State Auto Financial (STFC) 10-Q 3 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 26, 2019
Document Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Entity Registrant Name	State Auto Financial CORP
Entity Central Index Key	0000874977
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding (shares)		43,403,270
Entity Emerging Growth Company	false
Entity Small Business	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Document Period End Date	Mar. 31, 2019
Assets
Fixed maturities, available-for-sale, at fair value (amortized cost $2,130.9 and $2,188.2, respectively)	$ 2,136.6	$ 2,159.5
Equity securities	363.9	315
Other invested assets	53.5	48.8
Other invested assets, at cost	5.6	5.6
Notes receivable from affiliate	70	70
Total investments	2,629.6	2,598.9
Cash and cash equivalents	72.3	59.8
Accrued investment income and other assets	36.6	32.4
Deferred policy acquisition costs (affiliated net assumed $48.6 and $48.3, respectively)	104.3	101.9
Reinsurance recoverable on losses and loss expenses payable	4.6	5.5
Prepaid reinsurance premiums	6.7	6.6
Current federal income taxes	6.3	5.9
Net deferred federal income taxes	57.7	77.8
Property and equipment, at cost	6	7.1
Total assets	2,924.1	2,895.9
Liabilities and Stockholders’ Equity
Losses and loss expenses payable (affiliated net assumed $583.7 and $593.6, respectively)	1,128.9	1,146.8
Unearned premiums (affiliated net assumed $103.7 and $112.4, respectively)	587.5	584.2
Notes payable (affiliates $15.2 and $15.2, respectively)	122	122
Pension and postretirement benefits	82.4	83
Due to Affiliate	18.4	22.4
Other liabilities (affiliated net assumed $11.5 and $19.9, respectively)	89.6	119
Total liabilities	2,028.8	2,077.4
Stockholders’ equity:
Common stock, without par value. Authorized 100.0 shares; 50.1 and 50.0 shares issued, respectively, at stated value of $2.50 per share	125.3	125
Treasury stock, 6.8 and 6.8 shares, respectively, at cost	(117.5)	(117)
Additional paid-in capital	198.4	194.2
Accumulated other comprehensive (loss) income	(68.6)	(96.4)
Retained earnings	757.7	712.7
Total stockholders’ equity	895.3	818.5
Total liabilities and stockholders’ equity	2,924.1	2,895.9
Class A Preferred Stock [Member]
Stockholders’ equity:
Preferred stock value	0	0
Class B Preferred Stock [Member]
Stockholders’ equity:
Preferred stock value	$ 0	$ 0

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Fixed maturities, available-for-sale, amortized cost	$ 2,130.9	$ 2,188.2
Deferred policy acquisitions costs from affiliates	48.6	48.3
Losses and loss expenses payable, affiliates	583.7	593.6
Unearned premiums, affiliates	103.7	112.4
Notes payable, affiliates	15.2	15.2
Net Other Liabilities from Affiliates	$ 11.5	$ 19.9
Common stock, no par value (usd per share)	$ 0	$ 0
Common stock, shares authorized (shares)	100,000,000	100,000,000
Common stock, shares issued (shares)	50,100,000	50,000,000
Common stock, stated value per share (usd per share)	$ 2.50	$ 2.50
Treasury stock (shares)	6,800,000	6,800,000
Class A Preferred Stock [Member]
Preferred stock, no par value (usd per share)	$ 0	$ 0
Preferred stock, shares authorized (shares)	2,500,000	2,500,000
Preferred stock, shares issued (shares)	0	0
Class B Preferred Stock [Member]
Preferred stock, no par value (usd per share)	$ 0	$ 0
Preferred stock, shares authorized (shares)	2,500,000	2,500,000
Preferred stock, shares issued (shares)	0	0

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Earned premiums (affiliated net assumed $71.9 and $115.3, respectively, and $251.1 and $349.0, respectively)	$ 302.7	$ 314.9
Net investment income (affiliate $1.3 and $1.3, respectively, and $3.7 and $3.7, respectively)	19.4	19.9
Net realized gains on investments:
Total net realized gains on investments	44.9	(11.7)
Other income from affiliates	0.6	0.6
Total revenues	367.6	323.7
Losses and loss expenses (affiliated net assumed $34.7 and $128.9, respectively, and $105.4 and $298.8, respectively)	194.3	212.3
Acquisition and operating expenses (affiliated net ceded $26.8 and affiliated net assumed $78.9, respectively, and $52.3 and $231.0, respectively)	107.6	110.8
Interest expense (affiliates $0.2 and $0.2, respectively, and $0.7 and $0.6, respectively)	1.2	1.6
Other expenses	2.9	2.3
Costs and Expenses	306	327
Income before federal income taxes	61.6	(3.3)
Current Income Tax Expense (Benefit)	(0.4)	(1)
Deferred Income Tax Expense (Benefit)	12.6	(0.2)
Federal income tax expense	12.2	(1.2)
Net income	$ 49.4	$ (2.1)
Earnings (loss) per common share:
Basic (usd per share)	$ 1.14	$ (0.05)
Diluted (usd per share)	1.12	(0.05)
Dividends paid per common share (usd per share)	$ 0.10	$ 0.10

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Earned premiums, from affiliates	$ 59.7	$ 98
Net investment income, from affiliate	1.2	1.2
Losses and loss expenses, from affiliates	56.4	46.2
Net Acquisition and Operating Expenses, from affiliates	24.2	43.6
Interest Expense Debt To Affiliates	$ 0.2	$ 0.2

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 49.4	$ (2.1)
Net unrealized holding gains (losses) on fixed maturities:
Unrealized holding gains (losses)	34.5	(36.7)
Reclassification adjustments for gains realized in net income	(0.1)	(0.4)
Income tax (expense) benefit	(7.2)	7.8
Total net unrealized holding gains (losses) on available-for-sale investments	27.2	(29.3)
Reclassification adjustments for amortization to statements of income:
Negative prior service cost	(1.6)	(1.6)
Net actuarial loss	2.4	3.3
Income tax expense	(0.2)	(0.4)
Total net unrecognized benefit plan obligations	0.6	1.3
Other comprehensive income (loss)	27.8	(28)
Comprehensive income (loss)	$ 77.2	$ (30.1)

Condensed Consolidated Statem_3

Condensed Consolidated Statement of Stockholders' Equity Statement - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]
Balance at beginning of year (shares) at Dec. 31, 2017		(49.2)	(6.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares (shares)		0.3
Balance at end of year (shares) at Mar. 31, 2018		(49.5)	(6.8)
Balance at beginning of year at Dec. 31, 2017		$ 123	$ (116.8)	$ 171.8	$ 3.8	$ 653.2
Balance at end of year at Mar. 31, 2018	$ 809.8	123.8	(116.9)	180.3	(88.1)	710.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares		0.8		6.2
Shares acquired on stock award exercises and vested restricted shares			$ (0.1)
Stock awards granted				2.3
Change in net unrealized holding (losses) gains, net of tax	(29.3)				(29.3)
Change in unrecognized benefit plan obligations, net of tax and reclassification adjustments	1.3				1.3
Net income (loss)	(2.1)					(2.1)
Cash dividends paid		$ (4.3)
Cumulative Effect of change in accounting for equity securities and other invested assets and reclassification of stranded tax effects as of January 1, 2018					(63.9)	63.9
Cumulative Effect of change in accounting for equity securities and other invested assets and reclassification of stranded tax effects as of January 1, 2018	(63.9)
Balance at beginning of year (shares) at Dec. 31, 2018		(50)	(6.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares (shares)		0.1
Balance at end of year (shares) at Mar. 31, 2019		(50.1)	(6.8)
Balance at beginning of year at Dec. 31, 2018	818.5	$ 125	$ (117)	194.2	(96.4)	712.7
Balance at end of year at Mar. 31, 2019	895.3	125.3	(117.5)	198.4	(68.6)	757.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares		0.3		0.7
Shares acquired on stock award exercises and vested restricted shares			$ (0.5)
Stock awards granted				$ 3.5
Change in net unrealized holding (losses) gains, net of tax	27.2				27.2
Change in unrecognized benefit plan obligations, net of tax and reclassification adjustments	0.6				0.6
Net income (loss)	$ 49.4					49.4
Cash dividends paid		$ (4.4)
Cumulative Effect of change in accounting for equity securities and other invested assets and reclassification of stranded tax effects as of January 1, 2018					$ 0	$ 0

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net income (loss)	$ 49.4	$ (2.1)
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization, net	3.1	2.9
Share-based compensation	3.8	2.3
Net investment (gain) loss	(44.9)	11.7
Changes in operating assets and liabilities:
Deferred policy acquisition costs	(2.4)	5.2
Accrued investment income and other assets	(4.1)	(3.8)
Postretirement and pension benefits	(0.1)	(0.3)
Other liabilities and due to/from affiliates, net	0.8	1
Reinsurance recoverable on losses and loss expenses payable and prepaid reinsurance premiums	(33.6)	4.2
Losses and loss expenses payable	(17.9)	(8)
Unearned premiums	3.3	(22.6)
Excess Tax Benefit from Share-based Compensation, Operating Activities	0.2	0
Federal income taxes	12	(1.2)
Net cash used in operating activities	(30.4)	(10.7)
Cash flows from investing activities:
Purchases of fixed maturities available-for-sale	(137.2)	(99)
Purchases of equity securities	(19.5)	(61.5)
Purchases of other invested assets	(1)	(0.5)
Maturities, calls and pay downs of fixed maturities available-for-sale	125.9	55.5
Sales of fixed maturities available-for-sale	65.6	15.3
Sales of equity securities	12.7	65.1
Sales of other invested assets	0.3	0.3
Net cash provided by (used in) investing activities	46.8	(24.8)
Cash flows from financing activities:
Proceeds from issuance of common stock	1	9.3
Payments to acquire treasury stock	(0.5)	(0.1)
Payment of dividends	(4.4)	(4.3)
Net cash (used in) provided by financing activities	(3.9)	4.9
Net increase (decrease) in cash and cash equivalents	12.5	(30.6)
Cash and cash equivalents at beginning of period	59.8
Cash and cash equivalents at end of period	72.3	60.9
Supplemental disclosures:
Interest paid (affiliates $0.2 and $0.2, respectively)	$ 1.7	$ 1.6

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Cash Flows [Abstract]
Interest Expense Debt To Affiliates	$ 0.2	$ 0.2

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements of State Auto Financial Corporation and Subsidiaries (“State Auto Financial” or the “Company”) have been prepared in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. generally accepted accounting principles (“GAAP”) for complete financial statements. In the opinion of the Company, all adjustments (consisting of normal, recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three months ended March 31, 2019 , are not necessarily indicative of the results that may be expected for the year ending December 31, 2019 . The balance sheet at December 31, 2018 , has been derived from the audited financial statements at that date, but does not include all of the information and footnotes required by GAAP for complete financial statements. For further information, refer to the consolidated financial statements and footnotes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 (the “ 2018 Form 10-K”). Capitalized terms used herein and not otherwise defined shall have the meaning ascribed to them in the 2018 Form 10-K. Revisions of Previously Issued Financial Statements Revisions to certain line items in the consolidated statements of comprehensive income and consolidated statements of cash flows for the three months ended March 31, 2018, were affected by revisions of previously issued financial statements. All such changes to the consolidated statements of cash flows were included within cash flows from operating activities and all related changes in the consolidated statements of comprehensive income were isolated to unrecognized benefit plan obligations. The basis of these revisions were described in Note 2 to our Consolidated Financial Statements set forth in Part II, Item 8, "Financial Statements and Supplementary Data" included in our most recent Annual Report disclosures on Form 10-K for the year ended December 31, 2018. Adoption of Recent Accounting Pronouncements Leases In February 2016, the FASB issued ASU 2016-02, "Leases (Topic 842)" that amended previous guidance on lease accounting. The new guidance requires the recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases under previous GAAP. The guidance became effective beginning January 1, 2019 and it did not have a material impact on the Company’s results of operations, consolidated financial position or cash flows. The Company has elected the practical expedients contained in ASC 842-10-65-1(f) and therefore did not reassess the lease classification of its existing leases. Pending Adoption of Recent Accounting Pronouncements For information regarding other accounting pronouncements that the Company has not yet adopted, see the “Pending Adoption of Recent Accounting Pronouncements” section of Note 1 of the Notes to Consolidated Financial Statements in the 2018 Form 10-K.

Investments

Investments	3 Months Ended
	Mar. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Investments	Investments The following tables set forth the cost or amortized cost and fair value of investments by lot at March 31, 2019 and December 31, 2018 : ($ millions) Cost or amortized cost Gross unrealized holding gains Gross unrealized holding losses Fair value March 31, 2019 Available-for-sale fixed maturities: U.S. treasury securities and obligations of U.S. government agencies $ 399.9 $ 6.7 $ (5.0 ) $ 401.6 Obligations of states and political subdivisions 458.1 14.0 (0.1 ) 472.0 Corporate securities 515.2 4.2 (3.3 ) 516.1 U.S. government agencies mortgage-backed securities 757.7 4.9 (15.7 ) 746.9 Total available-for-sale fixed maturities $ 2,130.9 $ 29.8 $ (24.1 ) $ 2,136.6 ($ millions) Cost or amortized cost Gross unrealized holding gains Gross unrealized holding losses Fair value December 31, 2018 Available-for-sale fixed maturities: U.S. treasury securities and obligations of U.S. government agencies $ 438.4 $ 3.2 $ (9.2 ) $ 432.4 Obligations of states and political subdivisions 408.2 7.3 (0.9 ) 414.6 Corporate securities 551.7 0.6 (11.7 ) 540.6 U.S. government agencies mortgage-backed securities 789.9 3.3 (21.3 ) 771.9 Total available-for-sale fixed maturities $ 2,188.2 $ 14.4 $ (43.1 ) $ 2,159.5 The following tables set forth the Company’s gross unrealized losses and fair value on its investments by lot, aggregated by investment category and length of time for individual securities that have been in a continuous unrealized loss position at March 31, 2019 and December 31, 2018 : ($ millions, except # of positions) Less than 12 months 12 months or more Total Fair value Unrealized losses Number of positions Fair value Unrealized losses Number of positions Fair value Unrealized losses Number of positions March 31, 2019 Fixed maturities: U.S. treasury securities and obligations of U.S. government agencies $ 9.2 $ (0.1 ) 1 $ 235.4 $ (4.9 ) 30 $ 244.6 $ (5.0 ) 31 Obligations of states and political subdivisions — — — 42.5 (0.1 ) 7 42.5 (0.1 ) 7 Corporate securities 9.1 — 1 234.2 $ (3.3 ) 32 243.3 $ (3.3 ) 33 U.S. government agencies mortgage-backed securities 54.1 (1.6 ) 8 430.4 (14.1 ) 68 484.5 (15.7 ) 76 Total temporarily impaired securities $ 72.4 $ (1.7 ) 10 $ 942.5 $ (22.4 ) 137 $ 1,014.9 $ (24.1 ) 147 ($ millions, except # of positions) Less than 12 months 12 months or more Total Fair value Unrealized losses Number of positions Fair value Unrealized losses Number of positions Fair value Unrealized losses Number of positions December 31, 2018 Fixed maturities: U.S. treasury securities and obligations of U.S. government agencies $ 83.1 $ (1.8 ) 7 $ 259.6 $ (7.4 ) 35 $ 342.7 $ (9.2 ) 42 Obligations of states and political subdivisions 63.6 (0.5 ) 7 39.6 (0.4 ) 8 103.2 (0.9 ) 15 Corporate securities 244.0 (3.0 ) 31 189.5 (8.7 ) 30 433.5 (11.7 ) 61 U.S. government agencies mortgage-backed securities 169.5 (2.8 ) 18 385.5 (18.5 ) 70 555.0 (21.3 ) 88 Total fixed maturities $ 560.2 $ (8.1 ) 63 $ 874.2 $ (35.0 ) 143 $ 1,434.4 $ (43.1 ) 206 The Company reviewed its investments at March 31, 2019 , and determined that no other-than-temporary impairment ("OTTI") existed in the gross unrealized holding losses. The Company regularly monitors its available-for-sale investments that have fair values less than cost or amortized cost for signs of other-than-temporary impairment, an assessment that requires significant management judgment regarding the evidence known. Such judgments could change in the future as more information becomes known, which could negatively impact the amounts reported. Among the factors that management considers for fixed maturity securities are the financial condition of the issuer including receipt of scheduled principal and interest cash flows, and intent to sell, including if it is more likely than not that the Company will be required to sell the investments before recovery. When a fixed maturity has been determined to have an other-than-temporary impairment, the impairment charge is separated into an amount representing the credit loss, which is recognized in earnings as a realized loss, and the amount related to non-credit factors, which is recognized in accumulated other comprehensive income. Future increases or decreases in fair value, if not other-than-temporary, are included in accumulated other comprehensive income. The following table sets forth the amortized cost and fair value of available-for-sale fixed maturities by contractual maturity at March 31, 2019 : ($ millions) Amortized cost Fair value Due in 1 year or less $ 101.5 $ 101.5 Due after 1 year through 5 years 631.8 629.4 Due after 5 years through 10 years 208.5 214.4 Due after 10 years 431.4 444.4 U.S. government agencies mortgage-backed securities 757.7 746.9 Total $ 2,130.9 $ 2,136.6 Expected maturities may differ from contractual maturities because issuers may have the right to call or prepay the obligations with or without call or prepayment penalties. At March 31, 2019 , State Auto P&C had U.S. government agencies mortgage-backed fixed maturity securities, with a carrying value of approximately $106.5 million , that were pledged as collateral for the FHLB Loans (as defined in Note 3). In accordance with the terms of the FHLB Loans, State Auto P&C retains all rights regarding these pledged securities. At March 31, 2019 , State Auto P&C had fixed maturities with fair values of approximately $21.6 million pledged as collateral for the performance obligations under its reinsurance agreement with Home State County Mutual Insurance Company. In accordance with the terms of the trust agreement, State Auto P&C retains all rights regarding these securities, which are included in the “U.S. government agencies mortgage-backed securities” classification of the Company’s fixed maturity securities portfolio. Fixed maturities with fair values of $9.1 million and $8.9 million were on deposit with insurance regulators as required by law at March 31, 2019 , and December 31, 2018 , respectively. The Company retains all rights regarding these securities. The following table sets forth the components of net investment income for the three months ended March 31, 2019 and 2018 : ($ millions) Three months ended March 31 2019 2018 Fixed maturities $ 15.1 $ 16.1 Equity securities 2.8 2.5 Cash and cash equivalents, and other 1.7 1.7 Investment income 19.6 20.3 Investment expenses 0.2 0.4 Net investment income $ 19.4 $ 19.9 The Company’s current investment strategy does not rely on the use of derivative financial instruments. Proceeds on sales of investments were $78.6 million and $80.7 million for the three months ended March 31, 2019 , and 2018 , respectively. The following table sets forth the realized and unrealized holding gains (losses) on the Company’s investment portfolio for the three months ended March 31, 2019 and 2018 : ($ millions) Three months ended March 31 2019 2018 Realized gains on sales of securities: Fixed maturities $ 0.1 $ 0.4 Equity securities 0.3 3.3 Other invested assets — 0.1 Total realized gains 0.4 3.8 Realized losses on sales of securities: Sales of equity securities (2.2 ) (0.2 ) Total realized losses (2.2 ) (0.2 ) Net realized (loss) gain on investments $ (1.8 ) $ 3.6 Net unrealized gain (loss) on investments (1) Equity securities $ 44.1 $ (14.6 ) Other invested assets 3.9 (0.7 ) Net unrealized gain (loss) on investments 48.0 (15.3 ) Other net realized loss $ (1.3 ) $ — Net investment gain (loss) $ 44.9 $ (11.7 ) Change in unrealized holding gains (losses), net of tax: Fixed maturities $ 34.4 $ (37.1 ) Deferred federal income tax (liability) benefit (7.2 ) 7.8 Change in net unrealized holding gains (losses), net of tax $ 27.2 $ (29.3 ) (1) Unrealized holding gains (losses) recognized during the period on securities still held at the reporting date

Fair Value of Financial Instrum

Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments Below is the fair value hierarchy that categorizes into three levels the inputs to valuation techniques that are used to measure fair value: • Level 1 includes observable inputs which reflect quoted prices for identical assets or liabilities in active markets at the measurement date. • Level 2 includes observable inputs for assets or liabilities other than quoted prices included in Level 1, and it includes valuation techniques which use prices for similar assets and liabilities. • Level 3 includes unobservable inputs which reflect the reporting entity’s estimates of the assumptions that market participants would use in pricing the asset or liability (including assumptions about risk). The Company utilizes a nationally recognized pricing service to estimate the majority of its investment portfolio’s fair value. The Company obtains one price per security and the processes and control procedures employed by the Company are designed to ensure the value is accurately recorded on an unadjusted basis. Through discussions with the pricing service, the Company gains an understanding of the methodologies used to price the different types of securities, that the data and the valuation methods utilized are appropriate and consistently applied, and that the assumptions are reasonable and representative of fair value. To validate the reasonableness of the valuations obtained from the pricing service, the Company compares to other fair value pricing information gathered from other independent pricing sources. At March 31, 2019 , and December 31, 2018 , the Company did not adjust any of the prices received from the pricing service. Fixed Maturities The Company utilizes a nationally recognized third party pricing service to estimate fair value measurements for the majority of its fixed maturities. The fair value estimate of the Company’s fixed maturity investments are determined by evaluations that are based on observable market information rather than market quotes. Inputs to the evaluations include, but are not limited to, market prices from recently completed transactions and transactions of comparable securities, interest rate yield curves, credit spreads, and other market-observable information. The fixed maturity portfolio pricing obtained from the pricing service is reviewed for reasonableness. The Company regularly selects a sample of security prices which are compared to one or more alternative pricing sources for reasonableness. Any discrepancies with the pricing are returned to the pricing service for further explanation and, if necessary, adjustments are made. To date, the Company has not identified any significant discrepancies in the pricing provided by its third party pricing service. Investments valued using these inputs include U.S. treasury securities and obligations of U.S. government agencies, obligations of states and political subdivisions, corporate securities (except for a security discussed below), and U.S. government agencies' mortgage-backed securities. All unadjusted estimates of fair value for fixed maturities priced by the pricing service are included in the amounts disclosed in Level 2 of the hierarchy. If market inputs are unavailable, then no fair value is provided by the pricing service. For these securities, fair value is determined either by requesting brokers who are knowledgeable about these securities to provide a quote; or the Company internally determines the fair values by employing widely accepted pricing valuation models, and depending on the level of observable market inputs, renders the fair value estimate as Level 2 or Level 3. Transfers between level categorizations may occur due to changes in the availability of market observable inputs. Transfers in and out of level categorizations are reported as having occurred at the beginning of the quarter in which the transfer occurred. Equities The fair value of each equity security is based on an observable market price for an identical asset in an active market and is priced by the same pricing service discussed above. All equity securities are recorded using unadjusted market prices and have been disclosed in Level 1. Other Invested Assets Included in other invested assets is one international fund (“the fund”) that invests in equity securities of foreign issuers and is managed by a third party investment manager. The fund had a fair value of $41.2 million and $38.5 million at March 31, 2019 , and December 31, 2018 , respectively, which was determined using the fund’s net asset value. The Company employs procedures to assess the reasonableness of the fair value of the fund, including obtaining and reviewing the fund’s audited financial statements. There are no unfunded commitments related to the fund. The Company may not sell its investment in the fund; however, the Company may redeem all or a portion of its investment in the fund at net asset value per share with the appropriate prior written notice. In accordance with Accounting Standard Codification 820-10, this investment is measured at fair value using the net asset value per share practical expedient and has not been classified in the fair value hierarchy. Fair values presented here are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the condensed consolidated balance sheets. The remainder of the Company’s other invested assets consist primarily of holdings in publicly-traded mutual funds. The Company believes that its prices for these publicly-traded mutual funds based on an observable market price for an identical asset in an active market reflect their fair values and consequently these securities have been disclosed in Level 1. The following tables set forth the Company’s investments within the fair value hierarchy at March 31, 2019 and December 31, 2018 : ($ millions) Total Level 1 Level 2 March 31, 2019 Available-for-sale fixed maturities: U.S. treasury securities and obligations of U.S. government agencies $ 401.6 $ — $ 401.6 Obligations of states and political subdivisions 472.0 — 472.0 Corporate securities 516.1 — 516.1 U.S. government agencies mortgage-backed securities 746.9 — 746.9 Total available-for-sale fixed maturities 2,136.6 — 2,136.6 Equity securities: Large-cap securities 88.9 88.9 — Mutual and exchange traded funds 275.0 275.0 — Total equity securities 363.9 363.9 — Other invested assets 12.3 12.3 — Total investments $ 2,512.8 $ 376.2 $ 2,136.6 ($ millions) Total Level 1 Level 2 December 31, 2018 Fixed maturities: U.S. treasury securities and obligations of U.S. government agencies $ 432.4 $ — $ 432.4 Obligations of states and political subdivisions 414.6 — 414.6 Corporate securities 540.6 — 540.6 U.S. government agencies mortgage-backed securities 771.9 — 771.9 Total fixed maturities 2,159.5 — 2,159.5 Equity securities: Large-cap securities 77.2 77.2 — Mutual and exchange traded funds 237.8 237.8 — Total equity securities 315.0 315.0 — Other invested assets 10.3 10.3 — Total available-for-sale investments $ 2,484.8 $ 325.3 $ 2,159.5 The following sections describe the valuation methods used by the Company for each type of financial instrument it holds that is not measured at fair value but for which fair value is disclosed: Financial Instruments Disclosed, But Not Carried, At Fair Value Other Invested Assets, at Cost Included in other invested assets, at cost are common stock of the Federal Home Loan Bank of Cincinnati (the "FHLB") and the Trust Securities. The Trust Securities and FHLB common stock are carried at cost, which approximates fair value. The fair value of the FHLB common stock at March 31, 2019 , was $5.1 million and the fair value of the Trust Securities was $0.5 million . The investments have been placed in Level 3 of the fair value hierarchy. Notes Receivable from Affiliate In May 2009, the Company entered into two separate credit agreements with State Automobile Mutual Insurance Company (“State Auto Mutual") pursuant to which it loaned State Auto Mutual a total of $70.0 million . The Company estimates the fair value of the notes receivable from affiliate using market quotations for U.S. treasury securities with similar maturity dates and applies an appropriate credit spread. Consequently this has been placed in Level 2 of the fair value hierarchy. ($ millions, except interest rates) March 31, 2019 December 31, 2018 Carrying value Fair value Interest rate Carrying value Fair value Interest rate Notes receivable from affiliate $ 70.0 $ 72.1 7.00 % $ 70.0 $ 71.1 7.00 % Notes Payable Included in notes payable are the FHLB Loans and Subordinated Debentures. The Company estimates the fair value of the FHLB Loans by discounting cash flows using a borrowing rate currently available to the Company for loans with similar terms. The FHLB Loans have been placed in Level 3 of the fair value hierarchy. The carrying amount of the Subordinated Debentures approximates its fair value as the interest rate adjusts quarterly and has been disclosed in Level 3. ($ millions, except interest rates) March 31, 2019 December 31, 2018 Carrying value Fair Value Interest rate Carrying value Fair value Interest rate FHLB Loan due 2021: issued $21.5, September 2016 with fixed interest $ 21.5 $ 21.1 1.73 % $ 21.5 $ 20.9 1.73 % FHLB Loan due 2033: issued $85.0, May 2018 with fixed interest 85.3 92.8 3.96 % 85.3 89.0 3.96 % Affiliate Subordinated Debentures due 2033: issued $15.5, May 2003 with variable interest 15.2 15.2 6.83 % 15.2 15.2 6.94 % Total notes payable $ 122.0 $ 129.1 $ 122.0 $ 125.1

Losses and Loss Expenses Payabl

Losses and Loss Expenses Payable Losses and Loss Expenses Payable	3 Months Ended
	Mar. 31, 2019
Losses and Loss Expenses Payable [Abstract]
Liability for Future Policy Benefits and Unpaid Claims Disclosure [Text Block]	. Losses and Loss Expenses Payable The following table sets forth the activity in the liability for losses and loss expenses for the three months ended March 31, 2019 and 2018 : ($ millions) 2019 2018 Losses and loss expenses payable, at beginning of period $ 1,146.8 $ 1,255.6 Less: reinsurance recoverable on losses and loss expenses payable 5.5 3.1 Net balance at beginning of period 1,141.3 1,252.5 Incurred related to: Current year 215.7 232.7 Prior years (21.4 ) (20.4 ) Total incurred 194.3 212.3 Paid related to: Current year 59.3 63.0 Prior years 152.0 156.3 Total paid 211.3 219.3 Net balance at end of period 1,124.3 1,245.5 Plus: reinsurance recoverable on losses and loss expenses payable 4.6 2.1 Losses and loss expenses payable, at end of period $ 1,128.9 $ 1,247.6 The Company recorded favorable development related to prior years’ loss and loss expense reserves for the three months ended March 31, 2019 , of $21.4 million compared to favorable development of $20.4 million for the same 2018 period. Favorable development of prior accident years' non-catastrophe loss and ALAE reserves for the three months ended March 31, 2019 was $20.9 million . In the personal insurance segment, personal auto contributed $6.8 million of favorable development, primarily attributable to lower than anticipated severity from the 2018 accident year partially offset by $0.6 million of adverse development in homeowners, primarily from the 2018 accident year. In the commercial insurance segment, all products developed favorably, with small commercial package, workers' compensation, and middle market commercial contributing $4.8 million , $4.5 million , and $3.1 million , respectively. Slightly offsetting the favorable development was adverse development in the specialty run-off business of $1.3 million , primarily driven by large fire losses in the fourth quarter of 2018 in E&S property. Favorable development of prior accident years' non-catastrophe loss and ALAE reserves for the three months ended March 31, 2018 was primarily due to $16.3 million of favorable development in the commercial and personal insurance segments. In the personal insurance segment, personal auto contributed $4.0 million of favorable development, primarily attributable to the 2016 and 2017 accident years, and homeowners' contributed $2.8 million of favorable development, spread across several accident years. In the commercial insurance segment, commercial auto, middle market commercial and workers' compensation contributed $3.5 million , $2.5 million and $2.3 million , respectively, of favorable development. Slightly offsetting the favorable development was adverse development in the specialty insurance segment of $0.3 million . The specialty insurance segment was impacted by $1.9 million of adverse development in E&S casualty, due primarily to development within our general liability and healthcare books of business. Favorable development of prior years' unallocated loss adjustment expenses was approximately $3.8 million .

Reinsurance

Reinsurance	3 Months Ended
	Mar. 31, 2019
Insurance [Abstract]
Reinsurance	Reinsurance The insurance subsidiaries of State Auto Financial, including State Auto P&C, Milbank and SA Ohio (collectively referred to as the “STFC Pooled Companies”) participate in a quota share reinsurance pooling arrangement (“the Pooling Arrangement”) with State Auto Mutual and its subsidiaries and affiliates (collectively referred to as the “Mutual Pooled Companies”). The following table sets forth a summary of the Company’s external reinsurance transactions, as well as reinsurance transactions with State Auto Mutual under the Pooling Arrangement, for the three months ended March 31, 2019 and 2018 : ($ millions) Three months ended March 31 2019 2018 Premiums earned: Assumed from external insurers and reinsurers $ 18.2 $ 10.4 Assumed under Pooling Arrangement 302.7 314.9 Ceded to external insurers and reinsurers (5.9 ) (5.4 ) Ceded under Pooling Arrangement (243.0 ) (216.9 ) Net assumed premiums earned $ 72.0 $ 103.0 Losses and loss expenses incurred: Assumed from external insurers and reinsurers $ 14.2 $ 10.9 Assumed under Pooling Arrangement 200.2 202.7 Ceded to external insurers and reinsurers (0.6 ) (1.3 ) Ceded under Pooling Arrangement (143.8 ) (156.5 ) Net assumed losses and loss expenses incurred $ 70.0 $ 55.8

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	. Income Taxes The following table sets forth the reconciliation between actual federal income tax expense and the amount computed at the indicated statutory rate for the three months ended March 31, 2019 and 2018 : ($ millions) Three months ended March 31 2019 2018 Amount at statutory rate $ 12.9 21.0 % $ (0.7 ) 21.0 % Tax-exempt interest and dividends received deduction (0.7 ) (1.1 ) (0.7 ) 20.8 Other, net — — 0.2 (5.7 ) Federal income tax expense (benefit) 12.2 19.9 % $ (1.2 ) 36.1 %

Pension and Postretirement Bene

Pension and Postretirement Benefit Plans	3 Months Ended
	Mar. 31, 2019
Retirement Benefits [Abstract]
Pension and Postretirement Benefit Plans	Pension and Postretirement Benefit Plans The following table sets forth information regarding the Company’s share of pension and postretirement benefit plans’ components of net periodic cost for the three months ended March 31, 2019 and 2018 : ($ millions) Pension Postretirement Three months ended March 31 2019 2018 2019 2018 Service cost $ 1.0 $ 1.3 $ — $ — Interest cost 2.9 2.7 0.2 0.2 Expected return on plan assets (4.2 ) (4.5 ) — — Amortization of: Negative prior service cost — — (1.4 ) (1.4 ) Net actuarial loss 1.5 2.1 0.1 0.1 Net periodic cost (benefit) $ 1.2 $ 1.6 $ (1.1 ) $ (1.1 ) The Company expects to contribute $15.0 million to its pension plan in 2019 .

Other Comprehensive Income and

Other Comprehensive Income and Accumulated Other Comprehensive Income	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Other Comprehensive Income and Accumulated Other Comprehensive Income	Other Comprehensive Income and Accumulated Other Comprehensive Income The following tables set forth the changes in the Company’s accumulated other comprehensive (loss) income ("AOC(L)I"), net of tax, for the three months ended March 31, 2019 and 2018 : ($ millions) Unrealized Gains and Losses on Available-for-Sale Securities Benefit Plan Items Total Beginning balance at January 1, 2019 $ (20.2 ) $ (76.2 ) $ (96.4 ) Other comprehensive income before reclassifications 27.3 — 27.3 Amounts reclassified from AOCI (a) (0.1 ) 0.6 0.5 Net current period other comprehensive income 27.2 0.6 27.8 Ending balance at March 31, 2019 $ 7.0 $ (75.6 ) $ (68.6 ) Beginning balance at January 1, 2018 $ 66.0 $ (62.2 ) $ 3.8 Cumulative effect of change in accounting for equity securities and other invested assets and reclassification of stranded tax effects as of January 1, 2018 (47.9 ) (16.0 ) (63.9 ) Other comprehensive loss before reclassifications (29.0 ) — (29.0 ) Amounts reclassified from AOCI (a) (0.3 ) 1.3 1.0 Net current period other comprehensive (loss) income (29.3 ) 1.3 (28.0 ) Ending balance at March 31, 2018 $ (11.2 ) $ (76.9 ) $ (88.1 ) (a) See separate table below for details about these reclassifications The following tables set forth the reclassifications out of accumulated other comprehensive income, by component, to the Company’s condensed consolidated statement of income for the three months ended March 31, 2019 and 2018 : ($ millions) Details about Accumulated Other Three months ended March 31 Affected line item in the Condensed Comprehensive Income Components Consolidated Statements of Income 2019 Unrealized gains on available-for-sale fixed maturity investments $ 0.1 Realized gains on sale of securities 0.1 Total before tax — Tax expense 0.1 Net of tax Amortization of benefit plan items Negative prior service cost 1.6 (b) Net actuarial loss (2.4 ) (b) (0.8 ) Total before tax 0.2 Tax benefit (0.6 ) Net of tax Total reclassifications for the period $ (0.5 ) (b) These accumulated other comprehensive income components are included in the computation of net periodic pension cost (see pension and postretirement benefit plans footnote for additional details). ($ millions) Details about Accumulated Other Three months ended March 31 Affected line item in the Condensed Comprehensive Income Components Consolidated Statements of Income 2018 Unrealized gains on available for sale securities $ 0.4 Realized gain on sale of securities 0.4 Total before tax (0.1 ) Tax expense 0.3 Net of tax Amortization of benefit plan items Negative prior service cost 1.6 (b) Net actuarial loss (3.3 ) (b) (1.7 ) Total before tax 0.4 Tax benefit (1.3 ) Net of tax Total reclassifications for the period $ (1.0 ) (b) These accumulated other comprehensive income components are included in the computation of net periodic pension cost (see pension and postretirement benefit plans footnote for additional details).

Earnings per Common Share

Earnings per Common Share	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Earnings (Loss) per Common Share	Net Earnings (Loss) per Common Share The following table sets forth the compilation of basic and diluted earnings per common share for the three months ended March 31, 2019 and 2018 : ($ and shares in millions, except per share amounts) Three months ended March 31 2019 2018 Numerator: Net income (loss) for basic earnings per common share $ 49.4 $ (2.1 ) Denominator: Weighted average shares for basic earnings (loss) per common share 43.3 42.6 Effect of dilutive share-based awards 0.6 — Adjusted weighted average shares for diluted net earnings (loss) per common share 43.9 42.6 Basic net earnings (loss) per common share $ 1.14 $ (0.05 ) Diluted net earnings (loss) per common share $ 1.12 $ (0.05 ) The following table sets forth common stock options, stock awards and restricted share units ("RSU award") of the Company that were not included in the computation of diluted earnings per common share because the exercise price of the options, or awards, was greater than the average market price or their inclusion would have been antidilutive for the three months ended March 31, 2019 and 2018 : (shares in millions) Three months ended March 31 2019 2018 Total number of antidilutive options and awards — 0.7

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Segment Information	Segment Information The Company changed its reportable segments from four to three effective January 1, 2019. The exit from the specialty insurance business resulted in the elimination of specialty insurance as a reportable segment as it no longer is material to the Company's results and is disclosed as "specialty run-off." The three remaining reportable segments are: personal insurance, commercial insurance, and investment operations. The reportable insurance segments are business units managed separately because of the differences in the type of customers they serve, the products they provide or services they offer. The insurance segments market a broad line of property and casualty insurance products throughout the United States through independent insurance agencies, which include retail agents and wholesale brokers. The investment operations segment, managed by Stateco, provides investment services. The Company evaluates the performance of its insurance segments using industry financial measurements based on Statutory Accounting Practices (“SAP”), which include loss and loss adjustment expense ratios, underwriting expense ratios, combined ratios, statutory underwriting gain (loss), net premiums earned and net written premiums. One of the most significant differences between SAP and GAAP is that SAP requires all underwriting expenses to be expensed immediately and not deferred and amortized over the same period the premium is earned. The investment operations segment is evaluated based on investment returns of assets managed by Stateco. Asset information by segment is not reported for the insurance segments because the Company does not produce such information internally. The following table sets forth financial information regarding the Company’s reportable segments and specialty run-off for the three months ended March 31, 2019 and 2018 : ($ millions) Three months ended March 31 2019 2018 Revenue from external sources: Insurance operations Personal insurance $ 181.5 $ 156.3 Commercial insurance 116.4 114.9 Specialty run-off 4.8 43.7 Total insurance operations 302.7 314.9 Investment operations Net investment income 19.4 19.9 Net investment gain 44.9 (11.7 ) Total investment operations 64.3 8.2 All other 0.6 0.6 Total revenue from external sources 367.6 323.7 Intersegment revenue 1.6 1.6 Total revenue 369.2 325.3 Reconciling items: Eliminate intersegment revenue (1.6 ) (1.6 ) Total consolidated revenues $ 367.6 $ 323.7 Segment income before federal income tax: Insurance operations SAP underwriting gain (loss) Personal insurance $ 4.2 $ 1.7 Commercial insurance (5.9 ) (8.3 ) Specialty run-off (1.4 ) 1.6 Total insurance operations (3.1 ) (5.0 ) Investment operations Net investment income 19.4 19.9 Net investment gain (loss) 44.9 (11.7 ) Total investment operations 64.3 8.2 All other 0.1 0.1 Total segment income before reconciling items 61.3 3.3 Reconciling items: GAAP expense adjustments 4.1 (4.0 ) Interest expense on corporate debt 1.2 1.6 Corporate expenses (5.0 ) (4.2 ) Total reconciling items 0.3 (6.6 ) Total consolidated income (loss) before federal income tax expense $ 61.6 $ (3.3 ) Investable assets attributable to the Company’s investment operations segment totaled $2,701.9 million and $2,658.7 million at March 31, 2019 , and December 31, 2018 , respectively.

Contingencies and Litigation

Contingencies and Litigation	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Contingencies and Litigation	Contingencies and Litigation In accordance with the Contingencies Topic of the FASB's Accounting Standards Codification, the Company accrues for a litigation-related liability when it is probable that such a liability has been incurred and the amount can be reasonably estimated. The Company reviews all litigation on an ongoing basis when making accrual and disclosure decisions. For certain legal proceedings, the Company cannot reasonably estimate a loss or a range of loss, if any, particularly for proceedings that are in their early stages of development or where the plaintiffs seek indeterminate damages. Various factors, including, but not limited to, the outcome of potentially lengthy discovery and the resolution of important factual questions, may need to be determined before probability can be established or before a loss or range of loss can be reasonably estimated. If the loss contingency in question is not both probable and reasonably estimable, the Company does not establish an accrual and the matter will continue to be monitored for any developments that would make the loss contingency both probable and reasonably estimable. Based on currently available information known to the Company, it believes that its reserves for litigation-related liabilities are reasonable. However, in the event that a legal proceeding results in a substantial judgment against, or settlement by, the Company, there can be no assurance that any resulting liability or financial commitment would not have a material adverse effect on the financial condition, results of operations or cash flows of the consolidated financial statements of the Company. The Company is involved in lawsuits in the ordinary course of its business arising out of or otherwise related to its insurance policies. Additionally, from time to time the Company may be involved in lawsuits, including class actions, in the ordinary course of business but not arising out of or otherwise related to its insurance policies. These lawsuits are in various stages of development. The Company generally will contest these matters vigorously but may pursue settlement if appropriate. Based on currently available information, the Company does not believe it is reasonably possible that any such lawsuit or related lawsuits will be material to its results of operations or have a material adverse effect on its consolidated financial position, results of operations or cash flows. Additionally, the Company may be impacted by adverse regulatory actions and adverse court decisions where insurance coverages are expanded beyond the scope originally contemplated in its insurance policies. The Company believes that the effects, if any, of such regulatory actions and published court decisions are not likely to have a material adverse effect on its consolidated financial position, results of operations or cash flows.

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Cost or Amortized Cost and Fair Value of Available-for-Sale Securities	The following tables set forth the cost or amortized cost and fair value of investments by lot at March 31, 2019 and December 31, 2018 : ($ millions) Cost or amortized cost Gross unrealized holding gains Gross unrealized holding losses Fair value March 31, 2019 Available-for-sale fixed maturities: U.S. treasury securities and obligations of U.S. government agencies $ 399.9 $ 6.7 $ (5.0 ) $ 401.6 Obligations of states and political subdivisions 458.1 14.0 (0.1 ) 472.0 Corporate securities 515.2 4.2 (3.3 ) 516.1 U.S. government agencies mortgage-backed securities 757.7 4.9 (15.7 ) 746.9 Total available-for-sale fixed maturities $ 2,130.9 $ 29.8 $ (24.1 ) $ 2,136.6 ($ millions) Cost or amortized cost Gross unrealized holding gains Gross unrealized holding losses Fair value December 31, 2018 Available-for-sale fixed maturities: U.S. treasury securities and obligations of U.S. government agencies $ 438.4 $ 3.2 $ (9.2 ) $ 432.4 Obligations of states and political subdivisions 408.2 7.3 (0.9 ) 414.6 Corporate securities 551.7 0.6 (11.7 ) 540.6 U.S. government agencies mortgage-backed securities 789.9 3.3 (21.3 ) 771.9 Total available-for-sale fixed maturities $ 2,188.2 $ 14.4 $ (43.1 ) $ 2,159.5
Gross Unrealized Losses and Fair Value on its Investments	The following tables set forth the Company’s gross unrealized losses and fair value on its investments by lot, aggregated by investment category and length of time for individual securities that have been in a continuous unrealized loss position at March 31, 2019 and December 31, 2018 : ($ millions, except # of positions) Less than 12 months 12 months or more Total Fair value Unrealized losses Number of positions Fair value Unrealized losses Number of positions Fair value Unrealized losses Number of positions March 31, 2019 Fixed maturities: U.S. treasury securities and obligations of U.S. government agencies $ 9.2 $ (0.1 ) 1 $ 235.4 $ (4.9 ) 30 $ 244.6 $ (5.0 ) 31 Obligations of states and political subdivisions — — — 42.5 (0.1 ) 7 42.5 (0.1 ) 7 Corporate securities 9.1 — 1 234.2 $ (3.3 ) 32 243.3 $ (3.3 ) 33 U.S. government agencies mortgage-backed securities 54.1 (1.6 ) 8 430.4 (14.1 ) 68 484.5 (15.7 ) 76 Total temporarily impaired securities $ 72.4 $ (1.7 ) 10 $ 942.5 $ (22.4 ) 137 $ 1,014.9 $ (24.1 ) 147 ($ millions, except # of positions) Less than 12 months 12 months or more Total Fair value Unrealized losses Number of positions Fair value Unrealized losses Number of positions Fair value Unrealized losses Number of positions December 31, 2018 Fixed maturities: U.S. treasury securities and obligations of U.S. government agencies $ 83.1 $ (1.8 ) 7 $ 259.6 $ (7.4 ) 35 $ 342.7 $ (9.2 ) 42 Obligations of states and political subdivisions 63.6 (0.5 ) 7 39.6 (0.4 ) 8 103.2 (0.9 ) 15 Corporate securities 244.0 (3.0 ) 31 189.5 (8.7 ) 30 433.5 (11.7 ) 61 U.S. government agencies mortgage-backed securities 169.5 (2.8 ) 18 385.5 (18.5 ) 70 555.0 (21.3 ) 88 Total fixed maturities $ 560.2 $ (8.1 ) 63 $ 874.2 $ (35.0 ) 143 $ 1,434.4 $ (43.1 ) 206
Amortized Cost and Fair Value of Available-for-Sale Fixed Maturities by Contractual Maturity	The following table sets forth the amortized cost and fair value of available-for-sale fixed maturities by contractual maturity at March 31, 2019 : ($ millions) Amortized cost Fair value Due in 1 year or less $ 101.5 $ 101.5 Due after 1 year through 5 years 631.8 629.4 Due after 5 years through 10 years 208.5 214.4 Due after 10 years 431.4 444.4 U.S. government agencies mortgage-backed securities 757.7 746.9 Total $ 2,130.9 $ 2,136.6
Components of Net Investment Income	The following table sets forth the components of net investment income for the three months ended March 31, 2019 and 2018 : ($ millions) Three months ended March 31 2019 2018 Fixed maturities $ 15.1 $ 16.1 Equity securities 2.8 2.5 Cash and cash equivalents, and other 1.7 1.7 Investment income 19.6 20.3 Investment expenses 0.2 0.4 Net investment income $ 19.4 $ 19.9
Realized and Unrealized Holding Gains (Losses)	The following table sets forth the realized and unrealized holding gains (losses) on the Company’s investment portfolio for the three months ended March 31, 2019 and 2018 : ($ millions) Three months ended March 31 2019 2018 Realized gains on sales of securities: Fixed maturities $ 0.1 $ 0.4 Equity securities 0.3 3.3 Other invested assets — 0.1 Total realized gains 0.4 3.8 Realized losses on sales of securities: Sales of equity securities (2.2 ) (0.2 ) Total realized losses (2.2 ) (0.2 ) Net realized (loss) gain on investments $ (1.8 ) $ 3.6 Net unrealized gain (loss) on investments (1) Equity securities $ 44.1 $ (14.6 ) Other invested assets 3.9 (0.7 ) Net unrealized gain (loss) on investments 48.0 (15.3 ) Other net realized loss $ (1.3 ) $ — Net investment gain (loss) $ 44.9 $ (11.7 ) Change in unrealized holding gains (losses), net of tax: Fixed maturities $ 34.4 $ (37.1 ) Deferred federal income tax (liability) benefit (7.2 ) 7.8 Change in net unrealized holding gains (losses), net of tax $ 27.2 $ (29.3 ) (1) Unrealized holding gains (losses) recognized during the period on securities still held at the reporting date

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Company's Available-for-Sale Investments within Fair Value Hierarchy	The following tables set forth the Company’s investments within the fair value hierarchy at March 31, 2019 and December 31, 2018 : ($ millions) Total Level 1 Level 2 March 31, 2019 Available-for-sale fixed maturities: U.S. treasury securities and obligations of U.S. government agencies $ 401.6 $ — $ 401.6 Obligations of states and political subdivisions 472.0 — 472.0 Corporate securities 516.1 — 516.1 U.S. government agencies mortgage-backed securities 746.9 — 746.9 Total available-for-sale fixed maturities 2,136.6 — 2,136.6 Equity securities: Large-cap securities 88.9 88.9 — Mutual and exchange traded funds 275.0 275.0 — Total equity securities 363.9 363.9 — Other invested assets 12.3 12.3 — Total investments $ 2,512.8 $ 376.2 $ 2,136.6 ($ millions) Total Level 1 Level 2 December 31, 2018 Fixed maturities: U.S. treasury securities and obligations of U.S. government agencies $ 432.4 $ — $ 432.4 Obligations of states and political subdivisions 414.6 — 414.6 Corporate securities 540.6 — 540.6 U.S. government agencies mortgage-backed securities 771.9 — 771.9 Total fixed maturities 2,159.5 — 2,159.5 Equity securities: Large-cap securities 77.2 77.2 — Mutual and exchange traded funds 237.8 237.8 — Total equity securities 315.0 315.0 — Other invested assets 10.3 10.3 — Total available-for-sale investments $ 2,484.8 $ 325.3 $ 2,159.5
Company Estimates Receivable from Affiliate using Market Quotations for U.S. Treasury Securities	Consequently this has been placed in Level 2 of the fair value hierarchy. ($ millions, except interest rates) March 31, 2019 December 31, 2018 Carrying value Fair value Interest rate Carrying value Fair value Interest rate Notes receivable from affiliate $ 70.0 $ 72.1 7.00 % $ 70.0 $ 71.1 7.00 %
Included in Notes Payable are Senior Notes and Subordinated Debentures	The carrying amount of the Subordinated Debentures approximates its fair value as the interest rate adjusts quarterly and has been disclosed in Level 3. ($ millions, except interest rates) March 31, 2019 December 31, 2018 Carrying value Fair Value Interest rate Carrying value Fair value Interest rate FHLB Loan due 2021: issued $21.5, September 2016 with fixed interest $ 21.5 $ 21.1 1.73 % $ 21.5 $ 20.9 1.73 % FHLB Loan due 2033: issued $85.0, May 2018 with fixed interest 85.3 92.8 3.96 % 85.3 89.0 3.96 % Affiliate Subordinated Debentures due 2033: issued $15.5, May 2003 with variable interest 15.2 15.2 6.83 % 15.2 15.2 6.94 % Total notes payable $ 122.0 $ 129.1 $ 122.0 $ 125.1

Losses and Loss Expenses Paya_2

Losses and Loss Expenses Payable Losses and Loss Expenses Payable (Tables)	3 Months Ended
	Mar. 31, 2019
Losses and Loss Expenses Payable [Abstract]
Schedule Of Activity In Liability For Unpaid Losses And Loss Adjustment Expenses Table [Table Text Block]	($ millions) 2019 2018 Losses and loss expenses payable, at beginning of period $ 1,146.8 $ 1,255.6 Less: reinsurance recoverable on losses and loss expenses payable 5.5 3.1 Net balance at beginning of period 1,141.3 1,252.5 Incurred related to: Current year 215.7 232.7 Prior years (21.4 ) (20.4 ) Total incurred 194.3 212.3 Paid related to: Current year 59.3 63.0 Prior years 152.0 156.3 Total paid 211.3 219.3 Net balance at end of period 1,124.3 1,245.5 Plus: reinsurance recoverable on losses and loss expenses payable 4.6 2.1 Losses and loss expenses payable, at end of period $ 1,128.9 $ 1,247.6

Reinsurance (Tables)

Reinsurance (Tables)	3 Months Ended
	Mar. 31, 2019
Insurance [Abstract]
Summary of External Reinsurance Transactions with State Auto Mutual Under Pooling Arrangement	The following table sets forth a summary of the Company’s external reinsurance transactions, as well as reinsurance transactions with State Auto Mutual under the Pooling Arrangement, for the three months ended March 31, 2019 and 2018 : ($ millions) Three months ended March 31 2019 2018 Premiums earned: Assumed from external insurers and reinsurers $ 18.2 $ 10.4 Assumed under Pooling Arrangement 302.7 314.9 Ceded to external insurers and reinsurers (5.9 ) (5.4 ) Ceded under Pooling Arrangement (243.0 ) (216.9 ) Net assumed premiums earned $ 72.0 $ 103.0 Losses and loss expenses incurred: Assumed from external insurers and reinsurers $ 14.2 $ 10.9 Assumed under Pooling Arrangement 200.2 202.7 Ceded to external insurers and reinsurers (0.6 ) (1.3 ) Ceded under Pooling Arrangement (143.8 ) (156.5 ) Net assumed losses and loss expenses incurred $ 70.0 $ 55.8

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Reconciliation Between Actual Federal Income Tax Benefit and Amount Computed at Indicated Statutory Rate	The following table sets forth the reconciliation between actual federal income tax expense and the amount computed at the indicated statutory rate for the three months ended March 31, 2019 and 2018 : ($ millions) Three months ended March 31 2019 2018 Amount at statutory rate $ 12.9 21.0 % $ (0.7 ) 21.0 % Tax-exempt interest and dividends received deduction (0.7 ) (1.1 ) (0.7 ) 20.8 Other, net — — 0.2 (5.7 ) Federal income tax expense (benefit) 12.2 19.9 % $ (1.2 ) 36.1 %

Pension and Postretirement Be_2

Pension and Postretirement Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2019
Retirement Benefits [Abstract]
Company's Share of Net Periodic Cost Components	for the three months ended March 31, 2019 and 2018 : ($ millions) Pension Postretirement Three months ended March 31 2019 2018 2019 2018 Service cost $ 1.0 $ 1.3 $ — $ — Interest cost 2.9 2.7 0.2 0.2 Expected return on plan assets (4.2 ) (4.5 ) — — Amortization of: Negative prior service cost — — (1.4 ) (1.4 ) Net actuarial loss 1.5 2.1 0.1 0.1 Net periodic cost (benefit) $ 1.2 $ 1.6 $ (1.1 ) $ (1.1 )

Other Comprehensive Income an_2

Other Comprehensive Income and Accumulated Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Changes in Accumulated Other Comprehensive Income by Component, Net of Tax	The following tables set forth the changes in the Company’s accumulated other comprehensive (loss) income ("AOC(L)I"), net of tax, for the three months ended March 31, 2019 and 2018 : ($ millions) Unrealized Gains and Losses on Available-for-Sale Securities Benefit Plan Items Total Beginning balance at January 1, 2019 $ (20.2 ) $ (76.2 ) $ (96.4 ) Other comprehensive income before reclassifications 27.3 — 27.3 Amounts reclassified from AOCI (a) (0.1 ) 0.6 0.5 Net current period other comprehensive income 27.2 0.6 27.8 Ending balance at March 31, 2019 $ 7.0 $ (75.6 ) $ (68.6 ) Beginning balance at January 1, 2018 $ 66.0 $ (62.2 ) $ 3.8 Cumulative effect of change in accounting for equity securities and other invested assets and reclassification of stranded tax effects as of January 1, 2018 (47.9 ) (16.0 ) (63.9 ) Other comprehensive loss before reclassifications (29.0 ) — (29.0 ) Amounts reclassified from AOCI (a) (0.3 ) 1.3 1.0 Net current period other comprehensive (loss) income (29.3 ) 1.3 (28.0 ) Ending balance at March 31, 2018 $ (11.2 ) $ (76.9 ) $ (88.1 ) (a) See separate table below for details about these reclassifications
Schedule of Reclassifications Out of Accumulated Other Comprehensive Income by Component	The following tables set forth the reclassifications out of accumulated other comprehensive income, by component, to the Company’s condensed consolidated statement of income for the three months ended March 31, 2019 and 2018 : ($ millions) Details about Accumulated Other Three months ended March 31 Affected line item in the Condensed Comprehensive Income Components Consolidated Statements of Income 2019 Unrealized gains on available-for-sale fixed maturity investments $ 0.1 Realized gains on sale of securities 0.1 Total before tax — Tax expense 0.1 Net of tax Amortization of benefit plan items Negative prior service cost 1.6 (b) Net actuarial loss (2.4 ) (b) (0.8 ) Total before tax 0.2 Tax benefit (0.6 ) Net of tax Total reclassifications for the period $ (0.5 ) (b) These accumulated other comprehensive income components are included in the computation of net periodic pension cost (see pension and postretirement benefit plans footnote for additional details). ($ millions) Details about Accumulated Other Three months ended March 31 Affected line item in the Condensed Comprehensive Income Components Consolidated Statements of Income 2018 Unrealized gains on available for sale securities $ 0.4 Realized gain on sale of securities 0.4 Total before tax (0.1 ) Tax expense 0.3 Net of tax Amortization of benefit plan items Negative prior service cost 1.6 (b) Net actuarial loss (3.3 ) (b) (1.7 ) Total before tax 0.4 Tax benefit (1.3 ) Net of tax Total reclassifications for the period $ (1.0 ) (b) These accumulated other comprehensive income components are included in the computation of net periodic pension cost (see pension and postretirement benefit plans footnote for additional details).

Earnings per Common Share (Tabl

Earnings per Common Share (Tables)	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Compilation of Basic and Diluted Earnings Per Common Share	The following table sets forth the compilation of basic and diluted earnings per common share for the three months ended March 31, 2019 and 2018 : ($ and shares in millions, except per share amounts) Three months ended March 31 2019 2018 Numerator: Net income (loss) for basic earnings per common share $ 49.4 $ (2.1 ) Denominator: Weighted average shares for basic earnings (loss) per common share 43.3 42.6 Effect of dilutive share-based awards 0.6 — Adjusted weighted average shares for diluted net earnings (loss) per common share 43.9 42.6 Basic net earnings (loss) per common share $ 1.14 $ (0.05 ) Diluted net earnings (loss) per common share $ 1.12 $ (0.05 )
Options to Purchase Shares of Common Stock	The following table sets forth common stock options, stock awards and restricted share units ("RSU award") of the Company that were not included in the computation of diluted earnings per common share because the exercise price of the options, or awards, was greater than the average market price or their inclusion would have been antidilutive for the three months ended March 31, 2019 and 2018 : (shares in millions) Three months ended March 31 2019 2018 Total number of antidilutive options and awards — 0.7

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Financial Information Regarding Company's Reportable Segments	The following table sets forth financial information regarding the Company’s reportable segments and specialty run-off for the three months ended March 31, 2019 and 2018 : ($ millions) Three months ended March 31 2019 2018 Revenue from external sources: Insurance operations Personal insurance $ 181.5 $ 156.3 Commercial insurance 116.4 114.9 Specialty run-off 4.8 43.7 Total insurance operations 302.7 314.9 Investment operations Net investment income 19.4 19.9 Net investment gain 44.9 (11.7 ) Total investment operations 64.3 8.2 All other 0.6 0.6 Total revenue from external sources 367.6 323.7 Intersegment revenue 1.6 1.6 Total revenue 369.2 325.3 Reconciling items: Eliminate intersegment revenue (1.6 ) (1.6 ) Total consolidated revenues $ 367.6 $ 323.7 Segment income before federal income tax: Insurance operations SAP underwriting gain (loss) Personal insurance $ 4.2 $ 1.7 Commercial insurance (5.9 ) (8.3 ) Specialty run-off (1.4 ) 1.6 Total insurance operations (3.1 ) (5.0 ) Investment operations Net investment income 19.4 19.9 Net investment gain (loss) 44.9 (11.7 ) Total investment operations 64.3 8.2 All other 0.1 0.1 Total segment income before reconciling items 61.3 3.3 Reconciling items: GAAP expense adjustments 4.1 (4.0 ) Interest expense on corporate debt 1.2 1.6 Corporate expenses (5.0 ) (4.2 ) Total reconciling items 0.3 (6.6 ) Total consolidated income (loss) before federal income tax expense $ 61.6 $ (3.3 )

Investments - Cost or Amortized

Investments - Cost or Amortized Cost and Fair Value of Available-for-Sale Securities (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Document Period End Date	Mar. 31, 2019
Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or amortized cost	$ 2,130.9	$ 2,188.2
Gross unrealized holding gains	29.8	14.4
Gross unrealized holding losses	(24.1)	(43.1)
Fair value	2,136.6	2,159.5
Fixed Maturities [Member] | U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or amortized cost	399.9	438.4
Gross unrealized holding gains	6.7	3.2
Gross unrealized holding losses	(5)	(9.2)
Fair value	401.6	432.4
Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or amortized cost	458.1	408.2
Gross unrealized holding gains	14	7.3
Gross unrealized holding losses	(0.1)	(0.9)
Fair value	472	414.6
Fixed Maturities [Member] | Corporate Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or amortized cost	515.2	551.7
Gross unrealized holding gains	4.2	0.6
Gross unrealized holding losses	(3.3)	(11.7)
Fair value	516.1	540.6
Fixed Maturities [Member] | U.S. Government Agencies Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or amortized cost	757.7	789.9
Gross unrealized holding gains	4.9	3.3
Gross unrealized holding losses	(15.7)	(21.3)
Fair value	$ 746.9	$ 771.9

Investments - Available for Sal

Investments - Available for Sale Securities Continuous Unrealized Loss Position Fair Value and Aggregate Losses (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)position	Dec. 31, 2018USD ($)position
Debt Securities, Available-for-sale [Line Items]
Document Period End Date	Mar. 31, 2019
Less than 12 months, Number of positions | position	10
12 months or more, Number of positions | position	137
Total, Number of positions | position	147
Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair value	$ 72.4	$ 560.2
Less than 12 months, Unrealized losses	(1.7)	$ (8.1)
Less than 12 months, Number of positions | position		63
12 months or more, Fair value	942.5	$ 874.2
12 months or more, Unrealized losses	(22.4)	$ (35)
12 months or more, Number of positions | position		143
Total, Fair value	1,014.9	$ 1,434.4
Total, Unrealized losses	(24.1)	$ (43.1)
Total, Number of positions | position		206
Fixed Maturities [Member] | U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair value	9.2	$ 83.1
Less than 12 months, Unrealized losses	$ (0.1)	$ (1.8)
Less than 12 months, Number of positions | position	1	7
12 months or more, Fair value	$ 235.4	$ 259.6
12 months or more, Unrealized losses	$ (4.9)	$ (7.4)
12 months or more, Number of positions | position	30	35
Total, Fair value	$ 244.6	$ 342.7
Total, Unrealized losses	$ (5)	$ (9.2)
Total, Number of positions | position	31	42
Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair value	$ 0	$ 63.6
Less than 12 months, Unrealized losses	$ 0	$ (0.5)
Less than 12 months, Number of positions | position	0	7
12 months or more, Fair value	$ 42.5	$ 39.6
12 months or more, Unrealized losses	$ (0.1)	$ (0.4)
12 months or more, Number of positions | position	7	8
Total, Fair value	$ 42.5	$ 103.2
Total, Unrealized losses	$ (0.1)	$ (0.9)
Total, Number of positions | position	7	15
Fixed Maturities [Member] | Corporate Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair value	$ 9.1	$ 244
Less than 12 months, Unrealized losses	$ 0	$ (3)
Less than 12 months, Number of positions | position	1	31
12 months or more, Fair value	$ 234.2	$ 189.5
12 months or more, Unrealized losses	$ (3.3)	$ (8.7)
12 months or more, Number of positions | position	32	30
Total, Fair value	$ 243.3	$ 433.5
Total, Unrealized losses	$ (3.3)	$ (11.7)
Total, Number of positions | position	33	61
Fixed Maturities [Member] | U.S. Government Agencies Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair value	$ 54.1	$ 169.5
Less than 12 months, Unrealized losses	$ (1.6)	$ (2.8)
Less than 12 months, Number of positions | position	8	18
12 months or more, Fair value	$ 430.4	$ 385.5
12 months or more, Unrealized losses	$ (14.1)	$ (18.5)
12 months or more, Number of positions | position	68	70
Total, Fair value	$ 484.5	$ 555
Total, Unrealized losses	$ (15.7)	$ (21.3)
Total, Number of positions | position	76	88

Investments - Amortized Cost an

Investments - Amortized Cost and Fair Value of Available-for-Sale Fixed Maturities by Contractual Maturity (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Amortized cost
Due in 1 year or less, Amortized cost	$ 101.5
Due after 1 year through 5 years, Amortized cost	631.8
Due after 5 years through 10 years, Amortized cost	208.5
Due after 10 years, Amortized cost	431.4
U.S. government agencies mortgage-backed securities, Amortized cost	757.7
Total, Amortized cost	2,130.9	$ 2,188.2
Fair value
Due in 1 year or less, Fair value	101.5
Due after 1 year through 5 years, Fair value	629.4
Due after 5 years through 10 years, Fair value	214.4
Due after 10 years, Fair value	444.4
U.S. government agencies mortgage-backed securities, Fair value	746.9
Total, Fair value	$ 2,136.6	$ 2,159.5

Investments - Components of Net

Investments - Components of Net Investment Income (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net Investment Income [Line Items]
Investment income	$ 19.6	$ 20.3
Investment expenses	0.2	0.4
Net investment income	19.4	19.9
Fixed Maturities [Member]
Net Investment Income [Line Items]
Investment income	15.1	16.1
Equity Securities [Member]
Net Investment Income [Line Items]
Investment income	2.8	2.5
Cash and Cash Equivalents, and Other [Member]
Net Investment Income [Line Items]
Investment income	$ 1.7	$ 1.7

Investments - Realized and Unre

Investments - Realized and Unrealized Holding Gains (Losses) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Realized gains:
Total realized gains	$ 0.4	$ 3.8
Realized losses:
Total realized losses	(2.2)	(0.2)
Net realized gain on investments	(1.8)	3.6
Unrealized Gain (Loss) on Investments	48	(15.3)
Other net realized loss	(1.3)	0
Realized Investment Gains (Losses)	(44.9)	11.7
Change in unrealized holding gains (losses), net of tax:
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax	(7.2)	7.8
Change in net unrealized holding (losses) gains, net of tax	27.2	(29.3)
Fixed Maturities [Member]
Realized gains:
Total realized gains	0.1	0.4
Change in unrealized holding gains (losses), net of tax:
Change in net unrealized holding (losses) gains, net of tax	34.4	(37.1)
Equity Securities [Member]
Realized gains:
Total realized gains	0.3	3.3
Realized losses:
Unrealized Gain (Loss) on Investments	44.1	(14.6)
Equity Securities [Member] | Sales [Member]
Realized losses:
Total realized losses	(2.2)	(0.2)
Other Invested Assets [Member]
Realized gains:
Total realized gains	0	0.1
Realized losses:
Unrealized Gain (Loss) on Investments	$ 3.9	$ (0.7)

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Document Period End Date	Mar. 31, 2019
Financial Instruments, Owned and Pledged as Collateral, at Fair Value	$ 21.6
Fixed maturities fair value of deposit with insurance regulators	9.1		$ 8.9
Proceeds on sale of available-for-sale securities	78.6	$ 80.7
Federal Home Loan Bank of Cincinnati [Member]
Debt Securities, Available-for-sale [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	$ 106.5

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Company's Available-for-Sale Investments within Fair Value Hierarchy (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Document Period End Date	Mar. 31, 2019
Investments, Fair Value Disclosure	$ 2,512.8		$ 2,484.8
Sales of other invested assets	0.3	$ 0.3
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Investments, Fair Value Disclosure	401.6		432.4
Obligations of States and Political Subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Investments, Fair Value Disclosure	472		414.6
Corporate Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investments, Fair Value Disclosure	516.1		540.6
U.S. Government Agencies Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investments, Fair Value Disclosure	746.9		771.9
Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Investments, Fair Value Disclosure	2,136.6		2,159.5
Large-Cap Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investments, Fair Value Disclosure	88.9		77.2
Mutual and exchange traded funds [Domain] [Member]
Debt Securities, Available-for-sale [Line Items]
Investments, Fair Value Disclosure	275		237.8
Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Investments, Fair Value Disclosure	363.9		315
Other Invested Assets [Member]
Debt Securities, Available-for-sale [Line Items]
Investments, Fair Value Disclosure	12.3		10.3
Level 1 [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	376.2		325.3
Level 1 [Member] | U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	0		0
Level 1 [Member] | Obligations of States and Political Subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	0		0
Level 1 [Member] | Corporate Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	0		0
Level 1 [Member] | U.S. Government Agencies Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	0		0
Level 1 [Member] | Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	0		0
Level 1 [Member] | Large-Cap Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	88.9		77.2
Level 1 [Member] | Mutual and exchange traded funds [Domain] [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	275		237.8
Level 1 [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	363.9		315
Level 1 [Member] | Other Invested Assets [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	12.3		10.3
Level 2 [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	2,136.6		2,159.5
Level 2 [Member] | U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	401.6		432.4
Level 2 [Member] | Obligations of States and Political Subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	472		414.6
Level 2 [Member] | Corporate Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	516.1		540.6
Level 2 [Member] | U.S. Government Agencies Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	746.9		771.9
Level 2 [Member] | Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	2,136.6		2,159.5
Level 2 [Member] | Large-Cap Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	0		0
Level 2 [Member] | Mutual and exchange traded funds [Domain] [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	0		0
Level 2 [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	0		0
Level 2 [Member] | Other Invested Assets [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	$ 0		$ 0

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Company Estimates Receivable from Affiliate using Market Quotations for U.S. Treasury Securities (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2017	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Document Period End Date	Mar. 31, 2019
Affiliated Entity [Member] | Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable interest rate (percent)	7.00%	7.00%
Reported Value Measurement [Member] | Affiliated Entity [Member] | Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable from affiliate	$ 70		$ 70
Estimate of Fair Value Measurement [Member] | Affiliated Entity [Member] | Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable from affiliate	$ 72.1		$ 71.1

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Included in Notes Payable are the FHLB loan and Subordinated Debentures (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Document Period End Date	Mar. 31, 2019
Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Interest rate (percent)	1.73%	1.73%
FHLB loan due and issued with fixed interest, Senior notes due and issued with fixed interest and Affiliate subordinated debentures due with variable interest	$ 21,500,000
Federal Home Loan Bank of Cincinnati [Member]
Debt Instrument [Line Items]
FHLB loan due and issued with fixed interest, Senior notes due and issued with fixed interest and Affiliate subordinated debentures due with variable interest	$ 85,000,000
Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Interest rate (percent)	3.96%	3.96%
Affiliate Subordinated Debentures Due 2033 [Member]
Debt Instrument [Line Items]
Interest rate (percent)	6.82613%	6.93813%
FHLB loan due and issued with fixed interest, Senior notes due and issued with fixed interest and Affiliate subordinated debentures due with variable interest	$ 15,500,000
Reported Value Measurement [Member]
Debt Instrument [Line Items]
Total notes payable	122,000,000	$ 122,000,000
Reported Value Measurement [Member] | Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Total notes payable	21,500,000	21,500,000
Reported Value Measurement [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Total notes payable	85,300,000	85,300,000
Reported Value Measurement [Member] | Affiliate Subordinated Debentures Due 2033 [Member]
Debt Instrument [Line Items]
Total notes payable	15,200,000	15,200,000
Estimate of Fair Value Measurement [Member]
Debt Instrument [Line Items]
Total notes payable	129,100,000	125,100,000
Estimate of Fair Value Measurement [Member] | Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Total notes payable	21,100,000	20,900,000
Estimate of Fair Value Measurement [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Total notes payable	92,800,000	89,000,000
Estimate of Fair Value Measurement [Member] | Affiliate Subordinated Debentures Due 2033 [Member]
Debt Instrument [Line Items]
Total notes payable	$ 15,200,000	$ 15,200,000

Fair Value of Financial Instr_6

Fair Value of Financial Instruments - Additional Information (Detail) $ in Millions	1 Months Ended	3 Months Ended
	May 31, 2009Agreement	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Fair Value Measurements Disclosure [Line Items]
Document Period End Date		Mar. 31, 2019
Other invested assets, at cost		$ 5.6	$ 5.6
Number of Credit Agreements | Agreement	2
Notes receivable from affiliate		70	70
Level 3 [Member]
Fair Value Measurements Disclosure [Line Items]
Federal home loan bank stock		5.1
Other invested assets, at cost		0.5
Fair Value, Inputs, Level 2 [Member]
Fair Value Measurements Disclosure [Line Items]
Fair value		2,136.6	2,159.5
Corporate Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Measurements Disclosure [Line Items]
Fair value		$ 516.1	540.6
International funds [Member]
Fair Value Measurements Disclosure [Line Items]
Number of available for sale securities		1
Fair value		$ 41.2	$ 38.5
Affiliated Entity [Member]
Fair Value Measurements Disclosure [Line Items]
Notes receivable from affiliate		$ 70

Losses and Loss Expenses Paya_3

Losses and Loss Expenses Payable Losses and Loss Expenses Payable - Schedule of Activity in Liability for Unpaid Losses and Loss Expenses Payable (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2016
Losses and Loss Expenses Payable [Abstract]
Liability for Claims and Claims Adjustment Expense, Property Casualty Liability	$ 1,128.9	$ 1,247.6	$ 1,146.8	$ 1,255.6
Reinsurance Recoverables, Including Reinsurance Premium Paid	4.6	2.1	5.5	3.1
Liability for Unpaid Claims and Claims Adjustment Expense, Net	1,124.3	1,245.5	$ 1,141.3	$ 1,252.5
Current Year Claims and Claims Adjustment Expense	215.7	232.7
Prior Year Claims and Claims Adjustment Expense	(21.4)	(20.4)
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	194.3	212.3
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	59.3	63
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	152	156.3
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	$ 211.3	$ 219.3

Losses and Loss Expenses Paya_4

Losses and Loss Expenses Payable Losses and Loss Expenses Payable - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Liability for Claims and Claims Adjustment Expense [Line Items]
Document Period End Date	Mar. 31, 2019
Prior Year Claims and Claims Adjustment Expense	$ 21.4	$ 20.4
Unallocated loss adjustment expense [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		3.8
Business Insurance Segments [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense	16.3
Specialty Insurance [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense	1.3	0.3
Homeowners [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense	0.6	2.8
Middle Market Commercial [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense	3.1	2.5
Personal Auto [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense	6.8	4
Commercial Auto [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		3.5
Workers' compensation [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense	4.5	2.3
E&S Casualty [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		1.9
Small commercial [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense	4.8
Total Insurance Segments [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense	$ 20.9	$ 20.4

Reinsurance - Summary of Extern

Reinsurance - Summary of External Reinsurance Transactions, as well as reinsurance transactions with State Auto Mutual Under the Pooling Arrangement (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Premiums earned:
Assumed from external insurers and reinsurers	$ 18.2	$ 10.4
Assumed under Pooling Arrangement	302.7	314.9
Ceded to external insurers and reinsurers	(5.9)	(5.4)
Ceded under Pooling Arrangement	(243)	(216.9)
Net assumed premiums earned	72	103
Losses and loss expenses incurred:
Assumed from external insurers and reinsurers	14.2	10.9
Assumed under Pooling Arrangement	200.2	202.7
Ceded to external insurers and reinsurers	(0.6)	(1.3)
Ceded under Pooling Arrangement	(143.8)	(156.5)
Net assumed losses and loss expenses incurred	$ 70	$ 55.8

Income Taxes - Reconciliation B

Income Taxes - Reconciliation Between Actual Federal Income Tax Expense (Benefit) and Amount Computed at Indicated Statutory Rate (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Amount at statutory rate	$ 12.9	$ (0.7)
Tax-exempt interest and dividends received deduction	(0.7)	(0.7)
Other, net	0	0.2
Federal income tax expense and effective rate	12.2	(1.2)
Income Tax Expense (Benefit)	$ 12.2	$ (1.2)
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Amount at statutory rate (percent)	21.00%	21.00%
Tax-exempt interest and dividends received deduction (percent)	(1.10%)	20.80%
Other, net (percent)	0.00%	(5.70%)
Effective Income Tax Rate Reconciliation, Deduction, Percent	19.90%	36.10%

Pension and Postretirement Be_3

Pension and Postretirement Benefit Plans - Company's Share of Net Periodic Cost Components (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 1	$ 1.3
Interest cost	2.9	2.7
Expected return on plan assets	4.2	4.5
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0	0
Amortization of:
Defined Benefit Plan, Amortization of Gain (Loss)	1.5	2.1
Net periodic cost (benefit)	1.2	1.6
Postretirement [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	0	0
Interest cost	0.2	0.2
Expected return on plan assets	0	0
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(1.4)	(1.4)
Amortization of:
Defined Benefit Plan, Amortization of Gain (Loss)	0.1	0.1
Net periodic cost (benefit)	$ (1.1)	$ (1.1)

Pension and Postretirement Be_4

Pension and Postretirement Benefit Plans - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Retirement Benefits [Abstract]
Contributions by employer	$ 15

Other Comprehensive Income an_3

Other Comprehensive Income and Accumulated Other Comprehensive Income - Schedule of Changes in Accumulated Other Comprehensive Income by Component, Net of Tax (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance	$ (96.4)	$ 3.8
Cumulative Effect of change in accounting for equity securities and other invested assets and reclassification of stranded tax effects as of January 1, 2018			$ (63.9)
Other comprehensive income before reclassifications	27.3	(29)
Amounts reclassified from AOCI	0.5	1
Other comprehensive income (loss)	27.8	(28)
Ending balance	(68.6)	(88.1)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Amounts reclassified from AOCI	0.5	1
Unrealized Gains and Losses on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance	(20.2)	66
Cumulative Effect of change in accounting for equity securities and other invested assets and reclassification of stranded tax effects as of January 1, 2018			(47.9)
Other comprehensive income before reclassifications	27.3	(29)
Amounts reclassified from AOCI	(0.1)	(0.3)
Other comprehensive income (loss)	27.2	(29.3)
Ending balance	7	(11.2)
Benefit Plan Items [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance	(76.2)	(62.2)
Cumulative Effect of change in accounting for equity securities and other invested assets and reclassification of stranded tax effects as of January 1, 2018			$ (16)
Other comprehensive income before reclassifications	0	0
Amounts reclassified from AOCI	0.6	1.3
Other comprehensive income (loss)	0.6	1.3
Ending balance	$ (75.6)	$ (76.9)

Other Comprehensive Income an_4

Other Comprehensive Income and Accumulated Other Comprehensive Income - Schedule of Reclassifications Out of Accumulated Other Comprehensive Income by Component (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized gain/(loss) on sale of securities	$ 44.9	$ (11.7)
Tax (expense) benefit	(12.2)	1.2
Total reclassifications for the period	(0.5)	(1)
Unrealized Gains and Losses on Available-for-Sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period	0.1	0.3
Benefit Plan Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period	(0.6)	(1.3)
Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period	(0.5)	(1)
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains and Losses on Available-for-Sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized gain/(loss) on sale of securities	0.1	0.4
Total before tax	0.1	0.4
Tax (expense) benefit	0	(0.1)
Net of tax	0.1	0.3
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Benefit Plan Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income components/Negative prior-service costs	1.6	1.6
Accumulated other comprehensive income components/Net actuarial loss	(2.4)	(3.3)
Total before tax	(0.8)	(1.7)
Tax (expense) benefit	0.2	0.4
Net of tax	$ (0.6)	$ (1.3)

Earnings Per Common Share - Com

Earnings Per Common Share - Compilation of Basic and Diluted Earnings (Loss) Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator:
Net income (loss)	$ 49.4	$ (2.1)
Denominator:
Weighted average shares for basic net earnings per common share (shares)	43,300,000	42.6
Effect of dilutive share-based awards (shares)	600,000	0
Adjusted weighted average shares for diluted net earnings per common share (shares)	43,900,000	42.6
Basic net (loss) earnings per common share (usd per share)	$ 1.14	$ (0.05)
Diluted net (loss) earnings per common share (usd per share)	$ 1.12	$ (0.05)

Earnings Per Common Share - Opt

Earnings Per Common Share - Options to Purchase Shares of Common Stock (Detail) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Number of antidilutive options and awards	0	0.7

Segment Information - Financial

Segment Information - Financial Information Regarding Company's Reportable Segments (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues from external sources:
Revenue	$ 367.6	$ 323.7
Other Income	0.6	0.6
Net Investment Income	19.4	19.9
Realized Investment Gains (Losses)	44.9	(11.7)
Segment income before federal income tax:
Interest expense on corporate debt	(1.2)	(1.6)
Income before federal income taxes	61.6	(3.3)
Operating Segments [Member]
Revenues from external sources:
Revenue	367.6	323.7
Segment income before federal income tax:
Income before federal income taxes	61.3	3.3
Operating Segments [Member] | Personal Insurance Segments [Member]
Revenues from external sources:
Revenue	181.5	156.3
Operating Segments [Member] | Business Insurance Segments [Member]
Revenues from external sources:
Revenue	116.4	114.9
Operating Segments [Member] | Specialty Insurance Segment [Member]
Revenues from external sources:
Revenue	4.8	43.7
Operating Segments [Member] | Total Insurance Segments [Member]
Revenues from external sources:
Revenue	302.7	314.9
Segment income before federal income tax:
Income before federal income taxes	(3.1)	(5)
Operating Segments [Member] | Net Investment Income [Member]
Revenues from external sources:
Net Investment Income		19.9
Operating Segments [Member] | Total Investment Operations [Member]
Revenues from external sources:
Revenue	64.3	8.2
Segment income before federal income tax:
Income before federal income taxes	64.3	8.2
Operating Segments [Member] | Total Investment Operations [Member] | Net Realized Capital Gains [Member]
Segment income before federal income tax:
Income before federal income taxes	44.9	(11.7)
Operating Segments [Member] | All Other Segments [Member]
Revenues from external sources:
Revenue		0.6
Segment income before federal income tax:
Income before federal income taxes	0.1	0.1
Operating Segments [Member] | Personal Insurance [Member]
Segment income before federal income tax:
Income before federal income taxes	4.2	1.7
Operating Segments [Member] | Business Insurance [Member]
Segment income before federal income tax:
Income before federal income taxes	(5.9)	(8.3)
Operating Segments [Member] | Specialty Insurance [Member]
Segment income before federal income tax:
Income before federal income taxes	(1.4)	1.6
Eliminate Intersegment Revenues [Member]
Revenues from external sources:
Revenue	1.6	1.6
Segment Reconciling Items [Member]
Revenues from external sources:
Revenue	(1.6)	(1.6)
Segment income before federal income tax:
Corporate Expenses	(5)	(4.2)
Income before federal income taxes	0.3	(6.6)
Segment Reconciling Items [Member] | Segment Reconciling Items [Member]
Segment income before federal income tax:
Gaap Expense Adjustments	4.1	(4)
Interest expense on corporate debt	(1.2)	(1.6)
Corporate And Reconciling Items [Member]
Revenues from external sources:
Revenue	$ 369.2	$ 325.3

Segment Information - Additiona

Segment Information - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)Segment	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)
Segment Reporting Information [Line Items]
Acquisition And Operating Expenses	$ 107.6	$ 110.8
Number of reportable segments (segments) | Segment	3
Investable assets	$ 2,701.9		$ 2,658.7