Safety Insurance (SAFT) 10-K 17 Mar 14 2013 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2013	Mar. 11, 2014	Jun. 30, 2013
Document and Entity Information	'	'	'
Entity Registrant Name	'SAFETY INSURANCE GROUP INC	'	'
Entity Central Index Key	'0001172052	'	'
Document Type	'10-K	'	'
Document Period End Date	31-Dec-13	'	'
Amendment Flag	'false	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Well-known Seasoned Issuer	'No	'	'
Entity Voluntary Filers	'No	'	'
Entity Current Reporting Status	'Yes	'	'
Entity Filer Category	'Accelerated Filer	'	'
Entity Public Float	'	'	$678,718,982
Entity Common Stock, Shares Outstanding	'	15,389,382	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Investments: Securities available for sale:	'	'
Fixed maturities, at fair value (amortized cost: $1,087,232 and $1,100,414)	$1,104,957	$1,165,553
Equity securities, at fair value (cost: $83,134 and $21,237)	91,871	22,800
Other invested assets	5,748	'
Total investments	1,202,576	1,188,353
Cash and cash equivalents	55,877	35,383
Accounts receivable, net of allowance for doubtful accounts	169,304	165,750
Receivable for securities sold	1,320	835
Accrued investment income	10,329	10,587
Taxes recoverable	709	5,529
Receivable from reinsurers related to paid loss and loss adjustment expenses	4,588	6,610
Receivable from reinsurers related to unpaid loss and loss adjustment expenses	60,346	52,185
Ceded unearned premiums	17,900	16,206
Deferred policy acquisition costs	63,388	60,665
Deferred income taxes	3,984	'
Equity and deposits in pools	18,733	16,965
Other assets	16,403	15,278
Total assets	1,625,457	1,574,346
Liabilities	'	'
Loss and loss adjustment expense reserves	455,014	423,842
Unearned premium reserves	370,583	353,219
Accounts payable and accrued liabilities	66,508	65,458
Payable for securities purchased	13,327	2,630
Payable to reinsurers	7,094	7,056
Deferred income taxes	'	8,202
Other liabilities	17,744	19,580
Total liabilities	930,270	879,987
Commitments and contingencies (Note 7)	'	'
Shareholders' equity	'	'
Common stock: $0.01 par value; 30,000,000 shares authorized; 17,207,929 and 17,052,034 shares issued	172	170
Additional paid-in capital	170,391	163,041
Accumulated other comprehensive income, net of taxes	17,200	43,356
Retained earnings	567,792	543,361
Treasury stock, at cost: 1,819,547 and 1,728,645 shares	-60,368	-55,569
Total shareholders' equity	695,187	694,359
Total liabilities and shareholders' equity	$1,625,457	$1,574,346

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
Consolidated Balance Sheets	'	'
Fixed maturities, at amortized cost	$1,087,232	$1,100,414
Equity securities, at cost	$83,134	$21,237
Common stock par value (in dollars per share)	$0.01	$0.01
Common stock shares authorized	30,000,000	30,000,000
Common stock shares issued	17,207,929	17,052,034
Treasury stock shares	1,819,547	1,728,645

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues	'	'	'
Net earned premiums	$681,870	$642,469	$598,368
Net investment income	43,054	40,870	39,060
Net realized gains on investments	1,677	1,975	4,360
Finance and other service income	18,683	18,553	18,370
Total revenue	745,284	703,867	660,158
Expenses	'	'	'
Losses and loss adjustment expenses	447,749	422,217	466,640
Underwriting, operating and related expenses	209,758	200,138	179,157
Interest expense	89	88	88
Total expenses	657,596	622,443	645,885
Income before income taxes	87,688	81,424	14,273
Income tax expense	26,337	23,354	571
Net income	$61,351	$58,070	$13,702
Earnings per weighted average common share:	'	'	'
Basic (in dollars per share)	$4	$3.80	$0.90
Diluted (in dollars per share)	$3.98	$3.80	$0.90
Cash dividends paid per common share (in dollars per share)	$2.40	$2.20	$2
Number of shares used in computing earnings per share:	'	'	'
Basic (in shares)	15,354,468	15,288,346	15,165,065
Diluted (in shares)	15,399,801	15,295,452	15,176,006

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Consolidated Statements of Comprehensive Income	'	'	'
Net income	$61,351	$58,070	$13,702
Unrealized holding (losses) gains during the period, net of tax (benefit) expense of ($13,497), $4,856, and $8,875	-25,066	9,019	16,483
Reclassification adjustment for gains included in net income, net of tax expense of ($587), ($691), and ($1,526)	-1,090	-1,284	-2,834
Unrealized (losses) gains on securities available for sale	-26,156	7,735	13,649
Comprehensive income	$35,195	$65,805	$27,351

Consolidated_Statements_of_Com1

Consolidated Statements of Comprehensive Income (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Consolidated Statements of Comprehensive Income	'	'	'
Tax (benefit) expense on unrealized holding (losses) gains during the period	($13,497)	$4,856	$8,875
Tax expense on reclassification adjustment for gains included in net income	($587)	($691)	($1,526)

Consolidated_Statements_of_Cha

Consolidated Statements of Changes in Shareholders' Equity (USD $)	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income, Net of Taxes	Retained Earnings	Treasury Stock
In Thousands
Balance at Dec. 31, 2010	$653,476	$168	$151,317	$21,972	$535,545	($55,526)
Net income	13,702	'	'	'	13,702	'
Other comprehensive income (loss), net of deferred federal income taxes	13,649	'	'	13,649	'	'
Restricted shares awards issued	189	1	188	'	'	'
Recognition of employee share-based compensation, net of deferred federal income taxes	4,692	'	4,692	'	'	'
Exercise of options, net of federal income taxes	970	'	970	'	'	'
Dividends paid and accrued	-30,322	'	'	'	-30,322	'
Acquisition of treasury stock	-43	'	'	'	'	-43
Balance at Dec. 31, 2011	656,313	169	157,167	35,621	518,925	-55,569
Net income	58,070	'	'	'	58,070	'
Other comprehensive income (loss), net of deferred federal income taxes	7,735	'	'	7,735	'	'
Restricted shares awards issued	167	1	166	'	'	'
Recognition of employee share-based compensation, net of deferred federal income taxes	4,484	'	4,484	'	'	'
Exercise of options, net of federal income taxes	1,224	'	1,224	'	'	'
Dividends paid and accrued	-33,634	'	'	'	-33,634	'
Balance at Dec. 31, 2012	694,359	170	163,041	43,356	543,361	-55,569
Net income	61,351	'	'	'	61,351	'
Other comprehensive income (loss), net of deferred federal income taxes	-26,156	'	'	-26,156	'	'
Restricted shares awards issued	188	1	187	'	'	'
Recognition of employee share-based compensation, net of deferred federal income taxes	4,618	'	4,618	'	'	'
Exercise of options, net of federal income taxes	2,546	1	2,545	'	'	'
Dividends paid and accrued	-36,920	'	'	'	-36,920	'
Acquisition of treasury stock	-4,799	'	'	'	'	-4,799
Balance at Dec. 31, 2013	$695,187	$172	$170,391	$17,200	$567,792	($60,368)

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities:	'	'	'
Net income	$61,351	$58,070	$13,702
Adjustments to reconcile net income to net cash provided by operating activities:	'	'	'
Depreciation and amortization, net	12,326	14,322	13,554
Provision (benefit) for deferred income taxes	1,899	1,023	-693
Net realized gains on investments	-1,677	-1,975	-4,360
Gains on sales of fixed assets	-3	'	'
Changes in assets and liabilities:	'	'	'
Accounts receivable	-3,554	-11,607	-8,417
Accrued investment income	258	-418	-698
Receivable from reinsurers	-6,139	-3,495	2,426
Ceded unearned premiums	-1,694	-2,184	-1,561
Deferred policy acquisition costs	-2,723	-3,949	-3,892
Other assets	3,084	-1,444	2,151
Loss and loss adjustment expense reserves	31,172	19,970	-519
Unearned premium reserves	17,364	23,657	23,509
Accounts payable and accrued liabilities	1,050	13,426	-2,135
Payable to reinsurers	38	1,718	-233
Other liabilities	-1,891	-2,783	6,641
Net cash provided by operating activities	110,861	104,331	39,475
Cash flows from investing activities:	'	'	'
Fixed maturities purchased	-193,814	-333,603	-344,433
Equity securities purchased	-75,891	-9,397	-13,149
Other invested assets purchased	-5,600	'	'
Proceeds from sales and paydowns of fixed maturities	179,729	165,878	264,635
Proceeds from maturities, redemptions, and calls of fixed maturities	34,264	98,045	78,243
Proceed from sales of equity securities	14,934	8,837	6,668
Fixed assets purchased	-4,920	-4,205	-4,377
Fixed assets sold	3	'	'
Net cash used for investing activities	-51,295	-74,445	-12,413
Cash flows from financing activities:	'	'	'
Proceeds from stock options exercised	2,592	1,241	902
Dividends paid to shareholders	-36,865	-33,634	-30,322
Acquisition of treasury stock	-4,799	'	-43
Net cash used for financing activities	-39,072	-32,393	-29,463
Net increase (decrease) in cash and cash equivalents	20,494	-2,507	-2,401
Cash and cash equivalents at beginning of year	35,383	37,890	40,291
Cash and cash equivalents at end of period	55,877	35,383	37,890
Supplemental disclosure of cash flow information:	'	'	'
Cash paid during the year for federal and state income taxes	18,890	19,730	4,260
Cash paid during the year for interest	$75	$75	$75

Basis_of_Presentation

Basis of Presentation	12 Months Ended
	Dec. 31, 2013
Basis of Presentation	'
Basis of Presentation	'
	1.     Basis of Presentation
	The consolidated financial statements have been prepared on the basis of accounting principles generally accepted in the United States of America ("GAAP"). The consolidated financial statements include Safety Insurance Group, Inc. and its subsidiaries (the "Company"). The subsidiaries consist of Safety Insurance Company, Safety Indemnity Insurance Company, Safety Property and Casualty Insurance Company, Whiteshirts Asset Management Corporation ("WAMC"), and Whiteshirts Management Corporation, which is WAMC's holding company. All intercompany transactions have been eliminated. Certain amounts in the consolidated financial statements for prior years have been reclassified to conform to the current year presentation.
	The Company was incorporated on June 25, 2001 in the State of Delaware. On October 16, 2001, the Company acquired all of the issued and outstanding common stock of Thomas Black Corporation ("TBC") and its property and casualty subsidiaries. TBC subsequently merged with and into Safety Insurance Group, Inc. with Safety Insurance Group, Inc. being the corporation surviving the merger.
	The Company is a leading provider of personal lines property and casualty insurance focused primarily on the Massachusetts market. The Company's principal product line is private passenger automobile insurance, which accounted for 63.9% of its direct written premiums in 2013. The Company operates through its insurance company subsidiaries, Safety Insurance Company, Safety Indemnity Insurance Company, and Safety Property and Casualty Insurance Company (together referred to as the "Insurance Subsidiaries").
	The Insurance Subsidiaries began writing private passenger automobile and homeowners insurance in New Hampshire during 2008, personal umbrella insurance in New Hampshire during 2009, and commercial automobile insurance in New Hampshire during 2011.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2013
Summary of Significant Accounting Policies	'
Summary of Significant Accounting Policies	'
	2.     Summary of Significant Accounting Policies
	Investments
	Investments in fixed maturities available-for-sale, which include taxable and non-taxable bonds and redeemable preferred stocks, are reported at fair value. Investments in equity securities available-for-sale, which include interests in common stocks, mutual funds and a real estate investment trust ("REIT"), are reported at fair value. Fair values for fixed maturity securities are based on estimates obtained from independent pricing services. Fair values for equity securities are derived from external market quotations, with the exception of the REIT whose fair value was determined using the trust's net asset value obtained from its audited financial statements. Short-term investments, which consist of U.S. Treasury bills, are reported at amortized cost, which approximates fair value. Other long-term investments consist of an investment in a limited partnership. The partnership interest is accounted for using the equity method of accounting. The income from the investment partnership is accounted for using the equity method and is included in net investment income. The carrying value of this investment is written down, or impaired, to fair value when a decline in value is considered to be other-than-temporary. In applying the equity method (including assessment for other-than-temporary impairment), the Company uses financial information provided by the investee, generally on a one to three month lag. Unrealized gains or losses on fixed maturity and equity securities reported at fair value are excluded from earnings and reported in a separate component of shareholders' equity, known as "Accumulated other comprehensive income (loss), net of taxes," until realized. Realized gains or losses on the sale or maturity of investments are determined based on the specific cost identification method. Fixed maturities and equity securities that experience declines in value that are other-than-temporary are written down to fair value with a corresponding charge to net realized losses on investments.
	Investment income is recognized on an accrual basis of accounting. Bonds not backed by other loans are amortized using the interest method. Loan-backed bonds and structured securities are amortized using the interest method and significant changes in estimated cash flows from the original purchase assumptions are accounted for using the retrospective method.
	Cash and Cash Equivalents
	Cash and cash equivalents includes money market accounts and United States ("U.S.") Treasury bills with original maturities of three months or less. U.S. Treasury bills are stated at amortized cost, which approximates fair value.
	Accounts Receivable
	Amounts included in accounts receivable represent premiums as well as finance charges, the majority of which are both billed on a monthly installment basis. Accounts receivable are stated net of allowances for doubtful accounts. At December 31, 2013 and 2012, these allowances were $456 and $635, respectively. Uncollected premium balances over ninety days past due are written off.
	Deferred Policy Acquisition Costs
	Amounts that vary with and are primarily related to the successful acquisition of a new or renewal insurance contract, principally commissions and premium taxes, are deferred and amortized ratably over the effective period of the policies. All other acquisition expenses are expensed as incurred. Deferred policy acquisition costs are reviewed to determine if they are recoverable from future income, and if not, are charged to expense. Future investment income attributable to related premiums is not taken into account in measuring the recoverability of the carrying value of this asset. Amortization of acquisition costs in the amount of $126,201, $118,850, and $110,795 was charged to underwriting expenses for the years ended 2013, 2012 and 2011, respectively.
	Equity and Deposits in Pools
	Equity and deposits in pools represents the net receivable amounts from the residual market mechanisms, Commonwealth Automobile Reinsurers ("CAR") for automobile and Massachusetts Property Insurance Underwriting Association ("FAIR Plan") for homeowner insurance in Massachusetts. See Note 8 for a discussion of the Company's accounting for amounts assumed from residual markets.
	Equipment and Leasehold Improvements
	Property, equipment, leasehold improvements, and software are carried at cost less accumulated depreciation. Depreciation is provided using the straight-line or accelerated method over the estimated useful lives of the related assets, which range from 3 to 10 years. Amortization of leasehold improvements is provided using the straight-line method over the term of the lease. The costs of computer software developed or obtained for internal use are capitalized and amortized over the estimated life of the business system, beginning when the software is ready for its intended use. Maintenance and repairs are charged to expense as incurred.
	Losses and Loss Adjustment Expenses
	Liabilities for losses and loss adjustment expenses ("LAE") include case basis estimates for open claims reported prior to year-end and estimates of unreported claims and claim adjustment expenses. The estimates are continually reviewed and modified to reflect current conditions, and any resulting adjustments are reflected in current operating results. Adjustments for anticipated salvage and subrogation are recorded on incurred and reported and incurred but not reported losses.
	Premiums and Unearned Premiums
	Premiums are earned over the terms of the respective policies, which are generally one year. Unearned premiums represent the portion of premiums written applicable to the unexpired terms of the policies.
	Ceded premiums are charged to income over the terms of the respective policies and the applicable term of the reinsurance contracts with third-party reinsurers. Ceded unearned premiums represent the unexpired portion of premiums ceded to CAR and other reinsurers.
	Premiums received in advance of the policy effective date are recorded as a liability and not recognized as income until earned. Such amounts are included in accounts payable and accrued liabilities and totaled $15,453 and $15,199 at December 31, 2013 and 2012, respectively.
	Reinsurance
	Liabilities for unearned premiums and unpaid losses are stated before deductions for ceded reinsurance. The ceded amounts are carried as receivables. Earned premiums are stated net of deductions for ceded reinsurance.
	The Company, as primary insurer, will be required to pay losses in their entirety in the event that the reinsurers are unable to discharge their obligations under the reinsurance agreements.
	Finance and Other Service Income
	Finance and other service income primarily includes revenues from premium installment charges, which are recognized when earned.
	Income Taxes
	The Company and its subsidiaries file a consolidated U.S. federal income tax return. The method of allocation among members of the consolidated group is subject to a written agreement approved by the Board of Directors (the "Board"). The consolidated tax liability is allocated on the basis of the members' proportionate contribution to consolidated taxable income.
	Deferred income taxes are generally recognized when assets and liabilities have different values for financial statement and tax reporting purposes, and for other temporary taxable and deductible differences as defined by Accounting Standards Codification ("ASC") 740, Income Taxes. A valuation allowance is established where management has assessed that it is more likely than not that the Company will not be able to utilize the full deferred tax asset.
	Earnings per Weighted Average Common Share
	Basic earnings per weighted average common share ("EPS") is calculated by dividing net income by the weighted average number of basic common shares outstanding during the period including unvested restricted shares which are considered participating securities. Diluted earnings per share is calculated by dividing net income by the weighted average number of common shares including unvested restricted shares and the net effect of potentially dilutive common shares outstanding
	The following table sets forth the computation of basic and diluted EPS for the periods indicated.
		Years Ended December 31,
		2013		2012		2011
	Net income available to common shareholders for basic and diluted earnings per share	$	61,351	$	58,070	$	13,702
	Weighted average common and common equivalent shares outstanding used to calculate basic earnings per share		15,354,468		15,288,346		15,165,065
	Common equivalent shares—stock options		5,558		7,106		10,941
	Common equivalent shares—non-vested stock grants		39,775		—		—
	Weighted average common and common equivalent shares outstanding used to calculate diluted earnings per share		15,399,801		15,295,452		15,176,006
	Basic earnings per share	$	4	$	3.8	$	0.9
	Diluted earnings per share	$	3.98	$	3.8	$	0.9
	Diluted EPS excludes stock options with exercise prices and exercise tax benefits greater than the average market price of the Company's common stock during the period because their inclusion would be anti-dilutive. There were no anti-dilutive stock options for the years ended December 31, 2013 or 2012. There were 82,800 anti-dilutive stock options for the year ended December 31, 2011.
	Share-Based Compensation
	ASC 718, Share Based Compensation, requires the Company to measure and recognize the cost of employee services received in exchange for an award of equity instruments. Under the provisions of ASC 718, share-based compensation cost is measured at the grant date, based on the fair value of the award, and is recognized as an expense over the requisite service period (generally the vesting period of the equity grant).
	As permitted by ASC 718, the Company elected the modified prospective transition method. Under the modified prospective transition method, (i) compensation expense for share-based awards granted prior to January 1, 2006 is recognized over the remaining service period using the compensation cost calculated for pro forma disclosure purposes as adjusted to incorporate forfeiture assumptions, and (ii) compensation expense for all share-based awards granted subsequent to December 31, 2005 is based on the grant date fair value estimated in accordance with the provisions of ASC 718.
	See Note 6 for further information regarding share-based compensation.
	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 and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
	Recent Accounting Pronouncements
	In February 2013, the FASB issued ASU 2013-02, Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income. ASU 2013-02 requires entities to present in either a single note or parenthetically on the face of the financial statements, the effect of significant amounts reclassified from each component of accumulated other comprehensive income based on its source and the income statement line items affected by the reclassification. Items not required to be reclassified to net income in their entirety are cross referenced to a related footnote for additional information. The ASU is effective for interim and annual periods beginning after December 15, 2012. The impact of adoption was not material to the Company's consolidated financial condition and results of operations.
	Segments
	The Company comprises one business segment: property and casualty insurance operations. Management organizes the business around private passenger automobile insurance in Massachusetts sold exclusively through independent agents and offers other personal and commercial insurance as complementary products. In accordance with ASC 280, Segment Reporting, the financial information of the segment is presented consistent with the way results are regularly evaluated by the chief operating decision maker in deciding how to allocate resources and in assessing performance.

Investments

Investments	12 Months Ended
	Dec. 31, 2013
Investments	'
Investments	'
	3.     Investments
	The gross unrealized gains and losses on investments in fixed maturity securities, including redeemable preferred stocks that have characteristics of fixed maturities, and equity securities, including interests in mutual funds, were as follows for the periods indicated.
		As of December 31, 2013
								Gross Unrealized
								Losses(3)
		Cost or			Gross			Non-OTTI			OTTI		Estimated
		Amortized			Unrealized			Unrealized			Unrealized		Fair
		Cost			Gains			Losses			Losses(4)		Value
	U.S. Treasury securities	$	1,510		$	—		$	(7	)	$	—	$	1,503
	Obligations of states and political subdivisions		461,256			10,248			(4,179	)		—		467,325
	Residential mortgage-backed securities(1)		205,053			6,879			(3,230	)		—		208,702
	Commercial mortgage-backed securities		31,885			342			(8	)		—		32,219
	Other asset-backed securities		13,357			124			(36	)		—		13,445
	Corporate and other securities		374,171			9,882			(2,290	)		—		381,763
	Subtotal, fixed maturity securities		1,087,232			27,475			(9,750	)		—		1,104,957
	Equity securities(2)		83,134			8,821			(84	)		—		91,871
	Other invested assets(5)		5,748			—			—			—		5,748
	Totals	$	1,176,114		$	36,296		$	(9,834	)	$	—	$	1,202,576
		As of December 31, 2012
								Gross Unrealized
								Losses(3)
		Cost or			Gross			Non-OTTI			OTTI		Estimated
		Amortized			Unrealized			Unrealized			Unrealized		Fair Value
		Cost			Gains			Losses			Losses(4)
	U.S. Treasury securities	$	7,112		$	43		$	—		$	—	$	7,155
	Obligations of states and political subdivisions		455,249			35,951			(17	)		—		491,183
	Residential mortgage-backed securities(1)		215,438			11,465			(1,006	)		—		225,897
	Commercial mortgage-backed securities		39,388			1,086			—			—		40,474
	Other asset-backed securities		21,288			898			—			—		22,186
	Corporate and other securities		361,939			16,988			(269	)		—		378,658
	Subtotal, fixed maturity securities		1,100,414			66,431			(1,292	)		—		1,165,553
	Equity securities(2)		21,237			1,629			(66	)		—		22,800
	Totals	$	1,121,651		$	68,060		$	(1,358	)	$	—	$	1,188,353
	-1
	Residential mortgage-backed securities consists primarily of obligations of U.S. Government agencies including collateralized mortgage obligations issued, guaranteed and/or insured by the following issuers: Government National Mortgage Association (GNMA), Federal Home Loan Mortgage Corporation (FHLMC), Federal National Mortgage Association (FNMA) and the Federal Home Loan Bank (FHLB).
	-2
	Equity securities includes interests in mutual funds held to fund the Company's executive deferred compensation plan.
	-3
	The Company's investment portfolio included 220 and 75 securities in an unrealized loss position at December 31, 2013 and December 31, 2012, respectively.
	-4
	Amounts in this column represent other-than-temporary impairment ("OTTI") recognized in accumulated other comprehensive income.
	-5
	Other invested assets are accounted for under the equity method which approximates fair value.
	The amortized cost and the estimated fair value of fixed maturity securities, by maturity, are shown below for the period indicated. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.
		As of December 31, 2013
		Amortized			Estimated
		Cost			Fair Value
	Due in one year or less	$	28,170		$	28,660
	Due after one year through five years		342,290			351,975
	Due after five years through ten years		198,545			202,974
	Due after ten years		267,932			266,982
	Asset-backed securities		250,295			254,366
	Totals	$	1,087,232		$	1,104,957
	The gross realized gains (losses) on sales of investments were as follows for the periods indicated.
		Years Ended December 31,
		2013			2012			2011
	Gross realized gains
	Fixed maturity securities	$	854		$	1,845		$	4,935
	Equity securities		1,011			270			246
	Gross realized losses
	Fixed maturity securities		(141	)		(115	)		(821	)
	Equity securities		(47	)		(25	)		—
	Net realized gains on investments	$	1,677		$	1,975		$	4,360
In the normal course of business, the Company enters into transactions involving various types of financial instruments, including investments in fixed maturities and equity securities. Investment transactions have credit exposure to the extent that a counter party may default on an obligation to the Company. Credit risk is a consequence of carrying, trading and investing in securities. To manage credit risk, the Company focuses on higher quality fixed income securities, reviews the credit strength of all companies in which it invests, limits its exposure in any one investment and monitors the portfolio quality, taking into account credit ratings assigned by recognized statistical rating organizations.
The following tables as of December 31, 2013 and 2012 present the gross unrealized losses included in the Company's investment portfolio and the fair value of those securities aggregated by investment category. The tables also present the length of time that they have been in a continuous unrealized loss position.
	As of December 31, 2013
	Less than 12 Months						12 Months or More					Total
	Estimated			Unrealized			Estimated			Unrealized		Estimated		Unrealized
	Fair Value			Losses			Fair Value			Losses		Fair Value		Losses
U.S. Treasury securities	$	1,503		$	7		$	—		$	—	$	1,503	$	7
Obligations of states and political subdivisions		131,114			3,898			3,362			281		134,476		4,179
Residential mortgage-backed securities		50,048			1,570			37,166			1,660		87,214		3,230
Commercial mortgage-backed securities		6,008			8			—			—		6,008		8
Other asset-backed securities		3,240			31			4,608			5		7,848		36
Corporate and other securities		86,312			2,223			2,235			67		88,547		2,290
Subtotal, fixed maturity securities		278,225			7,737			47,371			2,013		325,596		9,750
Equity securities		3,933			73			299			11		4,232		84
Total temporarily impaired securities	$	282,158		$	7,810		$	47,670		$	2,024	$	329,828	$	9,834
	As of December 31, 2012
	Less than 12 Months						12 Months or More					Total
	Estimated			Unrealized			Estimated			Unrealized		Estimated		Unrealized
	Fair Value			Losses			Fair Value			Losses		Fair Value		Losses
Obligations of states and political subdivisions	$	2,868		$	17		$	—		$	—	$	2,868	$	17
Residential mortgage-backed securities		50,779			966			3,938			40		54,717		1,006
Commercial mortgage-backed securities		107			—			—			—		107		—
Corporate and other securities		22,979			269			—			—		22,979		269
Subtotal, fixed maturity securities		76,733			1,252			3,938			40		80,671		1,292
Equity securities		1,145			23			303			43		1,448		66
Total temporarily impaired securities	$	77,878		$	1,275		$	4,241		$	83	$	82,119	$	1,358
Other-Than-Temporary Impairments
ASC 320, Investments—Debt and Equity Securities requires entities to separate an OTTI of a debt security into two components when there are credit related losses associated with the impaired debt security for which the Company asserts that it does not have the intent to sell the security, and it is more likely than not that it will not be required to sell the security before recovery of its cost basis. Under ASC 320, the amount of the OTTI related to a credit loss is recognized in earnings, and the amount of the OTTI related to other factors is recorded as a component of other comprehensive income (loss). In instances where no credit loss exists but it is more likely than not that the Company will have to sell the debt security prior to the anticipated recovery, the decline in market value below amortized cost is recognized as an OTTI in earnings. In periods after the recognition of an OTTI on debt securities, the Company accounts for such securities as if they had been purchased on the measurement date of the OTTI at an amortized cost basis equal to the previous amortized cost basis less the OTTI recognized in earnings. For debt securities for which OTTI was recognized in earnings, the difference between the new amortized cost basis and the cash flows expected to be collected will be accreted or amortized into net investment income.
The Company holds no subprime mortgage debt securities. All of the Company's holdings in mortgage-backed securities are either U.S. Government or Agency guaranteed or are rated investment grade by either Moody's or Standard & Poor's.
The unrealized losses in the Company's fixed income and equity portfolio as of December 31, 2013 were reviewed for potential other-than-temporary asset impairments. The Company held no securities at December 31, 2013 with a material (20% or greater) unrealized loss for four or more consecutive quarters. Specific qualitative analysis was also performed for any additional securities appearing on the Company's "Watch List," if any. Qualitative analysis considered such factors as the financial condition and the near term prospects of the issuer, whether the debtor is current on its contractually obligated interest and principal payments, changes to the rating of the security by a rating agency and the historical volatility of the fair value of the security.
The qualitative analysis performed by the Company concluded that the unrealized losses recorded on the investment portfolio at December 31, 2013 resulted from fluctuations in market interest rates and other temporary market conditions as opposed to fundamental changes in the credit quality of the issuers of such securities. Therefore, decreases in fair values of the Company's securities are viewed as being temporary.
During the years ended December 31, 2013 and 2012, there was no significant deterioration in the credit quality of any of the Company's holdings and no OTTI charges were recorded related to the Company's portfolio of investment securities. At December 31, 2013 and December 31, 2012, there were no amounts included in accumulated other comprehensive income related to securities which were considered by the Company to be other-than-temporarily impaired.
Based upon the qualitative analysis performed, the Company's decision to hold these securities, the Company's current level of liquidity and its positive operating cash flows, management believes it is more likely than not that it will not be required to sell any of its securities before the anticipated recovery in the fair value to its amortized cost basis.
Net Investment Income
The components of net investment income were as follow for the periods indicated.
	Years Ended December 31,
	2013			2012			2011
Interest on fixed maturity securities	$	43,328		$	42,235		$	39,980
Dividends on equity securities		1,829			559			658
Equity in earnings of other invested assets		148			—			—
Interest on other assets		139			39			49
Interest on cash and cash equivalents		18			18			33
Total investment income		45,462			42,851			40,720
Investment expenses		2,408			1,981			1,660
Net investment income	$	43,054		$	40,870		$	39,060

Equipment_and_Leasehold_Improv

Equipment and Leasehold Improvements	12 Months Ended
	Dec. 31, 2013
Equipment and Leasehold Improvements	'
Equipment and Leasehold Improvements	'
	4.     Equipment and Leasehold Improvements
	The carrying value of equipment and leasehold improvements by classification was as follows for the periods indicated.
		As of December 31,
		2013		2012
	Software	$	20,608	$	16,784
	Computer equipment		6,365		4,879
	Leasehold improvements		2,524		2,524
	Other equipment		2,400		2,390
	Furniture and fixtures		1,186		963
	Automobiles		—		10
	Total cost		33,083		27,550
	Less accumulated depreciation and amortization		22,419		18,455
	Equipment and leasehold improvements, net	$	10,664	$	9,095
	Depreciation and amortization expense for the years ended December 31, 2013, 2012, and 2011 was $3,974, $4,450, and $3,277, respectively.

Employee_Benefit_Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2013
Employee Benefit Plan	'
Employee Benefit Plan	'
	5.     Employee Benefit Plan
	The Company sponsors the Safety Insurance Company 401(k) qualified defined contribution retirement plan (the "Retirement Plan"). The Retirement Plan is available to all eligible employees of the Company. An employee must be 21 years of age to be eligible to participate in the Retirement Plan and is allowed to contribute on a pre-tax basis up to the maximum allowed under federal law. The Retirement Plan is administered by the Company and is subject to the provisions of the Employee Retirement Income Security Act of 1974. At the close of each Retirement Plan year, the Company makes a matching contribution equal to 100% of the amount each participant contributed during the plan year from their total pay, up to a maximum amount of 8% of the participant's base salary, to those participants who have contributed to the Retirement Plan and were employed on the last day of the Retirement Plan year. Compensation expense related to the Retirement Plan was $2,649, $2,490, and $2,385 for the years ended December 31, 2013, 2012, and 2011, respectively.

ShareBased_Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2013
Share-Based Compensation	'
Share-Based Compensation	'
	6.     Share-Based Compensation
	Management Omnibus Incentive Plan
	Long-term incentive compensation is provided under the Company's 2002 Management Omnibus Incentive Plan ("the Incentive Plan") which provides for a variety of stock-based compensation awards, including nonqualified stock options, incentive stock options, stock appreciation rights and restricted stock ("RS") awards. The maximum number of shares of common stock with respect to which awards may be granted is 2,500,000. Shares of stock covered by an award under the Incentive Plan that are forfeited will again be available for issuance in connection with future grants of awards under the plan. At December 31, 2013, there were 531,862 shares available for future grant. The Board of Directors and the Compensation Committee intend to issue more awards under the Incentive Plan in the future.
	For the years ended December 31, 2013, 2012, and 2011, the Company recorded compensation expense related to awards under the Incentive Plan of $2,954, $2,877, and $2,915, net of income tax benefit of $1,591, $1,549, and $1,570, respectively.
	Stock Options
	The fair value of stock options used to compute net income and EPS for the years ended December 31, 2013, 2012, and 2011 is the estimated fair value at grant date using the Black-Scholes option-pricing model with the following assumptions:
		Years Ended December 31,
		2013		2012		2011
	Expected dividend yield	NA		NA		1.68%
	Expected volatility	NA		NA		0.36
	Risk-free interest rate	NA		NA		4.76%
	Expected holding period	NA		NA		6.5 years
	Expected dividend yield is the Company's dividend yield on the measurement date and is based on the assumption that the current yield will continue in the future. Expected volatility is based on historical volatility of the Company's common stock as well as the volatility of a peer group of property and casualty insurers measured for a period equal to the expected holding period of the option. The risk-free interest rate is based upon the yield on the measurement date of a zero-coupon U.S. Treasury bond with a maturity period equal to the expected holding period of the option. The expected holding period is based upon the simplified method provided in SEC Staff Accounting Bulletin No. 107, Share-Based Payment, which utilizes the mid-points between the vesting dates and the expiration date of the option award to calculate the overall expected term. There were no stock options granted during the years ended December 31, 2013, 2012, and 2011. As of March 31, 2011, all compensation expense related to non-vested option awards had been recognized.
	The following table summarizes stock option activity under the Incentive Plan.
		Years Ended December 31,
		2013					2012					2011
		Shares			Weighted		Shares			Weighted		Shares			Weighted
		Under			Average		Under			Average		Under			Average
		Option			Exercise Price		Option			Exercise Price		Option			Exercise Price
	Outstanding at beginning of year		87,500		$	39.24		125,700		$	37.63		151,003		$	37.3
	Exercised during the year		(67,300	)		38.52		(36,900	)		33.63		(25,303	)		35.66
	Forfeited during the year		—			—		(1,300	)		42.85		—			—
	Outstanding at end of year		20,200			41.64		87,500			39.24		125,700			37.63
	Exercisable at end of year		20,200		$	41.64		87,500		$	39.24		125,700		$	37.63
	At December 31, 2013, 2012, and 2011, the aggregate intrinsic value of outstanding shares under option was $296, $606, and $554 with a weighted average remaining contractual term of 2.1, 2.9, and 3.7 years, respectively. Aggregate intrinsic value represents the total pretax intrinsic value, which is the difference between the fair value based upon the Company's closing year-end stock price at December 31, 2013, 2012, and 2011 and the exercise price which would have been received by the option holders had all option holders exercised their options as of those dates. The range of exercise prices on stock options outstanding under the Incentive Plan was $18.50 to $42.85 at December 31, 2013, and $13.30 to $42.85 at December 31, 2012, and 2011. The total intrinsic value of options exercised during the years ended December 31, 2013, 2012, and 2011 was $1,197, $463, and $156, respectively.
	Restricted Stock
	Service-based restricted stock awarded to employees in the form of unvested shares is recorded at the market value of the Company's common stock on the grant date and amortized ratably as expense over the requisite service period. Service-based restricted stock awards generally vest over a three-year period and unrestrict 30% on the first and second anniversaries of the grant date and 40% on the third anniversary of the grant date, except for non-executive employees' restricted stock awards which vest ratable over a five-year service period and independent directors' stock awards which vest immediately. Independent directors' stock awards cannot be sold, assigned, pledged, or otherwise transferred, encumbered or disposed of until the recipient is no longer a member of the Board of Directors.
	In addition to service-based awards, the Company granted performance-based restricted shares in 2013 to certain employees. These performance shares will cliff vest after a three-year performance period provided certain performance measures are attained. A portion of these awards, which contain a market condition, vest according to the level of total shareholder return achieved by the Company compared to its property-casualty insurance peers over a three-year period. The remainder, which contain a performance condition, vest according to the level of Company's combined ratio results compared to its property-casualty insurance peers over the same three-year performance period.
	Actual payouts can range from 0% to 200% of target shares awarded depending upon the level of achievement of the respective market and performance conditions during a three fiscal-year performance period ending at the end of 2015. Compensation expense for performance share awards is based on the probable number of awards expected to vest using the performance level most likely to be achieved at the end of the performance period.
	Performance-based awards with market conditions are accounted for and measured differently from an award that has a performance or service condition. The effect of a market condition is reflected in the award's fair value on the grant date. That fair value is recognized as compensation cost over the requisite service period regardless of whether the market-based performance objective has been satisfied.
	All of the Company's restricted stock awards are issued as incentive compensation and are equity classified.
	The following tables summarize restricted stock and performance-based restricted stock activity under the Incentive Plan.
		Years Ended December 31,
		2013					2012					2011
		Shares			Weighted		Shares			Weighted		Shares			Weighted
		Under			Average		Under			Average		Under			Average
		Restriction			Fair Value		Restriction			Fair Value		Restriction			Fair Value
	Outstanding at beginning of year		263,883		$	41.47		282,117		$	39.24		301,501		$	35.13
	Granted during the year		57,632			47.87		102,756			41.79		95,204			46.78
	Vested and unrestricted during the year		(103,788	)		40.75		(117,936	)		36.5		(114,009	)		34.67
	Forfeited during the year		(6,493	)		43.48		(3,054	)		38.13		(579	)		37.75
	Outstanding at end of year		211,234		$	43.51		263,883		$	41.47		282,117		$	39.24
		Years Ended December 31,
		2013					2012					2011
		Performance-			Weighted		Performance-			Weighted		Performance-based			Weighted
		based			Average		based			Average		Shares Under			Average
		Shares Under			Fair Value		Shares Under			Fair Value		Restriction			Fair Value
		Restriction					Restriction
	Granted during the year		37,456			44.13		—			—		—			—
	Outstanding at end of year		37,456		$	44.13		—		$	—		—		$	—
	As of December 31, 2013, there was $6,318 of unrecognized compensation expense related to non-vested restricted stock awards that is expected to be recognized over a weighted average period of 1.1 years. The total fair value of the shares that were vested and unrestricted during the years ended December 31, 2013, 2012, and 2011 was $4,230, $4,304, and $3,953, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies	'
Commitments and Contingencies	'
	7.     Commitments and Contingencies
	Lease Commitments
	The Company has various non-cancelable long-term operating leases. The approximate minimum annual rental payments due under these lease agreements as of December 31, 2013 are presented in the following table.
	2014	$	4,151
	2015		4,076
	2016		4,034
	2017		3,855
	2018		3,822
	Total minimum lease payments	$	19,938
	Certain lease agreements contain renewal options and, in addition to the minimum annual rentals, generally provide for payment of a share of the real estate taxes and operating expenses in excess of a base amount. Rental expense was $4,150, $4,114, and $4,124 for the years ended December 31, 2013, 2012, and 2011, respectively. All leases expire prior to 2019. The Company expects that in the normal course of business, leases that expire will be renewed.
	An eighth amendment to a lease agreement for the lease of office space was executed on April 5, 2007. Under the provisions of this amendment, additional space was occupied and the lease term was extended an additional ten years commencing on January 1, 2009, with an option to renew for one additional five-year term.
	Contingencies
	Various claims, generally incidental to the conduct of normal business, are pending or alleged against the Company from time to time. In the opinion of management, based in part on the advice of legal counsel, the ultimate resolution of such claims will not have a material adverse effect on the Company's consolidated financial statements. However, if estimates of the ultimate resolutions of those proceedings are revised, liabilities related to those proceedings could be adjusted in the near term.
	Massachusetts law requires that insurers licensed to do business in Massachusetts participate in the Massachusetts Insurers Insolvency Fund ("Insolvency Fund"). Members of the Insolvency Fund are assessed a proportionate share of the obligations and expenses of the Insolvency Fund in connection with an insolvent insurer. It is anticipated that there will be additional assessments from time to time relating to various insolvencies. Although the timing and amounts of any future assessments are not known, based upon existing knowledge, management's opinion is that such future assessments will not have a material effect upon the financial position of the Company.

Debt

Debt	12 Months Ended
	Dec. 31, 2013
Debt	'
Debt	'
	8.     Debt
	The Company has a Revolving Credit Agreement (the "Credit Agreement") with RBS Citizens, NA ("RBS Citizens"). The Credit Agreement provides a $30,000 revolving credit facility with an accordion feature allowing for future expansion of the committed amount up to $50,000. Loans under the credit facility bear interest at the Company's option at either (i) the LIBOR rate plus 1.25% per annum or (ii) the higher of RBS Citizens prime rate or 0.5% above the federal funds rate plus 1.25% per annum. Interest only is payable prior to maturity. The Credit Agreement has a maturity date of August 14, 2018.
	The Company's obligations under the credit facility are secured by pledges of its assets and the capital stock of its operating subsidiaries. The credit facility is guaranteed by the Company's non-insurance company subsidiaries. The credit facility contains covenants including requirements to maintain minimum risk-based capital ratios and statutory surplus of Safety Insurance Company as well as limitations or restrictions on indebtedness, liens, and other matters. As of December 31, 2013, the Company was in compliance with all covenants. In addition, the credit facility includes customary events of default, including a cross-default provision permitting the lenders to accelerate the facility if the Company (i) defaults in any payment obligation under debt having a principal amount in excess of $10,000 or (ii) fails to perform any other covenant permitting acceleration of all such debt.
	The Company had no amounts outstanding on its credit facility at December 31, 2013 or 2012. The credit facility commitment fee included in interest expenses was computed at a rate of 0.25% per annum on the $30,000 commitment at December 31, 2013 and 2012.

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2013
Reinsurance	'
Reinsurance	'
	9.     Reinsurance
	The Company cedes insurance to CAR and to other reinsurers. The Company has a property catastrophe excess of loss agreement and a casualty excess of loss agreement that qualify as reinsurance treaties and are designed to protect against large or unusual loss and LAE activity. Reinsurance contracts do not relieve the Company from its obligations to policyholders. Failure of reinsurers to honor their obligations could result in losses to the Company. The Company evaluates the financial condition of its reinsurers and monitors economic characteristics of the reinsurers to minimize its exposure to significant losses from reinsurer insolvencies.
	The Company is subject to concentration of credit risk with respect to reinsurance ceded to CAR. At December 31, 2013, reinsurance receivables on paid and unpaid loss and LAE with a carrying value of $48,507 and ceded unearned premiums of $15,657 were associated with CAR. At December 31, 2012, reinsurance receivables on paid and unpaid loss and LAE with a carrying value of $41,755 and ceded unearned premiums of $13,876 were associated with CAR. The Company assumes a proportionate share of the obligations from CAR. The Company makes an estimate of its share of assumed activity from the most recent quarter reported by CAR and records adjustments to the reported activity to reflect its anticipated final assumed obligations. The Company's participation in CAR resulted in assumed net losses of $1,487 and $424 for the years ended December 31, 2013 and 2012, respectively and assumed net income of $697 for the year ended December 31, 2011.
	CAR has been, with few exceptions, required by law to issue a policy to any applicant who seeks it. As a servicing carrier of CAR, this requirement has applied to the Company.
	The effect of assumed and ceded premiums on net written and earned premiums and losses and LAE incurred is as follows.
		Years Ended December 31,
		2013			2012			2011
	Written Premiums
	Direct	$	731,680		$	696,220		$	649,262
	Assumed		20,593			17,943			16,521
	Ceded		(54,733	)		(50,221	)		(45,467	)
	Net written premiums	$	697,540		$	663,942		$	620,316
	Earned Premiums
	Direct	$	715,657		$	673,596		$	626,483
	Assumed		19,251			16,910			15,790
	Ceded		(53,038	)		(48,037	)		(43,905	)
	Net earned premiums	$	681,870		$	642,469		$	598,368
	Loss and LAE
	Direct	$	465,162		$	431,526		$	473,970
	Assumed		15,247			13,102			10,497
	Ceded		(32,660	)		(22,411	)		(17,827	)
	Net loss and LAE	$	447,749		$	422,217		$	466,640

Loss_and_Loss_Adjustment_Expen

Loss and Loss Adjustment Expense Reserves	12 Months Ended
	Dec. 31, 2013
Loss and Loss Adjustment Expense Reserves	'
Loss and Loss Adjustment Expense Reserves	'
	10.   Loss and Loss Adjustment Expense Reserves
	The following table sets forth a reconciliation of beginning and ending reserves for losses and loss adjustment expenses ("LAE"), as shown in the Company's consolidated financial statements for the periods indicated.
		Years Ended December 31,
		2013			2012			2011
	Reserves for losses and LAE at beginning of year	$	423,842		$	403,872		$	404,391
	Less receivable from reinsurers related to unpaid losses and LAE		(52,185	)		(51,774	)		(53,147	)
	Net reserves for losses and LAE at beginning of year		371,657			352,098			351,244
	Incurred losses and LAE, related to:
	Current year		476,638			439,527			503,323
	Prior years		(28,889	)		(17,310	)		(36,683	)
	Total incurred losses and LAE		447,749			422,217			466,640
	Paid losses and LAE related to:
	Current year		299,882			272,454			336,932
	Prior years		124,856			130,204			128,854
	Total paid losses and LAE		424,738			402,658			465,786
	Net reserves for losses and LAE at end of period		394,668			371,657			352,098
	Plus receivable from reinsurers related to unpaid losses and LAE		60,346			52,185			51,774
	Reserves for losses and LAE at end of period	$	455,014		$	423,842		$	403,872
	At the end of each period, the reserves were re-estimated for all prior accident years. The Company's prior year reserves decreased by $28,889, $17,310, and $36,683 for the years ended 2013, 2012, and 2011, respectively, and resulted from re-estimations of prior years ultimate loss and LAE liabilities. The decrease in prior year reserves during 2013 was primarily composed of a reduction in the Company's retained automobile and retained homeowners reserves. The decrease in prior year reserves during 2012 was primarily composed of a reduction in the Company's retained automobile reserves, partially offset by an increase in reserves of homeowners and all other lines of business. The decrease in prior year reserves during 2011 was primarily composed of reductions in the Company's retained automobile reserves.
	The Company's private passenger automobile line of business prior year reserves decreased during the years ended December 31, 2013, 2012 and 2011 primarily due to improved retained private passenger results. The improved retained private passenger results were primarily due to fewer incurred but not yet reported claims than previously estimated and better than previously estimated severity on the Company's established bodily injury and property damage case reserves.
	Due to the nature of the risks that the Company underwrites and has historically underwritten, management does not believe that it has an exposure to asbestos or environmental pollution liabilities.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2013
Income Taxes	'
Income Taxes	'
	11.   Income Taxes
	A summary of the income tax expense in the Consolidated Statements of Income is shown below.
		Years Ended December 31,
		2013			2012			2011
	Current Income Taxes:
	Federal	$	24,417		$	22,328		$	1,260
	State		21			3			4
			24,438			22,331			1,264
	Deferred Income Taxes:
	Federal		1,899			1,023			(693	)
	State		—			—			—
			1,899			1,023			(693	)
	Total income tax expense	$	26,337		$	23,354		$	571
	The income tax expense attributable to the consolidated results of operations is different from the amounts determined by multiplying income before federal income taxes by the statutory federal income tax rate. The sources of the difference and the tax effects of each were as follows for the periods indicated.
		Years Ended December 31,
		2013			2012			2011
	Federal income tax expense, at statutory rate	$	30,691		$	28,498		$	4,996
	Tax-exempt investment income, net		(4,711	)		(5,142	)		(4,635	)
	State taxes, net		14			2			2
	Nondeductible expenses		210			202			232
	Other, net		133			(206	)		(24	)
	Total income tax expense	$	26,337		$	23,354		$	571
	The deferred income tax asset (liability) represents the tax effects of temporary differences attributable to the Company's consolidated federal tax return group. Its components were as shown in the following table for the periods indicated.
		Years Ended December 31,
		2013			2012
	Deferred tax assets:
	Discounting of loss reserves	$	7,057		$	7,598
	Discounting of unearned premium reserve		25,770			24,655
	Bad debt allowance		384			673
	Employee benefits		7,248			6,734
	State loss carryforwards		—			20
	Rent incentive		635			767
	Other		—			27
	Total deferred tax assets before valuation allowance		41,094			40,474
	Valuation allowance for deferred tax assets		—			(20	)
	Total deferred tax assets, net of valuation allowance		41,094			40,454
	Deferred tax liabilities:
	Deferred acquisition costs		(22,186	)		(21,233	)
	Investments		(1,881	)		(596	)
	Net unrealized gains on investments		(9,261	)		(23,345	)
	Depreciation		(295	)		(247	)
	Software development costs		(2,505	)		(2,372	)
	Premium acquisition expenses		(890	)		(863	)
	Other		(92	)		—
	Total deferred tax liabilities		(37,110	)		(48,656	)
	Net deferred tax liability	$	3,984		$	(8,202	)
	The Company believes, based upon consideration of objective and verifiable evidence, including its recent earnings history and its future expectations, that the Company's taxable income in future years will be sufficient to realize all federal deferred tax assets. A valuation allowance of $0 and $20 was established against state deferred tax assets at December 31, 2013 and 2012, respectively. The net operating losses which generated this deferred tax asset was utilized in the current year. The valuation allowance was based upon management's assessment that it is more likely than not that the Company will not be able to utilize these state deferred tax assets.
	The Company adopted the provisions of ASC 740, Income Taxes on January 1, 2007. This interpretation prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. ASC 740 requires that the Company determine whether the benefits of its tax positions have a more likely than not chance of being sustained upon audit based upon the technical merits of the tax position. This interpretation also provides guidance on derecognition, classification, interest and penalties, accounting in interim periods, disclosure, and transition. The Company believes that the positions taken on its income tax returns for open tax years will be sustained upon examination by the IRS. Therefore, the Company has not recorded a liability under ASC 740.
	As of December 31, 2013, 2012 and 2011, the Company had no unrecognized tax benefits, and none which if recognized would affect the effective tax rate. The Company does not currently anticipate significant changes in the amount of unrecognized income tax benefits during the next twelve months.
	The Company records interest and penalties associated with audits as a component of Income before income taxes. Penalties are recorded in Underwriting, operating and other expenses, and interest expense is recorded in Interest expenses in the Consolidated Statement of Operations. The Company had no interest and penalties accrued as of December 31, 2013 and 2012.
	As of December 31, 2013 , the Company was no longer subject to examination of its U.S. federal tax returns for years prior to 2010. The Company's U.S. federal tax return for the year ended December 31, 2011 is currently under examination by the IRS.

Share_Repurchase_Program

Share Repurchase Program	12 Months Ended
	Dec. 31, 2013
Share Repurchase Program	'
Share Repurchase Program	'
	12.   Share Repurchase Program
	On August 3, 2007, the Board of Directors approved a share repurchase program of up to $30,000 of the Company's outstanding common shares. As of December 31, 2012, the Board of Directors had authorized increases to the existing share repurchase program of up to $90,000 of the Company's outstanding common shares. On November 4, 2013, the Board of Directors again increased the existing share repurchase program by authorizing repurchase of up to $150,000 of the Company's outstanding common shares. Under the program, the Company may repurchase shares of its common stock for cash in public or private transactions, in the open market or otherwise. The timing of such repurchases and actual number of shares repurchased will depend on a variety of factors including price, market conditions and applicable regulatory and corporate requirements. The program does not require the Company to repurchase any specific number of shares and it may be modified, suspended or terminated at any time without prior notice.
	During the year ended December 31, 2013, the Company purchased 90,902 of its common shares on the open market under the program at a cost of $4,799 resulting in total shares purchased since inception of the program of 1,819,547 at a cost of $60,368. No share purchases were made by the Company during the year ended December 31, 2012.

Statutory_Net_Income_and_Surpl

Statutory Net Income and Surplus	12 Months Ended
	Dec. 31, 2013
Statutory Net Income and Surplus	'
Statutory Net Income and Surplus	'
	13.   Statutory Net Income and Surplus
	Statutory Accounting Practices
	The Company's insurance company subsidiaries, domiciled in the Commonwealth of Massachusetts, prepare statutory financial statements in accordance with the accounting practices prescribed or permitted by the Division. Prescribed statutory accounting practices are those practices that are incorporated directly or by reference in state laws, regulations, and general administrative rules applicable to all insurance enterprises domiciled in a particular state. Permitted statutory accounting practices include practices not prescribed by the Division, but allowed by the Division. Statutory net income of the Company's insurance company subsidiaries was $57,518, $56,895, and $9,672 for the years ended December 31, 2013, 2012, and 2011, respectively. Statutory capital and surplus of the Company's insurance subsidiaries was $627,993 and $599,024 at December 31, 2013 and 2012, respectively.
	Dividends
	The Insurance Subsidiaries are subject to various regulatory restrictions that limit the maximum amount of dividends available to be paid to their parent without prior approval of the Commonwealth of Massachusetts Commissioner of Insurance (the "Commissioner"). Massachusetts statute limits the dividends an insurer may pay in any twelve month period, without the prior permission of the Commissioner, to the greater of (i) 10% of the insurer's surplus as of the preceding December 31 or (ii) the insurer's net income for the twelve-month period ending the preceding December 31, in each case determined in accordance with statutory accounting practices. Our insurance company subsidiaries may not declare an "extraordinary dividend" (defined as any dividend or distribution that, together with other distributions made within the preceding twelve months, exceeds the limits established by Massachusetts statute) until thirty days after the Commissioner has received notice of the intended dividend and has not objected. As historically administered by the Commissioner, this provision requires the Commissioner's prior approval of an extraordinary dividend. Under Massachusetts law, an insurer may pay cash dividends only from its unassigned funds, also known as earned surplus, and the insurer's remaining surplus must be both reasonable in relation to its outstanding liabilities and adequate to its financial needs. At year-end 2013, the statutory surplus of Safety Insurance was $627,993 and its net income for 2013 was $53,078. As a result, a maximum of $62,799 is available in 2014 for such dividends without prior approval of the Commissioner. During the year ended December 31, 2013, Safety Insurance recorded dividends to Safety of $36,114. As result of this Massachusetts statute, the Insurance Subsidiaries had restricted net assets in the amount of $565,194 at December 31, 2013.
	Risk-Based Capital Requirements
	The NAIC has adopted a formula and model law to implement risk-based capital requirements for most property and casualty insurance companies, which are designed to determine minimum capital requirements and to raise the level of protection that statutory surplus provides for policyholder obligations. Under Massachusetts law, insurers having less total adjusted capital than that required by the risk-based capital calculation will be subject to varying degrees of regulatory action, depending on the level of capital inadequacy. The risk-based capital law provides for four levels of regulatory action. The extent of regulatory intervention and action increases as the level of total adjusted capital to risk-based capital falls. As of December 31, 2013, the Insurance Subsidiaries had total adjusted capital of $627,993, which is in excess of amounts requiring company or regulatory action at any prescribed risk-based capital action level. Minimum statutory capital and surplus, or company action level risk-based capital, was $90,613 at December 31, 2013.

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2013
Fair Value of Financial Instruments	'
Fair Value of Financial Instruments	'
	14.   Fair Value of Financial Instruments
	ASC 820, Fair Value Measurements and Disclosure provides a revised definition of fair value, establishes a framework for measuring fair value and expands financial statement disclosure requirements for fair value information. Under ASC 820, fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants (an exit price). ASC 820 establishes a fair value hierarchy that distinguishes between inputs based on market data from independent sources ("observable inputs") and a reporting entity's internal assumptions based upon the best information available when external market data is limited or unavailable ("unobservable inputs"). The fair value hierarchy in ASC 820 prioritizes fair value measurements into three levels based on the nature of the inputs as follows:
	Level 1—Valuations based on quoted prices in active markets for identical assets and liabilities;
	Level 2—Valuations based on observable inputs that do not meet the criteria for Level 1, including quoted prices in inactive markets and quoted prices in active markets for similar, but not identical instruments; and
	Level 3—Valuations based on unobservable inputs.
	Fair values for the Company's fixed maturity securities are based on prices provided by its custodian bank and its investment managers. Both the Company's custodian bank and investment managers use a variety of independent, nationally recognized pricing services to determine market valuations. If the pricing service cannot provide fair value determinations, the Company obtains non-binding price quotes from broker-dealers. A minimum of two quoted prices is obtained for the majority of the Company's available-for-sale fixed maturity securities in its investment portfolio. The Company's custodian bank is its primary provider of quoted prices from third-party pricing services and broker-dealers. To provide reasonable assurance of the validity of each price or quote, a secondary third-party pricing service or broker-dealer quote is obtained from the Company's investment managers. An examination of the pricing data is then performed for each security. If the variance between the primary and secondary price quotes for a security is within an accepted tolerance level, the quoted price obtained from the Company's custodian bank is used in the financial statements for the security. If the variance between the primary and secondary price quotes exceeds an accepted tolerance level, the Company obtains a quote from an alternative source, if possible, and documents and resolves any differences between the pricing sources. In addition, the Company may request that its investment managers and their traders provide input as to which vendor is providing prices that its traders believe are reflective of fair value for the security. Following this process, the Company may decide to value the security in its financial statements using the secondary or alternative source if it believes that pricing is more reflective of the security's value than the primary pricing provided by its custodian bank. The Company analyzes market valuations received to verify reasonableness, to understand the key assumptions used and their sources, and to determine an appropriate ASC 820 fair value hierarchy level based upon trading activity and the observability of market inputs. Based on this evaluation and investment class analysis, each price is classified into Level 1, 2 or 3.
	Fair values of instruments are based on (i) quoted prices in active markets for identical assets (Level 1), (ii) quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active and model-derived valuations in which all significant inputs are observable in active markets (Level 2) or (iii) valuations derived from valuation techniques in which one or more significant inputs are unobservable in the marketplace (Level 3).
	The Company's Level 1 securities consist of equity securities whose values are based on quoted prices in active markets for identical assets. The Company's Level 2 securities are comprised of available-for-sale fixed maturity securities whose fair value was determined using observable market inputs. The Company's Level 3 security, is a real estate investment trust equity investment whose fair value is determined using the trust's net asset value obtained from its audited financial statements; however, the Company is required to submit a request 45 days before quarter end to dispose of the security. Fair values for securities for which quoted market prices were unavailable were estimated based upon reference to observable inputs such as benchmark interest rates, market comparables, and other relevant inputs. Investments valued using these inputs include U.S. Treasury securities and obligations of U.S. Government agencies, obligations of international government agencies, obligations of states and political subdivisions, corporate securities, commercial and residential mortgage-backed securities, and other asset-backed securities. Inputs into the fair value application that are utilized by asset class include but are not limited to:
	•
	States and political subdivisions:  overall credit quality, including assessments of market sectors and the level and variability of sources of payment such as general obligation, revenue or lease; credit support such as insurance, state or local economic and political base, prefunded and escrowed to maturity covenants.
	•
	Corporate fixed maturities:  overall credit quality, the establishment of a risk adjusted credit spread over the applicable risk free yield curve for discounted cash flow valuations; assessments of the level of industry economic sensitivity, company financial policies, indenture restrictive covenants, and/or security and collateral.
	•
	Residential mortgage-backed securities, U.S. agency pass-throughs, collateralized mortgage obligations ("CMOs"), non U.S. agency CMOs:  estimates of prepayment speeds based upon historical prepayment rate trends, underlying collateral interest rates, original weighted average maturity, vintage year, borrower credit quality characteristics, interest rate and yield curve forecasts, U.S. government support programs, tax policies, and delinquency/default trends.
	•
	Commercial mortgage-backed securities:  overall credit quality, including assessments of the level and variability of credit support and collateral type such as office, retail, or lodging, predictability of cash flows for the deal structure, prevailing economic market conditions.
	•
	Other asset-backed securities:  overall credit quality, estimates of prepayment speeds based upon historical trends and characteristics of underlying loans, including assessments of the level and variability of collateral, revenue generating agreements, area licenses agreements, product sourcing agreements and equipment and property leases.
	•
	Real estate investment trust ("REIT"):  net asset value per share derived from member ownership in capital venture to which a proportionate share of independently appraised net assets is attributed.
	All unadjusted estimates of fair value for our fixed maturities priced by the pricing services as described above are included in the amounts disclosed in Level 2.
	In order to ensure the fair value determination is representative of an exit price (consistent with ASC 820), the Company's procedures for validating quotes or prices obtained from third-parties include, but are not limited to, obtaining a minimum of two price quotes for each fixed maturity security if possible, as discussed above, the periodic testing of sales activity to determine if there are any significant differences between the market price used to value the security as of the balance sheet date and the sales price of the security for sales that occurred around the balance sheet date, and the periodic review of reports provided by its investment manager regarding those securities with ratings changes and securities placed on its "Watch List." In addition, valuation techniques utilized by pricing services and prices obtained from external sources are reviewed by the Company's external investment manager, whose investment professionals are familiar with the securities being priced and the markets in which they trade to ensure the fair value determination is representative of an exit price (consistent with ASC 820).
	With the exception of the REIT which is categorized as a Level 3 security, the Company's entire available-for-sale portfolio was priced based upon quoted market prices or other observable inputs as of December 31, 2013. There were no significant changes to the valuation process during the year ended December 31, 2013. As of December 31, 2013 and 2012, no quotes or prices obtained were adjusted by management. All broker quotes obtained were non-binding.
	At December 31, 2013 and 2012, investments in fixed maturities and equity securities classified as available-for-sale had a fair value which equaled carrying value of $1,196,828 and $1,188,353, respectively. At December 31, 2013 and 2012, we held no short-term investments. The carrying values of cash and cash equivalents and investment income accrued approximate fair value.
	The following tables summarize the Company's total fair value measurements for available-for-sale investments for the periods indicated.
		As of December 31, 2013
		Total		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs
	U.S. Treasury securities	$	1,503	$	—	$	1,503	$	—
	Obligations of states and political subdivisions		467,325		—		467,325		—
	Residential mortgage-backed securities		208,702		—		208,702		—
	Commercial mortgage-backed securities		32,219		—		32,219		—
	Other asset-backed securities		13,445		—		13,445		—
	Corporate and other securities		381,763		—		381,763		—
	Equity securities		91,871		75,951		—		15,920
	Total investment securities	$	1,196,828	$	75,951	$	1,104,957	$	15,920
		As of December 31, 2012
		Total		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs
	U.S. Treasury securities	$	7,155	$	—	$	7,155	$	—
	Obligations of states and political subdivisions		491,183		—		491,183		—
	Residential mortgage-backed securities		225,897		—		225,897		—
	Commercial mortgage-backed securities		40,474		—		40,474		—
	Other asset-backed securities		22,186		—		22,186		—
	Corporate and other securities		378,658		—		378,658		—
	Equity securities		22,800		17,454		—		5,346
	Total investment securities	$	1,188,353	$	17,454	$	1,165,553	$	5,346
	There were no transfers between Level 1 and Level 2 during the years ended December 31, 2013 or 2012.
	The following tables summarize the changes in the Company's Level 3 fair value securities for the periods indicated.
		Years Ended December 31,
		2013		2012		2011
	Balance at beginning of year	$	5,346	$	—	$	—
	Net gains included in other comprehensive income		574		—		—
	Purchases and sales		10,000		—		—
	Transfers into/(out) of Level 3		—		5,346		—
	Balance at end of year	$	15,920	$	5,346	$	—
	Amount of total losses included in earnings attributable to the change in unrealized losses related to assets still held at end of year	$	—	$	—	$	—
	Transfers in and out of Level 3 are attributable to changes in the ability to observe significant inputs in determining fair value exit pricing. As noted in the tables above, a transfer of the Company's investment in a real estate investment trust equity investment was made during 2012 into the Level 3 classification. No transfers were made in or out of Level 3 during 2011.

Quarterly_Results_of_Operation

Quarterly Results of Operations	12 Months Ended
	Dec. 31, 2013
Quarterly Results of Operations	'
Quarterly Results of Operations	'
	15.   Quarterly Results of Operations
	An unaudited summary of the Company's 2013 and 2012 quarterly performance, and audited annual performance, is as follows.
		Year ended December 31, 2013
		First		Second		Third		Fourth		Total
		Quarter		Quarter		Quarter		Quarter		Year
	Total revenue	$	181,796	$	184,001	$	187,694	$	191,793	$	745,284
	Net income		13,984		18,059		17,656		11,652		61,351
	Earnings per weighted average common share:
	Basic		0.91		1.17		1.15		0.76		4
	Diluted		0.91		1.17		1.14		0.76		3.98
	Cash dividends paid per common share		0.6		0.6		0.6		0.6		2.4
		Year ended December 31, 2012
		First		Second		Third		Fourth		Total
		Quarter		Quarter		Quarter		Quarter		Year
	Total revenue	$	170,406	$	174,708	$	177,531	$	181,222	$	703,867
	Net income		17,209		16,956		14,334		9,571		58,070
	Earnings per weighted average common share:
	Basic		1.13		1.11		0.94		0.62		3.8
	Diluted		1.13		1.11		0.94		0.62		3.8
	Cash dividends paid per common share		0.5		0.5		0.6		0.6		2.2

Related_Party_Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2013
Related Party Transactions	'
Related Party Transactions	'
	16.   Related Party Transactions
	In February 2012, the Company participated as a lender in a loan made by syndicates of lenders to a portfolio company in which funds managed by The Jordan Company, LP. are controlling or a significant investor. Mr. A. Richard Caputo, Jr., a member of the Company's Board of Directors and the Chairman of its Investment Committee, is a principal of The Jordan Company, LP. The loan, made to Vantage Specialties, Inc., currently bears interest at a rate of 7.0% per annum and matures on February 10, 2018. The loan amortizes in equal quarterly installments of 0.25% of the principal amount per quarter. The Company's participation in the loan was $2,500. The Company made the loan on the same terms as the other lenders participating in the syndicate. The loan was subject to the approval of the Company's full Investment Committee.

Subsequent_Events

Subsequent Events	12 Months Ended
	Dec. 31, 2013
Subsequent Events	'
Subsequent Events	'
	17.   Subsequent Events
	The Company has evaluated subsequent events for recognition or disclosure in the consolidated financial statements on Form 10-K filed herewith and no events have occurred that require recognition or disclosure.

Schedule_I_Summary_of_Investme

Schedule I - Summary of Investments - Other than Investments in Related Parties	12 Months Ended
	Dec. 31, 2013
Schedule I - Summary of Investments - Other than Investments in Related Parties	'
Schedule I - Summary of Investments - Other than Investments in Related Parties	'
	Safety Insurance Group, Inc,
	Summary of Investments—Other than Investments in Related Parties
	Schedule I
	At December 31, 2013
	(Dollars in thousands)
		Cost or		Estimated		Amount at
		Amortized Cost		Fair Value		which shown
						in the Balance
						Sheet
	Fixed maturities:
	U.S. government and government agencies and authorities	$	206,563	$	210,205	$	210,205
	Obligations of U.S. states and political subdivisions		461,256		467,325		467,325
	Corporate and other securities		419,413		427,427		427,427
	Total fixed maturities		1,087,232		1,104,957		1,104,957
	Equity securities:
	Common stocks:
	Industrial, miscellaneous and all other		83,134		91,871		91,871
	Total equity securities		83,134		91,871		91,871
	Other invested assets		5,748		5,748		5,748
	Total investments	$	1,176,114	$	1,202,576	$	1,202,576

Schedule_II_Condensed_Financia

Schedule II - Condensed Financial Information of the Registrant	12 Months Ended
	Dec. 31, 2013
Schedule II - Condensed Financial Information of the Registrant	'
Schedule II - Condensed Financial Information of the Registrant	'
	Safety Insurance Group, Inc.
	Condensed Financial Information of the Registrant
	Condensed Balance Sheets
	Schedule II
	(Dollars in thousands)
		December 31,
		2013			2012
	Assets
	Investments in consolidated affiliates	$	696,195		$	695,361
	Other		69			8
	Total assets	$	696,264		$	695,369
	Liabilities
	Accounts payable and other liabilities	$	1,077		$	1,010
	Total liabilities		1,077			1,010
	Shareholders' equity		695,187			694,359
	Total liabilities and shareholders' equity	$	696,264		$	695,369
	Safety Insurance Group, Inc.
	Condensed Financial Information of the Registrant
	Condensed Statements of Income and Comprehensive Income
	Schedule II
	(Dollars in thousands)
		Years Ended December 31,
		2013			2012			2011
	Revenues	$	—		$	—		$	—
	Expenses		1,201			1,194			1,078
	Net loss		(1,201	)		(1,194	)		(1,078	)
	Earnings from consolidated subsidiaries		62,552			59,264			14,780
	Net income		61,351			58,070			13,702
	Other net comprehensive income, net of taxes		(26,156	)		7,735			13,649
	Comprehensive net income	$	35,195		$	65,805		$	27,351
	Safety Insurance Group, Inc.
	Condensed Financial Information of the Registrant
	Condensed Statements of Cash Flows
	Schedule II
	(Dollars in thousands)
		Years Ended December 31,
		2013			2012			2011
	Net income	$	61,351		$	58,070		$	13,702
	Adjustments to reconcile net income to net cash provided by operating activities:
	Earnings from consolidated subsidiaries		(62,552	)		(59,264	)		(14,780	)
	Dividends received from consolidated subsidiaries(1)		36,114			29,137			25,744
	Amortization of restricted stock expense		4,153			4,430			4,747
	Changes in assets and liabilities:
	Other assets		(61	)		12			55
	Accounts payable and accrued liabilities		67			8			(5	)
	Net cash provided by operating activities		39,072			32,393			29,463
	Proceeds from exercise of stock options		2,592			1,241			902
	Dividends paid		(36,865	)		(33,634	)		(30,322	)
	Acquisition of treasury stock		(4,799	)		—			(43	)
	Net cash used for financing activities		(39,072	)		(32,393	)		(29,463	)
	Net increase in cash and cash equivalents		—			—			—
	Cash and cash equivalents, beginning of year		—			—			—
	Cash and cash equivalents, end of year	$	—		$	—		$	—
	-1
	The Company previously incorrectly presented dividends received from operating subsidiaries that represent returns on these investments as investing activities rather than as operating activities in the statements of cash flows. The Company has revised the presentation of all prior cash flows to correct this classification. No portion of the dividends received from operating subsidiaries during 2013, 2012 or 2011 represent returns of capital and therefore no portion is presented as an investing activity.

Schedule_III_Supplementary_Ins

Schedule III - Supplementary Insurance Information	12 Months Ended
	Dec. 31, 2013
Schedule III - Supplementary Insurance Information	'
Schedule III - Supplementary Insurance Information	'
	Safety Insurance Group, Inc.
	Supplementary Insurance Information
	Schedule III
	(Dollars in thousands)
		As of December 31,
	Segment	Deferred		Future Policy		Unearned
		Policy		Benefits,		Premiums
		Acquisition		Losses,
		Costs		Claims and Loss
				Expenses
	Property and Casualty Insurance
	2013	$	63,388	$	455,014	$	370,583
	2012		60,665		423,842		353,219
	2011		56,715		403,872		329,562
		Years Ended December 31,
	Segment	Premium		Net		Benefits,		Other		Premiums		Amortization of
		Revenue		Investment		Claims,		Operating		Written		Deferred
				Income		Losses, and		Expenses				Policy
						Settlement						Acquisition
						Expenses						Costs
	Property and Casualty Insurance
	2013	$	681,870	$	43,054	$	447,749	$	83,557	$	697,540	$	126,201
	2012		642,469		40,870		422,217		81,288		663,942		118,850
	2011		598,368		39,060		466,640		68,362		620,316		110,795

Schedule_IV_Reinsurance

Schedule IV - Reinsurance	12 Months Ended
	Dec. 31, 2013
Schedule IV - Reinsurance	'
Schedule IV - Reinsurance	'
	Safety Insurance Group, Inc.
	Reinsurance
	Schedule IV
	(Dollars in thousands)
	Property and Casualty	Gross		Ceded to Other		Assumed from		Net		Percentage of
	Insurance Earned Premiums	Amount		Companies		Other Companies		Amount		Amount
										Assumed
										to Net
	Years ended December 31,
	2013	$	715,657	$	53,038	$	19,251	$	681,870		2.8	%
	2012		673,596		48,037		16,910		642,469		2.6
	2011		626,483		43,905		15,790		598,368		2.6

Schedule_V_Valuation_and_Quali

Schedule V - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2013
Schedule V - Valuation and Qualifying Accounts	'
Schedule V - Valuation and Qualifying Accounts	'
	Safety Insurance Group, Inc.
	Valuation and Qualifying Accounts
	Schedule V
	(Dollars in thousands)
				Additions
		Balance at		Charged to		Charged to		Deductions(1)		Balance at
		Beginning		Costs and		Other				End of
		of Period		Expenses		Accounts				Period
	Allowance for doubtful accounts Years Ended December 31,
	2013	$	635	$	836	$	—	$	1,015	$	456
	2012		362		1,253		—		980		635
	2011		362		1,018		—		1,018		362
	-1
	Deductions represent write-offs of accounts determined to be uncollectible.

Schedule_VI_Supplemental_Infor

Schedule VI - Supplemental Information Concerning Property and Casualty Insurance Operations	12 Months Ended
	Dec. 31, 2013
Schedule VI - Supplemental Information Concerning Property and Casualty Insurance Operations	'
Schedule VI - Supplemental Information Concerning Property and Casualty Insurance Operations	'
	Safety Insurance Group, Inc.
	Supplemental Information Concerning Property and Casualty Insurance Operations
	Schedule VI
	(Dollars in thousands)
		As of December 31,							Years Ended December 31,
	Affiliation With Registrant	Deferred		Reserves for			Unearned		Earned		Net
		Policy		Unpaid Claims			Premiums		Premiums		Investment
		Acquisition		and Claims							Income
		Costs		Adjustment
				Expenses
	Consolidated Property & Casualty Subsidiaries
	2013	$	63,388	$	455,014		$	370,583	$	681,870	$	43,054
	2012		60,665		423,842			353,219		642,469		40,870
	2011		56,716		403,872			329,562		598,368		39,060
		Years Ended December 31,
		Claims and Claims
		Adjustment Expenses					Amortization
		Incurred Related to					of Deferred
							Policy
							Acquisition		Paid Claims
							Costs		and Claims
									Adjustment
	Affiliation With Registrant	Current		Prior					Expenses		Premiums
		Year		Year							Written
	Consolidated Property & Casualty Subsidiaries
	2013	$	476,638	$	(28,889	)	$	126,201	$	424,738	$	697,540
	2012		439,527		(17,310	)		118,850		402,658		663,942
	2011		503,323		(36,683	)		110,795		465,786		620,316

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
Summary of Significant Accounting Policies	'
Investments	'
	Investments
	Investments in fixed maturities available-for-sale, which include taxable and non-taxable bonds and redeemable preferred stocks, are reported at fair value. Investments in equity securities available-for-sale, which include interests in common stocks, mutual funds and a real estate investment trust ("REIT"), are reported at fair value. Fair values for fixed maturity securities are based on estimates obtained from independent pricing services. Fair values for equity securities are derived from external market quotations, with the exception of the REIT whose fair value was determined using the trust's net asset value obtained from its audited financial statements. Short-term investments, which consist of U.S. Treasury bills, are reported at amortized cost, which approximates fair value. Other long-term investments consist of an investment in a limited partnership. The partnership interest is accounted for using the equity method of accounting. The income from the investment partnership is accounted for using the equity method and is included in net investment income. The carrying value of this investment is written down, or impaired, to fair value when a decline in value is considered to be other-than-temporary. In applying the equity method (including assessment for other-than-temporary impairment), the Company uses financial information provided by the investee, generally on a one to three month lag. Unrealized gains or losses on fixed maturity and equity securities reported at fair value are excluded from earnings and reported in a separate component of shareholders' equity, known as "Accumulated other comprehensive income (loss), net of taxes," until realized. Realized gains or losses on the sale or maturity of investments are determined based on the specific cost identification method. Fixed maturities and equity securities that experience declines in value that are other-than-temporary are written down to fair value with a corresponding charge to net realized losses on investments.
	Investment income is recognized on an accrual basis of accounting. Bonds not backed by other loans are amortized using the interest method. Loan-backed bonds and structured securities are amortized using the interest method and significant changes in estimated cash flows from the original purchase assumptions are accounted for using the retrospective method.
Cash and Cash Equivalents	'
	Cash and Cash Equivalents
	Cash and cash equivalents includes money market accounts and United States ("U.S.") Treasury bills with original maturities of three months or less. U.S. Treasury bills are stated at amortized cost, which approximates fair value.
Accounts Receivable	'
	Accounts Receivable
	Amounts included in accounts receivable represent premiums as well as finance charges, the majority of which are both billed on a monthly installment basis. Accounts receivable are stated net of allowances for doubtful accounts. At December 31, 2013 and 2012, these allowances were $456 and $635, respectively. Uncollected premium balances over ninety days past due are written off.
Deferred Policy Acquisition Costs	'
	Deferred Policy Acquisition Costs
	Amounts that vary with and are primarily related to the successful acquisition of a new or renewal insurance contract, principally commissions and premium taxes, are deferred and amortized ratably over the effective period of the policies. All other acquisition expenses are expensed as incurred. Deferred policy acquisition costs are reviewed to determine if they are recoverable from future income, and if not, are charged to expense. Future investment income attributable to related premiums is not taken into account in measuring the recoverability of the carrying value of this asset. Amortization of acquisition costs in the amount of $126,201, $118,850, and $110,795 was charged to underwriting expenses for the years ended 2013, 2012 and 2011, respectively.
Equity and Deposits in Pools	'
	Equity and Deposits in Pools
	Equity and deposits in pools represents the net receivable amounts from the residual market mechanisms, Commonwealth Automobile Reinsurers ("CAR") for automobile and Massachusetts Property Insurance Underwriting Association ("FAIR Plan") for homeowner insurance in Massachusetts. See Note 8 for a discussion of the Company's accounting for amounts assumed from residual markets.
Equipment and Leasehold Improvements	'
	Equipment and Leasehold Improvements
	Property, equipment, leasehold improvements, and software are carried at cost less accumulated depreciation. Depreciation is provided using the straight-line or accelerated method over the estimated useful lives of the related assets, which range from 3 to 10 years. Amortization of leasehold improvements is provided using the straight-line method over the term of the lease. The costs of computer software developed or obtained for internal use are capitalized and amortized over the estimated life of the business system, beginning when the software is ready for its intended use. Maintenance and repairs are charged to expense as incurred.
Losses and Loss Adjustment Expenses	'
	Losses and Loss Adjustment Expenses
	Liabilities for losses and loss adjustment expenses ("LAE") include case basis estimates for open claims reported prior to year-end and estimates of unreported claims and claim adjustment expenses. The estimates are continually reviewed and modified to reflect current conditions, and any resulting adjustments are reflected in current operating results. Adjustments for anticipated salvage and subrogation are recorded on incurred and reported and incurred but not reported losses.
Premiums and Unearned Premiums	'
	Premiums and Unearned Premiums
	Premiums are earned over the terms of the respective policies, which are generally one year. Unearned premiums represent the portion of premiums written applicable to the unexpired terms of the policies.
	Ceded premiums are charged to income over the terms of the respective policies and the applicable term of the reinsurance contracts with third-party reinsurers. Ceded unearned premiums represent the unexpired portion of premiums ceded to CAR and other reinsurers.
	Premiums received in advance of the policy effective date are recorded as a liability and not recognized as income until earned. Such amounts are included in accounts payable and accrued liabilities and totaled $15,453 and $15,199 at December 31, 2013 and 2012, respectively.
Reinsurance	'
	Reinsurance
	Liabilities for unearned premiums and unpaid losses are stated before deductions for ceded reinsurance. The ceded amounts are carried as receivables. Earned premiums are stated net of deductions for ceded reinsurance.
	The Company, as primary insurer, will be required to pay losses in their entirety in the event that the reinsurers are unable to discharge their obligations under the reinsurance agreements.
Finance and Other Service Income	'
	Finance and Other Service Income
	Finance and other service income primarily includes revenues from premium installment charges, which are recognized when earned.
Income Taxes	'
	Income Taxes
	The Company and its subsidiaries file a consolidated U.S. federal income tax return. The method of allocation among members of the consolidated group is subject to a written agreement approved by the Board of Directors (the "Board"). The consolidated tax liability is allocated on the basis of the members' proportionate contribution to consolidated taxable income.
	Deferred income taxes are generally recognized when assets and liabilities have different values for financial statement and tax reporting purposes, and for other temporary taxable and deductible differences as defined by Accounting Standards Codification ("ASC") 740, Income Taxes. A valuation allowance is established where management has assessed that it is more likely than not that the Company will not be able to utilize the full deferred tax asset.
Earnings per Weighted Average Common Share	'
	Earnings per Weighted Average Common Share
	Basic earnings per weighted average common share ("EPS") is calculated by dividing net income by the weighted average number of basic common shares outstanding during the period including unvested restricted shares which are considered participating securities. Diluted earnings per share is calculated by dividing net income by the weighted average number of common shares including unvested restricted shares and the net effect of potentially dilutive common shares outstanding
	The following table sets forth the computation of basic and diluted EPS for the periods indicated.
		Years Ended December 31,
		2013		2012		2011
	Net income available to common shareholders for basic and diluted earnings per share	$	61,351	$	58,070	$	13,702
	Weighted average common and common equivalent shares outstanding used to calculate basic earnings per share		15,354,468		15,288,346		15,165,065
	Common equivalent shares—stock options		5,558		7,106		10,941
	Common equivalent shares—non-vested stock grants		39,775		—		—
	Weighted average common and common equivalent shares outstanding used to calculate diluted earnings per share		15,399,801		15,295,452		15,176,006
	Basic earnings per share	$	4	$	3.8	$	0.9
	Diluted earnings per share	$	3.98	$	3.8	$	0.9
	Diluted EPS excludes stock options with exercise prices and exercise tax benefits greater than the average market price of the Company's common stock during the period because their inclusion would be anti-dilutive. There were no anti-dilutive stock options for the years ended December 31, 2013 or 2012. There were 82,800 anti-dilutive stock options for the year ended December 31, 2011.
Share-Based Compensation	'
	Share-Based Compensation
	ASC 718, Share Based Compensation, requires the Company to measure and recognize the cost of employee services received in exchange for an award of equity instruments. Under the provisions of ASC 718, share-based compensation cost is measured at the grant date, based on the fair value of the award, and is recognized as an expense over the requisite service period (generally the vesting period of the equity grant).
	As permitted by ASC 718, the Company elected the modified prospective transition method. Under the modified prospective transition method, (i) compensation expense for share-based awards granted prior to January 1, 2006 is recognized over the remaining service period using the compensation cost calculated for pro forma disclosure purposes as adjusted to incorporate forfeiture assumptions, and (ii) compensation expense for all share-based awards granted subsequent to December 31, 2005 is based on the grant date fair value estimated in accordance with the provisions of ASC 718.
	See Note 6 for further information regarding share-based compensation.
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 and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Recent Accounting Pronouncements	'
	Recent Accounting Pronouncements
	In February 2013, the FASB issued ASU 2013-02, Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income. ASU 2013-02 requires entities to present in either a single note or parenthetically on the face of the financial statements, the effect of significant amounts reclassified from each component of accumulated other comprehensive income based on its source and the income statement line items affected by the reclassification. Items not required to be reclassified to net income in their entirety are cross referenced to a related footnote for additional information. The ASU is effective for interim and annual periods beginning after December 15, 2012. The impact of adoption was not material to the Company's consolidated financial condition and results of operations.
Segments	'
	Segments
	The Company comprises one business segment: property and casualty insurance operations. Management organizes the business around private passenger automobile insurance in Massachusetts sold exclusively through independent agents and offers other personal and commercial insurance as complementary products. In accordance with ASC 280, Segment Reporting, the financial information of the segment is presented consistent with the way results are regularly evaluated by the chief operating decision maker in deciding how to allocate resources and in assessing performance.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2013
Summary of Significant Accounting Policies	'
Computation of basic and diluted EPS	'
		Years Ended December 31,
		2013		2012		2011
	Net income available to common shareholders for basic and diluted earnings per share	$	61,351	$	58,070	$	13,702
	Weighted average common and common equivalent shares outstanding used to calculate basic earnings per share		15,354,468		15,288,346		15,165,065
	Common equivalent shares—stock options		5,558		7,106		10,941
	Common equivalent shares—non-vested stock grants		39,775		—		—
	Weighted average common and common equivalent shares outstanding used to calculate diluted earnings per share		15,399,801		15,295,452		15,176,006
	Basic earnings per share	$	4	$	3.8	$	0.9
	Diluted earnings per share	$	3.98	$	3.8	$	0.9

Investments_Tables

Investments (Tables)	12 Months Ended
	Dec. 31, 2013
Investments	'
Gross unrealized gains and losses on investments in securities	'
		As of December 31, 2013
								Gross Unrealized
								Losses(3)
		Cost or			Gross			Non-OTTI			OTTI		Estimated
		Amortized			Unrealized			Unrealized			Unrealized		Fair
		Cost			Gains			Losses			Losses(4)		Value
	U.S. Treasury securities	$	1,510		$	—		$	(7	)	$	—	$	1,503
	Obligations of states and political subdivisions		461,256			10,248			(4,179	)		—		467,325
	Residential mortgage-backed securities(1)		205,053			6,879			(3,230	)		—		208,702
	Commercial mortgage-backed securities		31,885			342			(8	)		—		32,219
	Other asset-backed securities		13,357			124			(36	)		—		13,445
	Corporate and other securities		374,171			9,882			(2,290	)		—		381,763
	Subtotal, fixed maturity securities		1,087,232			27,475			(9,750	)		—		1,104,957
	Equity securities(2)		83,134			8,821			(84	)		—		91,871
	Other invested assets(5)		5,748			—			—			—		5,748
	Totals	$	1,176,114		$	36,296		$	(9,834	)	$	—	$	1,202,576
		As of December 31, 2012
								Gross Unrealized
								Losses(3)
		Cost or			Gross			Non-OTTI			OTTI		Estimated
		Amortized			Unrealized			Unrealized			Unrealized		Fair Value
		Cost			Gains			Losses			Losses(4)
	U.S. Treasury securities	$	7,112		$	43		$	—		$	—	$	7,155
	Obligations of states and political subdivisions		455,249			35,951			(17	)		—		491,183
	Residential mortgage-backed securities(1)		215,438			11,465			(1,006	)		—		225,897
	Commercial mortgage-backed securities		39,388			1,086			—			—		40,474
	Other asset-backed securities		21,288			898			—			—		22,186
	Corporate and other securities		361,939			16,988			(269	)		—		378,658
	Subtotal, fixed maturity securities		1,100,414			66,431			(1,292	)		—		1,165,553
	Equity securities(2)		21,237			1,629			(66	)		—		22,800
	Totals	$	1,121,651		$	68,060		$	(1,358	)	$	—	$	1,188,353
	-1
	Residential mortgage-backed securities consists primarily of obligations of U.S. Government agencies including collateralized mortgage obligations issued, guaranteed and/or insured by the following issuers: Government National Mortgage Association (GNMA), Federal Home Loan Mortgage Corporation (FHLMC), Federal National Mortgage Association (FNMA) and the Federal Home Loan Bank (FHLB).
	-2
	Equity securities includes interests in mutual funds held to fund the Company's executive deferred compensation plan.
	-3
	The Company's investment portfolio included 220 and 75 securities in an unrealized loss position at December 31, 2013 and December 31, 2012, respectively.
	-4
	Amounts in this column represent other-than-temporary impairment ("OTTI") recognized in accumulated other comprehensive income.
	-5
	Other invested assets are accounted for under the equity method which approximates fair value.
Amortized cost and the estimated fair value of fixed maturity securities, by maturity	'
		As of December 31, 2013
		Amortized			Estimated
		Cost			Fair Value
	Due in one year or less	$	28,170		$	28,660
	Due after one year through five years		342,290			351,975
	Due after five years through ten years		198,545			202,974
	Due after ten years		267,932			266,982
	Asset-backed securities		250,295			254,366
	Totals	$	1,087,232		$	1,104,957
Gross realized gains (losses) on sales of investments	'
		Years Ended December 31,
		2013			2012			2011
	Gross realized gains
	Fixed maturity securities	$	854		$	1,845		$	4,935
	Equity securities		1,011			270			246
	Gross realized losses
	Fixed maturity securities		(141	)		(115	)		(821	)
	Equity securities		(47	)		(25	)		—
	Net realized gains on investments	$	1,677		$	1,975		$	4,360
Gross unrealized losses included in the Company's investment portfolio and the fair value of those securities	'
		As of December 31, 2013
		Less than 12 Months						12 Months or More					Total
		Estimated			Unrealized			Estimated			Unrealized		Estimated		Unrealized
		Fair Value			Losses			Fair Value			Losses		Fair Value		Losses
	U.S. Treasury securities	$	1,503		$	7		$	—		$	—	$	1,503	$	7
	Obligations of states and political subdivisions		131,114			3,898			3,362			281		134,476		4,179
	Residential mortgage-backed securities		50,048			1,570			37,166			1,660		87,214		3,230
	Commercial mortgage-backed securities		6,008			8			—			—		6,008		8
	Other asset-backed securities		3,240			31			4,608			5		7,848		36
	Corporate and other securities		86,312			2,223			2,235			67		88,547		2,290
	Subtotal, fixed maturity securities		278,225			7,737			47,371			2,013		325,596		9,750
	Equity securities		3,933			73			299			11		4,232		84
	Total temporarily impaired securities	$	282,158		$	7,810		$	47,670		$	2,024	$	329,828	$	9,834
		As of December 31, 2012
		Less than 12 Months						12 Months or More					Total
		Estimated			Unrealized			Estimated			Unrealized		Estimated		Unrealized
		Fair Value			Losses			Fair Value			Losses		Fair Value		Losses
	Obligations of states and political subdivisions	$	2,868		$	17		$	—		$	—	$	2,868	$	17
	Residential mortgage-backed securities		50,779			966			3,938			40		54,717		1,006
	Commercial mortgage-backed securities		107			—			—			—		107		—
	Corporate and other securities		22,979			269			—			—		22,979		269
	Subtotal, fixed maturity securities		76,733			1,252			3,938			40		80,671		1,292
	Equity securities		1,145			23			303			43		1,448		66
	Total temporarily impaired securities	$	77,878		$	1,275		$	4,241		$	83	$	82,119	$	1,358
Components of net investment income	'
		Years Ended December 31,
		2013			2012			2011
	Interest on fixed maturity securities	$	43,328		$	42,235		$	39,980
	Dividends on equity securities		1,829			559			658
	Equity in earnings of other invested assets		148			—			—
	Interest on other assets		139			39			49
	Interest on cash and cash equivalents		18			18			33
	Total investment income		45,462			42,851			40,720
	Investment expenses		2,408			1,981			1,660
	Net investment income	$	43,054		$	40,870		$	39,060

Equipment_and_Leasehold_Improv1

Equipment and Leasehold Improvements (Tables)	12 Months Ended
	Dec. 31, 2013
Equipment and Leasehold Improvements	'
Schedule of carrying value of equipment and leasehold improvements by classification	'
		As of December 31,
		2013		2012
	Software	$	20,608	$	16,784
	Computer equipment		6,365		4,879
	Leasehold improvements		2,524		2,524
	Other equipment		2,400		2,390
	Furniture and fixtures		1,186		963
	Automobiles		—		10
	Total cost		33,083		27,550
	Less accumulated depreciation and amortization		22,419		18,455
	Equipment and leasehold improvements, net	$	10,664	$	9,095

ShareBased_Compensation_Tables

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2013
Share-Based Compensation	'
Schedule of assumptions used to estimate fair value at grant date using Black-Scholes option-pricing model	'
		Years Ended December 31,
		2013		2012		2011
	Expected dividend yield	NA		NA		1.68%
	Expected volatility	NA		NA		0.36
	Risk-free interest rate	NA		NA		4.76%
	Expected holding period	NA		NA		6.5 years
Schedule of stock option activity	'
		Years Ended December 31,
		2013					2012					2011
		Shares			Weighted		Shares			Weighted		Shares			Weighted
		Under			Average		Under			Average		Under			Average
		Option			Exercise Price		Option			Exercise Price		Option			Exercise Price
	Outstanding at beginning of year		87,500		$	39.24		125,700		$	37.63		151,003		$	37.3
	Exercised during the year		(67,300	)		38.52		(36,900	)		33.63		(25,303	)		35.66
	Forfeited during the year		—			—		(1,300	)		42.85		—			—
	Outstanding at end of year		20,200			41.64		87,500			39.24		125,700			37.63
	Exercisable at end of year		20,200		$	41.64		87,500		$	39.24		125,700		$	37.63
Schedule of restricted stock and performance-based restricted stock activity	'
		Years Ended December 31,
		2013					2012					2011
		Shares			Weighted		Shares			Weighted		Shares			Weighted
		Under			Average		Under			Average		Under			Average
		Restriction			Fair Value		Restriction			Fair Value		Restriction			Fair Value
	Outstanding at beginning of year		263,883		$	41.47		282,117		$	39.24		301,501		$	35.13
	Granted during the year		57,632			47.87		102,756			41.79		95,204			46.78
	Vested and unrestricted during the year		(103,788	)		40.75		(117,936	)		36.5		(114,009	)		34.67
	Forfeited during the year		(6,493	)		43.48		(3,054	)		38.13		(579	)		37.75
	Outstanding at end of year		211,234		$	43.51		263,883		$	41.47		282,117		$	39.24
		Years Ended December 31,
		2013					2012					2011
		Performance-			Weighted		Performance-			Weighted		Performance-based			Weighted
		based			Average		based			Average		Shares Under			Average
		Shares Under			Fair Value		Shares Under			Fair Value		Restriction			Fair Value
		Restriction					Restriction
	Granted during the year		37,456			44.13		—			—		—			—
	Outstanding at end of year		37,456		$	44.13		—		$	—		—		$	—

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies	'
Schedule of minimum annual rental payments due under lease agreements	'
	The approximate minimum annual rental payments due under these lease agreements as of December 31, 2013 are presented in the following table.
	2014	$	4,151
	2015		4,076
	2016		4,034
	2017		3,855
	2018		3,822
	Total minimum lease payments	$	19,938

Reinsurance_Tables

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2013
Reinsurance	'
Schedule of effect of assumed and ceded premiums on net written and earned premiums and losses and LAE incurred	'
		Years Ended December 31,
		2013			2012			2011
	Written Premiums
	Direct	$	731,680		$	696,220		$	649,262
	Assumed		20,593			17,943			16,521
	Ceded		(54,733	)		(50,221	)		(45,467	)
	Net written premiums	$	697,540		$	663,942		$	620,316
	Earned Premiums
	Direct	$	715,657		$	673,596		$	626,483
	Assumed		19,251			16,910			15,790
	Ceded		(53,038	)		(48,037	)		(43,905	)
	Net earned premiums	$	681,870		$	642,469		$	598,368
	Loss and LAE
	Direct	$	465,162		$	431,526		$	473,970
	Assumed		15,247			13,102			10,497
	Ceded		(32,660	)		(22,411	)		(17,827	)
	Net loss and LAE	$	447,749		$	422,217		$	466,640

Loss_and_Loss_Adjustment_Expen1

Loss and Loss Adjustment Expense Reserves (Tables)	12 Months Ended
	Dec. 31, 2013
Loss and Loss Adjustment Expense Reserves	'
Schedule of reconciliation of beginning and ending reserves for losses and loss adjustment expenses (LAE)	'
		Years Ended December 31,
		2013			2012			2011
	Reserves for losses and LAE at beginning of year	$	423,842		$	403,872		$	404,391
	Less receivable from reinsurers related to unpaid losses and LAE		(52,185	)		(51,774	)		(53,147	)
	Net reserves for losses and LAE at beginning of year		371,657			352,098			351,244
	Incurred losses and LAE, related to:
	Current year		476,638			439,527			503,323
	Prior years		(28,889	)		(17,310	)		(36,683	)
	Total incurred losses and LAE		447,749			422,217			466,640
	Paid losses and LAE related to:
	Current year		299,882			272,454			336,932
	Prior years		124,856			130,204			128,854
	Total paid losses and LAE		424,738			402,658			465,786
	Net reserves for losses and LAE at end of period		394,668			371,657			352,098
	Plus receivable from reinsurers related to unpaid losses and LAE		60,346			52,185			51,774
	Reserves for losses and LAE at end of period	$	455,014		$	423,842		$	403,872

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2013
Income Taxes	'
Summary of income tax expense in the Consolidated Statements of Income	'
		Years Ended December 31,
		2013			2012			2011
	Current Income Taxes:
	Federal	$	24,417		$	22,328		$	1,260
	State		21			3			4
			24,438			22,331			1,264
	Deferred Income Taxes:
	Federal		1,899			1,023			(693	)
	State		—			—			—
			1,899			1,023			(693	)
	Total income tax expense	$	26,337		$	23,354		$	571
Schedule of sources of the difference and the tax effects	'
		Years Ended December 31,
		2013			2012			2011
	Federal income tax expense, at statutory rate	$	30,691		$	28,498		$	4,996
	Tax-exempt investment income, net		(4,711	)		(5,142	)		(4,635	)
	State taxes, net		14			2			2
	Nondeductible expenses		210			202			232
	Other, net		133			(206	)		(24	)
	Total income tax expense	$	26,337		$	23,354		$	571
Schedule of deferred income tax asset (liability) representing the tax effects of temporary differences attributable to the Company's consolidated federal tax return group	'
		Years Ended December 31,
		2013			2012
	Deferred tax assets:
	Discounting of loss reserves	$	7,057		$	7,598
	Discounting of unearned premium reserve		25,770			24,655
	Bad debt allowance		384			673
	Employee benefits		7,248			6,734
	State loss carryforwards		—			20
	Rent incentive		635			767
	Other		—			27
	Total deferred tax assets before valuation allowance		41,094			40,474
	Valuation allowance for deferred tax assets		—			(20	)
	Total deferred tax assets, net of valuation allowance		41,094			40,454
	Deferred tax liabilities:
	Deferred acquisition costs		(22,186	)		(21,233	)
	Investments		(1,881	)		(596	)
	Net unrealized gains on investments		(9,261	)		(23,345	)
	Depreciation		(295	)		(247	)
	Software development costs		(2,505	)		(2,372	)
	Premium acquisition expenses		(890	)		(863	)
	Other		(92	)		—
	Total deferred tax liabilities		(37,110	)		(48,656	)
	Net deferred tax liability	$	3,984		$	(8,202	)

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2013
Fair Value of Financial Instruments	'
Fair value measurements for available-for-sale investments	'
		As of December 31, 2013
		Total		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs
	U.S. Treasury securities	$	1,503	$	—	$	1,503	$	—
	Obligations of states and political subdivisions		467,325		—		467,325		—
	Residential mortgage-backed securities		208,702		—		208,702		—
	Commercial mortgage-backed securities		32,219		—		32,219		—
	Other asset-backed securities		13,445		—		13,445		—
	Corporate and other securities		381,763		—		381,763		—
	Equity securities		91,871		75,951		—		15,920
	Total investment securities	$	1,196,828	$	75,951	$	1,104,957	$	15,920
		As of December 31, 2012
		Total		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs
	U.S. Treasury securities	$	7,155	$	—	$	7,155	$	—
	Obligations of states and political subdivisions		491,183		—		491,183		—
	Residential mortgage-backed securities		225,897		—		225,897		—
	Commercial mortgage-backed securities		40,474		—		40,474		—
	Other asset-backed securities		22,186		—		22,186		—
	Corporate and other securities		378,658		—		378,658		—
	Equity securities		22,800		17,454		—		5,346
	Total investment securities	$	1,188,353	$	17,454	$	1,165,553	$	5,346
Changes in the Company's Level 3 fair value securities	'
		Years Ended December 31,
		2013		2012		2011
	Balance at beginning of year	$	5,346	$	—	$	—
	Net gains included in other comprehensive income		574		—		—
	Purchases and sales		10,000		—		—
	Transfers into/(out) of Level 3		—		5,346		—
	Balance at end of year	$	15,920	$	5,346	$	—
	Amount of total losses included in earnings attributable to the change in unrealized losses related to assets still held at end of year	$	—	$	—	$	—

Quarterly_Results_of_Operation1

Quarterly Results of Operations (Tables)	12 Months Ended
	Dec. 31, 2013
Quarterly Results of Operations	'
Summary of the Company's unaudited of quarterly performance, and audited annual performance results of operations	'
		Year ended December 31, 2013
		First		Second		Third		Fourth		Total
		Quarter		Quarter		Quarter		Quarter		Year
	Total revenue	$	181,796	$	184,001	$	187,694	$	191,793	$	745,284
	Net income		13,984		18,059		17,656		11,652		61,351
	Earnings per weighted average common share:
	Basic		0.91		1.17		1.15		0.76		4
	Diluted		0.91		1.17		1.14		0.76		3.98
	Cash dividends paid per common share		0.6		0.6		0.6		0.6		2.4
		Year ended December 31, 2012
		First		Second		Third		Fourth		Total
		Quarter		Quarter		Quarter		Quarter		Year
	Total revenue	$	170,406	$	174,708	$	177,531	$	181,222	$	703,867
	Net income		17,209		16,956		14,334		9,571		58,070
	Earnings per weighted average common share:
	Basic		1.13		1.11		0.94		0.62		3.8
	Diluted		1.13		1.11		0.94		0.62		3.8
	Cash dividends paid per common share		0.5		0.5		0.6		0.6		2.2

Basis_of_Presentation_Details

Basis of Presentation (Details)	12 Months Ended
	Dec. 31, 2013
Basis of Presentation	'
Percentage of private passenger automobile insurance to total direct written premiums	63.90%

Summary_of_Significant_Account3

Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investments	'	'	'	'	'	'	'	'	'	'	'
Minimum period considered for applying equity method accounting based on financial information provided by the investee	'	'	'	'	'	'	'	'	'1 month	'	'
Maximum period considered for applying equity method accounting based on financial information provided by the investee	'	'	'	'	'	'	'	'	'3 months	'	'
Accounts Receivable	'	'	'	'	'	'	'	'	'	'	'
Premiums receivable, allowance for doubtful accounts	$456	'	'	'	$635	'	'	'	$456	$635	'
Deferred Policy Acquisition Costs	'	'	'	'	'	'	'	'	'	'	'
Amortization expense	'	'	'	'	'	'	'	'	126,201	118,850	110,795
Premiums and Unearned Premiums	'	'	'	'	'	'	'	'	'	'	'
Term over which premiums are earned	'	'	'	'	'	'	'	'	'1 year	'	'
Deferred revenue	15,453	'	'	'	15,199	'	'	'	15,453	15,199	'
Computation of basic and diluted EPS	'	'	'	'	'	'	'	'	'	'	'
Net income available to common shareholders for basic and diluted earnings per share	$11,652	$17,656	$18,059	$13,984	$9,571	$14,334	$16,956	$17,209	$61,351	$58,070	$13,702
Weighted average common and common equivalent shares outstanding used to calculate basic earnings per share	'	'	'	'	'	'	'	'	15,354,468	15,288,346	15,165,065
Common equivalent shares - stock options	'	'	'	'	'	'	'	'	5,558	7,106	10,941
Common equivalent shares- non-vested stock grants	'	'	'	'	'	'	'	'	39,775	'	'
Weighted average common and common equivalent shares outstanding used to calculate diluted earnings per share	'	'	'	'	'	'	'	'	15,399,801	15,295,452	15,176,006
Basic earnings per share (in dollars per share)	$0.76	$1.15	$1.17	$0.91	$0.62	$0.94	$1.11	$1.13	$4	$3.80	$0.90
Diluted earnings per share (in dollars per share)	$0.76	$1.14	$1.17	$0.91	$0.62	$0.94	$1.11	$1.13	$3.98	$3.80	$0.90
Minimum	'	'	'	'	'	'	'	'	'	'	'
Property, plant and equipment	'	'	'	'	'	'	'	'	'	'	'
Estimated useful lives	'	'	'	'	'	'	'	'	'3 years	'	'
Maximum	'	'	'	'	'	'	'	'	'	'	'
Property, plant and equipment	'	'	'	'	'	'	'	'	'	'	'
Estimated useful lives	'	'	'	'	'	'	'	'	'10 years	'	'

Summary_of_Significant_Account4

Summary of Significant Accounting Policies (Details 2)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segments	'	'	'
Number of business segment	1	'	'
Stock options	'	'	'
Computation of basic and diluted EPS	'	'	'
Antidilutive common shares under options	0	0	82,800

Investments_Details

Investments (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
	item	item
Securities available-for-sale	'	'
Fixed maturity securities, Cost or Amortized Cost	$1,087,232	$1,100,414
Fixed maturity securities, Gross Unrealized Gains	27,475	66,431
Fixed maturity securities, Non-OTTI Gross Unrealized Losses	-9,750	-1,292
Fixed maturity securities, Estimated Fair Value	1,104,957	1,165,553
Equity securities, Cost or Amortized Cost	83,134	21,237
Equity securities, Gross Unrealized Gains	8,821	1,629
Equity securities, Non-OTTI Gross Unrealized Losses	-84	-66
Equity securities, Estimated Fair Value	91,871	22,800
Other invested assets, Cost or Amortized Cost	5,748	'
Other invested assets, Estimated Fair Value	5,748	'
Cost or Amortized Cost	1,176,114	1,121,651
Gross Unrealized Gains	36,296	68,060
Gross Unrealized Losses	-9,834	-1,358
Estimated Fair Value	1,202,576	1,188,353
Number of securities in an unrealized loss position	220	75
U.S. Treasury securities	'	'
Securities available-for-sale	'	'
Fixed maturity securities, Cost or Amortized Cost	1,510	7,112
Fixed maturity securities, Gross Unrealized Gains	'	43
Fixed maturity securities, Non-OTTI Gross Unrealized Losses	-7	'
Fixed maturity securities, Estimated Fair Value	1,503	7,155
Obligations of states and political subdivisions	'	'
Securities available-for-sale	'	'
Fixed maturity securities, Cost or Amortized Cost	461,256	455,249
Fixed maturity securities, Gross Unrealized Gains	10,248	35,951
Fixed maturity securities, Non-OTTI Gross Unrealized Losses	-4,179	-17
Fixed maturity securities, Estimated Fair Value	467,325	491,183
Residential mortgage-backed securities	'	'
Securities available-for-sale	'	'
Fixed maturity securities, Cost or Amortized Cost	205,053	215,438
Fixed maturity securities, Gross Unrealized Gains	6,879	11,465
Fixed maturity securities, Non-OTTI Gross Unrealized Losses	-3,230	-1,006
Fixed maturity securities, Estimated Fair Value	208,702	225,897
Commercial mortgage-backed securities	'	'
Securities available-for-sale	'	'
Fixed maturity securities, Cost or Amortized Cost	31,885	39,388
Fixed maturity securities, Gross Unrealized Gains	342	1,086
Fixed maturity securities, Non-OTTI Gross Unrealized Losses	-8	'
Fixed maturity securities, Estimated Fair Value	32,219	40,474
Other asset-backed securities	'	'
Securities available-for-sale	'	'
Fixed maturity securities, Cost or Amortized Cost	13,357	21,288
Fixed maturity securities, Gross Unrealized Gains	124	898
Fixed maturity securities, Non-OTTI Gross Unrealized Losses	-36	'
Fixed maturity securities, Estimated Fair Value	13,445	22,186
Corporate and other securities	'	'
Securities available-for-sale	'	'
Fixed maturity securities, Cost or Amortized Cost	374,171	361,939
Fixed maturity securities, Gross Unrealized Gains	9,882	16,988
Fixed maturity securities, Non-OTTI Gross Unrealized Losses	-2,290	-269
Fixed maturity securities, Estimated Fair Value	$381,763	$378,658

Investments_Details_2

Investments (Details 2) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Amortized Cost	'	'
Due in one year or less, Amortized Cost	$28,170	'
Due after one year through five years, Amortized Cost	342,290	'
Due after five years though ten years, Amortized Cost	198,545	'
Due after ten years, Amortized Cost	267,932	'
Asset-backed securities, Amortized Cost	250,295	'
Total, Amortized Cost	1,087,232	1,100,414
Fair Value	'	'
Due in one year or less, Fair Value	28,660	'
Due after one year through five years, Fair Value	351,975	'
Due after five years through ten years, Fair Value	202,974	'
Due after ten years, Fair Value	266,982	'
Asset-backed securities, Fair Value	254,366	'
Total, Fair Value	$1,104,957	$1,165,553

Investments_Details_3

Investments (Details 3) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Securities available-for-sale	'	'	'
Net realized gains on investments	$1,677	$1,975	$4,360
Fixed maturity securities	'	'	'
Securities available-for-sale	'	'	'
Gross realized gains	854	1,845	4,935
Gross realized losses	-141	-115	-821
Equity securities	'	'	'
Securities available-for-sale	'	'	'
Gross realized gains	1,011	270	246
Gross realized losses	($47)	($25)	'

Investments_Details_4

Investments (Details 4) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
	Q
Estimated Fair Value	'	'
Estimated Fair Value, Less than 12 Months	$282,158	$77,878
Estimated Fair Value, 12 Months or More	47,670	4,241
Estimated Fair Value, Total	329,828	82,119
Unrealized Losses	'	'
Unrealized Losses, Less than 12 Months	7,810	1,275
Unrealized Losses, 12 Months or More	2,024	83
Unrealized Losses, Total	9,834	1,358
Other-Than-Temporary Impairments	'	'
Securities held with a material (20% or greater) unrealized loss for four or more consecutive quarters	0	'
Material loss threshold, number of consecutive quarters	4	'
Material loss threshold, percentage	20.00%	'
OTTI charges	0	0
Amounts included in accumulated other comprehensive income related to OTTI securities	0	0
Subtotal, fixed maturity securities	'	'
Estimated Fair Value	'	'
Estimated Fair Value, Less than 12 Months	278,225	76,733
Estimated Fair Value, 12 Months or More	47,371	3,938
Estimated Fair Value, Total	325,596	80,671
Unrealized Losses	'	'
Unrealized Losses, Less than 12 Months	7,737	1,252
Unrealized Losses, 12 Months or More	2,013	40
Unrealized Losses, Total	9,750	1,292
U.S. Treasury securities	'	'
Estimated Fair Value	'	'
Estimated Fair Value, Less than 12 Months	1,503	'
Estimated Fair Value, Total	1,503	'
Unrealized Losses	'	'
Unrealized Losses, Less than 12 Months	7	'
Unrealized Losses, Total	7	'
Obligations of states and political subdivisions	'	'
Estimated Fair Value	'	'
Estimated Fair Value, Less than 12 Months	131,114	2,868
Estimated Fair Value, 12 Months or More	3,362	'
Estimated Fair Value, Total	134,476	2,868
Unrealized Losses	'	'
Unrealized Losses, Less than 12 Months	3,898	17
Unrealized Losses, 12 Months or More	281	'
Unrealized Losses, Total	4,179	17
Residential mortgage-backed securities	'	'
Estimated Fair Value	'	'
Estimated Fair Value, Less than 12 Months	50,048	50,779
Estimated Fair Value, 12 Months or More	37,166	3,938
Estimated Fair Value, Total	87,214	54,717
Unrealized Losses	'	'
Unrealized Losses, Less than 12 Months	1,570	966
Unrealized Losses, 12 Months or More	1,660	40
Unrealized Losses, Total	3,230	1,006
Commercial mortgage-backed securities	'	'
Estimated Fair Value	'	'
Estimated Fair Value, Less than 12 Months	6,008	107
Estimated Fair Value, Total	6,008	107
Unrealized Losses	'	'
Unrealized Losses, Less than 12 Months	8	'
Unrealized Losses, Total	8	'
Other asset-backed securities	'	'
Estimated Fair Value	'	'
Estimated Fair Value, Less than 12 Months	3,240	'
Estimated Fair Value, 12 Months or More	4,608	'
Estimated Fair Value, Total	7,848	'
Unrealized Losses	'	'
Unrealized Losses, Less than 12 Months	31	'
Unrealized Losses, 12 Months or More	5	'
Unrealized Losses, Total	36	'
Corporate and other debt securities	'	'
Estimated Fair Value	'	'
Estimated Fair Value, Less than 12 Months	86,312	22,979
Estimated Fair Value, 12 Months or More	2,235	'
Estimated Fair Value, Total	88,547	22,979
Unrealized Losses	'	'
Unrealized Losses, Less than 12 Months	2,223	269
Unrealized Losses, 12 Months or More	67	'
Unrealized Losses, Total	2,290	269
Equity securities	'	'
Estimated Fair Value	'	'
Estimated Fair Value, Less than 12 Months	3,933	1,145
Estimated Fair Value, 12 Months or More	299	303
Estimated Fair Value, Total	4,232	1,448
Unrealized Losses	'	'
Unrealized Losses, Less than 12 Months	73	23
Unrealized Losses, 12 Months or More	11	43
Unrealized Losses, Total	84	66
Subprime mortgage debt securities	'	'
Other-Than-Temporary Impairments	'	'
Securities held	$0	'

Investments_Details_5

Investments (Details 5) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Components of net investment income	'	'	'
Interest on fixed maturity securities	$43,328	$42,235	$39,980
Dividends on equity securities	1,829	559	658
Equity in earnings of other invested assets	148	'	'
Interest on other assets	139	39	49
Interest on cash and cash equivalents	18	18	33
Total investment income	45,462	42,851	40,720
Investment expenses	2,408	1,981	1,660
Net investment income	$43,054	$40,870	$39,060

Equipment_and_Leasehold_Improv2

Equipment and Leasehold Improvements (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property, plant and equipment	'	'	'
Total cost	$33,083	$27,550	'
Less accumulated depreciation and amortization	22,419	18,455	'
Equipment and leasehold improvements, net	10,664	9,095	'
Depreciation and amortization	3,974	4,450	3,277
Software	'	'	'
Property, plant and equipment	'	'	'
Total cost	20,608	16,784	'
Computer equipment	'	'	'
Property, plant and equipment	'	'	'
Total cost	6,365	4,879	'
Leasehold improvements	'	'	'
Property, plant and equipment	'	'	'
Total cost	2,524	2,524	'
Other equipment	'	'	'
Property, plant and equipment	'	'	'
Total cost	2,400	2,390	'
Furniture and fixtures	'	'	'
Property, plant and equipment	'	'	'
Total cost	1,186	963	'
Automobiles	'	'	'
Property, plant and equipment	'	'	'
Total cost	'	$10	'

Employee_Benefit_Plan_Details

Employee Benefit Plan (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Employee Benefit Plan	'	'	'
Minimum age required to be eligible for contribution under the Retirement Plan	'21 years	'	'
Employer matching contribution (as a percent)	100.00%	'	'
Maximum amount contributed by employee from employees base salary (as a percent)	8.00%	'	'
Compensation expense	$2,649	$2,490	$2,385

ShareBased_Compensation_Detail

Share-Based Compensation (Details) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-Based Compensation	'	'	'
Maximum number of shares of common stock with respect to which awards may be granted	2,500,000	'	'
Number of shares available for future grant	531,862	'	'
Allocated Share-based Compensation Expense, Net of Tax	$2,954	$2,877	$2,915
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	$1,591	$1,549	$1,570
Assumptions used to estimate fair value at grant date using Black-Scholes option-pricing model	'	'	'
Expected dividend yield (as a percent)	'	'	1.68%
Expected volatility (as a percent)	'	'	0.36%
Risk-free interest rate (as a percent)	'	'	4.76%
Expected holding period	'	'	'6 years 6 months
Number of stock options granted (in shares)	0	0	0

ShareBased_Compensation_Detail1

Share-Based Compensation (Details 2) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Shares Under Option	'	'	'
Outstanding at beginning of year (in shares)	87,500	125,700	151,003
Exercised during the year (in shares)	-67,300	-36,900	-25,303
Forfeited during the year (in shares)	'	-1,300	'
Outstanding at end of year (in shares)	20,200	87,500	125,700
Exercisable at end of year (in shares)	20,200	87,500	125,700
Weighted Average Exercise Price	'	'	'
Outstanding at beginning of year (in dollars per share)	$39.24	$37.63	$37.30
Exercised during the year (in dollars per share)	$38.52	$33.63	$35.66
Forfeited during the year (in dollars per share)	'	$42.85	'
Outstanding at end of year (in dollars per share)	$41.64	$39.24	$37.63
Exercisable at end of year (in dollars per share)	$41.64	$39.24	$37.63
Additional disclosure	'	'	'
Aggregate Intrinsic Value of Options Outstanding	$296	$606	$554
Weighted average remaining contractual term of options outstanding	'2 years 1 month 6 days	'2 years 10 months 24 days	'3 years 8 months 12 days
Exercise price range, low end of range	$18.50	$13.30	$13.30
Exercise price range, high end of range	$42.85	$42.85	$42.85
Total intrinsic value of options exercised	$1,197	$463	$156

ShareBased_Compensation_Detail2

Share-Based Compensation (Details 3) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Weighted Average Fair Value	'	'	'
Unrecognized compensation expense related to non-vested restricted stock awards	$6,318	'	'
Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition	'1 year 1 month 6 days	'	'
Total fair value of the shares that were vested and unrestricted during the period	$4,230	$4,304	$3,953
Restricted Stock	'	'	'
Shares Under Restriction	'	'	'
Outstanding at beginning of year (in shares)	263,883	282,117	301,501
Granted during the year (in shares)	57,632	102,756	95,204
Vested and unrestricted during the year (in shares)	-103,788	-117,936	-114,009
Forfeited during the year (in shares)	-6,493	-3,054	-579
Outstanding at end of year (in shares)	211,234	263,883	282,117
Weighted Average Fair Value	'	'	'
Outstanding at beginning of year (in dollars per share)	$41.47	$39.24	$35.13
Granted during the year (in dollars per share)	$47.87	$41.79	$46.78
Vested and unrestricted during the year (in dollars per share)	$40.75	$36.50	$34.67
Forfeited during the year (in dollars per share)	$43.48	$38.13	$37.75
Outstanding at end of year (in dollars per share)	$43.51	$41.47	$39.24
Restricted Stock | Non-executives	'	'	'
Share-Based Compensation	'	'	'
Vesting period	'5 years	'	'
Restricted Stock | Executives	'	'	'
Share-Based Compensation	'	'	'
Vesting period	'3 years	'	'
Restricted Stock | First anniversary of grant date | Executives	'	'	'
Share-Based Compensation	'	'	'
Actual Payouts (as a percent)	30.00%	'	'
Restricted Stock | Second anniversary of grant date | Executives	'	'	'
Share-Based Compensation	'	'	'
Actual Payouts (as a percent)	30.00%	'	'
Restricted Stock | Third anniversary of grant date | Executives	'	'	'
Share-Based Compensation	'	'	'
Actual Payouts (as a percent)	40.00%	'	'
Restricted Stock | Performance-based	'	'	'
Share-Based Compensation	'	'	'
Vesting period	'3 years	'	'
Shares Under Restriction	'	'	'
Granted during the year (in shares)	37,456	'	'
Outstanding at end of year (in shares)	37,456	'	'
Weighted Average Fair Value	'	'	'
Granted during the year (in dollars per share)	$44.13	'	'
Outstanding at end of year (in dollars per share)	$44.13	'	'
Restricted Stock | Performance-based | Minimum	'	'	'
Share-Based Compensation	'	'	'
Actual Payouts (as a percent)	0.00%	'	'
Restricted Stock | Performance-based | Maximum	'	'	'
Share-Based Compensation	'	'	'
Actual Payouts (as a percent)	200.00%	'	'

Commitments_and_Contingencies_1

Commitments and Contingencies (Details) (USD $)	12 Months Ended			0 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Apr. 05, 2007
				Eight Amendment to lease agreement
				item
Minimum annual rental payments due	'	'	'	'
2014	$4,151	'	'	'
2015	4,076	'	'	'
2016	4,034	'	'	'
2017	3,855	'	'	'
2018	3,822	'	'	'
Total minimum lease payments	19,938	'	'	'
Rental Expense	$4,150	$4,114	$4,124	'
Lease of office space	'	'	'	'
Lease extension, additional term commencing on January 1, 2009	'	'	'	'10 years
Number of renewal terms	'	'	'	1
Renewal term	'	'	'	'5 years

Debt_Details

Debt (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Debt	'	'
Current borrowing capacity	$30,000	'
Maximum borrowing capacity	50,000	'
Default trigger, principal amount	10,000	'
Outstanding amount	$0	$0
Commitment fee (as a percent)	0.25%	'
Revolving Credit Agreement | LIBOR rate	'	'
Debt	'	'
Spread on variable rate (as a percent)	1.25%	'
Revolving Credit Agreement | Prime rate and Federal funds rate	'	'
Debt	'	'
Spread on variable rate (as a percent)	1.25%	'
Additional spread on variable rate (as a percent)	0.50%	'
Revolving Credit Agreement | Federal funds rate	'	'
Debt	'	'
Spread on variable rate (as a percent)	1.25%	'

Reinsurance_Details

Reinsurance (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reinsurance	'	'	'
Ceded unearned premium	$370,583	$353,219	'
CAR | Concentration of credit risk	'	'	'
Reinsurance	'	'	'
Reinsurance receivables on paid and unpaid loss and LAE	48,507	41,755	'
Ceded unearned premium	15,657	13,876	'
Assumed net income (losses)	($1,487)	($424)	$697

Reinsurance_Details_2

Reinsurance (Details 2) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Written Premiums	'	'	'
Direct	$731,680	$696,220	$649,262
Assumed	20,593	17,943	16,521
Ceded	-54,733	-50,221	-45,467
Net written premiums	697,540	663,942	620,316
Earned Premiums	'	'	'
Direct	715,657	673,596	626,483
Assumed	19,251	16,910	15,790
Ceded	-53,038	-48,037	-43,905
Net earned premiums	681,870	642,469	598,368
Loss and LAE	'	'	'
Direct	465,162	431,526	473,970
Assumed	15,247	13,102	10,497
Ceded	-32,660	-22,411	-17,827
Net loss and LAE	$447,749	$422,217	$466,640

Loss_and_Loss_Adjustment_Expen2

Loss and Loss Adjustment Expense Reserves (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Loss and Loss Adjustment Expense Reserves	'	'	'
Reserves for losses and LAE at beginning of year	$423,842	$403,872	$404,391
Less receivable from reinsurers related to unpaid losses and LAE	-52,185	-51,774	-53,147
Net reserves for losses and LAE at beginning of year	371,657	352,098	351,244
Incurred losses and LAE, related to:	'	'	'
Current year	476,638	439,527	503,323
Prior years	-28,889	-17,310	-36,683
Total incurred losses and LAE	447,749	422,217	466,640
Paid losses and LAE related to:	'	'	'
Current year	299,882	272,454	336,932
Prior years	124,856	130,204	128,854
Total paid losses and LAE	424,738	402,658	465,786
Net reserves for losses and LAE at end of period	394,668	371,657	352,098
Plus receivable from reinsurers related to unpaid losses and LAE	60,346	52,185	51,774
Reserves for losses and LAE at end of period	455,014	423,842	403,872
Prior years reserves decrease	($28,889)	($17,310)	($36,683)

Income_Taxes_Details

Income Taxes (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Current Income Taxes:	'	'	'
Federal	$24,417	$22,328	$1,260
State	21	3	4
Total	24,438	22,331	1,264
Deferred Income Taxes:	'	'	'
Federal	1,899	1,023	-693
Total	1,899	1,023	-693
Total income tax expense	$26,337	$23,354	$571

Income_Taxes_Details_2

Income Taxes (Details 2) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Sources of the difference and the tax effects	'	'	'
Federal income tax expense, at statutory rate	$30,691	$28,498	$4,996
Tax-exempt investment income, net	-4,711	-5,142	-4,635
State taxes, net	14	2	2
Nondeductible expenses	210	202	232
Other, net	133	-206	-24
Total income tax expense	$26,337	$23,354	$571

Income_Taxes_Details_3

Income Taxes (Details 3) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Deferred tax assets:	'	'	'
Discounting of loss reserves	$7,057	$7,598	'
Discounting of unearned premium reserve	25,770	24,655	'
Bad debt allowance	384	673	'
Employee benefits	7,248	6,734	'
State loss carryforwards	'	20	'
Rent incentive	635	767	'
Other	'	27	'
Total deferred tax assets before valuation allowance	41,094	40,474	'
Valuation allowance for deferred tax assets	0	-20	'
Total deferred tax assets, net of valuation allowance	41,094	40,454	'
Deferred tax liabilities:	'	'	'
Deferred acquisition costs	-22,186	-21,233	'
Investments	-1,881	-596	'
Net unrealized gains on investments	-9,261	-23,345	'
Depreciation	-295	-247	'
Software development costs	-2,505	-2,372	'
Premium acquisition expenses	-890	-863	'
Other	-92	'	'
Total deferred tax liabilities	-37,110	-48,656	'
Net deferred tax liability	3,984	-8,202	'
Unrecognized tax benefits	0	0	0
Unrecognized tax benefits if recognized would affect the effective tax rate	0	0	0
Unrecognized tax benefits interest and penalties accrued	$0	$0	'

Share_Repurchase_Program_Detai

Share Repurchase Program (Details) (USD $)	0 Months Ended		12 Months Ended
In Thousands, except Share data, unless otherwise specified	Nov. 04, 2013	Aug. 03, 2007	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share Repurchase Program	'	'	'	'	'
Share Repurchase Program	$150,000	$30,000	'	$90,000	'
Number of common shares purchased during period under the program	'	'	90,902	0	'
Cost of shares purchased during period	'	'	4,799	'	43
Treasury stock shares	'	'	1,819,547	1,728,645	'
Treasury stock, at cost	'	'	$60,368	$55,569	'

Statutory_Net_Income_and_Surpl1

Statutory Net Income and Surplus (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
	item
Company's insurance company subsidiaries	'	'	'
Statutory Net Income and Surplus	'	'	'
Statutory net income	$57,518	$56,895	$9,672
Dividend limitation without prior permission, percentage of preceding surplus	10.00%	'	'
Period of statutory measurement of income and dividends	'12 months	'	'
Period allowed for Commissioner to object to notice of an extraordinary dividend	'30 days	'	'
Statutory capital and surplus	627,993	599,024	'
Restricted net assets amount	565,194	'	'
Number of levels of regulatory action, risk-based capital law	4	'	'
Minimum statutory capital and surplus or company action level risk-based capital	90,613	'	'
Safety Insurance Company	'	'	'
Statutory Net Income and Surplus	'	'	'
Statutory net income	53,078	'	'
Statutory capital and surplus	627,993	'	'
Maximum available for dividends without approval	62,799	'	'
Recorded dividends	$36,114	'	'

Fair_Value_of_Financial_Instru2

Fair Value of Financial Instruments (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair Value of Financial Instruments	'	'
Period of advance notice before quarter end to dispose of Level 3 security	'45 days	'
Fair value of financial instruments	'	'
Short-term investments	$0	$0
Total	'	'
Fair value of financial instruments	'	'
Fair value measurement	1,196,828	1,188,353
Total | U.S. Treasury securities	'	'
Fair value of financial instruments	'	'
Fair value measurement	1,503	7,155
Total | Obligations of states and political subdivisions	'	'
Fair value of financial instruments	'	'
Fair value measurement	467,325	491,183
Total | Residential mortgage-backed securities	'	'
Fair value of financial instruments	'	'
Fair value measurement	208,702	225,897
Total | Commercial mortgage-backed securities	'	'
Fair value of financial instruments	'	'
Fair value measurement	32,219	40,474
Total | Other asset-backed securities	'	'
Fair value of financial instruments	'	'
Fair value measurement	13,445	22,186
Total | Corporate and other securities	'	'
Fair value of financial instruments	'	'
Fair value measurement	381,763	378,658
Total | Equity securities	'	'
Fair value of financial instruments	'	'
Fair value measurement	91,871	22,800
Level 1 Inputs	'	'
Fair value of financial instruments	'	'
Fair value measurement	75,951	17,454
Level 1 Inputs | Equity securities	'	'
Fair value of financial instruments	'	'
Fair value measurement	75,951	17,454
Level 2 Inputs	'	'
Fair value of financial instruments	'	'
Fair value measurement	1,104,957	1,165,553
Level 2 Inputs | U.S. Treasury securities	'	'
Fair value of financial instruments	'	'
Fair value measurement	1,503	7,155
Level 2 Inputs | Obligations of states and political subdivisions	'	'
Fair value of financial instruments	'	'
Fair value measurement	467,325	491,183
Level 2 Inputs | Residential mortgage-backed securities	'	'
Fair value of financial instruments	'	'
Fair value measurement	208,702	225,897
Level 2 Inputs | Commercial mortgage-backed securities	'	'
Fair value of financial instruments	'	'
Fair value measurement	32,219	40,474
Level 2 Inputs | Other asset-backed securities	'	'
Fair value of financial instruments	'	'
Fair value measurement	13,445	22,186
Level 2 Inputs | Corporate and other securities	'	'
Fair value of financial instruments	'	'
Fair value measurement	381,763	378,658
Level 3 Inputs	'	'
Fair value of financial instruments	'	'
Fair value measurement	15,920	5,346
Level 3 Inputs | Equity securities	'	'
Fair value of financial instruments	'	'
Fair value measurement	$15,920	$5,346

Fair_Value_of_Financial_Instru3

Fair Value of Financial Instruments (Details 2) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Transfers between Levels	'	'	'
Transfers from Level 1 to Level 2	$0	$0	'
Transfers from Level 2 to Level 1	0	0	'
Changes in the Company's Level 3 fair value securities	'	'	'
Balance at beginning of period	5,346	'	'
Net gains included in other comprehensive income	574	'	'
Purchases and sales	10,000	'	'
Transfers in to/ (out) of Level 3	'	5,346	'
Balance at end of period	15,920	5,346	'
Transfers into Level 3	'	'	0
Transfers out of Level 3	'	'	$0

Quarterly_Results_of_Operation2

Quarterly Results of Operations (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Results of Operations	'	'	'	'	'	'	'	'	'	'	'
Total revenue	$191,793	$187,694	$184,001	$181,796	$181,222	$177,531	$174,708	$170,406	$745,284	$703,867	$660,158
Net income	$11,652	$17,656	$18,059	$13,984	$9,571	$14,334	$16,956	$17,209	$61,351	$58,070	$13,702
Earnings per weighted average common share:	'	'	'	'	'	'	'	'	'	'	'
Basic (in dollars per share)	$0.76	$1.15	$1.17	$0.91	$0.62	$0.94	$1.11	$1.13	$4	$3.80	$0.90
Diluted (in dollars per share)	$0.76	$1.14	$1.17	$0.91	$0.62	$0.94	$1.11	$1.13	$3.98	$3.80	$0.90
Cash dividends paid per common share (in dollars per share)	$0.60	$0.60	$0.60	$0.60	$0.60	$0.60	$0.50	$0.50	$2.40	$2.20	$2

Related_Party_Transactions_Det

Related Party Transactions (Details) (Mr. A. Richard Caputo, Jr., a member of the Company's Board of Directors and the Chairman of its Investment Committee, Loan to Vantage Specialties, USD $)	1 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Feb. 29, 2012	Dec. 31, 2013
Mr. A. Richard Caputo, Jr., a member of the Company's Board of Directors and the Chairman of its Investment Committee | Loan to Vantage Specialties	'	'
Related party transaction	'	'
Interest rate (as a percent)	'	7.00%
Repayment, percentage of principal per quarter	'	0.25%
Original participation in the loan	$2,500	'

Schedule_I_Summary_of_Investme1

Schedule I - Summary of Investments - Other than Investments in Related Parties (Details) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Summary of investments - other than investments in related parties	'
Cost or Amortized Cost	$1,176,114
Estimated Fair Value	1,202,576
Amount at which shown in the Balance Sheet	1,202,576
Total fixed maturities	'
Summary of investments - other than investments in related parties	'
Cost or Amortized Cost	1,087,232
Estimated Fair Value	1,104,957
Amount at which shown in the Balance Sheet	1,104,957
U.S. government and government agencies and authorities	'
Summary of investments - other than investments in related parties	'
Cost or Amortized Cost	206,563
Estimated Fair Value	210,205
Amount at which shown in the Balance Sheet	210,205
Obligations of U.S. states and political subdivisions	'
Summary of investments - other than investments in related parties	'
Cost or Amortized Cost	461,256
Estimated Fair Value	467,325
Amount at which shown in the Balance Sheet	467,325
Corporate and other securities	'
Summary of investments - other than investments in related parties	'
Cost or Amortized Cost	419,413
Estimated Fair Value	427,427
Amount at which shown in the Balance Sheet	427,427
Total equity securities	'
Summary of investments - other than investments in related parties	'
Cost or Amortized Cost	83,134
Estimated Fair Value	91,871
Amount at which shown in the Balance Sheet	91,871
Industrial, miscellaneous and all other	'
Summary of investments - other than investments in related parties	'
Cost or Amortized Cost	83,134
Estimated Fair Value	91,871
Amount at which shown in the Balance Sheet	91,871
Other invested assets	'
Summary of investments - other than investments in related parties	'
Cost or Amortized Cost	5,748
Estimated Fair Value	5,748
Amount at which shown in the Balance Sheet	$5,748

Schedule_II_Condensed_Financia1

Schedule II - Condensed Financial Information of the Registrant (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
In Thousands, unless otherwise specified
Assets	'	'	'	'
Investments in consolidated affiliates	$5,748	'	'	'
Other	16,403	15,278	'	'
Total assets	1,625,457	1,574,346	'	'
Liabilities	'	'	'	'
Total liabilities	930,270	879,987	'	'
Shareholders' equity	695,187	694,359	656,313	653,476
Total liabilities and shareholders' equity	1,625,457	1,574,346	'	'
Registrant	'	'	'	'
Assets	'	'	'	'
Investments in consolidated affiliates	696,195	695,361	'	'
Other	69	8	'	'
Total assets	696,264	695,369	'	'
Liabilities	'	'	'	'
Accounts payable and other liabilities	1,077	1,010	'	'
Total liabilities	1,077	1,010	'	'
Shareholders' equity	695,187	694,359	'	'
Total liabilities and shareholders' equity	$696,264	$695,369	'	'

Schedule_II_Condensed_Financia2

Schedule II - Condensed Financial Information of the Registrant (Details 2) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Statements of Income and Comprehensive Income	'	'	'	'	'	'	'	'	'	'	'
Revenues	$191,793	$187,694	$184,001	$181,796	$181,222	$177,531	$174,708	$170,406	$745,284	$703,867	$660,158
Expenses	'	'	'	'	'	'	'	'	657,596	622,443	645,885
Net income	11,652	17,656	18,059	13,984	9,571	14,334	16,956	17,209	61,351	58,070	13,702
Other comprehensive income (loss), net of deferred federal income taxes	'	'	'	'	'	'	'	'	-26,156	7,735	13,649
Comprehensive income	'	'	'	'	'	'	'	'	35,195	65,805	27,351
Registrant	'	'	'	'	'	'	'	'	'	'	'
Condensed Statements of Income and Comprehensive Income	'	'	'	'	'	'	'	'	'	'	'
Expenses	'	'	'	'	'	'	'	'	1,201	1,194	1,078
Net loss	'	'	'	'	'	'	'	'	-1,201	-1,194	-1,078
Earnings from consolidated subsidiaries	'	'	'	'	'	'	'	'	62,552	59,264	14,780
Net income	'	'	'	'	'	'	'	'	61,351	58,070	13,702
Other comprehensive income (loss), net of deferred federal income taxes	'	'	'	'	'	'	'	'	-26,156	7,735	13,649
Comprehensive income	'	'	'	'	'	'	'	'	$35,195	$65,805	$27,351

Schedule_II_Condensed_Financia3

Schedule II - Condensed Financial Information of the Registrant (Details 3) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Statements of Cash Flows	'	'	'	'	'	'	'	'	'	'	'
Net income	$11,652	$17,656	$18,059	$13,984	$9,571	$14,334	$16,956	$17,209	$61,351	$58,070	$13,702
Adjustments to reconcile net income to net cash provided by operating activities:	'	'	'	'	'	'	'	'	'	'	'
Earnings from consolidated subsidiaries	'	'	'	'	'	'	'	'	-148	'	'
Other assets	'	'	'	'	'	'	'	'	3,084	-1,444	2,151
Accounts payable and accrued liabilities	'	'	'	'	'	'	'	'	1,050	13,426	-2,135
Net cash provided by operating activities	'	'	'	'	'	'	'	'	110,861	104,331	39,475
Proceeds from exercise of stock options	'	'	'	'	'	'	'	'	2,592	1,241	902
Dividends paid	'	'	'	'	'	'	'	'	-36,865	-33,634	-30,322
Acquisition of treasury stock	'	'	'	'	'	'	'	'	-4,799	'	-43
Net cash used for financing activities	'	'	'	'	'	'	'	'	-39,072	-32,393	-29,463
Net increase (decrease) in cash and cash equivalents	'	'	'	'	'	'	'	'	20,494	-2,507	-2,401
Cash and cash equivalents at beginning of year	'	'	'	35,383	'	'	'	37,890	35,383	37,890	40,291
Cash and cash equivalents at end of period	55,877	'	'	'	35,383	'	'	'	55,877	35,383	37,890
Registrant	'	'	'	'	'	'	'	'	'	'	'
Condensed Statements of Cash Flows	'	'	'	'	'	'	'	'	'	'	'
Net income	'	'	'	'	'	'	'	'	61,351	58,070	13,702
Adjustments to reconcile net income to net cash provided by operating activities:	'	'	'	'	'	'	'	'	'	'	'
Earnings from consolidated subsidiaries	'	'	'	'	'	'	'	'	-62,552	-59,264	-14,780
Dividends received from consolidated subsidiaries	'	'	'	'	'	'	'	'	36,114	29,137	25,744
Amortization of restricted stock expense	'	'	'	'	'	'	'	'	4,153	4,430	4,747
Other assets	'	'	'	'	'	'	'	'	-61	12	55
Accounts payable and accrued liabilities	'	'	'	'	'	'	'	'	67	8	-5
Net cash provided by operating activities	'	'	'	'	'	'	'	'	39,072	32,393	29,463
Proceeds from exercise of stock options	'	'	'	'	'	'	'	'	2,592	1,241	902
Dividends paid	'	'	'	'	'	'	'	'	-36,865	-33,634	-30,322
Acquisition of treasury stock	'	'	'	'	'	'	'	'	-4,799	'	-43
Net cash used for financing activities	'	'	'	'	'	'	'	'	($39,072)	($32,393)	($29,463)

Schedule_III_Supplementary_Ins1

Schedule III - Supplementary Insurance Information (Details) (Property and Casualty Insurance, USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property and Casualty Insurance	'	'	'
Supplementary Insurance Information	'	'	'
Deferred Policy Acquisition Costs	$63,388	$60,665	$56,715
Future Policy Benefits, Losses, Claims and Loss Expenses	455,014	423,842	403,872
Unearned Premiums	370,583	353,219	329,562
Premium Revenue	681,870	642,469	598,368
Net Investment Income	43,054	40,870	39,060
Benefits, Claims, Losses, and Settlement Expenses	447,749	422,217	466,640
Other Operating Expenses	83,557	81,288	68,362
Premiums Written	697,540	663,942	620,316
Amortization of Deferred Policy Acquisition Costs	$126,201	$118,850	$110,795

Schedule_IV_Reinsurance_Detail

Schedule IV - Reinsurance (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Insurance Earned Premiums	'	'	'
Gross Amount	$715,657	$673,596	$626,483
Ceded to Other Companies	53,038	48,037	43,905
Assumed from Other Companies	19,251	16,910	15,790
Net earned premiums	681,870	642,469	598,368
Property and Casualty Insurance	'	'	'
Insurance Earned Premiums	'	'	'
Gross Amount	715,657	673,596	626,483
Ceded to Other Companies	53,038	48,037	43,905
Assumed from Other Companies	19,251	16,910	15,790
Net earned premiums	$681,870	$642,469	$598,368
Percentage of Amount Assumed to Net	2.80%	2.60%	2.60%

Schedule_V_Valuation_and_Quali1

Schedule V - Valuation and Qualifying Accounts (Details) (Allowance for doubtful accounts, USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Allowance for doubtful accounts	'	'	'
Movement in valuation and qualifying accounts	'	'	'
Balance at Beginning of Period	$635	$362	$362
Charged to Costs and Expenses	836	1,253	1,018
Deductions	1,015	980	1,018
Balance at End of Period	$456	$635	$362

Schedule_VI_Supplemental_Infor1

Schedule VI - Supplemental Information Concerning Property and Casualty Insurance Operations (Details) (Consolidated Property & Casualty Subsidiaries, USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Consolidated Property & Casualty Subsidiaries	'	'	'
Supplemental Information Concerning Property and Casualty Insurance Operations	'	'	'
Deferred Policy Acquisition Costs	$63,388	$60,665	$56,716
Reserves for Unpaid Claims and Claims Adjustment Expenses	455,014	423,842	403,872
Unearned Premiums	370,583	353,219	329,562
Earned Premiums	681,870	642,469	598,368
Net Investment Income	43,054	40,870	39,060
Claims and Claims Adjustment Expenses Incurred Related to Current Year	476,638	439,527	503,323
Claims and Claims Adjustment Expenses Incurred Related to Prior Year	-28,889	-17,310	-36,683
Amortization of Deferred Policy Acquisition Costs	126,201	118,850	110,795
Paid Claims and Claims Adjustment Expenses	424,738	402,658	465,786
Premiums Written	$697,540	$663,942	$620,316