Selective Insurance (SIGI) 10-Q 27 Jul 17 2017 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2017	Jul. 14, 2017
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
Entity Registrant Name	SELECTIVE INSURANCE GROUP INC
Entity Central Index Key	230,557
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock , Shares Outstanding		58,364,187

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
ASSETS
Fixed income securities, held-to-maturity – at carrying value (fair value: $75,540 – 2017; $105,211 – 2016)	$ 72,514	$ 101,556
Fixed income securities, available-for-sale – at fair value (amortized cost: $4,923,005 – 2017; $4,753,759 – 2016)	5,018,722	4,792,540
Equity securities, available-for-sale – at fair value (cost: $131,463 – 2017; $120,889 – 2016)	161,694	146,753
Short-term investments (at cost which approximates fair value)	133,706	221,701
Other investments	116,411	102,397
Total investments (Note 4 and 6)	5,503,047	5,364,947
Cash	8,628	458
Interest and dividends due or accrued	40,231	40,164
Premiums receivable, net of allowance for uncollectible accounts of: $6,627 – 2017; $5,980 – 2016	764,340	681,611
Reinsurance recoverable, net of allowance for uncollectible accounts of: $5,200 – 2017; $5,500 – 2016	601,887	621,537
Prepaid reinsurance premiums	151,898	146,282
Current federal income tax	0	2,486
Deferred federal income tax	60,388	84,840
Property and equipment – at cost, net of accumulated depreciation and amortization of: $206,847 – 2017; $198,729 – 2016	66,255	69,576
Deferred policy acquisition costs	234,903	222,564
Goodwill	7,849	7,849
Other assets	88,778	113,534
Total assets	7,528,204	7,355,848
Liabilities And Stockholders' Equity
Reserve for losses and loss expenses (Note 8)	3,731,221	3,691,719
Unearned premiums	1,352,068	1,262,819
Long-term debt	438,894	438,667
Current federal income tax	2,104	0
Accrued salaries and benefits	103,177	132,880
Other liabilities	248,184	298,393
Total liabilities	5,875,648	5,824,478
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: 102,150,866 – 2017; 101,620,436 – 2016	204,302	203,241
Additional paid-in capital	359,982	347,295
Retained earnings	1,641,820	1,568,881
Accumulated other comprehensive income (loss) (Note 11)	24,497	(15,950)
Treasury stock – at cost (shares: 43,788,147 – 2017; 43,653,237 – 2016)	(578,045)	(572,097)
Total stockholders' equity	1,652,556	1,531,370
Commitments and contingencies
Total liabilities and stockholders' equity	$ 7,528,204	$ 7,355,848

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fixed income securities, held-to-maturity, fair value	$ 75,540	$ 105,211
Fixed income securities, available-for-sale, amortized cost	4,923,005	4,753,759
Equity securities, available-for-sale, cost	131,463	120,889
Premiums receivable, allowance for uncollectible accounts	6,627	5,980
Reinsurance recoverable, allowance for uncollectible accounts	5,200	5,500
Property and equipment - at cost, accumulated depreciation and amortization	$ 206,847	$ 198,729
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	102,150,866	101,620,436
Treasury stock - at cost, shares	43,788,147	43,653,237

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenues:
Net premiums earned	$ 568,030	$ 531,932	$ 1,128,884	$ 1,054,390
Net investment income earned	41,430	31,182	78,849	61,951
Net realized gains (losses):
Net realized investment gains	2,951	2,314	5,381	3,203
Other-than-temporary impairments	(1,211)	(559)	(4,686)	(4,152)
Other-than-temporary impairments on fixed income securities recognized in other comprehensive income	(6)	10	(6)	10
Total net realized gains (losses)	1,734	1,765	689	(939)
Other income	3,291	3,868	6,532	4,819
Total revenues	614,485	568,747	1,214,954	1,120,221
Expenses:
Losses and loss expenses incurred	341,559	298,479	659,031	595,623
Policy acquisition costs	196,824	190,731	393,052	373,958
Interest expense	6,081	5,620	12,187	11,226
Other expenses	11,092	11,606	24,181	25,228
Total expenses	555,556	506,436	1,088,451	1,006,035
Income before federal income tax	58,929	62,311	126,503	114,186
Federal income tax expense:
Current	17,785	18,318	32,058	32,402
Deferred	(282)	392	2,579	1,151
Total federal income tax expense	17,503	18,710	34,637	33,553
Net income	$ 41,426	$ 43,601	$ 91,866	$ 80,633
Earnings per share:
Basic net income	$ 0.71	$ 0.75	$ 1.57	$ 1.40
Diluted net income	0.70	0.74	1.55	1.38
Dividends to stockholders	$ 0.16	$ 0.15	$ 0.32	$ 0.30

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net income	$ 41,426	$ 43,601	$ 91,866	$ 80,633
Unrealized holding gains arising during period	23,326	36,188	40,087	78,917
Non-Credit Portion of Other-Than-Temporary Impairments Recognized in Other Comprehensive Income	4	(6)	4	(6)
Amounts reclassified into net income: Held-to-maturity securities	(28)	(12)	(60)	(59)
Amounts reclassified into net income: Realized (gains) losses on available-for-sale securities	(1,225)	(1,145)	(244)	609
Total unrealized gains on investment securities	22,077	35,025	39,787	79,461
Amount reclassified into net income: Net actuarial loss	330	985	660	1,971
Total defined benefit pension and post-retirement plans	330	985	660	1,971
Other comprehensive income	22,407	36,010	40,447	81,432
Comprehensive income	$ 63,833	$ 79,611	$ 132,313	$ 162,065

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 income [Member]	Treasury stock [Member]
Beginning of year at Dec. 31, 2015		$ 201,723	$ 326,656	$ 1,446,192	$ (9,425)	$ (567,105)
Dividend reinvestment plan (shares: 15,419 – 2017; 20,808 – 2016)		42	696
Stock purchase and compensation plans (shares: 515,011 – 2017; 569,034 – 2016)		1,138	12,757
Net income	$ 80,633			80,633
Dividends to stockholders ($0.32 per share – 2017; $0.30 per share – 2016)				(17,583)
Other comprehensive income	81,432				81,432
Acquisition of treasury stock (shares: 134,910 – 2017; 138,007 – 2016)						(4,419)
End of period at Jun. 30, 2016	1,552,737	202,903	340,109	1,509,242	72,007	(571,524)
Beginning of year at Dec. 31, 2016	1,531,370	203,241	347,295	1,568,881	(15,950)	(572,097)
Dividend reinvestment plan (shares: 15,419 – 2017; 20,808 – 2016)		31	693
Stock purchase and compensation plans (shares: 515,011 – 2017; 569,034 – 2016)		1,030	11,994
Net income	91,866			91,866
Dividends to stockholders ($0.32 per share – 2017; $0.30 per share – 2016)				(18,927)
Other comprehensive income	40,447				40,447
Acquisition of treasury stock (shares: 134,910 – 2017; 138,007 – 2016)						(5,948)
End of period at Jun. 30, 2017	$ 1,652,556	$ 204,302	$ 359,982	$ 1,641,820	$ 24,497	$ (578,045)

Consolidated Statements of Sto7

Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Dividend reinvestment plan, shares			15,419	20,808
Stock purchase and compensation plans, shares			515,011	569,034
Dividends to stockholders, per share	$ 0.16	$ 0.15	$ 0.32	$ 0.30
Acquisition of treasury stock, shares			134,910	138,007
Preferred stock, par value per share	$ 0	$ 0	$ 0	$ 0	$ 0
Preferred stock, shares authorized	5,000,000	5,000,000	5,000,000	5,000,000	5,000,000
Preferred stock, shares issued	0	0	0	0	0
Series A Preferred Stock [Member]
Preferred stock, par value per share	$ 0	$ 0	$ 0	$ 0
Preferred stock, shares authorized	300,000	300,000	300,000	300,000

Consolidated Statements of Cash

Consolidated Statements of Cash Flow - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Operating Activities
Net income	$ 91,866	$ 80,633
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	25,409	30,155
Stock-based compensation expense	8,372	7,203
Undistributed (gains) losses of equity method investments	(3,575)	1,677
Loss on disposal of fixed assets	998	0
Net realized (gains) losses	(689)	939
Changes in assets and liabilities:
Increase in reserve for losses and loss expenses, net of reinsurance recoverable	59,152	41,986
Increase in unearned premiums, net of prepaid reinsurance	83,633	89,109
Decrease in net federal income taxes	7,263	2,380
Increase in premiums receivable	(82,729)	(91,391)
Increase in deferred policy acquisition costs	(12,339)	(15,395)
Increase in interest and dividends due or accrued	(204)	(1,030)
Decrease in accrued salaries and benefits	(29,703)	(48,603)
Decrease (increase) in other assets	24,953	(3,877)
Decrease in other liabilities	(48,684)	(34,659)
Net cash provided by operating activities	123,723	59,127
Investing Activities
Purchase of fixed income securities, held-to-maturity	0	(4,235)
Purchase of fixed income securities, available-for-sale	(1,194,142)	(411,538)
Purchase of equity securities, available-for-sale	(22,115)	(16,796)
Purchase of other investments	(22,121)	(17,734)
Purchase of short-term investments	(2,259,305)	(691,496)
Sale of fixed income securities, available-for-sale	717,072	22,114
Sale of short-term investments	2,348,892	680,865
Redemption and maturities of fixed income securities, held-to-maturity	28,730	44,615
Redemption and maturities of fixed income securities, available-for-sale	300,430	264,244
Sale of equity securities, available-for-sale	6,289	83,793
Distributions from other investments	9,843	13,380
Purchase of property and equipment	(7,047)	(8,187)
Net cash used in investing activities	(93,474)	(40,975)
Financing Activities
Dividends to stockholders	(17,922)	(16,569)
Acquisition of treasury stock	(5,948)	(4,419)
Net proceeds from stock purchase and compensation plans	4,045	4,368
Proceeds from borrowings	64,000	55,000
Repayments of borrowings	(64,000)	(55,000)
Excess tax benefits from share-based payment arrangements	0	1,761
Repayments of capital lease obligations	(2,254)	(2,661)
Net cash used in financing activities	(22,079)	(17,520)
Net increase in cash	8,170	632
Cash, beginning of year	458	898
Cash, end of period	$ 8,628	$ 1,530

Basis of Presentation

Basis of Presentation	6 Months Ended
	Jun. 30, 2017
Basis of Presentation And Significant Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation As used herein, the "Company,” “we,” “us,” or “our” refers to Selective Insurance Group, Inc. (the "Parent"), and its subsidiaries, except as expressly indicated or unless the context otherwise requires. Our interim unaudited consolidated financial statements (“Financial Statements”) have been prepared by us in conformity with U.S. generally accepted accounting principles (“GAAP”) and the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) regarding interim financial reporting. The preparation of the Financial Statements in conformity with GAAP requires us 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. All significant intercompany accounts and transactions between the Parent and its subsidiaries are eliminated in consolidation. Our Financial Statements reflect all adjustments that, in our opinion, are normal, recurring, and necessary for a fair presentation of our results of operations and financial condition. Our Financial Statements cover the second quarters ended June 30, 2017 (“ Second Quarter 2017 ”) and June 30, 2016 (“ Second Quarter 2016 ”) and the six-month periods ended June 30, 2017 (" Six Months 2017 ") and June 30, 2016 (" Six Months 2016 "). The Financial Statements do not include all of the information and disclosures required by GAAP and the SEC for audited annual financial statements. Results of operations for any interim period are not necessarily indicative of results for a full year. Consequently, our Financial Statements should be read in conjunction with the consolidated financial statements contained in our Annual Report on Form 10-K for the year ended December 31, 2016 (“ 2016 Annual Report ”) filed with the SEC.

Accounting Pronouncements

Accounting Pronouncements	6 Months Ended
	Jun. 30, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Accounting Pronouncements	Accounting Pronouncements In March 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standard Update ("ASU") 2016-09, Compensation - Stock Compensation: Improvements to Employee Share-based Payment Accounting (“ASU 2016-09”). ASU 2016-09 simplifies several aspects of the accounting for share-based payment transactions. We adopted this guidance on January 1, 2017, which resulted in the following impacts on our consolidated financial statements: Consolidated Statements of Income The new standard requires that the tax effects of share-based compensation be recognized in the income tax provision as discrete items outside of the annual estimated expected tax rate. In addition, all excess tax benefits and tax deficiencies should be recognized as income tax benefit or expense in the income statement. Previously, these amounts were recorded in additional paid-in capital. In addition, in calculating potential common shares used to determine diluted earnings per share, GAAP requires us to use the treasury stock method. The new standard requires that assumed proceeds under the treasury stock method be modified to exclude the amount of excess tax benefits that would have been recognized in additional paid-in capital. These changes were adopted on a prospective basis. As a result of adoption, we recognized an income tax benefit in the Consolidated Statements of Income of $0.4 million in Second Quarter 2017 and $3.3 million in Six Months 2017 related to stock grants that have vested this year. In recording share-based compensation expense, ASU 2016-09 allows companies to make a policy election as to whether they will include an estimate of awards expected to be forfeited or whether they will account for forfeitures as they occur. We have elected to include an estimate of forfeitures in the computation of our share-based compensation expense. As this treatment is consistent with previous guidance, this election had no impact on our consolidated financial statements. Consolidated Statements of Cash Flows ASU 2016-09 requires that excess tax benefits from share-based awards be reported as operating activities in the consolidated statement of cash flows. Previously, these cash flows were included in financing activities. We elected to apply this change on a prospective basis; therefore, no changes have been made to the prior periods disclosed in this report. The standard also requires that employee taxes paid when an employer withholds shares for tax-withholding purposes be reported as financing activities in the consolidated statement of cash flows. This requirement has no impact to us as we have historically reported these cash flows as part of financing activities. In October 2016, the FASB issued ASU 2016-17, Consolidation: Interests Held through Related Parties That Are Under Common Control ("ASU 2016-17"). ASU 2016-17 changes how a decision maker considers indirect interests in a variable interest entity ("VIE") held under common control in making the primary beneficiary determination. ASU 2016-17 was effective for annual periods beginning after December 15, 2016, including interim periods within those annual periods. The adoption of ASU 2016-17 did not impact us, as we are not the decision maker in any of the VIEs in which we are invested. Pronouncements to be effective in the future In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall: Recognition and Measurement of Financial Assets and Financial Liabilities (“ASU 2016-01”). ASU 2016-01 provides guidance to improve certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. Specifically the guidance: (i) requires equity investments to be measured at fair value with changes in fair value recognized in earnings; (ii) simplifies the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment; (iii) eliminates the requirement to disclose the methods and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost; (iv) requires the use of the exit price notion when measuring the fair value of financial instruments for disclosure purposes; and (v) clarifies that the need for a valuation allowance on a deferred tax asset related to an available-for-sale ("AFS") security should be evaluated with other deferred tax assets. ASU 2016-01 is effective for annual periods beginning after December 15, 2017, including interim periods within those annual periods. Our adoption of this guidance will require a cumulative-effect adjustment to the balance sheet as of January 1, 2018 in an amount equal to the after-tax net unrealized gain or loss on our equity portfolio as of year-end 2017. If this guidance had been adopted as of the beginning of 2017, the cumulative-effect adjustment would have been approximately $17 million and we would have recognized additional after-tax net income of approximately $3 million or $0.05 per diluted share, reflecting the change in fair value during Six Months 2017. In February 2016, the FASB issued ASU 2016-02, Leases (“ASU 2016-02”). ASU 2016-02 requires all lessees to recognize a lease liability and a right-of-use asset, measured at the present value of the future minimum lease payments, at the lease commencement date. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, including interim reporting periods within that fiscal year, with early adoption permitted. ASU 2016-02 requires the application of a modified retrospective approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. While we are currently evaluating ASU 2016-02, we do not expect a material impact on our financial condition or results of operations from the adoption of this guidance. In June 2016, the FASB issued ASU 2016-13 , Financial Instruments - Credit Losses (“ASU 2016-13”). ASU 2016-13 will change the way entities recognize impairment of financial assets by requiring immediate recognition of estimated credit losses expected to occur over the remaining life of many financial assets, including, among others, held-to-maturity debt securities, trade receivables, and reinsurance receivables. ASU 2016-13 requires a valuation allowance to be calculated on these financial assets and that they be presented on the financial statements net of the valuation allowance. The valuation allowance is a measurement of expected losses that is based on relevant information about past events, including historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. This methodology is referred to as the current expected credit loss model. ASU 2016-13 is effective for fiscal years beginning after December 15, 2019, including interim periods within those annual periods. Early adoption is permitted, but no earlier than fiscal years beginning after December 15, 2018. We are currently evaluating the impact of this guidance on our financial condition and results of operations. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (“ASU 2016-15”). ASU 2016-15 adds or clarifies guidance on the classification of certain cash receipts and payments in the statement of cash flows, including, but not limited to: (i) debt prepayment or debt extinguishment costs; (ii) proceeds from the settlement of corporate-owned life insurance policies, including bank-owned life insurance policies; (iii) distributions received from equity method investees; and (iv) separately identifiable cash flows and application of the predominance principle. ASU 2016-15 is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted. We are currently evaluating the impact of this guidance on our statement of cash flows. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows: Restricted Cash ("ASU 2016-18"). ASU 2016-18, requires that restricted cash and restricted cash equivalents be included with cash and cash equivalents in the reconciliation of beginning and ending cash on the statements of cash flows. This update also requires a reconciliation of the statement of the cash flows to the balance sheet if the balance sheet includes more than one line item of cash, cash equivalents, and restricted cash. ASU 2016-18 is effective, with retrospective adoption, for annual periods beginning after December 15, 2017, and interim periods within those annual periods. We currently have restricted cash associated with the National Flood Insurance Program ("NFIP") in "Other assets." This literature will impact the presentation of this item in both the Consolidated Balance Sheets and the Statements of Cash Flows. In January 2017, the FASB issued ASU 2017-04, Intangibles-Goodwill and Other: Simplifying the Test for Goodwill Impairment (“ASU 2017-04”). ASU 2017-04 eliminates the second step of the two part goodwill impairment test, which required entities to determine the fair value of individual assets and liabilities of a reporting unit to measure the goodwill impairment. Under the new guidance, a goodwill impairment is calculated as the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. An entity still has the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. The amendments in this update should be applied on a prospective basis for annual or interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. We do not expect a material impact on our financial condition or results of operations from the adoption of this guidance. In March 2017, the FASB issued ASU 2017-07, Compensation-Retirement Benefits: Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost ("ASU 2017-07"). ASU 2017-07 requires that an employer report a pension plan's service cost in the same line item or line items as other compensation costs arising from services rendered by pertinent employees during the period. ASU 2017-07 also requires that other components of net benefit cost be presented in the income statement separately from the service cost component. If a separate line item or items are not used, the line item or items used in the income statement to present the other components of net benefit cost must be disclosed. ASU 2017-07 is effective for annual periods beginning after December 15, 2017, including interim periods within those annual periods, with early adoption permitted at the beginning of an annual period. As our pension plan was frozen as of March 2016, we ceased accruing additional service fee costs at that time. Therefore, the application of this guidance is not anticipated to impact our financial condition, results of operations, or disclosures. In March 2017, the FASB issued ASU 2017-08, Receivables-Nonrefundable Fees and Other Costs: Premium Amortization on Purchased Callable Debt Securities ("ASU 2017-08"). ASU 2017-08 revises the amortization period for certain callable debt securities held at a premium, requiring the premium to be amortized to the earliest call date. Under current GAAP, entities generally amortize the premium as an adjustment of yield over the contractual life of the instrument. ASU 2017-08 is effective for annual periods and interim periods within those annual periods beginning after December 15, 2018, with early adoption permitted. This ASU does not impact us, as we amortize premium on these callable debt securities to the earliest call date. In May 2017, the FASB issued ASU 2017-09, Compensation - Stock Compensation: Scope of Modification Accounting ("ASU 2017-09"). ASU 2017-09 provides clarification about which changes to the terms or conditions of a share-based payment award would require the application of modification accounting. ASU 2017-09 is effective for annual and interim periods beginning after December 15, 2017, with early adoption permitted. The adoption of this guidance is not anticipated to impact us, as we currently record modifications in accordance with this ASU.

Statements of Cash Flow

Statements of Cash Flow	6 Months Ended
	Jun. 30, 2017
Supplemental Cash Flow Information [Abstract]
Statements of Cash Flow	Statements of Cash Flows Supplemental cash flow information was as follows: Six Months ended June 30, ($ in thousands) 2017 2016 Cash paid during the period for: Interest $ 11,963 10,986 Federal income tax 27,000 29,000 Non-cash items: Exchange of fixed income securities, AFS 1,029 17,702 Corporate actions related to equity securities, AFS 1 — 3,032 Assets acquired under capital lease arrangements 278 2,999 Non-cash purchase of property and equipment — 577 1 Examples of such corporate actions include non-cash acquisitions and stock splits. Included in "Other assets" on the Consolidated Balance Sheets was $8.1 million at June 30, 2017 and $8.9 million at June 30, 2016 of cash received from the NFIP, which is restricted to pay flood claims under the Write Your Own ("WYO") program.

Investments

Investments	6 Months Ended
	Jun. 30, 2017
Investments [Abstract]
Investments	Investments (a) Information regarding our held-to-maturity ("HTM") fixed income securities as of June 30, 2017 and December 31, 2016 was as follows: June 30, 2017 ($ in thousands) Amortized Cost Net Unrealized Gains (Losses) Carrying Value Unrecognized Holding Gains Unrecognized Holding Losses Fair Value Obligations of states and political subdivisions $ 53,734 185 53,919 1,703 — 55,622 Corporate securities 18,714 (119 ) 18,595 1,323 — 19,918 Total HTM fixed income securities $ 72,448 66 72,514 3,026 — 75,540 December 31, 2016 ($ in thousands) Amortized Cost Net Unrealized Gains (Losses) Carrying Value Unrecognized Holding Gains Unrecognized Holding Losses Fair Value Obligations of states and political subdivisions $ 77,466 317 77,783 2,133 — 79,916 Corporate securities 22,711 (143 ) 22,568 1,665 (158 ) 24,075 Commercial mortgage-backed securities ("CMBS") 1,220 (15 ) 1,205 15 — 1,220 Total HTM fixed income securities $ 101,397 159 101,556 3,813 (158 ) 105,211 Unrecognized holding gains and losses of HTM securities are not reflected in the Financial Statements, as they represent fair value fluctuations from the later of: (i) the date a security is designated as HTM; or (ii) the date that an other-than-temporary impairment (“OTTI”) charge is recognized on an HTM security, through the date of the balance sheet. (b) Information regarding our AFS securities as of June 30, 2017 and December 31, 2016 was as follows: June 30, 2017 ($ in thousands) Cost/ Amortized Cost Unrealized Gains Unrealized Losses Fair Value AFS fixed income securities: U.S. government and government agencies $ 66,932 1,103 (32 ) 68,003 Foreign government 18,157 557 — 18,714 Obligations of states and political subdivisions 1,360,211 45,641 (1,086 ) 1,404,766 Corporate securities 1,782,993 39,041 (524 ) 1,821,510 Collateralized loan obligations and other asset-backed securities ("CLO and other ABS") 698,594 4,108 (178 ) 702,524 CMBS 277,320 2,128 (243 ) 279,205 Residential mortgage-backed securities (“RMBS”) 718,798 6,068 (866 ) 724,000 Total AFS fixed income securities 4,923,005 98,646 (2,929 ) 5,018,722 AFS equity securities: Common stock 115,315 30,108 (987 ) 144,436 Preferred stock 16,148 1,110 — 17,258 Total AFS equity securities 131,463 31,218 (987 ) 161,694 Total AFS securities $ 5,054,468 129,864 (3,916 ) 5,180,416 December 31, 2016 ($ in thousands) Cost/ Amortized Cost Unrealized Gains Unrealized Losses Fair Value AFS fixed income securities: U.S. government and government agencies $ 75,139 2,230 (36 ) 77,333 Foreign government 26,559 322 (16 ) 26,865 Obligations of states and political subdivisions 1,366,287 18,610 (5,304 ) 1,379,593 Corporate securities 1,976,556 27,057 (5,860 ) 1,997,753 CLO and other ABS 527,876 1,439 (355 ) 528,960 CMBS 256,356 1,514 (1,028 ) 256,842 RMBS 524,986 3,006 (2,798 ) 525,194 Total AFS fixed income securities 4,753,759 54,178 (15,397 ) 4,792,540 AFS equity securities: Common stock 104,663 26,250 (305 ) 130,608 Preferred stock 16,226 274 (355 ) 16,145 Total AFS equity securities 120,889 26,524 (660 ) 146,753 Total AFS securities $ 4,874,648 80,702 (16,057 ) 4,939,293 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 "Accumulated other comprehensive income (loss)" ("AOCI") on the Consolidated Balance Sheets. (c) The severity of impairment on securities in an unrealized/unrecognized loss position averaged 1% of amortized cost at both June 30, 2017 and December 31, 2016 . Quantitative information regarding unrealized losses on our AFS portfolio is provided below. June 30, 2017 Less than 12 months 12 months or longer Total ($ in thousands) Fair Value Unrealized Losses 1 Fair Value Unrealized Losses 1 Fair Value Unrealized 1 AFS fixed income securities: U.S. government and government agencies $ 12,670 (32 ) — — 12,670 (32 ) Obligations of states and political subdivisions 107,387 (1,086 ) — — 107,387 (1,086 ) Corporate securities 72,991 (517 ) 2,531 (7 ) 75,522 (524 ) CLO and other ABS 156,406 (178 ) — — 156,406 (178 ) CMBS 42,671 (243 ) — — 42,671 (243 ) RMBS 179,293 (860 ) 449 (6 ) 179,742 (866 ) Total AFS fixed income securities 571,418 (2,916 ) 2,980 (13 ) 574,398 (2,929 ) AFS equity securities: Common stock 18,423 (987 ) — — 18,423 (987 ) Total AFS equity securities 18,423 (987 ) — — 18,423 (987 ) Total AFS $ 589,841 (3,903 ) 2,980 (13 ) 592,821 (3,916 ) December 31, 2016 Less than 12 months 12 months or longer Total ($ in thousands) Fair Value Unrealized Losses 1 Fair Value Unrealized Losses 1 Fair Value Unrealized 1 AFS fixed income securities: U.S. government and government agencies $ 6,419 (36 ) — — 6,419 (36 ) Foreign government 13,075 (16 ) — — 13,075 (16 ) Obligations of states and political subdivisions 306,509 (5,304 ) — — 306,509 (5,304 ) Corporate securities 462,902 (5,771 ) 4,913 (89 ) 467,815 (5,860 ) CLO and other ABS 189,795 (354 ) 319 (1 ) 190,114 (355 ) CMBS 82,492 (1,021 ) 1,645 (7 ) 84,137 (1,028 ) RMBS 279,480 (2,489 ) 8,749 (309 ) 288,229 (2,798 ) Total AFS fixed income securities 1,340,672 (14,991 ) 15,626 (406 ) 1,356,298 (15,397 ) AFS equity securities: Common stock 11,271 (305 ) — — 11,271 (305 ) Preferred stock 6,168 (355 ) — — 6,168 (355 ) Total AFS equity securities 17,439 (660 ) — — 17,439 (660 ) Total AFS $ 1,358,111 (15,651 ) 15,626 (406 ) 1,373,737 (16,057 ) 1 Gross unrealized losses include non-OTTI unrealized amounts and OTTI losses recognized in AOCI. We do not intend to sell any of the securities in the tables above, nor do we believe we will be required to sell any of these securities. We have also reviewed these securities under our OTTI policy, as described in Note 2. “Summary of Significant Accounting Policies” within Item 8. “Financial Statements and Supplementary Data.” of our 2016 Annual Report , and have concluded that they are temporarily impaired. This conclusion reflects our current judgment as to the financial position and future prospects of the entity that issued the investment security and underlying collateral. (d) Fixed income securities at June 30, 2017 , by contractual maturity, are shown below. Mortgage-backed securities ("MBS") are included in the maturity tables using the estimated average life of each security. Expected maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations, with or without call or prepayment penalties. Listed below are the contractual maturities of fixed income securities at June 30, 2017 : AFS HTM ($ in thousands) Fair Value Carrying Value Fair Value Due in one year or less $ 306,493 34,521 34,898 Due after one year through five years 2,095,055 29,648 31,498 Due after five years through 10 years 2,379,624 8,345 9,144 Due after 10 years 237,550 — — Total fixed income securities $ 5,018,722 72,514 75,540 (e) We evaluate the alternative investments and tax credit investments included in our other investments portfolio to determine whether those investments are VIEs and if so, whether consolidation is required. A VIE is an entity that either has equity investors that lack certain essential characteristics of a controlling financial interest or lacks sufficient funds to finance its own activities without financial support provided by other entities. We consider several significant factors in determining if our investments are VIEs and if we are the primary beneficiary, including whether we have: (i) the power to direct activities of the VIE; (ii) the ability to remove the decision maker of the VIE; (iii) the ability to participate in making decisions that are significant to the VIE; and (iv) the obligation to absorb losses and the right to receive benefits that could potentially be significant to the VIE. We have determined that the investments in our other investment portfolio are VIEs, but that we are not the primary beneficiary and therefore, consolidation is not required. The following table summarizes our other investment portfolio by strategy: Other Investments June 30, 2017 December 31, 2016 ($ in thousands) Carrying Value Remaining Commitment Maximum Exposure to Loss 1 Carrying Value Remaining Commitment Maximum Exposure to Loss 1 Alternative Investments Private equity $ 46,945 76,027 122,972 41,135 76,774 117,909 Private credit 29,942 57,391 87,333 28,193 40,613 68,806 Real assets 20,783 31,237 52,020 14,486 22,899 37,385 Total alternative investments 97,670 164,655 262,325 83,814 140,286 224,100 Other securities 18,741 — 18,741 18,583 3,400 21,983 Total other investments $ 116,411 164,655 281,066 102,397 143,686 246,083 1 The maximum exposure to loss includes both the carry value of these investments and the related unfunded commitments. In addition, tax credits that have been previously recognized in Other securities are subject to the risk of recapture, which we do not consider significant. We do not have a future obligation to fund losses or debts on behalf of the investments above; 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 2017 or 2016 . For a description of our alternative investment strategies, as well as information regarding redemption, restrictions, and fund liquidations, refer to Note 5. “Investments” in Item 8. “Financial Statements and Supplementary Data.” of our 2016 Annual Report . The following table sets forth gross summarized financial information for our other investments portfolio, including the portion not owned by us. The majority of these investments are carried under the equity method of accounting. The last line of the table below reflects our share of the aggregate income or loss, 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 for the three and six-month periods ended March 31 is included in our Second Quarter and Six Months results. This information is as follows: Income Statement Information Quarter ended June 30, Six Months ended June 30, ($ in millions) 2017 2016 2017 2016 Net investment (loss) income $ (9.9 ) (4.6 ) (62.4 ) 37.0 Realized gains (70.2 ) 193.2 (304.3 ) 981.1 Net change in unrealized depreciation 1,418.5 (253.9 ) 1,890.0 (1,236.5 ) Net gain $ 1,338.4 (65.3 ) 1,523.3 (218.4 ) Selective’s insurance subsidiaries’ other investments gain (loss) $ 5.2 (0.6 ) 6.8 (1.7 ) (f) 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 June 30, 2017 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 June 30, 2017 : ($ in millions) FHLBI Collateral FHLBNY Collateral State and Regulatory Deposits Total U.S. government and government agencies $ 3.1 — 23.9 27.0 Obligations of states and political subdivisions — — 2.0 2.0 CMBS 3.6 4.8 — 8.4 RMBS 60.6 51.9 — 112.5 Total pledged as collateral $ 67.3 56.7 25.9 149.9 (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-backed investments, as of June 30, 2017 or December 31, 2016 . (h) The components of pre-tax net investment income earned were as follows: Quarter ended June 30, Six Months ended June 30, ($ in thousands) 2017 2016 2017 2016 Fixed income securities $ 37,668 31,753 $ 74,559 63,397 Equity securities 1,419 2,204 2,887 4,434 Short-term investments 377 142 627 301 Other investments 5,231 (611 ) 6,834 (1,677 ) Investment expenses (3,265 ) (2,306 ) (6,058 ) (4,504 ) Net investment income earned $ 41,430 31,182 $ 78,849 61,951 (i) The following tables summarize OTTI by asset type for the periods indicated: Second Quarter 2017 Gross Included in Other Comprehensive Income ("OCI") Recognized in ($ in thousands) AFS fixed income securities: U.S. government and government agencies $ 2 — 2 Obligations of states and political subdivisions 239 — 239 Corporate securities 381 — 381 CLO and other ABS 62 — 62 CMBS 220 — 220 RMBS 71 (6 ) 77 Total AFS fixed income securities 975 (6 ) 981 AFS equity securities: Common stock 46 — 46 Total AFS equity securities 46 — 46 Other Investments 190 — 190 Total OTTI losses $ 1,211 $ (6 ) $ 1,217 Second Quarter 2016 Gross Included in OCI Recognized in ($ in thousands) AFS fixed income securities: Corporate securities $ 104 — 104 RMBS 98 10 88 Total AFS fixed income securities 202 10 192 AFS equity securities: Common stock 357 — 357 Total AFS equity securities 357 — 357 Total OTTI losses $ 559 10 549 Six Months 2017 Gross Included in Other Comprehensive Income ("OCI") Recognized in ($ in thousands) AFS fixed income securities: U.S. government and government agencies $ 31 — 31 Obligations of states and political subdivisions 612 — 612 Corporate securities 575 — 575 CLO and other ABS 85 — 85 CMBS 670 — 670 RMBS 1,163 (6 ) 1,169 Total AFS fixed income securities 3,136 (6 ) 3,142 AFS equity securities: Common stock 1,360 — 1,360 Total AFS equity securities 1,360 — 1,360 Other Investments 190 — 190 Total OTTI losses $ 4,686 $ (6 ) $ 4,692 Six Months 2016 Gross Included in OCI Recognized in ($ in thousands) AFS fixed income securities: Corporate securities $ 1,077 — 1,077 RMBS 98 10 88 Total AFS fixed income securities 1,175 10 1,165 AFS equity securities: Common stock 2,974 — 2,974 Preferred stock 3 — 3 Total AFS equity securities 2,977 — 2,977 Total OTTI losses $ 4,152 10 4,142 For a discussion of our evaluation for OTTI refer to Note 2. "Summary of Significant Accounting Policies" in Item 8. "Financial Statements and Supplementary Data." of our 2016 Annual Report . (j) The components of net realized gains, excluding OTTI charges, for the periods indicated were as follows: Quarter ended June 30, Six Months ended June 30, ($ in thousands) 2017 2016 2017 2016 HTM fixed income securities Gains $ 44 3 44 3 Losses — — (1 ) (1 ) AFS fixed income securities Gains 2,715 365 6,267 985 Losses (153 ) (5 ) (1,740 ) (41 ) AFS equity securities Gains 350 2,171 350 2,501 Losses — (220 ) — (240 ) Other investments Gains — — 480 — Losses (5 ) — (19 ) (4 ) Total net realized gains (excluding OTTI charges) $ 2,951 2,314 5,381 3,203 Realized gains and losses on the sale of investments are determined on the basis of the cost of the specific investments sold. Proceeds from the sale of AFS securities were $123.1 million and $88.7 million in Second Quarter 2017 and Second Quarter 2016 , respectively, and $723.4 million and $105.9 million in Six Months 2017 and Six Months 2016, respectively. This increase was driven by higher trading volume in our fixed income securities portfolio related to the recent hiring of new external investment managers.

Indebtedness Indebtedness

Indebtedness Indebtedness	6 Months Ended
	Jun. 30, 2017
Debt Disclosure [Abstract]
Debt Disclosure [Text Block]	Indebtedness Our long-term debt balance has not changed since December 31, 2016 . However, on February 28, 2017 , Selective Insurance Company of America ("SICA") borrowed $64 million in short-term funds from the FHLBNY at an interest rate of 0.75% . This borrowing was repaid on March 21, 2017 . For detailed information on our indebtedness, see Note 10. "Indebtedness" in Item 8. "Financial Statements and Supplementary Data." of our 2016 Annual Report .

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Our financial assets are measured at fair value as disclosed on the Consolidated Balance Sheets. The fair values of our long-term debt have improved since December 31, 2016, but not by more than 5% in the aggregate. For a discussion of the fair value and hierarchy of the techniques used to value our financial assets and liabilities, refer to Note 2. "Summary of Significant Accounting Policies" in Item 8. "Financial Statements and Supplementary Data." of our 2016 Annual Report . The following tables provide quantitative disclosures of our financial assets that were measured at fair value at June 30, 2017 and December 31, 2016 : June 30, 2017 Fair Value Measurements Using ($ in thousands) Assets Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) 1 Significant Other Observable Inputs (Level 2) 1 Significant Unobservable Inputs (Level 3) Description Measured on a recurring basis: AFS fixed income securities: U.S. government and government agencies $ 68,003 24,828 43,175 — Foreign government 18,714 — 18,714 — Obligations of states and political subdivisions 1,404,766 — 1,404,766 — Corporate securities 1,821,510 — 1,821,510 — CLO and other ABS 702,524 — 702,524 — CMBS 279,205 — 279,205 — RMBS 724,000 — 724,000 — Total AFS fixed income securities 5,018,722 24,828 4,993,894 — AFS equity securities: Common stock 144,436 135,966 — 8,470 Preferred stock 17,258 17,258 — — Total AFS equity securities 161,694 153,224 — 8,470 Total AFS securities 5,180,416 178,052 4,993,894 8,470 Short-term investments 133,706 133,706 — — Total assets measured at fair value $ 5,314,122 311,758 4,993,894 8,470 December 31, 2016 Fair Value Measurements Using ($ in thousands) Assets Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) 1 Significant Other Observable Inputs (Level 2) 1 Significant Unobservable Inputs (Level 3) Description Measured on a recurring basis: AFS fixed income securities: U.S. government and government agencies $ 77,333 27,520 49,813 — Foreign government 26,865 — 26,865 — Obligations of states and political subdivisions 1,379,593 — 1,379,593 — Corporate securities 1,997,753 — 1,997,753 — CLO and other ABS 528,960 — 528,960 — CMBS 256,842 — 256,842 — RMBS 525,194 — 525,194 — Total AFS fixed income securities 4,792,540 27,520 4,765,020 — AFS equity securities: Common stock 130,608 122,932 — 7,676 Preferred stock 16,145 16,145 — — Total AFS equity securities 146,753 139,077 — 7,676 Total AFS securities 4,939,293 166,597 4,765,020 7,676 Short-term investments 221,701 221,701 — — Total assets measured at fair value $ 5,160,994 388,298 4,765,020 7,676 1 There were no transfers of securities between Level 1 and Level 2. There were no material changes in the fair value of securities measured using Level 3 inputs since December 31, 2016 . The following tables provide quantitative information regarding our financial assets and liabilities that were disclosed at fair value at June 30, 2017 and December 31, 2016 : June 30, 2017 Fair Value Measurements Using ($ in thousands) Assets/ 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 $ 55,622 — 55,622 — Corporate securities 19,918 — 13,960 5,958 Total HTM fixed income securities $ 75,540 — 69,582 5,958 Financial Liabilities Long-term debt: 7.25% Senior Notes $ 58,690 — 58,690 — 6.70% Senior Notes 112,573 — 112,573 — 5.875% Senior Notes 188,767 188,767 — — 1.61% borrowings from FHLBNY 24,521 — 24,521 — 1.56% borrowings from FHLBNY 24,462 — 24,462 — 3.03% borrowings from FHLBI 60,837 — 60,837 — Total long-term debt $ 469,850 188,767 281,083 — December 31, 2016 Fair Value Measurements Using ($ in thousands) Assets/ Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Financial Assets HTM: Obligations of states and political subdivisions $ 79,916 — 79,916 — Corporate securities 24,075 — 16,565 7,510 CMBS 1,220 — 1,220 — Total HTM fixed income securities $ 105,211 — 97,701 7,510 Financial Liabilities Long-term debt: 7.25% Senior Notes $ 56,148 — 56,148 — 6.70% Senior Notes 108,333 — 108,333 — 5.875% Senior Notes 176,860 176,860 — — 1.61% borrowings from FHLBNY 24,286 — 24,286 — 1.56% borrowings from FHLBNY 24,219 — 24,219 — 3.03% borrowings from FHLBI 59,313 — 59,313 — Total long-term debt $ 449,159 176,860 272,299 —

Reinsurance

Reinsurance	6 Months Ended
	Jun. 30, 2017
Reinsurance Disclosures [Abstract]
Reinsurance	Reinsurance The following table contains a listing of direct, assumed, and ceded reinsurance amounts for premiums written, premiums earned, and loss and loss expenses incurred for the periods indicated. For more information concerning reinsurance, refer to Note 8. “Reinsurance” in Item 8. “Financial Statements and Supplementary Data.” of our 2016 Annual Report . Quarter ended June 30, Six Months ended June 30, ($ in thousands) 2017 2016 2017 2016 Premiums written: Direct $ 706,408 665,862 1,390,228 1,312,140 Assumed 6,488 7,788 12,179 14,108 Ceded (99,082 ) (95,510 ) (189,889 ) (182,749 ) Net $ 613,814 578,140 1,212,518 1,143,499 Premiums earned: Direct $ 654,588 612,406 1,301,316 1,219,067 Assumed 6,063 7,171 11,842 13,441 Ceded (92,621 ) (87,645 ) (184,274 ) (178,118 ) Net $ 568,030 531,932 1,128,884 1,054,390 Loss and loss expense incurred: Direct $ 389,550 362,064 731,672 723,703 Assumed 7,766 6,140 12,203 12,495 Ceded (55,757 ) (69,725 ) (84,844 ) (140,575 ) Net $ 341,559 298,479 659,031 595,623 Ceded premiums and losses related to our participation in the NFIP, under which 100% of our flood premiums, losses, and loss expenses are ceded to the NFIP, are as follows: Ceded to NFIP Quarter ended June 30, Six Months ended June 30, ($ in thousands) 2017 2016 2017 2016 Ceded premiums written $ (63,808 ) (63,906 ) (120,142 ) (117,154 ) Ceded premiums earned (57,655 ) (56,667 ) (114,932 ) (113,481 ) Ceded loss and loss expense incurred (15,140 ) (24,261 ) (21,681 ) (64,979 )

Reserve for Losses and Loss Exp

Reserve for Losses and Loss Expenses Reserves for Losses and Loss Expenses	6 Months Ended
	Jun. 30, 2017
Insurance Loss Reserves [Abstract]
Liability for Future Policy Benefits and Unpaid Claims Disclosure [Text Block]	Reserves for Losses and Loss Expenses The table below provides a roll forward of reserves for losses and loss expenses for beginning and ending reserve balances: Six Months ended June 30, ($ in thousands) 2017 2016 Gross reserves for losses and loss expenses, at beginning of year $ 3,691,719 3,517,728 Less: reinsurance recoverable on unpaid losses and loss expenses, at beginning of year 611,200 551,019 Net reserves for losses and loss expenses, at beginning of year 3,080,519 2,966,709 Incurred losses and loss expenses for claims occurring in the: Current year 684,877 624,159 Prior years (25,846 ) (28,536 ) Total incurred losses and loss expenses 659,031 595,623 Paid losses and loss expenses for claims occurring in the: Current year 171,724 146,849 Prior years 425,521 402,255 Total paid losses and loss expenses 597,245 549,104 Net reserves for losses and loss expenses, at end of period 3,142,305 3,013,228 Add: Reinsurance recoverable on unpaid losses and loss expenses, at end of period 588,916 576,941 Gross reserves for losses and loss expenses at end of period $ 3,731,221 3,590,169 Prior year development in Six Months 2017 of $25.8 million was primarily driven by favorable prior year casualty reserve development of $37.4 million in our general liability line of business and $15.3 million in our workers compensation line of business. This was partially offset by unfavorable casualty reserve development of $21.0 million in our commercial automobile line of business and $4.0 million in our personal automobile line of business. Prior year development in Six Months 2016 of $28.5 million was primarily due to favorable casualty reserve development of $22.0 million in our general liability line of business and $21.0 million in our workers compensation line of business. This was partially offset by unfavorable casualty reserve development of $13.0 million in our commercial automobile line of business and $3.0 million in our E&S segment.

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2017
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 Excess and Surplus ("E&S") Lines are evaluated based on statutory underwriting results (net premiums earned, incurred losses and loss expenses, policyholder dividends, policy acquisition costs, and other underwriting expenses), and statutory combined ratios. • Our Investments segment is evaluated based on after-tax net investment income and net realized gains and losses. In computing the results of each segment, we do not make adjustments for interest expense or net general corporate expenses; however, we do partially allocate taxes to various segments. Furthermore, we do not maintain separate investment portfolios for the segments and therefore, do not allocate assets to the segments. The following summaries present revenues (net investment income and net realized gains on investments in the case of the Investments segment) and pre-tax income for the individual segments: Revenue by Segment Quarter ended June 30, Six Months ended June 30, ($ in thousands) 2017 2016 2017 2016 Standard Commercial Lines: Net premiums earned: Commercial automobile $ 108,316 98,896 215,445 194,315 Workers compensation 79,460 75,251 158,786 151,251 General liability 141,503 129,283 281,487 257,368 Commercial property 78,052 73,591 154,443 143,769 Businessowners’ policies 24,989 24,651 49,834 48,555 Bonds 6,986 5,665 13,484 11,129 Other 4,288 3,940 8,529 7,779 Miscellaneous income 3,016 3,567 5,876 4,257 Total Standard Commercial Lines revenue 446,610 414,844 887,884 818,423 Standard Personal Lines: Net premiums earned: Personal automobile 37,663 35,881 74,613 71,661 Homeowners 32,467 33,411 65,167 66,311 Other 1,542 1,532 3,093 3,057 Miscellaneous income 275 301 656 561 Total Standard Personal Lines revenue 71,947 71,125 143,529 141,590 E&S Lines: Net premiums earned: Commercial liability 39,054 36,940 76,966 73,796 Commercial property 13,710 12,891 27,037 25,399 Miscellaneous income — — — 1 Total E&S Lines revenue 52,764 49,831 104,003 99,196 Investments: Net investment income 41,430 31,182 78,849 61,951 Net realized investment gains (losses) 1,734 1,765 689 (939 ) Total Investments revenue 43,164 32,947 79,538 61,012 Total revenues $ 614,485 568,747 1,214,954 1,120,221 Income Before Federal Income Tax Quarter ended June 30, Six Months ended June 30, ($ in thousands) 2017 2016 2017 2016 Standard Commercial Lines: Underwriting gain $ 34,759 40,173 77,305 71,105 GAAP combined ratio 92.2 % 90.2 91.2 91.3 Statutory combined ratio 90.6 88.6 89.5 89.1 Standard Personal Lines: Underwriting (loss) gain $ (5,768 ) 6,125 (662 ) 14,730 GAAP combined ratio 108.0 % 91.4 100.5 89.6 Statutory combined ratio 105.9 89.9 99.8 90.1 E&S Lines: Underwriting gain (loss) $ 1,319 (2,521 ) 2,889 (1,103 ) GAAP combined ratio 97.5 % 105.1 97.2 101.1 Statutory combined ratio 97.0 102.7 96.5 100.6 Investments: Net investment income $ 41,430 31,182 78,849 61,951 Net realized investment losses 1,734 1,765 689 (939 ) Total investment income, before federal income tax 43,164 32,947 79,538 61,012 Tax on investment income 11,734 8,275 21,336 14,538 Total investment income, after federal income tax $ 31,430 24,672 58,202 46,474 Reconciliation of Segment Results to Income Before Federal Income Tax Quarter ended June 30, Six Months ended June 30, ($ in thousands) 2017 2016 2017 2016 Underwriting gain (loss), before federal income tax Standard Commercial Lines $ 34,759 40,173 77,305 71,105 Standard Personal Lines (5,768 ) 6,125 (662 ) 14,730 E&S Lines 1,319 (2,521 ) 2,889 (1,103 ) Investment income, before federal income tax 43,164 32,947 79,538 61,012 Total all segments 73,474 76,724 159,070 145,744 Interest expense (6,081 ) (5,620 ) (12,187 ) (11,226 ) General corporate and other expenses (8,464 ) (8,793 ) (20,380 ) (20,332 ) Income, before federal income tax $ 58,929 62,311 126,503 114,186

Retirement Plans

Retirement Plans	6 Months Ended
	Jun. 30, 2017
Compensation and Retirement Disclosure [Abstract]
Retirement Plans	Retirement Plans SICA's primary pension plan is the Retirement Income Plan for Selective Insurance Company of America (the “Pension Plan”). SICA also sponsors the Supplemental Excess Retirement Plan (the “Excess Plan”) and a life insurance benefit plan. All plans are closed to new entrants and benefits ceased accruing under the Pension Plan and the Excess Plan after March 31, 2016. For more information concerning SICA's retirement plans, refer to Note 14. “Retirement Plans” in Item 8. “Financial Statements and Supplementary Data.” of our 2016 Annual Report . The following tables provide information regarding the Pension Plan: Pension Plan Pension Plan ($ in thousands) 2017 2016 2017 2016 Net Periodic Benefit Cost: Service cost $ — — — 1,606 Interest cost 3,110 3,101 6,221 6,203 Expected return on plan assets (4,855 ) (3,988 ) (9,709 ) (7,976 ) Amortization of unrecognized net actuarial loss 482 1,481 963 2,961 Total net periodic cost $ (1,263 ) 594 (2,525 ) 2,794 Pension Plan 2017 2016 Weighted-Average Expense Assumptions: Discount rate 4.41 % 4.69 % Effective interest rate for calculation of service cost n/a 4.52 Effective interest rate for calculation of interest cost 3.83 4.02 Expected return on plan assets 6.24 6.37 Rate of compensation increase n/a 4.00

Comprehensive Income

Comprehensive Income	6 Months Ended
	Jun. 30, 2017
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Comprehensive Income	Comprehensive Income The components of comprehensive income, both gross and net of tax, for Second Quarter and Six Months 2017 and 2016 are as follows: Second Quarter 2017 ($ in thousands) Gross Tax Net Net income $ 58,929 17,503 41,426 Components of OCI: Unrealized gains on investment securities : Unrealized holding gains during period 35,887 12,561 23,326 Non-credit portion of OTTI recognized in OCI 6 2 4 Amounts reclassified into net income: HTM securities (43 ) (15 ) (28 ) Realized gains on AFS securities (1,885 ) (660 ) (1,225 ) Total unrealized gains on investment securities 33,965 11,888 22,077 Defined benefit pension and post-retirement plans: Amounts reclassified into net income: Net actuarial loss 508 178 330 Total defined benefit pension and post-retirement plans 508 178 330 Other comprehensive income 34,473 12,066 22,407 Comprehensive income $ 93,402 29,569 63,833 Second Quarter 2016 ($ in thousands) Gross Tax Net Net income $ 62,311 18,710 43,601 Components of OCI: Unrealized gains on investment securities : Unrealized holding gains during period 55,675 19,487 36,188 Non-credit portion of OTTI recognized in OCI (10 ) (4 ) (6 ) Amounts reclassified into net income: HTM securities (19 ) (7 ) (12 ) Realized gains on AFS securities (1,762 ) (617 ) (1,145 ) Total unrealized gains on investment securities 53,884 18,859 35,025 Defined benefit pension and post-retirement plans: Amounts reclassified into net income: Net actuarial loss 1,517 532 985 Total defined benefit pension and post-retirement plans 1,517 532 985 Other comprehensive income 55,401 19,391 36,010 Comprehensive income $ 117,712 38,101 79,611 Six Months 2017 ($ in thousands) Gross Tax Net Net income $ 126,503 34,637 91,866 Components of OCI: Unrealized gains on investment securities : Unrealized holding gains during period 61,672 21,585 40,087 Non-credit portion of OTTI recognized in OCI 6 2 4 Amounts reclassified into net income: HTM securities (92 ) (32 ) (60 ) Realized gains on AFS securities (375 ) (131 ) (244 ) Total unrealized gains on investment securities 61,211 21,424 39,787 Defined benefit pension and post-retirement plans: Amounts reclassified into net income: Net actuarial loss 1,015 355 660 Total defined benefit pension and post-retirement plans 1,015 355 660 Other comprehensive income 62,226 21,779 40,447 Comprehensive income $ 188,729 56,416 132,313 Six Months 2016 ($ in thousands) Gross Tax Net Net income $ 114,186 33,553 80,633 Components of OCI: Unrealized gains on investment securities : Unrealized holding gains during period 121,412 42,495 78,917 Non-credit portion of OTTI recognized in OCI (10 ) (4 ) (6 ) Amounts reclassified into net income: HTM securities (91 ) (32 ) (59 ) Realized losses on AFS securities 937 328 609 Total unrealized gains on investment securities 122,248 42,787 79,461 Defined benefit pension and post-retirement plans: Amounts reclassified into net income: Net actuarial loss 3,033 1,062 1,971 Total defined benefit pension and post-retirement plans 3,033 1,062 1,971 Other comprehensive income 125,281 43,849 81,432 Comprehensive income $ 239,467 77,402 162,065 The balances of, and changes in, each component of AOCI (net of taxes) as of June 30, 2017 were as follows: June 30, 2017 Defined Benefit Pension and Post-Retirement Plans Net Unrealized Gain on Investment Securities Total AOCI ($ in thousands) OTTI Related HTM Related All Other Investments Subtotal Balance, December 31, 2016 $ (150 ) 102 42,170 42,122 (58,072 ) (15,950 ) OCI before reclassifications 4 — 40,087 40,091 — 40,091 Amounts reclassified from AOCI — (60 ) (244 ) (304 ) 660 356 Net current period OCI 4 (60 ) 39,843 39,787 660 40,447 Balance, June 30, 2017 $ (146 ) 42 82,013 81,909 (57,412 ) 24,497 The reclassifications out of AOCI were as follows: Quarter ended June 30, Six Months ended June 30, Affected Line Item in the Unaudited Consolidated Statement of Income ($ in thousands) 2017 2016 2017 2016 HTM related Unrealized losses on HTM disposals 17 60 30 88 Net realized gains (losses) Amortization of net unrealized gains on HTM securities (60 ) (79 ) (122 ) (179 ) Net investment income earned (43 ) (19 ) (92 ) (91 ) Income before federal income tax 15 7 32 32 Total federal income tax expense (28 ) (12 ) (60 ) (59 ) Net income Realized (gains) losses on AFS and OTTI Realized (gains) losses on AFS disposals and OTTI (1,885 ) (1,762 ) (375 ) 937 Net realized gains (losses) (1,885 ) (1,762 ) (375 ) 937 Income before federal income tax 660 617 131 (328 ) Total federal income tax expense (1,225 ) (1,145 ) (244 ) 609 Net income Defined benefit pension and post-retirement life plans Net actuarial loss 111 329 221 658 Losses and loss expenses incurred 397 1,188 794 2,375 Policy acquisition costs Total defined benefit pension and post-retirement life 508 1,517 1,015 3,033 Income before federal income tax (178 ) (532 ) (355 ) (1,062 ) Total federal income tax expense 330 985 660 1,971 Net income Total reclassifications for the period $ (923 ) (172 ) 356 2,521 Net income

Related Party Transactions Rela

Related Party Transactions Related Party Transactions	6 Months Ended
	Jun. 30, 2017
Related Party Transaction [Line Items]
Related Party Transactions Disclosure [Text Block]	Related Party Transactions 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 April 10, 2017 , BlackRock filed a Schedule 13G/A reporting beneficial ownership as of March 31, 2017, of 12.7% 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. In Second Quarter 2017 and Six Months 2017, we incurred BlackRock-related expenses of $0.5 million and $1.0 million for services rendered, respectively. No material expenses were incurred with BlackRock in Second Quarter 2016 and Six Months 2016. Amounts payable for such services at June 30, 2017 and December 31, 2016 , were $0.9 million and $0.4 million , respectively. All contracts with BlackRock were consummated in the ordinary course of business on an arm's-length basis. We have no additional material transactions with related parties other than those disclosed in Note 16. "Related Party Transactions" included in Item 8. "Financial Statements and Supplementary Data." of our 2016 Annual Report .

Litigation

Litigation	6 Months Ended
	Jun. 30, 2017
Loss Contingency, Information about Litigation Matters [Abstract]
Litigation	Litigation In the ordinary course of conducting business, we are named as defendants in various legal proceedings. Most of these proceedings are claims litigation involving our ten insurance subsidiaries ("Insurance Subsidiaries") as either: (i) liability insurers defending or providing indemnity for third-party claims brought against our customers; or (ii) insurers defending first-party coverage claims brought against them. We account for such activity through the establishment of unpaid losses and loss expense reserves. We expect that any potential ultimate liability in such ordinary course claims litigation will not be material to our consolidated financial condition, results of operations, or cash flows after consideration of provisions made for potential losses and costs of defense. From time to time, our Insurance Subsidiaries also are named as defendants in other legal actions, some of which assert claims for substantial amounts. These actions include, among others, putative class actions seeking certification of a state or national class. Such putative class actions have alleged, for example, improper reimbursement of medical providers paid under workers compensation and personal and commercial automobile insurance policies. Similarly, our Insurance Subsidiaries are also named from time-to-time in individual actions seeking extra-contractual damages, punitive damages, or penalties, some of which allege bad faith in the handling of insurance claims. We believe that we have valid defenses to these cases. We expect that any potential ultimate liability in any such lawsuit will not be material to our consolidated financial condition, after consideration of provisions made for estimated losses. Nonetheless, given the inherent unpredictability of litigation and the large or indeterminate amounts sought in certain of these actions, an adverse outcome in certain matters could possibly have a material adverse effect on our consolidated results of operations or cash flows in particular quarterly or annual periods. As of June 30, 2017 , we do not believe the Company was involved in any legal action that could have a material adverse effect on our consolidated financial condition, results of operations, or cash flows.

Statements of Cash Flow (Tables

Statements of Cash Flow (Tables)	6 Months Ended
	Jun. 30, 2017
Supplemental Cash Flow Information [Abstract]
Schedule of Cash Flow, Supplemental Disclosures	Six Months ended June 30, ($ in thousands) 2017 2016 Cash paid during the period for: Interest $ 11,963 10,986 Federal income tax 27,000 29,000 Non-cash items: Exchange of fixed income securities, AFS 1,029 17,702 Corporate actions related to equity securities, AFS 1 — 3,032 Assets acquired under capital lease arrangements 278 2,999 Non-cash purchase of property and equipment — 577 1 Examples of such corporate actions include non-cash acquisitions and stock splits.

Investments (Tables)

Investments (Tables)	6 Months Ended
	Jun. 30, 2017
Investments [Line Items]
Schedule of Held-to-maturity Securities	June 30, 2017 ($ in thousands) Amortized Cost Net Unrealized Gains (Losses) Carrying Value Unrecognized Holding Gains Unrecognized Holding Losses Fair Value Obligations of states and political subdivisions $ 53,734 185 53,919 1,703 — 55,622 Corporate securities 18,714 (119 ) 18,595 1,323 — 19,918 Total HTM fixed income securities $ 72,448 66 72,514 3,026 — 75,540 December 31, 2016 ($ in thousands) Amortized Cost Net Unrealized Gains (Losses) Carrying Value Unrecognized Holding Gains Unrecognized Holding Losses Fair Value Obligations of states and political subdivisions $ 77,466 317 77,783 2,133 — 79,916 Corporate securities 22,711 (143 ) 22,568 1,665 (158 ) 24,075 Commercial mortgage-backed securities ("CMBS") 1,220 (15 ) 1,205 15 — 1,220 Total HTM fixed income securities $ 101,397 159 101,556 3,813 (158 ) 105,211
Schedule of Available-for-sale Securities	June 30, 2017 ($ in thousands) Cost/ Amortized Cost Unrealized Gains Unrealized Losses Fair Value AFS fixed income securities: U.S. government and government agencies $ 66,932 1,103 (32 ) 68,003 Foreign government 18,157 557 — 18,714 Obligations of states and political subdivisions 1,360,211 45,641 (1,086 ) 1,404,766 Corporate securities 1,782,993 39,041 (524 ) 1,821,510 Collateralized loan obligations and other asset-backed securities ("CLO and other ABS") 698,594 4,108 (178 ) 702,524 CMBS 277,320 2,128 (243 ) 279,205 Residential mortgage-backed securities (“RMBS”) 718,798 6,068 (866 ) 724,000 Total AFS fixed income securities 4,923,005 98,646 (2,929 ) 5,018,722 AFS equity securities: Common stock 115,315 30,108 (987 ) 144,436 Preferred stock 16,148 1,110 — 17,258 Total AFS equity securities 131,463 31,218 (987 ) 161,694 Total AFS securities $ 5,054,468 129,864 (3,916 ) 5,180,416 December 31, 2016 ($ in thousands) Cost/ Amortized Cost Unrealized Gains Unrealized Losses Fair Value AFS fixed income securities: U.S. government and government agencies $ 75,139 2,230 (36 ) 77,333 Foreign government 26,559 322 (16 ) 26,865 Obligations of states and political subdivisions 1,366,287 18,610 (5,304 ) 1,379,593 Corporate securities 1,976,556 27,057 (5,860 ) 1,997,753 CLO and other ABS 527,876 1,439 (355 ) 528,960 CMBS 256,356 1,514 (1,028 ) 256,842 RMBS 524,986 3,006 (2,798 ) 525,194 Total AFS fixed income securities 4,753,759 54,178 (15,397 ) 4,792,540 AFS equity securities: Common stock 104,663 26,250 (305 ) 130,608 Preferred stock 16,226 274 (355 ) 16,145 Total AFS equity securities 120,889 26,524 (660 ) 146,753 Total AFS securities $ 4,874,648 80,702 (16,057 ) 4,939,293
Schedule of Fair Value and Gross Pre-Tax Net Unrealized/Unrecognized Loss of Securities by Length of Time	June 30, 2017 Less than 12 months 12 months or longer Total ($ in thousands) Fair Value Unrealized Losses 1 Fair Value Unrealized Losses 1 Fair Value Unrealized 1 AFS fixed income securities: U.S. government and government agencies $ 12,670 (32 ) — — 12,670 (32 ) Obligations of states and political subdivisions 107,387 (1,086 ) — — 107,387 (1,086 ) Corporate securities 72,991 (517 ) 2,531 (7 ) 75,522 (524 ) CLO and other ABS 156,406 (178 ) — — 156,406 (178 ) CMBS 42,671 (243 ) — — 42,671 (243 ) RMBS 179,293 (860 ) 449 (6 ) 179,742 (866 ) Total AFS fixed income securities 571,418 (2,916 ) 2,980 (13 ) 574,398 (2,929 ) AFS equity securities: Common stock 18,423 (987 ) — — 18,423 (987 ) Total AFS equity securities 18,423 (987 ) — — 18,423 (987 ) Total AFS $ 589,841 (3,903 ) 2,980 (13 ) 592,821 (3,916 ) December 31, 2016 Less than 12 months 12 months or longer Total ($ in thousands) Fair Value Unrealized Losses 1 Fair Value Unrealized Losses 1 Fair Value Unrealized 1 AFS fixed income securities: U.S. government and government agencies $ 6,419 (36 ) — — 6,419 (36 ) Foreign government 13,075 (16 ) — — 13,075 (16 ) Obligations of states and political subdivisions 306,509 (5,304 ) — — 306,509 (5,304 ) Corporate securities 462,902 (5,771 ) 4,913 (89 ) 467,815 (5,860 ) CLO and other ABS 189,795 (354 ) 319 (1 ) 190,114 (355 ) CMBS 82,492 (1,021 ) 1,645 (7 ) 84,137 (1,028 ) RMBS 279,480 (2,489 ) 8,749 (309 ) 288,229 (2,798 ) Total AFS fixed income securities 1,340,672 (14,991 ) 15,626 (406 ) 1,356,298 (15,397 ) AFS equity securities: Common stock 11,271 (305 ) — — 11,271 (305 ) Preferred stock 6,168 (355 ) — — 6,168 (355 ) Total AFS equity securities 17,439 (660 ) — — 17,439 (660 ) Total AFS $ 1,358,111 (15,651 ) 15,626 (406 ) 1,373,737 (16,057 ) 1 Gross unrealized losses include non-OTTI unrealized amounts and OTTI losses recognized in AOCI.
Schedule of Fixed Maturity Securities By Contractual Maturities	AFS HTM ($ in thousands) Fair Value Carrying Value Fair Value Due in one year or less $ 306,493 34,521 34,898 Due after one year through five years 2,095,055 29,648 31,498 Due after five years through 10 years 2,379,624 8,345 9,144 Due after 10 years 237,550 — — Total fixed income securities $ 5,018,722 72,514 75,540
Schedule of Other Investment Portfolio By Strategy And Remaining Commitment Amount and Maximum Exposure to Loss Associated With Each Strategy	Other Investments June 30, 2017 December 31, 2016 ($ in thousands) Carrying Value Remaining Commitment Maximum Exposure to Loss 1 Carrying Value Remaining Commitment Maximum Exposure to Loss 1 Alternative Investments Private equity $ 46,945 76,027 122,972 41,135 76,774 117,909 Private credit 29,942 57,391 87,333 28,193 40,613 68,806 Real assets 20,783 31,237 52,020 14,486 22,899 37,385 Total alternative investments 97,670 164,655 262,325 83,814 140,286 224,100 Other securities 18,741 — 18,741 18,583 3,400 21,983 Total other investments $ 116,411 164,655 281,066 102,397 143,686 246,083 1 The maximum exposure to loss includes both the carry value of these investments and the related unfunded commitments. In addition, tax credits that have been previously recognized in Other securities are subject to the risk of recapture, which we do not consider significant.
Schedule of Aggregated Summarized Income Statement Financial Information For Partnerships In Our Alternative Investment Portfolio	Income Statement Information Quarter ended June 30, Six Months ended June 30, ($ in millions) 2017 2016 2017 2016 Net investment (loss) income $ (9.9 ) (4.6 ) (62.4 ) 37.0 Realized gains (70.2 ) 193.2 (304.3 ) 981.1 Net change in unrealized depreciation 1,418.5 (253.9 ) 1,890.0 (1,236.5 ) Net gain $ 1,338.4 (65.3 ) 1,523.3 (218.4 ) Selective’s insurance subsidiaries’ other investments gain (loss) $ 5.2 (0.6 ) 6.8 (1.7 )
Schedule of Securities Pledged As Collateral	($ in millions) FHLBI Collateral FHLBNY Collateral State and Regulatory Deposits Total U.S. government and government agencies $ 3.1 — 23.9 27.0 Obligations of states and political subdivisions — — 2.0 2.0 CMBS 3.6 4.8 — 8.4 RMBS 60.6 51.9 — 112.5 Total pledged as collateral $ 67.3 56.7 25.9 149.9
Schedule of Net Investment Income Earned	Quarter ended June 30, Six Months ended June 30, ($ in thousands) 2017 2016 2017 2016 Fixed income securities $ 37,668 31,753 $ 74,559 63,397 Equity securities 1,419 2,204 2,887 4,434 Short-term investments 377 142 627 301 Other investments 5,231 (611 ) 6,834 (1,677 ) Investment expenses (3,265 ) (2,306 ) (6,058 ) (4,504 ) Net investment income earned $ 41,430 31,182 $ 78,849 61,951
Schedule of OTTI By Asset Type	Second Quarter 2017 Gross Included in Other Comprehensive Income ("OCI") Recognized in ($ in thousands) AFS fixed income securities: U.S. government and government agencies $ 2 — 2 Obligations of states and political subdivisions 239 — 239 Corporate securities 381 — 381 CLO and other ABS 62 — 62 CMBS 220 — 220 RMBS 71 (6 ) 77 Total AFS fixed income securities 975 (6 ) 981 AFS equity securities: Common stock 46 — 46 Total AFS equity securities 46 — 46 Other Investments 190 — 190 Total OTTI losses $ 1,211 $ (6 ) $ 1,217 Second Quarter 2016 Gross Included in OCI Recognized in ($ in thousands) AFS fixed income securities: Corporate securities $ 104 — 104 RMBS 98 10 88 Total AFS fixed income securities 202 10 192 AFS equity securities: Common stock 357 — 357 Total AFS equity securities 357 — 357 Total OTTI losses $ 559 10 549 Six Months 2017 Gross Included in Other Comprehensive Income ("OCI") Recognized in ($ in thousands) AFS fixed income securities: U.S. government and government agencies $ 31 — 31 Obligations of states and political subdivisions 612 — 612 Corporate securities 575 — 575 CLO and other ABS 85 — 85 CMBS 670 — 670 RMBS 1,163 (6 ) 1,169 Total AFS fixed income securities 3,136 (6 ) 3,142 AFS equity securities: Common stock 1,360 — 1,360 Total AFS equity securities 1,360 — 1,360 Other Investments 190 — 190 Total OTTI losses $ 4,686 $ (6 ) $ 4,692 Six Months 2016 Gross Included in OCI Recognized in ($ in thousands) AFS fixed income securities: Corporate securities $ 1,077 — 1,077 RMBS 98 10 88 Total AFS fixed income securities 1,175 10 1,165 AFS equity securities: Common stock 2,974 — 2,974 Preferred stock 3 — 3 Total AFS equity securities 2,977 — 2,977 Total OTTI losses $ 4,152 10 4,142
Schedule of Components of Net Realized Gains Excluding OTTI Charges	Quarter ended June 30, Six Months ended June 30, ($ in thousands) 2017 2016 2017 2016 HTM fixed income securities Gains $ 44 3 44 3 Losses — — (1 ) (1 ) AFS fixed income securities Gains 2,715 365 6,267 985 Losses (153 ) (5 ) (1,740 ) (41 ) AFS equity securities Gains 350 2,171 350 2,501 Losses — (220 ) — (240 ) Other investments Gains — — 480 — Losses (5 ) — (19 ) (4 ) Total net realized gains (excluding OTTI charges) $ 2,951 2,314 5,381 3,203

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Schedule of Quantitative Disclosures of Our Financial Assets That Were Measured At Fair Value	June 30, 2017 Fair Value Measurements Using ($ in thousands) Assets Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) 1 Significant Other Observable Inputs (Level 2) 1 Significant Unobservable Inputs (Level 3) Description Measured on a recurring basis: AFS fixed income securities: U.S. government and government agencies $ 68,003 24,828 43,175 — Foreign government 18,714 — 18,714 — Obligations of states and political subdivisions 1,404,766 — 1,404,766 — Corporate securities 1,821,510 — 1,821,510 — CLO and other ABS 702,524 — 702,524 — CMBS 279,205 — 279,205 — RMBS 724,000 — 724,000 — Total AFS fixed income securities 5,018,722 24,828 4,993,894 — AFS equity securities: Common stock 144,436 135,966 — 8,470 Preferred stock 17,258 17,258 — — Total AFS equity securities 161,694 153,224 — 8,470 Total AFS securities 5,180,416 178,052 4,993,894 8,470 Short-term investments 133,706 133,706 — — Total assets measured at fair value $ 5,314,122 311,758 4,993,894 8,470 December 31, 2016 Fair Value Measurements Using ($ in thousands) Assets Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) 1 Significant Other Observable Inputs (Level 2) 1 Significant Unobservable Inputs (Level 3) Description Measured on a recurring basis: AFS fixed income securities: U.S. government and government agencies $ 77,333 27,520 49,813 — Foreign government 26,865 — 26,865 — Obligations of states and political subdivisions 1,379,593 — 1,379,593 — Corporate securities 1,997,753 — 1,997,753 — CLO and other ABS 528,960 — 528,960 — CMBS 256,842 — 256,842 — RMBS 525,194 — 525,194 — Total AFS fixed income securities 4,792,540 27,520 4,765,020 — AFS equity securities: Common stock 130,608 122,932 — 7,676 Preferred stock 16,145 16,145 — — Total AFS equity securities 146,753 139,077 — 7,676 Total AFS securities 4,939,293 166,597 4,765,020 7,676 Short-term investments 221,701 221,701 — — Total assets measured at fair value $ 5,160,994 388,298 4,765,020 7,676 1 There were no transfers of securities between Level 1 and Level 2.
Schedule of Quantitative Information of Our Financial Assets and Liabilities That Were Disclosed at Fair Value	June 30, 2017 Fair Value Measurements Using ($ in thousands) Assets/ 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 $ 55,622 — 55,622 — Corporate securities 19,918 — 13,960 5,958 Total HTM fixed income securities $ 75,540 — 69,582 5,958 Financial Liabilities Long-term debt: 7.25% Senior Notes $ 58,690 — 58,690 — 6.70% Senior Notes 112,573 — 112,573 — 5.875% Senior Notes 188,767 188,767 — — 1.61% borrowings from FHLBNY 24,521 — 24,521 — 1.56% borrowings from FHLBNY 24,462 — 24,462 — 3.03% borrowings from FHLBI 60,837 — 60,837 — Total long-term debt $ 469,850 188,767 281,083 — December 31, 2016 Fair Value Measurements Using ($ in thousands) Assets/ Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Financial Assets HTM: Obligations of states and political subdivisions $ 79,916 — 79,916 — Corporate securities 24,075 — 16,565 7,510 CMBS 1,220 — 1,220 — Total HTM fixed income securities $ 105,211 — 97,701 7,510 Financial Liabilities Long-term debt: 7.25% Senior Notes $ 56,148 — 56,148 — 6.70% Senior Notes 108,333 — 108,333 — 5.875% Senior Notes 176,860 176,860 — — 1.61% borrowings from FHLBNY 24,286 — 24,286 — 1.56% borrowings from FHLBNY 24,219 — 24,219 — 3.03% borrowings from FHLBI 59,313 — 59,313 — Total long-term debt $ 449,159 176,860 272,299 —

Reinsurance (Tables)

Reinsurance (Tables)	6 Months Ended
	Jun. 30, 2017
Reinsurance Disclosures [Abstract]
Schedule of List Of Direct, Assumed, And Ceded Reinsurance Amounts	Quarter ended June 30, Six Months ended June 30, ($ in thousands) 2017 2016 2017 2016 Premiums written: Direct $ 706,408 665,862 1,390,228 1,312,140 Assumed 6,488 7,788 12,179 14,108 Ceded (99,082 ) (95,510 ) (189,889 ) (182,749 ) Net $ 613,814 578,140 1,212,518 1,143,499 Premiums earned: Direct $ 654,588 612,406 1,301,316 1,219,067 Assumed 6,063 7,171 11,842 13,441 Ceded (92,621 ) (87,645 ) (184,274 ) (178,118 ) Net $ 568,030 531,932 1,128,884 1,054,390 Loss and loss expense incurred: Direct $ 389,550 362,064 731,672 723,703 Assumed 7,766 6,140 12,203 12,495 Ceded (55,757 ) (69,725 ) (84,844 ) (140,575 ) Net $ 341,559 298,479 659,031 595,623
Schedule of Ceded Premiums and Losses Related to Flood Operations	Ceded premiums and losses related to our participation in the NFIP, under which 100% of our flood premiums, losses, and loss expenses are ceded to the NFIP, are as follows: Ceded to NFIP Quarter ended June 30, Six Months ended June 30, ($ in thousands) 2017 2016 2017 2016 Ceded premiums written $ (63,808 ) (63,906 ) (120,142 ) (117,154 ) Ceded premiums earned (57,655 ) (56,667 ) (114,932 ) (113,481 ) Ceded loss and loss expense incurred (15,140 ) (24,261 ) (21,681 ) (64,979 )

Reserve for Losses and Loss E26

Reserve for Losses and Loss Expenses Reserves for Losses and Loss Expenses (Tables)	6 Months Ended
	Jun. 30, 2017
Insurance Loss Reserves [Abstract]
Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block]	Six Months ended June 30, ($ in thousands) 2017 2016 Gross reserves for losses and loss expenses, at beginning of year $ 3,691,719 3,517,728 Less: reinsurance recoverable on unpaid losses and loss expenses, at beginning of year 611,200 551,019 Net reserves for losses and loss expenses, at beginning of year 3,080,519 2,966,709 Incurred losses and loss expenses for claims occurring in the: Current year 684,877 624,159 Prior years (25,846 ) (28,536 ) Total incurred losses and loss expenses 659,031 595,623 Paid losses and loss expenses for claims occurring in the: Current year 171,724 146,849 Prior years 425,521 402,255 Total paid losses and loss expenses 597,245 549,104 Net reserves for losses and loss expenses, at end of period 3,142,305 3,013,228 Add: Reinsurance recoverable on unpaid losses and loss expenses, at end of period 588,916 576,941 Gross reserves for losses and loss expenses at end of period $ 3,731,221 3,590,169

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2017
Segment Reporting [Abstract]
Schedule of Revenue By Segment	Revenue by Segment Quarter ended June 30, Six Months ended June 30, ($ in thousands) 2017 2016 2017 2016 Standard Commercial Lines: Net premiums earned: Commercial automobile $ 108,316 98,896 215,445 194,315 Workers compensation 79,460 75,251 158,786 151,251 General liability 141,503 129,283 281,487 257,368 Commercial property 78,052 73,591 154,443 143,769 Businessowners’ policies 24,989 24,651 49,834 48,555 Bonds 6,986 5,665 13,484 11,129 Other 4,288 3,940 8,529 7,779 Miscellaneous income 3,016 3,567 5,876 4,257 Total Standard Commercial Lines revenue 446,610 414,844 887,884 818,423 Standard Personal Lines: Net premiums earned: Personal automobile 37,663 35,881 74,613 71,661 Homeowners 32,467 33,411 65,167 66,311 Other 1,542 1,532 3,093 3,057 Miscellaneous income 275 301 656 561 Total Standard Personal Lines revenue 71,947 71,125 143,529 141,590 E&S Lines: Net premiums earned: Commercial liability 39,054 36,940 76,966 73,796 Commercial property 13,710 12,891 27,037 25,399 Miscellaneous income — — — 1 Total E&S Lines revenue 52,764 49,831 104,003 99,196 Investments: Net investment income 41,430 31,182 78,849 61,951 Net realized investment gains (losses) 1,734 1,765 689 (939 ) Total Investments revenue 43,164 32,947 79,538 61,012 Total revenues $ 614,485 568,747 1,214,954 1,120,221 Income Before Federal Income Tax Quarter ended June 30, Six Months ended June 30, ($ in thousands) 2017 2016 2017 2016 Standard Commercial Lines: Underwriting gain $ 34,759 40,173 77,305 71,105 GAAP combined ratio 92.2 % 90.2 91.2 91.3 Statutory combined ratio 90.6 88.6 89.5 89.1 Standard Personal Lines: Underwriting (loss) gain $ (5,768 ) 6,125 (662 ) 14,730 GAAP combined ratio 108.0 % 91.4 100.5 89.6 Statutory combined ratio 105.9 89.9 99.8 90.1 E&S Lines: Underwriting gain (loss) $ 1,319 (2,521 ) 2,889 (1,103 ) GAAP combined ratio 97.5 % 105.1 97.2 101.1 Statutory combined ratio 97.0 102.7 96.5 100.6 Investments: Net investment income $ 41,430 31,182 78,849 61,951 Net realized investment losses 1,734 1,765 689 (939 ) Total investment income, before federal income tax 43,164 32,947 79,538 61,012 Tax on investment income 11,734 8,275 21,336 14,538 Total investment income, after federal income tax $ 31,430 24,672 58,202 46,474
Schedule of Income Before Federal Income Tax	Income Before Federal Income Tax Quarter ended June 30, Six Months ended June 30, ($ in thousands) 2017 2016 2017 2016 Standard Commercial Lines: Underwriting gain $ 34,759 40,173 77,305 71,105 GAAP combined ratio 92.2 % 90.2 91.2 91.3 Statutory combined ratio 90.6 88.6 89.5 89.1 Standard Personal Lines: Underwriting (loss) gain $ (5,768 ) 6,125 (662 ) 14,730 GAAP combined ratio 108.0 % 91.4 100.5 89.6 Statutory combined ratio 105.9 89.9 99.8 90.1 E&S Lines: Underwriting gain (loss) $ 1,319 (2,521 ) 2,889 (1,103 ) GAAP combined ratio 97.5 % 105.1 97.2 101.1 Statutory combined ratio 97.0 102.7 96.5 100.6 Investments: Net investment income $ 41,430 31,182 78,849 61,951 Net realized investment losses 1,734 1,765 689 (939 ) Total investment income, before federal income tax 43,164 32,947 79,538 61,012 Tax on investment income 11,734 8,275 21,336 14,538 Total investment income, after federal income tax $ 31,430 24,672 58,202 46,474
Schedule of Reconciliation of Segment Results to Income Before Federal Income Tax	Reconciliation of Segment Results to Income Before Federal Income Tax Quarter ended June 30, Six Months ended June 30, ($ in thousands) 2017 2016 2017 2016 Underwriting gain (loss), before federal income tax Standard Commercial Lines $ 34,759 40,173 77,305 71,105 Standard Personal Lines (5,768 ) 6,125 (662 ) 14,730 E&S Lines 1,319 (2,521 ) 2,889 (1,103 ) Investment income, before federal income tax 43,164 32,947 79,538 61,012 Total all segments 73,474 76,724 159,070 145,744 Interest expense (6,081 ) (5,620 ) (12,187 ) (11,226 ) General corporate and other expenses (8,464 ) (8,793 ) (20,380 ) (20,332 ) Income, before federal income tax $ 58,929 62,311 126,503 114,186

Retirement Plans (Table)

Retirement Plans (Table)	6 Months Ended
	Jun. 30, 2017
Compensation and Retirement Disclosure [Abstract]
Schedule of Components of Net Periodic Benefit Cost	Pension Plan Pension Plan ($ in thousands) 2017 2016 2017 2016 Net Periodic Benefit Cost: Service cost $ — — — 1,606 Interest cost 3,110 3,101 6,221 6,203 Expected return on plan assets (4,855 ) (3,988 ) (9,709 ) (7,976 ) Amortization of unrecognized net actuarial loss 482 1,481 963 2,961 Total net periodic cost $ (1,263 ) 594 (2,525 ) 2,794 Pension Plan 2017 2016 Weighted-Average Expense Assumptions: Discount rate 4.41 % 4.69 % Effective interest rate for calculation of service cost n/a 4.52 Effective interest rate for calculation of interest cost 3.83 4.02 Expected return on plan assets 6.24 6.37 Rate of compensation increase n/a 4.00
Schedule of Weighted-Average Expense Assumptions	Pension Plan 2017 2016 Weighted-Average Expense Assumptions: Discount rate 4.41 % 4.69 % Effective interest rate for calculation of service cost n/a 4.52 Effective interest rate for calculation of interest cost 3.83 4.02 Expected return on plan assets 6.24 6.37 Rate of compensation increase n/a 4.00

Comprehensive Income (Tables)

Comprehensive Income (Tables)	6 Months Ended
	Jun. 30, 2017
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Schedule of Components of Comprehensive Income-Gross and Net of Tax	Second Quarter 2017 ($ in thousands) Gross Tax Net Net income $ 58,929 17,503 41,426 Components of OCI: Unrealized gains on investment securities : Unrealized holding gains during period 35,887 12,561 23,326 Non-credit portion of OTTI recognized in OCI 6 2 4 Amounts reclassified into net income: HTM securities (43 ) (15 ) (28 ) Realized gains on AFS securities (1,885 ) (660 ) (1,225 ) Total unrealized gains on investment securities 33,965 11,888 22,077 Defined benefit pension and post-retirement plans: Amounts reclassified into net income: Net actuarial loss 508 178 330 Total defined benefit pension and post-retirement plans 508 178 330 Other comprehensive income 34,473 12,066 22,407 Comprehensive income $ 93,402 29,569 63,833 Second Quarter 2016 ($ in thousands) Gross Tax Net Net income $ 62,311 18,710 43,601 Components of OCI: Unrealized gains on investment securities : Unrealized holding gains during period 55,675 19,487 36,188 Non-credit portion of OTTI recognized in OCI (10 ) (4 ) (6 ) Amounts reclassified into net income: HTM securities (19 ) (7 ) (12 ) Realized gains on AFS securities (1,762 ) (617 ) (1,145 ) Total unrealized gains on investment securities 53,884 18,859 35,025 Defined benefit pension and post-retirement plans: Amounts reclassified into net income: Net actuarial loss 1,517 532 985 Total defined benefit pension and post-retirement plans 1,517 532 985 Other comprehensive income 55,401 19,391 36,010 Comprehensive income $ 117,712 38,101 79,611 Six Months 2017 ($ in thousands) Gross Tax Net Net income $ 126,503 34,637 91,866 Components of OCI: Unrealized gains on investment securities : Unrealized holding gains during period 61,672 21,585 40,087 Non-credit portion of OTTI recognized in OCI 6 2 4 Amounts reclassified into net income: HTM securities (92 ) (32 ) (60 ) Realized gains on AFS securities (375 ) (131 ) (244 ) Total unrealized gains on investment securities 61,211 21,424 39,787 Defined benefit pension and post-retirement plans: Amounts reclassified into net income: Net actuarial loss 1,015 355 660 Total defined benefit pension and post-retirement plans 1,015 355 660 Other comprehensive income 62,226 21,779 40,447 Comprehensive income $ 188,729 56,416 132,313
Schedule of Components of Accumulated Other Comprehensive Income	June 30, 2017 Defined Benefit Pension and Post-Retirement Plans Net Unrealized Gain on Investment Securities Total AOCI ($ in thousands) OTTI Related HTM Related All Other Investments Subtotal Balance, December 31, 2016 $ (150 ) 102 42,170 42,122 (58,072 ) (15,950 ) OCI before reclassifications 4 — 40,087 40,091 — 40,091 Amounts reclassified from AOCI — (60 ) (244 ) (304 ) 660 356 Net current period OCI 4 (60 ) 39,843 39,787 660 40,447 Balance, June 30, 2017 $ (146 ) 42 82,013 81,909 (57,412 ) 24,497
Schedule of Reclassifications Out Of Accumulated Other Comprehensive Income	Quarter ended June 30, Six Months ended June 30, Affected Line Item in the Unaudited Consolidated Statement of Income ($ in thousands) 2017 2016 2017 2016 HTM related Unrealized losses on HTM disposals 17 60 30 88 Net realized gains (losses) Amortization of net unrealized gains on HTM securities (60 ) (79 ) (122 ) (179 ) Net investment income earned (43 ) (19 ) (92 ) (91 ) Income before federal income tax 15 7 32 32 Total federal income tax expense (28 ) (12 ) (60 ) (59 ) Net income Realized (gains) losses on AFS and OTTI Realized (gains) losses on AFS disposals and OTTI (1,885 ) (1,762 ) (375 ) 937 Net realized gains (losses) (1,885 ) (1,762 ) (375 ) 937 Income before federal income tax 660 617 131 (328 ) Total federal income tax expense (1,225 ) (1,145 ) (244 ) 609 Net income Defined benefit pension and post-retirement life plans Net actuarial loss 111 329 221 658 Losses and loss expenses incurred 397 1,188 794 2,375 Policy acquisition costs Total defined benefit pension and post-retirement life 508 1,517 1,015 3,033 Income before federal income tax (178 ) (532 ) (355 ) (1,062 ) Total federal income tax expense 330 985 660 1,971 Net income Total reclassifications for the period $ (923 ) (172 ) 356 2,521 Net income

Accounting Pronouncements Accou

Accounting Pronouncements Accounting Pronouncements (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	$ 400		$ 3,300
Unrealized gain on equity securities	$ 24,497		24,497		$ (15,950)
Change in unrealized gains on equity securities, net of tax			$ 3,000
Earnings per share impact	$ 0.70	$ 0.74	$ 1.55	$ 1.38
Equity Securities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Unrealized gain on equity securities					$ 17,000
Earnings per share impact			$ 0.05

Statements of Cash Flow (Cash F

Statements of Cash Flow (Cash Flow Supplemental Disclosures) (Details) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016
Interest		$ 11,963	$ 10,986
Federal income tax		27,000	29,000
Corporate actions related to equity securities, AFS	[1]	0	3,032
Assets acquired under capital lease arrangements		278	2,999
Non-cash purchase of property and equipment		0	577
AFS Fixed Maturity Securities [Member]
Exchange of fixed income securities		1,029	17,702
National Flood Insurance Program [Member]
Restricted cash		$ 8,100	$ 8,900
[1]	Examples of such corporate actions include non-cash acquisitions and stock splits.

Investments (Held-To-Maturity S

Investments (Held-To-Maturity Securities Disclosure) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 72,448	$ 101,397
Net Unrealized Gains (Losses)	66	159
Carrying Value	72,514	101,556
Unrecognized Holding Gains	3,026	3,813
Unrecognized Holding Losses	0	(158)
Held-to-maturity Securities, Fair Value	75,540	105,211
Obligations of States and Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	53,734	77,466
Net Unrealized Gains (Losses)	185	317
Carrying Value	53,919	77,783
Unrecognized Holding Gains	1,703	2,133
Unrecognized Holding Losses	0	0
Held-to-maturity Securities, Fair Value	55,622	79,916
Corporate Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	18,714	22,711
Net Unrealized Gains (Losses)	(119)	(143)
Carrying Value	18,595	22,568
Unrecognized Holding Gains	1,323	1,665
Unrecognized Holding Losses	0	(158)
Held-to-maturity Securities, Fair Value	$ 19,918	24,075
Commercial Mortgage Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost		1,220
Net Unrealized Gains (Losses)		(15)
Carrying Value		1,205
Unrecognized Holding Gains		15
Unrecognized Holding Losses		0
Held-to-maturity Securities, Fair Value		$ 1,220

Investments (Available-For-Sale

Investments (Available-For-Sale Securities Disclosure) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	$ 5,054,468	$ 4,874,648
Unrealized Gains	129,864	80,702
Unrealized Losses	(3,916)	(16,057)
Total AFS securities	5,180,416	4,939,293
AFS Fixed Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	4,923,005	4,753,759
Unrealized Gains	98,646	54,178
Unrealized Losses	(2,929)	(15,397)
Total AFS securities	5,018,722	4,792,540
AFS Fixed Income Securities [Member] | U.S. Government and Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	66,932	75,139
Unrealized Gains	1,103	2,230
Unrealized Losses	(32)	(36)
Total AFS securities	68,003	77,333
AFS Fixed Income Securities [Member] | Foreign Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	18,157	26,559
Unrealized Gains	557	322
Unrealized Losses	0	(16)
Total AFS securities	18,714	26,865
AFS Fixed Income Securities [Member] | Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	1,360,211	1,366,287
Unrealized Gains	45,641	18,610
Unrealized Losses	(1,086)	(5,304)
Total AFS securities	1,404,766	1,379,593
AFS Fixed Income Securities [Member] | Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	1,782,993	1,976,556
Unrealized Gains	39,041	27,057
Unrealized Losses	(524)	(5,860)
Total AFS securities	1,821,510	1,997,753
AFS Fixed Income Securities [Member] | Collateralized Loan Obligations and Other Asset Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	698,594	527,876
Unrealized Gains	4,108	1,439
Unrealized Losses	(178)	(355)
Total AFS securities	702,524	528,960
AFS Fixed Income Securities [Member] | Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	277,320	256,356
Unrealized Gains	2,128	1,514
Unrealized Losses	(243)	(1,028)
Total AFS securities	279,205	256,842
AFS Fixed Income Securities [Member] | Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	718,798	524,986
Unrealized Gains	6,068	3,006
Unrealized Losses	(866)	(2,798)
Total AFS securities	724,000	525,194
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	131,463	120,889
Unrealized Gains	31,218	26,524
Unrealized Losses	(987)	(660)
Total AFS securities	161,694	146,753
Equity Securities [Member] | Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	115,315	104,663
Unrealized Gains	30,108	26,250
Unrealized Losses	(987)	(305)
Total AFS securities	144,436	130,608
Equity Securities [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost/Amortized Cost	16,148	16,226
Unrealized Gains	1,110	274
Unrealized Losses	0	(355)
Total AFS securities	$ 17,258	$ 16,145

Investments (Fair Value and Gro

Investments (Fair Value and Gross Pre-Tax Net Unrealized Unrecognized Loss of Securities By Length of Time) (Details) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
AFS Fair Value, Less than 12 months		$ 589,841	$ 1,358,111
AFS Unrealized Losses, Less than 12 months	[1]	(3,903)	(15,651)
AFS Fair Value, 12 months or longer		2,980	15,626
AFS Unrealized Losses, 12 months or longer	[1]	(13)	(406)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		592,821	1,373,737
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	[1]	(3,916)	(16,057)
AFS Fixed Income Securities [Member]
AFS Fair Value, Less than 12 months		571,418	1,340,672
AFS Unrealized Losses, Less than 12 months	[1]	(2,916)	(14,991)
AFS Fair Value, 12 months or longer		2,980	15,626
AFS Unrealized Losses, 12 months or longer	[1]	(13)	(406)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		574,398	1,356,298
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	[1]	(2,929)	(15,397)
AFS Fixed Income Securities [Member] | U.S. Government and Government Agencies [Member]
AFS Fair Value, Less than 12 months		12,670	6,419
AFS Unrealized Losses, Less than 12 months	[1]	(32)	(36)
AFS Fair Value, 12 months or longer		0	0
AFS Unrealized Losses, 12 months or longer	[1]	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		12,670	6,419
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	[1]	(32)	(36)
AFS Fixed Income Securities [Member] | Foreign Government [Member]
AFS Fair Value, Less than 12 months			13,075
AFS Unrealized Losses, Less than 12 months	[1]		(16)
AFS Fair Value, 12 months or longer			0
AFS Unrealized Losses, 12 months or longer	[1]		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value			13,075
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	[1]		(16)
AFS Fixed Income Securities [Member] | Obligations of States and Political Subdivisions [Member]
AFS Fair Value, Less than 12 months		107,387	306,509
AFS Unrealized Losses, Less than 12 months	[1]	(1,086)	(5,304)
AFS Fair Value, 12 months or longer		0	0
AFS Unrealized Losses, 12 months or longer	[1]	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		107,387	306,509
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	[1]	(1,086)	(5,304)
AFS Fixed Income Securities [Member] | Corporate Securities [Member]
AFS Fair Value, Less than 12 months		72,991	462,902
AFS Unrealized Losses, Less than 12 months	[1]	(517)	(5,771)
AFS Fair Value, 12 months or longer		2,531	4,913
AFS Unrealized Losses, 12 months or longer	[1]	(7)	(89)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		75,522	467,815
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	[1]	(524)	(5,860)
AFS Fixed Income Securities [Member] | Collateralized Loan Obligations and Other Asset Backed Securities [Member]
AFS Fair Value, Less than 12 months		156,406	189,795
AFS Unrealized Losses, Less than 12 months	[1]	(178)	(354)
AFS Fair Value, 12 months or longer		0	319
AFS Unrealized Losses, 12 months or longer	[1]	0	(1)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		156,406	190,114
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	[1]	(178)	(355)
AFS Fixed Income Securities [Member] | Commercial Mortgage Backed Securities [Member]
AFS Fair Value, Less than 12 months		42,671	82,492
AFS Unrealized Losses, Less than 12 months	[1]	(243)	(1,021)
AFS Fair Value, 12 months or longer		0	1,645
AFS Unrealized Losses, 12 months or longer	[1]	0	(7)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		42,671	84,137
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	[1]	(243)	(1,028)
AFS Fixed Income Securities [Member] | Residential Mortgage Backed Securities [Member]
AFS Fair Value, Less than 12 months		179,293	279,480
AFS Unrealized Losses, Less than 12 months	[1]	(860)	(2,489)
AFS Fair Value, 12 months or longer		449	8,749
AFS Unrealized Losses, 12 months or longer	[1]	(6)	(309)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		179,742	288,229
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	[1]	(866)	(2,798)
Equity Securities [Member]
AFS Fair Value, Less than 12 months		18,423	17,439
AFS Unrealized Losses, Less than 12 months	[1]	(987)	(660)
AFS Fair Value, 12 months or longer		0	0
AFS Unrealized Losses, 12 months or longer	[1]	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		18,423	17,439
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	[1]	(987)	(660)
Equity Securities [Member] | Common Stock [Member]
AFS Fair Value, Less than 12 months		18,423	11,271
AFS Unrealized Losses, Less than 12 months	[1]	(987)	(305)
AFS Fair Value, 12 months or longer		0	0
AFS Unrealized Losses, 12 months or longer	[1]	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		18,423	11,271
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	[1]	$ (987)	(305)
Equity Securities [Member] | Preferred Stock [Member]
AFS Fair Value, Less than 12 months			6,168
AFS Unrealized Losses, Less than 12 months	[1]		(355)
AFS Fair Value, 12 months or longer			0
AFS Unrealized Losses, 12 months or longer	[1]		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value			6,168
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	[1]		$ (355)
[1]	Gross unrealized losses include non-OTTI unrealized amounts and OTTI losses recognized in AOCI.

Investments (Fixed Income Secur

Investments (Fixed Income Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less fair value	$ 306,493
Due after one year through five years fair value	2,095,055
Due after five years through 10 years fair value	2,379,624
Due after ten years fair value	237,550
AFS, Fair Value	5,018,722	$ 4,792,540
Due in one year or less carrying value	34,521
Due after one year through five years carrying value	29,648
Due after five years through 10 years carrying value	8,345
Due after 10 years carrying value	0
Carrying Value	72,514	101,556
Due in one year or less fair value	34,898
Due after one year through five years fair value	31,498
Due after five years through 10 years fair value	9,144
Due after 10 years fair value	0
HTM, Fair Value	$ 75,540	$ 105,211

Investments (Other Investment P

Investments (Other Investment Portfolio by Strategy and the Remaining Commitment Amount and Maximum Exposure to Loss Associated With Each Strategy) (Details) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Carrying Value		$ 116,411	$ 102,397
Other Investments [Member]
Carrying Value		116,411	102,397
Remaining Commitment		164,655	143,686
Maximum Exposure to Loss	[1]	281,066	246,083
Alternative Investments [Member]
Carrying Value		97,670	83,814
Remaining Commitment		164,655	140,286
Maximum Exposure to Loss	[1]	262,325	224,100
Private Equity [Member] | Alternative Investments [Member]
Carrying Value		46,945	41,135
Remaining Commitment		76,027	76,774
Maximum Exposure to Loss	[1]	122,972	117,909
Private Credit [Member] | Alternative Investments [Member]
Carrying Value		29,942	28,193
Remaining Commitment		57,391	40,613
Maximum Exposure to Loss	[1]	87,333	68,806
Real Assets [Member] | Alternative Investments [Member]
Carrying Value		20,783	14,486
Remaining Commitment		31,237	22,899
Maximum Exposure to Loss	[1]	52,020	37,385
Other Securities [Member]
Carrying Value		18,741	18,583
Remaining Commitment		0	3,400
Maximum Exposure to Loss	[1]	$ 18,741	$ 21,983
[1]	The maximum exposure to loss includes both the carry value of these investments and the related unfunded commitments. In addition, tax credits that have been previously recognized in Other securities are subject to the risk of recapture, which we do not consider significant.

Investments (Aggregated Income

Investments (Aggregated Income Statement Summarized Financial Information for Partnerhips in our Alternative Investment Portfolio) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Mar. 31, 2016
Schedule of Equity Method Investments [Line Items]
Net investment income earned	$ 41,430		$ 31,182		$ 78,849		$ 61,951
Alternative Investments [Member]
Schedule of Equity Method Investments [Line Items]
Net investment income earned	$ 5,200		$ (600)		$ 6,800		$ (1,700)
Investments accounted for under the equity method [Member]
Schedule of Equity Method Investments [Line Items]
Net investment (loss) income		$ (9,900)		$ (4,600)		$ (62,400)		$ 37,000
Realized gains		(70,200)		193,200		(304,300)		981,100
Net change in unrealized depreciation		1,418,500		(253,900)		1,890,000		(1,236,500)
Net gain		$ 1,338,400		$ (65,300)		$ 1,523,300		$ (218,400)

Investments (Investments Pledge

Investments (Investments Pledged as Collateral) (Details) $ in Millions	Jun. 30, 2017USD ($)
Investments Pledged As Collateral [Line Items]
Carrying Value Bonds On Deposit With Various State And Regulatory Agencies	$ 25.9
Securities Pledged As Collateral	149.9
U.S. Government and Government Agencies [Member]
Investments Pledged As Collateral [Line Items]
Carrying Value Bonds On Deposit With Various State And Regulatory Agencies	23.9
Securities Pledged As Collateral	27
Obligations of States and Political Subdivisions [Member]
Investments Pledged As Collateral [Line Items]
Carrying Value Bonds On Deposit With Various State And Regulatory Agencies	2
Securities Pledged As Collateral	2
Commercial Mortgage Backed Securities [Member]
Investments Pledged As Collateral [Line Items]
Carrying Value Bonds On Deposit With Various State And Regulatory Agencies	0
Securities Pledged As Collateral	8.4
Residential Mortgage Backed Securities [Member]
Investments Pledged As Collateral [Line Items]
Carrying Value Bonds On Deposit With Various State And Regulatory Agencies	0
Securities Pledged As Collateral	112.5
Federal Home Loan Bank of Indianapolis [Member]
Investments Pledged As Collateral [Line Items]
Fixed Income Securities Pledged For FHLB Collateral	67.3
Federal Home Loan Bank of Indianapolis [Member] | U.S. Government and Government Agencies [Member]
Investments Pledged As Collateral [Line Items]
Fixed Income Securities Pledged For FHLB Collateral	3.1
Federal Home Loan Bank of Indianapolis [Member] | Obligations of States and Political Subdivisions [Member]
Investments Pledged As Collateral [Line Items]
Fixed Income Securities Pledged For FHLB Collateral	0
Federal Home Loan Bank of Indianapolis [Member] | Commercial Mortgage Backed Securities [Member]
Investments Pledged As Collateral [Line Items]
Fixed Income Securities Pledged For FHLB Collateral	3.6
Federal Home Loan Bank of Indianapolis [Member] | Residential Mortgage Backed Securities [Member]
Investments Pledged As Collateral [Line Items]
Fixed Income Securities Pledged For FHLB Collateral	60.6
Federal Home Loan Bank of New York [Member]
Investments Pledged As Collateral [Line Items]
Fixed Income Securities Pledged For FHLB Collateral	56.7
Federal Home Loan Bank of New York [Member] | U.S. Government and Government Agencies [Member]
Investments Pledged As Collateral [Line Items]
Fixed Income Securities Pledged For FHLB Collateral	0
Federal Home Loan Bank of New York [Member] | Obligations of States and Political Subdivisions [Member]
Investments Pledged As Collateral [Line Items]
Fixed Income Securities Pledged For FHLB Collateral	0
Federal Home Loan Bank of New York [Member] | Commercial Mortgage Backed Securities [Member]
Investments Pledged As Collateral [Line Items]
Fixed Income Securities Pledged For FHLB Collateral	4.8
Federal Home Loan Bank of New York [Member] | Residential Mortgage Backed Securities [Member]
Investments Pledged As Collateral [Line Items]
Fixed Income Securities Pledged For FHLB Collateral	$ 51.9

Investments (Credit Concentrati

Investments (Credit Concentration Risk) (Details)	Jun. 30, 2017	Dec. 31, 2016
Investments [Abstract]
Maximum exposure to credit concentration risk of the Company's stockholder's equity other than certain U.S. government agencies	10.00%	10.00%

Investments (Net Investment Inc

Investments (Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net Investment Income [Line Items]
Net investment income earned	$ 41,430	$ 31,182	$ 78,849	$ 61,951
Fixed Income Securities [Member]
Net Investment Income [Line Items]
Net investment income earned	37,668	31,753	74,559	63,397
Equity Securities [Member]
Net Investment Income [Line Items]
Net investment income earned	1,419	2,204	2,887	4,434
Short-Term Investments [Member]
Net Investment Income [Line Items]
Net investment income earned	377	142	627	301
Other Investments [Member]
Net Investment Income [Line Items]
Net investment income earned	5,231	(611)	6,834	(1,677)
Investment Expenses [Member]
Net Investment Income [Line Items]
Net investment income earned	$ (3,265)	$ (2,306)	$ (6,058)	$ (4,504)

Investments (OTTI by Asset Type

Investments (OTTI by Asset Type) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
OTTI Losses Gross	$ 1,211	$ 559	$ 4,686	$ 4,152
Other-than-temporary impairments on fixed income securities recognized in other comprehensive income	(6)	10	(6)	10
OTTI Losses Recognized in Earnings	1,217	549	4,692	4,142
US Treasury and Government [Member]
OTTI Losses Gross	2		31
Other-than-temporary impairments on fixed income securities recognized in other comprehensive income	0		0
OTTI Losses Recognized in Earnings	2		31
Obligations of States and Political Subdivisions [Member]
OTTI Losses Gross	239		612
Other-than-temporary impairments on fixed income securities recognized in other comprehensive income	0		0
OTTI Losses Recognized in Earnings	239		612
Collateralized Loan Obligations and Other Asset Backed Securities [Member]
OTTI Losses Gross	62		85
Other-than-temporary impairments on fixed income securities recognized in other comprehensive income	0		0
OTTI Losses Recognized in Earnings	62		85
Commercial Mortgage Backed Securities [Member]
OTTI Losses Gross	220		670
Other-than-temporary impairments on fixed income securities recognized in other comprehensive income	0		0
OTTI Losses Recognized in Earnings	220		670
Other Investments [Member]
OTTI Losses Gross	190		190
Other-than-temporary impairments on fixed income securities recognized in other comprehensive income	0		0
OTTI Losses Recognized in Earnings	190		190
AFS Fixed Income Securities [Member]
OTTI Losses Gross	975	202	3,136	1,175
Other-than-temporary impairments on fixed income securities recognized in other comprehensive income	(6)	10	(6)	10
OTTI Losses Recognized in Earnings	981	192	3,142	1,165
AFS Fixed Income Securities [Member] | Corporate Securities [Member]
OTTI Losses Gross	381	104	575	1,077
Other-than-temporary impairments on fixed income securities recognized in other comprehensive income	0	0	0	0
OTTI Losses Recognized in Earnings	381	104	575	1,077
AFS Fixed Income Securities [Member] | Residential Mortgage Backed Securities [Member]
OTTI Losses Gross	71	98	1,163	98
Other-than-temporary impairments on fixed income securities recognized in other comprehensive income	(6)	10	(6)	10
OTTI Losses Recognized in Earnings	77	88	1,169	88
Total AFS Securities [Member] | Equity Securities [Member]
OTTI Losses Gross	46	357	1,360	2,977
Other-than-temporary impairments on fixed income securities recognized in other comprehensive income	0	0	0	0
OTTI Losses Recognized in Earnings	46	357	1,360	2,977
Common Stock [Member] | Total AFS Securities [Member] | Equity Securities [Member]
OTTI Losses Gross	46	357	1,360	2,974
Other-than-temporary impairments on fixed income securities recognized in other comprehensive income	0	0	0	0
OTTI Losses Recognized in Earnings	$ 46	$ 357	$ 1,360	2,974
Preferred Stock [Member] | Total AFS Securities [Member] | Equity Securities [Member]
OTTI Losses Gross				3
Other-than-temporary impairments on fixed income securities recognized in other comprehensive income				0
OTTI Losses Recognized in Earnings				$ 3

Investments (Components Of Net

Investments (Components Of Net Realized Gains, Excluding OTTI Charges) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Schedule of Available-for-sale and held-to-maturity Securities [Line Items]
HTM securities realized gain	$ 44	$ 3	$ 44	$ 3
HTM fixed income securities losses	0	0	(1)	(1)
Other investments gains	0	0	480	0
Other investments losses	(5)	0	(19)	(4)
Total net realized gains (excluding OTTI charges)	2,951	2,314	5,381	3,203
Proceeds from sale of available for sale securities	123,100	88,700	723,400	105,900
Fixed Income Securities [Member]
Schedule of Available-for-sale and held-to-maturity Securities [Line Items]
AFS securities gains	2,715	365	6,267	985
AFS securities losses	(153)	(5)	(1,740)	(41)
Equity Securities [Member]
Schedule of Available-for-sale and held-to-maturity Securities [Line Items]
AFS securities gains	350	2,171	350	2,501
AFS securities losses	$ 0	$ (220)	$ 0	$ (240)

Indebtedness Indebtedness (Deta

Indebtedness Indebtedness (Details) - Zero Point Seventy Five Percent Borrowing From Federal Home Loan Bank Due March 21, 2017 [Member] $ in Millions	Jun. 30, 2017USD ($)
Short-term Debt [Line Items]
Federal Home Loan Bank Advances	$ 64
Federal Home Loan Bank, Advances, Interest Rate	0.75%

Fair Value Measurements (Quanti

Fair Value Measurements (Quantitative Disclosures of Fair Value Assets) (Details) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Available-for-sale Securities, Debt Securities		$ 5,018,722	$ 4,792,540
Equity securities, AFS		161,694	146,753
Total AFS securities		5,180,416	4,939,293
Short-term investments		133,706	221,701
Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities		5,018,722	4,792,540
Equity securities, AFS		161,694	146,753
Total AFS securities		5,180,416	4,939,293
Short-term investments		133,706	221,701
Total assets measured at fair value		5,314,122	5,160,994
U.S. Government and Government Agencies [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities		68,003	77,333
Foreign Government [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities		18,714	26,865
Obligations of States and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities		1,404,766	1,379,593
Corporate Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities		1,821,510	1,997,753
Collateralized Loan Obligations and Other Asset Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities		702,524	528,960
Commercial Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities		279,205	256,842
Residential Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities		724,000	525,194
Common Stock [Member] | Fair Value, Measurements, Recurring [Member]
Equity securities, AFS		144,436	130,608
Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member]
Equity securities, AFS		17,258	16,145
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities	[1]	24,828	27,520
Equity securities, AFS	[1]	153,224	139,077
Total AFS securities	[1]	178,052	166,597
Short-term investments	[1]	133,706	221,701
Total assets measured at fair value	[1]	311,758	388,298
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | U.S. Government and Government Agencies [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities	[1]	24,828	27,520
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Foreign Government [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities	[1]	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Obligations of States and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities	[1]	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Corporate Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities	[1]	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Collateralized Loan Obligations and Other Asset Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities	[1]	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Commercial Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities	[1]	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Residential Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities	[1]	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Common Stock [Member] | Fair Value, Measurements, Recurring [Member]
Equity securities, AFS	[1]	135,966	122,932
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member]
Equity securities, AFS	[1]	17,258	16,145
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities	[1]	4,993,894	4,765,020
Equity securities, AFS	[1]	0	0
Total AFS securities	[1]	4,993,894	4,765,020
Short-term investments	[1]	0	0
Total assets measured at fair value	[1]	4,993,894	4,765,020
Significant Other Observable Inputs (Level 2) [Member] | U.S. Government and Government Agencies [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities	[1]	43,175	49,813
Significant Other Observable Inputs (Level 2) [Member] | Foreign Government [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities	[1]	18,714	26,865
Significant Other Observable Inputs (Level 2) [Member] | Obligations of States and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities	[1]	1,404,766	1,379,593
Significant Other Observable Inputs (Level 2) [Member] | Corporate Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities	[1]	1,821,510	1,997,753
Significant Other Observable Inputs (Level 2) [Member] | Collateralized Loan Obligations and Other Asset Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities	[1]	702,524	528,960
Significant Other Observable Inputs (Level 2) [Member] | Commercial Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities	[1]	279,205	256,842
Significant Other Observable Inputs (Level 2) [Member] | Residential Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities	[1]	724,000	525,194
Significant Other Observable Inputs (Level 2) [Member] | Common Stock [Member] | Fair Value, Measurements, Recurring [Member]
Equity securities, AFS	[1]	0	0
Significant Other Observable Inputs (Level 2) [Member] | Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member]
Equity securities, AFS	[1]	0	0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities		0	0
Equity securities, AFS		8,470	7,676
Total AFS securities		8,470	7,676
Short-term investments		0	0
Total assets measured at fair value		8,470	7,676
Significant Unobservable Inputs (Level 3) [Member] | U.S. Government and Government Agencies [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities		0	0
Significant Unobservable Inputs (Level 3) [Member] | Foreign Government [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities		0	0
Significant Unobservable Inputs (Level 3) [Member] | Obligations of States and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities		0	0
Significant Unobservable Inputs (Level 3) [Member] | Corporate Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities		0	0
Significant Unobservable Inputs (Level 3) [Member] | Collateralized Loan Obligations and Other Asset Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities		0	0
Significant Unobservable Inputs (Level 3) [Member] | Commercial Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities		0	0
Significant Unobservable Inputs (Level 3) [Member] | Residential Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale Securities, Debt Securities		0	0
Significant Unobservable Inputs (Level 3) [Member] | Common Stock [Member] | Fair Value, Measurements, Recurring [Member]
Equity securities, AFS		8,470	7,676
Significant Unobservable Inputs (Level 3) [Member] | Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member]
Equity securities, AFS		$ 0	$ 0
[1]	1 There were no transfers of securities between Level 1 and Level 2.

Fair Value Measurements (Quan45

Fair Value Measurements (Quantitative Information of Our Financial Assets and Liabilities That Were Disclosed at Fair Value) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity Securities, Fair Value	$ 75,540	$ 105,211
Long-term debt	438,894	438,667
Seven Point Twenty Five Percent Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	58,690	56,148
Six Point Seventy Percent Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	112,573	108,333
Five Point Eight Hundred Seventy Five Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	188,767	176,860
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	24,521	24,286
One Point Fifty Six Percent Borrowing From Federal Home Loan Bank Due August 16, 2021 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	24,462	24,219
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	60,837	59,313
Long-term Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	469,850	449,159
Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity Securities, Fair Value	55,622	79,916
Corporate Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity Securities, Fair Value	19,918	24,075
Commercial Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity Securities, Fair Value		1,220
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]
Held-to-maturity Securities, Fair Value	0	0
Long-term debt	188,767	176,860
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Seven Point Twenty Five Percent Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Six Point Seventy Percent Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Five Point Eight Hundred Seventy Five Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	188,767	176,860
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | 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	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | 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	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | 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	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity Securities, Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Corporate Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity Securities, Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity Securities, Fair Value		0
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity Securities, Fair Value	69,582	97,701
Long-term debt	281,083	272,299
Significant Other Observable Inputs (Level 2) [Member] | Seven Point Twenty Five Percent Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	58,690	56,148
Significant Other Observable Inputs (Level 2) [Member] | Six Point Seventy Percent Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	112,573	108,333
Significant Other Observable Inputs (Level 2) [Member] | Five Point Eight Hundred Seventy Five Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	0	0
Significant Other Observable Inputs (Level 2) [Member] | 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	24,521	24,286
Significant Other Observable Inputs (Level 2) [Member] | 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	24,462	24,219
Significant Other Observable Inputs (Level 2) [Member] | 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	60,837	59,313
Significant Other Observable Inputs (Level 2) [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity Securities, Fair Value	55,622	79,916
Significant Other Observable Inputs (Level 2) [Member] | Corporate Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity Securities, Fair Value	13,960	16,565
Significant Other Observable Inputs (Level 2) [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity Securities, Fair Value		1,220
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity Securities, Fair Value	5,958	7,510
Long-term debt	0	0
Significant Unobservable Inputs (Level 3) [Member] | Seven Point Twenty Five Percent Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	0	0
Significant Unobservable Inputs (Level 3) [Member] | Six Point Seventy Percent Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	0	0
Significant Unobservable Inputs (Level 3) [Member] | Five Point Eight Hundred Seventy Five Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	0	0
Significant Unobservable Inputs (Level 3) [Member] | 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	0	0
Significant Unobservable Inputs (Level 3) [Member] | 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	0	0
Significant Unobservable Inputs (Level 3) [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity Securities, Fair Value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Corporate Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity Securities, Fair Value	$ 5,958	7,510
Significant Unobservable Inputs (Level 3) [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity Securities, Fair Value		$ 0

Reinsurance (List of Direct, As

Reinsurance (List of Direct, Assumed, and Ceded Reinsurance Amounts) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Premiums written:
Direct	$ 706,408	$ 665,862	$ 1,390,228	$ 1,312,140
Assumed	6,488	7,788	12,179	14,108
Ceded	(99,082)	(95,510)	(189,889)	(182,749)
Net	613,814	578,140	1,212,518	1,143,499
Premiums earned:
Direct	654,588	612,406	1,301,316	1,219,067
Assumed	6,063	7,171	11,842	13,441
Ceded	(92,621)	(87,645)	(184,274)	(178,118)
Net	568,030	531,932	1,128,884	1,054,390
Loss and loss expense incurred:
Direct	389,550	362,064	731,672	723,703
Assumed	7,766	6,140	12,203	12,495
Ceded	(55,757)	(69,725)	(84,844)	(140,575)
Net	341,559	298,479	659,031	595,623
National Flood Insurance Program [Member]
Premiums written:
Ceded	(63,808)	(63,906)	(120,142)	(117,154)
Premiums earned:
Ceded	(57,655)	(56,667)	(114,932)	(113,481)
Loss and loss expense incurred:
Ceded	$ (15,140)	$ (24,261)	$ (21,681)	$ (64,979)

Reinsurance (Ceded Premiums and

Reinsurance (Ceded Premiums and Losses Related to Flood Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Ceded premiums written	$ (99,082)	$ (95,510)	$ (189,889)	$ (182,749)
Ceded premiums earned	(92,621)	(87,645)	(184,274)	(178,118)
Ceded loss and loss expense incurred	(55,757)	(69,725)	(84,844)	(140,575)
National Flood Insurance Program [Member]
Ceded premiums written	(63,808)	(63,906)	(120,142)	(117,154)
Ceded premiums earned	(57,655)	(56,667)	(114,932)	(113,481)
Ceded loss and loss expense incurred	$ (15,140)	$ (24,261)	$ (21,681)	$ (64,979)
Percentage of NFIP claims ceded by federal government			100.00%

Reserve for Losses and Loss E48

Reserve for Losses and Loss Expenses Reserves for Losses and Loss Expenses (Rollforward of Reserves for Losses and Loss Expenses) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Liability for Catastrophe Claims [Line Items]
Gross reserves for losses and loss expenses, at beginning of year	$ 3,691,719	$ 3,517,728
Less: reinsurance recoverable on unpaid losses and loss expenses, at beginning of year	611,200	551,019
Net reserves for losses and loss expenses, at beginning of year	3,080,519	2,966,709
Incurred losses and loss expenses for claims occurring in the current year	684,877	624,159
Incurred losses and loss expenses for claims occurring in the prior year	(25,846)	(28,536)
Total incurred losses and loss expenses	659,031	595,623
Paid losses and loss expenses for claims occurring in the current year	171,724	146,849
Paid losses and loss expenses for claims occurring in the prior years	425,521	402,255
Total paid losses and loss expenses	597,245	549,104
Net reserves for losses and loss expenses, at end of period	3,142,305	3,013,228
Add: reinsurance recoverable on unpaid losses and loss expenses, at end of period	588,916	576,941
Gross reserves for losses and loss expenses, at end of period	3,731,221	3,590,169
Change in Historical Claim Rate Experience [Member]
Liability for Catastrophe Claims [Line Items]
Incurred losses and loss expenses for claims occurring in the prior year	25,800	28,500
Change in Historical Claim Rate Experience [Member] | General Liability [Member]
Liability for Catastrophe Claims [Line Items]
Incurred losses and loss expenses for claims occurring in the prior year	37,400	22,000
Change in Historical Claim Rate Experience [Member] | Workers Compensation [Member]
Liability for Catastrophe Claims [Line Items]
Incurred losses and loss expenses for claims occurring in the prior year	15,300	21,000
Change in Historical Claim Rate Experience [Member] | Commercial Automobile [Member]
Liability for Catastrophe Claims [Line Items]
Incurred losses and loss expenses for claims occurring in the prior year	21,000	13,000
Change in Historical Claim Rate Experience [Member] | Personal Automobile [Member]
Liability for Catastrophe Claims [Line Items]
Incurred losses and loss expenses for claims occurring in the prior year	$ 4,000
Change in Historical Claim Rate Experience [Member] | Excess And Surplus Operations [Member]
Liability for Catastrophe Claims [Line Items]
Incurred losses and loss expenses for claims occurring in the prior year		$ 3,000

Segment Information Narrative (

Segment Information Narrative (Details)	6 Months Ended
	Jun. 30, 2017
Number of Operating Segments	4

Segment Information (Revenue by

Segment Information (Revenue by Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Total net premiums earned	$ 568,030	$ 531,932	$ 1,128,884	$ 1,054,390
Net investment income	41,430	31,182	78,849	61,951
Net realized investment gains (losses)	1,734	1,765	689	(939)
Total investment revenues	43,164	32,947	79,538	61,012
Other income	3,291	3,868	6,532	4,819
Total revenues	614,485	568,747	1,214,954	1,120,221
Standard Commercial Lines [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	446,610	414,844	887,884	818,423
Standard Commercial Lines [Member] | Commercial Automobile [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	108,316	98,896	215,445	194,315
Standard Commercial Lines [Member] | Workers Compensation [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	79,460	75,251	158,786	151,251
Standard Commercial Lines [Member] | General Liability [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	141,503	129,283	281,487	257,368
Standard Commercial Lines [Member] | Commercial Property [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	78,052	73,591	154,443	143,769
Standard Commercial Lines [Member] | Business Owners' Policies [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	24,989	24,651	49,834	48,555
Standard Commercial Lines [Member] | Bonds Segment [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	6,986	5,665	13,484	11,129
Standard Commercial Lines [Member] | Other Commercial [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	4,288	3,940	8,529	7,779
Standard Commercial Lines [Member] | Miscellaneous Income [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	3,016	3,567	5,876	4,257
Standard Personal Lines [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	71,947	71,125	143,529	141,590
Standard Personal Lines [Member] | Miscellaneous Income [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	275	301	656	561
Standard Personal Lines [Member] | Personal Automobile [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	37,663	35,881	74,613	71,661
Standard Personal Lines [Member] | Homeowners [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	32,467	33,411	65,167	66,311
Standard Personal Lines [Member] | Other Personal [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	1,542	1,532	3,093	3,057
Excess And Surplus Operations [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	52,764	49,831	104,003	99,196
Excess And Surplus Operations [Member] | General Liability [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	39,054	36,940	76,966	73,796
Excess And Surplus Operations [Member] | Commercial Property [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	13,710	12,891	27,037	25,399
Excess And Surplus Operations [Member] | Miscellaneous Income [Member]
Segment Reporting Information [Line Items]
Total net premiums earned	$ 0	$ 0	$ 0	$ 1

Segment Information (Income Bef

Segment Information (Income Before Federal Income Tax) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Net investment income	$ 41,430	$ 31,182	$ 78,849	$ 61,951
Net realized investment gains (losses)	1,734	1,765	689	(939)
Total investment income, before federal income tax	43,164	32,947	79,538	61,012
Tax on investment income	11,734	8,275	21,336	14,538
Total investment income, after federal income tax	31,430	24,672	58,202	46,474
Standard Commercial Lines [Member]
Segment Reporting Information [Line Items]
Underwriting gain (loss), before federal income tax	$ 34,759	$ 40,173	$ 77,305	$ 71,105
GAAP combined ratio	92.20%	90.20%	91.20%	91.30%
Statutory combined ratio	90.60%	88.60%	89.50%	89.10%
Standard Personal Lines [Member]
Segment Reporting Information [Line Items]
Underwriting gain (loss), before federal income tax	$ (5,768)	$ 6,125	$ (662)	$ 14,730
GAAP combined ratio	108.00%	91.40%	100.50%	89.60%
Statutory combined ratio	105.90%	89.90%	99.80%	90.10%
Excess And Surplus Operations [Member]
Segment Reporting Information [Line Items]
Underwriting gain (loss), before federal income tax	$ 1,319	$ (2,521)	$ 2,889	$ (1,103)
GAAP combined ratio	97.50%	105.10%	97.20%	101.10%
Statutory combined ratio	97.00%	102.70%	96.50%	100.60%

Segment Information (Reconcilia

Segment Information (Reconciliation of Segment Results to Income Before Federal Income Tax (Details)) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Investment income, before federal income tax	$ 43,164	$ 32,947	$ 79,538	$ 61,012
Interest expense	(6,081)	(5,620)	(12,187)	(11,226)
General corporate and other expenses	(8,464)	(8,793)	(20,380)	(20,332)
Income before federal income tax	58,929	62,311	126,503	114,186
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	34,759	40,173	77,305	71,105
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	(5,768)	6,125	(662)	14,730
Excess And Surplus Operations [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Underwriting gain (loss), before federal income tax	1,319	(2,521)	2,889	(1,103)
Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total all segments	$ 73,474	$ 76,724	$ 159,070	$ 145,744

Retirement Plans (Components of

Retirement Plans (Components of Net Periodic Benefit Cost) (Details) - Pension Plan [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 0	$ 0	$ 0	$ 1,606
Interest cost	3,110	3,101	6,221	6,203
Expected return on plan assets	(4,855)	(3,988)	(9,709)	(7,976)
Amortization of unrecognized net actuarial loss	482	1,481	963	2,961
Total net periodic cost	$ (1,263)	$ 594	$ (2,525)	$ 2,794

Retirement Plans (Weighted-Aver

Retirement Plans (Weighted-Average Expense Assumptions) (Details) - Pension Plan [Member]	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.41%	4.69%
Effective interest rate for calculation of service cost		4.52%
Effective interest rate for calculation of interest cost	3.83%	4.02%
Expected return on plan assets	6.24%	6.37%
Rate of compensation increase		4.00%

Comprehensive Income (Component

Comprehensive Income (Components of Comprehensive Income-Gross and Net of Tax) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net income, Gross	$ 58,929	$ 62,311	$ 126,503	$ 114,186
Unrealized holding gains during the period, Gross	35,887	55,675	61,672	121,412
Non Credit Portion Of Other Than Temporary Impairment Losses Recognized In Other Comprehensive Income Gross	6	(10)	6	(10)
Amounts reclassified into net income: HTM securities, Gross	(43)	(19)	(92)	(91)
Amounts reclassified into net income: Realized losses on AFS securities, Gross	(1,885)	(1,762)	(375)	937
Total unrealized gains on investment securities, Gross	33,965	53,884	61,211	122,248
Amount reclassified into net income: Net actuarial loss, Gross	508	1,517	1,015	3,033
Total defined pension and other post-retirement benefit plans, Gross	508	1,517	1,015	3,033
Other comprehensive income, Gross	34,473	55,401	62,226	125,281
Comprehensive income before tax	93,402	117,712	188,729	239,467
Net income, Tax	17,503	18,710	34,637	33,553
Unrealized holding gains during the period, Tax	12,561	19,487	21,585	42,495
Non-Credit Portion of Other-Than-Temporary Impairment Losses Recognized In Other Comprehensive Income, Tax	2	(4)	2	(4)
Amounts reclassified into net income: HTM securities, Tax	(15)	(7)	(32)	(32)
Amounts reclassified into net income: Realized losses on AFS securities, Tax	(660)	(617)	(131)	328
Total unrealized gains on investment securities, Tax	11,888	18,859	21,424	42,787
Amount reclassified into net income: Net actuarial loss, Tax	178	532	355	1,062
Total defined pension and other post-retirement benefit plans, Tax	178	532	355	1,062
Other comprehensive income, Tax	12,066	19,391	21,779	43,849
Comprehensive income, Tax	29,569	38,101	56,416	77,402
Net income	41,426	43,601	91,866	80,633
Unrealized holding gains arising during period	23,326	36,188	40,087	78,917
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, Net of Tax, Portion Attributable to Parent	4	6	4	6
Amounts reclassified into net income: HTM Securities	(28)	(12)	(60)	(59)
Amounts reclassified into net income: Realized (gains) losses on available-for-sale securities	(1,225)	(1,145)	(244)	609
Total unrealized gains on investment securities	22,077	35,025	39,787	79,461
Amount reclassified into net income: Net actuarial loss	330	985	660	1,971
Total defined benefit pension and post-retirement plans	330	985	660	1,971
Other comprehensive income	22,407	36,010	40,447	81,432
Comprehensive income	$ 63,833	$ 79,611	$ 132,313	$ 162,065

Comprehensive Income (Compone56

Comprehensive Income (Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2016			$ (15,950)
Amounts reclassified into net income: Non-credit OTTI			0
OCI before reclassifications, Defined Benefit Pension and Post Retirement Plans			0
Amount reclassified into net income: Net actuarial loss	$ 330	$ 985	660	$ 1,971
Amounts reclassified from AOCI, HTM related	(28)	(12)	(60)	(59)
Amounts reclassified from AOCI, All Other	(1,225)	(1,145)	(244)	609
Other comprehensive income	22,407	36,010	40,447	81,432
Other Comprehensive Income, Defined Benefit Pension and Post Retirement Plans, Adjustment, Net of Tax	330	$ 985	660	1,971
Ending Balance, June 30, 2017	24,497		24,497
Available-for-sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2016			42,170
OCI before reclassifications			40,087
Other comprehensive income			39,843
Ending Balance, June 30, 2017	82,013		82,013
Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2016			42,122
OCI before reclassifications			40,091
Amounts reclassified from AOCI			(304)
Other comprehensive income			39,787
Ending Balance, June 30, 2017	81,909		81,909
Accumulated Other-than-Temporary Impairment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2016			(150)
OCI before reclassifications			4
Other comprehensive income			4
Ending Balance, June 30, 2017	(146)		(146)
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Held-to-maturity Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2016			102
OCI before reclassifications			0
Other comprehensive income			(60)
Ending Balance, June 30, 2017	42		42
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2016			(58,072)
Amount reclassified into net income: Net actuarial loss			660
Ending Balance, June 30, 2017	(57,412)		(57,412)
Accumulated other comprehensive income (loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2016			(15,950)
OCI before reclassifications			40,091
Amounts reclassified from AOCI			356
Other comprehensive income			40,447	$ 81,432
Ending Balance, June 30, 2017	$ 24,497		$ 24,497

Comprehensive Income (Reclassif

Comprehensive Income (Reclassification out of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Total net realized gains (losses)	$ 1,734	$ 1,765	$ 689	$ (939)
Net investment income	41,430	31,182	78,849	61,951
Losses and loss expenses incurred	341,559	298,479	659,031	595,623
Policy acquisition costs	196,824	190,731	393,052	373,958
Income before federal income tax	58,929	62,311	126,503	114,186
Total federal income tax expense	(17,503)	(18,710)	(34,637)	(33,553)
Net income	41,426	43,601	91,866	80,633
Reclassification out of AOCI
Net income	(923)	(172)	356	2,521
Reclassification out of AOCI | Pension Plan [Member]
Losses and loss expenses incurred	111	329	221	658
Policy acquisition costs	397	1,188	794	2,375
Income before federal income tax	508	1,517	1,015	3,033
Total federal income tax expense	(178)	(532)	(355)	(1,062)
Net income	330	985	660	1,971
Reclassification out of AOCI | Held-to-maturity Securities [Member]
Total net realized gains (losses)	17	60	30	88
Net investment income	(60)	(79)	(122)	(179)
Income before federal income tax	(43)	(19)	(92)	(91)
Total federal income tax expense	15	7	32	32
Net income	(28)	(12)	(60)	(59)
Reclassification out of AOCI | Available-for-sale Securities [Member]
Total net realized gains (losses)	(1,885)	(1,762)	(375)	937
Income before federal income tax	(1,885)	(1,762)	(375)	937
Total federal income tax expense	660	617	131	(328)
Net income	$ (1,225)	$ (1,145)	$ (244)	$ 609

Related Party Transactions Re58

Related Party Transactions Related Party Transactions (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Percentage Common Stock Owned by Related Party					12.70%
Expenses Incurred, Related Parties	$ 0.5	$ 0	$ 1	$ 0
Due to Related Parties	$ 0.9		$ 0.9			$ 0.4