		322,947				18,712				(380	)		304,615
	Mortgage-backed and asset-backed securities:
	Agency mortgage-backed securities		384,445				13,652				(204	)		370,997
	Residential mortgage obligations		38,692				1,053				(549	)		38,188
	Asset-backed securities		50,382				1,133				(49	)		49,298
	Commercial mortgage-backed securities		204,821				17,996				(18	)		186,843
	Subtotal	$	678,340			$	33,834			$	(820	)	$	645,326
	Corporate bonds		470,854				27,129				(25	)		443,750
	Total fixed maturities	$	2,121,833			$	88,329			$	(1,261	)	$	2,034,765
	Equity securities—common stocks		101,297				16,919				(626	)		85,004
	Short-term investments		153,788				—				—			153,788
	Cash		45,336				—				—			45,336
	Total	$	2,422,254			$	105,248			$	(1,887	)	$	2,318,893
Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity	'
	The contractual maturity dates for fixed maturity securities categorized by the number of years until maturity as of September 30, 2013 are shown in the following table:
		September 30, 2013
		Fair				Amortized
	In thousands	Value				Cost
	Due in one year or less	$	79,192			$	78,621
	Due after one year through five years		616,576				603,165
	Due after five years through ten years		458,136				455,826
	Due after ten years		230,420				236,965
	Mortgage- and asset-backed securities		597,407				583,857
	Total	$	1,981,731			$	1,958,434
Amount and Percentage of Fixed Maturities by Rating	'
	The following table shows the amount and percentage of the Company’s fixed maturities as of September 30, 2013 by S&P credit rating or, if an S&P rating is not available, the equivalent Moody’s Investor Services (“Moody’s”) rating. The table includes fixed maturities at fair value, and the total rating is the weighted average quality rating.
		September 30, 2013
				Fair				Percent
	In thousands	Rating		Value				of Total
	Rating description:
	Extremely strong	AAA		$	305,979				15	%
	Very strong	AA			1,051,156				54	%
	Strong	A			440,063				22	%
	Adequate	BBB			163,614				8	%
	Speculative	BB & Below			11,722				1	%
	Not rated	NR			9,197				0	%
	Total	AA		$	1,981,731				100	%
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	'
	The following table summarizes all securities in a gross unrealized loss position as of September 30, 2013 and December 31, 2012, showing the aggregate fair value and gross unrealized loss by the length of time those securities had continuously been in a gross unrealized loss position as well as the relevant number of securities.
		September 30, 2013											December 31, 2012
										Gross									Gross
		Number of				Fair				Unrealized			Number of			Fair			Unrealized
	In thousands, except # of securities	Securities				Value				Loss			Securities			Value			Loss
	Fixed maturities:
	U.S. Treasury bonds, agency bonds, and foreign government bonds
	0-6 months		42			$	196,851			$	5,688			8		$	23,760		$	22
	7-12 months		1				928				6			3			14,118			11
	> 12 months		—				—				—			1			4,652			3
	Subtotal		43			$	197,779			$	5,694			12		$	42,530		$	36
	States, municipalities and political subdivisions
	0-6 months		100			$	196,987			$	9,485			10		$	21,299		$	325
	7-12 months		17				37,989				2,755			—			—			—
	> 12 months		1				303				—			4			2,908			55
	Subtotal		118			$	235,279			$	12,240			14		$	24,207		$	380
	Agency mortgage-backed securities
	0-6 months		71			$	90,215			$	2,472			10		$	62,516		$	174
	7-12 months		9				18,667				1,354			2			1,671			30
	> 12 months		2				5,130				99			—			—			—
	Subtotal		82			$	114,012			$	3,925			12		$	64,187		$	204
	Residential mortgage obligations
	0-6 months		12			$	2,016			$	43			6		$	1,825		$	22
	7-12 months		—				—				—			—			—			—
	> 12 months		17				2,955				181			35			7,252			527
	Subtotal		29			$	4,971			$	224			41		$	9,077		$	549
	Asset-backed securities
	0-6 months		3			$	32,019			$	189			—		$	—		$	—
	7-12 months		1				339				1			—			—			—
	> 12 months		—				—				—			2			2,369			49
	Subtotal		4			$	32,358			$	190			2		$	2,369		$	49
	Commercial mortgage-backed securities
	0-6 months		6			$	19,891			$	341			7		$	2,639		$	7
	7-12 months		—				—				—			—			—			—
	> 12 months		5				889				24			5			845			11
	Subtotal		11			$	20,780			$	365			12		$	3,484		$	18
	Corporate bonds
	0-6 months		37			$	123,673			$	2,856			2		$	3,528		$	6
	7-12 months		2				2,315				2			—			—			—
	> 12 months		—				—				—			4			6,689			19
	Subtotal		39			$	125,988			$	2,858			6		$	10,217		$	25
	Total fixed maturities		326			$	731,167			$	25,496			99		$	156,071		$	1,261
	Equity securities—common stocks
	0-6 months		13			$	33,429			$	1,340			13		$	23,345		$	522
	7-12 months		1				1,904				364			1			1,943			104
	> 12 months		—				—				—			—			—			—
	Total equity securities		14			$	35,333			$	1,704			14		$	25,288		$	626
Summary of Activity Related to Other-Than-Temporary Impairment Losses	'
	The table below summarizes the Company’s activity related to OTTI losses for the periods indicated:
		Three Months Ended September 30,														Nine Months Ended September 30,
		2013								2012						2013					2012
		Number of								Number of						Number of					Number of
	In thousands, except # of securities	Securities				Amount				Securities			Amount			Securities			Amount		Securities		Amount
	Total OTTI losses:
	Corporate and other bonds		1			$	1,821				—		$	—			1		$	1,821		—	$	—
	Commercial mortgage-backed securities		—				—				—			—			—			—		—		—
	Residential mortgage-backed securities		—				—				—			—			—			—		1		54
	Asset-backed securities		—				—				—			—			—			—		—		—
	Equities		—				—				—			—			2			42		3		639
	Total		1			$	1,821				—		$	—			3		$	1,863		4	$	693
	Less: Portion of loss in accumulated other comprehensive income (loss):
	Corporate and other bonds					$	—						$	—					$	—			$	—
	Commercial mortgage-backed securities						—							—						—				—
	Residential mortgage-backed securities						—							—						—				43
	Asset-backed securities						—							—						—				—
	Equities						—							—						—				—
	Total					$	—						$	—					$	—			$	43
	Impairment losses recognized in earnings:
	Corporate and other bonds					$	1,821						$	—					$	1,821			$	—
	Commercial mortgage-backed securities						—							—						—				—
	Residential mortgage-backed securities						—							—						—				11
	Asset-backed securities						—							—						—				—
	Equities						—							—						42				639
	Total					$	1,821						$	—					$	1,863			$	650
Summary of Cumulative Amounts Related to Credit Loss Portion of Other-Than-Temporary Impairment Losses on Debt Securities	'
	The following table summarizes the cumulative amounts related to the Company’s credit loss portion of the OTTI losses on debt securities for the three and nine months ended September 30, 2013 and 2012. The Company does not intend to sell and it is more likely than not that it will not be required to sell the securities prior to recovery of the amortized cost basis and for which the non-credit loss portion is included in OCI.
		Three Months Ended September 30,								Nine Months Ended September 30,
	In thousands	2013				2012				2013			2012
	Beginning balance	$	3,332			$	3,322			$	3,332		$	3,321
	Additions for credit loss impairments recognized in the current period on securities not previously impaired		1,821				—				1,821			—
	Additions for credit loss impairments recognized in the current period on securities previously impaired		—				—				—			11
	Reductions for credit loss impairments previously recognized on securities sold during the period		—				—				—			—
	Ending balance	$	5,153			$	3,332			$	5,153		$	3,332
Contractual Maturity by Number of Years Until Maturity for Fixed Maturity Securities with a Gross Unrealized Loss	'
	The contractual maturity dates for fixed maturity securities categorized by the number of years until maturity, with a gross unrealized loss as of September 30, 2013 is presented in the following table:
		September 30, 2013
		Gross Unrealized Losses								Fair Value
						Percent							Percent
	In thousands	Amount				of Total				Amount			of Total
	Due in one year or less	$	1				0	%		$	1,716			0	%
	Due after one year through five years		1,119				4	%			144,849			20	%
	Due after five years through ten years		9,803				38	%			250,290			34	%
	Due after ten years		9,869				40	%			162,191			22	%
	Mortgage- and asset-backed securities		4,704				18	%			172,121			24	%
	Total	$	25,496				100	%		$	731,167			100	%
Net Investment Income	'
	The Company’s net investment income was derived from the following sources:
		Three Months Ended September 30,								Nine Months Ended September 30,
	In thousands	2013				2012				2013			2012
	Fixed maturities	$	13,399			$	14,364			$	40,142		$	44,779
	Equity securities		1,315				989				3,603			2,930
	Short-term investments		187				437				575			1,452
	Total investment income	$	14,901			$	15,790			$	44,320		$	49,161
	Investment expenses		(807	)			(2,193	)			(2,323	)		(8,529	)
	Net investment income	$	14,094			$	13,597			$	41,997		$	40,632
Change in Net Unrealized Gains/(Losses)	'
	The change in net unrealized gains and losses, inclusive of the change in the non credit portion of other-than-temporary impairment losses, consisted of:
		Nine Months Ended September 30,
	In thousands	2013				2012
	Fixed maturities	$	(63,771	)		$	38,165
	Equity securities		11,551				8,817
	Gross unrealized gains (losses)	$	(52,220	)		$	46,982
	Deferred income tax		(18,296	)			15,702
	Change in net unrealized gains (losses), net	$	(33,924	)		$	31,280
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 September 30,								Nine Months Ended September 30,
	In thousands	2013				2012				2013			2012
	Fixed maturities:
	Gains	$	1,099			$	4,011			$	6,035		$	11,868
	Losses		(2,087	)			(216	)			(2,470	)		(1,746	)
	Fixed maturities, net	$	(988	)		$	3,795			$	3,565		$	10,122
	Equity securities:
	Gains	$	—			$	966			$	3,733		$	1,171
	Losses		—				—				(127	)		(473	)
	Equity securities, net	$	—			$	966			$	3,606		$	698
	Net realized gains (losses)	$	(988	)		$	4,761			$	7,171		$	10,820
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, the Company’s fixed maturities and equity securities by asset class that are measured at fair value on a recurring basis as of September 30, 2013 and December 31, 2012:
		September 30, 2013
	In thousands	Level 1				Level 2				Level 3			Total
	Fixed maturities:
	U.S. Treasury bonds, agency bonds and foreign government bonds	$	256,500			$	189,469			$	—		$	445,969
	States, municipalities and political subdivisions		—				445,281				—			445,281
	Mortgage-backed and asset-backed securities:													—
	Agency mortgage-backed securities		—				300,347				—			300,347
	Residential mortgage obligations		—				35,277				—			35,277
	Asset-backed securities		—				88,714				—			88,714
	Commercial mortgage-backed securities		—				173,069				—			173,069
	Subtotal	$	—			$	597,407			$	—		$	597,407
	Corporate bonds		—				488,512				4,562			493,074
	Total fixed maturities	$	256,500			$	1,720,669			$	4,562		$	1,981,731
	Equity securities—common stocks		158,890				—				—			158,890
	Total	$	415,390			$	1,720,669			$	4,562		$	2,140,621
		December 31, 2012
	In thousands	Level 1				Level 2				Level 3			Total
	Fixed maturities:
	U.S. Treasury bonds, agency bonds and foreign government bonds	$	414,502			$	235,190			$	—		$	649,692
	States, municipalities and political subdivisions		—				322,947				—			322,947
	Mortgage-backed and asset-backed securities:													—
	Agency mortgage-backed securities		—				384,445				—			384,445
	Residential mortgage obligations		—				38,692				—			38,692
	Asset-backed securities		—				50,382				—			50,382
	Commercial mortgage-backed securities		—				204,821				—			204,821
	Subtotal	$	—			$	678,340			$	—		$	678,340
	Corporate bonds		—				470,854				—			470,854
	Total fixed maturities	$	414,502			$	1,707,331			$	—		$	2,121,833
	Equity securities—common stocks		101,297				—				—			101,297
	Total	$	515,799			$	1,707,331			$	—		$	2,223,130
Reconciliation of Beginning and Ending Balances for All Investments Measured at Fair Value Using Level 3 Inputs	'
	The following tables present a reconciliation of the beginning and ending balances of all investments measured at fair value using Level 3 inputs during the three and nine months ended September 30, 2013.
		Three Months Ended September 30, 2013
	In thousands	Beginning				Realized				Unrealized			Purchases			Sales			Settlements		Transfers		Transfers		Ending
		Balance				Gains				Gains											into Level 3		out of Level 3		Balance
						(Losses)				(Losses)
	Assets:
	Corporate Bonds	$	—			$	—			$	(15	)	$	4,661		$	(84	)	$	—	$	—	$	—	$	4,562
	Total assets	$	—			$	—			$	(15	)	$	4,661		$	(84	)	$	—	$	—	$	—	$	4,562
		Nine Months Ended September 30, 2013
	In thousands	Beginning				Realized				Unrealized			Purchases			Sales			Settlements		Transfers		Transfers		Ending
		Balance				Gains				Gains											into Level 3		out of Level 3		Balance
						(Losses)				(Losses)
	Assets:
	Corporate Bonds	$	—			$	—			$	(15	)	$	4,661		$	(84	)	$	—	$	—	$	—	$	4,562
	Total assets	$	—			$	—			$	(15	)	$	4,661		$	(84	)	$	—	$	—	$	—	$	4,562

Segment_Information_Additional

Segment Information - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
			Segment
Segment Reporting Information [Line Items]	'	'	'	'
Number of business segments	'	'	2	'
Combined ratio indicating underwriting profit	'	'	100.00%	'
Combined ratio indicating underwriting loss	'	'	100.00%	'
Net earned premiums	$213,895	$201,262	$622,037	$580,398
Navigators Insurance Company	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Percentage of Navigators Specialty Insurance Company reinsured by Navigators Insurance Company	100.00%	'	100.00%	'
Lloyd's	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net earned premiums	50,933	52,172	148,197	158,183
Lloyd's | Syndicate 1221	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Percentage control of stamp capacity	100.00%	100.00%	100.00%	100.00%
Insurance	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net earned premiums	162,962	149,090	473,840	422,215
Insurance | UK Branch	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net earned premiums	$13,900	$16,900	$36,700	$56,000

Financial_Data_by_Segment_Deta

Financial Data by Segment (Detail) (USD $)	3 Months Ended				9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
Segment Reporting Information [Line Items]	'		'		'		'		'
Gross written premiums	$312,076		$298,742		$1,037,426		$964,878		'
Net written premiums	196,556		188,046		664,477		621,343		'
Net earned premiums	213,895		201,262		622,037		580,398		'
Net losses and loss adjustment expenses	-125,086		-128,850		-387,576		-370,242		'
Commission expenses	-27,685		-31,258		-82,631		-90,211		'
Other operating expenses	-39,056		-40,112		-120,608		-116,238		'
Other income (expense)	-210		789		-507		2,087		'
Underwriting profit (loss)	21,858		1,831		30,715		5,794		'
Net investment income	14,094		13,597		41,997		40,632		'
Net realized gains (losses)	-2,809		4,761		5,308		10,170		'
Interest expense	-2,053		-2,049		-6,156		-6,147		'
Income (loss) before income taxes	31,090		18,140		71,864		50,449		'
Income tax expense (benefit)	9,804		5,225		22,731		14,731		'
Net income (loss)	21,286		12,915		49,133		35,718		'
Identifiable assets	4,074,576		3,994,697		4,074,576		3,994,697		4,007,670
Losses and loss adjustment expenses ratio	58.50%		64.00%		62.30%		63.80%		'
Commission expense ratio	12.90%		15.50%		13.30%		15.50%		'
Other operating expense ratio	18.40%	[1]	19.60%	[1]	19.50%	[1]	19.70%	[1]	'
Combined ratio	89.80%		99.10%		95.10%		99.00%		'
Insurance	'		'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'		'
Gross written premiums	227,609		218,361		757,802		680,763		'
Net written premiums	149,290		142,148		508,989		457,463		'
Net earned premiums	162,962		149,090		473,840		422,215		'
Net losses and loss adjustment expenses	-95,315		-113,303		-308,968		-304,483		'
Commission expenses	-20,039		-20,827		-59,129		-61,245		'
Other operating expenses	-28,510		-29,387		-87,682		-83,646		'
Other income (expense)	955		1,229		2,303		3,750		'
Underwriting profit (loss)	20,053		-13,198		20,364		-23,409		'
Net investment income	12,285		12,004		36,751		34,225		'
Net realized gains (losses)	-1,890		2,609		6,001		6,809		'
Income (loss) before income taxes	30,448		1,415		63,116		17,625		'
Income tax expense (benefit)	9,355		-377		19,554		3,603		'
Net income (loss)	21,093		1,792		43,562		14,022		'
Identifiable assets	3,018,100		2,995,530		3,018,100		2,995,530		'
Losses and loss adjustment expenses ratio	58.50%		76.00%		65.20%		72.10%		'
Commission expense ratio	12.30%		14.00%		12.50%		14.50%		'
Other operating expense ratio	16.90%	[1]	18.90%	[1]	18.00%	[1]	18.90%	[1]	'
Combined ratio	87.70%		108.90%		95.70%		105.50%		'
Lloyd's	'		'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'		'
Gross written premiums	84,467		80,381		279,624		284,115		'
Net written premiums	47,266		45,898		155,488		163,880		'
Net earned premiums	50,933		52,172		148,197		158,183		'
Net losses and loss adjustment expenses	-29,771		-15,547		-78,608		-65,759		'
Commission expenses	-8,289		-10,911		-25,245		-30,735		'
Other operating expenses	-10,546		-10,725		-32,926		-32,592		'
Other income (expense)	-522		40		-1,067		106		'
Underwriting profit (loss)	1,805		15,029		10,351		29,203		'
Net investment income	1,807		1,552		5,237		6,289		'
Net realized gains (losses)	-919		2,152		-697		3,361		'
Income (loss) before income taxes	2,693		18,733		14,891		38,853		'
Income tax expense (benefit)	878		6,525		5,120		13,458		'
Net income (loss)	1,815		12,208		9,771		25,395		'
Identifiable assets	983,382		958,238		983,382		958,238		'
Losses and loss adjustment expenses ratio	58.50%		29.80%		53.00%		41.60%		'
Commission expense ratio	16.30%		20.90%		17.00%		19.40%		'
Other operating expense ratio	21.70%	[1]	20.50%	[1]	23.00%	[1]	20.50%	[1]	'
Combined ratio	96.50%		71.20%		93.00%		81.50%		'
Corporate	'		'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'		'
Commission expenses	643	[2]	480	[2]	1,743	[2]	1,769	[2]	'
Other income (expense)	-643	[2]	-480	[2]	-1,743	[2]	-1,769	[2]	'
Net investment income	2	[2]	41	[2]	9	[2]	118	[2]	'
Net realized gains (losses)	'		'		4	[2]	'		'
Interest expense	-2,053	[2]	-2,049	[2]	-6,156	[2]	-6,147	[2]	'
Income (loss) before income taxes	-2,051	[2]	-2,008	[2]	-6,143	[2]	-6,029	[2]	'
Income tax expense (benefit)	-429	[2]	-923	[2]	-1,943	[2]	-2,330	[2]	'
Net income (loss)	-1,622	[2]	-1,085	[2]	-4,200	[2]	-3,699	[2]	'
Identifiable assets	$73,094	[2]	$40,929	[2]	$73,094	[2]	$40,929	[2]	'
[1]	Includes Other operating expenses and Other income.
[2]	Includes Corporate segment intercompany eliminations.

Additional_Financial_Data_by_S

Additional Financial Data by Segment (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting Information [Line Items]	'	'	'	'
Gross written premiums	$312,076	$298,742	$1,037,426	$964,878
Net written premiums	196,556	188,046	664,477	621,343
Net earned premiums	213,895	201,262	622,037	580,398
Marine	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Gross written premiums	74,921	82,595	268,382	303,168
Net written premiums	53,232	60,554	195,357	216,755
Net earned premiums	65,754	74,594	202,945	212,940
Property Casualty	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Gross written premiums	192,097	172,737	629,431	532,557
Net written premiums	111,314	95,082	371,469	311,516
Net earned premiums	116,231	95,863	324,867	282,180
Professional Liability	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Gross written premiums	45,058	43,410	139,613	129,153
Net written premiums	32,010	32,410	97,651	93,072
Net earned premiums	31,910	30,805	94,225	85,278
Insurance	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Gross written premiums	227,609	218,361	757,802	680,763
Net written premiums	149,290	142,148	508,989	457,463
Net earned premiums	162,962	149,090	473,840	422,215
Insurance | Marine	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Gross written premiums	38,912	44,879	132,836	156,640
Net written premiums	26,437	32,615	94,944	107,266
Net earned premiums	31,490	40,592	100,013	111,402
Insurance | Property Casualty	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Gross written premiums	156,228	139,948	527,287	426,494
Net written premiums	97,553	83,449	338,215	274,823
Net earned premiums	105,759	83,993	297,954	240,536
Insurance | Professional Liability	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Gross written premiums	32,469	33,534	97,679	97,629
Net written premiums	25,300	26,084	75,830	75,374
Net earned premiums	25,713	24,505	75,873	70,277
Lloyd's	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Gross written premiums	84,467	80,381	279,624	284,115
Net written premiums	47,266	45,898	155,488	163,880
Net earned premiums	50,933	52,172	148,197	158,183
Lloyd's | Marine	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Gross written premiums	36,009	37,716	135,546	146,528
Net written premiums	26,795	27,939	100,413	109,489
Net earned premiums	34,264	34,002	102,932	101,538
Lloyd's | Property Casualty	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Gross written premiums	35,869	32,789	102,144	106,063
Net written premiums	13,761	11,633	33,254	36,693
Net earned premiums	10,472	11,870	26,913	41,644
Lloyd's | Professional Liability	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Gross written premiums	12,589	9,876	41,934	31,524
Net written premiums	6,710	6,326	21,821	17,698
Net earned premiums	$6,197	$6,300	$18,352	$15,001

Reinsurance_Ceded_Additional_I

Reinsurance Ceded - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
	Entity		Entity
Effects of Reinsurance [Line Items]	'	'	'	'
Ceded premiums earned	$114.20	$97.40	$340.50	$283.40
Ceded losses incurred	($37)	$31.20	$94.10	$154.40
Percentage of reinsurance recoverable of 20 largest reinsurers	'	'	76.30%	'
Number of largest reinsurers	20	'	20	'

Lists_of_20_Largest_Reinsurers

Lists of 20 Largest Reinsurers Measured by Reinsurance Recoverable (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	$253,435		$221,015
Reinsurance Recoverables Paid/Unpaid Losses	841,244		'
Reinsurance Recoverables Total	1,094,679	[1]	'
Collateral Held	240,576	[2]	'
Rating	'AA		'
National Indemnity Company | AM Best, A++ Rating | Standard & Poor's, AA+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	56,161		'
Reinsurance Recoverables Paid/Unpaid Losses	73,815		'
Reinsurance Recoverables Total	129,976	[1]	'
Collateral Held	37,385	[2]	'
National Indemnity Company | AM Best | AM Best, A++ Rating | Standard & Poor's, AA+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A++		'
National Indemnity Company | Standard & Poor's | AM Best, A++ Rating | Standard & Poor's, AA+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'AA+		'
Transatlantic Reinsurance Company | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	21,964		'
Reinsurance Recoverables Paid/Unpaid Losses	70,838		'
Reinsurance Recoverables Total	92,802	[1]	'
Collateral Held	10,052	[2]	'
Transatlantic Reinsurance Company | AM Best | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A		'
Transatlantic Reinsurance Company | Standard & Poor's | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A+		'
Everest Reinsurance Company | AM Best, A+ Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	22,082		'
Reinsurance Recoverables Paid/Unpaid Losses	64,313		'
Reinsurance Recoverables Total	86,395	[1]	'
Collateral Held	9,115	[2]	'
Everest Reinsurance Company | AM Best | AM Best, A+ Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A+		'
Everest Reinsurance Company | Standard & Poor's | AM Best, A+ Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A+		'
Swiss Reinsurance America Corporation | AM Best, A+ Rating | Standard & Poor's, AA- Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	6,094		'
Reinsurance Recoverables Paid/Unpaid Losses	76,895		'
Reinsurance Recoverables Total	82,989	[1]	'
Collateral Held	8,638	[2]	'
Swiss Reinsurance America Corporation | AM Best | AM Best, A+ Rating | Standard & Poor's, AA- Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A+		'
Swiss Reinsurance America Corporation | Standard & Poor's | AM Best, A+ Rating | Standard & Poor's, AA- Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'AA-		'
Munich Reinsurance America Inc. | AM Best, A+ Rating | Standard & Poor's, AA- Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	6,307		'
Reinsurance Recoverables Paid/Unpaid Losses	70,676		'
Reinsurance Recoverables Total	76,983	[1]	'
Collateral Held	4,440	[2]	'
Munich Reinsurance America Inc. | AM Best | AM Best, A+ Rating | Standard & Poor's, AA- Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A+		'
Munich Reinsurance America Inc. | Standard & Poor's | AM Best, A+ Rating | Standard & Poor's, AA- Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'AA-		'
Partner Reinsurance Europe | AM Best, A+ Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	11,141		'
Reinsurance Recoverables Paid/Unpaid Losses	40,623		'
Reinsurance Recoverables Total	51,764	[1]	'
Collateral Held	18,715	[2]	'
Partner Reinsurance Europe | AM Best | AM Best, A+ Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A+		'
Partner Reinsurance Europe | Standard & Poor's | AM Best, A+ Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A+		'
Lloyd Syndicate #2003 | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	8,493		'
Reinsurance Recoverables Paid/Unpaid Losses	37,427		'
Reinsurance Recoverables Total	45,920	[1]	'
Collateral Held	10,568	[2]	'
Lloyd Syndicate #2003 | AM Best | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A		'
Lloyd Syndicate #2003 | Standard & Poor's | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A+		'
Allied World Reinsurance | AM Best, A Rating | Standard & Poor's, A Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	14,006		'
Reinsurance Recoverables Paid/Unpaid Losses	28,718		'
Reinsurance Recoverables Total	42,724	[1]	'
Collateral Held	4,724	[2]	'
Allied World Reinsurance | AM Best | AM Best, A Rating | Standard & Poor's, A Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A		'
Allied World Reinsurance | Standard & Poor's | AM Best, A Rating | Standard & Poor's, A Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A		'
Scor Global P&C SE | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	12,212		'
Reinsurance Recoverables Paid/Unpaid Losses	25,127		'
Reinsurance Recoverables Total	37,339	[1]	'
Collateral Held	11,826	[2]	'
Scor Global P&C SE | AM Best | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A		'
Scor Global P&C SE | Standard & Poor's | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A+		'
Tower Insurance Company | AM Best, B++ Rating | Standard & Poor's, Not Rated	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	13,271		'
Reinsurance Recoverables Paid/Unpaid Losses	16,002		'
Reinsurance Recoverables Total	29,273	[1]	'
Collateral Held	8,305	[2]	'
Tower Insurance Company | AM Best | AM Best, B++ Rating | Standard & Poor's, Not Rated	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'B++		'
Tower Insurance Company | Standard & Poor's | AM Best, B++ Rating | Standard & Poor's, Not Rated	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'NR		'
Validus Reinsurance Ltd | AM Best, A Rating | Standard & Poor's, A Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	2,576		'
Reinsurance Recoverables Paid/Unpaid Losses	21,140		'
Reinsurance Recoverables Total	23,716	[1]	'
Collateral Held	12,756	[2]	'
Validus Reinsurance Ltd | AM Best | AM Best, A Rating | Standard & Poor's, A Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A		'
Validus Reinsurance Ltd | Standard & Poor's | AM Best, A Rating | Standard & Poor's, A Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A		'
Employers Mutual Casualty Company | AM Best, A Rating | Standard & Poor's, Not Rated	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	11,257		'
Reinsurance Recoverables Paid/Unpaid Losses	6,746		'
Reinsurance Recoverables Total	18,003	[1]	'
Collateral Held	11,050	[2]	'
Employers Mutual Casualty Company | AM Best | AM Best, A Rating | Standard & Poor's, Not Rated	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A		'
Employers Mutual Casualty Company | Standard & Poor's | AM Best, A Rating | Standard & Poor's, Not Rated	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'NR		'
Atlantic Specialty Insurance | AM Best, A Rating | Standard & Poor's, A- Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	8,626		'
Reinsurance Recoverables Paid/Unpaid Losses	8,406		'
Reinsurance Recoverables Total	17,032	[1]	'
Collateral Held	2,560	[2]	'
Atlantic Specialty Insurance | AM Best | AM Best, A Rating | Standard & Poor's, A- Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A		'
Atlantic Specialty Insurance | Standard & Poor's | AM Best, A Rating | Standard & Poor's, A- Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A-		'
QBE Reinsurance Corp | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	6,959		'
Reinsurance Recoverables Paid/Unpaid Losses	9,559		'
Reinsurance Recoverables Total	16,518	[1]	'
Collateral Held	2,416	[2]	'
QBE Reinsurance Corp | AM Best | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A		'
QBE Reinsurance Corp | Standard & Poor's | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A+		'
Scor Holding (Switzerland) AG | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	675		'
Reinsurance Recoverables Paid/Unpaid Losses	14,050		'
Reinsurance Recoverables Total	14,725	[1]	'
Collateral Held	4,927	[2]	'
Scor Holding (Switzerland) AG | AM Best | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A		'
Scor Holding (Switzerland) AG | Standard & Poor's | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A+		'
Berkley Insurance Company | AM Best, A+ Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	1,787		'
Reinsurance Recoverables Paid/Unpaid Losses	12,797		'
Reinsurance Recoverables Total	14,584	[1]	'
Collateral Held	519	[2]	'
Berkley Insurance Company | AM Best | AM Best, A+ Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A+		'
Berkley Insurance Company | Standard & Poor's | AM Best, A+ Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A+		'
Lloyd Syndicate #4000 | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	345		'
Reinsurance Recoverables Paid/Unpaid Losses	13,930		'
Reinsurance Recoverables Total	14,275	[1]	'
Collateral Held	305	[2]	'
Lloyd Syndicate #4000 | AM Best | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A		'
Lloyd Syndicate #4000 | Standard & Poor's | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A+		'
AXIS Re Europe | AM Best, A+ Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	4,750		'
Reinsurance Recoverables Paid/Unpaid Losses	9,511		'
Reinsurance Recoverables Total	14,261	[1]	'
Collateral Held	4,486	[2]	'
AXIS Re Europe | AM Best | AM Best, A+ Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A+		'
AXIS Re Europe | Standard & Poor's | AM Best, A+ Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A+		'
Lloyd's Syndicate #1955 | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	2,459		'
Reinsurance Recoverables Paid/Unpaid Losses	10,931		'
Reinsurance Recoverables Total	13,390	[1]	'
Collateral Held	2,397	[2]	'
Lloyd's Syndicate #1955 | AM Best | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A		'
Lloyd's Syndicate #1955 | Standard & Poor's | AM Best, A Rating | Standard & Poor's, A+ Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A+		'
Platinum Underwriters Re | AM Best, A Rating | Standard & Poor's, A- Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	259		'
Reinsurance Recoverables Paid/Unpaid Losses	12,700		'
Reinsurance Recoverables Total	12,959	[1]	'
Collateral Held	1,692	[2]	'
Platinum Underwriters Re | AM Best | AM Best, A Rating | Standard & Poor's, A- Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A		'
Platinum Underwriters Re | Standard & Poor's | AM Best, A Rating | Standard & Poor's, A- Rating	'		'
Ceded Credit Risk [Line Items]	'		'
Rating	'A-		'
Insurance	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	211,424		'
Reinsurance Recoverables Paid/Unpaid Losses	624,204		'
Reinsurance Recoverables Total	835,628	[1]	'
Collateral Held	166,876	[2]	'
All Other	'		'
Ceded Credit Risk [Line Items]	'		'
Reinsurance Recoverables Unearned Premium	42,011		'
Reinsurance Recoverables Paid/Unpaid Losses	217,040		'
Reinsurance Recoverables Total	259,051	[1]	'
Collateral Held	$73,700	[2]	'
[1]	Net of reserve for uncollectible reinsurance of approximately $11.3 million.
[2]	Collateral of $240.6 million consists of $180.6 million in ceded balances payable, $57.2 million in letters of credit, and $2.8 million of other balances held by the Company's Insurance Companies and Lloyd's Operations.

Lists_of_20_Largest_Reinsurers1

Lists of 20 Largest Reinsurers Measured by Reinsurance Recoverable (Parenthetical) (Detail) (USD $)	Sep. 30, 2013
Ceded Credit Risk [Line Items]	'
Reserve for uncollectible reinsurance amount	$11,300,000
Collateral Held	240,576,000	[1]
Ceded Balances Payable	'
Ceded Credit Risk [Line Items]	'
Collateral Held	180,600,000
Letter of Credit	'
Ceded Credit Risk [Line Items]	'
Collateral Held	57,200,000
All Other	'
Ceded Credit Risk [Line Items]	'
Collateral Held	$2,800,000
[1]	Collateral of $240.6 million consists of $180.6 million in ceded balances payable, $57.2 million in letters of credit, and $2.8 million of other balances held by the Company's Insurance Companies and Lloyd's Operations.

StockBased_Compensation_Additi

Stock-Based Compensation - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2013
Maximum	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Options expiration term (in years)	'10 years
Options and Non Performance Based Grants | Minimum	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Share based payment award, award vesting period	'3 years
Options and Non Performance Based Grants | Maximum	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Share based payment award, award vesting period	'4 years
Non Performance Based Shares	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Share based payment award, award vesting period	'5 years
Non Performance Based Shares | Year Three	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Percentage of shares vesting over the period	33.33%
Non Performance Based Shares | Year Four	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Percentage of shares vesting over the period	33.33%
Non Performance Based Shares | Year Five	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Percentage of shares vesting over the period	33.33%
Performance Based Shares Issued in 2011	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Share based payment award, award vesting period	'3 years
Percentage of shares vesting over the period	50.00%
Restricted stock units | Minimum	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Percentage of shares vesting over the period	0.00%
Restricted stock units | Maximum	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Percentage of shares vesting over the period	150.00%
Performance Based Shares Issued Prior to 2011	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Share based payment award, award vesting period	'5 years
Performance Based Shares Issued Prior to 2011 | Year Three	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Percentage of shares vesting over the period	33.33%
Performance Based Shares Issued Prior to 2011 | Year Four	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Percentage of shares vesting over the period	33.33%
Performance Based Shares Issued Prior to 2011 | Year Five	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Percentage of shares vesting over the period	33.33%
Performance Based Shares Issued Prior to 2011 | Minimum	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Percentage of shares vesting over the period	0.00%
Performance Based Shares Issued Prior to 2011 | Maximum	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Percentage of shares vesting over the period	150.00%

Amounts_Charged_to_Expense_for

Amounts Charged to Expense for Stock-based Compensation (Detail) (USD $)	3 Months Ended				9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'		'		'
Stock based compensation	$175		$2,015		$3,902		$5,336
Restricted stock units	'		'		'		'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'		'		'
Stock based compensation	17		1,818		3,491		5,004
Directors restricted stock grants	'		'		'		'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'		'		'
Stock based compensation	103	[1]	170	[1]	309	[1]	290	[1]
Employee stock purchase plan	'		'		'		'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'		'		'
Stock based compensation	$55		$27		$102		$42
[1]	Relates to non-employee directors serving on the Parent Company's Board of Directors, all of whom have been elected by the Company's stockholders, as well as non-employee directors serving on NUAL's Board of Directors.

Lloyds_Syndicate_1221_Addition

Lloyd's Syndicate 1221 - Additional Information (Detail) (Lloyd's, Syndicate 1221)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2012
	USD ($)	GBP (£)	USD ($)	GBP (£)
Supplementary Insurance Information, by Segment [Line Items]	'	'	'	'
Syndicate 1221's stamp capacity	$316	£ 195	$300	£ 184
Percentage control of stamp capacity	100.00%	100.00%	100.00%	100.00%
Letters of credit	143	'	'	'
Cash collateral posted	$1	'	'	'

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)

3 Months Ended

9 Months Ended

1 Months Ended

3 Months Ended

9 Months Ended

9 Months Ended

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Apr. 30, 2013

Apr. 30, 2012

Mar. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

United Kingdom

United Kingdom

United Kingdom

United Kingdom

United Kingdom

United Kingdom

State and Local Jurisdiction

State and Local Jurisdiction

Syndicate 1221

Syndicate 1221

Minimum

Maximum

Minimum

Maximum

Income Taxes [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

Foreign effective income tax rate

'

'

'

'

'

'

'

'

35.00%

35.00%

'

'

'

Percentage of premiums

'

'

'

'

'

'

'

'

'

'

50.00%

'

'

Corporate tax rate

'

'

'

'

'

23.00%

24.00%

26.00%

'

'

'

'

'

Undistributed earnings of non-U.S. subsidiaries

$18,900,000

'

$18,900,000

'

'

'

'

'

'

'

'

'

'

Taxes payable on undistributed earnings

2,000,000

'

2,000,000

'

'

'

'

'

'

'

'

'

'

Income tax (benefit) expense

9,804,000

5,225,000

22,731,000

14,731,000

'

'

'

'

'

'

'

'

'

Effective income tax rate

31.50%

28.80%

31.60%

29.20%

'

'

'

'

'

'

'

'

'

Deferred Tax Assets: State and Local

500,000

'

500,000

'

500,000

'

'

'

'

'

'

'

'

State and local net operating loss carry-forwards

$100,000

'

$100,000

'

$200,000

'

'

'

'

'

'

'

'

State and local tax carry-forwards expiration year

'

'

'

'

'

'

'

'

'

'

'

'2023

'2031

Senior_Note_Due_May_1_2016_Add

Senior Note Due May 1, 2016 - Additional Information (Detail) (USD $)	1 Months Ended		3 Months Ended		9 Months Ended
	Apr. 30, 2009	Apr. 17, 2006	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Debt Instrument [Line Items]	'	'	'	'	'	'	'
Senior Notes	'	'	$114,542,000	'	$114,542,000	'	$114,424,000
Senior Notes due May 1, 2016	'	'	'	'	'	'	'
Debt Instrument [Line Items]	'	'	'	'	'	'	'
Principal amount of senior notes	'	125,000,000	'	'	'	'	'
Interest rate stated on senior notes	'	7.00%	'	'	'	'	'
Senior notes due date	'	1-May-16	'	'	'	'	'
Net proceeds from issuance of senior notes	'	123,500,000	'	'	'	'	'
Aggregate principal amount of senior notes repurchased from unaffiliated note holder	10,000,000	'	'	'	'	'	'
Repurchased senior notes	7,000,000	'	'	'	'	'	'
Pretax gain from repurchase of senior notes	3,000,000	'	'	'	'	'	'
Outstanding principal amount of senior notes	'	'	114,500,000	'	114,500,000	'	'
Unamortized discount	'	'	500,000	'	500,000	'	'
Senior Notes	'	'	115,000,000	'	115,000,000	'	'
Fair value of senior notes	'	'	125,200,000	'	125,200,000	'	123,200,000
Interest expense on senior notes	'	'	$2,100,000	$2,100,000	$6,100,000	$6,100,000	'
Effective interest rate related to senior notes	'	'	7.17%	'	7.17%	'	'
Debt instrument, covenant compliance	'	'	'	'	'As of September 30, 2013, the Company was in compliance with all such covenants.	'	'
Senior Notes due May 1, 2016 | Semi Annual Payment, First Payment	'	'	'	'	'	'	'
Debt Instrument [Line Items]	'	'	'	'	'	'	'
Interest payment date on senior notes	'	'	'--05-01	'	'--05-01	'	'
Senior Notes due May 1, 2016 | Semi Annual Payment, Second Payment	'	'	'	'	'	'	'
Debt Instrument [Line Items]	'	'	'	'	'	'	'
Interest payment date on senior notes	'	'	'--11-01	'	'--11-01	'	'

Cash_and_Investments_Including

Cash and Investments Including Other-Than-Temporarily Impaired Securities Recognized within Other Comprehensive Income (Detail) (USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Gain (Loss) on Investments [Line Items]	'	'
Total investments and cash	$2,140,621	$2,223,130
Total investments and cash	2,424,121	2,422,254
Gross Unrealized Gains	78,341	105,248
Gross Unrealized Losses	-27,200	-1,887
Amortized Cost	2,372,980	2,318,893
Fixed maturities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Total investments and cash	1,981,731	2,121,833
Gross Unrealized Gains	48,793	88,329
Gross Unrealized Losses	-25,496	-1,261
Amortized Cost	1,958,434	2,034,765
Fixed maturities | U.S. Treasury bonds, agency bonds, and foreign	'	'
Gain (Loss) on Investments [Line Items]	'	'
Total investments and cash	445,969	649,692
Gross Unrealized Gains	3,683	8,654
Gross Unrealized Losses	-5,694	-36
Amortized Cost	447,980	641,074
Fixed maturities | States, municipalities and political subdivisions	'	'
Gain (Loss) on Investments [Line Items]	'	'
Total investments and cash	445,281	322,947
Gross Unrealized Gains	9,752	18,712
Gross Unrealized Losses	-12,240	-380
Amortized Cost	447,769	304,615
Fixed maturities | Agency mortgage-backed securities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Total investments and cash	300,347	384,445
Gross Unrealized Gains	7,966	13,652
Gross Unrealized Losses	-3,925	-204
Amortized Cost	296,306	370,997
Fixed maturities | Residential Mortgage Backed Securities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Total investments and cash	35,277	38,692
Gross Unrealized Gains	1,107	1,053
Gross Unrealized Losses	-224	-549
Amortized Cost	34,394	38,188
Fixed maturities | Asset-backed securities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Total investments and cash	88,714	50,382
Gross Unrealized Gains	795	1,133
Gross Unrealized Losses	-190	-49
Amortized Cost	88,109	49,298
Fixed maturities | Commercial mortgage-backed securities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Total investments and cash	173,069	204,821
Gross Unrealized Gains	8,386	17,996
Gross Unrealized Losses	-365	-18
Amortized Cost	165,048	186,843
Fixed maturities | Mortgage-backed and asset-backed securities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Total investments and cash	597,407	678,340
Gross Unrealized Gains	18,254	33,834
Gross Unrealized Losses	-4,704	-820
Amortized Cost	583,857	645,326
Fixed maturities | Corporate bonds	'	'
Gain (Loss) on Investments [Line Items]	'	'
Total investments and cash	493,074	470,854
Gross Unrealized Gains	17,104	27,129
Gross Unrealized Losses	-2,858	-25
Amortized Cost	478,828	443,750
Equity Securities | Common Stock	'	'
Gain (Loss) on Investments [Line Items]	'	'
Total investments and cash	158,890	101,297
Gross Unrealized Gains	29,548	16,919
Gross Unrealized Losses	-1,704	-626
Amortized Cost	131,046	85,004
Short-term investments	'	'
Gain (Loss) on Investments [Line Items]	'	'
Total investments and cash	152,987	153,788
Amortized Cost	152,987	153,788
Cash	'	'
Gain (Loss) on Investments [Line Items]	'	'
Total investments and cash	130,513	45,336
Amortized Cost	$130,513	$45,336

Investments_Additional_Informa

Investments - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Schedule of Investments [Line Items]	'	'	'	'	'
Non-credit OTTI on debt securities in an unrealized gain position	'	'	$400,000	'	$20,000
Investment Expenses	807,000	2,193,000	2,323,000	8,529,000	'
Portfolio duration of investments	'	'	'3 years 10 months 24 days	'3 years 9 months 18 days	'
Net realized gains(losses) from sale of investments	-988,000	4,761,000	7,171,000	10,820,000	'
Settlement Agreement	'	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'	'
Investment Expenses	'	'	9,200,000	4,500,000	'
Mortgage-backed and asset-backed securities	'	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'	'
Securities, effective maturities	4.6	'	4.6	'	'
Non-government backed securities | Maximum	'	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'	'
Percentage of investment	5.00%	'	5.00%	'	5.00%
Non-government backed securities | Investments	'	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'	'
Gross Unrealized Loss	'	'	$1,000,000	'	$200,000
Equity Securities | Maximum	'	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'	'
Percentage of fair value over cost	80.00%	'	80.00%	'	'

Scheduled_Maturity_Dates_for_F

Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Fair Value	'	'
Due in one year or less	$79,192	'
Due after one year through five years	616,576	'
Due after five years through ten years	458,136	'
Due after ten years	230,420	'
Mortgage- and asset-backed securities	597,407	'
Total	1,981,731	2,121,833
Amortized Cost	'	'
Due in one year or less	78,621	'
Due after one year through five years	603,165	'
Due after five years through ten years	455,826	'
Due after ten years	236,965	'
Mortgage- and asset-backed securities	583,857	'
Total	$1,958,434	$2,034,765

Amount_and_Percentage_of_Fixed

Amount and Percentage of Fixed Maturities by Rating (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Investment Securities [Line Items]	'	'
Rating	'AA	'
Fair Value	$1,981,731	$2,121,833
Percent of Total	100.00%	'
Extremely strong	'	'
Investment Securities [Line Items]	'	'
Rating	'AAA	'
Fair Value	305,979	'
Percent of Total	15.00%	'
Very strong	'	'
Investment Securities [Line Items]	'	'
Rating	'AA	'
Fair Value	1,051,156	'
Percent of Total	54.00%	'
Strong	'	'
Investment Securities [Line Items]	'	'
Rating	'A	'
Fair Value	440,063	'
Percent of Total	22.00%	'
Adequate	'	'
Investment Securities [Line Items]	'	'
Rating	'BBB	'
Fair Value	163,614	'
Percent of Total	8.00%	'
Speculative	'	'
Investment Securities [Line Items]	'	'
Rating	'BB & Below	'
Fair Value	11,722	'
Percent of Total	1.00%	'
Not rated	'	'
Investment Securities [Line Items]	'	'
Rating	'NR	'
Fair Value	$9,197	'
Percent of Total	0.00%	'

Summary_of_Aggregate_Fair_Valu

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 $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Investment	Investment
Fixed maturities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	326	99
Fair Value	$731,167	$156,071
Gross Unrealized Loss	25,496	1,261
Fixed maturities | U.S. Treasury bonds, agency bonds, and foreign	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	43	12
Fair Value	197,779	42,530
Gross Unrealized Loss	5,694	36
Fixed maturities | U.S. Treasury bonds, agency bonds, and foreign | 0-6 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	42	8
Fair Value	196,851	23,760
Gross Unrealized Loss	5,688	22
Fixed maturities | U.S. Treasury bonds, agency bonds, and foreign | 7-12 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	1	3
Fair Value	928	14,118
Gross Unrealized Loss	6	11
Fixed maturities | U.S. Treasury bonds, agency bonds, and foreign | > 12 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	'	1
Fair Value	'	4,652
Gross Unrealized Loss	'	3
Fixed maturities | States, municipalities and political subdivisions	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	118	14
Fair Value	235,279	24,207
Gross Unrealized Loss	12,240	380
Fixed maturities | States, municipalities and political subdivisions | 0-6 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	100	10
Fair Value	196,987	21,299
Gross Unrealized Loss	9,485	325
Fixed maturities | States, municipalities and political subdivisions | 7-12 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	17	'
Fair Value	37,989	'
Gross Unrealized Loss	2,755	'
Fixed maturities | States, municipalities and political subdivisions | > 12 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	1	4
Fair Value	303	2,908
Gross Unrealized Loss	'	55
Fixed maturities | Agency mortgage-backed securities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	82	12
Fair Value	114,012	64,187
Gross Unrealized Loss	3,925	204
Fixed maturities | Agency mortgage-backed securities | 0-6 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	71	10
Fair Value	90,215	62,516
Gross Unrealized Loss	2,472	174
Fixed maturities | Agency mortgage-backed securities | 7-12 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	9	2
Fair Value	18,667	1,671
Gross Unrealized Loss	1,354	30
Fixed maturities | Agency mortgage-backed securities | > 12 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	2	'
Fair Value	5,130	'
Gross Unrealized Loss	99	'
Fixed maturities | Residential Mortgage Backed Securities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	29	41
Fair Value	4,971	9,077
Gross Unrealized Loss	224	549
Fixed maturities | Residential Mortgage Backed Securities | 0-6 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	12	6
Fair Value	2,016	1,825
Gross Unrealized Loss	43	22
Fixed maturities | Residential Mortgage Backed Securities | > 12 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	17	35
Fair Value	2,955	7,252
Gross Unrealized Loss	181	527
Fixed maturities | Asset-backed securities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	4	2
Fair Value	32,358	2,369
Gross Unrealized Loss	190	49
Fixed maturities | Asset-backed securities | 0-6 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	3	'
Fair Value	32,019	'
Gross Unrealized Loss	189	'
Fixed maturities | Asset-backed securities | 7-12 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	1	'
Fair Value	339	'
Gross Unrealized Loss	1	'
Fixed maturities | Asset-backed securities | > 12 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	'	2
Fair Value	'	2,369
Gross Unrealized Loss	'	49
Fixed maturities | Commercial mortgage-backed securities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	11	12
Fair Value	20,780	3,484
Gross Unrealized Loss	365	18
Fixed maturities | Commercial mortgage-backed securities | 0-6 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	6	7
Fair Value	19,891	2,639
Gross Unrealized Loss	341	7
Fixed maturities | Commercial mortgage-backed securities | > 12 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	5	5
Fair Value	889	845
Gross Unrealized Loss	24	11
Fixed maturities | Corporate bonds	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	39	6
Fair Value	125,988	10,217
Gross Unrealized Loss	2,858	25
Fixed maturities | Corporate bonds | 0-6 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	37	2
Fair Value	123,673	3,528
Gross Unrealized Loss	2,856	6
Fixed maturities | Corporate bonds | 7-12 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	2	'
Fair Value	2,315	'
Gross Unrealized Loss	2	'
Fixed maturities | Corporate bonds | > 12 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	'	4
Fair Value	'	6,689
Gross Unrealized Loss	'	19
Common Stock	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	14	14
Fair Value	35,333	25,288
Gross Unrealized Loss	1,704	626
Common Stock | 0-6 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	13	13
Fair Value	33,429	23,345
Gross Unrealized Loss	1,340	522
Common Stock | 7-12 months	'	'
Gain (Loss) on Investments [Line Items]	'	'
Number of Securities	1	1
Fair Value	1,904	1,943
Gross Unrealized Loss	$364	$104

Summary_of_Activity_Related_to

Summary of Activity Related to Other-Than-Temporary Impairment Losses (Detail) (USD $)	3 Months Ended	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2012
	Investment	Investment	Investment
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]	'	'	'
Number of Securities	1	3	4
Total other-than-temporary impairment losses	$1,821	$1,863	$693
Portion of loss recognized in other comprehensive income	'	'	43
Net other-than-temporary impairment losses recognized in earnings	1,821	1,863	650
Corporate And Other Bonds	'	'	'
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]	'	'	'
Number of Securities	1	1	'
Total other-than-temporary impairment losses	1,821	1,821	'
Net other-than-temporary impairment losses recognized in earnings	1,821	1,821	'
Residential Mortgage Backed Securities	'	'	'
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]	'	'	'
Number of Securities	'	'	1
Total other-than-temporary impairment losses	'	'	54
Portion of loss recognized in other comprehensive income	'	'	43
Net other-than-temporary impairment losses recognized in earnings	'	'	11
Equity Securities	'	'	'
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]	'	'	'
Number of Securities	'	2	3
Total other-than-temporary impairment losses	'	42	639
Net other-than-temporary impairment losses recognized in earnings	'	$42	$639

Summary_of_Cumulative_Amounts_

Summary of Cumulative Amounts Related to Credit Loss Portion of Other-Than-Temporary Impairment Losses on Debt Securities (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]	'	'	'	'
Beginning balance	$3,332	$3,322	$3,332	$3,321
Additions for credit loss impairments recognized in the current period on securities not previously impaired	1,821	'	1,821	'
Additions for credit loss impairments recognized in the current period on securities previously impaired	'	'	'	11
Reductions for credit loss impairments previously recognized on securities sold during the period	'	'	'	'
Ending balance	$5,153	$3,332	$5,153	$3,332

Contractual_Maturity_by_Number

Contractual Maturity by Number of Years Until Maturity for Fixed Maturity Securities with Gross Unrealized Loss (Detail) (Fixed maturities, USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Gross Unrealized Loss Amount	$25,496	$1,261
Percent of Total Gross Unrealized Loss	100.00%	'
Fair Value Amount	731,167	156,071
Percent of Total Fair Value	100.00%	'
Due in one year or less	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Gross Unrealized Loss Amount	1	'
Percent of Total Gross Unrealized Loss	0.00%	'
Fair Value Amount	1,716	'
Percent of Total Fair Value	0.00%	'
Due After One Year Through Five Years	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Gross Unrealized Loss Amount	1,119	'
Percent of Total Gross Unrealized Loss	4.00%	'
Fair Value Amount	144,849	'
Percent of Total Fair Value	20.00%	'
Due After Five Years Through Ten Years	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Gross Unrealized Loss Amount	9,803	'
Percent of Total Gross Unrealized Loss	38.00%	'
Fair Value Amount	250,290	'
Percent of Total Fair Value	34.00%	'
Due After Ten Years	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Gross Unrealized Loss Amount	9,869	'
Percent of Total Gross Unrealized Loss	40.00%	'
Fair Value Amount	162,191	'
Percent of Total Fair Value	22.00%	'
Mortgage- and asset-backed securities	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Gross Unrealized Loss Amount	4,704	'
Percent of Total Gross Unrealized Loss	18.00%	'
Fair Value Amount	$172,121	'
Percent of Total Fair Value	24.00%	'

Net_Investment_Income_Detail

Net Investment Income (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net Investment Income [Line Items]	'	'	'	'
Investment Income	$14,901	$15,790	$44,320	$49,161
Investment expenses	-807	-2,193	-2,323	-8,529
Net investment income	14,094	13,597	41,997	40,632
Fixed maturities	'	'	'	'
Net Investment Income [Line Items]	'	'	'	'
Investment Income	13,399	14,364	40,142	44,779
Equity Securities	'	'	'	'
Net Investment Income [Line Items]	'	'	'	'
Investment Income	1,315	989	3,603	2,930
Short-term investments	'	'	'	'
Net Investment Income [Line Items]	'	'	'	'
Investment Income	$187	$437	$575	$1,452

Change_in_Net_Unrealized_Gains

Change in Net Unrealized Gains and Losses (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Gross unrealized gains (losses)	($52,220)	$46,982
Deferred income tax	-18,296	15,702
Change in net unrealized gains (losses), net	-33,924	31,280
Fixed maturities	'	'
Gross unrealized gains (losses)	-63,771	38,165
Equity Securities	'	'
Gross unrealized gains (losses)	$11,551	$8,817

Realized_Gains_and_Losses_Excl

Realized Gains and Losses Excluding Net Other-Than-Temporary Impairment Losses Recognized in Earnings (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Gain (Loss) on Investments [Line Items]	'	'	'	'
Net realized gains (losses)	($988)	$4,761	$7,171	$10,820
Fixed maturities	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Gains	1,099	4,011	6,035	11,868
Losses	-2,087	-216	-2,470	-1,746
Net realized gains (losses)	-988	3,795	3,565	10,122
Equity Securities	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Gains	'	966	3,733	1,171
Losses	'	'	-127	-473
Net realized gains (losses)	'	$966	$3,606	$698

Fixed_Maturities_and_Equity_Se

Fixed Maturities and Equity Securities by Asset Class that are Measured at Fair Value (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fixed maturities and equity securities, at fair Value	$2,140,621	$2,223,130
Fixed maturities	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fixed maturities and equity securities, at fair Value	1,981,731	2,121,833
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	445,969	649,692
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	445,281	322,947
Fixed maturities | Agency mortgage-backed securities	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fixed maturities and equity securities, at fair Value	300,347	384,445
Fixed maturities | Residential Mortgage Backed Securities	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fixed maturities and equity securities, at fair Value	35,277	38,692
Fixed maturities | Asset-backed securities	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fixed maturities and equity securities, at fair Value	88,714	50,382
Fixed maturities | Commercial mortgage-backed securities	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fixed maturities and equity securities, at fair Value	173,069	204,821
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	597,407	678,340
Fixed maturities | Corporate bonds	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fixed maturities and equity securities, at fair Value	493,074	470,854
Equity Securities | Common Stock	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fixed maturities and equity securities, at fair Value	158,890	101,297
Level 1	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fixed maturities and equity securities, at fair Value	415,390	515,799
Level 1 | Fixed maturities	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fixed maturities and equity securities, at fair Value	256,500	414,502
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	256,500	414,502
Level 1 | Equity Securities | Common Stock	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fixed maturities and equity securities, at fair Value	158,890	101,297
Level 2	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fixed maturities and equity securities, at fair Value	1,720,669	1,707,331
Level 2 | Fixed maturities	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fixed maturities and equity securities, at fair Value	1,720,669	1,707,331
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	189,469	235,190
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	445,281	322,947
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	300,347	384,445
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	35,277	38,692
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	88,714	50,382
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	173,069	204,821
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	597,407	678,340
Level 2 | Fixed maturities | Corporate bonds	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fixed maturities and equity securities, at fair Value	488,512	470,854
Level 3	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fixed maturities and equity securities, at fair Value	4,562	'
Level 3 | Fixed maturities	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fixed maturities and equity securities, at fair Value	4,562	'
Level 3 | Fixed maturities | Corporate bonds	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fixed maturities and equity securities, at fair Value	$4,562	'

Reconciliation_of_Beginning_an

Reconciliation of Beginning and Ending Balances for all Investments Measured at Fair Value Using Level 3 Inputs (Detail) (USD $)	3 Months Ended	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'
Realized Gains (Losses)	'	'
Unrealized Gains (Losses)	-15	-15
Purchases	4,661	4,661
Sales	-84	-84
Settlements	'	'
Transfers into Level 3	'	'
Transfers out of Level 3	'	'
Ending Balance	4,562	4,562
Corporate bonds	'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'
Realized Gains (Losses)	'	'
Unrealized Gains (Losses)	-15	-15
Purchases	4,661	4,661
Sales	-84	-84
Settlements	'	'
Transfers into Level 3	'	'
Transfers out of Level 3	'	'
Ending Balance	$4,562	$4,562

Credit_Facility_Additional_Inf

Credit Facility - Additional Information (Detail) (USD $)	9 Months Ended			1 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Mar. 28, 2011	Sep. 30, 2013	Nov. 22, 2012
			Lloyd's	Amended and Restated Credit Agreement
			Syndicate 1221
Line of Credit Facility [Line Items]	'	'	'	'
Line of credit facility	'	$165	'	$165
Issuance of new letters of credit, expiry date	'	'	'	31-Dec-14
Aggregate face amount of letters of credit outstanding	'	'	143	'
Cash collateral posted	'	'	$1	'
Line of credit facility, covenant terms	'This credit facility contains customary covenants for facilities of this type, including restrictions on indebtedness and liens, limitations on mergers, dividends and the sale of assets, and requirements as to maintaining certain consolidated tangible net worth, statutory surplus and other financial ratios. The credit facility also provides for customary events of default, including failure to pay principal, interest or fees when due, failure to comply with covenants, any representation or warranty made by the Company being false in any material respect, default under certain other indebtedness, certain insolvency or receivership events affecting the Company and its subsidiaries, the occurrence of certain material judgments, or a change in control of the Company.	'	'	'
Line of credit facility, covenant compliance	'The Company was in compliance with all covenants under the credit facility as of September 30, 2013.	'	'	'

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (USD $)	1 Months Ended					1 Months Ended			1 Months Ended
In Millions, unless otherwise specified	Apr. 30, 2009	Apr. 17, 2006	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Oct. 04, 2013	Oct. 04, 2013	Oct. 04, 2013	Oct. 04, 2013
	Senior Notes due May 1, 2016	Senior Notes due May 1, 2016	Senior Notes due May 1, 2016	Senior Notes due May 1, 2016	Senior Notes due May 1, 2016	Subsequent Event	Subsequent Event	Subsequent Event	Subsequent Event
				Semi Annual Payment, First Payment	Semi Annual Payment, Second Payment	5.75% Senior Notes	5.75% Senior Notes	5.75% Senior Notes	Senior Notes due May 1, 2016
							Semi Annual Payment, First Payment	Semi Annual Payment, Second Payment
Subsequent Event [Line Items]	'	'	'	'	'	'	'	'	'
Principal amount of senior notes	'	$125	'	'	'	$265	'	'	'
Interest rate stated on senior notes	'	7.00%	'	'	'	5.75%	'	'	7.00%
Senior notes due date	'	1-May-16	'	'	'	15-Oct-23	'	'	1-May-16
Net proceeds from issuance of senior notes	'	123.5	'	'	'	263	'	'	'
Redemption of senior notes	7	'	'	'	'	'	'	'	115
Incurred charge for payment of call premium	'	'	'	'	'	'	'	'	$17.90
Effective interest rate	'	'	7.17%	'	'	5.84%	'	'	'
Interest payment date on senior notes	'	'	'	'--05-01	'--11-01	'	'--04-15	'--10-15	'
First Interest payment date	'	'	'	'	'	15-Apr-14	'	'	'