Tower Group International (TWGP) 10-Q/A 26 Nov 13 2013 Q1 Quarterly report (amended) Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2013	7-May-13
Document Information [Line Items]	'	'
Document Type	'10-Q/A	'
Amendment Flag	'true	'
AmendmentDescription	'This Quarterly Report on Form 10-Q/A (“Form 10-Q/A”) is being filed as Amendment No. 1 (the “Amendment”) to our Quarterly Report on Form 10-Q for the quarter ended March 31, 2013, which was filed with the Securities and Exchange Commission (the “SEC”) on May 10, 2013 (the “Original Quarterly Report”). This Form 10-Q/A is being filed to revise the consolidated balance sheet as of March 31, 2013, the consolidated statements of operations, comprehensive income, changes in stockholders’ equity and cash flows for the three months ended March 31, 2013 and certain footnote disclosures thereto. Management of Tower Group International, Ltd. (“Tower” or the “Company”) is revising its March 31, 2013 Form 10-Q to correct for certain loss reserve and premium receivables errors that were recorded in 2011 and 2012, as discussed below, and is also correcting for other immaterial adjustments that were initially recorded in the period they were identified. These immaterial adjustments are being recast into the periods in which they originated. On November 14, 2013, Tower issued a Current Report on Form 8-K stating that it had reached a determination to restate Tower’s audited annual consolidated financial statements as of and for the years ended December 31, 2011 and 2012 contained in Amendment No. 1 to Tower’s Annual Report on Form 10-K for the year ended December 31, 2012, which was filed with the SEC on March 13, 2013 (the “2012 Form 10-K/A”), and that such financial statements should no longer be relied upon. In addition, Tower will revise its (i) audited annual consolidated financial statements for the year ended December 31, 2010 contained in the 2012 Form 10-K/A and (ii) unaudited interim consolidated financial statements as of and for the three months ended March 31, 2013 and 2012 contained in its Original Quarterly Report. Following management review of the matter with the Audit Committee of Tower’s Board of Directors (the “Audit Committee”), and upon management’s recommendation, the Audit Committee reached a conclusion on November 7, 2013 that previously issued financial statements of the Company covering one or more periods for which the Company is required to provide financial statements need to be revised or restated and may no longer be relied upon because of the inadvertent mistakes described below. At such meeting, the Audit Committee authorized the Company’s Chief Financial Officer and Chief Accounting Officer to determine, in consultation with the Company’s independent registered public accounting firm, the specific financial statements that should be revised or restated and should no longer be relied upon. Acting upon such authority, on November 12, 2013, these officers reached a conclusion, and advised Tower’s Board of Directors, as to the specific financial statements that need to be so revised or restated and should no longer be relied upon, as described above. The Company had previously determined and announced on October 7, 2013 that its June 30, 2013 loss reserves were strengthened by approximately $365 million. The Company then undertook to review its reserve analyses for prior years. During this evaluation, the Company considered its historical loss reserve analyses and the analyses of its independent actuaries and reviewed and discussed its conclusions with its independent registered public accounting firm. Upon completion of this evaluation, the Company determined that inadvertent mistakes in classification of insurance premiums by line of business used in the loss reserving process resulted in (1) an increase in the loss and loss adjustment expenses of $9.6 million, $21.7 million and $5.7 million, for the years ended December 31, 2012, 2011 and 2010, respectively, and (2) a decrease in the reinsurance recoverables on unpaid losses asset balance by $37.0 million, $27.4 million and $5.7 million as of December 31, 2012, 2011 and 2010, respectively. In addition, subsequent to the announcement on October 7, 2013, the Company identified errors in its historical premiums receivable balances due to inadvertent mistakes in its premiums receivable reconciliation process. This resulted in (1) a decrease of premiums receivable asset balance of $11.0 million, $10.0 million, $5.6 million and $7.2 million as of the years ended December 31, 2012, 2011, 2010 and 2009, respectively, and (2) an increase (decrease) of other operating expenses of $1.0 million, $4.4 million, ($1.6) million and $7.2 million for the years ended December 31, 2012, 2011, 2010 and 2009, respectively. The Company also will correct other immaterial adjustments that were initially recorded in the period they were identified. Management has concluded, as a result of the items discussed above, that material weaknesses exist in internal controls over financial reporting related to the Company’s loss reserving and premiums receivable reconciliation processes and as a result has now concluded the Company’s internal control over financial reporting was not effective as of December 31, 2012 and its disclosure controls procedures were not effective as of December 31, 2012 and March 31, 2013. A material weakness is a deficiency, or combination of deficiencies, in internal control over financial reporting, such that there is a reasonable possibility that a material misstatement of the Company’s annual or interim financial statements will not be prevented or detected on a timely basis. The effects of this revision to our consolidated financial statements are described in Note 2 Revision of Previously Issued Financial Statements to the consolidated financial statements. In addition, we have updated the financial statement disclosures for significant events that have occurred subsequent to the filing of the Original Quarterly Report. See “Note 1 – Nature of Business” and “Note 18 – Subsequent Events” to the consolidated financial statements for further description. The following sections have been amended from the Original Quarterly Report as a result of the restatement and revisions described above: • Part I – Item 1. Financial Statements • Part I – Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations • Part I – Item 4. Controls and Procedures • Part II – Item 1. Legal Proceedings • Part II – Item 6. Exhibits This Form 10-Q/A also includes as exhibits certifications from our Chief Executive Officer and Chief Financial Officer dated as of the date of this filing. Except as described above, no other sections have been amended from the Original Quarterly Report. Accordingly, this Form 10-Q/A should be read in conjunction with the Company’s Original Quarterly Report.	'
Document Period End Date	31-Mar-13	'
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q1	'
Trading Symbol	'TWGP	'
Entity Registrant Name	'Tower Group International, Ltd.	'
Entity Central Index Key	'0001289592	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	57,432,150

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Mar. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Available-for-sale investments, at fair value:	'	'
Fixed-maturity securities	$2,407,771	$2,344,711
Total investments	2,638,242	2,553,505
Cash and cash equivalents	229,946	102,269
Investment income receivable	29,490	25,332
Investment in unconsolidated affiliate	68,411	71,894
Premiums receivable	408,289	412,045
Reinsurance recoverable on paid losses	49,668	17,609
Reinsurance recoverable on unpaid losses	850,188	459,457
Prepaid reinsurance premiums	234,181	63,923
Deferred acquisition costs, net	199,092	181,198
Intangible assets	104,550	106,768
Goodwill	269,589	241,458
Funds held by reinsured companies	829,659	137,545
Other assets	436,439	338,769
Total assets	6,347,744	4,711,772
Liabilities	'	'
Loss and loss adjustment expenses	2,431,250	1,895,679
Unearned premium	1,122,428	921,271
Reinsurance balances payable	39,227	40,569
Funds held under reinsurance agreements	634,080	98,581
Other liabilities	464,325	296,960
Deferred income taxes	19,842	24,763
Debt	450,470	449,731
Total liabilities	5,161,622	3,727,554
Contingencies (Note 17)	'	'
Stockholders' equity	'	'
Common stock ($0.01 par value; 100,000,000 shares authorized, 57,432,150 and 53,048,011 shares issued, and 57,432,150 and 43,513,678 shares outstanding)	574	530
Treasury stock (0 and 9,534,333 shares)	'	-181,435
Paid-in-capital	812,156	780,036
Accumulated other comprehensive income	78,311	82,756
Retained earnings	273,887	268,171
Tower Group International, Ltd. stockholders' equity	1,164,928	950,058
Noncontrolling interests	21,194	34,160
Total stockholders' equity	1,186,122	984,218
Total liabilities and stockholders' equity	6,347,744	4,711,772
Tower	'	'
Available-for-sale investments, at fair value:	'	'
Fixed-maturity securities	2,136,807	2,064,148
Equity securities	139,794	140,695
Short-term investments	28,822	4,750
Other invested assets	58,941	57,786
Liabilities	'	'
Loss and loss adjustment expenses	2,303,324	1,759,888
Reciprocal Exchanges	'	'
Available-for-sale investments, at fair value:	'	'
Fixed-maturity securities	270,964	280,563
Equity securities	2,914	5,563
Cash and cash equivalents	5,604	9,782
Investment income receivable	2,768	2,610
Premiums receivable	43,655	44,285
Reinsurance recoverable on paid losses	5,913	682
Reinsurance recoverable on unpaid losses	27,554	52,389
Prepaid reinsurance premiums	18,424	17,803
Deferred acquisition costs, net	9,933	11,364
Intangible assets	6,725	6,854
Other assets	5,753	1,559
Liabilities	'	'
Loss and loss adjustment expenses	127,926	135,791
Unearned premium	99,962	103,216
Reinsurance balances payable	5,734	6,979
Funds held under reinsurance agreements	0	500
Other liabilities	46,475	21,321
Deferred income taxes	$19,818	$19,719

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
Fixed-maturity securities, amortized cost	$2,268,076	$2,190,186
Cash and cash equivalents	229,946	102,269
Investment income receivable	29,490	25,332
Premiums receivable	408,289	412,045
Reinsurance recoverable on paid losses	49,668	17,609
Reinsurance recoverable on unpaid losses	850,188	459,457
Prepaid reinsurance premiums	234,181	63,923
Deferred acquisition costs, net	199,092	181,198
Intangible assets	104,550	106,768
Other assets	436,439	338,769
Loss and loss adjustment expenses	2,431,250	1,895,679
Unearned premium	1,122,428	921,271
Reinsurance balances payable	39,227	40,569
Funds held under reinsurance agreements	634,080	98,581
Other liabilities	464,325	296,960
Deferred income taxes	19,842	24,763
Common stock, par value	$0.01	$0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	57,432,150	53,048,011
Common stock, shares outstanding	57,432,150	43,513,678
Treasury stock, shares	0	9,534,333
Tower	'	'
Fixed-maturity securities, amortized cost	2,012,296	1,926,236
Equity securities, cost	135,075	144,204
Short-term investments, cost	28,485	4,749
Loss and loss adjustment expenses	2,303,324	1,759,888
Reciprocal Exchanges	'	'
Fixed-maturity securities, amortized cost	255,780	263,950
Equity securities, cost	2,751	5,144
Cash and cash equivalents	5,604	9,782
Investment income receivable	2,768	2,610
Premiums receivable	43,655	44,285
Reinsurance recoverable on paid losses	5,913	682
Reinsurance recoverable on unpaid losses	27,554	52,389
Prepaid reinsurance premiums	18,424	17,803
Deferred acquisition costs, net	9,933	11,364
Intangible assets	6,725	6,854
Other assets	5,753	1,559
Loss and loss adjustment expenses	127,926	135,791
Unearned premium	99,962	103,216
Reinsurance balances payable	5,734	6,979
Funds held under reinsurance agreements	0	500
Other liabilities	46,475	21,321
Deferred income taxes	$19,818	$19,719

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Revenues	'	'
Net premiums earned	$421,886	$420,158
Ceding commission revenue	14,151	5,163
Insurance services revenue	128	497
Policy billing fees	3,150	3,134
Net investment income	30,317	33,943
Net realized investment gains (losses):	'	'
Other-than-temporary impairments	-689	-2,976
Other net realized investment gains	7,540	6,304
Total net realized investment gains	6,851	3,328
Total revenues	476,483	466,223
Expenses	'	'
Loss and loss adjustment expenses	275,732	267,493
Commission expense	89,576	80,385
Other operating expenses	84,393	77,071
Acquisition-related transaction costs	19,056	1,262
Interest expense	7,808	8,611
Total expenses	476,565	434,822
Other income	'	'
Equity income in unconsolidated affiliate	128	'
Income before income taxes	46	31,401
Income tax expense (benefit)	-1,590	9,224
Net income	1,636	22,177
Less: Net income (loss) attributable to Noncontrolling interests	-11,281	3,011
Net income attributable to Tower Group International, Ltd.	$12,917	$19,166
Earnings per share attributable to Tower Group International, Ltd. stockholders:	'	'
Basic	$0.28	$0.43
Diluted	$0.28	$0.43
Weighted average common shares outstanding:	'	'
Basic	45,614	43,326
Diluted	45,688	43,411
Dividends declared and paid per common share	$0.17	$0.17

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Net income	$1,636	$22,177
Other comprehensive income (loss) before tax	'	'
Gross unrealized investment holding gains (losses) arising during periods	-371	24,972
Less: Reclassification adjustment for investment gains included in net income	-6,467	-3,328
Cumulative translation adjustment	-3,611	'
Deferred gain (loss) on cash flow hedge	1,598	-231
Other comprehensive income (loss) before tax	-8,851	21,413
Income tax benefit (expense) related to items of other comprehensive income (loss)	2,721	-6,738
Other comprehensive income (loss), net of income tax	-6,130	14,675
Comprehensive income	-4,494	36,852
Less: Comprehensive income (loss) attributable to Noncontrolling interests	-12,966	6,385
Comprehensive income attributable to Tower Group International, Ltd.	$8,472	$30,467

Consolidated_Statements_of_Cha

Consolidated Statements of Changes in Stockholders' Equity (USD $)	Total	Common Stock	Treasury Stock	Paid-in Capital	Accumulated Other Comprehensive Income (loss)	Retained Earnings	Noncontrolling Interests
In Thousands
Balance at beginning of period at Dec. 31, 2011	$1,037,131	$526	($158,185)	$772,877	$63,053	$331,480	$27,380
Balance at beginning of period (in shares) at Dec. 31, 2011	'	52,626	'	'	'	'	'
Dividends declared	-7,398	'	'	'	'	-7,398	'
Stock based compensation (in shares)	'	364	'	'	'	'	'
Stock based compensation	-114	4	-2,142	2,024	'	'	'
Repurchase of common stock	'	'	'	'	'	'	'
Net income (loss)	22,177	'	'	'	'	19,166	3,011
Transfer of assets to Reciprocal Exchange	'	'	'	-1,778	'	'	1,778
Other comprehensive income (loss)	14,675	'	'	'	11,291	'	3,384
Balance at end of period at Mar. 31, 2012	1,066,471	530	-160,327	773,123	74,344	343,248	35,553
Balance at end of period (in shares) at Mar. 31, 2012	'	52,990	'	'	'	'	'
Balance at beginning of period at Dec. 31, 2012	984,218	530	-181,435	780,036	82,756	268,171	34,160
Balance at beginning of period (in shares) at Dec. 31, 2012	'	53,048	'	'	'	'	'
Dividends declared	-7,201	'	'	'	'	-7,201	'
Stock based compensation (in shares)	'	240	'	'	'	'	'
Stock based compensation	5,711	3	-5,853	11,561	'	'	'
Merger Transaction with Canopius Bermuda (in shares)	'	14,026	'	'	'	'	'
Merger Transaction with Canopius Bermuda	207,347	140	'	207,207	'	'	'
Extinguishment of treasury stock in connection with Merger Transaction (in shares)	'	-9,882	'	'	'	'	'
Extinguishment of treasury stock in connection with Merger Transaction	'	-99	187,288	-187,189	'	'	'
Termination of convertible senior notes hedge and warrants	541	'	'	541	'	'	'
Net income (loss)	1,636	'	'	'	'	12,917	-11,281
Other comprehensive income (loss)	-6,130	'	'	'	-4,445	'	-1,685
Balance at end of period at Mar. 31, 2013	$1,186,122	$574	'	$812,156	$78,311	$273,887	$21,194
Balance at end of period (in shares) at Mar. 31, 2013	'	57,432	'	'	'	'	'

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Cash flows provided by (used in) operating activities:	'	'
Net income	$1,636	$22,177
Adjustments to reconcile net income to net cash provided by (used in) operations:	'	'
Gain on investment in acquired unconsolidated affiliate	-128	'
Net realized investment (gains) losses	-6,851	-3,328
Depreciation and amortization	9,493	9,111
Amortization of bond premium or discount	3,262	2,462
Amortization of restricted stock	12,281	2,025
Deferred income taxes	-5,433	2,674
Changes in operating assets and liabilities:	'	'
Investment income receivable	-4,158	-2,568
Premiums receivable	3,756	-9,206
Reinsurance recoverable	45,937	33,327
Prepaid reinsurance premiums	-17,827	1,298
Deferred acquisition costs, net	-12,076	-2,793
Funds held by reinsured companies	6,705	-19,773
Other assets	34,681	42,288
Loss and loss adjustment expenses	-95,042	-34,674
Unearned premium	31,194	4,226
Reinsurance balances payable	-1,342	-1,440
Funds held under reinsurance agreements	-25,215	-995
Other liabilities	-35,956	-13,946
Net cash flows provided by (used in) operations	-55,083	30,865
Cash flows provided by (used in) investing activities:	'	'
Cash acquired in Merger Transaction	134,741	'
Purchase of fixed assets	-5,866	-10,553
Purchase - fixed-maturity securities	-124,322	-586,772
Purchase - equity securities	-365,055	-399,789
Short-term investments, net	2,746	-3,492
Purchase of other invested assets	-1,155	'
Sale of fixed-maturity securities	123,684	605,206
Maturity of fixed-maturity securities	52,233	34,684
Sale - equity securities	375,180	368,145
Change in restricted cash	1,134	'
Net cash flows provided by (used in) investing activities	193,320	7,429
Cash flows provided by (used in) financing activities:	'	'
Proceeds from convertible senior notes hedge termination	2,380	'
Payment for warrants termination	-1,000	'
Issuance of common stock under stock-based compensation programs	2	3
Excess tax benefits from share-based payment arrangements	1,111	225
Treasury stock acquired-net employee share-based compensation	-5,853	-2,141
Dividends paid	-7,200	-7,398
Net cash flows provided by (used in) financing activities	-10,560	-9,311
Increase (decrease) in cash and cash equivalents	127,677	28,983
Cash and cash equivalents, beginning of period	102,269	114,098
Cash and cash equivalents, end of period	$229,946	$143,081

Nature_of_Business

Nature of Business	3 Months Ended
	Mar. 31, 2013
Nature of Business	'
	Note 1—Nature of Business
	Tower Group International, Ltd. (the “Company” or “Tower”) offers a broad range of commercial, specialty and personal property and casualty insurance products and services through its subsidiaries to businesses and to individuals. On March 13, 2013, the Company and Tower Group, Inc. (“TGI”) completed a merger transaction under which the Company, formerly known as Canopius Holdings Bermuda Limited (“Canopius Bermuda”), was re-named Tower Group International, Ltd. and became the ultimate parent company (“Merger Transaction”). The Company’s common shares are publicly traded on the NASDAQ Global Select Market under the symbol “TWGP”, which was also the symbol of TGI common shares on that exchange prior to the Merger Transaction. See “Note 4 – Merger Transaction” for further discussion of the Merger Transaction and the Company’s succession to TGI as registrant.
	Significant Business Developments and Risks and Uncertainties Resulting From Events Occurring in 2013
	In the preparation of Tower’s June 30, 2013 consolidated financial statements, subsequent to March 31, 2013, the company reported an increase in its loss and loss adjustment expense reserves of approximately $365 million relating to reserve strengthening associated with losses from prior accident years. This adverse loss development arose primarily from accident years 2008-2011 within the workers’ compensation, commercial multi-peril liability (“CMP”), other liability and commercial auto liability lines of business. In the second quarter of 2013, the Company performed a comprehensive update to its internal reserve study in response to continued observance in the second quarter of 2013 of higher than expected reported loss development. In conjunction with its comprehensive internal review, the Company also retained its consulting actuary to perform an independent reserve study covering lines of business comprising over 90% of the Company’s loss reserves. Since 2010, the Company has changed the mix of business by reducing the amount of program and middle market workers’ compensation and liability business that it underwrites.
	The reserve strengthening was viewed by the Company as an event or circumstance that required the Company to perform in the second quarter of 2013, a detailed quantitative analysis of whether its recorded goodwill was impaired. After performing the quantitative analysis, it was determined that $214.0 million of goodwill, which represents all of the goodwill allocated to the Commercial Insurance reporting unit, was impaired. Accordingly, the consolidated statement of operations in the second quarter of 2013, subsequent to March 31, 2013, includes a non-cash charge of $214.0 million associated with the write-down of goodwill.
	As a result of the reserve strengthening, the Company is expecting its U.S. based operations to have a pre-tax loss for 2013, which would result in a three-year cumulative loss position on its U.S. subsidiaries. After considering this negative evidence and uncertainty regarding the Company’s ability to generate sufficient future taxable income in the United States, the Company concluded that it should not recognize any net deferred tax assets (comprised principally of net operating loss carryforwards). The Company, therefore provided a full valuation allowance against its deferred tax asset at June 30, 2013. This valuation allowance was not recorded as of March 31, 2013.
	Reinsurance Agreements
	On October 1, 2013, Tower announced that it entered into agreements with three reinsurers, Arch Reinsurance Ltd. (“Arch”), Hannover Re (Ireland) Plc. (“Hannover”) and Southport Re (Cayman), Ltd. (“Southport Re”). These agreements provided for surplus enhancement and improved certain financial leverage ratios, while increasing the Company’s financial flexibility. The agreements with Arch and Hannover each consist of one reinsurance agreement while the arrangement with Southport Re consists of several reinsurance agreements. Each of these is described below.
	The first agreement was between Tower Insurance Company of New York (“TICNY”), on its behalf and on behalf of each of its pool participants, and Arch. Under this multi-line quota share agreement, TICNY will cede 17.5% on a quota share of certain commercial automobile liability, commercial multi-peril property, commercial multi-peril liability and brokerage other liability (mono line liability) businesses. The agreement covers losses occurring on or after July 1, 2013 for policies in-force as at June 30, 2013 and policies written or renewed from July 1, 2013 to December 31, 2013. The agreement has a special termination clause whereby either party may terminate the agreement upon the occurrence of certain circumstances, including an A.M. Best financial strength rating downgrade to below A-. As noted below, A.M. Best downgraded Tower’s financial strength rating to B++. Neither party has provided notice to terminate the agreement.
	The second agreement was between TICNY, on its behalf and on behalf of each of its pool participants, and Hannover. Under this multi-line quota share agreement, TICNY will cede 14% on a quota share of certain brokerage commercial automobile liability, brokerage commercial multi-peril property, brokerage commercial multi-peril liability, brokerage other liability (mono line liability) and brokerage workers’ compensation businesses. The agreement covers losses occurring on or after July 1, 2013 for policies in-force as at June 30, 2013 and policies written or renewed from July 1, 2013 to December 31, 2013. The agreement has a special termination clause whereby either party may terminate the agreement upon the occurrence of certain circumstances, including an A.M. Best financial strength rating downgrade to below A-. As noted below, A.M. Best downgraded Tower’s financial strength rating to B++. Neither party has provided notice to terminate the agreement.
	The third reinsurance arrangement with Southport Re consisted of two separate reinsurance agreements with TICNY, on its behalf and on behalf of each of its pool participants, and a third reinsurance agreement with Tower Reinsurance, Ltd. (“TRL”). Under the first of the agreements with TICNY, TICNY ceded to Southport Re a 30% quota share of its workers’ compensation and employer’s liability business. The agreement covers losses occurring on or after July 1, 2013 for policies in force at June 30, 2013 and policies written or renewed during the term of the agreement. Under the second of these agreements with TICNY, an aggregate excess of loss agreement, Southport Re assumed a portion of the losses incurred by TICNY on its workers’ compensation and employer’s liability business between January 1, 2011 and June 30, 2013, but paid by TICNY on or after June 1, 2013. Finally, TRL, a wholly-owned Bermuda-domiciled reinsurance subsidiary of Tower, also entered into an aggregate excess of loss agreement with Southport Re, in which Southport Re assumed a portion of the losses incurred by TRL on its assumed workers’ compensation and employer’s liability business between January 1, 2011 and June 30, 2013, but paid by TRL on or after June 1, 2013. The agreement has a special termination clause whereby either party may terminate the agreement upon the occurrence of certain circumstances, including an A.M. Best financial strength rating downgrade to below A-. As noted below, A.M. Best downgraded Tower’s financial strength rating to B++. Neither party has provided notice to terminate the agreement.
	A.M. Best, Fitch and Demotech Downgrade the Company’s Financial Strength and Issuer Credit Ratings
	On October 7, 2013, Fitch Ratings (“Fitch”), downgraded Tower’s Issuer Default Rating from “BBB” to “B” and Tower’s insurance subsidiaries’ Insurer Financial Strength ratings from “A-” to “BB”. The ratings will continue to remain on negative watch until, at the earliest, the completion of Tower’s exploration of strategic alternatives.
	On October 8, 2013, A.M. Best Company (“A.M. Best”), lowered Tower’s issuer credit, as well as its financial strength ratings, from “A-” (Excellent) to “B++” (Good). The ratings remain under review with negative implications pending further discussions between A.M. Best and Tower’s management.
	On October 7, 2013, Demotech, Inc. (“Demotech”) lowered its rating on TICNY and three other U.S. based insurance subsidiaries (Kodiak Insurance Company, Massachusetts Homeland Insurance Company and York Insurance Company of Maine) from A’ (A prime) to A (A exceptional). In addition, Demotech removed its previous A’ (A prime) rating on six other U.S. based insurance subsidiaries (CastlePoint Florida Insurance Company, CastlePoint Insurance Company, CastlePoint National Insurance Company, Hermitage Insurance Company, North East Insurance Company and Preserver Insurance Company). Demotech also affirmed its A ratings on Adirondack Insurance Exchange, New Jersey Skylands Insurance Association, New Jersey Skylands Insurance Company, and Mountain Valley Indemnity Company.
	Management expects these rating actions, in combination with other items that have impacted the Company in the second quarter of 2013, to result in a decrease in the amount of premiums the insurance subsidiaries are able to write. The net written premiums in the Commercial Insurance segment was $343.6 million for the six months ended June 30, 2013. The net written premiums in the Specialty Insurance and Reinsurance segment was $306.6 million for the six months ended June 30, 2013. Business written through certain program underwriting agents requires an A.M. Best rating of A- or greater.
	In addition, one of Tower’s ceding companies requested as a result of contractual provisions that $26.3 million of additional collateral be provided to support the recoverability of their reinsurance receivable from Tower. The $26.3 million was funded in October 2013. Tower’s U.S. based insurance subsidiaries are also required to post collateral for various statutory purposes, and such requests are received from time to time from various regulatory authorities.
	Statutory Capital
	The Company is required to maintain minimum capital and surplus for each of its insurance subsidiaries.
	U.S. based insurance companies are required to maintain capital and surplus above Company Action Level, which is a calculated capital and surplus number using a risk-based formula adopted by the state insurance regulators. The basis for this formula is the National Association of Insurance Commissioners’ (“NAIC’s”) risk-based capital (“RBC”) system and is designed to measure the adequacy of a U.S. regulated insurer’s statutory capital and surplus compared to risks inherent in its business. If an insurance entity falls into Company Action Level, its management is required to submit a comprehensive financial plan that identifies the conditions that contributed to the financial condition. This plan must contain proposals to correct the financial problems and provide projections of the financial condition, both with and without the proposed corrections. The plan must also outline the key assumptions underlying the projections and identify the quality of, and problems associated with, the underlying business. Depending on the level of actual capital and surplus in comparison to the Company Action Level, the state insurance regulators could increase their regulatory oversight, restrict the placement of new business, or place the company under regulatory control. Bermuda based insurance entities minimum capital and surplus requirements are calculated from a solvency formula prescribed by the Bermuda Monetary Authority (the “BMA”).
	As of June 30, 2013, Tower Reinsurance, Ltd. (“TRL”), one the Company’s two Bermuda-based reinsurers had capital and surplus that did not meet the minimum capital and surplus requirements of the BMA.
	The Company has discussed with the BMA its intention to combine a substantial portion of the business and the capital of CastlePoint Reinsurance Company (“CastlePoint Re”), the Company’s other Bermuda based reinsurer, with TRL. Through this combination, management believes that the combined entity’s capital would meet the minimum capital and surplus thresholds determined by the BMA. The Company is currently developing this plan and expects to deliver this plan to its Bermuda regulators in the next several weeks. The Company cannot provide assurance that it will be successful in pursuing this alternative. Should the business combination not be approved, TRL would be operating at a capital level that is below the regulatory minimums as designated by the BMA. As such, TRL be subject to significant additional regulatory oversight or, in the event that such oversight did not satisfy the BMA, placed into liquidation.
	Tower has in place several intercompany reinsurance transactions between its U.S. based insurance subsidiaries and its Bermuda based insurance subsidiaries. The U.S. based insurance subsidiaries have historically reinsured on a quota share basis obligations to CastlePoint Re. The 2013 obligations that CastlePoint Re assumes from the U.S. based insurance subsidiaries are then retroceded to TRL. In addition, CastlePoint Re also entered into a loss portfolio transaction with TRL where its reserves associated with the U.S. insurance subsidiary business for underwriting years prior to 2013 were all transferred to TRL. Therefore, TRL recorded $175 million of reserve strengthening on its balance sheet as of June 30, 2013 and, consequently, the financial result of such development was a reduction in the capital of TRL to $8.3 million at June 30, 2013. In addition TRL is required to collateralize the additional $175 million of assumed reserves in a trust for the benefit of TICNY, the lead pool company of the U.S. insurance companies. TRL had unencumbered liquid assets of $96 million at June 30, 2013, and during October of 2013, TRL commuted two reinsurance treaties which provided an additional $79 million in unencumbered assets.
	The funding of the trust to support TICNY’s reinsurance recoverable has not yet occurred and requires approval by the BMA. The Company can provide no assurance that it will be successful in finalizing could result in the business combination or in funding the trust. If the trust funding is not approved, 1) the statutory capital of TICNY would be at a level that the New York Department of Financial Services placing TICNY under regulatory control; and 2) Tower Group, Inc. could violate the revised debt covenants of the bank credit facility at December 31, 2013, which violation, if not waived, would result in a cross default of our convertible notes. Statutory capital and surplus would be further reduced by whatever amounts are due from CastlePoint Re or from TRL that are not supported by assets held in trust. At June 30, 2013, all other U.S. based insurance subsidiaries maintained capital and surplus above company action level.
	Two insurance subsidiaries that do not constitute “significant subsidiaries” of the Company under Regulation S-X are in discussions with the insurance regulatory authority in their state of domicile with respect to the imposition of restrictions on the operation of their businesses. These discussions may result in such subsidiaries’ agreeing to provide the regulatory authority with increased information with respect to their business, operations and financial condition, as well as limitations on payments and transactions outside the ordinary course of business and material changes in their management and related matters.
	Liquidity
	TGI is the obligor under the bank credit facility agreement dated as of February 15, 2012, as amended, with Bank of America, N.A. and other lenders named therein. ($70 million outstanding as of June 30,2013) and the Convertible Senior Notes (“Notes”) due September 2014 ($150 million par amount outstanding as of June 30,2013). The indebtedness of TGI is guaranteed by Tower Group International, Ltd. (“TGIL”) as well as several of TGIL’s non-insurance subsidiaries.
	TGI amended its credit facility on October 11, 2013, and agreed to several restrictions under the credit facility, including:
		•	To not enter into any new borrowings under the credit facility;
		•	To pledge to the lending banks any proceeds of new capital raises by TGI or TGIL until such time as the credit facility is paid in full;
		•	To pledge to the lending banks proceeds from any sales of assets occurring at TGI; and
		•	To submit to regulatory authorities, as appropriate, a request for approval to pledge the capital stock of the U.S. based and Bermuda based insurance subsidiaries.
	In addition, the following financial covenants are included in the credit facility:
		•	Minimum Consolidated Net Worth is the greater of $553,400,000 or 90 % of Consolidated Net Worth as of June 30, 2013; this covenant increases by 90% of any new capital plus 50% of Net Income above $20,000,000;
		•	Debt to capitalization ratio limit of 46%;
		•	Minimum risk based capital ratio of 175% at December 31, 2013 for Tower Insurance Company of New York and any other insurance subsidiary that exceeds 10% of the consolidated statutory surplus of all insurances subsidiaries;
		•	Bermuda enhanced minimum capital requirement of 150% for CastlePoint Re at December 31, 2013 and 110% for TRL;
		•	Minimum statutory surplus for all insurance companies of the greater of $419,000,000 or 85% of Combined Surplus at June 30, 2013. The Company was in compliance with this covenant as of June 30, 2013; and
		•	Independent accountant’s annual report shall not be subject to any “going concern” or like qualification or exception. This financial covenant will remain in effect for the year ending December 31, 2013. Although the independent accountant’s report on the consolidated financial statements for the years ended December 31, 2010, 2011 and 2012 contains a “going concern” explanatory paragraph, on November 14, 2013, the Company received a waiver from the lenders under the credit facility in respect of such “going concern” paragraph.
	Tower currently is in compliance with all covenants contained in the credit facility.
	The credit facility matures on May 30, 2014, at which point any unpaid balance becomes due.
	The Company is evaluating potential opportunities to raise additional capital in private sales transactions as well as through other strategic alternatives currently being considered by TGIL’s Board of Directors, and intends to liquidate certain investments at TGI to repay the credit facility. Should the Company default on the credit facility and should such default not be waived by the credit banks, it would cause an acceleration of the maturity of the Notes, and such notes would become due concurrently with the unpaid balance on the credit facility.
	The Company’s plan to repay the Notes includes a combination of using proceeds from the sale of assets held at TGI as well as using proceeds generated by future strategic alternatives being evaluated by TGIL’s Board of Directors, and to the extent necessary, issuing debt and/or equity securities to pay down the principal of the Notes. To the extent that such asset sales and debt securities issuances are not executed or are not successful, the Company may seek to sell certain of its operating assets to satisfy this obligation. The Company cannot currently provide assurance that it will be successful in finalizing the liquidation of the assets held at TGI, issuing new debt and/or equity securities or selling certain of its operating assets.
	As of June 30, 2013, there are $235 million of subordinated debentures outstanding. The subordinated debentures do not have financial covenants that would cause an acceleration of their stated maturities. The earliest stated maturity date is on a $10 million debenture, with a stated maturity in May 2033. The Company has the ability to defer interest payments on its subordinated debentures for up to twenty quarters.
	There are currently no commitments or assurances to raise additional capital, execute on any strategic alternatives or to liquidate certain investments at prices sufficient to liquidate the credit facility. In addition, there can be no guarantees that the company will be able to remedy current statutory capital deficiencies in certain insurance subsidiaries or maintain adequate levels of statutory capital in the future. Consequently, there is substantial doubt about the Company’s ability to continue as a going concern. Should the Company no longer continue to support its capital or liquidity needs, or should the Company be unable to successfully execute the above mentioned initiatives, the above items would have a material adverse effect on its business, results of operations and financial position.
	The Company and certain of its senior officers have been named as defendants in several class action lawsuits instituted against them by certain shareholders.

Restatement_and_Revision_of_Pr

Restatement and Revision of Previously Issued Financial Statements	3 Months Ended
	Mar. 31, 2013
Restatement and Revision of Previously Issued Financial Statements	'
	Note 2—Restatement and Revision of Previously Issued Financial Statements
	On November 14, 2013, Tower Group International, Ltd. (“Tower” or the “Company”) issued a Current Report on Form 8-K stating that it had reached a determination to restate Tower’s audited annual consolidated financial statements as of and for the years ended December 31, 2011 and 2012 contained in Amendment No. 1 to Tower’s Annual Report on Form 10-K for the year ended December 31, 2012, which was filed with the SEC on March 13, 2013 (the “2012 Form 10-K/A”), and that such financial statements should no longer be relied upon. In addition, Tower will revise its (i) audited annual consolidated financial statements for the year ended December 31, 2010 contained in the 2012 Form 10-K/A and (ii) unaudited interim consolidated financial statements as of and for the three months ended March 31, 2013 and 2012 contained in its Quarterly Report on Form 10-Q for the Quarter ended March 31, 2013, which was filed with the SEC on May 10, 2013 (the “Original Quarterly Report”). Following management review of the matter with the Audit Committee of Tower’s Board of Directors (the “Audit Committee”), and upon management’s recommendation, the Audit Committee reached a conclusion on November 7, 2013 that previously issued financial statements of the Company covering one or more periods for which the Company is required to provide financial statements need to be revised or restated and may no longer be relied upon because of the inadvertent mistakes described below. At such meeting, the Audit Committee authorized the Company’s Chief Financial Officer and Chief Accounting Officer to determine, in consultation with the Company’s independent registered public accounting firm, the specific financial statements that should be revised or restated and should no longer be relied upon. Acting upon such authority, on November 12, 2013, these officers reached a conclusion, and advised Tower’s Board of Directors, as to the specific financial statements that need to be so revised or restated and should no longer be relied upon, as described above. The Company had previously determined and announced on October 7, 2013 that its June 30, 2013 loss reserves were strengthened by approximately $365 million. The Company then undertook to review its reserve analyses for prior years. During this evaluation, the Company considered its historical loss reserve analyses and the analyses of its independent actuaries and reviewed and discussed its conclusions with its independent registered public accounting firm. Upon completion of this evaluation, the Company determined that inadvertent mistakes in classification of insurance premiums by line of business used in the loss reserving process resulted in (1) an increase in the loss and loss adjustment expenses of $9.6 million, $21.7 million and $5.7 million, for the years ended December 31, 2012, 2011 and 2010, respectively, and (2) a decrease in the reinsurance recoverables on unpaid losses asset balance by $37.0 million, $27.4 million and $5.7 million as of December 31, 2012, 2011 and 2010, respectively.
	In addition, subsequent to the announcement on October 7, 2013, the Company identified errors in its historical premiums receivable balances due to inadvertent mistakes in its premiums receivable reconciliation process. This resulted in (1) a decrease of premiums receivable asset balance of $11.0 million, $10.0 million, $5.6 million and $7.2 million as of the years ended December 31, 2012, 2011, 2010 and 2009, respectively, and (2) an increase (decrease) of other operating expenses of $1.0 million, $4.4 million, ($1.6) million and $7.2 million for the years ended December 31, 2012, 2011, 2010 and 2009, respectively. The Company has also corrected other immaterial adjustments that were initially recorded in the period they were identified.
	The effect of the revisions and restatements on the consolidated balance sheets are presented in the table below:
		As of March 31, 2013									December 31, 2012
		As						Effect			As						Effect
		Previously						of			Previously						of
	($ in thousands, except par value and share amounts)	Filed			Revised			Adjustments			Reported			Restated			Adjustments
	Assets
	Total investments		2,638,543			2,638,242			(301	)		2,554,505			2,553,505			(1,000	)
	Cash and cash equivalents		229,946			229,946			—			100,293			102,269			1,976
	Investment income receivable		29,490			29,490			—			25,332			25,332			—
	Investment in uncolsolidated affiliate		68,411			68,411			—			70,830			71,894			1,064
	Premiums receivable		418,161			408,289			(9,872	)		422,112			412,045			(10,067	)
	Reinsurance recoverable on paid losses		49,668			49,668			—			17,609			17,609			—
	Reinsurance recoverable on unpaid losses		887,188			850,188			(37,000	)		496,192			459,457			(36,735	)
	Prepaid reinsurance premiums		234,181			234,181			—			63,923			63,923			—
	Deferred acquisition costs, net		199,137			199,092			(45	)		180,941			181,198			257
	Intangible assets		104,550			104,550			—			106,768			106,768			—
	Goodwill		269,589			269,589			—			241,458			241,458			—
	Funds held by reinsured companies		829,659			829,659			—			137,545			137,545			—
	Other assets		430,108			436,439			6,331			331,506			338,769			7,263
	Total Assets	$	6,388,631		$	6,347,744		$	(40,887	)		4,749,014		$	4,711,772		$	(37,242	)
	Liabilities
	Loss and loss adjustment expenses		2,429,857			2,431,250			1,393			1,895,073		$	1,895,679		$	606
	Unearned premium		1,123,022			1,122,428			(594	)		920,859			921,271			412
	Reinsurance balances payable		39,227			39,227			—			40,569			40,569			—
	Funds held under reinsurance agreements		634,080			634,080			—			98,581			98,581			—
	Other liabilities		463,303			464,325			1,022			292,239			296,960			4,721
	Deferred income taxes		29,677			19,842			(9,835	)		36,464			24,763			(11,701	)
	Debt		450,470			450,470			—			449,731			449,731			—
	Total liabilities	$	5,169,636			5,161,622			(8,014	)		3,733,516			3,727,554			(5,962	)
	Contingencies		—			—			—			—			—			—
	Stockholders’ equity
	Common stock		574			574			—			530			530			—
	Treasury stock		—			—			—			(181,435	)		(181,435	)		—
	Paid-in-capital		812,156			812,156			—			780,036			780,036			—
	Accumulated other comprehensive income		78,377			78,311			(66	)		83,406			82,756			(650	)
	Retained earnings		306,192			273,887			(32,305	)		298,299			268,171			(30,128	)
	Tower Group International, Ltd. stockholders’ equity		1,197,299			1,164,928			(32,371	)		980,836			950,058			(30,778	)
	Noncontrolling interests		21,696			21,194			(502	)		34,662			34,160			(502	)
	Total stockholders’ equity		1,218,995			1,186,122			(32,873	)		1,015,498			984,218			(31,280	)
	Total liabilities and stockholders’ equity		6,388,631		$	6,347,744		$	(40,887	)		4,749,014		$	4,711,772		$	(37,242	)
	The effect of the revision on the consolidated statements of operations and comprehensive income are presented in the table below:
		Three Months Ended March 31, 2013
		As						Effect
		Previously						of
	(in thousands, except per share amounts)	Filed			Revised			Adjustments
	Revenues
	Net premiums earned	$	420,486		$	421,886		$	1,400
	Ceding commission revenue		14,151			14,151			—
	Insurance services revenue		128			128			—
	Policy billing fees		3,150			3,150			—
	Net investment income		30,317			30,317			—
	Other-than-temporary impairments		(489	)		(689	)		(200	)
	Other net realized investment gains		7,540			7,540			—
	Total net realized gains (losses)		7,051			6,851			(200	)
	Total revenues		475,283			476,483			1,200
	Expenses
	Loss and loss adjustment expenses		274,680			275,732			1,052
	Direct and ceding commission expense		88,398			89,576			1,178
	Other operating expenses		84,393			84,393			—
	Acquisition-related transaction costs		19,056			19,056			—
Interest expense		7,808			7,808			—
Total expenses		474,335			476,565			2,230
Other income (expense)
Earnings in Canopius Group		1,192			128			(1,064	)
Income before taxes		2,140			46			(2,094	)
Income tax expense (benefit)		(1,673	)		(1,590	)		83
Net Income	$	3,813		$	1,636		$	(2,177	)
Less: Net income (loss) attributable to Noncontrolling interests		(11,281	)		(11,281	)		—
Net income attributable to Tower Group International, Ltd.	$	15,094		$	12,917		$	(2,177	)
Earnings per share attributable to Tower Group International, Ltd. stockholders:
Basic	$	0.33		$	0.28		$	(0.05	)
Diluted	$	0.33		$	0.28		$	(0.05	)
Comprehensive Income (loss)	$	(2,901	)	$	(4,494	)	$	(1,593	)
Less: Comprehensive income attributable to Noncontrolling interests		(12,966	)		(12,966	)		—
Comprehensive income (loss) attributable to Tower Group International, Ltd.	$	10,065		$	8,472		$	(1,593	)
The effect of the revision on the consolidated statement of cash flows:
	Three Months Ended March 31, 2013
($ in thousands)	As			Revised			Effect
	Previously						of
	Filed						Adjustments
Cash flows provided by (used in) operating activities:
Net cash flows provided by (used in) operations	$	(53,107	)	$	(55,083	)	$	(1,976	)
Net cash flows provided by (used in) investing activities		193,320			193,320			—
Net cash flows provided by (used in) financing activities		(10,560	)		(10,560	)		—
Increase (decrease) in cash and cash equivalents		129,653			127,677			(1,976	)
Cash and cash equivalents, beginning of period		100,293			102,269			1,976
Cash and cash equivalents, end of period	$	229,946		$	229,946		$	—

Accounting_Policies_and_Basis_

Accounting Policies and Basis of Presentation	3 Months Ended
	Mar. 31, 2013
Accounting Policies and Basis of Presentation	'
	Note 3—Accounting Policies and Basis of Presentation
	Basis of Presentation
	The Merger Transaction was accounted for as a reverse acquisition, under which TGI was identified and treated as the accounting acquirer. As such, the Company’s unaudited consolidated financial statements include the accounts and operations of TGI and its insurance subsidiaries, managing general agencies and management companies as its historical financial statements, with the results of Tower Group International, Ltd., as accounting acquiree, being included from March 13, 2013, the effective date of the Merger Transaction. The unaudited consolidated financial statements also include the accounts of Adirondack Insurance Exchange, a New York reciprocal insurer, and New Jersey Skylands Insurance Association, a New Jersey reciprocal insurer (together, the “Reciprocal Exchanges”). The Company does not own the Reciprocal Exchanges but manages their business operations through its wholly-owned management companies.
	The accompanying unaudited consolidated financial statements included in this report have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial information and with the instructions to Securities and Exchange Commission (“SEC”) Form 10-Q/A and Article 10 of SEC Regulation S-X. The principles for condensed interim financial information do not require the inclusion of all the information and footnotes required by GAAP for complete financial statements. Therefore, these financial statements should be read in conjunction with TGI’s consolidated financial statements as of and for the year ended December 31, 2012 and notes thereto included in TGI’s Amendment No. 2 to the Annual Report on Form 10-K for the year ended December 31, 2012. The accompanying consolidated financial statements have not been audited by an independent registered public accounting firm in accordance with standards of the Public Company Accounting Oversight Board (United States) but, in the opinion of management, such financial statements include all adjustments, consisting only of normal recurring adjustments, necessary for a fair statement of the Company’s financial position, results of operations and cash flows. All intercompany transactions have been eliminated in consolidation.
	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
	Moreover, the results of operations for the three months ended March 31, 2013 may not be indicative of the results that may be expected for the year ending December 31, 2013.
	Intercompany transactions
	In the first quarter 2012, the Company transferred a licensed insurance subsidiary shell to the Reciprocal Exchanges and received cash for its statutory book value. At the date of the transfer, the Company’s GAAP carrying basis in this subsidiary exceeded the statutory book value and the transfer resulted in a loss to the Company of $1.8 million. Since this was a non-recurring transaction between entities under common control, assets were transferred at historical book value. The difference in the consideration paid and the book value of the assets transferred was treated as an adjustment to equity. This transaction had no effect on consolidated stockholders’ equity.
	Reclassifications and Adjustments
	Since the Company accounted for the Merger Transaction as a reverse acquisition and recapitalization, it has retroactively restated Common Stock, Treasury Stock and Paid-in-Capital accounts and earnings per share for periods prior to the Merger Transaction to reflect the historical capitalization of TGI, adjusted for the 1.1330 conversion ratio as discussed in “Note 4 – Merger Transaction”. Certain other reclassifications have also been made to prior years’ financial information to conform to the current year presentation. Refer to Item 2. Management’s Discussion and Analysis, the Consolidated Results of Operations discussion for out-of-period adjustments recorded in the three months ended March 31, 2013.
	The table below reflects the previously reported and restated stockholders’ equity accounts resulting from the Merger Transaction:
		Merger			Revised
	($ in thousands, except per share amounts)	Transaction			Amount
	As of December 31, 2012
	Common stock	$	469		$	530
	Treasury stock		(181,435	)		(181,435	)
	Paid-in-capital		780,097			780,036
	For the three-months ended March 31, 2012
	Earnings (Loss) per Share:
	Basic	$	0.49		$	0.43
	Diluted		0.49			0.43
	Weighted average common shares outstanding
	Basic		39,233			43,326
	Diluted		39,307			43,411
	See “Note 15 – Earnings (loss) per Share” for the computation of the earnings per share.
	Accounting Pronouncements
	Accounting guidance adopted in 2012 and 2013
	In July 2012, the Financial Accounting Standards Board (“FASB”) issued amended guidance on testing indefinite-lived intangible assets for impairment. This guidance is intended to reduce the cost and complexity of the annual impairment test by allowing an entity to utilize more qualitative factors and is effective for annual and interim tests performed for fiscal years beginning after September 15, 2012. The Company will consider this guidance in connection with the annual impairment testing of its indefinite-lived intangible assets, which is performed annually in the fourth quarter based on data as of September 30. This guidance does not affect existing guidance on recognition or measurement of impairment losses on indefinite-lived intangible assets, and as such it will not affect the Company’s financial position, results of operations or cash flows.
	In February 2013, the FASB issued amended guidance on the presentation of amounts reclassified out of accumulated other comprehensive income in one place, either on the face of the income statement or in the footnotes to the financial statements. The Company adopted this guidance effective January 1, 2013 on a prospective basis as prescribed by the amended guidance. As all of the information that this guidance requires to be disclosed is already presented elsewhere in the Company’s financial statements under existing GAAP, and it does not affect the classification, recognition or measurement of items within other comprehensive income, the adoption will not affect the Company’s financial position, results of operations or cash flows.
	Accounting guidance not yet effective
	In July 2013, the FASB issued new guidance that permits the use of a new benchmark for hedges. This guidance is effective prospectively for new or re-designated hedges as of July 17, 2013. The Company will consider this guidance if and when it enters into any new hedging relationships.

Merger_Transaction

Merger Transaction	3 Months Ended
	Mar. 31, 2013
Merger Transaction	'
	Note 4 – Merger Transaction
	On August 20, 2012, TGI closed on its previously announced $74.9 million acquisition of a 10.7% stake in Canopius Group Limited (“Canopius Group”), a privately owned Lloyd’s insurance holding company domiciled in Guernsey, Channel Islands. In connection with this acquisition, TGI also entered into an agreement dated April 25, 2012 (the “Master Transaction Agreement”) under which Canopius Group committed to assist TGI with the establishment of a presence at Lloyd’s of London through a special purpose syndicate (“SPS Transaction Right and Acquisition Right”) (subject to required approvals) and granted TGI an option (the “Merger Option”) to combine with Canopius Bermuda. On July 30, 2012, TGI announced that it had exercised the Merger Option and executed an Agreement and Plan of Merger (the “Original Merger Agreement”) with Canopius Bermuda pursuant to which a wholly-owned subsidiary of Canopius Bermuda would acquire all of TGI’s common stock. TGI paid Canopius Group a fee of $1,000,000 to exercise the Merger Option. On November 8, 2012, the Original Merger Agreement was amended by Amendment No. 1 to the Agreement and Plan of Merger to reflect changes to the merger consideration to be received by TGI stockholders (the Original Merger Agreement as so amended, the “Merger Agreement”).
	Prior to the Merger Transaction date, Canopius Group priced on March 6, 2013, a private sale of 100% of the shares of Canopius Bermuda to third party investors for net consideration for $205,862,755. This investment resulted in 14,025,737 shares being issued in the private placement immediately preceding the merger.
	On March 13, 2013, Canopius Bermuda and TGI consummated the Merger Transaction contemplated by the Merger Agreement. Canopius Bermuda was re-named Tower Group International, Ltd. and became the ultimate parent company of TGI, with TGI becoming its indirect wholly-owned subsidiary. Pursuant to the terms of the Merger Agreement, among other things, (i) 100% of the issued and outstanding shares of TGI common stock was cancelled and automatically converted into the right to receive 1.1330 common shares of the Company, par value $0.01 per share (the “ Common Shares”), (ii) each outstanding option to acquire TGI common stock, whether vested or unvested and whether granted under TGI’s 2008 Long-Term Equity Compensation Plan or otherwise, automatically vested, free of any forfeiture conditions, and constituted a fully vested option to acquire that number of Common Shares (rounded down to the nearest whole number) equal to the number of shares of TGI common stock subject to such option multiplied by 1.1330, on the same terms and conditions (other than vesting and performance conditions) as were applicable to such TGI stock option immediately prior to the Merger Transaction, with the exercise price of such option adjusted to be the original exercise price divided by 1.1330, and (iii) substantially all issued and outstanding shares of TGI restricted stock, whether granted under TGI’s 2008 Long-Term Equity Compensation Plan or otherwise, automatically vested, free of any forfeiture conditions, and was converted into the right to receive, as soon as reasonably practicable after the effective time, 1.1330 Common Shares.
	Immediately after giving effect to the issuance of Common Shares to the former TGI stockholders in the Merger Transaction, approximately 57,432,150 Common Shares were outstanding, of which 76% was held by the former TGI stockholders. The remaining 24% of Common Shares outstanding immediately after giving effect to the Merger Transaction was held by third party investors. As the Company is the successor issuer to TGI, succeeding to the attributes of TGI as registrant, including TGI’s SEC file number, its Common Shares trade on the same exchange, the NASDAQ Global Select Market, and under the same trading symbol, “TWGP,” that the shares of TGI common stock traded on and under prior to the Merger Transaction.
	The Merger Transaction is expected to advance the Company’s strategy and create a more efficient global, diversified specialty insurance company consisting of commercial, specialty and personal lines, reinsurance and international specialty products. In addition, the establishment of a Bermuda domicile will provide the Company with an international platform through which it has access to the U.S., Bermuda and the Lloyd’s of London (“Lloyds”) markets.
	Accounting for the Merger Transaction
	The Company has accounted for the Merger Transaction as a reverse acquisition in which TGI, the legal acquiree, was identified and treated as the accounting acquirer and Tower Group International, Ltd., the legal acquirer, was identified and treated as the accounting acquiree. The identification of the accounting acquirer and acquiree in the Merger Transaction was primarily based on the fact that immediately following the close of the Merger Transaction there was a change in control of the Company with TGI designees to the Company’s Board of Directors comprising all of its directors and TGI’s former senior management comprising the Company’s entire senior management team. In accordance with accounting guidance for reverse acquisitions, the unaudited consolidated financial statements of the Company following the Merger Transaction have been issued under the name of the Company, as the legal parent, but reflect a continuation of the financial statements of TGI, as the accounting acquirer, with one exception, which was the retroactive adjustment of TGI’s historical legal capital to reflect the transaction as a recapitalization of TGI’s historical capital accounts. On the effective date of the Merger Transaction, the assets and liabilities of Tower Group International, Ltd. were accounted for under the acquisition method, under which they have been reflected at their respective acquisition date fair values.
	Prior to the Merger Transaction, Canopius Bermuda restructured its insurance operations as contemplated in the Master Transaction Agreement. This restructuring occurred primarily through the execution of retrocession agreements with an indirectly wholly-owned subsidiary of Canopius Group to retrocede a percentage of Lloyd’s of London Syndicate 4444 (“Syndicate 4444”) business for the Year of Account (“YOA”) 2012, YOA 2011 and prior years, which Canopius Bermuda assumed from Canopius Group. Syndicate 4444 is an insurance syndicate managed by Canopius Group. The Company will account for these retrocession agreements in accordance with prospective accounting treatment, and will report the assumed and ceded assets and liabilities on a gross basis on the consolidated balance sheet.
	In addition, pursuant to the terms of the Master Transaction Agreement, prior to the Merger Transaction, TGI entered into a commutation agreement whereby the TGI commuted Syndicate 4444 YOA 2012 and YOA 2011 business TGI previously reinsured from Canopius Group. There was no gain or loss recognized on this commutation.
	The following provides details of the purchase consideration, the fair values of the respective assets acquired and liabilities assumed and the resulting amount of goodwill recorded in connection with the Merger Transaction.
	The purchase consideration was determined based on the total consideration received by Canopius Group for its sale of 100% of its equity ownership of Canopius Bermuda, and the proceeds received for the issuance and exercise of the Merger Option from TGI.
	(in thousands)
	Consideration received by Canopius Group from the third party sale		205,863
	Fair value of Merger Option received in connection with TGI’s investment in Canopius Group		484
	Exercise price of Merger Right received from TGI upon exercise		1,000
	Total preliminary purchase consideration	$	207,347
	($ in thousands)
	Assets
	Cash and cash equivalents	$	134,741
	Investments		26,485
	Reinsurance recoverables		468,727
	Prepaid reinsurance		152,431
	Funds held by reinsured companies		698,819
	Other assets		75,219
	Liabilities
	Loss and loss adjustment expenses		630,613
	Unearned premiums		169,963
	Funds held under reinsurance agreements		560,714
	Other liabilities		15,916
	Net assets acquired	$	179,216
	Purchase Consideration		207,347
	Goodwill	$	28,131
	As the Merger Transaction was completed in close proximity to the end of the first quarter of 2013, values of certain assets and liabilities in the above table are preliminary, and as such they may be subject to adjustment as additional information is obtained. Once completed, any adjustments resulting from these valuations may impact the amounts recorded for individual assets acquired and liabilities assumed, as well as the residual goodwill.
	Direct costs of the acquisition were expensed as incurred. During the three months ended March 31, 2013, the Company recognized approximately $19.1 million of such costs, all of which have been classified within “acquisition-related transaction costs” on the consolidated statement of operations. Such costs included $11.4 million in compensation expense (of which accelerated vesting of restricted stock was $10.3 million) and $7.7 million in legal and accounting fees.
	The resulting goodwill recognized in connection with the Merger Transaction is mainly derived from the synergies and economies of scale expected to result from the combined operations of the Company, as well as intangible assets that did not qualify for separate recognition. The goodwill presented in the table above were allocated to the Commercial Insurance reporting unit. As discussed in “Note 1—Nature of Business,” this goodwill amount was fully impaired in the second quarter of 2013 as a result of the significant business developments.
	The fair value of loss and loss adjustment expenses includes $19.1 million of reserves for risk premiums (“risk premiums”). The risk premium was determined using a cash flow model. This model used an estimate of net nominal future cash flows related to liabilities for losses and loss adjustment expenses that a market participant would expect as of the date of the transaction. These future cash flows were adjusted for the time value of money at a risk free rate and a risk margin to compensate an acquirer for bearing the risk associated with the liabilities.
	Since the effective date of the Merger Transaction on March 13, 2013 through March 31, 2013, the operations of the acquired business accounted for approximately $6.6 million and $3.0 million of the Company’s consolidated revenues and net income, respectively.
	The following unaudited pro forma financial information presents the consolidated revenues and net income of the Company for the three months ended March 31, 2013 and 2012, as if the Merger Transaction had been completed as of January 1, 2012.
		Three Months Ended
		March 31,
	($ in thousands)	2013		2012
		(revised)
	Revenues	$	479,627	$	469,367
	Net Income		20,628		26,961

Variable_Interest_Entities_VIE

Variable Interest Entities ("VIEs")	3 Months Ended
	Mar. 31, 2013
Variable Interest Entities ("VIEs")	'
	Note 5–Variable Interest Entities (“VIEs”)
	Through its management companies, Tower is the attorney-in-fact for the Reciprocal Exchanges and has the ability to direct their activities. The Reciprocal Exchanges are policyholder-owned insurance carriers organized as unincorporated associations. Each policyholder insured by the Reciprocal Exchanges shares risk with the other policyholders.
	In the event of dissolution, policyholders would share any residual unassigned surplus in the same proportion as the amount of insurance purchased but are not subject to assessment for any deficit in unassigned surplus of the Reciprocal Exchanges. Tower receives management fee income for the services provided to the Reciprocal Exchanges. The assets of the Reciprocal Exchanges can be used only to settle the obligations of the Reciprocal Exchanges and general creditors to their liabilities have no recourse to Tower as the primary beneficiary.
	In addition, Tower holds the surplus notes issued by the Reciprocal Exchanges when they were originally capitalized. The obligation to repay principal and interest on the surplus notes is subordinated to the Reciprocal Exchanges’ other liabilities including obligations to policyholders and claimants for benefits under insurance policies. Principal and interest on the surplus notes are payable only with regulatory approval. The Company has no ownership interest in the Reciprocal Exchanges.
	The Company determined that each of the Reciprocal Exchanges qualifies as a VIE and that the Company is the primary beneficiary as it has both the power to direct the activities of the Reciprocal Exchanges that most significantly impact their economic performance and the risk of economic loss through its ownership of the surplus notes. Accordingly, the Company consolidates these Reciprocal Exchanges and eliminates all intercompany balances and transactions with Tower.
	For the three months ended March 31, 2013, the Reciprocal Exchanges recognized total revenues, total expenses and net income (loss) of $47.3 million, $58.5 million and $(11.3) million, respectively. For the three months ended March 31, 2012, the Reciprocal Exchanges recognized total revenues, total expenses and net income of $50.2 million, $47.2 million and $3.0 million, respectively.

Investments

Investments	3 Months Ended
	Mar. 31, 2013
Investments	'
	Note 6—Investments
	The cost or amortized cost and fair value of the Company’s investments in fixed maturity and equity securities, gross unrealized gains and losses, and other-than-temporary impairment losses (“OTTI”) as of March 31, 2013 and December 31, 2012 are summarized as follows:
	($ in thousands)		Cost or			Gross			Gross			Fair			Unrealized
			Amortized			Unrealized			Unrealized			Value			OTTI
			Cost			Gains			Losses						Losses (1)
	March 31, 2013, as revised
	U.S. Treasury securities		$	315,281		$	1,486		$	(35	)	$	316,732		$	—
	U.S. Agency securities			105,081			4,056			(132	)		109,005			—
	Municipal bonds			642,188			47,034			(291	)		688,931			—
	Corporate and other bonds
	Finance			222,601			20,881			(728	)		242,754			—
	Industrial			390,344			23,408			(807	)		412,945			—
	Utilities			60,134			2,798			(469	)		62,463			—
	Commercial mortgage-backed securities			207,944			28,337			(360	)		235,921			(121	)
	Residential mortgage-backed securities
	Agency backed securities			253,395			9,478			(674	)		262,199			—
	Non-agency backed securities			37,257			4,394			(27	)		41,624			—
	Asset-backed securities			33,851			1,346			—			35,197			—
	Total fixed-maturity securities			2,268,076			143,218			(3,523	)		2,407,771			(121	)
	Preferred stocks, principally financial sector			28,879			632			(334	)		29,177			—
	Common stocks, principally financial and industrial sectors			108,947			5,985			(1,401	)		113,531			—
	Short-term investments			28,485			350			(13	)		28,822			—
	Total, March 31, 2013, as revised		$	2,434,387		$	150,185		$	(5,271	)	$	2,579,301		$	(121	)
	Tower		$	2,175,856		$	133,986		$	(4,419	)	$	2,305,423		$	(121	)
	Reciprocal Exchanges			258,531			16,199			(852	)		273,878			—
	Total, March 31, 2013, as revised		$	2,434,387		$	150,185		$	(5,271	)	$	2,579,301		$	(121	)
	December 31, 2012, as restated
	U.S. Treasury securities		$	183,462		$	1,500		$	(13	)	$	184,949		$	—
	U.S. Agency securities			98,502			4,351			(76	)		102,777			—
	Municipal bonds			633,373			52,914			(244	)		686,043			—
	Corporate and other bonds
	Finance			233,849			21,293			(1,095	)		254,047			—
	Industrial			412,465			26,556			(868	)		438,153			—
	Utilities			51,698			2,958			(191	)		54,465			—
	Commercial mortgage-backed securities			211,819			30,375			(141	)		242,053			—
	Residential mortgage-backed securities
	Agency backed securities			283,652			12,326			(262	)		295,716			—
	Non-agency backed securities			38,615			3,575			(34	)		42,156			(6	)
	Asset-backed securities			42,751			1,615			(14	)		44,352			—
	Total fixed-maturity securities			2,190,186			157,463			(2,938	)		2,344,711			(6	)
	Preferred stocks, principally financial sector			31,272			730			(481	)		31,521			—
	Common stocks, principally industrial and financial sectors			118,076			953			(4,292	)		114,737			—
	Short-term investments			4,749			1			—			4,750			—
	Total, December 31, 2012, as restated		$	2,344,283		$	159,147		$	(7,711	)	$	2,495,719		$	(6	)
	Tower		$	2,075,189		$	141,614		$	(7,210	)	$	2,209,593		$	(6	)
	Reciprocal Exchanges			269,094			17,533			(501	)		286,126			—
	Total, December 31, 2012, as restated		$	2,344,283		$	159,147		$	(7,711	)	$	2,495,719		$	(6	)
	-1	Represents the gross unrealized loss on other-than-temporarily impaired securities recognized in accumulated other comprehensive income (loss).
	In accordance with Lloyd’s operating guidelines, the Company deposits funds at Lloyd’s to support underwriting operations. These funds are available only to fund claims obligations. These restricted assets consisted of approximately $33.9 million of cash and cash equivalents as of March 31, 2013. In addition, the Company had $481.7 million and $481.5 million of cash and cash equivalents and investments as of March 31, 2013 and December 31, 2012, respectively, held by counterparties as collateral or in trusts to support letters of credit issued on the Company’s behalf, reinsurance liabilities on certain assumed reinsurance treaties, collateral posted for certain leases and other purposes.
	The Company also deposits funds with various state and governmental authorities in the U.S. For a discussion of the Company’s deposits with state and governmental authorities, see “Note 6 – Investments” of the Notes to Consolidated Financial Statements in TGI’s Amendment No. 2 to its Annual Report on Form 10-K for the year ended December 31, 2012.
	Major categories of net investment income are summarized as follows:
			Three Months Ended
			March 31,
	($ in thousands)		2013			2012
	Income
	Fixed-maturity securities		$	20,973		$	25,412
	Equity securities			6,484			7,636
	Cash and cash equivalents			51			290
	Other invested assets			4,256			1,925
	Other			327			57
	Total			32,091			35,320
	Expenses
	Investment expenses			(1,774	)		(1,377	)
Net investment income		$	30,317		$	33,943
Tower			29,980			32,257
Reciprocal Exchanges			2,380			3,349
Elimination of interest on Reciprocal Exchange surplus notes			(2,043	)		(1,663	)
Net investment income		$	30,317		$	33,943
Proceeds from the sale of fixed-maturity securities were $191.7 million and $606.2 million for the three months ended March 31, 2013 and 2012, respectively. Proceeds from the sale of equity securities were $375.2 million and $368.1 million for the three months ended March 31, 2013 and 2012, respectively.
Gross realized gains, losses and impairment write-downs on investments are summarized as follows:
		Three Months Ended
		March 31,
($ in thousands)		2013			2012
		(revised)
Fixed-maturity securities
Gross realized gains		$	7,364		$	13,991
Gross realized losses			(190	)		(2,858	)
			7,174			11,133
Equity securities
Gross realized gains			4,236			1,546
Gross realized losses			(4,813	)		(6,375	)
			(577	)		(4,829	)
Other
Gross realized gains			1,755			—
Gross realized losses			(812	)		—
			943			—
Net realized gains (losses) on investments			7,540			6,304
Other-than-temporary impairment losses:
Fixed-maturity securities			(164	)		(117	)
Equity securities			(525	)		(2,859	)
Total other-than-temporary impairment losses recognized in earnings			(689	)		(2,976	)
Total net realized investment gains (losses)		$	6,851		$	3,328
Tower		$	6,233		$	1,138
Reciprocal Exchanges			618			2,190
Total net realized investment gains (losses)		$	6,851		$	3,328
Management may dispose of a particular security due to changes in facts and circumstances related to the invested asset that have arisen since the last analysis supporting management’s determination whether or not it intended to sell the security, and if not, whether it is more likely than not that the Company would be required to sell the security before recovery of its amortized cost basis.
Impairment Review
Management regularly reviews the Company’s fixed-maturity and equity security portfolios in accordance with its impairment policy to evaluate the necessity of recording impairment losses for OTTI. The determination of OTTI is a subjective process and different judgments and assumptions could affect the timing of loss realization.
Management, in conjunction with its outside portfolio managers, analyzes its non-agency residential mortgage-backed securities (“RMBS”) using default loss models based on the performance of the underlying loans. Performance metrics include delinquencies, defaults, foreclosures, anticipated cash flow prepayments and cumulative losses incurred. The expected losses for a mortgage pool are compared to the break-even loss, which represents the point at which the Company’s tranche begins to experience losses.
The commercial mortgage-backed securities (“CMBS”) holdings are evaluated using analytical techniques and various metrics including the level of subordination, debt-service-coverage ratios, loan-to-value ratios, delinquencies, defaults and foreclosures.
For the non-structured fixed-maturity securities (U.S. Treasury and Agency securities, municipal bonds, and corporate debt), unrealized losses are reviewed to determine whether full recovery of principal and interest will be received. The estimate of expected cash flows is determined by projecting a recovery value and a recovery time frame and assessing whether further principal and interest will be received. The determination of recovery value incorporates an issuer valuation assumption utilizing one or a combination of valuation methods as deemed appropriate by management. The present value of the cash flows is determined by applying the effective yield of the security at the date of acquisition (or the most recent implied rate used to accrete the security if the implied rate has changed as a result of a previous impairment) and an estimated recovery time frame. For securities for which the issuer is financially troubled but not in bankruptcy, that time frame is generally longer. Included in the present value calculation are expected principal and interest payments; however, for securities for which the issuer is classified as bankrupt or in default, the present value calculation assumes no interest payments and a single recovery amount. In situations for which a present value of cash flows cannot be estimated, a write-down to fair value is recorded.
In estimating the recovery value, significant judgment is involved in the development of assumptions relating to a number of factors related to the issuer including, but not limited to, revenue, margin and earnings projections, the likely market or liquidation values of assets, potential additional debt to be incurred pre- or post- bankruptcy/restructuring, the ability to shift existing or new debt to different priority layers, the amount of restructuring/bankruptcy expenses, the size and priority of unfunded pension obligations, litigation or other contingent claims, the treatment of intercompany claims and the likely outcome with respect to inter-creditor conflicts.
The evaluation of equity securities includes management’s intent and ability to hold the security to recovery. Management will record OTTI in those situations where it does not intend to hold the security to recovery or if the security is not expected to recover in value in the near term.
The following table shows the fixed-maturity and equity securities OTTI amounts for the three months ended March 31, 2013 and 2012:
		Three Months Ended
		March 31,
($ in thousands)		2013			2012
		(revised)
Corporate and other bonds		$	—		$	(89	)
Commercial mortgage-backed securities			(24	)		—
Residential mortgage-backed securities			(140	)		(28	)
Equities			(525	)		(2,859	)
Other-than-temporary-impairments			(689	)		(2,976	)
Portion of loss recognized in accumulated other comprehensive income (loss)			—			—
Impairment losses recognized in earnings		$	(689	)	$	(2,976	)
Tower		$	(689	)	$	(2,976	)
Reciprocal Exchanges			—			—
Impairment losses recognized in earnings		$	(689	)	$	(2,976	)
The following table provides a rollforward of the cumulative amounts of credit OTTI for securities still held showing the amounts that have been included in earnings on a pretax basis for the three months ended March 31, 2013 and 2012:
		Three Months Ended
		March 31,
($ in thousands)		2013			2012
		(revised)
Balance, January 1,		$	4,492		$	12,666
Additional credit losses recognized during the period, related to securities for which:
No OTTI has been previously recognized			164			89
OTTI has been previously recognized			—			28
Reductions due to:
Securities sold during the period (realized)			(140	)		(6,699	)
Balance, March 31,		$	4,516		$	6,084
Unrealized Losses
There are 225 securities at March 31, 2013, including fixed maturities and equity securities, which account for the gross unrealized loss, none of which is deemed by management to be OTTI. Temporary losses on corporate and other bonds result from purchases made in a lower yield spread environment. In addition, there have been some ratings downgrades on certain of these securities. After analyzing the credit quality, balance sheet strength and company outlook, management believes these securities will recover in value. The structured securities that had significant unrealized losses resulted primarily from declines in both residential and commercial real estate prices. To the extent projected cash flows on structured securities change adversely, they would be considered OTTI, and an impairment loss would be recognized in the current period. Management considered all relevant factors, including expected recoverability of cash flows, in assessing whether a loss was other-than-temporary. The Company does not intend to sell these fixed maturity securities, and it is not more likely than not that these securities will be sold before recovering their cost basis.
For all fixed-maturity securities in an unrealized loss position at March 31, 2013, the Company has received all contractual interest payments (and principal if applicable). Based on the continuing receipt of cash flow and the foregoing analyses, management expects continued timely payments of principal and interest and considers the losses to be temporary.
The unrealized loss position associated with the fixed-maturity portfolio was $3.5 million as of March 31, 2013, consisting primarily of corporate bonds and mortgage-backed securities of $3.1 million. The total fixed-maturity portfolio of gross unrealized losses included 202 securities which were, in aggregate, approximately 1.0% below amortized cost. Of the 202 fixed maturity investments identified, 20 have been in an unrealized loss position for more than 12 months. The total unrealized loss on these investments at March 31, 2013 was $0.03 million. Management does not consider these investments to be other-than-temporarily impaired.
For common stocks, there were 16 securities in a loss position at March 31, 2013 totaling $1.5 million. Management evaluated the financial condition of the common stock issuers, the severity and duration of the impairment, and the Company’s ability and intent to hold to recovery. The evaluation consisted of a detailed review, including but not limited to some or all of the following factors for each security: the current S&P rating, analysts’ reports, past earnings trends and analysts’ earnings expectations for the next 12 months, liquidity, near-term financing risk, and whether the company was currently paying dividends on its equity securities. Management does not consider these investments to be other-than-temporarily impaired.
The following table presents information regarding invested assets that were in an unrealized loss position at March 31, 2013 and December 31, 2012 by amount of time in a continuous unrealized loss position:
		Less than 12 Months						12 Months or Longer						Total
($ in thousands)		Fair			Unrealized			Fair			Unrealized			Aggregate			Unrealized
		Value			Losses			Value			Losses			Fair Value			Losses
March 31, 2013, as revised
U.S. Treasury securities		$	190,145		$	(35	)	$	—		$	—		$	190,145		$	(35	)
U.S. Agency securities			22,282			(132	)		—			—			22,282			(132	)
Municipal bonds			24,848			(282	)		252			(9	)		25,100			(291	)
Corporate and other bonds
Finance			22,057			(728	)		—			—			22,057			(728	)
Industrial			49,396			(805	)		348			(2	)		49,744			(807	)
Utilities			25,245			(469	)		7			—			25,252			(469	)
Commercial mortgage-backed securities			27,602			(360	)		—			—			27,602			(360	)
Residential mortgage-backed securities
Agency backed			63,720			(674	)		23			—			63,743			(674	)
Non-agency backed			—			—			547			(27	)		547			(27	)
Asset-backed securities			—			—			—			—			—			—
Total fixed-maturity securities			425,295			(3,485	)		1,177			(38	)		426,472			(3,523	)
Preferred stocks			5,169			(31	)		6,651			(303	)		11,820			(334	)
Common stocks			41,600			(1,401	)		—			—			41,600			(1,401	)
Short-term investments			26,822			(13	)		—			—			26,822			(13	)
Total, March 31, 2013, as revised		$	498,886		$	(4,930	)	$	7,828		$	(341	)	$	506,714		$	(5,271	)
Tower		$	442,293		$	(4,093	)	$	7,627		$	(326	)	$	449,920		$	(4,419	)
Reciprocal Exchanges			56,593			(837	)		201			(15	)		56,794			(852	)
Total, March 31, 2013, as revised		$	498,886		$	(4,930	)	$	7,828		$	(341	)	$	506,714		$	(5,271	)
December 31, 2012, as restated
U.S. Treasury securities		$	44,347		$	(13	)	$	—		$	—		$	44,347		$	(13	)
U.S. Agency securities			22,345			(76	)		—			—			22,345			(76	)
Municipal bonds			21,532			(235	)		251			(9	)		21,783			(244	)
Corporate and other bonds
Finance			16,853			(1,095	)		—			—			16,853			(1,095	)
Industrial			53,576			(667	)		4,188			(201	)		57,764			(868	)
Utilities			20,143			(191	)		7			—			20,150			(191	)
Commercial mortgage-backed securities			23,223			(141	)		95			—			23,318			(141	)
Residential mortgage-backed securities
Agency backed			59,009			(261	)		25			(1	)		59,034			(262	)
Non-agency backed			815			(6	)		588			(28	)		1,403			(34	)
Asset-backed securities			1,499			(2	)		4,232			(12	)		5,731			(14	)
Total fixed-maturity securities			263,342			(2,687	)		9,386			(251	)		272,728			(2,938	)
Preferred stocks			9,716			(155	)		5,724			(326	)		15,440			(481	)
Common stocks			55,560			(4,292	)		—			—			55,560			(4,292	)
Total, December 31, 2012, as restated		$	328,618		$	(7,134	)	$	15,110		$	(577	)	$	343,728		$	(7,711	)
Tower		$	270,609		$	(6,732	)	$	13,338		$	(478	)	$	283,947		$	(7,210	)
Reciprocal Exchanges			58,009			(402	)		1,772			(99	)		59,781			(501	)
Total, December 31, 2012, as restated		$	328,618		$	(7,134	)	$	15,110		$	(577	)	$	343,728		$	(7,711	)
Management evaluated the severity of the impairment in relation to the carrying values for the securities referred to above and considered all relevant factors in assessing whether the loss was other-than-temporary. Management does not intend to sell its fixed-maturity securities, and it is not more likely than not that fixed maturity and equity securities will be sold until there is a recovery of fair value to the original cost basis; which may be at maturity for the fixed income securities.
Fixed-Maturity Investment—Time to Maturity
The following table shows the amortized cost and fair value of the fixed-maturity portfolio by contractual time to maturity at March 31, 2013 and December 31, 2012:
		Tower						Reciprocal Exchanges						Total
($ in thousands)		Amortized			Fair			Amortized			Fair			Amortized			Fair
		Cost			Value			Cost			Value			Cost			Value
March 31, 2013, as revised
Remaining Time to Maturity
Less than one year		$	22,678		$	23,060		$	2,000		$	2,008		$	24,678		$	25,068
One to five years			636,015			656,679			40,795			42,693			676,810			699,372
Five to ten years			556,748			594,311			76,334			79,921			633,082			674,232
More than 10 years			343,277			372,246			57,782			61,912			401,059			434,158
Mortgage and asset-backed securities			453,578			490,511			78,869			84,430			532,447			574,941
Total, March 31, 2013, as revised		$	2,012,296		$	2,136,807		$	255,780		$	270,964		$	2,268,076		$	2,407,771
December 31, 2012, as restated
Remaining Time to Maturity
Less than one year		$	30,082		$	30,614		$	2,678		$	2,715		$	32,760		$	33,329
One to five years			489,939			510,523			45,576			47,275			535,515			557,798
Five to ten years			564,556			607,711			76,480			80,009			641,036			687,720
More than 10 years			346,410			379,045			57,628			62,542			404,038			441,587
Mortgage and asset-backed securities			495,249			536,255			81,588			88,022			576,837			624,277
Total, December 31, 2012, as restated		$	1,926,236		$	2,064,148		$	263,950		$	280,563		$	2,190,186		$	2,344,711
Other Invested Assets
The following table shows the composition of the other invested assets as of March 31, 2013 and December 31, 2012:
($ in thousands)		March 31,			December 31,
		2013			2012
Limited partnerships, equity method		$	24,517		$	23,864
Real estate, amortized cost			7,223			7,422
Securities reported under the fair value option			25,000			25,000
Other			2,201			1,500
Total		$	58,941		$	57,786
Securities reported under the fair value option include two securities for which the Company has elected the fair value option. This election was made to simplify the accounting for these instruments which contain embedded derivatives and other features.
The fair value of the limited partnerships in the table above approximates their carrying value under the equity method of accounting. The significant inputs used to determine fair value of these limited partnerships are considered Level 3 pursuant to the fair value hierarchy. See “Note 7 – Fair Value Measurements” below. As of March 31, 2013, the Company had future funding commitments of $28.2 million to these limited partnerships.

Fair_Value_Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2013
Fair Value Measurements	'
	Note 7—Fair Value Measurements
	GAAP establishes a three-level hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). If the inputs used to measure the assets or liabilities fall within different levels of the hierarchy, the classification is based on the lowest level input that is significant to the fair value measurement of the asset or liability. Classification of assets and liabilities within the hierarchy considers the markets in which the assets and liabilities are traded, including during periods of market disruption, and the reliability and transparency of the assumptions used to determine fair value. The hierarchy requires the use of observable market data when available. The levels of the hierarchy are as follows:
	Level 1 — Inputs to the valuation methodology are quoted prices (unadjusted) for identical assets or liabilities traded in active markets. Included are those equity securities that are traded on active exchanges, such as the NASDAQ Global Select Market.
	Level 2 — Inputs to the valuation methodology include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability and market-corroborated inputs. Included are investments in U.S. Treasury and Agency securities and, together with municipal bonds, corporate debt securities, commercial mortgages, residential mortgage-backed securities and asset-backed securities. Additionally, interest-rate swap contracts utilize Level 2 inputs in deriving fair values.
	Level 3 — Inputs to the valuation methodology are unobservable in the market for the asset or liability and are significant to the fair value measurement. Material assumptions and factors considered in pricing investment securities may include projected cash flows, collateral performance including delinquencies, defaults and recoveries, and any market clearing activity or liquidity circumstances in the security or similar securities that may have occurred since the prior pricing period.
	The availability of observable inputs varies and is affected by a wide variety of factors. When the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires significantly more judgment. The degree of judgment exercised by management in determining fair value is greatest for investments categorized as Level 3. For investments in this category, management considers prices and inputs that are current as of the measurement date. In periods of market dislocation, as characterized by current market conditions, the ability to observe stable prices and inputs may be reduced for many instruments. This condition could cause a security to be reclassified between levels.
	As at March 31, 2013 and December 31, 2012, the Company’s financial instruments carried at fair value are allocated among levels as follows:
	($ in thousands)		Level 1		Level 2			Level 3		Total
	March 31, 2013, as revised
	Fixed-maturity securities
	U.S. Treasury securities		$	—	$	316,732		$	—	$	316,732
	U.S. Agency securities			—		109,005			—		109,005
	Municipal bonds			—		688,931			—		688,931
	Corporate and other bonds			—		718,162			—		718,162
	Commercial mortgage-backed securities			—		235,921			—		235,921
	Residential mortgage-backed securities
	Agency			—		262,199			—		262,199
	Non-agency			—		41,624			—		41,624
	Asset-backed securities			—		35,197			—		35,197
	Total fixed-maturities			—		2,407,771			—		2,407,771
	Equity securities			142,708		—			—		142,708
	Short-term investments			—		28,822			—		28,822
	Total investments at fair value			142,708		2,436,593			—		2,579,301
	Other invested assets (1)			—		—			25,000		25,000
	Other liabilities										—
	Interest rate swap contracts			—		(8,203	)		—		(8,203	)
	Debt and equity securities sold, not yet purchased			—		(22,513	)		—		(22,513	)
	Total, March 31, 2013, as revised		$	142,708	$	2,405,877		$	25,000	$	2,573,585
	Tower		$	139,794	$	2,134,913		$	25,000	$	2,299,707
	Reciprocal Exchanges			2,914		270,964			—		273,878
	Total, March 31, 2013, as revised		$	142,708	$	2,405,877		$	25,000	$	2,573,585
	December 31, 2012, as restated
	Fixed-maturity securities
	U.S. Treasury securities		$	—	$	184,949		$	—	$	184,949
	U.S. Agency securities			—		102,777			—		102,777
	Municipal bonds			—		686,043			—		686,043
	Corporate and other bonds			—		746,665			—		746,665
	Commercial mortgage-backed securities			—		242,053			—		242,053
	Residential mortgage-backed securities
	Agency			—		295,716			—		295,716
	Non-agency			—		42,156			—		42,156
	Asset-backed securities			—		44,352			—		44,352
	Total fixed-maturities			—		2,344,711			—		2,344,711
	Equity securities			146,258		—			—		146,258
	Short-term investments			—		4,750			—		4,750
	Total investments at fair value			146,258		2,349,461			—		2,495,719
	Other invested assets (2)			—		—			25,000		25,000
	Other liabilities
	Interest rate swap contracts			—		(9,016	)		—		(9,016	)
	Debt and equity securities sold, not yet purchased			—		(17,101	)		—		(17,101	)
	Total, December 31, 2012, as restated		$	146,258	$	2,323,344		$	25,000	$	2,494,602
	Tower		$	140,695	$	2,042,780		$	25,000	$	2,208,475
	Reciprocal Exchanges			5,563		280,564			—		286,127
	Total, December 31, 2012, as restated		$	146,258	$	2,323,344		$	25,000	$	2,494,602
	-1	$25.0 million of the $58.9 million Other invested assets reported on the consolidated balance sheet at March 31, 2013 is reported at fair value. The remaining $33.9 million of Other invested assets is reported under the equity method of accounting or at amortized cost.
	-2	$25.0 million of the $57.8 million Other invested assets reported on the consolidated balance sheet at December 31, 2012 is reported at fair value. The remaining $32.8 million of Other invested assets is reported under the equity method of accounting or at amortized cost.
	As of March 31, 2013, substantially all of the investment portfolio recorded at fair value was priced based upon quoted market prices or other observable inputs. For investments in active markets, the Company used the quoted market prices provided by the outside pricing services to determine fair value. In circumstances where quoted market prices were unavailable, the Company used fair value estimates based upon other observable inputs including matrix pricing, benchmark interest rates, market comparables and other relevant inputs. When observable inputs were adjusted to reflect management’s best estimate of fair value, such fair value measurements are considered a lower level measurement in the GAAP fair value hierarchy.
	The Company’s process to validate the market prices obtained from the outside pricing sources includes, but is not limited to, periodic, evaluation of model pricing methodologies and analytical reviews of certain prices. The Company also periodically performs testing of the market to determine trading activity, or lack of trading activity, as well as market prices. Several securities sold during the quarter were “back-tested” (i.e., the sales price is compared to the previous month end reported market price to determine reasonableness of the reported market price). If management believes that the price provided from the pricing source is distressed, management will use a valuation method that reflects an orderly transaction between market participants, generally a discounted cash flow method that incorporates relevant interest rate, risk and liquidity factors.
	The ability to observe stable prices and inputs may be reduced for highly-customized and illiquid instruments which had been the case for certain non-agency residential and commercial mortgage-backed securities and asset-backed securities in previous periods.
	Substantially all of the portfolio valuations at March 31, 2013 classified as Level 1 or Level 2 in the above table are priced by utilizing the services of several independent pricing services that provide the Company with a price quote for each security. There were no adjustments made to the prices obtained from the independent pricing sources and dealers on securities classified as Level 1 or Level 2.
	In 2013 and 2012, there were no transfers of investments between Level 1 and Level 2 or between Level 2 and Level 3.
	The fair values of the interest rate swaps were derived using an industry standard swap valuation model with market based inputs for swaps having similar characteristics.
	The fair values of the debt and equity securities sold, not yet purchased were derived by using quoted prices for similar securities in active markets. These instruments resulted in net realized gains (losses) of $0.2 million for the three months ended March 31, 2013.
The Company holds two securities which are reported in other invested assets and have been classified as Level 3 of the fair value hierarchy. Management utilizes a discounted cash flow analysis to derive the fair values. For one security, which matures in 2015 and whose cash flows are supported by underlying short-term loans, the significant unobservable inputs include the underlying short-term loans’ probability of default and loss severity, and a discount for the security’s lack of marketability. Increases in the probability of default and loss severity assumptions (which generally move directionally with each other) would have the effect of decreasing the fair value of this security. The Company obtains credit ratings on the underlying short-term loans quarterly and considers these ratings when updating its assumptions. The second security is an equity instrument which entitles the Company to residual interests of a finite life special purpose vehicle. The significant unobservable inputs include the estimated losses to be incurred by the vehicle and the equity instrument’s lack of marketability. The Company obtains quarterly financial data from the vehicle and evaluates the estimated incurred loss figure. An increase in the vehicle’s estimated incurred losses would have the effect of decreasing the instrument’s fair value.
Management is responsible for the determination of the value of the investments carried at fair value and the supporting methodologies and assumptions. Management has reviewed the pricing techniques and methodologies of the independent pricing sources and believes that their policies adequately consider market activity, either based on specific transactions for the issue valued or based on modeling of securities with similar credit quality, duration, yield and structure that were recently traded. Management monitors security-specific valuation trends and discusses material changes or the absence of expected changes with the portfolio managers to understand the underlying factors and inputs and to validate the reasonableness of pricing. Management also back-tests the prices on numerous sales of securities during the year to validate the previous pricing provided as well as utilizes other pricing sources to validate the pricing provided by the Company’s primary provider of the majority of the non-U.S. Treasury securities and non-agency securities included in Level 2.
The following table summarizes the changes in Level 3 assets measured at fair value for the three months ended March 31, 2013 and 2012 for Tower (the Reciprocal Exchanges have no Level 3 assets):
		Three Months Ended
		March 31,
($ in thousands)		2013		2012
Beginning balance, January 1		$	25,000	$	25,000
Total gains (losses)-realized / unrealized - included in net income			—		(86	)
Ending balance, March 31,		$	25,000	$	24,914

Reinsurance

Reinsurance	3 Months Ended
	Mar. 31, 2013
Reinsurance	'
	Note 8 – Reinsurance
	Impact of Reinsurance on Premiums
	The table below shows direct, assumed and ceded premiums for the three months ended March 31, 2013 and 2012:
		Three Months Ended March 31,
	($ in thousands)	Direct			Assumed			Ceded			Net
		(revised)									(revised)
	2013, as revised
	Premiums written	$	445,715		$	105,514		$	98,032		$	453,197
	Change in unearned premiums		(16,128	)		(44,389	)		(29,206	)		(31,311	)
	Premiums earned	$	429,587		$	61,125		$	68,826		$	421,886
	2012
	Premiums written	$	404,840		$	62,521		$	41,678		$	425,683
	Change in unearned premiums		27,169			(31,394	)		1,300			(5,525	)
	Premiums earned	$	432,009		$	31,127		$	42,978		$	420,158

Loss_and_Loss_Adjustment_Expen

Loss and Loss Adjustment Expense	3 Months Ended
	Mar. 31, 2013
Loss and Loss Adjustment Expense	'
	Note 9 – Loss and Loss Adjustment Expense
	The following table provides a reconciliation of the beginning and ending consolidated balances for unpaid losses and loss adjustment expense (“LAE”) for the three months ended March 31, 2013 and 2012:
		Three Months Ended March 31,
		2013									2012
	($ in thousands)	Tower			Reciprocal			Total			Tower			Reciprocal			Total
		(revised)			Exchanges			(revised)						Exchanges
	Balance at January 1,	$	1,759,888		$	135,791		$	1,895,679		$	1,495,839		$	136,274		$	1,632,113
	Less reinsurance recoverables on unpaid losses		(407,068	)		(52,389	)		(459,457	)		(280,968	)		(11,253	)		(292,221	)
			1,352,820			83,402			1,436,222			1,214,871			125,021			1,339,892
	Net reserves, at fair value, of acquired entities		161,886			—			161,886			—			—			—
	Incurred related to:
	Current year		239,210			28,827			268,037			229,994			24,531			254,525
	Prior years unfavorable/(favorable) development		1,124			6,571			7,695			13,256			(288	)		12,968
	Total incurred		240,334			35,398			275,732			243,250			24,243			267,493
	Paid related to:
	Current year		103,324			17,721			121,045			79,504			17,428			96,932
	Prior years		171,026			707			171,733			158,829			12,123			170,952
	Total paid		274,350			18,428			292,778			238,333			29,551			267,884
	Net balance at end of period		1,480,690			100,372			1,581,062			1,219,788			119,713			1,339,501
	Add reinsurance recoverables on unpaid losses		822,634			27,554			850,188			235,033			22,905			257,938
	Balance at March 31,	$	2,303,324		$	127,926		$	2,431,250		$	1,454,821		$	142,618		$	1,597,439
	Incurred losses and LAE for the three months ended March 31, 2013 attributable to events of prior years were $7.7 million including the Reciprocal Exchanges and $1.1 million excluding the Reciprocal Exchanges.
	The consolidated net loss ratio, which includes the Reciprocal Exchanges, was 65.4% and 63.7% for the three months ended March 31, 2013 and 2012, respectively. Excluding the Reciprocal Exchanges, the net loss ratio was 63.1% and 64.2% for the three months ended March 31, 2013 and 2012, respectively.
	Prior year development is based upon numerous estimates by line of business and accident year. The Company’s management continually monitors claims activity to assess the appropriateness of carried case and incurred but not reported (“IBNR”) reserves, giving consideration to Company and industry trends.
	Included in the reserves for the loss and LAE reserves at both March 31, 2013 and December 31, 2012 are $8.4 million of tabular reserve discount for workers’ compensation and excess workers’ compensation claims.
	As of March 31, 2013 the Company had $19.1 million of unamortized reserve for risk premium related to the Merger Transaction. The reserve for risk premium is included in unpaid losses and LAE. There was no unamortized reserve for risk premium recorded as of December 31, 2012.

Stockholders_Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2013
Stockholders' Equity	'
	Note 10—Stockholders’ Equity
	Shares of Common Stock Issued
	As previously discussed in “Note 4 – Merger Transaction”, the Merger Transaction was accounted for as a reverse acquisition with TGI treated as the accounting acquirer. Accordingly, TGI’s historical common stock balance immediately prior to the Merger is the historical common stock of TGI adjusted for the number of shares issued in the Merger Transaction by the Company to TGI shareholders (i.e., TGI’s outstanding shares immediately prior to the Merger Transaction multiplied by the conversion ratio of 1.1330).
	Canopius Bermuda had 14,025,737 outstanding common shares outstanding on March 13, 2013 which were sold by Canopius Group to third-party investors in connection with the Merger Transaction.
	For the three months ended March 31, 2013, no new common shares were issued as the result of employee stock option exercises. For the three months ended March 31, 2013, 240,293 new common shares were issued after the Merger Transaction as the result of the Company’s restricted stock grants. For the three months ended March 31, 2012, no new common shares were issued as the result of employee stock option exercises and 363,894 new common shares, (adjusted for the 1.1330 conversion ratio), were issued as the result of restricted stock grants.
	For the three months ended March 31, 2013, 340,707 shares of common stock were purchased from employees in connection with the vesting of restricted stock issued under the 2008 Long Term Equity Compensation Plan (the “Plan”). For the three months ended March 31, 2012, 109,743 shares of common stock were purchased from employees in connection with the vesting of restricted stock issued under the Plan. The shares were withheld at the direction of employees as permitted under the Plan in order to pay the expected amount of tax liability owed by the employees from the vesting of those shares. In addition, for the three months ended March 31, 2013, 6,848 shares of common stock were surrendered as a result of restricted stock forfeitures. For the three months ended March 31, 2012, 4,852 shares of common stock were surrendered as a result of restricted stock forfeitures.
	In connection with the Merger Transaction, all Treasury shares held by TGI were cancelled. There were no Treasury shares of the Company held at March 31, 2013.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income	3 Months Ended
	Mar. 31, 2013
Accumulated Other Comprehensive Income	'
	Note 11—Accumulated Other Comprehensive Income
	The following table provides a summary of changes in accumulated other comprehensive income, by component, for the three months ended March 31, 2013, with all amounts reflected net of income taxes and noncontrolling interest:
	($ in thousands)	Unrealized			Gains			Cumulative			Total
		gains (losses)			(losses) on			translation
		on available for			cash flow			adjustments
		sale securities			hedges
	Balance at December 31, 2012, as restated	$	87,412		$	(5,860	)	$	1,204		$	82,756
	Other comprehensive income before reclassifications, net of tax		906			514			(2,347	)		(927	)
	Amounts reclassified from accumulated other comprehensive income, net of tax		(4,051	)		533			—			(3,518	)
	Net current period other comprehensive income		(3,145	)		1,047			(2,347	)		(4,445	)
	Balance at March 31, 2013, as revised	$	84,267		$	(4,813	)	$	(1,143	)	$	78,311
	The following provides a summary of the items that have been reclassified from accumulated other comprehensive income to net income in their entirety during the three months ended March 31, 2013, including the line item on the consolidated statement of operations on which the impact is reflected. Unrealized gains (losses) on available for sale securities are reclassified from accumulated other comprehensive income when a security is sold or when a non-credit impairment is recorded. Gains (losses) on cash flow hedges are reclassified from accumulated other comprehensive income when the related hedged item (subordinated debentures floating rate interest payments) are recorded in the statement of operations.
	($ in thousands)
	Accumulated other comprehensive	Amounts reclassified			Affected line item in the consolidated
		from accumulated other			statement of operations
	income components	comprehensive income
		(revised)
	Unrealized gains (losses) on available for sale securities	$	(6,232	)	Other net realized investment gains
			2,181		Income tax expense
		$	(4,051	)	Total net of income taxes
	Gains (losses) on cash flow hedges interest rate swaps	$	820		Interest expense
			(287	)	Income tax expense
		$	533		Total net of income taxes

Debt

Debt

3 Months Ended

Mar. 31, 2013

Debt

'

Note 12—Debt

The Company’s borrowings consisted of the following at March 31, 2013 and December 31, 2012:

March 31, 2013

December 31, 2012

($ in thousands)

Carrying

Fair

Carrying

Fair

Value

Value

Value

Value

Credit facility

$

70,000

$

70,000

$

70,000

$

70,000

Convertible senior notes

145,412

156,375

144,673

152,063

Subordinated debentures

235,058

236,875

235,058

232,678

Total

$

450,470

$

463,250

$

449,731

$

454,741

The fair value of the convertible senior notes are determined utilizing recent transaction prices for these securities between third-party market participants. The fair value of the subordinated debentures are based on discounted cash flow analysis. The significant inputs used for fair value are considered Level 2 in the fair value hierarchy.

Total interest expense incurred, including interest expense on the funds held liabilities, was $7.8 million and $8.6 million for the three months ended March 31, 2013 and 2012, respectively.

Subordinated Debentures

The Company and its wholly-owned subsidiaries have issued trust preferred securities through wholly-owned Delaware statutory business trusts. The trusts use the proceeds of the sale of the trust preferred securities and common securities that the Company acquired from the trusts to purchase junior subordinated debentures from the Company with terms that match the terms of the trust preferred securities. Interest on the junior subordinated debentures and the trust preferred securities is payable quarterly. In some cases, the interest rate is fixed for an initial period of five years after issuance and then floats with changes in the London Interbank Offered Rate (“LIBOR”) and in other cases the interest rate floats with LIBOR without any initial fixed-rate period. As of March 31, 2013, The Company had outstanding par of $235.1 million relating to the subordinated debentures.

Interest Rate Swaps

In October 2010, the Company entered into interest rate swap contracts (the “Swaps”) with $190 million notional value to manage interest costs and cash flows associated with the floating rate subordinated debentures. The Swaps have terms of five years. The Swaps convert the subordinated debentures to rates ranging from 5.1% to 5.9%. As of March 31, 2013 and December 31, 2012, the Swaps had a fair value of $8.2 million and $9.0 million in a liability position, respectively, and are reported in Other Liabilities.

The Company has designated and accounts for the Swaps as cash flow hedges. The Swaps are considered to have no ineffectiveness and changes in their fair values are recorded in accumulated other comprehensive income (“AOCI”), net of tax. For the three months ended March 31, 2013 and 2012, $0.5 million and $0.5 million, respectively, were reclassified from AOCI to interest expense for the effects of the hedges. As of March 31, 2013, the Company had collateral on deposit with the counterparty amounting to $8.3 million pursuant to a Credit Support Annex.

Credit Facility

On April 3, 2013, an increase in borrowing capacity up to $220 million became effective pursuant to the second amendment to the credit agreement and consent by and between TGI and Bank of America, N.A., as administrative agent for the lenders party to the credit agreement, dated as of November 26, 2012, and the limited waiver and amendment agreement, dated as of March 3, 2013. The increase in the Credit Facility was negotiated in the event that holders of the convertible senior notes put their bonds to Tower as a result of the Merger Transaction. This put option expired on April 26, 2013. This second amendment and consent also included (i) TGIL as a guarantor of TGI’s obligations under the credit facility and (ii) consent by the lenders to the change in control triggered by the completion of the Merger Transaction. The maturity date and borrowing fees were not changed in this amendment.

The 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 to maintain certain consolidated net worth, debt to capitalization ratios, minimum risk-based capital and minimum statutory surplus. The credit facility also provides for customary events of default, including failure to pay principal when due, failure to pay interest or fees within three days after becoming due, failure to comply with covenants, any representation or warranty made by TGI or the Company as a guarantor being false in any material respect, default under certain other indebtedness, certain insolvency or receivership events affecting the TGI or the Company as guarantor and its material subsidiaries, the occurrence of certain material judgments, or a change in control of the Company, and upon an event of default, the administrative agent (subject to the consent of the requisite percentage of the lenders) may immediately terminate the obligations to make loans and to issue letters of credit, declare the Company’s obligations under the credit facility to become immediately due and payable, and require the Company to deposit in a collateral account cash collateral with a value equal to the then outstanding amount of the aggregate face amount of any outstanding letters of credit. The Company was in compliance with or obtained waivers for all covenants under the credit facility at June 30, 2013.

The Company had $70.0 million outstanding as of June 30, 2013 and December 31, 2012, respectively. The weighted average interest rate on the amount outstanding as of June 30, 2013 was 1.94%.

On October 11, 2013, the Company amended its credit facility to reduce its capacity from $220 million to $70 million and the maturity date was changed to May 30, 2014. In addition, the Company agreed to several restrictions under the credit facility, including:

•

To not enter into any new borrowings under the credit facility;

•

To pledge to the lending banks any proceeds of new capital raises by TGI or TGIL until such time as the credit facility is paid in full;

•

To pledge to the lending banks proceeds from any sales of assets occurring at TGI; and

•

To submit to regulatory authorities, as appropriate, a request for approval to pledge the capital stock of the U.S. based and Bermuda based insurance subsidiaries.

In addition, the following financial covenants are included in the credit facility:

•

Minimum Consolidated Net Worth is the greater of $553,400,000 or 90 % of Consolidated Net Worth as of June 30, 2013; this covenant increases by 90% of any new capital plus 50% of Net Income above $20,000,000;

•

Debt to capitalization ratio limit of 46%;

•

Minimum risk based capital ratio of 175% at December 31, 2013 for Tower Insurance Company of New York and any other insurance subsidiary that exceeds 10% of the consolidated statutory surplus of all insurances subsidiaries;

•

Bermuda enhanced minimum capital requirement of 150% for CastlePoint Re at December 31, 2013 and 110% for TRL;

•

Minimum statutory surplus for all insurance companies of the greater of $419,000,000 or 85% of Combined Surplus at June 30, 2013; and

•

Independent accountant’s annual report shall not be subject to any “going concern” or like qualification or exception. This financial covenant will remain in effect for the year ending December 31, 2013. Although the independent accountant’s report on the consolidated financial statements for the years ended December 31, 2010, 2011 and 2012 contains a “going concern” explanatory paragraph, on November 14, 2013, the Company received a waiver from the lenders under the credit facility in respect of such “going concern” paragraph.

Tower currently is in compliance with all covenants contained in the credit facility.

The credit facility matures on May 30, 2014, at which point any unpaid balance becomes due.

Convertible Senior Notes

In September 2010, the Company issued $150.0 million principal amount of 5.0% convertible senior notes (“the Notes”), which mature on September 15, 2014. Interest on the Notes is payable semi-annually in arrears on March 15 and September 15 of each year, commencing March 15, 2011. The original terms of the Notes allowed Holders to convert their Notes into cash or common shares, at the Company’s option, at any time on or after March 15, 2014 or earlier under certain circumstances determined by: (i) the market price of the Company’s stock, (ii) the trading price of the Notes, or (iii) the occurrence of specified corporate transactions. Upon conversion, the Company intends to settle its obligation either entirely or partially in cash. Upon completion of the merger, the change in control provision of the Indenture was triggered and the Holders were allowed, at their option, to convert their notes into cash or common shares of Tower Group International, Limited. As required by the terms of the Indenture, the Company filed a Fundamental Company Change Notice (“Change Notice”) to the Holders on March 23, 2013. The Change Notice provided Holders the option to convert the Notes into cash or common shares up to and including April 26, 2013. There were no bonds tendered or converted as a result of the Change Notice filing.

The adjusted conversion rate at March 31, 2013 is 42.2491 shares of common stock per $1,000 principal amount of the Notes (equivalent to a conversion price of $23.67 per share), subject to further adjustment upon the occurrence of certain events, including the following: if Tower issues shares of common stock as a dividend or distribution on shares of the common stock , or if Tower effects a share split or share combination; if Tower issues to all or substantially all holders of common stock any rights, options or warrants entitling them, for a period of not more than 45 calendar days after the announcement date of such issuance, to subscribe for or purchase shares of the common stock at a price per share that is less than the average of the last reported sales price of the common stock for the ten consecutive trading day period ending on the date of announcement of such issuance; if Tower distributes shares of its capital stock, other indebtedness, other assets or property of Tower or rights, options or warrants to acquire capital stock or other securities of Tower, to all or substantially all holders of capital stock; if any cash dividend or distribution is made to all or substantially all holders of the common stock, other than a regular quarterly cash dividend that does not exceed $0.110 per share; if Tower makes a payment in respect of a tender offer or exchange offer for common stock, and the cash and value of any other consideration included in the payment per share of common stock exceeds the last reported sale price of the common stock on the trading day next succeeding the last day on which the tenders or exchange may be made.

As a result of the Merger, it was determined that a fundamental change occurred that would permit the debt holders to tender their bonds to the Company at par plus any accrued and unpaid interest or to convert such debt. Notice of the fundamental change was sent to the debt holders on March 22, 2013, and such notice permitted the debt holders to redeem or convert the securities until April 26, 2013. There were no bonds tendered or converted as a result of the fundamental change.

The proceeds from the issuance of the Notes were allocated to the liability component and the embedded conversion option, or equity component. The equity component was reported as an adjustment to paid-in-capital, net of tax, and is reflected as an original issue discount (“OID”). After considering the contractual interest payments and amortization of the original issue discount, the Notes’ effective interest rate is 7.2%. Transaction costs of $0.4 million associated with the equity component were netted with the equity component in paid-in-capital. Interest expense, including amortization of deferred origination costs, recognized on the Notes was $2.9 million for the three months ended March 31, 2013.

The following table shows the amounts recorded for the Notes as of March 31, 2013 and December 31, 2012:

($ in thousands)

March 31,

December 31,

2013

2012

Liability component

Outstanding principal

$

150,000

$

150,000

Unamortized OID

(4,588

)

(5,327

)

Liability component

145,412

144,673

Equity component, net of tax

$

7,469

$

7,469

To the extent the market value per share of the Company’s common stock exceeds the conversion price, the Company will use the “treasury stock” method in calculating the dilutive effect on earnings per share.

Convertible Senior Notes Hedge and Warrant Transactions

In connection with the offering of the Notes, the Company also entered into convertible senior notes hedge transactions (the “Note Hedges” or “purchased call options”) and warrant transactions (the “Warrants”) with respect to its common stock with financial institutions. The Note Hedges and Warrants were intended generally to reduce the potential dilution of the Company’s common stock and to offset potential cash payments in excess of the principal of the Notes upon conversion. The Note Hedges and Warrants were separate transactions, entered into by the Company with the financial institutions, and were not part of the terms of the Notes.

In March 2013, as a result of the Merger Transaction, the Company terminated the Note Hedges and Warrants. The Company received $2.4 million and paid $1.0 to terminate the Note Hedges and Warrants, respectively. The effects of the terminations and an associated tax adjustment of $0.8 million were recorded directly to paid-in-capital in stockholders’ equity.

Stock_Based_Compensation

Stock Based Compensation	3 Months Ended
	Mar. 31, 2013
Stock Based Compensation	'
	Note 13—Stock Based Compensation
	2008 Long-Term Equity Compensation Plan (“2008 LTEP”)
	In 2008, the Company’s Board of Directors adopted and its stockholders approved the 2008 LTEP, which amended and revised the 2004 Long-Term Equity Compensation Plan.
	The 2008 LTEP provides for the granting of non-qualified stock options, incentive stock options (within the meaning of Section 422 of the Internal Revenue Code), stock appreciation rights (“SARs”), restricted stock and restricted stock unit awards, performance shares and other cash or share-based awards. The maximum amount of share-based awards authorized is 2,325,446 of which 28,216 are available for future grants as of March 31, 2013.
	2013 Long-Term Incentive Plan (“2013 LTIP”)
	The Compensation Committee of the Board of Directors has established, beginning in 2013 and subject to stockholder approval, a new Long Term Incentive Plan (the “2013 LTIP”), to replace the Company’s existing 2008 Long Term Equity Compensation Plan.
	Restricted Stock
	The following table provides an analysis of restricted stock activity for the three months ended March 31, 2013 and 2012 (historical share counts and fair values have been adjusted for the 1.1330 share conversion ratio, as discussed more fully in “Note 4 – Merger Transaction”):
		Three Months Ended March 31,
		2013					2012
		Number of			Weighted		Number of			Weighted
		Shares			Average		Shares			Average
					Grant Date					Grant Date
					Fair Value					Fair Value
	Outstanding, January 1		1,015,902		$	20.19		1,120,091		$	20.69
	Granted		240,293			18.08		363,894			20.37
	Vested		(950,773	)		20.44		(428,687	)		21.08
	Forfeitures		(6,848	)		20.51		(4,852	)		20.8
	Outstanding, March 31,		298,574		$	17.67		1,050,446		$	20.38
	On March 13, 2013, 525,548 shares vested as a result of the Merger Transaction.
	Stock Options
	The following table provides an analysis of stock option activity for the three months ended March 31, 2013 and 2012 (historical share counts and fair values have been adjusted for the 1.1330 share conversion ratio, as discussed more fully in “Note 4 – Merger Transaction”):
		Three Months Ended March 31,
		2013					2012
		Number of			Average		Number of			Average
		Shares			Exercise		Shares			Exercise
					Price					Price
	Outstanding, January 1		969,307		$	17.78		969,312		$	17.78
	Exercised		—			—		—			—
	Forfeitures and expirations		—			—		—			—
	Outstanding, March 31		969,307		$	17.78		969,312		$	17.78
	Exercisable, March 31		969,307		$	17.78		969,312		$	17.78
	Stock Based Compensation Expense
	The following table provides an analysis of stock based compensation expense for the three months ended March 31, 2013 and 2012:
		Three Months Ended
		March 31,
	($ in thousands)	2013			2012
	Restricted stock
	Expense, net of tax	$	7,982		$	1,464
	Value of shares vested		9,485			5,622
	Value of unvested shares		5,509			20,796
	Stock options
	Intrinsic value of outstanding options		1,149			2,704
	Intrinsic value of vested outstanding options		1,149			2,704
	Unrecognized compensation expense
	Unvested restricted stock, net of tax		5,509			12,791
	Weighted average years over which expense will be recognized		3.9			2.8

Income_Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2013
Income Taxes	'
	Note 14—Income Taxes
	Under current Bermuda Law the Company is not required to pay any taxes on Bermuda based income or capital gains. The Company has received an undertaking from the Minister of Finance in Bermuda that in the event of such taxes being imposed, the Company will be exempted from taxation until the year 2035 pursuant to the Bermuda Exempted Undertakings Tax Protection Act of 1966. The Company’s United States based subsidiaries are subject to federal, state and local taxes, as applicable, on income and capital gains earned by those subsidiaries.
	The Company and Tower Reinsurance, Ltd. (“TRL”) its Bermuda reinsurance subsidiary are deemed to have permanent establishments in Bermuda. The Bermuda companies have not and do not expect to conduct business that is through a permanent establishment in the U.S. All transactions between Tower’s U.S. based subsidiaries and the Bermuda companies are subject to transfer pricing rules. The Company has executed certain reinsurance treaties and service agreements between its U.S. based subsidiaries and TRL and management believes these arrangements to be conducted at current market rates and in accordance with transfer pricing rules.
	Income (loss) before income tax and income tax expense (benefit) by taxing jurisdiction are presented in the table below for the three months ended March 31, 2013 and 2012, respectively:
		March 31, 2013											March 31, 2012
		U.S.											U.S.
	($ in thousands)	Tower			Reciprocal			Non - U.S.		Total			Tower			Reciprocal			Total
		(revised)								(revised)
	Income (loss) before income tax	$	(15,433	)	$	(11,281	)	$	26,760	$	46		$	27,773		$	3,628		$	31,401
	Income tax expense (benefit)	$	(1,590	)	$	—		$	—	$	(1,590	)	$	8,607		$	617		$	9,224
	Effective tax rate		10.3	%		—			—		-3456.5	%		31	%		17	%		29.4	%
	The Company calculates an estimated annual effective tax rate on its U.S. taxed subsidiaries. Tower U.S. Company’s annualized effective tax rate differs from the U.S. statutory rate due to costs associated with tax exempt interest and dividends received deductions. For interim reporting purposes, Tower U.S. has calculated its effective tax rate for the full year of 2013 by adjusting for discrete items related to the Tower-Canopius merger transaction. Accordingly, Tower U.S. Company’s effective tax rate for the three months ended March 31, 2013 is 10.3%. The Reciprocal Exchange entities’ effective tax rate for the three months ended March 31, 2013 is zero due to a full valuation allowance.
	The United States also imposes an excise tax on insurance and reinsurance premiums paid to non-U.S. insurers or reinsurers with respect to risks located in the United States. The rates of tax, unless reduced by an applicable U.S. tax treaty, are four percent for non-life insurance premiums and one percent for life insurance and all reinsurance premiums. The Company incurs federal excise taxes on certain of its reinsurance transactions, including amounts ceded through intercompany transactions.

Earnings_per_Share

Earnings per Share	3 Months Ended
	Mar. 31, 2013
Earnings per Share	'
	Note 15—Earnings per Share
	Undistributed net earnings (net income less dividends declared during the period) are allocated to both common stock and unvested share-based payment awards (“unvested restricted stock”). Because the common shareholders and unvested restricted stock holders share in dividends on a 1:1 basis, the earnings per share on undistributed earnings is equivalent, however, undistributed losses are allocated only to common stock holders. Undistributed earnings are allocated to all outstanding share-based payment awards, including those for which the requisite service period is not expected to be rendered.
	The following table shows the computation of the earnings per share (historical earnings per share amounts have been adjusted for the 1.1330 share conversion ratio, as discussed more fully in “Note 4 – Merger Transaction”):
		Three Months Ended
		March 31,
	($ in thousands, except per share amounts)	2013			2012
		(revised)
	Numerator
	Net income (loss) attributable to Tower Group International, Ltd.	$	12,917		$	19,166
	Less: Allocation of income for unvested participating restricted stock		(37	)		(298	)
	Less: Dividends on unvested participating restricted stock		(166	)		(174	)
	Net income available to common shareholders - Basic		12,714			18,694
	Reallocation of income for unvested participating restricted stock		—			—
	Net income available to common shareholders - Diluted		12,714			18,694
	Denominator
	Basic earning per share denominator		45,614			43,326
	Effect of dilutive securities		74			85
	Diluted earnings per share denominator		45,688			43,411
	Earnings (loss) per share attributable to Tower Group International, Ltd. - Basic
	Common stock:
	Distributed earnings	$	0.17		$	0.17
	Undistributed earnings	$	0.11		$	0.26
	Total	$	0.28		$	0.43
	Earnings (loss) per share attributable to Tower Group International, Ltd. - Diluted	$	0.28		$	0.43
	The computation of diluted earnings per share excludes outstanding options and other common stock equivalents in periods where inclusion of such potential common stock instruments would be anti-dilutive. For the three months ended March 31, 2013 and 2012 190,500 and, 188,900, respectively, options to purchase Company shares were excluded from the computation of diluted earnings per share because the exercise price of the options was greater than the average market price.

Segment_Information

Segment Information	3 Months Ended
	Mar. 31, 2013
Segment Information	'
	Note 16—Segment Information
	The accounting policies of the segments are the same as those described in TGI’s summary of significant accounting policies in its Amendment No. 2 to the Annual Report on Form 10-K for the year ended December 31, 2012.
	The Company is currently re-evaluating its internal reporting structure due to the recently completed Merger Transaction, the result of which may require changes to its segment reporting. Until this re-evaluation is completed, the Company’s operations, including those acquired in connection with the Merger Transaction, continue to be reported within its three business segments, Commercial Insurance, Personal Insurance and Insurance Services.
	The Personal Insurance segment includes revenues and expenses associated with the Reciprocal Exchanges, including fees paid to Tower for underwriting, claims, investment management and other services provided pursuant to management services agreements with the Reciprocal Exchanges. The Insurance Services segment reports revenues earned by Tower from the Reciprocal Exchanges as management fee income, which is calculated as a percentage of the Reciprocal Exchanges’ gross written premiums. The effects of these management services agreements between Tower and the Reciprocal Exchanges are eliminated in consolidation to derive consolidated net income. However, the management fee income is reported in net income attributable to Tower Group International, Ltd. and included in basic and diluted earnings per share.
	Segment performance is evaluated based on segment profit, which excludes investment income, realized gains and losses, interest expense, income taxes and incidental corporate expenses. Assets, other than intangibles and goodwill, are not allocated to segments because investments and assets other than intangible assets and goodwill are considered in total by management for decision-making purposes.
	Business segment results are as follows:
		Three Months Ended
		March 31,
	($ in thousands)	2013			2012
		(revised)
	Commercial Insurance Segment
	Revenues
	Premiums earned	$	307,784		$	297,835
	Ceding commission revenue		3,287			10
	Policy billing fees		1,370			1,513
	Total revenues		312,441			299,358
	Expenses
	Loss and loss adjustment expenses		196,363			201,438
	Underwriting expenses		112,912			103,142
	Total expenses		309,275			304,580
	Underwriting profit (loss)	$	3,166		$	(5,222	)
	Personal Insurance Segment
	Revenues
	Premiums earned	$	114,102		$	122,323
	Ceding commission revenue		10,864			5,153
	Policy billing fees		1,780			1,621
	Total revenues		126,746			129,097
	Expenses
	Loss and loss adjustment expenses		79,369			66,055
	Underwriting expenses		60,528			53,852
	Total expenses		139,897			119,907
	Underwriting profit (loss)	$	(13,151	)	$	9,190
	Tower	$	(524	)	$	9,438
	Reciprocal Exchanges		(12,627	)		(248	)
	Total underwriting profit (loss)	$	(13,151	)	$	9,190
	Insurance Services Segment
	Revenues
	Management fee income	$	7,161		$	6,862
	Other revenue		128			497
	Total revenues		7,289			7,359
	Expenses
	Other expenses		4,621			4,463
	Total expenses		4,621			4,463
	Insurance services pretax income	$	2,668		$	2,896
	The following table reconciles revenue by segment to consolidated revenues:
		Three Months Ended
		March 31,
	($ in thousands)	2013			2012
		(revised)
	Commercial insurance segment	$	312,441		$	299,358
	Personal insurance segment		126,746			129,097
	Insurance services segment		7,289			7,359
	Total segment revenues		446,476			435,814
	Elimination of management fee income		(7,161	)		(6,862	)
	Net investment income		30,317			33,943
	Net realized gains (losses) on investments, including other-than-temporary impairments		6,851			3,328
	Consolidated revenues	$	476,483		$	466,223
	The following table reconciles the results of the Company’s individual segments to consolidated income before income taxes:
		Three Months Ended
		March 31,
	($ in thousands)	2013			2012
		(revised)
	Commercial insurance segment underwriting profit (loss)	$	3,166		$	(5,222	)
Personal insurance segment underwriting profit (loss)		(13,151	)		9,190
Insurance services segment pretax income		2,668			2,896
Net investment income		30,317			33,943
Net realized gains on investments, including other-than-temporary impairments		6,851			3,328
Corporate expenses		(3,069	)		(2,861	)
Acquisition-related transaction costs		(19,056	)		(1,262	)
Interest expense		(7,808	)		(8,611	)
Other income		128			—
Income before income taxes	$	46		$	31,401
The Company is currently re-evaluating its internal reporting structure due to the recently completed Merger Transaction, the results of which may require a change to its segment reporting. Until this re-evaluation is completed, the Company’s operations, including those acquired in connection with the Merger Transaction, continue to be reported within its three business segments.

Contingencies

Contingencies	3 Months Ended
	Mar. 31, 2013
Contingencies	'
	Note 17—Contingencies
	Legal Proceedings
	On August 20, 2013, Robert P. Lang, a purported shareholder of Tower Group International Ltd. (“Tower”), filed a purported class action complaint (the “Lang Complaint”) against Tower and certain of its officers in the United States District Court for the Southern District of New York. The Lang Complaint alleges that Tower and certain of its officers violated federal securities laws and seeks unspecified damages. On September 3, 2013, a second purported shareholder class action complaint was filed by Dennis Feighay, another purported Tower shareholder, containing similar allegations to those set forth in the Lang Complaint (the “Feighay Complaint”). On October 4, 2013, a third complaint was filed by Sanju Sharma (the “Sharma Complaint”). The Sharma Complaint names as defendants Tower and certain of its officers, and purports to be asserted on behalf of a plaintiff class who purchased Tower stock between May 10, 2011 and September 17, 2013. On October 18, 2013, an amended complaint was filed in the Sharma case (the “Sharma Amended Complaint”). The Sharma Amended Complaint alleges additional false and misleading statements, and purports to be asserted on behalf of a plaintiff class who purchased Tower stock between March 1, 2011 and October 7, 2013. On October 21, 2013, a number of motions were filed seeking to consolidate the shareholder class actions into one matter and for appointment of a lead plaintiff. The Company believes that it is not probable that the Lang and Feighay Complaints and the Sharma Amended Complaint will result in a loss, and that the amount of any loss cannot reasonably be estimated.
	On October 18, 2013, Cinium Financial Services Corporation (“Cinium”) and certain other affiliated parties (collectively, “Plaintiffs”) filed a complaint against, among others, Tower, CastlePoint Insurance Company (“CastlePoint”), an indirect wholly owned subsidiary of Tower, and certain officers of Tower (the “Cinium Complaint”) in New York State Supreme Court. CastlePoint is a party to a Securityholders’ Agreement, dated as of June 14, 2012 (the “Securityholders’ Agreement”), among certain parties including Plaintiffs, and is also the holder of a senior note issued by Cinium dated May 15, 2012 that is convertible into shares of Cinium common stock (the “Senior Note”). Plaintiffs seek, among other things, (i) a declaratory judgment that CastlePoint has no right to exercise any control over Cinium under the Securityholders’ Agreement or to convert the Senior Note without prior regulatory approval; (ii) rescission of the Senior Note and Securityholders’ Agreement based on alleged fraudulent misrepresentations by Tower at the time these agreements were entered into; and (iii) damages of $150 million for alleged breach of fiduciary duties to Cinium and its shareholders by certain directors. The Company believes that it is not probable that the Cinium Complaint will result in a loss, and that the amount of any loss cannot reasonably be estimated.
	From time to time, the Company is involved in other various legal proceedings in the ordinary course of business. The Company does not believe that the resolution of any currently pending legal proceedings, either individually or taken as a whole, will have a material adverse effect on its business, results of operations or financial condition.

Subsequent_Events

Subsequent Events	3 Months Ended
	Mar. 31, 2013
Subsequent Events	'
	Note 18 – Subsequent Events
	On August 19, 2013, Tower announced it terminated its previously announced agreement to acquire American Safety Reinsurance, Ltd., the Bermuda-based reinsurance subsidiary of American Safety Insurance Holdings, Ltd., from Fairfax Financial Holdings Limited. Tower received $5 million in exchange for the termination of such agreement.
	In August 2013, management has begun to reorganize the way in which it will manage the business for operating decisions and assessing profitability. This reorganization is attributed to events occurring subsequent to the second quarter of 2013. As a result, the Company will reassess its segment reporting for the third quarter 2013 financial reporting purposes.
	On October 11, 2013, the Company amended its Credit Facility to reduce its capacity from $220 million to $70 million and change its maturity date to May 30, 2014.
	See the Liquidity section in “Note 4—Nature of Business” to the consolidated financial statements for further discussion on Liquidity and Capital Resources.
	Reinsurance Agreements
	On October 1, 2013, Tower announced that it entered into agreements with three reinsurers, Arch Reinsurance Ltd. (“Arch”), Hannover Re (Ireland) Plc. (“Hannover”) and Southport Re (Cayman), Ltd. (“Southport Re”). These agreements provided for surplus enhancement and improved certain financial leverage ratios, while increasing the Company’s financial flexibility. The agreements with Arch and Hannover each consists of one reinsurance agreement while the arrangement with Southport Re consists of several reinsurance agreements. Each of these is described below.
	The first agreement was between TICNY on its behalf and on behalf of each of its pool participants and Arch. Under this multi-line quota share agreement, TICNY will cede 17.5% on a quota share certain brokerage commercial automobile liability, brokerage commercial multi-peril property, brokerage commercial multi-peril liability and brokerage other liability (mono line liability) business. The agreement covers losses occurring on or after July 1, 2013 for policies in-force as at June 30, 2013 and policies written or renewed from July 1, 2013 to December 31, 2013. The agreement has a special termination clause whereby either party may terminate the agreement upon the occurrence of certain circumstances, including an A.M. Best financial strength rating downgrade to below A-. As noted below, A.M. Best downgraded Tower’s financial strength rating to B++. Neither party has provided notice to terminate the agreement.
	The second agreement was between TICNY, on its behalf and on behalf of each of its pool participants, and Hannover. Under this multi-line quota share agreement, TICNY will cede 14% on a quota share certain brokerage commercial automobile liability, brokerage commercial multi-peril property, brokerage commercial multi-peril liability, brokerage other liability (mono line liability) and brokerage workers’ compensation business. The agreement covers losses occurring on or after July 1, 2013 for policies in-force as at June 30, 2013 and policies written or renewed from July 1, 2013 to December 31, 2013. The agreement has a special termination clause whereby either party may terminate the agreement upon the occurrence of certain circumstances, including an A.M. Best financial strength rating downgrade to below A-. As noted below, A.M. Best downgraded Tower’s financial strength rating to B++. Neither party has provided notice to terminate the agreement.
	The third reinsurance arrangement with Southport Re consisted of two separate reinsurance agreements with TICNY, on its behalf and on behalf of each of its pool participants, and a third reinsurance agreement with Tower Reinsurance, Ltd. (“TRL”). Under the first of the agreements with TICNY, TICNY ceded to Southport Re a 30% quota share of its workers’ compensation and employer’s liability business. The agreement covers losses occurring on or after July 1, 2013 for policies in force at June 30, 2013 and policies written or renewed during the term of the agreement. Under the second of these agreements with TICNY, an aggregate excess of loss agreement, Southport Re assumed a portion of the losses incurred by TICNY on its workers’ compensation and employer’s liability business between January 1, 2011 and June 30, 2013, but paid by TICNY on or after June 1, 2013. Finally, TRL, a wholly-owned Bermuda-domiciled reinsurance subsidiary of Tower, also entered into an aggregate excess of loss agreement with Southport Re, in which Southport Re assumed a portion of the losses incurred by TRL on its assumed workers’ compensation and employer’s liability business between January 1, 2011 and June 30, 2013, but paid by TRL on or after June 1, 2013. The agreement has a special termination clause whereby either party may terminate the agreement upon the occurrence of certain circumstances, including an A.M. Best financial strength rating downgrade to below A-. As noted below, A.M. Best downgraded Tower’s financial strength rating to B++. Neither party has provided notice to terminate the agreement.
	A.M. Best, Fitch and Demotech Downgrade the Company’s Financial Strength and Issuer Credit Ratings
	On October 7, 2013, Fitch downgraded Tower’s Issuer Default Rating from “BBB” to “B” and Tower’s insurance subsidiaries’ Insurer Financial Strength ratings from “A-” to “BB”. The ratings will continue to remain on negative watch until Tower’s exploration of strategic alternatives.
	On October 8, 2013, A.M. Best, lowered Tower’s issuer credit, as well as its financial strength ratings, from “A-” (Excellent) to “B++” (Good). The ratings remain under review with negative implications pending further discussions between A.M. Best and Tower’s management.
	On October 7, 2013, Demotech lowered its rating on TICNY and three other U.S. based insurance subsidiaries (Kodiak Insurance Company, Massachusetts Homeland Insurance Company and York Insurance Company of Maine) from A’ (A prime) to A (A exceptional). In addition, Demotech removed its previous A’ (A prime) rating on six other U.S. based insurance subsidiaries (CastlePoint Florida Insurance Company, CastlePoint Insurance Company, CastlePoint National Insurance Company, Hermitage Insurance Company, North East Insurance Company and Preserver Insurance Company). Demotech also affirmed its A ratings on Adirondack Insurance Exchange, New Jersey Skylands Insurance Association, New Jersey Skylands Insurance Company, and Mountain Valley Indemnity Company.
	Management expects these rating actions, in combination with other items that have impacted the Company in the second quarter of 2013, to result in a decrease in the amount of premiums the insurance subsidiaries are able to write. The net written premiums in the Commercial Insurance segment were $169.1 million and $343.6 million for the three and six months ended June 30, 2013. The net written premiums in the Specialty Insurance and Reinsurance segment were $103.7 million and $306.6 million for the three and six months ended June 30, 2013. Business written through program underwriting agents and assumed reinsurance generally requires an A.M. Best rating of A- or greater.
	Regulation
	Two insurance subsidiaries that do not constitute “significant subsidiaries” of the Company under Regulation S-X are in discussions with the insurance regulatory authority in their state of domicile with respect to the imposition of restrictions on the operation of their businesses. These discussions may result in such subsidiaries’ agreeing to provide the regulatory authority with increased information with respect to their business, operations and financial condition, as well as limitations on payments and transactions outside the ordinary course of business and material changes in their management and related matters.
	Share Repurchase Program
	As part of Tower’s capital management strategy, Tower’s Board of Directors approved on May 7, 2013 a $50 million share repurchase program. Purchases will be made from time to time in the open market or in privately negotiated transactions in accordance with applicable laws and regulations.
	TGI’s previously approved share repurchase program was terminated as a result of the Merger Transaction.
	Credit Facility Amendments
	TGI amended its credit facility on October 11, 2013, and agreed to several restrictions under the credit facility, including:
	In addition, the following financial covenants are included in the credit facility:
		•	To not enter into any new borrowings under the credit facility;
		•	To pledge to the lending banks any proceeds of new capital raises by TGI or TGIL until such time as the credit facility is paid in full;
		•	To pledge to the lending banks proceeds from any sales of assets occurring at TGI; and
		•	To submit to regulatory authorities, as appropriate, a request for approval to pledge the capital stock of the U.S. based and Bermuda based insurance subsidiaries.
		•	Minimum consolidated Net Worth is the greater of $553,400,000 or 90% of Consolidated Net Worth as of June 30, 2013; this covenant increases by 90% of any new capital plus 50% of Net Income above $20,000,000;
		•	Debt to capitalization ratio limit of 46%;
		•	Minimum risk based capital ratio of 175% at December 31, 2013 for Tower Insurance Company of New York and any other insurance subsidiary that exceeds 10% of the consolidated statutory surplus of all insurance subsidiaries;
		•	Bermuda enhanced minimum capital requirement of 150% for CastlePoint Re at December 31, 2013 and 110% for TRL;
		•	Minimum statutory surplus for all insurance companies of the greater of $419,000,000 or 85% of Combined Surplus at June 30, 2013; and
		•	Independent accountant’s annual report shall not be subject to any “going concern” or like qualification or exception. This financial covenant will remain in effect for the year ending December 31, 2013. Although the independent accountant’s report on the consolidated financial statements for the years ended December 31, 2010, 2011 and 2012 contains a “going concern” explanatory paragraph, on November 14, 2013, the Company received a waiver from the lenders under the credit facility in respect of such “going concern” paragraph.
	Tower currently is in compliance with all covenants of the credit facility.
	The credit facility matures on May 30, 2014, at which point any unpaid balance becomes due.
	Legal Proceedings
	On August 20, 2013, Robert P. Lang, a purported shareholder of Tower Group International Ltd. (“Tower”), filed a purported class action complaint (the “Lang Complaint”) against Tower and certain of its officers in the United States District Court for the Southern District of New York. The Lang Complaint alleges that Tower and certain of its officers violated federal securities laws and seeks unspecified damages. On September 3, 2013, a second purported shareholder class action complaint was filed by Dennis Feighay, another purported Tower shareholder, containing similar allegations to those set forth in the Lang Complaint (the “Feighay Complaint”). On October 4, 2013, a third complaint was filed by Sanju Sharma (the “Sharma Complaint”). The Sharma Complaint names as defendants Tower and certain of its officers, and purports to be asserted on behalf of a plaintiff class who purchased Tower stock between May 10, 2011 and September 17, 2013. On October 18, 2013, an amended complaint was filed in the Sharma case (the “Sharma Amended Complaint”). The Sharma Amended Complaint alleges additional false and misleading statements, and purports to be asserted on behalf of a plaintiff class who purchased Tower stock between March 1, 2011 and October 7, 2013. On October 21, 2013, a number of motions were filed seeking to consolidate the shareholder class actions into one matter and for appointment of a lead plaintiff. The Company believes that it is not probable that the Lang and Feighay Complaints and the Sharma Amended Complaint will result in a loss, and that the amount of any loss cannot reasonably be estimated.
	On October 18, 2013, Cinium Financial Services Corporation (“Cinium”) and certain other affiliated parties (collectively, “Plaintiffs”) filed a complaint against, among others, Tower, CastlePoint Insurance Company (“CastlePoint”), an indirect wholly owned subsidiary of Tower, and certain officers of Tower (the “Cinium Complaint”) in New York State Supreme Court. CastlePoint is a party to a Securityholders’ Agreement, dated as of June 14, 2012 (the “Securityholders’ Agreement”), among certain parties including Plaintiffs, and is also the holder of a senior note issued by Cinium dated May 15, 2012 that is convertible into shares of Cinium common stock (the “Senior Note”). Plaintiffs seek, among other things, (i) a declaratory judgment that CastlePoint has no right to exercise any control over Cinium under the Securityholders’ Agreement or to convert the Senior Note without prior regulatory approval; (ii) rescission of the Senior Note and Securityholders’ Agreement based on alleged fraudulent misrepresentations by Tower at the time these agreements were entered into; and (iii) damages of $150 million for alleged breach of fiduciary duties to Cinium and its shareholders by certain directors. The Company believes that it is not probable that the Cinium Complaint will result in a loss, and that the amount of any loss cannot reasonably be estimated.

Accounting_Policies_and_Basis_1

Accounting Policies and Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2013
Basis of Presentation	'
	Basis of Presentation
	The Merger Transaction was accounted for as a reverse acquisition, under which TGI was identified and treated as the accounting acquirer. As such, the Company’s unaudited consolidated financial statements include the accounts and operations of TGI and its insurance subsidiaries, managing general agencies and management companies as its historical financial statements, with the results of Tower Group International, Ltd., as accounting acquiree, being included from March 13, 2013, the effective date of the Merger Transaction. The unaudited consolidated financial statements also include the accounts of Adirondack Insurance Exchange, a New York reciprocal insurer, and New Jersey Skylands Insurance Association, a New Jersey reciprocal insurer (together, the “Reciprocal Exchanges”). The Company does not own the Reciprocal Exchanges but manages their business operations through its wholly-owned management companies.
	The accompanying unaudited consolidated financial statements included in this report have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial information and with the instructions to Securities and Exchange Commission (“SEC”) Form 10-Q/A and Article 10 of SEC Regulation S-X. The principles for condensed interim financial information do not require the inclusion of all the information and footnotes required by GAAP for complete financial statements. Therefore, these financial statements should be read in conjunction with TGI’s consolidated financial statements as of and for the year ended December 31, 2012 and notes thereto included in TGI’s Amendment No. 2 to the Annual Report on Form 10-K for the year ended December 31, 2012. The accompanying consolidated financial statements have not been audited by an independent registered public accounting firm in accordance with standards of the Public Company Accounting Oversight Board (United States) but, in the opinion of management, such financial statements include all adjustments, consisting only of normal recurring adjustments, necessary for a fair statement of the Company’s financial position, results of operations and cash flows. All intercompany transactions have been eliminated in consolidation.
Use of Estimates	'
	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
	Moreover, the results of operations for the three months ended March 31, 2013 may not be indicative of the results that may be expected for the year ending December 31, 2013.
Intercompany transactions	'
	Intercompany transactions
	In the first quarter 2012, the Company transferred a licensed insurance subsidiary shell to the Reciprocal Exchanges and received cash for its statutory book value. At the date of the transfer, the Company’s GAAP carrying basis in this subsidiary exceeded the statutory book value and the transfer resulted in a loss to the Company of $1.8 million. Since this was a non-recurring transaction between entities under common control, assets were transferred at historical book value. The difference in the consideration paid and the book value of the assets transferred was treated as an adjustment to equity. This transaction had no effect on consolidated stockholders’ equity.
Reclassifications and Adjustments	'
	Reclassifications and Adjustments
	Since the Company accounted for the Merger Transaction as a reverse acquisition and recapitalization, it has retroactively restated Common Stock, Treasury Stock and Paid-in-Capital accounts and earnings per share for periods prior to the Merger Transaction to reflect the historical capitalization of TGI, adjusted for the 1.1330 conversion ratio as discussed in “Note 4 – Merger Transaction”. Certain other reclassifications have also been made to prior years’ financial information to conform to the current year presentation. Refer to Item 2. Management’s Discussion and Analysis, the Consolidated Results of Operations discussion for out-of-period adjustments recorded in the three months ended March 31, 2013.
	The table below reflects the previously reported and restated stockholders’ equity accounts resulting from the Merger Transaction:
		Merger			Revised
	($ in thousands, except per share amounts)	Transaction			Amount
	As of December 31, 2012
	Common stock	$	469		$	530
	Treasury stock		(181,435	)		(181,435	)
	Paid-in-capital		780,097			780,036
	For the three-months ended March 31, 2012
	Earnings (Loss) per Share:
	Basic	$	0.49		$	0.43
	Diluted		0.49			0.43
	Weighted average common shares outstanding
	Basic		39,233			43,326
	Diluted		39,307			43,411
	See “Note 15 – Earnings (loss) per Share” for the computation of the earnings per share.
Accounting Pronouncements	'
	Accounting Pronouncements
	Accounting guidance adopted in 2012 and 2013
	In July 2012, the Financial Accounting Standards Board (“FASB”) issued amended guidance on testing indefinite-lived intangible assets for impairment. This guidance is intended to reduce the cost and complexity of the annual impairment test by allowing an entity to utilize more qualitative factors and is effective for annual and interim tests performed for fiscal years beginning after September 15, 2012. The Company will consider this guidance in connection with the annual impairment testing of its indefinite-lived intangible assets, which is performed annually in the fourth quarter based on data as of September 30. This guidance does not affect existing guidance on recognition or measurement of impairment losses on indefinite-lived intangible assets, and as such it will not affect the Company’s financial position, results of operations or cash flows.
	In February 2013, the FASB issued amended guidance on the presentation of amounts reclassified out of accumulated other comprehensive income in one place, either on the face of the income statement or in the footnotes to the financial statements. The Company adopted this guidance effective January 1, 2013 on a prospective basis as prescribed by the amended guidance. As all of the information that this guidance requires to be disclosed is already presented elsewhere in the Company’s financial statements under existing GAAP, and it does not affect the classification, recognition or measurement of items within other comprehensive income, the adoption will not affect the Company’s financial position, results of operations or cash flows.
Accounting for the Merger Transaction	'
	Accounting for the Merger Transaction
	The Company has accounted for the Merger Transaction as a reverse acquisition in which TGI, the legal acquiree, was identified and treated as the accounting acquirer and Tower Group International, Ltd., the legal acquirer, was identified and treated as the accounting acquiree. The identification of the accounting acquirer and acquiree in the Merger Transaction was primarily based on the fact that immediately following the close of the Merger Transaction there was a change in control of the Company with TGI designees to the Company’s Board of Directors comprising all of its directors and TGI’s former senior management comprising the Company’s entire senior management team. In accordance with accounting guidance for reverse acquisitions, the unaudited consolidated financial statements of the Company following the Merger Transaction have been issued under the name of the Company, as the legal parent, but reflect a continuation of the financial statements of TGI, as the accounting acquirer, with one exception, which was the retroactive adjustment of TGI’s historical legal capital to reflect the transaction as a recapitalization of TGI’s historical capital accounts. On the effective date of the Merger Transaction, the assets and liabilities of Tower Group International, Ltd. were accounted for under the acquisition method, under which they have been reflected at their respective acquisition date fair values.
	Prior to the Merger Transaction, Canopius Bermuda restructured its insurance operations as contemplated in the Master Transaction Agreement. This restructuring occurred primarily through the execution of retrocession agreements with an indirectly wholly-owned subsidiary of Canopius Group to retrocede a percentage of Lloyd’s of London Syndicate 4444 (“Syndicate 4444”) business for the Year of Account (“YOA”) 2012, YOA 2011 and prior years, which Canopius Bermuda assumed from Canopius Group. Syndicate 4444 is an insurance syndicate managed by Canopius Group. The Company will account for these retrocession agreements in accordance with prospective accounting treatment, and will report the assumed and ceded assets and liabilities on a gross basis on the consolidated balance sheet.
	In addition, pursuant to the terms of the Master Transaction Agreement, prior to the Merger Transaction, TGI entered into a commutation agreement whereby the TGI commuted Syndicate 4444 YOA 2012 and YOA 2011 business TGI previously reinsured from Canopius Group. There was no gain or loss recognized on this commutation.
Variable Interest Entities	'
	The Company determined that each of the Reciprocal Exchanges qualifies as a VIE and that the Company is the primary beneficiary as it has both the power to direct the activities of the Reciprocal Exchanges that most significantly impact their economic performance and the risk of economic loss through its ownership of the surplus notes. Accordingly, the Company consolidates these Reciprocal Exchanges and eliminates all intercompany balances and transactions with Tower.
Impairment Review	'
	Impairment Review
	Management regularly reviews the Company’s fixed-maturity and equity security portfolios in accordance with its impairment policy to evaluate the necessity of recording impairment losses for OTTI. The determination of OTTI is a subjective process and different judgments and assumptions could affect the timing of loss realization.
	Management, in conjunction with its outside portfolio managers, analyzes its non-agency residential mortgage-backed securities (“RMBS”) using default loss models based on the performance of the underlying loans. Performance metrics include delinquencies, defaults, foreclosures, anticipated cash flow prepayments and cumulative losses incurred. The expected losses for a mortgage pool are compared to the break-even loss, which represents the point at which the Company’s tranche begins to experience losses.
	The commercial mortgage-backed securities (“CMBS”) holdings are evaluated using analytical techniques and various metrics including the level of subordination, debt-service-coverage ratios, loan-to-value ratios, delinquencies, defaults and foreclosures.
	For the non-structured fixed-maturity securities (U.S. Treasury and Agency securities, municipal bonds, and corporate debt), unrealized losses are reviewed to determine whether full recovery of principal and interest will be received. The estimate of expected cash flows is determined by projecting a recovery value and a recovery time frame and assessing whether further principal and interest will be received. The determination of recovery value incorporates an issuer valuation assumption utilizing one or a combination of valuation methods as deemed appropriate by management. The present value of the cash flows is determined by applying the effective yield of the security at the date of acquisition (or the most recent implied rate used to accrete the security if the implied rate has changed as a result of a previous impairment) and an estimated recovery time frame. For securities for which the issuer is financially troubled but not in bankruptcy, that time frame is generally longer. Included in the present value calculation are expected principal and interest payments; however, for securities for which the issuer is classified as bankrupt or in default, the present value calculation assumes no interest payments and a single recovery amount. In situations for which a present value of cash flows cannot be estimated, a write-down to fair value is recorded.
	In estimating the recovery value, significant judgment is involved in the development of assumptions relating to a number of factors related to the issuer including, but not limited to, revenue, margin and earnings projections, the likely market or liquidation values of assets, potential additional debt to be incurred pre- or post- bankruptcy/restructuring, the ability to shift existing or new debt to different priority layers, the amount of restructuring/bankruptcy expenses, the size and priority of unfunded pension obligations, litigation or other contingent claims, the treatment of intercompany claims and the likely outcome with respect to inter-creditor conflicts.
	The evaluation of equity securities includes management’s intent and ability to hold the security to recovery. Management will record OTTI in those situations where it does not intend to hold the security to recovery or if the security is not expected to recover in value in the near term.
Fair Value Measurements	'
	GAAP establishes a three-level hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). If the inputs used to measure the assets or liabilities fall within different levels of the hierarchy, the classification is based on the lowest level input that is significant to the fair value measurement of the asset or liability. Classification of assets and liabilities within the hierarchy considers the markets in which the assets and liabilities are traded, including during periods of market disruption, and the reliability and transparency of the assumptions used to determine fair value. The hierarchy requires the use of observable market data when available. The levels of the hierarchy are as follows:
	Level 1 — Inputs to the valuation methodology are quoted prices (unadjusted) for identical assets or liabilities traded in active markets. Included are those equity securities that are traded on active exchanges, such as the NASDAQ Global Select Market.
	Level 2 — Inputs to the valuation methodology include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability and market-corroborated inputs. Included are investments in U.S. Treasury and Agency securities and, together with municipal bonds, corporate debt securities, commercial mortgages, residential mortgage-backed securities and asset-backed securities. Additionally, interest-rate swap contracts utilize Level 2 inputs in deriving fair values.
	Level 3 — Inputs to the valuation methodology are unobservable in the market for the asset or liability and are significant to the fair value measurement. Material assumptions and factors considered in pricing investment securities may include projected cash flows, collateral performance including delinquencies, defaults and recoveries, and any market clearing activity or liquidity circumstances in the security or similar securities that may have occurred since the prior pricing period.
Earnings Per Share	'
	Undistributed net earnings (net income less dividends declared during the period) are allocated to both common stock and unvested share-based payment awards (“unvested restricted stock”). Because the common shareholders and unvested restricted stock holders share in dividends on a 1:1 basis, the earnings per share on undistributed earnings is equivalent, however, undistributed losses are allocated only to common stock holders. Undistributed earnings are allocated to all outstanding share-based payment awards, including those for which the requisite service period is not expected to be rendered.
Segment Information	'
	The accounting policies of the segments are the same as those described in TGI’s summary of significant accounting policies in its Amendment No. 2 to the Annual Report on Form 10-K for the year ended December 31, 2012.
	The Company is currently re-evaluating its internal reporting structure due to the recently completed Merger Transaction, the result of which may require changes to its segment reporting. Until this re-evaluation is completed, the Company’s operations, including those acquired in connection with the Merger Transaction, continue to be reported within its three business segments, Commercial Insurance, Personal Insurance and Insurance Services.
	The Personal Insurance segment includes revenues and expenses associated with the Reciprocal Exchanges, including fees paid to Tower for underwriting, claims, investment management and other services provided pursuant to management services agreements with the Reciprocal Exchanges. The Insurance Services segment reports revenues earned by Tower from the Reciprocal Exchanges as management fee income, which is calculated as a percentage of the Reciprocal Exchanges’ gross written premiums. The effects of these management services agreements between Tower and the Reciprocal Exchanges are eliminated in consolidation to derive consolidated net income. However, the management fee income is reported in net income attributable to Tower Group International, Ltd. and included in basic and diluted earnings per share.
	Segment performance is evaluated based on segment profit, which excludes investment income, realized gains and losses, interest expense, income taxes and incidental corporate expenses. Assets, other than intangibles and goodwill, are not allocated to segments because investments and assets other than intangible assets and goodwill are considered in total by management for decision-making purposes.

Restatement_and_Revision_of_Pr1

Restatement and Revision of Previously Issued Financial Statements (Tables)	3 Months Ended
	Mar. 31, 2013
Effect of Revisions and Restatements on Consolidated Balance Sheets	'
	The effect of the revisions and restatements on the consolidated balance sheets are presented in the table below:
		As of March 31, 2013									December 31, 2012
		As						Effect			As						Effect
		Previously						of			Previously						of
	($ in thousands, except par value and share amounts)	Filed			Revised			Adjustments			Reported			Restated			Adjustments
	Assets
	Total investments		2,638,543			2,638,242			(301	)		2,554,505			2,553,505			(1,000	)
	Cash and cash equivalents		229,946			229,946			—			100,293			102,269			1,976
	Investment income receivable		29,490			29,490			—			25,332			25,332			—
	Investment in uncolsolidated affiliate		68,411			68,411			—			70,830			71,894			1,064
	Premiums receivable		418,161			408,289			(9,872	)		422,112			412,045			(10,067	)
	Reinsurance recoverable on paid losses		49,668			49,668			—			17,609			17,609			—
	Reinsurance recoverable on unpaid losses		887,188			850,188			(37,000	)		496,192			459,457			(36,735	)
	Prepaid reinsurance premiums		234,181			234,181			—			63,923			63,923			—
	Deferred acquisition costs, net		199,137			199,092			(45	)		180,941			181,198			257
	Intangible assets		104,550			104,550			—			106,768			106,768			—
	Goodwill		269,589			269,589			—			241,458			241,458			—
	Funds held by reinsured companies		829,659			829,659			—			137,545			137,545			—
	Other assets		430,108			436,439			6,331			331,506			338,769			7,263
	Total Assets	$	6,388,631		$	6,347,744		$	(40,887	)		4,749,014		$	4,711,772		$	(37,242	)
	Liabilities
	Loss and loss adjustment expenses		2,429,857			2,431,250			1,393			1,895,073		$	1,895,679		$	606
	Unearned premium		1,123,022			1,122,428			(594	)		920,859			921,271			412
	Reinsurance balances payable		39,227			39,227			—			40,569			40,569			—
	Funds held under reinsurance agreements		634,080			634,080			—			98,581			98,581			—
	Other liabilities		463,303			464,325			1,022			292,239			296,960			4,721
	Deferred income taxes		29,677			19,842			(9,835	)		36,464			24,763			(11,701	)
	Debt		450,470			450,470			—			449,731			449,731			—
	Total liabilities	$	5,169,636			5,161,622			(8,014	)		3,733,516			3,727,554			(5,962	)
	Contingencies		—			—			—			—			—			—
	Stockholders’ equity
	Common stock		574			574			—			530			530			—
	Treasury stock		—			—			—			(181,435	)		(181,435	)		—
	Paid-in-capital		812,156			812,156			—			780,036			780,036			—
	Accumulated other comprehensive income		78,377			78,311			(66	)		83,406			82,756			(650	)
	Retained earnings		306,192			273,887			(32,305	)		298,299			268,171			(30,128	)
	Tower Group International, Ltd. stockholders’ equity		1,197,299			1,164,928			(32,371	)		980,836			950,058			(30,778	)
	Noncontrolling interests		21,696			21,194			(502	)		34,662			34,160			(502	)
	Total stockholders’ equity		1,218,995			1,186,122			(32,873	)		1,015,498			984,218			(31,280	)
	Total liabilities and stockholders’ equity		6,388,631		$	6,347,744		$	(40,887	)		4,749,014		$	4,711,772		$	(37,242	)
Effect of Revision on Consolidated Statement of Operations and Comprehensive Income	'
	The effect of the revision on the consolidated statements of operations and comprehensive income are presented in the table below:
		Three Months Ended March 31, 2013
		As						Effect
		Previously						of
	(in thousands, except per share amounts)	Filed			Revised			Adjustments
	Revenues
	Net premiums earned	$	420,486		$	421,886		$	1,400
	Ceding commission revenue		14,151			14,151			—
	Insurance services revenue		128			128			—
	Policy billing fees		3,150			3,150			—
	Net investment income		30,317			30,317			—
	Other-than-temporary impairments		(489	)		(689	)		(200	)
	Other net realized investment gains		7,540			7,540			—
	Total net realized gains (losses)		7,051			6,851			(200	)
	Total revenues		475,283			476,483			1,200
	Expenses
	Loss and loss adjustment expenses		274,680			275,732			1,052
	Direct and ceding commission expense		88,398			89,576			1,178
	Other operating expenses		84,393			84,393			—
	Acquisition-related transaction costs		19,056			19,056			—
	Interest expense		7,808			7,808			—
	Total expenses		474,335			476,565			2,230
	Other income (expense)
	Earnings in Canopius Group		1,192			128			(1,064	)
	Income before taxes		2,140			46			(2,094	)
	Income tax expense (benefit)		(1,673	)		(1,590	)		83
	Net Income	$	3,813		$	1,636		$	(2,177	)
	Less: Net income (loss) attributable to Noncontrolling interests		(11,281	)		(11,281	)		—
	Net income attributable to Tower Group International, Ltd.	$	15,094		$	12,917		$	(2,177	)
	Earnings per share attributable to Tower Group International, Ltd. stockholders:
	Basic	$	0.33		$	0.28		$	(0.05	)
	Diluted	$	0.33		$	0.28		$	(0.05	)
	Comprehensive Income (loss)	$	(2,901	)	$	(4,494	)	$	(1,593	)
	Less: Comprehensive income attributable to Noncontrolling interests		(12,966	)		(12,966	)		—
	Comprehensive income (loss) attributable to Tower Group International, Ltd.	$	10,065		$	8,472		$	(1,593	)
Effect of Revision on Consolidated Statement of Cash Flows	'
	The effect of the revision on the consolidated statement of cash flows:
		Three Months Ended March 31, 2013
	($ in thousands)	As			Revised			Effect
		Previously						of
		Filed						Adjustments
	Cash flows provided by (used in) operating activities:
	Net cash flows provided by (used in) operations	$	(53,107	)	$	(55,083	)	$	(1,976	)
	Net cash flows provided by (used in) investing activities		193,320			193,320			—
	Net cash flows provided by (used in) financing activities		(10,560	)		(10,560	)		—
	Increase (decrease) in cash and cash equivalents		129,653			127,677			(1,976	)
	Cash and cash equivalents, beginning of period		100,293			102,269			1,976
	Cash and cash equivalents, end of period	$	229,946		$	229,946		$	—

Accounting_Policies_and_Basis_2

Accounting Policies and Basis of Presentation (Tables)	3 Months Ended
	Mar. 31, 2013
Reflects the Previously Reported and Restated Stockholders' Equity Accounts Resulting from the Merger Transaction	'
	The table below reflects the previously reported and restated stockholders’ equity accounts resulting from the Merger Transaction:
		Merger			Revised
	($ in thousands, except per share amounts)	Transaction			Amount
	As of December 31, 2012
	Common stock	$	469		$	530
	Treasury stock		(181,435	)		(181,435	)
	Paid-in-capital		780,097			780,036
	For the three-months ended March 31, 2012
	Earnings (Loss) per Share:
	Basic	$	0.49		$	0.43
	Diluted		0.49			0.43
	Weighted average common shares outstanding
	Basic		39,233			43,326
	Diluted		39,307			43,411

Merger_Transaction_Tables

Merger Transaction (Tables)	3 Months Ended
	Mar. 31, 2013
Fair Values of the Respective Assets Acquired and Liabilities Assumed	'
	The following provides details of the purchase consideration, the fair values of the respective assets acquired and liabilities assumed and the resulting amount of goodwill recorded in connection with the Merger Transaction.
	($ in thousands)
	Assets
	Cash and cash equivalents	$	134,741
	Investments		26,485
	Reinsurance recoverables		468,727
	Prepaid reinsurance		152,431
	Funds held by reinsured companies		698,819
	Other assets		75,219
	Liabilities
	Loss and loss adjustment expenses		630,613
	Unearned premiums		169,963
	Funds held under reinsurance agreements		560,714
	Other liabilities		15,916
	Net assets acquired	$	179,216
	Purchase Consideration		207,347
	Goodwill	$	28,131
Preliminary Purchase Consideration	'
	The purchase consideration was determined based on the total consideration received by Canopius Group for its sale of 100% of its equity ownership of Canopius Bermuda, and the proceeds received for the issuance and exercise of the Merger Option from TGI.
	(in thousands)
	Consideration received by Canopius Group from the third party sale		205,863
	Fair value of Merger Option received in connection with TGI’s investment in Canopius Group		484
	Exercise price of Merger Right received from TGI upon exercise		1,000
	Total preliminary purchase consideration	$	207,347
Pro Forma Financial Information	'
	The following unaudited pro forma financial information presents the consolidated revenues and net income of the Company for the three months ended March 31, 2013 and 2012, as if the Merger Transaction had been completed as of January 1, 2012.
		Three Months Ended
		March 31,
	($ in thousands)	2013		2012
		(revised)
	Revenues	$	479,627	$	469,367
	Net Income		20,628		26,961

Investments_Tables

Investments (Tables)	3 Months Ended
	Mar. 31, 2013
Summary of Cost or Amortized Cost and Fair Value of Investments in Fixed Maturity and Equity Securities, Gross Unrealized Gains and Losses, and Other-Than-Temporary Impairment Losses	'
	The cost or amortized cost and fair value of the Company’s investments in fixed maturity and equity securities, gross unrealized gains and losses, and other-than-temporary impairment losses (“OTTI”) as of March 31, 2013 and December 31, 2012 are summarized as follows:
	($ in thousands)		Cost or			Gross			Gross			Fair			Unrealized
			Amortized			Unrealized			Unrealized			Value			OTTI
			Cost			Gains			Losses						Losses (1)
	March 31, 2013, as revised
	U.S. Treasury securities		$	315,281		$	1,486		$	(35	)	$	316,732		$	—
	U.S. Agency securities			105,081			4,056			(132	)		109,005			—
	Municipal bonds			642,188			47,034			(291	)		688,931			—
	Corporate and other bonds
	Finance			222,601			20,881			(728	)		242,754			—
	Industrial			390,344			23,408			(807	)		412,945			—
	Utilities			60,134			2,798			(469	)		62,463			—
	Commercial mortgage-backed securities			207,944			28,337			(360	)		235,921			(121	)
	Residential mortgage-backed securities
	Agency backed securities			253,395			9,478			(674	)		262,199			—
	Non-agency backed securities			37,257			4,394			(27	)		41,624			—
	Asset-backed securities			33,851			1,346			—			35,197			—
	Total fixed-maturity securities			2,268,076			143,218			(3,523	)		2,407,771			(121	)
	Preferred stocks, principally financial sector			28,879			632			(334	)		29,177			—
	Common stocks, principally financial and industrial sectors			108,947			5,985			(1,401	)		113,531			—
	Short-term investments			28,485			350			(13	)		28,822			—
	Total, March 31, 2013, as revised		$	2,434,387		$	150,185		$	(5,271	)	$	2,579,301		$	(121	)
	Tower		$	2,175,856		$	133,986		$	(4,419	)	$	2,305,423		$	(121	)
	Reciprocal Exchanges			258,531			16,199			(852	)		273,878			—
	Total, March 31, 2013, as revised		$	2,434,387		$	150,185		$	(5,271	)	$	2,579,301		$	(121	)
	December 31, 2012, as restated
	U.S. Treasury securities		$	183,462		$	1,500		$	(13	)	$	184,949		$	—
	U.S. Agency securities			98,502			4,351			(76	)		102,777			—
	Municipal bonds			633,373			52,914			(244	)		686,043			—
	Corporate and other bonds
	Finance			233,849			21,293			(1,095	)		254,047			—
	Industrial			412,465			26,556			(868	)		438,153			—
	Utilities			51,698			2,958			(191	)		54,465			—
	Commercial mortgage-backed securities			211,819			30,375			(141	)		242,053			—
	Residential mortgage-backed securities
	Agency backed securities			283,652			12,326			(262	)		295,716			—
	Non-agency backed securities			38,615			3,575			(34	)		42,156			(6	)
	Asset-backed securities			42,751			1,615			(14	)		44,352			—
	Total fixed-maturity securities			2,190,186			157,463			(2,938	)		2,344,711			(6	)
	Preferred stocks, principally financial sector			31,272			730			(481	)		31,521			—
	Common stocks, principally industrial and financial sectors			118,076			953			(4,292	)		114,737			—
	Short-term investments			4,749			1			—			4,750			—
	Total, December 31, 2012, as restated		$	2,344,283		$	159,147		$	(7,711	)	$	2,495,719		$	(6	)
	Tower		$	2,075,189		$	141,614		$	(7,210	)	$	2,209,593		$	(6	)
	Reciprocal Exchanges			269,094			17,533			(501	)		286,126			—
	Total, December 31, 2012, as restated		$	2,344,283		$	159,147		$	(7,711	)	$	2,495,719		$	(6	)
	-1	Represents the gross unrealized loss on other-than-temporarily impaired securities recognized in accumulated other comprehensive income (loss).
Summary of Major Categories of Net Investment Income	'
	Major categories of net investment income are summarized as follows:
			Three Months Ended
			March 31,
	($ in thousands)		2013			2012
	Income
	Fixed-maturity securities		$	20,973		$	25,412
	Equity securities			6,484			7,636
	Cash and cash equivalents			51			290
	Other invested assets			4,256			1,925
	Other			327			57
	Total			32,091			35,320
	Expenses
	Investment expenses			(1,774	)		(1,377	)
	Net investment income		$	30,317		$	33,943
	Tower			29,980			32,257
	Reciprocal Exchanges			2,380			3,349
	Elimination of interest on Reciprocal Exchange surplus notes			(2,043	)		(1,663	)
	Net investment income		$	30,317		$	33,943
Summary of Gross Realized Gains, Losses and Impairment Write-Downs on Investments	'
	Gross realized gains, losses and impairment write-downs on investments are summarized as follows:
			Three Months Ended
			March 31,
	($ in thousands)		2013			2012
			(revised)
	Fixed-maturity securities
	Gross realized gains		$	7,364		$	13,991
	Gross realized losses			(190	)		(2,858	)
				7,174			11,133
	Equity securities
	Gross realized gains			4,236			1,546
	Gross realized losses			(4,813	)		(6,375	)
				(577	)		(4,829	)
	Other
	Gross realized gains			1,755			—
	Gross realized losses			(812	)		—
				943			—
	Net realized gains (losses) on investments			7,540			6,304
	Other-than-temporary impairment losses:
	Fixed-maturity securities			(164	)		(117	)
	Equity securities			(525	)		(2,859	)
	Total other-than-temporary impairment losses recognized in earnings			(689	)		(2,976	)
	Total net realized investment gains (losses)		$	6,851		$	3,328
	Tower		$	6,233		$	1,138
	Reciprocal Exchanges			618			2,190
	Total net realized investment gains (losses)		$	6,851		$	3,328
Amount of Fixed-Maturity and Equity Securities that were Other-Than-Temporary Impairment	'
	The following table shows the fixed-maturity and equity securities OTTI amounts for the three months ended March 31, 2013 and 2012:
			Three Months Ended
			March 31,
	($ in thousands)		2013			2012
			(revised)
	Corporate and other bonds		$	—		$	(89	)
	Commercial mortgage-backed securities			(24	)		—
	Residential mortgage-backed securities			(140	)		(28	)
	Equities			(525	)		(2,859	)
	Other-than-temporary-impairments			(689	)		(2,976	)
	Portion of loss recognized in accumulated other comprehensive income (loss)			—			—
	Impairment losses recognized in earnings		$	(689	)	$	(2,976	)
	Tower		$	(689	)	$	(2,976	)
	Reciprocal Exchanges			—			—
	Impairment losses recognized in earnings		$	(689	)	$	(2,976	)
Rollforward of Cumulative Amount of Other-Than-Temporary Impairment for Securities Still Held Showing Amounts that have been Included in Earnings on Pretax Basis	'
	The following table provides a rollforward of the cumulative amounts of credit OTTI for securities still held showing the amounts that have been included in earnings on a pretax basis for the three months ended March 31, 2013 and 2012:
			Three Months Ended
			March 31,
	($ in thousands)		2013			2012
			(revised)
	Balance, January 1,		$	4,492		$	12,666
	Additional credit losses recognized during the period, related to securities for which:
	No OTTI has been previously recognized			164			89
	OTTI has been previously recognized			—			28
	Reductions due to:
	Securities sold during the period (realized)			(140	)		(6,699	)
	Balance, March 31,		$	4,516		$	6,084
Information Regarding Invested Assets that were in Unrealized Loss Position	'
	The following table presents information regarding invested assets that were in an unrealized loss position at March 31, 2013 and December 31, 2012 by amount of time in a continuous unrealized loss position:
			Less than 12 Months						12 Months or Longer						Total
	($ in thousands)		Fair			Unrealized			Fair			Unrealized			Aggregate			Unrealized
			Value			Losses			Value			Losses			Fair Value			Losses
	March 31, 2013, as revised
	U.S. Treasury securities		$	190,145		$	(35	)	$	—		$	—		$	190,145		$	(35	)
	U.S. Agency securities			22,282			(132	)		—			—			22,282			(132	)
	Municipal bonds			24,848			(282	)		252			(9	)		25,100			(291	)
	Corporate and other bonds
	Finance			22,057			(728	)		—			—			22,057			(728	)
	Industrial			49,396			(805	)		348			(2	)		49,744			(807	)
	Utilities			25,245			(469	)		7			—			25,252			(469	)
	Commercial mortgage-backed securities			27,602			(360	)		—			—			27,602			(360	)
	Residential mortgage-backed securities
	Agency backed			63,720			(674	)		23			—			63,743			(674	)
	Non-agency backed			—			—			547			(27	)		547			(27	)
	Asset-backed securities			—			—			—			—			—			—
	Total fixed-maturity securities			425,295			(3,485	)		1,177			(38	)		426,472			(3,523	)
	Preferred stocks			5,169			(31	)		6,651			(303	)		11,820			(334	)
	Common stocks			41,600			(1,401	)		—			—			41,600			(1,401	)
	Short-term investments			26,822			(13	)		—			—			26,822			(13	)
	Total, March 31, 2013, as revised		$	498,886		$	(4,930	)	$	7,828		$	(341	)	$	506,714		$	(5,271	)
	Tower		$	442,293		$	(4,093	)	$	7,627		$	(326	)	$	449,920		$	(4,419	)
	Reciprocal Exchanges			56,593			(837	)		201			(15	)		56,794			(852	)
	Total, March 31, 2013, as revised		$	498,886		$	(4,930	)	$	7,828		$	(341	)	$	506,714		$	(5,271	)
	December 31, 2012, as restated
	U.S. Treasury securities		$	44,347		$	(13	)	$	—		$	—		$	44,347		$	(13	)
	U.S. Agency securities			22,345			(76	)		—			—			22,345			(76	)
	Municipal bonds			21,532			(235	)		251			(9	)		21,783			(244	)
	Corporate and other bonds
	Finance			16,853			(1,095	)		—			—			16,853			(1,095	)
	Industrial			53,576			(667	)		4,188			(201	)		57,764			(868	)
	Utilities			20,143			(191	)		7			—			20,150			(191	)
	Commercial mortgage-backed securities			23,223			(141	)		95			—			23,318			(141	)
	Residential mortgage-backed securities
	Agency backed			59,009			(261	)		25			(1	)		59,034			(262	)
	Non-agency backed			815			(6	)		588			(28	)		1,403			(34	)
	Asset-backed securities			1,499			(2	)		4,232			(12	)		5,731			(14	)
	Total fixed-maturity securities			263,342			(2,687	)		9,386			(251	)		272,728			(2,938	)
	Preferred stocks			9,716			(155	)		5,724			(326	)		15,440			(481	)
	Common stocks			55,560			(4,292	)		—			—			55,560			(4,292	)
	Total, December 31, 2012, as restated		$	328,618		$	(7,134	)	$	15,110		$	(577	)	$	343,728		$	(7,711	)
	Tower		$	270,609		$	(6,732	)	$	13,338		$	(478	)	$	283,947		$	(7,210	)
	Reciprocal Exchanges			58,009			(402	)		1,772			(99	)		59,781			(501	)
	Total, December 31, 2012, as restated		$	328,618		$	(7,134	)	$	15,110		$	(577	)	$	343,728		$	(7,711	)
Amortized Cost and Fair Value of Fixed-Maturity Portfolio by Contractual Time to Maturity	'
	The following table shows the amortized cost and fair value of the fixed-maturity portfolio by contractual time to maturity at March 31, 2013 and December 31, 2012:
			Tower						Reciprocal Exchanges						Total
	($ in thousands)		Amortized			Fair			Amortized			Fair			Amortized			Fair
			Cost			Value			Cost			Value			Cost			Value
	March 31, 2013, as revised
	Remaining Time to Maturity
	Less than one year		$	22,678		$	23,060		$	2,000		$	2,008		$	24,678		$	25,068
	One to five years			636,015			656,679			40,795			42,693			676,810			699,372
	Five to ten years			556,748			594,311			76,334			79,921			633,082			674,232
	More than 10 years			343,277			372,246			57,782			61,912			401,059			434,158
	Mortgage and asset-backed securities			453,578			490,511			78,869			84,430			532,447			574,941
	Total, March 31, 2013, as revised		$	2,012,296		$	2,136,807		$	255,780		$	270,964		$	2,268,076		$	2,407,771
	December 31, 2012, as restated
	Remaining Time to Maturity
	Less than one year		$	30,082		$	30,614		$	2,678		$	2,715		$	32,760		$	33,329
	One to five years			489,939			510,523			45,576			47,275			535,515			557,798
	Five to ten years			564,556			607,711			76,480			80,009			641,036			687,720
	More than 10 years			346,410			379,045			57,628			62,542			404,038			441,587
	Mortgage and asset-backed securities			495,249			536,255			81,588			88,022			576,837			624,277
	Total, December 31, 2012, as restated		$	1,926,236		$	2,064,148		$	263,950		$	280,563		$	2,190,186		$	2,344,711
Composition of Other Invested Assets	'
	The following table shows the composition of the other invested assets as of March 31, 2013 and December 31, 2012:
	($ in thousands)		March 31,			December 31,
			2013			2012
	Limited partnerships, equity method		$	24,517		$	23,864
	Real estate, amortized cost			7,223			7,422
	Securities reported under the fair value option			25,000			25,000
	Other			2,201			1,500
	Total		$	58,941		$	57,786

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2013
Financial Instruments at Fair Value among Levels	'
	As at March 31, 2013 and December 31, 2012, the Company’s financial instruments carried at fair value are allocated among levels as follows:
	($ in thousands)		Level 1		Level 2			Level 3		Total
	March 31, 2013, as revised
	Fixed-maturity securities
	U.S. Treasury securities		$	—	$	316,732		$	—	$	316,732
	U.S. Agency securities			—		109,005			—		109,005
	Municipal bonds			—		688,931			—		688,931
	Corporate and other bonds			—		718,162			—		718,162
	Commercial mortgage-backed securities			—		235,921			—		235,921
	Residential mortgage-backed securities
	Agency			—		262,199			—		262,199
	Non-agency			—		41,624			—		41,624
	Asset-backed securities			—		35,197			—		35,197
	Total fixed-maturities			—		2,407,771			—		2,407,771
	Equity securities			142,708		—			—		142,708
	Short-term investments			—		28,822			—		28,822
	Total investments at fair value			142,708		2,436,593			—		2,579,301
	Other invested assets (1)			—		—			25,000		25,000
	Other liabilities										—
	Interest rate swap contracts			—		(8,203	)		—		(8,203	)
	Debt and equity securities sold, not yet purchased			—		(22,513	)		—		(22,513	)
	Total, March 31, 2013, as revised		$	142,708	$	2,405,877		$	25,000	$	2,573,585
	Tower		$	139,794	$	2,134,913		$	25,000	$	2,299,707
	Reciprocal Exchanges			2,914		270,964			—		273,878
	Total, March 31, 2013, as revised		$	142,708	$	2,405,877		$	25,000	$	2,573,585
	December 31, 2012, as restated
	Fixed-maturity securities
	U.S. Treasury securities		$	—	$	184,949		$	—	$	184,949
	U.S. Agency securities			—		102,777			—		102,777
	Municipal bonds			—		686,043			—		686,043
	Corporate and other bonds			—		746,665			—		746,665
	Commercial mortgage-backed securities			—		242,053			—		242,053
	Residential mortgage-backed securities
	Agency			—		295,716			—		295,716
	Non-agency			—		42,156			—		42,156
	Asset-backed securities			—		44,352			—		44,352
	Total fixed-maturities			—		2,344,711			—		2,344,711
	Equity securities			146,258		—			—		146,258
	Short-term investments			—		4,750			—		4,750
	Total investments at fair value			146,258		2,349,461			—		2,495,719
	Other invested assets (2)			—		—			25,000		25,000
	Other liabilities
	Interest rate swap contracts			—		(9,016	)		—		(9,016	)
	Debt and equity securities sold, not yet purchased			—		(17,101	)		—		(17,101	)
	Total, December 31, 2012, as restated		$	146,258	$	2,323,344		$	25,000	$	2,494,602
	Tower		$	140,695	$	2,042,780		$	25,000	$	2,208,475
	Reciprocal Exchanges			5,563		280,564			—		286,127
	Total, December 31, 2012, as restated		$	146,258	$	2,323,344		$	25,000	$	2,494,602
	-1	$25.0 million of the $58.9 million Other invested assets reported on the consolidated balance sheet at March 31, 2013 is reported at fair value. The remaining $33.9 million of Other invested assets is reported under the equity method of accounting or at amortized cost.
	-2	$25.0 million of the $57.8 million Other invested assets reported on the consolidated balance sheet at December 31, 2012 is reported at fair value. The remaining $32.8 million of Other invested assets is reported under the equity method of accounting or at amortized cost.
Summary of Changes in Level Three Assets Measured at Fair Value	'
	The following table summarizes the changes in Level 3 assets measured at fair value for the three months ended March 31, 2013 and 2012 for Tower (the Reciprocal Exchanges have no Level 3 assets):
			Three Months Ended
			March 31,
	($ in thousands)		2013		2012
	Beginning balance, January 1		$	25,000	$	25,000
	Total gains (losses)-realized / unrealized - included in net income			—		(86	)
	Ending balance, March 31,		$	25,000	$	24,914

Reinsurance_Tables

Reinsurance (Tables)	3 Months Ended
	Mar. 31, 2013
Premiums, Written, Ceded and Earned	'
	The table below shows direct, assumed and ceded premiums for the three months ended March 31, 2013 and 2012:
		Three Months Ended March 31,
	($ in thousands)	Direct			Assumed			Ceded			Net
		(revised)									(revised)
	2013, as revised
	Premiums written	$	445,715		$	105,514		$	98,032		$	453,197
	Change in unearned premiums		(16,128	)		(44,389	)		(29,206	)		(31,311	)
	Premiums earned	$	429,587		$	61,125		$	68,826		$	421,886
	2012
	Premiums written	$	404,840		$	62,521		$	41,678		$	425,683
	Change in unearned premiums		27,169			(31,394	)		1,300			(5,525	)
	Premiums earned	$	432,009		$	31,127		$	42,978		$	420,158

Loss_and_Loss_Adjustment_Expen1

Loss and Loss Adjustment Expense (Tables)	3 Months Ended
	Mar. 31, 2013
Reconciliation of Beginning and Ending Consolidated Balances for Unpaid Losses and Loss Adjustment Expense	'
	The following table provides a reconciliation of the beginning and ending consolidated balances for unpaid losses and loss adjustment expense (“LAE”) for the three months ended March 31, 2013 and 2012:
		Three Months Ended March 31,
		2013									2012
	($ in thousands)	Tower			Reciprocal			Total			Tower			Reciprocal			Total
		(revised)			Exchanges			(revised)						Exchanges
	Balance at January 1,	$	1,759,888		$	135,791		$	1,895,679		$	1,495,839		$	136,274		$	1,632,113
	Less reinsurance recoverables on unpaid losses		(407,068	)		(52,389	)		(459,457	)		(280,968	)		(11,253	)		(292,221	)
			1,352,820			83,402			1,436,222			1,214,871			125,021			1,339,892
	Net reserves, at fair value, of acquired entities		161,886			—			161,886			—			—			—
	Incurred related to:
	Current year		239,210			28,827			268,037			229,994			24,531			254,525
	Prior years unfavorable/(favorable) development		1,124			6,571			7,695			13,256			(288	)		12,968
	Total incurred		240,334			35,398			275,732			243,250			24,243			267,493
	Paid related to:
	Current year		103,324			17,721			121,045			79,504			17,428			96,932
	Prior years		171,026			707			171,733			158,829			12,123			170,952
	Total paid		274,350			18,428			292,778			238,333			29,551			267,884
	Net balance at end of period		1,480,690			100,372			1,581,062			1,219,788			119,713			1,339,501
	Add reinsurance recoverables on unpaid losses		822,634			27,554			850,188			235,033			22,905			257,938
	Balance at March 31,	$	2,303,324		$	127,926		$	2,431,250		$	1,454,821		$	142,618		$	1,597,439

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2013
Summary of Changes in Accumulated Other Comprehensive Income	'
	The following table provides a summary of changes in accumulated other comprehensive income, by component, for the three months ended March 31, 2013, with all amounts reflected net of income taxes and noncontrolling interest:
	($ in thousands)	Unrealized			Gains			Cumulative			Total
		gains (losses)			(losses) on			translation
		on available for			cash flow			adjustments
		sale securities			hedges
	Balance at December 31, 2012, as restated	$	87,412		$	(5,860	)	$	1,204		$	82,756
	Other comprehensive income before reclassifications, net of tax		906			514			(2,347	)		(927	)
	Amounts reclassified from accumulated other comprehensive income, net of tax		(4,051	)		533			—			(3,518	)
	Net current period other comprehensive income		(3,145	)		1,047			(2,347	)		(4,445	)
	Balance at March 31, 2013, as revised	$	84,267		$	(4,813	)	$	(1,143	)	$	78,311
Reclassified from Accumulated Other Comprehensive Income to Net Income	'
	The following provides a summary of the items that have been reclassified from accumulated other comprehensive income to net income in their entirety during the three months ended March 31, 2013, including the line item on the consolidated statement of operations on which the impact is reflected. Unrealized gains (losses) on available for sale securities are reclassified from accumulated other comprehensive income when a security is sold or when a non-credit impairment is recorded. Gains (losses) on cash flow hedges are reclassified from accumulated other comprehensive income when the related hedged item (subordinated debentures floating rate interest payments) are recorded in the statement of operations.
	($ in thousands)
	Accumulated other comprehensive	Amounts reclassified			Affected line item in the consolidated
		from accumulated other			statement of operations
	income components	comprehensive income
		(revised)
	Unrealized gains (losses) on available for sale securities	$	(6,232	)	Other net realized investment gains
			2,181		Income tax expense
		$	(4,051	)	Total net of income taxes
	Gains (losses) on cash flow hedges interest rate swaps	$	820		Interest expense
			(287	)	Income tax expense
		$	533		Total net of income taxes

Debt_Tables

Debt (Tables)	3 Months Ended
	Mar. 31, 2013
Borrowings	'
	The Company’s borrowings consisted of the following at March 31, 2013 and December 31, 2012:
		March 31, 2013						December 31, 2012
	($ in thousands)	Carrying			Fair			Carrying		Fair
		Value			Value			Value		Value
	Credit facility	$	70,000		$	70,000		$	70,000	$	70,000
	Convertible senior notes		145,412			156,375			144,673		152,063
	Subordinated debentures		235,058			236,875			235,058		232,678
	Total	$	450,470		$	463,250		$	449,731	$	454,741
Amounts Recorded for Notes	'
	The following table shows the amounts recorded for the Notes as of March 31, 2013 and December 31, 2012:
	($ in thousands)	March 31,			December 31,
		2013			2012
	Liability component
	Outstanding principal	$	150,000		$	150,000
	Unamortized OID		(4,588	)		(5,327	)
	Liability component		145,412			144,673
	Equity component, net of tax	$	7,469		$	7,469

Stock_Based_Compensation_Table

Stock Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2013
Analysis of Restricted Stock Activity	'
	The following table provides an analysis of restricted stock activity for the three months ended March 31, 2013 and 2012 (historical share counts and fair values have been adjusted for the 1.1330 share conversion ratio, as discussed more fully in “Note 4 – Merger Transaction”):
		Three Months Ended March 31,
		2013					2012
		Number of			Weighted		Number of			Weighted
		Shares			Average		Shares			Average
					Grant Date					Grant Date
					Fair Value					Fair Value
	Outstanding, January 1		1,015,902		$	20.19		1,120,091		$	20.69
	Granted		240,293			18.08		363,894			20.37
	Vested		(950,773	)		20.44		(428,687	)		21.08
	Forfeitures		(6,848	)		20.51		(4,852	)		20.8
	Outstanding, March 31,		298,574		$	17.67		1,050,446		$	20.38
Analysis of Stock Option Activity	'
	The following table provides an analysis of stock option activity for the three months ended March 31, 2013 and 2012 (historical share counts and fair values have been adjusted for the 1.1330 share conversion ratio, as discussed more fully in “Note 4 – Merger Transaction”):
		Three Months Ended March 31,
		2013					2012
		Number of			Average		Number of			Average
		Shares			Exercise		Shares			Exercise
					Price					Price
	Outstanding, January 1		969,307		$	17.78		969,312		$	17.78
	Exercised		—			—		—			—
	Forfeitures and expirations		—			—		—			—
	Outstanding, March 31		969,307		$	17.78		969,312		$	17.78
	Exercisable, March 31		969,307		$	17.78		969,312		$	17.78
Analysis of Stock Based Compensation Expense	'
	The following table provides an analysis of stock based compensation expense for the three months ended March 31, 2013 and 2012:
		Three Months Ended
		March 31,
	($ in thousands)	2013			2012
	Restricted stock
	Expense, net of tax	$	7,982		$	1,464
	Value of shares vested		9,485			5,622
	Value of unvested shares		5,509			20,796
	Stock options
	Intrinsic value of outstanding options		1,149			2,704
	Intrinsic value of vested outstanding options		1,149			2,704
	Unrecognized compensation expense
	Unvested restricted stock, net of tax		5,509			12,791
	Weighted average years over which expense will be recognized		3.9			2.8

Income_Taxes_Tables

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2013
Provision for Income Taxes	'
	Income (loss) before income tax and income tax expense (benefit) by taxing jurisdiction are presented in the table below for the three months ended March 31, 2013 and 2012, respectively:
		March 31, 2013											March 31, 2012
		U.S.											U.S.
	($ in thousands)	Tower			Reciprocal			Non - U.S.		Total			Tower			Reciprocal			Total
		(revised)								(revised)
	Income (loss) before income tax	$	(15,433	)	$	(11,281	)	$	26,760	$	46		$	27,773		$	3,628		$	31,401
	Income tax expense (benefit)	$	(1,590	)	$	—		$	—	$	(1,590	)	$	8,607		$	617		$	9,224
	Effective tax rate		10.3	%		—			—		-3456.5	%		31	%		17	%		29.4	%

Earnings_per_Share_Tables

Earnings per Share (Tables)	3 Months Ended
	Mar. 31, 2013
Computation of Earnings Per Share	'
	The following table shows the computation of the earnings per share (historical earnings per share amounts have been adjusted for the 1.1330 share conversion ratio, as discussed more fully in “Note 4 – Merger Transaction”):
		Three Months Ended
		March 31,
	($ in thousands, except per share amounts)	2013			2012
		(revised)
	Numerator
	Net income (loss) attributable to Tower Group International, Ltd.	$	12,917		$	19,166
	Less: Allocation of income for unvested participating restricted stock		(37	)		(298	)
	Less: Dividends on unvested participating restricted stock		(166	)		(174	)
	Net income available to common shareholders - Basic		12,714			18,694
	Reallocation of income for unvested participating restricted stock		—			—
	Net income available to common shareholders - Diluted		12,714			18,694
	Denominator
	Basic earning per share denominator		45,614			43,326
	Effect of dilutive securities		74			85
	Diluted earnings per share denominator		45,688			43,411
	Earnings (loss) per share attributable to Tower Group International, Ltd. - Basic
	Common stock:
	Distributed earnings	$	0.17		$	0.17
	Undistributed earnings	$	0.11		$	0.26
	Total	$	0.28		$	0.43
	Earnings (loss) per share attributable to Tower Group International, Ltd. - Diluted	$	0.28		$	0.43

Segment_Information_Tables

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2013
Business Segments Results	'
	Business segment results are as follows:
		Three Months Ended
		March 31,
	($ in thousands)	2013			2012
		(revised)
	Commercial Insurance Segment
	Revenues
	Premiums earned	$	307,784		$	297,835
	Ceding commission revenue		3,287			10
	Policy billing fees		1,370			1,513
	Total revenues		312,441			299,358
	Expenses
	Loss and loss adjustment expenses		196,363			201,438
	Underwriting expenses		112,912			103,142
	Total expenses		309,275			304,580
	Underwriting profit (loss)	$	3,166		$	(5,222	)
	Personal Insurance Segment
	Revenues
	Premiums earned	$	114,102		$	122,323
	Ceding commission revenue		10,864			5,153
	Policy billing fees		1,780			1,621
	Total revenues		126,746			129,097
	Expenses
	Loss and loss adjustment expenses		79,369			66,055
	Underwriting expenses		60,528			53,852
	Total expenses		139,897			119,907
	Underwriting profit (loss)	$	(13,151	)	$	9,190
	Tower	$	(524	)	$	9,438
	Reciprocal Exchanges		(12,627	)		(248	)
	Total underwriting profit (loss)	$	(13,151	)	$	9,190
	Insurance Services Segment
	Revenues
	Management fee income	$	7,161		$	6,862
	Other revenue		128			497
	Total revenues		7,289			7,359
	Expenses
	Other expenses		4,621			4,463
	Total expenses		4,621			4,463
	Insurance services pretax income	$	2,668		$	2,896
Reconciliation of Revenue by Segment to Consolidated Revenues	'
	The following table reconciles revenue by segment to consolidated revenues:
		Three Months Ended
		March 31,
	($ in thousands)	2013			2012
		(revised)
	Commercial insurance segment	$	312,441		$	299,358
	Personal insurance segment		126,746			129,097
	Insurance services segment		7,289			7,359
	Total segment revenues		446,476			435,814
	Elimination of management fee income		(7,161	)		(6,862	)
	Net investment income		30,317			33,943
	Net realized gains (losses) on investments, including other-than-temporary impairments		6,851			3,328
	Consolidated revenues	$	476,483		$	466,223
Reconciliation of Results of Individual Segments to Consolidated Income Before Income Taxes	'
	The following table reconciles the results of the Company’s individual segments to consolidated income before income taxes:
		Three Months Ended
		March 31,
	($ in thousands)	2013			2012
		(revised)
	Commercial insurance segment underwriting profit (loss)	$	3,166		$	(5,222	)
	Personal insurance segment underwriting profit (loss)		(13,151	)		9,190
	Insurance services segment pretax income		2,668			2,896
	Net investment income		30,317			33,943
	Net realized gains on investments, including other-than-temporary impairments		6,851			3,328
	Corporate expenses		(3,069	)		(2,861	)
	Acquisition-related transaction costs		(19,056	)		(1,262	)
	Interest expense		(7,808	)		(8,611	)
	Other income		128			—
	Income before income taxes	$	46		$	31,401

Nature_of_Business_Additional_

Nature of Business - Additional Information (Detail) (USD $)

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

6 Months Ended

6 Months Ended

Mar. 31, 2013

Mar. 31, 2012

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Mar. 31, 2013

Dec. 31, 2012

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Oct. 01, 2013

Oct. 01, 2013

Oct. 01, 2013

Jun. 30, 2013

Oct. 31, 2013

Jun. 30, 2013

Jun. 30, 2013

Scenario, Forecast

Scenario, Forecast

Scenario, Forecast

Convertible Senior Notes

Convertible Senior Notes

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Minimum

TRL

CastlePoint Re

Minimum

Maximum

Specialty Insurance and Reinsurance

Specialty Insurance and Reinsurance

Commercial Insurance

Commercial Insurance

Tower Insurance Company of New York

Tower Insurance Company of New York

Tower Insurance Company of New York

TRL

TRL

TRL

Convertible Senior Notes

Minimum

Minimum

Arch

Hannover

Southport Re

New Reinsurance Program

Nature Of Business [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Increase in loss and loss adjustment expense reserves from adverse development associated with prior accident years

$7,695,000

$12,968,000

'

'

'

'

'

'

$365,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of loss reserves covered by reserve study

'

'

'

'

'

'

'

'

90.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

Goodwill impairment charge

'

'

'

'

'

'

'

'

214,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Quota share reinsurance cede, percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

17.50%

14.00%

30.00%

'

'

'

'

Net written premiums

453,197,000

425,683,000

'

'

'

'

'

'

'

'

'

103,700,000

306,600,000

169,100,000

343,600,000

'

'

'

'

'

'

'

Additional collateral requested

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

26,300,000

'

'

Adverse loss reserve development from loss portfolio transaction

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

175,000,000

'

'

'

Reinsurance capital reserve

829,659,000

'

137,545,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

8,300,000

'

'

'

Amount required to be collateralized against adverse loss reserve development

634,080,000

'

98,581,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

175,000,000

'

'

'

Unencumbered liquid assets

49,668,000

'

17,609,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

96,000,000

'

79,000,000

'

Number of reinsurance treaties commuted

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2

'

Credit facility outstanding

70,000,000

'

70,000,000

'

'

'

'

'

70,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Convertible senior notes outstanding

'

'

'

'

'

'

150,000,000

150,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

150,000,000

Credit facility covenant, Consolidated Net Worth

'

'

'

'

'

'

'

'

'

553,400,000

'

'

'

'

'

'

'

'

'

'

'

'

Credit facility covenant, percentage of Consolidated Net Worth

'

'

'

'

'

'

'

'

'

90.00%

'

'

'

'

'

'

'

'

'

'

'

'

Credit facility covenant, covenant increase as a percentage of any new capital

'

'

'

'

'

'

'

'

90.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

Credit facility covenant, additional covenant increase as a percentage of net income above base

'

'

'

'

'

'

'

'

50.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

Credit facility covenant, net income amount base for additional covenant increase

'

'

'

'

'

'

'

'

20,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Credit facility covenant, Debt to capitalization ratio limit

'

'

'

'

'

'

'

'

46.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

Credit facility covenant, risk based capital ratio

'

'

'

175.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Credit facility covenant, consolidated statutory surplus

'

'

'

10.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Credit facility covenant, percentage of required capital

'

'

'

'

110.00%

150.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Credit facility covenant, minimum statutory surplus

'

'

'

'

'

'

'

'

419,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Credit facility covenant, combined surplus

'

'

'

'

'

'

'

'

85.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

Subordinated debentures outstanding

235,058,000

'

235,058,000

'

'

'

'

'

235,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Subordinated debentures

'

'

'

'

'

'

'

'

$10,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Subordinated debentures maturity date

'

'

'

'

'

'

'

'

'May 2033

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of quarters to defer interest payments

'

'

'

'

'

'

'

'

'

'

'60 months

'

'

'

'

'

'

'

'

'

'

'

Restatement_and_Revision_of_Pr2

Restatement and Revision of Previously Issued Financial Statements - Additional Information (Detail) (USD $)	3 Months Ended			3 Months Ended		12 Months Ended				6 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Jun. 30, 2013
				Effect of Adjustments	Effect of Adjustments	Material Error in Liability for Unpaid Claims and Claims Adjustment Expense	Material Error in Liability for Unpaid Claims and Claims Adjustment Expense	Material Error in Liability for Unpaid Claims and Claims Adjustment Expense	Material Error in Liability for Unpaid Claims and Claims Adjustment Expense	Subsequent Event
						Effect of Adjustments	Effect of Adjustments	Effect of Adjustments	Effect of Adjustments
Reserve charge from adverse development associated with prior accident years	$7,695	$12,968	'	'	'	'	'	'	'	$365,000
Reinsurance recoverable on unpaid losses	850,188	'	459,457	-37,000	-36,735	-37,000	-27,400	-5,700	'	'
Loss and loss adjustment expenses	275,732	267,493	'	1,052	'	9,600	21,700	5,700	'	'
Premiums receivable	408,289	'	412,045	-9,872	-10,067	-11,000	-10,000	-5,600	-7,200	'
Other operating expenses	$84,393	$77,071	'	'	'	$1,000	$4,400	($1,600)	$7,200	'

Effect_of_Revisions_and_Restat

Effect of Revisions and Restatements on Consolidated Balance Sheets (Detail) (USD $)	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Assets	'	'	'	'
Total investments	$2,638,242	$2,553,505	'	'
Cash and cash equivalents	229,946	102,269	143,081	114,098
Investment income receivable	29,490	25,332	'	'
Investment in uncolsolidated affiliate	68,411	71,894	'	'
Premiums receivable	408,289	412,045	'	'
Reinsurance recoverable on paid losses	49,668	17,609	'	'
Reinsurance recoverable on unpaid losses	850,188	459,457	'	'
Prepaid reinsurance premiums	234,181	63,923	'	'
Deferred acquisition costs, net	199,092	181,198	'	'
Intangible assets	104,550	106,768	'	'
Goodwill	269,589	241,458	'	'
Funds held by reinsured companies	829,659	137,545	'	'
Other assets	436,439	338,769	'	'
Total Assets	6,347,744	4,711,772	'	'
Liabilities	'	'	'	'
Loss and loss adjustment expenses	2,431,250	1,895,679	1,597,439	1,632,113
Unearned premium	1,122,428	921,271	'	'
Reinsurance balances payable	39,227	40,569	'	'
Funds held under reinsurance agreements	634,080	98,581	'	'
Other liabilities	464,325	296,960	'	'
Deferred income taxes	19,842	24,763	'	'
Debt	450,470	449,731	'	'
Total liabilities	5,161,622	3,727,554	'	'
Contingencies	'	'	'	'
Stockholders' equity	'	'	'	'
Common stock	574	530	'	'
Treasury stock	'	-181,435	'	'
Paid-in-capital	812,156	780,036	'	'
Accumulated other comprehensive income	78,311	82,756	'	'
Retained earnings	273,887	268,171	'	'
Tower Group International, Ltd. stockholders' equity	1,164,928	950,058	'	'
Noncontrolling interests	21,194	34,160	'	'
Total stockholders' equity	1,186,122	984,218	1,066,471	1,037,131
Total liabilities and stockholders' equity	6,347,744	4,711,772	'	'
As previously Reported	'	'	'	'
Assets	'	'	'	'
Total investments	2,638,543	2,554,505	'	'
Cash and cash equivalents	229,946	100,293	'	'
Investment income receivable	29,490	25,332	'	'
Investment in uncolsolidated affiliate	68,411	70,830	'	'
Premiums receivable	418,161	422,112	'	'
Reinsurance recoverable on paid losses	49,668	17,609	'	'
Reinsurance recoverable on unpaid losses	887,188	496,192	'	'
Prepaid reinsurance premiums	234,181	63,923	'	'
Deferred acquisition costs, net	199,137	180,941	'	'
Intangible assets	104,550	106,768	'	'
Goodwill	269,589	241,458	'	'
Funds held by reinsured companies	829,659	137,545	'	'
Other assets	430,108	331,506	'	'
Total Assets	6,388,631	4,749,014	'	'
Liabilities	'	'	'	'
Loss and loss adjustment expenses	2,429,857	1,895,073	'	'
Unearned premium	1,123,022	920,859	'	'
Reinsurance balances payable	39,227	40,569	'	'
Funds held under reinsurance agreements	634,080	98,581	'	'
Other liabilities	463,303	292,239	'	'
Deferred income taxes	29,677	36,464	'	'
Debt	450,470	449,731	'	'
Total liabilities	5,169,636	3,733,516	'	'
Contingencies	'	'	'	'
Stockholders' equity	'	'	'	'
Common stock	574	530	'	'
Treasury stock	'	-181,435	'	'
Paid-in-capital	812,156	780,036	'	'
Accumulated other comprehensive income	78,377	83,406	'	'
Retained earnings	306,192	298,299	'	'
Tower Group International, Ltd. stockholders' equity	1,197,299	980,836	'	'
Noncontrolling interests	21,696	34,662	'	'
Total stockholders' equity	1,218,995	1,015,498	'	'
Total liabilities and stockholders' equity	6,388,631	4,749,014	'	'
Effect of Adjustments	'	'	'	'
Assets	'	'	'	'
Total investments	-301	-1,000	'	'
Cash and cash equivalents	'	1,976	'	'
Investment in uncolsolidated affiliate	'	1,064	'	'
Premiums receivable	-9,872	-10,067	'	'
Reinsurance recoverable on unpaid losses	-37,000	-36,735	'	'
Deferred acquisition costs, net	-45	257	'	'
Other assets	6,331	7,263	'	'
Total Assets	-40,887	-37,242	'	'
Liabilities	'	'	'	'
Loss and loss adjustment expenses	1,393	606	'	'
Unearned premium	-594	412	'	'
Other liabilities	1,022	4,721	'	'
Deferred income taxes	-9,835	-11,701	'	'
Total liabilities	-8,014	-5,962	'	'
Contingencies	'	'	'	'
Stockholders' equity	'	'	'	'
Accumulated other comprehensive income	-66	-650	'	'
Retained earnings	-32,305	-30,128	'	'
Tower Group International, Ltd. stockholders' equity	-32,371	-30,778	'	'
Noncontrolling interests	-502	-502	'	'
Total stockholders' equity	-32,873	-31,280	'	'
Total liabilities and stockholders' equity	($40,887)	($37,242)	'	'

Effect_of_Revision_on_Consolid

Effect of Revision on Consolidated Statements of Operations and Comprehensive Income (Detail) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Revenues	'	'
Net premiums earned	$421,886	$420,158
Ceding commission revenue	14,151	5,163
Insurance services revenue	128	497
Policy billing fees	3,150	3,134
Net investment income	30,317	33,943
Other-than-temporary impairments	-689	-2,976
Other net realized investment gains	7,540	6,304
Total net realized gains (losses)	6,851	3,328
Total revenues	476,483	466,223
Expenses	'	'
Loss and loss adjustment expenses	275,732	267,493
Direct and ceding commission expense	89,576	80,385
Other operating expenses	84,393	77,071
Acquisition-related transaction costs	19,056	1,262
Interest expense	7,808	8,611
Total expenses	476,565	434,822
Other income (expense)	'	'
Earnings in Canopius Group	128	'
Income before taxes	46	31,401
Income tax expense (benefit)	-1,590	9,224
Net income	1,636	22,177
Less: Net income (loss) attributable to Noncontrolling interests	-11,281	3,011
Net income attributable to Tower Group International, Ltd.	12,917	19,166
Earnings per share attributable to Tower Group International, Ltd. stockholders:	'	'
Basic	$0.28	'
Diluted	$0.28	'
Comprehensive Income (loss)	-4,494	36,852
Less: Comprehensive income attributable to Noncontrolling interests	-12,966	6,385
Comprehensive income (loss) attributable to Tower Group International, Ltd.	8,472	30,467
As previously Reported	'	'
Revenues	'	'
Net premiums earned	420,486	'
Ceding commission revenue	14,151	'
Insurance services revenue	128	'
Policy billing fees	3,150	'
Net investment income	30,317	'
Other-than-temporary impairments	-489	'
Other net realized investment gains	7,540	'
Total net realized gains (losses)	7,051	'
Total revenues	475,283	'
Expenses	'	'
Loss and loss adjustment expenses	274,680	'
Direct and ceding commission expense	88,398	'
Other operating expenses	84,393	'
Acquisition-related transaction costs	19,056	'
Interest expense	7,808	'
Total expenses	474,335	'
Other income (expense)	'	'
Earnings in Canopius Group	1,192	'
Income before taxes	2,140	'
Income tax expense (benefit)	-1,673	'
Net income	3,813	'
Less: Net income (loss) attributable to Noncontrolling interests	-11,281	'
Net income attributable to Tower Group International, Ltd.	15,094	'
Earnings per share attributable to Tower Group International, Ltd. stockholders:	'	'
Basic	$0.33	'
Diluted	$0.33	'
Comprehensive Income (loss)	-2,901	'
Less: Comprehensive income attributable to Noncontrolling interests	-12,966	'
Comprehensive income (loss) attributable to Tower Group International, Ltd.	10,065	'
Effect of Adjustments	'	'
Revenues	'	'
Net premiums earned	1,400	'
Other-than-temporary impairments	-200	'
Total net realized gains (losses)	-200	'
Total revenues	1,200	'
Expenses	'	'
Loss and loss adjustment expenses	1,052	'
Direct and ceding commission expense	1,178	'
Total expenses	2,230	'
Other income (expense)	'	'
Earnings in Canopius Group	-1,064	'
Income before taxes	-2,094	'
Income tax expense (benefit)	83	'
Net income	-2,177	'
Net income attributable to Tower Group International, Ltd.	-2,177	'
Earnings per share attributable to Tower Group International, Ltd. stockholders:	'	'
Basic	($0.05)	'
Diluted	($0.05)	'
Comprehensive Income (loss)	-1,593	'
Comprehensive income (loss) attributable to Tower Group International, Ltd.	($1,593)	'

Effect_of_Revision_on_Consolid1

Effect of Revision on Consolidated Statement of Cash Flows (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Cash flows provided by (used in) operating activities:	'	'
Net cash flows provided by (used in) operations	($55,083)	$30,865
Net cash flows provided by (used in) investing activities	193,320	7,429
Net cash flows provided by (used in) financing activities	-10,560	-9,311
Increase (decrease) in cash and cash equivalents	127,677	28,983
Cash and cash equivalents, beginning of period	102,269	114,098
Cash and cash equivalents, end of period	229,946	143,081
As previously Reported	'	'
Cash flows provided by (used in) operating activities:	'	'
Net cash flows provided by (used in) operations	-53,107	'
Net cash flows provided by (used in) investing activities	193,320	'
Net cash flows provided by (used in) financing activities	-10,560	'
Increase (decrease) in cash and cash equivalents	129,653	'
Cash and cash equivalents, beginning of period	100,293	'
Cash and cash equivalents, end of period	229,946	'
Effect of Adjustments	'	'
Cash flows provided by (used in) operating activities:	'	'
Net cash flows provided by (used in) operations	-1,976	'
Increase (decrease) in cash and cash equivalents	-1,976	'
Cash and cash equivalents, beginning of period	$1,976	'

Accounting_Policies_and_Basis_3

Accounting Policies and Basis of Presentation - Additional Information (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2012
Reciprocal Exchanges	'
Significant Accounting Policies [Line Items]	'
Transfer of assets	$1,800
Tower	'
Significant Accounting Policies [Line Items]	'
Transfer of assets	$1,800

Reflects_the_Previously_Report

Reflects the Previously Reported and Restated Stockholders' Equity Accounts (Detail) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Common stock	$574	'	$530
Treasury stock	'	'	-181,435
Paid-in-capital	812,156	'	780,036
Earnings (Loss) per Share:	'	'	'
Basic	$0.28	$0.43	'
Diluted	$0.28	$0.43	'
Weighted average common shares outstanding	'	'	'
Basic	45,614	43,326	'
Diluted	45,688	43,411	'
Merger Transaction	'	'	'
Common stock	'	'	469
Treasury stock	'	'	-181,435
Paid-in-capital	'	'	780,097
Earnings (Loss) per Share:	'	'	'
Basic	'	$0.49	'
Diluted	'	$0.49	'
Weighted average common shares outstanding	'	'	'
Basic	'	39,233	'
Diluted	'	39,307	'
Revised Amount	'	'	'
Common stock	'	'	530
Treasury stock	'	'	-181,435
Paid-in-capital	'	'	$780,036
Earnings (Loss) per Share:	'	'	'
Basic	'	$0.43	'
Diluted	'	$0.43	'
Weighted average common shares outstanding	'	'	'
Basic	'	43,326	'
Diluted	'	43,411	'

Merger_Transaction_Additional_

Merger Transaction - Additional Information (Detail) (USD $)

1 Months Ended

3 Months Ended

3 Months Ended

1 Months Ended

1 Months Ended

Mar. 31, 2013

Mar. 31, 2013

Mar. 31, 2012

Dec. 31, 2012

Mar. 31, 2013

Mar. 31, 2013

Mar. 31, 2013

Mar. 31, 2013

Mar. 31, 2013

Mar. 31, 2013

Jul. 30, 2012

Mar. 31, 2013

Mar. 06, 2013

Aug. 20, 2012

Mar. 06, 2013

Direct cost

Compensation expense

Compensation expense

Legal and accounting fees

Tower Group International Ltd

Third Party Investors

Canopius Group Limited

Canopius Group Limited

Canopius Group Limited

Canopius Group Limited

Canopius Group Limited

Restricted Stock

Third Party Investors

Business Acquisition [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Investments

$26,485,000

$26,485,000

'

'

'

'

'

'

'

'

'

'

'

$74,900,000

'

Percentage of ownership interest

'

'

'

'

'

'

'

'

'

'

'

100.00%

'

10.70%

'

Payment to exercise merger option

'

'

'

'

'

'

'

'

'

'

1,000,000

'

'

'

'

Percentage of private sale of shares to third party investor

'

'

'

'

'

'

'

'

'

'

'

'

100.00%

'

'

Net consideration of sale of shares to third party

'

'

'

'

'

'

'

'

'

'

'

'

'

'

205,862,755

Shares issued in private placement

'

'

'

'

'

'

'

'

'

'

'

'

14,025,737

'

'

Merger agreement terms

'

'(i) 100% of the issued and outstanding shares of TGI common stock was cancelled and automatically converted into the right to receive 1.1330 common shares of the Company, par value $0.01 per share (the "Common Share"), (ii) each outstanding option to acquire TGI common stock, whether vested or unvested and whether granted under TGIbs 2008 Long-Term Equity Compensation Plan or otherwise, automatically vested, free of any forfeiture conditions, and constituted a fully vested option to acquire that number of Common Shares (rounded down to the nearest whole number) equal to the number of shares of TGI common stock subject to such option multiplied by 1.1330, on the same terms and conditions (other than vesting and performance conditions) as were applicable to such TGI stock option immediately prior to the Merger Transaction, with the exercise price of such option adjusted to be the original exercise price divided by 1.1330, and (iii) substantially all issued and outstanding shares of TGI restricted stock, whether granted under TGI's 2008 Long-Term Equity Compensation Plan or otherwise, automatically vested, free of any forfeiture conditions, and was converted into the right to receive, as soon as reasonably practicable after the effective time, 1.1330 Common Shares.

'

'

'

'

'

'

'

'

'

'

'

'

'

Conversion ratio

1.133

1.133

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of outstanding shares

57,432,150

57,432,150

'

43,513,678

'

'

'

'

'

'

'

'

'

'

'

Percentage of outstanding shares held

'

'

'

'

'

'

'

'

76.00%

24.00%

'

'

'

'

'

Direct cost of the acquisition

'

19,056,000

1,262,000

'

19,100,000

11,400,000

10,300,000

7,700,000

'

'

'

'

'

'

'

Unamortized reserve for risk premium

19,100,000

19,100,000

'

0

'

'

'

'

'

'

'

'

'

'

'

Consolidated revenue since effective date of merger

6,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Consolidated net income since effective date of merger

$3,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Preliminary_Purchase_Considera

Preliminary Purchase Consideration (Detail) (USD $)	Mar. 31, 2013
In Thousands, unless otherwise specified
Business Acquisition [Line Items]	'
Preliminary purchase consideration	$207,347
Canopius Group Limited | Consideration received by Canopius Group from the third party sale	'
Business Acquisition [Line Items]	'
Preliminary purchase consideration	205,863
Canopius Group Limited | Fair value of Merger Option received in connection with TGI's investment in Canopius Group	'
Business Acquisition [Line Items]	'
Preliminary purchase consideration	484
Canopius Group Limited | Exercise price of Merger Right received from TGI upon exercise	'
Business Acquisition [Line Items]	'
Preliminary purchase consideration	$1,000

Fair_Value_of_Assets_Acquired_

Fair Value of Assets Acquired and Liabilities Assumed (Detail) (USD $)	Mar. 31, 2013
In Thousands, unless otherwise specified
Assets	'
Cash and cash equivalents	$134,741
Investments	26,485
Reinsurance recoverables	468,727
Prepaid reinsurance	152,431
Other assets	75,219
Liabilities	'
Unearned premiums	169,963
Other Liabilities	15,916
Net assets acquired	179,216
Purchase Consideration	207,347
Goodwill	28,131
Reinsured Companies	'
Assets	'
Other assets	698,819
Losses and Loss Adjustment Expenses	'
Liabilities	'
Other Liabilities	630,613
Reinsurance Agreements	'
Liabilities	'
Other Liabilities	$560,714

Pro_Forma_Financial_Informatio

Pro Forma Financial Information (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Business Acquisition, Pro Forma Information [Line Items]	'	'
Revenues	$479,627	$469,367
Net Income	$20,628	$26,961

Variable_Interest_Entities_VIE1

Variable Interest Entities ("VIEs") - Additional Information (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Variable Interest Entity [Line Items]	'	'
Total revenues	$476,483	$466,223
Total expenses	476,565	434,822
Net income (loss)	-11,281	3,011
Reciprocal Exchanges	'	'
Variable Interest Entity [Line Items]	'	'
Total revenues	47,300	50,200
Total expenses	58,500	47,200
Net income (loss)	($11,300)	$3,000

Summary_of_Cost_or_Amortized_C

Summary of Cost or Amortized Cost and Fair Value of Investments in Fixed Maturity and Equity Securities, Gross Unrealized Gains and Losses, and Other-Than-Temporary Impairment Losses (Detail) (USD $)	Mar. 31, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'		'
Cost or Amortized Cost	$2,434,387		$2,344,283
Gross Unrealized Gains	150,185		159,147
Gross Unrealized Losses	-5,271		-7,711
Investments	2,579,301		2,495,719
Unrealized OTTI Losses	-121	[1]	-6	[1]
Tower	'		'
Schedule of Available-for-sale Securities [Line Items]	'		'
Cost or Amortized Cost	2,175,856		2,075,189
Gross Unrealized Gains	133,986		141,614
Gross Unrealized Losses	-4,419		-7,210
Investments	2,305,423		2,209,593
Unrealized OTTI Losses	-121	[1]	-6	[1]
Reciprocal Exchanges	'		'
Schedule of Available-for-sale Securities [Line Items]	'		'
Cost or Amortized Cost	258,531		269,094
Gross Unrealized Gains	16,199		17,533
Gross Unrealized Losses	-852		-501
Investments	273,878		286,126
Unrealized OTTI Losses	'	[1]	'	[1]
Fixed-maturity securities	'		'
Schedule of Available-for-sale Securities [Line Items]	'		'
Cost or Amortized Cost	2,268,076		2,190,186
Gross Unrealized Gains	143,218		157,463
Gross Unrealized Losses	-3,523		-2,938
Investments	2,407,771		2,344,711
Unrealized OTTI Losses	-121	[1]	-6	[1]
Fixed-maturity securities | U.S. Treasury Securities	'		'
Schedule of Available-for-sale Securities [Line Items]	'		'
Cost or Amortized Cost	315,281		183,462
Gross Unrealized Gains	1,486		1,500
Gross Unrealized Losses	-35		-13
Investments	316,732		184,949
Unrealized OTTI Losses	'	[1]	'	[1]
Fixed-maturity securities | U.S. Agency securities	'		'
Schedule of Available-for-sale Securities [Line Items]	'		'
Cost or Amortized Cost	105,081		98,502
Gross Unrealized Gains	4,056		4,351
Gross Unrealized Losses	-132		-76
Investments	109,005		102,777
Unrealized OTTI Losses	'	[1]	'	[1]
Fixed-maturity securities | Municipal Bonds	'		'
Schedule of Available-for-sale Securities [Line Items]	'		'
Cost or Amortized Cost	642,188		633,373
Gross Unrealized Gains	47,034		52,914
Gross Unrealized Losses	-291		-244
Investments	688,931		686,043
Unrealized OTTI Losses	'	[1]	'	[1]
Fixed-maturity securities | Corporate Securities	'		'
Schedule of Available-for-sale Securities [Line Items]	'		'
Investments	718,162		746,665
Fixed-maturity securities | Corporate Securities | Finance	'		'
Schedule of Available-for-sale Securities [Line Items]	'		'
Cost or Amortized Cost	222,601		233,849
Gross Unrealized Gains	20,881		21,293
Gross Unrealized Losses	-728		-1,095
Investments	242,754		254,047
Unrealized OTTI Losses	'	[1]	'	[1]
Fixed-maturity securities | Corporate Securities | Industrial	'		'
Schedule of Available-for-sale Securities [Line Items]	'		'
Cost or Amortized Cost	390,344		412,465
Gross Unrealized Gains	23,408		26,556
Gross Unrealized Losses	-807		-868
Investments	412,945		438,153
Unrealized OTTI Losses	'	[1]	'	[1]
Fixed-maturity securities | Corporate Securities | Utilities	'		'
Schedule of Available-for-sale Securities [Line Items]	'		'
Cost or Amortized Cost	60,134		51,698
Gross Unrealized Gains	2,798		2,958
Gross Unrealized Losses	-469		-191
Investments	62,463		54,465
Unrealized OTTI Losses	'	[1]	'	[1]
Fixed-maturity securities | Commercial mortgage-backed securities	'		'
Schedule of Available-for-sale Securities [Line Items]	'		'
Cost or Amortized Cost	207,944		211,819
Gross Unrealized Gains	28,337		30,375
Gross Unrealized Losses	-360		-141
Investments	235,921		242,053
Unrealized OTTI Losses	-121	[1]	'	[1]
Fixed-maturity securities | Residential Mortgage-Backed Securities, Agency Backed Securities	'		'
Schedule of Available-for-sale Securities [Line Items]	'		'
Cost or Amortized Cost	253,395		283,652
Gross Unrealized Gains	9,478		12,326
Gross Unrealized Losses	-674		-262
Investments	262,199		295,716
Unrealized OTTI Losses	'	[1]	'	[1]
Fixed-maturity securities | Residential mortgage-backed securities, Non-agency backed securities	'		'
Schedule of Available-for-sale Securities [Line Items]	'		'
Cost or Amortized Cost	37,257		38,615
Gross Unrealized Gains	4,394		3,575
Gross Unrealized Losses	-27		-34
Investments	41,624		42,156
Unrealized OTTI Losses	'	[1]	-6	[1]
Fixed-maturity securities | Asset-Backed Securities	'		'
Schedule of Available-for-sale Securities [Line Items]	'		'
Cost or Amortized Cost	33,851		42,751
Gross Unrealized Gains	1,346		1,615
Gross Unrealized Losses	'		-14
Investments	35,197		44,352
Unrealized OTTI Losses	'	[1]	'	[1]
Preferred stocks	'		'
Schedule of Available-for-sale Securities [Line Items]	'		'
Cost or Amortized Cost	28,879		31,272
Gross Unrealized Gains	632		730
Gross Unrealized Losses	-334		-481
Investments	29,177		31,521
Unrealized OTTI Losses	'	[1]	'	[1]
Common Stocks	'		'
Schedule of Available-for-sale Securities [Line Items]	'		'
Cost or Amortized Cost	108,947		118,076
Gross Unrealized Gains	5,985		953
Gross Unrealized Losses	-1,401		-4,292
Investments	113,531		114,737
Unrealized OTTI Losses	'	[1]	'	[1]
Short-term investments	'		'
Schedule of Available-for-sale Securities [Line Items]	'		'
Cost or Amortized Cost	28,485		4,749
Gross Unrealized Gains	350		1
Gross Unrealized Losses	-13		'
Investments	28,822		4,750
Unrealized OTTI Losses	'	[1]	'	[1]
[1]	Represents the gross unrealized loss on other-than-temporarily impaired securities recognized in accumulated other comprehensive income (loss).

Investments_Additional_Informa

Investments - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
	Investment
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Restricted assets, cash and cash equivalents	$33,900,000	'	'
Investment, carrying values	2,434,387,000	'	2,344,283,000
Proceeds from sale or maturity of fixed maturity securities	191,700,000	606,200,000	'
Proceeds from sale of equity securities	375,180,000	368,145,000	'
Number of securities in unrealized loss position not deemed OTTI	225	'	'
Unrealized losses	5,271,000	'	7,711,000
Unrealized losses related to securities in loss position for more than 12 months	341,000	'	577,000
Future funding commitments to limited partnerships	28,200,000	'	'
US Treasury Notes and Other Securities | Held by Counterparties	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Restricted assets, cash and cash equivalents	481,700,000	'	'
Investment, carrying values	'	'	481,500,000
Fixed-maturity securities	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Number of securities in unrealized loss position not deemed OTTI	202	'	'
Unrealized losses	3,500,000	'	'
Percentage of fixed maturity securities in unrealized loss position below amortized cost	1.00%	'	'
Number of securities in unrealized loss position for more than 12 months	20	'	'
Unrealized losses related to securities in loss position for more than 12 months	30,000	'	'
Fixed-maturity securities | Corporate bonds and mortgage-backed securities	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Unrealized losses	3,100,000	'	'
Common Stocks	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Number of securities in unrealized loss position not deemed OTTI	16	'	'
Unrealized losses	1,500,000	'	'
Tower	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Investment, carrying values	2,175,856,000	'	2,075,189,000
Unrealized losses	4,419,000	'	7,210,000
Unrealized losses related to securities in loss position for more than 12 months	$326,000	'	$478,000
Tower | Other	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Number of securities purchased	2	'	'

Summary_of_Major_Categories_of

Summary of Major Categories of Net Investment Income (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]	'	'
Income	$32,091	$35,320
Investment expenses	-1,774	-1,377
Net investment income	30,317	33,943
Tower	'	'
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]	'	'
Net investment income	29,980	32,257
Reciprocal Exchanges	'	'
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]	'	'
Net investment income	2,380	3,349
Consolidation, Eliminations	'	'
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]	'	'
Net investment income	-2,043	-1,663
Fixed-maturity securities	'	'
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]	'	'
Income	20,973	25,412
Equity securities	'	'
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]	'	'
Income	6,484	7,636
Cash and cash equivalents	'	'
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]	'	'
Income	51	290
Other invested asset	'	'
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]	'	'
Income	4,256	1,925
Other	'	'
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]	'	'
Income	$327	$57

Summary_of_Gross_Realized_Gain

Summary of Gross Realized Gains, Losses and Impairment Write-Downs on Investments (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Gain (Loss) on Investments [Line Items]	'	'
Net realized gains (losses) on investments	$7,540	$6,304
Other-than-temporary impairment losses	-689	-2,976
Total net realized investment gains (losses)	6,851	3,328
Tower	'	'
Gain (Loss) on Investments [Line Items]	'	'
Other-than-temporary impairment losses	-689	-2,976
Total net realized investment gains (losses)	6,233	1,138
Reciprocal Exchanges	'	'
Gain (Loss) on Investments [Line Items]	'	'
Other-than-temporary impairment losses	'	'
Total net realized investment gains (losses)	618	2,190
Fixed-maturity securities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Gross realized gains	7,364	13,991
Gross realized losses	-190	-2,858
Net realized gains (losses) on investments	7,174	11,133
Other-than-temporary impairment losses	-164	-117
Equity securities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Gross realized gains	4,236	1,546
Gross realized losses	-4,813	-6,375
Net realized gains (losses) on investments	-577	-4,829
Other-than-temporary impairment losses	-525	-2,859
Other	'	'
Gain (Loss) on Investments [Line Items]	'	'
Gross realized gains	1,755	'
Gross realized losses	-812	'
Net realized gains (losses) on investments	$943	'

Amount_of_FixedMaturity_and_Eq

Amount of Fixed-Maturity and Equity Securities that were Other-Than-Temporary Impairment (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]	'	'
Other-than-temporary impairments	($689)	($2,976)
Portion of loss recognized in accumulated other comprehensive income (loss)	'	'
Other-than-temporary impairment losses	689	2,976
Tower	'	'
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]	'	'
Other-than-temporary impairment losses	689	2,976
Reciprocal Exchanges	'	'
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]	'	'
Other-than-temporary impairment losses	'	'
Corporate Securities	'	'
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]	'	'
Other-than-temporary impairments	'	-89
Commercial mortgage-backed securities	'	'
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]	'	'
Other-than-temporary impairments	-24	'
Residential mortgage-backed securities	'	'
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]	'	'
Other-than-temporary impairments	-140	-28
Equity securities	'	'
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]	'	'
Other-than-temporary impairments	($525)	($2,859)

Rollforward_of_Cumulative_Amou

Rollforward of Cumulative Amount of Other-Than-Temporary Impairment for Securities Still Held Showing Amounts that have been Included in Earnings on Pretax Basis (Detail) (Tower, USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Tower	'	'
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]	'	'
Balance at beginning of period	$4,492	$12,666
Additional credit losses recognized during the period, related to securities for which no OTTI has been previously recognized	164	89
Additional credit losses recognized during the period, related to securities for which OTTI has been previously recognized	'	28
Reductions due to Securities sold during the period (realized)	-140	-6,699
Balance at end of period	$4,516	$6,084

Information_Regarding_Invested

Information Regarding Invested Assets that were in Unrealized Loss Position (Detail) (USD $)	Mar. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Investments, Unrealized Loss Position [Line Items]	'	'
Less than 12 Months, Fair Value	$498,886	$328,618
Less than 12 Months, Unrealized Losses	-4,930	-7,134
12 Months or Longer, Fair Value	7,828	15,110
12 Months or Longer, Unrealized Losses	-341	-577
Total, Aggregate Fair Value	506,714	343,728
Total, Unrealized Losses	-5,271	-7,711
Tower	'	'
Investments, Unrealized Loss Position [Line Items]	'	'
Less than 12 Months, Fair Value	442,293	270,609
Less than 12 Months, Unrealized Losses	-4,093	-6,732
12 Months or Longer, Fair Value	7,627	13,338
12 Months or Longer, Unrealized Losses	-326	-478
Total, Aggregate Fair Value	449,920	283,947
Total, Unrealized Losses	-4,419	-7,210
Reciprocal Exchanges	'	'
Investments, Unrealized Loss Position [Line Items]	'	'
Less than 12 Months, Fair Value	56,593	58,009
Less than 12 Months, Unrealized Losses	-837	-402
12 Months or Longer, Fair Value	201	1,772
12 Months or Longer, Unrealized Losses	-15	-99
Total, Aggregate Fair Value	56,794	59,781
Total, Unrealized Losses	-852	-501
Fixed-maturity securities	'	'
Investments, Unrealized Loss Position [Line Items]	'	'
Less than 12 Months, Fair Value	425,295	263,342
Less than 12 Months, Unrealized Losses	-3,485	-2,687
12 Months or Longer, Fair Value	1,177	9,386
12 Months or Longer, Unrealized Losses	-38	-251
Total, Aggregate Fair Value	426,472	272,728
Total, Unrealized Losses	-3,523	-2,938
Fixed-maturity securities | U.S. Treasury Securities	'	'
Investments, Unrealized Loss Position [Line Items]	'	'
Less than 12 Months, Fair Value	190,145	44,347
Less than 12 Months, Unrealized Losses	-35	-13
12 Months or Longer, Fair Value	'	'
12 Months or Longer, Unrealized Losses	'	'
Total, Aggregate Fair Value	190,145	44,347
Total, Unrealized Losses	-35	-13
Fixed-maturity securities | U.S. Agency securities	'	'
Investments, Unrealized Loss Position [Line Items]	'	'
Less than 12 Months, Fair Value	22,282	22,345
Less than 12 Months, Unrealized Losses	-132	-76
12 Months or Longer, Fair Value	'	'
12 Months or Longer, Unrealized Losses	'	'
Total, Aggregate Fair Value	22,282	22,345
Total, Unrealized Losses	-132	-76
Fixed-maturity securities | Municipal Bonds	'	'
Investments, Unrealized Loss Position [Line Items]	'	'
Less than 12 Months, Fair Value	24,848	21,532
Less than 12 Months, Unrealized Losses	-282	-235
12 Months or Longer, Fair Value	252	251
12 Months or Longer, Unrealized Losses	-9	-9
Total, Aggregate Fair Value	25,100	21,783
Total, Unrealized Losses	-291	-244
Fixed-maturity securities | Corporate Securities | Finance	'	'
Investments, Unrealized Loss Position [Line Items]	'	'
Less than 12 Months, Fair Value	22,057	16,853
Less than 12 Months, Unrealized Losses	-728	-1,095
12 Months or Longer, Fair Value	'	'
12 Months or Longer, Unrealized Losses	'	'
Total, Aggregate Fair Value	22,057	16,853
Total, Unrealized Losses	-728	-1,095
Fixed-maturity securities | Corporate Securities | Industrial	'	'
Investments, Unrealized Loss Position [Line Items]	'	'
Less than 12 Months, Fair Value	49,396	53,576
Less than 12 Months, Unrealized Losses	-805	-667
12 Months or Longer, Fair Value	348	4,188
12 Months or Longer, Unrealized Losses	-2	-201
Total, Aggregate Fair Value	49,744	57,764
Total, Unrealized Losses	-807	-868
Fixed-maturity securities | Corporate Securities | Utilities	'	'
Investments, Unrealized Loss Position [Line Items]	'	'
Less than 12 Months, Fair Value	25,245	20,143
Less than 12 Months, Unrealized Losses	-469	-191
12 Months or Longer, Fair Value	7	7
12 Months or Longer, Unrealized Losses	'	'
Total, Aggregate Fair Value	25,252	20,150
Total, Unrealized Losses	-469	-191
Fixed-maturity securities | Commercial mortgage-backed securities	'	'
Investments, Unrealized Loss Position [Line Items]	'	'
Less than 12 Months, Fair Value	27,602	23,223
Less than 12 Months, Unrealized Losses	-360	-141
12 Months or Longer, Fair Value	'	95
12 Months or Longer, Unrealized Losses	'	'
Total, Aggregate Fair Value	27,602	23,318
Total, Unrealized Losses	-360	-141
Fixed-maturity securities | Residential Mortgage-Backed Securities, Agency Backed Securities	'	'
Investments, Unrealized Loss Position [Line Items]	'	'
Less than 12 Months, Fair Value	63,720	59,009
Less than 12 Months, Unrealized Losses	-674	-261
12 Months or Longer, Fair Value	23	25
12 Months or Longer, Unrealized Losses	'	-1
Total, Aggregate Fair Value	63,743	59,034
Total, Unrealized Losses	-674	-262
Fixed-maturity securities | Residential mortgage-backed securities, Non-agency backed securities	'	'
Investments, Unrealized Loss Position [Line Items]	'	'
Less than 12 Months, Fair Value	'	815
Less than 12 Months, Unrealized Losses	'	-6
12 Months or Longer, Fair Value	547	588
12 Months or Longer, Unrealized Losses	-27	-28
Total, Aggregate Fair Value	547	1,403
Total, Unrealized Losses	-27	-34
Fixed-maturity securities | Asset-Backed Securities	'	'
Investments, Unrealized Loss Position [Line Items]	'	'
Less than 12 Months, Fair Value	'	1,499
Less than 12 Months, Unrealized Losses	'	-2
12 Months or Longer, Fair Value	'	4,232
12 Months or Longer, Unrealized Losses	'	-12
Total, Aggregate Fair Value	'	5,731
Total, Unrealized Losses	'	-14
Preferred stocks	'	'
Investments, Unrealized Loss Position [Line Items]	'	'
Less than 12 Months, Fair Value	5,169	9,716
Less than 12 Months, Unrealized Losses	-31	-155
12 Months or Longer, Fair Value	6,651	5,724
12 Months or Longer, Unrealized Losses	-303	-326
Total, Aggregate Fair Value	11,820	15,440
Total, Unrealized Losses	-334	-481
Common Stocks	'	'
Investments, Unrealized Loss Position [Line Items]	'	'
Less than 12 Months, Fair Value	41,600	55,560
Less than 12 Months, Unrealized Losses	-1,401	-4,292
12 Months or Longer, Fair Value	'	'
12 Months or Longer, Unrealized Losses	'	'
Total, Aggregate Fair Value	41,600	55,560
Total, Unrealized Losses	-1,401	-4,292
Short-term investments	'	'
Investments, Unrealized Loss Position [Line Items]	'	'
Less than 12 Months, Fair Value	26,822	'
Less than 12 Months, Unrealized Losses	-13	'
12 Months or Longer, Unrealized Losses	'	'
Total, Aggregate Fair Value	26,822	'
Total, Unrealized Losses	($13)	'

Amortized_Cost_and_Fair_Value_

Amortized Cost and Fair Value of Fixed-Maturity Portfolio by Contractual Time to Maturity (Detail) (USD $)	Mar. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Less than one year, amortized cost	$24,678	$32,760
One to five years, amortized cost	676,810	535,515
Five to ten years, amortized cost	633,082	641,036
More than 10 years, amortized cost	401,059	404,038
Mortgage and asset-backed securities, amortized cost	532,447	576,837
Total at end of period, amortized cost	2,268,076	2,190,186
Less than one year, fair value	25,068	33,329
One to five years, fair value	699,372	557,798
Five to ten years, fair value	674,232	687,720
More than 10 years, fair value	434,158	441,587
Mortgage and asset-backed securities, fair value	574,941	624,277
Total at end of period, fair value	2,407,771	2,344,711
Tower	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Less than one year, amortized cost	22,678	30,082
One to five years, amortized cost	636,015	489,939
Five to ten years, amortized cost	556,748	564,556
More than 10 years, amortized cost	343,277	346,410
Mortgage and asset-backed securities, amortized cost	453,578	495,249
Total at end of period, amortized cost	2,012,296	1,926,236
Less than one year, fair value	23,060	30,614
One to five years, fair value	656,679	510,523
Five to ten years, fair value	594,311	607,711
More than 10 years, fair value	372,246	379,045
Mortgage and asset-backed securities, fair value	490,511	536,255
Total at end of period, fair value	2,136,807	2,064,148
Reciprocal Exchanges	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Less than one year, amortized cost	2,000	2,678
One to five years, amortized cost	40,795	45,576
Five to ten years, amortized cost	76,334	76,480
More than 10 years, amortized cost	57,782	57,628
Mortgage and asset-backed securities, amortized cost	78,869	81,588
Total at end of period, amortized cost	255,780	263,950
Less than one year, fair value	2,008	2,715
One to five years, fair value	42,693	47,275
Five to ten years, fair value	79,921	80,009
More than 10 years, fair value	61,912	62,542
Mortgage and asset-backed securities, fair value	84,430	88,022
Total at end of period, fair value	$270,964	$280,563

Composition_of_Other_Invested_

Composition of Other Invested Assets (Detail) (Tower, USD $)	Mar. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule of Investments [Line Items]	'	'
Other invested assets	$58,941	$57,786
Limited partnerships, equity method	'	'
Schedule of Investments [Line Items]	'	'
Other invested assets	24,517	23,864
Real estate, amortized cost	'	'
Schedule of Investments [Line Items]	'	'
Other invested assets	7,223	7,422
Securities reported under the fair value option	'	'
Schedule of Investments [Line Items]	'	'
Other invested assets	25,000	25,000
Other	'	'
Schedule of Investments [Line Items]	'	'
Other invested assets	$2,201	$1,500

Financial_Instruments_at_Fair_

Financial Instruments at Fair Value among Levels (Detail) (USD $)	Mar. 31, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	$2,579,301		$2,495,719
Other invested assets	25,000	[1]	25,000	[2]
Interest rate swap contracts	-8,203		-9,016
Debt and equity securities sold, not yet purchased	-22,513		-17,101
Total investments and Other liabilities	2,573,585		2,494,602
Tower	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	2,305,423		2,209,593
Total investments and Other liabilities	2,299,707		2,208,475
Reciprocal Exchanges	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	273,878		286,126
Total investments and Other liabilities	273,878		286,127
Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	142,708		146,258
Other invested assets	'	[1]	'	[2]
Interest rate swap contracts	'		'
Debt and equity securities sold, not yet purchased	'		'
Total investments and Other liabilities	142,708		146,258
Level 1 | Tower	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total investments and Other liabilities	139,794		140,695
Level 1 | Reciprocal Exchanges	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total investments and Other liabilities	2,914		5,563
Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	2,436,593		2,349,461
Other invested assets	'	[1]	'
Interest rate swap contracts	-8,203		-9,016
Debt and equity securities sold, not yet purchased	-22,513		-17,101
Total investments and Other liabilities	2,405,877		2,323,344
Level 2 | Tower	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total investments and Other liabilities	2,134,913		2,042,780
Level 2 | Reciprocal Exchanges	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total investments and Other liabilities	270,964		280,564
Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Other invested assets	25,000	[1]	25,000	[2]
Interest rate swap contracts	'		'
Debt and equity securities sold, not yet purchased	'		'
Total investments and Other liabilities	25,000		25,000
Level 3 | Tower	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total investments and Other liabilities	25,000		25,000
Level 3 | Reciprocal Exchanges	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total investments and Other liabilities	'		'
Fixed-maturity securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	2,407,771		2,344,711
Fixed-maturity securities | U.S. Treasury Securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	316,732		184,949
Fixed-maturity securities | U.S. Agency securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	109,005		102,777
Fixed-maturity securities | Municipal Bonds	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	688,931		686,043
Fixed-maturity securities | Corporate Securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	718,162		746,665
Fixed-maturity securities | Commercial mortgage-backed securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	235,921		242,053
Fixed-maturity securities | Residential Mortgage-Backed Securities, Agency Backed Securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	262,199		295,716
Fixed-maturity securities | Residential mortgage-backed securities, Non-agency backed securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	41,624		42,156
Fixed-maturity securities | Asset-Backed Securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	35,197		44,352
Fixed-maturity securities | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Fixed-maturity securities | Level 1 | U.S. Treasury Securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Fixed-maturity securities | Level 1 | U.S. Agency securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Fixed-maturity securities | Level 1 | Municipal Bonds	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Fixed-maturity securities | Level 1 | Corporate Securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Fixed-maturity securities | Level 1 | Commercial mortgage-backed securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Fixed-maturity securities | Level 1 | Residential Mortgage-Backed Securities, Agency Backed Securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Fixed-maturity securities | Level 1 | Residential mortgage-backed securities, Non-agency backed securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Fixed-maturity securities | Level 1 | Asset-Backed Securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Fixed-maturity securities | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	2,407,771		2,344,711
Fixed-maturity securities | Level 2 | U.S. Treasury Securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	316,732		184,949
Fixed-maturity securities | Level 2 | U.S. Agency securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	109,005		102,777
Fixed-maturity securities | Level 2 | Municipal Bonds	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	688,931		686,043
Fixed-maturity securities | Level 2 | Corporate Securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	718,162		746,665
Fixed-maturity securities | Level 2 | Commercial mortgage-backed securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	235,921		242,053
Fixed-maturity securities | Level 2 | Residential Mortgage-Backed Securities, Agency Backed Securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	262,199		295,716
Fixed-maturity securities | Level 2 | Residential mortgage-backed securities, Non-agency backed securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	41,624		42,156
Fixed-maturity securities | Level 2 | Asset-Backed Securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	35,197		44,352
Fixed-maturity securities | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Fixed-maturity securities | Level 3 | U.S. Treasury Securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Fixed-maturity securities | Level 3 | U.S. Agency securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Fixed-maturity securities | Level 3 | Municipal Bonds	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Fixed-maturity securities | Level 3 | Corporate Securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Fixed-maturity securities | Level 3 | Commercial mortgage-backed securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Fixed-maturity securities | Level 3 | Residential Mortgage-Backed Securities, Agency Backed Securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Fixed-maturity securities | Level 3 | Residential mortgage-backed securities, Non-agency backed securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Fixed-maturity securities | Level 3 | Asset-Backed Securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Equity securities	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	142,708		146,258
Equity securities | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	142,708		146,258
Equity securities | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Equity securities | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Short-term investments	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	28,822		4,750
Short-term investments | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
Short-term investments | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	28,822		4,750
Short-term investments | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Investments	'		'
[1]	$25.0 million of the $58.9 million Other invested assets reported on the consolidated balance sheet at March 31, 2013 is reported at fair value. The remaining $33.9 million of Other invested assets is reported under the equity method of accounting or at amortized cost.
[2]	$25.0 million of the $57.8 million Other invested assets reported on the consolidated balance sheet at December 31, 2012 is reported at fair value. The remaining $32.8 million of Other invested assets is reported under the equity method of accounting or at amortized cost.

Financial_Instruments_at_Fair_1

Financial Instruments at Fair Value among Levels (Parenthetical) (Detail) (USD $)	Mar. 31, 2013		Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Other invested assets, fair value	$25,000,000	[1]	$25,000,000	[2]
Other invested assets, amortized cost	33,900,000		32,800,000
Tower	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Other invested asset	$58,941,000		$57,786,000
[1]	$25.0 million of the $58.9 million Other invested assets reported on the consolidated balance sheet at March 31, 2013 is reported at fair value. The remaining $33.9 million of Other invested assets is reported under the equity method of accounting or at amortized cost.
[2]	$25.0 million of the $57.8 million Other invested assets reported on the consolidated balance sheet at December 31, 2012 is reported at fair value. The remaining $32.8 million of Other invested assets is reported under the equity method of accounting or at amortized cost.

Fair_Value_Measurements_Additi

Fair Value Measurements - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Fair Value [Line Items]	'	'
Gross transfers out of Level 3	$0	$0
Gross transfers out of Level 1 into Level 2	0	0
Gross transfers out of Level 2 into Level 1	0	0
Net realized gains (losses) from fair value of debt and equity securities sold, not yet purchased	$200,000	'
Tower | Other	'	'
Fair Value [Line Items]	'	'
Number of securities purchased	2	'

Summary_of_Changes_in_Level_Th

Summary of Changes in Level Three Assets Measured at Fair Value (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'
Beginning balance	$25,000	$25,000
Total gains (losses)-realized / unrealized - included in net income	'	-86
Ending balance	$25,000	$24,914

Premiums_Written_Ceded_and_Ear

Premiums Written, Ceded and Earned (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]	'	'
Premiums written	$445,715	$404,840
Change in unearned premiums	-16,128	27,169
Premiums earned, Direct	429,587	432,009
Premiums written, Assumed	105,514	62,521
Change in unearned premiums, Assumed	-44,389	-31,394
Premiums earned, Assumed	61,125	31,127
Premiums written, Ceded	98,032	41,678
Change in unearned premiums, Ceded	-29,206	1,300
Premiums earned, Ceded	68,826	42,978
Premiums written, Net	453,197	425,683
Change in unearned premiums, Net	-31,311	-5,525
Premiums earned, Net	$421,886	$420,158

Reconciliation_of_Beginning_an

Reconciliation of Beginning and Ending Consolidated Balances for Unpaid Losses and Loss Adjustment Expense (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]	'	'
Balance at beginning of year	$1,895,679	$1,632,113
Less reinsurance recoverables on unpaid losses	-459,457	-292,221
Liability for Unpaid Claims and Claims Adjustment Expense, Net	1,436,222	1,339,892
Net reserves, at fair value, of acquired entities	161,886	'
Incurred related to:	'	'
Current year	268,037	254,525
Prior years unfavorable/(favorable) development	7,695	12,968
Total incurred	275,732	267,493
Paid related to:	'	'
Current year	121,045	96,932
Prior years	171,733	170,952
Total paid	292,778	267,884
Net balance at end of period	1,581,062	1,339,501
Add reinsurance recoverables on unpaid losses	850,188	257,938
Net balance at end of year	2,431,250	1,597,439
Tower	'	'
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]	'	'
Balance at beginning of year	1,759,888	1,495,839
Less reinsurance recoverables on unpaid losses	-407,068	-280,968
Liability for Unpaid Claims and Claims Adjustment Expense, Net	1,352,820	1,214,871
Net reserves, at fair value, of acquired entities	161,886	'
Incurred related to:	'	'
Current year	239,210	229,994
Prior years unfavorable/(favorable) development	1,124	13,256
Total incurred	240,334	243,250
Paid related to:	'	'
Current year	103,324	79,504
Prior years	171,026	158,829
Total paid	274,350	238,333
Net balance at end of period	1,480,690	1,219,788
Add reinsurance recoverables on unpaid losses	822,634	235,033
Net balance at end of year	2,303,324	1,454,821
Reciprocal Exchanges	'	'
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]	'	'
Balance at beginning of year	135,791	136,274
Less reinsurance recoverables on unpaid losses	-52,389	-11,253
Liability for Unpaid Claims and Claims Adjustment Expense, Net	83,402	125,021
Net reserves, at fair value, of acquired entities	'	'
Incurred related to:	'	'
Current year	28,827	24,531
Prior years unfavorable/(favorable) development	6,571	-288
Total incurred	35,398	24,243
Paid related to:	'	'
Current year	17,721	17,428
Prior years	707	12,123
Total paid	18,428	29,551
Net balance at end of period	100,372	119,713
Add reinsurance recoverables on unpaid losses	27,554	22,905
Net balance at end of year	$127,926	$142,618

Loss_and_Loss_Adjustment_Expen2

Loss and Loss Adjustment Expense - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]	'	'	'
Prior years unfavorable/(favorable) development	$7,695,000	$12,968,000	'
Loss and loss adjustment expenses ratio	65.40%	63.70%	'
Worker compensation discount amount	8,400,000	'	8,400,000
Unamortized reserve for risk premium	19,100,000	'	0
Tower	'	'	'
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]	'	'	'
Prior years unfavorable/(favorable) development	$1,124,000	$13,256,000	'
Loss and loss adjustment expenses ratio	63.10%	64.20%	'

Stockholders_Equity_Additional

Stockholders' Equity - Additional Information (Detail) (USD $)	3 Months Ended			3 Months Ended		1 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Mar. 31, 2013	Mar. 31, 2012	7-May-13	Mar. 13, 2013
				Restricted Stock	Restricted Stock	Subsequent Event	Bermuda
						Dividend Declared
Stockholders Equity Note [Line Items]	'	'	'	'	'	'	'
Conversion ratio	1.133	'	'	'	'	'	'
Common shares, outstanding	57,432,150	'	43,513,678	'	'	'	14,025,737
Employee stock option exercises	'	'	'	'	'	'	'
Number of option, grants	'	'	'	240,293	363,894	'	'
Common stock purchased from employees to pay expected amount of tax liability	'	'	'	340,707	109,743	'	'
Number of shares, forfeitures	'	'	'	6,848	4,852	'	'
Dividends declared	$7,201	$7,398	'	'	'	'	'
Dividends payable, amount per share	'	'	'	'	'	$0.17	'
Dividend payable date	'	'	'	'	'	21-Jun-13	'
Dividend record date	'	'	'	'	'	10-Jun-13	'
Historical dividend per share	$0.19	'	'	'	'	'	'

Summary_of_Changes_in_Accumula

Summary of Changes in Accumulated Other Comprehensive Income, by Component (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013
Components of Net Unrealized Investment Gains Losses Included in Accumulated Other Comprehensive Income Loss [Line Items]	'
Beginning Balance	$87,412
Other comprehensive income before reclassifications, net of tax	906
Amounts reclassified from accumulated other comprehensive income, net of tax	-4,051
Net current period other comprehensive income	-3,145
Ending Balance	84,267
Beginning Balance	-5,860
Other comprehensive income before reclassifications, net of tax	514
Amounts reclassified from accumulated other comprehensive income, net of tax	533
Net current period other comprehensive income	1,047
Ending Balance	-4,813
Beginning Balance	1,204
Other comprehensive income before reclassifications, net of tax	-2,347
Amounts reclassified from accumulated other comprehensive income, net of tax	'
Net current period other comprehensive income	-2,347
Ending Balance	-1,143
Beginning Balance	82,756
Other comprehensive income before reclassifications, net of tax	-927
Amounts reclassified from accumulated other comprehensive income, net of tax	-3,518
Net current period other comprehensive income	-4,445
Ending Balance	$78,311

Reclassified_from_Accumulated_

Reclassified from Accumulated Other Comprehensive Income to Net Income (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'
Unrealized gains (losses) on available for sale securities, before income tax	($6,467)	($3,328)
Unrealized gains (losses) on available for sale securities, net income tax	-4,051	'
Gains (losses) on cash flow hedges interest rate swaps, net of income taxes	533	'
Income Tax Expense	'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'
Unrealized gains (losses) on available for sale securities, Income tax expense	2,181	'
Interest Rate Swaps	'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'
Gains (losses) on cash flow hedges interest rate swaps, net of income taxes	533	'
Interest Rate Swaps | Income Tax Expense	'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'
Gains (losses) on cash flow hedges interest rate swaps, income tax expense	-287	'
Interest Rate Swaps | Interest Expense	'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'
Gains (losses) on cash flow hedges interest rate swaps, interest expense	820	'
Other Net Unrealized Investment Gains and Losses	'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'
Unrealized gains (losses) on available for sale securities, before income tax	($6,232)	'

Borrowings_Detail

Borrowings (Detail) (USD $)	Mar. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Debt Instrument [Line Items]	'	'
Credit facility	$70,000	$70,000
Subordinated debentures	235,058	235,058
Total	450,470	449,731
Credit facility	70,000	70,000
Subordinated debentures	236,875	232,678
Total	463,250	454,741
Convertible Senior Notes	'	'
Debt Instrument [Line Items]	'	'
Convertible senior notes	145,412	144,673
Convertible senior notes	$156,375	$152,063

Debt_Additional_Information_De

Debt - Additional Information (Detail) (USD $)

3 Months Ended

1 Months Ended

6 Months Ended

6 Months Ended

1 Months Ended

3 Months Ended

Mar. 31, 2013

Mar. 31, 2012

Dec. 31, 2012

Oct. 31, 2010

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Mar. 31, 2013

Dec. 31, 2012

Oct. 11, 2013

Jun. 30, 2013

Apr. 03, 2013

Jun. 30, 2013

Sep. 30, 2010

Mar. 31, 2013

Interest Rate Swaps

Minimum

Minimum

Minimum

Other liability

Other liability

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Convertible Senior Notes

Convertible Senior Notes

Scenario, Forecast

CastlePoint Re

TRL

Interest Rate Swaps

Interest Rate Swaps

Minimum

Scenario, Forecast

Scenario, Forecast

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest expense

$7,808,000

$8,611,000

'

'

'

'

'

'

'

'

'

'

'

'

$2,900,000

Subordinated debentures, carrying value

235,058,000

'

235,058,000

'

'

'

'

'

'

'

235,000,000

'

'

'

'

Notional amount, interest rate swap contracts

'

'

'

190,000,000

'

'

'

'

'

'

'

'

'

'

'

Interest rate swap contracts, terms

'

'

'

'5 years

'

'

'

'

'

'

'

'

'

'

'

Interest rate range on swaps, minimum

'

'

'

5.10%

'

'

'

'

'

'

'

'

'

'

'

Interest rate range on swaps, maximum

'

'

'

5.90%

'

'

'

'

'

'

'

'

'

'

'

Interest rate swap contracts liabilities, fair value

8,203,000

'

9,016,000

'

'

'

'

8,200,000

9,000,000

'

'

'

'

'

'

Gain (loss) on Swaps designated as cash flow hedges reclassified from AOCI to interest expense

500,000

500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Collateral on deposit with the counterparty

8,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Credit facility agreement, borrowing capacity

'

'

'

'

'

'

'

'

'

70,000,000

'

220,000,000

'

'

'

Outstanding credit facility amount

70,000,000

'

70,000,000

'

'

'

'

'

'

'

70,000,000

'

'

'

'

Weighted average interest rate

'

'

'

'

'

'

'

'

'

'

1.94%

'

'

'

'

Credit facility agreement, maturity date

'

'

'

'

'

'

'

'

'

30-May-14

'

'

'

'

'

Credit facility covenant, Minimum Consolidated Net Worth

'

'

'

'

'

'

'

'

'

'

'

'

553,400,000

'

'

Credit facility covenant, percentage of Consolidated Net Worth

'

'

'

'

'

'

'

'

'

'

'

'

90.00%

'

'

Credit facility covenant, covenant increase as a percentage of any new capital

'

'

'

'

'

'

'

'

'

'

90.00%

'

'

'

'

Credit facility covenant, additional covenant increase as a percentage of net income above base

'

'

'

'

'

'

'

'

'

'

50.00%

'

'

'

'

Credit facility covenant, net income amount base for additional covenant increase

'

'

'

'

'

'

'

'

'

'

20,000,000

'

'

'

'

Credit facility covenant, Debt to capitalization ratio limit

'

'

'

'

'

'

'

'

'

'

46.00%

'

'

'

'

Credit facility covenant, risk based capital ratio

'

'

'

'

175.00%

'

'

'

'

'

'

'

'

'

'

Credit facility covenant, consolidated statutory surplus

'

'

'

'

10.00%

'

'

'

'

'

'

'

'

'

'

Credit facility covenant, percentage of required capital

'

'

'

'

'

150.00%

110.00%

'

'

'

'

'

'

'

'

Credit facility covenant, minimum statutory surplus

'

'

'

'

'

'

'

'

'

'

419,000,000

'

'

'

'

Credit facility covenant, combined surplus

'

'

'

'

'

'

'

'

'

'

85.00%

'

'

'

'

Convertible senior notes principal amount

'

'

'

'

'

'

'

'

'

'

'

'

'

150,000,000

'

Interest rate on convertible senior note, percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

5.00%

'

Maturity date of convertible senior notes

'

'

'

'

'

'

'

'

'

'

'

'

'

15-Sep-14

'

Frequency of interest payment, term

'

'

'

'

'

'

'

'

'

'

'

'

'

'Interest on the Notes is payable semi-annually in arrears on March 15 and September 15 of each year, commencing March 15, 2011.

'

First interest payment date

'

'

'

'

'

'

'

'

'

'

'

'

'

15-Mar-11

'

Earliest conversion date for notes

'

'

'

'

'

'

'

'

'

'

'

'

'

15-Mar-14

'

Conversion rate of shares of common stock per principal amount of notes

'

'

'

'

'

'

'

'

'

'

'

'

'

'

42.2491

Principal amount of Notes

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,000

Initial conversion price

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$23.67

Debt conversion term

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'The adjusted conversion rate at March 31, 2013 is 42.2491 shares of common stock per $1,000 principal amount of the Notes (equivalent to a conversion price of $23.67 per share), subject to further adjustment upon the occurrence of certain events, including the following: if Tower issues shares of common stock as a dividend or distribution on shares of the common stock , or if Tower effects a share split or share combination; if Tower issues to all or substantially all holders of common stock any rights, options or warrants entitling them, for a period of not more than 45 calendar days after the announcement date of such issuance, to subscribe for or purchase shares of the common stock at a price per share that is less than the average of the last reported sales price of the common stock for the ten consecutive trading day period ending on the date of announcement of such issuance; if Tower distributes shares of its capital stock, other indebtedness, other assets or property of Tower or rights, options or warrants to acquire capital stock or other securities of Tower, to all or substantially all holders of capital stock; if any cash dividend or distribution is made to all or substantially all holders of the common stock, other than a regular quarterly cash dividend that does not exceed $0.110 per share; if Tower makes a payment in respect of a tender offer or exchange offer for common stock, and the cash and value of any other consideration included in the payment per share of common stock exceeds the last reported sale price of the common stock on the trading day next succeeding the last day on which the tenders or exchange may be made.

Effective interest rate on convertible senior note

'

'

'

'

'

'

'

'

'

'

'

'

'

'

7.20%

Transaction costs associated with equity component

'

'

'

'

'

'

'

'

'

'

'

'

'

'

400,000

Proceeds from issuance of note hedge

2,380,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Payments for warrants

1,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Tax adjustment recorded in paid-in-capital

$800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Amounts_Recorded_for_Notes_Det

Amounts Recorded for Notes (Detail) (Convertible Senior Notes, USD $)	Mar. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Convertible Senior Notes	'	'
Liability component	'	'
Outstanding principal	$150,000	$150,000
Unamortized OID	-4,588	-5,327
Liability component	145,412	144,673
Equity component, net of tax	$7,469	$7,469

Stock_Based_Compensation_Addit

Stock Based Compensation - Additional Information (Detail)	Mar. 31, 2013	Mar. 13, 2013
		Canopius Group Limited
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Maximum Share based awards authorized	2,325,446	'
Shares available for future grants	28,216	'
Number of shares, vested	'	525,548
Conversion ratio	1.133	'

Analysis_of_Restricted_Stock_A

Analysis of Restricted Stock Activity (Detail) (Restricted Stock, USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Restricted Stock	'	'
Number of Shares	'	'
Number of Shares, Beginning Balance	1,015,902	1,120,091
Number of Shares, Granted	240,293	363,894
Number of Shares, Vested	-950,773	-428,687
Number of Shares, Forfeitures	-6,848	-4,852
Number of Shares, Ending Balance	298,574	1,050,446
Weighted Average Grant Date Fair Value	'	'
Weighted Average Grant Date Fair Value, Beginning Balance	$20.19	$20.69
Weighted Average Grant Date Fair Value, Granted	$18.08	$20.37
Weighted Average Grant Date Fair Value, Vested	$20.44	$21.08
Weighted Average Grant Date Fair Value, Forfeitures	$20.51	$20.80
Weighted Average Grant Date Fair Value, Ending Balance	$17.67	$20.38

Analysis_of_Stock_Option_Activ

Analysis of Stock Option Activity (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Number of Shares	'	'
Number of Shares Outstanding, Beginning Balance	969,307	969,312
Number of Shares, Exercised	'	'
Number of Shares, Forfeitures and expirations	'	'
Number of Shares Outstanding, Ending Balance	969,307	969,312
Number of Shares Exercisable, Ending Balance	969,307	969,312
Average Exercise Price	'	'
Average Exercise Price Outstanding, Beginning Balance	$17.78	$17.78
Average Exercise Price, Exercised	'	'
Average Exercise Price, Forfeitures and expirations	'	'
Average Exercise Price Outstanding, Ending Balance	$17.78	$17.78
Average Exercise Price Exercisable, Ending Balance	$17.78	$17.78

Analysis_of_Stock_Based_Compen

Analysis of Stock Based Compensation Expense (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Weighted average years over which expense will be recognized	'3 years 10 months 24 days	'2 years 9 months 18 days
Restricted Stock	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Expense, net of tax	7,982	1,464
Value of shares vested	9,485	5,622
Value of unvested shares	5,509	20,796
Unrecognized compensation expense	5,509	12,791
Stock Options	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Intrinsic value of outstanding options	1,149	2,704
Intrinsic value of vested outstanding options	1,149	2,704

Provision_Income_Taxes_Detail

Provision Income Taxes (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Reconciliation of Provision of Income Taxes [Line Items]	'	'
Income (loss) before income tax	$46	$31,401
Income tax expense (benefit)	-1,590	9,224
Effective tax rate	-3456.50%	29.40%
U S | Tower	'	'
Reconciliation of Provision of Income Taxes [Line Items]	'	'
Income (loss) before income tax	-15,433	27,773
Income tax expense (benefit)	-1,590	8,607
Effective tax rate	10.30%	31.00%
U S | Reciprocal Exchanges	'	'
Reconciliation of Provision of Income Taxes [Line Items]	'	'
Income (loss) before income tax	-11,281	3,628
Income tax expense (benefit)	'	617
Effective tax rate	'	17.00%
Non U S	'	'
Reconciliation of Provision of Income Taxes [Line Items]	'	'
Income (loss) before income tax	$26,760	'

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Income Taxes [Line Items]	'	'
Effective tax rate	-3456.50%	29.40%
U S | Tower	'	'
Income Taxes [Line Items]	'	'
Effective tax rate	10.30%	31.00%
Non Life Insurance Premiums	'	'
Income Taxes [Line Items]	'	'
Percentage of excise tax rate	4.00%	'
Life Insurance and Reinsurance Premiums	'	'
Income Taxes [Line Items]	'	'
Percentage of excise tax rate	1.00%	'

Earnings_per_Share_Additional_

Earnings per Share - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share Disclosure [Line Items]	'	'
Conversion ratio	1.133	'
Options and other common stock equivalents excluded from computation of diluted earnings per share	190,500	188,900

Computation_of_Earnings_Per_Sh

Computation of Earnings Per Share (Detail) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Numerator	'	'
Net income (loss) attributable to Tower Group International, Ltd.	$12,917	$19,166
Less: Allocation of income for unvested participating restricted stock	-37	-298
Less: Dividends on unvested participating restricted stock	-166	-174
Net income available to common shareholders - Basic	12,714	18,694
Reallocation of income for unvested participating restricted stock	'	'
Net income available to common shareholders - Diluted	$12,714	$18,694
Denominator	'	'
Basic earning per share denominator	45,614	43,326
Effect of dilutive securities	74	85
Diluted earnings per share denominator	45,688	43,411
Common stock:	'	'
Distributed earnings	$0.17	$0.17
Undistributed earnings	$0.11	$0.26
Total	$0.28	$0.43
Earnings (loss) per share attributable to Tower Group International, Ltd. - Diluted	$0.28	$0.43

Business_Segments_Results_Deta

Business Segments Results (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Revenues	'	'
Premiums earned	$421,886	$420,158
Ceding commission revenue	14,151	5,163
Policy billing fees	3,150	3,134
Total revenues	446,476	435,814
Expenses	'	'
Loss and loss adjustment expenses	275,732	267,493
Total expenses	476,565	434,822
Reciprocal Exchanges	'	'
Expenses	'	'
Total expenses	58,500	47,200
Commercial Insurance	'	'
Revenues	'	'
Premiums earned	307,784	297,835
Ceding commission revenue	3,287	10
Policy billing fees	1,370	1,513
Total revenues	312,441	299,358
Expenses	'	'
Loss and loss adjustment expenses	196,363	201,438
Underwriting expenses	112,912	103,142
Total expenses	309,275	304,580
Underwriting profit (loss)	3,166	-5,222
Personal Insurance	'	'
Revenues	'	'
Premiums earned	114,102	122,323
Ceding commission revenue	10,864	5,153
Policy billing fees	1,780	1,621
Total revenues	126,746	129,097
Expenses	'	'
Loss and loss adjustment expenses	79,369	66,055
Underwriting expenses	60,528	53,852
Total expenses	139,897	119,907
Underwriting profit (loss)	-13,151	9,190
Personal Insurance | Tower	'	'
Expenses	'	'
Underwriting profit (loss)	-524	9,438
Personal Insurance | Reciprocal Exchanges	'	'
Expenses	'	'
Underwriting profit (loss)	-12,627	-248
Insurance Services Segment	'	'
Revenues	'	'
Management fee income	7,161	6,862
Other revenue	128	497
Total revenues	7,289	7,359
Expenses	'	'
Other expenses	4,621	4,463
Total expenses	4,621	4,463
Insurance services pretax income	$2,668	$2,896

Reconciliation_of_Revenue_by_S

Reconciliation of Revenue by Segment to Consolidated Revenues (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Segment Reporting, Revenue Reconciling Item [Line Items]	'	'
Total segment revenues	$446,476	$435,814
Net investment income	30,317	33,943
Net realized gains (losses) on investments, including other-than-temporary impairments	6,851	3,328
Consolidated revenues	476,483	466,223
Commercial Insurance	'	'
Segment Reporting, Revenue Reconciling Item [Line Items]	'	'
Total segment revenues	312,441	299,358
Personal Insurance	'	'
Segment Reporting, Revenue Reconciling Item [Line Items]	'	'
Total segment revenues	126,746	129,097
Insurance Services Segment	'	'
Segment Reporting, Revenue Reconciling Item [Line Items]	'	'
Total segment revenues	7,289	7,359
Management fee income	-7,161	-6,862
Elimination	'	'
Segment Reporting, Revenue Reconciling Item [Line Items]	'	'
Management fee income	($7,161)	($6,862)

Reconciliation_of_Results_of_I

Reconciliation of Results of Individual Segments to Consolidated Income Before Income Taxes (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'	'
Net investment income	$30,317	$33,943
Net realized gains on investments, including other-than-temporary impairments	6,851	3,328
Corporate expenses	-3,069	-2,861
Acquisition-related transaction costs	-19,056	-1,262
Interest expense	-7,808	-8,611
Other income	128	'
Income before income taxes	46	31,401
Commercial Insurance	'	'
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'	'
Underwriting profit (loss)	3,166	-5,222
Personal Insurance	'	'
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'	'
Underwriting profit (loss)	-13,151	9,190
Insurance Services Segment	'	'
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'	'
Segment pretax income (loss)	$2,668	$2,896

Contingencies_Additional_Infor

Contingencies - Additional Information (Detail) (Subsequent Event, USD $)	1 Months Ended
In Millions, unless otherwise specified	Oct. 18, 2013
Subsequent Event	'
Contingencies, damages sought	$150

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (USD $)

3 Months Ended

1 Months Ended

6 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

Mar. 31, 2013

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Oct. 18, 2013

Oct. 11, 2013

Aug. 19, 2013

7-May-13

Jun. 30, 2013

Apr. 03, 2013

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Oct. 01, 2013

Oct. 01, 2013

Oct. 01, 2013

Scenario, Forecast

Scenario, Forecast

Scenario, Forecast

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Subsequent Event

Minimum

CastlePoint Re

TRL

Minimum

Commercial Insurance

Commercial Insurance

Specialty Insurance and Reinsurance

Specialty Insurance and Reinsurance

Tower Insurance Company of New York

Tower Insurance Company of New York

Tower Insurance Company of New York

Minimum

Minimum

Arch

Hannover

Southport Re

Subsequent Event [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Gain on agreement termination

'

'

'

'

'

'

'

$5,000,000

'

'

'

'

'

'

'

'

'

'

'

Credit facility agreement, borrowing capacity

'

'

'

'

'

'

70,000,000

'

'

'

220,000,000

'

'

'

'

'

'

'

'

Credit facility agreement, maturity date

'

'

'

'

'

'

30-May-14

'

'

'

'

'

'

'

'

'

'

'

'

Quota share reinsurance cede, percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

17.50%

14.00%

30.00%

Net written premiums

453,197,000

425,683,000

'

'

'

'

'

'

'

'

'

'

169,100,000

343,600,000

103,700,000

306,600,000

'

'

'

Stock repurchase program authorized amount

'

'

'

'

'

'

'

'

50,000,000

'

'

'

'

'

'

'

'

'

'

Credit facility covenant, Consolidated Net Worth

'

'

'

'

'

'

'

'

'

'

'

553,400,000

'

'

'

'

'

'

'

Credit facility covenant, percentage of Consolidated Net Worth

'

'

'

'

'

'

'

'

'

'

'

90.00%

'

'

'

'

'

'

'

Credit facility covenant, covenant increase as a percentage of any new capital

'

'

'

'

'

'

'

'

'

90.00%

'

'

'

'

'

'

'

'

'

Credit facility covenant, additional covenant increase as a percentage of net income above base

'

'

'

'

'

'

'

'

'

50.00%

'

'

'

'

'

'

'

'

'

Credit facility covenant, net income amount base for additional covenant increase

'

'

'

'

'

'

'

'

'

20,000,000

'

'

'

'

'

'

'

'

'

Credit facility covenant, Debt to capitalization ratio limit

'

'

'

'

'

'

'

'

'

46.00%

'

'

'

'

'

'

'

'

'

Credit facility covenant, risk based capital ratio

'

'

175.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Credit facility covenant, consolidated statutory surplus

'

'

10.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Credit facility covenant, percentage of required capital

'

'

'

150.00%

110.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Credit facility covenant, minimum statutory surplus

'

'

'

'

'

'

'

'

'

419,000,000

'

'

'

'

'

'

'

'

'

Credit facility covenant, combined surplus

'

'

'

'

'

'

'

'

'

85.00%

'

'

'

'

'

'

'

'

'

Contingencies, damages sought

'

'

'

'

'

$150,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'