Selective Insurance (SIGI) 10-K 12 Feb 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 06, 2020	Jun. 30, 2019
Document and Entity Information [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-33067
Entity Registrant Name	SELECTIVE INSURANCE GROUP, INC.
Entity Incorporation, State or Country Code	NJ
Entity Tax Identification Number	22-2168890
Entity Address, Address Line One	40 Wantage Avenue
Entity Address, City or Town	Branchville
Entity Address, State or Province	NJ
Entity Address, Postal Zip Code	07890
City Area Code	973
Local Phone Number	948-3000
Title of 12(b) Security	Common Stock, par value $2 per share
Trading Symbol	SIGI
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 4,357,013,702
Entity Common Stock, Shares Outstanding		59,670,192
Entity Central Index Key	0000230557
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Documents Incorporated by Reference	Portions of the registrant’s definitive Proxy Statement for the 2020 Annual Meeting of Stockholders to be held on April 29, 2020 are incorporated by reference into Part III of this report.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
ASSETS
Fixed income securities, held-to-maturity – at carrying value (fair value: $21,975 – 2019; $38,317 – 2018)	$ 20,800	$ 37,110
Fixed income securities, available-for-sale – at fair value (amortized cost: $5,879,986 – 2019; $5,270,798 – 2018)	6,095,620	5,273,100
Equity securities - at fair value (cost: $72,061 - 2019; $138,114 - 2018)	72,937	147,639
Short-term investments (at cost which approximates fair value)	282,490	323,864
Other investments	216,807	178,938
Total investments (Notes 5 and 7)	6,688,654	5,960,651
Cash	300	505
Restricted cash	7,675	16,414
Interest and dividends due or accrued	44,846	41,620
Premiums receivable, net of allowance for uncollectible accounts of: $6,400 – 2019; $9,400 – 2018	823,901	770,518
Reinsurance recoverable, net of allowance for uncollectible accounts of: $4,400 – 2019; $4,500 – 2018 (Note 8)	573,235	549,172
Prepaid reinsurance premiums (Note 8)	166,705	157,723
Deferred federal income tax (Note 13)	6,776	53,540
Property and equipment – at cost, net of accumulated depreciation and amortization of: $227,566 – 2019; $211,657 – 2018	77,409	65,248
Deferred policy acquisition costs (Note 2)	271,186	252,612
Goodwill (Note 11)	7,849	7,849
Other assets	128,614	76,877
Total assets	8,797,150	7,952,729
LIABILITIES AND STOCKHOLDERS’ EQUITY
Reserve for loss and loss expense (Note 9)	4,067,163	3,893,868
Unearned premiums	1,523,167	1,431,932
Long-term debt (Note 10)	550,597	439,540
Current federal income tax	2,987	1,302
Accrued salaries and benefits	126,753	116,706
Other liabilities	331,547	277,579
Total liabilities	6,602,214	6,160,927
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: 103,484,159 - 2019; 102,848,394 - 2018	206,968	205,697
Additional paid-in capital	418,521	390,315
Retained earnings	2,080,529	1,858,414
Accumulated other comprehensive income (loss) (Note 6)	81,750	(77,956)
Treasury stock – at cost (shares: 44,023,006 – 2019; 43,899,840 – 2018)	(592,832)	(584,668)
Total stockholders’ equity	2,194,936	1,791,802
Commitments and contingencies (Notes 17 and 18)
Total liabilities and stockholders’ equity	$ 8,797,150	$ 7,952,729

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Fixed income securities, held-to-maturity, fair value	$ 21,975	$ 38,317
Fixed income securities, available-for-sale, amortized cost	5,879,986	5,270,798
Equity securities, cost	72,061	138,114
Premiums receivable, allowance for uncollectible accounts	6,400	9,400
Reinsurance recoverable, allowance for uncollectible accounts	4,400	4,500
Property and equipment, accumulated depreciation and amortization	$ 227,566	$ 211,657
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	103,484,159	102,848,394
Treasury stock, shares	44,023,006	43,899,840

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Net premiums earned	$ 2,597,171	$ 2,436,229	$ 2,291,027
Net investment income earned	222,543	195,336	161,882
Net realized and unrealized gains (losses):
Net realized investment gains (losses) on disposals	26,715	(18,975)	11,204
Net unrealized losses on equity securities	(8,649)	(29,369)	0
Other-than-temporary impairments	(3,644)	(6,579)	(4,809)
Other-than-temporary impairments on fixed income securities recognized in other comprehensive income	0	0	(36)
Total net realized and unrealized gains (losses)	14,422	(54,923)	6,359
Other income	12,355	9,438	10,716
Total revenues	2,846,491	2,586,080	2,469,984
Expenses:
Loss and loss expense incurred	1,551,491	1,498,134	1,345,074
Amortization of deferred policy acquisition costs	535,973	495,042	469,236
Other insurance expenses	358,069	331,318	333,097
Interest expense	33,668	24,419	24,354
Corporate expenses	30,900	25,446	36,255
Total expenses	2,510,101	2,374,359	2,208,016
Income before federal income tax	336,390	211,721	261,968
Federal income tax expense:
Current	60,640	35,012	62,184
Deferred	4,127	(2,230)	30,958
Total federal income tax expense	64,767	32,782	93,142
Net income	$ 271,623	$ 178,939	$ 168,826
Earnings per share:
Basic net income	$ 4.57	$ 3.04	$ 2.89
Diluted net income	$ 4.53	$ 3	$ 2.84

Consolidation Statements of Com

Consolidation Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net income	$ 271,623	$ 178,939	$ 168,826
Unrealized holding gains (losses) arising during year	168,021	(97,284)	43,015
Non-credit portion of other-than-temporary impairments recognized in other comprehensive income	0	0	23
Amounts reclassified into net income: Held-to-maturity securities	(46)	87	(116)
Amounts reclassified into net income: Non-credit other-than-temporary impairment	0	0	68
Amounts reclassified into net income: Realized losses (gains) on available for sale securities	530	31,316	(4,537)
Total unrealized gains (losses) on investment securities	168,505	(65,881)	38,453
Net actuarial loss	(10,898)	(8,906)	(3,700)
Amounts reclassified into net income: Net actuarial loss	2,099	1,680	1,367
Total defined benefit pension and post-retirement plans	(8,799)	(7,226)	(2,333)
Other comprehensive income (loss)	159,706	(73,107)	36,120
Comprehensive income	$ 431,329	$ 105,832	$ 204,946

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional paid-in capital [Member]	Retained Earnings [Member]	Accumulated other comprehensive (loss) income [Member]	Treasury stock [Member]
Cumulative effect adjustment | Accounting Standards Update 2016-01 [Member]				$ 0	$ 0
Cumulative effect adjustment | Accounting Standards Update 2018-02 [Member]				0	0
Cumulative effect adjustment | Accounting Standards Update 2016-02 [Member]				0
Balance at beginning of year, as adjusted				1,568,881	(15,950)
Beginning of year at Dec. 31, 2016		$ 203,241	$ 347,295	1,568,881	(15,950)	$ (572,097)
Dividend reinvestment plan		57	1,395
Stock purchase and compensation plans		1,271	19,027
Net income	$ 168,826			168,826
Dividends to stockholders				(39,094)
Other comprehensive income (loss)	$ 36,120				36,120
Acquisition of treasury stock						(6,015)
Dividends declared per share to stockholders	$ 0.66
End of year at Dec. 31, 2017	$ 1,712,957	204,569	367,717	1,698,613	20,170	(578,112)
Common Stock, shares outstanding, beginning of period at Dec. 31, 2016	57,967,199
Dividend reinvestment plan	28,607
Stock purchase and compensation plan	635,521
Acquisition of treasury stock	(136,205)
Common Stock, shares outstanding, end of period at Dec. 31, 2017	58,495,122
Cumulative effect adjustment	$ (25,000)				25,019
Cumulative effect adjustment | Accounting Standards Update 2016-01 [Member]	0			30,726	(30,726)
Cumulative effect adjustment | Accounting Standards Update 2018-02 [Member]				(5,707)	5,707
Cumulative effect adjustment | Accounting Standards Update 2016-02 [Member]				0
Balance at beginning of year, as adjusted				1,723,632	(4,849)
Dividend reinvestment plan		47	1,379
Stock purchase and compensation plans		1,081	21,219
Net income	178,939			178,939
Dividends to stockholders				(44,157)
Other comprehensive income (loss)	$ (73,107)				(73,107)
Acquisition of treasury stock						(6,556)
Dividends declared per share to stockholders	$ 0.74
End of year at Dec. 31, 2018	$ 1,791,802	205,697	390,315	1,858,414	(77,956)	(584,668)
Dividend reinvestment plan	23,493
Stock purchase and compensation plan	540,337
Acquisition of treasury stock	(110,398)
Common Stock, shares outstanding, end of period at Dec. 31, 2018	58,948,554
Cumulative effect adjustment | Accounting Standards Update 2016-01 [Member]	$ 30,726			0	0
Cumulative effect adjustment | Accounting Standards Update 2018-02 [Member]				0	0
Balance at beginning of year, as adjusted				1,858,756	(77,956)
Dividend reinvestment plan		44	1,510
Stock purchase and compensation plans		1,227	26,696
Net income	271,623			271,623
Dividends to stockholders				(49,850)
Other comprehensive income (loss)	$ 159,706				159,706
Acquisition of treasury stock						(8,164)
Dividends declared per share to stockholders	$ 0.83
End of year at Dec. 31, 2019	$ 2,194,936	$ 206,968	$ 418,521	$ 2,080,529	$ 81,750	$ (592,832)
Dividend reinvestment plan	22,087
Stock purchase and compensation plan	613,678
Acquisition of treasury stock	(123,166)
Common Stock, shares outstanding, end of period at Dec. 31, 2019	59,461,153
Cumulative effect adjustment | Accounting Standards Update 2016-01 [Member]	$ 0

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
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
Series A Preferred Stock [Member]
Preferred stock, par value per share	$ 0	$ 0	$ 0
Preferred stock, shares authorized	300,000	300,000	300,000

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities
Net income	$ 271,623	$ 178,939	$ 168,826
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	55,205	44,874	52,100
Stock-based compensation expense	19,077	14,507	12,089
Undistributed gains of equity method investments	(12,773)	(8,341)	(5,362)
Distributions in excess of current year income of equity method investments	2,807	2,924	552
Net realized and unrealized (gains) losses	(14,422)	54,923	(6,359)
Loss on disposal of fixed assets	42	63	998
Changes in assets and liabilities:
Increase in reserves for loss and loss expense, net of reinsurance recoverables	149,232	168,288	106,226
Increase in unearned premiums, net of prepaid reinsurance	82,253	78,058	79,614
Decrease in net federal income taxes	7,721	2,428	30,918
Increase in premiums receivable	(53,383)	(23,489)	(65,418)
Increase (Decrease) Deferred Policy Acquisition Costs	(18,574)	(17,557)	(12,491)
Increase in interest and dividends due or accrued	(3,226)	(540)	(1,088)
Decrease in accrued salaries and benefits	(3,748)	(26,418)	(5,714)
Increase in other assets	(39,337)	(372)	(2,643)
Increase (decrease) in other liabilities	34,998	(13,343)	27,297
Net cash provided by operating activities	477,495	454,944	379,545
Investing Activities
Purchase of fixed income securities, held-to-maturity	0	(7,150)	0
Purchase of fixed income securities, available-for-sale	(1,856,125)	(2,918,203)	(2,130,362)
Purchase of equity securities	(46,397)	(94,344)	(61,931)
Purchase of other investments	(64,908)	(68,578)	(55,830)
Purchase of short-term investments	(6,087,909)	(4,259,734)	(4,280,553)
Sale of fixed income securities, available-for-sale	594,743	2,030,664	1,197,920
Sale of short-term investments	6,129,885	4,101,530	4,338,318
Redemption and maturities of fixed income securities, held-to-maturity	16,149	12,106	58,832
Redemption and maturities of fixed income securities, available-for-sale	626,686	638,916	555,216
Sale of equity securities	137,294	113,339	37,960
Sale of other investments	17,964	3,497	0
Distributions from other investments	19,972	28,379	21,843
Fixed asset disposals	9	0	0
Purchase of property and equipment	(30,986)	(16,110)	(14,071)
Net cash used in investing activities	(543,623)	(435,688)	(332,658)
Financing Activities
Dividends to stockholders	(47,675)	(42,097)	(37,045)
Acquisition of treasury stock	(8,164)	(6,556)	(6,015)
Net proceeds from stock purchase and compensation plans	8,243	7,252	7,599
Proceeds from borrowings	355,757	130,000	84,000
Repayment of borrowings	(250,000)	(130,000)	(84,000)
Repayment of finance lease obligations	(977)	(5,646)	(4,121)
Net cash provided by (used in) financing activities	57,184	(47,047)	(39,582)
Net (decrease) increase in cash and restricted cash	(8,944)	(27,791)	7,305
Cash and restricted cash, beginning of year	16,919	44,710	37,405
Cash and restricted cash, end of year	$ 7,975	$ 16,919	$ 44,710

Organization

Organization	12 Months Ended
	Dec. 31, 2019
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 corporate headquarters is 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, 2019
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) United States ("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) Investments Portfolio Composition and Presentation in the Consolidated Balance Sheets Our investment portfolio is primarily comprised of fixed income securities. We also hold equity securities, short-term investments, and other investments. A description of our portfolio holdings, and the related presentation in our Consolidated Balance Sheets, is provided below. Fixed Income Portfolio We hold the following types of securities in our fixed income securities portfolio: • U.S. government and government agency obligations; • Foreign government obligations; • State and municipal obligations, including special revenue and general obligation bonds; • Corporate securities, which may include investment grade and below investment grade bonds, bank loan investments, redeemable preferred stock, and non-redeemable preferred stock with certain debt-like characteristics; • Collateralized loan obligations ("CLOs") and other asset-backed securities ("ABS"); • Residential mortgage-backed securities ("RMBS"); and • Commercial mortgage-backed securities ("CMBS"). We have designated substantially all of our fixed income securities portfolio as available-for-sale ("AFS"), with the remainder being designated as held-to-maturity ("HTM"), as we have the ability and positive intent to hold these securities to maturity. Our AFS securities are reported at fair value in our consolidated balance sheets, with unrealized gains or losses recognized in accumulated other comprehensive income (loss) ("AOCI"), net of tax. HTM securities are recorded at either: (i) amortized cost; or (ii) market value at the date of transfer into the HTM category, adjusted for subsequent amortization. After-tax unrealized gains and losses on securities that were transferred into an HTM designation from an AFS designation, are also included in AOCI. 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. Callable debt securities held at a premium are amortized to the earliest call date. Premiums and discounts arising from the purchase of RMBS, CMBS, CLO and other ABS are amortized over the expected life of the security based on future principal payments, giving additional consideration to 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. Other Portfolio Holdings Equity securities may include common and non-redeemable preferred stocks. Equity securities with readily determinable fair values are recorded at fair value. Equity securities without readily determinable fair values are recorded at net asset value ("NAV") as a practical expedient. Short-term investments may include money market instruments, savings accounts, commercial paper, and fixed income securities purchased with a maturity of less than one year. We also enter into reverse repurchase agreements that are included in short-term investments. These repurchase agreements are fully collateralized by high-quality, readily-marketable instruments that support the principal amount. At maturity, we receive principal and interest income on these agreements. Short-term investments are generally recorded at cost, which approximates fair value. Other investments include alternative investments, which principally include limited partnership investments in private equity, private credit, real estate, and infrastructure investment funds, Federal Home Loan Bank stock (“FHLB stock”), and tax credit investments. Alternative investments are accounted for using the equity method, with income typically recognized on a one-quarter lag. The FHLB stock is recorded at cost. Accounting for our tax credit investments is dependent on the type of credit we have purchased, as follows: • Federal low income housing tax credits are accounted for under the proportional amortization method; and • All other tax credits in our investment portfolio are accounted for using the equity method. For federal 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 Income Statement as a component of "Federal income tax expense" proportionately over the life of the investment. We categorize distributions from our investments accounted for using the equity method on our Consolidated Statements of Cash Flows using the cumulative earnings approach. Under this approach, distributions received are classified as cash flows from operating activities until such time that the cumulative distributions exceed cumulative earnings for the investment. When such an excess occurs, the current period distribution up to this excess amount is considered a return of investment and is classified as a cash flow from investing activities. We evaluate the alternative investments and tax credit investments included in our other investments portfolio to determine whether those investments are variable interest entities ("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 reviewed our alternative and tax credit investments and have concluded that they are VIEs, but that we are not the primary beneficiary and therefore, consolidation is not required. Presentation in the Consolidated Statements of Income Net investment income earned on our Consolidated Statements of Income includes the following: • Interest income, as well as amortization and accretion, on fixed income securities; • Dividend income on equity securities; • Interest income on our short-term investments; and • Income recognized on our alternative and other investments accounted for under the equity method of accounting, except for federal tax credits, as discussed below. Income related to federal tax credits (either low income housing tax credits or other federal credits) is recorded in our Consolidated Statements of Income as a component of “Federal income tax expense” proportionately over the life of the investment. Net realized and unrealized gains and losses on our Consolidated Statements of Income include the following: • Realized gains and losses on the disposal of investment securities, which are determined on the basis of the cost of the specific investments sold; • Changes in unrealized gains or losses on our equity securities that are recorded at fair value; and • Other-than-temporary impairment ("OTTI") charges that are credit related or related to our intent to sell. 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, and our other investments. OTTI Charges on Fixed Income Securities and Short-Term Investments We review our fixed income securities and short-term investments 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 security before its anticipated recovery; (iii) if the decline is other than interest-rate related; and (iv) 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 an OTTI charge to earnings. 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. To determine if an impairment is other than temporary, we perform assessments that may include, but are not limited to, a discounted cash flow analysis ("DCF") to determine the security's present value of future cash flows. This analysis is also performed on all previously-impaired debt securities that continue to be held by us and all RMBS, CMBS, CLOs and ABS 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 used in a DCF is one of the following: • The current yield in effect at the reporting date to accrete the beneficial interest for RMBS, CMBS, CLO and other ABS that were not of high credit quality at acquisition; • The effective interest rate in effect as of the reporting date for non-fixed rate securities; and • The effective interest rate implicit in the security at the date of acquisition for all other securities. DCFs 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. Non-redeemable preferred stocks that are classified as fixed income securities are evaluated using the OTTI method described above unless the security is below investment grade. In this situation, we would 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 recovery in the near term. If we determine either that we do not intend to hold the security, or the decline is other than temporary, we write down the security's cost to its fair value through an OTTI charge to earnings. OTTI Charges on Other Investments Our evaluation for OTTI of 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. Our evaluation for OTTI of our other investments (tax credits and FHLB stock) include a qualitative assessment of impairment indicators, which include, but are not limited to, the following: • An adverse development of the expected receipt of remaining tax credits and other tax benefits; and • A significant deterioration in the financial condition or liquidity of the Federal Home Loan Bank. If there is a decline in the fair value of an alternative or other investment that we do not intend to hold, or if we determine the decline is other than temporary, we write down the carrying value of the investment through an OTTI charge to earnings. (d) 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. 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 generally recorded 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. RMBS, CMBS, CLO and other ABS Evaluations are based on a DCF, 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 by 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 valuations performed by the issuer or non-binding broker quotes to determine the fair value of these securities. We internally review these fair value measurements for reasonableness. 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; 5.375% 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 are consistent with the remaining term of the borrowing. (e) Allowance for Uncollectible Accounts We estimate an allowance for uncollectible accounts on our premiums receivable. This allowance is based on historical write-off percentages adjusted for the effects of current 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 or through collection agencies. (f) 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. The fair value of both 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 tax withholding obligations, as permitted under our stock-based compensation plans. This activity is disclosed in our Consolidated Statements of Stockholders' Equity. (g) Reinsurance Reinsurance recoverable represents 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 all, or a portion of, 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 reinsurer's 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. (h) 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 recorded 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 Software licenses 3 to 5 Furniture and fixtures 10 Buildings and improvements 5 to 40 We recorded depreciation expense of $18.7 million , $19.5 million , and $17.8 million for 2019 , 2018 , and 2017 , respectively. (i) 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 operations, 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 loss and loss expense, 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 were based on our actual average investment yield before tax as of the September 30 calculation date, were 3.5% for 2019 , 3.3% for 2018 , and 2.9% for 2017 . (j) 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, 2019 , goodwill was not impaired. (k) Reserve for Loss and Loss Expense Reserves for loss and loss expense 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 include: (i) reserves on IBNR claims; and (ii) provisions for future emergence on known or 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 review 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 loss and loss expense experience organized by line of business, accident year, and maturity (i.e., “triangles”). Generally accepted actuarial techniques are applied to this history, producing a set of estimated ultimate loss and loss expenses. Ultimate loss and loss 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 generally accepted actuarial techniques. 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 expenses. • Some insured events may span multiple years and trigger multiple policies, as in the case of asbestos, environmental, and abuse and molestation claims, where the injury is deemed to occur over an extended period of time. These types of losses often do not lend themselves to traditional actuarial methods. Where we deem appropriate, our experience may be analyzed without differentiating by accident year, using alternative methods and metrics. In these cases, the associated selected ultimate loss and loss expenses are then allocated to the applicable accident years for reporting. • Another example of exposures that do not lend themselves to generally accepted actuarial techniques relate to loss expenses that cannot be attributed to a specific claim (referred to as “unallocated loss expenses”). These expenses are first allocated to line of business, and alternative projection methods are then applied to estimate expenses by calendar year, which are then allocated back to the applicable accident years for reporting. The selected ultimate loss and loss expenses are translated into indicated IBNR reserves, which are then compared to the recorded IBNR reserves, which are assessed in aggregate. Management's judgment is applied in determining any required adjustments to IBNR and the resulting adjustments are then recorded and assigned or allocated to accident year using the results of the actuarial analysis. While the reserve review is the primary basis for determining the recorded IBNR reserves, other internal and external factors are considered. Internal factors include (i) changes to our underwriting and claims practice, (ii) supplemental data regarding claims reporting and settlement trends, (iii) exposure estimates for reported claims, along with recent development on those estimates with respect to individual large claims and the aggregate of all claims, (iv) the rate at which new large or complex claims are being reported, and (v) additional trends observed by claims personnel or reported to them by defense counsel. External factors considered include (i) legislative enactments, (ii) judicial decisions, (iii) social inflation and heightened awareness of sources of liability, 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 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 loss and loss expense. These reserves are expected to be sufficient for settling loss and loss expense 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 loss and loss expense. 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 loss 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 a 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. As the associated claims are not processed by us, they are not captured within our claims system. Therefore, the claim cou

Adoption of Accounting Pronounc

Adoption of Accounting Pronouncements	12 Months Ended
	Dec. 31, 2019
Adoption of Accounting Pronouncements [Abstract]
New Accounting Pronouncements and Changes in Accounting Principles [Text Block]	Adoption of Accounting Pronouncements The Financial Accounting Standards Board ("FASB") issued new leasing guidance through ASU 2016-02, Leases , which was issued in February 2016, as well as additional implementation guidance that was issued in 2018 and 2019 (collectively referred to as "ASU 2016-02"). ASU 2016-02 requires all lessees to recognize assets and liabilities on their balance sheets for the rights and obligations created by leases with terms longer than 12 months. For leases with a term of 12 months or less, an accounting policy election is allowed to recognize lease expense on a straight-line basis over the lease term. ASU 2016-02 allows for certain practical expedients, accounting policy elections, and a transition method election. We adopted practical expedients related to reassessing: (i) whether our existing contracts are, or contain, leases; (ii) lease classification for existing leases; and (iii) initial direct costs for existing leases. Additionally, we adopted accounting policy elections to: (i) aggregate lease and non-lease components of a contract into a single lease component; and (ii) expense short-term leases on a straight-line basis over the lease term. We adopted ASU 2016-02 effective January 1, 2019. See Note 17. "Leases" in this Form 10-K for additional information regarding our leases and the impact of this guidance on our financial condition and results of operations. In June 2018, the FASB issued ASU 2018-07, Compensation - Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting ("ASU 2018-07"). The amendments in ASU 2018-07 expand the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. We adopted ASU 2018-07 in the first quarter of 2019 and it did not have a material impact on our financial condition or results of operations. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement: Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement (“ASU 2018-13”). ASU 2018-13 modifies the disclosure requirements for fair value measurements. The modifications removed the following disclosure requirements: (i) the amount of, and reasons for, transfers between Level 1 and Level 2 of the fair value hierarchy; (ii) the policy for timing of transfers between levels; and (iii) the valuation processes for Level 3 fair value measurements. This ASU added the following disclosure requirements: (i) the changes in unrealized gains and losses for the period included in other comprehensive income ("OCI") for recurring Level 3 fair value measurements held at the end of the reporting period; and (ii) the range and weighted average of significant observable inputs used to develop Level 3 fair value measurements. We elected to early adopt the provisions related to removed disclosures in the fourth quarter of 2019 and will adopt the remaining disclosure requirements in the first quarter of 2020 as permitted under ASU 2018-13. As the requirements of this literature are disclosure only, ASU 2018-13 has no impact our financial condition or results of operations. In August 2018, the FASB issued ASU 2018-14, Compensation - Retirement Benefits - Defined Benefit Plans - General: Disclosure Framework - Changes to the Disclosure Requirements for Defined Benefit Plans (“ASU 2018-14”). ASU 2018-14 modifies the disclosure requirements for employers that sponsor defined benefit pension or other postretirement plans. These modifications include: (i) removing the requirement to disclose the amount in accumulated other comprehensive income ("AOCI") expected to be recognized as components of net periodic benefit cost over the next fiscal year; and (ii) adding the requirement to disclose an explanation of the reasons for significant gains or losses related to changes in the benefit obligation for the period. We elected to early adopt this update in the fourth quarter of 2019. As the requirements of this literature are disclosure only, ASU 2018-14 does not have impact our financial condition or results of operations. Pronouncements to be effective in the future In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses , as well as additional implementation guidance issued in 2018 and 2019 (collectively referred to as “ASU 2016-13”) that changes the way entities recognize impairment of financial assets. The new guidance requires immediate recognition of estimated credit losses expected to occur over the remaining life of many financial assets through the establishment of a valuation allowance. The valuation allowance is a measurement of expected losses 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. Additionally, ASU 2016-03 requires the presentation of the impacted financial assets on the consolidated balance sheet net of the valuation allowance. We will adopt this guidance on January 1, 2020 and it will not be material to our financial condition or results of operations. We will apply a modified retrospective approach for the adoption and we anticipate recording a cumulative-effect adjustment to the opening balance of 2020 retained earnings, which is not expected to be material. Also, as prescribed in the literature, we will not adjust the amortized cost basis of any securities for which we had previously recorded an OTTI charge. The cumulative-effect adjustment to increase retained earnings represents the net adjustment required to establish valuation allowances on our held-to-maturity ("HTM") debt securities and to re-estimate valuation allowances on our trade receivables and reinsurance recoverables under ASU 2016-13. In August 2018, the FASB issued ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software: Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (“ASU 2018-15”). ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. We will adopt this guidance on January 1, 2020 and we do not expect that it will have a material impact to our financial condition or results of operations. In December 2019, the FASB issued ASU 2019-12, Income Taxes - Simplifying the Accounting for Income Taxes (“ASU 2019-12”). Among other items, the amendments in ASU 2019-12 simplify the accounting treatment of tax law changes and year-to-date losses in interim periods. An entity generally recognizes the effects of a change in tax law in the period of enactment; however, there is an exception for tax laws with delayed effective dates. Under current guidance, an entity may not adjust its annual effective tax rate for a tax law change until the period in which the law is effective. This exception was removed under ASU 2019-12, thereby providing that all effects of a tax law change are recognized in the period of enactment, including adjustment of the estimated annual effective tax rate. Regarding year-to-date losses in interim periods, an entity is required to estimate its annual effective tax rate for the full fiscal year at the end of each interim period and use that rate to calculate its income taxes on a year-to-date basis. However, current guidance provides an exception that when a loss in an interim period exceeds the anticipate loss for the year, the income tax benefit is limited to the amount that would be recognized if the year-to-date loss were the anticipated loss for the full year. ASU 2019-12 removes this exception and provides that in this situation, an entity would compute its income tax benefit at each interim period based on its estimated annual effective tax rate. ASU 2019-12 is effective for fiscal years beginning after December 15, 2020, including interim periods within those annual periods. Early adoption is permitted. We are currently evaluating the impact of this guidance on our financial condition and results of operations.

Statements of Cash Flow

Statements of Cash Flow	12 Months Ended
	Dec. 31, 2019
Supplemental Cash Flow Information [Abstract]
Statements of Cash Flow	Statements of Cash Flows Supplemental cash flow information for the years ended December 31, 2019, 2018, and 2017 is as follows: ($ in thousands) 2019 2018 2017 Cash paid during the period for: Interest $ 25,089 23,992 23,905 Federal income tax 55,825 29,193 62,000 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases 1 8,138 — — Operating cash flows from financing leases 16 — — Financing cash flows from finance leases 977 5,646 4,121 Non-cash items: Corporate actions related to fixed income securities, AFS 2 61,369 52,277 22,511 Corporate actions related to equity securities 2 14,250 944 4,725 Assets acquired under finance lease arrangements 824 4,119 278 Assets acquired under operating lease arrangements 1 13,808 — — Non-cash purchase of property and equipment 89 291 — 1 Upon adoption of ASU 2016-02, effective January 1, 2019, we are required to disclose cash paid for amounts included in the measurement of operating lease liabilities, as well as supplemental non-cash information on operating lease liabilities arising from obtaining operating lease assets. 2 Examples of corporate actions include exchanges, non-cash acquisitions, and stock-splits. The following table provides a reconciliation of cash and restricted cash reported within the Consolidated Balance Sheets that equate to the amount reported in the Consolidated Statements of Cash Flows: ($ in thousands) December 31, 2019 December 31, 2018 Cash $ 300 505 Restricted cash 7,675 16,414 Total cash and restricted cash shown in the Statements of Cash Flows $ 7,975 16,919 Amounts included in restricted cash represent cash received from the National Flood Insurance Program ("NFIP"), which is restricted to pay flood claims under the Write Your Own Program.

Investments

Investments	12 Months Ended
	Dec. 31, 2019
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, 2019, 2018, and 2017 : ($ in thousands) 2019 2018 2017 AFS securities: Fixed income securities $ 215,634 2,302 85,806 Equity securities — — 38,894 Total AFS securities 215,634 2,302 124,700 HTM securities: Fixed income securities 31 89 (21 ) Total HTM securities 31 89 (21 ) Short-term securities 23 — — Total net unrealized gains 215,688 2,391 124,679 Deferred income tax (45,294 ) (502 ) (44,103 ) Net unrealized gains, net of deferred income tax 170,394 1,889 80,576 Cumulative effect adjustment due to accounting change for equity unrealized 1 — 30,726 — Cumulative effect adjustment due to accounting changes due to accounting change for stranded tax assets 1 — (17,920 ) — Increase (decrease) in net unrealized gains in OCI, net of deferred income tax $ 168,505 (65,881 ) 38,453 1 Upon adoption of ASU 2016-01, we recognized a $30.7 million cumulative-effect adjustment to the opening balance of AOCI, which represents the after-tax net unrealized gain on our equity portfolio as of December 31, 2017. Additionally, upon adoption of ASU 2018-02, we recognized a one-time reclassification from AOCI to retained earnings for $17.9 million representing the stranded tax assets related to our investment portfolio that were created in AOCI from the enactment of the Tax Cuts and Jobs Act of 2017 ("Tax Reform"). (b) Information regarding our HTM fixed income securities as of December 31, 2019 and December 31, 2018 was as follows: December 31, 2019 Net Unrealized Unrecognized Unrecognized Amortized Gains Carrying Holding Holding Fair ($ in thousands) Cost (Losses) Value Gains Losses Value Obligations of state and political subdivisions $ 4,573 7 4,580 342 (1 ) 4,921 Corporate securities 16,196 24 16,220 834 — 17,054 Total HTM fixed income securities $ 20,769 31 20,800 1,176 (1 ) 21,975 December 31, 2018 Net Unrealized Unrecognized Unrecognized Amortized Gains Carrying Holding Holding Fair ($ in thousands) Cost (Losses) Value Gains Losses Value Obligations of state and political subdivisions 17,431 39 17,470 504 (5 ) 17,969 Corporate securities 19,590 50 19,640 855 (147 ) 20,348 Total HTM fixed income securities $ 37,021 89 37,110 1,359 (152 ) 38,317 Unrecognized holding gains and losses of HTM securities are not reflected in the Financial Statements, as they represent fair value fluctuations from the date a security is designated as HTM through the date of the balance sheet. (c) Information regarding our AFS securities as of December 31, 2019 and December 31, 2018 were as follows: December 31, 2019 Cost/ Amortized Unrealized Unrealized Fair ($ in thousands) Cost Gains Losses Value AFS fixed income securities: U.S. government and government agencies $ 112,680 3,506 — 116,186 Foreign government 18,011 533 (2 ) 18,542 Obligations of states and political subdivisions 1,168,185 62,175 (270 ) 1,230,090 Corporate securities 1,866,881 81,906 (1,310 ) 1,947,477 CLO and other ABS 790,517 7,929 (5,434 ) 793,012 CMBS 514,709 23,902 (267 ) 538,344 RMBS 1,409,003 43,421 (455 ) 1,451,969 Total AFS fixed income securities $ 5,879,986 223,372 (7,738 ) 6,095,620 December 31, 2018 Cost/ Amortized Unrealized Unrealized Fair ($ in thousands) Cost Gains Losses Value AFS fixed income securities: U.S. government and government agencies $ 120,092 1,810 (592 ) 121,310 Foreign government 23,202 36 (107 ) 23,131 Obligations of states and political subdivisions 1,121,615 19,485 (2,631 ) 1,138,469 Corporate securities 1,639,852 5,521 (27,965 ) 1,617,408 CLO and other ABS 720,193 4,112 (6,943 ) 717,362 CMBS 527,409 3,417 (3,748 ) 527,078 RMBS 1,118,435 12,988 (3,081 ) 1,128,342 Total AFS fixed income securities $ 5,270,798 47,369 (45,067 ) 5,273,100 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 severity of impairment on the securities in an unrealized/unrecognized loss position averaged approximately 1% of amortized cost at December 31, 2019 and approximately 2% at December 31, 2018 . Quantitative information regarding unrealized losses on our AFS portfolio is provided below. Our HTM portfolio had less than $0.1 million in unrealized/unrecognized losses at December 31, 2019 and $0.2 million in unrealized/unrecognized losses at December 31, 2018 . December 31, 2019 Less than 12 months 12 months or longer Total ($ in thousands) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Unrealized AFS fixed income securities: Foreign government 1,416 (2 ) — — 1,416 (2 ) Obligations of states and political subdivisions 35,838 (270 ) — — 35,838 (270 ) Corporate securities 84,832 (480 ) 20,182 (830 ) 105,014 (1,310 ) CLO and other ABS 205,191 (1,938 ) 204,385 (3,496 ) 409,576 (5,434 ) CMBS 62,893 (264 ) 828 (3 ) 63,721 (267 ) RMBS 126,089 (425 ) 5,375 (30 ) 131,464 (455 ) Total AFS fixed income securities $ 516,259 (3,379 ) 230,770 (4,359 ) 747,029 (7,738 ) December 31, 2018 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 $ 6,693 (174 ) 23,163 (418 ) 29,856 (592 ) Foreign government 12,208 (93 ) 1,482 (14 ) 13,690 (107 ) Obligations of states and political subdivisions 196,798 (2,074 ) 42,821 (557 ) 239,619 (2,631 ) Corporate securities 1,041,952 (23,649 ) 78,953 (4,316 ) 1,120,905 (27,965 ) CLO and other ABS 516,106 (6,750 ) 16,800 (193 ) 532,906 (6,943 ) CMBS 229,338 (2,548 ) 66,294 (1,200 ) 295,632 (3,748 ) RMBS 139,338 (1,660 ) 45,661 (1,421 ) 184,999 (3,081 ) Total AFS fixed income securities $ 2,142,433 (36,948 ) 275,174 (8,119 ) 2,417,607 (45,067 ) The $37.3 million decrease in the unrealized loss position reflected: (i) lower interest rates, with a 90-basis point decrease in the 2-year U.S. Treasury Note yields and a 77-basis point decrease in 10-year U.S. Treasury Note yields during 2019; and (ii) tightening option adjusted corporate credit spreads with a 60-basis point decrease in the Bloomberg Barclays U.S. Aggregate Corporate Bond Index during 2019. We do not currently intend to sell any of the securities in the tables above, nor will we be required to sell any of these securities. Considering these factors and our review of these securities under our OTTI policy as described in Note 2. “Summary of Significant Accounting Policies” of this Form 10-K, we have concluded that they are temporarily impaired as we believe: (i) they will mature at par value; (ii) they have not incurred a credit impairment; and (iii) future values of these securities will fluctuate with changes in interest rates. This conclusion reflects our current judgment as to the financial position and future prospects of the entity that issued the investment security and underlying collateral. (e) Fixed income securities at December 31, 2019 , by contractual maturity are shown below. Mortgage-backed securities are included in the maturity tables using the estimated average life of each security. Expected maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. Listed below are the contractual maturities of fixed income securities at December 31, 2019 : AFS HTM ($ in thousands) Fair Value Carrying Value Fair Value Due in one year or less $ 394,027 1,211 1,229 Due after one year through five years 3,001,602 13,856 14,820 Due after five years through 10 years 2,531,172 5,733 5,926 Due after 10 years 168,819 — — Total fixed income securities $ 6,095,620 20,800 21,975 (f) The following table summarizes our other investment portfolio by strategy: Other Investments December 31, 2019 December 31, 2018 ($ in thousands) Carrying Value Remaining Commitment Maximum Exposure to Loss 1 Carrying Value Remaining Maximum 1 Alternative Investments Private equity $ 118,352 93,138 211,490 84,352 93,688 178,040 Private credit 42,532 105,340 147,872 41,682 81,453 123,135 Real assets 23,256 20,741 43,997 27,862 27,129 54,991 Total alternative investments 184,140 219,219 403,359 153,896 202,270 356,166 Other securities 2 32,667 — 32,667 25,042 — 25,042 Total other investments $ 216,807 219,219 436,026 178,938 202,270 381,208 1 The maximum exposure to loss includes both the carrying 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. 2 Other securities primarily consists of tax credit investments. We have reviewed various investments included in the table above and have concluded that they are VIEs, but that we are not the primary beneficiary and therefore, consolidation is not required. We do not have a future obligation to fund losses or debts on behalf of these investments; however, we are contractually committed to make additional investments up to the remaining commitment outlined above. We have not provided any non-contractual financial support at any time during 2019 or 2018. 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, with an emphasis on North America. • 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: • Direct 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 are made to companies that may or may not have private equity sponsors 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. • Opportunistic and Distressed Debt : This strategy makes investments in debt and equity securities of companies that are experiencing financial distress, operational issues, or dislocated pricing of publicly-traded securities. 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: • Infrastructure : This strategy invests in the equity or debt of cash flow generating assets, diversified across a variety of industries, including transportation, energy infrastructure, renewable power, such as wind and solar, social infrastructure, power generation, water, telecom, and other regulated entities principally located in North America and Western Europe. • Real Estate : This strategy invests 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 may employ leverage and may use hedging to reduce foreign exchange or interest rate volatility. At this time, our alternative investment strategies do not include hedge funds. We typically 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 or income generated in the limited partnerships. The following tables set forth summarized financial information for our other investments portfolio, including the portion not owned by us. The investments are recorded 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 December 31, ($ in millions) 2019 2018 Investments $ 43,857 28,292 Total assets 45,432 30,377 Total liabilities 5,670 4,532 Total partners’ capital 39,762 25,845 Income Statement Information 12 months ended September 30, ($ in millions) 2019 2018 2017 Net investment (loss) income $ (8 ) 134 (143 ) Realized gains 695 1,981 325 Net change in unrealized appreciation 5,543 1,303 2,894 Net income before tax $ 6,230 3,418 3,076 Insurance Subsidiaries' alternative investments income before tax 17.9 17.6 12.7 (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, 2019 or December 31, 2018 . (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, 2019 to comply with insurance laws. We retain all rights regarding all securities pledged as collateral. The following table summarizes the market value of these securities at December 31, 2019 : ($ in millions) FHLBI Collateral FHLBNY Collateral State and Regulatory Deposits Total U.S. government and government agencies $ — — 22.8 22.8 Obligations of states and political subdivisions — — 4.0 4.0 Corporate securities — — 0.3 0.3 CMBS 7.2 17.9 — 25.1 RMBS 59.0 77.6 — 136.6 Total pledged as collateral $ 66.2 95.5 27.1 188.8 (i) The components of pre-tax net investment income earned were as follows: ($ in thousands) 2019 2018 2017 Fixed income securities $ 203,255 178,104 153,230 Equity securities 6,996 7,764 6,442 Short-term investments 6,653 3,472 1,526 Other investments 18,778 17,799 12,871 Investment expenses (13,139 ) (11,803 ) (12,187 ) Net investment income earned $ 222,543 195,336 161,882 (j) The following tables summarize OTTI by asset type for the periods indicated: 2019 Recognized in Earnings ($ in thousands) Gross Included in OCI AFS fixed income securities: Obligations of states and political subdivisions 66 — 66 Corporate securities $ 2,529 — 2,529 Total AFS fixed income securities 2,595 — 2,595 Other investments 1,049 — 1,049 Total OTTI losses $ 3,644 — 3,644 2018 Recognized in Earnings ($ in thousands) Gross Included in OCI AFS fixed income securities: Corporate securities $ 1,783 — 1,783 RMBS 2,903 — 2,903 Total AFS fixed income securities 4,686 — 4,686 Other investments 1,893 — 1,893 Total OTTI losses $ 6,579 — 6,579 2017 Recognized in Earnings ($ in thousands) Gross Included in OCI AFS fixed income securities: U.S. government and government agencies $ 36 — 36 Obligations of states and political subdivisons 612 — 612 Corporate securities 587 — 587 CLO and other ABS 96 — 96 CMBS 670 — 670 RMBS 1,183 (36 ) 1,219 Total AFS fixed income securities 3,184 (36 ) 3,220 AFS equity securities: Common stock 1,435 — 1,435 Total AFS equity securities 1,435 — 1,435 Other investments 190 — 190 Total OTTI losses $ 4,809 (36 ) 4,845 (k) Net realized and unrealized gains and losses included the following: ($ in thousands) 2019 2018 2017 Net realized gains (losses) on the disposals of securities: Fixed income securities $ 1,910 (34,953 ) 6,944 Equity securities 24,844 18,695 4,629 Short-term investments (16 ) (3 ) (4 ) Other investments (23 ) (2,714 ) (365 ) Net realized gains (losses) on the disposal of securities 26,715 (18,975 ) 11,204 OTTI charges (3,644 ) (6,579 ) (4,845 ) Net realized gains (losses) 23,071 (25,554 ) 6,359 Unrealized (losses) recognized in income on equity securities (8,649 ) (29,369 ) — Total net realized and unrealized investment gains (losses) $ 14,422 (54,923 ) 6,359 Unrealized (losses) recognized in income on equity securities, as reflected in the table above, include the following: ($ in thousands) 2019 2018 Unrealized gains (losses) recognized in income on equity securities: On securities remaining in our portfolio at December 31, 2019 1,219 (3,098 ) On securities sold in each respective period (9,868 ) (26,271 ) Total unrealized (losses) recognized in income on equity securities $ (8,649 ) (29,369 ) The components of net realized gains (losses) on disposals were as follows: ($ in thousands) 2019 2018 2017 HTM fixed income securities Gains $ 1 2 44 Losses (15 ) — (1 ) AFS fixed income securities Gains 6,899 5,460 10,193 Losses (4,975 ) (40,415 ) (3,292 ) Equity securities Gains 24,980 23,203 5,829 Losses (136 ) (4,508 ) (1,200 ) Short-term investments Gains 24 7 2 Losses (40 ) (10 ) (6 ) Other investments Gains 6 — 494 Losses (29 ) (2,714 ) (859 ) Total net realized investment gains (losses) $ 26,715 (18,975 ) 11,204 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 fixed income securities were $594.7 million , $2,030.7 million , and $1,197.9 million in 2019 , 2018 , and 2017 , respectively. Proceeds from sale of equity securities were $137.3 million , $113.3 million , and $38.0 million in 2019, 2018, and 2017, respectively. Net realized gains (losses) in the table above were driven by the following: • 2019 : Opportunistic sales in our equity portfolio. • 2018 : Higher trading volume driven by opportunistic sales in both our fixed income securities and equity portfolios. • 2017 : Higher trading volume in our fixed income securities portfolio related to a more active external investment management approach and opportunistic sales in our equity portfolio.

Comprehensive Income

Comprehensive Income	12 Months Ended
	Dec. 31, 2019
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 2019 , 2018 , and 2017 were as follows: 2019 ($ in thousands) Gross Tax Net Net income $ 336,390 64,767 271,623 Components of OCI: Unrealized gains (losses) on investment securities : Unrealized holding gains during the year 212,683 44,662 168,021 Amounts reclassified into net income: HTM securities (58 ) (12 ) (46 ) Realized losses on disposals and OTTI of AFS securities 671 141 530 Total unrealized gains on investment securities 213,296 44,791 168,505 Defined benefit pension and post-retirement plans: Net actuarial loss (13,795 ) (2,897 ) (10,898 ) Amounts reclassified into net income: Net actuarial loss 2,657 558 2,099 Total defined benefit pension and post-retirement plans (11,138 ) (2,339 ) (8,799 ) Other comprehensive income 202,158 42,452 159,706 Comprehensive income $ 538,548 107,219 431,329 2018 ($ in thousands) Gross Tax Net Net income $ 211,721 32,782 178,939 Components of OCI: Unrealized (losses) gains on investment securities : Unrealized holding losses during the year (123,145 ) (25,861 ) (97,284 ) Amounts reclassified into net income: HTM securities 110 23 87 Realized losses on disposals and OTTI of AFS securities 39,641 8,325 31,316 Total unrealized losses on investment securities (83,394 ) (17,513 ) (65,881 ) Defined benefit pension and post-retirement plans: Net actuarial loss (11,273 ) (2,367 ) (8,906 ) Amounts reclassified into net income: Net actuarial loss 2,127 447 1,680 Total defined benefit pension and post-retirement plans (9,146 ) (1,920 ) (7,226 ) Other comprehensive loss (92,540 ) (19,433 ) (73,107 ) Comprehensive income $ 119,181 13,349 105,832 2017 ($ in thousands) Gross Tax Net Net income $ 261,968 93,142 168,826 Components of OCI: Unrealized gains (losses) on investment securities : Unrealized holding gains during the year 66,894 23,879 43,015 Non-credit portion of OTTI recognized in OCI 36 13 23 Amounts reclassified into net income: HTM securities (179 ) (63 ) (116 ) Non-credit OTTI 104 36 68 Realized gains on disposals and OTTI of AFS securities (6,979 ) (2,442 ) (4,537 ) Total unrealized gains on investment securities 59,876 21,423 38,453 Defined benefit pension and post-retirement plans: Net actuarial loss (4,684 ) (984 ) (3,700 ) Amounts reclassified into net income: Net actuarial loss 2,102 735 1,367 Total defined benefit pension and post-retirement plans (2,582 ) (249 ) (2,333 ) Other comprehensive income 57,294 21,174 36,120 Comprehensive income $ 319,262 114,316 204,946 (b) The balances of, and changes in, each component of AOCI (net of taxes) as of December 31, 2019 and 2018 were as follows: Net Unrealized (Losses) Gains on Investment Securities Defined Benefit Pension and Post-retirement Plans ($ in thousands) OTTI Related HTM Related All Other Investments Subtotal Total AOCI Balance, December 31, 2017 $ (59 ) (14 ) 80,648 80,575 (60,405 ) 20,170 Cumulative effect adjustments 1 (12 ) (2 ) (12,792 ) (12,806 ) (12,213 ) (25,019 ) Balance: December 31, 2017, as adjusted (71 ) (16 ) 67,856 67,769 (72,618 ) (4,849 ) OCI before reclassifications — — (97,284 ) (97,284 ) (8,906 ) (106,190 ) Amounts reclassified from AOCI — 87 31,316 31,403 1,680 33,083 Net current period OCI — 87 (65,968 ) (65,881 ) (7,226 ) (73,107 ) Balance, December 31, 2018 (71 ) 71 1,888 1,888 (79,844 ) (77,956 ) OCI before reclassifications — — 168,021 168,021 (10,898 ) 157,123 Amounts reclassified from AOCI — (46 ) 530 484 2,099 2,583 Net current period OCI — (46 ) 168,551 168,505 (8,799 ) 159,706 Balance, December 31, 2019 $ (71 ) 25 170,439 170,393 (88,643 ) 81,750 1 Upon adoption of ASU 2016-01 and ASU 2018-02 in the first quarter of 2018, we recognized a $25.0 million cumulative-effect adjustment to the opening balance of AOCI, which represents the after-tax net unrealized gain on our equity portfolio as of December 31, 2017 and the one-time reclassification from AOCI to retained earnings for the stranded tax assets that were created in AOCI from the enactment of Tax Reform. The reclassifications out of AOCI are as follows: ($ in thousands) Year ended December 31, 2019 Year ended December 31, 2018 Affected Line Item in the Consolidated Statements of Income HTM related Unrealized (gains) losses on HTM disposals $ (46 ) 137 Net realized and unrealized gains (losses) Amortization of net unrealized gains on HTM securities (12 ) (27 ) Net investment income earned (58 ) 110 Income before federal income tax 12 (23 ) Total federal income tax expense (46 ) 87 Net income Realized losses (gains) on AFS Realized losses on AFS disposals and OTTI 671 39,641 Net realized and unrealized gains (losses) 671 39,641 Income before federal income tax (141 ) (8,325 ) Total federal income tax expense 530 31,316 Net income Defined benefit pension and post-retirement life plans Net actuarial loss 582 450 Loss and loss expense incurred 2,075 1,677 Other insurance expenses Total defined benefit pension and post-retirement life 2,657 2,127 Income before federal income tax (558 ) (447 ) Total federal income tax expense 2,099 1,680 Net income Total reclassifications for the period $ 2,583 33,083 Net income

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The financial assets in our investment portfolio are primarily measured at fair value as disclosed on the Consolidated Balance Sheets. The following table presents the carrying amounts and estimated fair values of our financial liabilities as of December 31, 2019 and 2018 : December 31, 2019 December 31, 2018 ($ in thousands) Carrying Amount Fair Value Carrying Amount Fair Value Financial Liabilities Long-term debt: 7.25% Senior Notes $ 49,910 66,365 49,907 57,032 6.70% Senior Notes 99,480 123,104 99,462 107,075 5.875% Senior Notes — — 185,000 177,230 5.375% Senior Notes 294,157 357,025 — — 1.61% Borrowings from FHLBNY 25,000 24,901 25,000 24,218 1.56% Borrowings from FHLBNY 25,000 24,875 25,000 24,162 3.03% Borrowings from FHLBI 60,000 63,002 60,000 58,905 Subtotal long-term debt 553,547 659,272 444,369 448,622 Unamortized debt issuance costs (3,687 ) (4,829 ) Finance lease obligations 737 — Total long-term debt $ 550,597 439,540 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 and recorded at fair value at December 31, 2019 and 2018 : December 31, 2019 Fair Value Measurements Using ($ in thousands) Assets Measured at Fair Value Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Description Measured on a recurring basis: AFS fixed income securities: U.S. government and government agencies $ 116,186 41,083 75,103 — Foreign government 18,542 — 18,542 — Obligations of states and political subdivisions 1,230,090 — 1,230,090 — Corporate securities 1,947,477 — 1,930,426 17,051 CLO and other ABS 793,012 3,635 772,343 17,034 CMBS 538,344 — 538,344 — RMBS 1,451,969 — 1,451,969 — Total AFS fixed income securities 6,095,620 44,718 6,016,817 34,085 Equity securities: Common stock 1 69,900 32,145 — — Preferred stock 3,037 3,037 — — Total equity securities 72,937 35,182 — — Short-term investments 282,490 265,306 17,184 — Total assets measured at fair value $ 6,451,047 345,206 6,034,001 34,085 December 31, 2018 Fair Value Measurements Using ($ in thousands) Assets Measured at Fair Value Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Description Measured on a recurring basis: AFS fixed income securities: U.S. government and government agencies $ 121,310 78,381 42,929 — Foreign government 23,131 — 23,131 — Obligations of states and political subdivisions 1,138,469 — 1,138,469 — Corporate securities 1,617,408 — 1,617,408 — CLO and other ABS 717,362 — 709,953 7,409 CMBS 527,078 — 527,078 — RMBS 1,128,342 — 1,128,342 — Total AFS fixed income securities 5,273,100 78,381 5,187,310 7,409 Equity securities: Common stock 1 144,727 107,397 — — Preferred stock 2,912 2,912 — — Total equity securities 147,639 110,309 — — Short-term investments 323,864 321,370 2,494 — Total assets measured at fair value $ 5,744,603 510,060 5,189,804 7,409 1 In accordance with ASU 2015-07, investments amounting to $37.8 million and $37.3 million at December 31, 2019 and December 31, 2018, respectively, were measured at fair value using the net asset value per share (or its practical expedient) and have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to total assets measured at fair value. The following table provides a summary of the changes in the fair value of securities measured using Level 3 inputs and related quantitative information during 2019 : 2019 ($ in thousands) Corporate Securities CLO and Other ABS Total Fair value, December 31, 2018 $ — 7,409 7,409 Total net (losses) gains for the period included in: OCI (118 ) (261 ) (379 ) Net income — 245 245 Purchases — 21,282 21,282 Sales — — — Issuances — — — Settlements — (279 ) (279 ) Transfers into Level 3 17,169 18,853 36,022 Transfers out of Level 3 — (30,215 ) (30,215 ) Fair value, December 31, 2019 $ 17,051 17,034 34,085 There were no material changes in the fair value of securities measured using Level 3 prices during 2018. The following tables provide quantitative information regarding our financial assets and liabilities that were not measured, but were disclosed at fair value at December 31, 2019 and 2018 : December 31, 2019 Fair Value Measurements Using ($ in thousands) Assets/Liabilities Disclosed at Fair Value 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 $ 4,921 — 4,921 — Corporate securities 17,054 — 17,054 — Total HTM fixed income securities $ 21,975 — 21,975 — Financial Liabilities Long-term debt: 7.25% Senior Notes $ 66,365 — 66,365 — 6.70% Senior Notes 123,104 — 123,104 — 5.375% Senior Notes 357,025 — 357,025 — 1.61% Borrowings from FHLBNY 24,901 — 24,901 — 1.56% Borrowings from FHLBNY 24,875 — 24,875 — 3.03% Borrowings from FHLBI 63,002 — 63,002 — Total long-term debt $ 659,272 — 659,272 — December 31, 2018 Fair Value Measurements Using ($ in thousands) Assets/Liabilities Disclosed at Fair Value 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 $ 17,969 — 17,969 — Corporate securities 20,348 — 20,348 — Total HTM fixed income securities $ 38,317 — 38,317 — Financial Liabilities Long-term debt: 7.25% Senior Notes $ 57,032 — 57,032 — 6.70% Senior Notes 107,075 — 107,075 — 5.875% Senior Notes 177,230 177,230 — — 1.61% Borrowings from FHLBNY 24,218 — 24,218 — 1.56% Borrowings from FHLBNY 24,162 — 24,162 — 3.03% Borrowings from FHLBI 58,905 — 58,905 — Total long-term debt $ 448,622 177,230 271,392 —

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2019
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 reinsurance treaties. As a Standard Commercial Lines and E&S Lines writer, we are subject to the Terrorism Risk Insurance Program Reauthorization Act ("TRIPRA"), which was extended by Congress to December 31, 2027. TRIPRA requires private insurers and the U. S. 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 2020 , our deductible, before tax, is approximately $359 million . For losses above the deductible, the federal government will pay 80% of losses to an industry limit of $100 billion , and the insurer retains 20% . The Insurance Subsidiaries remain liable to policyholders to the extent that any reinsurer becomes unable to meet their contractual obligations. In addition to this direct counterparty credit risk, we have indirect counterparty credit risk as our reinsurers often enter into their own reinsurance programs, or retrocessions, as part of managing their exposure to large losses. We evaluate and monitor the financial condition of our reinsurers under voluntary reinsurance arrangements to minimize our exposure to significant losses from reinsurer insolvencies. The allowance for uncollectible reinsurance recoverables was $4.4 million at December 31, 2019 and $4.5 million at December 31, 2018 . The following table represents our total reinsurance balances segregated by reinsurer to illustrate our concentration of risk throughout our reinsurance portfolio: As of December 31, 2019 As of December 31, 2018 ($ in thousands) Reinsurance Balances % of Reinsurance Balance Reinsurance Balances % of Reinsurance Balance Total reinsurance recoverables $ 573,235 $ 549,172 Total prepaid reinsurance premiums 166,705 157,723 Total reinsurance balance 739,940 706,895 Federal and state pools 1 : NFIP 175,472 24 % 170,453 24 % New Jersey Unsatisfied Claim Judgment Fund 53,732 6 55,167 7 Other 2,449 1 3,602 1 Total federal and state pools 231,653 31 229,222 32 Remaining reinsurance balance $ 508,287 69 $ 477,673 68 Munich Re Group (A.M. Best rated "A+") $ 119,748 16 $ 112,841 16 Hannover Ruckversicherungs AG (A.M. Best rated "A+") 107,474 15 101,835 14 AXIS Reinsurance Company (A.M. Best rated "A+") 73,009 10 69,102 10 Swiss Re Group (A.M. Best rated "A+") 37,190 5 37,519 5 Transatlantic Reinsurance Company (A.M. Best rated “A+”) 21,824 3 17,686 3 All other reinsurers 149,042 20 138,690 20 Total reinsurers 508,287 69 % 477,673 68 % Less: collateral 2 (110,549 ) (112,201 ) Reinsurers, net of collateral $ 397,738 $ 365,472 1 Considered to have minimal risk of default. 2 Includes letters of credit, trust funds, and funds held against reinsurance recoverables. 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 loss and loss expense incurred: ($ in thousands) 2019 2018 2017 Premiums written: Direct $ 3,084,451 2,890,633 2,733,459 Assumed 24,339 26,250 26,685 Ceded (429,366 ) (402,597 ) (389,503 ) Net $ 2,679,424 2,514,286 2,370,641 Premiums earned: Direct $ 2,993,157 2,808,764 2,647,488 Assumed 24,399 25,831 25,831 Ceded (420,385 ) (398,366 ) (382,292 ) Net $ 2,597,171 2,436,229 2,291,027 Loss and loss expense incurred: Direct $ 1,714,880 1,706,951 1,570,678 Assumed 22,879 21,469 17,588 Ceded (186,268 ) (230,286 ) (243,192 ) Net $ 1,551,491 1,498,134 1,345,074 The ceded premiums and losses related to our participation in the NFIP, under which 100% of our flood premiums, and loss and loss expense are ceded to the NFIP, are as follows: Ceded to NFIP ($ in thousands) 2019 2018 2017 Ceded premiums written $ (266,925 ) (248,053 ) (241,345 ) Ceded premiums earned (259,119 ) (244,238 ) (235,088 ) Ceded loss and loss expense incurred (71,676 ) (144,967 ) (160,922 )

Reserve for Loss and Loss Expen

Reserve for Loss and Loss Expense	12 Months Ended
	Dec. 31, 2019
Insurance Loss Reserves [Abstract]
Reserve for Loss and Loss Expense	Reserve for Loss and Loss Expense (a) The table below provides a roll forward of reserves for loss and loss expense for beginning and ending reserve balances: ($ in thousands) 2019 2018 2017 Gross reserves for loss and loss expense, at beginning of year $ 3,893,868 3,771,240 3,691,719 Less: reinsurance recoverable on unpaid loss and loss expense, at beginning of year 537,388 585,855 611,200 Net reserves for loss and loss expense, at beginning of year 3,356,480 3,185,385 3,080,519 Incurred loss and loss expense for claims occurring in the: Current year 1,601,780 1,527,997 1,384,266 Prior years (50,289 ) (29,863 ) (39,192 ) Total incurred loss and loss expense 1,551,491 1,498,134 1,345,074 Paid loss and loss expense for claims occurring in the: Current year 579,527 573,718 497,486 Prior years 805,443 753,321 742,722 Total paid loss and loss expense 1,384,970 1,327,039 1,240,208 Net reserves for loss and loss expense, at end of year 3,523,001 3,356,480 3,185,385 Add: Reinsurance recoverable on unpaid loss and loss expense, at end of year 544,162 537,388 585,855 Gross reserves for loss and loss expense at end of year $ 4,067,163 3,893,868 3,771,240 Our net loss and loss expense reserves increased by $166.5 million in 2019 , $171.1 million in 2018 , and $104.9 million in 2017 . The loss and loss expense reserves are net of anticipated recoveries for salvage and subrogation claims, which amounted to $76.7 million for 2019 , $67.7 million for 2018 , and $64.8 million for 2017 . The increase in net loss and loss expense reserves in 2019 was primarily driven by increases in exposure due to premium growth. This increase was partially offset by favorable prior year loss development, largely driven by the workers compensation line of business. In 2019 , we experienced overall net favorable prior year loss development of $50.3 million , compared to $ 29.9 million in 2018 and $39.2 million in 2017 . The following table summarizes the prior year reserve development by line of business: (Favorable)/Unfavorable Prior Year Development ($ in millions) 2019 2018 2017 General Liability $ (5.0 ) (9.5 ) (48.3 ) Commercial Automobile 0.7 36.7 35.6 Workers Compensation (68.0 ) (83.0 ) (52.3 ) Businessowners' Policies 1.9 (1.5 ) 1.9 Commercial Property 5.1 7.5 8.7 Homeowners 7.5 9.8 0.4 Personal Automobile 4.4 3.0 6.7 E&S Casualty Lines 2.0 12.0 10.0 E&S Property Lines 1.0 (4.8 ) 0.1 Other 0.1 (0.1 ) (2.0 ) Total $ (50.3 ) (29.9 ) (39.2 ) The Insurance Subsidiaries had $50.3 million of favorable prior accident year reserve development during 2019 , which included $61.0 million of net favorable casualty reserve development and $10.7 million of unfavorable property reserve development. The net favorable casualty reserve development was largely driven by the workers compensation line of business, which was impacted by continued favorable medical trends in accident years 2017 and prior. The Insurance Subsidiaries had $29.9 million of favorable prior accident year reserve development during 2018 , which included $ 41.5 million of net favorable casualty reserve development and $ 11.6 million of unfavorable property reserve development. The net favorable casualty reserve development was largely driven by the workers compensation line of business, reflecting continued favorable medical trends in accident years 2017 and prior. Partially offsetting this net favorable reserve development was $37.5 million of unfavorable casualty reserve development in the commercial auto line of business, driven by increases in frequencies and severities in accident years 2015 through 2017. In addition, our E&S casualty lines experienced unfavorable reserve development of $12.0 million in 2018 . The Insurance Subsidiaries had $ 39.2 million of favorable prior accident year reserve development during 2017 . The net favorable casualty reserve development was largely driven by the workers compensation and general liability lines of business in accident years 2014 and prior. Partially offsetting this net favorable reserve development was $ 36.0 million of unfavorable casualty reserve development in the commercial automobile line of business, which was primarily driven by accident years 2012 through 2016. In addition, our E&S casualty lines experienced unfavorable reserve development of $10.0 million in 2017 , primarily related to accident years 2015 and 2016. (b) We have exposure to abuse and molestation claims within our general liability line of business through insurance policies that we issue to schools, religious institutions, daycares, and other social services. We also have exposure to abuse and molestation claims from recently enacted state laws that extend the statute of limitations or permit windows to be opened for abuse and molestation claims and lawsuits that were previously barred by statutes of limitations. The emergence of these claims is slow and highly unpredictable. There are significant uncertainties in estimating our exposure to abuse and molestation claims (for both case and IBNR reserves) resulting from (i) lack of relevant historical data, (ii) the delayed and inconsistent reporting patterns associated with these claims, (iii) the obligation of an insurer to defend a claim, (iv) the extent to which a party can prove the existence of coverage, and (v) uncertainty as to the number and identity of claimants. It is possible, as a result, that we may receive claims decades after the allegations occurred from coverages provided by us, including predecessor companies, that will require complex claims coverage determinations, potential litigation, and the need to collect from reinsurers under older reinsurance agreements. We do not discount to present value that portion of our loss and loss expense reserves expected to be paid in future periods. (c) 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 loss and loss expense reserves expected to be paid in future periods. The following table details our loss and loss expense reserves for various asbestos and environmental claims: 2019 ($ in millions) Gross Net Asbestos $ 6.3 5.1 Landfill sites 12.1 7.3 Underground storage tanks 10.3 9.2 Total $ 28.7 21.6 Reserves for asbestos and environmental claims are highly uncertain. 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. Estimating IBNR is challenging because of the delayed and inconsistent reporting patterns associated with these claims. Traditional actuarial approaches cannot be applied because past loss history is not necessarily indicative of future behavior. While certain alternative projection models can be applied, such models can produce significantly different results with small changes in assumptions. As a result, reserves for asbestos and environmental require a high degree of judgment. Because of the significant uncertainty in the estimate, we do not calculate an asbestos and environmental loss range. Historically, our asbestos and environmental claims have been significantly lower in volume than many other standard commercial lines carriers since, prior to the introduction of the absolute pollution exclusion endorsement in the mid-1980’s, we primarily wrote Standard Personal Lines, and therefore, our exposure to asbestos and environmental claims has been limited. The following table provides a roll forward of gross and net asbestos and environmental incurred loss and loss expense and related reserves thereon: 2019 2018 2017 ($ in thousands) Gross Net Gross Net Gross Net Asbestos Reserves for loss and loss expense at beginning of year $ 7,328 6,097 7,577 6,346 7,847 6,615 Incurred loss and loss expense (375 ) (375 ) — — — — Less: loss and loss expense paid (665 ) (665 ) (249 ) (249 ) (270 ) (269 ) Reserves for loss and loss expense at the end of year $ 6,288 5,057 7,328 6,097 7,577 6,346 Environmental Reserves for loss and loss expense at beginning of year $ 22,692 16,686 20,838 14,866 22,115 16,101 Incurred loss and loss expense 723 609 3,059 2,877 126 — Less: loss and loss expense paid (1,002 ) (763 ) (1,205 ) (1,057 ) (1,403 ) (1,235 ) Reserves for loss and loss expense at the end of year $ 22,413 16,532 22,692 16,686 20,838 14,866 Total Asbestos and Environmental Claims Reserves for loss and loss expense at beginning of year $ 30,020 22,783 28,415 21,212 29,962 22,716 Incurred loss and loss expense 348 234 3,059 2,877 126 — Less: loss and loss expense paid (1,667 ) (1,428 ) (1,454 ) (1,306 ) (1,673 ) (1,504 ) Reserves for loss and loss expense at the end of year $ 28,701 21,589 30,020 22,783 28,415 21,212 (d) The following is information about incurred and paid claims development as of December 31, 2019 , net of reinsurance, as well as cumulative claim frequency and the associated 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 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. All Lines (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 950,114 973,742 977,959 956,600 943,118 922,404 915,131 907,074 904,561 902,258 38,152 94,526 2011 1,042,576 1,061,667 1,062,233 1,056,107 1,033,518 1,023,726 1,019,351 1,013,115 1,013,175 44,453 104,861 2012 1,065,437 1,071,290 1,020,655 998,028 973,089 973,644 973,411 968,536 50,942 104,148 2013 1,044,142 1,062,045 1,047,230 1,021,007 1,002,316 987,763 984,858 72,970 91,326 2014 1,107,513 1,133,798 1,146,990 1,124,014 1,104,218 1,100,208 83,392 95,081 2015 1,114,081 1,130,513 1,144,830 1,138,313 1,119,441 111,657 94,128 2016 1,188,608 1,203,634 1,227,142 1,199,734 205,126 94,579 2017 1,270,110 1,313,372 1,313,585 336,155 98,014 2018 1,413,800 1,461,603 501,519 104,187 2019 1,483,945 759,853 93,947 Total 11,547,343 All Lines (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 328,826 509,910 625,229 704,895 773,536 803,773 823,770 835,532 846,386 851,633 2011 391,944 585,867 692,730 782,655 852,202 901,801 924,111 940,626 950,836 2012 378,067 555,819 651,544 743,742 810,135 856,195 879,372 898,269 2013 335,956 518,872 644,475 748,758 833,823 872,331 891,841 2014 405,898 614,075 736,154 855,959 936,425 981,868 2015 376,641 581,203 725,385 845,868 929,222 2016 387,272 617,958 764,331 892,390 2017 433,440 678,453 829,134 2018 511,271 779,466 2019 510,091 Total 8,514,750 All outstanding liabilities before 2010, net of reinsurance 360,119 Liabilities for loss and loss expenses, net of reinsurance 3,392,713 General Liability (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 215,208 228,680 242,499 237,154 222,328 211,619 208,968 202,394 206,146 205,322 17,542 12,705 2011 227,769 228,720 239,480 230,785 217,256 211,196 212,011 211,500 213,485 19,913 11,649 2012 238,979 245,561 215,083 194,144 175,305 175,268 180,659 182,085 21,005 9,994 2013 250,609 251,421 239,776 225,709 210,785 203,831 202,697 28,857 10,378 2014 244,312 249,946 257,132 239,333 234,082 237,125 42,388 10,586 2015 254,720 245,710 246,990 233,249 219,204 55,244 10,381 2016 277,214 272,048 277,986 263,245 98,385 10,526 2017 293,747 293,128 301,384 161,114 10,706 2018 317,934 336,326 223,228 10,656 2019 347,150 296,257 8,626 Total 2,508,023 General Liability (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 15,726 46,201 80,018 113,050 143,360 161,487 172,394 178,179 183,988 185,962 2011 13,924 42,692 73,643 102,978 135,377 159,768 170,525 181,856 187,276 2012 13,030 35,241 56,580 89,008 109,448 130,866 144,451 156,186 2013 12,789 35,113 72,127 104,587 139,114 153,628 163,764 2014 14,901 46,825 79,972 121,969 154,957 179,192 2015 14,665 39,978 78,668 116,804 144,216 2016 15,684 46,549 89,431 133,757 2017 17,366 49,470 92,355 2018 19,531 60,784 2019 18,097 Total 1,321,589 All outstanding liabilities before 2010, net of reinsurance 93,982 Liabilities for loss and loss expenses, net of reinsurance 1,280,416 Workers Compensation (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 198,371 214,469 212,815 211,030 214,916 212,448 208,155 204,423 199,539 197,095 19,514 12,192 2011 205,238 218,973 214,743 215,114 210,591 205,708 200,674 194,821 192,863 22,717 11,860 2012 203,864 208,036 199,360 195,197 188,596 187,359 183,314 178,774 24,605 11,618 2013 199,794 194,318 187,658 173,160 166,662 162,787 159,767 26,260 11,375 2014 199,346 187,065 182,579 172,515 164,420 160,646 28,320 10,495 2015 193,729 194,639 183,604 179,642 176,242 27,927 10,549 2016 196,774 184,946 176,248 166,009 41,146 10,572 2017 195,202 184,306 175,853 53,654 10,793 2018 193,894 193,818 74,399 11,078 2019 188,625 100,336 9,805 Total 1,789,692 Workers Compensation (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 46,795 93,281 122,442 137,184 149,086 153,795 158,078 162,796 165,526 167,478 2011 42,941 90,836 118,847 134,646 139,232 149,269 154,320 158,535 161,696 2012 40,911 86,909 108,211 122,755 132,052 139,477 143,281 146,739 2013 36,829 74,568 96,376 109,739 118,669 124,130 126,822 2014 35,924 78,944 100,876 113,626 119,392 124,077 2015 33,857 77,320 98,195 112,601 120,097 2016 34,525 78,531 98,037 109,166 2017 40,375 82,216 100,645 2018 41,122 84,780 2019 37,826 Total 1,179,326 All outstanding liabilities before 2010, net of reinsurance 240,140 Liabilities for loss and loss expenses, net of reinsurance 850,505 Commercial Automobile (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 187,562 189,305 187,778 181,923 179,854 172,969 173,157 173,471 173,080 172,995 682 25,512 2011 174,006 183,044 182,325 178,421 172,617 174,882 174,514 173,507 173,401 899 25,524 2012 179,551 191,947 183,527 184,289 184,367 186,128 184,633 185,357 1,920 24,160 2013 188,289 205,282 209,197 207,994 210,410 207,975 209,602 2,928 25,722 2014 200,534 212,725 216,824 219,925 218,172 217,334 4,831 27,714 2015 220,994 240,958 253,074 259,495 260,565 7,966 29,340 2016 255,187 274,367 285,302 285,304 21,279 31,167 2017 301,274 329,389 324,291 57,165 32,474 2018 347,908 352,487 109,922 35,034 2019 385,212 183,477 33,438 Total 2,566,548 Commercial Automobile (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 68,098 99,254 128,015 146,913 163,513 167,227 169,100 169,793 171,693 171,941 2011 69,849 99,196 121,576 142,507 157,291 166,082 170,000 170,913 172,365 2012 73,316 105,371 127,235 148,669 168,114 176,656 179,501 181,353 2013 76,469 109,893 140,015 169,850 189,626 200,750 202,622 2014 80,810 117,169 148,884 180,701 202,821 209,655 2015 91,347 132,260 175,866 211,515 238,142 2016 106,022 155,720 200,701 233,939 2017 117,287 178,823 220,422 2018 134,867 193,788 2019 149,538 Total 1,973,765 All outstanding liabilities before 2010, net of reinsurance 3,904 Liabilities for loss and loss expenses, net of reinsurance 596,686 Businessowners' Policies (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 53,669 49,285 42,408 39,915 40,899 40,581 41,239 41,197 40,920 41,156 333 3,920 2011 54,469 57,083 51,047 58,242 59,256 58,966 58,456 58,735 58,948 362 4,960 2012 54,342 48,029 46,303 44,172 44,077 43,747 43,418 43,717 703 5,543 2013 49,617 42,618 41,005 40,624 41,369 39,709 39,699 803 3,482 2014 55,962 60,949 62,548 59,806 58,517 58,093 1,390 4,064 2015 52,871 53,768 57,245 55,925 54,454 3,235 3,959 2016 52,335 53,792 54,993 53,835 4,245 3,843 2017 46,624 48,698 51,524 10,252 3,864 2018 55,024 57,202 12,432 4,159 2019 53,531 15,068 3,210 Total 512,159 Businessowners' Policies (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 20,821 28,131 31,027 34,705 37,819 38,900 40,279 40,395 40,439 40,823 2011 27,884 37,362 41,011 46,444 52,114 55,856 57,045 57,365 57,380 2012 22,199 31,833 35,089 37,215 38,766 40,627 41,326 41,356 2013 17,412 26,592 30,845 34,760 37,993 38,464 39,085 2014 28,914 40,584 44,911 49,460 52,940 55,458 2015 24,189 36,014 42,710 46,571 49,073 2016 24,655 36,848 39,973 45,308 2017 21,865 31,337 36,950 2018 29,995 39,791 2019 27,718 Total 432,942 All outstanding liabilities before 2010, net of reinsurance 7,530 Liabilities for loss and loss expenses, net of reinsurance 86,747 Commercial Property (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 105,647 96,851 97,386 96,127 95,530 95,363 95,178 95,155 95,142 95,338 4 7,669 2011 136,954 131,667 130,942 131,282 131,353 131,113 131,049 131,009 131,002 7 9,038 2012 118,464 114,224 115,375 116,658 117,102 117,170 117,225 117,220 10 8,517 2013 88,101 90,639 90,103 90,005 90,436 90,278 90,218 18 5,713 2014 141,192 136,249 136,820 138,751 138,155 136,212 33 6,515 2015 110,270 109,513 111,750 111,566 112,496 56 6,404 2016 121,927 126,185 125,937 124,487 (96 ) 6,739 2017 138,773 149,106 149,044 (884 ) 6,886 2018 183,177 190,834 (329 ) 8,240 2019 173,826 15,732 6,722 Total 1,320,677 Commercial Property (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 69,543 91,918 94,602 95,111 95,270 95,147 95,156 95,150 95,138 95,334 2011 94,538 127,580 129,579 130,681 131,060 131,115 131,089 131,100 131,092 2012 81,528 108,834 111,503 114,699 116,291 116,625 116,671 116,674 2013 60,244 87,874 90,446 90,350 90,840 90,696 90,646 2014 101,131 132,909 136,634 137,883 137,418 136,008 2015 79,048 106,182 109,829 110,994 110,969 2016 83,966 118,789 122,930 123,828 2017 99,047 142,338 148,589 2018 135,416 184,813 2019 130,891 Total 1,268,844 All outstanding liabilities before 2010, net of reinsurance 237 Liabilities for loss and loss expenses, net of reinsurance 52,071 Personal Automobile (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 103,340 110,075 112,346 109,515 107,490 107,405 107,224 107,054 106,887 106,785 64 20,823 2011 113,232 116,164 113,686 112,993 114,241 113,830 113,988 113,921 114,056 121 22,700 2012 113,771 114,921 109,832 109,324 110,294 110,300 109,795 109,701 155 22,332 2013 108,417 109,620 106,225 106,703 107,759 107,680 107,916 348 22,375 2014 102,250 109,325 106,757 107,452 106,821 107,104 307 22,506 2015 96,387 99,698 100,214 99,570 98,718 742 20,863 2016 92,727 98,032 100,202 101,140 2,565 19,819 2017 101,880 105,139 103,653 6,342 20,725 2018 111,594 113,569 14,259 22,621 2019 114,043 25,832 21,988 Total 1,076,685 Personal Automobile (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 58,786 82,490 95,300 101,540 104,061 105,849 106,453 106,733 106,722 106,716 2011 61,323 82,102 93,878 105,068 111,085 112,732 113,551 113,664 113,856 2012 63,704 82,729 94,842 102,977 107,890 109,355 109,447 109,482 2013 61,384 80,861 92,637 100,528 105,131 106,679 106,876 2014 62,519 83,739 92,589 99,173 104,055 105,709 2015 58,725 76,470 87,163 92,102 95,997 2016 57,961 76,823 86,752 94,372 2017 62,854 82,730 91,479 2018 69,721 89,628 2019 69,699 Total 983,814 All outstanding liabilities before 2010, net of reinsurance 7,462 Liabilities for loss and loss expenses, net of reinsurance 100,331 Homeowners (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 68,373 67,525 63,285 61,927 62,462 62,402 62,339 62,392 62,402 62,380 48 9,132 2011 103,804 98,211 97,761 94,167 94,543 94,183 94,378 94,587 94,572 82 15,111 2012 87,260 82,744 86,560 86,667 86,271 86,330 86,483 86,567 94 16,941 2013 73,670 72,528 71,494 72,145 71,714 72,148 72,318 420 7,749 2014 80,111 82,461 83,637 83,844 83,539 83,824 682 8,773 2015 76,637 76,400 76,559 74,723 74,978 660 7,746 2016 60,105 60,931 62,391 61,723 1,221 6,885 2017 59,167 67,978 70,365 2,500 7,370 2018 62,961 68,526 2,366 7,554 2019 64,306 6,299 6,468 Total 739,559 Homeowners (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 43,699 58,638 60,295 61,106 62,155 62,227 62,241 62,272 62,283 62,329 2011 71,668 89,963 91,718 92,185 93,312 93,720 94,007 94,412 94,458 2012 69,056 79,584 82,720 84,250 85,196 85,562 85,642 85,897 2013 50,664 65,528 67,838 69,775 71,776 72,197 72,433 2014 61,561 76,007 79,751 81,664 82,583 82,836 2015 52,589 70,078 72,202 72,927 74,079 2016 42,252 57,333 59,546 60,082 2017 45,466 63,290 67,193 2018 49,430 64,137 2019 49,680 Total 713,124 All outstanding liabilities before 2010, net of reinsurance 5,316 Liabilities for loss and loss expenses, net of reinsurance 31,752 E&S Casualty Lines (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 3,294 $ 4,106 3,369 4,299 3,831 3,055 4,932 5,168 5,534 — 815 2011 8,127 7,102 9,853 12,207 10,273 9,652 10,228 12,119 11,554 177 1,332 2012 42,367 42,621 43,175 46,149 46,165 45,988 46,444 44,622 2,474 2,045 2013 55,468 60,309 67,099 69,112 67,647 68,972 68,451 13,816 2,280 2014 55,316 63,505 69,929 71,719 71,206 71,153 5,559 2,071 2015 75,498 76,432 82,404 90,488 90,355 15,752 2,799 2016 94,451 96,416 104,655 105,120 35,987 2,859 2017 91,438 95,783 99,866 47,074 2,614 2018 98,324 103,004 62,754 2,392 2019 117,087 103,146 1,679 Total 716,746 E&S Casualty Lines (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ — $ 1,218 2,570 3,574 4,078 4,513 4,610 4,908 5,362 2011 — 806 3,200 6,445 9,954 9,912 10,256 9,819 9,604 2012 3,722 7,914 16,430 25,064 32,343 36,278 38,298 39,832 2013 2,715 9,470 21,980 35,200 46,108 51,142 54,974 2014 2,353 12,234 25,571 43,877 53,780 60,092 2015 3,036 13,057 29,389 50,712 64,529 2016 3,720 16,195 33,950 56,581 2017 5,057 14,672 34,179 2018 5,509 21,337 2019 4,422 Total 350,912 All outstanding liabilities before 2010, net of reinsurance 109 Liabilities for loss and loss expenses, net of reinsurance 365,943 In 2011, the Parent purchased Mesa Underwriters Specialty Insurance Company ("MUSIC"), a wholly-owned E&S Lines subsidiary of Montpelier Re Holdings, Ltd. Under the terms of the purchase agreement, the Parent acquired net loss and loss reserves amounting to approximately $15 million . All development on this acquired business was fully reinsured as of the acquisition date. (e) The reconciliation of the net incurred and paid claims development tables to the liability for loss and loss expenses in the consolidated statement of financial position is as follows: (in thousands) December 31, 2019 Net outstanding liabilities: Standard Commercial Lines General liability $ 1,280,416 Workers compensation 850,505 Commercial automobile 596,686 Businessowners' policies 86,747 Commercial property 52,071 Other Standard Commercial Lines 9,399 Total Standard Commercial Lines net outstanding liabilities 2,875,824 Standard Personal Lines Personal automobile 100,331 Homeowners 31,752 Other Standard Personal Lines 10,664 Total Standard Personal Lines net outstanding liabilities 142,747 E&S Lines Casualty lines 365,943 Property lines 8,199 Total E&S Lines net outstanding liabilities 374,142 Total liabilities for unpaid loss and loss expenses, net of reinsurance 3,392,713 Reinsurance recoverable on unpaid claims: Standard Commercial Lines General liability 195,830 Workers compensation 206,414 Commercial automobile 14,352 Businessowners' policies 3,012 Commercial property 26,526 Other Standard Commercial Lines 9,113 Total Standard Commercial Lines reinsurance recoverable on unpaid loss 455,247 Standard Personal Lines Personal automobile 44,104 Homeowners 1,182 Other Standard Personal Lines 28,993 Total Standard Personal Lines reinsurance recoverable on unpaid loss 74,279 E&S Lines Casualty lines 14,319 Property lines 317 Total E&S Lines reinsurance recoverable on unpaid loss 14,636 Total reinsurance recoverable on unpaid loss 544,162 Unallocated loss expenses 130,288 Total gross liability for unpaid loss and loss expenses $ 4,067,163 (f) 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 6.3% of its ultimate losses in the first year, 12.5% in the second year, and so forth. The following is supplementary information about average historical claims duration as of December 31, 2019 : 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 6.3% 12.5 15.5 17.0 14.2 9.8 5.6 4.9 2.8 1.9 Workers compensation 21.9 24.9 13.2 8.2 4.9 4.6 2.3 2.4 1.6 1.1 Commercial automobile 37.8 17.0 14.4 12.9 9.8 4.1 1.3 0.9 1.1 0.1 Businessowners’ policies 47.9 19.5 8.2 8.8 6.6 3.9 2.0 0.8 0.8 0.8 Commercial property 70.6 25.4 2.8 0.8 0.3 0.1 — — — — Personal automobile 58.2 18.4 9.9 6.8 4.2 1.5 0.5 0.3 0.1 0.1 Homeowners 72.2 20.3 3.3 1.5 1.6 0.4 0.3 0.2 0.1 0.1 E&S Lines - casualty 4.9 12.2 18.1 22.6 14.9 9.4 6.4 3.5 2.0

Indebtedness

Indebtedness	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Indebtedness	Indebtedness The table below provides a summary of our outstanding debt at December 31, 2019 and 2018 : Outstanding Debt 2019 Carry Value Issuance Date Maturity Date Interest Rate Original Amount Unamortized Issuance Costs Debt Discount December 31, 2019 December 31, 2018 ($ in thousands) Description Long term Issuance: (1) Senior Notes 3/1/2019 3/1/2049 5.375 % $ 300,000 (3,147 ) (5,843 ) 291,010 — Redemption: (1) Senior Notes 2/8/2013 2/9/2043 5.875 % 185,000 — — — 180,771 Other Outstanding: (2) FHLBI 12/16/2016 12/16/2026 3.03 % 60,000 — — 60,000 60,000 (3) FHLBNY 8/15/2016 8/16/2021 1.56 % 25,000 — — 25,000 25,000 (3) FHLBNY 7/21/2016 7/21/2021 1.61 % 25,000 — — 25,000 25,000 (4) Senior Notes 11/3/2005 11/1/2035 6.70 % 100,000 (355 ) (520 ) 99,125 99,069 (5) Senior Notes 11/16/2004 11/15/2034 7.25 % 50,000 (185 ) (90 ) 49,725 49,700 Finance lease obligations 1 737 — Total long-term debt (3,687 ) (6,453 ) 550,597 439,540 1 Concurrent with the adoption of ASU 2016-02 discussed in Note 3. "Adoption of Accounting Pronouncements," finance lease obligations are now captured in Long-term debt on our Consolidated Balance Sheets. Short-term Debt Activity Short-term debt activity included the following in 2019: • On March 7, 2019 , Selective Insurance Company of America ("SICA") borrowed short-term funds of $50 million from the FHLBNY at an interest rate of 2.64% . This borrowing was repaid on March 28, 2019 . • On August 5, 2019 , SICA borrowed short-term funds of $15 million from the FHLBNY at an interest rate of 2.29% . This borrowing was repaid on August 12, 2019 . On December 20, 2019, the Parent entered into a Credit Agreement (the “Line of Credit”) among the Parent, the lenders named therein (the “Lenders”), and Bank of Montreal, Chicago Branch, as Administrative Agent. Under the Line of Credit, the Lenders have agreed to provide the Parent with a $50 million revolving credit facility, which can be increased to $125 million with the consent of the Lenders. The Line of Credit will mature on December 20, 2022 and has an interest rate, which varies and is based on, among other factors, the Parent’s debt ratings. The Parent, as borrower, was a party to a Credit Agreement, dated December 1, 2015, for a $30 million revolving credit facility, which could be increased to $50 million with the consent of the lenders, with the lenders named therein, and Wells Fargo Bank, National Association, as Administrative Agent (“Wells Fargo”), which was scheduled to mature on December 1, 2020 (the “Prior Credit Agreement”). In anticipation of entering into the Line of Credit, the Parent exercised termination rights under the Prior Credit Agreement by sending a termination letter to Wells Fargo on December 20, 2019. The effective date of the termination of the Prior Credit Agreement was December 30, 2019. Our Line of Credit 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, a 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 covenants in the Line of Credit: Required as of Actual as of December 31, 2019 December 31, 2019 Consolidated net worth 1 Not less than $1.4 billion $2.1 billion Debt to total capitalization ratio 1 Not to exceed 35% 20.7% 1 Calculated in accordance with the Line of Credit. In addition to the above requirements, the Line of Credit 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. Additionally, the Line of Credit limits borrowings from the FHLBI and the FHLBNY to 10% of the respective member company's admitted assets for the previous year. Long-term Debt Activity (1) In the first quarter of 2019, we issued $ 300 million of 5.375% Senior Notes due 2049 at a discount of $5.9 million which, when coupled with debt issuance costs of approximately $3.3 million , resulted in net proceeds from the offering of $290.8 million . The 5.375% Senior Notes will pay interest on March 1 and September 1 of each year. The first payment was made on September 1, 2019. A portion of the proceeds from this debt issuance was used to fully redeem the $185 million aggregate principal amount of our 5.875% Senior Notes due 2043 , with the remaining $106 million being used for general corporate purposes. The 5.875% Senior Notes had pre-tax debt retirement costs of $4.2 million , or $3.3 million after tax, which was recorded in Interest expense on the Consolidated Statements of Income in the first quarter of 2019. There are no financial debt covenants to which we are required to comply in regards to the 5.375% Senior Notes. (2) In the first quarter of 2009, Selective Insurance Company of South Carolina ("SICSC") and Selective Insurance Company of the Southeast ("SICSE"), which are collectively referred to as the "Indiana Subsidiaries" as they are domiciled in Indiana, 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, 2019 and December 31, 2018 . 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. The proceeds from the FHLBI borrowing on December 16, 2016 of $60 million were used to repay a $45 million borrowing from the FHLBI that was outstanding at the time, with the remaining $15 million used for general corporate purposes. All borrowings from the FHLBI require security. There are no financial debt covenants to which we are required to comply with in regards to these borrowings. For information on investments that are pledged as collateral for these borrowings, see Note 5. "Investments" above. (3) 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 $3.1 million at December 31, 2019 and $2.7 million at December 31, 2018 . 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 2016, SICA borrowed the following amounts from the FHLBNY: (i) $25 million in August 2016 at an interest rate of 1.56% , which is due on August 16, 2021; and (ii) $25 million in July 2016 at an interest rate of 1.61% , which is due on July 21, 2021. All borrowings from the FHLBNY require security. There are no financial debt covenants to which we are required to comply with in regards to these borrowings. For information on investments that are pledged as collateral for these borrowings, see Note 5. "Investments" above. (4) 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 that subsequently funded 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. (5) 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, 2019
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 before and after-tax underwriting results (net premiums earned, incurred loss and loss expense, policyholders dividends, policy acquisition costs, and other underwriting expenses), return on equity ("ROE") contribution, and combined ratios. • Our Investments segment is evaluated based on after-tax net investment income and its ROE contribution. Also included in our Investment segment results are after-tax net realized and unrealized gains and losses, which are not included in non-GAAP operating income. In computing the results of each segment, we do not make adjustments for interest expense or corporate expenses. We do not maintain separate investment portfolios for the segments and therefore, do not allocate assets to the segments. Our combined insurance operations are subject to certain geographic concentrations, particularly in the Eastern region of the country. In 2019 , approximately 19% of NPW were related to insurance policies written in New Jersey. We had a goodwill balance of $7.8 million at both December 31, 2019 and 2018 on our Consolidated Balance Sheet that relates to our Standard Commercial Lines reporting unit. The following summaries present revenues (net investment income and net realized and unrealized gains and losses on investments in the case of the Investments segment) and pre-tax income for the individual segments: Revenue by Segment Years ended December 31, ($ in thousands) 2019 2018 2017 Standard Commercial Lines: Net premiums earned: Commercial automobile $ 554,256 493,093 442,818 Workers compensation 311,370 317,616 317,982 General liability 669,895 616,187 569,217 Commercial property 353,834 329,660 311,932 Businessowners’ policies 105,252 103,412 100,266 Bonds 35,726 33,991 29,086 Other 19,281 18,263 17,198 Miscellaneous income 10,889 8,180 9,488 Total Standard Commercial Lines revenue 2,060,503 1,920,402 1,797,987 Standard Personal Lines: Net premiums earned: Personal automobile 172,606 168,250 153,147 Homeowners 127,543 128,961 129,699 Other 7,590 7,230 6,855 Miscellaneous income 1,466 1,257 1,228 Total Standard Personal Lines revenue 309,205 305,698 290,929 E&S Lines: Net premiums earned: Casualty lines 182,864 164,313 157,366 Property lines 56,954 55,253 55,461 Miscellaneous income — 1 — Total E&S Lines revenue 239,818 219,567 212,827 Investments: Net investment income 222,543 195,336 161,882 Net realized and unrealized investment gains (losses) 14,422 (54,923 ) 6,359 Total Investments revenues 236,965 140,413 168,241 Total revenues $ 2,846,491 2,586,080 2,469,984 Income Before and After Federal Income Tax Years ended December 31, ($ in thousands) 2019 2018 2017 Standard Commercial Lines: Underwriting gain, before federal income tax $ 145,990 109,104 149,514 Underwriting gain, after federal income tax 115,332 86,192 97,184 Combined ratio 92.9 % 94.3 % 91.6 % ROE contribution 5.8 % 4.9 6.1 Standard Personal Lines: Underwriting gain, before federal income tax 8,260 12,764 11,104 Underwriting gain, after federal income tax 6,525 10,084 7,217 Combined ratio 97.3 % 95.8 % 96.2 % ROE contribution 0.3 % 0.6 0.4 E&S Lines: Underwriting gain (loss), before federal income tax 9,743 (695 ) (6,282 ) Underwriting gain (loss), after federal income tax 7,697 (549 ) (4,083 ) Combined ratio 95.9 % 100.3 % 103.0 % ROE contribution 0.4 % — (0.3 ) Investments: Net investment income $ 222,543 195,336 161,882 Net realized and unrealized investment gains (losses) 14,422 (54,923 ) 6,359 Total investment segment income, before federal income tax 236,965 140,413 168,241 Tax on investment segment income 45,301 19,560 45,588 Total investment segment income, after federal income tax $ 191,664 120,853 122,653 ROE contribution of after-tax net investment income 9.6 % 6.9 7.5 Reconciliation of Segment Results to Income Before Federal Income Tax Years ended December 31, ($ in thousands) 2019 2018 2017 Underwriting gain (loss) Standard Commercial Lines $ 145,990 109,104 149,514 Standard Personal Lines 8,260 12,764 11,104 E&S Lines 9,743 (695 ) (6,282 ) Investment income 236,965 140,413 168,241 Total all segments 400,958 261,586 322,577 Interest expense (33,668 ) (24,419 ) (24,354 ) Corporate expenses (30,900 ) (25,446 ) (36,255 ) Income, before federal income tax $ 336,390 211,721 261,968

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2019
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"): 2019 Income Shares Per Share ($ in thousands, except per share amounts) (Numerator) (Denominator) Amount Basic EPS: Net income available to common stockholders $ 271,623 59,421 $ 4.57 Effect of dilutive securities: Stock compensation plans — 583 Diluted EPS: Net income available to common stockholders $ 271,623 60,004 $ 4.53 2018 Income Shares Per Share ($ in thousands, except per share amounts) (Numerator) (Denominator) Amount Basic EPS: Net income available to common stockholders $ 178,939 58,950 $ 3.04 Effect of dilutive securities: Stock compensation plans — 763 Diluted EPS: Net income available to common stockholders $ 178,939 59,713 $ 3.00 2017 Income Shares Per Share ($ in thousands, except per share amounts) (Numerator) (Denominator) Amount Basic EPS: Net income available to common stockholders $ 168,826 58,458 $ 2.89 Effect of dilutive securities: Stock compensation plans — 899 Diluted EPS: Net income available to common stockholders $ 168,826 59,357 $ 2.84

Federal Income Taxes

Federal Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Federal Income Taxes	Federal Income Taxes (a) On December 22, 2017, Tax Reform was signed into law, which among other implications, reduced our statutory corporate tax rate from 35% to 21% beginning with our 2018 tax year. We revalued our deferred tax inventory at December 31, 2017 to reflect this reduction, which resulted in a $20.2 million charge to income as illustrated in the rate table below. As of December 31, 2017, our accounting for the impact of Tax Reform on our deferred tax assets and liabilities was complete, with the exception of amounts related to loss reserve discounting. Prior to Tax Reform, we had elected to use our own loss reserve payment patterns for determining the factors to be used for calculating our discounted loss reserves for federal income tax purposes. Under Tax Reform, this election was eliminated and we are now required to use discount factors based on industry experience and a corporate bond yield curve, which the Internal Revenue Service ("IRS") had not finalized as of December 31, 2017. Considering this, at December 31, 2017, we calculated a pre-tax decrease to our discounted loss reserves of $35 million by using the industry experience approach under the tax law that existed prior to Tax Reform. This increased the deferred tax asset related to loss reserves by $7.5 million . A Tax Reform transition rule allows this change in accounting method to be amortized into expense over an eight-year period beginning in 2018. As a result, we established an offsetting deferred tax liability of $7.5 million as of December 31, 2017. In the fourth quarter of 2018, the IRS published the loss reserve discount factors to be used for calculating the beginning and ending 2018 discounted loss reserves under the industry experience approach. Based on these factors, we calculated a pre-tax decrease to our discounted loss reserves of $125 million , which resulted in a deferred tax asset of $26.3 million , an increase from the $7.5 million estimate described above. The $26.3 million adjustment was being taken into income over eight years, beginning with 2018, at approximately $3.3 million per year. In June 2019, the IRS published the final loss reserve discount factors to be used for calculating the beginning and ending 2018 discounted loss reserves under the industry experience approach. Based on these factors, we calculated a revised pre-tax decrease to our discounted loss reserves of $109.5 million , which resulted in a deferred tax asset of $23.0 million , a decrease from the $26.3 million estimate described above. The $23.0 million will be taken into income over eight years, beginning with the 2018 tax year, at approximately $2.9 million per year. (b) A reconciliation of federal income tax on income at the corporate rate to the effective tax rate is as follows: ($ in thousands) 2019 2018 2017 Tax at statutory rate (21% in 2019 and 2018 and 35% in 2017) $ 70,642 44,461 91,689 Tax-advantaged interest (4,909 ) (5,518 ) (11,510 ) Dividends received deduction (443 ) (647 ) (1,961 ) Executive compensation 2,985 2,279 — Stock-based compensation (3,253 ) (3,093 ) (4,281 ) Tax Reform deferred tax write off — — 20,205 Other 1 (255 ) (4,700 ) (1,000 ) Federal income tax expense $ 64,767 32,782 93,142 1 2018 includes approximately $3.8 million of capital loss carry back items to prior tax years at the previous 35% statutory tax rate. (c) The tax effects of the significant temporary differences that gave rise to deferred tax assets and liabilities were as follows: ($ in thousands) 2019 2018 Deferred tax assets: Net loss reserve discounting $ 48,193 43,285 Net unearned premiums 57,004 53,556 Employee benefits 10,646 8,862 Long-term incentive compensation plans 5,727 9,095 Temporary investment write-downs 1,059 1,155 Other 6,478 5,744 Total deferred tax assets 129,107 121,697 Deferred tax liabilities: Deferred policy acquisition costs 56,949 53,049 Unrealized gains on investment securities 45,294 502 Other investment-related items, net 7,576 4,904 Accelerated depreciation and amortization 12,512 9,702 Total deferred tax liabilities 122,331 68,157 Net deferred federal income tax asset $ 6,776 53,540 Net deferred income tax assets decreased by $46.8 million in 2019, primarily driven by a $44.8 million increase in gross deferred tax liabilities as reduced interest rates increased unrealized gains on our fixed income securities portfolio. 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 had no valuation allowance recognized for federal deferred tax assets at December 31, 2019 or 2018 . We do not have unrecognized tax expense or benefit as of December 31, 2019 . We have analyzed our tax positions in all open tax years, which as of December 31, 2019 were 2016 through 2018 . The 2018 tax year is currently under audit. We do not expect any material adjustments to arise out of the 2018 audit.

Retirement Plans

Retirement Plans	12 Months Ended
	Dec. 31, 2019
Retirement Benefits [Abstract]
Retirement Plans	Retirement Plans (a) Selective Insurance Retirement Savings Plan (“Retirement Savings Plan”) SICA offers a voluntary defined contribution 401(k) plan that is available to most of our employees and is a tax-qualified retirement plan subject to ERISA. Expense recorded for this plan was $17.0 million in 2019 , and $15.8 million in both 2018 and 2017 . (b) Deferred Compensation Plan SICA offers a non-qualified deferred compensation plan, the Selective Insurance Company of America 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 2019 , $0.4 million in 2018 , and $0.2 million in 2017 . (c) Retirement Income Plan and Retirement Life Plan SICA maintains a defined benefit pension plan, the Retirement Income Plan for Selective Insurance Company of America (the "Pension Plan"). This qualified, noncontributory 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, 2019 and December 31, 2018 of $10.9 million and $9.5 million , respectively, for the Excess Plan and $6.6 million and $5.8 million , respectively, for the Retirement Life Plan. Expense recorded for the Excess Plan was $0.4 million in each of 2019 , 2018 , and 2017 . Expense recorded for the Retirement Life Plan was $0.3 million in each of 2019 , 2018 , and 2017 . The following tables provide details on the Pension Plan for 2019 and 2018 : December 31, Pension Plan ($ in thousands) 2019 2018 Change in Benefit Obligation: Benefit obligation, beginning of year $ 334,679 364,411 Interest cost 13,506 12,428 Actuarial losses (gains) 54,478 (31,738 ) Benefits paid (11,642 ) (10,422 ) Benefit obligation, end of year $ 391,021 334,679 Change in Fair Value of Assets: Fair value of assets, beginning of year $ 331,680 363,673 Actual return on plan assets, net of expenses 63,949 (21,571 ) Contributions by the employer to funded plans 1,100 — Benefits paid (11,642 ) (10,422 ) Fair value of assets, end of year $ 385,087 331,680 Funded status $ (5,934 ) (2,999 ) Amounts Recognized in the Consolidated Balance Sheet: Liabilities $ (5,934 ) (2,999 ) Net pension liability, end of year $ (5,934 ) (2,999 ) Amounts Recognized in AOCI: Net actuarial loss $ 107,125 98,057 Total $ 107,125 98,057 Other Information as of December 31: Accumulated benefit obligation $ 391,021 334,679 Weighted-Average Liability Assumptions as of December 31: Discount rate 3.33 % 4.46 Pension Plan ($ in thousands) 2019 2018 2017 Components of Net Periodic Benefit Cost and Other Amounts Recognized in Other Comprehensive Income: Net Periodic Benefit Cost (Benefit): Interest cost $ 13,506 12,428 12,490 Expected return on plan assets (21,114 ) (22,767 ) (19,419 ) Amortization of unrecognized actuarial loss 2,575 1,981 2,001 Total net periodic pension cost (benefit) 1 $ (5,033 ) (8,358 ) (4,928 ) Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income: Net actuarial loss (gain) $ 11,643 12,600 3,594 Reversal of amortization of net actuarial loss (2,575 ) (1,981 ) (2,001 ) Total recognized in other comprehensive income $ 9,068 10,619 1,593 Total recognized in net periodic benefit cost and other comprehensive income $ 4,035 2,261 (3,335 ) 1 The components of net periodic pension cost (benefit) are included within "Loss and loss expense incurred" and "Other insurance expenses" on the Consolidated Statements of Income. Pension Plan 2019 2018 2017 Weighted-Average Expense Assumptions for the years ended December 31: Discount rate 4.46 % 3.78 4.41 Expected return on plan assets 6.50 6.36 6.24 Our latest measurement date was December 31, 2019 , at which time we decreased our expected return on plan assets to 5.80% , due to lower expected returns within our longer-dated fixed income portfolio, as interest rates and credit spreads declined significantly year-over-year. 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. The approach we utilize discounts the individual expected cash flows using the applicable spot rates derived from the yield curve over the projected cash flow period. Our discount rate decreased 113 basis points, to 3.33% , as of December 31, 2019 , compared to 4.46% as of December 31, 2018 , which resulted in a significant increase in the actuarial loss driving the increase in the benefit obligation for the period. The weighted average discount rate used to determine 2020 interest cost is 2.95% . Pension Plan Assets Assets of the Pension Plan are invested to adequately support the liability associated with the Pension Plan's defined benefit obligation. 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 2020, 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. Over time, the target and actual asset allocations may change based on the funded status of the Pension Plan and market return expectations. The Pension Plan’s target ranges, as well as the actual weighted average asset allocation by strategy, at December 31 were as follows: 2019 2018 Target Percentage Actual Percentage Actual Percentage Return seeking assets 1 15%-70% 59 % 43 % Liability hedging assets 35%-75% 38 % 38 % Short-term investments - 3 % 19 % Total 100 % 100 % 100 % 1 Includes limited partnerships. The use of derivative instruments is permitted under certain circumstances for the Pension Plan portfolio, but may not be used for unrelated speculative purposes or to create exposures that are not permitted in the Pension Plan's investment guidelines. Within the liability hedging assets, derivatives may be used to mitigate interest rate risk and reduce the interest duration mismatch between assets and liabilities of the Pension Plan to help insulate the funded status of the plan. We currently invest in a U.S. Treasury overlay derivative strategy, within the funds in our liability hedging assets, to manage the interest rate duration mismatch between the assets and liabilities of the Pension Plan. Considering the impact of this derivative overlay, the liability hedging assets provide for an approximate 57% hedge against the projected benefit obligation. The Pension Plan had no investments in the Parent’s common stock as of December 31, 2019 or 2018 . For information regarding investments in funds of our related parties, refer to Note 16. "Related Party Transactions" below. The techniques used to determine the fair value of the Pension Plan's invested assets that appear on the following page are as follows: • The investments in the equities and liability hedging funds include collective investment funds and fund of funds that utilize a market approach wherein the published prices in the active market for identical assets are used. These investments are traded at their net asset value per share. These investments are classified as Level 1 in the fair value hierarchy. • The investments in private limited partnerships and other private equity securities are valued utilizing net asset value as a practical expedient for fair value. These investments are not classified in the fair value hierarchy. • Short-term investments are recorded 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 recorded 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. 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 secondary private equity and direct lending strategies as these investments are currently not part of the Pension Plan's investment portfolio. 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, 2019 Fair Value Measurements at 12/31/19 Using ($ in thousands) Assets Measured at Fair Value At 12/31/19 Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Description Return seeking assets: Equities: Global Equity $ 113,212 113,212 — — Diversified Credit 59,009 59,009 — — Real Assets 57,414 57,414 — — Total Equities 229,635 229,635 — — Limited partnerships (at net asset value) 1 : Real assets 228 — — — Private equity 583 — — — Private credit 43 — — — Total limited partnerships 854 — — — Total return seeking assets 230,489 229,635 — — Liability hedging assets: Fixed income 114,395 114,395 — — U.S. Treasury overlay 30,997 30,997 — — Total liability hedging assets 145,392 145,392 — — Cash and short-term investments: Short-term investments 8,824 8,824 — — Deposit administration contracts 2,215 — 2,215 — Total cash and short-term investments 11,039 8,824 2,215 — Total invested assets $ 386,920 383,851 2,215 — December 31, 2018 Fair Value Measurements at 12/31/18 Using ($ in thousands) Assets Measured at Fair Value At 12/31/18 Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Description Return seeking assets: Global Equity $ 113,409 113,409 — — Private assets 1 : Limited partnerships (at net asset value): Real assets 16,818 — — — Private equity 878 — — — Private credit 262 — — — Hedge fund 7,889 — — — Total limited partnerships 25,847 — — — Other private assets 3,780 — — — Total private assets 29,627 — — — Total return seeking assets 143,036 113,409 — — Liability hedging assets: Fixed income 106,000 106,000 — — U.S. Treasury overlay 18,528 18,528 — — Total liability hedging assets 124,528 124,528 — — Cash and short-term investments: Short-term investments 62,788 62,788 — — Deposit administration contracts 1,482 — 1,482 — Total cash and short-term investments 64,270 62,788 1,482 — Total invested assets $ 331,834 300,725 1,482 — 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 2020 , as we have no minimum required contribution amounts. Benefit Payments ($ in thousands) Pension Plan Benefits Expected to be Paid in Future Fiscal Years: 2020 $ 14,968 2021 14,947 2022 16,115 2023 17,144 2024 18,146 2025-2029 103,669

Share-Based Payments

Share-Based Payments	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Share-based Payment Arrangement [Text Block]	Share-Based Payments Active Plans As of December 31, 2019 , the following four plans were available for the issuance of share-based payment awards: • The 2014 Omnibus Stock Plan, As Amended and Restated Effective as of May 2, 2018 (the "Stock Plan"); • The Cash Incentive Plan, As Amended and Restated 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 (2010), Amended and Restated as of February 1, 2017 (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. Most recently amended and restated plan was approved effective May 2, 2018 by stockholders on May 2, 2018. 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 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, 2019 are as follows: As of December 31, 2019 Authorized Available for Issuance Awards Outstanding Stock Plan 4,750,000 3,208,968 760,639 ESPP 1,500,000 356,229 — Agent Plan 3,000,000 1,728,471 — 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, 2019 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. 1,985,129 59,729 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. 44,468 44,468 1 Awards outstanding under the 2005 Stock Plan consisted of 32,906 shares deferred by our non-employee directors and 26,823 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, 2018 846,305 $ 44.00 Granted in 2019 265,680 63.60 Vested in 2019 (337,525 ) 36.08 Forfeited in 2019 (27,735 ) 51.89 Unvested RSU awards at December 31, 2019 746,725 $ 53.48 As of December 31, 2019 , total unrecognized compensation expense related to unvested RSU awards granted under our Stock Plan was $8.9 million . That expense is expected to be recognized over a weighted-average period of 1.7 years . The total intrinsic value of RSUs vested was $22.0 million for 2019 , $18.0 million for 2018 , and $16.0 million for 2017 . In connection with vested RSUs, the total value of the DEUs that vested was $0.8 million in 2019 and 2018 , and $0.9 million in 2017 . Option Transactions A summary of the stock option transactions under our 2005 Stock Plan is as follows: Number Weighted Weighted Aggregate Outstanding at December 31, 2018 126,735 $ 14.37 Granted in 2019 — — Exercised in 2019 (99,912 ) 13.74 Forfeited or expired in 2019 — — Outstanding at December 31, 2019 26,823 $ 16.71 0.33 $ 1,300 Exercisable at December 31, 2019 26,823 $ 16.71 0.33 $ 1,300 The total intrinsic value of options exercised was $5.2 million in 2019 , $4.5 million in 2018 , and $4.0 million in 2017 . CIU Transactions The liability recorded in connection with our Cash Plan was $8.6 million at December 31, 2019 and $21.6 million at December 31, 2018 . The decrease of $13 million in the liability recorded is primarily due to the structural changes we made to our Cash Plan in early 2017. The remaining cost associated with the CIUs is expected to be recognized over a weighted average period of 1.1 years . The CIU payments made were $18.4 million in 2019 , $20.2 million in 2018 , and $14.2 million in 2017 . ESPP and Agent Plan Transactions A summary of ESPP and Agent Plan share issuances is as follows: 2019 2018 2017 ESPP Issuances 72,952 70,448 75,093 Agent Plan Issuances 47,888 41,134 49,794 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 2019 2018 2017 Risk-free interest rate 2.33 % 1.88 1.07 Expected term 6 months 6 months 6 months Dividend yield 1.2 % 1.3 1.3 Expected volatility 26 % 18 24 The weighted-average fair value of options and stock per share, including RSUs granted under the Parent's stock plans, during 2019 , 2018 , and 2017 was as follows: 2019 2018 2017 RSUs $ 63.60 55.96 42.66 ESPP: Six month option 4.32 2.67 2.73 Discount of grant date market value 9.99 8.50 7.06 Total ESPP 14.31 11.17 9.79 Agent Plan: Discount of grant date market value 7.00 5.99 5.04 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 CIU agreements established under the Cash Plan, is adjusted to reflect our performance on specified indicators compared to targeted peer companies. Expense Recognition The following table provides share-based compensation expense in 2019 , 2018 , and 2017 : ($ in millions) 2019 2018 2017 Share-based compensation expense, pre-tax $ 24.5 19.3 31.2 Income tax benefit, including the benefit related to stock grants that vested during the year (8.2 ) (7.0 ) (15.0 ) Share-based compensation expense, after-tax $ 16.3 12.3 16.2

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2019
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, which includes the right to participate in the Agent Plan. Mr. Rue’s son is President, and an employee, of Rue Insurance, and owns more than 10% of the equity of Rue Insurance. 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 $11.0 million in 2019 , $10.1 million in 2018 , and $11.1 million in 2017 . In return, the Insurance Subsidiaries paid standard market commissions, including supplemental commissions, to Rue Insurance of $2.0 million in 2019 , $2.1 million in 2018 , and $2.3 million in 2017 . Amounts due to Rue Insurance at December 31, 2019 and December 31, 2018 were $0.3 million and $0.4 million , respectively. All contracts and transactions with Rue Insurance were consummated in the ordinary course of business on an arm's-length basis. 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 $1.3 million of contributions to the Foundation in 2019 , $0.5 million in 2018 , and no contributions in 2017 . BlackRock, Inc., a leading publicly-traded investment management firm (“BlackRock”), has purchased our common shares in the ordinary course of its investment business and has previously filed Schedules 13G/A with the SEC. On February 4, 2020 , BlackRock filed a Schedule 13G/A reporting beneficial ownership as of December 31, 2019 , of 11.7% of our common stock. In connection with purchasing our common shares, BlackRock filed the necessary filings with insurance regulatory authorities. On the basis of those filings, BlackRock is deemed not to be a controlling person for the purposes of applicable insurance law. We are required to disclose related party information for our transactions with BlackRock. BlackRock is highly regulated, serves its clients as a fiduciary, and has a diverse platform of active (alpha) and index (beta) investment strategies across asset classes that enables it to tailor investment outcomes and asset allocation solutions for clients. BlackRock also offers the BlackRock Solutions ® investment and risk management technology platform, Aladdin ® , risk analytics, advisory, and technology services and solutions to a broad base of institutional and wealth management investors. We incurred expenses related to BlackRock for services rendered of $2.2 million in 2019 , and $2.0 million in both 2018 and 2017 . Amounts payable for such services at December 31, 2019 and December 31, 2018 , were $1.1 million and $1.0 million , respectively. As part of our overall investment diversification, we invest in various BlackRock funds from time to time. These funds accounted for less than 1% of our invested assets at December 31, 2019 and December 31, 2018, and are predominately reflected in Equity securities on our Consolidated Balance Sheet. During 2019 , with regard to BlackRock funds, we (i) purchased $21.7 million , (ii) sold $59.5 million , (iii) recognized a $5.7 million net realized and unrealized gain, and (iv) recorded $0.8 million in income. During 2018 , we purchased $41.4 million in securities and recognized net realized and unrealized losses of $3.6 million . There were no material transactions related to these holdings in 2017 . There were no amounts payable on the settlement of these investment transactions at December 31, 2019 , December 31, 2018 , or December 31, 2017 . Our Pension Plan's investment portfolio contained investments in BlackRock funds of $144.2 million at December 31, 2019 and $131.9 million at December 31, 2018 . During 2019, with regard to BlackRock funds, the Pension Plan (i) purchased $19.7 million , (ii) sold $44.1 million , and (iii) recorded net investment income of $36.7 million . In 2018, with regard to BlackRock funds, the Pension Plan (i) purchased $132.5 million , (ii) sold $125.6 million , and (iii) recorded net investment income of $9.3 million . In 2017, with regard to BlackRock funds, the Pension Plan (i) purchased $10.0 million , (ii) sold $4.1 million , and (iii) recorded net investment income of $25.2 million . In addition, our Deferred Compensation Plan and Retirement Savings Plan may offer our employees the option to invest in various BlackRock funds. All contracts and transactions with BlackRock were consummated in the ordinary course of business on an arm's-length basis. As of December 31, 2019 , the Vanguard Group ("Vanguard") held 9.4% of our common stock. Vanguard is one of the world's largest investment management companies, offering low cost mutual funds, exchange-trade funds ("ETFs"), and other investment related services. On January 10, 2019 , Vanguard filed a Schedule 13G/A reporting beneficial ownership as of December 31, 2018 , of 10.1% of our common stock. In connection with purchasing our common shares in the prior year, Vanguard filed the necessary filings with insurance regulatory authorities to disclaim control and we do not expect Vanguard to be deemed a controlling person by any insurance regulator. As part of our overall investment diversification, we may invest in various Vanguard funds from time to time. As of December 31, 2019 , we had no investments in Vanguard funds, and our investment in these funds at December 31, 2018 was less than 1% of invested assets at that time and was recorded within Equity securities on our Consolidated Balance Sheet. During 2019 , we sold $11.8 million of a Vanguard ETF, recorded dividend income of $0.2 million and recorded capital gains of $1.3 million from such ETF, with no amounts receivable on the settlement of this transaction at December 31, 2019 . During 2018 , we purchased $11.5 million of a Vanguard ETF and recorded dividend income of $0.4 million from such ETF, with no amounts payable on the settlement of this transaction at December 31, 2018 . We had no transactions with Vanguard in 2017 . Our Pension Plan's investment portfolio contained no investments in Vanguard funds at December 31, 2019 and December 31, 2018 . Our Pension Plan's investment portfolio contained investments in Vanguard funds of $86.3 million in 2017 . The Pension Plan had no transactions with Vanguard in 2019 . During 2018 and 2017 , the Pension Plan purchased $8.4 million and $5.2 million of Vanguard funds, respectively. In 2018 , the Pension Plan sold $85.4 million of Vanguard funds. The Pension Plan recorded a net investment loss on Vanguard funds of $5.5 million in 2018 , and net investment income of $9.1 million in 2017 . In addition, our Deferred Compensation Plan and Retirement Savings Plan may offer our employees the option to invest in various Vanguard funds. All transactions with Vanguard are consummated in the ordinary course of business on an arm's-length basis.

Leases (Notes)

Leases (Notes)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Lessee Disclosure [Text Block]	Leases We have various operating leases for office space, equipment, and fleet vehicles. In addition, we have various finance leases for computer hardware. Such lease agreements, which expire at various dates through 2030, are generally renewed or replaced by similar leases. Upon adoption of ASU 2016-02 on January 1, 2019, we recorded operating lease right-of-use assets of $20.7 million with related lease liabilities of $21.0 million . The differential of $0.3 million was recognized, on an after-tax basis, as a cumulative-effect adjustment to the opening balance of retained earnings as of January 1, 2019. Financing lease right-of-use assets and the related lease liabilities were $0.9 million as of January 1, 2019. See Note 2. "Summary of Significant Accounting Policies" and Note 3. "Adoption of Accounting Pronouncements" in this Form 10-K for additional information regarding our accounting policy on leases and ASU 2016-02, respectively. The components of lease expense for the year ended December 31, 2019 were as follows: ($ in thousands) 2019 Operating lease cost, included in Other insurance expenses on the Consolidated Statements of Income $ 8,808 Finance lease cost: Amortization of assets, included in Other insurance expenses on the Consolidated Statements of Income 984 Interest on lease liabilities, included in Interest expense on the Consolidated Statements of Income 16 Total finance lease cost 1,000 Variable lease cost, included in Other insurance expenses on the Consolidated Statements of Income 48 Short-term lease cost, included in Other insurance expenses on the Consolidated Statements of Income $ 2,165 The following table provides supplemental information regarding our operating and finance leases. December 31, 2019 Weighted-average remaining lease term Operating leases 6 years Finance leases 2 Weighted-average discount rate Operating leases 3.4 % Finance leases 1 2.1 1 Prior to adoption of ASU 2016-02, our historical capital lease liabilities and assets were measured using an un-discounted cash flow stream due to immateriality of the capital lease population. Operating and finance lease asset and liability balances are included within the following line items on the Consolidated Balance Sheets: ($ in thousands) December 31, 2019 Operating leases Other assets $ 26,535 Other liabilities 27,506 Finance leases Property and equipment - at cost, net of accumulated depreciation and amortization 731 Long-term debt $ 737 At December 31, 2019 , the maturities of our lease liabilities were as follows: ($ in thousands) Finance Leases Operating Leases Total Year ended December 31, 2020 $ 451 8,244 8,695 2021 248 6,168 6,416 2022 54 4,590 4,644 2023 — 3,329 3,329 2024 — 2,920 2,920 Thereafter — 8,638 8,638 Total lease payments 753 33,889 34,642 Less: imputed interest 16 2,995 3,011 Less: leases that have not yet commenced — 3,388 3,388 Total lease liabilities $ 737 27,506 28,243 At December 31, 2018 , the maturities of our lease liabilities for capital and operating leases were as follows: ($ in thousands) Capital Leases Operating Leases Total 2019 $ 728 7,762 8,490 2020 141 7,355 7,496 2021 22 5,083 5,105 2022 — 3,641 3,641 2023 — 2,900 2,900 Thereafter — 9,698 9,698 Total minimum payment required $ 891 36,439 37,330 Refer to Note. 4 "Statements of Cash Flows" in this Form 10-K for supplemental cash and non-cash transactions included in the measurement of operating and finance lease liabilities.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
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, 2019 , we had purchased such annuities with a present value of $25.5 million for settlement of claims on a structured basis for which we are contingently liable. To our knowledge, there are no material defaults from any of the issuers of such annuities. (b) As of December 31, 2019 , we have made commitments that may require us to invest additional amounts into our investment portfolio, which are as follows: ($ in millions) Amount of Obligation Year of Expiration of Obligation Alternative and other investments $ 219.2 2036 Non-publicly traded collateralized loan obligations in our fixed income securities portfolio 35.4 2030 Non-publicly traded common stock within our equity portfolio 3.9 2023 Commercial mortgage loans 10.0 Less than 1 year Privately-placed corporate securities 15.0 Less than 1 year Total $ 283.5 There is no certainty that any such additional investment will be required. We expect to have the capacity to repay or refinance these obligations as they come due.

Litigation

Litigation	12 Months Ended
	Dec. 31, 2019
Loss Contingency, Information about Litigation Matters [Abstract]
Litigation	Litigation As of December 31, 2019 , we do not believe we are involved in any legal action that could have a material adverse effect on our consolidated financial condition, results of operations, or cash flows. In the ordinary course of conducting business, we are parties in various legal actions. Most are claims litigation involving our Insurance Subsidiaries as either: (i) liability insurers defending or providing indemnity for third-party claims brought against our customers; (ii) insurers defending first-party coverage claims brought against them; or (iii) liability insurers seeking declaratory judgment on our insurance coverage obligations. We account for such activity through the establishment of unpaid loss and loss expense reserves. In ordinary course claims litigation, we expect that any potential ultimate liability, after consideration of provisions made for potential losses and costs of defense, will not be material to our consolidated financial condition, results of operations, or cash flows. From time to time, our Insurance Subsidiaries also are named as defendants in other legal actions, some of which assert claims for substantial amounts. Plaintiffs may style these actions as putative class actions and seek judicial certification of a state or national class for allegations involving our business practices, such as improper reimbursement of medical providers paid under workers compensation and personal and commercial automobile insurance policies or improper reimbursement for automobile parts. Similarly, our Insurance Subsidiaries can be named in individual actions seeking extra-contractual damages, punitive damages, or penalties, often alleging bad faith in the handling of insurance claims. We believe that we have valid defenses to these allegations and we account for such activity through the establishment of unpaid loss and loss expense reserves. In these other legal actions, we expect that any potential ultimate liability, after consideration of provisions made for estimated losses, will not be material to our consolidated financial condition. Nonetheless, litigation outcomes are inherently unpredictable and, because the amounts sought in certain of these actions are large or indeterminate, it is possible that any adverse outcomes could have a material adverse effect on our consolidated results of operations or cash flows in particular quarterly or annual periods.

Statutory Financial Information

Statutory Financial Information, Capital Requirements, and Restrictions on Dividends and Transfers of Funds	12 Months Ended
	Dec. 31, 2019
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 affect the determination of statutory surplus, statutory net income, or risk-based capital (“RBC”). As of December 31, 2019 , the various state insurance departments of domicile have adopted the March 2019 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) 2019 2018 2019 2018 2019 2018 2017 SICA New Jersey $ 525.9 478.6 680.1 632.8 113.9 78.0 84.6 Selective Way Insurance Company ("SWIC") New Jersey 339.2 300.2 388.2 349.3 59.2 47.5 43.6 SICSC Indiana 132.6 119.4 163.8 150.7 23.9 16.5 17.9 SICSE Indiana 103.1 92.2 128.7 117.7 18.5 12.9 14.7 SICNY New York 99.4 86.5 127.1 114.2 17.0 12.0 13.4 Selective Insurance Company of New England ("SICNE") New Jersey 25.3 19.9 55.4 50.0 7.8 5.6 6.3 Selective Auto Insurance Company of New Jersey ("SAICNJ") New Jersey 62.5 50.3 105.4 93.2 14.9 9.9 11.4 MUSIC New Jersey 27.1 23.0 95.6 91.5 13.2 9.4 10.3 Selective Casualty Insurance Company ("SCIC") New Jersey 58.2 44.9 132.7 119.3 16.8 13.3 13.4 Selective Fire and Casualty Insurance Company ("SFCIC") New Jersey 23.5 17.8 55.4 49.7 7.5 5.5 5.6 Total $ 1,396.8 1,232.8 1,932.4 1,768.4 292.7 210.6 221.2 (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 2019 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. In addition to regulatory restrictions on the availability of dividends that our Insurance Subsidiaries can pay to the Parent, the maximum amount of dividends the Parent can pay our shareholders is limited by certain New Jersey corporate law provisions that limit dividends if either: (i) the Parent would be unable to pay its debts as they became due in the usual course of business; or (ii) the Parent’s total assets would be less than its total liabilities. The Parent’s ability to pay dividends to shareholders also are impacted by covenants in its Line of Credit agreement that obligate it, among other things, to maintain a minimum consolidated net worth and a maximum ratio of consolidated debt to total capitalization. As of December 31, 2019 , the Parent had an aggregate of $278.0 million in investments and cash available to fund future dividends and interest payments. These amounts are not subject to any regulatory restrictions other than the standard state insolvency restrictions noted above, whereas our consolidated retained earnings of $2.1 billion is predominately restricted due to the regulation associated with our Insurance Subsidiaries. In 2020 , the Insurance Subsidiaries have the ability to provide for $266.7 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 $89.4 million as of December 31, 2019 , based on restrictions in these agreements that limit borrowings to 10% of the admitted assets of the Indiana Subsidiaries. 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 laws 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 is consistent with New Jersey's, except that it does not exclude capital gains from net income. 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 table below provides the following information: (i) quantitative data regarding all Insurance Subsidiaries' dividends paid to the Parent in 2019 for debt service, shareholder dividends, and general operating purposes; and (ii) the maximum ordinary dividends that can be paid to the Parent by the Insurance Subsidiaries in 2020 , based on the 2019 statutory financial statements. Dividends Twelve Months ended December 31, 2019 2020 ($ in millions) State of Domicile Ordinary Dividends Paid Maximum Ordinary Dividends SICA New Jersey $ 55.5 $ 98.4 SWIC New Jersey 19.0 53.7 SICSC Indiana 9.5 23.9 SICSE Indiana 6.7 18.6 SICNY New York 3.3 12.7 SICNE New Jersey 2.0 7.6 SAICNJ New Jersey 1.5 14.7 MUSIC New Jersey 8.0 12.9 SCIC New Jersey 3.0 16.8 SFCIC New Jersey 1.5 7.4 Total $ 110.0 $ 266.7

Quarterly Financial Information

Quarterly Financial Information	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	Quarterly Financial Information First Quarter Second Quarter Third Quarter Fourth Quarter (unaudited, $ in thousands, except per share data) 2019 2018 2019 2018 2019 2018 2019 2018 Net premiums earned $ 632,573 591,828 642,619 604,836 653,620 614,277 668,359 625,288 Net investment income earned 50,618 43,231 58,505 45,553 55,826 52,443 57,594 54,109 Net realized and unrealized gains (losses) 13,451 (10,549 ) 4,027 (1,652 ) (2,183 ) (4,787 ) (873 ) (37,935 ) Other income 2,320 2,179 3,053 3,179 3,162 2,538 3,820 1,542 Total revenues 698,962 626,689 708,204 651,916 710,425 664,471 728,900 643,004 Income before federal income taxes 73,694 19,931 90,225 72,525 71,178 67,130 101,293 52,135 Net income 61,348 18,925 72,266 58,819 56,150 55,435 81,859 45,760 Net income per share: Basic 1.04 0.32 1.22 1.00 0.94 0.94 1.38 0.77 Diluted 1.02 0.32 1.21 0.99 0.93 0.93 1.36 0.76 The addition of all quarters may not agree to annual amounts on the Financial Statements due to rounding.

Schedule I - Summary of Investm

Schedule I - Summary of Investments - Other Than Investments in Related Parties	12 Months Ended
	Dec. 31, 2019
SEC Schedule, 12-15, Insurance Companies, 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 $ 4,573 4,921 4,580 Public utilities 3,608 3,967 3,673 All other corporate securities 12,588 13,087 12,547 Total fixed income securities, held-to-maturity 20,769 21,975 20,800 Available-for-sale: U.S. government and government agencies 112,680 116,186 116,186 Foreign government 18,011 18,542 18,542 Obligations of states and political subdivisions 1,168,185 1,230,090 1,230,090 Public utilities 35,679 37,084 37,084 All other corporate securities 1,831,202 1,910,393 1,910,393 Collateralized loan obligation securities and other asset-backed securities 790,517 793,012 793,012 Commercial mortgage-backed securities 514,709 538,344 538,344 Residential mortgage-backed securities 1,409,003 1,451,969 1,451,969 Total fixed income securities, available-for-sale 5,879,986 6,095,620 6,095,620 Equity securities: Common stock: Banks, trusts and insurance companies 17,357 17,368 17,368 Industrial, miscellaneous and all other 51,815 52,532 52,532 Nonredeemable preferred stock 2,889 3,037 3,037 Total equity securities 72,061 72,937 72,937 Short-term investments 282,490 282,490 282,490 Other investments 216,807 216,807 Total investments $ 6,472,113 6,688,654 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, 2019
Condensed Financial Information 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) 2019 2018 Assets: Fixed income securities, available-for-sale – at fair value (amortized cost: $233,753 – 2019; $111,208 – 2018) $ 241,526 110,098 Short-term investments 36,219 35,358 Cash 300 505 Investment in subsidiaries 2,416,209 2,057,218 Current federal income tax 16,116 14,161 Deferred federal income tax 4,875 10,346 Other assets 1,692 1,186 Total assets $ 2,716,937 2,228,872 Liabilities: Long-term debt $ 439,860 329,540 Intercompany notes payable 61,163 77,517 Accrued long-term stock compensation 8,604 21,574 Other liabilities 12,374 8,439 Total liabilities $ 522,001 437,070 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: 103,484,159 – 2019; 102,848,394 – 2018 206,968 205,697 Additional paid-in capital 418,521 390,315 Retained earnings 2,080,529 1,858,414 Accumulated other comprehensive income (loss) 81,750 (77,956 ) Treasury stock – at cost (shares: 44,023,006 – 2019; 43,899,840 – 2018) (592,832 ) (584,668 ) Total stockholders’ equity 2,194,936 1,791,802 Total liabilities and stockholders’ equity $ 2,716,937 2,228,872 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) 2019 2018 2017 Revenues: Dividends from subsidiaries $ 110,004 100,060 80,096 Net investment income earned 7,301 3,425 2,044 Net realized gains (losses) 207 (1,567 ) (15 ) Total revenues 117,512 101,918 82,125 Expenses: Interest expense 33,426 24,652 24,721 Other expenses 30,900 25,446 36,251 Total expenses 64,326 50,098 60,972 Income before federal income tax 53,186 51,820 21,153 Federal income tax (benefit) expense: Current (16,080 ) (14,173 ) (22,187 ) Deferred 3,606 3,141 6,311 Total federal income tax benefit (12,474 ) (11,032 ) (15,876 ) Net income before equity in undistributed income of subsidiaries 65,660 62,852 37,029 Equity in undistributed income of subsidiaries, net of tax 205,963 116,087 131,797 Net income $ 271,623 178,939 168,826 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) 2019 2018 2017 Operating Activities: Net income $ 271,623 178,939 168,826 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed income of subsidiaries, net of tax (205,963 ) (116,087 ) (131,797 ) Stock-based compensation expense 19,077 14,507 12,089 Net realized (gains) losses (207 ) 1,567 15 Amortization – other 4,614 567 678 Changes in assets and liabilities: (Decrease) increase in accrued long-term stock compensation (12,970 ) (15,443 ) 4,988 Decrease in net federal income taxes 1,651 11,246 3,811 Increase in other assets (533 ) (343 ) (60 ) Increase in other liabilities 3,919 1,712 714 Net cash provided by operating activities 81,211 76,665 59,264 Investing Activities: Purchase of fixed income securities, available-for-sale (153,482 ) (75,046 ) (58,832 ) Redemption and maturities of fixed income securities, available-for-sale 10,579 6,849 10,465 Sale of fixed income securities, available-for-sale 20,189 45,099 31,819 Purchase of equity securities (10,824 ) — — Sale of equity securities 10,828 — — Purchase of short-term investments (1,116,766 ) (207,115 ) (185,590 ) Sale of short-term investments 1,116,253 195,846 179,292 Net cash used in investing activities (123,223 ) (34,367 ) (22,846 ) Financing Activities: Dividends to stockholders (47,675 ) (42,097 ) (37,045 ) Acquisition of treasury stock (8,164 ) (6,556 ) (6,015 ) Proceeds from issuance of notes payable, net of debt issuance costs 290,757 — — Principal payment on notes payable (185,000 ) — — Net proceeds from stock purchase and compensation plans 8,243 7,252 7,599 Principal payment on borrowings from subsidiaries (16,354 ) (926 ) (881 ) Net cash provided by (used in) financing activities 41,807 (42,327 ) (36,342 ) Net (decrease) increase in cash (205 ) (29 ) 76 Cash, beginning of year 505 534 458 Cash, end of year $ 300 505 534 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, 2019
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Abstract]
Schedule III- Supplementary Insurance Information	($ in thousands) Deferred policy acquisition costs Reserve for loss and loss expense Unearned premiums Net premiums earned Net investment income 1 Loss and loss expense incurred Amortization of deferred policy acquisition costs Other operating expenses 2 Net premiums written Standard Commercial Lines Segment $ 226,464 3,436,363 1,108,009 2,049,614 — 1,187,856 445,661 270,107 2,137,071 Standard Personal Lines Segment 16,848 224,200 309,125 307,739 — 211,300 34,477 53,702 304,592 E&S Lines Segment 27,874 406,600 106,033 239,818 — 152,335 55,835 21,905 237,761 Investments Segment — — — — 236,965 — — — — Total $ 271,186 4,067,163 1,523,167 2,597,171 236,965 1,551,491 535,973 345,714 2,679,424 1 Includes “Net investment income earned” and “Total net realized and unrealized gains (losses)” on the Consolidated Statements of Income. 2 “Other operating expenses” of $345,714 reconciles to the Consolidated Statements of Income as follows: Other insurance expenses $ 358,069 Other income (12,355 ) Total $ 345,714 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, 2018 ($ in thousands) Deferred policy acquisition costs Reserve for loss and loss expense Unearned premiums Net premiums earned Net investment income 1 Loss and loss expense incurred Amortization of deferred policy acquisition costs Other operating expenses 2 Net premiums written Standard Commercial Lines Segment $ 206,391 3,283,531 1,020,054 1,912,222 — 1,141,038 412,420 249,660 1,975,683 Standard Personal Lines Segment 18,070 223,223 304,085 304,441 — 206,752 33,617 51,308 309,277 E&S Lines Segment 28,151 387,114 107,793 219,566 — 150,344 49,005 20,912 229,326 Investments Segment — — — — 140,413 — — — — Total $ 252,612 3,893,868 1,431,932 2,436,229 140,413 1,498,134 495,042 321,880 2,514,286 1 Includes “Net investment income earned” and “Total net realized and unrealized gains (losses)” on the Consolidated Statements of Income. 2 “Other operating expenses” of $321,880 reconciles to the Consolidated Statements of Income as follows: Other insurance expenses $ 331,318 Other income (9,438 ) Total $ 321,880 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, 2017 ($ in thousands) Deferred policy acquisition costs Reserve for loss and loss expense Unearned premiums Net premiums earned Net investment income 1 Loss and loss expense incurred Amortization of deferred policy acquisition costs Other operating expenses 2 Net premiums written Standard Commercial Lines Segment $ 193,408 3,165,217 956,173 1,788,499 — 1,008,150 387,552 243,283 1,858,735 Standard Personal Lines Segment 16,952 263,166 295,435 289,701 — 189,294 32,542 56,761 296,775 E&S Lines Segment 24,695 342,857 98,036 212,827 — 147,630 49,142 22,337 215,131 Investments Segment — — — — 168,241 — — — — Total $ 235,055 3,771,240 1,349,644 2,291,027 168,241 1,345,074 469,236 322,381 2,370,641 1 Includes “Net investment income earned” and “Total net realized and unrealized gains (losses)” on the Consolidated Statements of Income. 2 “Other operating expenses” of $322,381 reconciles to the Consolidated Statements of Income as follows: Other insurance expenses $ 333,097 Other income (10,716 ) Total $ 322,381 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, 2019
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Abstract]
Schedule IV - Reinsurance	($ thousands) Direct Amount Assumed from Other Companies Ceded to Other Companies Net Amount % of Amount Assumed to Net 2019 Premiums earned: Accident and health insurance $ 17 — 17 — — Property and liability insurance 2,993,140 24,399 420,368 2,597,171 1 % Total premiums earned 2,993,157 24,399 420,385 2,597,171 1 % 2018 Premiums earned: Accident and health insurance $ 19 — 19 — — Property and liability insurance 2,808,745 25,831 398,347 2,436,229 1 % Total premiums earned 2,808,764 25,831 398,366 2,436,229 1 % 2017 Premiums earned: Accident and health insurance $ 24 — 24 — — Property and liability insurance 2,647,464 25,831 382,268 2,291,027 1 % Total premiums earned 2,647,488 25,831 382,292 2,291,027 1 % 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, 2019
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule V - Allowance for Uncollectible Premiums and Other Receivables	($ in thousands) 2019 2018 2017 Balance, January 1 $ 13,900 14,600 11,480 Additions 2,730 4,022 6,414 Deductions (5,830 ) (4,722 ) (3,294 ) Balance, December 31 $ 10,800 13,900 14,600 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 Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
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) United States ("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.
Investments	Investments Portfolio Composition and Presentation in the Consolidated Balance Sheets Our investment portfolio is primarily comprised of fixed income securities. We also hold equity securities, short-term investments, and other investments. A description of our portfolio holdings, and the related presentation in our Consolidated Balance Sheets, is provided below. Fixed Income Portfolio We hold the following types of securities in our fixed income securities portfolio: • U.S. government and government agency obligations; • Foreign government obligations; • State and municipal obligations, including special revenue and general obligation bonds; • Corporate securities, which may include investment grade and below investment grade bonds, bank loan investments, redeemable preferred stock, and non-redeemable preferred stock with certain debt-like characteristics; • Collateralized loan obligations ("CLOs") and other asset-backed securities ("ABS"); • Residential mortgage-backed securities ("RMBS"); and • Commercial mortgage-backed securities ("CMBS"). We have designated substantially all of our fixed income securities portfolio as available-for-sale ("AFS"), with the remainder being designated as held-to-maturity ("HTM"), as we have the ability and positive intent to hold these securities to maturity. Our AFS securities are reported at fair value in our consolidated balance sheets, with unrealized gains or losses recognized in accumulated other comprehensive income (loss) ("AOCI"), net of tax. HTM securities are recorded at either: (i) amortized cost; or (ii) market value at the date of transfer into the HTM category, adjusted for subsequent amortization. After-tax unrealized gains and losses on securities that were transferred into an HTM designation from an AFS designation, are also included in AOCI. 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. Callable debt securities held at a premium are amortized to the earliest call date. Premiums and discounts arising from the purchase of RMBS, CMBS, CLO and other ABS are amortized over the expected life of the security based on future principal payments, giving additional consideration to 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. Other Portfolio Holdings Equity securities may include common and non-redeemable preferred stocks. Equity securities with readily determinable fair values are recorded at fair value. Equity securities without readily determinable fair values are recorded at net asset value ("NAV") as a practical expedient. Short-term investments may include money market instruments, savings accounts, commercial paper, and fixed income securities purchased with a maturity of less than one year. We also enter into reverse repurchase agreements that are included in short-term investments. These repurchase agreements are fully collateralized by high-quality, readily-marketable instruments that support the principal amount. At maturity, we receive principal and interest income on these agreements. Short-term investments are generally recorded at cost, which approximates fair value. Other investments include alternative investments, which principally include limited partnership investments in private equity, private credit, real estate, and infrastructure investment funds, Federal Home Loan Bank stock (“FHLB stock”), and tax credit investments. Alternative investments are accounted for using the equity method, with income typically recognized on a one-quarter lag. The FHLB stock is recorded at cost. Accounting for our tax credit investments is dependent on the type of credit we have purchased, as follows: • Federal low income housing tax credits are accounted for under the proportional amortization method; and • All other tax credits in our investment portfolio are accounted for using the equity method. For federal 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 Income Statement as a component of "Federal income tax expense" proportionately over the life of the investment. We categorize distributions from our investments accounted for using the equity method on our Consolidated Statements of Cash Flows using the cumulative earnings approach. Under this approach, distributions received are classified as cash flows from operating activities until such time that the cumulative distributions exceed cumulative earnings for the investment. When such an excess occurs, the current period distribution up to this excess amount is considered a return of investment and is classified as a cash flow from investing activities. We evaluate the alternative investments and tax credit investments included in our other investments portfolio to determine whether those investments are variable interest entities ("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 reviewed our alternative and tax credit investments and have concluded that they are VIEs, but that we are not the primary beneficiary and therefore, consolidation is not required. Presentation in the Consolidated Statements of Income Net investment income earned on our Consolidated Statements of Income includes the following: • Interest income, as well as amortization and accretion, on fixed income securities; • Dividend income on equity securities; • Interest income on our short-term investments; and • Income recognized on our alternative and other investments accounted for under the equity method of accounting, except for federal tax credits, as discussed below. Income related to federal tax credits (either low income housing tax credits or other federal credits) is recorded in our Consolidated Statements of Income as a component of “Federal income tax expense” proportionately over the life of the investment. Net realized and unrealized gains and losses on our Consolidated Statements of Income include the following: • Realized gains and losses on the disposal of investment securities, which are determined on the basis of the cost of the specific investments sold; • Changes in unrealized gains or losses on our equity securities that are recorded at fair value; and • Other-than-temporary impairment ("OTTI") charges that are credit related or related to our intent to sell. 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, and our other investments. OTTI Charges on Fixed Income Securities and Short-Term Investments We review our fixed income securities and short-term investments 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 security before its anticipated recovery; (iii) if the decline is other than interest-rate related; and (iv) 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 an OTTI charge to earnings. 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. To determine if an impairment is other than temporary, we perform assessments that may include, but are not limited to, a discounted cash flow analysis ("DCF") to determine the security's present value of future cash flows. This analysis is also performed on all previously-impaired debt securities that continue to be held by us and all RMBS, CMBS, CLOs and ABS 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 used in a DCF is one of the following: • The current yield in effect at the reporting date to accrete the beneficial interest for RMBS, CMBS, CLO and other ABS that were not of high credit quality at acquisition; • The effective interest rate in effect as of the reporting date for non-fixed rate securities; and • The effective interest rate implicit in the security at the date of acquisition for all other securities. DCFs 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. Non-redeemable preferred stocks that are classified as fixed income securities are evaluated using the OTTI method described above unless the security is below investment grade. In this situation, we would 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 recovery in the near term. If we determine either that we do not intend to hold the security, or the decline is other than temporary, we write down the security's cost to its fair value through an OTTI charge to earnings. OTTI Charges on Other Investments Our evaluation for OTTI of 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. Our evaluation for OTTI of our other investments (tax credits and FHLB stock) include a qualitative assessment of impairment indicators, which include, but are not limited to, the following: • An adverse development of the expected receipt of remaining tax credits and other tax benefits; and • A significant deterioration in the financial condition or liquidity of the Federal Home Loan Bank. If there is a decline in the fair value of an alternative or other investment that we do not intend to hold, or if we determine the decline is other than temporary, we write down the carrying value of the investment through an OTTI charge to earnings.
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. 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 generally recorded 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. RMBS, CMBS, CLO and other ABS Evaluations are based on a DCF, 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 by 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 valuations performed by the issuer or non-binding broker quotes to determine the fair value of these securities. We internally review these fair value measurements for reasonableness. 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; 5.375% 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 are consistent with the remaining term of the borrowing.
Allowance for Uncollectible Accounts	Allowance for Uncollectible Accounts We estimate an allowance for uncollectible accounts on our premiums receivable. This allowance is based on historical write-off percentages adjusted for the effects of current 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 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. The fair value of both 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 tax withholding obligations, as permitted under our stock-based compensation plans. This activity is disclosed in our Consolidated Statements of Stockholders' Equity.
Reinsurance	Reinsurance Reinsurance recoverable represents 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 all, or a portion of, 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 reinsurer's 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 recorded 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 Software licenses 3 to 5 Furniture and fixtures 10 Buildings and improvements 5 to 40 We recorded depreciation expense of $18.7 million , $19.5 million , and $17.8 million for 2019 , 2018 , and 2017 , 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 operations, 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 loss and loss expense, 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 were based on our actual average investment yield before tax as of the September 30 calculation date, were 3.5% for 2019 , 3.3% for 2018 , and 2.9% for 2017 .
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, 2019 , goodwill was not impaired.
Reserve for Loss and Loss Expense	Reserve for Loss and Loss Expense Reserves for loss and loss expense 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 include: (i) reserves on IBNR claims; and (ii) provisions for future emergence on known or 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 review 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 loss and loss expense experience organized by line of business, accident year, and maturity (i.e., “triangles”). Generally accepted actuarial techniques are applied to this history, producing a set of estimated ultimate loss and loss expenses. Ultimate loss and loss 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 generally accepted actuarial techniques. 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 expenses. • Some insured events may span multiple years and trigger multiple policies, as in the case of asbestos, environmental, and abuse and molestation claims, where the injury is deemed to occur over an extended period of time. These types of losses often do not lend themselves to traditional actuarial methods. Where we deem appropriate, our experience may be analyzed without differentiating by accident year, using alternative methods and metrics. In these cases, the associated selected ultimate loss and loss expenses are then allocated to the applicable accident years for reporting. • Another example of exposures that do not lend themselves to generally accepted actuarial techniques relate to loss expenses that cannot be attributed to a specific claim (referred to as “unallocated loss expenses”). These expenses are first allocated to line of business, and alternative projection methods are then applied to estimate expenses by calendar year, which are then allocated back to the applicable accident years for reporting. The selected ultimate loss and loss expenses are translated into indicated IBNR reserves, which are then compared to the recorded IBNR reserves, which are assessed in aggregate. Management's judgment is applied in determining any required adjustments to IBNR and the resulting adjustments are then recorded and assigned or allocated to accident year using the results of the actuarial analysis. While the reserve review is the primary basis for determining the recorded IBNR reserves, other internal and external factors are considered. Internal factors include (i) changes to our underwriting and claims practice, (ii) supplemental data regarding claims reporting and settlement trends, (iii) exposure estimates for reported claims, along with recent development on those estimates with respect to individual large claims and the aggregate of all claims, (iv) the rate at which new large or complex claims are being reported, and (v) additional trends observed by claims personnel or reported to them by defense counsel. External factors considered include (i) legislative enactments, (ii) judicial decisions, (iii) social inflation and heightened awareness of sources of liability, 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 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 loss and loss expense. These reserves are expected to be sufficient for settling loss and loss expense 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 loss and loss expense. 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 loss 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 a 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. As 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 business, 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 report these dividends within "Other insurance expenses" on the Consolidated Statements of Income. 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 either “Other insurance expenses” or "Corporate expenses" on the Consolidated Statements of Income depending on the nature of what caused the occurrence of such an item.
Leases	Leases We have various operating leases for office space, equipment, and fleet vehicles. In addition, we have various finance leases for computer hardware. We determine if an arrangement is a lease on the commencement date of the contract. Lease assets represent our right to use an underlying asset for the lease term, and lease liabilities represent our obligation to make lease payments arising from the lease. The lease asset and liability are measured by the present value of the future minimum lease payments over the lease term. Our fleet vehicle leases include a residual value guarantee; however, it is not probable of being owed. Therefore, there is no impact to the lease liability or lease asset. To measure the present value, the discount rate available in the contract is used. If the discount rate is not readily determinable, our incremental borrowing rate is used. The lease asset is then adjusted to exclude lease incentives. We recognize variable lease payments in the periods in which the obligations for those payments are incurred. Our lease terms may include options to extend or terminate the lease at which time it is reasonably certain that we will exercise that option. Lease expense is calculated using the straight-line method. In addition, we have adopted accounting policy elections to: (i) aggregate lease and non-lease components into a single lease component; and (ii) expense short-term leases on a straight-line basis over 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 of 1974 ("ERISA"), 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 Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
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 Software licenses 3 to 5 Furniture and fixtures 10 Buildings and improvements 5 to 40

Statements of Cash Flow (Tables

Statements of Cash Flow (Tables)	12 Months Ended
	Dec. 31, 2019
Supplemental Cash Flow Information [Abstract]
Schedule of Cash Flow, Supplemental Disclosures	($ in thousands) 2019 2018 2017 Cash paid during the period for: Interest $ 25,089 23,992 23,905 Federal income tax 55,825 29,193 62,000 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases 1 8,138 — — Operating cash flows from financing leases 16 — — Financing cash flows from finance leases 977 5,646 4,121 Non-cash items: Corporate actions related to fixed income securities, AFS 2 61,369 52,277 22,511 Corporate actions related to equity securities 2 14,250 944 4,725 Assets acquired under finance lease arrangements 824 4,119 278 Assets acquired under operating lease arrangements 1 13,808 — — Non-cash purchase of property and equipment 89 291 —
Schedule of Cash and Cash Equivalents	($ in thousands) December 31, 2019 December 31, 2018 Cash $ 300 505 Restricted cash 7,675 16,414 Total cash and restricted cash shown in the Statements of Cash Flows $ 7,975 16,919

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2019
Investment [Line Items]
Schedule of Unrealized Gains (Losses) On Investments	($ in thousands) 2019 2018 2017 AFS securities: Fixed income securities $ 215,634 2,302 85,806 Equity securities — — 38,894 Total AFS securities 215,634 2,302 124,700 HTM securities: Fixed income securities 31 89 (21 ) Total HTM securities 31 89 (21 ) Short-term securities 23 — — Total net unrealized gains 215,688 2,391 124,679 Deferred income tax (45,294 ) (502 ) (44,103 ) Net unrealized gains, net of deferred income tax 170,394 1,889 80,576 Cumulative effect adjustment due to accounting change for equity unrealized 1 — 30,726 — Cumulative effect adjustment due to accounting changes due to accounting change for stranded tax assets 1 — (17,920 ) — Increase (decrease) in net unrealized gains in OCI, net of deferred income tax $ 168,505 (65,881 ) 38,453
Schedule of Held-to-maturity Securities	December 31, 2019 Net Unrealized Unrecognized Unrecognized Amortized Gains Carrying Holding Holding Fair ($ in thousands) Cost (Losses) Value Gains Losses Value Obligations of state and political subdivisions $ 4,573 7 4,580 342 (1 ) 4,921 Corporate securities 16,196 24 16,220 834 — 17,054 Total HTM fixed income securities $ 20,769 31 20,800 1,176 (1 ) 21,975 December 31, 2018 Net Unrealized Unrecognized Unrecognized Amortized Gains Carrying Holding Holding Fair ($ in thousands) Cost (Losses) Value Gains Losses Value Obligations of state and political subdivisions 17,431 39 17,470 504 (5 ) 17,969 Corporate securities 19,590 50 19,640 855 (147 ) 20,348 Total HTM fixed income securities $ 37,021 89 37,110 1,359 (152 ) 38,317
Schedule of Available For Sale Securities	December 31, 2019 Cost/ Amortized Unrealized Unrealized Fair ($ in thousands) Cost Gains Losses Value AFS fixed income securities: U.S. government and government agencies $ 112,680 3,506 — 116,186 Foreign government 18,011 533 (2 ) 18,542 Obligations of states and political subdivisions 1,168,185 62,175 (270 ) 1,230,090 Corporate securities 1,866,881 81,906 (1,310 ) 1,947,477 CLO and other ABS 790,517 7,929 (5,434 ) 793,012 CMBS 514,709 23,902 (267 ) 538,344 RMBS 1,409,003 43,421 (455 ) 1,451,969 Total AFS fixed income securities $ 5,879,986 223,372 (7,738 ) 6,095,620 December 31, 2018 Cost/ Amortized Unrealized Unrealized Fair ($ in thousands) Cost Gains Losses Value AFS fixed income securities: U.S. government and government agencies $ 120,092 1,810 (592 ) 121,310 Foreign government 23,202 36 (107 ) 23,131 Obligations of states and political subdivisions 1,121,615 19,485 (2,631 ) 1,138,469 Corporate securities 1,639,852 5,521 (27,965 ) 1,617,408 CLO and other ABS 720,193 4,112 (6,943 ) 717,362 CMBS 527,409 3,417 (3,748 ) 527,078 RMBS 1,118,435 12,988 (3,081 ) 1,128,342 Total AFS fixed income securities $ 5,270,798 47,369 (45,067 ) 5,273,100
Schedule of Fair Value and Gross Pre-Tax Net Unrealized/Unrecognized Loss of Securities by Length of Time	December 31, 2019 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: Foreign government 1,416 (2 ) — — 1,416 (2 ) Obligations of states and political subdivisions 35,838 (270 ) — — 35,838 (270 ) Corporate securities 84,832 (480 ) 20,182 (830 ) 105,014 (1,310 ) CLO and other ABS 205,191 (1,938 ) 204,385 (3,496 ) 409,576 (5,434 ) CMBS 62,893 (264 ) 828 (3 ) 63,721 (267 ) RMBS 126,089 (425 ) 5,375 (30 ) 131,464 (455 ) Total AFS fixed income securities $ 516,259 (3,379 ) 230,770 (4,359 ) 747,029 (7,738 ) December 31, 2018 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 $ 6,693 (174 ) 23,163 (418 ) 29,856 (592 ) Foreign government 12,208 (93 ) 1,482 (14 ) 13,690 (107 ) Obligations of states and political subdivisions 196,798 (2,074 ) 42,821 (557 ) 239,619 (2,631 ) Corporate securities 1,041,952 (23,649 ) 78,953 (4,316 ) 1,120,905 (27,965 ) CLO and other ABS 516,106 (6,750 ) 16,800 (193 ) 532,906 (6,943 ) CMBS 229,338 (2,548 ) 66,294 (1,200 ) 295,632 (3,748 ) RMBS 139,338 (1,660 ) 45,661 (1,421 ) 184,999 (3,081 ) Total AFS fixed income securities $ 2,142,433 (36,948 ) 275,174 (8,119 ) 2,417,607 (45,067 )
Schedule of Investments Classified by Contractual Maturity Date	AFS HTM ($ in thousands) Fair Value Carrying Value Fair Value Due in one year or less $ 394,027 1,211 1,229 Due after one year through five years 3,001,602 13,856 14,820 Due after five years through 10 years 2,531,172 5,733 5,926 Due after 10 years 168,819 — — Total fixed income securities $ 6,095,620 20,800 21,975
Schedule of Other Investment Portfolio by Strategy and the Remaining Commitment Amount Associated With Each Strategy	Other Investments December 31, 2019 December 31, 2018 ($ in thousands) Carrying Value Remaining Commitment Maximum Exposure to Loss 1 Carrying Value Remaining Maximum 1 Alternative Investments Private equity $ 118,352 93,138 211,490 84,352 93,688 178,040 Private credit 42,532 105,340 147,872 41,682 81,453 123,135 Real assets 23,256 20,741 43,997 27,862 27,129 54,991 Total alternative investments 184,140 219,219 403,359 153,896 202,270 356,166 Other securities 2 32,667 — 32,667 25,042 — 25,042 Total other investments $ 216,807 219,219 436,026 178,938 202,270 381,208
Schedule of Aggregated Summarized Balance Sheet Financial Information For Partnerships In Our Alternative Investment Portfolio	Balance Sheet Information December 31, ($ in millions) 2019 2018 Investments $ 43,857 28,292 Total assets 45,432 30,377 Total liabilities 5,670 4,532 Total partners’ capital 39,762 25,845
Schedule of Aggregated Summarized Income Statement Financial Information For Partnerships In Our Alternative Investment Portfolio	Income Statement Information 12 months ended September 30, ($ in millions) 2019 2018 2017 Net investment (loss) income $ (8 ) 134 (143 ) Realized gains 695 1,981 325 Net change in unrealized appreciation 5,543 1,303 2,894 Net income before tax $ 6,230 3,418 3,076 Insurance Subsidiaries' alternative investments income before tax 17.9 17.6 12.7
Schedule Of Securities Pledged As Collateral	($ in millions) FHLBI Collateral FHLBNY Collateral State and Regulatory Deposits Total U.S. government and government agencies $ — — 22.8 22.8 Obligations of states and political subdivisions — — 4.0 4.0 Corporate securities — — 0.3 0.3 CMBS 7.2 17.9 — 25.1 RMBS 59.0 77.6 — 136.6 Total pledged as collateral $ 66.2 95.5 27.1 188.8
Schedule of Components of Pre-Tax Net Investment Income Earned	($ in thousands) 2019 2018 2017 Fixed income securities $ 203,255 178,104 153,230 Equity securities 6,996 7,764 6,442 Short-term investments 6,653 3,472 1,526 Other investments 18,778 17,799 12,871 Investment expenses (13,139 ) (11,803 ) (12,187 ) Net investment income earned $ 222,543 195,336 161,882
Schedule of OTTI by Asset Type	2019 Recognized in Earnings ($ in thousands) Gross Included in OCI AFS fixed income securities: Obligations of states and political subdivisions 66 — 66 Corporate securities $ 2,529 — 2,529 Total AFS fixed income securities 2,595 — 2,595 Other investments 1,049 — 1,049 Total OTTI losses $ 3,644 — 3,644 2018 Recognized in Earnings ($ in thousands) Gross Included in OCI AFS fixed income securities: Corporate securities $ 1,783 — 1,783 RMBS 2,903 — 2,903 Total AFS fixed income securities 4,686 — 4,686 Other investments 1,893 — 1,893 Total OTTI losses $ 6,579 — 6,579 2017 Recognized in Earnings ($ in thousands) Gross Included in OCI AFS fixed income securities: U.S. government and government agencies $ 36 — 36 Obligations of states and political subdivisons 612 — 612 Corporate securities 587 — 587 CLO and other ABS 96 — 96 CMBS 670 — 670 RMBS 1,183 (36 ) 1,219 Total AFS fixed income securities 3,184 (36 ) 3,220 AFS equity securities: Common stock 1,435 — 1,435 Total AFS equity securities 1,435 — 1,435 Other investments 190 — 190 Total OTTI losses $ 4,809 (36 ) 4,845
Components of Net Realized and Unrealized Gains (Losses)	($ in thousands) 2019 2018 2017 Net realized gains (losses) on the disposals of securities: Fixed income securities $ 1,910 (34,953 ) 6,944 Equity securities 24,844 18,695 4,629 Short-term investments (16 ) (3 ) (4 ) Other investments (23 ) (2,714 ) (365 ) Net realized gains (losses) on the disposal of securities 26,715 (18,975 ) 11,204 OTTI charges (3,644 ) (6,579 ) (4,845 ) Net realized gains (losses) 23,071 (25,554 ) 6,359 Unrealized (losses) recognized in income on equity securities (8,649 ) (29,369 ) — Total net realized and unrealized investment gains (losses) $ 14,422 (54,923 ) 6,359
Schedule of Components of Net Realized Gains Excluding OTTI Charges	($ in thousands) 2019 2018 2017 HTM fixed income securities Gains $ 1 2 44 Losses (15 ) — (1 ) AFS fixed income securities Gains 6,899 5,460 10,193 Losses (4,975 ) (40,415 ) (3,292 ) Equity securities Gains 24,980 23,203 5,829 Losses (136 ) (4,508 ) (1,200 ) Short-term investments Gains 24 7 2 Losses (40 ) (10 ) (6 ) Other investments Gains 6 — 494 Losses (29 ) (2,714 ) (859 ) Total net realized investment gains (losses) $ 26,715 (18,975 ) 11,204
Equity Securities [Member]
Investment [Line Items]
Unrealized Gain (Loss) on Securities [Table Text Block]	($ in thousands) 2019 2018 Unrealized gains (losses) recognized in income on equity securities: On securities remaining in our portfolio at December 31, 2019 1,219 (3,098 ) On securities sold in each respective period (9,868 ) (26,271 ) Total unrealized (losses) recognized in income on equity securities $ (8,649 ) (29,369 )

Comprehensive Income (Tables)

Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2019
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Schedule of Components of Comprehensive Income-Gross and Net of Tax	2019 ($ in thousands) Gross Tax Net Net income $ 336,390 64,767 271,623 Components of OCI: Unrealized gains (losses) on investment securities : Unrealized holding gains during the year 212,683 44,662 168,021 Amounts reclassified into net income: HTM securities (58 ) (12 ) (46 ) Realized losses on disposals and OTTI of AFS securities 671 141 530 Total unrealized gains on investment securities 213,296 44,791 168,505 Defined benefit pension and post-retirement plans: Net actuarial loss (13,795 ) (2,897 ) (10,898 ) Amounts reclassified into net income: Net actuarial loss 2,657 558 2,099 Total defined benefit pension and post-retirement plans (11,138 ) (2,339 ) (8,799 ) Other comprehensive income 202,158 42,452 159,706 Comprehensive income $ 538,548 107,219 431,329 2018 ($ in thousands) Gross Tax Net Net income $ 211,721 32,782 178,939 Components of OCI: Unrealized (losses) gains on investment securities : Unrealized holding losses during the year (123,145 ) (25,861 ) (97,284 ) Amounts reclassified into net income: HTM securities 110 23 87 Realized losses on disposals and OTTI of AFS securities 39,641 8,325 31,316 Total unrealized losses on investment securities (83,394 ) (17,513 ) (65,881 ) Defined benefit pension and post-retirement plans: Net actuarial loss (11,273 ) (2,367 ) (8,906 ) Amounts reclassified into net income: Net actuarial loss 2,127 447 1,680 Total defined benefit pension and post-retirement plans (9,146 ) (1,920 ) (7,226 ) Other comprehensive loss (92,540 ) (19,433 ) (73,107 ) Comprehensive income $ 119,181 13,349 105,832 2017 ($ in thousands) Gross Tax Net Net income $ 261,968 93,142 168,826 Components of OCI: Unrealized gains (losses) on investment securities : Unrealized holding gains during the year 66,894 23,879 43,015 Non-credit portion of OTTI recognized in OCI 36 13 23 Amounts reclassified into net income: HTM securities (179 ) (63 ) (116 ) Non-credit OTTI 104 36 68 Realized gains on disposals and OTTI of AFS securities (6,979 ) (2,442 ) (4,537 ) Total unrealized gains on investment securities 59,876 21,423 38,453 Defined benefit pension and post-retirement plans: Net actuarial loss (4,684 ) (984 ) (3,700 ) Amounts reclassified into net income: Net actuarial loss 2,102 735 1,367 Total defined benefit pension and post-retirement plans (2,582 ) (249 ) (2,333 ) Other comprehensive income 57,294 21,174 36,120 Comprehensive income $ 319,262 114,316 204,946
Schedule of Components of Accumulated Other Comprehensive Income	Net Unrealized (Losses) Gains on Investment Securities Defined Benefit Pension and Post-retirement Plans ($ in thousands) OTTI Related HTM Related All Other Investments Subtotal Total AOCI Balance, December 31, 2017 $ (59 ) (14 ) 80,648 80,575 (60,405 ) 20,170 Cumulative effect adjustments 1 (12 ) (2 ) (12,792 ) (12,806 ) (12,213 ) (25,019 ) Balance: December 31, 2017, as adjusted (71 ) (16 ) 67,856 67,769 (72,618 ) (4,849 ) OCI before reclassifications — — (97,284 ) (97,284 ) (8,906 ) (106,190 ) Amounts reclassified from AOCI — 87 31,316 31,403 1,680 33,083 Net current period OCI — 87 (65,968 ) (65,881 ) (7,226 ) (73,107 ) Balance, December 31, 2018 (71 ) 71 1,888 1,888 (79,844 ) (77,956 ) OCI before reclassifications — — 168,021 168,021 (10,898 ) 157,123 Amounts reclassified from AOCI — (46 ) 530 484 2,099 2,583 Net current period OCI — (46 ) 168,551 168,505 (8,799 ) 159,706 Balance, December 31, 2019 $ (71 ) 25 170,439 170,393 (88,643 ) 81,750 1 Upon adoption of ASU 2016-01 and ASU 2018-02 in the first quarter of 2018, we recognized a $25.0 million cumulative-effect adjustment to the opening balance of AOCI, which represents the after-tax net unrealized gain on our equity portfolio as of December 31, 2017 and the one-time reclassification from AOCI to retained earnings for the stranded tax assets that were created in AOCI from the enactment of Tax Reform.
Schedule of Reclassification out of Accumulated Other Comprehensive Income	($ in thousands) Year ended December 31, 2019 Year ended December 31, 2018 Affected Line Item in the Consolidated Statements of Income HTM related Unrealized (gains) losses on HTM disposals $ (46 ) 137 Net realized and unrealized gains (losses) Amortization of net unrealized gains on HTM securities (12 ) (27 ) Net investment income earned (58 ) 110 Income before federal income tax 12 (23 ) Total federal income tax expense (46 ) 87 Net income Realized losses (gains) on AFS Realized losses on AFS disposals and OTTI 671 39,641 Net realized and unrealized gains (losses) 671 39,641 Income before federal income tax (141 ) (8,325 ) Total federal income tax expense 530 31,316 Net income Defined benefit pension and post-retirement life plans Net actuarial loss 582 450 Loss and loss expense incurred 2,075 1,677 Other insurance expenses Total defined benefit pension and post-retirement life 2,657 2,127 Income before federal income tax (558 ) (447 ) Total federal income tax expense 2,099 1,680 Net income Total reclassifications for the period $ 2,583 33,083 Net income

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Schedule of Carrying Amounts and Estimated Fair Values of Financial Instruments	December 31, 2019 December 31, 2018 ($ in thousands) Carrying Amount Fair Value Carrying Amount Fair Value Financial Liabilities Long-term debt: 7.25% Senior Notes $ 49,910 66,365 49,907 57,032 6.70% Senior Notes 99,480 123,104 99,462 107,075 5.875% Senior Notes — — 185,000 177,230 5.375% Senior Notes 294,157 357,025 — — 1.61% Borrowings from FHLBNY 25,000 24,901 25,000 24,218 1.56% Borrowings from FHLBNY 25,000 24,875 25,000 24,162 3.03% Borrowings from FHLBI 60,000 63,002 60,000 58,905 Subtotal long-term debt 553,547 659,272 444,369 448,622 Unamortized debt issuance costs (3,687 ) (4,829 ) Finance lease obligations 737 — Total long-term debt $ 550,597 439,540
Schedule of Quantitative Disclosures of our Financial Assets that were Measured at Fair Value	December 31, 2019 Fair Value Measurements Using ($ in thousands) Assets Measured at Fair Value Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Description Measured on a recurring basis: AFS fixed income securities: U.S. government and government agencies $ 116,186 41,083 75,103 — Foreign government 18,542 — 18,542 — Obligations of states and political subdivisions 1,230,090 — 1,230,090 — Corporate securities 1,947,477 — 1,930,426 17,051 CLO and other ABS 793,012 3,635 772,343 17,034 CMBS 538,344 — 538,344 — RMBS 1,451,969 — 1,451,969 — Total AFS fixed income securities 6,095,620 44,718 6,016,817 34,085 Equity securities: Common stock 1 69,900 32,145 — — Preferred stock 3,037 3,037 — — Total equity securities 72,937 35,182 — — Short-term investments 282,490 265,306 17,184 — Total assets measured at fair value $ 6,451,047 345,206 6,034,001 34,085 December 31, 2018 Fair Value Measurements Using ($ in thousands) Assets Measured at Fair Value Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Description Measured on a recurring basis: AFS fixed income securities: U.S. government and government agencies $ 121,310 78,381 42,929 — Foreign government 23,131 — 23,131 — Obligations of states and political subdivisions 1,138,469 — 1,138,469 — Corporate securities 1,617,408 — 1,617,408 — CLO and other ABS 717,362 — 709,953 7,409 CMBS 527,078 — 527,078 — RMBS 1,128,342 — 1,128,342 — Total AFS fixed income securities 5,273,100 78,381 5,187,310 7,409 Equity securities: Common stock 1 144,727 107,397 — — Preferred stock 2,912 2,912 — — Total equity securities 147,639 110,309 — — Short-term investments 323,864 321,370 2,494 — Total assets measured at fair value $ 5,744,603 510,060 5,189,804 7,409 1 In accordance with ASU 2015-07, investments amounting to $37.8 million and $37.3 million at December 31, 2019 and December 31, 2018, respectively, were measured at fair value using the net asset value per share (or its practical expedient) and have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to total assets measured at fair value.
Schedule of Summary of the Changes in Fair Value of Securities Using Level 3 Inputs	2019 ($ in thousands) Corporate Securities CLO and Other ABS Total Fair value, December 31, 2018 $ — 7,409 7,409 Total net (losses) gains for the period included in: OCI (118 ) (261 ) (379 ) Net income — 245 245 Purchases — 21,282 21,282 Sales — — — Issuances — — — Settlements — (279 ) (279 ) Transfers into Level 3 17,169 18,853 36,022 Transfers out of Level 3 — (30,215 ) (30,215 ) Fair value, December 31, 2019 $ 17,051 17,034 34,085 There were no material changes in the fair value of securities measured using Level 3 prices during 2018.
Schedule of Quantitative Information of our Financial Assets and Liabilities that were Disclosed at Fair Value	December 31, 2019 Fair Value Measurements Using ($ in thousands) Assets/Liabilities Disclosed at Fair Value 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 $ 4,921 — 4,921 — Corporate securities 17,054 — 17,054 — Total HTM fixed income securities $ 21,975 — 21,975 — Financial Liabilities Long-term debt: 7.25% Senior Notes $ 66,365 — 66,365 — 6.70% Senior Notes 123,104 — 123,104 — 5.375% Senior Notes 357,025 — 357,025 — 1.61% Borrowings from FHLBNY 24,901 — 24,901 — 1.56% Borrowings from FHLBNY 24,875 — 24,875 — 3.03% Borrowings from FHLBI 63,002 — 63,002 — Total long-term debt $ 659,272 — 659,272 — December 31, 2018 Fair Value Measurements Using ($ in thousands) Assets/Liabilities Disclosed at Fair Value 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 $ 17,969 — 17,969 — Corporate securities 20,348 — 20,348 — Total HTM fixed income securities $ 38,317 — 38,317 — Financial Liabilities Long-term debt: 7.25% Senior Notes $ 57,032 — 57,032 — 6.70% Senior Notes 107,075 — 107,075 — 5.875% Senior Notes 177,230 177,230 — — 1.61% Borrowings from FHLBNY 24,218 — 24,218 — 1.56% Borrowings from FHLBNY 24,162 — 24,162 — 3.03% Borrowings from FHLBI 58,905 — 58,905 — Total long-term debt $ 448,622 177,230 271,392 —

Reinsurance (Tables)

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2019
Reinsurance Disclosures [Abstract]
Schedule of Total Reinsurance Balances Segregated By Reinsurer	As of December 31, 2019 As of December 31, 2018 ($ in thousands) Reinsurance Balances % of Reinsurance Balance Reinsurance Balances % of Reinsurance Balance Total reinsurance recoverables $ 573,235 $ 549,172 Total prepaid reinsurance premiums 166,705 157,723 Total reinsurance balance 739,940 706,895 Federal and state pools 1 : NFIP 175,472 24 % 170,453 24 % New Jersey Unsatisfied Claim Judgment Fund 53,732 6 55,167 7 Other 2,449 1 3,602 1 Total federal and state pools 231,653 31 229,222 32 Remaining reinsurance balance $ 508,287 69 $ 477,673 68 Munich Re Group (A.M. Best rated "A+") $ 119,748 16 $ 112,841 16 Hannover Ruckversicherungs AG (A.M. Best rated "A+") 107,474 15 101,835 14 AXIS Reinsurance Company (A.M. Best rated "A+") 73,009 10 69,102 10 Swiss Re Group (A.M. Best rated "A+") 37,190 5 37,519 5 Transatlantic Reinsurance Company (A.M. Best rated “A+”) 21,824 3 17,686 3 All other reinsurers 149,042 20 138,690 20 Total reinsurers 508,287 69 % 477,673 68 % Less: collateral 2 (110,549 ) (112,201 ) Reinsurers, net of collateral $ 397,738 $ 365,472 1 Considered to have minimal risk of default. 2 Includes letters of credit, trust funds, and funds held against reinsurance recoverables.
List Of Direct, Assumed, And Ceded Reinsurance Amounts	($ in thousands) 2019 2018 2017 Premiums written: Direct $ 3,084,451 2,890,633 2,733,459 Assumed 24,339 26,250 26,685 Ceded (429,366 ) (402,597 ) (389,503 ) Net $ 2,679,424 2,514,286 2,370,641 Premiums earned: Direct $ 2,993,157 2,808,764 2,647,488 Assumed 24,399 25,831 25,831 Ceded (420,385 ) (398,366 ) (382,292 ) Net $ 2,597,171 2,436,229 2,291,027 Loss and loss expense incurred: Direct $ 1,714,880 1,706,951 1,570,678 Assumed 22,879 21,469 17,588 Ceded (186,268 ) (230,286 ) (243,192 ) Net $ 1,551,491 1,498,134 1,345,074
Schedule of Ceded Premiums and Losses Related to Flood Operations	Ceded to NFIP ($ in thousands) 2019 2018 2017 Ceded premiums written $ (266,925 ) (248,053 ) (241,345 ) Ceded premiums earned (259,119 ) (244,238 ) (235,088 ) Ceded loss and loss expense incurred (71,676 ) (144,967 ) (160,922 )

Reserve for Loss and Loss Exp_2

Reserve for Loss and Loss Expense (Tables)	12 Months Ended
	Dec. 31, 2019
Insurance Loss Reserves [Abstract]
Schedule of Roll Forward of Reserve for Loss and Loss Expense	($ in thousands) 2019 2018 2017 Gross reserves for loss and loss expense, at beginning of year $ 3,893,868 3,771,240 3,691,719 Less: reinsurance recoverable on unpaid loss and loss expense, at beginning of year 537,388 585,855 611,200 Net reserves for loss and loss expense, at beginning of year 3,356,480 3,185,385 3,080,519 Incurred loss and loss expense for claims occurring in the: Current year 1,601,780 1,527,997 1,384,266 Prior years (50,289 ) (29,863 ) (39,192 ) Total incurred loss and loss expense 1,551,491 1,498,134 1,345,074 Paid loss and loss expense for claims occurring in the: Current year 579,527 573,718 497,486 Prior years 805,443 753,321 742,722 Total paid loss and loss expense 1,384,970 1,327,039 1,240,208 Net reserves for loss and loss expense, at end of year 3,523,001 3,356,480 3,185,385 Add: Reinsurance recoverable on unpaid loss and loss expense, at end of year 544,162 537,388 585,855 Gross reserves for loss and loss expense at end of year $ 4,067,163 3,893,868 3,771,240
Schedule of (Favorable)/ Unfavorable Prior Year Development	(Favorable)/Unfavorable Prior Year Development ($ in millions) 2019 2018 2017 General Liability $ (5.0 ) (9.5 ) (48.3 ) Commercial Automobile 0.7 36.7 35.6 Workers Compensation (68.0 ) (83.0 ) (52.3 ) Businessowners' Policies 1.9 (1.5 ) 1.9 Commercial Property 5.1 7.5 8.7 Homeowners 7.5 9.8 0.4 Personal Automobile 4.4 3.0 6.7 E&S Casualty Lines 2.0 12.0 10.0 E&S Property Lines 1.0 (4.8 ) 0.1 Other 0.1 (0.1 ) (2.0 ) Total $ (50.3 ) (29.9 ) (39.2 )
Schedule of Exposure to Various Asbestos and Environmental Claims	2019 ($ in millions) Gross Net Asbestos $ 6.3 5.1 Landfill sites 12.1 7.3 Underground storage tanks 10.3 9.2 Total $ 28.7 21.6
Schedule of Roll Forward of Gross and Net Asbestos and Environmental Incurred Losses and Loss Expenses and Related Reserves	2019 2018 2017 ($ in thousands) Gross Net Gross Net Gross Net Asbestos Reserves for loss and loss expense at beginning of year $ 7,328 6,097 7,577 6,346 7,847 6,615 Incurred loss and loss expense (375 ) (375 ) — — — — Less: loss and loss expense paid (665 ) (665 ) (249 ) (249 ) (270 ) (269 ) Reserves for loss and loss expense at the end of year $ 6,288 5,057 7,328 6,097 7,577 6,346 Environmental Reserves for loss and loss expense at beginning of year $ 22,692 16,686 20,838 14,866 22,115 16,101 Incurred loss and loss expense 723 609 3,059 2,877 126 — Less: loss and loss expense paid (1,002 ) (763 ) (1,205 ) (1,057 ) (1,403 ) (1,235 ) Reserves for loss and loss expense at the end of year $ 22,413 16,532 22,692 16,686 20,838 14,866 Total Asbestos and Environmental Claims Reserves for loss and loss expense at beginning of year $ 30,020 22,783 28,415 21,212 29,962 22,716 Incurred loss and loss expense 348 234 3,059 2,877 126 — Less: loss and loss expense paid (1,667 ) (1,428 ) (1,454 ) (1,306 ) (1,673 ) (1,504 ) Reserves for loss and loss expense at the end of year $ 28,701 21,589 30,020 22,783 28,415 21,212
Schedule of Short-duration Insurance Contracts, Claims Development	All Lines (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 950,114 973,742 977,959 956,600 943,118 922,404 915,131 907,074 904,561 902,258 38,152 94,526 2011 1,042,576 1,061,667 1,062,233 1,056,107 1,033,518 1,023,726 1,019,351 1,013,115 1,013,175 44,453 104,861 2012 1,065,437 1,071,290 1,020,655 998,028 973,089 973,644 973,411 968,536 50,942 104,148 2013 1,044,142 1,062,045 1,047,230 1,021,007 1,002,316 987,763 984,858 72,970 91,326 2014 1,107,513 1,133,798 1,146,990 1,124,014 1,104,218 1,100,208 83,392 95,081 2015 1,114,081 1,130,513 1,144,830 1,138,313 1,119,441 111,657 94,128 2016 1,188,608 1,203,634 1,227,142 1,199,734 205,126 94,579 2017 1,270,110 1,313,372 1,313,585 336,155 98,014 2018 1,413,800 1,461,603 501,519 104,187 2019 1,483,945 759,853 93,947 Total 11,547,343 All Lines (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 328,826 509,910 625,229 704,895 773,536 803,773 823,770 835,532 846,386 851,633 2011 391,944 585,867 692,730 782,655 852,202 901,801 924,111 940,626 950,836 2012 378,067 555,819 651,544 743,742 810,135 856,195 879,372 898,269 2013 335,956 518,872 644,475 748,758 833,823 872,331 891,841 2014 405,898 614,075 736,154 855,959 936,425 981,868 2015 376,641 581,203 725,385 845,868 929,222 2016 387,272 617,958 764,331 892,390 2017 433,440 678,453 829,134 2018 511,271 779,466 2019 510,091 Total 8,514,750 All outstanding liabilities before 2010, net of reinsurance 360,119 Liabilities for loss and loss expenses, net of reinsurance 3,392,713 General Liability (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 215,208 228,680 242,499 237,154 222,328 211,619 208,968 202,394 206,146 205,322 17,542 12,705 2011 227,769 228,720 239,480 230,785 217,256 211,196 212,011 211,500 213,485 19,913 11,649 2012 238,979 245,561 215,083 194,144 175,305 175,268 180,659 182,085 21,005 9,994 2013 250,609 251,421 239,776 225,709 210,785 203,831 202,697 28,857 10,378 2014 244,312 249,946 257,132 239,333 234,082 237,125 42,388 10,586 2015 254,720 245,710 246,990 233,249 219,204 55,244 10,381 2016 277,214 272,048 277,986 263,245 98,385 10,526 2017 293,747 293,128 301,384 161,114 10,706 2018 317,934 336,326 223,228 10,656 2019 347,150 296,257 8,626 Total 2,508,023 General Liability (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 15,726 46,201 80,018 113,050 143,360 161,487 172,394 178,179 183,988 185,962 2011 13,924 42,692 73,643 102,978 135,377 159,768 170,525 181,856 187,276 2012 13,030 35,241 56,580 89,008 109,448 130,866 144,451 156,186 2013 12,789 35,113 72,127 104,587 139,114 153,628 163,764 2014 14,901 46,825 79,972 121,969 154,957 179,192 2015 14,665 39,978 78,668 116,804 144,216 2016 15,684 46,549 89,431 133,757 2017 17,366 49,470 92,355 2018 19,531 60,784 2019 18,097 Total 1,321,589 All outstanding liabilities before 2010, net of reinsurance 93,982 Liabilities for loss and loss expenses, net of reinsurance 1,280,416 Workers Compensation (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 198,371 214,469 212,815 211,030 214,916 212,448 208,155 204,423 199,539 197,095 19,514 12,192 2011 205,238 218,973 214,743 215,114 210,591 205,708 200,674 194,821 192,863 22,717 11,860 2012 203,864 208,036 199,360 195,197 188,596 187,359 183,314 178,774 24,605 11,618 2013 199,794 194,318 187,658 173,160 166,662 162,787 159,767 26,260 11,375 2014 199,346 187,065 182,579 172,515 164,420 160,646 28,320 10,495 2015 193,729 194,639 183,604 179,642 176,242 27,927 10,549 2016 196,774 184,946 176,248 166,009 41,146 10,572 2017 195,202 184,306 175,853 53,654 10,793 2018 193,894 193,818 74,399 11,078 2019 188,625 100,336 9,805 Total 1,789,692 Workers Compensation (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 46,795 93,281 122,442 137,184 149,086 153,795 158,078 162,796 165,526 167,478 2011 42,941 90,836 118,847 134,646 139,232 149,269 154,320 158,535 161,696 2012 40,911 86,909 108,211 122,755 132,052 139,477 143,281 146,739 2013 36,829 74,568 96,376 109,739 118,669 124,130 126,822 2014 35,924 78,944 100,876 113,626 119,392 124,077 2015 33,857 77,320 98,195 112,601 120,097 2016 34,525 78,531 98,037 109,166 2017 40,375 82,216 100,645 2018 41,122 84,780 2019 37,826 Total 1,179,326 All outstanding liabilities before 2010, net of reinsurance 240,140 Liabilities for loss and loss expenses, net of reinsurance 850,505 Commercial Automobile (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 187,562 189,305 187,778 181,923 179,854 172,969 173,157 173,471 173,080 172,995 682 25,512 2011 174,006 183,044 182,325 178,421 172,617 174,882 174,514 173,507 173,401 899 25,524 2012 179,551 191,947 183,527 184,289 184,367 186,128 184,633 185,357 1,920 24,160 2013 188,289 205,282 209,197 207,994 210,410 207,975 209,602 2,928 25,722 2014 200,534 212,725 216,824 219,925 218,172 217,334 4,831 27,714 2015 220,994 240,958 253,074 259,495 260,565 7,966 29,340 2016 255,187 274,367 285,302 285,304 21,279 31,167 2017 301,274 329,389 324,291 57,165 32,474 2018 347,908 352,487 109,922 35,034 2019 385,212 183,477 33,438 Total 2,566,548 Commercial Automobile (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 68,098 99,254 128,015 146,913 163,513 167,227 169,100 169,793 171,693 171,941 2011 69,849 99,196 121,576 142,507 157,291 166,082 170,000 170,913 172,365 2012 73,316 105,371 127,235 148,669 168,114 176,656 179,501 181,353 2013 76,469 109,893 140,015 169,850 189,626 200,750 202,622 2014 80,810 117,169 148,884 180,701 202,821 209,655 2015 91,347 132,260 175,866 211,515 238,142 2016 106,022 155,720 200,701 233,939 2017 117,287 178,823 220,422 2018 134,867 193,788 2019 149,538 Total 1,973,765 All outstanding liabilities before 2010, net of reinsurance 3,904 Liabilities for loss and loss expenses, net of reinsurance 596,686 Businessowners' Policies (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 53,669 49,285 42,408 39,915 40,899 40,581 41,239 41,197 40,920 41,156 333 3,920 2011 54,469 57,083 51,047 58,242 59,256 58,966 58,456 58,735 58,948 362 4,960 2012 54,342 48,029 46,303 44,172 44,077 43,747 43,418 43,717 703 5,543 2013 49,617 42,618 41,005 40,624 41,369 39,709 39,699 803 3,482 2014 55,962 60,949 62,548 59,806 58,517 58,093 1,390 4,064 2015 52,871 53,768 57,245 55,925 54,454 3,235 3,959 2016 52,335 53,792 54,993 53,835 4,245 3,843 2017 46,624 48,698 51,524 10,252 3,864 2018 55,024 57,202 12,432 4,159 2019 53,531 15,068 3,210 Total 512,159 Businessowners' Policies (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 20,821 28,131 31,027 34,705 37,819 38,900 40,279 40,395 40,439 40,823 2011 27,884 37,362 41,011 46,444 52,114 55,856 57,045 57,365 57,380 2012 22,199 31,833 35,089 37,215 38,766 40,627 41,326 41,356 2013 17,412 26,592 30,845 34,760 37,993 38,464 39,085 2014 28,914 40,584 44,911 49,460 52,940 55,458 2015 24,189 36,014 42,710 46,571 49,073 2016 24,655 36,848 39,973 45,308 2017 21,865 31,337 36,950 2018 29,995 39,791 2019 27,718 Total 432,942 All outstanding liabilities before 2010, net of reinsurance 7,530 Liabilities for loss and loss expenses, net of reinsurance 86,747 Commercial Property (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 105,647 96,851 97,386 96,127 95,530 95,363 95,178 95,155 95,142 95,338 4 7,669 2011 136,954 131,667 130,942 131,282 131,353 131,113 131,049 131,009 131,002 7 9,038 2012 118,464 114,224 115,375 116,658 117,102 117,170 117,225 117,220 10 8,517 2013 88,101 90,639 90,103 90,005 90,436 90,278 90,218 18 5,713 2014 141,192 136,249 136,820 138,751 138,155 136,212 33 6,515 2015 110,270 109,513 111,750 111,566 112,496 56 6,404 2016 121,927 126,185 125,937 124,487 (96 ) 6,739 2017 138,773 149,106 149,044 (884 ) 6,886 2018 183,177 190,834 (329 ) 8,240 2019 173,826 15,732 6,722 Total 1,320,677 Commercial Property (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 69,543 91,918 94,602 95,111 95,270 95,147 95,156 95,150 95,138 95,334 2011 94,538 127,580 129,579 130,681 131,060 131,115 131,089 131,100 131,092 2012 81,528 108,834 111,503 114,699 116,291 116,625 116,671 116,674 2013 60,244 87,874 90,446 90,350 90,840 90,696 90,646 2014 101,131 132,909 136,634 137,883 137,418 136,008 2015 79,048 106,182 109,829 110,994 110,969 2016 83,966 118,789 122,930 123,828 2017 99,047 142,338 148,589 2018 135,416 184,813 2019 130,891 Total 1,268,844 All outstanding liabilities before 2010, net of reinsurance 237 Liabilities for loss and loss expenses, net of reinsurance 52,071 Personal Automobile (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 103,340 110,075 112,346 109,515 107,490 107,405 107,224 107,054 106,887 106,785 64 20,823 2011 113,232 116,164 113,686 112,993 114,241 113,830 113,988 113,921 114,056 121 22,700 2012 113,771 114,921 109,832 109,324 110,294 110,300 109,795 109,701 155 22,332 2013 108,417 109,620 106,225 106,703 107,759 107,680 107,916 348 22,375 2014 102,250 109,325 106,757 107,452 106,821 107,104 307 22,506 2015 96,387 99,698 100,214 99,570 98,718 742 20,863 2016 92,727 98,032 100,202 101,140 2,565 19,819 2017 101,880 105,139 103,653 6,342 20,725 2018 111,594 113,569 14,259 22,621 2019 114,043 25,832 21,988 Total 1,076,685 Personal Automobile (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 58,786 82,490 95,300 101,540 104,061 105,849 106,453 106,733 106,722 106,716 2011 61,323 82,102 93,878 105,068 111,085 112,732 113,551 113,664 113,856 2012 63,704 82,729 94,842 102,977 107,890 109,355 109,447 109,482 2013 61,384 80,861 92,637 100,528 105,131 106,679 106,876 2014 62,519 83,739 92,589 99,173 104,055 105,709 2015 58,725 76,470 87,163 92,102 95,997 2016 57,961 76,823 86,752 94,372 2017 62,854 82,730 91,479 2018 69,721 89,628 2019 69,699 Total 983,814 All outstanding liabilities before 2010, net of reinsurance 7,462 Liabilities for loss and loss expenses, net of reinsurance 100,331 Homeowners (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 68,373 67,525 63,285 61,927 62,462 62,402 62,339 62,392 62,402 62,380 48 9,132 2011 103,804 98,211 97,761 94,167 94,543 94,183 94,378 94,587 94,572 82 15,111 2012 87,260 82,744 86,560 86,667 86,271 86,330 86,483 86,567 94 16,941 2013 73,670 72,528 71,494 72,145 71,714 72,148 72,318 420 7,749 2014 80,111 82,461 83,637 83,844 83,539 83,824 682 8,773 2015 76,637 76,400 76,559 74,723 74,978 660 7,746 2016 60,105 60,931 62,391 61,723 1,221 6,885 2017 59,167 67,978 70,365 2,500 7,370 2018 62,961 68,526 2,366 7,554 2019 64,306 6,299 6,468 Total 739,559 Homeowners (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 43,699 58,638 60,295 61,106 62,155 62,227 62,241 62,272 62,283 62,329 2011 71,668 89,963 91,718 92,185 93,312 93,720 94,007 94,412 94,458 2012 69,056 79,584 82,720 84,250 85,196 85,562 85,642 85,897 2013 50,664 65,528 67,838 69,775 71,776 72,197 72,433 2014 61,561 76,007 79,751 81,664 82,583 82,836 2015 52,589 70,078 72,202 72,927 74,079 2016 42,252 57,333 59,546 60,082 2017 45,466 63,290 67,193 2018 49,430 64,137 2019 49,680 Total 713,124 All outstanding liabilities before 2010, net of reinsurance 5,316 Liabilities for loss and loss expenses, net of reinsurance 31,752 E&S Casualty Lines (in thousands, except for claim counts) Incurred Loss and Allocated Loss Expenses, Net of Reinsurance As of Accident Year Unaudited IBNR Cumulative Number of Reported Claims 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ 3,294 $ 4,106 3,369 4,299 3,831 3,055 4,932 5,168 5,534 — 815 2011 8,127 7,102 9,853 12,207 10,273 9,652 10,228 12,119 11,554 177 1,332 2012 42,367 42,621 43,175 46,149 46,165 45,988 46,444 44,622 2,474 2,045 2013 55,468 60,309 67,099 69,112 67,647 68,972 68,451 13,816 2,280 2014 55,316 63,505 69,929 71,719 71,206 71,153 5,559 2,071 2015 75,498 76,432 82,404 90,488 90,355 15,752 2,799 2016 94,451 96,416 104,655 105,120 35,987 2,859 2017 91,438 95,783 99,866 47,074 2,614 2018 98,324 103,004 62,754 2,392 2019 117,087 103,146 1,679 Total 716,746 E&S Casualty Lines (in thousands) Cumulative Paid Loss and Allocated Loss Expenses, Net of Reinsurance Accident Year Unaudited 2011 2012 2013 2014 2015 2016 2017 2018 2019 2010 $ — $ 1,218 2,570 3,574 4,078 4,513 4,610 4,908 5,362 2011 — 806 3,200 6,445 9,954 9,912 10,256 9,819 9,604 2012 3,722 7,914 16,430 25,064 32,343 36,278 38,298 39,832 2013 2,715 9,470 21,980 35,200 46,108 51,142 54,974 2014 2,353 12,234 25,571 43,877 53,780 60,092 2015 3,036 13,057 29,389 50,712 64,529 2016 3,720 16,195 33,950 56,581 2017 5,057 14,672 34,179 2018 5,509 21,337 2019 4,422 Total 350,912 All outstanding liabilities before 2010, net of reinsurance 109 Liabilities for loss and loss expenses, net of reinsurance 365,943
Schedule of Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability	(in thousands) December 31, 2019 Net outstanding liabilities: Standard Commercial Lines General liability $ 1,280,416 Workers compensation 850,505 Commercial automobile 596,686 Businessowners' policies 86,747 Commercial property 52,071 Other Standard Commercial Lines 9,399 Total Standard Commercial Lines net outstanding liabilities 2,875,824 Standard Personal Lines Personal automobile 100,331 Homeowners 31,752 Other Standard Personal Lines 10,664 Total Standard Personal Lines net outstanding liabilities 142,747 E&S Lines Casualty lines 365,943 Property lines 8,199 Total E&S Lines net outstanding liabilities 374,142 Total liabilities for unpaid loss and loss expenses, net of reinsurance 3,392,713 Reinsurance recoverable on unpaid claims: Standard Commercial Lines General liability 195,830 Workers compensation 206,414 Commercial automobile 14,352 Businessowners' policies 3,012 Commercial property 26,526 Other Standard Commercial Lines 9,113 Total Standard Commercial Lines reinsurance recoverable on unpaid loss 455,247 Standard Personal Lines Personal automobile 44,104 Homeowners 1,182 Other Standard Personal Lines 28,993 Total Standard Personal Lines reinsurance recoverable on unpaid loss 74,279 E&S Lines Casualty lines 14,319 Property lines 317 Total E&S Lines reinsurance recoverable on unpaid loss 14,636 Total reinsurance recoverable on unpaid loss 544,162 Unallocated loss expenses 130,288 Total gross liability for unpaid loss and loss expenses $ 4,067,163
Schedule of Short-duration Insurance Contracts, Schedule of Historical Claims Duration	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 6.3% 12.5 15.5 17.0 14.2 9.8 5.6 4.9 2.8 1.9 Workers compensation 21.9 24.9 13.2 8.2 4.9 4.6 2.3 2.4 1.6 1.1 Commercial automobile 37.8 17.0 14.4 12.9 9.8 4.1 1.3 0.9 1.1 0.1 Businessowners’ policies 47.9 19.5 8.2 8.8 6.6 3.9 2.0 0.8 0.8 0.8 Commercial property 70.6 25.4 2.8 0.8 0.3 0.1 — — — — Personal automobile 58.2 18.4 9.9 6.8 4.2 1.5 0.5 0.3 0.1 0.1 Homeowners 72.2 20.3 3.3 1.5 1.6 0.4 0.3 0.2 0.1 0.1 E&S Lines - casualty 4.9 12.2 18.1 22.6 14.9 9.4 6.4 3.5 2.0

Indebtedness (Tables)

Indebtedness (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Line of Credit Covenant Requirements	Required as of Actual as of December 31, 2019 December 31, 2019 Consolidated net worth 1 Not less than $1.4 billion $2.1 billion Debt to total capitalization ratio 1 Not to exceed 35% 20.7%
Schedule of Long-term Debt Instruments	Outstanding Debt 2019 Carry Value Issuance Date Maturity Date Interest Rate Original Amount Unamortized Issuance Costs Debt Discount December 31, 2019 December 31, 2018 ($ in thousands) Description Long term Issuance: (1) Senior Notes 3/1/2019 3/1/2049 5.375 % $ 300,000 (3,147 ) (5,843 ) 291,010 — Redemption: (1) Senior Notes 2/8/2013 2/9/2043 5.875 % 185,000 — — — 180,771 Other Outstanding: (2) FHLBI 12/16/2016 12/16/2026 3.03 % 60,000 — — 60,000 60,000 (3) FHLBNY 8/15/2016 8/16/2021 1.56 % 25,000 — — 25,000 25,000 (3) FHLBNY 7/21/2016 7/21/2021 1.61 % 25,000 — — 25,000 25,000 (4) Senior Notes 11/3/2005 11/1/2035 6.70 % 100,000 (355 ) (520 ) 99,125 99,069 (5) Senior Notes 11/16/2004 11/15/2034 7.25 % 50,000 (185 ) (90 ) 49,725 49,700 Finance lease obligations 1 737 — Total long-term debt (3,687 ) (6,453 ) 550,597 439,540

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Schedule of Revenue from Continuing Operations By Segment	Revenue by Segment Years ended December 31, ($ in thousands) 2019 2018 2017 Standard Commercial Lines: Net premiums earned: Commercial automobile $ 554,256 493,093 442,818 Workers compensation 311,370 317,616 317,982 General liability 669,895 616,187 569,217 Commercial property 353,834 329,660 311,932 Businessowners’ policies 105,252 103,412 100,266 Bonds 35,726 33,991 29,086 Other 19,281 18,263 17,198 Miscellaneous income 10,889 8,180 9,488 Total Standard Commercial Lines revenue 2,060,503 1,920,402 1,797,987 Standard Personal Lines: Net premiums earned: Personal automobile 172,606 168,250 153,147 Homeowners 127,543 128,961 129,699 Other 7,590 7,230 6,855 Miscellaneous income 1,466 1,257 1,228 Total Standard Personal Lines revenue 309,205 305,698 290,929 E&S Lines: Net premiums earned: Casualty lines 182,864 164,313 157,366 Property lines 56,954 55,253 55,461 Miscellaneous income — 1 — Total E&S Lines revenue 239,818 219,567 212,827 Investments: Net investment income 222,543 195,336 161,882 Net realized and unrealized investment gains (losses) 14,422 (54,923 ) 6,359 Total Investments revenues 236,965 140,413 168,241 Total revenues $ 2,846,491 2,586,080 2,469,984
Schedule of Income from Continuing Operations before and after Federal Income Tax	Income Before and After Federal Income Tax Years ended December 31, ($ in thousands) 2019 2018 2017 Standard Commercial Lines: Underwriting gain, before federal income tax $ 145,990 109,104 149,514 Underwriting gain, after federal income tax 115,332 86,192 97,184 Combined ratio 92.9 % 94.3 % 91.6 % ROE contribution 5.8 % 4.9 6.1 Standard Personal Lines: Underwriting gain, before federal income tax 8,260 12,764 11,104 Underwriting gain, after federal income tax 6,525 10,084 7,217 Combined ratio 97.3 % 95.8 % 96.2 % ROE contribution 0.3 % 0.6 0.4 E&S Lines: Underwriting gain (loss), before federal income tax 9,743 (695 ) (6,282 ) Underwriting gain (loss), after federal income tax 7,697 (549 ) (4,083 ) Combined ratio 95.9 % 100.3 % 103.0 % ROE contribution 0.4 % — (0.3 ) Investments: Net investment income $ 222,543 195,336 161,882 Net realized and unrealized investment gains (losses) 14,422 (54,923 ) 6,359 Total investment segment income, before federal income tax 236,965 140,413 168,241 Tax on investment segment income 45,301 19,560 45,588 Total investment segment income, after federal income tax $ 191,664 120,853 122,653 ROE contribution of after-tax net investment income 9.6 % 6.9 7.5
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) 2019 2018 2017 Underwriting gain (loss) Standard Commercial Lines $ 145,990 109,104 149,514 Standard Personal Lines 8,260 12,764 11,104 E&S Lines 9,743 (695 ) (6,282 ) Investment income 236,965 140,413 168,241 Total all segments 400,958 261,586 322,577 Interest expense (33,668 ) (24,419 ) (24,354 ) Corporate expenses (30,900 ) (25,446 ) (36,255 ) Income, before federal income tax $ 336,390 211,721 261,968

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Schedule of Reconciliation of Earnings Per Share	2019 Income Shares Per Share ($ in thousands, except per share amounts) (Numerator) (Denominator) Amount Basic EPS: Net income available to common stockholders $ 271,623 59,421 $ 4.57 Effect of dilutive securities: Stock compensation plans — 583 Diluted EPS: Net income available to common stockholders $ 271,623 60,004 $ 4.53 2018 Income Shares Per Share ($ in thousands, except per share amounts) (Numerator) (Denominator) Amount Basic EPS: Net income available to common stockholders $ 178,939 58,950 $ 3.04 Effect of dilutive securities: Stock compensation plans — 763 Diluted EPS: Net income available to common stockholders $ 178,939 59,713 $ 3.00 2017 Income Shares Per Share ($ in thousands, except per share amounts) (Numerator) (Denominator) Amount Basic EPS: Net income available to common stockholders $ 168,826 58,458 $ 2.89 Effect of dilutive securities: Stock compensation plans — 899 Diluted EPS: Net income available to common stockholders $ 168,826 59,357 $ 2.84

Federal Income Taxes (Tables)

Federal Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Reconciliation of Federal Income Tax on Income at the Corporate Rate to the Effective Tax Rate	($ in thousands) 2019 2018 2017 Tax at statutory rate (21% in 2019 and 2018 and 35% in 2017) $ 70,642 44,461 91,689 Tax-advantaged interest (4,909 ) (5,518 ) (11,510 ) Dividends received deduction (443 ) (647 ) (1,961 ) Executive compensation 2,985 2,279 — Stock-based compensation (3,253 ) (3,093 ) (4,281 ) Tax Reform deferred tax write off — — 20,205 Other 1 (255 ) (4,700 ) (1,000 ) Federal income tax expense $ 64,767 32,782 93,142
Schedule of Deferred Tax Assets and Liabilities	($ in thousands) 2019 2018 Deferred tax assets: Net loss reserve discounting $ 48,193 43,285 Net unearned premiums 57,004 53,556 Employee benefits 10,646 8,862 Long-term incentive compensation plans 5,727 9,095 Temporary investment write-downs 1,059 1,155 Other 6,478 5,744 Total deferred tax assets 129,107 121,697 Deferred tax liabilities: Deferred policy acquisition costs 56,949 53,049 Unrealized gains on investment securities 45,294 502 Other investment-related items, net 7,576 4,904 Accelerated depreciation and amortization 12,512 9,702 Total deferred tax liabilities 122,331 68,157 Net deferred federal income tax asset $ 6,776 53,540

Retirement Plans (Tables)

Retirement Plans (Tables)	12 Months Ended
	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Schedule of Funded Status Of Retirement Income Plan And Retirement Life Plan	December 31, Pension Plan ($ in thousands) 2019 2018 Change in Benefit Obligation: Benefit obligation, beginning of year $ 334,679 364,411 Interest cost 13,506 12,428 Actuarial losses (gains) 54,478 (31,738 ) Benefits paid (11,642 ) (10,422 ) Benefit obligation, end of year $ 391,021 334,679 Change in Fair Value of Assets: Fair value of assets, beginning of year $ 331,680 363,673 Actual return on plan assets, net of expenses 63,949 (21,571 ) Contributions by the employer to funded plans 1,100 — Benefits paid (11,642 ) (10,422 ) Fair value of assets, end of year $ 385,087 331,680 Funded status $ (5,934 ) (2,999 )
Schedule of Amounts Recognized in Consolidated Balance Sheet	Amounts Recognized in the Consolidated Balance Sheet: Liabilities $ (5,934 ) (2,999 ) Net pension liability, end of year $ (5,934 ) (2,999 )
Schedule of Amounts recognized in Accumulated Other than Comprehensive Income	Amounts Recognized in AOCI: Net actuarial loss $ 107,125 98,057 Total $ 107,125 98,057
Schedule of Other Information as of December 31	Other Information as of December 31: Accumulated benefit obligation $ 391,021 334,679
Schedule of Components Of Net Periodic Benefit Cost And Other Amounts Recognized In Other Comprehensive Income	Pension Plan ($ in thousands) 2019 2018 2017 Components of Net Periodic Benefit Cost and Other Amounts Recognized in Other Comprehensive Income: Net Periodic Benefit Cost (Benefit): Interest cost $ 13,506 12,428 12,490 Expected return on plan assets (21,114 ) (22,767 ) (19,419 ) Amortization of unrecognized actuarial loss 2,575 1,981 2,001 Total net periodic pension cost (benefit) 1 $ (5,033 ) (8,358 ) (4,928 ) Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income: Net actuarial loss (gain) $ 11,643 12,600 3,594 Reversal of amortization of net actuarial loss (2,575 ) (1,981 ) (2,001 ) Total recognized in other comprehensive income $ 9,068 10,619 1,593 Total recognized in net periodic benefit cost and other comprehensive income $ 4,035 2,261 (3,335 )
Schedule Of Weighted- Average Expense and Liability Assumptions	Pension Plan 2019 2018 2017 Weighted-Average Expense Assumptions for the years ended December 31: Discount rate 4.46 % 3.78 4.41 Expected return on plan assets 6.50 6.36 6.24 Weighted-Average Liability Assumptions as of December 31: Discount rate 3.33 % 4.46
Schedule of Allocation of Plan Assets	2019 2018 Target Percentage Actual Percentage Actual Percentage Return seeking assets 1 15%-70% 59 % 43 % Liability hedging assets 35%-75% 38 % 38 % Short-term investments - 3 % 19 % Total 100 % 100 % 100 %
Schedule of Quantitative Disclosures of our Financial Assets that were Measured at Fair Value	December 31, 2019 Fair Value Measurements Using ($ in thousands) Assets Measured at Fair Value Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Description Measured on a recurring basis: AFS fixed income securities: U.S. government and government agencies $ 116,186 41,083 75,103 — Foreign government 18,542 — 18,542 — Obligations of states and political subdivisions 1,230,090 — 1,230,090 — Corporate securities 1,947,477 — 1,930,426 17,051 CLO and other ABS 793,012 3,635 772,343 17,034 CMBS 538,344 — 538,344 — RMBS 1,451,969 — 1,451,969 — Total AFS fixed income securities 6,095,620 44,718 6,016,817 34,085 Equity securities: Common stock 1 69,900 32,145 — — Preferred stock 3,037 3,037 — — Total equity securities 72,937 35,182 — — Short-term investments 282,490 265,306 17,184 — Total assets measured at fair value $ 6,451,047 345,206 6,034,001 34,085 December 31, 2018 Fair Value Measurements Using ($ in thousands) Assets Measured at Fair Value Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Description Measured on a recurring basis: AFS fixed income securities: U.S. government and government agencies $ 121,310 78,381 42,929 — Foreign government 23,131 — 23,131 — Obligations of states and political subdivisions 1,138,469 — 1,138,469 — Corporate securities 1,617,408 — 1,617,408 — CLO and other ABS 717,362 — 709,953 7,409 CMBS 527,078 — 527,078 — RMBS 1,128,342 — 1,128,342 — Total AFS fixed income securities 5,273,100 78,381 5,187,310 7,409 Equity securities: Common stock 1 144,727 107,397 — — Preferred stock 2,912 2,912 — — Total equity securities 147,639 110,309 — — Short-term investments 323,864 321,370 2,494 — Total assets measured at fair value $ 5,744,603 510,060 5,189,804 7,409 1 In accordance with ASU 2015-07, investments amounting to $37.8 million and $37.3 million at December 31, 2019 and December 31, 2018, respectively, were measured at fair value using the net asset value per share (or its practical expedient) and have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to total assets measured at fair value.
Schedule of Expected Benefit Payments	Payments ($ in thousands) Pension Plan Benefits Expected to be Paid in Future Fiscal Years: 2020 $ 14,968 2021 14,947 2022 16,115 2023 17,144 2024 18,146 2025-2029 103,669
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, 2019 Fair Value Measurements at 12/31/19 Using ($ in thousands) Assets Measured at Fair Value At 12/31/19 Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Description Return seeking assets: Equities: Global Equity $ 113,212 113,212 — — Diversified Credit 59,009 59,009 — — Real Assets 57,414 57,414 — — Total Equities 229,635 229,635 — — Limited partnerships (at net asset value) 1 : Real assets 228 — — — Private equity 583 — — — Private credit 43 — — — Total limited partnerships 854 — — — Total return seeking assets 230,489 229,635 — — Liability hedging assets: Fixed income 114,395 114,395 — — U.S. Treasury overlay 30,997 30,997 — — Total liability hedging assets 145,392 145,392 — — Cash and short-term investments: Short-term investments 8,824 8,824 — — Deposit administration contracts 2,215 — 2,215 — Total cash and short-term investments 11,039 8,824 2,215 — Total invested assets $ 386,920 383,851 2,215 — December 31, 2018 Fair Value Measurements at 12/31/18 Using ($ in thousands) Assets Measured at Fair Value At 12/31/18 Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Description Return seeking assets: Global Equity $ 113,409 113,409 — — Private assets 1 : Limited partnerships (at net asset value): Real assets 16,818 — — — Private equity 878 — — — Private credit 262 — — — Hedge fund 7,889 — — — Total limited partnerships 25,847 — — — Other private assets 3,780 — — — Total private assets 29,627 — — — Total return seeking assets 143,036 113,409 — — Liability hedging assets: Fixed income 106,000 106,000 — — U.S. Treasury overlay 18,528 18,528 — — Total liability hedging assets 124,528 124,528 — — Cash and short-term investments: Short-term investments 62,788 62,788 — — Deposit administration contracts 1,482 — 1,482 — Total cash and short-term investments 64,270 62,788 1,482 — Total invested assets $ 331,834 300,725 1,482 — 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, 2019
Share-based Payment Arrangement [Abstract]
Schedule Of Share-Based Compensation Plan Approval	Plan Approvals Stock Plan Approved effective as of May 1, 2014 by stockholders on April 23, 2014. Most recently amended and restated plan was approved effective May 2, 2018 by stockholders on May 2, 2018. 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 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 Share-Based Compensation Shares Authorized and Available for Issuance	As of December 31, 2019 Authorized Available for Issuance Awards Outstanding Stock Plan 4,750,000 3,208,968 760,639 ESPP 1,500,000 356,229 — Agent Plan 3,000,000 1,728,471 —
Schedule of Share-Based Compensation Retired Plans	December 31, 2019 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. 1,985,129 59,729 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. 44,468 44,468 1 Awards outstanding under the 2005 Stock Plan consisted of 32,906 shares deferred by our non-employee directors and 26,823 stock options.
Schedule of Summary of Restricted Stock Units Transactions under Share-Based Payment Plans	Number Weighted Unvested RSU awards at December 31, 2018 846,305 $ 44.00 Granted in 2019 265,680 63.60 Vested in 2019 (337,525 ) 36.08 Forfeited in 2019 (27,735 ) 51.89 Unvested RSU awards at December 31, 2019 746,725 $ 53.48
Schedule of Summary of Stock Option Transactions under Share Based Payment Plans	Number Weighted Weighted Aggregate Outstanding at December 31, 2018 126,735 $ 14.37 Granted in 2019 — — Exercised in 2019 (99,912 ) 13.74 Forfeited or expired in 2019 — — Outstanding at December 31, 2019 26,823 $ 16.71 0.33 $ 1,300 Exercisable at December 31, 2019 26,823 $ 16.71 0.33 $ 1,300
Schedule of Share-Based Compensation ESPP and ASPP Shares Granted	2019 2018 2017 ESPP Issuances 72,952 70,448 75,093 Agent Plan Issuances 47,888 41,134 49,794
Schedule of Weighted Average Assumptions for Employee Stock Purchase Plan	ESPP 2019 2018 2017 Risk-free interest rate 2.33 % 1.88 1.07 Expected term 6 months 6 months 6 months Dividend yield 1.2 % 1.3 1.3 Expected volatility 26 % 18 24
Schedule of Weighted-Average Fair Value of Options and Stock Per Share	2019 2018 2017 RSUs $ 63.60 55.96 42.66 ESPP: Six month option 4.32 2.67 2.73 Discount of grant date market value 9.99 8.50 7.06 Total ESPP 14.31 11.17 9.79 Agent Plan: Discount of grant date market value 7.00 5.99 5.04
Schedule of Compensation Cost for Share-based Payment Arrangements	($ in millions) 2019 2018 2017 Share-based compensation expense, pre-tax $ 24.5 19.3 31.2 Income tax benefit, including the benefit related to stock grants that vested during the year (8.2 ) (7.0 ) (15.0 ) Share-based compensation expense, after-tax $ 16.3 12.3 16.2

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Components of Lease Expense	($ in thousands) 2019 Operating lease cost, included in Other insurance expenses on the Consolidated Statements of Income $ 8,808 Finance lease cost: Amortization of assets, included in Other insurance expenses on the Consolidated Statements of Income 984 Interest on lease liabilities, included in Interest expense on the Consolidated Statements of Income 16 Total finance lease cost 1,000 Variable lease cost, included in Other insurance expenses on the Consolidated Statements of Income 48 Short-term lease cost, included in Other insurance expenses on the Consolidated Statements of Income $ 2,165
Supplemental Lease Information	December 31, 2019 Weighted-average remaining lease term Operating leases 6 years Finance leases 2 Weighted-average discount rate Operating leases 3.4 % Finance leases 1 2.1
Lease Assets and Liabilities	($ in thousands) December 31, 2019 Operating leases Other assets $ 26,535 Other liabilities 27,506 Finance leases Property and equipment - at cost, net of accumulated depreciation and amortization 731 Long-term debt $ 737
Maturities of Lease Liabilities	($ in thousands) Finance Leases Operating Leases Total Year ended December 31, 2020 $ 451 8,244 8,695 2021 248 6,168 6,416 2022 54 4,590 4,644 2023 — 3,329 3,329 2024 — 2,920 2,920 Thereafter — 8,638 8,638 Total lease payments 753 33,889 34,642 Less: imputed interest 16 2,995 3,011 Less: leases that have not yet commenced — 3,388 3,388 Total lease liabilities $ 737 27,506 28,243 At December 31, 2018 , the maturities of our lease liabilities for capital and operating leases were as follows: ($ in thousands) Capital Leases Operating Leases Total 2019 $ 728 7,762 8,490 2020 141 7,355 7,496 2021 22 5,083 5,105 2022 — 3,641 3,641 2023 — 2,900 2,900 Thereafter — 9,698 9,698 Total minimum payment required $ 891 36,439 37,330

Commitments and Contingencies I

Commitments and Contingencies Investments Contractual Obligations (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Investments Classified by Contractual Maturity Date [Table Text Block]	($ in millions) Amount of Obligation Year of Expiration of Obligation Alternative and other investments $ 219.2 2036 Non-publicly traded collateralized loan obligations in our fixed income securities portfolio 35.4 2030 Non-publicly traded common stock within our equity portfolio 3.9 2023 Commercial mortgage loans 10.0 Less than 1 year Privately-placed corporate securities 15.0 Less than 1 year Total $ 283.5

Statutory Financial Informati_2

Statutory Financial Information, Capital Requirements, and Restrictions on Dividends and Transfers of Funds (Tables)	12 Months Ended
	Dec. 31, 2019
Insurance [Abstract]
Schedule of Insurance Subsidiaries Statutory Surplus Data	State of Domicile Unassigned Surplus Statutory Surplus Statutory Net Income ($ in millions) 2019 2018 2019 2018 2019 2018 2017 SICA New Jersey $ 525.9 478.6 680.1 632.8 113.9 78.0 84.6 Selective Way Insurance Company ("SWIC") New Jersey 339.2 300.2 388.2 349.3 59.2 47.5 43.6 SICSC Indiana 132.6 119.4 163.8 150.7 23.9 16.5 17.9 SICSE Indiana 103.1 92.2 128.7 117.7 18.5 12.9 14.7 SICNY New York 99.4 86.5 127.1 114.2 17.0 12.0 13.4 Selective Insurance Company of New England ("SICNE") New Jersey 25.3 19.9 55.4 50.0 7.8 5.6 6.3 Selective Auto Insurance Company of New Jersey ("SAICNJ") New Jersey 62.5 50.3 105.4 93.2 14.9 9.9 11.4 MUSIC New Jersey 27.1 23.0 95.6 91.5 13.2 9.4 10.3 Selective Casualty Insurance Company ("SCIC") New Jersey 58.2 44.9 132.7 119.3 16.8 13.3 13.4 Selective Fire and Casualty Insurance Company ("SFCIC") New Jersey 23.5 17.8 55.4 49.7 7.5 5.5 5.6 Total $ 1,396.8 1,232.8 1,932.4 1,768.4 292.7 210.6 221.2
Schedule of Insurance Subsidiaries Dividend Paid To Parent	Dividends Twelve Months ended December 31, 2019 2020 ($ in millions) State of Domicile Ordinary Dividends Paid Maximum Ordinary Dividends SICA New Jersey $ 55.5 $ 98.4 SWIC New Jersey 19.0 53.7 SICSC Indiana 9.5 23.9 SICSE Indiana 6.7 18.6 SICNY New York 3.3 12.7 SICNE New Jersey 2.0 7.6 SAICNJ New Jersey 1.5 14.7 MUSIC New Jersey 8.0 12.9 SCIC New Jersey 3.0 16.8 SFCIC New Jersey 1.5 7.4 Total $ 110.0 $ 266.7

Quarterly Financial Informati_2

Quarterly Financial Information (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	First Quarter Second Quarter Third Quarter Fourth Quarter (unaudited, $ in thousands, except per share data) 2019 2018 2019 2018 2019 2018 2019 2018 Net premiums earned $ 632,573 591,828 642,619 604,836 653,620 614,277 668,359 625,288 Net investment income earned 50,618 43,231 58,505 45,553 55,826 52,443 57,594 54,109 Net realized and unrealized gains (losses) 13,451 (10,549 ) 4,027 (1,652 ) (2,183 ) (4,787 ) (873 ) (37,935 ) Other income 2,320 2,179 3,053 3,179 3,162 2,538 3,820 1,542 Total revenues 698,962 626,689 708,204 651,916 710,425 664,471 728,900 643,004 Income before federal income taxes 73,694 19,931 90,225 72,525 71,178 67,130 101,293 52,135 Net income 61,348 18,925 72,266 58,819 56,150 55,435 81,859 45,760 Net income per share: Basic 1.04 0.32 1.22 1.00 0.94 0.94 1.38 0.77 Diluted 1.02 0.32 1.21 0.99 0.93 0.93 1.36 0.76 The addition of all quarters may not agree to annual amounts on the Financial Statements due to rounding.

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended			12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Percent of Portfolio Level 3 Securities				1.00%
Depreciation expense				$ 18.7	$ 19.5	$ 17.8
Investment yields before tax assumed in premium deficiency assessment	3.50%	3.30%	2.90%

Summary of Significant Accoun_5

Summary of Significant Accounting Policies (Property and Equipment) (Details)	12 Months Ended
	Dec. 31, 2019
Computer hardware [Member]
Property, Plant and Equipment, Estimated Useful Lives	3
Internally developed software [Member]
Property, Plant and Equipment, Estimated Useful Lives	5
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] | 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] | Building and improvements [Member]
Property, Plant and Equipment, Estimated Useful Lives	5

Statements of Cash Flow (Cash F

Statements of Cash Flow (Cash Flow Supplemental Disclosures) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest		$ 25,089	$ 23,992	$ 23,905
Federal income tax		55,825	29,193	62,000
Operating cash flows from operating leases	[1]	8,138	0	0
Operating cash flows from financing leases		16	0	0
Financing cash flows from financing leases		977	5,646	4,121
Corporate actions related to equity securities	[2]	14,250	944	4,725
Assets acquired under finance lease arrangements		824	4,119	278
Assets acquired under operating lease arrangements	[1]	13,808	0	0
Non-cash purchase of property and equipment		89	291	0
AFS Fixed Income Securities [Member]
Corporate actions related to fixed income securities, AFS	[2]	$ 61,369	$ 52,277	$ 22,511
[1]	1 Upon adoption of ASU 2016-02, effective January 1, 2019, we are required to disclose cash paid for amounts included in the measurement of operating lease liabilities, as well as supplemental non-cash information on operating lease liabilities arising from obtaining operating lease assets.
[2]	2 Examples of corporate actions include exchanges, non-cash acquisitions, and stock-splits.

Statements of Cash Flow Stateme

Statements of Cash Flow Statements of Cash Flow (Cash and Restricted Cash) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Information [Abstract]
Cash	$ 300	$ 505
Restricted cash	7,675	16,414
Total cash and restricted cash shown in the Statements of Cash Flows	$ 7,975	$ 16,919	$ 44,710	$ 37,405

Investments (Unrealized Gains o

Investments (Unrealized Gains on Investments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Proceeds from Sale of Equity Securities	$ 137,294	$ 113,339	$ 37,960
Net unrealized gains	215,688	2,391	124,679
Deferred income tax expense	(45,294)	(502)	(44,103)
Net unrealized gains, net of deferred income tax	170,394	1,889	80,576
Cumulative effect adjustment			(25,000)
Increase (decrease) in net unrealized gains in OCI, net of deferred income tax	168,505	(65,881)	38,453
Equity Securities [Member]
Net unrealized gains	0	0	38,894
Available-for-sale Securities [Member]
Net unrealized gains	215,634	2,302	85,806
AFS Fixed Income Securities [Member]
Net unrealized gains			124,700
Total HTM Securities [Member]
Net unrealized gains	31	89	(21)
Short-term Investments [Member]
Net unrealized gains	23	0	0
Accounting Standards Update 2018-02 [Member] | Investments [Member]
Cumulative effect adjustment	0	(17,920)	0
Accounting Standards Update 2018-02 [Member] | Retained Earnings [Member]
Cumulative effect adjustment		0	(5,707)	$ 0
Accounting Standards Update 2018-02 [Member] | Retained Earnings [Member] | Investments [Member]
Cumulative effect adjustment		(17,900)
Accounting Standards Update 2016-01 [Member]
Cumulative effect adjustment	$ 0	30,726	0
Accounting Standards Update 2016-01 [Member] | Retained Earnings [Member]
Cumulative effect adjustment		$ 0	$ 30,726	$ 0

Investments (Held-To-Maturity S

Investments (Held-To-Maturity Securities Disclosure) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Amortized Cost	$ 20,769	$ 37,021
Net Unrealized Gains (Losses)	31	89
Fixed income securities, held-to-maturity	20,800	37,110
Unrecognized Holding Gains	1,176	1,359
Unrecognized Holding Losses	(1)	(152)
Total HTM fixed income securities fair value	21,975	38,317
Obligations of States and Political Subdivisions [Member]
Amortized Cost	4,573	17,431
Net Unrealized Gains (Losses)	7	39
Fixed income securities, held-to-maturity	4,580	17,470
Unrecognized Holding Gains	342	504
Unrecognized Holding Losses	(1)	(5)
Total HTM fixed income securities fair value	4,921	17,969
Corporate Securities [Member]
Amortized Cost	16,196	19,590
Net Unrealized Gains (Losses)	24	50
Fixed income securities, held-to-maturity	16,220	19,640
Unrecognized Holding Gains	834	855
Unrecognized Holding Losses	0	(147)
Total HTM fixed income securities fair value	$ 17,054	$ 20,348

Investments (Available-For-Sale

Investments (Available-For-Sale Securities Disclosure) (Details) - Available-for-sale Securities [Member] - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Cost/Amortized Cost	$ 5,879,986	$ 5,270,798
Unrealized Gains	223,372	47,369
Unrealized Losses	(7,738)	(45,067)
Total AFS securities	6,095,620	5,273,100
U.S. Government and Government Agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Cost/Amortized Cost	112,680	120,092
Unrealized Gains	3,506	1,810
Unrealized Losses	0	(592)
Total AFS securities	116,186	121,310
Foreign Government [Member]
Debt Securities, Available-for-sale [Line Items]
Cost/Amortized Cost	18,011	23,202
Unrealized Gains	533	36
Unrealized Losses	(2)	(107)
Total AFS securities	18,542	23,131
Obligations of States and Political Subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Cost/Amortized Cost	1,168,185	1,121,615
Unrealized Gains	62,175	19,485
Unrealized Losses	(270)	(2,631)
Total AFS securities	1,230,090	1,138,469
Corporate Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost/Amortized Cost	1,866,881	1,639,852
Unrealized Gains	81,906	5,521
Unrealized Losses	(1,310)	(27,965)
Total AFS securities	1,947,477	1,617,408
Collateralized Loan Obligations and Other Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost/Amortized Cost	790,517	720,193
Unrealized Gains	7,929	4,112
Unrealized Losses	(5,434)	(6,943)
Total AFS securities	793,012	717,362
Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost/Amortized Cost	514,709	527,409
Unrealized Gains	23,902	3,417
Unrealized Losses	(267)	(3,748)
Total AFS securities	538,344	527,078
Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost/Amortized Cost	1,409,003	1,118,435
Unrealized Gains	43,421	12,988
Unrealized Losses	(455)	(3,081)
Total AFS securities	$ 1,451,969	$ 1,128,342

Investments (Number of Securiti

Investments (Number of Securities in an Unrealized Unrecognized Loss Position) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Percentage Decline in Fair Value Percentage of Amortized Cost	1.00%	2.00%
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	$ 100	$ 200
Available-for-sale Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	516,259	2,142,433
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(3,379)	(36,948)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	230,770	275,174
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(4,359)	(8,119)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	747,029	2,417,607
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(7,738)	(45,067)
U.S. Government and Government Agencies [Member] | Available-for-sale Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		6,693
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(174)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		23,163
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		(418)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value		29,856
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		(592)
Foreign Government [Member] | Available-for-sale Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,416	12,208
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2)	(93)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	1,482
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	(14)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	1,416	13,690
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(2)	(107)
Obligations of States and Political Subdivisions [Member] | Available-for-sale Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	35,838	196,798
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(270)	(2,074)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	42,821
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	(557)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	35,838	239,619
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(270)	(2,631)
Corporate Securities [Member] | Available-for-sale Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	84,832	1,041,952
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(480)	(23,649)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	20,182	78,953
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(830)	(4,316)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	105,014	1,120,905
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(1,310)	(27,965)
Collateralized Loan Obligations and Other Asset-Backed Securities [Member] | Available-for-sale Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	205,191	516,106
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,938)	(6,750)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	204,385	16,800
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(3,496)	(193)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	409,576	532,906
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(5,434)	(6,943)
Commercial Mortgage Backed Securities [Member] | Available-for-sale Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	62,893	229,338
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(264)	(2,548)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	828	66,294
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(3)	(1,200)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	63,721	295,632
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(267)	(3,748)
Residential Mortgage Backed Securities [Member] | Available-for-sale Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	126,089	139,338
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(425)	(1,660)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	5,375	45,661
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(30)	(1,421)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	131,464	184,999
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (455)	$ (3,081)

Investments (Fixed Maturity Sec

Investments (Fixed Maturity Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
AFS due in one year or less fair value	$ 394,027
AFS due after one year through five years fair value	3,001,602
AFS due after five years through 10 years fair value	2,531,172
AFS due after 10 years fair value	168,819
Fixed income securities, available-for-sale securities	6,095,620	$ 5,273,100
HTM due in one year or less carrying value	1,211
HTM due after one year through five years carrying value	13,856
HTM due after five years through 10 years carrying value	5,733
HTM due after 10 years carrying value	0
Total HTM fixed income securities carrying value	20,800	37,110
HTM due in one year or less fair value	1,229
HTM due after one year through five years fair value	14,820
HTM due after five years through 10 years fair value	5,926
HTM due after 10 years fair value	0
Total HTM fixed income securities fair value	$ 21,975	$ 38,317

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, 2019	Dec. 31, 2018
Carrying Value		$ 216,807	$ 178,938
Other Securities [Member]
Carrying Value	[1]	32,667	25,042
Remaining Commitment	[1]	0	0
Maximum Exposure to Loss	[1]	32,667	25,042
Real Assets [Member]
Carrying Value		23,256	27,862
Remaining Commitment		20,741	27,129
Maximum Exposure to Loss		43,997	54,991
Private Credit Funds [Member]
Carrying Value		42,532	41,682
Remaining Commitment		105,340	81,453
Maximum Exposure to Loss		147,872	123,135
Private Equity [Member]
Carrying Value		118,352	84,352
Remaining Commitment		93,138	93,688
Maximum Exposure to Loss		211,490	178,040
Other Investment Portfolio [Member]
Carrying Value		216,807	178,938
Remaining Commitment		219,219	202,270
Maximum Exposure to Loss		436,026	381,208
Alternative Investments [Member]
Carrying Value		184,140	153,896
Remaining Commitment		219,219	202,270
Maximum Exposure to Loss		$ 403,359	$ 356,166
[1]	Other securities primarily consists of tax credit investments.

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, 2019	Sep. 30, 2018
Investments	$ 43,857	$ 28,292
Total assets	45,432	30,377
Total liabilities	5,670	4,532
Partners' capital	$ 39,762	$ 25,845

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, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Schedule of Equity Method Investments [Line Items]
Net investment income earned	$ 57,594	$ 55,826	$ 58,505	$ 50,618	$ 54,109	$ 52,443	$ 45,553	$ 43,231	$ 222,543		$ 195,336		$ 161,882
Investments Accounted For Under The Equity Method [Member]
Schedule of Equity Method Investments [Line Items]
Net investment (loss) income										$ (8,000)		$ 134,000		$ (143,000)
Realized gains										695,000		1,981,000		325,000
Net change in unrealized appreciation										5,543,000		1,303,000		2,894,000
Net Income										6,230,000		3,418,000		3,076,000
Alternative Investments [Member]
Schedule of Equity Method Investments [Line Items]
Net investment income earned										$ 17,900		$ 17,600		$ 12,700

Investments (Credit Concentrati

Investments (Credit Concentration Risk) (Details)	Dec. 31, 2019	Dec. 31, 2018
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 (Investments Pledge

Investments (Investments Pledged as Collateral) (Details) $ in Millions	Dec. 31, 2019USD ($)
Available-for-sale Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Assets Held by Insurance Regulators	$ 27.1
Securities pledged as collateral for reinsurance obligations	188.8
U.S. Government and Government Agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Assets Held by Insurance Regulators	22.8
Securities pledged as collateral for reinsurance obligations	22.8
Obligations of States and Political Subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	0
Assets Held by Insurance Regulators	4
Securities pledged as collateral for reinsurance obligations	4
Corporate Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Assets Held by Insurance Regulators	0.3
Securities pledged as collateral for reinsurance obligations	0.3
Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Assets Held by Insurance Regulators	0
Securities pledged as collateral for reinsurance obligations	25.1
Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Assets Held by Insurance Regulators	0
Securities pledged as collateral for reinsurance obligations	136.6
Federal Home Loan Bank of New York [Member] | Available-for-sale Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	95.5
Federal Home Loan Bank of New York [Member] | U.S. Government and Government Agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	0
Federal Home Loan Bank of New York [Member] | Corporate Securities [Member]
Debt Securities, Available-for-sale [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]
Debt Securities, Available-for-sale [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	17.9
Federal Home Loan Bank of New York [Member] | Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	77.6
Federal Home Loan Bank of Indianapolis [Member] | Available-for-sale Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	66.2
Federal Home Loan Bank of Indianapolis [Member] | U.S. Government and Government Agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	0
Federal Home Loan Bank of Indianapolis [Member] | Obligations of States and Political Subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	0
Federal Home Loan Bank of Indianapolis [Member] | Corporate Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	0
Federal Home Loan Bank of Indianapolis [Member] | Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	7.2
Federal Home Loan Bank of Indianapolis [Member] | Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	$ 59

Investments (Net Investment Inc

Investments (Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement [Line Items]
Net investment income earned	$ 57,594	$ 55,826	$ 58,505	$ 50,618	$ 54,109	$ 52,443	$ 45,553	$ 43,231	$ 222,543	$ 195,336	$ 161,882
Fixed Income Securities [Member]
Statement [Line Items]
Net investment income earned									203,255	178,104	153,230
Equity Securities [Member]
Statement [Line Items]
Net investment income earned									6,996	7,764	6,442
Short-term Investments [Member]
Statement [Line Items]
Net investment income earned									6,653	3,472	1,526
Other Investment Portfolio [Member]
Statement [Line Items]
Net investment income earned									18,778	17,799	12,871
Investment Expenses [Member]
Statement [Line Items]
Net investment income earned									$ (13,139)	$ (11,803)	$ (12,187)

Investments (OTTI by Asset Type

Investments (OTTI by Asset Type) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
OTTI Losses Gross	$ 3,644	$ 6,579	$ 4,809
OTTI included in OCI	0	0	(36)
Total OTTI charges recognized in earnings	3,644	6,579	4,845
Other Investments [Member]
OTTI Losses Gross	1,049	1,893	190
OTTI included in OCI	0	0	0
Total OTTI charges recognized in earnings	1,049	1,893	190
Available-for-sale Securities [Member]
OTTI Losses Gross	2,595	4,686	3,184
OTTI included in OCI	0	0	(36)
Total OTTI charges recognized in earnings	2,595	4,686	3,220
Available-for-sale Securities [Member] | US Government Agencies Debt Securities [Member]
OTTI Losses Gross			36
OTTI included in OCI			0
Total OTTI charges recognized in earnings			36
Available-for-sale Securities [Member] | Obligations of States and Political Subdivisions [Member]
OTTI Losses Gross	66		612
OTTI included in OCI	0		0
Total OTTI charges recognized in earnings	66		612
Available-for-sale Securities [Member] | Corporate Securities [Member]
OTTI Losses Gross	2,529	1,783	587
OTTI included in OCI	0	0	0
Total OTTI charges recognized in earnings	$ 2,529	1,783	587
Available-for-sale Securities [Member] | Collateralized Loan Obligations and Other Asset-Backed Securities [Member]
OTTI Losses Gross			96
OTTI included in OCI			0
Total OTTI charges recognized in earnings			96
Available-for-sale Securities [Member] | Commercial Mortgage Backed Securities [Member]
OTTI Losses Gross			670
OTTI included in OCI			0
Total OTTI charges recognized in earnings			670
Available-for-sale Securities [Member] | Residential Mortgage Backed Securities [Member]
OTTI Losses Gross		2,903	1,183
OTTI included in OCI		0	(36)
Total OTTI charges recognized in earnings		$ 2,903	1,219
Available-for-sale Securities [Member] | Equity Securities [Member]
OTTI Losses Gross			1,435
OTTI included in OCI			0
Total OTTI charges recognized in earnings			1,435
Common Stock [Member] | Available-for-sale Securities [Member] | Equity Securities [Member]
OTTI Losses Gross			1,435
OTTI included in OCI			0
Total OTTI charges recognized in earnings			$ 1,435

Investments (Components of Net

Investments (Components of Net Realized and Unrealized Gains (Losses)) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Gain (Loss) on Securities [Line Items]
Unrealized Gain (Loss) on Investments									$ 1,219	$ (3,098)
Proceeds from Sale of Equity Securities									137,294	113,339	$ 37,960
Net realized investment gains (losses) on disposals									26,715	(18,975)	11,204
OTTI charges									(3,644)	(6,579)	(4,845)
Net realized gains (losses)									23,071	(25,554)	6,359
Unrealized losses recognized in income on equity securities									(8,649)	(29,369)	0
Total net realized and unrealized gains (losses)	$ (873)	$ (2,183)	$ 4,027	$ 13,451	$ (37,935)	$ (4,787)	$ (1,652)	$ (10,549)	14,422	(54,923)	6,359
Unrealized (losses) gains recognized in income on equity securities that were sold in the respective period									(9,868)	(26,271)
Fixed Income Securities [Member]
Gain (Loss) on Securities [Line Items]
Net realized investment gains (losses) on disposals									1,910	(34,953)	6,944
Equity Securities [Member]
Gain (Loss) on Securities [Line Items]
Net realized investment gains (losses) on disposals									24,844	18,695	4,629
Short-term Investments [Member]
Gain (Loss) on Securities [Line Items]
Net realized investment gains (losses) on disposals									(16)	(3)	(4)
Other Investments [Member]
Gain (Loss) on Securities [Line Items]
Net realized investment gains (losses) on disposals									$ (23)	$ (2,714)	$ (365)

Investments (Net Realized Gains

Investments (Net Realized Gains Losses on Disposal) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
HTM fixed income securities gains	$ 1	$ 2	$ 44
HTM fixed income securities losses	(15)	0	(1)
Equity securities gains	24,980	23,203	5,829
Equity securities losses	(136)	(4,508)	(1,200)
Short term investments gains	24	7	2
Short term investments losses	(40)	(10)	(6)
Other investment securities gains	6	0	494
Other investment securities losses	(29)	(2,714)	(859)
Net realized investment gains (losses) on disposals	26,715	(18,975)	11,204
Sale of fixed income securities, available-for-sale	594,743	2,030,664	1,197,920
Sale of equity securities	137,294	113,339	37,960
Fixed Income Securities [Member]
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
AFS securities gains	6,899	5,460	10,193
AFS securities losses	(4,975)	(40,415)	(3,292)
Equity Securities [Member]
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Net realized investment gains (losses) on disposals	$ 24,844	$ 18,695	$ 4,629

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, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income before federal income tax	$ 101,293	$ 71,178	$ 90,225	$ 73,694	$ 52,135	$ 67,130	$ 72,525	$ 19,931	$ 336,390	$ 211,721	$ 261,968
Income Tax Expense (Benefit)									64,767	32,782	93,142
Net income	$ 81,859	$ 56,150	$ 72,266	$ 61,348	$ 45,760	$ 55,435	$ 58,819	$ 18,925	271,623	178,939	168,826
Unrealized holding gains (losses) during the period, Gross									212,683	(123,145)	66,894
Unrealized holding gains (losses) during the period, Tax									44,662	(25,861)	23,879
Unrealized holding gains (losses) arising during period, Net									168,021	(97,284)	43,015
Non-credit portion of other-than-temporary impairment losses recognized in other comprehensive income, Gross											36
Non-Credit Portion of Other-Than-Temporary Impairment Losses Recognized In Other Comprehensive Income, Tax											13
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, Net of Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities											(23)
Amount reclassified into net income: HTM securities, Gross									(58)	110	(179)
Amounts reclassified into net income: HTM securities, Tax									(12)	23	(63)
Amount reclassified into net income: HTM securities, Net									(46)	87	(116)
Non-credit OTTI, Gross											104
Non-credit OTTI, Tax											36
Amounts reclassified into net income: Non-credit other-than-temporary impairment									0	0	68
Realized losses (gains) on disposals and OTTI of AFS securities, Gross									671	39,641	(6,979)
Realized losses (gains) on disposals and OTTI of AFS securities, Tax									141	8,325	(2,442)
Realized losses (gains) on disposals and OTTI of AFS securities									530	31,316	(4,537)
Net unrealized gains (losses), Gross									213,296	(83,394)	59,876
Net unrealized gains (losses), Tax									44,791	(17,513)	21,423
Total unrealized gains (losses) on investment securities									168,505	(65,881)	38,453
Net actuarial (loss), Gross									(13,795)	(11,273)	(4,684)
Net actuarial (loss), Tax									(2,897)	(2,367)	(984)
Net actuarial (loss), Net									(10,898)	(8,906)	(3,700)
Amount reclassified into net income: Net actuarial loss, Gross									2,657	2,127	2,102
Amount reclassified into Net Income: Net actuarial loss, Tax									558	447	735
Amount reclassified into net income: Net actuarial loss, Net									2,099	1,680	1,367
Defined pension and other post-retirement benefit plans, Gross									(11,138)	(9,146)	(2,582)
Defined pension and other post-retirement benefit plans, Tax									(2,339)	(1,920)	(249)
Total defined benefit pension and post-retirement plans									(8,799)	(7,226)	(2,333)
Other Comprehensive Income (Loss), Gross									202,158	(92,540)	57,294
Other Comprehensive Income (Loss), Tax									42,452	(19,433)	21,174
Other comprehensive income (loss)									159,706	(73,107)	36,120
Comprehensive Income, Before Tax									538,548	119,181	319,262
Comprehensive Income, Tax									107,219	13,349	114,316
Comprehensive income									$ 431,329	$ 105,832	$ 204,946

Comprehensive Income (Compone_2

Comprehensive Income (Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance December,	$ (77,956)
Cumulative effect adjustment			$ 25,000
Amounts reclassified into net income: Non-credit other-than-temporary impairment	0	$ 0	68
Amount reclassified from AOCI, HTM	(46)	87	(116)
OCI before reclassifications, Defined Benefit Pension and Post Retirement Plans	(10,898)	(8,906)	(3,700)
Amounts reclassified from AOCI,All other	530	31,316	(4,537)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	(8,799)	(7,226)	(2,333)
Other comprehensive income (loss)	159,706	(73,107)	36,120
Balance December,	81,750	(77,956)
Accumulated Other-than-Temporary Impairment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, December 31, 2017			(59)
Balance December,	(71)	(71)
Cumulative effect adjustment			(12)
OCI before reclassifications	0	0
Other comprehensive income (loss)	0	0
Balance December,	(71)	(71)	(71)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, December 31, 2017			(60,405)
Balance December,	(79,844)	(72,618)
Cumulative effect adjustment			(12,213)
OCI before reclassifications, Defined Benefit Pension and Post Retirement Plans	(10,898)	(8,906)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	2,099	1,680
Balance December,	(88,643)	(79,844)	(72,618)
Accumulated other comprehensive (loss) income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, December 31, 2017			20,170
Balance December,	(77,956)	(4,849)
Cumulative effect adjustment			(25,019)
OCI before reclassifications	157,123	(106,190)
Amount reclassified from AOCI	2,583	33,083
Other comprehensive income (loss)	159,706	(73,107)	36,120
Balance December,	81,750	(77,956)	(4,849)
Held-to-maturity Securities [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, December 31, 2017			(14)
Balance December,	71	(16)
Cumulative effect adjustment			(2)
OCI before reclassifications	0	0
Other comprehensive income (loss)	(46)	87
Balance December,	25	71	(16)
Available-for-sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, December 31, 2017			80,648
Balance December,	1,888	67,856
Cumulative effect adjustment			(12,792)
OCI before reclassifications	168,021	(97,284)
Amounts reclassified from AOCI,All other	530	31,316
Other comprehensive income (loss)	168,551	(65,968)
Balance December,	170,439	1,888	67,856
Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, December 31, 2017			80,575
Balance December,	1,888	67,769
Cumulative effect adjustment			(12,806)
OCI before reclassifications	168,021	(97,284)
Amount reclassified from AOCI	484	31,403
Other comprehensive income (loss)	168,505	(65,881)
Balance December,	170,393	1,888	67,769
Accounting Standards Update 2016-01 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect adjustment	$ 0	(30,726)	0
Accounting Standards Update 2016-01 [Member] | Accumulated other comprehensive (loss) income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect adjustment		$ 0	$ 30,726	$ 0

Comprehensive Income (Reclassif

Comprehensive Income (Reclassification out of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net realized gains (losses)									$ 23,071	$ (25,554)	$ 6,359
Net investment income	$ 57,594	$ 55,826	$ 58,505	$ 50,618	$ 54,109	$ 52,443	$ 45,553	$ 43,231	222,543	195,336	161,882
Income before federal income tax	101,293	71,178	90,225	73,694	52,135	67,130	72,525	19,931	336,390	211,721	261,968
Income Tax Expense (Benefit)									64,767	32,782	93,142
Net income	$ 81,859	$ 56,150	$ 72,266	$ 61,348	$ 45,760	$ 55,435	$ 58,819	$ 18,925	271,623	178,939	168,826
Loss and loss expense incurred									1,551,491	1,498,134	1,345,074
Policy acquisition costs									358,069	331,318	333,097
Total defined benefit pension and post-retirement plans									(8,799)	(7,226)	$ (2,333)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Net income									2,583	33,083
Reclassification out of Accumulated Other Comprehensive Income [Member] | Retirement Income Plan [Member]
Income before federal income tax									2,657	2,127
Income Tax Expense (Benefit)									(558)	(447)
Net income									2,099	1,680
Loss and loss expense incurred									582	450
Policy acquisition costs									2,075	1,677
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]
Net realized gains (losses)									(46)	137
Net investment income									(12)	(27)
Income before federal income tax									(58)	110
Income Tax Expense (Benefit)									12	(23)
Net income									(46)	87
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]
Net realized gains (losses)									671	39,641
Income before federal income tax									671	39,641
Income Tax Expense (Benefit)									(141)	(8,325)
Net income									$ 530	$ 31,316

Fair Value Measurements (Carryi

Fair Value Measurements (Carrying Value and Estimated Fair Value of Financial Instruments) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Carrying Amount [Member]
Long-term debt	$ 550,597	$ 439,540
Carrying Amount [Member] | Seven Point Twenty Five Percent Senior Notes [Member]
Long-term debt	49,910	49,907
Carrying Amount [Member] | Six Point Seventy Percent Senior Notes [Member]
Long-term debt	99,480	99,462
Carrying Amount [Member] | Five Point Eight Hundred Seventy Five Percent Senior Notes [Member]
Long-term debt	0	185,000
Carrying Amount [Member] | Five Point Three Hundred Seventy Five [Member]
Long-term debt	294,157	0
Carrying Amount [Member] | One Point Sixty One Percent Borrowing From Federal Home Loan Bank Due July 21, 2021 [Member]
Long-term debt	25,000	25,000
Carrying Amount [Member] | One Point Fifty Six Percent Borrowing From Federal Home Loan Bank Due August 16, 2021 [Member]
Long-term debt	25,000	25,000
Carrying Amount [Member] | Three Point Zero Three Percent Borrowing From Federal Home Loan Bank Due December 16, 2026 [Member]
Long-term debt	60,000	60,000
Carrying Amount [Member] | Long Term Debt Excluding Issuance Costs [Member]
Long-term debt	553,547	444,369
Carrying Amount [Member] | Unamortized Debt Issuance Costs [Member]
Unamortized Debt Issuance Costs	(3,687)	(4,829)
Carrying Amount [Member] | Finance lease obligation [Member]
Finance Lease, Liability	737	0
Fair Value [Member]
Long-term Debt, Fair Value	659,272	448,622
Fair Value [Member] | Seven Point Twenty Five Percent Senior Notes [Member]
Long-term Debt, Fair Value	66,365	57,032
Fair Value [Member] | Six Point Seventy Percent Senior Notes [Member]
Long-term Debt, Fair Value	123,104	107,075
Fair Value [Member] | Five Point Eight Hundred Seventy Five Percent Senior Notes [Member]
Long-term Debt, Fair Value	0	177,230
Fair Value [Member] | Five Point Three Hundred Seventy Five [Member]
Long-term Debt, Fair Value	357,025	0
Fair Value [Member] | One Point Sixty One Percent Borrowing From Federal Home Loan Bank Due July 21, 2021 [Member]
Long-term Debt, Fair Value	24,901	24,218
Fair Value [Member] | One Point Fifty Six Percent Borrowing From Federal Home Loan Bank Due August 16, 2021 [Member]
Long-term Debt, Fair Value	24,875	24,162
Fair Value [Member] | Three Point Zero Three Percent Borrowing From Federal Home Loan Bank Due December 16, 2026 [Member]
Long-term Debt, Fair Value	$ 63,002	$ 58,905

Fair Value Measurements (Quanti

Fair Value Measurements (Quantitative Disclosures at Fair Value Assets) (Details) - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments Net Asset Value		$ 37,800	$ 37,300
Debt Securities, Available-for-sale		6,095,620	5,273,100
Equity securities		72,937	147,639
Short-term investments		282,490	323,864
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		6,095,620	5,273,100
Equity securities		72,937	147,639
Short-term investments		282,490	323,864
Total Assets		6,451,047	5,744,603
U.S. Government and Government Agencies and Authorities [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		116,186	121,310
Foreign Government [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		18,542	23,131
Obligations of States and Political Subdivisions [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		1,230,090	1,138,469
Corporate Securities [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		1,947,477	1,617,408
Collateralized Loan Obligations and Other Asset-Backed Securities [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		793,012	717,362
Commercial Mortgage-backed Securities (CMBS) [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		538,344	527,078
Residential Mortgage Backed Securities [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		1,451,969	1,128,342
Common Stock [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	[1]	69,900	144,727
Nonredeemable Preferred Stock [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		3,037	2,912
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		44,718	78,381
Equity securities		35,182	110,309
Short-term investments		265,306	321,370
Total Assets		345,206	510,060
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | U.S. Government and Government Agencies and Authorities [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		41,083	78,381
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Foreign Government [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Obligations of States and Political Subdivisions [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Corporate Securities [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		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, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		3,635	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Commercial Mortgage-backed Securities (CMBS) [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Residential Mortgage Backed Securities [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Common Stock [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	[1]	32,145	107,397
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Nonredeemable Preferred Stock [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		3,037	2,912
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		6,016,817	5,187,310
Equity securities		0	0
Short-term investments		17,184	2,494
Total Assets		6,034,001	5,189,804
Significant Other Observable Inputs (Level 2) [Member] | U.S. Government and Government Agencies and Authorities [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		75,103	42,929
Significant Other Observable Inputs (Level 2) [Member] | Foreign Government [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		18,542	23,131
Significant Other Observable Inputs (Level 2) [Member] | Obligations of States and Political Subdivisions [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		1,230,090	1,138,469
Significant Other Observable Inputs (Level 2) [Member] | Corporate Securities [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		1,930,426	1,617,408
Significant Other Observable Inputs (Level 2) [Member] | Collateralized Loan Obligations and Other Asset-Backed Securities [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		772,343	709,953
Significant Other Observable Inputs (Level 2) [Member] | Commercial Mortgage-backed Securities (CMBS) [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		538,344	527,078
Significant Other Observable Inputs (Level 2) [Member] | Residential Mortgage Backed Securities [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		1,451,969	1,128,342
Significant Other Observable Inputs (Level 2) [Member] | Common Stock [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	[1]	0	0
Significant Other Observable Inputs (Level 2) [Member] | Nonredeemable Preferred Stock [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		0	0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		34,085	7,409
Equity securities		0	0
Short-term investments		0	0
Total Assets		34,085	7,409
Significant Unobservable Inputs (Level 3) [Member] | U.S. Government and Government Agencies and Authorities [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		0	0
Significant Unobservable Inputs (Level 3) [Member] | Foreign Government [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		0	0
Significant Unobservable Inputs (Level 3) [Member] | Obligations of States and Political Subdivisions [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		0	0
Significant Unobservable Inputs (Level 3) [Member] | Corporate Securities [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		17,051	0
Significant Unobservable Inputs (Level 3) [Member] | Collateralized Loan Obligations and Other Asset-Backed Securities [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		17,034	7,409
Significant Unobservable Inputs (Level 3) [Member] | Commercial Mortgage-backed Securities (CMBS) [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		0	0
Significant Unobservable Inputs (Level 3) [Member] | Residential Mortgage Backed Securities [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		0	0
Significant Unobservable Inputs (Level 3) [Member] | Common Stock [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	[1]	0	0
Significant Unobservable Inputs (Level 3) [Member] | Nonredeemable Preferred Stock [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		$ 0	$ 0
[1]	In accordance with ASU 2015-07, investments amounting to $37.8 million and $37.3 million at December 31, 2019 and December 31, 2018, respectively, were measured at fair value using the net asset value per share (or its practical expedient) and 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 assets measured at fair value.

Fair Value Measurements (Change

Fair Value Measurements (Changes in Fair Value of Securities Using Level 3 Inputs) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Beginning Balance	$ 7,409
Total net (losses) gains for the period included in OCI	(379)
Total net (losses) gains for the period included in net income	245
Purchases	21,282
Sales	0
Issuances	0
Settlements	(279)
Transfers into Level 3	36,022
Transfers out of Level 3	(30,215)
Fair Value, Ending Balance	34,085
AFS Fixed Income Securities [Member] | Corporate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Beginning Balance	0
Total net (losses) gains for the period included in OCI	(118)
Total net (losses) gains for the period included in net income	0
Purchases	0
Sales	0
Issuances	0
Settlements	0
Transfers into Level 3	17,169
Transfers out of Level 3	0
Fair Value, Ending Balance	17,051
AFS Fixed Income Securities [Member] | Collateralized Loan Obligations and Other Asset-Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Beginning Balance	7,409
Total net (losses) gains for the period included in OCI	(261)
Total net (losses) gains for the period included in net income	245
Purchases	21,282
Sales	0
Issuances	0
Settlements	(279)
Transfers into Level 3	18,853
Transfers out of Level 3	(30,215)
Fair Value, Ending Balance	$ 17,034

Fair Value Measurements (Quan_2

Fair Value Measurements (Quantitative Information of Our Financial Assets and Liabilities That Were Disclosed at Fair Value) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total HTM fixed income securities fair value	$ 21,975	$ 38,317
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
Long-term Debt, Fair Value	0	177,230
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	21,975	38,317
Long-term Debt, Fair Value	659,272	271,392
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
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	4,921	17,969
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	4,921	17,969
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	17,054	20,348
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	17,054	20,348
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	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	66,365	57,032
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	66,365	57,032
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	123,104	107,075
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	123,104	107,075
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 Percent Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value		177,230
Five Point Eight Hundred Seventy 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		177,230
Five Point Eight Hundred Seventy 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		0
Five Point Eight Hundred Seventy 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
Five Point Three Hundred Seventy Five [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	357,025
Five Point Three 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	0
Five Point Three 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	357,025
Five Point Three 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
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	24,901	24,218
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	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	24,901	24,218
One Point Sixty One Percent Borrowing From Federal Home Loan Bank Due July 21, 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	0
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	24,875	24,162
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	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	24,875	24,162
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	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	63,002	58,905
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	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	63,002	58,905
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	0
Long-term Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	$ 659,272	$ 448,622

Reinsurance (Total Reinsurance

Reinsurance (Total Reinsurance Balances Segregated By Reinsurer) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Terrorism Risk Insurance Program Companys Estimated Deductible		$ 359,000
Terrorism Risk Insurance Program Reimbursed Percentage Maximum		80.00%
Terrorism Risk Insurance Program Annual Cap		$ 100,000,000
Terrorism Risk Insurance Program Insurer Retainer		20.00%
Allowance For Reinsurance Recoverable		$ 10,800	$ 13,900	$ 14,600	$ 11,480
Total reinsurance recoverables		573,235	549,172
Total prepaid reinsurance premiums		166,705	157,723
Total reinsurance balance		739,940	706,895
Less: collateral	[1]	(110,549)	(112,201)
National Flood Insurance Program [Member]
Total reinsurance balance	[2]	$ 175,472	$ 170,453
% of Net Unsecured Reinsurance	[2]	24.00%	24.00%
NJ Unsatisfied Claim Judgment Fund [Member]
Total reinsurance balance	[2]	$ 53,732	$ 55,167
% of Net Unsecured Reinsurance	[2]	6.00%	7.00%
Other Federal And State Pools [Member]
Total reinsurance balance	[2]	$ 2,449	$ 3,602
% of Net Unsecured Reinsurance	[2]	1.00%	1.00%
Total Federal And State Pools [Member]
Total reinsurance balance	[2]	$ 231,653	$ 229,222
% of Net Unsecured Reinsurance	[2]	31.00%	32.00%
Remaining Unsecured Reinsurance [Member]
Total reinsurance balance		$ 508,287	$ 477,673
% of Net Unsecured Reinsurance		69.00%	68.00%
Munich Re Group [Member]
Total reinsurance balance		$ 119,748	$ 112,841
% of Net Unsecured Reinsurance		16.00%	16.00%
Hanover Ruckversicherungs AG [Member]
Total reinsurance balance		$ 107,474	$ 101,835
% of Net Unsecured Reinsurance		15.00%	14.00%
AXIS Reinsurance Company [Member]
Total reinsurance balance		$ 73,009	$ 69,102
% of Net Unsecured Reinsurance		10.00%	10.00%
Swiss Re Group [Member]
Total reinsurance balance		$ 37,190	$ 37,519
% of Net Unsecured Reinsurance		5.00%	5.00%
Transatlantic Reinsurance Company [Member]
Total reinsurance balance		$ 21,824	$ 17,686
% of Net Unsecured Reinsurance		3.00%	3.00%
All Other Reinsurers [Member]
Total reinsurance balance		$ 149,042	$ 138,690
% of Net Unsecured Reinsurance		20.00%	20.00%
Remaining Unsecured Reinsurance, Net of Collateral [Member]
Total reinsurance balance		$ 397,738	$ 365,472
SEC Schedule, 12-09, Allowance, Reinsurance Recoverable [Member]
Allowance For Reinsurance Recoverable		$ 4,400	$ 4,500
[1]	Includes letters of credit, trust funds, and funds held against reinsurance recoverables.
[2]	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, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Premiums Written:
Direct									$ 3,084,451	$ 2,890,633	$ 2,733,459
Assumed									24,339	26,250	26,685
Ceded premiums written									(429,366)	(402,597)	(389,503)
Net									2,679,424	2,514,286	2,370,641
Premiums Earned:
Direct									2,993,157	2,808,764	2,647,488
Assumed									24,399	25,831	25,831
Ceded premiums earned									(420,385)	(398,366)	(382,292)
Total Net Premiums Earned	$ 668,359	$ 653,620	$ 642,619	$ 632,573	$ 625,288	$ 614,277	$ 604,836	$ 591,828	2,597,171	2,436,229	2,291,027
Loss and loss expense incurred:
Direct									1,714,880	1,706,951	1,570,678
Assumed									22,879	21,469	17,588
Ceded loss and loss expense									(186,268)	(230,286)	(243,192)
Net									$ 1,551,491	$ 1,498,134	$ 1,345,074

Reinsurance (Ceded Premiums and

Reinsurance (Ceded Premiums and Losses Related to Flood Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Percentage of NFIP claims ceded to the federal government	100.00%
Ceded premiums written	$ (429,366)	$ (402,597)	$ (389,503)
Ceded premiums earned	(420,385)	(398,366)	(382,292)
Ceded loss and loss expense	(186,268)	(230,286)	(243,192)
National Flood Insurance Program [Member]
Ceded premiums written	(266,925)	(248,053)	(241,345)
Ceded premiums earned	(259,119)	(244,238)	(235,088)
Ceded loss and loss expense	$ (71,676)	$ (144,967)	$ (160,922)

Reserve for Loss and Loss Exp_3

Reserve for Loss and Loss Expense (Rollforward of Reserve for Loss and Loss Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Gross reserve for loss and loss expense, at beginning of year	$ 3,893,868	$ 3,771,240	$ 3,691,719
Less: reinsurance recoverable on unpaid loss and loss expense, at beginning of year	537,388	585,855	611,200
Net reserves for loss and loss expense, at beginning of year	3,356,480	3,185,385	3,080,519
Incurred loss and loss expense for claims occurring in the current year	1,601,780	1,527,997	1,384,266
Incurred loss and loss expense for claims occurring in the prior years	(50,289)	(29,863)	(39,192)
Total incurred loss and loss expense	1,551,491	1,498,134	1,345,074
Paid loss and loss expense for claims occurring in current year	579,527	573,718	497,486
Paid loss and loss expense for claims occurring in prior years	805,443	753,321	742,722
Total paid loss and loss expense	1,384,970	1,327,039	1,240,208
Net reserves for loss and loss expense, at end of year	3,523,001	3,356,480	3,185,385
Add: reinsurance recoverable on unpaid loss and loss expense, at end of year	544,162	537,388	585,855
Gross reserve for loss and loss expense, at end of year	4,067,163	3,893,868	3,771,240
Increase of net loss and loss expense reserves	166,500	171,100	104,900
Anticipated recoveries for salvage and subrogation claims	$ 76,700	$ 67,700	$ 64,800

Reserve for Loss and Loss Exp_4

Reserve for Loss and Loss Expense (Reserve Loss Development) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Favorable or adverse loss development	$ 50,289	$ 29,863	$ 39,192
Favorable or unfavorable loss development [Member]
Favorable or adverse loss development	(50,300)	(29,900)	(39,200)
Favorable or unfavorable loss development [Member] | Casualty Insurance Product Line [Member]
Favorable or adverse loss development	(61,000)	(41,500)
Favorable or unfavorable loss development [Member] | Property Insurance [Member]
Favorable or adverse loss development	10,700	11,600
Favorable or unfavorable loss development [Member] | General Liability [Member]
Favorable or adverse loss development	(5,000)	(9,500)	(48,300)
Favorable or unfavorable loss development [Member] | Commercial Automobile [Member]
Favorable or adverse loss development	700	36,700	35,600
Casualty Development		37,500	36,000
Favorable or unfavorable loss development [Member] | Workers Compensation [Member]
Favorable or adverse loss development	(68,000)	(83,000)	(52,300)
Favorable or unfavorable loss development [Member] | Business Owners' Policies [Member]
Favorable or adverse loss development	1,900	(1,500)	1,900
Favorable or unfavorable loss development [Member] | Commercial Property [Member]
Favorable or adverse loss development	5,100	7,500	8,700
Favorable or unfavorable loss development [Member] | Homeowners [Member]
Favorable or adverse loss development	7,500	9,800	400
Favorable or unfavorable loss development [Member] | Personal Automobile [Member]
Favorable or adverse loss development	4,400	3,000	6,700
Favorable or unfavorable loss development [Member] | E&S Casualty Lines [Member]
Favorable or adverse loss development	2,000	12,000	10,000
Favorable or unfavorable loss development [Member] | E&S Property Lines [Member]
Favorable or adverse loss development	1,000	(4,800)	100
Favorable or unfavorable loss development [Member] | Insurance, Other [Member]
Favorable or adverse loss development	$ 100	$ (100)	$ (2,000)

Reserve for Loss and Loss Exp_5

Reserve for Loss and Loss Expense (Exposure to Environmental Claims) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Liability for Claims and Claims Adjustment Expense [Line Items]
Loss and Loss expense reserves, Gross	$ 28,701	$ 30,020	$ 28,415	$ 29,962
Liability for Asbestos and Environmental Claims, Net	21,589	$ 22,783	$ 21,212	$ 22,716
Asbestos Claim [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Loss and Loss expense reserves, Gross	6,300
Liability for Asbestos and Environmental Claims, Net	5,100
Landfill Sites Related Claims [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Loss and Loss expense reserves, Gross	12,100
Liability for Asbestos and Environmental Claims, Net	7,300
Leaking Underground Storage Tanks Claims [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Loss and Loss expense reserves, Gross	10,300
Liability for Asbestos and Environmental Claims, Net	$ 9,200

Reserve for Loss and Loss Exp_6

Reserve for Loss and Loss Expense (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, 2019	Dec. 31, 2018	Dec. 31, 2017
Liability for Claims and Claims Adjustment Expense [Line Items]
Reserve for loss and loss expense at beginning of year, gross	$ 30,020	$ 28,415	$ 29,962
Incurred loss and loss expense, gross	(348)	(3,059)	(126)
Less: loss and loss expense paid, gross	(1,667)	(1,454)	(1,673)
Reserve for loss and loss expense at the end of year, gross	28,701	30,020	28,415
Reserve for loss and loss expense at beginning of year, net	22,783	21,212	22,716
Incurred loss and loss expense, net	234	2,877	0
Less: loss and loss expense paid, net	(1,428)	(1,306)	(1,504)
Reserve for loss and loss expense at the end of year, net	21,589	22,783	21,212
Asbestos [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Reserve for loss and loss expense at beginning of year, gross	7,328	7,577	7,847
Incurred loss and loss expense, gross	(375)	0	0
Less: loss and loss expense paid, gross	(665)	(249)	(270)
Reserve for loss and loss expense at the end of year, gross	6,288	7,328	7,577
Reserve for loss and loss expense at beginning of year, net	6,097	6,346	6,615
Incurred loss and loss expense, net	(375)	0	0
Less: loss and loss expense paid, net	(665)	(249)	(269)
Reserve for loss and loss expense at the end of year, net	5,057	6,097	6,346
Enviromental [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Reserve for loss and loss expense at beginning of year, gross	22,692	20,838	22,115
Incurred loss and loss expense, gross	(723)	(3,059)	(126)
Less: loss and loss expense paid, gross	(1,002)	(1,205)	(1,403)
Reserve for loss and loss expense at the end of year, gross	22,413	22,692	20,838
Reserve for loss and loss expense at beginning of year, net	16,686	14,866	16,101
Incurred loss and loss expense, net	609	2,877	0
Less: loss and loss expense paid, net	(763)	(1,057)	(1,235)
Reserve for loss and loss expense at the end of year, net	$ 16,532	$ 16,686	$ 14,866

Reserve for Loss and Loss Exp_7

Reserve for Loss and Loss Expense (Claims Development) (Details)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2012USD ($)	Dec. 31, 2011USD ($)	Dec. 31, 2010USD ($)
Claims Development [Line Items]
Net outstanding liabilities	$ 11,547,343,000
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	8,514,750,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	3,392,713,000
Reserve for loss and loss expense	4,067,163,000	$ 3,893,868,000
Short-Duration Insurance Contracts, Accident Years Prior to 2010 [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	360,119,000
Short-Duration Insurance Contracts, Accident Years 2010 [Member]
Claims Development [Line Items]
Net outstanding liabilities	902,258,000	904,561,000	$ 907,074,000	$ 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	$ 38,152,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	94,526
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 851,633,000	846,386,000	835,532,000	823,770,000	803,773,000	773,536,000	704,895,000	625,229,000	509,910,000	328,826,000
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Claims Development [Line Items]
Net outstanding liabilities	1,013,175,000	1,013,115,000	1,019,351,000	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	$ 44,453,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	104,861
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 950,836,000	940,626,000	924,111,000	901,801,000	852,202,000	782,655,000	692,730,000	585,867,000	391,944,000
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Claims Development [Line Items]
Net outstanding liabilities	968,536,000	973,411,000	973,644,000	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	$ 50,942,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	104,148
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 898,269,000	879,372,000	856,195,000	810,135,000	743,742,000	651,544,000	555,819,000	378,067,000
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Claims Development [Line Items]
Net outstanding liabilities	984,858,000	987,763,000	1,002,316,000	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	$ 72,970,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	91,326
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 891,841,000	872,331,000	833,823,000	748,758,000	644,475,000	518,872,000	335,956,000
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Claims Development [Line Items]
Net outstanding liabilities	1,100,208,000	1,104,218,000	1,124,014,000	1,146,990,000	1,133,798,000	1,107,513,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 83,392,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	95,081
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 981,868,000	936,425,000	855,959,000	736,154,000	614,075,000	405,898,000
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Claims Development [Line Items]
Net outstanding liabilities	1,119,441,000	1,138,313,000	1,144,830,000	1,130,513,000	1,114,081,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 111,657,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	94,128
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 929,222,000	845,868,000	725,385,000	581,203,000	376,641,000
Short-duration Insurance Contracts, Accident Year 2016 [Member]
Claims Development [Line Items]
Net outstanding liabilities	1,199,734,000	1,227,142,000	1,203,634,000	1,188,608,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 205,126,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	94,579
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 892,390,000	764,331,000	617,958,000	387,272,000
Short-duration Insurance Contracts, Accident Year 2017 [Member]
Claims Development [Line Items]
Net outstanding liabilities	1,313,585,000	1,313,372,000	1,270,110,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 336,155,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	98,014
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 829,134,000	678,453,000	433,440,000
Short-duration Insurance Contracts, Accident Year 2018 [Member]
Claims Development [Line Items]
Net outstanding liabilities	1,461,603,000	1,413,800,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 501,519,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	104,187
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 779,466,000	511,271,000
Short-Duration Insurance Contract, Accident Year 2019 [Member]
Claims Development [Line Items]
Net outstanding liabilities	1,483,945,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 759,853,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	93,947
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 510,091,000
Standard Commercial Lines [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	2,508,023,000
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	1,321,589,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	1,280,416,000
Standard Commercial Lines [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Net outstanding liabilities	1,789,692,000
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	1,179,326,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	850,505,000
Standard Commercial Lines [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	2,566,548,000
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	1,973,765,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	596,686,000
Standard Commercial Lines [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Net outstanding liabilities	512,159,000
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	432,942,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	86,747,000
Standard Commercial Lines [Member] | Commercial Property [Member]
Claims Development [Line Items]
Net outstanding liabilities	1,320,677,000
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	1,268,844,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	52,071,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contracts, Accident Years Prior to 2010 [Member] | General Liability [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	93,982,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contracts, Accident Years Prior to 2010 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	240,140,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contracts, Accident Years Prior to 2010 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	3,904,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contracts, Accident Years Prior to 2010 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	7,530,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contracts, Accident Years Prior to 2010 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	237,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contracts, Accident Years 2010 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	205,322,000	206,146,000	202,394,000	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	$ 17,542,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	12,705
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 185,962,000	183,988,000	178,179,000	172,394,000	161,487,000	143,360,000	113,050,000	80,018,000	46,201,000	15,726,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contracts, Accident Years 2010 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Net outstanding liabilities	197,095,000	199,539,000	204,423,000	208,155,000	212,448,000	214,916,000	211,030,000	212,815,000	214,469,000	198,371,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 19,514,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	12,192
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 167,478,000	165,526,000	162,796,000	158,078,000	153,795,000	149,086,000	137,184,000	122,442,000	93,281,000	46,795,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contracts, Accident Years 2010 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	172,995,000	173,080,000	173,471,000	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	$ 682,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	25,512
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 171,941,000	171,693,000	169,793,000	169,100,000	167,227,000	163,513,000	146,913,000	128,015,000	99,254,000	68,098,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contracts, Accident Years 2010 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Net outstanding liabilities	41,156,000	40,920,000	41,197,000	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	$ 333,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	3,920
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 40,823,000	40,439,000	40,395,000	40,279,000	38,900,000	37,819,000	34,705,000	31,027,000	28,131,000	20,821,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contracts, Accident Years 2010 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Net outstanding liabilities	95,338,000	95,142,000	95,155,000	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	$ 4,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	7,669
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 95,334,000	95,138,000	95,150,000	95,156,000	95,147,000	95,270,000	95,111,000	94,602,000	91,918,000	69,543,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	213,485,000	211,500,000	212,011,000	211,196,000	217,256,000	230,785,000	239,480,000	228,720,000	227,769,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 19,913,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	11,649
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 187,276,000	181,856,000	170,525,000	159,768,000	135,377,000	102,978,000	73,643,000	42,692,000	13,924,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Net outstanding liabilities	192,863,000	194,821,000	200,674,000	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	$ 22,717,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	11,860
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 161,696,000	158,535,000	154,320,000	149,269,000	139,232,000	134,646,000	118,847,000	90,836,000	42,941,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	173,401,000	173,507,000	174,514,000	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	$ 899,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	25,524
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 172,365,000	170,913,000	170,000,000	166,082,000	157,291,000	142,507,000	121,576,000	99,196,000	69,849,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Net outstanding liabilities	58,948,000	58,735,000	58,456,000	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	$ 362,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	4,960
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 57,380,000	57,365,000	57,045,000	55,856,000	52,114,000	46,444,000	41,011,000	37,362,000	27,884,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Net outstanding liabilities	131,002,000	131,009,000	131,049,000	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	$ 7,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	9,038
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 131,092,000	131,100,000	131,089,000	131,115,000	131,060,000	130,681,000	129,579,000	127,580,000	94,538,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	182,085,000	180,659,000	175,268,000	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	$ 21,005,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	9,994
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 156,186,000	144,451,000	130,866,000	109,448,000	89,008,000	56,580,000	35,241,000	13,030,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Net outstanding liabilities	178,774,000	183,314,000	187,359,000	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	$ 24,605,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	11,618
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 146,739,000	143,281,000	139,477,000	132,052,000	122,755,000	108,211,000	86,909,000	40,911,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	185,357,000	184,633,000	186,128,000	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	$ 1,920,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	24,160
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 181,353,000	179,501,000	176,656,000	168,114,000	148,669,000	127,235,000	105,371,000	73,316,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Net outstanding liabilities	43,717,000	43,418,000	43,747,000	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	$ 703,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	5,543
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 41,356,000	41,326,000	40,627,000	38,766,000	37,215,000	35,089,000	31,833,000	22,199,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Net outstanding liabilities	117,220,000	117,225,000	117,170,000	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	$ 10,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	8,517
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 116,674,000	116,671,000	116,625,000	116,291,000	114,699,000	111,503,000	108,834,000	81,528,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	202,697,000	203,831,000	210,785,000	225,709,000	239,776,000	251,421,000	250,609,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 28,857,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	10,378
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 163,764,000	153,628,000	139,114,000	104,587,000	72,127,000	35,113,000	12,789,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Net outstanding liabilities	159,767,000	162,787,000	166,662,000	173,160,000	187,658,000	194,318,000	199,794,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 26,260,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	11,375
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 126,822,000	124,130,000	118,669,000	109,739,000	96,376,000	74,568,000	36,829,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	209,602,000	207,975,000	210,410,000	207,994,000	209,197,000	205,282,000	188,289,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 2,928,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	25,722
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 202,622,000	200,750,000	189,626,000	169,850,000	140,015,000	109,893,000	76,469,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Net outstanding liabilities	39,699,000	39,709,000	41,369,000	40,624,000	41,005,000	42,618,000	49,617,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 803,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	3,482
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 39,085,000	38,464,000	37,993,000	34,760,000	30,845,000	26,592,000	17,412,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Net outstanding liabilities	90,218,000	90,278,000	90,436,000	90,005,000	90,103,000	90,639,000	88,101,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 18,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	5,713
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 90,646,000	90,696,000	90,840,000	90,350,000	90,446,000	87,874,000	60,244,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	237,125,000	234,082,000	239,333,000	257,132,000	249,946,000	244,312,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 42,388,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	10,586
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 179,192,000	154,957,000	121,969,000	79,972,000	46,825,000	14,901,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Net outstanding liabilities	160,646,000	164,420,000	172,515,000	182,579,000	187,065,000	199,346,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 28,320,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	10,495
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 124,077,000	119,392,000	113,626,000	100,876,000	78,944,000	35,924,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	217,334,000	218,172,000	219,925,000	216,824,000	212,725,000	200,534,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 4,831,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	27,714
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 209,655,000	202,821,000	180,701,000	148,884,000	117,169,000	80,810,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Net outstanding liabilities	58,093,000	58,517,000	59,806,000	62,548,000	60,949,000	55,962,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 1,390,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	4,064
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 55,458,000	52,940,000	49,460,000	44,911,000	40,584,000	28,914,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Net outstanding liabilities	136,212,000	138,155,000	138,751,000	136,820,000	136,249,000	141,192,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 33,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	6,515
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 136,008,000	137,418,000	137,883,000	136,634,000	132,909,000	101,131,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	219,204,000	233,249,000	246,990,000	245,710,000	254,720,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 55,244,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	10,381
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 144,216,000	116,804,000	78,668,000	39,978,000	14,665,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Net outstanding liabilities	176,242,000	179,642,000	183,604,000	194,639,000	193,729,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 27,927,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	10,549
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 120,097,000	112,601,000	98,195,000	77,320,000	33,857,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	260,565,000	259,495,000	253,074,000	240,958,000	220,994,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 7,966,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	29,340
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 238,142,000	211,515,000	175,866,000	132,260,000	91,347,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Net outstanding liabilities	54,454,000	55,925,000	57,245,000	53,768,000	52,871,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 3,235,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	3,959
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 49,073,000	46,571,000	42,710,000	36,014,000	24,189,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Net outstanding liabilities	112,496,000	111,566,000	111,750,000	109,513,000	110,270,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 56,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	6,404
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 110,969,000	110,994,000	109,829,000	106,182,000	79,048,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	263,245,000	277,986,000	272,048,000	277,214,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 98,385,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	10,526
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 133,757,000	89,431,000	46,549,000	15,684,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Net outstanding liabilities	166,009,000	176,248,000	184,946,000	196,774,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 41,146,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	10,572
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 109,166,000	98,037,000	78,531,000	34,525,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	285,304,000	285,302,000	274,367,000	255,187,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 21,279,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	31,167
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 233,939,000	200,701,000	155,720,000	106,022,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Net outstanding liabilities	53,835,000	54,993,000	53,792,000	52,335,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 4,245,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	3,843
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 45,308,000	39,973,000	36,848,000	24,655,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Net outstanding liabilities	124,487,000	125,937,000	126,185,000	121,927,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ (96,000)
Short-duration Insurance Contract, Cumulative Number of Reported Claims	6,739
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 123,828,000	122,930,000	118,789,000	83,966,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2017 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	301,384,000	293,128,000	293,747,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 161,114,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	10,706
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 92,355,000	49,470,000	17,366,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2017 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Net outstanding liabilities	175,853,000	184,306,000	195,202,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 53,654,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	10,793
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 100,645,000	82,216,000	40,375,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2017 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	324,291,000	329,389,000	301,274,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 57,165,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	32,474
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 220,422,000	178,823,000	117,287,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2017 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Net outstanding liabilities	51,524,000	48,698,000	46,624,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 10,252,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	3,864
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 36,950,000	31,337,000	21,865,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2017 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Net outstanding liabilities	149,044,000	149,106,000	138,773,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ (884,000)
Short-duration Insurance Contract, Cumulative Number of Reported Claims	6,886
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 148,589,000	142,338,000	99,047,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2018 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	336,326,000	317,934,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 223,228,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	10,656
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 60,784,000	19,531,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2018 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Net outstanding liabilities	193,818,000	193,894,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 74,399,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	11,078
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 84,780,000	41,122,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2018 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	352,487,000	347,908,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 109,922,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	35,034
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 193,788,000	134,867,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2018 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Net outstanding liabilities	57,202,000	55,024,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 12,432,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	4,159
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 39,791,000	29,995,000
Standard Commercial Lines [Member] | Short-duration Insurance Contracts, Accident Year 2018 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Net outstanding liabilities	190,834,000	183,177,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ (329,000)
Short-duration Insurance Contract, Cumulative Number of Reported Claims	8,240
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 184,813,000	135,416,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contract, Accident Year 2019 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	347,150,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 296,257,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	8,626
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 18,097,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contract, Accident Year 2019 [Member] | Workers Compensation [Member]
Claims Development [Line Items]
Net outstanding liabilities	188,625,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 100,336,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	9,805
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 37,826,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contract, Accident Year 2019 [Member] | Commercial Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	385,212,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 183,477,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	33,438
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 149,538,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contract, Accident Year 2019 [Member] | Business Owners' Policies [Member]
Claims Development [Line Items]
Net outstanding liabilities	53,531,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 15,068,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	3,210
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 27,718,000
Standard Commercial Lines [Member] | Short-Duration Insurance Contract, Accident Year 2019 [Member] | Commercial Property [Member]
Claims Development [Line Items]
Net outstanding liabilities	173,826,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 15,732,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	6,722
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 130,891,000
Standard Personal Lines [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	1,076,685,000
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	983,814,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	100,331,000
Standard Personal Lines [Member] | Homeowners [Member]
Claims Development [Line Items]
Net outstanding liabilities	739,559,000
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	713,124,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	31,752,000
Standard Personal Lines [Member] | Short-Duration Insurance Contracts, Accident Years Prior to 2010 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	7,462,000
Standard Personal Lines [Member] | Short-Duration Insurance Contracts, Accident Years Prior to 2010 [Member] | Homeowners [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	5,316,000
Standard Personal Lines [Member] | Short-Duration Insurance Contracts, Accident Years 2010 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	106,785,000	106,887,000	107,054,000	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	$ 64,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	20,823
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 106,716,000	106,722,000	106,733,000	106,453,000	105,849,000	104,061,000	101,540,000	95,300,000	82,490,000	58,786,000
Standard Personal Lines [Member] | Short-Duration Insurance Contracts, Accident Years 2010 [Member] | Homeowners [Member]
Claims Development [Line Items]
Net outstanding liabilities	62,380,000	62,402,000	62,392,000	62,339,000	62,402,000	62,462,000	61,927,000	63,285,000	67,525,000	68,373,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 48,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	9,132
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 62,329,000	62,283,000	62,272,000	62,241,000	62,227,000	62,155,000	61,106,000	60,295,000	58,638,000	$ 43,699,000
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	114,056,000	113,921,000	113,988,000	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	$ 121,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	22,700
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 113,856,000	113,664,000	113,551,000	112,732,000	111,085,000	105,068,000	93,878,000	82,102,000	61,323,000
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member] | Homeowners [Member]
Claims Development [Line Items]
Net outstanding liabilities	94,572,000	94,587,000	94,378,000	94,183,000	94,543,000	94,167,000	97,761,000	98,211,000	103,804,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 82,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	15,111
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 94,458,000	94,412,000	94,007,000	93,720,000	93,312,000	92,185,000	91,718,000	89,963,000	71,668,000
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	109,701,000	109,795,000	110,300,000	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	$ 155,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	22,332
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 109,482,000	109,447,000	109,355,000	107,890,000	102,977,000	94,842,000	82,729,000	63,704,000
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member] | Homeowners [Member]
Claims Development [Line Items]
Net outstanding liabilities	86,567,000	86,483,000	86,330,000	86,271,000	86,667,000	86,560,000	82,744,000	87,260,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 94,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	16,941
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 85,897,000	85,642,000	85,562,000	85,196,000	84,250,000	82,720,000	79,584,000	69,056,000
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	107,916,000	107,680,000	107,759,000	106,703,000	106,225,000	109,620,000	108,417,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 348,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	22,375
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 106,876,000	106,679,000	105,131,000	100,528,000	92,637,000	80,861,000	61,384,000
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member] | Homeowners [Member]
Claims Development [Line Items]
Net outstanding liabilities	72,318,000	72,148,000	71,714,000	72,145,000	71,494,000	72,528,000	73,670,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 420,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	7,749
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 72,433,000	72,197,000	71,776,000	69,775,000	67,838,000	65,528,000	50,664,000
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	107,104,000	106,821,000	107,452,000	106,757,000	109,325,000	102,250,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 307,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	22,506
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 105,709,000	104,055,000	99,173,000	92,589,000	83,739,000	62,519,000
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member] | Homeowners [Member]
Claims Development [Line Items]
Net outstanding liabilities	83,824,000	83,539,000	83,844,000	83,637,000	82,461,000	80,111,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 682,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	8,773
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 82,836,000	82,583,000	81,664,000	79,751,000	76,007,000	61,561,000
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	98,718,000	99,570,000	100,214,000	99,698,000	96,387,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 742,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	20,863
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 95,997,000	92,102,000	87,163,000	76,470,000	58,725,000
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member] | Homeowners [Member]
Claims Development [Line Items]
Net outstanding liabilities	74,978,000	74,723,000	76,559,000	76,400,000	76,637,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 660,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	7,746
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 74,079,000	72,927,000	72,202,000	70,078,000	52,589,000
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	101,140,000	100,202,000	98,032,000	92,727,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 2,565,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	19,819
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 94,372,000	86,752,000	76,823,000	57,961,000
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member] | Homeowners [Member]
Claims Development [Line Items]
Net outstanding liabilities	61,723,000	62,391,000	60,931,000	60,105,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 1,221,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	6,885
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 60,082,000	59,546,000	57,333,000	42,252,000
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2017 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	103,653,000	105,139,000	101,880,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 6,342,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	20,725
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 91,479,000	82,730,000	62,854,000
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2017 [Member] | Homeowners [Member]
Claims Development [Line Items]
Net outstanding liabilities	70,365,000	67,978,000	59,167,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 2,500,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	7,370
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 67,193,000	63,290,000	45,466,000
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2018 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	113,569,000	111,594,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 14,259,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	22,621
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 89,628,000	69,721,000
Standard Personal Lines [Member] | Short-duration Insurance Contracts, Accident Year 2018 [Member] | Homeowners [Member]
Claims Development [Line Items]
Net outstanding liabilities	68,526,000	62,961,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 2,366,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	7,554
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 64,137,000	49,430,000
Standard Personal Lines [Member] | Short-Duration Insurance Contract, Accident Year 2019 [Member] | Personal Automobile [Member]
Claims Development [Line Items]
Net outstanding liabilities	114,043,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 25,832,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	21,988
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 69,699,000
Standard Personal Lines [Member] | Short-Duration Insurance Contract, Accident Year 2019 [Member] | Homeowners [Member]
Claims Development [Line Items]
Net outstanding liabilities	64,306,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 6,299,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	6,468
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 49,680,000
E&S Lines [Member]
Claims Development [Line Items]
Reserve for loss and loss expense									15,000,000
E&S Lines [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	716,746,000
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	350,912,000
Liability for Unpaid Claims and Claims Adjustment Expense, Net	365,943,000
E&S Lines [Member] | Short-Duration Insurance Contracts, Accident Years Prior to 2010 [Member] | General Liability [Member]
Claims Development [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	109,000
E&S Lines [Member] | Short-Duration Insurance Contracts, Accident Years 2010 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	5,534,000	5,168,000	4,932,000	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	$ 0
Short-duration Insurance Contract, Cumulative Number of Reported Claims	815
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 5,362,000	4,908,000	4,610,000	4,513,000	4,078,000	3,574,000	2,570,000	1,218,000	0
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2011 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	11,554,000	12,119,000	10,228,000	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	$ 177,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	1,332
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 9,604,000	9,819,000	10,256,000	9,912,000	9,954,000	6,445,000	3,200,000	806,000	$ 0
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2012 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	44,622,000	46,444,000	45,988,000	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	$ 2,474,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	2,045
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 39,832,000	38,298,000	36,278,000	32,343,000	25,064,000	16,430,000	7,914,000	$ 3,722,000
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2013 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	68,451,000	68,972,000	67,647,000	69,112,000	67,099,000	60,309,000	55,468,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 13,816,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	2,280
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 54,974,000	51,142,000	46,108,000	35,200,000	21,980,000	9,470,000	$ 2,715,000
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2014 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	71,153,000	71,206,000	71,719,000	69,929,000	63,505,000	55,316,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 5,559,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	2,071
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 60,092,000	53,780,000	43,877,000	25,571,000	12,234,000	$ 2,353,000
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2015 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	90,355,000	90,488,000	82,404,000	76,432,000	75,498,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 15,752,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	2,799
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 64,529,000	50,712,000	29,389,000	13,057,000	$ 3,036,000
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	105,120,000	104,655,000	96,416,000	94,451,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 35,987,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	2,859
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 56,581,000	33,950,000	16,195,000	$ 3,720,000
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2017 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	99,866,000	95,783,000	91,438,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 47,074,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	2,614
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 34,179,000	14,672,000	$ 5,057,000
E&S Lines [Member] | Short-duration Insurance Contracts, Accident Year 2018 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	103,004,000	98,324,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 62,754,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	2,392
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 21,337,000	$ 5,509,000
E&S Lines [Member] | Short-Duration Insurance Contract, Accident Year 2019 [Member] | General Liability [Member]
Claims Development [Line Items]
Net outstanding liabilities	117,087,000
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 103,146,000
Short-duration Insurance Contract, Cumulative Number of Reported Claims	1,679
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 4,422,000

Reserve for Loss and Loss Exp_8

Reserve for Loss and Loss Expense (Reconciliation of Claims Development to Liability) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	$ 1,551,491	$ 1,498,134	$ 1,345,074
Liability for Unpaid Claims and Claims Adjustment Expense, Net	3,392,713
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	544,162	537,388	585,855	$ 611,200
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claims Adjustment Expense, Accumulated Unallocated Claim Adjustment Expense	130,288
Liability for Claims and Claims Adjustment Expense	4,067,163	$ 3,893,868	$ 3,771,240	$ 3,691,719
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	1,280,416
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	195,830
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	365,943
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	14,319
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	850,505
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	206,414
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	596,686
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	14,352
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	86,747
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	3,012
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	52,071
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	26,526
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	8,199
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	317
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	9,399
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	9,113
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	2,875,824
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	455,247
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	100,331
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	44,104
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	31,752
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	1,182
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	10,664
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	28,993
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	142,747
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	74,279
Total E&S 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	374,142
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	$ 14,636

Reserve for Loss and Loss Exp_9

Reserve for Loss and Loss Expense (Historical Claims Duration) (Details)	Dec. 31, 2019
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	6.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	12.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	15.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	17.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	14.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	9.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	5.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	4.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	2.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	1.90%
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	4.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	12.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	18.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	22.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	14.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	9.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	6.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	3.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	2.00%
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	21.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	24.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	13.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	8.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	4.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	4.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	2.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	2.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	1.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	1.10%
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	37.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	17.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	14.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	12.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	9.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	4.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	1.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	0.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	1.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.10%
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	47.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	19.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	8.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	8.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	6.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	3.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	2.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	0.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	0.80%
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	70.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	25.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	2.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	0.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	0.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	0.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	0.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	0.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	0.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.00%
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	58.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	18.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	9.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	6.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	4.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	1.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	0.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	0.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	0.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.10%
Homeowners [Member] | Standard Personal Lines [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	72.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	20.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	3.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	1.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	1.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	0.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	0.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	0.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	0.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.10%

Indebtedness Indebtedness (Sche

Indebtedness Indebtedness (Schedule of Long-Term Debt) (Details) - USD ($) $ in Thousands		Dec. 31, 2019	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Schedule of Debt Instruments [Line Items]
Long-term debt		$ 550,597			$ 439,540
Unamortized Debt Issuance Costs		(3,687)
Unamortized Debt Discount		(6,453)
Finance Lease, Liability		$ 737		$ 900
Five Point Three Hundred Seventy Five [Member]
Schedule of Debt Instruments [Line Items]
Interest Rate		5.375%
Long-term Debt, Gross		$ 300,000	$ 300,000
Unamortized Debt Issuance Costs		(3,147)
Unamortized Debt Discount		(5,843)
Long-term Debt		$ 291,010			0
Five Point Eight Hundred Seventy Five Percent Senior Notes [Member]
Schedule of Debt Instruments [Line Items]
Interest Rate		5.875%
Long-term Debt, Gross		$ 185,000
Unamortized Debt Issuance Costs		0
Unamortized Debt Discount		0
Long-term Debt		$ 0			180,771
Three Point Zero Three Percent Borrowing From Federal Home Loan Bank Due December 16, 2026 [Member]
Schedule of Debt Instruments [Line Items]
Interest Rate		3.03%
Long-term Debt, Gross		$ 60,000
Unamortized Debt Issuance Costs		0
Unamortized Debt Discount		0
Long-term Debt		$ 60,000			60,000
One Point Fifty Six Percent Borrowing From Federal Home Loan Bank Due August 16, 2021 [Member]
Schedule of Debt Instruments [Line Items]
Interest Rate		1.56%
Long-term Debt, Gross		$ 25,000
Unamortized Debt Issuance Costs		0
Unamortized Debt Discount		0
Long-term Debt		$ 25,000			25,000
One Point Sixty One Percent Borrowing From Federal Home Loan Bank Due July 21, 2021 [Member]
Schedule of Debt Instruments [Line Items]
Interest Rate		1.61%
Long-term Debt, Gross		$ 25,000
Unamortized Debt Issuance Costs		0
Unamortized Debt Discount		0
Long-term Debt		$ 25,000			25,000
Six Point Seventy Percent Senior Notes [Member]
Schedule of Debt Instruments [Line Items]
Interest Rate		6.70%
Long-term Debt, Gross		$ 100,000
Unamortized Debt Issuance Costs		(355)
Unamortized Debt Discount		(520)
Long-term Debt		$ 99,125			99,069
Seven Point Twenty Five Percent Senior Notes [Member]
Schedule of Debt Instruments [Line Items]
Interest Rate		7.25%
Long-term Debt, Gross		$ 50,000
Unamortized Debt Issuance Costs		(185)
Unamortized Debt Discount		(90)
Long-term Debt		49,725			49,700
Finance lease obligation [Member]
Schedule of Debt Instruments [Line Items]
Finance Lease, Liability	[1]	$ 737			$ 0
[1]	Concurrent with the adoption of ASU 2016-02 discussed in Note 3. "Adoption of Accounting Pronouncements," finance lease obligations are now captured in Long-term debt on our Consolidated Balance Sheets.

Indebtedness (Narrative) (Detai

Indebtedness (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2005	Dec. 31, 2019	Dec. 31, 2018	Aug. 05, 2019	Mar. 31, 2019	Mar. 07, 2019	Dec. 31, 2004
Maximum borrowing percentage		10.00%
Borrowing threshold of FHLBI		20
Debt Issuance Costs, Gross					$ 3,300
Long-term debt		$ 550,597	$ 439,540
Five Point Three Hundred Seventy Five [Member]
Long-term Debt, Gross		$ 300,000			$ 300,000
Interest Rate		5.375%
Discount for notes issued		$ 5,900
Net proceeds from the issuance		290,800
Five Point Eight Hundred Seventy Five Percent Senior Notes [Member]
Long-term Debt, Gross		$ 185,000
Interest Rate		5.875%
Debt Retirement Costs Before Tax		$ 4,200
Debt Retirement Costs Net of Tax		3,300
Proceeds From Debt Issuance After Redemption		106,000
Three Point Zero Three Percent Borrowing From Federal Home Loan Bank Due December 16, 2026 [Member]
Long-term Debt, Gross		$ 60,000
Interest Rate		3.03%
Federal Home Loan Bank Advances			45,000
Net proceeds from the issuance			15,000
Six Point Seventy Percent Senior Notes due 2035 [Member]
Long-term Debt, Gross		$ 100,000
Interest Rate		6.70%
Acceleration of principal		$ 10,000
Discount for notes issued	$ 700
Effective yield	6.754%
Net proceeds from the issuance	$ 50,000
Seven Point Twenty Five Percent Senior Notes due 2034 [Member]
Long-term Debt, Gross		$ 50,000
Interest Rate		7.25%
Acceleration of principal		$ 10,000
Discount for notes issued							$ 100
Effective yield							7.27%
Bond proceeds to Insurance Subsidiaries as capital							$ 25,000
Line of Credit expires Dec.20, 2022 [Member]
Line of credit borrowing capacity		50,000	30,000
Line of credit, maximum borrowing capacity		125,000	50,000
Acceleration of principal		$ 20,000
Maximum borrowing percentage		10.00%
One Point Sixty One Percent Borrowing From Federal Home Loan Bank Due July 21, 2021 [Member]
Long-term Debt, Gross		$ 25,000
Interest 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
Interest Rate		1.56%
Two Point Sixty Four Percent Borrowing From Federal Home Loan Bank Due March 28, 2019 [Member]
Federal Home Loan Bank Advances						$ 50,000
Federal Home Loan Bank, Advances, Interest Rate						2.64%
Two Point Twenty Nine Percent Borrowing From Federal Home Loan Bank Due August 12, 2019 [Member]
Federal Home Loan Bank Advances				$ 15,000
Federal Home Loan Bank, Advances, Interest Rate				2.29%
Federal Home Loan Bank of Indianapolis [Member]
Aggregate investment in FHLBI		$ 2,800
Federal Home Loan Bank of New York [Member]
Aggregate investment in FHLBI		$ 3,100	$ 2,700

Indebtedness (Covenants in the

Indebtedness (Covenants in the Line of Credit) (Details) $ in Thousands	Dec. 31, 2019USD ($)	[1]
Debt Disclosure [Abstract]
Consolidated Net Worth Requirement	$ 1,400,000
Consolidated Net Worth, Actual	$ 2,100,000
Debt-to-capitalization ratio, required	35.00%
Debt-to-capitalization ratio, actual	20.70%
[1]	Calculated in accordance with Line of Credit agreement.

Segment Information (Narrative)

Segment Information (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
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	19.00%

Segment Information (Revenue Fr

Segment Information (Revenue From Continuing Operations by Segment) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue from External Customer [Line Items]
Net premiums earned	$ 668,359	$ 653,620	$ 642,619	$ 632,573	$ 625,288	$ 614,277	$ 604,836	$ 591,828	$ 2,597,171	$ 2,436,229	$ 2,291,027
Other income	3,820	3,162	3,053	2,320	1,542	2,538	3,179	2,179	12,355	9,438	10,716
Net investment income	57,594	55,826	58,505	50,618	54,109	52,443	45,553	43,231	222,543	195,336	161,882
Total net realized and unrealized gains (losses)	(873)	(2,183)	4,027	13,451	(37,935)	(4,787)	(1,652)	(10,549)	14,422	(54,923)	6,359
Total investment revenues									236,965	140,413	168,241
Total revenues	$ 728,900	$ 710,425	$ 708,204	$ 698,962	$ 643,004	$ 664,471	$ 651,916	$ 626,689	2,846,491	2,586,080	2,469,984
Standard Commercial Lines [Member]
Revenue from External Customer [Line Items]
Other income									10,889	8,180	9,488
Total revenues									2,060,503	1,920,402	1,797,987
Standard Commercial Lines [Member] | Commercial Automobile [Member]
Revenue from External Customer [Line Items]
Net premiums earned									554,256	493,093	442,818
Standard Commercial Lines [Member] | Workers Compensation [Member]
Revenue from External Customer [Line Items]
Net premiums earned									311,370	317,616	317,982
Standard Commercial Lines [Member] | General Liability [Member]
Revenue from External Customer [Line Items]
Net premiums earned									669,895	616,187	569,217
Standard Commercial Lines [Member] | Commercial Property [Member]
Revenue from External Customer [Line Items]
Net premiums earned									353,834	329,660	311,932
Standard Commercial Lines [Member] | Business Owners' Policies [Member]
Revenue from External Customer [Line Items]
Net premiums earned									105,252	103,412	100,266
Standard Commercial Lines [Member] | Bonds Segment [Member]
Revenue from External Customer [Line Items]
Net premiums earned									35,726	33,991	29,086
Standard Commercial Lines [Member] | Other Commercial [Member]
Revenue from External Customer [Line Items]
Net premiums earned									19,281	18,263	17,198
Standard Personal Lines [Member]
Revenue from External Customer [Line Items]
Other income									1,466	1,257	1,228
Total revenues									309,205	305,698	290,929
Standard Personal Lines [Member] | Personal Automobile [Member]
Revenue from External Customer [Line Items]
Net premiums earned									172,606	168,250	153,147
Standard Personal Lines [Member] | Homeowners [Member]
Revenue from External Customer [Line Items]
Net premiums earned									127,543	128,961	129,699
Standard Personal Lines [Member] | Other Personal [Member]
Revenue from External Customer [Line Items]
Net premiums earned									7,590	7,230	6,855
E&S Lines [Member]
Revenue from External Customer [Line Items]
Other income									0	1	0
Total revenues									239,818	219,567	212,827
E&S Lines [Member] | Casualty Insurance Product Line [Member]
Revenue from External Customer [Line Items]
Net premiums earned									182,864	164,313	157,366
E&S Lines [Member] | Property Insurance [Member]
Revenue from External Customer [Line Items]
Net premiums earned									$ 56,954	$ 55,253	$ 55,461

Segment Information (Income Fro

Segment Information (Income From Continuing Operations, Before and After Federal Income Tax) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net investment income	$ 57,594	$ 55,826	$ 58,505	$ 50,618	$ 54,109	$ 52,443	$ 45,553	$ 43,231	$ 222,543	$ 195,336	$ 161,882
Total net realized and unrealized gains (losses)	$ (873)	$ (2,183)	$ 4,027	$ 13,451	$ (37,935)	$ (4,787)	$ (1,652)	$ (10,549)	14,422	(54,923)	6,359
Total investment revenues									236,965	140,413	168,241
Tax on investment income									45,301	19,560	45,588
Total investment income, after federal income tax									191,664	120,853	122,653
Standard Commercial Lines [Member]
Underwriting gain (loss), before federal income tax									145,990	109,104	149,514
Underwriting gain (loss), after federal income tax									$ 115,332	$ 86,192	$ 97,184
Combined Ratio									92.90%	94.30%	91.60%
Return on Equity									5.80%	4.90%	6.10%
Standard Personal Lines [Member]
Underwriting gain (loss), before federal income tax									$ 8,260	$ 12,764	$ 11,104
Underwriting gain (loss), after federal income tax									$ 6,525	$ 10,084	$ 7,217
Combined Ratio									97.30%	95.80%	96.20%
Return on Equity									0.30%	0.60%	0.40%
E&S Lines [Member]
Underwriting gain (loss), before federal income tax									$ 9,743	$ (695)	$ (6,282)
Underwriting gain (loss), after federal income tax									$ 7,697	$ (549)	$ (4,083)
Combined Ratio									95.90%	100.30%	103.00%
Return on Equity									0.40%	0.00%	(0.30%)
Investments [Member]
Return on Equity									9.60%	6.90%	7.50%

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, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total investment revenues									$ 236,965	$ 140,413	$ 168,241
Interest expense									(33,668)	(24,419)	(24,354)
Corporate expenses									(30,900)	(25,446)	(36,255)
Income before federal income tax	$ 101,293	$ 71,178	$ 90,225	$ 73,694	$ 52,135	$ 67,130	$ 72,525	$ 19,931	336,390	211,721	261,968
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									145,990	109,104	149,514
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									8,260	12,764	11,104
E&S Lines [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Underwriting gain (loss), before federal income tax									9,743	(695)	(6,282)
Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total all segments									$ 400,958	$ 261,586	$ 322,577

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, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Basic EPS: [Abstract]
Net income	$ 81,859	$ 56,150	$ 72,266	$ 61,348	$ 45,760	$ 55,435	$ 58,819	$ 18,925	$ 271,623	$ 178,939	$ 168,826
Net income, basic shares									59,421	58,950	58,458
Basic net income per share	$ 1.38	$ 0.94	$ 1.22	$ 1.04	$ 0.77	$ 0.94	$ 1	$ 0.32	$ 4.57	$ 3.04	$ 2.89
Effect of dilutive securities: [Abstract]
Stock compensation plans, shares									583	763	899
Earnings Per Share, Diluted [Abstract]
Net income	$ 81,859	$ 56,150	$ 72,266	$ 61,348	$ 45,760	$ 55,435	$ 58,819	$ 18,925	$ 271,623	$ 178,939	$ 168,826
Shares net income, Diluted									60,004	59,713	59,357
Diluted net income per share	$ 1.36	$ 0.93	$ 1.21	$ 1.02	$ 0.76	$ 0.93	$ 0.99	$ 0.32	$ 4.53	$ 3	$ 2.84

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, 2019	Dec. 31, 2018		Dec. 31, 2017
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	35.00%
Capital Loss Carrybacks		$ 3,800
Decrease in Discounted Loss Reserve	$ 109,500	125,000		$ 35,000
Provisional Increase to Deferred Tax Asset	23,000	26,300		7,500
Provisional Increase to Deferred Tax Asset Per Year	2,900	3,300
Tax at statutory rate (21% in 2019 and 2018 and 35% in 2017)	70,642	44,461		91,689
Tax-advantaged interest	(4,909)	(5,518)		(11,510)
Dividends received deduction	(443)	(647)		(1,961)
Federal Income Tax Expense Benefit Related to Executive Compensation	2,985	2,279		0
Share-based compensation expense income tax benefit	(3,253)	(3,093)		(4,281)
Tax Reform Deferred Tax Asset Impact	0	0		20,205
Other	(255)	(4,700)	[1]	(1,000)
Total federal income tax expense	$ 64,767	$ 32,782		$ 93,142
[1]	2018 includes approximately $3.8 million of capital loss carry back items to prior tax years at the previous 35% statutory tax rate.

Federal Income Taxes (Deferred

Federal Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Change in Net Deferred Federal Income Tax Assets	$ 46,800
Net loss reserve discounting	48,193	$ 43,285
Net unearned premiums	57,004	53,556
Employee benefits	10,646	8,862
Long-term incentive compensation plans	5,727	9,095
Temporary investment write-downs	1,059	1,155
Other	6,478	5,744
Total deferred tax assets	129,107	121,697
Deferred policy acquisition costs	56,949	53,049
Unrealized gains on investment securities	45,294	502
Other investment-related items, net	7,576	4,904
Accelerated depreciation and amortization	12,512	9,702
Total deferred tax liabilities	122,331	68,157
Deferred federal income tax	6,776	$ 53,540
Investments [Member]
Change in Net Deferred Federal Income Tax Assets	$ 44,800

Retirement Plans (Retirement Sa

Retirement Plans (Retirement Savings Plan) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Savings Plan [Member]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 17	$ 15.8	$ 15.8

Retirement Plans (Deferred Comp

Retirement Plans (Deferred Compensation Plan) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred Compensation Plan Contributions By Employer	$ 0.3	$ 0.4	$ 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, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		$ 400	$ 400	$ 400
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year		9,500
Benefit obligation, end of year		$ 10,900	$ 9,500
Retirement Income Plan [Member]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate		3.33%	4.46%
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	[1]	$ (5,033)	$ (8,358)	(4,928)
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year		334,679	364,411
Interest cost		13,506	12,428	12,490
Actuarial losses (gains)		54,478	(31,738)
Benefits paid fair value		(11,642)	(10,422)
Benefit obligation, end of year		391,021	334,679	364,411
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of assets, beginning of year		331,680	363,673
Actual return on plan assets, net of expenses		63,949	(21,571)
Contributions by the employer to funded plans		1,100	0
Fair value of assets, end of year		385,087	331,680	363,673
Funded status		(5,934)	(2,999)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Liabilities		(5,934)	(2,999)
Net pension liability, end of year		(5,934)	(2,999)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax [Abstract]
Net actuarial loss		107,125	98,057
Total		107,125	98,057
Weighted-Average Liability Asumptions
Accumulated benefit obligation		391,021	334,679
Retirement Life Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		300	300	300
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year		5,800
Benefit obligation, end of year		6,600	5,800
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Contributions by the employer to funded plans		$ 17,000	$ 15,800	$ 15,800
[1]	The components of net periodic pension cost (benefit) are included within "Loss and loss expense incurred" and "Other insurance expenses" on the Consolidated Statements of Income.

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, 2019	Dec. 31, 2018	Dec. 31, 2017
Net actuarial loss (gain)		$ 13,795	$ 11,273	$ 4,684
Reversal of amortization of net actuarial loss		$ (2,657)	$ (2,127)	(2,102)
Retirement Income Plan [Member]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate		3.33%	4.46%
Interest cost		$ 13,506	$ 12,428	12,490
Expected return on plan assets		(21,114)	(22,767)	(19,419)
Amortization of unrecognized actuarial loss		2,575	1,981	2,001
Total net periodic cost	[1]	(5,033)	(8,358)	(4,928)
Net actuarial loss (gain)		11,643	12,600	3,594
Reversal of amortization of net actuarial loss		(2,575)	(1,981)	(2,001)
Total recognized in other comprehensive income		9,068	10,619	1,593
Total recognized in net periodic benefit cost and OCI		$ 4,035	$ 2,261	$ (3,335)
[1]	The components of net periodic pension cost (benefit) are included within "Loss and loss expense incurred" and "Other insurance expenses" on the Consolidated Statements of Income.

Retirement Plans (Weighted-Aver

Retirement Plans (Weighted-Average Expense Assumptions) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Discount rate	2.95%
Expected return on plan assets	5.80%
Change in Defined Benefit Plan Discount Rate	$ 113
Retirement Income Plan [Member]
Discount rate	4.46%	3.78%	4.41%
Expected return on plan assets	6.50%	6.36%	6.24%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	3.33%	4.46%

Retirement Plans (Plan's Alloca

Retirement Plans (Plan's Allocated Target Ranges and Actual Weighted Average Asset Allocation by Investment Categories) (Details)		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Percent Hedge Against Projected Benefit Obligation		57.00%
Actual percentage		100.00%	100.00%
Return Seeking Assets [Member]
Actual percentage	[1]	59.00%	43.00%
Liability Hedging Assets [Member]
Actual percentage		38.00%	38.00%
Short-term Investments [Member]
Actual percentage		3.00%	19.00%
Minimum [Member] | Return Seeking Assets [Member]
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description		0.15
Minimum [Member] | Liability Hedging Assets [Member]
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description		0.35
Minimum [Member] | Short-term Investments [Member]
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description		0
Maximum [Member] | Return Seeking Assets [Member]
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description		0.7
Maximum [Member] | Liability Hedging Assets [Member]
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description		0.75
Maximum [Member] | Short-term Investments [Member]
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description		0
[1]	Includes limited partnerships.

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, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Total Assets		$ 385,087	$ 331,680	$ 363,673
Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		386,920	331,834
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		383,851	300,725
Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		2,215	1,482
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		113,212	113,409
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		113,212	113,409
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
Diversified Credit [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		59,009
Diversified Credit [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		59,009
Diversified Credit [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		0
Diversified Credit [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		0
Real Assets Equity [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		57,414
Real Assets 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		57,414
Real Assets Equity [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		0
Real Assets Equity [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		0
Total Equities [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		229,635
Total Equities [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		229,635
Total Equities [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		0
Total Equities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		0
Real Assets [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	[1]		16,818
Real Assets [Member] | Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	[1]	228
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	[1]	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	[1]	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	[1]	0	0
Private Equity Funds [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	[1]		878
Private Equity Funds [Member] | Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	[1]	583
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	[1]	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	[1]	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	[1]	0	0
Private Credit Funds [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	[1]		262
Private Credit Funds [Member] | Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	[1]	43
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	[1]	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	[1]	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	[1]	0	0
Hedge Funds [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	[1]		7,889
Hedge 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	[1]		0
Hedge Funds [Member] | Significant Other Observable Inputs (Level 2) [Member] | Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	[1]		0
Hedge Funds [Member] | Significant Unobservable Inputs (Level 3) [Member] | Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	[1]		0
Alternative Investments [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	[1]	854	25,847
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	[1]	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	[1]	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	[1]	0	0
Other Private Assets [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	[1]		3,780
Other Private Assets [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	[1]		0
Other Private Assets [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	[1]		0
Other Private Assets [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	[1]		0
Total Private Assets [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	[1]		29,627
Total Private Assets [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	[1]		0
Total Private Assets [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	[1]		0
Total Private Assets [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets	[1]		0
Return Seeking Assets [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		230,489	143,036
Return Seeking Assets [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		229,635	113,409
Return Seeking Assets [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		0	0
Return Seeking Assets [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		0	0
Fixed Income Securities [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		114,395	106,000
Fixed Income Securities [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		114,395	106,000
Fixed Income Securities [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		0	0
Fixed Income Securities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		0	0
US Treasury Securities [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		30,997	18,528
US Treasury Securities [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		30,997	18,528
US Treasury Securities [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		0	0
US Treasury Securities [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		8,824	62,788
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		8,824	62,788
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		2,215	1,482
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		2,215	1,482
Deposit Administration Contracts [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		0	0
Liability Hedging Assets [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		145,392	124,528
Liability Hedging Assets [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		145,392	124,528
Liability Hedging Assets [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair value, recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Assets		0	0
Liability Hedging Assets [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		11,039	64,270
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		8,824	62,788
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		2,215	1,482
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
[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.

Retirement Plans (Benefit Payme

Retirement Plans (Benefit Payments) (Details) - Retirement Income Plan [Member] $ in Thousands	Dec. 31, 2019USD ($)
2020	$ 14,968
2021	14,947
2022	16,115
2023	17,144
2024	18,146
2025 - 2029	$ 103,669

Share-Based Payments (Summary o

Share-Based Payments (Summary of Shares Available for Issuance) (Details)	Dec. 31, 2019shares
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	4,750,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	3,208,968
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	760,639
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	356,229
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	1,728,471
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, 2019shares
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	1,985,129
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	59,729	[1]
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	44,468
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	44,468	[1]
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	32,906	[1]
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	26,823	[1]
[1]	Awards outstanding under the 2005 Stock Plan consisted of 32,906 shares deferred by our non-employee directors and 26,823 stock options.

Share-Based Payments (Summary_2

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, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Incentive Plan [Member]
Weighted average remaining expense life	1 year 1 month 6 days
Change in Share Based Compensation Liability	$ 13
Share Based Compensation Liability Awards Amount Of Liability	8.6	$ 21.6
Cash incentive unit payments made	$ 18.4	$ 20.2	$ 14.2
Restricted Stock Units (RSUs) [Member]
Unvested RSU awards at December 31, 2018	846,305
Granted in 2019, number of shares	265,680
Vested in 2019, number of shares	(337,525)
Forfeited in 2019, number of shares	(27,735)
Unvested RSU awards at December 31, 2019, number of shares	746,725	846,305
Unvested RSU awards at December 31, 2018, weighted average grant date fair value	$ 44
Granted in 2019, weighted average grant date fair value	63.60	$ 55.96	$ 42.66
Vested in 2019, weighted average grant date value	36.08
Forfeited in 2019, weighted average grant date fair value	51.89
Unvested RSU awards at December 31, 2019, weighted average grant date fair value	$ 53.48	$ 44
Total unrecognized compensation cost related to unvested RSU awards	$ 8.9
Weighted average remaining expense life	1 year 8 months 12 days
Total intrinsic value of shares vested	$ 22	$ 18	$ 16
Dividend Equivalent Units [Member]
Total intrinsic value of shares vested	$ 0.8	$ 0.8	$ 0.9

Share-Based Payments (Summary_3

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, 2019	Dec. 31, 2018	Dec. 31, 2017
Outstanding at December 31, 2018, number of shares	126,735
Granted in 2019, numbers of shares	0
Exercised in 2019, number of shares	(99,912)
Forfeited or expired in 2019, number of shares	0
Outstanding at December 31, 2019, number of shares	26,823	126,735
Exercisable at December 31, 2019, number of shares	26,823
Outstanding at December 31, 2018, weighted average exercise price	$ 14.37
Granted in 2019, weighted average exercise price	0
Exercised in 2019, weighted average exercise price	13.74
Forfeited or expired in 2019, weighted average exercise price	0
Outstanding at December 31, 2019, weighted average exercise price	16.71	$ 14.37
Exercisable as December 31, 2019, weighted average exercise price	$ 16.71
Outstanding at December 31, 2019, weighted average remaining contractual life in years	3 months 29 days
Exercisable at December 31, 2019, weighted average remaining contractual life in years	3 months 29 days
Outstanding at December 31, 2019, aggregate intrinsic value	$ 1,300
Exerciseable at December 31, 2019, aggregate intrinsic value	1,300
Total intrinsic value of options exercised	$ 5,200	$ 4,500	$ 4,000

Shared-Based Payments (Summar_2

Shared-Based Payments (Summary of ESPP and ASPP Shares Issued) (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Share-Based Compensation ESPP and ASPP Shares Granted [Line Items]
Stock Issued During Period Shares	613,678	540,337	635,521
Employee Stock [Member]
Schedule of Share-Based Compensation ESPP and ASPP Shares Granted [Line Items]
Stock Issued During Period Shares	72,952	70,448	75,093
Agent Stock Purchase Plan [Member]
Schedule of Share-Based Compensation ESPP and ASPP Shares Granted [Line Items]
Stock Issued During Period Shares	47,888	41,134	49,794

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, 2019	Dec. 31, 2018	Dec. 31, 2017
Risk-free interest rate	2.33%	1.88%	1.07%
Expected term	6 months	6 months	6 months
Dividend yield	1.20%	1.30%	1.30%
Expected volatility	26.00%	18.00%	24.00%

Share-Based Payments (Weighted-

Share-Based Payments (Weighted-Average Fair Value of Options and Stock Per Share) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restricted Stock Units (RSUs) [Member]
Stock, weighted average grant date fair value	$ 63.60	$ 55.96	$ 42.66
Employee Stock Purchase Plan [Member]
Options, weighted average grant date fair value	4.32	2.67	2.73
Discount of grant date market value	9.99	8.50	7.06
Total ESPP	14.31	11.17	9.79
Agent Stock Purchase Plan [Member]
Stock, weighted average grant date fair value	$ 7	$ 5.99	$ 5.04

Shared-Based Payments (Summar_3

Shared-Based Payments (Summary of Share-Based Compensation Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure of Share-Based Compensation Expenses [Abstract]
Share-based compensation expense, pre-tax	$ 24.5	$ 19.3	$ 31.2
Income tax benefit, including the benefit related to stock grants that vested during the year	(8.2)	(7)	(15)
Share-based Compensation Expense, Net of Tax	$ 16.3	$ 12.3	$ 16.2

Related Party Transactions (Nar

Related Party Transactions (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investments	$ 6,688,654	$ 5,960,651
Direct premiums written	3,084,451	2,890,633	$ 2,733,459
Contributions to the Selective Insurance Group Foundation	1,300	500	0
Costs and Expenses, Related Party	2,200	2,000	2,000
Due to Related Parties	$ 1,100	1,000
Related Party Insurance Agency [Member]
Equity ownership percentage of director of parent of general independent retail insurance agency	10.00%
Equity Ownership Percentage Of Son Of Director Of Parent	10.00%
Direct premiums written	$ 11,000	10,100	11,100
Commissions paid to Rue Insurance	2,000	2,100	2,300
Due to Related Parties, Current	$ 300	$ 400
Vanguard Group [Member]
Percentage Common Stock Owned by Related Party	9.40%	10.10%
Related Party Transaction, Purchases from Related Party		$ 11,500
Sale of Related Party Investments	$ 11,800
Investment Income, Dividend	200	400
Related Party Capital Gains (Losses)	$ 1,300
BlackRock Inc [Member]
Percentage Common Stock Owned by Related Party	11.70%
Investments			500
Related Party Transaction, Purchases from Related Party	$ 21,700	41,400
Sale of Related Party Investments	59,500
Net realized and unrealized gain (loss)	5,700	(3,600)
Investment Income (Loss), Net	800
Retirement Income Plan [Member] | Vanguard Group [Member]
Investments			86,300
Related Party Transaction, Purchases from Related Party		8,400	5,200
Sale of Related Party Investments		85,400
Investment Income (Loss), Net		(5,500)	9,100
Retirement Income Plan [Member] | BlackRock Inc [Member]
Investments	144,200	131,900
Related Party Transaction, Purchases from Related Party	19,700	132,500	10,000
Sale of Related Party Investments	44,100	125,600	4,100
Investment Income (Loss), Net	$ 36,700	$ 9,300	$ 25,200

Leases Narrative (Details)

Leases Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Right-of-Use Asset	$ 26,535	$ 20,700
Operating Lease, Liability	27,506	21,000
Finance Lease, Right-of-Use Asset	731	900
Finance Lease, Liability	$ 737	900
Cumulative effect adjustment			$ (25,000)
Accounting Standards Update 2016-02 [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment		$ 342	$ 0	$ 0

Leases Components of Lease Expe

Leases Components of Lease Expense (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Lease Expense [Line Items]
Operating lease cost	$ 8,808
Finance lease cost: Amortization of assets	984
Finance lease cost: Interest on lease liabilities	16
Total finance lease cost	1,000
Variable lease cost	48
Short-term lease cost	$ 2,165

Leases Supplemental Lease Infor

Leases Supplemental Lease Information (Details)	Dec. 31, 2019
Supplemental Lease Information [Line Items]
Weighted average remaining lease term, operating leases	6 years
Weighted average remaining lease term, finance leases	2 years
Weighted average discount rate, operating leases	3.40%
Weighted average discount rate, finance leases	2.10%	[1]
[1]	Prior to adoption of ASU 2016-02, our historical capital lease liabilities and assets were measured using an un-discounted cash flow stream due to immateriality of the capital lease population.

Leases Lease Assets and Liabili

Leases Lease Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019
Lease Assets and Liabilities [Abstract]
Operating leases, Other assets	$ 26,535	$ 20,700
Operating leases, Other liabilities	27,506	21,000
Finance leases, Property and equipment - at cost, net of accumulated depreciation and amortization	731	900
Finance lease, Long-term debt	$ 737	$ 900

Leases Maturities of Lease Liab

Leases Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019
Maturities of Lease Liabilities [Abstract]
Finance Lease Liability, Due 2020	$ 451
Finance Lease Liability, Due 2021	248
Finance Lease Liability, Due 2022	54
Finance Lease Liability, Due 2023	0
Finance Lease Liability, Due 2024	0
Total finance leases due thereafter	0
Finance Lease Liability, total payments	753
Finance Lease imputed interest	16
Finance Lease Liability Not Yet Commenced	0
Finance Lease, Liability	737	$ 900
Operating Lease Liability, Due 2020	8,244
Operating Lease Liability, Due 2021	6,168
Operating Lease Liability, Due 2022	4,590
Operating Lease Liability, Due 2023	3,329
Operating Lease Liability, Due 2024	2,920
Total operating lease due thereafter	8,638
Operating Lease Liability, total payments	33,889
Operating Lease imputed interest	2,995
Operating Lease Liability Not Yet Commenced	3,388
Operating Lease, Liability	27,506	$ 21,000
Total Lease Liability, Due 2020	8,695
Total Lease Liability, Due 2021	6,416
Total Lease Liability, Due 2022	4,644
Total Lease Liability, Due 2023	3,329
Total Lease Liability, Due 2024	2,920
Total Lease Due Thereafter	8,638
Total Lease Liability, total payments	34,642
Total imputed interest	3,011
Total lease liability not yet commenced	3,388
Total lease liability	$ 28,243

Leases Schedule of Future Minim

Leases Schedule of Future Minimum Rental Payments Prior Year (Details) $ in Thousands	Dec. 31, 2018USD ($)
Schedule of Future Minimum Rental Payments Prior Year [Abstract]
Capital leases, due 2019	$ 728
Capital leases, due 2020	141
Capital leases, due 2021	22
Capital leases, due 2022	0
Capital leases, due 2023	0
Total capital leases due thereafter	0
Total capital lease payments	891
Operating leases, due 2019	7,762
Operating leases, due 2020	7,355
Operating leases, due 2021	5,083
Operating leases, due 2022	3,641
Operating leases, due 2023	2,900
Total operating leases due thereafter	9,698
Total operating lease payments	36,439
Total leases due 2019	8,490
Total leases due 2020	7,496
Total leases due 2021	5,105
Total leases due 2022	3,641
Total leases due 2023	2,900
Total leases due thereafter	9,698
Total minimum payment required	$ 37,330

Commitments and Contingencies (

Commitments and Contingencies (Narrative) (Details) $ in Millions	Dec. 31, 2019USD ($)
Total contractually obligated investments
Contractual Obligation Additional Investment in Alternative or Other Investments	$ 283.5
Alternative and Other Investments
Contractual Obligation Additional Investment in Alternative or Other Investments	219.2
Non-publicly traded collateralized loan obligations in our fixed income securities portfolio
Contractual Obligation	35.4
Non-publicly traded common stock within our equity portfolio
Contractual Obligation	3.9
Commercial Mortgage Loans [Member]
Contractual Obligation	10
Privately placed corporate securities
Contractual Obligation	$ 15

Commitments and Contingencies S

Commitments and Contingencies Stuctured Settlement Annuity (Details) $ in Millions	Dec. 31, 2019USD ($)
Commitments and Contingencies Disclosure [Abstract]
Purchase Amount Of Annuities	$ 25.5

Statutory Financial Informati_3

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, 2019	Dec. 31, 2018	Dec. 31, 2017
Statutory unassigned surplus	$ 1,396.8	$ 1,232.8
Statutory surplus	1,932.4	1,768.4
Statutory net income	292.7	210.6	$ 221.2
Selective Insurace Company of America (SICA) [Member]
Statutory unassigned surplus	525.9	478.6
Statutory surplus	680.1	632.8
Statutory net income	113.9	78	84.6
Selective Way Insurance Company (SWIC) [Member]
Statutory unassigned surplus	339.2	300.2
Statutory surplus	388.2	349.3
Statutory net income	59.2	47.5	43.6
Selective Insurance Company of South Carolina (SICSC) [Member]
Statutory unassigned surplus	132.6	119.4
Statutory surplus	163.8	150.7
Statutory net income	23.9	16.5	17.9
Selective Insurance Company of the Southeast (SICSE) [Member]
Statutory unassigned surplus	103.1	92.2
Statutory surplus	128.7	117.7
Statutory net income	18.5	12.9	14.7
Selective Insurance Company of New York (SICNY) [Member]
Statutory unassigned surplus	99.4	86.5
Statutory surplus	127.1	114.2
Statutory net income	17	12	13.4
Selective Insurance Company of New England (SICNE) [Member]
Statutory unassigned surplus	25.3	19.9
Statutory surplus	55.4	50
Statutory net income	7.8	5.6	6.3
Selective Auto Insurance Company of New Jersey (SAICNJ) [Member]
Statutory unassigned surplus	62.5	50.3
Statutory surplus	105.4	93.2
Statutory net income	14.9	9.9	11.4
Mesa Underwriting Specialty Insurance Company (MUSIC) [Member]
Statutory unassigned surplus	27.1	23
Statutory surplus	95.6	91.5
Statutory net income	13.2	9.4	10.3
Selective Casualty Insurance Company (SCIC) [Member]
Statutory unassigned surplus	58.2	44.9
Statutory surplus	132.7	119.3
Statutory net income	16.8	13.3	13.4
Selective Fire and Casualty Insurance Company (SFCIC) [Member]
Statutory unassigned surplus	23.5	17.8
Statutory surplus	55.4	49.7
Statutory net income	$ 7.5	$ 5.5	$ 5.6

Statutory Financial Informati_4

Statutory Financial Information, Capital Requirements, and Restrictions on Dividends and Transfers of Funds (Dividends) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Retained Earnings	$ 2,080,529	$ 1,858,414
Ordinary dividends paid	110,000
Investments and cash available to fund future dividends and interest payments	$ 266,700
Maximum borrowing percentage	10.00%
New Jersey Dividend Restriction	10.00%
New York Dividend Restriction on Insurer's Statutory Surplus	10.00%
New York Dividend Restriction on Adjusted Net Investment Income	100.00%
Selective Insurace Company of America (SICA) [Member]
Ordinary dividends paid	$ 55,500
Investments and cash available to fund future dividends and interest payments	98,400
Selective Way Insurance Company (SWIC) [Member]
Ordinary dividends paid	19,000
Investments and cash available to fund future dividends and interest payments	53,700
Selective Insurance Company of South Carolina (SICSC) [Member]
Ordinary dividends paid	9,500
Investments and cash available to fund future dividends and interest payments	23,900
Selective Insurance Company of the Southeast (SICSE) [Member]
Ordinary dividends paid	6,700
Investments and cash available to fund future dividends and interest payments	18,600
Selective Insurance Company of New York (SICNY) [Member]
Ordinary dividends paid	3,300
Investments and cash available to fund future dividends and interest payments	12,700
Selective Insurance Company of New England (SICNE) [Member]
Ordinary dividends paid	2,000
Investments and cash available to fund future dividends and interest payments	7,600
Selective Auto Insurance Company of New Jersey (SAICNJ) [Member]
Ordinary dividends paid	1,500
Investments and cash available to fund future dividends and interest payments	14,700
Mesa Underwriting Specialty Insurance Company (MUSIC) [Member]
Ordinary dividends paid	8,000
Investments and cash available to fund future dividends and interest payments	12,900
Selective Casualty Insurance Company (SCIC) [Member]
Ordinary dividends paid	3,000
Investments and cash available to fund future dividends and interest payments	16,800
Selective Fire and Casualty Insurance Company (SFCIC) [Member]
Ordinary dividends paid	1,500
Investments and cash available to fund future dividends and interest payments	7,400
Parent Company [Member]
Assets Designated to Closed Block, Cash and Cash Equivalents	278,000
Retained Earnings	2,100,000
Additional Borrowing Capacity for Parent	$ 89,400

Quarterly Financial Informati_3

Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net premiums earned	$ 668,359	$ 653,620	$ 642,619	$ 632,573	$ 625,288	$ 614,277	$ 604,836	$ 591,828	$ 2,597,171	$ 2,436,229	$ 2,291,027
Net investment income earned	57,594	55,826	58,505	50,618	54,109	52,443	45,553	43,231	222,543	195,336	161,882
Net realized and unrealized gains (losses)	(873)	(2,183)	4,027	13,451	(37,935)	(4,787)	(1,652)	(10,549)	14,422	(54,923)	6,359
Other income	3,820	3,162	3,053	2,320	1,542	2,538	3,179	2,179	12,355	9,438	10,716
Total revenues	728,900	710,425	708,204	698,962	643,004	664,471	651,916	626,689	2,846,491	2,586,080	2,469,984
Income before federal income tax	101,293	71,178	90,225	73,694	52,135	67,130	72,525	19,931	336,390	211,721	261,968
Net income	$ 81,859	$ 56,150	$ 72,266	$ 61,348	$ 45,760	$ 55,435	$ 58,819	$ 18,925	$ 271,623	$ 178,939	$ 168,826
Basic net income per share	$ 1.38	$ 0.94	$ 1.22	$ 1.04	$ 0.77	$ 0.94	$ 1	$ 0.32	$ 4.57	$ 3.04	$ 2.89
Diluted net income per share	$ 1.36	$ 0.93	$ 1.21	$ 1.02	$ 0.76	$ 0.93	$ 0.99	$ 0.32	$ 4.53	$ 3	$ 2.84

Schedule I - Summary of Inves_2

Schedule I - Summary of Investments - Other Than Investments in Related Parties (Details) $ in Thousands	Dec. 31, 2019USD ($)
Amortized Cost or Cost	$ 6,472,113
Carrying Amount	6,688,654
Short-term Investments [Member]
Amortized Cost or Cost	282,490
Fair Value	282,490
Carrying Amount	282,490
Other Investments [Member]
Amortized Cost or Cost	216,807
Carrying Amount	216,807
Held-to-maturity Securities [Member] | Obligations of States and Political Subdivisions [Member]
Amortized Cost or Cost	4,573
Fair Value	4,921
Carrying Amount	4,580
Held-to-maturity Securities [Member] | Public Utilities
Amortized Cost or Cost	3,608
Fair Value	3,967
Carrying Amount	3,673
Held-to-maturity Securities [Member] | All other corporate securities
Amortized Cost or Cost	12,588
Fair Value	13,087
Carrying Amount	12,547
Held-to-maturity Securities [Member] | Fixed Income Securities [Member]
Amortized Cost or Cost	20,769
Fair Value	21,975
Carrying Amount	20,800
AFS Fixed Income Securities [Member] | US Government Agencies Debt Securities [Member]
Amortized Cost or Cost	112,680
Fair Value	116,186
Carrying Amount	116,186
AFS Fixed Income Securities [Member] | Foreign Government
Amortized Cost or Cost	18,011
Fair Value	18,542
Carrying Amount	18,542
AFS Fixed Income Securities [Member] | Obligations of States and Political Subdivisions [Member]
Amortized Cost or Cost	1,168,185
Fair Value	1,230,090
Carrying Amount	1,230,090
AFS Fixed Income Securities [Member] | Public Utilities
Amortized Cost or Cost	35,679
Fair Value	37,084
Carrying Amount	37,084
AFS Fixed Income Securities [Member] | All other corporate securities
Amortized Cost or Cost	1,831,202
Fair Value	1,910,393
Carrying Amount	1,910,393
AFS Fixed Income Securities [Member] | CLO and Other ABS
Amortized Cost or Cost	790,517
Fair Value	793,012
Carrying Amount	793,012
AFS Fixed Income Securities [Member] | Commercial Mortgage-backed Securities (CMBS) [Member]
Amortized Cost or Cost	514,709
Fair Value	538,344
Carrying Amount	538,344
AFS Fixed Income Securities [Member] | Residential Mortgage Backed Securities [Member]
Amortized Cost or Cost	1,409,003
Fair Value	1,451,969
Carrying Amount	1,451,969
AFS Fixed Income Securities [Member] | Fixed Income Securities [Member]
Amortized Cost or Cost	5,879,986
Fair Value	6,095,620
Carrying Amount	6,095,620
Equity Securities [Member] | Banks, trusts, and insurance companies
Amortized Cost or Cost	17,357
Fair Value	17,368
Carrying Amount	17,368
Equity Securities [Member] | Industrial, miscellaneous and all other
Amortized Cost or Cost	51,815
Fair Value	52,532
Carrying Amount	52,532
Equity Securities [Member] | Preferred Stock [Member]
Amortized Cost or Cost	2,889
Fair Value	3,037
Carrying Amount	3,037
Equity Securities [Member] | Equity Securities [Member]
Amortized Cost or Cost	72,061
Fair Value	72,937
Carrying Amount	$ 72,937

Parent Corporation Balance Shee

Parent Corporation Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
ASSETS
Fixed income securities, available-for-sale – at fair value (amortized cost: $233,753 – 2019; $111,208 – 2018)	$ 6,095,620	$ 5,273,100
Short-term investments	282,490	323,864
Cash	300	505
Deferred federal income tax	6,776	53,540
Other assets	128,614	76,877
Total assets	8,797,150	7,952,729
Liabilities:
Long-term debt	550,597	439,540
Other liabilities	331,547	277,579
Total liabilities	6,602,214	6,160,927
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: 103,484,159 - 2019; 102,848,394 - 2018	206,968	205,697
Additional paid-in capital	418,521	390,315
Retained earnings	2,080,529	1,858,414
Accumulated other comprehensive income (loss)	81,750	(77,956)
Treasury stock – at cost (shares: 44,023,006 – 2019; 43,899,840 – 2018)	(592,832)	(584,668)
Total stockholders’ equity	2,194,936	1,791,802	$ 1,712,957
Total liabilities and stockholders’ equity	8,797,150	7,952,729
Parent Company [Member]
ASSETS
Fixed income securities, available-for-sale – at fair value (amortized cost: $233,753 – 2019; $111,208 – 2018)	241,526	110,098
Short-term investments	36,219	35,358
Cash	300	505	$ 534	$ 458
Investment in subsidiaries	2,416,209	2,057,218
Current federal income tax	16,116	14,161
Deferred federal income tax	4,875	10,346
Other assets	1,692	1,186
Total assets	2,716,937	2,228,872
Liabilities:
Long-term debt	439,860	329,540
Intercompany notes payable	61,163	77,517
Accrued long-term stock compensation	8,604	21,574
Other liabilities	12,374	8,439
Total liabilities	522,001	437,070
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: 103,484,159 - 2019; 102,848,394 - 2018	206,968	205,697
Additional paid-in capital	418,521	390,315
Retained earnings	2,080,529	1,858,414
Accumulated other comprehensive income (loss)	81,750	(77,956)
Treasury stock – at cost (shares: 44,023,006 – 2019; 43,899,840 – 2018)	(592,832)	(584,668)
Total stockholders’ equity	2,194,936	1,791,802
Total liabilities and stockholders’ equity	$ 2,716,937	$ 2,228,872

Parent Corporation Balance Sh_2

Parent Corporation Balance Sheets (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fixed income securities, available-for-sale, amortized cost	$ 5,879,986	$ 5,270,798
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	103,484,159	102,848,394
Treasury stock, shares	44,023,006	43,899,840
Parent Company [Member]
Fixed income securities, available-for-sale, amortized cost	$ 233,753	$ 111,208
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	103,484,159	102,848,394
Treasury stock, shares	44,023,006	43,899,840

Parent Corporation Statements o

Parent Corporation Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Net investment income earned	$ 57,594	$ 55,826	$ 58,505	$ 50,618	$ 54,109	$ 52,443	$ 45,553	$ 43,231	$ 222,543	$ 195,336	$ 161,882
Net realized gains (losses)									23,071	(25,554)	6,359
Total revenues	728,900	710,425	708,204	698,962	643,004	664,471	651,916	626,689	2,846,491	2,586,080	2,469,984
Expenses:
Interest expense									33,668	24,419	24,354
Total expenses									2,510,101	2,374,359	2,208,016
Federal income tax (benefit) expense:
Current									60,640	35,012	62,184
Deferred									4,127	(2,230)	30,958
Total federal income tax benefit									64,767	32,782	93,142
Net income	$ 81,859	$ 56,150	$ 72,266	$ 61,348	$ 45,760	$ 55,435	$ 58,819	$ 18,925	271,623	178,939	168,826
Parent Company [Member]
Revenues:
Dividends from subsidaries									110,004	100,060	80,096
Net investment income earned									7,301	3,425	2,044
Net realized gains (losses)									207	(1,567)	(15)
Total revenues									117,512	101,918	82,125
Expenses:
Interest expense									33,426	24,652	24,721
Other expenses									30,900	25,446	36,251
Total expenses									64,326	50,098	60,972
Income before federal income tax									53,186	51,820	21,153
Federal income tax (benefit) expense:
Current									(16,080)	(14,173)	(22,187)
Deferred									3,606	3,141	6,311
Total federal income tax benefit									(12,474)	(11,032)	(15,876)
Net income before equity in undistributed income of subsidiaries									65,660	62,852	37,029
Equity In Undistributed Income Of Continuing Subsidiaries, Net Of Tax									205,963	116,087	131,797
Net income									$ 271,623	$ 178,939	$ 168,826

Parent Corporation Statements_2

Parent Corporation Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities
Net income	$ 81,859	$ 56,150	$ 72,266	$ 61,348	$ 45,760	$ 55,435	$ 58,819	$ 18,925	$ 271,623	$ 178,939	$ 168,826
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense									19,077	14,507	12,089
Net realized (gains) losses									(23,071)	25,554	(6,359)
Amortization - other									55,205	44,874	52,100
Changes in assets and liabilities:
Decrease in net federal income taxes									7,721	2,428	30,918
Increase in other assets									(39,337)	(372)	(2,643)
Increase in other liabilities									34,998	(13,343)	27,297
Investing Activities
Purchase of fixed income securities, available-for-sale									(1,856,125)	(2,918,203)	(2,130,362)
Redemption and maturities of fixed income securities, available-for-sale									626,686	638,916	555,216
Sale of fixed income securities, available-for-sale									594,743	2,030,664	1,197,920
Purchase of equity securities									(46,397)	(94,344)	(61,931)
Sale of equity securities									137,294	113,339	37,960
Purchase of short-term investments									(6,087,909)	(4,259,734)	(4,280,553)
Sale of short-term investments									6,129,885	4,101,530	4,338,318
Financing Activities
Dividends to stockholders									(47,675)	(42,097)	(37,045)
Acquisition of treasury stock									(8,164)	(6,556)	(6,015)
Net proceeds from stock purchase and compensation plans									8,243	7,252	7,599
Cash, beginning of year				505					505
Cash, end of year	300				505				300	505
Parent Company [Member]
Operating Activities
Net income									271,623	178,939	168,826
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed income of subsidiaries, net of tax									(205,963)	(116,087)	(131,797)
Stock-based compensation expense									19,077	14,507	12,089
Net realized (gains) losses									(207)	1,567	15
Amortization - other									4,614	567	678
Changes in assets and liabilities:
(Decrease) increase in accrued long-term stock compensation									(12,970)	(15,443)	4,988
Decrease in net federal income taxes									1,651	11,246	3,811
Increase in other assets									(533)	(343)	(60)
Increase in other liabilities									3,919	1,712	714
Net cash provided by operating activities									81,211	76,665	59,264
Investing Activities
Purchase of fixed income securities, available-for-sale									(153,482)	(75,046)	(58,832)
Redemption and maturities of fixed income securities, available-for-sale									10,579	6,849	10,465
Sale of fixed income securities, available-for-sale									20,189	45,099	31,819
Purchase of equity securities									(10,824)	0	0
Sale of equity securities									10,828	0	0
Purchase of short-term investments									(1,116,766)	(207,115)	(185,590)
Sale of short-term investments									1,116,253	195,846	179,292
Net cash used in investing activities									(123,223)	(34,367)	(22,846)
Financing Activities
Dividends to stockholders									(47,675)	(42,097)	(37,045)
Acquisition of treasury stock									(8,164)	(6,556)	(6,015)
Proceeds from issuance of notes payable, net of debt issuance costs									290,757	0	0
Principal payment on notes payable									(185,000)	0	0
Net proceeds from stock purchase and compensation plans									8,243	7,252	7,599
Principal payments of borrowings from subsidiaries									(16,354)	(926)	(881)
Net cash provided by (used in) financing activities									41,807	(42,327)	(36,342)
Net (decrease) increase in cash									(205)	(29)	76
Cash, beginning of year				$ 505				$ 534	505	534	458
Cash, end of year	$ 300				$ 505				$ 300	$ 505	$ 534

Schedule III - Supplementary _2

Schedule III - Supplementary Insurance Information (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Deferred policy acquisition costs		$ 271,186				$ 252,612				$ 271,186		$ 252,612		$ 235,055
Reserve for loss and loss expenses		4,067,163				3,893,868				4,067,163		3,893,868		3,771,240
Unearned premiums		1,523,167				1,431,932				1,523,167		1,431,932		1,349,644
Net premiums earned										2,597,171		2,436,229		2,291,027
Net investment income	[1]									236,965		140,413		168,241
Loss and loss expense incurred										1,551,491		1,498,134		1,345,074
Amortization of deferred policy acquisition costs										535,973		495,042		469,236
Other operating expenses										345,714	[2]	321,880	[3]	322,381	[4]
Net premiums written										2,679,424		2,514,286		2,370,641
Other insurance expenses										358,069		331,318		333,097
Other income		3,820	$ 3,162	$ 3,053	$ 2,320	1,542	$ 2,538	$ 3,179	$ 2,179	12,355		9,438		10,716
Standard Commercial Lines [Member]
Deferred policy acquisition costs		226,464				206,391				226,464		206,391		193,408
Reserve for loss and loss expenses		3,436,363				3,283,531				3,436,363		3,283,531		3,165,217
Unearned premiums		1,108,009				1,020,054				1,108,009		1,020,054		956,173
Net premiums earned										2,049,614		1,912,222		1,788,499
Net investment income										0		0		0
Loss and loss expense incurred										1,187,856		1,141,038		1,008,150
Amortization of deferred policy acquisition costs										445,661		412,420		387,552
Other operating expenses										270,107		249,660		243,283
Net premiums written										2,137,071		1,975,683		1,858,735
Standard Personal Lines [Member]
Deferred policy acquisition costs		16,848				18,070				16,848		18,070		16,952
Reserve for loss and loss expenses		224,200				223,223				224,200		223,223		263,166
Unearned premiums		309,125				304,085				309,125		304,085		295,435
Net premiums earned										307,739		304,441		289,701
Net investment income										0		0		0
Loss and loss expense incurred										211,300		206,752		189,294
Amortization of deferred policy acquisition costs										34,477		33,617		32,542
Other operating expenses										53,702		51,308		56,761
Net premiums written										304,592		309,277		296,775
E&S Lines [Member]
Deferred policy acquisition costs		27,874				28,151				27,874		28,151		24,695
Reserve for loss and loss expenses		406,600				387,114				406,600		387,114		342,857
Unearned premiums		106,033				107,793				106,033		107,793		98,036
Net premiums earned										239,818		219,566		212,827
Net investment income										0		0		0
Loss and loss expense incurred										152,335		150,344		147,630
Amortization of deferred policy acquisition costs										55,835		49,005		49,142
Other operating expenses										21,905		20,912		22,337
Net premiums written										237,761		229,326		215,131
Investments Segment [Member]
Deferred policy acquisition costs		0				0				0		0		0
Reserve for loss and loss expenses		0				0				0		0		0
Unearned premiums		$ 0				$ 0				0		0		0
Net premiums earned										0		0		0
Net investment income	[1]									236,965		140,413		168,241
Loss and loss expense 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										$ 12,355		$ 9,438		$ 10,716
[1]	Includes “Net investment income earned” and “Total net realized and unrealized gains (losses)” on the Consolidated Statements of Income.
[2]	“Other operating expenses” of $345,714
[3]	“Other operating expenses” of $321,880
[4]	“Other operating expenses” of $322,381

Schedule IV - Reinsurance (Deta

Schedule IV - Reinsurance (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Direct Amount									$ 2,993,157	$ 2,808,764	$ 2,647,488
Assumed From Other Companies									24,399	25,831	25,831
Ceded to Other Companies									420,385	398,366	382,292
Total Net Premiums Earned	$ 668,359	$ 653,620	$ 642,619	$ 632,573	$ 625,288	$ 614,277	$ 604,836	$ 591,828	$ 2,597,171	$ 2,436,229	$ 2,291,027
Percentage of Amount Assumed to Net									1.00%	1.00%	1.00%
Accident and Health Insurance Segment [Member]
Direct Amount									$ 17	$ 19	$ 24
Assumed From Other Companies									0	0	0
Ceded to Other Companies									17	19	24
Total Net Premiums Earned									$ 0	$ 0	$ 0
Percentage of Amount Assumed to Net									0.00%	0.00%	0.00%
Property and liability insurance [Member]
Direct Amount									$ 2,993,140	$ 2,808,745	$ 2,647,464
Assumed From Other Companies									24,399	25,831	25,831
Ceded to Other Companies									420,368	398,347	382,268
Total Net Premiums Earned									$ 2,597,171	$ 2,436,229	$ 2,291,027
Percentage of Amount Assumed to Net									1.00%	1.00%	1.00%

Schedule V - Allowance for Unc

Schedule V - Allowance for Uncollectible Premiums and Other Receivables (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Balance, January 1	$ 13,900	$ 14,600	$ 11,480
Additions	2,730	4,022	6,414
Deductions	(5,830)	(4,722)	(3,294)
Balance, December 31	$ 10,800	$ 13,900	$ 14,600