Selective Insurance (SIGI) 10-K 22 Feb 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2016	Feb. 14, 2017	Jun. 30, 2016
Document and Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Entity Registrant Name	SELECTIVE INSURANCE GROUP INC
Entity Central Index Key	230,557
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 2,154,552,276
Entity Common Stock, Shares Outstanding		58,204,352

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($)	Dec. 31, 2016	Dec. 31, 2015
ASSETS
Fixed income securities, held-to-maturity – at carrying value (fair value: $105,211 – 2016; $209,544 – 2015)	$ 101,556,000	$ 201,354,000
Fixed income securities, available-for-sale – at fair value (amortized cost: $4,753,759 – 2016; $4,352,514 – 2015)	4,792,540,000	4,408,203,000
Equity securities, available-for-sale – at fair value (cost: $120,889 – 2016; $193,816 – 2015)	146,753,000	207,051,000
Short-term investments (at cost which approximates fair value)	221,701,000	194,819,000
Other investments	102,397,000	77,842,000
Total investments (Notes 5 and 7)	5,364,947,000	5,089,269,000
Cash	458,000	898,000
Interest and dividends due or accrued	40,164,000	38,501,000
Premiums receivable, net of allowance for uncollectible accounts of: $5,980 – 2016; $4,422 – 2015	681,611,000	615,164,000
Reinsurance recoverable, net of allowance for uncollectible accounts of: $5,500 – 2016; $5,700 – 2015 (Note 8)	621,537,000	561,968,000
Prepaid reinsurance premiums (Note 8)	146,282,000	140,889,000
Current federal income tax (Note 13)	2,486,000	0
Deferred federal income tax (Note 13)	84,840,000	92,696,000
Property and equipment – at cost, net of accumulated depreciation and amortization of: $198,729 – 2016; $188,548 – 2015	69,576,000	65,701,000
Deferred policy acquisition costs (Note 2)	222,564,000	213,159,000
Goodwill (Note 11)	7,849,000	7,849,000
Other assets	113,534,000	78,339,000
Total assets	7,355,848,000	6,904,433,000
LIABILITIES AND STOCKHOLDERS’ EQUITY
Reserve for losses and loss expenses (Note 9)	3,691,719,000	3,517,728,000
Unearned premiums	1,262,819,000	1,169,710,000
Short-term debt (Note 10)	0	60,000,000
Long-term debt (Note 10)	438,667,000	328,192,000
Current federal income tax (Note 13)	0	7,442,000
Accrued salaries and benefits	132,880,000	167,336,000
Other liabilities	298,393,000	255,984,000
Total liabilities	5,824,478,000	5,506,392,000
Stockholders’ Equity:
Preferred stock of $0 par value per share: Authorized shares: 5,000,000; no shares issued or outstanding	0	0
Common stock of $2 par value per share Authorized shares: 360,000,000 Issued: 101,620,436 - 2016; 100,861,372 - 2015	203,241,000	201,723,000
Additional paid-in capital	347,295,000	326,656,000
Retained earnings	1,568,881,000	1,446,192,000
Accumulated other comprehensive loss (Note 6)	(15,950,000)	(9,425,000)
Treasury stock – at cost (shares: 43,653,237 – 2016; 43,500,642 – 2015)	(572,097,000)	(567,105,000)
Total stockholders’ equity	1,531,370,000	1,398,041,000
Commitments and contingencies (Notes 17 and 18)
Total liabilities and stockholders’ equity	$ 7,355,848,000	$ 6,904,433,000

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Fixed income securities, held-to-maturity, fair value	$ 105,211	$ 209,544
Fixed income securities, available-for-sale, amortized cost	4,753,759	4,352,514
Equity securities, available-for-sale, cost	120,889	193,816
Premiums receivable, allowance for uncollectible accounts	5,980	4,422
Reinsurance recoverable, allowance for uncollectible accounts	5,500	5,700
Property and equipment, accumulated depreciation and amortization	$ 198,729	$ 188,548
Preferred stock, par value per share	$ 0	$ 0
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value per share	$ 2	$ 2
Common stock, shares authorized	360,000,000	360,000,000
Common stock, shares issued	101,620,436	100,861,372
Treasury stock, shares	43,653,237	43,500,642

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Net premiums earned	$ 2,149,572	$ 1,989,909	$ 1,852,609
Net investment income earned	130,754	121,316	138,708
Net realized (losses) gains:
Net realized investment gains	3,562	31,537	37,703
Other-than-temporary impairments	(8,509)	(18,366)	(11,104)
Other-than-temporary impairments on fixed income securities recognized in other comprehensive income	(10)	0	0
Total net realized (losses) gains	(4,937)	13,171	26,599
Other income	8,881	7,456	16,945
Total revenues	2,284,270	2,131,852	2,034,861
Expenses:
Losses and loss expenses incurred	1,234,797	1,148,541	1,157,501
Policy acquisition costs	763,758	689,820	624,470
Interest expense	22,771	22,428	23,063
Other expenses	42,989	38,371	32,696
Total expenses	2,064,315	1,899,160	1,837,730
Income before federal income tax	219,955	232,692	197,131
Federal income tax expense:
Current	48,581	45,347	28,415
Deferred	12,879	21,484	26,889
Total federal income tax expense	61,460	66,831	55,304
Net income	$ 158,495	$ 165,861	$ 141,827
Earnings per share:
Basic net income	$ 2.74	$ 2.90	$ 2.52
Diluted net income	2.70	2.85	2.47
Dividends to stockholders	$ 0.61	$ 0.57	$ 0.53

Consolidation Statements of Com

Consolidation Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net income	$ 158,495	$ 165,861	$ 141,827
Unrealized holding (losses) gains arising during year	(5,977)	(26,143)	47,411
Non-credit portion of other-than-temporary impairments recognized in other comprehensive income	(6)	0	0
Amounts reclassified into net income: Held-to-maturity securities	(92)	(377)	(844)
Amounts reclassified into net income: Non-credit other-than-temporary impairment	138	232	1,085
Amounts reclassified into net income: Realized losses (gains) on available for sale securities	3,064	(9,110)	(18,762)
Total unrealized (losses) gains on investment securities	(2,873)	(35,398)	28,890
Net actuarial (loss) gain	(7,852)	1,585	(35,189)
Amounts reclassified into net income: Net actuarial loss	4,200	4,600	1,236
Total defined benefit pension and post-retirement plans	(3,652)	6,185	(33,953)
Other comprehensive loss	(6,525)	(29,213)	(5,063)
Comprehensive income	$ 151,970	$ 136,648	$ 136,764

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($)	Total	Common Stock [Member]	Additional paid-in capital [Member]	Retained earnings [Member]	Accumulated other comprehensive (loss) income [Member]	Treasury stock [Member]
Beginning of year at Dec. 31, 2013		$ 198,240,000	$ 288,182,000	$ 1,202,015,000	$ 24,851,000	$ (559,360,000)
Dividend reinvestment plan (shares: 38,741 – 2016; 50,013 – 2015; 58,309 – 2014)		117,000	1,306,000
Stock purchase and compensation plans (shares: 720,323 – 2016; 863,426 – 2015; 769,389 – 2014)		1,539,000	15,897,000
Net income	$ 141,827,000			141,827,000
Dividends to stockholders ($0.61 per share – 2016; $0.57 per share – 2015; $0.53 per share – 2014)				(30,402,000)
Other comprehensive loss	(5,063,000)				(5,063,000)
Acquisition of treasury stock (shares: 152,595 – 2016; 147,461 – 2015; 154,559 – 2014)						(3,563,000)
End of year at Dec. 31, 2014	1,275,586,000	199,896,000	305,385,000	1,313,440,000	19,788,000	(562,923,000)
Dividend reinvestment plan (shares: 38,741 – 2016; 50,013 – 2015; 58,309 – 2014)		100,000	1,374,000
Stock purchase and compensation plans (shares: 720,323 – 2016; 863,426 – 2015; 769,389 – 2014)		1,727,000	19,897,000
Net income	165,861,000			165,861,000
Dividends to stockholders ($0.61 per share – 2016; $0.57 per share – 2015; $0.53 per share – 2014)				(33,109,000)
Other comprehensive loss	(29,213,000)				(29,213,000)
Acquisition of treasury stock (shares: 152,595 – 2016; 147,461 – 2015; 154,559 – 2014)						(4,182,000)
End of year at Dec. 31, 2015	1,398,041,000	201,723,000	326,656,000	1,446,192,000	(9,425,000)	(567,105,000)
Dividend reinvestment plan (shares: 38,741 – 2016; 50,013 – 2015; 58,309 – 2014)		77,000	1,389,000
Stock purchase and compensation plans (shares: 720,323 – 2016; 863,426 – 2015; 769,389 – 2014)		1,441,000	19,250,000
Net income	158,495,000			158,495,000
Dividends to stockholders ($0.61 per share – 2016; $0.57 per share – 2015; $0.53 per share – 2014)				(35,806,000)
Other comprehensive loss	(6,525,000)				(6,525,000)
Acquisition of treasury stock (shares: 152,595 – 2016; 147,461 – 2015; 154,559 – 2014)						(4,992,000)
End of year at Dec. 31, 2016	$ 1,531,370,000	$ 203,241,000	$ 347,295,000	$ 1,568,881,000	$ (15,950,000)	$ (572,097,000)

Consolidated Statements of Sto7

Consolidated Statements of Stockholders' Equity (Parenthetical)	12 Months Ended
	Dec. 31, 2016$ / sharesshares	Dec. 31, 2015$ / sharesshares	Dec. 31, 2014$ / sharesshares
Dividend reinvestment plan, shares	38,741	50,013	58,309
Stock purchase and compensation plans, shares	720,323	863,426	769,389
Dividends to stockholders, per share | $ / shares	$ 0.61	$ 0.57	$ 0.53
Acquisition of treasury stock, shares	152,595	147,461	154,559
Preferred stock, par value per share | $ / shares	$ 0	$ 0	$ 0
Preferred stock, shares authorized	5,000,000	5,000,000	5,000,000
Preferred stock, shares issued	0	0	0
Series A Preferred Stock [Member]
Preferred stock, par value per share | $ / shares	$ 0	$ 0	$ 0
Preferred stock, shares authorized	300,000	300,000	300,000

Consolidated Statements of Cash

Consolidated Statements of Cashflow - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Activities
Net income	$ 158,495	$ 165,861	$ 141,827
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	61,671	59,688	45,346
Sale of renewal rights	0	0	(8,000)
Stock-based compensation expense	10,449	8,973	8,702
Undistributed (gains) losses of equity method investments	(2,316)	1,889	(153)
Net realized losses (gains)	4,937	(13,171)	(26,599)
Net gain on disposal of property and equipment	0	0	(104)
Changes in assets and liabilities:
Increase in reserves for losses and loss expenses, net of reinsurance recoverables	114,422	59,438	97,449
Increase in unearned premiums, net of prepaid reinsurance	87,716	79,995	32,671
Decrease in net federal income taxes	11,150	25,004	31,323
Increase in premiums receivable	(66,447)	(56,386)	(33,908)
Increase in deferred policy acquisition costs	(9,405)	(27,551)	(12,627)
(Increase) decrease in interest and dividends due or accrued	(1,473)	407	(1,536)
(Decrease) increase in accrued salaries and benefits	(46,536)	11,392	(7,182)
(Increase) decrease in other assets	(30,071)	(11,523)	1,186
Increase (decrease) in other liabilities	9,191	77,564	(35,632)
Net cash provided by operating activities	301,783	381,580	232,763
Investing Activities
Purchase of fixed income securities, held-to-maturity	(4,235)	(3,316)	0
Purchase of fixed income securities, available-for-sale	(1,982,023)	(1,041,916)	(843,616)
Purchase of equity securities, available-for-sale	(35,490)	(195,720)	(186,019)
Purchase of other investments	(66,164)	(12,170)	(10,617)
Purchase of short-term investments	(3,499,380)	(1,602,327)	(1,410,123)
Sale of fixed income securities, available-for-sale	926,470	61,571	51,002
Sale of short-term investments	3,470,022	1,539,480	1,452,402
Redemption and maturities of fixed income securities, held-to-maturity	102,868	106,621	73,415
Redemption and maturities of fixed income securities, available-for-sale	641,524	567,445	482,816
Sale of equity securities, available-for-sale	119,617	172,561	208,008
Distributions from other investments	26,837	32,457	20,774
Purchase of property and equipment	(18,147)	(16,229)	(15,510)
Sale of renewal rights	0	0	8,000
Net cash used in investing activities	(318,101)	(391,543)	(169,468)
Financing Activities
Dividends to stockholders	(33,758)	(31,052)	(28,428)
Acquisition of treasury stock	(4,992)	(4,182)	(3,563)
Net proceeds from stock purchase and compensation plans	7,811	10,089	7,283
Proceeds from borrowings	165,000	15,000	0
Repayment of borrowings	(115,000)	0	(13,000)
Excess tax benefits from share-based payment arrangements	1,819	1,736	1,020
Repayment of capital lease obligations	(5,002)	(4,689)	(2,841)
Net cash provided by (used in) financing activities	15,878	(13,098)	(39,529)
Net (decrease) increase in cash	(440)	(23,061)	23,766
Cash, beginning of year	898	23,959	193
Cash, end of year	$ 458	$ 898	$ 23,959

Organization

Organization	12 Months Ended
	Dec. 31, 2016
Organization [Abstract]
Organization	Organization Selective Insurance Group, Inc., through its subsidiaries, (collectively referred to as “we,” “us,” or “our”) offers standard commercial, standard personal, and excess and surplus ("E&S") lines property and casualty insurance products. Selective Insurance Group, Inc. (referred to as the “Parent”) was incorporated in New Jersey in 1977 and its main offices are located in Branchville, New Jersey. The Parent’s common stock is publicly traded on the NASDAQ Global Select Market under the symbol “SIGI.” We have provided a glossary of terms as Exhibit 99.1 to this Form 10-K, which defines certain industry-specific and other terms that are used in this Form 10-K. We classify our business into four reportable segments, which are as follows: • Standard Commercial Lines - comprised of insurance products and services provided in the standard marketplace to commercial enterprises, which are typically businesses, non-profit organizations, and local government agencies. • Standard Personal Lines - comprised of insurance products and services, including flood insurance coverage, provided primarily to individuals acquiring coverage in the standard marketplace. • E&S Lines - comprised of insurance products and services provided to customers who have not obtained coverage in the standard marketplace. • Investments - invests the premiums collected by our insurance operations, as well as amounts generated through our capital management strategies, which may include the issuance of debt and equity securities.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Summary of Signifcant Accounting Policies	Summary of Significant Accounting Policies (a) Principles of Consolidation The accompanying consolidated financial statements (“Financial Statements”) include the accounts of the Parent and its subsidiaries, and have been prepared in conformity with: (i) U.S. generally accepted accounting principles ("GAAP"); and (ii) the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”). All significant intercompany accounts and transactions are eliminated in consolidation. (b) Use of Estimates The preparation of our Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported financial statement balances, as well as the disclosure of contingent assets and liabilities. Actual results could differ from those estimates. (c) Reclassifications Certain amounts in our prior years' Financial Statements and related notes have been reclassified to conform to the 2016 presentation. Such reclassifications had no effect on our net income, stockholders' equity, or cash flows. (d) Investments Fixed income securities may include investment grade and below investment grade rated bonds, redeemable preferred stocks, non-redeemable preferred stocks with certain debt-like characteristics, mortgage-backed securities (“MBS”), collateralized loan obligations ("CLO") and other asset-backed securities (“ABS”). MBS, CLO, and other ABS are jointly referred to as structured securities. Fixed income securities classified as available-for-sale (“AFS”) are reported at fair value. Those fixed income securities that we have the ability and positive intent to hold to maturity are classified as held-to-maturity (“HTM”) and are carried at either: (i) amortized cost; or (ii) market value at the date of transfer into the HTM category, adjusted for subsequent amortization. The amortized cost of fixed income securities is adjusted for the amortization of premiums and the accretion of discounts over the expected life of the security using the effective yield method. Premiums and discounts arising from the purchase of structured securities are amortized over the expected life of the security based on future principal payments, and considering prepayments. These prepayments are estimated based on historical and projected cash flows. Prepayment assumptions are reviewed quarterly and adjusted to reflect actual prepayments and changes in expectations. Future amortization of any premium and/or discount is adjusted to reflect the revised assumptions. Interest income, as well as amortization and accretion, is included in "Net investment income earned" on our Consolidated Statements of Income. The amortized cost of a fixed income security is written down to fair value when a decline in value is considered to be other than temporary. See the discussion below on realized investment gains and losses for a description of the accounting for impairments. After-tax unrealized gains and losses on: (i) fixed income securities classified as AFS; and (ii) fixed income securities that were transferred into an HTM designation from an AFS designation, are included in accumulated other comprehensive income (loss) ("AOCI"). Equity securities, which are classified as AFS, may include common and non-redeemable preferred stocks. These securities are carried at fair value and the related dividend income is included in "Net investment income earned" on our Consolidated Statements of Income. The cost of equity securities is written down to fair value when a decline in value is considered to be other than temporary. See the discussion below on realized investment gains and losses for a description of the accounting for impairments. After-tax unrealized gains and losses are included in AOCI. Short-term investments may include certain money market instruments, savings accounts, commercial paper, and debt issues purchased with a maturity of less than one year. We also enter into reverse repurchase agreements that are included in short-term investments. These loans are fully collateralized with high quality, readily marketable instruments at a minimum of 102% of the loan principal. At maturity, we receive principal and interest income on these agreements. All short-term investments are carried at cost, which approximates fair value. The associated income is included in "Net investment income earned" on our Consolidated Statement of Income. Other investments may include alternative investments and other securities. Alternative investments are accounted for using the equity method. Our share of distributed and undistributed net income from alternative investments is included in "Net investment income earned" on our Consolidated Statement of Income. Other securities are primarily comprised of tax credit investments. Low income housing tax credits are accounted for under the proportional amortization method and all other tax credits are accounted for using the equity method. Under the proportional amortization method, our share of the investment’s performance is recorded in our Consolidated Statement of Income as a component of “Federal income tax expense.” Under the equity method, our share of distributed and undistributed net income is included in "Net investment income earned" on our Consolidated Statement of Income. For federal income tax credits accounted for under the equity method, we use the deferral method for recognizing the benefit of the tax credit with the related deferred revenue being recognized in our Consolidated Statement of Income as a component of "Federal income tax expense" ratably over the life of the investment. Realized gains and losses on the sale of investments are determined on the basis of the cost of the specific investments sold and are credited or charged to income. Included in realized gains and losses are the other-than-temporary impairment ("OTTI") charges recognized in earnings, which are discussed below. On a quarterly basis, we review our investment portfolio for impairments that are other than temporary. The following provides information on this analysis for our fixed income securities and short-term investments, our equity securities, and our other investments. Fixed Income Securities and Short-Term Investments We review securities that are in an unrealized loss position to determine: (i) if we have the intent to sell the security; (ii) if it is more likely than not that we will be required to sell the debt security before its anticipated recovery; and (iii) if the decline is other than temporary. Broad changes in the overall market or interest rate environment generally will not lead to a write down. If we determine that we have either the intent or requirement to sell the security, we write down its amortized cost to its fair value through a charge to earnings as a component of realized losses. If we do not have either the intent or requirement to sell the security, our evaluation for OTTI may include, but is not limited to, evaluation of the following factors: • Whether the decline appears to be issuer or industry specific; • The degree to which the issuer is current or in arrears in making principal and interest payments on the fixed income security; • The issuer’s current financial condition and ability to make future scheduled principal and interest payments on a timely basis; • Evaluation of projected cash flows; • Buy/hold/sell recommendations published by outside investment advisors and analysts; and • Relevant rating history, analysis, and guidance provided by rating agencies and analysts. Non-redeemable preferred stocks that are classified as fixed income securities are evaluated under this OTTI method unless the security is below investment grade, at which time they are evaluated under the equity securities OTTI model discussed below. To determine if an impairment is other than temporary, we perform assessments that may include, but are not limited to, discounted cash flow analyses ("DCFs") to determine the security's present value of future cash flows. In addition, this analysis is performed on all previously-impaired debt securities that continue to be held by us and all structured securities that were not of high-credit quality at the date of purchase. Any shortfall in the expected present value of the future cash flows, based on the DCF, from the amortized cost basis of a security is considered a “credit impairment,” with the remaining decline in fair value of a security considered a “non-credit impairment.” Credit impairments are charged to earnings as a component of realized losses, while non-credit impairments are recorded to Other Comprehensive Income ("OCI") as a component of unrealized losses. The discount rate we use in a DCF is the effective interest rate implicit in the security at the date of acquisition for those structured securities that were not of high-credit quality at acquisition. For all other securities, we use a discount rate that equals the current yield, excluding the impact of previous OTTI charges, used to accrete the beneficial interest. Discounted cash flow models may include, but are not necessarily limited to: (i) generating cash flows for each tranche considering tranche-specific data, market data, and other pertinent information such as the historical performance of the underlying collateral, including net operating income generated by underlying properties, conditional default rate assumptions, loan loss severity assumptions, consensus projections, prepayment projections, and actual pool and collateral information; (ii) identifying applicable benchmark yields; and (iii) applying market-based tranche specific spreads to determine an appropriate yield by incorporating collateral performance, tranche-level attributes, trades, bids, and offers. Equity Securities We review securities that are in an unrealized loss position to determine: (i) if we do not intend to hold the security to its forecasted recovery; or (ii) if the decline is other than temporary, which includes declines driven by market volatility for which we cannot assert will recover in the near term. If we determine either that we do not intend to hold a security, or the decline is other than temporary, we write down the security's cost to its fair value through a charge to earnings as a component of realized losses. If we intend to hold the security, our evaluation for OTTI may include, but is not limited to, an evaluation of the following factors: • Whether the decline appears to be issuer or industry specific; • The relationship of market prices per share to book value per share at the date of acquisition and date of evaluation; • The price-earnings ratio at the time of acquisition and date of evaluation; • The financial condition and near-term prospects of the issuer, including any specific events that may influence the issuer's operations, coupled with our intention to hold the securities in the near-term; • The recent income or loss of the issuer; • The independent auditors' report on the issuer's recent financial statements; • The dividend policy of the issuer at the date of acquisition and the date of evaluation; • Buy/hold/sell recommendations or price projections published by outside investment advisors; • Rating agency announcements; • The length of time and the extent to which the fair value has been, or is expected to be, less than its cost in the near term; and • Our expectation of when the cost of the security will be recovered. Other Investments Our evaluation for OTTI of an other investment (i.e., an alternative investment) may include, but is not limited to, conversations with the management of the alternative investment concerning the following: • The current investment strategy; • Changes made or future changes to be made to the investment strategy; • Emerging issues that may affect the success of the strategy; and • The appropriateness of the valuation methodology used regarding the underlying investments. If there is a decline in the fair value of an other investment that we do not intend to hold, or if we determine the decline is other than temporary, we write down the carry value of the investment and record the charge through earnings as a component of realized losses. (e) Fair Values of Financial Instruments Assets The fair values of our investments are generated using various valuation techniques and are placed into the fair value hierarchy considering the following: (i) the highest priority is given to quoted prices in active markets for identical assets (Level 1); (ii) the next highest priority is given to quoted prices in markets that are not active or inputs that are observable either directly or indirectly, including quoted prices for similar assets in markets that are not active and other inputs that can be derived principally from, or corroborated by, observable market data for substantially the full term of the assets (Level 2); and (iii) the lowest priority is given to unobservable inputs supported by little or no market activity and that reflect our assumptions about the exit price, including assumptions that market participants would use in pricing the asset (Level 3). An asset’s classification within the fair value hierarchy is based on the lowest level of significant input to its valuation. Transfers between levels in the fair value hierarchy are recognized at the end of the reporting period. The techniques used to value our financial assets are as follows: Level 1 Pricing Security Type Methodology Equity Securities; U.S. Treasury Notes Equity and U.S. Treasury Note prices are received from an independent pricing service that are based on observable market transactions. We validate these prices against a second external pricing service, and if established market value comparison thresholds are breached, further analysis is performed to determine the price to be used. Short-Term Investments Short-term investments are carried at cost, which approximates fair value. Given the liquid nature of our short-term investments, we generally validate their fair value by way of active trades within approximately one week of the financial statement close. Level 2 Pricing We utilize a market approach for our Level 2 securities, using primarily matrix pricing models prepared by external pricing services. Matrix pricing models use mathematical techniques to value debt securities by relying on the securities' relationship to other benchmark quoted securities, and not relying exclusively on quoted prices for specific securities, as the specific securities are not always frequently traded. As a matter of policy, we consistently use one pricing service as our primary source and secondary pricing services if prices are not available from the primary pricing service. Fixed income securities portfolio pricing is reviewed for reasonableness in the following ways: (i) comparing our pricing to other third-party pricing services as well as benchmark indexed pricing; (ii) comparing fair value fluctuations between months for reasonableness; and (iii) reviewing stale prices. If further analysis is needed, a challenge is sent to the pricing service for review and confirmation of the price. Further information on our Level 2 asset pricing is included in the following table: Security Type Methodology Corporate Securities including preferred stocks classified as Fixed Income Securities, and U.S. Government and Government Agencies Evaluations include obtaining relevant trade data, benchmark quotes and spreads and incorporating this information into either spread-based or price-based evaluations as determined by the observed market data. Spread-based evaluations include: (i) creating a range of spreads for relevant maturities of each issuer based on the new issue market, secondary trading, and dealer quotes; and (ii) incorporating option adjusted spreads for issues that have early redemption features. Based on the findings in (i) and (ii) above, final spreads are derived and added to benchmark curves. Price-based evaluations include matching each issue to its best-known market maker and contacting firms that transact in these securities. Obligations of States and Political Subdivisions Evaluations are based on yield curves that are developed based on factors such as: (i) benchmarks to issues with interest rates near prevailing market rates; (ii) established trading spreads over widely-accepted market benchmarks; (iii) yields on new issues; and (iv) market information from third-party sources such as reportable trades, broker-dealers, or issuers. Structured Securities (including CLO and other ABS, CMBS, RMBS) Evaluations are based on a discounted cash flow model, including: (i) generating cash flows for each tranche considering tranche-specific data, market data, and other pertinent information such as historical performance of the underlying collateral, including net operating income generated by the underlying properties, conditional default rate assumptions, loan loss severity assumptions, consensus projections, prepayment projections, and actual pool and loan level collateral information; (ii) identifying applicable benchmark yields; and (iii) applying market-based tranche-specific spreads to determine an appropriate yield by incorporating collateral performance, tranche-level attributes, trades, bids, and offers. Foreign Government Evaluations are performed using a DCF model and incorporating observed market yields of benchmarks as inputs, adjusting for varied maturities. Level 3 Pricing Less than 1% of our portfolio cannot be priced using our primary or secondary pricing service. At times, we may use non-binding broker quotes to value some of these securities. These prices are from various broker/dealers that use bid or ask prices, or benchmarks to indices, in measuring the fair value of a security. We review these fair value measurements for reasonableness. This review typically includes an analysis of price fluctuations between months with variances over established thresholds being analyzed further. Further information on our current Level 3 asset pricing is included in the following table: Security Type Methodology Corporate Securities These tax credit investments are priced internally using spread-based evaluations. Equity Securities These non-publicly traded stocks are valued by the issuer and reviewed internally. Liabilities The techniques used to value our notes payable are as follows: Level 1 Pricing Security Type Methodology 5.875% Senior Notes Based on the quoted market prices. Level 2 Pricing Security Type Methodology 7.25% Senior Notes; 6.70% Senior Notes Based on matrix pricing models prepared by external pricing services. Borrowings from Federal Home Loan Banks Evaluations are performed using a DCF model based on current borrowing rates provided by the Federal Home Loan Banks that is consistent with the remaining term of the borrowing. See Note 7. “Fair Value Measurements” for a summary table of the fair value and related carrying amounts of financial instruments. (f) Allowance for Doubtful Accounts We estimate an allowance for doubtful accounts on our premiums receivable. This allowance is based on historical write-off percentages adjusted for the effects of current and anticipated trends. An account is charged off when we believe it is probable that we will not collect a receivable. In making this determination, we consider information obtained from our efforts to collect amounts due directly and/or through collection agencies. (g) Share-Based Compensation Share-based compensation consists of all share-based payment transactions in which an entity acquires goods or services by issuing (or offering to issue) its shares, share units, share options, or other equity instruments. The cost resulting from all share-based payment transactions are recognized in the Financial Statements based on the fair value of both equity and liability awards. The fair value is measured at grant date for equity awards, whereas the fair value for liability awards are remeasured at each reporting period. Both the fair value of equity and liability awards is recognized over the requisite service period. The requisite service period is typically the lesser of the vesting period or the period of time from the grant date to the date of retirement eligibility. The expense recognized for share-based awards, which, in some cases, contain performance criteria, is based on the number of shares or units expected to be issued at the end of the performance period. We repurchase the Parent’s stock from our employees in connection with, and as permitted under, our stock-based compensation plans. This activity is disclosed in our Consolidated Statements of Stockholders' Equity. (h) Reinsurance Reinsurance recoverables represent estimates of amounts that will be recovered from reinsurers under our various treaties. Generally, amounts recoverable from reinsurers are recognized as assets at the same time and in a manner consistent with the paid and unpaid losses associated with the reinsured policies. We require collateral to secure reinsurance recoverables primarily from our reinsurance carriers that are not authorized, otherwise approved, or certified to do business in one or more of our ten insurance subsidiaries' domiciliary states. Our ten insurance subsidiaries are collectively referred to as the "Insurance Subsidiaries". This collateral is typically in the form of a letter of credit or cash. An allowance for estimated uncollectible reinsurance is recorded based on an evaluation of balances due from reinsurers and other available information, such as each reinsurers' credit rating from A.M. Best Company ("A.M. Best") or Standard & Poor's Rating Services ("S&P"). We charge off reinsurance recoverables on paid losses when it becomes probable that we will not collect the balance. (i) Property and Equipment Property and equipment used in operations, including certain costs incurred to develop or obtain computer software for internal use, are capitalized and carried at cost less accumulated depreciation. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets. The following estimated useful lives can be considered as general guidelines: Asset Category Years Computer hardware 3 Computer software 3 to 5 Internally developed software 5 to 10 Software licenses 3 to 5 Furniture and fixtures 10 Buildings and improvements 5 to 40 We recorded depreciation expense of $17.4 million , $16.4 million , and $12.6 million for 2016 , 2015 , and 2014 , respectively. (j) Deferred Policy Acquisition Costs Deferred policy acquisition costs are limited to costs directly related to the successful acquisition of insurance contracts. Costs meeting this definition typically include, among other things, sales commissions paid to our distribution partners, premium taxes, and the portion of employee salaries and benefits directly related to time spent on acquired contracts. These costs are deferred and amortized over the life of the contracts. Accounting guidance requires a premium deficiency analysis to be performed at the level an entity acquires, services, and measures the profitability of its insurance contracts. We currently perform three premium deficiency analyses for our insurance segments, consistent with our reportable segments of Standard Commercial Lines, Standard Personal Lines, and E&S Lines. A combined ratio of over 100% does not necessarily indicate a premium deficiency, as any year's combined ratio includes a portion of underwriting expenses that are expensed at policy inception and therefore are not covered by the remaining unearned premium. In addition, investment income is not contemplated in the combined ratio calculation. There were no premium deficiencies for any of the reported years, as the sum of the anticipated losses and loss expenses, unamortized acquisition costs, policyholder dividends, and other expenses for each segment did not exceed that segment’s related unearned premium and anticipated investment income. The investment yields assumed in the premium deficiency assessment for each reporting period, which are based on our actual average investment yield before tax as of the September 30 calculation date, were 2.4% for 2016 , 2.5% for 2015 , and 3.0% for 2014 . Deferred policy acquisition costs amortized to expense were $450.3 million for 2016 , $399.4 million for 2015 , and $364.3 million for 2014 . (k) Goodwill Goodwill results from business acquisitions where the cost of assets and liabilities acquired exceeds the fair value of those assets and liabilities. A quantitative goodwill impairment analysis is performed if our quarterly qualitative analysis indicates that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. Goodwill is allocated to the reporting units for purposes of these analyses. Based on our analysis at December 31, 2016, goodwill was not impaired. (l) Reserves for Losses and Loss Expenses Reserves for losses and loss expenses are comprised of both case reserves on individual claims, and reserves for claims incurred but not reported ("IBNR"). Case reserves result from claims that have been reported to one or more of our Insurance Subsidiaries, and are estimated at the amount of the expected ultimate payment. IBNR reserves are established at more aggregated levels than case basis reserves, and in addition to reserves on claims that have been incurred but not reported, they include provisions for future emergence on known claims, as well as reopened claims. IBNR reserves are established based on the results of the Insurance Subsidiaries’ internal reserve analysis, supplemented with other internal and external information. The internal reserve analysis is performed quarterly, and relies upon generally accepted actuarial techniques. Such techniques assume that past experience, adjusted for the effects of current developments and anticipated trends, are an appropriate basis for predicting future events. Our analyses rely upon historical paid and case losses and loss adjustment expense experience organized by line of business, accident year and maturity (i.e., “triangles”). Standard actuarial projection methods are applied to this history, producing a set of estimated ultimate losses and loss adjustment expenses. Ultimate losses and loss adjustment expenses are selected from the various methods, considering the strengths and weaknesses of the methods as they apply to the specific line and accident year. Certain types of exposures do not lend themselves to standard actuarial methods. Examples of these are: • Certain property catastrophe events may be low in frequency and high in severity. These events may affect many insureds simultaneously. Due to the unique nature of these events, ultimate liabilities are estimated for each event, based on surveys of our portfolio of exposures, in conjunction with individual claims estimates. While generally short-tailed, the liabilities associated with these events are subject to a higher degree of uncertainty. We maintain significant reinsurance protection that greatly limits the impact that these extreme events have on net loss and loss adjustment expenses. • In some limited cases, an insured event may span multiple years and multiple policies, as in the case of asbestos and environmental claims, where the injury is deemed to occur over an extended period of time. These claims are analyzed without accident year detail, using alternative methods and metrics. The associated selected ultimate loss and loss adjustment expenses are then allocated to accident year for reporting. • Another example of non-standard methods relate to loss adjustment expenses that cannot be attributed to a specific claim (referred to as “unallocated loss adjustment expenses”). These expenses are first allocated to accident year and alternative projection methods are then applied to these expenses. The resulting ultimate expenses by accident year are then used for reporting purposes. The selected ultimate losses and loss adjustment expenses are translated into indicated IBNR reserves, which are then compared to the recorded IBNR reserves. Management's judgment is applied in determining any required adjustments and the resulting adjustments are then recorded and assigned or allocated to accident year using the results of the actuarial analysis. While the reserve analysis is the primary basis for determining the recorded IBNR reserves, other internal and external factors are considered. Internal factors include: (i) supplemental data regarding claims reporting and settlement trends; (ii) exposure estimates for reported claims, along with recent development on those estimates with respect to individual large claims and the aggregate of all claims; (iii) the rate at which new large or complex claims are being reported; and (iv) additional trends observed by claims personnel or reported to them by defense counsel. External factors considered include: (i) legislative enactments; (ii) judicial decisions; (iii) legal developments in the determination of liability and the imposition of damages; and (iv) trends in general economic conditions, including the effects of inflation. Loss reserves are estimates, and as such, we also consider a range of possible loss and loss expense reserve estimates. This range is determined at the beginning of each year, using prior year-end data, and reflects the fact that there is no single precise method for estimating the required reserves, due to the many factors that may influence the amounts ultimately paid. Considering the reserve range along with all of the items described above, as well as current market conditions, IBNR estimates are then established and recorded. The combination of the IBNR estimates along with the case reserve estimates on individual claims results in our total reserves for losses and loss expenses. These reserves are expected to be sufficient for settling losses and loss reserve obligations under our policies on unpaid claims, including changes in the volume of business written, claims frequency and severity, the mix of business, claims processing, and other items that management expects to affect our ultimate settlement of losses and loss expenses. However, the ultimate claim settlements may be higher or lower than reserves established. As our experience emerges and other information develops, we revise our reserve estimates accordingly. The changes in these estimates, resulting from the continuous review process and the differences between estimates and ultimate payments, are reflected in the Consolidated Statements of Income for the period in which such estimates are changed. The associated impacts may be material to the results of operations in future periods. We do not discount to present value that portion of our losses and loss expense reserves expected to be paid in future periods. Our loss and loss expense reserves implicitly include anticipated recoveries for salvage and subrogation claims. Claims are counted at the occurrence, line of business, and policy level. For example, if a single occurrence (e.g. an auto accident) leads to a claim under an auto and an associated umbrella policy, they are each counted separately. Conversely, multiple claimants under the same occurrence/line/policy would contribute only a single count. The claim counts provided are on a reported basis. A claim is considered reported when a reserve is established or payment is made. Therefore, claims closed without payment are included in the count as long as there was an associated case reserve at some point in its life cycle. We also write a small amount of assumed reinsurance. Currently, this business is limited to our share of certain involuntary pools. Since the associated claims are not processed by us, they are not captured within our claims system. Therefore, the claim counts reported exclude this business. (m) Revenue Recognition The Insurance Subsidiaries' net premiums written (“NPW”) include direct insurance policy writings, plus reinsurance assumed and estimates of premiums earned but unbilled on the workers compensation and general liability lines of insurance, less reinsurance ceded. The estimated premium on the workers compensation and general liability lines is referred to as audit premium. We estimate this premium, as it is anticipated to be either billed or returned on policies subsequent to expiration based on exposure levels (i.e. payroll or sales). Audit premium is based on historical trends adjusted for the uncertainty of future economic

Adoption of Accounting Pronounc

Adoption of Accounting Pronouncements Adoption of Accounting Pronouncements (Notes)	12 Months Ended
	Dec. 31, 2016
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Accounting Pronouncements	Adoption of Accounting Pronouncements In January 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2014-01, Accounting for Investments in Qualified Affordable Housing Projects ("ASU 2014-01"). ASU 2014-01 applies to all reporting entities that invest in flow-through limited liability entities that manage or invest in affordable housing projects that qualify for a low-income housing tax credit. ASU 2014-01 permits reporting entities to make an accounting policy election to account for their investments in qualified affordable housing projects using a newly defined "proportional amortization method" if certain conditions are met. This policy election is required to be applied consistently to all qualifying investments, rather than a decision to be applied to individual investments. Under the proportional amortization method, an entity amortizes the initial cost of the investment in proportion to the tax credits and other tax benefits received, and recognizes the net investment performance in the Consolidated Statements of Income as components of "Federal income tax expense". We adopted this guidance in the third quarter of 2014 and have made a policy election to use the proportional amortization method. The adoption of this guidance did not materially impact our financial condition or results of operations. In June 2014, the FASB issued ASU 2014-12, Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period (“ASU 2014-12”). ASU 2014-12 requires that performance targets that affect vesting and could be achieved after the requisite service period be treated as performance conditions. The adoption of ASU 2014-12 in the first quarter of 2016 did not affect us, as we have historically recorded expense consistent with the requirements of this accounting update. In August 2014, the FASB issued ASU 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (“ASU 2014-15”). ASU 2014-15 is intended to define management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and provide related footnote disclosures. Our adoption of this amendment in the fourth quarter of 2016 did not affect us, as the additional disclosure requirements are applicable only to entities that have been subject to events or conditions that cast substantial doubt as to whether the entity has the ability to continue as a going concern. In February 2015, the FASB issued ASU 2015-02, Amendments to the Consolidation Analysis (“ASU 2015-02”). ASU 2015-02 affects the following areas: (i) limited partnerships and similar legal entities; (ii) the evaluation of fees paid to a decision maker or a service provider as a variable interest; (iii) the effect of fee arrangements on the primary beneficiary determination; (iv) the effect of related parties on the primary beneficiary determination; and (v) certain investment funds. We adopted this guidance in the first quarter of 2016. Under the new guidance, our limited partnership and tax credit investments are variable interest entities ("VIEs"); however, we are not the primary beneficiary of any of these investments. As such, the adoption had no impact on our financial condition or results of operations. The required disclosures related to our VIEs are included in Note 5. “Investments” below. In April 2015, the FASB issued ASU 2015-03, Simplifying the Presentation of Debt Issuance Costs (“ASU 2015-03”). ASU 2015-03 requires debt issuance costs to be netted against the related debt liability in the balance sheet rather than presented as a separate asset. However, ASU 2015-03 does not address the presentation or subsequent measurement of debt issuance costs related to line-of-credit arrangements. Therefore, in August 2015, the FASB issued ASU 2015-15, Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements - Amendments to SEC Paragraphs Pursuant to Staff Announcement at June 18, 2015 EITF Meeting (“ASU 2015-15”). ASU 2015-15 clarifies that, in the absence of authoritative guidance on line-of-credit arrangements within ASU 2015-03, the SEC would not object to the deferral and presentation of debt issuance costs as an asset and the subsequent amortization of the deferred costs over the term of the line-of-credit arrangement. We adopted this guidance retrospectively, effective in the fourth quarter of 2015. As such, 2014 balances in this Form 10-K have been restated to reflect the revised guidance, as follows: Income Statement Information Year ended December 31, 2014 ($ in thousands) As Originally Reported As Restated Interest Expense $ 22,086 23,063 Other Expense 33,673 32,696 In April 2015, the FASB issued ASU 2015-05, Customer's Accounting for Fees Paid in a Cloud Computing Arrangement (“ASU 2015-05”). ASU 2015-05 provides guidance to customers with cloud computing arrangements that include a software license. If a cloud computing arrangement includes a software license, the customer's accounting for the software license element of the arrangement is consistent with the acquisition of other software licenses. If a cloud computing arrangement does not include a software license, the customer accounts for the arrangement as a service contract. We adopted this guidance in the first quarter of 2016, with prospective application. The impact of this adoption did not have a material effect on our financial condition or results of operations. In May 2015, the FASB issued ASU 2015-07, Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent) (“ASU 2015-07”). ASU 2015-07 provides that investments for which the practical expedient is used to measure fair value at net asset value per share ("NAV") must be removed from the fair value hierarchy. Instead, those investments must be included as a reconciling line item so that the total fair value amount of investments in the disclosure is consistent with the amount on the balance sheet. ASU 2015-07 also includes disclosure requirements for investments for which the NAV practical expedient was used to determine fair value. We adopted this guidance in the first quarter of 2016 and have included the related disclosures in Note 14. "Retirement Plans" below. In May 2015, the FASB issued ASU 2015-09, Disclosures about Short-Duration Contracts (“ASU 2015-09”). ASU 2015-09 requires companies that issue short duration contracts to disclose additional information, including: (i) incurred and paid claims development tables; (ii) frequency and severity of claims; and (iii) information about material changes in judgments made in calculating the liability for unpaid claim adjustment expenses, including reasons for the change and the effects on the financial statements. We adopted this guidance in the fourth quarter of 2016 and have included the related disclosures in Note 9. "Reserves for Losses and Loss Expenses" below. Pronouncements to be effective in the future In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall (Sub-topic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities (“ASU 2016-01”). ASU 2016-01 provides guidance to improve certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. Specifically the guidance: (i) requires equity investments to be measured at fair value with changes in fair value recognized in earnings; (ii) simplifies the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment; (iii) eliminates the requirement to disclose the methods and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost; (iv) requires the use of the exit price notion when measuring the fair value of financial instruments for disclosure purposes; and (v) clarifies that the need for a valuation allowance on a deferred tax asset related to an available-for-sale ("AFS") security should be evaluated with other deferred tax assets. ASU 2016-01 is effective for annual periods beginning after December 15, 2017, including interim periods within those annual periods. Early application to financial statements of annual or interim periods that have not yet been issued are permitted as of the beginning of the year of adoption, otherwise early adoption of ASU 2016-01 is not permitted. We are currently evaluating the impact of this guidance on our financial condition and results of operations. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) (“ASU 2016-02”). ASU 2016-02 requires all lessees to recognize a lease liability and a right-of-use asset, measured at the present value of the future minimum lease payments, at the lease commencement date. ASU 2016-02 is effective for annual periods beginning after December 15, 2018, including interim reporting periods within that annual period, with early adoption permitted. ASU 2016-02 requires the application of a modified retrospective approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. While we are currently evaluating ASU 2016-02, we do not expect a material impact on our financial condition or results of operations from the adoption of this guidance. In March 2016, the FASB issued ASU 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-based Payment Accounting (“ASU 2016-09”). ASU 2016-09 simplifies several aspects of the accounting for share-based payment transactions including: (i) income tax consequences; (ii) classification of awards as either equity or liabilities; (iii) forfeitures assumptions; and (iv) cash flow classification. ASU 2016-09 is effective for annual periods beginning after December 15, 2016, and interim periods within those annual periods. Early adoption is permitted. We do not expect this ASU to have a material impact on our financial condition or results of operations. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (“ASU 2016-13”). ASU 2016-13 will change the way entities recognize impairment of financial assets by requiring immediate recognition of estimated credit losses expected to occur over the remaining life of many financial assets, including, among others, HTM debt securities, trade receivables, and reinsurance receivables. ASU 2016-13 requires a valuation allowance to be calculated on these financial assets and that they be presented on the financial statements net of the valuation allowance. The valuation allowance is a measurement of expected losses that is based on relevant information about past events, including historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. This methodology is referred to as the current expected credit loss model. ASU 2016-13 is effective for annual periods beginning after December 15, 2019, including interim periods within those annual periods. Early adoption is permitted, but no earlier than annual periods beginning after December 15, 2018. We are currently evaluating the impact of this guidance on our financial condition and results of operations. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (“ASU 2016-15”). ASU 2016-15 adds or clarifies guidance on the classification of certain cash receipts and payments in the statements of cash flows including, but not limited to: (i) debt prepayment or debt extinguishment costs; (ii) proceeds from the settlement of corporate-owned life insurance policies including bank-owned life insurance policies; (iii) distributions received from equity method investees; and (iv) separately identifiable cash flows and application of the predominance principle. ASU 2016-15 is effective for annual periods beginning after December 15, 2017, and interim periods within those annual periods. Early adoption is permitted. We are currently evaluating the impact of this guidance on our statements of cash flows. In October 2016, the FASB issued ASU 2016-17, Consolidation: Interests Held through Related Parties That Are Under Common Control ("ASU 2016-17"). ASU 2016-17 changes how a decision maker considers indirect interests in a VIE held under common control in making the primary beneficiary determination. ASU 2016-17 will be effective for annual periods beginning after December 15, 2016, including interim periods within those annual periods. We do not expect this ASU to impact us as we are not the decision maker in any of the VIEs in which we are invested. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows: Restricted Cash ("ASU 2016-18"). ASU 2016-18, requires that restricted cash and restricted cash equivalents be included with cash and cash equivalents in the reconciliation of beginning and ending cash on the statements of cash flows. This update also requires a reconciliation of the statement of the cash flows to the balance sheet if the balance sheet includes more than one line item of cash, cash equivalents, and restricted cash. ASU 2016-18 is effective, with retrospective adoption, for annual periods beginning after December 15, 2017, and interim periods within those annual periods. We are currently evaluating the impact of this guidance on our statements of cash flows.

Statements of Cash Flow

Statements of Cash Flow	12 Months Ended
	Dec. 31, 2016
Supplemental Cash Flow Information [Abstract]
Statements of Cash Flow	Statements of Cash Flows Supplemental cash flow information for the years ended December 31, 2016, 2015, and 2014 is as follows: ($ in thousands) 2016 2015 2014 Cash paid during the period for: Interest $ 22,098 21,892 22,221 Federal income tax 46,405 39,500 22,699 Non-cash items: Exchange of fixed income securities, AFS 23,579 36,792 20,781 Exchange of fixed income securities, HTM — 15,257 4,289 Corporate actions related to equity securities, AFS 1 3,263 4,239 334 Assets acquired under capital lease arrangements 3,151 6,760 5,642 Non-cash purchase of property and equipment 78 — 338 1 Examples of such corporate actions include non-cash acquisitions and stock-splits. Included in "Other assets" on the Consolidated Balance Sheet was $36.9 million at December 31, 2016 and $11.9 million at December 31, 2015 of cash received from the National Flood Insurance Program ("NFIP"), which is restricted to pay flood claims under the Write Your Own ("WYO") Program.

Investments

Investments	12 Months Ended
	Dec. 31, 2016
Investments [Abstract]
Investments	Investments (a) Net unrealized gains on investments included in OCI by asset class were as follows for the years ended December 31, 2016, 2015, and 2014 : ($ in thousands) 2016 2015 2014 AFS securities: Fixed income securities $ 38,781 55,689 90,336 Equity securities 25,864 13,235 32,389 Total AFS securities 64,645 68,924 122,725 HTM securities: Fixed income securities 159 300 958 Total HTM securities 159 300 958 Total net unrealized gains 64,804 69,224 123,683 Deferred income tax expense (22,681 ) (24,228 ) (43,289 ) Net unrealized gains, net of deferred income tax 42,123 44,996 80,394 (Decrease) increase in net unrealized gains in OCI, net of deferred income tax $ (2,873 ) (35,398 ) 28,890 (b) The amortized cost, net unrealized gains and losses, carrying value, unrecognized holding gains and losses, and fair value of HTM fixed income securities were as follows: December 31, 2016 Net Unrealized Unrecognized Unrecognized Amortized Gains Carrying Holding Holding Fair ($ in thousands) Cost (Losses) Value Gains Losses Value Obligations of state and political subdivisions $ 77,466 317 77,783 2,133 — 79,916 Corporate securities 22,711 (143 ) 22,568 1,665 (158 ) 24,075 CMBS 1,220 (15 ) 1,205 15 — 1,220 Total HTM fixed income securities $ 101,397 159 101,556 3,813 (158 ) 105,211 December 31, 2015 Net Unrealized Unrecognized Unrecognized Amortized Gains Carrying Holding Holding Fair ($ in thousands) Cost (Losses) Value Gains Losses Value Obligations of state and political subdivisions 175,269 848 176,117 5,763 — 181,880 Corporate securities 20,228 (185 ) 20,043 1,972 — 22,015 CLO and other ABS 1,030 (120 ) 910 118 — 1,028 CMBS 4,527 (243 ) 4,284 337 — 4,621 Total HTM fixed income securities $ 201,054 300 201,354 8,190 — 209,544 Unrecognized holding gains and losses of HTM securities are not reflected in the Financial Statements, as they represent fair value fluctuations from the later of: (i) the date a security is designated as HTM either through purchase or transfer from AFS; or (ii) the date that an OTTI charge is recognized on an HTM security, through the date of the balance sheet. (c) The cost/amortized cost, unrealized gains and losses, and fair value of AFS securities were as follows: December 31, 2016 Cost/ Amortized Unrealized Unrealized Fair ($ in thousands) Cost Gains Losses Value AFS fixed income securities: U.S. government and government agencies $ 75,139 2,230 (36 ) 77,333 Foreign government 26,559 322 (16 ) 26,865 Obligations of states and political subdivisions 1,366,287 18,610 (5,304 ) 1,379,593 Corporate securities 1,976,556 27,057 (5,860 ) 1,997,753 CLO and other ABS 527,876 1,439 (355 ) 528,960 CMBS 256,356 1,514 (1,028 ) 256,842 RMBS 524,986 3,006 (2,798 ) 525,194 Total AFS fixed income securities 4,753,759 54,178 (15,397 ) 4,792,540 AFS equity securities: Common stock 104,663 26,250 (305 ) 130,608 Preferred stock 16,226 274 (355 ) 16,145 Total AFS equity securities 120,889 26,524 (660 ) 146,753 Total AFS securities $ 4,874,648 80,702 (16,057 ) 4,939,293 December 31, 2015 Cost/ Amortized Unrealized Unrealized Fair ($ in thousands) Cost Gains Losses Value AFS fixed income securities: U.S. government and government agencies $ 99,485 4,721 (91 ) 104,115 Foreign government 14,885 298 (2 ) 15,181 Obligations of states and political subdivisions 1,314,779 44,523 (160 ) 1,359,142 Corporate securities 1,892,296 23,407 (15,521 ) 1,900,182 CLO and other ABS 244,541 531 (918 ) 244,154 CMBS 245,252 750 (2,410 ) 243,592 RMBS 541,276 4,274 (3,713 ) 541,837 Total AFS fixed income securities 4,352,514 78,504 (22,815 ) 4,408,203 AFS equity securities: Common stock 181,991 14,796 (1,998 ) 194,789 Preferred stock 11,825 477 (40 ) 12,262 Total AFS equity securities 193,816 15,273 (2,038 ) 207,051 Total AFS securities $ 4,546,330 93,777 (24,853 ) 4,615,254 Unrealized gains and losses of AFS securities represent fair value fluctuations from the later of: (i) the date a security is designated as AFS; or (ii) the date that an OTTI charge is recognized on an AFS security, through the date of the balance sheet. These unrealized gains and losses are recorded in AOCI on the Consolidated Balance Sheets. (d) The table below provides our net unrealized/unrecognized loss positions by impairment severity for both AFS and HTM securities as of December 31, 2016 compared to the prior year: ($ in thousands) December 31, 2016 December 31, 2015 Number of Issues % of Market/Book Unrealized/Unrecognized Loss Number of Issues % of Market/Book Unrealized/ Unrecognized Loss 456 80% - 99% $ 16,215 606 80% - 99% $ 22,971 — 60% - 79% — 3 60% - 79% 1,888 — 40% - 59% — — 40% - 59% — — 20% - 39% — — 20% - 39% — — 0% - 19% — — 0% - 19% — $ 16,215 $ 24,859 The severity of impairment on the securities in the table above averaged 1% of amortized cost at December 31, 2016 and December 31, 2015 . The decrease in the unrealized/unrecognized loss balance during 2016 was primarily from our AFS corporate fixed income securities portfolio, which was positively impacted by tightening credit spreads. Quantitative information regarding unrealized losses on our AFS portfolio is provided below. Our HTM portfolio had $0.2 million in unrealized/unrecognized losses at December 31, 2016 and no unrealized/unrecognized losses at December 31, 2015 . December 31, 2016 Less than 12 months 12 months or longer Total ($ in thousands) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Unrealized AFS fixed income securities: U.S. government and government agencies $ 6,419 (36 ) — — 6,419 (36 ) Foreign government 13,075 (16 ) — — 13,075 (16 ) Obligations of states and political subdivisions 306,509 (5,304 ) — — 306,509 (5,304 ) Corporate securities 462,902 (5,771 ) 4,913 (89 ) 467,815 (5,860 ) CLO and other ABS 189,795 (354 ) 319 (1 ) 190,114 (355 ) CMBS 82,492 (1,021 ) 1,645 (7 ) 84,137 (1,028 ) RMBS 279,480 (2,489 ) 8,749 (309 ) 288,229 (2,798 ) Total AFS fixed income securities 1,340,672 (14,991 ) 15,626 (406 ) 1,356,298 (15,397 ) AFS equity securities: Common stock 11,271 (305 ) — — 11,271 (305 ) Preferred stock 6,168 (355 ) — — 6,168 (355 ) Total AFS equity securities 17,439 (660 ) — — 17,439 (660 ) Total AFS securities $ 1,358,111 (15,651 ) 15,626 (406 ) 1,373,737 (16,057 ) December 31, 2015 Less than 12 months 12 months or longer Total ($ in thousands) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Unrealized AFS fixed income securities: U.S. government and government agencies $ 16,006 (87 ) 396 (4 ) $ 16,402 $ (91 ) Foreign government 1,067 (2 ) — — 1,067 (2 ) Obligations of states and political subdivisions 28,617 (160 ) — — 28,617 (160 ) Corporate securities 761,479 (12,671 ) 50,382 (2,850 ) 811,861 (15,521 ) CLO and other ABS 197,477 (807 ) 12,022 (111 ) 209,499 (918 ) CMBS 146,944 (2,196 ) 15,385 (214 ) 162,329 (2,410 ) RMBS 264,914 (1,992 ) 63,395 (1,721 ) 328,309 (3,713 ) Total AFS fixed income securities 1,416,504 (17,915 ) 141,580 (4,900 ) 1,558,084 (22,815 ) AFS equity securities: Common stock 31,148 (1,998 ) — — 31,148 (1,998 ) Preferred stock 1,531 (40 ) — — 1,531 (40 ) Total AFS equity securities 32,679 (2,038 ) — — 32,679 (2,038 ) Total AFS securities $ 1,449,183 (19,953 ) 141,580 (4,900 ) $ 1,590,763 $ (24,853 ) We do not intend to sell any of the securities in the tables above, nor do we believe we will be required to sell any of these securities. Additionally, we have reviewed these securities in accordance with our OTTI policy, as described in Note 2. “Summary of Significant Accounting Policies” of this Form 10-K and have concluded that they are temporarily impaired. This conclusion reflects our current judgment as to the financial position and future prospects of the entity that issued the security and underlying collateral. If our judgment about an individual security changes in the future, we may ultimately record a credit loss after having originally concluded that one did not exist, which could have a material impact on our net income and financial position in future periods. (e) Fixed income securities at December 31, 2016 , by contractual maturity are shown below. MBS are included in the maturity tables using the estimated average life of each security. Expected maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. Listed below are HTM fixed income securities at December 31, 2016 : ($ in thousands) Carrying Value Fair Value Due in one year or less $ 55,505 56,249 Due after one year through five years 37,536 39,853 Due after five years through 10 years 8,515 9,109 Total HTM fixed income securities $ 101,556 105,211 Listed below are AFS fixed income securities at December 31, 2016 : ($ in thousands) Fair Value Due in one year or less $ 374,080 Due after one year through five years 2,141,596 Due after five years through 10 years 2,090,677 Due after 10 years 186,187 Total AFS fixed income securities $ 4,792,540 (f) We evaluate the alternative investments and tax credit investments included in our other investments portfolio to determine whether those investments are VIEs and if so, whether consolidation is required. A VIE is an entity that either has equity investors that lack certain essential characteristics of a controlling financial interest or lack sufficient funds to finance its own activities without financial support provided by other entities. We consider several significant factors in determining if our investments are VIEs and if we are the primary beneficiary, including whether we have: (i) the power to direct activities of the VIE; (ii) the ability to remove the decision maker of the VIE; (iii) the ability to participate in making decisions that are significant to the VIE; and (iv) the obligation to absorb losses and the right to receive benefits that could potentially be significant to the VIE. We have determined that the investments in our other investment portfolio are VIEs, but that we are not the primary beneficiary and therefore, consolidation is not required. The following table summarizes our other investment portfolio by strategy: Other Investments December 31, 2016 December 31, 2015 ($ in thousands) Carrying Value Remaining Commitment Maximum Exposure to Loss 1 Carrying Value Remaining Maximum 1 Alternative Investments Private equity $ 41,135 76,774 117,909 35,088 30,204 65,292 Private credit 28,193 40,613 68,806 13,246 15,129 28,375 Real assets 14,486 22,899 37,385 19,500 25,820 45,320 Total alternative investments 83,814 140,286 224,100 67,834 71,153 138,987 Other securities 18,583 3,400 21,983 10,008 3,200 13,208 Total other investments $ 102,397 143,686 246,083 77,842 74,353 152,195 1 The maximum exposure to loss includes both the carry value of these investments and the related unfunded commitments. In addition, tax credits that have been previously recognized in Other securities are subject to the risk of recapture, which we do not consider significant. The following is a description of our alternative investment strategies: Our private equity strategy includes the following: • Primary Private Equity : This strategy makes private equity investments, primarily in established large and middle market companies across diverse industries globally. • Secondary Private Equity : This strategy purchases seasoned private equity funds from investors desiring liquidity prior to normal fund termination. Investments are made across all sectors of the private equity market, including leveraged buyouts ("LBO"), venture capital, distressed securities, mezzanine financing, real estate, and infrastructure. • Venture Capital : In general, these investments are made principally by investing in equity securities of privately-held corporations, for long-term capital appreciation. This strategy makes private equity investments in growth equity and buyout partnerships. Our private credit strategy includes the following: • Middle Market Lending : This strategy provides privately negotiated loans to U.S. middle market companies. Typically, these are floating rate, senior secured loans diversified across industries. Loans can be made to private equity sponsor-backed companies or non-sponsored companies to finance LBOs, recapitalizations, and acquisitions. • Mezzanine Financing : This strategy provides privately negotiated fixed income securities, generally with an equity component, to LBO firms and private and publicly traded large, mid, and small-cap companies to finance LBOs, recapitalizations, and acquisitions. • Distressed Debt : This strategy makes direct and indirect investments in debt and equity securities of companies that are experiencing financial and/or operational distress. Investments include buying indebtedness of bankrupt or financially troubled companies, small balance loan portfolios, special situations and capital structure arbitrage trades, commercial real estate mortgages, and similar non-U.S. securities and debt obligations. Our real assets strategy includes the following: • Energy & Power Generation : This strategy makes energy and power generation investments in cash flow generating infrastructure assets. Energy investments are made in a variety of industries including oil, natural gas, and coal. These investments are diversified across the energy supply chain and include assets in the exploration and production, pipeline, and refining sectors. Power generation includes investments in: (i) conventional power, such as natural gas and oil; (ii) renewable power, such as wind and solar; and (iii) electric transmission and distribution. • Real Estate : This strategy invests opportunistically in real estate in North America, Europe, and Asia via direct property ownership, joint ventures, mortgages, and investments in equity and debt instruments. Our alternative investment strategies generally employ low or moderate levels of leverage and use hedging only to reduce foreign exchange or interest rate volatility. At this time, our alternative investment strategies do not include hedge funds. We cannot redeem our investments with the general partners of these investments; however, occasionally these partnerships can be traded on the secondary market. Once liquidation is triggered by clauses within the limited partnership agreements or at the funds’ stated end date, we will receive our final allocation of capital and any earned appreciation of the underlying investments, assuming we have not divested ourselves of our partnership interests prior to that time. We currently receive distributions from these alternative investments through the realization of the underlying investments in the limited partnerships. We anticipate that the general partners of these alternative investments will liquidate their underlying investment portfolios through 2030. The following tables set forth summarized financial information for our other investments portfolio, including the portion not owned by us. The investments are carried under the equity method of accounting. The last line in the income statement information table below reflects our share of the aggregate income, which is the portion included in our Financial Statements. As the majority of these investments report results to us on a one quarter lag, the summarized financial statement information is as of, and for the 12-month period ended, September 30: Balance Sheet Information September 30, ($ in millions) 2016 2015 Investments $ 11,244 7,527 Total assets 12,075 8,515 Total liabilities 1,802 316 Total partners’ capital 10,273 8,199 Income Statement Information 12 months ended September 30, ($ in millions) 2016 2015 2014 Net investment income $ (44 ) 129 226 Realized gains 1,374 1,187 581 Net change in unrealized (depreciation) appreciation (719 ) (1,364 ) 1,098 Net income $ 611 (48 ) 1,905 Insurance Subsidiaries' alternative investments income 3.1 (1.9 ) 13.6 (g) We did not have exposure to any credit concentration risk of a single issuer greater than 10% of our stockholders' equity, other than certain U.S. government agencies, as of December 31, 2016 or December 31, 2015 . (h) We have pledged certain AFS fixed income securities as collateral related to our relationships with the Federal Home Loan Bank of Indianapolis ("FHLBI") and the Federal Home Loan Bank of New York ("FHLBNY"). In addition, certain securities were on deposit with various state and regulatory agencies at December 31, 2016 to comply with insurance laws. We retain all rights regarding securities pledged as collateral. The following table summarizes the market value of these securities at December 31, 2016 : ($ in millions) FHLBI Collateral FHLBNY Collateral State and Regulatory Deposits Total U.S. government and government agencies $ 7.4 — 24.8 32.2 CMBS 0.5 — — 0.5 RMBS 59.6 58.2 — 117.8 Total pledged as collateral $ 67.5 58.2 24.8 150.5 (i) The components of pre-tax net investment income earned were as follows: ($ in thousands) 2016 2015 2014 Fixed income securities $ 129,306 123,230 126,489 Equity securities 7,368 9,161 7,449 Short-term investments 686 112 66 Other investments 2,940 (1,890 ) 13,580 Investment expenses (9,546 ) (9,297 ) (8,876 ) Net investment income earned $ 130,754 121,316 138,708 (j) The following tables summarize OTTI by asset type for the periods indicated: 2016 Recognized in Earnings ($ in thousands) Gross Included in OCI AFS fixed income securities: Obligations of states and political subdivisions $ 2,797 — 2,797 Corporate securities 1,880 — 1,880 CLO and other ABS 19 — 19 CMBS 220 — 220 RMBS 275 10 265 Total AFS fixed income securities 5,191 10 5,181 AFS equity securities: Common stock 3,316 — 3,316 Preferred stock 2 — 2 Total AFS equity securities 3,318 — 3,318 Total OTTI losses $ 8,509 10 8,499 2015 Recognized in Earnings ($ in thousands) Gross Included in OCI AFS fixed income securities: Corporate securities $ 2,188 — 2,188 RMBS 1 — 1 Total AFS fixed income securities 2,189 — 2,189 AFS equity securities: Common stock 15,996 — 15,996 Preferred stock 181 — 181 Total AFS equity securities 16,177 — 16,177 Total OTTI losses $ 18,366 — 18,366 2014 Recognized in Earnings ($ in thousands) Gross Included in OCI AFS fixed income securities: RMBS $ 7 — 7 Total AFS fixed income securities 7 — 7 AFS equity securities: Common stock 10,517 — 10,517 Total AFS equity securities 10,517 — 10,517 Other investments 580 — 580 Total OTTI losses $ 11,104 — 11,104 The majority of the OTTI charges in 2016 were on securities for which we had the intent to sell to facilitate our fixed income strategy change to more actively manage the portfolio to maximize after-tax income and total return, while maintaining a similar level of credit quality and duration risk. Charges in 2015 and 2014 related to equity securities for which we had the intent to sell in relation to a change in our high-dividend yield strategy, with the remaining charges relating to securities that we did not believe would recover in the near term. (k) The components of net realized gains, excluding OTTI charges, were as follows: ($ in thousands) 2016 2015 2014 HTM fixed income securities Gains $ 3 5 2 Losses (1 ) (1 ) (20 ) AFS fixed income securities Gains 7,741 4,515 1,945 Losses (11,411 ) (312 ) (392 ) AFS equity securities Gains 8,108 29,168 36,871 Losses (864 ) (1,347 ) (704 ) Short-term investments Gains — — — Losses (13 ) — — Other investments Gains 3 162 1 Losses (4 ) (653 ) — Total net realized investment gains $ 3,562 31,537 37,703 Realized gains and losses on the sale of investments are determined on the basis of the cost of the specific investments sold. Proceeds from the sale of AFS securities were $1,046.1 million in 2016 , $234.1 million in 2015 , and $259.0 million in 2014 . Net realized gains in the table above were driven by the following: • 2016 : A repositioning of our equity portfolio partially offset by net losses in our AFS fixed income portfolio related to the change in our strategy to more actively manage this portfolio. • 2015 : A change in our dividend strategy from a quantitative, model-driven stock selection strategy to a fundamentally-based stock selection approach that incorporates an assessment of the sustainability and growth rate of a company's dividends and future cash flow. • 2014 : A quantitative rebalancing of our dividend yield strategy holdings within our equity portfolio.

Comprehensive Income

Comprehensive Income	12 Months Ended
	Dec. 31, 2016
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Comprehensive Income	Comprehensive Income (a) The components of comprehensive income, both gross and net of tax, for 2016 , 2015 , and 2014 were as follows: 2016 ($ in thousands) Gross Tax Net Net income $ 219,955 61,460 158,495 Components of OCI: Unrealized losses (gains) on investment securities : Unrealized holding losses during the year (9,195 ) (3,218 ) (5,977 ) Non-credit portion of other-than-temporary impairments recognized in other comprehensive income (10 ) (4 ) (6 ) Amounts reclassified into net income: HTM securities (141 ) (49 ) (92 ) Non-credit OTTI 213 75 138 Realized losses on AFS securities 4,713 1,649 3,064 Net unrealized losses (4,420 ) (1,547 ) (2,873 ) Defined benefit pension and post-retirement plans: Net actuarial loss (12,079 ) (4,227 ) (7,852 ) Amounts reclassified into net income: Net actuarial loss 6,462 2,262 4,200 Defined benefit pension and post-retirement plans (5,617 ) (1,965 ) (3,652 ) Other comprehensive loss (10,037 ) (3,512 ) (6,525 ) Comprehensive income $ 209,918 57,948 151,970 2015 ($ in thousands) Gross Tax Net Net income $ 232,692 66,831 165,861 Components of OCI: Unrealized gains on investment securities : Unrealized holding losses during the year (40,221 ) (14,078 ) (26,143 ) Amounts reclassified into net income: HTM securities (580 ) (203 ) (377 ) Non-credit OTTI 357 125 232 Realized gains on AFS securities (14,016 ) (4,906 ) (9,110 ) Net unrealized losses (54,460 ) (19,062 ) (35,398 ) Defined benefit pension and post-retirement plans: Net actuarial gain 2,438 853 1,585 Amounts reclassified into net income: Net actuarial loss 7,077 2,477 4,600 Defined benefit pension and post-retirement plans 9,515 3,330 6,185 Other comprehensive loss (44,945 ) (15,732 ) (29,213 ) Comprehensive income $ 187,747 51,099 136,648 2014 ($ in thousands) Gross Tax Net Net income $ 197,131 55,304 141,827 Components of OCI: Unrealized gains on investment securities : Unrealized holding gains during the year 72,940 25,529 47,411 Amounts reclassified into net income: HTM securities (1,299 ) (455 ) (844 ) Non-credit OTTI 1,669 584 1,085 Realized gains on AFS securities (28,864 ) (10,102 ) (18,762 ) Net unrealized gains 44,446 15,556 28,890 Defined benefit pension and post-retirement plans: Net actuarial loss (54,136 ) (18,947 ) (35,189 ) Amounts reclassified into net income: Net actuarial loss 1,902 666 1,236 Defined benefit pension and post-retirement plans (52,234 ) (18,281 ) (33,953 ) Other comprehensive loss (7,788 ) (2,725 ) (5,063 ) Comprehensive income $ 189,343 52,579 136,764 (b) The balances of, and changes in, each component of AOCI (net of taxes) as of December 31, 2016 and 2015 were as follows: Net Unrealized (Loss) Gain on Investment Securities ($ in thousands) OTTI Related HTM Related All Other Investments Subtotal Defined Benefit Pension and Post- retirement Plans Total AOCI Balance, December 31, 2014 $ (514 ) 623 80,284 80,393 (60,605 ) 19,788 OCI before reclassifications — (52 ) (26,091 ) (26,143 ) 1,585 (24,558 ) Amounts reclassified from AOCI 232 (377 ) (9,110 ) (9,255 ) 4,600 (4,655 ) Net current period OCI 232 (429 ) (35,201 ) (35,398 ) 6,185 (29,213 ) Balance, December 31, 2015 (282 ) 194 45,083 44,995 (54,420 ) (9,425 ) OCI before reclassifications (6 ) — (5,977 ) (5,983 ) (7,852 ) (13,835 ) Amounts reclassified from AOCI 138 (92 ) 3,064 3,110 4,200 7,310 Net current period OCI 132 (92 ) (2,913 ) (2,873 ) (3,652 ) (6,525 ) Balance, December 31, 2016 $ (150 ) 102 42,170 42,122 (58,072 ) (15,950 ) The reclassifications out of AOCI are as follows: ($ in thousands) Year ended December 31, 2016 Year ended December 31, 2015 Affected Line Item in the Consolidated Statement of Income HTM related Unrealized losses on HTM disposals $ 169 308 Net realized (losses) gains Amortization of net unrealized gains on HTM securities (310 ) (888 ) Net investment income earned (141 ) (580 ) Income before federal income tax 49 203 Total federal income tax expense (92 ) (377 ) Net income OTTI related Non-credit OTTI on disposed securities 213 357 Net realized (losses) gains 213 357 Income before federal income tax (75 ) (125 ) Total federal income tax expense 138 232 Net income Realized (losses) gains on AFS Realized (losses) gains on AFS disposals 4,713 (14,016 ) Net realized (losses) gains 4,713 (14,016 ) Income before federal income tax (1,649 ) 4,906 Total federal income tax expense 3,064 (9,110 ) Net income Defined benefit pension and post-retirement life plans Net actuarial loss 1,486 1,538 Losses and loss expenses incurred 4,976 5,539 Policy acquisition costs Total defined benefit pension and post-retirement life 6,462 7,077 Income before federal income tax (2,262 ) (2,477 ) Total federal income tax expense 4,200 4,600 Net income Total reclassifications for the period $ 7,310 (4,655 ) Net income

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The following table presents the carrying amounts and estimated fair values of our financial instruments as of December 31, 2016 and 2015 : December 31, 2016 December 31, 2015 ($ in thousands) Carrying Amount Fair Value Carrying Amount Fair Value Financial Assets Fixed income securities: HTM $ 101,556 105,211 201,354 209,544 AFS 4,792,540 4,792,540 4,408,203 4,408,203 Equity securities, AFS 146,753 146,753 207,051 207,051 Short-term investments 221,701 221,701 194,819 194,819 Financial Liabilities Short-term debt: 0.63% borrowings from FHLBI — — 15,000 14,977 1.25% borrowings from FHLBI — — 45,000 45,083 Total short-term debt — — 60,000 60,060 Long-term debt: 7.25% Senior Notes 49,901 56,148 49,898 56,929 6.70% Senior Notes 99,430 108,333 99,415 110,363 5.875% Senior Notes 185,000 176,860 185,000 192,474 1.61% Borrowings from FHLBNY 25,000 24,286 — — 1.56% Borrowings from FHLBNY 25,000 24,219 — — 3.03% Borrowings from FHLBI 60,000 59,313 — — Subtotal long-term debt 444,331 449,159 334,313 359,766 Unamortized debt issuance costs (5,664 ) (6,121 ) Total long-term debt $ 438,667 328,192 For discussion regarding the fair value techniques of our financial instruments, refer to Note 2. "Summary of Significant Accounting Policies" in this Form 10-K. The following tables provide quantitative disclosures of our financial assets that were measured at fair value at December 31, 2016 and 2015 : December 31, 2016 Fair Value Measurements Using ($ in thousands) Assets Measured at Fair Value 12/31/16 Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) 1 Significant Other Observable Inputs (Level 2) 1 Significant Unobservable Inputs (Level 3) Description Measured on a recurring basis: AFS fixed income securities: U.S. government and government agencies $ 77,333 27,520 49,813 — Foreign government 26,865 — 26,865 — Obligations of states and political subdivisions 1,379,593 — 1,379,593 — Corporate securities 1,997,753 — 1,997,753 — CLO and other ABS 528,960 — 528,960 — CMBS 256,842 — 256,842 — RMBS 525,194 — 525,194 — Total AFS fixed income securities 4,792,540 27,520 4,765,020 — AFS equity securities: Common stock 130,608 122,932 — 7,676 Preferred stock 16,145 16,145 — — Total AFS equity securities 146,753 139,077 — 7,676 Total AFS securities 4,939,293 166,597 4,765,020 7,676 Short-term investments 221,701 221,701 — — Total assets measured at fair value $ 5,160,994 388,298 4,765,020 7,676 December 31, 2015 Fair Value Measurements Using ($ in thousands) Assets Measured at Fair Value 12/31/15 Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) 1 Significant Other Observable Inputs (Level 2) 1 Significant Unobservable Inputs (Level 3) Description Measured on a recurring basis: AFS fixed income securities: U.S. government and government agencies $ 104,115 42,702 61,413 — Foreign government 15,181 — 15,181 — Obligations of states and political subdivisions 1,359,142 — 1,359,142 — Corporate securities 1,900,182 — 1,900,182 — CLO and other ABS 244,154 — 244,154 — CMBS 243,592 — 243,592 — RMBS 541,837 — 541,837 — Total AFS fixed income securities 4,408,203 42,702 4,365,501 — AFS equity securities: Common stock 194,789 191,517 — 3,272 Preferred stock 12,262 12,262 — — Total AFS equity securities 207,051 203,779 — 3,272 Total AFS securities 4,615,254 246,481 4,365,501 3,272 Short-term investments 194,819 194,819 — — Total assets measured at fair value $ 4,810,073 441,300 4,365,501 3,272 1 There were no transfers of securities between Level 1 and Level 2. The following table provides a summary of the changes in the fair value of securities measured using Level 3 inputs and related quantitative information during 2016: 2016 ($ in thousands) Common Stock Fair value, December 31, 2015 $ 3,272 Total net (losses) gains for the period included in: OCI — Net income — Purchases 6,204 Sales (1,800 ) Issuances — Settlements — Transfers into Level 3 — Transfers out of Level 3 — Fair value, December 31, 2016 $ 7,676 The following tables provide quantitative information regarding our financial assets and liabilities that were disclosed at fair value at December 31, 2016 and 2015 : December 31, 2016 Fair Value Measurements Using ($ in thousands) Assets/Liabilities Disclosed at Fair Value 12/31/2016 Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Financial Assets HTM: Obligations of states and political subdivisions $ 79,916 — 79,916 — Corporate securities 24,075 — 16,565 7,510 CMBS 1,220 — 1,220 — Total HTM fixed income securities $ 105,211 — 97,701 7,510 Financial Liabilities Long-term debt: 7.25% Senior Notes $ 56,148 — 56,148 — 6.70% Senior Notes 108,333 — 108,333 — 5.875% Senior Notes 176,860 176,860 — — 1.61% Borrowings from FHLBNY 24,286 — 24,286 — 1.56% Borrowings from FHLBNY 24,219 — 24,219 — 3.03% Borrowings from FHLBI 59,313 — 59,313 — Total long-term debt $ 449,159 176,860 272,299 — December 31, 2015 Fair Value Measurements Using ($ in thousands) Assets/Liabilities Disclosed at Fair Value 12/31/2015 Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Financial Assets HTM: Obligations of states and political subdivisions $ 181,880 — 181,880 — Corporate securities 22,015 — 18,679 3,336 CLO and other ABS 1,028 — 1,028 — CMBS 4,621 — 4,621 — Total HTM fixed income securities $ 209,544 — 206,208 3,336 Financial Liabilities Short-term debt: 0.63% borrowings from FHLBI $ 14,977 — 14,977 — 1.25% borrowings from FHLBI 45,083 — 45,083 — Total short-term debt 60,060 — 60,060 — Long-term debt: 7.25% Senior Notes 56,929 — 56,929 — 6.70% Senior Notes 110,363 — 110,363 — 5.875% Senior Notes 192,474 192,474 — — Total long-term debt $ 359,766 192,474 167,292 —

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2016
Reinsurance Disclosures [Abstract]
Reinsurance	Reinsurance Our Financial Statements reflect the effects of assumed and ceded reinsurance transactions. Assumed reinsurance refers to the acceptance of certain insurance risks that other insurance entities have underwritten. Ceded reinsurance involves transferring certain insurance risks (along with the related written and earned premiums) that we have underwritten to other insurance companies that agree to share these risks. The primary purpose of ceded reinsurance is to protect the Insurance Subsidiaries from potential losses in excess of the amount that we are prepared to accept. Our major treaties covering property, property catastrophe, and casualty business are excess of loss contracts. In addition, we have an intercompany quota share pooling arrangement and other minor quota share treaties. As a Standard Commercial Lines and E&S Lines writer, we are required to participate in Terrorism Risk Insurance Program Reauthorization Act ("TRIPRA"), which was extended by Congress to December 31, 2020. TRIPRA requires private insurers and the United States government to share the risk of loss on future acts of terrorism certified by the U.S. Secretary of the Treasury. Under TRIPRA, each participating insurer is responsible for paying a deductible of specified losses before federal assistance is available. This deductible is based on a percentage of the prior year’s applicable Standard Commercial Lines and E&S Lines premiums. In 2017 , our deductible is approximately $304 million . For losses above the deductible, the federal government will pay 83% of losses to an industry limit of $100 billion , and the insurer retains 17% . The federal share of losses will be reduced by 1% each year to 80% by 2020. The Insurance Subsidiaries remain liable to policyholders to the extent that any reinsurer becomes unable to meet their contractual obligations. We evaluate and monitor the financial condition of our reinsurers under voluntary reinsurance arrangements to minimize our exposure to significant losses from reinsurer insolvencies. On an ongoing basis, we review amounts outstanding, length of collection period, changes in reinsurer credit ratings, and other relevant factors to determine collectability of reinsurance recoverables. The allowance for uncollectible reinsurance recoverables was $5.5 million at December 31, 2016 and $5.7 million at December 31, 2015 . The following table represents our total reinsurance balances segregated by reinsurer to depict our concentration of risk throughout our reinsurance portfolio: As of December 31, 2016 As of December 31, 2015 ($ in thousands) Reinsurance Balances % of Reinsurance Balance Reinsurance Balances % of Reinsurance Balance Total reinsurance recoverables $ 621,537 $ 561,968 Total prepaid reinsurance premiums 146,282 140,889 Total reinsurance balance 767,819 702,857 Federal and state pools 1 : NFIP 211,181 27 % 164,130 24 % New Jersey Unsatisfied Claim Judgment Fund 65,574 9 71,884 10 Other 3,227 — 3,136 — Total federal and state pools 279,982 36 239,150 34 Remaining reinsurance balance $ 487,837 64 $ 463,707 66 Munich Re Group (A.M. Best rated "A+") $ 119,520 16 $ 112,889 16 Hannover Ruckversicherungs AG (A.M. Best rated "A+") 106,298 13 99,535 14 AXIS Reinsurance Company (A.M. Best rated "A+") 59,737 8 53,374 8 Swiss Re Group (A.M. Best rated "A+") 50,494 7 51,340 7 Partner Reinsurance Company of the U.S. (A.M. Best rated “A”) 21,125 3 20,748 3 All other reinsurers 130,663 17 125,821 18 Total reinsurers 487,837 64 % 463,707 66 % Less: collateral 2 (113,763 ) (106,449 ) Reinsurers, net of collateral $ 374,074 $ 357,258 1 Considered to have minimal risk of default. 2 Includes letters of credit, trust funds, and funds held against reinsurance recoverables. Note: Some amounts may not foot due to rounding. Under our reinsurance arrangements, which are prospective in nature, reinsurance premiums ceded are recorded as prepaid reinsurance and amortized over the remaining contract period in proportion to the reinsurance protection provided, or recorded periodically, as per the terms of the contract, in a direct relationship to the gross premium recording. Reinsurance recoveries are recognized as gross losses are incurred. The following table contains a listing of direct, assumed, and ceded reinsurance amounts for premiums written, premiums earned, and losses and loss expenses incurred: ($ in thousands) 2016 2015 2014 Premiums written: Direct $ 2,577,259 2,403,519 2,228,270 Assumed 28,779 23,848 26,306 Ceded (368,750 ) (357,463 ) (369,296 ) Net $ 2,237,288 2,069,904 1,885,280 Premiums earned: Direct $ 2,484,715 2,330,267 2,183,258 Assumed 28,214 23,209 34,653 Ceded (363,357 ) (363,567 ) (365,302 ) Net $ 2,149,572 1,989,909 1,852,609 Losses and loss expenses incurred: Direct $ 1,560,356 1,274,872 1,314,864 Assumed 22,708 16,996 26,187 Ceded (348,267 ) (143,327 ) (183,550 ) Net $ 1,234,797 1,148,541 1,157,501 The ceded premiums and losses related to our participation in the NFIP, under which 100% of our flood premiums, and losses and loss expenses are ceded to the NFIP, are as follows: Ceded to NFIP ($ in thousands) 2016 2015 2014 Ceded premiums written $ (232,245 ) (228,907 ) (237,718 ) Ceded premiums earned (227,882 ) (233,940 ) (234,224 ) Ceded losses and loss expenses incurred (239,891 ) (62,078 ) (57,323 )

Reserve for Losses and Loss Exp

Reserve for Losses and Loss Expenses	12 Months Ended
	Dec. 31, 2016
Insurance Loss Reserves [Abstract]
Reserves for Losses and Loss Expenses	Reserves for Losses and Loss Expenses (a) The table below provides a roll forward of reserves for losses and loss expenses for beginning and ending reserve balances: ($ in thousands) 2016 2015 2014 Gross reserves for losses and loss expenses, at beginning of year $ 3,517,728 3,477,870 3,349,770 Less: reinsurance recoverable on unpaid losses and loss expenses, at beginning of year 551,019 571,978 540,839 Net reserves for losses and loss expenses, at beginning of year 2,966,709 2,905,892 2,808,931 Incurred losses and loss expenses for claims occurring in the: Current year 1,300,565 1,217,550 1,216,770 Prior years (65,768 ) (69,009 ) (59,269 ) Total incurred losses and loss expenses 1,234,797 1,148,541 1,157,501 Paid losses and loss expenses for claims occurring in the: Current year 450,811 446,550 468,478 Prior years 670,176 641,174 592,062 Total paid losses and loss expenses 1,120,987 1,087,724 1,060,540 Net reserves for losses and loss expenses, at end of year 3,080,519 2,966,709 2,905,892 Add: Reinsurance recoverable on unpaid losses and loss expenses, at end of year 611,200 551,019 571,978 Gross reserves for losses and loss expenses at end of year $ 3,691,719 3,517,728 3,477,870 Our net losses and loss expense reserves increased by $113.8 million in 2016 , $60.8 million in 2015 , and $97.0 million in 2014 . The losses and loss expense reserves are net of anticipated recoveries for salvage and subrogation claims, which amounted to $64.9 million for 2016 , $62.1 million for 2015 , and $65.1 million for 2014 . The changes in the net losses and loss expense reserves were the result of growth in exposures, particularly associated with our E&S Lines of business, anticipated loss trends, and normal reserve changes inherent in the uncertainty in establishing reserves for losses and loss expenses. As additional information is collected in the loss settlement process, reserves are adjusted accordingly. These adjustments are reflected in the Consolidated Statements of Income in the period in which such adjustments are identified. These changes could have a material impact on the results of operations of future periods when the adjustments are made. In 2016 , we experienced overall net favorable loss development of $65.8 million , compared to $ 69.0 million in 2015 , and $59.3 million in 2014 . The following table summarizes the prior year development by line of business: (Favorable)/Unfavorable Prior Year Development ($ in millions) 2016 2015 2014 General Liability $ (45.0 ) (51.0 ) (43.9 ) Commercial Automobile 25.3 2.4 (4.1 ) Workers Compensation (56.0 ) (37.0 ) — Businessowners' Policies 1.8 2.2 1.9 Commercial Property 0.3 (3.0 ) (2.1 ) Homeowners 1.7 1.5 (4.0 ) Personal Automobile 1.0 0.4 (10.8 ) E&S 7.1 15.5 3.7 Other (2.0 ) — — Total $ (65.8 ) (69.0 ) (59.3 ) The prior accident year development during 2016 was favorable by $65.8 million , which included $69.0 million of net favorable casualty development and $3.2 million of unfavorable property development. The net favorable casualty reserve development was largely driven by the general liability line of business, including products liability and excess liability, and by the workers compensation line. Partially offsetting this net favorable development was the commercial auto line of business, which experienced $25.0 million of unfavorable casualty development in 2016. In addition, our E&S Lines experienced unfavorable casualty development of $6.0 million in 2016. The majority of the 2016 net favorable development was attributable to accident years 2013 and prior, driven by the general liability and workers compensation lines of business. This net favorable development was partially offset by unfavorable development in accident years 2014 and 2015, which was attributable to our commercial auto and E&S Lines of business. The unfavorable development in our commercial auto line of business was driven primarily by bodily injury liability for accident years 2014 and 2015. The unfavorable development in accident year 2014 was driven by higher than expected severity, whereas accident year 2015 was driven by higher than expected frequency and severity. The prior accident year development during 2015 was favorable by $ 69.0 million , which included $ 67.0 million of net favorable casualty development and $ 2.0 million of favorable property development. The net favorable casualty reserve development was largely driven by the general liability and workers compensation lines of business. For workers compensation, this was a significant change from 2014, during which period this line experienced no development. Our E&S Lines experienced unfavorable casualty development of $15.5 million in 2015. The majority of the 2015 net favorable development was attributable to accident years 2009 through 2013, driven by general liability and workers compensation lines of business. This net favorable development was partially offset by unfavorable development in accident years 2012 through 2014, which was attributable to our E&S Lines. The prior accident year development during 2014 was favorable by $ 59.3 million , which included $ 48.2 million of net favorable casualty development and $ 11.1 million of property development. The property development was primarily related to a prior year reinsurance recoverable. The net favorable casualty reserve development was largely driven by the general liability and personal automobile lines of business. Conversely, businessowners' policies and our E&S Lines experienced unfavorable emergence in 2014 . The majority of the 2014 net favorable development was attributable to accident years 2010 through 2012, although earlier accident years also developed favorably. The general liability, commercial automobile, and personal automobile lines of business all contributed to this development, partially offset by businessowners’ liability. The overall favorable development for accident years 2012 and prior was partially offset by unfavorable development in accident year 2013, which was largely attributable to commercial automobile liability, and partially E&S Lines casualty. (b) Reserves established for liability insurance include exposure to asbestos and environmental claims. These claims have arisen primarily from insured exposures in municipal government, small non-manufacturing commercial risk, and homeowners policies. The emergence of these claims is slow and highly unpredictable. There are significant uncertainties in estimating our exposure to asbestos and environmental claims (for both case and IBNR reserves) resulting from lack of relevant historical data, the delayed and inconsistent reporting patterns associated with these claims, and uncertainty as to the number and identity of claimants and complex legal and coverage issues. Legal issues that arise in asbestos and environmental cases include federal or state venue, choice of law, causation, admissibility of evidence, allocation of damages and contribution among joint defendants, successor and predecessor liability, and whether direct action against insurers can be maintained. Coverage issues that arise in asbestos and environmental cases include the interpretation and application of policy exclusions, the determination and calculation of policy limits, the determination of the ultimate amount of a loss, the extent to which a loss is covered by a policy, if at all, the obligation of an insurer to defend a claim, and the extent to which a party can prove the existence of coverage. Courts have reached different and sometimes inconsistent conclusions on these legal and coverage issues. We do not discount to present value that portion of our losses and loss expense reserves expected to be paid in future periods. The following table details our losses and loss expense reserves for various asbestos and environmental claims: 2016 ($ in millions) Gross Net Asbestos $ 7.9 6.6 Landfill sites 12.8 8.1 Leaking underground storage tanks 9.3 8.0 Total $ 30.0 22.7 Estimating IBNR reserves for asbestos and environmental claims is difficult because of the delayed and inconsistent reporting patterns associated with these claims. In addition, there are significant uncertainties associated with estimating critical assumptions, such as average clean-up costs, third-party costs, potentially responsible party shares, allocation of damages, litigation and coverage costs, and potential state and federal legislative changes. Normal historically based actuarial approaches cannot be applied to asbestos and environmental claims because past loss history is not indicative of future potential asbestos and environmental losses. In addition, while certain alternative models can be applied, such models can produce significantly different results with small changes in assumptions. As a result, we do not calculate an asbestos and environmental loss range. Historically, our asbestos and environmental claims have been significantly lower in volume as, prior to the introduction of the absolute pollution exclusion endorsement in the mid-1980’s, we were primarily a personal lines carrier and therefore do not have broad exposure to asbestos and environmental claims. Additionally, we are the primary insurance carrier on the majority of these exposures, which provides more certainty in our reserve position compared to other insurance carriers. The following table provides a roll forward of gross and net asbestos and environmental incurred losses and loss expenses and related reserves thereon: 2016 2015 2014 ($ in thousands) Gross Net Gross Net Gross Net Asbestos Reserves for losses and loss expenses at beginning of year $ 8,024 6,793 8,751 7,314 8,897 7,518 Incurred losses and loss expenses 77 77 (428 ) (77 ) 60 — Less: losses and loss expenses paid (254 ) (255 ) (299 ) (444 ) (206 ) (204 ) Reserves for losses and loss expenses at the end of year $ 7,847 6,615 8,024 6,793 8,751 7,314 Environmental Reserves for losses and loss expenses at beginning of year $ 22,387 16,368 21,902 15,680 23,867 17,649 Incurred losses and loss expenses 1,406 1,303 3,396 3,397 107 — Less: losses and loss expenses paid (1,678 ) (1,570 ) (2,911 ) (2,709 ) (2,072 ) (1,969 ) Reserves for losses and loss expenses at the end of year $ 22,115 16,101 22,387 16,368 21,902 15,680 Total Asbestos and Environmental Claims Reserves for losses and loss expenses at beginning of year $ 30,411 23,161 30,653 22,994 32,764 25,167 Incurred losses and loss expenses 1,483 1,380 2,968 3,320 167 — Less: losses and loss expenses paid (1,932 ) (1,825 ) (3,210 ) (3,153 ) (2,278 ) (2,173 ) Reserves for losses and loss expenses at the end of year $ 29,962 22,716 30,411 23,161 30,653 22,994 (c) The following is information about incurred and paid claims development as of December 31, 2016 , net of reinsurance, as well as cumulative claim frequency and the total of IBNR liabilities. During the experience period, we implemented a series of claims-related initiatives and claims management changes. These initiatives focused on claims handling and reserving, medical claims costs, and loss adjustment expenses. As a result of these initiatives, several historical patterns have changed and may no longer be appropriate to use as the sole basis for projections. The information about incurred and paid claims development for the years ended December 31, 2007 to 2015 is presented as supplementary information. All Lines (in thousands) Incurred Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ 1,038,585 1,066,670 1,047,912 1,028,546 1,028,956 1,015,897 1,003,552 998,496 992,673 989,709 42,970 84,996 2008 957,247 988,584 990,931 964,862 947,306 936,975 927,958 931,785 926,017 48,590 85,264 2009 920,143 941,972 916,691 883,590 870,057 869,927 857,960 853,401 49,532 85,444 2010 950,114 973,742 977,959 956,600 943,118 922,404 915,131 65,625 94,093 2011 1,042,576 1,061,667 1,062,233 1,056,107 1,033,518 1,023,726 82,565 104,303 2012 1,065,437 1,071,290 1,020,655 998,028 973,089 101,992 103,498 2013 1,044,142 1,062,045 1,047,230 1,021,007 182,613 90,330 2014 1,107,513 1,133,798 1,146,990 278,689 93,747 2015 1,114,081 1,130,513 375,894 91,410 2016 1,188,608 589,938 85,202 Total 10,168,191 All Lines (in thousands) Cumulative Paid Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2007 $ 350,369 543,949 665,277 762,422 835,347 877,933 896,590 912,683 920,931 929,082 2008 286,314 489,633 609,851 690,016 764,196 798,996 819,280 839,392 853,769 2009 277,275 442,417 540,982 634,902 695,249 736,100 760,589 775,885 2010 328,826 509,910 625,229 704,895 773,536 803,773 823,770 2011 391,944 585,867 692,730 782,655 852,202 901,801 2012 378,067 555,819 651,544 743,742 810,135 2013 335,956 518,872 644,475 748,758 2014 405,898 614,075 736,154 2015 376,641 581,203 2016 387,272 Total 7,547,829 All outstanding liabilities before 2007, net of reinsurance 324,070 Liabilities for loss and loss adjustment expenses, net of reinsurance 2,944,432 General Liability (in thousands) Incurred Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ 252,732 256,627 255,538 250,834 248,807 242,878 234,173 234,697 231,439 230,717 17,815 14,016 2008 250,239 243,755 243,536 234,770 233,712 224,236 219,551 221,640 221,203 19,939 13,721 2009 237,913 241,625 233,530 223,146 212,947 211,243 206,387 205,741 22,858 13,815 2010 215,208 228,680 242,499 237,154 222,328 211,619 208,968 29,380 12,629 2011 229,967 228,720 239,480 230,785 217,256 211,196 36,350 11,533 2012 238,979 245,561 215,083 194,144 175,305 44,493 9,864 2013 250,609 251,421 239,776 225,709 90,026 10,107 2014 244,312 249,946 257,132 135,883 10,157 2015 254,720 245,710 167,995 9,371 2016 277,214 233,794 7,790 Total 2,258,895 General Liability (in thousands) Cumulative Paid Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2007 $ 14,695 44,356 80,621 123,108 158,424 181,641 191,405 201,842 204,159 208,449 2008 16,397 45,595 82,421 113,088 151,055 166,394 176,873 186,896 194,257 2009 14,346 37,143 64,970 103,213 130,554 151,920 166,767 176,316 2010 15,726 46,201 80,018 113,050 143,360 161,487 172,394 2011 13,924 42,692 73,643 102,978 135,377 159,768 2012 13,030 35,241 56,580 89,008 109,448 2013 12,789 35,113 72,127 104,587 2014 14,901 46,825 79,972 2015 14,665 39,978 2016 15,684 Total 1,260,853 All outstanding liabilities before 2007, net of reinsurance 72,887 Liabilities for loss and loss adjustment expenses, net of reinsurance 1,070,929 Workers Compensation (in thousands) Incurred Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ 231,462 236,993 231,104 226,095 230,109 225,165 225,904 222,623 218,828 216,177 23,152 16,344 2008 219,616 243,186 255,810 250,423 241,921 245,993 244,100 243,512 238,836 26,983 14,400 2009 197,504 215,946 213,036 210,109 210,756 216,992 212,536 208,611 24,238 12,214 2010 198,371 214,469 212,838 211,030 214,916 212,448 208,155 34,437 12,181 2011 205,238 218,973 214,743 215,114 210,591 205,708 38,227 11,843 2012 203,864 208,036 199,360 195,197 188,596 39,122 11,601 2013 199,794 194,318 187,658 173,160 43,058 11,361 2014 199,346 187,065 182,579 55,599 10,464 2015 193,729 194,639 63,496 10,479 2016 196,774 107,977 9,910 Total 2,013,235 Workers Compensation (in thousands) Cumulative Paid Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2007 $ 31,478 88,786 123,681 144,713 156,320 164,373 169,941 175,205 179,011 180,865 2008 39,628 100,678 139,144 158,083 171,403 180,556 188,206 191,265 195,962 2009 37,885 87,299 117,019 133,116 145,417 154,726 160,529 164,336 2010 46,795 93,281 122,442 137,184 149,086 153,795 158,078 2011 42,941 90,836 118,847 134,646 139,232 149,269 2012 40,911 86,909 108,211 122,755 132,052 2013 36,829 74,568 96,376 109,739 2014 35,924 78,944 100,876 2015 33,857 77,320 2016 34,525 Total 1,303,022 All outstanding liabilities before 2007, net of reinsurance 226,553 Liabilities for loss and loss adjustment expenses, net of reinsurance 936,766 Commercial Automobile (in thousands) Incurred Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ 185,733 194,567 187,966 182,030 179,739 178,956 176,049 175,342 175,431 175,894 1,434 24,074 2008 196,370 195,823 190,349 187,100 187,417 182,785 180,902 183,736 183,618 1,332 24,105 2009 199,541 191,079 182,724 169,858 166,682 162,911 161,251 161,923 1,873 24,554 2010 187,562 189,305 187,778 181,923 179,854 172,969 173,157 2,318 25,194 2011 174,006 183,044 182,325 178,421 172,617 174,882 5,153 25,146 2012 179,551 191,947 183,527 184,289 184,367 6,421 23,751 2013 188,289 205,282 209,197 207,994 18,464 25,215 2014 200,534 212,725 216,824 37,432 27,129 2015 220,994 240,958 65,528 28,475 2016 255,187 106,894 28,740 Total 1,974,804 Commercial Automobile (in thousands) Cumulative Paid Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2007 $ 65,544 102,233 126,507 146,690 163,629 170,241 171,622 171,839 173,050 173,980 2008 69,053 104,711 130,857 151,741 166,487 173,795 175,244 180,779 181,779 2009 63,126 94,406 113,697 137,564 149,949 155,560 158,303 159,723 2010 68,098 99,254 128,015 146,913 163,513 167,227 169,100 2011 69,849 99,196 121,576 142,507 157,291 166,082 2012 73,316 105,371 127,235 148,669 168,114 2013 76,469 109,893 140,015 169,850 2014 80,810 117,169 148,884 2015 91,347 132,260 2016 106,022 Total 1,575,794 All outstanding liabilities before 2007, net of reinsurance 3,271 Liabilities for loss and loss adjustment expenses, net of reinsurance 402,281 Businessowners' Policies (in thousands) Incurred Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ 32,749 34,011 33,397 31,212 29,270 29,393 28,440 28,503 29,691 29,288 124 2,956 2008 39,660 38,986 39,334 32,974 30,250 29,793 31,066 31,340 30,967 94 3,258 2009 48,535 51,762 46,645 43,828 43,553 44,938 44,299 44,273 730 3,473 2010 53,669 49,285 42,408 39,915 40,899 40,581 41,239 693 3,917 2011 54,469 57,083 51,047 58,242 59,256 58,966 2,177 4,956 2012 54,342 48,029 46,303 44,172 44,077 834 5,533 2013 49,617 42,618 41,005 40,624 4,189 3,474 2014 55,962 60,949 62,548 10,891 4,038 2015 52,871 53,768 12,089 3,860 2016 52,335 16,027 3,398 Total 458,085 Businessowners' Policies (in thousands) Cumulative Paid Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2007 $ 14,051 18,870 22,583 24,978 25,759 27,273 28,073 28,095 28,368 29,048 2008 15,019 21,765 24,449 25,738 28,026 28,660 28,589 29,778 30,873 2009 18,915 29,612 32,689 36,073 40,052 42,895 43,358 43,448 2010 20,821 28,131 31,027 34,705 37,819 38,900 40,279 2011 27,884 37,362 41,011 46,444 52,114 55,856 2012 22,199 31,833 35,089 37,215 38,766 2013 17,412 26,592 30,845 34,760 2014 28,914 40,584 44,911 2015 24,189 36,014 2016 24,655 Total 378,610 All outstanding liabilities before 2007, net of reinsurance 7,327 Liabilities for loss and loss adjustment expenses, net of reinsurance 86,802 Commercial Property (in thousands) Incurred Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ 98,167 104,160 100,809 101,027 103,183 103,381 102,998 102,732 102,679 103,077 2 6,919 2008 97,578 102,860 101,436 101,470 101,265 101,702 101,043 100,881 101,043 4 7,604 2009 82,619 82,124 82,025 82,014 80,774 80,455 80,558 80,545 10 7,009 2010 105,647 96,851 97,386 96,127 95,530 95,363 95,178 21 7,667 2011 136,954 131,667 130,942 131,282 131,353 131,113 22 9,035 2012 118,464 114,224 115,375 116,658 117,102 (22 ) 8,512 2013 88,101 90,639 90,103 90,005 (78 ) 5,704 2014 141,192 136,249 136,820 (1,052 ) 6,503 2015 110,270 109,513 (1,320 ) 6,380 2016 121,927 7,112 6,253 Total 1,086,323 Commercial Property (in thousands) Cumulative Paid Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2007 $ 63,159 95,050 99,036 99,942 101,805 102,310 102,370 102,532 102,663 103,061 2008 68,211 98,921 100,465 99,288 100,213 100,752 100,908 100,868 101,034 2009 59,933 78,695 80,433 80,894 80,251 80,352 80,529 80,509 2010 69,543 91,918 94,602 95,111 95,270 95,147 95,156 2011 94,538 127,580 129,579 130,681 131,060 131,115 2012 81,528 108,834 111,503 114,699 116,291 2013 60,244 87,874 90,446 90,350 2014 101,131 132,909 136,634 2015 79,048 106,182 2016 83,966 Total 1,044,298 All outstanding liabilities before 2007, net of reinsurance 254 Liabilities for loss and loss adjustment expenses, net of reinsurance 42,279 Personal Automobile (in thousands) Incurred Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ 97,161 102,932 103,283 102,325 101,744 101,654 101,814 101,747 101,750 101,714 254 15,354 2008 100,311 106,999 106,842 103,934 100,213 99,912 99,686 99,255 99,116 264 16,042 2009 93,808 103,319 105,033 103,908 104,734 103,866 103,393 103,412 256 17,346 2010 103,340 110,075 112,346 109,515 107,490 107,405 107,224 277 20,821 2011 113,232 116,164 113,686 112,993 114,241 113,830 644 22,700 2012 113,771 114,921 109,832 109,324 110,294 988 22,332 2013 108,417 109,620 106,225 106,703 2,252 22,359 2014 102,250 109,325 106,757 6,945 22,478 2015 96,387 99,698 13,594 20,797 2016 92,727 18,187 19,044 Total 1,041,475 Personal Automobile (in thousands) Cumulative Paid Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2007 $ 45,846 66,884 82,455 92,019 97,335 99,454 100,539 100,667 101,099 101,134 2008 50,396 73,194 84,715 91,834 95,932 97,723 98,174 98,604 98,668 2009 51,039 71,911 86,431 96,229 100,566 102,187 102,322 102,437 2010 58,786 82,490 95,300 101,540 104,061 105,849 106,453 2011 61,323 82,102 93,878 105,068 111,085 112,732 2012 63,704 82,729 94,842 102,977 107,890 2013 61,384 80,861 92,637 100,528 2014 62,519 83,739 92,589 2015 58,725 76,470 2016 57,961 Total 956,862 All outstanding liabilities before 2007, net of reinsurance 5,803 Liabilities for loss and loss adjustment expenses, net of reinsurance 90,416 Homeowners (in thousands) Incurred Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ 38,589 36,547 34,926 34,273 34,186 34,422 34,566 34,056 34,025 34,010 58 4,570 2008 41,224 41,747 39,342 39,203 38,062 38,410 38,111 38,042 38,045 65 5,139 2009 47,636 44,511 42,609 40,313 61,927 40,400 40,465 40,457 74 5,631 2010 68,373 67,525 63,285 97,761 62,462 62,402 62,339 86 9,128 2011 103,804 98,211 82,744 94,167 94,543 94,183 143 15,102 2012 87,260 82,745 86,560 86,667 86,271 251 16,927 2013 73,670 72,528 71,494 72,145 1,545 7,738 2014 80,111 82,461 83,637 1,928 8,739 2015 76,637 76,400 2,984 7,677 2016 60,105 5,646 6,402 Total 647,592 Homeowners (in thousands) Cumulative Paid Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2007 $ 20,840 30,104 31,846 32,228 33,081 33,862 33,857 33,869 33,953 33,951 2008 21,277 33,535 36,271 37,086 37,763 37,837 37,933 37,939 37,930 2009 28,299 36,965 38,078 39,342 39,731 39,819 39,907 40,189 2010 43,699 58,638 60,295 61,106 62,155 62,227 62,241 2011 71,668 89,963 91,718 92,185 93,312 93,720 2012 69,056 79,584 82,720 84,250 85,196 2013 50,664 65,528 67,838 69,775 2014 61,561 76,007 79,751 2015 52,589 70,078 2016 42,252 Total 615,083 All outstanding liabilities before 2007, net of reinsurance 6,469 Liabilities for loss and loss adjustment expenses, net of reinsurance 38,978 E&S - Liability (in thousands) Incurred Loss and Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ — — — — — — — — 2008 92 169 146 119 52 (162 ) (270 ) 35 2009 885 1,053 938 728 710 96 (630 ) 274 2010 3,294 4,106 3,369 4,299 3,831 3,055 (1,778 ) 797 2011 8,127 7,102 9,853 12,207 10,273 9,652 (599 ) 1,303 2012 42,367 42,621 43,175 46,149 46,165 9,289 1,982 2013 55,468 60,309 67,099 69,112 21,956 2,128 2014 55,316 63,505 69,929 29,236 1,888 2015 75,498 76,432 48,390 2,313 2016 94,451 84,328 1,760 Total 368,730 E&S - Liability (in thousands) Cumulative Paid Loss and Loss Adjustment Expenses, Net of Reinsurance Accident Year 2011 2012 2013 2014 2015 2016 2007 $ — — — — — — 2008 — 24 70 80 79 92 2009 — 198 431 605 626 709 2010 — 1,218 2,570 3,574 4,078 4,513 2011 — 806 3,200 6,445 9,954 9,912 2012 3,722 7,914 16,430 25,064 32,343 2013 2,715 9,470 21,980 35,200 2014 2,353 12,234 25,571 2015 3,036 13,057 2016 3,720 Total 125,117 All outstanding liabilities before 2007, net of reinsurance — Liabilities for loss and loss adjustment expenses, net of reinsurance 243,613 In 2011, the Parent purchased MUSIC, a wholly-owned E&S Lines subsidiary of Montpelier Re Holdings, Ltd. Under the terms of the purchase agreement, the Parent acquired loss and loss adjustment reserves amounting to approximately $15 million . All development on this acquired business was fully reinsured as of the acquisition date. (d) The reconciliation of the net incurred and paid claims development tables to the liability for loss and loss adjustment expenses in the consolidated statement of financial position is as follows: (in thousands) December 31, 2016 Net outstanding liabilities: Standard Commercial Lines General liability 1,070,929 Workers compensation 936,766 Commercial automobile 402,281 Businessowners' policies 86,802 Commercial property 42,279 Other Commercial Lines 11,389 Total Standard Commercial Lines net outstanding liabilities 2,550,446 Standard Personal Lines Personal automobile 90,416 Homeowners 38,978 Other Personal Lines 7,728 Total Personal Lines net outstanding liabilities 137,122 E&S Lines Commercial liability 243,613 Commercial property 13,251 Total E&S Lines net outstanding liabilities 256,864 Total liabilities for unpaid loss and loss adjustment expenses, net of reinsurance 2,944,432 Reinsurance recoverable on unpaid claims: Standard Commercial Lines General liability 179,997 Workers compensation 223,327 Commercial automobile 17,373 Businessowners' policies 7,012 Commercial property 13,615 Other Commercial Lines 2,613 Total Standard Commercial Lines reinsurance recoverable on unpaid loss 443,937 Standard Personal Lines Personal automobile 55,223 Homeowners 3,206 Other Personal Lines 82,625 Total Personal Lines reinsurance recoverable on unpaid loss 141,054 E&S Lines Commercial liability 25,741 Commercial property 468 Total E&S Lines reinsurance recoverable on unpaid loss 26,209 Total reinsurance recoverable on unpaid loss 611,200 Unallocated loss adjustment expenses 136,087 Total gross liability for unpaid loss and loss adjustment expenses 3,691,719 (e) The table below reflects the historical average annual percentage payout of incurred claims by age. For example, the general liability line of business averages payout of 6.5% of its ultimate losses in the first year, 12.4% in the second year, and so forth. The following is supplementary information about average historical claims duration as of December 31, 2016 : Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 7 8 9 10 General liability 6.5% 12.4 15.1 16.6 15.3 10.2 5.5 4.3 2.3 2.2 Workers compensation 19.0 23.9 14.2 8.2 5.3 3.9 3.1 2.4 2.5 1.2 Commercial automobile 38.6 17.6 14.0 12.6 9.2 3.8 1.3 1.2 0.4 0.2 Businessowners’ policies 46.9 20.1 8.3 8.0 6.2 4.8 1.6 1.5 0.9 0.8 Commercial property 70.0 26.3 2.4 0.4 0.4 0.2 0.1 0.1 0.1 0.1 Personal automobile 54.9 18.9 11.3 7.8 4.1 1.6 0.4 0.1 0.3 — Homeowners 69.6 21.8 3.8 1.8 1.6 0.6 0.2 0.1 0.1 0.1 E&S Lines - liability 3.9 12.2 17.8 19.8 16.0 9.5

Indebtedness

Indebtedness	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Indebtedness	Indebtedness The table below provides a summary of our outstanding debt at December 31, 2016 and 2015: Outstanding Debt 2016 Carry Value ($ in thousands) Issuance Date Maturity Date Interest Rate Original Amount Debt Discount and Unamortized Issuance Costs December 31, 2016 December 31, 2015 Description Short-term: (1) FHLBI 1/22/2015 7/22/2016 0.63 % $ 15,000 — — 15,000 (2) FHLBI 12/16/2011 12/16/2016 1.25 % 45,000 — — 45,000 Total short-term debt $ 60,000 — — 60,000 Long-term: (3) FHLBI 12/16/2016 12/16/2026 3.03 % $ 60,000 — 60,000 — (4) FHLBNY 8/15/2016 8/16/2021 1.56 % 25,000 — 25,000 — (5) FHLBNY 7/21/2016 7/21/2021 1.61 % 25,000 — 25,000 — (6) Senior Notes 2/8/2013 2/9/2043 5.875 % 185,000 (4,932 ) 180,068 179,684 (7) Senior Notes 11/3/2005 11/1/2035 6.70 % 100,000 (1,048 ) 98,952 98,890 (8) Senior Notes 11/16/2004 11/15/2034 7.25 % 50,000 (353 ) 49,647 49,618 Total long-term debt $ 445,000 (6,333 ) 438,667 328,192 Short-term Debt (1) In January 2015, Selective Insurance Company of South Carolina ("SICSC") and Selective Insurance Company of the Southeast ("SICSE"), collectively referred to as the "Indiana Subsidiaries," borrowed $15 million in the aggregate from the FHLBI with an interest rate of 0.63% . The funds were used for general corporate purposes. We repaid this borrowing on July 22, 2016. (2) In December 2011, the Indiana Subsidiaries borrowed $45 million in the aggregate from the FHLBI with an interest rate of 1.25% . The funds were loaned to the Parent for use in the acquisition of Mesa Underwriters Specialty Insurance Company ("MUSIC") on December 31, 2011. We repaid this borrowing in December 2016. In addition to the above borrowings, the Parent's line of credit with Wells Fargo Bank, National Association, as administrative agent, and Branch Banking and Trust Company (BB&T) (referred to as our "Line of Credit"), was renewed effective December 1, 2015 , with a borrowing capacity of $30 million , which can be increased to $50 million with the approval of both lending partners. Our Line of Credit expires on December 1, 2020, and has an interest rate, which varies and is based on, among other factors, the Parent’s debt ratings. There were no balances outstanding under our Line of Credit at December 31, 2016 or at any time during 2016 . Our Line of Credit agreement contains representations, warranties, and covenants that are customary for credit facilities of this type, including, without limitation, financial covenants under which we are obligated to maintain a minimum consolidated net worth, minimum combined statutory surplus, maximum ratio of consolidated debt to total capitalization, and covenants limiting our ability to: (i) merge or liquidate; (ii) incur debt or liens; (iii) dispose of assets; (iv) make investments and acquisitions; and (v) engage in transactions with affiliates. The table below outlines information regarding certain of the covenants in the Line of Credit: Required as of Actual as of December 31, 2016 December 31, 2016 Consolidated net worth Not less than $1.1 billion $1.5 billion Statutory surplus Not less than $750 million $1.6 billion Debt-to-capitalization ratio 1 Not to exceed 35% 22.5% A.M. Best financial strength rating Minimum of A- A 1 Calculated in accordance with the Line of Credit agreement. In addition to the above requirements, the Line of Credit agreement contains a cross-default provision that provides that the Line of Credit will be in default if we fail to comply with any condition, covenant, or agreement (including payment of principal and interest when due on any debt with an aggregate principal amount of at least $20 million ), which causes or permits the acceleration of principal. Refer to "Financial Condition, Liquidity, and Capital Resources" in Item 7. "Management's Discussion and Analysis of Financial Condition and Results of Operations." for further discussion regarding limitations on aggregate borrowings by the FHLBI and FHLBNY permitted by our Line of Credit. Long-term Debt (3) In the first quarter of 2009 , the Indiana Subsidiaries joined, and invested in, the FHLBI, which provides them with access to additional liquidity. The Indiana Subsidiaries’ aggregate investment in the FHLBI was $2.8 million at December 31, 2016 and $2.8 million at December 31, 2015 . Our investment provides us the ability to borrow approximately 20 times the total amount of the FHLBI common stock purchased with additional collateral, at comparatively low borrowing rates. In December 2016, the Indiana Subsidiaries borrowed $60 million from the FHLBI at an interest rate of 3.03% . The principal amount of this borrowing is due on December 16, 2026 . $45 million of the proceeds were used to repay the then outstanding $45 million borrowing from the FHLBI and the remaining $15 million was used for general corporate purposes. All borrowings from the FHLBI require security. For information on investments that are pledged as collateral for these borrowings, see Note 5. "Investments" above. (4) In the fourth quarter of 2015 , SICA and Selective Insurance Company of New York ("SICNY") joined, and invested in, the FHLBNY, which provides them with access to additional liquidity. The aggregate investment for both subsidiaries was $2.8 million at December 31, 2016 and $0.5 million at December 31, 2015 . Our investment provides us the ability to borrow approximately 20 times the total amount of the FHLBNY common stock purchased with additional collateral, at comparatively low borrowing rates. In August 2016 , SICA borrowed $25 million from the FHLBNY. The unpaid principal amount accrues interest of 1.56% . The principal amount is due on August 16, 2021 . All borrowings from the FHLBNY require security. For information on investments that are pledged as collateral for these borrowings, see Note 5. "Investments" above. (5) In July 2016 , SICA borrowed $25 million from the FHLBNY. The unpaid principal amount accrues interest of 1.61% . The principal amount is due on July 21, 2021 . (6) In February 2013, we issued $185 million of 5.875% Senior Notes due 2043. The notes are callable by us on or after February 8, 2018, at a price equal to 100% of their principal outstanding amount, plus accrued and unpaid interest to, but excluding, the date of redemption. A portion of the proceeds from this debt issuance was used to fully redeem the $100 million aggregate principal amount of our 7.5% Junior Subordinated Notes due 2066. Of the remaining net proceeds, $57.1 million was used to make capital contributions to the Insurance Subsidiaries, while the balance was used for general corporate purposes. There are no financial debt covenants to which we are required to comply in regards to these Senior Notes. (7) In November 2005, we issued $100 million of 6.70% Senior Notes due 2035 . These notes were issued at a discount of $0.7 million resulting in an effective yield of 6.754% . Net proceeds of approximately $50 million were used to fund an irrevocable trust to provide for certain payment obligations in respect of our outstanding debt. The remainder of the proceeds was used for general corporate purposes. The agreements covering these notes contain a standard default cross-acceleration provision that provides the 6.70% Senior Notes will enter a state of default upon the failure to pay principal when due or upon any event or condition that results in an acceleration of principal of any other debt instrument in excess of $10 million that we have outstanding concurrently with the 6.70% Senior Notes. There are no financial debt covenants to which we are required to comply in regards to these notes. (8) In November 2004, we issued $50 million of 7.25% Senior Notes due 2034 . These notes were issued at a discount of $0.1 million , resulting in an effective yield of 7.27% . We contributed $25 million of the bond proceeds to the Insurance Subsidiaries as capital. The remainder of the proceeds was used for general corporate purposes. The agreements covering these notes contain a standard default cross-acceleration provision that provides the 7.25% Senior Notes will enter a state of default upon the failure to pay principal when due or upon any event or condition that results in an acceleration of principal of any other debt instrument in excess of $10 million that we have outstanding concurrently with the 7.25% Senior Notes. There are no financial debt covenants to which we are required to comply in regards to these notes.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Segment Information	Segment Information The disaggregated results of our four reportable segments are used by senior management to manage our operations. These reportable segments are evaluated as follows: • Our Standard Commercial Lines, Standard Personal Lines, and E&S Lines are evaluated based on statutory underwriting results (net premiums earned, incurred losses and loss expenses, policyholders dividends, policy acquisition costs, and other underwriting expenses), and statutory combined ratios. • Our Investments segment is evaluated based on after-tax net investment income and net realized gains and losses. In computing the results of each segment, we do not make adjustments for interest expense or net general corporate expenses. While we do not fully allocate taxes to all segments, we do allocate taxes to our investments segment as we manage that segment on after-tax results. We do not maintain separate investment portfolios for the segments and therefore, do not allocate assets to the segments. Our combined insurance segments are subject to certain geographic concentrations, particularly in the Northeast and Mid-Atlantic regions of the country. In 2016 , approximately 20% of NPW were related to insurance policies written in New Jersey. The goodwill balance of $7.8 million at both December 31, 2016 and 2015 relates to our Standard Commercial Lines reporting unit. The following summaries present revenues from continuing operations (net investment income and net realized gains on investments in the case of the Investments segment) and pre-tax income for the individual segments: Revenue by Segment Years ended December 31, ($ in thousands) 2016 2015 2014 Standard Commercial Lines: Net premiums earned: Commercial automobile $ 398,942 358,909 333,310 Workers compensation 308,233 290,075 274,585 General liability 527,859 483,291 444,938 Commercial property 293,438 269,022 244,792 Businessowners’ policies 97,754 93,428 85,788 Bonds 23,227 20,350 19,288 Other 16,030 14,367 13,011 Miscellaneous income 7,782 6,343 14,747 Total Standard Commercial Lines revenue 1,673,265 1,535,785 1,430,459 Standard Personal Lines: Net premiums earned: Personal automobile 142,876 146,784 151,317 Homeowners 130,973 134,382 134,273 Other 6,758 6,968 11,157 Miscellaneous income 1,098 1,113 1,834 Total Standard Personal Lines revenue 281,705 289,247 298,581 E&S Lines: Net premiums earned: Commercial liability 151,638 126,064 99,086 Commercial property 51,844 46,269 41,064 Miscellaneous income 1 — 17 Total E&S Lines revenue 203,483 172,333 140,167 Investments: Net investment income 130,754 121,316 138,708 Net realized investment (losses) gains (4,937 ) 13,171 26,599 Total investment revenues 125,817 134,487 165,307 Total all segments 2,284,270 2,131,852 2,034,514 Other income — — 347 Total revenues $ 2,284,270 2,131,852 2,034,861 Income before Federal Income Tax Years ended December 31, ($ in thousands) 2016 2015 2014 Standard Commercial Lines: Underwriting gain, before federal income tax $ 146,435 164,496 61,221 GAAP combined ratio 91.2 % 89.2 % 95.7 % Statutory combined ratio 89.9 % 89.2 % 95.5 % Standard Personal Lines: Underwriting gain, before federal income tax 12,419 1,336 16,536 GAAP combined ratio 95.6 % 99.5 % 94.4 % Statutory combined ratio 95.2 % 99.9 % 94.5 % E&S Lines: Underwriting (loss) gain, before federal income tax (6,921 ) (16,803 ) 386 GAAP combined ratio 103.4 % 109.8 % 99.7 % Statutory combined ratio 102.1 % 108.4 % 99.2 % Investments: Net investment income $ 130,754 121,316 138,708 Net realized investment (losses) gains (4,937 ) 13,171 26,599 Total investment income, before federal income tax 125,817 134,487 165,307 Tax on investment income 30,621 32,090 43,811 Total investment income, after federal income tax $ 95,196 102,397 121,496 Reconciliation of Segment Results to Income before Federal Income Tax Years ended December 31, ($ in thousands) 2016 2015 2014 Underwriting gain (loss), before federal income tax Standard Commercial Lines $ 146,435 164,496 61,221 Standard Personal Lines 12,419 1,336 16,536 E&S Lines (6,921 ) (16,803 ) 386 Investment income, before federal income tax 125,817 134,487 165,307 Total all segments 277,750 283,516 243,450 Interest expense (22,771 ) (22,428 ) (23,063 ) General corporate and other expenses (35,024 ) (28,396 ) (23,256 ) Income, before federal income tax $ 219,955 232,692 197,131

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Earnings Per Share	Earnings per Share The following table provides a reconciliation of the numerators and denominators of basic and diluted earnings per share ("EPS"): 2016 Income Shares Per Share ($ in thousands, except per share amounts) (Numerator) (Denominator) Amount Basic EPS: Net income available to common stockholders $ 158,495 57,889 $ 2.74 Effect of dilutive securities: Stock compensation plans — 858 Diluted EPS: Net income available to common stockholders $ 158,495 58,747 $ 2.70 2015 Income Shares Per Share ($ in thousands, except per share amounts) (Numerator) (Denominator) Amount Basic EPS: Net income available to common stockholders $ 165,861 57,212 $ 2.90 Effect of dilutive securities: Stock compensation plans — 944 Diluted EPS: Net income available to common stockholders $ 165,861 58,156 $ 2.85 2014 Income Shares Per Share ($ in thousands, except per share amounts) (Numerator) (Denominator) Amount Basic EPS: Net income available to common stockholders $ 141,827 56,310 $ 2.52 Effect of dilutive securities: Stock compensation plans — 1,041 Diluted EPS: Net income available to common stockholders $ 141,827 57,351 $ 2.47

Federal Income Taxes

Federal Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal Income Taxes	Federal Income Taxes (a) A reconciliation of federal income tax on income at the corporate rate to the effective tax rate is as follows: ($ in thousands) 2016 2015 2014 Tax at statutory rate of 35% $ 76,984 81,442 68,996 Tax-advantaged interest (12,126 ) (13,164 ) (12,926 ) Dividends received deduction (1,114 ) (1,817 ) (1,121 ) Other (2,284 ) 370 355 Federal income tax expense from continuing operations $ 61,460 66,831 55,304 (b) The tax effects of the significant temporary differences that give rise to deferred tax assets and liabilities are as follows: ($ in thousands) 2016 2015 Deferred tax assets: Net loss reserve discounting $ 70,065 74,436 Net unearned premiums 78,201 72,057 Employee benefits 17,881 30,432 Long-term incentive compensation plans 17,750 15,551 Temporary investment write-downs 2,475 5,419 Other investment related items, net 1,484 — Net operating loss 771 1,454 Other 8,344 8,132 Total deferred tax assets 196,971 207,481 Deferred tax liabilities: Deferred policy acquisition costs 75,310 72,481 Unrealized gains on investment securities 22,681 24,228 Other investment-related items, net — 5,566 Accelerated depreciation and amortization 14,140 12,510 Total deferred tax liabilities 112,131 114,785 Net deferred federal income tax asset $ 84,840 92,696 After considering all evidence, both positive and negative, with respect to our federal tax loss carryback availability, expected levels of pre-tax financial statement income, and federal taxable income, we believe it is more likely than not that the existing deductible temporary differences will reverse during periods in which we generate net federal taxable income or have adequate federal carryback availability. As a result, we have no valuation allowance recognized for federal deferred tax assets at December 31, 2016 or 2015 . As of December 31, 2016 , we had federal tax net operating loss ("NOL") carryforwards of $2.2 million . These NOLs, which are subject to an annual limitation of $1.9 million , will expire between 2030 and 2031 as follows: ($ in thousands) Gross NOL Tax Effected NOL 2030 $ 2,124 744 2031 79 28 Total NOL carryforwards $ 2,203 772 Stockholders' equity reflects tax benefits related to compensation expense deductions for share-based compensation awards of $23.8 million at December 31, 2016 , $22.0 million at December 31, 2015 , and $20.2 million at December 31, 2014 . We have analyzed our tax positions in all open tax years, which as of December 31, 2016 were 2013 through 2015 . The 2013 tax year is currently under audit. We do not expect any material adjustments to arise out of the 2013 audit. We do not have unrecognized tax expense or benefit as of December 31, 2016 . We believe our tax positions will more likely than not be sustained upon examination, including related appeals or litigation. In the event we had a tax position that did not meet the more likely than not criteria, any tax, interest, and penalties incurred related to such a position would be reflected in "Total federal income tax expense" on our Consolidated Statements of Income.

Retirement Plans

Retirement Plans	12 Months Ended
	Dec. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Retirement Plans	Retirement Plans (a) Selective Insurance Retirement Savings Plan (“Retirement Savings Plan”) SICA offers a voluntary defined contribution 401(k) plan, which is available to most of our employees and is a tax-qualified retirement plan subject to the Employee Retirement Income Security Act of 1974 ("ERISA"). Expense recorded for this plan was $15.0 million in 2016 , $14.1 million in 2015 , and $13.4 million in 2014 . (b) Deferred Compensation Plan SICA offers a nonqualified deferred compensation plan ("Deferred Compensation Plan") to a group of management or highly compensated employees as a method of recognizing and retaining such employees. The Deferred Compensation Plan provides these employees the opportunity to elect to defer receipt of specified portions of compensation and to have such deferred amounts deemed to be invested in specified investment options. In addition to the employee deferrals, SICA may choose to make matching contributions to some or all of the participants in this plan to the extent the participant did not receive the maximum matching or non-elective contributions permissible under the Retirement Savings Plan due to limitations under the Internal Revenue Code or the Retirement Savings Plan. Expense recorded for these contributions was $0.3 million in 2016 and $0.2 million in both 2015 and 2014 . (c) Retirement Income Plan and Retirement Life Plan SICA's primary pension plan is the Retirement Income Plan for Selective Insurance Company of America (the "Pension Plan"). This qualified, noncontributory defined benefit plan is closed to new entrants and existing participants ceased accruing benefits after March 31, 2016 . In addition to the Pension Plan, SICA also sponsors the Supplemental Excess Retirement Plan (the "Excess Plan") and a life insurance benefit plan (the "Retirement Life Plan"). Both of these plans are closed to new entrants and participants in the Excess Plan ceased accruing benefits after March 31, 2016 . The Retirement Life Plan does not accrue benefits and this plan applies only to retirees who terminated employment with SICA on or before March 31, 2009. These are both unfunded plans with benefit obligations as of December 31, 2016 and December 31, 2015 of $9.1 million and $8.5 million , respectively, for the Excess Plan and $6.3 million and $6.0 million , respectively, for the Retiree Life Plan. Expense recorded for the Excess Plan was $0.5 million in 2016 , $0.8 million in 2015 , and $0.6 million in 2014 . Expense recorded for the Retiree Life Plan was $0.3 million in 2016 and 2015 , and $0.4 million in 2014 . The following tables provide details on the Pension Plan for 2016 and 2015 : December 31, Pension Plan ($ in thousands) 2016 2015 Change in Benefit Obligation: Benefit obligation, beginning of year $ 310,308 322,271 Service cost 1,647 7,215 Interest cost 12,336 13,668 Actuarial losses (gains) 15,086 (24,994 ) Benefits paid (8,789 ) (7,852 ) Benefit obligation, end of year $ 330,588 310,308 Change in Fair Value of Assets: Fair value of assets, beginning of year $ 249,700 253,452 Actual return on plan assets, net of expenses 21,079 (7,600 ) Contributions by the employer to funded plans 54,525 11,700 Benefits paid (8,789 ) (7,852 ) Fair value of assets, end of year $ 316,515 249,700 Funded status $ (14,073 ) (60,608 ) Amounts Recognized in the Consolidated Balance Sheet: Liabilities $ (14,073 ) (60,608 ) Net pension liability, end of year $ (14,073 ) (60,608 ) Amounts Recognized in AOCI: Net actuarial loss $ 85,845 80,828 Total $ 85,845 80,828 Other Information as of December 31: Accumulated benefit obligation $ 330,588 310,307 Weighted-Average Liability Assumptions as of December 31: Discount rate 4.41 % 4.69 Rate of compensation increase — 4.00 Pension Plan ($ in thousands) 2016 2015 2014 Components of Net Periodic Benefit Cost and Other Amounts Recognized in Other Comprehensive Income: Net Periodic Benefit Cost: Service cost $ 1,647 7,215 5,763 Interest cost 12,336 13,668 12,776 Expected return on plan assets (17,309 ) (15,969 ) (15,671 ) Amortization of unrecognized actuarial loss 6,299 6,831 1,776 Total net periodic cost $ 2,973 11,745 4,644 Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income: Net actuarial loss (gain) $ 11,316 (1,425 ) 52,556 Reversal of amortization of net actuarial loss (6,299 ) (6,831 ) (1,776 ) Total recognized in other comprehensive income $ 5,017 (8,256 ) 50,780 Total recognized in net periodic benefit cost and other comprehensive income $ 7,990 3,489 55,424 The estimated net actuarial loss for the Pension Plan that will be amortized from AOCI into net periodic benefit cost during the 2017 fiscal year is $1.9 million . This is lower than the $6.3 million amortized in 2016 due to a change in the amortization period for the net actuarial loss. Historically, the amortization period was the average remaining service life of the active participants. However, as the Pension Plan is no longer accruing service benefits, the amortization period has changed to the average remaining life expectancy of plan participants. Pension Plan 2016 2015 2014 Weighted-Average Expense Assumptions for the years ended December 31: Discount rate 4.69 % 4.29 5.16 Expected return on plan assets 6.37 6.27 6.92 Rate of compensation increase 1 — 4.00 4.00 1 This assumption was 4.00% through March 31, 2016, the date after which benefits ceased accruing for all participants of the Pension Plan. Our latest measurement date was December 31, 2016 and we decreased our expected return on plan assets to 6.24% , reflecting the current interest rate environment. When determining the most appropriate discount rate to be used in the valuation, we consider, among other factors, our expected payout patterns of the Pension Plan's obligations as well as our investment strategy and we ultimately select the rate that we believe best represents our estimate of the inherent interest rate at which our pension and post-retirement life benefits can be effectively settled. Effective January 1, 2016, the approach used to calculate the service and interest components of net periodic benefit cost for benefit plans was changed to provide a more precise measurement of service and interest costs. Prior to 2016, we calculated these service and interest components utilizing a single weighted-average discount rate derived from the yield curve used to measure the benefit obligation at the beginning of the period. Beginning in 2016, we elected to utilize an approach that discounts the individual expected cash flows using the applicable spot rates derived from the yield curve over the projected cash flow period. We have accounted for this change prospectively as a change in accounting estimate. The weighted average discount rate used to determine 2017 interest cost is 3.83% . Plan Assets Assets of the Pension Plan are invested to ensure that principal is preserved and enhanced over time. Our return objective is to exceed the returns of the plan's policy benchmark, which is the return the plan would have earned if the assets were invested according to the target asset class weightings and earned index returns shown below. In 2017, we will continue to phase in adjustments to the asset allocation to steadily close the gap between the duration of the assets and the duration of the liabilities, provided certain improved funding targets are achieved. The Pension Plan’s equity investments may not contain investments in any one security greater than 8% of the portfolio value without notification to our management investment committee, nor have more than 5% of the outstanding shares of any one corporation or other entity. The use of derivative instruments is permitted under certain circumstances, but shall not be used for unrelated speculative hedging or to apply leverage to portfolio positions. Within the alternative investments portfolio, some leverage is permitted as defined and limited by the partnership agreements. The plan’s target ranges, as well as the actual weighted average asset allocation by asset class, at December 31 were as follows: 2016 2015 Target Ranges Actual Percentage Actual Percentage Long duration fixed income 40%-100% 53 % 60 % Global equity 0%-40% 33 % 36 % Alternatives & other return seeking assets 1 0%-30% 6 % 3 % Cash and short-term investments 0%-5% 8 % 1 % Total — % 100 % 100 % 1 Includes limited partnerships. At December 31, 2016, the Pension Plan's allocation to cash and short-term investments was slightly above the targeted range, as we were analyzing the most effective deployment of these balances considering current market conditions. The Pension Plan had no investments in the Parent’s common stock as of December 31, 2016 or 2015 . The techniques used to determine the fair value of the Pension Plan's invested assets are as follows: • Short-term investments are carried at cost, which approximates fair value. Given that these investments are listed on active exchanges, coupled with their liquid nature, these investments are classified as Level 1 in the fair value hierarchy. • The deposit administration contract is carried at cost, which approximates fair value. Given the liquid nature of the underlying investments in overnight cash deposits and other short-term duration products, we have determined that a correlation exists between the deposit administration contract and other short-term investments, such as money market funds. As such, this investment is classified as Level 2 in the fair value hierarchy. • The long-duration fixed income mutual funds utilize a market approach wherein the quoted prices in the active market for identical assets are used. All of the mutual funds are traded in active markets at their net asset value per share. These investments are classified as Level 1 in the fair value hierarchy. • The investments in global equity collective investment funds and in private equity limited partnerships are valued utilizing net asset value as a practical expedient for fair value. These investments are not classified in the fair value hierarchy. For discussion regarding the levels within the fair value hierarchy, see Note 2. "Summary of Significant Accounting Policies." In addition, refer to Note 5. "Investments" for discussion regarding the limited partnership investment strategies, excluding the middle market lending strategy, as these investments are not part of the Pension Plan. The following tables provide quantitative disclosures of the Pension Plan’s invested assets that are measured at fair value on a recurring basis: December 31, 2016 Fair Value Measurements at 12/31/16 Using ($ in thousands) Assets Measured at Fair Value At 12/31/16 Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Description Long-duration fixed income: Global asset allocation fund $ 37,878 37,878 — — Extended duration fixed income 131,457 131,457 — — Total long duration fixed income 169,335 169,335 — — Cash and short-term investments: Short-term investments 23,722 23,722 — — Deposit administration contracts 1,832 — 1,832 — Total cash and short-term investments 25,554 23,722 1,832 — Global equity, at net asset value 1 : Non-U.S. equity 48,836 — — — U.S. equity 55,073 — — — Total global equity 103,909 — — — Private equity (limited partnerships, at net asset value) 1 : Real assets 15,466 — — — Private equity 1,615 — — — Private credit 1,108 — — — Total private equity 18,189 — — — Total invested assets $ 316,987 193,057 1,832 — December 31, 2015 Fair Value Measurements at 12/31/15 Using ($ in thousands) Assets Measured at Fair Value At 12/31/15 Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Description Long-duration fixed income: Global asset allocation fund $ 33,565 33,565 — — Extended duration fixed income 117,297 117,297 — — Total long duration fixed income 150,862 150,862 — — Cash and short-term investments: Short-term investments 1,600 1,600 — — Deposit administration contracts 1,418 — 1,418 — Total cash and short-term investments 3,018 1,600 1,418 — Global equity, at net asset value 1 : Non-U.S. equity 42,603 — — — U.S. equity 46,840 — — — Total global equity 89,443 — — — Private equity (limited partnerships, at net asset value) 1 : Private equity 2,626 — — — Real assets 2,514 — — — Private credit 1,318 — — — Total private equity 6,458 — — — Total invested assets $ 249,781 152,462 1,418 — 1 In accordance with ASU 2015-07, certain investments that are measured at fair value using the net asset value per share (or its practical expedient) have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to total Pension Plan invested assets. Contributions We presently do not anticipate contributing to the Pension Plan in 2017 , as we have no minimum required contribution amounts. Benefit Payments ($ in thousands) Pension Plan Benefits Expected to be Paid in Future Fiscal Years: 2017 $ 10,830 2018 12,041 2019 13,125 2020 14,184 2021 15,124 2022-2026 89,771

Share-Based Payments

Share-Based Payments	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]	Share-Based Payments Active Plans As of December 31, 2016 , the following four plans were available for the issuance of share-based payment awards: • The 2014 Omnibus Stock Plan (the "Stock Plan"); • The Cash Incentive Plan, amended and restated effective as of May 1, 2014 (the "Cash Plan"); • The Employee Stock Purchase Plan (2009) ("ESPP"); and • The Amended and Restated Stock Purchase Plan for Independent Insurance Agencies (the "Agent Plan"). The following table provides information regarding the approval of these plans: Plan Approvals Stock Plan Approved effective as of May 1, 2014 by stockholders on April 23, 2014. Cash Plan Approved effective April 1, 2005 by stockholders on April 27, 2005. ESPP Approved by stockholders on April 29, 2009 effective July 1, 2009. Agent Plan Approved by stockholders on April 26, 2006. The types of awards that can be issued under each of these plans are as follows: Plan Types of Share-Based Payments Issued Stock Plan Qualified and nonqualified stock options, stock appreciation rights ("SARs"), restricted stock, restricted stock units ("RSUs"), stock grants, and other awards valued in whole or in part by reference to the Parent's common stock. The maximum exercise period for an option grant under this plan is 10 years from the date of the grant. Dividend equivalent units ("DEUs") are earned during the vesting period on RSU grants. The DEUs are reinvested in the Parent's common stock at fair value on each dividend payment date. The requisite service period for grants to employees under this plan is the lesser of: (i) the stated vested date, which is typically three years from issuance; or (ii) the date the employee becomes eligible to retire. Cash Plan Cash incentive units (“CIUs”). The initial dollar value of each CIU will be adjusted to reflect the percentage increase or decrease in the total shareholder return on the Parent's common stock over a specified performance period. In addition, for certain grants, the number of CIUs granted will be increased or decreased to reflect our performance on specified performance indicators as compared to targeted peer companies. The requisite service period for grants under this plan is the lesser of: (i) the stated vested date, which is typically three years from issuance; or (ii) the date the employee becomes eligible to retire. ESPP Enables employees to purchase shares of the Parent’s common stock. The purchase price is the lower of: (i) 85% of the closing market price at the time the option is granted; or (ii) 85% of the closing price at the time the option is exercised. Shares are generally issued on June 30 and December 31 of each year. Agent Plan Quarterly offerings to purchase the Parent's common stock at a 10% discount with a one year restricted period during which the shares purchased cannot be sold or transferred. Only our independent retail insurance agencies and wholesale general agencies, and certain eligible persons associated with the agencies, are eligible to participate in this plan. Shares authorized and available for issuance as of December 31, 2016 are as follows: As of December 31, 2016 Authorized Available for Issuance Awards Outstanding Stock Plan 3,500,000 2,835,694 607,156 ESPP 1,500,000 574,722 — Agent Plan 3,000,000 1,867,287 — Retired Plans The following plans are closed for the issuance of new awards, although awards outstanding continue in effect according to the terms of the applicable award agreements: December 31, 2016 Types of Share-Based Payments Issued Reserve Shares Awards Outstanding 1 Plan 2005 Omnibus Stock Plan ("2005 Stock Plan") Qualified and nonqualified stock options, SARs, restricted stock, RSUs, phantom stock, stock bonuses, and other awards in such amounts and with such terms and conditions as it determined, subject to the provisions of the 2005 Stock Plan. The maximum exercise period for an option grant under this plan is 10 years from the date of the grant. DEUs are earned during the vesting period on RSU grants. The DEUs are reinvested in the Parent's common stock at fair value on each dividend payment date. 2,664,594 726,394 Parent's Stock Compensation Plan for Non-employee Directors ("Directors Stock Compensation Plan") Directors could elect to receive a portion of their annual compensation in shares of the Parent's common stock. 67,242 67,242 1 Awards outstanding under the 2005 Stock Plan consisted of 371,003 RSUs and 355,391 stock options. RSU Transactions A summary of the RSU transactions under our share-based payment plans is as follows: Number Weighted Unvested RSU awards at December 31, 2015 1,018,530 $ 22.55 Granted in 2016 299,670 32.53 Vested in 2016 (389,245 ) 21.56 Forfeited in 2016 (12,315 ) 24.97 Unvested RSU awards at December 31, 2016 916,640 $ 26.20 As of December 31, 2016 , total unrecognized compensation expense related to unvested RSU awards granted under our stock plans was $5.3 million . That expense is expected to be recognized over a weighted-average period of 1.8 years . The total intrinsic value of RSUs vested was $12.6 million for 2016 , $10.3 million for 2015 , and $8.5 million for 2014 . In connection with vested RSUs, the total value of the DEU shares that vested was $0.7 million during each of 2016 , 2015 , and 2014 . Option Transactions A summary of the stock option transactions under our share-based payment plans is as follows: Number Weighted Weighted Aggregate Outstanding at December 31, 2015 493,428 $ 17.84 Granted in 2016 — — Exercised in 2016 (138,037 ) 20.33 Forfeited or expired in 2016 — — Outstanding at December 31, 2016 355,391 $ 16.87 2.14 $ 9,304 Exercisable at December 31, 2016 355,391 $ 16.87 2.14 $ 9,304 The total intrinsic value of options exercised was $2.3 million during 2016 , $2.2 million in 2015 , and $0.8 million in 2014 . CIU Transactions The liability recorded in connection with our Cash Plan was $32.0 million at December 31, 2016 and $26.5 million at December 31, 2015 . The remaining cost associated with the CIUs is expected to be recognized over a weighted average period of 1.2 years . The CIU payments made were $14.3 million in 2016 , $10.2 million in 2015 , and $9.0 million in 2014 . ESPP and Agent Plan Transactions A summary of ESPP and Agent Plan share issuances is as follows: 2016 2015 2014 ESPP Issuances 88,432 100,944 106,832 Agent Plan Issuances 69,867 82,142 78,724 Fair Value Measurements The grant date fair value of RSUs is based on the market price of our common stock on the grant date, adjusted for the present value of our expected dividend payments. The expense recognized for share-based awards is based on the number of shares or units expected to be issued at the end of the performance period and the grant date fair value. The grant date fair value of each option award is estimated using the Black Scholes option valuation model ("Black Scholes"). The following are the significant assumptions used in applying Black Scholes: (i) the risk-free interest rate, which is the implied yield currently available on U.S. Treasury zero-coupon issues with an equal remaining term; (ii) the expected term, which is based on historical experience of similar awards; (iii) the dividend yield, which is determined by dividing the expected per share dividend during the coming year by the grant date stock price; and (iv) the expected volatility, which is based on the volatility of the Parent's stock price over a historical period comparable to the expected term. In applying Black Scholes, we use the weighted average assumptions illustrated in the following table: ESPP 2016 2015 2014 Risk-free interest rate 0.47 % 0.10 0.07 Expected term 6 months 6 months 6 months Dividend yield 1.7 % 2.0 2.0 Expected volatility 31 % 20 21 The weighted-average fair value of options and stock per share, including RSUs granted for the Parent's stock plans, during 2016 , 2015 , and 2014 was as follows: 2016 2015 2014 RSUs $ 32.53 25.22 21.58 ESPP: Six month option 2.63 1.26 1.24 Discount of grant date market value 5.23 4.16 3.87 Total ESPP 7.86 5.42 5.11 Agent Plan: Discount of grant date market value 3.79 2.94 2.42 The fair value of the CIU liability is remeasured at each reporting period through the settlement date of the awards, which is three years from the date of grant based on an amount expected to be paid. A Monte Carlo simulation is performed to approximate the projected fair value of the CIUs that, in accordance with the Cash Plan, is adjusted to reflect our performance on specified indicators as compared to targeted peer companies. Expense Recognition The following table provides share-based compensation expense in 2016 , 2015 , and 2014 : ($ in millions) 2016 2015 2014 Share-based compensation expense, pre-tax $ 30.3 23.8 18.6 Income tax benefit (10.3 ) (8.0 ) (6.2 ) Share-based compensation expense, after-tax $ 20.0 15.8 12.4

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2016
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions William M. Rue, a Director of the Parent, is Chairman of, and owns more than 10% of the equity of, Chas. E. Rue & Son, Inc., t/a Rue Insurance, a general independent retail insurance agency ("Rue Insurance"). Rue Insurance is an appointed distribution partner of the Insurance Subsidiaries on terms and conditions similar to those of our other distribution partners and includes the right to participate in the Agent Plan. Mr. Rue’s son is President, and an employee, of Rue Insurance and Mr. Rue’s daughter is an employee of Rue Insurance. Our relationship with Rue Insurance has existed since 1928. Rue Insurance placed insurance policies with the Insurance Subsidiaries for its customers and itself. Direct premiums written associated with these policies were $10.4 million in 2016 , $9.6 million in 2015 , and $9.0 million in 2014 . In return, the Insurance Subsidiaries paid standard market commissions to Rue Insurance of $2.1 million in 2016 , $1.7 million in 2015 , and $1.6 million in 2014 including supplemental commissions. Amounts due to Rue Insurance at December 31, 2016 and December 31, 2015 were $0.7 million and $0.6 million , respectively. In 2005, we established a private foundation, now named The Selective Insurance Group Foundation (the "Foundation"), under Section 501(c)(3) of the Internal Revenue Code. The Board of Directors of the Foundation is comprised of some of the Parent's officers. We made no contributions to the Foundation in 2016 . We made contributions to the Foundation in the amount of $1.0 million in 2015 and $0.8 million in 2014 .

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies (a) We purchase annuities from life insurance companies to fulfill obligations under claim settlements that provide for periodic future payments to claimants. As of December 31, 2016 , we had purchased such annuities with a present value of $17.9 million for settlement of claims on a structured basis for which we are contingently liable. To our knowledge, there are no material defaults from any of the issuers of such annuities. (b) We have various operating leases for office space, equipment, and fleet vehicles. Such lease agreements, which expire at various times, are generally renewed or replaced by similar leases. Rental expense under these leases amounted to $17.3 million in 2016 , $17.4 million in 2015 , and $15.6 million in 2014 . We also lease computer hardware and software under capital lease agreements expiring at various dates through 2019 . See item (p) of Note 2. "Summary of Significant Accounting Policies" in this Form 10-K for information on our accounting policy regarding leases. In addition, certain of these leases are non-cancelable, and liability for payment will continue even though the leased asset may no longer be in use. At December 31, 2016 , the total future minimum rental commitments under non-cancelable leases were as follows: ($ in millions) Capital Leases Operating Leases Total 2017 $ 4.0 9.1 13.1 2018 2.2 7.7 9.9 2019 0.1 5.6 5.7 2020 — 4.4 4.4 2021 — 2.9 2.9 After 2021 — 4.7 4.7 Total minimum payment required $ 6.3 34.4 40.7 (c) At December 31, 2016 , we have contractual obligations that expire at various dates through 2030 to invest up to an additional $143.7 million in alternative and other investments. There is no certainty that any such additional investment will be required. For additional information regarding these investments, see item (f) of Note 5. "Investments" in this Form 10-K.

Litigation

Litigation	12 Months Ended
	Dec. 31, 2016
Loss Contingency, Information about Litigation Matters [Abstract]
Litigation	Litigation In the ordinary course of conducting business, we are named as defendants in various legal proceedings. Most of these proceedings are claims litigation involving our Insurance Subsidiaries as either: (i) liability insurers defending or providing indemnity for third-party claims brought against our customers; or (ii) insurers defending first-party coverage claims brought against them. We account for such activity through the establishment of unpaid losses and loss expense reserves. We expect that any potential ultimate liability in such ordinary course claims litigation will not be material to our consolidated financial condition, results of operations, or cash flows after consideration of provisions made for potential losses and costs of defense. From time to time, our Insurance Subsidiaries also are named as defendants in other legal actions, some of which assert claims for substantial amounts. These actions include, among others, putative class actions seeking certification of a state or national class. Such putative class actions have alleged, for example, improper reimbursement of medical providers paid under workers compensation and personal and commercial automobile insurance policies. Similarly, our Insurance Subsidiaries are also named from time-to-time in individual actions seeking extra-contractual damages, punitive damages, or penalties, some of which allege bad faith in the handling of insurance claims. We believe that we have valid defenses to these cases. We expect that any potential ultimate liability in any such lawsuit will not be material to our consolidated financial condition, after consideration of provisions made for estimated losses. Nonetheless, given the inherent unpredictability of litigation and the large or indeterminate amounts sought in certain of these actions, an adverse outcome in certain matters could possibly have a material adverse effect on our consolidated results of operations or cash flows in particular quarterly or annual periods. As of December 31, 2016 , we do not believe the Company was involved in any legal action that could have a material adverse effect on our consolidated financial condition, results of operations, or cash flows.

Statutory Financial Information

Statutory Financial Information, Capital Requirements, and Restrictions on Dividends and Transfers of Funds	12 Months Ended
	Dec. 31, 2016
Insurance [Abstract]
Statutory Financial Information, Capital Requirments, and Retrictions on Dividends and Transfers of Funds	Statutory Financial Information, Capital Requirements, and Restrictions on Dividends and Transfers of Funds (a) Statutory Financial Information The Insurance Subsidiaries prepare their statutory financial statements in accordance with accounting principles prescribed or permitted by the various state insurance departments of domicile. Prescribed statutory accounting principles include state laws, regulations, and general administrative rules, as well as a variety of publications of the National Association of Insurance Commissioners (“NAIC"). Permitted statutory accounting principles encompass all accounting principles that are not prescribed; such principles differ from state to state, may differ from company to company within a state and may change in the future. The Insurance Subsidiaries do not utilize any permitted statutory accounting principles that materially affect the determination of statutory surplus, statutory net income, or risk-based capital (“RBC”). As of December 31, 2016 , the various state insurance departments of domicile have adopted the March 2016 version of the NAIC Accounting Practices and Procedures manual in its entirety, as a component of prescribed or permitted practices. The following table provides statutory data for each of our Insurance Subsidiaries: State of Domicile Unassigned Surplus Statutory Surplus Statutory Net Income ($ in millions) 2016 2015 2016 2015 2016 2015 2014 SICA New Jersey $ 414.4 366.6 568.6 520.8 72.2 69.6 83.9 Selective Way Insurance Company ("SWIC") New Jersey 260.5 223.6 309.5 272.6 41.2 42.3 37.0 SICSC Indiana 110.6 96.6 141.9 127.9 17.4 15.9 14.0 SICSE Indiana 83.5 70.7 109.1 96.2 13.4 12.1 10.5 SICNY New York 74.1 65.3 101.8 93.0 12.9 12.7 10.3 Selective Insurance Company of New England ("SICNE") New Jersey 13.6 9.2 43.7 39.4 5.9 5.5 4.4 Selective Auto Insurance Company of New Jersey ("SAICNJ") New Jersey 36.9 26.4 79.8 69.2 11.5 10.8 9.1 MUSIC New Jersey 16.7 7.0 85.2 75.5 9.7 9.5 7.3 Selective Casualty Insurance Company ("SCIC") New Jersey 26.6 17.8 101.0 92.3 12.6 12.1 9.6 Selective Fire and Casualty Insurance Company ("SFCIC") New Jersey 11.3 7.5 43.2 39.4 5.5 5.3 4.2 Total $ 1,048.2 890.7 1,583.8 1,426.3 202.3 195.8 190.3 (b) Capital Requirements The Insurance Subsidiaries are required to maintain certain minimum amounts of statutory surplus to satisfy the requirements of their various state insurance departments of domicile. RBC requirements for property and casualty insurance companies are designed to assess capital adequacy and to raise the level of protection that statutory surplus provides for policyholders. The Insurance Subsidiaries' combined total adjusted capital exceeded the authorized control level RBC, as defined by the NAIC based on their 2016 statutory financial statements. In addition to statutory capital requirements, we are impacted by various rating agency requirements related to certain rating levels. These required capital levels may be more than statutory requirements. (c) Restrictions on Dividends and Transfers of Funds Our ability to declare and pay dividends on the Parent's common stock is dependent on liquidity at the Parent coupled with the ability of the Insurance Subsidiaries to declare and pay dividends, if necessary, and/or the availability of other sources of liquidity to the Parent. As of December 31, 2016 , the Parent had an aggregate of $91.7 million in investments and cash available to fund future dividends and interest payments. These amounts are not subject to any regulatory restrictions other than standard state insolvency restrictions, whereas our consolidated retained earnings of $1.5 billion is predominately restricted due to the regulation associated with our Insurance Subsidiaries. In 2017 , the Insurance Subsidiaries have the ability to provide for $192.7 million in annual dividends to the Parent; however, as regulated entities, these dividends are subject to certain restrictions, which are further discussed below. The Parent also has available to it other potential sources of liquidity, such as: (i) borrowings from our Indiana Subsidiaries; (ii) debt issuances; (iii) common stock issuances; and (iv) borrowings under our Line of Credit. Borrowings from our Indiana Subsidiaries are governed by approved intercompany lending agreements with the Parent that provide for additional capacity of $68.6 million as of December 31, 2016 , after considering that borrowings under these lending agreements are restricted to 10% of the admitted assets of these respective subsidiaries. For additional information regarding the Parent's Line of Credit, refer to "Financial Condition, Liquidity, and Capital Resources" in Item 7. "Management’s Discussion and Analysis of Financial Condition and Results of Operations.” of this Form 10-K. For additional restrictions on the Parent's debt, see Note 10. "Indebtedness" in this Form 10-K. Insurance Subsidiaries Dividend Restrictions As noted above, the restriction on our net assets and retained earnings is predominantly driven by our Insurance Subsidiaries' ability to pay dividends to the Parent under applicable law and regulations. Under the insurance laws of the domiciliary states of the Insurance Subsidiaries, New Jersey, Indiana, and New York, an insurer can potentially make an ordinary dividend payment if its statutory surplus following such dividend is reasonable in relation to its outstanding liabilities, is adequate to its financial needs, and the dividend does not exceed the insurer's unassigned surplus. In general, New Jersey defines an ordinary dividend as a dividend whose fair market value, together with other dividends made within the preceding 12 months, is less than the greater of 10% of the insurer's statutory surplus as of the preceding December 31, or the insurer's net income (excluding capital gains) for the 12-month period ending on the preceding December 31 . Indiana's ordinary dividend calculation differs from New Jersey's, in that it is the lessor of 10% of the insurer's statutory surplus, or the insurer's net income. Indiana's net income is computed by subtracting the amount of dividends paid in the first and second preceding calendar years from the aggregate net income (excluding capital gains), of the second and third preceding calendar years. In general, New York defines an ordinary dividend as a dividend whose fair market value, together with other dividends made within the preceding 12 months, is less than the lesser of 10% of the insurer's statutory surplus, or 100% of adjusted net investment income. New Jersey and Indiana require notice of the declaration of any ordinary dividend distribution. During the notice period, the relevant state regulatory authority may disallow all or part of the proposed dividend if it determines that the dividend is not appropriate given the above considerations. New York does not require notice of ordinary dividends. Dividend payments exceeding ordinary dividends are referred to as extraordinary dividends and require review and approval by the applicable domiciliary insurance regulatory authority prior to payment. The following table provides quantitative data regarding all Insurance Subsidiaries' dividends paid to the Parent in 2016 for debt service, shareholder dividends, and general operating purposes: Dividends Twelve Months ended December 31, 2016 ($ in millions) State of Domicile Ordinary Dividends Paid SICA New Jersey $ 26.0 SWIC New Jersey 12.0 SICSC Indiana 5.0 SICSE Indiana 2.0 SICNY New York 5.0 SICNE New Jersey 2.0 SAICNJ New Jersey 1.5 SCIC New Jersey 5.5 SFCIC New Jersey 2.0 Total $ 61.0 Based on the 2016 statutory financial statements, the maximum ordinary dividends that can be paid to the Parent by the Insurance Subsidiaries in 2017 are as follows: 2017 ($ in millions) State of Domicile Maximum Ordinary Dividends SICA New Jersey $ 72.2 SWIC New Jersey 40.4 SICSC Indiana 13.8 SICSE Indiana 10.9 SICNY New York 10.2 SICNE New Jersey 5.9 SAICNJ New Jersey 11.5 MUSIC New Jersey 9.7 SCIC New Jersey 12.6 SFCIC New Jersey 5.5 Total $ 192.7

Quarterly Financial Information

Quarterly Financial Information	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	Quarterly Financial Information (unaudited, $ in thousands, First Quarter Second Quarter Third Quarter Fourth Quarter except per share data) 2016 2015 2016 2015 2016 2015 2016 2015 Net premiums earned $ 522,458 476,123 531,932 490,309 542,429 507,390 552,753 516,087 Net investment income earned 30,769 26,917 31,182 32,230 33,375 32,061 35,428 30,108 Net realized (losses) gains (2,704 ) 18,883 1,765 (3,420 ) 3,688 308 (7,686 ) (2,600 ) Underwriting income 40,955 26,021 43,777 29,124 32,033 44,831 35,168 49,053 Net income 37,032 39,708 43,601 33,768 38,502 46,996 39,360 45,389 Other comprehensive income (loss) 45,422 3,827 36,010 (35,944 ) (9,798 ) 6,290 (78,159 ) (3,386 ) Comprehensive income (loss) 82,454 43,535 79,611 (2,176 ) 28,704 53,286 (38,799 ) 42,003 Net income per share: Basic 0.64 0.70 0.75 0.59 0.66 0.82 0.68 0.79 Diluted 0.63 0.69 0.74 0.58 0.66 0.81 0.67 0.78 Dividends to stockholders 1 0.15 0.14 0.15 0.14 0.15 0.14 0.16 0.15 Price range of common stock: 2 High 36.92 30.10 38.67 29.60 41.30 32.50 44.00 37.91 Low 29.27 25.49 33.60 26.28 35.90 28.10 34.95 30.36 The addition of all quarters may not agree to annual amounts on the Financial Statements due to rounding. 1 See Note 19. “Statutory Financial Information, Capital Requirements, and Restrictions on Dividends and Transfers of Funds” for a discussion of dividend restrictions. 2 These ranges of high and low prices of the Parent’s common stock, as reported by the NASDAQ Global Select Market, represent actual transactions. Price quotations do not include retail markups, markdowns, and commissions. The range of high and low prices for common stock for the period beginning January 3, 2017 and ending February 14, 2017 was $38.50 to $44.35 .

Schedule I - Summay of Investme

Schedule I - Summay of Investments - Other Than Investments in Related Parties	12 Months Ended
	Dec. 31, 2016
Summary of Investments, Other than Investments in Related Parties [Abstract]
Schedule I - Summary of Investments- Other than Investments in Related Parties	Types of investment ($ in thousands) Amortized Cost or Cost Fair Value Carrying Amount Fixed income securities: Held-to-maturity: Obligations of states and political subdivisions $ 77,466 79,916 77,783 Public utilities 8,589 9,292 8,579 All other corporate securities 14,122 14,783 13,989 Commercial mortgage-backed securities 1,220 1,220 1,205 Total fixed income securities, held-to-maturity 101,397 105,211 101,556 Available-for-sale: U.S. government and government agencies 75,139 77,333 77,333 Foreign government 26,559 26,865 26,865 Obligations of states and political subdivisions 1,366,287 1,379,593 1,379,593 Public utilities 108,664 110,000 110,000 All other corporate securities 1,867,892 1,887,753 1,887,753 Collateralized loan obligation securities and other asset-backed securities 527,876 528,960 528,960 Commercial mortgage-backed securities 256,356 256,842 256,842 Residential mortgage-backed securities 524,986 525,194 525,194 Total fixed income securities, available-for-sale 4,753,759 4,792,540 4,792,540 Equity securities: Common stock: Banks, trusts and insurance companies 14,056 17,648 17,648 Industrial, miscellaneous and all other 90,607 112,960 112,960 Total common stock, available-for-sale 104,663 130,608 130,608 Preferred stock: Banks, trusts and insurance companies 16,226 16,145 16,145 Total preferred stock, available-for-sale 16,226 16,145 16,145 Total equity securities, available-for-sale 120,889 146,753 146,753 Short-term investments 221,701 221,701 221,701 Other investments 102,397 102,397 Total investments $ 5,300,143 5,364,947 See accompanying Report of Independent Registered Public Accounting Firm in Item 8. "Financial Statements and Supplementary Data." of this Form 10-K.

Schedule II - Parent Corporatio

Schedule II - Parent Corporation Finanical Statements	12 Months Ended
	Dec. 31, 2016
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Schedule II- Parent Corporation Financial Statements	SCHEDULE II SELECTIVE INSURANCE GROUP, INC. (Parent Corporation) Balance Sheets December 31, ($ in thousands, except share amounts) 2016 2015 Assets: Fixed income securities, available-for-sale – at fair value (amortized cost: $73,471 – 2016; $61,794 – 2015) $ 73,509 61,567 Short-term investments 17,777 29,116 Cash 458 898 Investment in subsidiaries 1,845,410 1,716,681 Current federal income tax 19,766 18,297 Deferred federal income tax 19,562 17,513 Other assets 840 670 Total assets $ 1,977,322 1,844,742 Liabilities: Long-term debt $ 328,667 328,192 Intercompany notes payable 79,324 86,163 Accrued long-term stock compensation 32,029 26,465 Other liabilities 5,932 5,881 Total liabilities $ 445,952 446,701 Stockholders’ Equity: Preferred stock at $0 par value per share: Authorized shares 5,000,000; no shares issued or outstanding $ — — Common stock of $2 par value per share: Authorized shares: 360,000,000 Issued: 101,620,436 – 2016; 100,861,372 – 2015 203,241 201,723 Additional paid-in capital 347,295 326,656 Retained earnings 1,568,881 1,446,192 Accumulated other comprehensive loss (15,950 ) (9,425 ) Treasury stock – at cost (shares: 43,653,237 – 2016; 43,500,642 – 2015) (572,097 ) (567,105 ) Total stockholders’ equity 1,531,370 1,398,041 Total liabilities and stockholders’ equity $ 1,977,322 1,844,742 See accompanying Report of Independent Registered Public Accounting Firm. Information should be read in conjunction with the Notes to Consolidated Financial Statements of Selective Insurance Group, Inc. and its subsidiaries. Both items are in Item 8. “Financial Statements and Supplementary Data.” of this Form 10-K. SCHEDULE II (continued) SELECTIVE INSURANCE GROUP, INC. (Parent Corporation) Statements of Income Year ended December 31, ($ in thousands) 2016 2015 2014 Revenues: Dividends from subsidiaries $ 61,014 57,752 57,511 Net investment income earned 1,259 852 620 Net realized (losses) gains (220 ) — 2 Other income — — 340 Total revenues 62,053 58,604 58,473 Expenses: Interest expense 24,030 24,057 24,817 Other expenses 35,020 28,393 23,598 Total expenses 59,050 52,450 48,415 Income before federal income tax 3,003 6,154 10,058 Federal income tax benefit: Current (17,924 ) (16,609 ) (15,920 ) Deferred (2,143 ) (1,603 ) (646 ) Total federal income tax benefit (20,067 ) (18,212 ) (16,566 ) Net income before equity in undistributed income of subsidiaries 23,070 24,366 26,624 Equity in undistributed income of subsidiaries, net of tax 135,425 141,495 115,203 Net income $ 158,495 165,861 141,827 See accompanying Report of Independent Registered Public Accounting Firm. Information should be read in conjunction with the Notes to Consolidated Financial Statements of Selective Insurance Group, Inc. and its subsidiaries. Both items are in Item 8. “Financial Statements and Supplementary Data.” of this Form 10-K. SCHEDULE II (continued) SELECTIVE INSURANCE GROUP, INC. (Parent Corporation) Statements of Cash Flows Year ended December 31, ($ in thousands) 2016 2015 2014 Operating Activities: Net income $ 158,495 165,861 141,827 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed income of subsidiaries, net of tax (135,425 ) (141,495 ) (115,203 ) Stock-based compensation expense 10,449 8,973 8,702 Net realized losses (gains) 220 — (2 ) Amortization – other 648 740 1,421 Changes in assets and liabilities: Increase in accrued long-term stock compensation 5,564 4,575 1,062 (Increase) decrease in net federal income taxes (3,612 ) (3,052 ) 10,977 (Decrease) increase in other assets (202 ) (12 ) 1,165 Increase (decrease) in other liabilities 80 (202 ) (120 ) Net cash provided by operating activities 36,217 35,388 49,829 Investing Activities: Purchase of fixed income securities, available-for-sale (45,789 ) (33,717 ) (18,511 ) Redemption and maturities of fixed income securities, available-for-sale 14,983 21,578 23,210 Sale of fixed income securities, available-for-sale 18,768 — 300 Purchase of short-term investments (119,501 ) (106,933 ) (102,717 ) Sale of short-term investments 130,841 94,422 101,510 Net cash (used in) provided by investing activities (698 ) (24,650 ) 3,792 Financing Activities: Dividends to stockholders (33,758 ) (31,052 ) (28,428 ) Acquisition of treasury stock (4,992 ) (4,182 ) (3,563 ) Net proceeds from stock purchase and compensation plans 7,811 10,089 7,283 Excess tax benefits from share-based payment arrangements 1,819 1,736 1,020 Principal payment on borrowings from subsidiaries (6,839 ) (2,798 ) (13,759 ) Net cash used in financing activities (35,959 ) (26,207 ) (37,447 ) Net (decrease) increase in cash (440 ) (15,469 ) 16,174 Cash, beginning of year 898 16,367 193 Cash, end of year $ 458 898 16,367 See accompanying Report of Independent Registered Public Accounting Firm. Information should be read in conjunction with the Notes to Consolidated Financial Statements of Selective Insurance Group, Inc. and its subsidiaries. Both items are in Item 8. “Financial Statements and Supplementary Data.” of this Form 10-K.

Schedule III - Supplementary In

Schedule III - Supplementary Insurance Information	12 Months Ended
	Dec. 31, 2016
Supplementary Insurance Information [Abstract]
Schedule III- Supplementary Insurance Information	($ in thousands) Deferred policy acquisition costs Reserve for losses and loss expenses Unearned premiums Net premiums earned Net investment income 1 Losses and loss expenses incurred Amortization of deferred policy acquisition costs 2 Other operating expenses 3 Net premiums written Standard Commercial Lines Segment $ 181,193 3,098,554 884,976 1,665,483 — 913,506 367,813 237,730 1,745,782 Standard Personal Lines Segment 16,664 286,081 282,111 280,607 — 177,749 34,105 56,334 281,822 E&S Lines Segment 24,707 307,084 95,732 203,482 — 143,542 48,410 18,451 209,684 Investments Segment — — — — 125,817 — — — — Total $ 222,564 3,691,719 1,262,819 2,149,572 125,817 1,234,797 450,328 312,515 2,237,288 1 Includes “Net investment income earned” and “Net realized investment gains” on the Consolidated Statements of Income. 2 The total of “Amortization of deferred policy acquisition costs” of $450,328 and “Other operating expenses” of $312,515 reconciles to the Consolidated Statements of Income as follows: Policy acquisition costs $ 763,758 Other income 3 (8,881 ) Other expenses 3 7,966 Total $ 762,843 3 In addition to amounts related to the Standard Commercial Lines, Standard Personal Lines, and E&S Lines, “Other income” and “Other expenses” on the Consolidated Statements of Income includes holding company income and expense amounts of $0 and $35,023 , respectively. See accompanying Report of Independent Registered Public Accounting Firm in Item 8. "Financial Statements and Supplementary Data." of this Form 10-K. Year ended December 31, 2015 ($ in thousands) Deferred policy acquisition costs Reserve for losses and loss expenses Unearned premiums Net premiums earned Net investment income 1 Losses and loss expenses incurred Amortization of deferred policy acquisition costs 2 Other operating expenses 3 Net premiums written Standard Commercial Lines Segment $ 171,476 2,998,749 803,648 1,529,442 — 819,573 323,753 221,620 1,596,965 Standard Personal Lines Segment 17,258 265,054 276,533 288,134 — 200,237 33,638 52,923 283,926 E&S Lines Segment 24,425 253,925 89,529 172,333 — 128,731 42,044 18,361 189,013 Investments Segment — — — — 134,487 — — — — Total $ 213,159 3,517,728 1,169,710 1,989,909 134,487 1,148,541 399,435 292,904 2,069,904 1 Includes “Net investment income earned” and “Net realized investment gains” on the Consolidated Statements of Income. 2 The total of “Amortization of deferred policy acquisition costs” of $399,435 and “Other operating expenses” of $292,904 reconciles to the Consolidated Statements of Income as follows: Policy acquisition costs $ 689,820 Other income 3 (7,456 ) Other expenses 3 9,975 Total $ 692,339 3 In addition to amounts related to the Standard Commercial Lines, Standard Personal Lines, and E&S Lines, “Other income” and “Other expenses” on the Consolidated Statements of Income includes holding company income and expense amounts of $0 and $28,396 , respectively. See accompanying Report of Independent Registered Public Accounting Firm in Item 8. "Financial Statements and Supplementary Data." of this Form 10-K. SCHEDULE III (continued) SELECTIVE INSURANCE GROUP, INC. AND CONSOLIDATED SUBSIDIARIES SUPPLEMENTARY INSURANCE INFORMATION Year ended December 31, 2014 ($ in thousands) Deferred policy acquisition costs Reserve for losses and loss expenses Unearned premiums Net premiums earned Net investment income 1 Losses and loss expenses incurred Amortization of deferred policy acquisition costs 2 Other operating expenses 3 Net premiums written Standard Commercial Lines Segment $ 147,285 3,000,796 734,697 1,415,712 — 870,018 295,774 188,699 1,441,047 Standard Personal Lines Segment 17,495 279,761 285,777 296,747 — 197,182 34,851 48,178 292,061 E&S Lines Segment 20,828 197,313 75,345 140,150 — 90,301 33,670 15,793 152,172 Investments Segment — — — — 165,307 — — — — Total $ 185,608 3,477,870 1,095,819 1,852,609 165,307 1,157,501 364,295 252,670 1,885,280 1 Includes “Net investment income earned” and “Net realized investment gains” on the Consolidated Statements of Income. 2 The total of “Amortization of deferred policy acquisition costs” of $364,295 and “Other operating expenses” of $252,670 reconciles to the Consolidated Statements of Income as follows: Policy acquisition costs $ 624,470 Other income 3 (16,598 ) Other expenses 3 9,093 Total $ 616,965 3 In addition to amounts related to the Standard Commercial Lines, Standard Personal Lines, and E&S Lines, “Other income” and “Other expenses” on the Consolidated Statements of Income includes holding company income and expense amounts of $347 and $23,603 , respectively. See accompanying Report of Independent Registered Public Accounting Firm in Item 8. "Financial Statements and Supplementary Data." of this Form 10-K.

Schedule IV - Reinsurance

Schedule IV - Reinsurance	12 Months Ended
	Dec. 31, 2016
Supplemental Schedule of Reinsurance Premiums for Insurance Companies [Abstract]
Schedule IV - Reinsurance	($ thousands) Direct Amount Assumed From Other Companies Ceded to Other Companies Net Amount % of Amount Assumed To Net 2016 Premiums earned: Accident and health insurance $ 32 — — 32 — Property and liability insurance 2,484,683 28,214 363,357 2,149,540 1 % Total premiums earned 2,484,715 28,214 363,357 2,149,572 1 % 2015 Premiums earned: Accident and health insurance $ 37 — 37 — — Property and liability insurance 2,330,230 23,209 363,530 1,989,909 1 % Total premiums earned 2,330,267 23,209 363,567 1,989,909 1 % 2014 Premiums earned: Accident and health insurance $ 44 — 44 — — Property and liability insurance 2,183,214 34,653 365,258 1,852,609 2 % Total premiums earned 2,183,258 34,653 365,302 1,852,609 2 % See accompanying Report of Independent Registered Public Accounting Firm in Item 8. "Financial Statements and Supplementary Data." of this Form 10-K.

Schedule V - Allowance for Unco

Schedule V - Allowance for Uncollectible Premiums and Other Receivables	12 Months Ended
	Dec. 31, 2016
Valuation and Qualifying Accounts [Abstract]
Schedule V - Allowance for Uncollectible Premiums and Other Receivables	($ in thousands) 2016 2015 2014 Balance, January 1 $ 10,122 11,037 9,542 Additions 4,669 3,604 4,617 Deductions (3,311 ) (4,519 ) (3,122 ) Balance, December 31 $ 11,480 10,122 11,037 See accompanying Report of Independent Registered Public Accounting Firm in Item 8. "Financial Statements and Supplementary Data." of this Form 10-K.

Summary of Significant Accoun34

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The accompanying consolidated financial statements (“Financial Statements”) include the accounts of the Parent and its subsidiaries, and have been prepared in conformity with: (i) U.S. generally accepted accounting principles ("GAAP"); and (ii) the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”). All significant intercompany accounts and transactions are eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of our Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported financial statement balances, as well as the disclosure of contingent assets and liabilities. Actual results could differ from those estimates.
Reclassifications	Reclassifications Certain amounts in our prior years' Financial Statements and related notes have been reclassified to conform to the 2016 presentation. Such reclassifications had no effect on our net income, stockholders' equity, or cash flows.
Investments	Investments Fixed income securities may include investment grade and below investment grade rated bonds, redeemable preferred stocks, non-redeemable preferred stocks with certain debt-like characteristics, mortgage-backed securities (“MBS”), collateralized loan obligations ("CLO") and other asset-backed securities (“ABS”). MBS, CLO, and other ABS are jointly referred to as structured securities. Fixed income securities classified as available-for-sale (“AFS”) are reported at fair value. Those fixed income securities that we have the ability and positive intent to hold to maturity are classified as held-to-maturity (“HTM”) and are carried at either: (i) amortized cost; or (ii) market value at the date of transfer into the HTM category, adjusted for subsequent amortization. The amortized cost of fixed income securities is adjusted for the amortization of premiums and the accretion of discounts over the expected life of the security using the effective yield method. Premiums and discounts arising from the purchase of structured securities are amortized over the expected life of the security based on future principal payments, and considering prepayments. These prepayments are estimated based on historical and projected cash flows. Prepayment assumptions are reviewed quarterly and adjusted to reflect actual prepayments and changes in expectations. Future amortization of any premium and/or discount is adjusted to reflect the revised assumptions. Interest income, as well as amortization and accretion, is included in "Net investment income earned" on our Consolidated Statements of Income. The amortized cost of a fixed income security is written down to fair value when a decline in value is considered to be other than temporary. See the discussion below on realized investment gains and losses for a description of the accounting for impairments. After-tax unrealized gains and losses on: (i) fixed income securities classified as AFS; and (ii) fixed income securities that were transferred into an HTM designation from an AFS designation, are included in accumulated other comprehensive income (loss) ("AOCI"). Equity securities, which are classified as AFS, may include common and non-redeemable preferred stocks. These securities are carried at fair value and the related dividend income is included in "Net investment income earned" on our Consolidated Statements of Income. The cost of equity securities is written down to fair value when a decline in value is considered to be other than temporary. See the discussion below on realized investment gains and losses for a description of the accounting for impairments. After-tax unrealized gains and losses are included in AOCI. Short-term investments may include certain money market instruments, savings accounts, commercial paper, and debt issues purchased with a maturity of less than one year. We also enter into reverse repurchase agreements that are included in short-term investments. These loans are fully collateralized with high quality, readily marketable instruments at a minimum of 102% of the loan principal. At maturity, we receive principal and interest income on these agreements. All short-term investments are carried at cost, which approximates fair value. The associated income is included in "Net investment income earned" on our Consolidated Statement of Income. Other investments may include alternative investments and other securities. Alternative investments are accounted for using the equity method. Our share of distributed and undistributed net income from alternative investments is included in "Net investment income earned" on our Consolidated Statement of Income. Other securities are primarily comprised of tax credit investments. Low income housing tax credits are accounted for under the proportional amortization method and all other tax credits are accounted for using the equity method. Under the proportional amortization method, our share of the investment’s performance is recorded in our Consolidated Statement of Income as a component of “Federal income tax expense.” Under the equity method, our share of distributed and undistributed net income is included in "Net investment income earned" on our Consolidated Statement of Income. For federal income tax credits accounted for under the equity method, we use the deferral method for recognizing the benefit of the tax credit with the related deferred revenue being recognized in our Consolidated Statement of Income as a component of "Federal income tax expense" ratably over the life of the investment. Realized gains and losses on the sale of investments are determined on the basis of the cost of the specific investments sold and are credited or charged to income. Included in realized gains and losses are the other-than-temporary impairment ("OTTI") charges recognized in earnings, which are discussed below. On a quarterly basis, we review our investment portfolio for impairments that are other than temporary. The following provides information on this analysis for our fixed income securities and short-term investments, our equity securities, and our other investments. Fixed Income Securities and Short-Term Investments We review securities that are in an unrealized loss position to determine: (i) if we have the intent to sell the security; (ii) if it is more likely than not that we will be required to sell the debt security before its anticipated recovery; and (iii) if the decline is other than temporary. Broad changes in the overall market or interest rate environment generally will not lead to a write down. If we determine that we have either the intent or requirement to sell the security, we write down its amortized cost to its fair value through a charge to earnings as a component of realized losses. If we do not have either the intent or requirement to sell the security, our evaluation for OTTI may include, but is not limited to, evaluation of the following factors: • Whether the decline appears to be issuer or industry specific; • The degree to which the issuer is current or in arrears in making principal and interest payments on the fixed income security; • The issuer’s current financial condition and ability to make future scheduled principal and interest payments on a timely basis; • Evaluation of projected cash flows; • Buy/hold/sell recommendations published by outside investment advisors and analysts; and • Relevant rating history, analysis, and guidance provided by rating agencies and analysts. Non-redeemable preferred stocks that are classified as fixed income securities are evaluated under this OTTI method unless the security is below investment grade, at which time they are evaluated under the equity securities OTTI model discussed below. To determine if an impairment is other than temporary, we perform assessments that may include, but are not limited to, discounted cash flow analyses ("DCFs") to determine the security's present value of future cash flows. In addition, this analysis is performed on all previously-impaired debt securities that continue to be held by us and all structured securities that were not of high-credit quality at the date of purchase. Any shortfall in the expected present value of the future cash flows, based on the DCF, from the amortized cost basis of a security is considered a “credit impairment,” with the remaining decline in fair value of a security considered a “non-credit impairment.” Credit impairments are charged to earnings as a component of realized losses, while non-credit impairments are recorded to Other Comprehensive Income ("OCI") as a component of unrealized losses. The discount rate we use in a DCF is the effective interest rate implicit in the security at the date of acquisition for those structured securities that were not of high-credit quality at acquisition. For all other securities, we use a discount rate that equals the current yield, excluding the impact of previous OTTI charges, used to accrete the beneficial interest. Discounted cash flow models may include, but are not necessarily limited to: (i) generating cash flows for each tranche considering tranche-specific data, market data, and other pertinent information such as the historical performance of the underlying collateral, including net operating income generated by underlying properties, conditional default rate assumptions, loan loss severity assumptions, consensus projections, prepayment projections, and actual pool and collateral information; (ii) identifying applicable benchmark yields; and (iii) applying market-based tranche specific spreads to determine an appropriate yield by incorporating collateral performance, tranche-level attributes, trades, bids, and offers. Equity Securities We review securities that are in an unrealized loss position to determine: (i) if we do not intend to hold the security to its forecasted recovery; or (ii) if the decline is other than temporary, which includes declines driven by market volatility for which we cannot assert will recover in the near term. If we determine either that we do not intend to hold a security, or the decline is other than temporary, we write down the security's cost to its fair value through a charge to earnings as a component of realized losses. If we intend to hold the security, our evaluation for OTTI may include, but is not limited to, an evaluation of the following factors: • Whether the decline appears to be issuer or industry specific; • The relationship of market prices per share to book value per share at the date of acquisition and date of evaluation; • The price-earnings ratio at the time of acquisition and date of evaluation; • The financial condition and near-term prospects of the issuer, including any specific events that may influence the issuer's operations, coupled with our intention to hold the securities in the near-term; • The recent income or loss of the issuer; • The independent auditors' report on the issuer's recent financial statements; • The dividend policy of the issuer at the date of acquisition and the date of evaluation; • Buy/hold/sell recommendations or price projections published by outside investment advisors; • Rating agency announcements; • The length of time and the extent to which the fair value has been, or is expected to be, less than its cost in the near term; and • Our expectation of when the cost of the security will be recovered. Other Investments Our evaluation for OTTI of an other investment (i.e., an alternative investment) may include, but is not limited to, conversations with the management of the alternative investment concerning the following: • The current investment strategy; • Changes made or future changes to be made to the investment strategy; • Emerging issues that may affect the success of the strategy; and • The appropriateness of the valuation methodology used regarding the underlying investments. If there is a decline in the fair value of an other investment that we do not intend to hold, or if we determine the decline is other than temporary, we write down the carry value of the investment and record the charge through earnings as a component of realized losses.
Fair Value of Financial Instruments	Fair Values of Financial Instruments Assets The fair values of our investments are generated using various valuation techniques and are placed into the fair value hierarchy considering the following: (i) the highest priority is given to quoted prices in active markets for identical assets (Level 1); (ii) the next highest priority is given to quoted prices in markets that are not active or inputs that are observable either directly or indirectly, including quoted prices for similar assets in markets that are not active and other inputs that can be derived principally from, or corroborated by, observable market data for substantially the full term of the assets (Level 2); and (iii) the lowest priority is given to unobservable inputs supported by little or no market activity and that reflect our assumptions about the exit price, including assumptions that market participants would use in pricing the asset (Level 3). An asset’s classification within the fair value hierarchy is based on the lowest level of significant input to its valuation. Transfers between levels in the fair value hierarchy are recognized at the end of the reporting period. The techniques used to value our financial assets are as follows: Level 1 Pricing Security Type Methodology Equity Securities; U.S. Treasury Notes Equity and U.S. Treasury Note prices are received from an independent pricing service that are based on observable market transactions. We validate these prices against a second external pricing service, and if established market value comparison thresholds are breached, further analysis is performed to determine the price to be used. Short-Term Investments Short-term investments are carried at cost, which approximates fair value. Given the liquid nature of our short-term investments, we generally validate their fair value by way of active trades within approximately one week of the financial statement close. Level 2 Pricing We utilize a market approach for our Level 2 securities, using primarily matrix pricing models prepared by external pricing services. Matrix pricing models use mathematical techniques to value debt securities by relying on the securities' relationship to other benchmark quoted securities, and not relying exclusively on quoted prices for specific securities, as the specific securities are not always frequently traded. As a matter of policy, we consistently use one pricing service as our primary source and secondary pricing services if prices are not available from the primary pricing service. Fixed income securities portfolio pricing is reviewed for reasonableness in the following ways: (i) comparing our pricing to other third-party pricing services as well as benchmark indexed pricing; (ii) comparing fair value fluctuations between months for reasonableness; and (iii) reviewing stale prices. If further analysis is needed, a challenge is sent to the pricing service for review and confirmation of the price. Further information on our Level 2 asset pricing is included in the following table: Security Type Methodology Corporate Securities including preferred stocks classified as Fixed Income Securities, and U.S. Government and Government Agencies Evaluations include obtaining relevant trade data, benchmark quotes and spreads and incorporating this information into either spread-based or price-based evaluations as determined by the observed market data. Spread-based evaluations include: (i) creating a range of spreads for relevant maturities of each issuer based on the new issue market, secondary trading, and dealer quotes; and (ii) incorporating option adjusted spreads for issues that have early redemption features. Based on the findings in (i) and (ii) above, final spreads are derived and added to benchmark curves. Price-based evaluations include matching each issue to its best-known market maker and contacting firms that transact in these securities. Obligations of States and Political Subdivisions Evaluations are based on yield curves that are developed based on factors such as: (i) benchmarks to issues with interest rates near prevailing market rates; (ii) established trading spreads over widely-accepted market benchmarks; (iii) yields on new issues; and (iv) market information from third-party sources such as reportable trades, broker-dealers, or issuers. Structured Securities (including CLO and other ABS, CMBS, RMBS) Evaluations are based on a discounted cash flow model, including: (i) generating cash flows for each tranche considering tranche-specific data, market data, and other pertinent information such as historical performance of the underlying collateral, including net operating income generated by the underlying properties, conditional default rate assumptions, loan loss severity assumptions, consensus projections, prepayment projections, and actual pool and loan level collateral information; (ii) identifying applicable benchmark yields; and (iii) applying market-based tranche-specific spreads to determine an appropriate yield by incorporating collateral performance, tranche-level attributes, trades, bids, and offers. Foreign Government Evaluations are performed using a DCF model and incorporating observed market yields of benchmarks as inputs, adjusting for varied maturities. Level 3 Pricing Less than 1% of our portfolio cannot be priced using our primary or secondary pricing service. At times, we may use non-binding broker quotes to value some of these securities. These prices are from various broker/dealers that use bid or ask prices, or benchmarks to indices, in measuring the fair value of a security. We review these fair value measurements for reasonableness. This review typically includes an analysis of price fluctuations between months with variances over established thresholds being analyzed further. Further information on our current Level 3 asset pricing is included in the following table: Security Type Methodology Corporate Securities These tax credit investments are priced internally using spread-based evaluations. Equity Securities These non-publicly traded stocks are valued by the issuer and reviewed internally. Liabilities The techniques used to value our notes payable are as follows: Level 1 Pricing Security Type Methodology 5.875% Senior Notes Based on the quoted market prices. Level 2 Pricing Security Type Methodology 7.25% Senior Notes; 6.70% Senior Notes Based on matrix pricing models prepared by external pricing services. Borrowings from Federal Home Loan Banks Evaluations are performed using a DCF model based on current borrowing rates provided by the Federal Home Loan Banks that is consistent with the remaining term of the borrowing. See Note 7. “Fair Value Measurements” for a summary table of the fair value and related carrying amounts of financial instruments.
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts We estimate an allowance for doubtful accounts on our premiums receivable. This allowance is based on historical write-off percentages adjusted for the effects of current and anticipated trends. An account is charged off when we believe it is probable that we will not collect a receivable. In making this determination, we consider information obtained from our efforts to collect amounts due directly and/or through collection agencies.
Share-Based Compensation	Share-Based Compensation Share-based compensation consists of all share-based payment transactions in which an entity acquires goods or services by issuing (or offering to issue) its shares, share units, share options, or other equity instruments. The cost resulting from all share-based payment transactions are recognized in the Financial Statements based on the fair value of both equity and liability awards. The fair value is measured at grant date for equity awards, whereas the fair value for liability awards are remeasured at each reporting period. Both the fair value of equity and liability awards is recognized over the requisite service period. The requisite service period is typically the lesser of the vesting period or the period of time from the grant date to the date of retirement eligibility. The expense recognized for share-based awards, which, in some cases, contain performance criteria, is based on the number of shares or units expected to be issued at the end of the performance period. We repurchase the Parent’s stock from our employees in connection with, and as permitted under, our stock-based compensation plans. This activity is disclosed in our Consolidated Statements of Stockholders' Equity.
Reinsurance	Reinsurance Reinsurance recoverables represent estimates of amounts that will be recovered from reinsurers under our various treaties. Generally, amounts recoverable from reinsurers are recognized as assets at the same time and in a manner consistent with the paid and unpaid losses associated with the reinsured policies. We require collateral to secure reinsurance recoverables primarily from our reinsurance carriers that are not authorized, otherwise approved, or certified to do business in one or more of our ten insurance subsidiaries' domiciliary states. Our ten insurance subsidiaries are collectively referred to as the "Insurance Subsidiaries". This collateral is typically in the form of a letter of credit or cash. An allowance for estimated uncollectible reinsurance is recorded based on an evaluation of balances due from reinsurers and other available information, such as each reinsurers' credit rating from A.M. Best Company ("A.M. Best") or Standard & Poor's Rating Services ("S&P"). We charge off reinsurance recoverables on paid losses when it becomes probable that we will not collect the balance.
Property and Equipment	Property and Equipment Property and equipment used in operations, including certain costs incurred to develop or obtain computer software for internal use, are capitalized and carried at cost less accumulated depreciation. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets. The following estimated useful lives can be considered as general guidelines: Asset Category Years Computer hardware 3 Computer software 3 to 5 Internally developed software 5 to 10 Software licenses 3 to 5 Furniture and fixtures 10 Buildings and improvements 5 to 40 We recorded depreciation expense of $17.4 million , $16.4 million , and $12.6 million for 2016 , 2015 , and 2014 , respectively.
Deferred Policy Acquisition Costs	Deferred Policy Acquisition Costs Deferred policy acquisition costs are limited to costs directly related to the successful acquisition of insurance contracts. Costs meeting this definition typically include, among other things, sales commissions paid to our distribution partners, premium taxes, and the portion of employee salaries and benefits directly related to time spent on acquired contracts. These costs are deferred and amortized over the life of the contracts. Accounting guidance requires a premium deficiency analysis to be performed at the level an entity acquires, services, and measures the profitability of its insurance contracts. We currently perform three premium deficiency analyses for our insurance segments, consistent with our reportable segments of Standard Commercial Lines, Standard Personal Lines, and E&S Lines. A combined ratio of over 100% does not necessarily indicate a premium deficiency, as any year's combined ratio includes a portion of underwriting expenses that are expensed at policy inception and therefore are not covered by the remaining unearned premium. In addition, investment income is not contemplated in the combined ratio calculation. There were no premium deficiencies for any of the reported years, as the sum of the anticipated losses and loss expenses, unamortized acquisition costs, policyholder dividends, and other expenses for each segment did not exceed that segment’s related unearned premium and anticipated investment income. The investment yields assumed in the premium deficiency assessment for each reporting period, which are based on our actual average investment yield before tax as of the September 30 calculation date, were 2.4% for 2016 , 2.5% for 2015 , and 3.0% for 2014 . Deferred policy acquisition costs amortized to expense were $450.3 million for 2016 , $399.4 million for 2015 , and $364.3 million for 2014 .
Goodwill	Goodwill Goodwill results from business acquisitions where the cost of assets and liabilities acquired exceeds the fair value of those assets and liabilities. A quantitative goodwill impairment analysis is performed if our quarterly qualitative analysis indicates that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. Goodwill is allocated to the reporting units for purposes of these analyses. Based on our analysis at December 31, 2016, goodwill was not impaired.
Reserves for Losses and Loss Expenses	Reserves for Losses and Loss Expenses Reserves for losses and loss expenses are comprised of both case reserves on individual claims, and reserves for claims incurred but not reported ("IBNR"). Case reserves result from claims that have been reported to one or more of our Insurance Subsidiaries, and are estimated at the amount of the expected ultimate payment. IBNR reserves are established at more aggregated levels than case basis reserves, and in addition to reserves on claims that have been incurred but not reported, they include provisions for future emergence on known claims, as well as reopened claims. IBNR reserves are established based on the results of the Insurance Subsidiaries’ internal reserve analysis, supplemented with other internal and external information. The internal reserve analysis is performed quarterly, and relies upon generally accepted actuarial techniques. Such techniques assume that past experience, adjusted for the effects of current developments and anticipated trends, are an appropriate basis for predicting future events. Our analyses rely upon historical paid and case losses and loss adjustment expense experience organized by line of business, accident year and maturity (i.e., “triangles”). Standard actuarial projection methods are applied to this history, producing a set of estimated ultimate losses and loss adjustment expenses. Ultimate losses and loss adjustment expenses are selected from the various methods, considering the strengths and weaknesses of the methods as they apply to the specific line and accident year. Certain types of exposures do not lend themselves to standard actuarial methods. Examples of these are: • Certain property catastrophe events may be low in frequency and high in severity. These events may affect many insureds simultaneously. Due to the unique nature of these events, ultimate liabilities are estimated for each event, based on surveys of our portfolio of exposures, in conjunction with individual claims estimates. While generally short-tailed, the liabilities associated with these events are subject to a higher degree of uncertainty. We maintain significant reinsurance protection that greatly limits the impact that these extreme events have on net loss and loss adjustment expenses. • In some limited cases, an insured event may span multiple years and multiple policies, as in the case of asbestos and environmental claims, where the injury is deemed to occur over an extended period of time. These claims are analyzed without accident year detail, using alternative methods and metrics. The associated selected ultimate loss and loss adjustment expenses are then allocated to accident year for reporting. • Another example of non-standard methods relate to loss adjustment expenses that cannot be attributed to a specific claim (referred to as “unallocated loss adjustment expenses”). These expenses are first allocated to accident year and alternative projection methods are then applied to these expenses. The resulting ultimate expenses by accident year are then used for reporting purposes. The selected ultimate losses and loss adjustment expenses are translated into indicated IBNR reserves, which are then compared to the recorded IBNR reserves. Management's judgment is applied in determining any required adjustments and the resulting adjustments are then recorded and assigned or allocated to accident year using the results of the actuarial analysis. While the reserve analysis is the primary basis for determining the recorded IBNR reserves, other internal and external factors are considered. Internal factors include: (i) supplemental data regarding claims reporting and settlement trends; (ii) exposure estimates for reported claims, along with recent development on those estimates with respect to individual large claims and the aggregate of all claims; (iii) the rate at which new large or complex claims are being reported; and (iv) additional trends observed by claims personnel or reported to them by defense counsel. External factors considered include: (i) legislative enactments; (ii) judicial decisions; (iii) legal developments in the determination of liability and the imposition of damages; and (iv) trends in general economic conditions, including the effects of inflation. Loss reserves are estimates, and as such, we also consider a range of possible loss and loss expense reserve estimates. This range is determined at the beginning of each year, using prior year-end data, and reflects the fact that there is no single precise method for estimating the required reserves, due to the many factors that may influence the amounts ultimately paid. Considering the reserve range along with all of the items described above, as well as current market conditions, IBNR estimates are then established and recorded. The combination of the IBNR estimates along with the case reserve estimates on individual claims results in our total reserves for losses and loss expenses. These reserves are expected to be sufficient for settling losses and loss reserve obligations under our policies on unpaid claims, including changes in the volume of business written, claims frequency and severity, the mix of business, claims processing, and other items that management expects to affect our ultimate settlement of losses and loss expenses. However, the ultimate claim settlements may be higher or lower than reserves established. As our experience emerges and other information develops, we revise our reserve estimates accordingly. The changes in these estimates, resulting from the continuous review process and the differences between estimates and ultimate payments, are reflected in the Consolidated Statements of Income for the period in which such estimates are changed. The associated impacts may be material to the results of operations in future periods. We do not discount to present value that portion of our losses and loss expense reserves expected to be paid in future periods. Our loss and loss expense reserves implicitly include anticipated recoveries for salvage and subrogation claims. Claims are counted at the occurrence, line of business, and policy level. For example, if a single occurrence (e.g. an auto accident) leads to a claim under an auto and an associated umbrella policy, they are each counted separately. Conversely, multiple claimants under the same occurrence/line/policy would contribute only a single count. The claim counts provided are on a reported basis. A claim is considered reported when a reserve is established or payment is made. Therefore, claims closed without payment are included in the count as long as there was an associated case reserve at some point in its life cycle. We also write a small amount of assumed reinsurance. Currently, this business is limited to our share of certain involuntary pools. Since the associated claims are not processed by us, they are not captured within our claims system. Therefore, the claim counts reported exclude this business.
Revenue Recognition	Revenue Recognition The Insurance Subsidiaries' net premiums written (“NPW”) include direct insurance policy writings, plus reinsurance assumed and estimates of premiums earned but unbilled on the workers compensation and general liability lines of insurance, less reinsurance ceded. The estimated premium on the workers compensation and general liability lines is referred to as audit premium. We estimate this premium, as it is anticipated to be either billed or returned on policies subsequent to expiration based on exposure levels (i.e. payroll or sales). Audit premium is based on historical trends adjusted for the uncertainty of future economic conditions. Economic instability could ultimately impact our estimates and assumptions, and changes in our estimate may be material to the results of operations in future periods. Premiums written are recognized as revenue over the period that coverage is provided using the semi-monthly pro-rata method. Unearned premiums and prepaid reinsurance premiums represent that portion of premiums written that are applicable to the unexpired terms of policies in force.
Dividends to Policyholders	Dividends to Policyholders We establish reserves for dividends to policyholders on certain policies, most significantly workers compensation policies. These dividends are based on the policyholders' loss experience. Dividend reserves are established based on past experience, adjusted for the effects of current developments and anticipated trends. The expense for these dividends is recognized over a period that begins at policy inception and ends with the payment of the dividend. We do not issue policies that entitle the policyholder to participate in the earnings or surplus of our Insurance Subsidiaries.
Federal Income Tax	Federal Income Tax We use the asset and liability method of accounting for income taxes. Current federal income taxes are recognized for the estimated taxes payable or refundable on tax returns for the current year. Deferred federal income taxes arise from the recognition of temporary differences between financial statement carrying amounts and the tax basis of assets and liabilities. We consider all evidence, both positive and negative, with respect to our federal tax loss carryback availability, expected levels of pre-tax financial statement income, and federal taxable income, when evaluating whether the temporary differences will be realized. In projecting future taxable income, we begin with budgeted pre-tax income adjusted for estimated non-taxable items. The assumptions about future taxable income require significant judgment and are consistent with the plans and estimates we use to manage our businesses. A valuation allowance is established when it is more likely than not that some portion of the deferred tax asset will not be realized. A liability for uncertain tax positions is recorded when it is more likely than not that a tax position will not be sustained upon examination by taxing authorities. The effect of a change in tax rates is recognized in the period of enactment. If we were to be levied interest and penalties by the Internal Revenue Service (“IRS”), the interest would be recognized as “Interest expense” and the penalties would be recognized as “Other expenses” on the Consolidated Statements of Income.
Leases	Leases We have various operating leases for office space, equipment, and fleet vehicles. Rental expense for such leases is recorded on a straight-line basis over the lease term. If a lease has a fixed and determinable escalation clause, or periods of rent holidays, the difference between rental expense and rent paid is included in "Other liabilities" as deferred rent in the Consolidated Balance Sheets. In addition, we have various capital leases for computer hardware and software. These leases are accounted for as an acquisition of an asset and an incurrence of an obligation. Depreciation is calculated using the straight-line method over the shorter of the estimated useful life of the asset or the lease term.
Pension	Pension Our pension and post-retirement life benefit obligations and related costs are calculated using actuarial methods, within the framework of GAAP. Our pension benefit obligation is determined as the actuarial present value of the vested benefits to which the employee is currently entitled, based on the average life expectancy of the employee. Our funding policy provides that payments to our pension trust shall be equal to the minimum funding requirements of the Employee Retirement Income Security Act, plus additional amounts that the Board of Directors of Selective Insurance Company of America (“SICA”) may approve from time to time. Two key assumptions, the discount rate and the expected return on plan assets, are important elements of expense and/or liability measurement. We evaluate these key assumptions annually unless facts indicate that a more frequent review is required. The discount rate enables us to state expected future cash flows at their present value on the measurement date. The purpose of the discount rate is to determine the interest rates inherent in the price at which pension benefits could be effectively settled. Our discount rate selection is based on high-quality, long-term corporate bonds. To determine the expected long-term rate of return on the plan assets, we consider the current and expected asset allocation, as well as historical and expected returns on each plan asset class. Other assumptions involve demographic factors such as retirement age and mortality.

Summary of Significant Accoun35

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Estimated Useful Life for Property and Equipment	Asset Category Years Computer hardware 3 Computer software 3 to 5 Internally developed software 5 to 10 Software licenses 3 to 5 Furniture and fixtures 10 Buildings and improvements 5 to 40

Adoption of Accounting Pronou36

Adoption of Accounting Pronouncements Adoption of Accounting Pronouncements (Tables)	12 Months Ended
	Dec. 31, 2016
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	Income Statement Information Year ended December 31, 2014 ($ in thousands) As Originally Reported As Restated Interest Expense $ 22,086 23,063 Other Expense 33,673 32,696

Statements of Cash Flow (Tables

Statements of Cash Flow (Tables)	12 Months Ended
	Dec. 31, 2016
Supplemental Cash Flow Information [Abstract]
Schedule of Cash Flow, Supplemental Disclosures	($ in thousands) 2016 2015 2014 Cash paid during the period for: Interest $ 22,098 21,892 22,221 Federal income tax 46,405 39,500 22,699 Non-cash items: Exchange of fixed income securities, AFS 23,579 36,792 20,781 Exchange of fixed income securities, HTM — 15,257 4,289 Corporate actions related to equity securities, AFS 1 3,263 4,239 334 Assets acquired under capital lease arrangements 3,151 6,760 5,642 Non-cash purchase of property and equipment 78 — 338

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2016
Investment [Line Items]
Schedule of Unrealized Gains On Investments	($ in thousands) 2016 2015 2014 AFS securities: Fixed income securities $ 38,781 55,689 90,336 Equity securities 25,864 13,235 32,389 Total AFS securities 64,645 68,924 122,725 HTM securities: Fixed income securities 159 300 958 Total HTM securities 159 300 958 Total net unrealized gains 64,804 69,224 123,683 Deferred income tax expense (22,681 ) (24,228 ) (43,289 ) Net unrealized gains, net of deferred income tax 42,123 44,996 80,394 (Decrease) increase in net unrealized gains in OCI, net of deferred income tax $ (2,873 ) (35,398 ) 28,890
Schedule of Held-to-maturity Securities	December 31, 2016 Net Unrealized Unrecognized Unrecognized Amortized Gains Carrying Holding Holding Fair ($ in thousands) Cost (Losses) Value Gains Losses Value Obligations of state and political subdivisions $ 77,466 317 77,783 2,133 — 79,916 Corporate securities 22,711 (143 ) 22,568 1,665 (158 ) 24,075 CMBS 1,220 (15 ) 1,205 15 — 1,220 Total HTM fixed income securities $ 101,397 159 101,556 3,813 (158 ) 105,211 December 31, 2015 Net Unrealized Unrecognized Unrecognized Amortized Gains Carrying Holding Holding Fair ($ in thousands) Cost (Losses) Value Gains Losses Value Obligations of state and political subdivisions 175,269 848 176,117 5,763 — 181,880 Corporate securities 20,228 (185 ) 20,043 1,972 — 22,015 CLO and other ABS 1,030 (120 ) 910 118 — 1,028 CMBS 4,527 (243 ) 4,284 337 — 4,621 Total HTM fixed income securities $ 201,054 300 201,354 8,190 — 209,544
Schedule of Available For Sale Securities	December 31, 2016 Cost/ Amortized Unrealized Unrealized Fair ($ in thousands) Cost Gains Losses Value AFS fixed income securities: U.S. government and government agencies $ 75,139 2,230 (36 ) 77,333 Foreign government 26,559 322 (16 ) 26,865 Obligations of states and political subdivisions 1,366,287 18,610 (5,304 ) 1,379,593 Corporate securities 1,976,556 27,057 (5,860 ) 1,997,753 CLO and other ABS 527,876 1,439 (355 ) 528,960 CMBS 256,356 1,514 (1,028 ) 256,842 RMBS 524,986 3,006 (2,798 ) 525,194 Total AFS fixed income securities 4,753,759 54,178 (15,397 ) 4,792,540 AFS equity securities: Common stock 104,663 26,250 (305 ) 130,608 Preferred stock 16,226 274 (355 ) 16,145 Total AFS equity securities 120,889 26,524 (660 ) 146,753 Total AFS securities $ 4,874,648 80,702 (16,057 ) 4,939,293 December 31, 2015 Cost/ Amortized Unrealized Unrealized Fair ($ in thousands) Cost Gains Losses Value AFS fixed income securities: U.S. government and government agencies $ 99,485 4,721 (91 ) 104,115 Foreign government 14,885 298 (2 ) 15,181 Obligations of states and political subdivisions 1,314,779 44,523 (160 ) 1,359,142 Corporate securities 1,892,296 23,407 (15,521 ) 1,900,182 CLO and other ABS 244,541 531 (918 ) 244,154 CMBS 245,252 750 (2,410 ) 243,592 RMBS 541,276 4,274 (3,713 ) 541,837 Total AFS fixed income securities 4,352,514 78,504 (22,815 ) 4,408,203 AFS equity securities: Common stock 181,991 14,796 (1,998 ) 194,789 Preferred stock 11,825 477 (40 ) 12,262 Total AFS equity securities 193,816 15,273 (2,038 ) 207,051 Total AFS securities $ 4,546,330 93,777 (24,853 ) 4,615,254
Schedule of Fair Value and Gross Pre-Tax Net Unrealized/Unrecognized Loss of Securities by Length of Time	December 31, 2016 Less than 12 months 12 months or longer Total ($ in thousands) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Unrealized AFS fixed income securities: U.S. government and government agencies $ 6,419 (36 ) — — 6,419 (36 ) Foreign government 13,075 (16 ) — — 13,075 (16 ) Obligations of states and political subdivisions 306,509 (5,304 ) — — 306,509 (5,304 ) Corporate securities 462,902 (5,771 ) 4,913 (89 ) 467,815 (5,860 ) CLO and other ABS 189,795 (354 ) 319 (1 ) 190,114 (355 ) CMBS 82,492 (1,021 ) 1,645 (7 ) 84,137 (1,028 ) RMBS 279,480 (2,489 ) 8,749 (309 ) 288,229 (2,798 ) Total AFS fixed income securities 1,340,672 (14,991 ) 15,626 (406 ) 1,356,298 (15,397 ) AFS equity securities: Common stock 11,271 (305 ) — — 11,271 (305 ) Preferred stock 6,168 (355 ) — — 6,168 (355 ) Total AFS equity securities 17,439 (660 ) — — 17,439 (660 ) Total AFS securities $ 1,358,111 (15,651 ) 15,626 (406 ) 1,373,737 (16,057 ) December 31, 2015 Less than 12 months 12 months or longer Total ($ in thousands) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Unrealized AFS fixed income securities: U.S. government and government agencies $ 16,006 (87 ) 396 (4 ) $ 16,402 $ (91 ) Foreign government 1,067 (2 ) — — 1,067 (2 ) Obligations of states and political subdivisions 28,617 (160 ) — — 28,617 (160 ) Corporate securities 761,479 (12,671 ) 50,382 (2,850 ) 811,861 (15,521 ) CLO and other ABS 197,477 (807 ) 12,022 (111 ) 209,499 (918 ) CMBS 146,944 (2,196 ) 15,385 (214 ) 162,329 (2,410 ) RMBS 264,914 (1,992 ) 63,395 (1,721 ) 328,309 (3,713 ) Total AFS fixed income securities 1,416,504 (17,915 ) 141,580 (4,900 ) 1,558,084 (22,815 ) AFS equity securities: Common stock 31,148 (1,998 ) — — 31,148 (1,998 ) Preferred stock 1,531 (40 ) — — 1,531 (40 ) Total AFS equity securities 32,679 (2,038 ) — — 32,679 (2,038 ) Total AFS securities $ 1,449,183 (19,953 ) 141,580 (4,900 ) $ 1,590,763 $ (24,853 )
Schedule of Other Investment Portfolio by Strategy and the Remaining Commitment Amount Associated With Each Strategy	Other Investments December 31, 2016 December 31, 2015 ($ in thousands) Carrying Value Remaining Commitment Maximum Exposure to Loss 1 Carrying Value Remaining Maximum 1 Alternative Investments Private equity $ 41,135 76,774 117,909 35,088 30,204 65,292 Private credit 28,193 40,613 68,806 13,246 15,129 28,375 Real assets 14,486 22,899 37,385 19,500 25,820 45,320 Total alternative investments 83,814 140,286 224,100 67,834 71,153 138,987 Other securities 18,583 3,400 21,983 10,008 3,200 13,208 Total other investments $ 102,397 143,686 246,083 77,842 74,353 152,195
Schedule of Aggregated Summarized Balance Sheet Financial Information For Partnerhips In Our Alternative Investment Portfolio	Balance Sheet Information September 30, ($ in millions) 2016 2015 Investments $ 11,244 7,527 Total assets 12,075 8,515 Total liabilities 1,802 316 Total partners’ capital 10,273 8,199
Schedule of Aggregated Summarized Income Statement Financial Information For Partnerhips In Our Alternative Investment Portfolio	Income Statement Information 12 months ended September 30, ($ in millions) 2016 2015 2014 Net investment income $ (44 ) 129 226 Realized gains 1,374 1,187 581 Net change in unrealized (depreciation) appreciation (719 ) (1,364 ) 1,098 Net income $ 611 (48 ) 1,905 Insurance Subsidiaries' alternative investments income 3.1 (1.9 ) 13.6
Schedule Of Securities Pledged As Collateral	The following table summarizes the market value of these securities at December 31, 2016 : ($ in millions) FHLBI Collateral FHLBNY Collateral State and Regulatory Deposits Total U.S. government and government agencies $ 7.4 — 24.8 32.2 CMBS 0.5 — — 0.5 RMBS 59.6 58.2 — 117.8 Total pledged as collateral $ 67.5 58.2 24.8 150.5
Schedule of Components of Net Investment Income Earned	($ in thousands) 2016 2015 2014 Fixed income securities $ 129,306 123,230 126,489 Equity securities 7,368 9,161 7,449 Short-term investments 686 112 66 Other investments 2,940 (1,890 ) 13,580 Investment expenses (9,546 ) (9,297 ) (8,876 ) Net investment income earned $ 130,754 121,316 138,708
Schedule of OTTI by Asset Type	2016 Recognized in Earnings ($ in thousands) Gross Included in OCI AFS fixed income securities: Obligations of states and political subdivisions $ 2,797 — 2,797 Corporate securities 1,880 — 1,880 CLO and other ABS 19 — 19 CMBS 220 — 220 RMBS 275 10 265 Total AFS fixed income securities 5,191 10 5,181 AFS equity securities: Common stock 3,316 — 3,316 Preferred stock 2 — 2 Total AFS equity securities 3,318 — 3,318 Total OTTI losses $ 8,509 10 8,499 2015 Recognized in Earnings ($ in thousands) Gross Included in OCI AFS fixed income securities: Corporate securities $ 2,188 — 2,188 RMBS 1 — 1 Total AFS fixed income securities 2,189 — 2,189 AFS equity securities: Common stock 15,996 — 15,996 Preferred stock 181 — 181 Total AFS equity securities 16,177 — 16,177 Total OTTI losses $ 18,366 — 18,366 2014 Recognized in Earnings ($ in thousands) Gross Included in OCI AFS fixed income securities: RMBS $ 7 — 7 Total AFS fixed income securities 7 — 7 AFS equity securities: Common stock 10,517 — 10,517 Total AFS equity securities 10,517 — 10,517 Other investments 580 — 580 Total OTTI losses $ 11,104 — 11,104
Schedule of Components of Net Realized Gains Excluding OTTI Charges	($ in thousands) 2016 2015 2014 HTM fixed income securities Gains $ 3 5 2 Losses (1 ) (1 ) (20 ) AFS fixed income securities Gains 7,741 4,515 1,945 Losses (11,411 ) (312 ) (392 ) AFS equity securities Gains 8,108 29,168 36,871 Losses (864 ) (1,347 ) (704 ) Short-term investments Gains — — — Losses (13 ) — — Other investments Gains 3 162 1 Losses (4 ) (653 ) — Total net realized investment gains $ 3,562 31,537 37,703
Held-to-maturity Securities [Member]
Investment [Line Items]
Investments Classified by Contractual Maturity Date [Table Text Block]	($ in thousands) Carrying Value Fair Value Due in one year or less $ 55,505 56,249 Due after one year through five years 37,536 39,853 Due after five years through 10 years 8,515 9,109 Total HTM fixed income securities $ 101,556 105,211
AFS Fixed Income Securities [Member]
Investment [Line Items]
Investments Classified by Contractual Maturity Date [Table Text Block]	($ in thousands) Fair Value Due in one year or less $ 374,080 Due after one year through five years 2,141,596 Due after five years through 10 years 2,090,677 Due after 10 years 186,187 Total AFS fixed income securities $ 4,792,540

Investments Investments (AFS Fi

Investments Investments (AFS Fixed Maturity Securities by Contractual Maturity) (Tables) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Due in one year or less fair value	$ 374,080
Due after one year through five years fair value	2,141,596
Due after five years through 10 years fair value	2,090,677
Due after 10 years fair value	186,187
Available-for-sale Securities, Debt Securities	$ 4,792,540	$ 4,408,203

Comprehensive Income (Tables)

Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2016
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Schedule of Components of Comprehensive Income-Gross and Net of Tax	2016 ($ in thousands) Gross Tax Net Net income $ 219,955 61,460 158,495 Components of OCI: Unrealized losses (gains) on investment securities : Unrealized holding losses during the year (9,195 ) (3,218 ) (5,977 ) Non-credit portion of other-than-temporary impairments recognized in other comprehensive income (10 ) (4 ) (6 ) Amounts reclassified into net income: HTM securities (141 ) (49 ) (92 ) Non-credit OTTI 213 75 138 Realized losses on AFS securities 4,713 1,649 3,064 Net unrealized losses (4,420 ) (1,547 ) (2,873 ) Defined benefit pension and post-retirement plans: Net actuarial loss (12,079 ) (4,227 ) (7,852 ) Amounts reclassified into net income: Net actuarial loss 6,462 2,262 4,200 Defined benefit pension and post-retirement plans (5,617 ) (1,965 ) (3,652 ) Other comprehensive loss (10,037 ) (3,512 ) (6,525 ) Comprehensive income $ 209,918 57,948 151,970 2015 ($ in thousands) Gross Tax Net Net income $ 232,692 66,831 165,861 Components of OCI: Unrealized gains on investment securities : Unrealized holding losses during the year (40,221 ) (14,078 ) (26,143 ) Amounts reclassified into net income: HTM securities (580 ) (203 ) (377 ) Non-credit OTTI 357 125 232 Realized gains on AFS securities (14,016 ) (4,906 ) (9,110 ) Net unrealized losses (54,460 ) (19,062 ) (35,398 ) Defined benefit pension and post-retirement plans: Net actuarial gain 2,438 853 1,585 Amounts reclassified into net income: Net actuarial loss 7,077 2,477 4,600 Defined benefit pension and post-retirement plans 9,515 3,330 6,185 Other comprehensive loss (44,945 ) (15,732 ) (29,213 ) Comprehensive income $ 187,747 51,099 136,648 2014 ($ in thousands) Gross Tax Net Net income $ 197,131 55,304 141,827 Components of OCI: Unrealized gains on investment securities : Unrealized holding gains during the year 72,940 25,529 47,411 Amounts reclassified into net income: HTM securities (1,299 ) (455 ) (844 ) Non-credit OTTI 1,669 584 1,085 Realized gains on AFS securities (28,864 ) (10,102 ) (18,762 ) Net unrealized gains 44,446 15,556 28,890 Defined benefit pension and post-retirement plans: Net actuarial loss (54,136 ) (18,947 ) (35,189 ) Amounts reclassified into net income: Net actuarial loss 1,902 666 1,236 Defined benefit pension and post-retirement plans (52,234 ) (18,281 ) (33,953 ) Other comprehensive loss (7,788 ) (2,725 ) (5,063 ) Comprehensive income $ 189,343 52,579 136,764
Schedule of Components of Accumulated Other Comprehensive Income	Net Unrealized (Loss) Gain on Investment Securities ($ in thousands) OTTI Related HTM Related All Other Investments Subtotal Defined Benefit Pension and Post- retirement Plans Total AOCI Balance, December 31, 2014 $ (514 ) 623 80,284 80,393 (60,605 ) 19,788 OCI before reclassifications — (52 ) (26,091 ) (26,143 ) 1,585 (24,558 ) Amounts reclassified from AOCI 232 (377 ) (9,110 ) (9,255 ) 4,600 (4,655 ) Net current period OCI 232 (429 ) (35,201 ) (35,398 ) 6,185 (29,213 ) Balance, December 31, 2015 (282 ) 194 45,083 44,995 (54,420 ) (9,425 ) OCI before reclassifications (6 ) — (5,977 ) (5,983 ) (7,852 ) (13,835 ) Amounts reclassified from AOCI 138 (92 ) 3,064 3,110 4,200 7,310 Net current period OCI 132 (92 ) (2,913 ) (2,873 ) (3,652 ) (6,525 ) Balance, December 31, 2016 $ (150 ) 102 42,170 42,122 (58,072 ) (15,950 )
Schedule of Reclassification out of Accumulated Other Comprehensive Income	($ in thousands) Year ended December 31, 2016 Year ended December 31, 2015 Affected Line Item in the Consolidated Statement of Income HTM related Unrealized losses on HTM disposals $ 169 308 Net realized (losses) gains Amortization of net unrealized gains on HTM securities (310 ) (888 ) Net investment income earned (141 ) (580 ) Income before federal income tax 49 203 Total federal income tax expense (92 ) (377 ) Net income OTTI related Non-credit OTTI on disposed securities 213 357 Net realized (losses) gains 213 357 Income before federal income tax (75 ) (125 ) Total federal income tax expense 138 232 Net income Realized (losses) gains on AFS Realized (losses) gains on AFS disposals 4,713 (14,016 ) Net realized (losses) gains 4,713 (14,016 ) Income before federal income tax (1,649 ) 4,906 Total federal income tax expense 3,064 (9,110 ) Net income Defined benefit pension and post-retirement life plans Net actuarial loss 1,486 1,538 Losses and loss expenses incurred 4,976 5,539 Policy acquisition costs Total defined benefit pension and post-retirement life 6,462 7,077 Income before federal income tax (2,262 ) (2,477 ) Total federal income tax expense 4,200 4,600 Net income Total reclassifications for the period $ 7,310 (4,655 ) Net income

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Schedule of Carrying Amounts and Estimated Fair Values of Financial Instruments	December 31, 2016 December 31, 2015 ($ in thousands) Carrying Amount Fair Value Carrying Amount Fair Value Financial Assets Fixed income securities: HTM $ 101,556 105,211 201,354 209,544 AFS 4,792,540 4,792,540 4,408,203 4,408,203 Equity securities, AFS 146,753 146,753 207,051 207,051 Short-term investments 221,701 221,701 194,819 194,819 Financial Liabilities Short-term debt: 0.63% borrowings from FHLBI — — 15,000 14,977 1.25% borrowings from FHLBI — — 45,000 45,083 Total short-term debt — — 60,000 60,060 Long-term debt: 7.25% Senior Notes 49,901 56,148 49,898 56,929 6.70% Senior Notes 99,430 108,333 99,415 110,363 5.875% Senior Notes 185,000 176,860 185,000 192,474 1.61% Borrowings from FHLBNY 25,000 24,286 — — 1.56% Borrowings from FHLBNY 25,000 24,219 — — 3.03% Borrowings from FHLBI 60,000 59,313 — — Subtotal long-term debt 444,331 449,159 334,313 359,766 Unamortized debt issuance costs (5,664 ) (6,121 ) Total long-term debt $ 438,667 328,192
Schedule of Quantitative Disclosures of our Financial Assets that were Measured at Fair Value	December 31, 2016 Fair Value Measurements Using ($ in thousands) Assets Measured at Fair Value 12/31/16 Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) 1 Significant Other Observable Inputs (Level 2) 1 Significant Unobservable Inputs (Level 3) Description Measured on a recurring basis: AFS fixed income securities: U.S. government and government agencies $ 77,333 27,520 49,813 — Foreign government 26,865 — 26,865 — Obligations of states and political subdivisions 1,379,593 — 1,379,593 — Corporate securities 1,997,753 — 1,997,753 — CLO and other ABS 528,960 — 528,960 — CMBS 256,842 — 256,842 — RMBS 525,194 — 525,194 — Total AFS fixed income securities 4,792,540 27,520 4,765,020 — AFS equity securities: Common stock 130,608 122,932 — 7,676 Preferred stock 16,145 16,145 — — Total AFS equity securities 146,753 139,077 — 7,676 Total AFS securities 4,939,293 166,597 4,765,020 7,676 Short-term investments 221,701 221,701 — — Total assets measured at fair value $ 5,160,994 388,298 4,765,020 7,676 December 31, 2015 Fair Value Measurements Using ($ in thousands) Assets Measured at Fair Value 12/31/15 Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) 1 Significant Other Observable Inputs (Level 2) 1 Significant Unobservable Inputs (Level 3) Description Measured on a recurring basis: AFS fixed income securities: U.S. government and government agencies $ 104,115 42,702 61,413 — Foreign government 15,181 — 15,181 — Obligations of states and political subdivisions 1,359,142 — 1,359,142 — Corporate securities 1,900,182 — 1,900,182 — CLO and other ABS 244,154 — 244,154 — CMBS 243,592 — 243,592 — RMBS 541,837 — 541,837 — Total AFS fixed income securities 4,408,203 42,702 4,365,501 — AFS equity securities: Common stock 194,789 191,517 — 3,272 Preferred stock 12,262 12,262 — — Total AFS equity securities 207,051 203,779 — 3,272 Total AFS securities 4,615,254 246,481 4,365,501 3,272 Short-term investments 194,819 194,819 — — Total assets measured at fair value $ 4,810,073 441,300 4,365,501 3,272 1 There were no transfers of securities between Level 1 and Level 2.
Schedule of Summary of the Changes in Fair Value of Securities Using Level 3 Inputs	2016 ($ in thousands) Common Stock Fair value, December 31, 2015 $ 3,272 Total net (losses) gains for the period included in: OCI — Net income — Purchases 6,204 Sales (1,800 ) Issuances — Settlements — Transfers into Level 3 — Transfers out of Level 3 — Fair value, December 31, 2016 $ 7,676
Schedule of Quantitative Information of our Financial Assets and Liabilities that were Disclosed at Fair Value	December 31, 2016 Fair Value Measurements Using ($ in thousands) Assets/Liabilities Disclosed at Fair Value 12/31/2016 Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Financial Assets HTM: Obligations of states and political subdivisions $ 79,916 — 79,916 — Corporate securities 24,075 — 16,565 7,510 CMBS 1,220 — 1,220 — Total HTM fixed income securities $ 105,211 — 97,701 7,510 Financial Liabilities Long-term debt: 7.25% Senior Notes $ 56,148 — 56,148 — 6.70% Senior Notes 108,333 — 108,333 — 5.875% Senior Notes 176,860 176,860 — — 1.61% Borrowings from FHLBNY 24,286 — 24,286 — 1.56% Borrowings from FHLBNY 24,219 — 24,219 — 3.03% Borrowings from FHLBI 59,313 — 59,313 — Total long-term debt $ 449,159 176,860 272,299 — December 31, 2015 Fair Value Measurements Using ($ in thousands) Assets/Liabilities Disclosed at Fair Value 12/31/2015 Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Financial Assets HTM: Obligations of states and political subdivisions $ 181,880 — 181,880 — Corporate securities 22,015 — 18,679 3,336 CLO and other ABS 1,028 — 1,028 — CMBS 4,621 — 4,621 — Total HTM fixed income securities $ 209,544 — 206,208 3,336 Financial Liabilities Short-term debt: 0.63% borrowings from FHLBI $ 14,977 — 14,977 — 1.25% borrowings from FHLBI 45,083 — 45,083 — Total short-term debt 60,060 — 60,060 — Long-term debt: 7.25% Senior Notes 56,929 — 56,929 — 6.70% Senior Notes 110,363 — 110,363 — 5.875% Senior Notes 192,474 192,474 — — Total long-term debt $ 359,766 192,474 167,292 —

Reinsurance (Tables)

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2016
Reinsurance Disclosures [Abstract]
Schedule of Total Reinsurance Balances Segregated By Reinsurer	As of December 31, 2016 As of December 31, 2015 ($ in thousands) Reinsurance Balances % of Reinsurance Balance Reinsurance Balances % of Reinsurance Balance Total reinsurance recoverables $ 621,537 $ 561,968 Total prepaid reinsurance premiums 146,282 140,889 Total reinsurance balance 767,819 702,857 Federal and state pools 1 : NFIP 211,181 27 % 164,130 24 % New Jersey Unsatisfied Claim Judgment Fund 65,574 9 71,884 10 Other 3,227 — 3,136 — Total federal and state pools 279,982 36 239,150 34 Remaining reinsurance balance $ 487,837 64 $ 463,707 66 Munich Re Group (A.M. Best rated "A+") $ 119,520 16 $ 112,889 16 Hannover Ruckversicherungs AG (A.M. Best rated "A+") 106,298 13 99,535 14 AXIS Reinsurance Company (A.M. Best rated "A+") 59,737 8 53,374 8 Swiss Re Group (A.M. Best rated "A+") 50,494 7 51,340 7 Partner Reinsurance Company of the U.S. (A.M. Best rated “A”) 21,125 3 20,748 3 All other reinsurers 130,663 17 125,821 18 Total reinsurers 487,837 64 % 463,707 66 % Less: collateral 2 (113,763 ) (106,449 ) Reinsurers, net of collateral $ 374,074 $ 357,258 1 Considered to have minimal risk of default. 2 Includes letters of credit, trust funds, and funds held against reinsurance recoverables. Note: Some amounts may not foot due to rounding.
List Of Direct, Assumed, And Ceded Reinsurance Amounts	($ in thousands) 2016 2015 2014 Premiums written: Direct $ 2,577,259 2,403,519 2,228,270 Assumed 28,779 23,848 26,306 Ceded (368,750 ) (357,463 ) (369,296 ) Net $ 2,237,288 2,069,904 1,885,280 Premiums earned: Direct $ 2,484,715 2,330,267 2,183,258 Assumed 28,214 23,209 34,653 Ceded (363,357 ) (363,567 ) (365,302 ) Net $ 2,149,572 1,989,909 1,852,609 Losses and loss expenses incurred: Direct $ 1,560,356 1,274,872 1,314,864 Assumed 22,708 16,996 26,187 Ceded (348,267 ) (143,327 ) (183,550 ) Net $ 1,234,797 1,148,541 1,157,501
Schedule of Ceded Premiums and Losses Related to Flood Operations	Ceded to NFIP ($ in thousands) 2016 2015 2014 Ceded premiums written $ (232,245 ) (228,907 ) (237,718 ) Ceded premiums earned (227,882 ) (233,940 ) (234,224 ) Ceded losses and loss expenses incurred (239,891 ) (62,078 ) (57,323 )

Reserve for Losses and Loss E43

Reserve for Losses and Loss Expenses (Tables)	12 Months Ended
	Dec. 31, 2016
Insurance Loss Reserves [Abstract]
Schedule of Roll Forward of Reserves for Losses and Loss Expenses	($ in thousands) 2016 2015 2014 Gross reserves for losses and loss expenses, at beginning of year $ 3,517,728 3,477,870 3,349,770 Less: reinsurance recoverable on unpaid losses and loss expenses, at beginning of year 551,019 571,978 540,839 Net reserves for losses and loss expenses, at beginning of year 2,966,709 2,905,892 2,808,931 Incurred losses and loss expenses for claims occurring in the: Current year 1,300,565 1,217,550 1,216,770 Prior years (65,768 ) (69,009 ) (59,269 ) Total incurred losses and loss expenses 1,234,797 1,148,541 1,157,501 Paid losses and loss expenses for claims occurring in the: Current year 450,811 446,550 468,478 Prior years 670,176 641,174 592,062 Total paid losses and loss expenses 1,120,987 1,087,724 1,060,540 Net reserves for losses and loss expenses, at end of year 3,080,519 2,966,709 2,905,892 Add: Reinsurance recoverable on unpaid losses and loss expenses, at end of year 611,200 551,019 571,978 Gross reserves for losses and loss expenses at end of year $ 3,691,719 3,517,728 3,477,870
Schedule of(Favorable)/ Unfavorable Prior Year Development	(Favorable)/Unfavorable Prior Year Development ($ in millions) 2016 2015 2014 General Liability $ (45.0 ) (51.0 ) (43.9 ) Commercial Automobile 25.3 2.4 (4.1 ) Workers Compensation (56.0 ) (37.0 ) — Businessowners' Policies 1.8 2.2 1.9 Commercial Property 0.3 (3.0 ) (2.1 ) Homeowners 1.7 1.5 (4.0 ) Personal Automobile 1.0 0.4 (10.8 ) E&S 7.1 15.5 3.7 Other (2.0 ) — — Total $ (65.8 ) (69.0 ) (59.3 )
Schedule of Exposure to Various Asbestos and Environmental Claims	2016 ($ in millions) Gross Net Asbestos $ 7.9 6.6 Landfill sites 12.8 8.1 Leaking underground storage tanks 9.3 8.0 Total $ 30.0 22.7
Schedule of Roll Forward of Gross and Net Asbestos and Environmental Incurred Losses and Loss Expenses and Related Reserves	2016 2015 2014 ($ in thousands) Gross Net Gross Net Gross Net Asbestos Reserves for losses and loss expenses at beginning of year $ 8,024 6,793 8,751 7,314 8,897 7,518 Incurred losses and loss expenses 77 77 (428 ) (77 ) 60 — Less: losses and loss expenses paid (254 ) (255 ) (299 ) (444 ) (206 ) (204 ) Reserves for losses and loss expenses at the end of year $ 7,847 6,615 8,024 6,793 8,751 7,314 Environmental Reserves for losses and loss expenses at beginning of year $ 22,387 16,368 21,902 15,680 23,867 17,649 Incurred losses and loss expenses 1,406 1,303 3,396 3,397 107 — Less: losses and loss expenses paid (1,678 ) (1,570 ) (2,911 ) (2,709 ) (2,072 ) (1,969 ) Reserves for losses and loss expenses at the end of year $ 22,115 16,101 22,387 16,368 21,902 15,680 Total Asbestos and Environmental Claims Reserves for losses and loss expenses at beginning of year $ 30,411 23,161 30,653 22,994 32,764 25,167 Incurred losses and loss expenses 1,483 1,380 2,968 3,320 167 — Less: losses and loss expenses paid (1,932 ) (1,825 ) (3,210 ) (3,153 ) (2,278 ) (2,173 ) Reserves for losses and loss expenses at the end of year $ 29,962 22,716 30,411 23,161 30,653 22,994
Short-duration Insurance Contracts, Claims Development [Table Text Block]	All Lines (in thousands) Incurred Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ 1,038,585 1,066,670 1,047,912 1,028,546 1,028,956 1,015,897 1,003,552 998,496 992,673 989,709 42,970 84,996 2008 957,247 988,584 990,931 964,862 947,306 936,975 927,958 931,785 926,017 48,590 85,264 2009 920,143 941,972 916,691 883,590 870,057 869,927 857,960 853,401 49,532 85,444 2010 950,114 973,742 977,959 956,600 943,118 922,404 915,131 65,625 94,093 2011 1,042,576 1,061,667 1,062,233 1,056,107 1,033,518 1,023,726 82,565 104,303 2012 1,065,437 1,071,290 1,020,655 998,028 973,089 101,992 103,498 2013 1,044,142 1,062,045 1,047,230 1,021,007 182,613 90,330 2014 1,107,513 1,133,798 1,146,990 278,689 93,747 2015 1,114,081 1,130,513 375,894 91,410 2016 1,188,608 589,938 85,202 Total 10,168,191 All Lines (in thousands) Cumulative Paid Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2007 $ 350,369 543,949 665,277 762,422 835,347 877,933 896,590 912,683 920,931 929,082 2008 286,314 489,633 609,851 690,016 764,196 798,996 819,280 839,392 853,769 2009 277,275 442,417 540,982 634,902 695,249 736,100 760,589 775,885 2010 328,826 509,910 625,229 704,895 773,536 803,773 823,770 2011 391,944 585,867 692,730 782,655 852,202 901,801 2012 378,067 555,819 651,544 743,742 810,135 2013 335,956 518,872 644,475 748,758 2014 405,898 614,075 736,154 2015 376,641 581,203 2016 387,272 Total 7,547,829 All outstanding liabilities before 2007, net of reinsurance 324,070 Liabilities for loss and loss adjustment expenses, net of reinsurance 2,944,432 General Liability (in thousands) Incurred Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ 252,732 256,627 255,538 250,834 248,807 242,878 234,173 234,697 231,439 230,717 17,815 14,016 2008 250,239 243,755 243,536 234,770 233,712 224,236 219,551 221,640 221,203 19,939 13,721 2009 237,913 241,625 233,530 223,146 212,947 211,243 206,387 205,741 22,858 13,815 2010 215,208 228,680 242,499 237,154 222,328 211,619 208,968 29,380 12,629 2011 229,967 228,720 239,480 230,785 217,256 211,196 36,350 11,533 2012 238,979 245,561 215,083 194,144 175,305 44,493 9,864 2013 250,609 251,421 239,776 225,709 90,026 10,107 2014 244,312 249,946 257,132 135,883 10,157 2015 254,720 245,710 167,995 9,371 2016 277,214 233,794 7,790 Total 2,258,895 General Liability (in thousands) Cumulative Paid Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2007 $ 14,695 44,356 80,621 123,108 158,424 181,641 191,405 201,842 204,159 208,449 2008 16,397 45,595 82,421 113,088 151,055 166,394 176,873 186,896 194,257 2009 14,346 37,143 64,970 103,213 130,554 151,920 166,767 176,316 2010 15,726 46,201 80,018 113,050 143,360 161,487 172,394 2011 13,924 42,692 73,643 102,978 135,377 159,768 2012 13,030 35,241 56,580 89,008 109,448 2013 12,789 35,113 72,127 104,587 2014 14,901 46,825 79,972 2015 14,665 39,978 2016 15,684 Total 1,260,853 All outstanding liabilities before 2007, net of reinsurance 72,887 Liabilities for loss and loss adjustment expenses, net of reinsurance 1,070,929 Workers Compensation (in thousands) Incurred Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ 231,462 236,993 231,104 226,095 230,109 225,165 225,904 222,623 218,828 216,177 23,152 16,344 2008 219,616 243,186 255,810 250,423 241,921 245,993 244,100 243,512 238,836 26,983 14,400 2009 197,504 215,946 213,036 210,109 210,756 216,992 212,536 208,611 24,238 12,214 2010 198,371 214,469 212,838 211,030 214,916 212,448 208,155 34,437 12,181 2011 205,238 218,973 214,743 215,114 210,591 205,708 38,227 11,843 2012 203,864 208,036 199,360 195,197 188,596 39,122 11,601 2013 199,794 194,318 187,658 173,160 43,058 11,361 2014 199,346 187,065 182,579 55,599 10,464 2015 193,729 194,639 63,496 10,479 2016 196,774 107,977 9,910 Total 2,013,235 Workers Compensation (in thousands) Cumulative Paid Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2007 $ 31,478 88,786 123,681 144,713 156,320 164,373 169,941 175,205 179,011 180,865 2008 39,628 100,678 139,144 158,083 171,403 180,556 188,206 191,265 195,962 2009 37,885 87,299 117,019 133,116 145,417 154,726 160,529 164,336 2010 46,795 93,281 122,442 137,184 149,086 153,795 158,078 2011 42,941 90,836 118,847 134,646 139,232 149,269 2012 40,911 86,909 108,211 122,755 132,052 2013 36,829 74,568 96,376 109,739 2014 35,924 78,944 100,876 2015 33,857 77,320 2016 34,525 Total 1,303,022 All outstanding liabilities before 2007, net of reinsurance 226,553 Liabilities for loss and loss adjustment expenses, net of reinsurance 936,766 Commercial Automobile (in thousands) Incurred Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ 185,733 194,567 187,966 182,030 179,739 178,956 176,049 175,342 175,431 175,894 1,434 24,074 2008 196,370 195,823 190,349 187,100 187,417 182,785 180,902 183,736 183,618 1,332 24,105 2009 199,541 191,079 182,724 169,858 166,682 162,911 161,251 161,923 1,873 24,554 2010 187,562 189,305 187,778 181,923 179,854 172,969 173,157 2,318 25,194 2011 174,006 183,044 182,325 178,421 172,617 174,882 5,153 25,146 2012 179,551 191,947 183,527 184,289 184,367 6,421 23,751 2013 188,289 205,282 209,197 207,994 18,464 25,215 2014 200,534 212,725 216,824 37,432 27,129 2015 220,994 240,958 65,528 28,475 2016 255,187 106,894 28,740 Total 1,974,804 Commercial Automobile (in thousands) Cumulative Paid Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2007 $ 65,544 102,233 126,507 146,690 163,629 170,241 171,622 171,839 173,050 173,980 2008 69,053 104,711 130,857 151,741 166,487 173,795 175,244 180,779 181,779 2009 63,126 94,406 113,697 137,564 149,949 155,560 158,303 159,723 2010 68,098 99,254 128,015 146,913 163,513 167,227 169,100 2011 69,849 99,196 121,576 142,507 157,291 166,082 2012 73,316 105,371 127,235 148,669 168,114 2013 76,469 109,893 140,015 169,850 2014 80,810 117,169 148,884 2015 91,347 132,260 2016 106,022 Total 1,575,794 All outstanding liabilities before 2007, net of reinsurance 3,271 Liabilities for loss and loss adjustment expenses, net of reinsurance 402,281 Businessowners' Policies (in thousands) Incurred Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ 32,749 34,011 33,397 31,212 29,270 29,393 28,440 28,503 29,691 29,288 124 2,956 2008 39,660 38,986 39,334 32,974 30,250 29,793 31,066 31,340 30,967 94 3,258 2009 48,535 51,762 46,645 43,828 43,553 44,938 44,299 44,273 730 3,473 2010 53,669 49,285 42,408 39,915 40,899 40,581 41,239 693 3,917 2011 54,469 57,083 51,047 58,242 59,256 58,966 2,177 4,956 2012 54,342 48,029 46,303 44,172 44,077 834 5,533 2013 49,617 42,618 41,005 40,624 4,189 3,474 2014 55,962 60,949 62,548 10,891 4,038 2015 52,871 53,768 12,089 3,860 2016 52,335 16,027 3,398 Total 458,085 Businessowners' Policies (in thousands) Cumulative Paid Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2007 $ 14,051 18,870 22,583 24,978 25,759 27,273 28,073 28,095 28,368 29,048 2008 15,019 21,765 24,449 25,738 28,026 28,660 28,589 29,778 30,873 2009 18,915 29,612 32,689 36,073 40,052 42,895 43,358 43,448 2010 20,821 28,131 31,027 34,705 37,819 38,900 40,279 2011 27,884 37,362 41,011 46,444 52,114 55,856 2012 22,199 31,833 35,089 37,215 38,766 2013 17,412 26,592 30,845 34,760 2014 28,914 40,584 44,911 2015 24,189 36,014 2016 24,655 Total 378,610 All outstanding liabilities before 2007, net of reinsurance 7,327 Liabilities for loss and loss adjustment expenses, net of reinsurance 86,802 Commercial Property (in thousands) Incurred Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ 98,167 104,160 100,809 101,027 103,183 103,381 102,998 102,732 102,679 103,077 2 6,919 2008 97,578 102,860 101,436 101,470 101,265 101,702 101,043 100,881 101,043 4 7,604 2009 82,619 82,124 82,025 82,014 80,774 80,455 80,558 80,545 10 7,009 2010 105,647 96,851 97,386 96,127 95,530 95,363 95,178 21 7,667 2011 136,954 131,667 130,942 131,282 131,353 131,113 22 9,035 2012 118,464 114,224 115,375 116,658 117,102 (22 ) 8,512 2013 88,101 90,639 90,103 90,005 (78 ) 5,704 2014 141,192 136,249 136,820 (1,052 ) 6,503 2015 110,270 109,513 (1,320 ) 6,380 2016 121,927 7,112 6,253 Total 1,086,323 Commercial Property (in thousands) Cumulative Paid Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2007 $ 63,159 95,050 99,036 99,942 101,805 102,310 102,370 102,532 102,663 103,061 2008 68,211 98,921 100,465 99,288 100,213 100,752 100,908 100,868 101,034 2009 59,933 78,695 80,433 80,894 80,251 80,352 80,529 80,509 2010 69,543 91,918 94,602 95,111 95,270 95,147 95,156 2011 94,538 127,580 129,579 130,681 131,060 131,115 2012 81,528 108,834 111,503 114,699 116,291 2013 60,244 87,874 90,446 90,350 2014 101,131 132,909 136,634 2015 79,048 106,182 2016 83,966 Total 1,044,298 All outstanding liabilities before 2007, net of reinsurance 254 Liabilities for loss and loss adjustment expenses, net of reinsurance 42,279 Personal Automobile (in thousands) Incurred Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ 97,161 102,932 103,283 102,325 101,744 101,654 101,814 101,747 101,750 101,714 254 15,354 2008 100,311 106,999 106,842 103,934 100,213 99,912 99,686 99,255 99,116 264 16,042 2009 93,808 103,319 105,033 103,908 104,734 103,866 103,393 103,412 256 17,346 2010 103,340 110,075 112,346 109,515 107,490 107,405 107,224 277 20,821 2011 113,232 116,164 113,686 112,993 114,241 113,830 644 22,700 2012 113,771 114,921 109,832 109,324 110,294 988 22,332 2013 108,417 109,620 106,225 106,703 2,252 22,359 2014 102,250 109,325 106,757 6,945 22,478 2015 96,387 99,698 13,594 20,797 2016 92,727 18,187 19,044 Total 1,041,475 Personal Automobile (in thousands) Cumulative Paid Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2007 $ 45,846 66,884 82,455 92,019 97,335 99,454 100,539 100,667 101,099 101,134 2008 50,396 73,194 84,715 91,834 95,932 97,723 98,174 98,604 98,668 2009 51,039 71,911 86,431 96,229 100,566 102,187 102,322 102,437 2010 58,786 82,490 95,300 101,540 104,061 105,849 106,453 2011 61,323 82,102 93,878 105,068 111,085 112,732 2012 63,704 82,729 94,842 102,977 107,890 2013 61,384 80,861 92,637 100,528 2014 62,519 83,739 92,589 2015 58,725 76,470 2016 57,961 Total 956,862 All outstanding liabilities before 2007, net of reinsurance 5,803 Liabilities for loss and loss adjustment expenses, net of reinsurance 90,416 Homeowners (in thousands) Incurred Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ 38,589 36,547 34,926 34,273 34,186 34,422 34,566 34,056 34,025 34,010 58 4,570 2008 41,224 41,747 39,342 39,203 38,062 38,410 38,111 38,042 38,045 65 5,139 2009 47,636 44,511 42,609 40,313 61,927 40,400 40,465 40,457 74 5,631 2010 68,373 67,525 63,285 97,761 62,462 62,402 62,339 86 9,128 2011 103,804 98,211 82,744 94,167 94,543 94,183 143 15,102 2012 87,260 82,745 86,560 86,667 86,271 251 16,927 2013 73,670 72,528 71,494 72,145 1,545 7,738 2014 80,111 82,461 83,637 1,928 8,739 2015 76,637 76,400 2,984 7,677 2016 60,105 5,646 6,402 Total 647,592 Homeowners (in thousands) Cumulative Paid Loss and Allocated Loss Adjustment Expenses, Net of Reinsurance Accident Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2007 $ 20,840 30,104 31,846 32,228 33,081 33,862 33,857 33,869 33,953 33,951 2008 21,277 33,535 36,271 37,086 37,763 37,837 37,933 37,939 37,930 2009 28,299 36,965 38,078 39,342 39,731 39,819 39,907 40,189 2010 43,699 58,638 60,295 61,106 62,155 62,227 62,241 2011 71,668 89,963 91,718 92,185 93,312 93,720 2012 69,056 79,584 82,720 84,250 85,196 2013 50,664 65,528 67,838 69,775 2014 61,561 76,007 79,751 2015 52,589 70,078 2016 42,252 Total 615,083 All outstanding liabilities before 2007, net of reinsurance 6,469 Liabilities for loss and loss adjustment expenses, net of reinsurance 38,978 E&S - Liability (in thousands) Incurred Loss and Loss Adjustment Expenses, Net of Reinsurance As of December 31, 2016 Accident Year 2011 2012 2013 2014 2015 2016 IBNR Cumulative Number of Reported Claims 2007 $ — — — — — — — — 2008 92 169 146 119 52 (162 ) (270 ) 35 2009 885 1,053 938 728 710 96 (630 ) 274 2010 3,294 4,106 3,369 4,299 3,831 3,055 (1,778 ) 797 2011 8,127 7,102 9,853 12,207 10,273 9,652 (599 ) 1,303 2012 42,367 42,621 43,175 46,149 46,165 9,289 1,982 2013 55,468 60,309 67,099 69,112 21,956 2,128 2014 55,316 63,505 69,929 29,236 1,888 2015 75,498 76,432 48,390 2,313 2016 94,451 84,328 1,760 Total 368,730 E&S - Liability (in thousands) Cumulative Paid Loss and Loss Adjustment Expenses, Net of Reinsurance Accident Year 2011 2012 2013 2014 2015 2016 2007 $ — — — — — — 2008 — 24 70 80 79 92 2009 — 198 431 605 626 709 2010 — 1,218 2,570 3,574 4,078 4,513 2011 — 806 3,200 6,445 9,954 9,912 2012 3,722 7,914 16,430 25,064 32,343 2013 2,715 9,470 21,980 35,200 2014 2,353 12,234 25,571 2015 3,036 13,057 2016 3,720 Total 125,117 All outstanding liabilities before 2007, net of reinsurance — Liabilities for loss and loss adjustment expenses, net of reinsurance 243,613
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table Text Block]	(in thousands) December 31, 2016 Net outstanding liabilities: Standard Commercial Lines General liability 1,070,929 Workers compensation 936,766 Commercial automobile 402,281 Businessowners' policies 86,802 Commercial property 42,279 Other Commercial Lines 11,389 Total Standard Commercial Lines net outstanding liabilities 2,550,446 Standard Personal Lines Personal automobile 90,416 Homeowners 38,978 Other Personal Lines 7,728 Total Personal Lines net outstanding liabilities 137,122 E&S Lines Commercial liability 243,613 Commercial property 13,251 Total E&S Lines net outstanding liabilities 256,864 Total liabilities for unpaid loss and loss adjustment expenses, net of reinsurance 2,944,432 Reinsurance recoverable on unpaid claims: Standard Commercial Lines General liability 179,997 Workers compensation 223,327 Commercial automobile 17,373 Businessowners' policies 7,012 Commercial property 13,615 Other Commercial Lines 2,613 Total Standard Commercial Lines reinsurance recoverable on unpaid loss 443,937 Standard Personal Lines Personal automobile 55,223 Homeowners 3,206 Other Personal Lines 82,625 Total Personal Lines reinsurance recoverable on unpaid loss 141,054 E&S Lines Commercial liability 25,741 Commercial property 468 Total E&S Lines reinsurance recoverable on unpaid loss 26,209 Total reinsurance recoverable on unpaid loss 611,200 Unallocated loss adjustment expenses 136,087 Total gross liability for unpaid loss and loss adjustment expenses 3,691,719
Short-duration Insurance Contracts, Schedule of Historical Claims Duration [Table Text Block]	Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 7 8 9 10 General liability 6.5% 12.4 15.1 16.6 15.3 10.2 5.5 4.3 2.3 2.2 Workers compensation 19.0 23.9 14.2 8.2 5.3 3.9 3.1 2.4 2.5 1.2 Commercial automobile 38.6 17.6 14.0 12.6 9.2 3.8 1.3 1.2 0.4 0.2 Businessowners’ policies 46.9 20.1 8.3 8.0 6.2 4.8 1.6 1.5 0.9 0.8 Commercial property 70.0 26.3 2.4 0.4 0.4 0.2 0.1 0.1 0.1 0.1 Personal automobile 54.9 18.9 11.3 7.8 4.1 1.6 0.4 0.1 0.3 — Homeowners 69.6 21.8 3.8 1.8 1.6 0.6 0.2 0.1 0.1 0.1 E&S Lines - liability 3.9 12.2 17.8 19.8 16.0 9.5

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Schedule of Revenue from Continuing Operations By Segment	Revenue by Segment Years ended December 31, ($ in thousands) 2016 2015 2014 Standard Commercial Lines: Net premiums earned: Commercial automobile $ 398,942 358,909 333,310 Workers compensation 308,233 290,075 274,585 General liability 527,859 483,291 444,938 Commercial property 293,438 269,022 244,792 Businessowners’ policies 97,754 93,428 85,788 Bonds 23,227 20,350 19,288 Other 16,030 14,367 13,011 Miscellaneous income 7,782 6,343 14,747 Total Standard Commercial Lines revenue 1,673,265 1,535,785 1,430,459 Standard Personal Lines: Net premiums earned: Personal automobile 142,876 146,784 151,317 Homeowners 130,973 134,382 134,273 Other 6,758 6,968 11,157 Miscellaneous income 1,098 1,113 1,834 Total Standard Personal Lines revenue 281,705 289,247 298,581 E&S Lines: Net premiums earned: Commercial liability 151,638 126,064 99,086 Commercial property 51,844 46,269 41,064 Miscellaneous income 1 — 17 Total E&S Lines revenue 203,483 172,333 140,167 Investments: Net investment income 130,754 121,316 138,708 Net realized investment (losses) gains (4,937 ) 13,171 26,599 Total investment revenues 125,817 134,487 165,307 Total all segments 2,284,270 2,131,852 2,034,514 Other income — — 347 Total revenues $ 2,284,270 2,131,852 2,034,861
Schedule of Income from Continuing Operations before Federal Income Tax	Income before Federal Income Tax Years ended December 31, ($ in thousands) 2016 2015 2014 Standard Commercial Lines: Underwriting gain, before federal income tax $ 146,435 164,496 61,221 GAAP combined ratio 91.2 % 89.2 % 95.7 % Statutory combined ratio 89.9 % 89.2 % 95.5 % Standard Personal Lines: Underwriting gain, before federal income tax 12,419 1,336 16,536 GAAP combined ratio 95.6 % 99.5 % 94.4 % Statutory combined ratio 95.2 % 99.9 % 94.5 % E&S Lines: Underwriting (loss) gain, before federal income tax (6,921 ) (16,803 ) 386 GAAP combined ratio 103.4 % 109.8 % 99.7 % Statutory combined ratio 102.1 % 108.4 % 99.2 % Investments: Net investment income $ 130,754 121,316 138,708 Net realized investment (losses) gains (4,937 ) 13,171 26,599 Total investment income, before federal income tax 125,817 134,487 165,307 Tax on investment income 30,621 32,090 43,811 Total investment income, after federal income tax $ 95,196 102,397 121,496
Schedule of Reconciliation of Segment Results to Income From Continuing Operations, Before Federal Income Tax	Reconciliation of Segment Results to Income before Federal Income Tax Years ended December 31, ($ in thousands) 2016 2015 2014 Underwriting gain (loss), before federal income tax Standard Commercial Lines $ 146,435 164,496 61,221 Standard Personal Lines 12,419 1,336 16,536 E&S Lines (6,921 ) (16,803 ) 386 Investment income, before federal income tax 125,817 134,487 165,307 Total all segments 277,750 283,516 243,450 Interest expense (22,771 ) (22,428 ) (23,063 ) General corporate and other expenses (35,024 ) (28,396 ) (23,256 ) Income, before federal income tax $ 219,955 232,692 197,131

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Schedule of Reconciliation of Earnings Per Share	2016 Income Shares Per Share ($ in thousands, except per share amounts) (Numerator) (Denominator) Amount Basic EPS: Net income available to common stockholders $ 158,495 57,889 $ 2.74 Effect of dilutive securities: Stock compensation plans — 858 Diluted EPS: Net income available to common stockholders $ 158,495 58,747 $ 2.70 2015 Income Shares Per Share ($ in thousands, except per share amounts) (Numerator) (Denominator) Amount Basic EPS: Net income available to common stockholders $ 165,861 57,212 $ 2.90 Effect of dilutive securities: Stock compensation plans — 944 Diluted EPS: Net income available to common stockholders $ 165,861 58,156 $ 2.85 2014 Income Shares Per Share ($ in thousands, except per share amounts) (Numerator) (Denominator) Amount Basic EPS: Net income available to common stockholders $ 141,827 56,310 $ 2.52 Effect of dilutive securities: Stock compensation plans — 1,041 Diluted EPS: Net income available to common stockholders $ 141,827 57,351 $ 2.47

Federal Income Taxes (Tables)

Federal Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Schedule of Reconciliation of Federal Income Tax on Income at the Corporate Rate to the Effective Tax Rate	($ in thousands) 2016 2015 2014 Tax at statutory rate of 35% $ 76,984 81,442 68,996 Tax-advantaged interest (12,126 ) (13,164 ) (12,926 ) Dividends received deduction (1,114 ) (1,817 ) (1,121 ) Other (2,284 ) 370 355 Federal income tax expense from continuing operations $ 61,460 66,831 55,304
Schedule of Deferred Tax Assets and Liabilities	($ in thousands) 2016 2015 Deferred tax assets: Net loss reserve discounting $ 70,065 74,436 Net unearned premiums 78,201 72,057 Employee benefits 17,881 30,432 Long-term incentive compensation plans 17,750 15,551 Temporary investment write-downs 2,475 5,419 Other investment related items, net 1,484 — Net operating loss 771 1,454 Other 8,344 8,132 Total deferred tax assets 196,971 207,481 Deferred tax liabilities: Deferred policy acquisition costs 75,310 72,481 Unrealized gains on investment securities 22,681 24,228 Other investment-related items, net — 5,566 Accelerated depreciation and amortization 14,140 12,510 Total deferred tax liabilities 112,131 114,785 Net deferred federal income tax asset $ 84,840 92,696
Summary of Operating Loss Carryforwards	As of December 31, 2016 , we had federal tax net operating loss ("NOL") carryforwards of $2.2 million . These NOLs, which are subject to an annual limitation of $1.9 million , will expire between 2030 and 2031 as follows: ($ in thousands) Gross NOL Tax Effected NOL 2030 $ 2,124 744 2031 79 28 Total NOL carryforwards $ 2,203 772

Retirement Plans (Tables)

Retirement Plans (Tables)	12 Months Ended
	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Schedule Of Plan Terms In Effect And Revisions Of Retirement Savings Plan	(a) Selective Insurance Retirement Savings Plan (“Retirement Savings Plan”) SICA offers a voluntary defined contribution 401(k) plan, which is available to most of our employees and is a tax-qualified retirement plan subject to the Employee Retirement Income Security Act of 1974 ("ERISA"). Expense recorded for this plan was $15.0 million in 2016 , $14.1 million in 2015 , and $13.4 million in 2014 .
Schedule of Funded Status Of Retirement Income Plan And Retirement Life Plan	December 31, Pension Plan ($ in thousands) 2016 2015 Change in Benefit Obligation: Benefit obligation, beginning of year $ 310,308 322,271 Service cost 1,647 7,215 Interest cost 12,336 13,668 Actuarial losses (gains) 15,086 (24,994 ) Benefits paid (8,789 ) (7,852 ) Benefit obligation, end of year $ 330,588 310,308 Change in Fair Value of Assets: Fair value of assets, beginning of year $ 249,700 253,452 Actual return on plan assets, net of expenses 21,079 (7,600 ) Contributions by the employer to funded plans 54,525 11,700 Benefits paid (8,789 ) (7,852 ) Fair value of assets, end of year $ 316,515 249,700 Funded status $ (14,073 ) (60,608 )
Schedule of Amounts Recognized in Consolidated Balance Sheet	Amounts Recognized in the Consolidated Balance Sheet: Liabilities $ (14,073 ) (60,608 ) Net pension liability, end of year $ (14,073 ) (60,608 )
Schedule of Amounts recognized in Accumulated Other than Comprehensive Income	Amounts Recognized in AOCI: Net actuarial loss $ 85,845 80,828 Total $ 85,845 80,828
Schedule of Other Information as of December 31	Other Information as of December 31: Accumulated benefit obligation $ 330,588 310,307
Schedule of Components Of Net Periodic Benefit Cost And Other Amounts Recognized In Other Comprehensive Income	Pension Plan ($ in thousands) 2016 2015 2014 Components of Net Periodic Benefit Cost and Other Amounts Recognized in Other Comprehensive Income: Net Periodic Benefit Cost: Service cost $ 1,647 7,215 5,763 Interest cost 12,336 13,668 12,776 Expected return on plan assets (17,309 ) (15,969 ) (15,671 ) Amortization of unrecognized actuarial loss 6,299 6,831 1,776 Total net periodic cost $ 2,973 11,745 4,644 Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income: Net actuarial loss (gain) $ 11,316 (1,425 ) 52,556 Reversal of amortization of net actuarial loss (6,299 ) (6,831 ) (1,776 ) Total recognized in other comprehensive income $ 5,017 (8,256 ) 50,780 Total recognized in net periodic benefit cost and other comprehensive income $ 7,990 3,489 55,424
Schedule Of Weighted- Average Expense and Liability Assumptions	Weighted-Average Liability Assumptions as of December 31: Discount rate 4.41 % 4.69 Rate of compensation increase — 4.00 Pension Plan 2016 2015 2014 Weighted-Average Expense Assumptions for the years ended December 31: Discount rate 4.69 % 4.29 5.16 Expected return on plan assets 6.37 6.27 6.92 Rate of compensation increase 1 — 4.00 4.00
Schedule of Allocation of Plan Assets	2016 2015 Target Ranges Actual Percentage Actual Percentage Long duration fixed income 40%-100% 53 % 60 % Global equity 0%-40% 33 % 36 % Alternatives & other return seeking assets 1 0%-30% 6 % 3 % Cash and short-term investments 0%-5% 8 % 1 % Total — % 100 % 100 %
Schedule of Quantitative Disclosures of our Financial Assets that were Measured at Fair Value	December 31, 2016 Fair Value Measurements Using ($ in thousands) Assets Measured at Fair Value 12/31/16 Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) 1 Significant Other Observable Inputs (Level 2) 1 Significant Unobservable Inputs (Level 3) Description Measured on a recurring basis: AFS fixed income securities: U.S. government and government agencies $ 77,333 27,520 49,813 — Foreign government 26,865 — 26,865 — Obligations of states and political subdivisions 1,379,593 — 1,379,593 — Corporate securities 1,997,753 — 1,997,753 — CLO and other ABS 528,960 — 528,960 — CMBS 256,842 — 256,842 — RMBS 525,194 — 525,194 — Total AFS fixed income securities 4,792,540 27,520 4,765,020 — AFS equity securities: Common stock 130,608 122,932 — 7,676 Preferred stock 16,145 16,145 — — Total AFS equity securities 146,753 139,077 — 7,676 Total AFS securities 4,939,293 166,597 4,765,020 7,676 Short-term investments 221,701 221,701 — — Total assets measured at fair value $ 5,160,994 388,298 4,765,020 7,676 December 31, 2015 Fair Value Measurements Using ($ in thousands) Assets Measured at Fair Value 12/31/15 Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) 1 Significant Other Observable Inputs (Level 2) 1 Significant Unobservable Inputs (Level 3) Description Measured on a recurring basis: AFS fixed income securities: U.S. government and government agencies $ 104,115 42,702 61,413 — Foreign government 15,181 — 15,181 — Obligations of states and political subdivisions 1,359,142 — 1,359,142 — Corporate securities 1,900,182 — 1,900,182 — CLO and other ABS 244,154 — 244,154 — CMBS 243,592 — 243,592 — RMBS 541,837 — 541,837 — Total AFS fixed income securities 4,408,203 42,702 4,365,501 — AFS equity securities: Common stock 194,789 191,517 — 3,272 Preferred stock 12,262 12,262 — — Total AFS equity securities 207,051 203,779 — 3,272 Total AFS securities 4,615,254 246,481 4,365,501 3,272 Short-term investments 194,819 194,819 — — Total assets measured at fair value $ 4,810,073 441,300 4,365,501 3,272 1 There were no transfers of securities between Level 1 and Level 2.
Schedule of Expected Benefit Payments	Payments ($ in thousands) Pension Plan Benefits Expected to be Paid in Future Fiscal Years: 2017 $ 10,830 2018 12,041 2019 13,125 2020 14,184 2021 15,124 2022-2026 89,771
Retirement Income Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Schedule of Quantitative Disclosures of our Financial Assets that were Measured at Fair Value	December 31, 2016 Fair Value Measurements at 12/31/16 Using ($ in thousands) Assets Measured at Fair Value At 12/31/16 Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Description Long-duration fixed income: Global asset allocation fund $ 37,878 37,878 — — Extended duration fixed income 131,457 131,457 — — Total long duration fixed income 169,335 169,335 — — Cash and short-term investments: Short-term investments 23,722 23,722 — — Deposit administration contracts 1,832 — 1,832 — Total cash and short-term investments 25,554 23,722 1,832 — Global equity, at net asset value 1 : Non-U.S. equity 48,836 — — — U.S. equity 55,073 — — — Total global equity 103,909 — — — Private equity (limited partnerships, at net asset value) 1 : Real assets 15,466 — — — Private equity 1,615 — — — Private credit 1,108 — — — Total private equity 18,189 — — — Total invested assets $ 316,987 193,057 1,832 — December 31, 2015 Fair Value Measurements at 12/31/15 Using ($ in thousands) Assets Measured at Fair Value At 12/31/15 Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Description Long-duration fixed income: Global asset allocation fund $ 33,565 33,565 — — Extended duration fixed income 117,297 117,297 — — Total long duration fixed income 150,862 150,862 — — Cash and short-term investments: Short-term investments 1,600 1,600 — — Deposit administration contracts 1,418 — 1,418 — Total cash and short-term investments 3,018 1,600 1,418 — Global equity, at net asset value 1 : Non-U.S. equity 42,603 — — — U.S. equity 46,840 — — — Total global equity 89,443 — — — Private equity (limited partnerships, at net asset value) 1 : Private equity 2,626 — — — Real assets 2,514 — — — Private credit 1,318 — — — Total private equity 6,458 — — — Total invested assets $ 249,781 152,462 1,418 — 1 In accordance with ASU 2015-07, certain investments that are measured at fair value using the net asset value per share (or its practical expedient) have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to total Pension Plan invested assets.

Share-Based Payments (Tables)

Share-Based Payments (Tables)	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-Based Compensation Retired Plans	December 31, 2016 Types of Share-Based Payments Issued Reserve Shares Awards Outstanding 1 Plan 2005 Omnibus Stock Plan ("2005 Stock Plan") Qualified and nonqualified stock options, SARs, restricted stock, RSUs, phantom stock, stock bonuses, and other awards in such amounts and with such terms and conditions as it determined, subject to the provisions of the 2005 Stock Plan. The maximum exercise period for an option grant under this plan is 10 years from the date of the grant. DEUs are earned during the vesting period on RSU grants. The DEUs are reinvested in the Parent's common stock at fair value on each dividend payment date. 2,664,594 726,394 Parent's Stock Compensation Plan for Non-employee Directors ("Directors Stock Compensation Plan") Directors could elect to receive a portion of their annual compensation in shares of the Parent's common stock. 67,242 67,242 1 Awards outstanding under the 2005 Stock Plan consisted of 371,003 RSUs and 355,391 stock options.
Schedule of Share-Based Compensation ESPP and ASPP Shares Granted	2016 2015 2014 ESPP Issuances 88,432 100,944 106,832 Agent Plan Issuances 69,867 82,142 78,724
Schedule of Share-Based Compensation Shares Available for Issuance	As of December 31, 2016 Authorized Available for Issuance Awards Outstanding Stock Plan 3,500,000 2,835,694 607,156 ESPP 1,500,000 574,722 — Agent Plan 3,000,000 1,867,287 —
Schedule Of Share-Based Compensation Plan Approval	Plan Approvals Stock Plan Approved effective as of May 1, 2014 by stockholders on April 23, 2014. Cash Plan Approved effective April 1, 2005 by stockholders on April 27, 2005. ESPP Approved by stockholders on April 29, 2009 effective July 1, 2009. Agent Plan Approved by stockholders on April 26, 2006.
Schedule of Types of Share-Based Payments Issued	Plan Types of Share-Based Payments Issued Stock Plan Qualified and nonqualified stock options, stock appreciation rights ("SARs"), restricted stock, restricted stock units ("RSUs"), stock grants, and other awards valued in whole or in part by reference to the Parent's common stock. The maximum exercise period for an option grant under this plan is 10 years from the date of the grant. Dividend equivalent units ("DEUs") are earned during the vesting period on RSU grants. The DEUs are reinvested in the Parent's common stock at fair value on each dividend payment date. The requisite service period for grants to employees under this plan is the lesser of: (i) the stated vested date, which is typically three years from issuance; or (ii) the date the employee becomes eligible to retire. Cash Plan Cash incentive units (“CIUs”). The initial dollar value of each CIU will be adjusted to reflect the percentage increase or decrease in the total shareholder return on the Parent's common stock over a specified performance period. In addition, for certain grants, the number of CIUs granted will be increased or decreased to reflect our performance on specified performance indicators as compared to targeted peer companies. The requisite service period for grants under this plan is the lesser of: (i) the stated vested date, which is typically three years from issuance; or (ii) the date the employee becomes eligible to retire. ESPP Enables employees to purchase shares of the Parent’s common stock. The purchase price is the lower of: (i) 85% of the closing market price at the time the option is granted; or (ii) 85% of the closing price at the time the option is exercised. Shares are generally issued on June 30 and December 31 of each year. Agent Plan Quarterly offerings to purchase the Parent's common stock at a 10% discount with a one year restricted period during which the shares purchased cannot be sold or transferred. Only our independent retail insurance agencies and wholesale general agencies, and certain eligible persons associated with the agencies, are eligible to participate in this plan.
Schedule of Summary of Stock Option Transactions under Share Based Payment Plans	Number Weighted Weighted Aggregate Outstanding at December 31, 2015 493,428 $ 17.84 Granted in 2016 — — Exercised in 2016 (138,037 ) 20.33 Forfeited or expired in 2016 — — Outstanding at December 31, 2016 355,391 $ 16.87 2.14 $ 9,304 Exercisable at December 31, 2016 355,391 $ 16.87 2.14 $ 9,304
Schedule of Summary of Restricted Stock Units Transactions under Share-Based Payment Plans	Number Weighted Unvested RSU awards at December 31, 2015 1,018,530 $ 22.55 Granted in 2016 299,670 32.53 Vested in 2016 (389,245 ) 21.56 Forfeited in 2016 (12,315 ) 24.97 Unvested RSU awards at December 31, 2016 916,640 $ 26.20
Schedule of Weighted Average Assumptions for Employee Stock Purchase Plan	ESPP 2016 2015 2014 Risk-free interest rate 0.47 % 0.10 0.07 Expected term 6 months 6 months 6 months Dividend yield 1.7 % 2.0 2.0 Expected volatility 31 % 20 21
Schedule of Weighted-Average Fair Value of Stock Per Share	2016 2015 2014 RSUs $ 32.53 25.22 21.58 ESPP: Six month option 2.63 1.26 1.24 Discount of grant date market value 5.23 4.16 3.87 Total ESPP 7.86 5.42 5.11 Agent Plan: Discount of grant date market value 3.79 2.94 2.42
Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan	($ in millions) 2016 2015 2014 Share-based compensation expense, pre-tax $ 30.3 23.8 18.6 Income tax benefit (10.3 ) (8.0 ) (6.2 ) Share-based compensation expense, after-tax $ 20.0 15.8 12.4

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Commitments For Non-Cancelable Leases	($ in millions) Capital Leases Operating Leases Total 2017 $ 4.0 9.1 13.1 2018 2.2 7.7 9.9 2019 0.1 5.6 5.7 2020 — 4.4 4.4 2021 — 2.9 2.9 After 2021 — 4.7 4.7 Total minimum payment required $ 6.3 34.4 40.7

Statutory Financial Informati50

Statutory Financial Information, Capital Requirements, and Restrictions on Dividends and Transfers of Funds (Tables)	12 Months Ended
	Dec. 31, 2016
Insurance [Abstract]
Schedule of Insurance Subsidiaries Statutory Surplus Data	State of Domicile Unassigned Surplus Statutory Surplus Statutory Net Income ($ in millions) 2016 2015 2016 2015 2016 2015 2014 SICA New Jersey $ 414.4 366.6 568.6 520.8 72.2 69.6 83.9 Selective Way Insurance Company ("SWIC") New Jersey 260.5 223.6 309.5 272.6 41.2 42.3 37.0 SICSC Indiana 110.6 96.6 141.9 127.9 17.4 15.9 14.0 SICSE Indiana 83.5 70.7 109.1 96.2 13.4 12.1 10.5 SICNY New York 74.1 65.3 101.8 93.0 12.9 12.7 10.3 Selective Insurance Company of New England ("SICNE") New Jersey 13.6 9.2 43.7 39.4 5.9 5.5 4.4 Selective Auto Insurance Company of New Jersey ("SAICNJ") New Jersey 36.9 26.4 79.8 69.2 11.5 10.8 9.1 MUSIC New Jersey 16.7 7.0 85.2 75.5 9.7 9.5 7.3 Selective Casualty Insurance Company ("SCIC") New Jersey 26.6 17.8 101.0 92.3 12.6 12.1 9.6 Selective Fire and Casualty Insurance Company ("SFCIC") New Jersey 11.3 7.5 43.2 39.4 5.5 5.3 4.2 Total $ 1,048.2 890.7 1,583.8 1,426.3 202.3 195.8 190.3
Schedule of Insurance Subsidiaries Dividend Paid To Parent	Dividends Twelve Months ended December 31, 2016 ($ in millions) State of Domicile Ordinary Dividends Paid SICA New Jersey $ 26.0 SWIC New Jersey 12.0 SICSC Indiana 5.0 SICSE Indiana 2.0 SICNY New York 5.0 SICNE New Jersey 2.0 SAICNJ New Jersey 1.5 SCIC New Jersey 5.5 SFCIC New Jersey 2.0 Total $ 61.0
Schedule of Maximum Payments Insurance Subsidiaries Of Ordinary Dividends	2017 ($ in millions) State of Domicile Maximum Ordinary Dividends SICA New Jersey $ 72.2 SWIC New Jersey 40.4 SICSC Indiana 13.8 SICSE Indiana 10.9 SICNY New York 10.2 SICNE New Jersey 5.9 SAICNJ New Jersey 11.5 MUSIC New Jersey 9.7 SCIC New Jersey 12.6 SFCIC New Jersey 5.5 Total $ 192.7

Quarterly Financial Informati51

Quarterly Financial Information (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	(unaudited, $ in thousands, First Quarter Second Quarter Third Quarter Fourth Quarter except per share data) 2016 2015 2016 2015 2016 2015 2016 2015 Net premiums earned $ 522,458 476,123 531,932 490,309 542,429 507,390 552,753 516,087 Net investment income earned 30,769 26,917 31,182 32,230 33,375 32,061 35,428 30,108 Net realized (losses) gains (2,704 ) 18,883 1,765 (3,420 ) 3,688 308 (7,686 ) (2,600 ) Underwriting income 40,955 26,021 43,777 29,124 32,033 44,831 35,168 49,053 Net income 37,032 39,708 43,601 33,768 38,502 46,996 39,360 45,389 Other comprehensive income (loss) 45,422 3,827 36,010 (35,944 ) (9,798 ) 6,290 (78,159 ) (3,386 ) Comprehensive income (loss) 82,454 43,535 79,611 (2,176 ) 28,704 53,286 (38,799 ) 42,003 Net income per share: Basic 0.64 0.70 0.75 0.59 0.66 0.82 0.68 0.79 Diluted 0.63 0.69 0.74 0.58 0.66 0.81 0.67 0.78 Dividends to stockholders 1 0.15 0.14 0.15 0.14 0.15 0.14 0.16 0.15 Price range of common stock: 2 High 36.92 30.10 38.67 29.60 41.30 32.50 44.00 37.91 Low 29.27 25.49 33.60 26.28 35.90 28.10 34.95 30.36 The addition of all quarters may not agree to annual amounts on the Financial Statements due to rounding. 1 See Note 19. “Statutory Financial Information, Capital Requirements, and Restrictions on Dividends and Transfers of Funds” for a discussion of dividend restrictions. 2 These ranges of high and low prices of the Parent’s common stock, as reported by the NASDAQ Global Select Market, represent actual transactions. Price quotations do not include retail markups, markdowns, and commissions. The range of high and low prices for common stock for the period beginning January 3, 2017 and ending February 14, 2017 was $38.50 to $44.35 .

Summary of Significant Accoun52

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended			12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Depreciation expense				$ 17.4	$ 16.4	$ 12.6
Investment yields before tax assumed in premium deficiency assessment	2.40%	2.50%	3.00%
Deferred policy acquisition costs amortized to expense				$ 450.3	$ 399.4	$ 364.3

Summary of Significant Accoun53

Summary of Significant Accounting Policies (Property and Equipment) (Details)	12 Months Ended
	Dec. 31, 2016
Computer hardware [Member]
Property, Plant and Equipment, Estimated Useful Lives	3
Furniture and fixtures [Member]
Property, Plant and Equipment, Estimated Useful Lives	10
Maximum [Member] | Computer software [Member]
Property, Plant and Equipment, Estimated Useful Lives	5
Maximum [Member] | Software licenses [Member]
Property, Plant and Equipment, Estimated Useful Lives	5
Maximum [Member] | Internally developed software [Member]
Property, Plant and Equipment, Estimated Useful Lives	10
Maximum [Member] | Building and improvements [Member]
Property, Plant and Equipment, Estimated Useful Lives	40
Minimum [Member] | Computer software [Member]
Property, Plant and Equipment, Estimated Useful Lives	3
Minimum [Member] | Software licenses [Member]
Property, Plant and Equipment, Estimated Useful Lives	3
Minimum [Member] | Internally developed software [Member]
Property, Plant and Equipment, Estimated Useful Lives	5
Minimum [Member] | Building and improvements [Member]
Property, Plant and Equipment, Estimated Useful Lives	5

Adoption of Accounting Pronou54

Adoption of Accounting Pronouncements(Other Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other assets	$ 113,534	$ 78,339
Total Assets	7,355,848	6,904,433
Long-term debt	438,667	328,192
Liabilities	5,824,478	5,506,392
Total Liabilities and Stockholders' Equity	7,355,848	6,904,433
Interest expense	22,771	22,428	$ 23,063
Other expenses	$ 42,989	$ 38,371	32,696
Restatement Adjustment [Member]
Interest expense			23,063
Other expenses			32,696
Scenario, Previously Reported [Member]
Interest expense			22,086
Other expenses			$ 33,673

Statements of Cash Flow (Cash F

Statements of Cash Flow (Cash Flow Supplemental Disclosures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest	$ 22,098	$ 21,892	$ 22,221
Federal income tax	46,405	39,500	22,699
Corporate actions related to equity securities, AFS	3,263	4,239	334
Assets acquired under capital lease arrangements	3,151	6,760	5,642
Non-cash purchase of property and equipment	78	0	338
AFS Fixed Income Securities [Member]
Exchange of fixed income securities	23,579	36,792	20,781
Held-to-maturity Securities [Member]
Exchange of fixed income securities	0	15,257	$ 4,289
National Flood Insurance Program [Member]
Restricted cash	$ 36,900	$ 11,900

Investments (Unrealized Gains o

Investments (Unrealized Gains on Investments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net unrealized gains	$ 64,804	$ 69,224	$ 123,683
Deferred income tax expense	(22,681)	(24,228)	(43,289)
Net unrealized gains, net of deferred income tax	42,123	44,996	80,394
(Decrease) increase in net unrealized gains in OCI, net of deferred income tax	(2,873)	(35,398)	28,890
AFS Fixed Income Securities [Member]
Net unrealized gains	38,781	55,689	90,336
Equity Securities [Member]
Net unrealized gains	25,864	13,235	32,389
Available-for-sale Securities [Member]
Net unrealized gains	64,645	68,924	122,725
Total HTM Securities [Member]
Net unrealized gains	$ 159	$ 300	$ 958

Investments (Held-To-Maturity S

Investments (Held-To-Maturity Securities Disclosure) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Amortized Cost	$ 101,397	$ 201,054
Net Unrealized Gains (Losses)	159	300
Total HTM fixed income securities carrying value	101,556	201,354
Unrecognized Holding Gains	3,813	8,190
Unrecognized Holding Losses	(158)	0
Total HTM fixed income securities fair value	105,211	209,544
Obligations of States and Political Subdivisions [Member]
Amortized Cost	77,466	175,269
Net Unrealized Gains (Losses)	317	848
Total HTM fixed income securities carrying value	77,783	176,117
Unrecognized Holding Gains	2,133	5,763
Unrecognized Holding Losses	0	0
Total HTM fixed income securities fair value	79,916	181,880
Corporate Securities [Member]
Amortized Cost	22,711	20,228
Net Unrealized Gains (Losses)	(143)	(185)
Total HTM fixed income securities carrying value	22,568	20,043
Unrecognized Holding Gains	1,665	1,972
Unrecognized Holding Losses	(158)	0
Total HTM fixed income securities fair value	24,075	22,015
Collateralized Loan Obligations and Other Asset-Backed Securities [Member]
Amortized Cost		1,030
Net Unrealized Gains (Losses)		(120)
Total HTM fixed income securities carrying value		910
Unrecognized Holding Gains		118
Unrecognized Holding Losses		0
Total HTM fixed income securities fair value		1,028
Commercial Mortgage Backed Securities [Member]
Amortized Cost	1,220	4,527
Net Unrealized Gains (Losses)	(15)	(243)
Total HTM fixed income securities carrying value	1,205	4,284
Unrecognized Holding Gains	15	337
Unrecognized Holding Losses	0	0
Total HTM fixed income securities fair value	$ 1,220	$ 4,621

Investments (Available-For-Sale

Investments (Available-For-Sale Securities Disclosure) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	$ 4,874,648	$ 4,546,330
Unrealized Gains	80,702	93,777
Unrealized Losses	(16,057)	(24,853)
Total AFS securities	4,939,293	4,615,254
AFS Fixed Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	4,753,759	4,352,514
Unrealized Gains	54,178	78,504
Unrealized Losses	(15,397)	(22,815)
Total AFS securities	4,792,540	4,408,203
AFS Fixed Income Securities [Member] | U.S. Government and Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	75,139	99,485
Unrealized Gains	2,230	4,721
Unrealized Losses	(36)	(91)
Total AFS securities	77,333	104,115
AFS Fixed Income Securities [Member] | Foreign Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	26,559	14,885
Unrealized Gains	322	298
Unrealized Losses	(16)	(2)
Total AFS securities	26,865	15,181
AFS Fixed Income Securities [Member] | Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	1,366,287	1,314,779
Unrealized Gains	18,610	44,523
Unrealized Losses	(5,304)	(160)
Total AFS securities	1,379,593	1,359,142
AFS Fixed Income Securities [Member] | Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	1,976,556	1,892,296
Unrealized Gains	27,057	23,407
Unrealized Losses	(5,860)	(15,521)
Total AFS securities	1,997,753	1,900,182
AFS Fixed Income Securities [Member] | Collateralized Loan Obligations and Other Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	527,876	244,541
Unrealized Gains	1,439	531
Unrealized Losses	(355)	(918)
Total AFS securities	528,960	244,154
AFS Fixed Income Securities [Member] | Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	256,356	245,252
Unrealized Gains	1,514	750
Unrealized Losses	(1,028)	(2,410)
Total AFS securities	256,842	243,592
AFS Fixed Income Securities [Member] | Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	524,986	541,276
Unrealized Gains	3,006	4,274
Unrealized Losses	(2,798)	(3,713)
Total AFS securities	525,194	541,837
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	120,889	193,816
Unrealized Gains	26,524	15,273
Unrealized Losses	(660)	(2,038)
Total AFS securities	146,753	207,051
Equity Securities [Member] | Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	104,663	181,991
Unrealized Gains	26,250	14,796
Unrealized Losses	(305)	(1,998)
Total AFS securities	130,608	194,789
Equity Securities [Member] | Nonredeemable Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	16,226	11,825
Unrealized Gains	274	477
Unrealized Losses	(355)	(40)
Total AFS securities	$ 16,145	$ 12,262

Investments (Number of Securiti

Investments (Number of Securities in an Unrealized Unrecognized Loss Position) (Details) $ in Thousands	Dec. 31, 2016USD ($)Securities	Dec. 31, 2015USD ($)Securities
Unrealized Unrecognized Loss	$ 16,215	$ 24,859
Percentage Decline in Fair Value Percentage	1.00%
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 1,358,111	1,449,183
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(15,651)	(19,953)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	15,626	141,580
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(406)	(4,900)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,373,737	1,590,763
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (16,057)	$ (24,853)
Eighty Percent to Ninety-Nine Percent [Member]
Number of securities in an unrealized/unrecognized loss position | Securities	456	606
Unrealized Unrecognized Loss	$ 16,215	$ 22,971
Sixty Percent to Seventy-Nine Percent [Member]
Number of securities in an unrealized/unrecognized loss position | Securities	0	3
Unrealized Unrecognized Loss	$ 0	$ 1,888
Forty Percent to Fifty-Nine Percent [Member]
Number of securities in an unrealized/unrecognized loss position | Securities	0	0
Unrealized Unrecognized Loss	$ 0	$ 0
Twenty Percent to Thirty-Nine Percent [Member]
Number of securities in an unrealized/unrecognized loss position | Securities	0	0
Unrealized Unrecognized Loss	$ 0	$ 0
Zero Percent to Nineteen Percent [Member]
Number of securities in an unrealized/unrecognized loss position | Securities	0	0
Unrealized Unrecognized Loss	$ 0	$ 0
Afs Fixed Maturity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,340,672	1,416,504
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(14,991)	(17,915)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	15,626	141,580
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(406)	(4,900)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,356,298	1,558,084
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(15,397)	(22,815)
Equity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	17,439	32,679
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(660)	(2,038)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	17,439	32,679
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(660)	(2,038)
U.S. Government and Government Agencies [Member] | Afs Fixed Maturity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	6,419	16,006
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(36)	(87)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	396
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	(4)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	6,419	16,402
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(36)	(91)
Foreign Government [Member] | Afs Fixed Maturity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	13,075	1,067
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(16)	(2)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	13,075	1,067
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(16)	(2)
Obligations of States and Political Subdivisions [Member] | Afs Fixed Maturity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	306,509	28,617
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(5,304)	(160)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	306,509	28,617
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(5,304)	(160)
Corporate Securities [Member] | Afs Fixed Maturity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	462,902	761,479
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(5,771)	(12,671)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	4,913	50,382
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(89)	(2,850)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	467,815	811,861
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(5,860)	(15,521)
Collateralized Loan Obligations and Other Asset-Backed Securities [Member] | Afs Fixed Maturity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	189,795	197,477
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(354)	(807)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	319	12,022
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1)	(111)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	190,114	209,499
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(355)	(918)
Commercial Mortgage Backed Securities [Member] | Afs Fixed Maturity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	82,492	146,944
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,021)	(2,196)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,645	15,385
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(7)	(214)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	84,137	162,329
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(1,028)	(2,410)
Residential Mortgage Backed Securities [Member] | Afs Fixed Maturity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	279,480	264,914
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2,489)	(1,992)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	8,749	63,395
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(309)	(1,721)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	288,229	328,309
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(2,798)	(3,713)
Common Stock [Member] | Equity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	11,271	31,148
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(305)	(1,998)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	11,271	31,148
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(305)	(1,998)
Nonredeemable Preferred Stock [Member] | Equity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	6,168	1,531
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(355)	(40)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	6,168	1,531
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (355)	$ (40)

Investments (HTM Fixed Maturity

Investments (HTM Fixed Maturity Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Due in one year or less carrying value	$ 55,505
Due after one year through five years carrying value	37,536
Due after five years through 10 years carrying value	8,515
Total HTM fixed income securities carrying value	101,556	$ 201,354
Due in one year or less fair value	56,249
Due after one year through five years fair value	39,853
Due after five years through 10 years fair value	9,109
Total HTM fixed income securities fair value	$ 105,211	$ 209,544

Investments (Other Investment P

Investments (Other Investment Portfolio by Strategy and the Remaining Commitment Amount Associated With Each Strategy) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Carrying Value	$ 102,397	$ 77,842
Other Investment Portfolio [Member]
Carrying Value	102,397	77,842
Remaining Commitment	143,686	74,353
Maximum Exposure to Loss	246,083	152,195
Alternative Investments [Member]
Carrying Value	83,814	67,834
Remaining Commitment	140,286	71,153
Maximum Exposure to Loss	224,100	138,987
Private Equity [Member] | Alternative Investments [Member]
Carrying Value	41,135	35,088
Remaining Commitment	76,774	30,204
Maximum Exposure to Loss	117,909	65,292
Private Credit Funds [Member] | Alternative Investments [Member]
Carrying Value	28,193	13,246
Remaining Commitment	40,613	15,129
Maximum Exposure to Loss	68,806	28,375
Real Assets [Member] | Alternative Investments [Member]
Carrying Value	14,486	19,500
Remaining Commitment	22,899	25,820
Maximum Exposure to Loss	37,385	45,320
Other Securities [Member]
Carrying Value	18,583	10,008
Remaining Commitment	3,400	3,200
Maximum Exposure to Loss	$ 21,983	$ 13,208

Investments (Aggregated Balance

Investments (Aggregated Balance Sheet Summarized Financial Information for Partnerships in our Alternative Investment Portfolio) (Details) - Investments Accounted For Under The Equity Method [Member] - USD ($) $ in Millions	Sep. 30, 2016	Sep. 30, 2015
Investments	$ 11,244	$ 7,527
Total assets	12,075	8,515
Total liabilities	1,802	316
Partners' capital	$ 10,273	$ 8,199

Investments (Aggregated Income

Investments (Aggregated Income Statement Summarized Financial Information for Partnerships in our Alternative Investment Portfolio) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Schedule of Equity Method Investments [Line Items]
Net investment income earned	$ 35,428	$ 33,375	$ 31,182	$ 30,769	$ 30,108	$ 32,061	$ 32,230	$ 26,917	$ 130,754		$ 121,316		$ 138,708
Investments Accounted For Under The Equity Method [Member]
Schedule of Equity Method Investments [Line Items]
Net Investment Income										$ (44,000)		$ 129,000		$ 226,000
Realized gains										1,374,000		1,187,000		581,000
Net change in unrealized (depreciation) appreciation										(719,000)		(1,364,000)		1,098,000
Net Income										$ 611,000		$ (48,000)		$ 1,905,000
Alternative Investments [Member]
Schedule of Equity Method Investments [Line Items]
Net investment income earned									$ 3,100		$ (1,900)		$ 13,600

Investments (Investments Pledge

Investments (Investments Pledged as Collateral) (Details) $ in Millions	Dec. 31, 2016USD ($)
Schedule of Available-for-sale Securities [Line Items]
Assets Held by Insurance Regulators	$ 24.8
Securities pledged as collateral for reinsurance obligations	150.5
U.S. Government and Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets Held by Insurance Regulators	24.8
Securities pledged as collateral for reinsurance obligations	32.2
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets Held by Insurance Regulators	0
Securities pledged as collateral for reinsurance obligations	0.5
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets Held by Insurance Regulators	0
Securities pledged as collateral for reinsurance obligations	117.8
Federal Home Loan Bank of New York [Member]
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	58.2
Federal Home Loan Bank of New York [Member] | U.S. Government and Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	0
Federal Home Loan Bank of New York [Member] | Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	0
Federal Home Loan Bank of New York [Member] | Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	58.2
Federal Home Loan Bank of Indianapolis [Member]
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	67.5
Federal Home Loan Bank of Indianapolis [Member] | U.S. Government and Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	7.4
Federal Home Loan Bank of Indianapolis [Member] | Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	0.5
Federal Home Loan Bank of Indianapolis [Member] | Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	$ 59.6

Investments (Credit Concentrati

Investments (Credit Concentration Risk) (Details)	Dec. 31, 2016	Dec. 31, 2015
Investments [Abstract]
Maximum exposure to credit concentration risk of the Company's stockholder's equity other than certain U.S. government agencies	10.00%	10.00%

Investments (Net Investment Inc

Investments (Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement [Line Items]
Net investment income earned	$ 35,428	$ 33,375	$ 31,182	$ 30,769	$ 30,108	$ 32,061	$ 32,230	$ 26,917	$ 130,754	$ 121,316	$ 138,708
Fixed Income Securities [Member]
Statement [Line Items]
Net investment income earned									129,306	123,230	126,489
Equity Securities [Member]
Statement [Line Items]
Net investment income earned									7,368	9,161	7,449
Short-term Investments [Member]
Statement [Line Items]
Net investment income earned									686	112	66
Other Investment Portfolio [Member]
Statement [Line Items]
Net investment income earned									2,940	(1,890)	13,580
Investment Expenses [Member]
Statement [Line Items]
Net investment income earned									$ (9,546)	$ (9,297)	$ (8,876)

Investments (OTTI by Asset Type

Investments (OTTI by Asset Type) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
OTTI Losses Gross	$ 8,509	$ 18,366	$ 11,104
OTTI included in OCI	(10)	0	0
Total OTTI charges recognized in earnings	8,499	18,366	11,104
Other Investments [Member]
OTTI Losses Gross			580
OTTI included in OCI			0
Total OTTI charges recognized in earnings			580
AFS Fixed Income Securities [Member]
OTTI Losses Gross	5,191	2,189	7
OTTI included in OCI	(10)	0	0
Total OTTI charges recognized in earnings	5,181	2,189	7
AFS Fixed Income Securities [Member] | Obligations of States and Political Subdivisions [Member]
OTTI Losses Gross	2,797
OTTI included in OCI	0
Total OTTI charges recognized in earnings	2,797
AFS Fixed Income Securities [Member] | Corporate Securities [Member]
OTTI Losses Gross	1,880	2,188
OTTI included in OCI	0	0
Total OTTI charges recognized in earnings	1,880	2,188
AFS Fixed Income Securities [Member] | Collateralized Loan Obligations and Other Asset-Backed Securities [Member]
OTTI Losses Gross	19
OTTI included in OCI	0
Total OTTI charges recognized in earnings	19
AFS Fixed Income Securities [Member] | Commercial Mortgage Backed Securities [Member]
OTTI Losses Gross	220
OTTI included in OCI	0
Total OTTI charges recognized in earnings	220
AFS Fixed Income Securities [Member] | Residential Mortgage Backed Securities [Member]
OTTI Losses Gross	275	1	7
OTTI included in OCI	(10)	0	0
Total OTTI charges recognized in earnings	265	1	7
Available-for-sale Securities [Member] | Equity Securities [Member]
OTTI Losses Gross	3,318	16,177	10,517
OTTI included in OCI	0	0	0
Total OTTI charges recognized in earnings	3,318	16,177	10,517
Common Stock [Member] | Available-for-sale Securities [Member] | Equity Securities [Member]
OTTI Losses Gross	3,316	15,996	10,517
OTTI included in OCI	0	0	0
Total OTTI charges recognized in earnings	3,316	15,996	$ 10,517
Nonredeemable Preferred Stock [Member] | Available-for-sale Securities [Member] | Equity Securities [Member]
OTTI Losses Gross	2	181
OTTI included in OCI	0	0
Total OTTI charges recognized in earnings	$ 2	$ 181

Investments (Components Of Net

Investments (Components Of Net Realized Gains, Excluding OTTI Charges) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
HTM fixed income securities gains									$ 3	$ 5	$ 2
HTM fixed income securities losses									(1)	(1)	(20)
Short Term Investments Realized Gains									0	0	0
Short Term Investments Realized Losses									(13)	0	0
Other investment securities gains									3	162	1
Other investment securities losses									(4)	(653)	0
Net realized investment gains	$ (7,686)	$ 3,688	$ 1,765	$ (2,704)	$ (2,600)	$ 308	$ (3,420)	$ 18,883	3,562	31,537	37,703
Proceeds from sale of available-for-sale securities									1,046,100	234,100	259,000
Fixed Income Securities [Member]
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
AFS securities gains									7,741	4,515	1,945
AFS securities losses									(11,411)	(312)	(392)
Equity Securities [Member]
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
AFS securities gains									8,108	29,168	36,871
AFS securities losses									$ (864)	$ (1,347)	$ (704)

Comprehensive Income (Component

Comprehensive Income (Components of Comprehensive Income-Gross and Net of Tax) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income from continuing operations, before federal income tax									$ 219,955	$ 232,692	$ 197,131
Income Tax Expense (Benefit)									61,460	66,831	55,304
Net income	$ 39,360	$ 38,502	$ 43,601	$ 37,032	$ 45,389	$ 46,996	$ 33,768	$ 39,708	158,495	165,861	141,827
Unrealized holding (losses) gains during the period, Gross									(9,195)	(40,221)	72,940
Unrealized holding (losses) gains during the period, Tax									(3,218)	(14,078)	25,529
Unrealized holding (losses) gains arising during period									(5,977)	(26,143)	47,411
Non-credit portion of other-than-temporary impairment losses recognized in other comprehensive income, Gross									(10)
Non-Credit Portion of Other-Than-Temporary Impairment Losses Recognized In Other Comprehensive Income, Tax									(4)
Non-credit portion of other-than-temporary impairments recognized in other comprehensive income									(6)
Amount reclassified into net income: HTM securities, Gross									(141)	(580)	(1,299)
Amortization Of Net Unrealized Gains Losses On Held-to-Maturity Transferred From Available-for-Sale Tax									(49)	(203)	(455)
Amount reclassified from AOCI, HTM									(92)	(377)	(844)
Non-credit OTTI, Gross									213	357	1,669
Non-credit OTTI, Tax									75	125	584
Amounts reclassified into net income: Non-credit other-than-temporary impairment									138	232	1,085
Realized losses (gains) on AFS securities, Gross									4,713	(14,016)	(28,864)
Realized losses (gains) on AFS securities, Tax									1,649	(4,906)	(10,102)
Realized losses (gains) on available for sale securities									3,064	(9,110)	(18,762)
Net unrealized (losses) gains, Gross									(4,420)	(54,460)	44,446
Net unrealized (losses) gains, Tax									(1,547)	(19,062)	15,556
Total unrealized (losses) gains on investment securities									(2,873)	(35,398)	28,890
Net actuarial (loss) gain, Gross									(12,079)	2,438	(54,136)
Net actuarial (loss) gain, Tax									(4,227)	853	(18,947)
Net actuarial (loss) gain									(7,852)	1,585	(35,189)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax									6,462	7,077	1,902
Amount reclassified into Net Income: Net actuarial loss, Tax									2,262	2,477	666
Amount reclassified into net income: Net actuarial loss									4,200	4,600	1,236
Defined pension and other post-retirement benefit plans, Gross									(5,617)	9,515	(52,234)
Defined pension and other post-retirement benefit plans, Tax									(1,965)	3,330	(18,281)
Total defined benefit pension and post-retirement plans									(3,652)	6,185	(33,953)
Other Comprehensive Loss, Gross									(10,037)	(44,945)	(7,788)
Other Comprehensive Loss, Tax									(3,512)	(15,732)	(2,725)
Other comprehensive loss	(78,159)	(9,798)	36,010	45,422	(3,386)	6,290	(35,944)	3,827	(6,525)	(29,213)	(5,063)
Comprehensive Income, Before Tax									209,918	187,747	189,343
Comprehensive Income, Tax									57,948	51,099	52,579
Comprehensive income	$ (38,799)	$ 28,704	$ 79,611	$ 82,454	$ 42,003	$ 53,286	$ (2,176)	$ 43,535	151,970	136,648	136,764
Accumulated Other-than-Temporary Impairment [Member]
Other comprehensive loss									132	232
Accumulated Defined Benefit Plans Adjustment [Member]
Total defined benefit pension and post-retirement plans									4,200	4,600
Accumulated other comprehensive income (loss) [Member]
Other comprehensive loss									$ (6,525)	$ (29,213)	$ (5,063)

Comprehensive Income (Compone70

Comprehensive Income (Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance December,				$ (9,425)					$ (9,425)
Other Comprehensive Income Loss Reclassification Adjustment From AOCI For Non Credit Other Than Temporary Impaired Securities Net Of Tax									(138)	$ (232)	$ (1,085)
Amount reclassified from AOCI, HTM									92	377	844
OCI before reclassifications, Defined Benefit Pension and Post Retirement Plans									(7,852)	1,585	(35,189)
Amounts reclassified from AOCI,All other									3,064	(9,110)	(18,762)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax									(3,652)	6,185	(33,953)
Other comprehensive loss	$ (78,159)	$ (9,798)	$ 36,010	45,422	$ (3,386)	$ 6,290	$ (35,944)	$ 3,827	(6,525)	(29,213)	(5,063)
Balance December,	(15,950)				(9,425)				(15,950)	(9,425)
Accumulated Other-than-Temporary Impairment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance December,				(282)				(514)	(282)	(514)
OCI before reclassifications									(6)	0
Other comprehensive loss									132	232
Balance December,	(150)				(282)				(150)	(282)	(514)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance December,				(54,420)				(60,605)	(54,420)	(60,605)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax									4,200	4,600
Balance December,	(58,072)				(54,420)				(58,072)	(54,420)	(60,605)
Accumulated other comprehensive income (loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance December,				(9,425)				19,788	(9,425)	19,788
OCI before reclassifications									(13,835)	(24,558)
Amount reclassified from AOCI									7,310	(4,655)
Other comprehensive loss									(6,525)	(29,213)	(5,063)
Balance December,	(15,950)				(9,425)				(15,950)	(9,425)	19,788
Held-to-maturity Securities [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance December,				194				623	194	623
OCI before reclassifications									0	(52)
Other comprehensive loss									(92)	(429)
Balance December,	102				194				102	194	623
Available-for-sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance December,				45,083				80,284	45,083	80,284
OCI before reclassifications									(5,977)	(26,091)
Other comprehensive loss									(2,913)	(35,201)
Balance December,	42,170				45,083				42,170	45,083	80,284
Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance December,				$ 44,995				$ 80,393	44,995	80,393
OCI before reclassifications									(5,983)	(26,143)
Amount reclassified from AOCI									3,110	(9,255)
Other comprehensive loss									(2,873)	(35,398)
Balance December,	$ 42,122				$ 44,995				$ 42,122	$ 44,995	$ 80,393

Comprehensive Income (Reclassif

Comprehensive Income (Reclassification out of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Realized investment (losses) gains									$ (4,937)	$ 13,171	$ 26,599
Net investment income	$ 35,428	$ 33,375	$ 31,182	$ 30,769	$ 30,108	$ 32,061	$ 32,230	$ 26,917	130,754	121,316	138,708
Income from continuing operations, before federal income tax									219,955	232,692	197,131
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, before Tax									5,617	(9,515)	52,234
Income Tax Expense (Benefit)									(61,460)	(66,831)	(55,304)
Net income	$ 39,360	$ 38,502	$ 43,601	$ 37,032	$ 45,389	$ 46,996	$ 33,768	$ 39,708	158,495	165,861	141,827
Losses and loss expenses incurred									1,234,797	1,148,541	1,157,501
Policy acquisition costs									763,758	689,820	624,470
Total defined benefit pension and post-retirement plans									(3,652)	6,185	$ (33,953)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Net income									7,310	(4,655)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Retirement Income Plan [Member]
Income from continuing operations, before federal income tax									6,462	7,077
Income Tax Expense (Benefit)									(2,262)	(2,477)
Net income									4,200	4,600
Losses and loss expenses incurred									1,486	1,538
Policy acquisition costs									4,976	5,539
Accumulated other-than-temporary impairments including portion attributable to noncontrolling interest [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Realized investment (losses) gains									213	357
Income from continuing operations, before federal income tax									213	357
Income Tax Expense (Benefit)									(75)	(125)
Net income									138	232
Held-to-maturity Securities [Member] | Accumulated net investment gain (loss) including portion attributable to noncontrolling interest [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Realized investment (losses) gains									169	308
Net investment income									(310)	(888)
Income from continuing operations, before federal income tax									(141)	(580)
Income Tax Expense (Benefit)									49	203
Net income									(92)	(377)
Available-for-sale Securities [Member] | Accumulated net investment gain (loss) including portion attributable to noncontrolling interest [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Realized investment (losses) gains									4,713	(14,016)
Income from continuing operations, before federal income tax									4,713	(14,016)
Income Tax Expense (Benefit)									(1,649)	4,906
Net income									$ 3,064	$ (9,110)

Fair Value Measurements (Carryi

Fair Value Measurements (Carrying Value and Estimated Fair Value of Financial Instruments) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Held-to-maturity Securities	$ 101,556	$ 201,354
Available-for-sale Securities, Debt Securities	4,792,540	4,408,203
Equity securities, AFS	146,753	207,051
Short-term investments	221,701	194,819
Short-term debt	0	60,000
Long-term debt	438,667	328,192
Seven Point Twenty Five Percent Senior Notes [Member]
Long-term Debt, Fair Value	56,148	56,929
Six Point Seventy Percent Senior Notes [Member]
Long-term Debt, Fair Value	108,333	110,363
Five Point Eight Hundred Seventy Five [Member]
Long-term Debt, Fair Value	176,860	192,474
One Point Sixty One Percent Borrowing From Federal Home Loan Bank Due July 21, 2021 [Member]
Long-term Debt, Fair Value	24,286
One Point Fifty Six Percent Borrowing From Federal Home Loan Bank Due August 16, 2021 [Member]
Long-term Debt, Fair Value	24,219
Three Point Zero Three Percent Borrowing From Federal Home Loan Bank Due December 16, 2026 [Member]
Long-term Debt, Fair Value	59,313
Zero Point Sixty Three Percent Borrowing From Federal Home Loan Bank Due July 22, 2016 [Member]
Short-term debt	0	15,000
Short-term Debt fair value		14,977
One Point Twenty Five Percent Borrowing From Federal Home Loan Bank [Member]
Short-term debt	0	45,000
Short-term Debt fair value		45,083
Carrying Amount [Member]
Held-to-maturity Securities	101,556	201,354
Available-for-sale Securities, Debt Securities	4,792,540	4,408,203
Equity securities, AFS	146,753	207,051
Short-term investments	221,701	194,819
Short-term debt	0	60,000
Long-term debt	438,667	328,192
Carrying Amount [Member] | Seven Point Twenty Five Percent Senior Notes [Member]
Long-term debt	49,901	49,898
Carrying Amount [Member] | Six Point Seventy Percent Senior Notes [Member]
Long-term debt	99,430	99,415
Carrying Amount [Member] | Five Point Eight Hundred Seventy Five [Member]
Long-term debt	185,000	185,000
Carrying Amount [Member] | One Point Sixty One Percent Borrowing From Federal Home Loan Bank Due July 21, 2021 [Member]
Long-term debt	25,000	0
Carrying Amount [Member] | One Point Fifty Six Percent Borrowing From Federal Home Loan Bank Due August 16, 2021 [Member]
Long-term debt	25,000	0
Carrying Amount [Member] | Three Point Zero Three Percent Borrowing From Federal Home Loan Bank Due December 16, 2026 [Member]
Long-term debt	60,000	0
Carrying Amount [Member] | Long Term Debt Excluding Issuance Costs [Member]
Long-term debt	444,331	334,313
Carrying Amount [Member] | Unamortized Debt Issuance Costs [Member]
Unamortized Debt Issuance Costs Related to Long-Term Debt	(5,664)	(6,121)
Carrying Amount [Member] | Zero Point Sixty Three Percent Borrowing From Federal Home Loan Bank Due July 22, 2016 [Member]
Short-term debt	0	15,000
Carrying Amount [Member] | One Point Twenty Five Percent Borrowing From Federal Home Loan Bank [Member]
Short-term debt	0	45,000
Fair Value [Member]
Held-to-maturity Securities	105,211	209,544
Available-for-sale Securities, Debt Securities	4,792,540	4,408,203
Equity securities, AFS	146,753	207,051
Short-term investments	221,701	194,819
Short-term Debt fair value	0	60,060
Long-term Debt, Fair Value	449,159	359,766
Fair Value [Member] | Seven Point Twenty Five Percent Senior Notes [Member]
Long-term Debt, Fair Value	56,148	56,929
Fair Value [Member] | Six Point Seventy Percent Senior Notes [Member]
Long-term Debt, Fair Value	108,333	110,363
Fair Value [Member] | Five Point Eight Hundred Seventy Five [Member]
Long-term Debt, Fair Value	176,860	192,474
Fair Value [Member] | One Point Sixty One Percent Borrowing From Federal Home Loan Bank Due July 21, 2021 [Member]
Long-term Debt, Fair Value	24,286	0
Fair Value [Member] | One Point Fifty Six Percent Borrowing From Federal Home Loan Bank Due August 16, 2021 [Member]
Long-term Debt, Fair Value	24,219	0
Fair Value [Member] | Three Point Zero Three Percent Borrowing From Federal Home Loan Bank Due December 16, 2026 [Member]
Long-term Debt, Fair Value	59,313	0
Fair Value [Member] | Zero Point Sixty Three Percent Borrowing From Federal Home Loan Bank Due July 22, 2016 [Member]
Short-term Debt fair value	0	14,977
Fair Value [Member] | One Point Twenty Five Percent Borrowing From Federal Home Loan Bank [Member]
Short-term Debt fair value	$ 0	$ 45,083

Fair Value Measurements (Quanti

Fair Value Measurements (Quantitative Disclosures at Fair Value Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	$ 4,792,540	$ 4,408,203
Equity securities, AFS	146,753	207,051
Total AFS securities	4,939,293	4,615,254
Short-term investments	221,701	194,819
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	4,792,540	4,408,203
Equity securities, AFS	146,753	207,051
Total AFS securities	4,939,293	4,615,254
Short-term investments	221,701	194,819
Total Assets	5,160,994	4,810,073
U.S. Government and Government Agencies and Authorities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	77,333	104,115
Foreign Government [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	26,865	15,181
Obligations of States and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	1,379,593	1,359,142
Corporate Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	1,997,753	1,900,182
Collateralized Loan Obligations and Other Asset-Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	528,960	244,154
Commercial Mortgage-backed Securities (CMBS) [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	256,842	243,592
Residential Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	525,194	541,837
Common Stock [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities, AFS	130,608	194,789
Nonredeemable Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities, AFS	16,145	12,262
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	27,520	42,702
Equity securities, AFS	139,077	203,779
Total AFS securities	166,597	246,481
Short-term investments	221,701	194,819
Total Assets	388,298	441,300
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | U.S. Government and Government Agencies and Authorities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	27,520	42,702
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Foreign Government [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Obligations of States and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Corporate Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Collateralized Loan Obligations and Other Asset-Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Commercial Mortgage-backed Securities (CMBS) [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Residential Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Common Stock [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities, AFS	122,932	191,517
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Nonredeemable Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities, AFS	16,145	12,262
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	4,765,020	4,365,501
Equity securities, AFS	0	0
Total AFS securities	4,765,020	4,365,501
Short-term investments	0	0
Total Assets	4,765,020	4,365,501
Significant Other Observable Inputs (Level 2) [Member] | U.S. Government and Government Agencies and Authorities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	49,813	61,413
Significant Other Observable Inputs (Level 2) [Member] | Foreign Government [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	26,865	15,181
Significant Other Observable Inputs (Level 2) [Member] | Obligations of States and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	1,379,593	1,359,142
Significant Other Observable Inputs (Level 2) [Member] | Corporate Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	1,997,753	1,900,182
Significant Other Observable Inputs (Level 2) [Member] | Collateralized Loan Obligations and Other Asset-Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	528,960	244,154
Significant Other Observable Inputs (Level 2) [Member] | Commercial Mortgage-backed Securities (CMBS) [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	256,842	243,592
Significant Other Observable Inputs (Level 2) [Member] | Residential Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	525,194	541,837
Significant Other Observable Inputs (Level 2) [Member] | Common Stock [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities, AFS	0	0
Significant Other Observable Inputs (Level 2) [Member] | Nonredeemable Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities, AFS	0	0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Equity securities, AFS	7,676	3,272
Total AFS securities	7,676	3,272
Short-term investments	0	0
Total Assets	7,676	3,272
Significant Unobservable Inputs (Level 3) [Member] | U.S. Government and Government Agencies and Authorities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Foreign Government [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Obligations of States and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Corporate Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Collateralized Loan Obligations and Other Asset-Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Commercial Mortgage-backed Securities (CMBS) [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Residential Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Common Stock [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities, AFS	7,676	3,272
Significant Unobservable Inputs (Level 3) [Member] | Nonredeemable Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities, AFS	$ 0	$ 0

Fair Value Measurements (Change

Fair Value Measurements (Changes in Fair Value of Securities Using Level 3 Inputs) (Details) - Equity Securities [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Beginning Balance	$ 3,272
Total net (losses) gains for the period included in OCI	0
Total net (losses) gains for the period included in net income	0
Purchases	6,204
Sales	(1,800)
Issuances	0
Settlements	0
Transfers into Level 3	0
Transfers out of Level 3	0
Fair Value, Ending Balance	$ 7,676

Fair Value Measurements (Quan75

Fair Value Measurements (Quantitative Information of Our Financial Assets and Liabilities That Were Disclosed at Fair Value) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value	$ 105,211	$ 209,544
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value	0	0
Short-term Debt fair value		0
Long-term Debt, Fair Value	176,860	192,474
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value	97,701	206,208
Short-term Debt fair value		60,060
Long-term Debt, Fair Value	272,299	167,292
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value	7,510	3,336
Short-term Debt fair value		0
Long-term Debt, Fair Value	0	0
Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value	79,916	181,880
Obligations of States and Political Subdivisions [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value	0	0
Obligations of States and Political Subdivisions [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value	79,916	181,880
Obligations of States and Political Subdivisions [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value	0	0
Corporate Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value	24,075	22,015
Corporate Securities [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value	0	0
Corporate Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value	16,565	18,679
Corporate Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value	7,510	3,336
Collateralized Loan Obligations and Other Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value		1,028
Collateralized Loan Obligations and Other Asset-Backed Securities [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value		0
Collateralized Loan Obligations and Other Asset-Backed Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value		1,028
Collateralized Loan Obligations and Other Asset-Backed Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value		0
Commercial Mortgage-backed Securities (CMBS) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value	1,220	4,621
Commercial Mortgage-backed Securities (CMBS) [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value	0	0
Commercial Mortgage-backed Securities (CMBS) [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value	1,220	4,621
Commercial Mortgage-backed Securities (CMBS) [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value	0	0
Seven Point Twenty Five Percent Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	56,148	56,929
Seven Point Twenty Five Percent Senior Notes [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	0	0
Seven Point Twenty Five Percent Senior Notes [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	56,148	56,929
Seven Point Twenty Five Percent Senior Notes [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	0	0
Six Point Seventy Percent Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	108,333	110,363
Six Point Seventy Percent Senior Notes [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	0	0
Six Point Seventy Percent Senior Notes [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	108,333	110,363
Six Point Seventy Percent Senior Notes [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	0	0
Five Point Eight Hundred Seventy Five [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	176,860	192,474
Five Point Eight Hundred Seventy Five [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	176,860	192,474
Five Point Eight Hundred Seventy Five [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	0	0
Five Point Eight Hundred Seventy Five [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	0	0
One Point Sixty One Percent Borrowing From Federal Home Loan Bank Due July 21, 2021 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	24,286
One Point Sixty One Percent Borrowing From Federal Home Loan Bank Due July 21, 2021 [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	0
One Point Sixty One Percent Borrowing From Federal Home Loan Bank Due July 21, 2021 [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	24,286
One Point Fifty Six Percent Borrowing From Federal Home Loan Bank Due August 16, 2021 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	24,219
One Point Fifty Six Percent Borrowing From Federal Home Loan Bank Due August 16, 2021 [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	0
One Point Fifty Six Percent Borrowing From Federal Home Loan Bank Due August 16, 2021 [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	24,219
One Point Fifty Six Percent Borrowing From Federal Home Loan Bank Due August 16, 2021 [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	0
Three Point Zero Three Percent Borrowing From Federal Home Loan Bank Due December 16, 2026 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	59,313
Three Point Zero Three Percent Borrowing From Federal Home Loan Bank Due December 16, 2026 [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	0
Three Point Zero Three Percent Borrowing From Federal Home Loan Bank Due December 16, 2026 [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	59,313
Three Point Zero Three Percent Borrowing From Federal Home Loan Bank Due December 16, 2026 [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	0
Long-term Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	$ 449,159	359,766
One Point Twenty Five Percent Borrowing From Federal Home Loan Bank [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt fair value		45,083
One Point Twenty Five Percent Borrowing From Federal Home Loan Bank [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt fair value		0
One Point Twenty Five Percent Borrowing From Federal Home Loan Bank [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt fair value		45,083
One Point Twenty Five Percent Borrowing From Federal Home Loan Bank [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt fair value		0
Zero Point Sixty Three Percent Borrowing From Federal Home Loan Bank Due July 22, 2016 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt fair value		14,977
Zero Point Sixty Three Percent Borrowing From Federal Home Loan Bank Due July 22, 2016 [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt fair value		0
Zero Point Sixty Three Percent Borrowing From Federal Home Loan Bank Due July 22, 2016 [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt fair value		14,977
Zero Point Sixty Three Percent Borrowing From Federal Home Loan Bank Due July 22, 2016 [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt fair value		0
Short-term Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt fair value		$ 60,060

Reinsurance (Total Reinsurance

Reinsurance (Total Reinsurance Balances Segregated By Reinsurer) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Terrorism Risk Insurance Program Companys Estimated Deductible		$ 304,000
Terrorism Risk Insurance Program Reimbursed Percentage Maximum		83.00%
Terrorism Risk Insurance Program Annual Cap		$ 100,000,000
Terrorism Risk Insurance Program Insurer Retainer		17.00%
Annual Terrorism Risk Insurance Program Federal Share Reduction		1.00%
Terrorism Risk Insurance Program Reimbursed Percentage Minimum		80.00%
Allowance For Reinsurance Recoverable		$ 11,480	$ 10,122	$ 11,037	$ 9,542
Total reinsurance recoverables		621,537	561,968
Total prepaid reinsurance premiums		146,282	140,889
Net unsecured reinsurance balances		767,819	702,857
Less: collateral		(113,763)	(106,449)
National Flood Insurance Program [Member]
Net unsecured reinsurance balances	[1]	$ 211,181	$ 164,130
% of Net Unsecured Reinsurance	[1]	27.00%	24.00%
NJ Unsatisfied Claim Judgment Fund [Member]
Net unsecured reinsurance balances	[1]	$ 65,574	$ 71,884
% of Net Unsecured Reinsurance	[1]	9.00%	10.00%
Other Federal And State Pools [Member]
Net unsecured reinsurance balances	[1]	$ 3,227	$ 3,136
% of Net Unsecured Reinsurance	[1]	0.00%	0.00%
Total Federal And State Pools [Member]
Net unsecured reinsurance balances	[1]	$ 279,982	$ 239,150
% of Net Unsecured Reinsurance	[1]	36.00%	34.00%
Remaining Unsecured Reinsurance [Member]
Net unsecured reinsurance balances		$ 487,837	$ 463,707
% of Net Unsecured Reinsurance		64.00%	66.00%
Munich Re Group [Member]
Net unsecured reinsurance balances		$ 119,520	$ 112,889
% of Net Unsecured Reinsurance		16.00%	16.00%
Hanover Ruckversicherungs AG [Member]
Net unsecured reinsurance balances		$ 106,298	$ 99,535
% of Net Unsecured Reinsurance		13.00%	14.00%
AXIS Reinsurance Company [Member]
Net unsecured reinsurance balances		$ 59,737	$ 53,374
% of Net Unsecured Reinsurance		8.00%	8.00%
Swiss Re Group [Member]
Net unsecured reinsurance balances		$ 50,494	$ 51,340
% of Net Unsecured Reinsurance		7.00%	7.00%
Partner Reinsurance Company Of The US [Member]
Net unsecured reinsurance balances		$ 21,125	$ 20,748
% of Net Unsecured Reinsurance		3.00%	3.00%
All Other Reinsurers [Member]
Net unsecured reinsurance balances		$ 130,663	$ 125,821
% of Net Unsecured Reinsurance		17.00%	18.00%
Remaining Unsecured Reinsurance, Net of Collateral [Member]
Net unsecured reinsurance balances		$ 374,074	$ 357,258
Allowance for Reinsurance Recoverable [Member]
Allowance For Reinsurance Recoverable		$ 5,500	$ 5,700
[1]	Considered to have minimal risk of default.

Reinsurance (List of direct, as

Reinsurance (List of direct, assumed and ceded Reinsurance Amounts) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Premiums Written:
Direct									$ 2,577,259	$ 2,403,519	$ 2,228,270
Assumed									28,779	23,848	26,306
Ceded premiums written									(368,750)	(357,463)	(369,296)
Net									2,237,288	2,069,904	1,885,280
Premiums Earned:
Direct									2,484,715	2,330,267	2,183,258
Assumed									28,214	23,209	34,653
Ceded premiums earned									(363,357)	(363,567)	(365,302)
Total Net Premiums Earned	$ 552,753	$ 542,429	$ 531,932	$ 522,458	$ 516,087	$ 507,390	$ 490,309	$ 476,123	2,149,572	1,989,909	1,852,609
Losses and loss expenes incurred:
Direct									1,560,356	1,274,872	1,314,864
Assumed									22,708	16,996	26,187
Ceded losses and loss expenses incurred									(348,267)	(143,327)	(183,550)
Net									$ 1,234,797	$ 1,148,541	$ 1,157,501

Reinsurance (Ceded Premiums and

Reinsurance (Ceded Premiums and Losses Related to Flood Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Percentage of unpaid NFIP claims ceded by federal government	100.00%
Ceded premiums written	$ (368,750)	$ (357,463)	$ (369,296)
Ceded premiums earned	(363,357)	(363,567)	(365,302)
Ceded losses and loss expenses incurred	(348,267)	(143,327)	(183,550)
National Flood Insurance Program [Member]
Ceded premiums written	(232,245)	(228,907)	(237,718)
Ceded premiums earned	(227,882)	(233,940)	(234,224)
Ceded losses and loss expenses incurred	$ (239,891)	$ (62,078)	$ (57,323)

Reserve of Losses and Loss Expe

Reserve of Losses and Loss Expenses (Rollforward of Reserves for Losses and Loss Expenses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Gross reserves for losses and loss expenses, at beginning of year	$ 3,517,728	$ 3,477,870	$ 3,349,770
Less: reinsurance recoverable on unpaid losses and loss expenses, at beginning of year	551,019	571,978	540,839
Net reserves for losses and loss expenses, at beginning of year	2,966,709	2,905,892	2,808,931
Incurred losses and loss expense for claims occurring in the current year	1,300,565	1,217,550	1,216,770
Incurred losses and loss expenses for claims occurring in the prior years	(65,768)	(69,009)	(59,269)
Total incurred losses and loss expenses	1,234,797	1,148,541	1,157,501
Paid losses and loss expenses for claims occurring in current year	450,811	446,550	468,478
Paid losses and loss expenses for claims occurring in prior years	670,176	641,174	592,062
Total paid losses and loss expenses	1,120,987	1,087,724	1,060,540
Net reserves for losses and loss expenses, at end of year	3,080,519	2,966,709	2,905,892
Add: reinsurance recoverable on unpaid losses and loss expenses, at end of year	611,200	551,019	571,978
Gross reserves for losses and loss expenses, at end of year	3,691,719	3,517,728	3,477,870
Increase of net loss and loss expense reserves	113,800	60,800	97,000
Anticipated recoveries for salvage and subrogation claims	$ 64,900	$ 62,100	$ 65,100

Reserve for Losses and Loss E80

Reserve for Losses and Loss Expenses (Reserve Loss Development) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	$ 670,176	$ 641,174	$ 592,062
Favorable or adverse loss development	(65,768)	(69,009)	(59,269)
Favorable or unfavorable loss development [Member]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	65,800	69,000	59,300
Favorable or adverse loss development	(65,800)	(69,000)	(59,300)
Favorable or unfavorable loss development [Member] | Casualty Insurance Product Line [Member]
Favorable or adverse loss development	69,000	67,000	48,200
Favorable or unfavorable loss development [Member] | Property Insurance Product Line [Member]
Favorable or adverse loss development	3,200	2,000	11,100
Favorable or unfavorable loss development [Member] | General Liability [Member]
Favorable or adverse loss development	(45,000)	(51,000)	(43,900)
Favorable or unfavorable loss development [Member] | Commercial Automobile [Member]
Favorable or adverse loss development	25,300	2,400	(4,100)
Favorable or unfavorable loss development [Member] | Workers Compensation [Member]
Favorable or adverse loss development	(56,000)	(37,000)	0
Favorable or unfavorable loss development [Member] | Business Owners' Policies [Member]
Favorable or adverse loss development	1,800	2,200	1,900
Favorable or unfavorable loss development [Member] | Commercial Property [Member]
Favorable or adverse loss development	300	(3,000)	(2,100)
Favorable or unfavorable loss development [Member] | Homeowners [Member]
Favorable or adverse loss development	1,700	1,500	(4,000)
Favorable or unfavorable loss development [Member] | Personal Automobile [Member]
Favorable or adverse loss development	1,000	400	(10,800)
Favorable or unfavorable loss development [Member] | Excess And Surplus Operations [Member]
Favorable or adverse loss development	7,100	15,500	3,700
Casualty Development	6,000
Favorable or unfavorable loss development [Member] | Other Insurance Product Line [Member]
Favorable or adverse loss development	$ (2,000)	$ 0	$ 0

Reserve for Losses and Loss E81

Reserve for Losses and Loss Expenses (Exposure to Environmental Claims) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Liability for Claims and Claims Adjustment Expense [Line Items]
Losses and Loss expense reserves, Gross	$ 29,962	$ 30,411	$ 30,653	$ 32,764
Liability for Asbestos and Environmental Claims, Net	22,716	23,161	22,994	25,167
Asbestos Claim [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Losses and Loss expense reserves, Gross	7,900
Asbestos [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Losses and Loss expense reserves, Gross	7,847	8,024	8,751	8,897
Liability for Asbestos and Environmental Claims, Net	6,615	$ 6,793	$ 7,314	$ 7,518
Landfill Sites Related Claims [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Losses and Loss expense reserves, Gross	12,800
Liability for Asbestos and Environmental Claims, Net	8,100
Leaking Underground Storage Tanks Claims [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Losses and Loss expense reserves, Gross	9,300
Liability for Asbestos and Environmental Claims, Net	$ 8,000

Reserve for Losses and Loss E82

Reserve for Losses and Loss Expenses (Roll Forward of Gross and Net Asbestos and Net Environmental Incurred Losses and Loss Expenses and Related Reserves) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Liability for Claims and Claims Adjustment Expense [Line Items]
Salvage and Subrogation Recoveries, Value	$ 64,900	$ 62,100	$ 65,100
Reserves for losses and loss expenses at beginning of year, gross	30,411	30,653	32,764
Incurred losses and loss expenses, gross	1,483	2,968	167
Less: losses and loss expenses paid, gross	(1,932)	(3,210)	(2,278)
Reserves for losses and loss expenses at the end of year, gross	29,962	30,411	30,653
Reserves for losses and loss expenses at beginning of year, net	23,161	22,994	25,167
Incurred losses and loss expenses, net	1,380	3,320	0
Less: losses and loss expenses paid, net	(1,825)	(3,153)	(2,173)
Reserves for losses and loss expenses at the end of year, net	22,716	23,161	22,994
Asbestos [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Reserves for losses and loss expenses at beginning of year, gross	8,024	8,751	8,897
Incurred losses and loss expenses, gross	77	(428)	60
Less: losses and loss expenses paid, gross	(254)	(299)	(206)
Reserves for losses and loss expenses at the end of year, gross	7,847	8,024	8,751
Reserves for losses and loss expenses at beginning of year, net	6,793	7,314	7,518
Incurred losses and loss expenses, net	77	(77)	0
Less: losses and loss expenses paid, net	(255)	(444)	(204)
Reserves for losses and loss expenses at the end of year, net	6,615	6,793	7,314
Enviromental [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Reserves for losses and loss expenses at beginning of year, gross	22,387	21,902	23,867
Incurred losses and loss expenses, gross	1,406	3,396	107
Less: losses and loss expenses paid, gross	(1,678)	(2,911)	(2,072)
Reserves for losses and loss expenses at the end of year, gross	22,115	22,387	21,902
Reserves for losses and loss expenses at beginning of year, net	16,368	15,680	17,649
Incurred losses and loss expenses, net	1,303	3,397	0
Less: losses and loss expenses paid, net	(1,570)	(2,709)	(1,969)
Reserves for losses and loss expenses at the end of year, net	$ 16,101	$ 16,368	$ 15,680

Reserve for Losses and Loss E83

Reserve for Losses and Loss Expenses Reserve for Losses and Loss Expenses (Claims Development) (Details)	12 Months Ended
	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2012USD ($)	Dec. 31, 2011USD ($)	Dec. 31, 2010USD ($)	Dec. 31, 2009USD ($)	Dec. 31, 2008USD ($)	Dec. 31, 2007USD ($)
Claims Development [Line Items]
Reserve for losses and loss expenses	$ 3,691,719,000	$ 3,517,728,000
Incurred losses and loss expenses for claims occurring in the prior years	(65,768,000)	(69,009,000)	$ (59,269,000)
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	7,547,829,000
Net outstanding liabilities	10,168,191,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	2,944,432,000
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	929,082,000	920,931,000	912,683,000	$ 896,590,000	$ 877,933,000	$ 835,347,000	$ 762,422,000	$ 665,277,000	$ 543,949,000	$ 350,369,000
Net outstanding liabilities	989,709,000	992,673,000	998,496,000	1,003,552,000	1,015,897,000	1,028,956,000	1,028,546,000	1,047,912,000	1,066,670,000	1,038,585,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 42,970,000
Short-duration Insurance Contracts, Number of Reported Claims	84,996
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 853,769,000	839,392,000	819,280,000	798,996,000	764,196,000	690,016,000	609,851,000	489,633,000	286,314,000
Net outstanding liabilities	926,017,000	931,785,000	927,958,000	936,975,000	947,306,000	964,862,000	990,931,000	988,584,000	957,247,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 48,590,000
Short-duration Insurance Contracts, Number of Reported Claims	85,264
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 775,885,000	760,589,000	736,100,000	695,249,000	634,902,000	540,982,000	442,417,000	277,275,000
Net outstanding liabilities	853,401,000	857,960,000	869,927,000	870,057,000	883,590,000	916,691,000	941,972,000	920,143,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 49,532,000
Short-duration Insurance Contracts, Number of Reported Claims	85,444
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 823,770,000	803,773,000	773,536,000	704,895,000	625,229,000	509,910,000	328,826,000
Net outstanding liabilities	915,131,000	922,404,000	943,118,000	956,600,000	977,959,000	973,742,000	950,114,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 65,625,000
Short-duration Insurance Contracts, Number of Reported Claims	94,093
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 901,801,000	852,202,000	782,655,000	692,730,000	585,867,000	391,944,000
Net outstanding liabilities	1,023,726,000	1,033,518,000	1,056,107,000	1,062,233,000	1,061,667,000	1,042,576,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 82,565,000
Short-duration Insurance Contracts, Number of Reported Claims	104,303
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 810,135,000	743,742,000	651,544,000	555,819,000	378,067,000
Net outstanding liabilities	973,089,000	998,028,000	1,020,655,000	1,071,290,000	1,065,437,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 101,992,000
Short-duration Insurance Contracts, Number of Reported Claims	103,498
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 748,758,000	644,475,000	518,872,000	335,956,000
Net outstanding liabilities	1,021,007,000	1,047,230,000	1,062,045,000	1,044,142,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 182,613,000
Short-duration Insurance Contracts, Number of Reported Claims	90,330
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 736,154,000	614,075,000	405,898,000
Net outstanding liabilities	1,146,990,000	1,133,798,000	1,107,513,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 278,689,000
Short-duration Insurance Contracts, Number of Reported Claims	93,747
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 581,203,000	376,641,000
Net outstanding liabilities	1,130,513,000	1,114,081,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 375,894,000
Short-duration Insurance Contracts, Number of Reported Claims	91,410
Short-duration Insurance Contracts, Accident Year 2016 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 387,272,000
Net outstanding liabilities	1,188,608,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 589,938,000
Short-duration Insurance Contracts, Number of Reported Claims	85,202
Short-Duration Insurance Contracts, Accident Years Prior to 2007 [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	$ 324,070,000
Standard Commercial Lines [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	1,260,853,000
Net outstanding liabilities	2,258,895,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	1,070,929,000
Standard Commercial Lines [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	1,303,022,000
Net outstanding liabilities	2,013,235,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	936,766,000
Standard Commercial Lines [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	1,575,794,000
Net outstanding liabilities	1,974,804,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	402,281,000
Standard Commercial Lines [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	378,610,000
Net outstanding liabilities	458,085,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	86,802,000
Standard Commercial Lines [Member] | Commercial Property [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	1,044,298,000
Net outstanding liabilities	1,086,323,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	42,279,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2007 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	208,449,000	204,159,000	201,842,000	191,405,000	181,641,000	158,424,000	123,108,000	80,621,000	44,356,000	14,695,000
Net outstanding liabilities	230,717,000	231,439,000	234,697,000	234,173,000	242,878,000	248,807,000	250,834,000	255,538,000	256,627,000	252,732,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 17,815,000
Short-duration Insurance Contracts, Number of Reported Claims	14,016
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2007 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 180,865,000	179,011,000	175,205,000	169,941,000	164,373,000	156,320,000	144,713,000	123,681,000	88,786,000	31,478,000
Net outstanding liabilities	216,177,000	218,828,000	222,623,000	225,904,000	225,165,000	230,109,000	226,095,000	231,104,000	236,993,000	231,462,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 23,152,000
Short-duration Insurance Contracts, Number of Reported Claims	16,344
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2007 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 173,980,000	173,050,000	171,839,000	171,622,000	170,241,000	163,629,000	146,690,000	126,507,000	102,233,000	65,544,000
Net outstanding liabilities	175,894,000	175,431,000	175,342,000	176,049,000	178,956,000	179,739,000	182,030,000	187,966,000	194,567,000	185,733,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 1,434,000
Short-duration Insurance Contracts, Number of Reported Claims	24,074
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2007 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 29,048,000	28,368,000	28,095,000	28,073,000	27,273,000	25,759,000	24,978,000	22,583,000	18,870,000	14,051,000
Net outstanding liabilities	29,288,000	29,691,000	28,503,000	28,440,000	29,393,000	29,270,000	31,212,000	33,397,000	34,011,000	32,749,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 124,000
Short-duration Insurance Contracts, Number of Reported Claims	2,956
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2007 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 103,061,000	102,663,000	102,532,000	102,370,000	102,310,000	101,805,000	99,942,000	99,036,000	95,050,000	63,159,000
Net outstanding liabilities	103,077,000	102,679,000	102,732,000	102,998,000	103,381,000	103,183,000	101,027,000	100,809,000	104,160,000	98,167,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 2,000
Short-duration Insurance Contracts, Number of Reported Claims	6,919
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2008 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 194,257,000	186,896,000	176,873,000	166,394,000	151,055,000	113,088,000	82,421,000	45,595,000	16,397,000
Net outstanding liabilities	221,203,000	221,640,000	219,551,000	224,236,000	233,712,000	234,770,000	243,536,000	243,755,000	250,239,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 19,939,000
Short-duration Insurance Contracts, Number of Reported Claims	13,721
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2008 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 195,962,000	191,265,000	188,206,000	180,556,000	171,403,000	158,083,000	139,144,000	100,678,000	39,628,000
Net outstanding liabilities	238,836,000	243,512,000	244,100,000	245,993,000	241,921,000	250,423,000	255,810,000	243,186,000	219,616,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 26,983,000
Short-duration Insurance Contracts, Number of Reported Claims	14,400
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2008 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 181,779,000	180,779,000	175,244,000	173,795,000	166,487,000	151,741,000	130,857,000	104,711,000	69,053,000
Net outstanding liabilities	183,618,000	183,736,000	180,902,000	182,785,000	187,417,000	187,100,000	190,349,000	195,823,000	196,370,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 1,332,000
Short-duration Insurance Contracts, Number of Reported Claims	24,105
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2008 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 30,873,000	29,778,000	28,589,000	28,660,000	28,026,000	25,738,000	24,449,000	21,765,000	15,019,000
Net outstanding liabilities	30,967,000	31,340,000	31,066,000	29,793,000	30,250,000	32,974,000	39,334,000	38,986,000	39,660,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 94,000
Short-duration Insurance Contracts, Number of Reported Claims	3,258
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2008 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 101,034,000	100,868,000	100,908,000	100,752,000	100,213,000	99,288,000	100,465,000	98,921,000	68,211,000
Net outstanding liabilities	101,043,000	100,881,000	101,043,000	101,702,000	101,265,000	101,470,000	101,436,000	102,860,000	97,578,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 4,000
Short-duration Insurance Contracts, Number of Reported Claims	7,604
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2009 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 176,316,000	166,767,000	151,920,000	130,554,000	103,213,000	64,970,000	37,143,000	14,346,000
Net outstanding liabilities	205,741,000	206,387,000	211,243,000	212,947,000	223,146,000	233,530,000	241,625,000	237,913,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 22,858,000
Short-duration Insurance Contracts, Number of Reported Claims	13,815
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2009 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 164,336,000	160,529,000	154,726,000	145,417,000	133,116,000	117,019,000	87,299,000	37,885,000
Net outstanding liabilities	208,611,000	212,536,000	216,992,000	210,756,000	210,109,000	213,036,000	215,946,000	197,504,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 24,238,000
Short-duration Insurance Contracts, Number of Reported Claims	12,214
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2009 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 159,723,000	158,303,000	155,560,000	149,949,000	137,564,000	113,697,000	94,406,000	63,126,000
Net outstanding liabilities	161,923,000	161,251,000	162,911,000	166,682,000	169,858,000	182,724,000	191,079,000	199,541,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 1,873,000
Short-duration Insurance Contracts, Number of Reported Claims	24,554
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2009 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 43,448,000	43,358,000	42,895,000	40,052,000	36,073,000	32,689,000	29,612,000	18,915,000
Net outstanding liabilities	44,273,000	44,299,000	44,938,000	43,553,000	43,828,000	46,645,000	51,762,000	48,535,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 730,000
Short-duration Insurance Contracts, Number of Reported Claims	3,473
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2009 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 80,509,000	80,529,000	80,352,000	80,251,000	80,894,000	80,433,000	78,695,000	59,933,000
Net outstanding liabilities	80,545,000	80,558,000	80,455,000	80,774,000	82,014,000	82,025,000	82,124,000	82,619,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 10,000
Short-duration Insurance Contracts, Number of Reported Claims	7,009
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2010 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 172,394,000	161,487,000	143,360,000	113,050,000	80,018,000	46,201,000	15,726,000
Net outstanding liabilities	208,968,000	211,619,000	222,328,000	237,154,000	242,499,000	228,680,000	215,208,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 29,380,000
Short-duration Insurance Contracts, Number of Reported Claims	12,629
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2010 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 158,078,000	153,795,000	149,086,000	137,184,000	122,442,000	93,281,000	46,795,000
Net outstanding liabilities	208,155,000	212,448,000	214,916,000	211,030,000	212,838,000	214,469,000	198,371,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 34,437,000
Short-duration Insurance Contracts, Number of Reported Claims	12,181
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2010 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 169,100,000	167,227,000	163,513,000	146,913,000	128,015,000	99,254,000	68,098,000
Net outstanding liabilities	173,157,000	172,969,000	179,854,000	181,923,000	187,778,000	189,305,000	187,562,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 2,318,000
Short-duration Insurance Contracts, Number of Reported Claims	25,194
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2010 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 40,279,000	38,900,000	37,819,000	34,705,000	31,027,000	28,131,000	20,821,000
Net outstanding liabilities	41,239,000	40,581,000	40,899,000	39,915,000	42,408,000	49,285,000	53,669,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 693,000
Short-duration Insurance Contracts, Number of Reported Claims	3,917
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2010 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 95,156,000	95,147,000	95,270,000	95,111,000	94,602,000	91,918,000	69,543,000
Net outstanding liabilities	95,178,000	95,363,000	95,530,000	96,127,000	97,386,000	96,851,000	105,647,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 21,000
Short-duration Insurance Contracts, Number of Reported Claims	7,667
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 159,768,000	135,377,000	102,978,000	73,643,000	42,692,000	13,924,000
Net outstanding liabilities	211,196,000	217,256,000	230,785,000	239,480,000	228,720,000	229,967,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 36,350,000
Short-duration Insurance Contracts, Number of Reported Claims	11,533
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 149,269,000	139,232,000	134,646,000	118,847,000	90,836,000	42,941,000
Net outstanding liabilities	205,708,000	210,591,000	215,114,000	214,743,000	218,973,000	205,238,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 38,227,000
Short-duration Insurance Contracts, Number of Reported Claims	11,843
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 166,082,000	157,291,000	142,507,000	121,576,000	99,196,000	69,849,000
Net outstanding liabilities	174,882,000	172,617,000	178,421,000	182,325,000	183,044,000	174,006,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 5,153,000
Short-duration Insurance Contracts, Number of Reported Claims	25,146
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 55,856,000	52,114,000	46,444,000	41,011,000	37,362,000	27,884,000
Net outstanding liabilities	58,966,000	59,256,000	58,242,000	51,047,000	57,083,000	54,469,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 2,177,000
Short-duration Insurance Contracts, Number of Reported Claims	4,956
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 131,115,000	131,060,000	130,681,000	129,579,000	127,580,000	94,538,000
Net outstanding liabilities	131,113,000	131,353,000	131,282,000	130,942,000	131,667,000	136,954,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 22,000
Short-duration Insurance Contracts, Number of Reported Claims	9,035
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 109,448,000	89,008,000	56,580,000	35,241,000	13,030,000
Net outstanding liabilities	175,305,000	194,144,000	215,083,000	245,561,000	238,979,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 44,493,000
Short-duration Insurance Contracts, Number of Reported Claims	9,864
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 132,052,000	122,755,000	108,211,000	86,909,000	40,911,000
Net outstanding liabilities	188,596,000	195,197,000	199,360,000	208,036,000	203,864,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 39,122,000
Short-duration Insurance Contracts, Number of Reported Claims	11,601
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 168,114,000	148,669,000	127,235,000	105,371,000	73,316,000
Net outstanding liabilities	184,367,000	184,289,000	183,527,000	191,947,000	179,551,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 6,421,000
Short-duration Insurance Contracts, Number of Reported Claims	23,751
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 38,766,000	37,215,000	35,089,000	31,833,000	22,199,000
Net outstanding liabilities	44,077,000	44,172,000	46,303,000	48,029,000	54,342,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 834,000
Short-duration Insurance Contracts, Number of Reported Claims	5,533
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 116,291,000	114,699,000	111,503,000	108,834,000	81,528,000
Net outstanding liabilities	117,102,000	116,658,000	115,375,000	114,224,000	118,464,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ (22,000)
Short-duration Insurance Contracts, Number of Reported Claims	8,512
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 104,587,000	72,127,000	35,113,000	12,789,000
Net outstanding liabilities	225,709,000	239,776,000	251,421,000	250,609,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 90,026,000
Short-duration Insurance Contracts, Number of Reported Claims	10,107
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 109,739,000	96,376,000	74,568,000	36,829,000
Net outstanding liabilities	173,160,000	187,658,000	194,318,000	199,794,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 43,058,000
Short-duration Insurance Contracts, Number of Reported Claims	11,361
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 169,850,000	140,015,000	109,893,000	76,469,000
Net outstanding liabilities	207,994,000	209,197,000	205,282,000	188,289,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 18,464,000
Short-duration Insurance Contracts, Number of Reported Claims	25,215
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 34,760,000	30,845,000	26,592,000	17,412,000
Net outstanding liabilities	40,624,000	41,005,000	42,618,000	49,617,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 4,189,000
Short-duration Insurance Contracts, Number of Reported Claims	3,474
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 90,350,000	90,446,000	87,874,000	60,244,000
Net outstanding liabilities	90,005,000	90,103,000	90,639,000	88,101,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ (78,000)
Short-duration Insurance Contracts, Number of Reported Claims	5,704
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 79,972,000	46,825,000	14,901,000
Net outstanding liabilities	257,132,000	249,946,000	244,312,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 135,883,000
Short-duration Insurance Contracts, Number of Reported Claims	10,157
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 100,876,000	78,944,000	35,924,000
Net outstanding liabilities	182,579,000	187,065,000	199,346,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 55,599,000
Short-duration Insurance Contracts, Number of Reported Claims	10,464
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 148,884,000	117,169,000	80,810,000
Net outstanding liabilities	216,824,000	212,725,000	200,534,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 37,432,000
Short-duration Insurance Contracts, Number of Reported Claims	27,129
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 44,911,000	40,584,000	28,914,000
Net outstanding liabilities	62,548,000	60,949,000	55,962,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 10,891,000
Short-duration Insurance Contracts, Number of Reported Claims	4,038
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 136,634,000	132,909,000	101,131,000
Net outstanding liabilities	136,820,000	136,249,000	141,192,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ (1,052,000)
Short-duration Insurance Contracts, Number of Reported Claims	6,503
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 39,978,000	14,665,000
Net outstanding liabilities	245,710,000	254,720,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 167,995,000
Short-duration Insurance Contracts, Number of Reported Claims	9,371
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 77,320,000	33,857,000
Net outstanding liabilities	194,639,000	193,729,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 63,496,000
Short-duration Insurance Contracts, Number of Reported Claims	10,479
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 132,260,000	91,347,000
Net outstanding liabilities	240,958,000	220,994,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 65,528,000
Short-duration Insurance Contracts, Number of Reported Claims	28,475
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 36,014,000	24,189,000
Net outstanding liabilities	53,768,000	52,871,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 12,089,000
Short-duration Insurance Contracts, Number of Reported Claims	3,860
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 106,182,000	79,048,000
Net outstanding liabilities	109,513,000	110,270,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ (1,320,000)
Short-duration Insurance Contracts, Number of Reported Claims	6,380
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 15,684,000
Net outstanding liabilities	277,214,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 233,794,000
Short-duration Insurance Contracts, Number of Reported Claims	7,790
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 34,525,000
Net outstanding liabilities	196,774,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 107,977,000
Short-duration Insurance Contracts, Number of Reported Claims	9,910
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 106,022,000
Net outstanding liabilities	255,187,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 106,894,000
Short-duration Insurance Contracts, Number of Reported Claims	28,740
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 24,655,000
Net outstanding liabilities	52,335,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 16,027,000
Short-duration Insurance Contracts, Number of Reported Claims	3,398
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 83,966,000
Net outstanding liabilities	121,927,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 7,112,000
Short-duration Insurance Contracts, Number of Reported Claims	6,253
Standard Commercial Lines [Member] | Short-Duration Insurance Contracts, Accident Years Prior to 2007 [Member] | General Liability [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	$ 72,887,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contracts, Accident Years Prior to 2007 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	226,553,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contracts, Accident Years Prior to 2007 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	3,271,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contracts, Accident Years Prior to 2007 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	7,327,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contracts, Accident Years Prior to 2007 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	254,000
Standard Personal Lines [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	956,862,000
Net outstanding liabilities	1,041,475,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	90,416,000
Standard Personal Lines [Member] | Homeowners [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	615,083,000
Net outstanding liabilities	647,592,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	38,978,000
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2007 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	101,134,000	101,099,000	100,667,000	100,539,000	99,454,000	97,335,000	92,019,000	82,455,000	66,884,000	45,846,000
Net outstanding liabilities	101,714,000	101,750,000	101,747,000	101,814,000	101,654,000	101,744,000	102,325,000	103,283,000	102,932,000	97,161,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 254,000
Short-duration Insurance Contracts, Number of Reported Claims	15,354
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2007 [Member] | Homeowners [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 33,951,000	33,953,000	33,869,000	33,857,000	33,862,000	33,081,000	32,228,000	31,846,000	30,104,000	20,840,000
Net outstanding liabilities	34,010,000	34,025,000	34,056,000	34,566,000	34,422,000	34,186,000	34,273,000	34,926,000	36,547,000	$ 38,589,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 58,000
Short-duration Insurance Contracts, Number of Reported Claims	4,570
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2008 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 98,668,000	98,604,000	98,174,000	97,723,000	95,932,000	91,834,000	84,715,000	73,194,000	50,396,000
Net outstanding liabilities	99,116,000	99,255,000	99,686,000	99,912,000	100,213,000	103,934,000	106,842,000	106,999,000	100,311,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 264,000
Short-duration Insurance Contracts, Number of Reported Claims	16,042
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2008 [Member] | Homeowners [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 37,930,000	37,939,000	37,933,000	37,837,000	37,763,000	37,086,000	36,271,000	33,535,000	21,277,000
Net outstanding liabilities	38,045,000	38,042,000	38,111,000	38,410,000	38,062,000	39,203,000	39,342,000	41,747,000	$ 41,224,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 65,000
Short-duration Insurance Contracts, Number of Reported Claims	5,139
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2009 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 102,437,000	102,322,000	102,187,000	100,566,000	96,229,000	86,431,000	71,911,000	51,039,000
Net outstanding liabilities	103,412,000	103,393,000	103,866,000	104,734,000	103,908,000	105,033,000	103,319,000	93,808,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 256,000
Short-duration Insurance Contracts, Number of Reported Claims	17,346
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2009 [Member] | Homeowners [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 40,189,000	39,907,000	39,819,000	39,731,000	39,342,000	38,078,000	36,965,000	28,299,000
Net outstanding liabilities	40,457,000	40,465,000	40,400,000	61,927,000	40,313,000	42,609,000	44,511,000	$ 47,636,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 74,000
Short-duration Insurance Contracts, Number of Reported Claims	5,631
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2010 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 106,453,000	105,849,000	104,061,000	101,540,000	95,300,000	82,490,000	58,786,000
Net outstanding liabilities	107,224,000	107,405,000	107,490,000	109,515,000	112,346,000	110,075,000	103,340,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 277,000
Short-duration Insurance Contracts, Number of Reported Claims	20,821
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2010 [Member] | Homeowners [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 62,241,000	62,227,000	62,155,000	61,106,000	60,295,000	58,638,000	43,699,000
Net outstanding liabilities	62,339,000	62,402,000	62,462,000	97,761,000	63,285,000	67,525,000	$ 68,373,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 86,000
Short-duration Insurance Contracts, Number of Reported Claims	9,128
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 112,732,000	111,085,000	105,068,000	93,878,000	82,102,000	61,323,000
Net outstanding liabilities	113,830,000	114,241,000	112,993,000	113,686,000	116,164,000	113,232,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 644,000
Short-duration Insurance Contracts, Number of Reported Claims	22,700
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member] | Homeowners [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 93,720,000	93,312,000	92,185,000	91,718,000	89,963,000	71,668,000
Net outstanding liabilities	94,183,000	94,543,000	94,167,000	82,744,000	98,211,000	103,804,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 143,000
Short-duration Insurance Contracts, Number of Reported Claims	15,102
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 107,890,000	102,977,000	94,842,000	82,729,000	63,704,000
Net outstanding liabilities	110,294,000	109,324,000	109,832,000	114,921,000	113,771,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 988,000
Short-duration Insurance Contracts, Number of Reported Claims	22,332
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member] | Homeowners [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 85,196,000	84,250,000	82,720,000	79,584,000	69,056,000
Net outstanding liabilities	86,271,000	86,667,000	86,560,000	82,745,000	87,260,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 251,000
Short-duration Insurance Contracts, Number of Reported Claims	16,927
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 100,528,000	92,637,000	80,861,000	61,384,000
Net outstanding liabilities	106,703,000	106,225,000	109,620,000	108,417,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 2,252,000
Short-duration Insurance Contracts, Number of Reported Claims	22,359
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member] | Homeowners [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 69,775,000	67,838,000	65,528,000	50,664,000
Net outstanding liabilities	72,145,000	71,494,000	72,528,000	73,670,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 1,545,000
Short-duration Insurance Contracts, Number of Reported Claims	7,738
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 92,589,000	83,739,000	62,519,000
Net outstanding liabilities	106,757,000	109,325,000	102,250,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 6,945,000
Short-duration Insurance Contracts, Number of Reported Claims	22,478
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member] | Homeowners [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 79,751,000	76,007,000	61,561,000
Net outstanding liabilities	83,637,000	82,461,000	80,111,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 1,928,000
Short-duration Insurance Contracts, Number of Reported Claims	8,739
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 76,470,000	58,725,000
Net outstanding liabilities	99,698,000	96,387,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 13,594,000
Short-duration Insurance Contracts, Number of Reported Claims	20,797
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member] | Homeowners [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 70,078,000	52,589,000
Net outstanding liabilities	76,400,000	76,637,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 2,984,000
Short-duration Insurance Contracts, Number of Reported Claims	7,677
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 57,961,000
Net outstanding liabilities	92,727,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 18,187,000
Short-duration Insurance Contracts, Number of Reported Claims	19,044
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member] | Homeowners [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 42,252,000
Net outstanding liabilities	60,105,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 5,646,000
Short-duration Insurance Contracts, Number of Reported Claims	6,402
Standard Personal Lines [Member] | Short-Duration Insurance Contracts, Accident Years Prior to 2007 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	$ 5,803,000
Standard Personal Lines [Member] | Short-Duration Insurance Contracts, Accident Years Prior to 2007 [Member] | Homeowners [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	6,469,000
E&S Lines [Member]
Claims Development [Line Items]
Reserve for losses and loss expenses						15,000,000
E&S Lines [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	125,117,000
Net outstanding liabilities	368,730,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	243,613,000
E&S Lines [Member] | Commercial Property [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	13,251,000
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2007 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	0	0	0	0	0	0
Net outstanding liabilities	0	0	0	0	0	0
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Short-duration Insurance Contracts, Number of Reported Claims	0
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2008 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 92,000	79,000	80,000	70,000	24,000	0
Net outstanding liabilities	(162,000)	52,000	119,000	146,000	169,000	92,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ (270,000)
Short-duration Insurance Contracts, Number of Reported Claims	35
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2009 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 709,000	626,000	605,000	431,000	198,000	0
Net outstanding liabilities	96,000	710,000	728,000	938,000	1,053,000	885,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ (630,000)
Short-duration Insurance Contracts, Number of Reported Claims	274
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2010 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 4,513,000	4,078,000	3,574,000	2,570,000	1,218,000	0
Net outstanding liabilities	3,055,000	3,831,000	4,299,000	3,369,000	4,106,000	3,294,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ (1,778,000)
Short-duration Insurance Contracts, Number of Reported Claims	797
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 9,912,000	9,954,000	6,445,000	3,200,000	806,000	0
Net outstanding liabilities	9,652,000	10,273,000	12,207,000	9,853,000	7,102,000	$ 8,127,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ (599,000)
Short-duration Insurance Contracts, Number of Reported Claims	1,303
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 32,343,000	25,064,000	16,430,000	7,914,000	3,722,000
Net outstanding liabilities	46,165,000	46,149,000	43,175,000	42,621,000	$ 42,367,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 9,289,000
Short-duration Insurance Contracts, Number of Reported Claims	1,982
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 35,200,000	21,980,000	9,470,000	2,715,000
Net outstanding liabilities	69,112,000	67,099,000	60,309,000	$ 55,468,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 21,956,000
Short-duration Insurance Contracts, Number of Reported Claims	2,128
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 25,571,000	12,234,000	2,353,000
Net outstanding liabilities	69,929,000	63,505,000	$ 55,316,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 29,236,000
Short-duration Insurance Contracts, Number of Reported Claims	1,888
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 13,057,000	3,036,000
Net outstanding liabilities	76,432,000	$ 75,498,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 48,390,000
Short-duration Insurance Contracts, Number of Reported Claims	2,313
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member] | General Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 3,720,000
Net outstanding liabilities	94,451,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 84,328,000
Short-duration Insurance Contracts, Number of Reported Claims	1,760
E&S Lines [Member] | Short-Duration Insurance Contracts, Accident Years Prior to 2007 [Member] | General Liability [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	$ 0

Reserve for Losses and Loss E84

Reserve for Losses and Loss Expenses Reserve for Losses and Loss Expenses (Reconciliation of Claims Development to Liability) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	$ 1,234,797	$ 1,148,541	$ 1,157,501
Liability for Unpaid Claims and Claims Adjustment Expense, Net	2,944,432
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	611,200	551,019	571,978	$ 540,839
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claims Adjustment Expense, Accumulated Unallocated Claim Adjustment Expense	136,087
Liability for Claims and Claims Adjustment Expense	3,691,719	$ 3,517,728	$ 3,477,870	$ 3,349,770
General Liability [Member] | Standard Commercial Lines [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	1,070,929
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	179,997
General Liability [Member] | E&S Lines [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	243,613
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	25,741
Workers Compensation [Member] | Standard Commercial Lines [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	936,766
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	223,327
Commercial Automobile [Member] | Standard Commercial Lines [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	402,281
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	17,373
Business Owners' Policies [Member] | Standard Commercial Lines [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	86,802
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	7,012
Commercial Property [Member] | Standard Commercial Lines [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	42,279
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	13,615
Commercial Property [Member] | E&S Lines [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	13,251
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	468
Other Commercial [Member] | Standard Commercial Lines [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	11,389
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	2,613
Total standard Commercial Lines [Member] | Standard Commercial Lines [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	2,550,446
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	443,937
Total standard Commercial Lines [Member] | E&S Lines [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	256,864
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	26,209
Personal Automobile [Member] | Standard Personal Lines [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	90,416
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	55,223
Homeowners [Member] | Standard Personal Lines [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	38,978
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	3,206
Other Personal [Member] | Standard Personal Lines [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	7,728
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	82,625
Standard Personal Lines [Member] | Standard Personal Lines [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	137,122
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	$ 141,054

Reserve for Losses and Loss E85

Reserve for Losses and Loss Expenses Reserve for Losses and Loss Expenses (Historical Claims Duration) (Details)	Dec. 31, 2016
General Liability [Member] | Standard Commercial Lines [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	6.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	12.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	15.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	16.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	15.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	10.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	5.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	4.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	2.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	2.20%
General Liability [Member] | E&S Lines [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	3.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	12.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	17.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	19.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	16.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	9.50%
Workers Compensation [Member] | Standard Commercial Lines [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	19.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	23.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	14.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	8.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	5.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	3.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	3.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	2.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	2.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	1.20%
Commercial Automobile [Member] | Standard Commercial Lines [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	38.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	17.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	14.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	12.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	9.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	3.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	1.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	1.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	0.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.20%
Business Owners' Policies [Member] | Standard Commercial Lines [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	46.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	20.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	8.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	8.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	6.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	4.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	1.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	1.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	0.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.80%
Commercial Property [Member] | Standard Commercial Lines [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	70.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	26.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	2.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	0.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	0.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	0.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	0.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	0.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	0.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.10%
Personal Automobile [Member] | Standard Personal Lines [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	54.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	18.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	11.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	7.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	4.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	1.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	0.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	0.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	0.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.00%
Homeowners [Member] | Standard Personal Lines [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	69.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	21.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	3.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	1.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	1.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	0.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	0.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	0.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	0.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.10%

Indebtedness (Narrative) (Detai

Indebtedness (Narrative) (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2005USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Mar. 31, 2014USD ($)	Dec. 31, 2004USD ($)
Short Term Debt Gross		$ 60,000
Aggregate investment in FHLBI		$ 2,800	$ 2,800
Borrowing threshold of FHLBI		20
Five Point Eight Hundred Seventy Five Percent Senior Notes Due 2043 [Member]
Aggregate principal amount of notes				$ 185,000
Bond proceeds to Insurance Subsidiaries as capital				57,100
Long-term Debt, Gross		$ 185,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		5.88%
Redemption Of Seven Point Fifty Percent Junior Notes [Member]
Aggregate principal amount of notes				$ 100,000
Six Point Seventy Percent Senior Notes due 2035 [Member]
Aggregate principal amount of notes	$ 100,000
Discount for notes issued	$ 700
Effective yield	6.754%
Acceleration of principal		$ 10,000
Net proceeds from the issuance	$ 50,000
Long-term Debt, Gross		$ 100,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		6.70%
Seven Point Twenty Five Percent Senior Notes due 2034 [Member]
Aggregate principal amount of notes					$ 50,000
Discount for notes issued					$ 100
Effective yield					7.27%
Bond proceeds to Insurance Subsidiaries as capital					$ 25,000
Acceleration of principal		$ 10,000
Long-term Debt, Gross		$ 50,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		7.25%
Line of Credit expires Dec.1, 2020 [Member]
Acceleration of principal		$ 20,000
Line of credit borrowing capacity		30,000
Line of credit, maximum borrowing capacity		50,000
One Point Sixty One Percent Borrowing From Federal Home Loan Bank Due July 21, 2021 [Member]
Long-term Debt, Gross		$ 25,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		1.61%
One Point Fifty Six Percent Borrowing From Federal Home Loan Bank Due August 16, 2021 [Member]
Long-term Debt, Gross		$ 25,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		1.56%
Zero Point Sixty Three Percent Borrowing From Federal Home Loan Bank Due July 22, 2016 [Member]
Short Term Debt Gross		$ 15,000
Short-term Debt, Percentage Bearing Fixed Interest Rate		0.63%
One Point Twenty Five Percent Borrowing From Federal Home Loan Bank due Dec. 16, 2016 [Member]
Short Term Debt Gross		$ 45,000
Short-term Debt, Percentage Bearing Fixed Interest Rate		1.25%

Indebtedness (Covenants in the

Indebtedness (Covenants in the Line of Credit) (Details) - USD ($)		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
Consolidated net worth, required		$ 1,100,000,000
Statutory surplus, required		$ 750,000,000
Debt-to-capitalization ratio, required	[1]	35.00%
Consolidated net worth, actual		$ 1,531,370,000	$ 1,398,041,000	$ 1,275,586,000
Statutory surplus, actual		$ 1,583,800,000	$ 1,426,300,000
Debt-to-capitalization ratio, actual	[1]	22.50%
[1]	Calculated in accordance with Line of Credit agreement.

Indebtedness Schedule of Long-T

Indebtedness Schedule of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Debt Instruments [Line Items]
Short Term Debt Gross	$ 60,000
Short-term debt	0	$ 60,000
Three Point Zero Three Percent Borrowing From Federal Home Loan Bank Due December 16, 2026 [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 0
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.03%
Long-term Debt, Gross	$ 60,000
Long-term Debt	60,000	0
One Point Fifty Six Percent Borrowing From Federal Home Loan Bank Due August 16, 2021 [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 0
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	1.56%
Long-term Debt, Gross	$ 25,000
Long-term Debt	25,000	0
One Point Sixty One Percent Borrowing From Federal Home Loan Bank Due July 21, 2021 [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 0
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	1.61%
Long-term Debt, Gross	$ 25,000
Long-term Debt	25,000	0
Five Point Eight Hundred Seventy Five [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (4,932)
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	5.88%
Long-term Debt, Gross	$ 185,000
Long-term Debt	180,068	179,684
Six Point Seventy Percent Senior Notes [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (1,048)
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	6.70%
Long-term Debt, Gross	$ 100,000
Long-term Debt	98,952	98,890
Seven Point Twenty Five Percent Senior Notes [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (353)
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	7.25%
Long-term Debt, Gross	$ 50,000
Long-term Debt	49,647	49,618
Long-term Debt [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	(6,333)
Long-term Debt, Gross	445,000
Long-term Debt	$ 438,667	328,192
Zero Point Sixty Three Percent Borrowing From Federal Home Loan Bank Due July 22, 2016 [Member]
Schedule of Debt Instruments [Line Items]
Short-term Debt, Percentage Bearing Fixed Interest Rate	0.63%
Short Term Debt Gross	$ 15,000
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	0
Short-term debt	$ 0	15,000
One Point Twenty Five Percent Borrowing From Federal Home Loan Bank [Member]
Schedule of Debt Instruments [Line Items]
Short-term Debt, Percentage Bearing Fixed Interest Rate	1.25%
Short Term Debt Gross	$ 45,000
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	0
Short-term debt	0	$ 45,000
Short-term Debt [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 0

Segment Information (Narrative)

Segment Information (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting [Abstract]
Number of Operating Segments	4
Goodwill balance for our Standard Commercial Lines reporting unit	$ 7,849	$ 7,849
Percentage of net premiums written related to insurance policies written in New Jersey	20.00%

Segment Information (Revenue Fr

Segment Information (Revenue From Continuing Operations by Segment) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue from External Customer [Line Items]
Net premiums earned	$ 552,753	$ 542,429	$ 531,932	$ 522,458	$ 516,087	$ 507,390	$ 490,309	$ 476,123	$ 2,149,572	$ 1,989,909	$ 1,852,609
Other income									8,881	7,456	16,945
Net investment income	$ 35,428	$ 33,375	$ 31,182	$ 30,769	$ 30,108	$ 32,061	$ 32,230	$ 26,917	130,754	121,316	138,708
Realized investment (losses) gains									(4,937)	13,171	26,599
Total investment revenues									125,817	134,487	165,307
Total all segments									2,284,270	2,131,852	2,034,514
Total revenues									2,284,270	2,131,852	2,034,861
Miscellaneous Income [Member]
Revenue from External Customer [Line Items]
Other income									8,881	7,456	16,598
Other Income [Member]
Revenue from External Customer [Line Items]
Other income									0	0	347
Standard Commercial Lines [Member] | Commercial Automobile [Member]
Revenue from External Customer [Line Items]
Net premiums earned									398,942	358,909	333,310
Standard Commercial Lines [Member] | Workers Compensation [Member]
Revenue from External Customer [Line Items]
Net premiums earned									308,233	290,075	274,585
Standard Commercial Lines [Member] | General Liability [Member]
Revenue from External Customer [Line Items]
Net premiums earned									527,859	483,291	444,938
Standard Commercial Lines [Member] | Commercial Property [Member]
Revenue from External Customer [Line Items]
Net premiums earned									293,438	269,022	244,792
Standard Commercial Lines [Member] | Business Owners' Policies [Member]
Revenue from External Customer [Line Items]
Net premiums earned									97,754	93,428	85,788
Standard Commercial Lines [Member] | Bonds Segment [Member]
Revenue from External Customer [Line Items]
Net premiums earned									23,227	20,350	19,288
Standard Commercial Lines [Member] | Other Commercial [Member]
Revenue from External Customer [Line Items]
Net premiums earned									16,030	14,367	13,011
Standard Commercial Lines [Member] | Miscellaneous Income [Member]
Revenue from External Customer [Line Items]
Net premiums earned									7,782	6,343	14,747
Standard Commercial Lines [Member] | Total standard Commercial Lines [Member]
Revenue from External Customer [Line Items]
Net premiums earned									1,673,265	1,535,785	1,430,459
Standard Personal Lines [Member] | Miscellaneous Income [Member]
Revenue from External Customer [Line Items]
Net premiums earned									1,098	1,113	1,834
Standard Personal Lines [Member] | Personal Automobile [Member]
Revenue from External Customer [Line Items]
Net premiums earned									142,876	146,784	151,317
Standard Personal Lines [Member] | Homeowners [Member]
Revenue from External Customer [Line Items]
Net premiums earned									130,973	134,382	134,273
Standard Personal Lines [Member] | Other Personal [Member]
Revenue from External Customer [Line Items]
Net premiums earned									6,758	6,968	11,157
Standard Personal Lines [Member] | Standard Personal Lines [Member]
Revenue from External Customer [Line Items]
Net premiums earned									281,705	289,247	298,581
E&S Lines [Member] | General Liability [Member]
Revenue from External Customer [Line Items]
Net premiums earned									151,638	126,064	99,086
E&S Lines [Member] | Commercial Property [Member]
Revenue from External Customer [Line Items]
Net premiums earned									51,844	46,269	41,064
E&S Lines [Member] | Miscellaneous Income [Member]
Revenue from External Customer [Line Items]
Other income									1	0	17
E&S Lines [Member] | Total standard Commercial Lines [Member]
Revenue from External Customer [Line Items]
Net premiums earned									$ 203,483	$ 172,333	$ 140,167

Segment Information (Income Fro

Segment Information (Income From Continuing Operations, Before Federal Income Tax) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Underwriting gain (loss), before federal income tax	$ 35,168	$ 32,033	$ 43,777	$ 40,955	$ 49,053	$ 44,831	$ 29,124	$ 26,021
Net investment income	$ 35,428	$ 33,375	$ 31,182	$ 30,769	$ 30,108	$ 32,061	$ 32,230	$ 26,917	$ 130,754	$ 121,316	$ 138,708
Realized investment (losses) gains									(4,937)	13,171	26,599
Total investment revenues									125,817	134,487	165,307
Tax on investment income									30,621	32,090	43,811
Total investment income, after federal income tax									95,196	102,397	121,496
Standard Commercial Lines [Member]
Underwriting gain (loss), before federal income tax									$ 146,435	$ 164,496	$ 61,221
GAAP Combined Ratio									91.20%	89.20%	95.70%
Statutory Combined Ratio									89.90%	89.20%	95.50%
Standard Personal Lines [Member]
Underwriting gain (loss), before federal income tax									$ 12,419	$ 1,336	$ 16,536
GAAP Combined Ratio									95.60%	99.50%	94.40%
Statutory Combined Ratio									95.20%	99.90%	94.50%
Excess And Surplus Operations [Member]
Underwriting gain (loss), before federal income tax									$ (6,921)	$ (16,803)	$ 386
GAAP Combined Ratio									103.40%	109.80%	99.70%
Statutory Combined Ratio									102.10%	108.40%	99.20%

Segment Information (Reconcilia

Segment Information (Reconciliation of Segment Results to Income from Continuing Operations, before Federal Income Tax (Details)) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Underwriting gain (loss), before federal income tax	$ 35,168	$ 32,033	$ 43,777	$ 40,955	$ 49,053	$ 44,831	$ 29,124	$ 26,021
Total investment revenues									$ 125,817	$ 134,487	$ 165,307
Interest expense									(22,771)	(22,428)	(23,063)
General corporate and other expenses									(35,024)	(28,396)	(23,256)
Income from continuing operations, before federal income tax									219,955	232,692	197,131
Standard Commercial Lines [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Underwriting gain (loss), before federal income tax									146,435	164,496	61,221
Standard Personal Lines [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Underwriting gain (loss), before federal income tax									12,419	1,336	16,536
Excess And Surplus Operations [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Underwriting gain (loss), before federal income tax									(6,921)	(16,803)	386
Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total all segments									$ 277,750	$ 283,516	$ 243,450

Earnings Per Share (Reconciliat

Earnings Per Share (Reconciliation of EPS) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Basic EPS: [Abstract]
Net income	$ 39,360	$ 38,502	$ 43,601	$ 37,032	$ 45,389	$ 46,996	$ 33,768	$ 39,708	$ 158,495	$ 165,861	$ 141,827
Net income, basic shares									57,889	57,212	56,310
Basic net income	$ 0.68	$ 0.66	$ 0.75	$ 0.64	$ 0.79	$ 0.82	$ 0.59	$ 0.70	$ 2.74	$ 2.90	$ 2.52
Effect of dilutive securities: [Abstract]
Stock compensation plans, shares									$ 858	$ 944	$ 1,041
Earnings Per Share, Diluted [Abstract]
Net income	$ 39,360	$ 38,502	$ 43,601	$ 37,032	$ 45,389	$ 46,996	$ 33,768	$ 39,708	$ 158,495	$ 165,861	$ 141,827
Shares net income, Diluted									58,747	58,156	57,351
Diluted net income	$ 0.67	$ 0.66	$ 0.74	$ 0.63	$ 0.78	$ 0.81	$ 0.58	$ 0.69	$ 2.70	$ 2.85	$ 2.47

Federal Income Taxes (Reconcili

Federal Income Taxes (Reconciliation of Federal Income Tax on Income at the Corporate Rate to the Effective Tax Rate) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Tax at statutory rate of 35%	$ 76,984	$ 81,442	$ 68,996
Tax-advantaged interest	(12,126)	(13,164)	(12,926)
Dividends received deduction	(1,114)	(1,817)	(1,121)
Other	(2,284)	370	355
Total federal income tax expense	$ 61,460	$ 66,831	$ 55,304

Federal Income Taxes (Deferred

Federal Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net loss reserve discounting	$ 70,065	$ 74,436
Net unearned premiums	78,201	72,057
Employee benefits	17,881	30,432
Long-term incentive compensation plans	17,750	15,551
Temporary investment write-downs	2,475	5,419
Other investment-related items, net	1,484	0
Net operating loss	771	1,454
Other	8,344	8,132
Total deferred tax assets	196,971	207,481
Deferred policy acquisition costs	75,310	72,481
Unrealized gains on investment securities	22,681	24,228
Other investment-related items, net	0	5,566
Accelerated depreciation and amortization	14,140	12,510
Total deferred tax liabilities	112,131	114,785
Net deferred federal income tax asset	84,840	92,696
Tax benefits related to compensation expense deductions for share-based compensation awards	$ 23,800	$ 22,000	$ 20,200

Federal Income Tax (Federal Tax

Federal Income Tax (Federal Tax Net Operating Loss Carryforwards) (Details) $ in Thousands	Dec. 31, 2016USD ($)
Operating Loss Carryforwards [Line Items]
Annual Limitation Of Net Operating Loss Carryforwards	$ 1,900
Operating Loss Carryforwards	2,203
Operating Loss Carryforwards Tax Effect	772
Tax Year 2030 [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	2,124
Operating Loss Carryforwards Tax Effect	744
Tax Year 2031 [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	79
Operating Loss Carryforwards Tax Effect	$ 28

Retirement Plans (Retirement Sa

Retirement Plans (Retirement Savings Plan) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Retirement Savings Plan [Member]
Defined Benefit Plan, Contributions by Employer	$ 15	$ 14.1	$ 13.4

Retirement Plans (Deferred Comp

Retirement Plans (Deferred Compensation Plan) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred Compensation Plan Contributions By Employer	$ 0.3	$ 0.2	$ 0.2

Retirement Plans (Funded Status

Retirement Plans (Funded Status of Retirement Income Plan and Retirement Life Plan) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net actuarial gain (loss), Gross	$ 12,079	$ (2,438)	$ 54,136
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	8,500
Benefit obligation, end of year	9,100	8,500
Retirement Income Plan [Member]
Defined Benefit Plan, Amortization of Gains (Losses)	(6,299)	(6,831)	(1,776)
Net actuarial gain (loss), Gross	11,316	(1,425)	52,556
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	310,308	322,271
Service cost	1,647	7,215	5,763
Interest cost	12,336	13,668	12,776
Actuarial losses (gains)	15,086	(24,994)
Benefit obligation, end of year	330,588	310,308	322,271
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of assets, beginning of year	249,700	253,452
Actual return on plan assets, net of expenses	21,079	(7,600)
Contributions by the employer to funded plans	54,525	11,700
Benefits paid fair value	(8,789)	(7,852)
Fair value of assets, end of year	316,515	249,700	$ 253,452
Funded status	(14,073)	(60,608)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Liabilities	(14,073)	(60,608)
Net pension liability, end of year	(14,073)	(60,608)
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax [Abstract]
Net actuarial loss	85,845	80,828
Total	$ 85,845	$ 80,828
Weighted-Average Liability Asumptions
Discount rate	4.41%	4.69%
Rate of compensation increase	0.00%	4.00%
Accumulated benefit obligation	$ 330,588	$ 310,307
Retirement Life Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	6,000
Benefit obligation, end of year	$ 6,300	$ 6,000

Retirement Plans (Components of

Retirement Plans (Components of Net Periodic Benefit Cost and Other Amounts Recognized in Other Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net actuarial loss (gain)	$ 12,079	$ (2,438)	$ 54,136
Reversal of amortization of net actuarial loss	(6,462)	(7,077)	(1,902)
Retirement Income Plan [Member]
Service cost	1,647	7,215	5,763
Interest cost	12,336	13,668	12,776
Expected return on plan assets	(17,309)	(15,969)	(15,671)
Amortization of unrecognized actuarial loss	6,299	6,831	1,776
Total net periodic cost	2,973	11,745	4,644
Net actuarial loss (gain)	11,316	(1,425)	52,556
Reversal of amortization of net actuarial loss	(6,299)	(6,831)	(1,776)
Total recognized in other comprehensive income	5,017	(8,256)	50,780
Total recognized in net periodic benefit cost and OCI	7,990	3,489	55,424
Estimated net actuarial loss that will be amortized from AOCI into net periodic benefit cost	1,900
Retirement Life Plan [Member]
Total net periodic cost	300		400
Supplemental Employee Retirement Plan [Member]
Total net periodic cost	$ 500	$ 800	$ 600

Retirement Plans (Weighted-Aver

Retirement Plans (Weighted-Average Expense Assumptions) (Details)		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Discount rate	[1]	3.83%
Expected return on plan assets		6.24%
Retirement Income Plan [Member]
Discount rate		4.69%	4.29%	5.16%
Expected return on plan assets		6.37%	6.27%	6.92%
Rate of compensation increase		0.00%	4.00%	4.00%
Discount rate used to value the liability		4.41%	4.69%
[1]	This assumption was 4.00% through March 31, 2016, the date after which benefits ceased accruing for all participants of the Pension Plan.

Retirement Plans (Plan's Alloca

Retirement Plans (Plan's Allocated Target and Ranges and Actual Weighted Average Asset Allocation by Investment Categories) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Actual percentage	100.00%	100.00%
Range minimum	0.00%
Range maximum	0.00%
Maximum percentage of equity security value of total plans portfolio value that is allowed	8.00%
Maximum percentage of any corporation outstanding shares that is allowed for retirement income plan equity portfolio	5.00%
Extended Duration Fixed Maturity [Member]
Actual percentage	53.00%	60.00%
Range minimum	40.00%
Range maximum	100.00%
Global Equity [Member]
Actual percentage	33.00%	36.00%
Range minimum	0.00%
Range maximum	40.00%
Private Equity Funds [Member]
Actual percentage	6.00%	3.00%
Range minimum	0.00%
Range maximum	30.00%
Cash And Short Term Investments [Member]
Actual percentage	8.00%	1.00%
Range minimum	0.00%
Range maximum	5.00%

Retirement Plans (Quantitative

Retirement Plans (Quantitative Disclosures of Retirement Income Plan's Invested Assets that are Measured at Fair Value on a Recurring Basis) (Details) - Retirement Income Plan [Member] - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Total Assets	$ 316,515	$ 249,700	$ 253,452
Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	316,987	249,781
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	193,057	152,462
Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	1,832	1,418
Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Global Asset Allocation Fund [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	37,878	33,565
Global Asset Allocation Fund [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	37,878	33,565
Global Asset Allocation Fund [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Global Asset Allocation Fund [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Extended Duration Fixed Income [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	131,457	117,297
Extended Duration Fixed Income [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	131,457	117,297
Extended Duration Fixed Income [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Extended Duration Fixed Income [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Total Long Duration Fixed Income [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	169,335	150,862
Total Long Duration Fixed Income [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	169,335	150,862
Total Long Duration Fixed Income [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Total Long Duration Fixed Income [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Short-term Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	23,722	1,600
Short-term Investments [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	23,722	1,600
Short-term Investments [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Short-term Investments [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Deposit Administration Contracts [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	1,832	1,418
Deposit Administration Contracts [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Deposit Administration Contracts [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	1,832	1,418
Deposit Administration Contracts [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Cash And Short Term Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	25,554	3,018
Cash And Short Term Investments [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	23,722	1,600
Cash And Short Term Investments [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	1,832	1,418
Cash And Short Term Investments [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
International equity [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	48,836	42,603
International equity [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
International equity [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
International equity [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
US Global Equity [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	55,073	46,840
US Global Equity [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
US Global Equity [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
US Global Equity [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Global Equity [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	103,909	89,443
Global Equity [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Global Equity [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Global Equity [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Real Assets [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	15,466	2,514
Real Assets [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Real Assets [Member] | Significant Other Observable Inputs (Level 2) [Member] | Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Real Assets [Member] | Significant Unobservable Inputs (Level 3) [Member] | Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Private Equity Funds [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	1,615	2,626
Private Equity Funds [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Private Equity Funds [Member] | Significant Other Observable Inputs (Level 2) [Member] | Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Private Equity Funds [Member] | Significant Unobservable Inputs (Level 3) [Member] | Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Private Credit Funds [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	1,108	1,318
Private Credit Funds [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Private Credit Funds [Member] | Significant Other Observable Inputs (Level 2) [Member] | Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Private Credit Funds [Member] | Significant Unobservable Inputs (Level 3) [Member] | Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	18,189	6,458
Alternative Investments [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Alternative Investments [Member] | Significant Other Observable Inputs (Level 2) [Member] | Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	0	0
Alternative Investments [Member] | Significant Unobservable Inputs (Level 3) [Member] | Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	$ 0	$ 0

Retirement Plans (Benefit Payme

Retirement Plans (Benefit Payments) (Details) - Retirement Income Plan [Member] $ in Thousands	Dec. 31, 2016USD ($)
2,017	$ 10,830
2,018	12,041
2,019	13,125
2,020	14,184
2,021	15,124
2022 - 2026	$ 89,771

Share-Based Payments (Summary o

Share-Based Payments (Summary of Shares Available for Issuance) (Details)	Dec. 31, 2016shares
Omnibus Stock Plan 2014 [Member]
Schedule of Share-Based Compensation Shares Available for Issuance [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	3,500,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	2,835,694
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	607,156
Employee Stock [Member]
Schedule of Share-Based Compensation Shares Available for Issuance [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	1,500,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	574,722
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	0
Agent Stock Purchase Plan [Member]
Schedule of Share-Based Compensation Shares Available for Issuance [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	3,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	1,867,287
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	0

Shared-Based Payments (Summary

Shared-Based Payments (Summary of Retired Plans) (Details)	Dec. 31, 2016shares
Omnibus Stock Plan [Member]
Schedule of Share-Based Compensation Retired Plans [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	2,664,594
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	726,394
Stock Compensation Plan For Non Employee Directors [Member]
Schedule of Share-Based Compensation Retired Plans [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	67,242
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	67,242
Stock Option Share Based Compensation [Member] | Omnibus Stock Plan [Member]
Schedule of Share-Based Compensation Retired Plans [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	355,391
Restricted Stock Units (RSUs) [Member] | Omnibus Stock Plan [Member]
Schedule of Share-Based Compensation Retired Plans [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	371,003

Share-Based Payments (Summar107

Share-Based Payments (Summary of the Restricted Stock Unit Transactions under Share-Based Payment Plans) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash Incentive Plan [Member]
Weighted average remaining expense life	1 year 2 months
Cash incentive unit payments made	$ 14.3	$ 10.2	$ 9
Restricted Stock Units (RSUs) [Member]
Unvested RSU awards at December 31, 2015	1,018,530
Granted in 2016, number of shares	299,670
Vested in 2016, number of shares	(389,245)
Forfeited in 2016, number of shares	(12,315)
Unvested RSU awards at Decemeber 31, 2016, number of shares	916,640	1,018,530
Unvested RSU awards at December 31, 2015, weighted average grant date fair value	$ 22.55
Granted in 2016, weighted average grant date fair value	32.53	$ 25.22	$ 21.58
Vested in 2016, weighted average grant date value	21.56
Forfeited in 2016, weighted average grant date fair value	24.97
Unvested RSU awards at December 31, 2016, weighted average grant date fair value	$ 26.20	$ 22.55
Total unrecognized compensation cost related to unvested RSU awards	$ 5.3
Weighted average remaining expense life	1 year 9 months
Total intrinsic value of shares vested	$ 12.6	$ 10.3	$ 8.5
Dividend Equivalent Units [Member]
Total intrinsic value of shares vested	$ 0.7	$ 0.7	$ 0.7

Share-Based Payments (Summar108

Share-Based Payments (Summary of Stock Option Transactions under Share-Based Payment Plans) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Outstanding at December 31, 2015, number of shares	493,428
Granted in 2016, numbers of shares	0
Exercised in 2016, number of shares	(138,037)
Forfeited or expired 2016, number of shares	0
Outstanding at December 31, 2016, number of shares	355,391	493,428
Exercisable at December 31, 2016, number of shares	355,391
Outstanding at December 31, 2015, weighted average exercise price	$ 17.84
Granted in 2016, weighted average exercise price	0
Exercised in 2016, weighted average exercise price	20.33
Forfeited or expired 2016, weighted average exercise price	0
Outstanding at December 31, 2016, weighted average exercise price	16.87	$ 17.84
Exercisable as December 31, 2016, weighted average exercise price	$ 16.87
Outstanding at December 31, 2016, weighted average remaining contractual life in years	2 years 1 month 22 days
Exercisable at December 31, 2016, weighted average remaining contractual life in years	2 years 1 month 22 days
Outstanding at December 31, 2016, aggregate intrinsic value	$ 9,304
Exerciseable at December 31, 2016, aggregate intrinsic value	9,304
Total intrinsic value of options exercised	2,300	$ 2,200	$ 800
Cash Incentive Plan [Member]
Share Based Compensation Liability Awards Amount Of Liability	$ 32,000	$ 26,500

Shared-Based Payments (Summa109

Shared-Based Payments (Summary of ESPP and ASPP Shares Issued) (Details) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Share-Based Compensation ESPP and ASPP Shares Granted [Line Items]
Stock Issued During Period Shares	720,323	863,426	769,389
Employee Stock [Member]
Schedule of Share-Based Compensation ESPP and ASPP Shares Granted [Line Items]
Stock Issued During Period Shares	88,432	100,944	106,832
Agent Stock Purchase Plan [Member]
Schedule of Share-Based Compensation ESPP and ASPP Shares Granted [Line Items]
Stock Issued During Period Shares	69,867	82,142	78,724

Share-Based Payments (Weighted

Share-Based Payments (Weighted Average Assumptions for Employee Stock Purchase Plan and Other Options) (Details) - Employee Stock Purchase Plan [Member]	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Risk-free interest rate	0.47%	0.10%	0.07%
Expected term	6 months	6 months	6 months
Dividend yield	1.70%	2.00%	2.00%
Expected volatility	31.00%	20.00%	21.00%

Share-Based Payments (Weighted-

Share-Based Payments (Weighted-Average Fair Value of Options and Stock Per Share) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restricted Stock Units (RSUs) [Member]
Stock, weighted average grant date fair value	$ 32.53	$ 25.22	$ 21.58
Employee Stock Purchase Plan [Member]
Options, weighted average grant date fair value	2.63	1.26	1.24
15% of grant date market value	5.23	4.16	3.87
Total ESPP	7.86	5.42	5.11
Agent Stock Purchase Plan [Member]
Stock, weighted average grant date fair value	$ 3.79	$ 2.94	$ 2.42

Shared-Based Payments (Summa112

Shared-Based Payments (Summary of Share-Based Compensation Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of Share-Based Compensation Expenses [Abstract]
Share-based compensation expense charged against net income, Before Tax	$ 30.3	$ 23.8	$ 18.6
Share-based compensation expense income tax benefit	(10.3)	(8)	(6.2)
Share-based Compensation Expense, Net of Tax	$ 20	$ 15.8	$ 12.4

Related Party Transactions (Nar

Related Party Transactions (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Equity ownership percentage of director of parent of general independent retail insurance agency	10.00%
Direct premiums written	$ 2,577,259	$ 2,403,519	$ 2,228,270
Due to Related Parties, Current	700	600
Contributions to the Selective Insurance Group Foundation	0	1,000	800
Related Party Insurance Agency [Member]
Direct premiums written	10,400	9,600	9,000
Commissions paid to Rue Insurance	$ 2,100	$ 1,700	$ 1,600

Commitments and Contingencie114

Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Contractual Obligation Additional Investment in Alternative or Other Investments	$ 143,700
Purchase amount of annuities	17,900
Rental expense for operating leases for office space, equipment, and vehicles	$ 17,300	$ 17,400	$ 15,600
Capital Lease Agreements Expiration Period	2,019
Other Investments [Member]
Remaining Commitment	$ 143,686	$ 74,353

Commitments and Contingencie115

Commitments and Contingencies (Future Minimum Rental Commitments) (Details) $ in Millions	Dec. 31, 2016USD ($)
2017- Capital Leases	$ 4
2018- Capital Leases	2.2
2019- Capital Leases	0.1
2020- Capital Leases	0
2021- Capital Leases	0
After 2021- Capital Leases	0
Total minimum payment required- Capital Leases	6.3
2017- Operating Leases	9.1
2018- Operating Leases	7.7
2019- Operating Leases	5.6
2020- Operating Leases	4.4
2021- Operating Leases	2.9
After 2021- Operating Leases	4.7
Total minimum payment required- Operating Leases	34.4
2017- Total Leases	13.1
2018- Total Leases	9.9
2019- Total Leases	5.7
2020- Total Leases	4.4
2021- Total Leases	2.9
After 2021- Total Leases	4.7
Total minimum payment required	$ 40.7

Statutory Financial Informat116

Statutory Financial Information, Capital Requirements and Restrictions on Dividends and Transfers of Funds (Statutory Financial Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statutory unassigned surplus	$ 1,048.2	$ 890.7
Statutory surplus	1,583.8	1,426.3
Statutory net income	202.3	195.8	$ 190.3
Selective Insurace Company of America (SICA) [Member]
Statutory unassigned surplus	414.4	366.6
Statutory surplus	568.6	520.8
Statutory net income	72.2	69.6	83.9
Selective Way Insurance Company (SWIC) [Member]
Statutory unassigned surplus	260.5	223.6
Statutory surplus	309.5	272.6
Statutory net income	41.2	42.3	37
Selective Insurance Company of South Carolina (SICSC) [Member]
Statutory unassigned surplus	110.6	96.6
Statutory surplus	141.9	127.9
Statutory net income	17.4	15.9	14
Selective Insurance Company of the Southeast (SICSE) [Member]
Statutory unassigned surplus	83.5	70.7
Statutory surplus	109.1	96.2
Statutory net income	13.4	12.1	10.5
Selective Insurance Company of New York (SICNY) [Member]
Statutory unassigned surplus	74.1	65.3
Statutory surplus	101.8	93
Statutory net income	12.9	12.7	10.3
Selective Insurance Company of New England (SICNE) [Member]
Statutory unassigned surplus	13.6	9.2
Statutory surplus	43.7	39.4
Statutory net income	5.9	5.5	4.4
Selective Auto Insurance Company of New Jersey (SAICNJ) [Member]
Statutory unassigned surplus	36.9	26.4
Statutory surplus	79.8	69.2
Statutory net income	11.5	10.8	9.1
Mesa Underwriting Specialty Insurance Company (MUSIC) [Member]
Statutory unassigned surplus	16.7	7
Statutory surplus	85.2	75.5
Statutory net income	9.7	9.5	7.3
Selective Casualty Insurance Company (SCIC) [Member]
Statutory unassigned surplus	26.6	17.8
Statutory surplus	101	92.3
Statutory net income	12.6	12.1	9.6
Selective Fire and Casualty Insurance Company (SFCIC) [Member]
Statutory unassigned surplus	11.3	7.5
Statutory surplus	43.2	39.4
Statutory net income	$ 5.5	$ 5.3	$ 4.2

Statutory Financial Informat117

Statutory Financial Information, Capital Requirements, and Restrictions on Dividends and Transfers of Funds (Dividends) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Total stockholders’ equity	$ 1,531,370,000	$ 1,398,041,000	$ 1,275,586,000
Ordinary dividends paid	61,000,000
Maximum ordinary dividends	$ 192,700,000
Maximum borrowing percentage	10.00%
New Jersey Dividend Restriction	10.00%
New York Dividend Restriction	10.00%
Dividend Restriction New York	100.00%
Selective Insurace Company of America (SICA) [Member]
Ordinary dividends paid	$ 26,000,000
Maximum ordinary dividends	72,200,000
Selective Way Insurance Company (SWIC) [Member]
Ordinary dividends paid	12,000,000
Maximum ordinary dividends	40,400,000
Selective Insurance Company of South Carolina (SICSC) [Member]
Ordinary dividends paid	5,000,000
Maximum ordinary dividends	13,800,000
Selective Insurance Company of the Southeast (SICSE) [Member]
Ordinary dividends paid	2,000,000
Maximum ordinary dividends	10,900,000
Selective Insurance Company of New York (SICNY) [Member]
Ordinary dividends paid	5,000,000
Maximum ordinary dividends	10,200,000
Selective Insurance Company of New England (SICNE) [Member]
Ordinary dividends paid	2,000,000
Maximum ordinary dividends	5,900,000
Selective Auto Insurance Company of New Jersey (SAICNJ) [Member]
Ordinary dividends paid	1,500,000
Maximum ordinary dividends	11,500,000
Mesa Underwriting Specialty Insurance Company (MUSIC) [Member]
Maximum ordinary dividends	9,700,000
Selective Casualty Insurance Company (SCIC) [Member]
Ordinary dividends paid	5,500,000
Maximum ordinary dividends	12,600,000
Selective Fire and Casualty Insurance Company (SFCIC) [Member]
Ordinary dividends paid	2,000,000
Maximum ordinary dividends	5,500,000
Parent Company [Member]
Total stockholders’ equity	1,500,000,000
Maximum ordinary dividends	91,700,000
Additional Borrowing Capacity for Parent	$ 68,600,000

Quarterly Financial Informat118

Quarterly Financial Information (Details) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended																12 Months Ended
	Feb. 14, 2017	Dec. 31, 2016USD ($)$ / shares		Sep. 30, 2016USD ($)$ / shares		Jun. 30, 2016USD ($)$ / shares		Mar. 31, 2016USD ($)$ / shares		Dec. 31, 2015USD ($)$ / shares		Sep. 30, 2015USD ($)$ / shares		Jun. 30, 2015USD ($)$ / shares		Mar. 31, 2015USD ($)$ / shares		Dec. 31, 2016USD ($)$ / shares	Dec. 31, 2015USD ($)$ / shares	Dec. 31, 2014USD ($)$ / shares
Net premiums earned		$ 552,753		$ 542,429		$ 531,932		$ 522,458		$ 516,087		$ 507,390		$ 490,309		$ 476,123		$ 2,149,572	$ 1,989,909	$ 1,852,609
Net investment income earned		35,428		33,375		31,182		30,769		30,108		32,061		32,230		26,917		130,754	121,316	138,708
Net realized (losses) gains		(7,686)		3,688		1,765		(2,704)		(2,600)		308		(3,420)		18,883		3,562	31,537	37,703
Underwriting income		35,168		32,033		43,777		40,955		49,053		44,831		29,124		26,021
Net income		39,360		38,502		43,601		37,032		45,389		46,996		33,768		39,708		158,495	165,861	141,827
Other comprehensive income (loss)		(78,159)		(9,798)		36,010		45,422		(3,386)		6,290		(35,944)		3,827		(6,525)	(29,213)	(5,063)
Comprehensive income (loss)		$ (38,799)		$ 28,704		$ 79,611		$ 82,454		$ 42,003		$ 53,286		$ (2,176)		$ 43,535		$ 151,970	$ 136,648	$ 136,764
Basic net income per share | $ / shares		$ 0.68		$ 0.66		$ 0.75		$ 0.64		$ 0.79		$ 0.82		$ 0.59		$ 0.70		$ 2.74	$ 2.90	$ 2.52
Diluted net income per share | $ / shares		0.67		0.66		0.74		0.63		0.78		0.81		0.58		0.69		2.70	2.85	2.47
Dividends to stockholders | $ / shares		$ 0.16	[1]	$ 0.15	[1]	$ 0.15	[1]	$ 0.15	[1]	$ 0.15	[1]	$ 0.14	[1]	$ 0.14	[1]	$ 0.14	[1]	$ 0.61	$ 0.57	$ 0.53
Price range common stock, high	44.35	44	[2]	41.30	[2]	38.67	[2]	36.92	[2]	37.91	[2]	32.50	[2]	29.60	[2]	30.10	[2]
Price range of common stock, low	38.50	34.95	[2]	35.90	[2]	33.60	[2]	29.27	[2]	30.36	[2]	28.10	[2]	26.28	[2]	25.49	[2]
Accumulated other comprehensive income (loss) [Member]
Other comprehensive income (loss)																		$ (6,525)	$ (29,213)	$ (5,063)
[1]	1 See Note 19. “Statutory Financial Information, Capital Requirements, and Restrictions on Dividends and Transfers of Funds” for a discussion of dividend restrictions.
[2]	2 These ranges of high and low prices of the Parent’s common stock, as reported by the NASDAQ Global Select Market, represent actual transactions. Price quotations do not include retail markups, markdowns, and commissions. The range of high and low prices for common stock for the period beginning January 3, 2017 and ending February 14, 2017 was $38.50 to $44.35.

Schedule I - Summay of Inves119

Schedule I - Summay of Investments - Other Than Investments in Related Parties (Details) $ in Thousands	Dec. 31, 2016USD ($)
Amortized Cost or Cost	$ 5,300,143
Carrying Amount	5,364,947
Short-term Investments [Member]
Amortized Cost or Cost	221,701
Fair Value	221,701
Carrying Amount	221,701
Other Investments [Member]
Amortized Cost or Cost	102,397
Carrying Amount	102,397
Preferred Stock [Member] | Banks, trusts, and insurance companies
Amortized Cost or Cost	16,226
Fair Value	16,145
Carrying Amount	16,145
Held-to-maturity Securities [Member] | Obligations of States and Political Subdivisions [Member]
Amortized Cost or Cost	77,466
Fair Value	79,916
Carrying Amount	77,783
Held-to-maturity Securities [Member] | Public Utilities
Amortized Cost or Cost	8,589
Fair Value	9,292
Carrying Amount	8,579
Held-to-maturity Securities [Member] | All other corporate securities
Amortized Cost or Cost	14,122
Fair Value	14,783
Carrying Amount	13,989
Held-to-maturity Securities [Member] | Commercial Mortgage-backed Securities (CMBS) [Member]
Amortized Cost or Cost	1,220
Fair Value	1,220
Carrying Amount	1,205
Held-to-maturity Securities [Member] | Fixed Income Securities [Member]
Amortized Cost or Cost	101,397
Fair Value	105,211
Carrying Amount	101,556
AFS Fixed Income Securities [Member] | US Government Agencies Debt Securities [Member]
Amortized Cost or Cost	75,139
Fair Value	77,333
Carrying Amount	77,333
AFS Fixed Income Securities [Member] | Foreign Government
Amortized Cost or Cost	26,559
Fair Value	26,865
Carrying Amount	26,865
AFS Fixed Income Securities [Member] | Obligations of States and Political Subdivisions [Member]
Amortized Cost or Cost	1,366,287
Fair Value	1,379,593
Carrying Amount	1,379,593
AFS Fixed Income Securities [Member] | Public Utilities
Amortized Cost or Cost	108,664
Fair Value	110,000
Carrying Amount	110,000
AFS Fixed Income Securities [Member] | All other corporate securities
Amortized Cost or Cost	1,867,892
Fair Value	1,887,753
Carrying Amount	1,887,753
AFS Fixed Income Securities [Member] | CLO and Other ABS
Amortized Cost or Cost	527,876
Fair Value	528,960
Carrying Amount	528,960
AFS Fixed Income Securities [Member] | Commercial Mortgage-backed Securities (CMBS) [Member]
Amortized Cost or Cost	256,356
Fair Value	256,842
Carrying Amount	256,842
AFS Fixed Income Securities [Member] | Fixed Income Securities [Member]
Amortized Cost or Cost	4,753,759
Fair Value	4,792,540
Carrying Amount	4,792,540
AFS Fixed Income Securities [Member] | Residential Mortgage Backed Securities [Member]
Amortized Cost or Cost	524,986
Fair Value	525,194
Carrying Amount	525,194
Equity Securities [Member] | Common Stock [Member]
Amortized Cost or Cost	104,663
Fair Value	130,608
Carrying Amount	130,608
Equity Securities [Member] | Preferred Stock [Member]
Amortized Cost or Cost	16,226
Fair Value	16,145
Carrying Amount	16,145
Equity Securities [Member] | Equity Securities [Member]
Amortized Cost or Cost	120,889
Fair Value	146,753
Carrying Amount	146,753
Common Stock [Member] | Banks, trusts, and insurance companies
Amortized Cost or Cost	14,056
Fair Value	17,648
Carrying Amount	17,648
Common Stock [Member] | Industrial, miscellaneous and all other
Amortized Cost or Cost	90,607
Fair Value	112,960
Carrying Amount	$ 112,960

Parent Corporation Balance Shee

Parent Corporation Balance Sheet (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
ASSETS
Fixed income securities, available-for-sale – at fair value (amortized cost: $73,471 – 2016; $61,794 – 2015)	$ 4,792,540,000	$ 4,408,203,000
Short-term investments	221,701,000	194,819,000
Cash	458,000	898,000	$ 23,959,000	$ 193,000
Current federal income tax	2,486,000	0
Deferred federal income tax	84,840,000	92,696,000
Other assets	113,534,000	78,339,000
Total assets	7,355,848,000	6,904,433,000
Liabilities:
Long-term debt	438,667,000	328,192,000
Other liabilities	298,393,000	255,984,000
Total liabilities	5,824,478,000	5,506,392,000
Stockholders’ Equity:
Preferred stock of $0 par value per share: Authorized shares: 5,000,000; no shares issued or outstanding	0	0
Common stock of $2 par value per share Authorized shares: 360,000,000 Issued: 101,620,436 - 2016; 100,861,372 - 2015	203,241,000	201,723,000
Additional paid-in capital	347,295,000	326,656,000
Retained earnings	1,568,881,000	1,446,192,000
Accumulated other comprehensive loss	(15,950,000)	(9,425,000)
Treasury stock – at cost (shares: 43,653,237 – 2016; 43,500,642 – 2015)	(572,097,000)	(567,105,000)
Total stockholders’ equity	1,531,370,000	1,398,041,000	1,275,586,000
Total liabilities and stockholders’ equity	7,355,848,000	6,904,433,000
Parent Company [Member]
ASSETS
Fixed income securities, available-for-sale – at fair value (amortized cost: $73,471 – 2016; $61,794 – 2015)	73,509,000	61,567,000
Short-term investments	17,777,000	29,116,000
Cash	458,000	898,000	$ 16,367,000	$ 193,000
Investment in subsidiaries	1,845,410,000	1,716,681,000
Current federal income tax	19,766,000	18,297,000
Deferred federal income tax	19,562,000	17,513,000
Other assets	840,000	670,000
Total assets	1,977,322,000	1,844,742,000
Liabilities:
Long-term debt	328,667,000	328,192,000
Intercompany notes payable	79,324,000	86,163,000
Accrued long-term stock compensation	32,029,000	26,465,000
Other liabilities	5,932,000	5,881,000
Total liabilities	445,952,000	446,701,000
Stockholders’ Equity:
Preferred stock of $0 par value per share: Authorized shares: 5,000,000; no shares issued or outstanding	0	0
Common stock of $2 par value per share Authorized shares: 360,000,000 Issued: 101,620,436 - 2016; 100,861,372 - 2015	203,241,000	201,723,000
Additional paid-in capital	347,295,000	326,656,000
Retained earnings	1,568,881,000	1,446,192,000
Accumulated other comprehensive loss	(15,950,000)	(9,425,000)
Treasury stock – at cost (shares: 43,653,237 – 2016; 43,500,642 – 2015)	(572,097,000)	(567,105,000)
Total stockholders’ equity	1,531,370,000	1,398,041,000
Total liabilities and stockholders’ equity	$ 1,977,322,000	$ 1,844,742,000

Parent Corporation Balance S121

Parent Corporation Balance Sheets (Parenthetical) (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fixed income securities, available-for-sale, amortized cost	$ 4,753,759	$ 4,352,514
Preferred stock, par value per share	$ 0	$ 0	$ 0
Preferred stock, shares authorized	5,000,000	5,000,000	5,000,000
Preferred stock, shares issued	0	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value per share	$ 2	$ 2
Common stock, shares authorized	360,000,000	360,000,000
Common stock, shares issued	101,620,436	100,861,372
Treasury stock, shares	43,653,237	43,500,642
Parent Company [Member]
Fixed income securities, available-for-sale, amortized cost	$ 73,471	$ 61,794
Preferred stock, par value per share	$ 0	$ 0
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value per share	$ 2	$ 2
Common stock, shares authorized	360,000,000	360,000,000
Common stock, shares issued	101,620,436	100,861,372
Treasury stock, shares	43,653,237	43,500,642

Parent Corporation Statements o

Parent Corporation Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Dividends Paid to Parent Company									$ (61,000)
Net investment income earned	$ 35,428	$ 33,375	$ 31,182	$ 30,769	$ 30,108	$ 32,061	$ 32,230	$ 26,917	130,754	$ 121,316	$ 138,708
Realized Investment Gains (Losses)									(4,937)	13,171	26,599
Other income									8,881	7,456	16,945
Total revenues									2,284,270	2,131,852	2,034,861
Expenses:
Interest expense									22,771	22,428	23,063
Other expenses									42,989	38,371	32,696
Total expenses									2,064,315	1,899,160	1,837,730
Federal income tax benefit:
Current									48,581	45,347	28,415
Deferred									12,879	21,484	26,889
Total federal income tax expense									61,460	66,831	55,304
Net income	$ 39,360	$ 38,502	$ 43,601	$ 37,032	$ 45,389	$ 46,996	$ 33,768	$ 39,708	158,495	165,861	141,827
Parent Company [Member]
Revenues:
Dividends Paid to Parent Company									61,014	57,752	57,511
Net investment income earned									1,259	852	620
Realized Investment Gains (Losses)									(220)	0	2
Other income									0	0	340
Total revenues									62,053	58,604	58,473
Expenses:
Interest expense									24,030	24,057	24,817
Other expenses									35,020	28,393	23,598
Total expenses									59,050	52,450	48,415
Income before federal income tax									3,003	6,154	10,058
Federal income tax benefit:
Current									(17,924)	(16,609)	(15,920)
Deferred									(2,143)	(1,603)	(646)
Total federal income tax expense									(20,067)	(18,212)	(16,566)
Net income before equity in undistributed income of subsidiaries									23,070	24,366	26,624
Equity In Undistributed Income Of Continuing Subsidiaries, Net Of Tax									135,425	141,495	115,203
Net income									$ 158,495	$ 165,861	$ 141,827

Parent Corporation Statement123

Parent Corporation Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Activities
Net income	$ 39,360	$ 38,502	$ 43,601	$ 37,032	$ 45,389	$ 46,996	$ 33,768	$ 39,708	$ 158,495	$ 165,861	$ 141,827
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense									10,449	8,973	8,702
Net realized losses (gains)									4,937	(13,171)	(26,599)
Amortization - other									61,671	59,688	45,346
Changes in assets and liabilities:
(Increase) decrease in net federal income taxes									11,150	25,004	31,323
(Decrease) increase in other assets									30,071	11,523	(1,186)
Increase (decrease) in other liabilities									9,191	77,564	(35,632)
Net cash provided by operating activities									301,783	381,580	232,763
Investing Activities
Purchase of fixed income securities, available-for-sale									(1,982,023)	(1,041,916)	(843,616)
Redemption and maturities of fixed income securities, available-for-sale									641,524	567,445	482,816
Sale of fixed income securities, available for sale									102,868	106,621	73,415
Purchase of short-term investments									(3,499,380)	(1,602,327)	(1,410,123)
Sale of short-term investments									3,470,022	1,539,480	1,452,402
Net cash (used in) provided by investing activities									(318,101)	(391,543)	(169,468)
Financing Activities
Dividends to stockholders									(33,758)	(31,052)	(28,428)
Acquisition of treasury stock									(4,992)	(4,182)	(3,563)
Net proceeds from stock purchase and compensation plans									7,811	10,089	7,283
Excess tax benefits from share-based payment arrangements									1,819	1,736	1,020
Net cash used in financing activities									15,878	(13,098)	(39,529)
Cash, beginning of year				898				23,959	898	23,959	193
Cash, end of year	458				898				458	898	23,959
Parent Company [Member]
Operating Activities
Net income									158,495	165,861	141,827
Adjustments to reconcile net income to net cash provided by operating activities:
Equity In Undistributed Income Of Continuing Subsidiaries, Net Of Tax									(135,425)	(141,495)	(115,203)
Stock-based compensation expense									10,449	8,973	8,702
Net realized losses (gains)									220	0	(2)
Amortization - other									648	740	1,421
Changes in assets and liabilities:
Increase in accrued long-term stock compensation									5,564	4,575	1,062
(Increase) decrease in net federal income taxes									(3,612)	(3,052)	10,977
(Decrease) increase in other assets									(202)	(12)	1,165
Increase (decrease) in other liabilities									80	(202)	(120)
Net cash provided by operating activities									36,217	35,388	49,829
Investing Activities
Purchase of fixed income securities, available-for-sale									(45,789)	(33,717)	(18,511)
Redemption and maturities of fixed income securities, available-for-sale									14,983	21,578	23,210
Sale of fixed income securities, available for sale									18,768	0	300
Purchase of short-term investments									(119,501)	(106,933)	(102,717)
Sale of short-term investments									130,841	94,422	101,510
Net cash (used in) provided by investing activities									(698)	(24,650)	3,792
Financing Activities
Dividends to stockholders									(33,758)	(31,052)	(28,428)
Acquisition of treasury stock									(4,992)	(4,182)	(3,563)
Net proceeds from stock purchase and compensation plans									7,811	10,089	7,283
Excess tax benefits from share-based payment arrangements									1,819	1,736	1,020
Principal payments of borrowings from subsidiaries									(6,839)	(2,798)	(13,759)
Net cash used in financing activities									(35,959)	(26,207)	(37,447)
Net (decrease) increase in cash									(440)	(15,469)	16,174
Cash, beginning of year				$ 898				$ 16,367	898	16,367	193
Cash, end of year	$ 458				$ 898				$ 458	$ 898	$ 16,367

Schedule III - Supplementary124

Schedule III - Supplementary Insurance Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred policy acquisition costs	$ 222,564	$ 213,159	$ 185,608
Reserve for loss and loss expenses	3,691,719	3,517,728	3,477,870
Unearned premiums	1,262,819	1,169,710	1,095,819
Net premiums earned	2,149,572	1,989,909	1,852,609
Net investment income	125,817	134,487	165,307
Losses and loss expenses incurred	1,234,797	1,148,541	1,157,501
Amortization of deferred policy acquisition costs	450,328	399,435	364,295
Other operating expenses	312,515	292,904	252,670
Net premiums written	2,237,288	2,069,904	1,885,280
Policy acquisition costs	763,758	689,820	624,470
Other income	(8,881)	(7,456)	(16,945)
Other expenses	42,989	38,371	32,696
Total	762,843	692,339	616,965
Standard Commercial Lines [Member]
Deferred policy acquisition costs	181,193	171,476	147,285
Reserve for loss and loss expenses	3,098,554	2,998,749	3,000,796
Unearned premiums	884,976	803,648	734,697
Net premiums earned	1,665,483	1,529,442	1,415,712
Net investment income	0	0	0
Losses and loss expenses incurred	913,506	819,573	870,018
Amortization of deferred policy acquisition costs	367,813	323,753	295,774
Other operating expenses	237,730	221,620	188,699
Net premiums written	1,745,782	1,596,965	1,441,047
Standard Personal Lines [Member]
Deferred policy acquisition costs	16,664	17,258	17,495
Reserve for loss and loss expenses	286,081	265,054	279,761
Unearned premiums	282,111	276,533	285,777
Net premiums earned	280,607	288,134	296,747
Net investment income	0	0	0
Losses and loss expenses incurred	177,749	200,237	197,182
Amortization of deferred policy acquisition costs	34,105	33,638	34,851
Other operating expenses	56,334	52,923	48,178
Net premiums written	281,822	283,926	292,061
Excess And Surplus Operations [Member]
Deferred policy acquisition costs	24,707	24,425	20,828
Reserve for loss and loss expenses	307,084	253,925	197,313
Unearned premiums	95,732	89,529	75,345
Net premiums earned	203,482	172,333	140,150
Net investment income	0	0	0
Losses and loss expenses incurred	143,542	128,731	90,301
Amortization of deferred policy acquisition costs	48,410	42,044	33,670
Other operating expenses	18,451	18,361	15,793
Net premiums written	209,684	189,013	152,172
Investments Segment [Member]
Deferred policy acquisition costs	0	0	0
Reserve for loss and loss expenses	0	0	0
Unearned premiums	0	0	0
Net premiums earned	0	0	0
Net investment income	125,817	134,487	165,307
Losses and loss expenses incurred	0	0	0
Amortization of deferred policy acquisition costs	0	0	0
Other operating expenses	0	0	0
Net premiums written	0	0	0
Miscellaneous Income [Member]
Other income	(8,881)	(7,456)	(16,598)
Other Income [Member]
Other income	0	0	(347)
Miscellaneous Expense [Member]
Other expenses	7,966	9,975	9,093
Other Expense [Member]
Other expenses	$ 35,023	$ 28,396	$ 23,603

Schedule IV - Reinsurance (Deta

Schedule IV - Reinsurance (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Direct Amount									$ 2,484,715	$ 2,330,267	$ 2,183,258
Assumed From Other Companies									28,214	23,209	34,653
Ceded to Other Companies									363,357	363,567	365,302
Total Net Premiums Earned	$ 552,753	$ 542,429	$ 531,932	$ 522,458	$ 516,087	$ 507,390	$ 490,309	$ 476,123	$ 2,149,572	$ 1,989,909	$ 1,852,609
Percentage of Amount Assumed to Net									1.00%	1.00%	2.00%
Accident and Health Insurance Segment [Member]
Direct Amount									$ 32	$ 37	$ 44
Assumed From Other Companies									0	0	0
Ceded to Other Companies									0	37	44
Total Net Premiums Earned									$ 32	$ 0	$ 0
Percentage of Amount Assumed to Net									0.00%	0.00%	0.00%
Property and liability insurance [Member]
Direct Amount									$ 2,484,683	$ 2,330,230	$ 2,183,214
Assumed From Other Companies									28,214	23,209	34,653
Ceded to Other Companies									363,357	363,530	365,258
Total Net Premiums Earned									$ 2,149,540	$ 1,989,909	$ 1,852,609
Percentage of Amount Assumed to Net									1.00%	1.00%	2.00%

Schedule V - Allowance for Unc

Schedule V - Allowance for Uncollectible Premiums and Other Receivables (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Balance, January 1	$ 10,122	$ 11,037	$ 9,542
Additions	4,669	3,604	4,617
Deductions	(3,311)	(4,519)	(3,122)
Balance, December 31	$ 11,480	$ 10,122	$ 11,037