The Progressive Corporation (PGR) 10-Q 1 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	3 Months Ended
	Mar. 31, 2019shares
Document Document And Entity Information [Abstract]
Entity Registrant Name	PROGRESSIVE CORP/OH/
Entity Central Index Key	0000080661
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding	583,985,804
Trading Symbol	PGR
Entity Small Business	false
Entity Emerging Growth Company	false

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues
Net premiums earned	$ 8,459.8	$ 7,174
Investment income	252.9	166.3
Net realized gains (losses) on securities:
Gross Realized Gain (Loss), excluding Holding Period and OTTI	46.1	107
Net Holding Period Realized Gain (Loss)	392.7	(155.2)
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net	(24.3)	0
Total net realized gains (losses) on securities	414.5	(48.2)
Fees and other revenues	130.2	103.8
Service revenues	42.6	34.2
Total revenues	9,300	7,430.1
Expenses
Losses and loss adjustment expenses	5,759	4,870.8
Policy acquisition costs	710.6	596.2
Other underwriting expenses	1,171.2	980.2
Investment expenses	6.2	6
Service expenses	38.1	29.3
Interest expense	47.4	36.8
Total expenses	7,732.5	6,519.3
Net Income
Income before income taxes	1,567.5	910.8
Provision for income taxes	484.7	181
Net income	1,082.8	729.8
Net (income) loss attributable to noncontrolling interest (NCI)	(4.4)	(11.8)
Net income attributable to Progressive	1,078.4	718
Other Comprehensive Income (Loss)
Total net unrealized gains (losses) on fixed-maturity securities	301.1	(154.5)
Net unrealized losses on forecasted transactions	0.2	0.2
Other comprehensive income (loss)	301.3	(154.3)
Other comprehensive (income) loss attributable to NCI	(2.3)	4
Comprehensive income attributable to Progressive	1,377.4	567.7
Computation of Earnings Per Common Share
Net income attributable to Progressive	1,078.4	718
Less: Preferred share dividends	6.7	1.2
Net Income (Loss) Available to Common Stockholders, Basic	$ 1,071.7	$ 716.8
Average common shares outstanding - Basic	583.5	582
Net effect of dilutive stock-based compensation	3.1	3.6
Total average equivalent common shares - Diluted	586.6	585.6
Basic: Earnings per common share	$ 1.84	$ 1.23
Diluted: Earnings per common share	$ 1.83	$ 1.22

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Assets
Fixed maturities (amortized cost: $27,574.5, $22,627.2, and $28,255.9)		$ 27,821.9	$ 28,111.5	$ 22,420.1
Short-term investments (amortized cost: $2,584.7, $3,052.4, and $1,795.9)		2,584.7	1,795.9	3,052.4
Total available-for-sale securities		30,406.6	29,907.4	25,472.5
Nonredeemable preferred stocks (cost: $1,021.1, $659.6, and $1,002.6)		1,095.4	1,033.9	745.9
Common equities (cost: $1,194.3, $1,265.5, and $1,148.9)		3,010.5	2,626.1	3,033.2
Total equity securities		4,105.9	3,660	3,779.1
Total investments		34,512.5	33,567.4	29,251.6
Cash and cash equivalents		158	69.5	190.1
Restricted cash		0.7	5.5	6.5
Cash and cash equivalents		158.7	75	196.6
Accrued investment income		172.1	190.8	139.2
Premiums receivable, net of allowance for doubtful accounts of $236.9, $205.4, and $252.1		7,189.8	6,497.1	6,043.8
Reinsurance recoverables		2,842.8	2,696.1	2,239.1
Prepaid reinsurance premiums		446.7	309.7	342.8
Deferred acquisition costs		999.1	951.6	842.3
Property and equipment, net of accumulated depreciation of $1,064.9, $973.8, and $1,033.2		1,127.3	1,131.7	1,112
Goodwill		452.7	452.7	452.7
Intangible assets, net of accumulated amortization of $265.6, $193.7, and $247.7		276.7	294.6	348.6
Net deferred income taxes		0	43.2	0
Other assets		671.9	365.1	362.2
Total assets		48,850.3	46,575	41,330.9
Liabilities
Unearned premiums		11,603.6	10,686.5	9,837.8
Loss and loss adjustment expense reserves		15,876.6	15,400.8	13,329
Net deferred income taxes		38.5	0	53.2
Accounts payable, accrued expenses, and other liabilities		4,594.3	5,046.5	3,414.3
Debt	[1]	4,405.4	4,404.9	3,859.2
Total liabilities		36,518.4	35,538.7	30,493.5
Redeemable noncontrolling interest (NCI)	[2]	221.2	214.5	514.2
Shareholders’ Equity
Serial Preferred Shares, Series B, no par value (cumulative, liquidation preference $1,000 per share) (authorized, issued, and outstanding 0.5)		493.9	493.9	493.9
Common shares, $1.00 par value (authorized 900.0; issued 797.5, including treasury shares of 213.5, 215.1, and 214.3)		584	583.2	582.4
Paid-in capital		1,496.6	1,479	1,401.6
Retained earnings		9,358.1	8,386.6	8,017.9
Accumulated other comprehensive income (loss):
Net unrealized gains (losses) on fixed-maturity securities		195.5	(105.6)	(160.8)
Net unrealized losses on forecasted transactions		(17)	(17.2)	(17.8)
Accumulated other comprehensive (income) loss attributable to NCI		(0.4)	1.9	6
Total accumulated other comprehensive income (loss) attributable to Progressive		178.1	(120.9)	(172.6)
Total shareholders’ equity		12,110.7	10,821.8	10,323.2
Total liabilities, redeemable NCI, and shareholders’ equity		$ 48,850.3	$ 46,575	$ 41,330.9
[1]	Consists of long-term debt. See Note 4 – Debt
[2]	See Note 12 – Redeemable Noncontrolling Interest for further discussion

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Fixed maturities, amortized cost	$ 27,574.5	$ 28,255.9	$ 22,627.2
Nonredeemable preferred stocks, cost	1,021.1	1,002.6	659.6
Common equities, cost	1,194.3	1,148.9	1,265.5
Short-term investments, amortized cost	2,584.7	1,795.9	3,052.4
Premiums receivable, allowance for doubtful accounts	236.9	252.1	205.4
Intangible Assets, Accumulated Amortization	265.6	247.7	193.7
Property and equipment, accumulated depreciation	$ 1,064.9	$ 1,033.2	$ 973.8
Common Shares, par value (USD per share)	$ 1	$ 1	$ 1
Common Shares, authorized (shares)	900,000,000	900,000,000	900,000,000
Common Shares, issued (shares)	797,500,000	797,500,000	797,500,000
Common Shares, treasury shares (shares)	213,500,000	214,300,000	215,100,000
Serial Preferred Stock
Preferred Stock, Shares Authorized (shares)	20,000,000	20,000,000	20,000,000
Series B Preferred Stock
Preferred Stock, Shares Outstanding (shares)	500,000
Preferred Stock, Liquidation Preference Per Share (USD per share)	$ 1,000
Series B Preferred Stock | Serial Preferred Stock
Preferred Stock, No Par Value	$ 0	$ 0	$ 0
Preferred Stock, Shares Authorized (shares)	500,000	500,000	500,000
Preferred Stock, Shares Issued (shares)	500,000	500,000	500,000
Preferred Stock, Shares Outstanding (shares)	500,000	500,000	500,000
Preferred Stock, Liquidation Preference Per Share (USD per share)	$ 1,000	$ 1,000	$ 1,000

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity Statement - USD ($) $ in Millions	Total	Serial Preferred Stock	Preferred Shares, No Par Value	Common Shares, $1.00 Par Value	Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss) Attributable to Progressive	Series B Preferred Stock	Series B Preferred StockSerial Preferred Stock	Voting Preference Shares
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle	$ 1,300.2
Reclassification of disproportionate tax effects	$ 4.3
Common Stock, Dividends, Per Share, Declared	$ 0
Preferred Stock, Dividends Per Share, Declared									$ 0
Balance, Beginning of period at Dec. 31, 2017			$ 0	$ 581.7	$ 1,389.2	$ 6,031.7	$ 1,282.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Serial Preferred Shares, Series B			493.9
Treasury shares purchased				(0.7)	(1.6)	(34.9)
Net restricted equity awards issued/vested				1.4	(1.4)
Amortization of equity-based compensation					17.2
Reinvested dividends on restricted stock units					(0.5)	0.5
Adjustment to carrying amount of redeemable noncontrolling interest	$ 1.3				(1.3)
Net income attributable to Progressive	718					718
Cash dividends declared on common shares ($0.10 per share and $0)						0
Cash dividends declared on Serial Preferred Shares, Series B ($26.875 per share and $0)						0
Attributable to noncontrolling interest	4						4
Other comprehensive income							(154.3)
Other, net						(1.9)
Balance, End of period at Mar. 31, 2018	10,323.2		493.9	582.4	1,401.6	8,017.9	(172.6)
Balance, Beginning of period at Dec. 31, 2017			0	581.7	1,389.2	6,031.7	1,282.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustment to carrying amount of redeemable noncontrolling interest	(2.8)
Attributable to noncontrolling interest	3.3
Balance, End of period at Dec. 31, 2018	$ 10,821.8		493.9	583.2	1,479	8,386.6	(120.9)
Preferred Stock, No Par Value									$ 0
Preferred Stock, Shares Authorized (shares)		20,000,000							500,000	5,000,000
Preferred Stock, Shares Issued (shares)									500,000	0
Common Shares, par value (USD per share)	$ 1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle | Accounting Standards Update 2016-01						1,300.2	(1,300.2)
Reclassification of disproportionate tax effects | Accounting Standards Update 2018-02						4.3	(4.3)
Preferred Stock, No Par Value									$ 0
Preferred Stock, Shares Authorized (shares)		20,000,000							500,000
Preferred Stock, Shares Issued (shares)									500,000
Common Shares, par value (USD per share)	1
Common Stock, Dividends, Per Share, Declared	$ 0.10
Preferred Stock, Dividends Per Share, Declared								$ 26.875	$ 26.875
Issuance of Serial Preferred Shares, Series B			0
Treasury shares purchased				(0.4)	(1.1)	(24.6)
Net restricted equity awards issued/vested				1.2	(1.2)
Amortization of equity-based compensation					19.6
Reinvested dividends on restricted stock units					0.3	(0.3)
Adjustment to carrying amount of redeemable noncontrolling interest	$ 0				0
Net income attributable to Progressive	1,078.4					1,078.4
Cash dividends declared on common shares ($0.10 per share and $0)						58.3
Cash dividends declared on Serial Preferred Shares, Series B ($26.875 per share and $0)						(13.4)		$ (13.4)
Attributable to noncontrolling interest	(2.3)						(2.3)
Other comprehensive income							301.3
Other, net						(10.3)
Balance, End of period at Mar. 31, 2019	$ 12,110.7		$ 493.9	$ 584	$ 1,496.6	9,358.1	178.1
Preferred Stock, No Par Value									$ 0
Preferred Stock, Shares Authorized (shares)		20,000,000							500,000	5,000,000
Preferred Stock, Shares Issued (shares)									500,000	0
Common Shares, par value (USD per share)	$ 1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle | Accounting Standards Update 2016-01						0	0
Reclassification of disproportionate tax effects | Accounting Standards Update 2018-02						$ 0	$ 0

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Cash Flows [Abstract]
Net income	$ 1,082.8	$ 729.8
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	52.6	40.9
Amortization of intangible assets	17.9	18
Net amortization of fixed-income securities	0.2	15
Amortization of equity-based compensation	19.2	17.4
Net realized (gains) losses on securities	(414.5)	48.2
Net (gains) losses on disposition of property and equipment	5.1	1.2
Changes in:
Premiums receivable	(692.7)	(621.3)
Reinsurance recoverables	(146.7)	34.3
Prepaid reinsurance premiums	(137)	(139.5)
Deferred acquisition costs	(47.5)	(61.8)
Income taxes	465.2	181.1
Unearned premiums	917.1	934.3
Loss and loss adjustment expense reserves	475.8	242.1
Accounts payable, accrued expenses, and other liabilities	291.5	283.2
Other, net	(20.5)	24.2
Net cash provided by operating activities	1,868.5	1,747.1
Purchases:
Fixed maturities	(4,711.1)	(5,563)
Equity securities	(93.6)	(39.9)
Sales:
Fixed maturities	4,214.7	1,692.4
Equity securities	39	428
Maturities, paydowns, calls, and other:
Fixed maturities	1,199.7	1,422.6
Net sales (purchases) of short-term investments	(774.1)	(175.8)
Net unsettled security transactions	(82.4)	89.4
Purchases of property and equipment	(75.8)	(35.8)
Sales of property and equipment	6.2	1.5
Net cash used in investing activities	(277.4)	(2,180.6)
Cash Flows From Financing Activities
Dividends paid to common shareholders	(1,467.9)	(654.9)
Dividends paid to preferred shareholders	(13.4)	0
Acquisition of treasury shares for restricted stock tax liabilities	(26.1)	(36.8)
Acquisition of treasury shares acquired in open market	0	(0.4)
Net proceeds from issuance of Serial Preferred Shares, Series B	0	493.9
Net proceeds from debt issuances	0	589.5
Payments of debt	0	(37.1)
Proceeds from exercise of equity options	0	0.6
Net cash provided by (used in) financing activities	(1,507.4)	354.8
Increase (decrease) in cash, cash equivalents, and restricted cash	83.7	(78.7)
Cash, cash equivalents, and restricted cash – January 1	75	275.3
Cash, cash equivalents, and restricted cash – March 31	$ 158.7	$ 196.6

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation — The accompanying consolidated financial statements include the accounts of The Progressive Corporation and ARX Holding Corp. (ARX), and their respective wholly owned insurance and non-insurance subsidiaries and affiliates in which Progressive or ARX has a controlling financial interest. The Progressive Corporation owned 86.8% of the outstanding capital stock of ARX at March 31, 2019 and December 31, 2018 and 68.9% at March 31, 2018 . The increase in Progressive’s ownership of ARX since March 31, 2018 is primarily due to the minority ARX shareholders exercising their rights to “ put ” a portion of their shares, including exercised stock options to Progressive pursuant to the ARX stockholders’ agreement. See Note 12 – Redeemable Noncontrolling Interest for further discussion. The consolidated financial statements reflect all normal recurring adjustments that, in the opinion of management, were necessary for a fair statement of the results for the interim periods presented. The results of operations for the period ended March 31, 2019 , are not necessarily indicative of the results expected for the full year. These consolidated financial statements and the notes thereto should be read in conjunction with Progressive’s audited financial statements and accompanying notes included in Exhibit 13 to our Annual Report on Form 10-K for the year ended December 31, 2018 ( “ 2018 Annual Report to Shareholders ” ). Other assets on the consolidated balance sheets include properties that are considered “ held for sale, ” if any. The fair value of these properties, less the estimated cost to sell them, was $52.6 million at March 31, 2019 , $5.3 million at March 31, 2018, and $39.3 million

Investments

Investments	3 Months Ended
	Mar. 31, 2019
Investments Schedule [Abstract]
Investments	Investments — The following tables present the composition of our investment portfolio by major security type, consistent with our classification of how we manage, monitor, and measure the portfolio. Our securities are reported in our Consolidated Balance Sheets at fair value. The changes in fair value for our fixed-maturity securities (other than hybrid securities) are reported as a component of accumulated other comprehensive income, net of deferred income taxes, in our Consolidated Balance Sheets. The net holding period gains (losses) reported below represent the inception-to-date changes in fair value. The changes in the net holding period gains (losses) between periods for the hybrid securities and equity securities are recorded as a component of net realized gains (losses) on securities in our Consolidated Statements of Comprehensive Income. ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) Fair Value % of Value March 31, 2019 Available-for-sale securities: Fixed maturities: U.S. government obligations $ 9,685.6 $ 105.5 $ (20.6 ) $ 0 $ 9,770.5 28.3 % State and local government obligations 1,505.5 15.4 (5.1 ) 0 1,515.8 4.4 Corporate debt securities 7,870.1 126.3 (19.0 ) 0.6 7,978.0 23.1 Residential mortgage-backed securities 609.9 5.7 (2.6 ) 0 613.0 1.8 Commercial mortgage-backed securities 3,825.6 35.9 (7.9 ) 0 3,853.6 11.2 Other asset-backed securities 3,834.2 10.0 (4.5 ) 0.1 3,839.8 11.1 Redeemable preferred stocks 243.6 9.0 (1.2 ) (0.2 ) 251.2 0.7 Total fixed maturities 27,574.5 307.8 (60.9 ) 0.5 27,821.9 80.6 Short-term investments 2,584.7 0 0 0 2,584.7 7.5 Total available-for-sale securities 30,159.2 307.8 (60.9 ) 0.5 30,406.6 88.1 Equity securities: Nonredeemable preferred stocks 1,021.1 0 0 74.3 1,095.4 3.2 Common equities 1,194.3 0 0 1,816.2 3,010.5 8.7 Total equity securities 2,215.4 0 0 1,890.5 4,105.9 11.9 Total portfolio 1,2 $ 32,374.6 $ 307.8 $ (60.9 ) $ 1,891.0 $ 34,512.5 100.0 % ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) Fair Value % of Value March 31, 2018 Available-for-sale securities: Fixed maturities: U.S. government obligations $ 9,081.6 $ 3.9 $ (127.4 ) $ 0 $ 8,958.1 30.6 % State and local government obligations 1,732.3 4.3 (16.4 ) (0.1 ) 1,720.1 5.9 Corporate debt securities 6,102.6 4.8 (64.8 ) (1.5 ) 6,041.1 20.7 Residential mortgage-backed securities 746.7 9.9 (4.8 ) 0 751.8 2.6 Commercial mortgage-backed securities 2,289.8 4.5 (24.8 ) 0 2,269.5 7.8 Other asset-backed securities 2,472.4 2.4 (12.9 ) 0.2 2,462.1 8.4 Redeemable preferred stocks 201.8 18.6 (1.4 ) (1.6 ) 217.4 0.7 Total fixed maturities 22,627.2 48.4 (252.5 ) (3.0 ) 22,420.1 76.7 Short-term investments 3,052.4 0 0 0 3,052.4 10.4 Total available-for-sale securities 25,679.6 48.4 (252.5 ) (3.0 ) 25,472.5 87.1 Equity securities: Nonredeemable preferred stocks 659.6 0 0 86.3 745.9 2.5 Common equities 1,265.5 0 0 1,767.7 3,033.2 10.4 Total equity securities 1,925.1 0 0 1,854.0 3,779.1 12.9 Total portfolio 1,2 $ 27,604.7 $ 48.4 $ (252.5 ) $ 1,851.0 $ 29,251.6 100.0 % ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) Fair Value % of Value December 31, 2018 Available-for-sale securities: Fixed maturities: U.S. government obligations $ 9,897.4 $ 71.2 $ (52.1 ) $ 0 $ 9,916.5 29.5 % State and local government obligations 1,654.6 7.3 (12.8 ) 0 1,649.1 4.9 Corporate debt securities 8,808.5 13.6 (125.3 ) (2.5 ) 8,694.3 25.9 Residential mortgage-backed securities 733.5 6.0 (5.1 ) 0 734.4 2.2 Commercial mortgage-backed securities 3,332.8 7.8 (39.0 ) 0 3,301.6 9.8 Other asset-backed securities 3,585.4 3.6 (11.8 ) 0.1 3,577.3 10.7 Redeemable preferred stocks 243.7 5.9 (3.5 ) (7.8 ) 238.3 0.7 Total fixed maturities 28,255.9 115.4 (249.6 ) (10.2 ) 28,111.5 83.7 Short-term investments 1,795.9 0 0 0 1,795.9 5.4 Total available-for-sale securities 30,051.8 115.4 (249.6 ) (10.2 ) 29,907.4 89.1 Equity securities: Nonredeemable preferred stocks 1,002.6 0 0 31.3 1,033.9 3.1 Common equities 1,148.9 0 0 1,477.2 2,626.1 7.8 Total equity securities 2,151.5 0 0 1,508.5 3,660.0 10.9 Total portfolio 1,2 $ 32,203.3 $ 115.4 $ (249.6 ) $ 1,498.3 $ 33,567.4 100.0 % 1 Our portfolio reflects the effect of unsettled security transactions; at March 31, 2019 , we had $76.5 million included in “other assets,” compared to $83.6 million and $5.9 million at March 31, 2018 and December 31, 2018 , respectively, included in “other liabilities.” 2 The total fair value of the portfolio at March 31, 2019 and 2018 , and December 31, 2018 , included $1.2 billion , $2.1 billion , and $2.9 billion , respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions. At March 31, 2019 , bonds and certificates of deposit in the principal amount of $250.7 million were on deposit to meet state insurance regulatory and/or rating agency requirements. Short-Term Investments Our short-term investments may include commercial paper and other investments that are expected to mature or are redeemable within one year. We did no t have any open repurchase or reverse repurchase transactions in our short-term investment portfolio at March 31, 2019 and 2018 , or December 31, 2018 . To the extent we enter into repurchase or reverse repurchase transactions, and consistent with past practice, we would elect not to offset these transactions and would report them on a gross basis on our balance sheets, despite the option to elect to offset these transactions as long as they were with the same counterparty and subject to an enforceable master netting arrangement. Hybrid Securities Included in our fixed-maturity securities are hybrid securities, which are reported at fair value: March 31, (millions) 2019 2018 December 31, 2018 Fixed maturities: State and local government obligations $ 3.6 $ 3.7 $ 3.6 Corporate debt securities 161.7 86.4 158.9 Other asset-backed securities 4.0 6.1 4.5 Redeemable preferred stocks 85.4 37.8 77.7 Total hybrid securities $ 254.7 $ 134.0 $ 244.7 Certain securities in our portfolio are accounted for as hybrid securities because they contain embedded derivatives that are not deemed to be clearly and closely related to the host investments. Since the embedded derivatives (e.g., change-in-control put option, debt-to-equity conversion, or any other feature unrelated to the credit quality or risk of default of the issuer that could impact the amount or timing of our expected future cash flows) do not have observable intrinsic values, we have elected to record the changes in fair value of these securities through income as realized gains or losses. Fixed Maturities The composition of fixed maturities by maturity at March 31, 2019 , was: (millions) Cost Fair Value Less than one year $ 4,929.9 $ 4,934.2 One to five years 16,765.4 16,878.8 Five to ten years 5,818.5 5,945.9 Ten years or greater 60.7 63.0 Total $ 27,574.5 $ 27,821.9 Asset-backed securities are classified in the maturity distribution table based upon their projected cash flows. All other securities which do not have a single maturity date are reported based upon expected average maturity. Contractual maturities may differ from expected maturities because the issuers of the securities may have the right to call or prepay obligations. Gross Unrealized Losses As of March 31, 2019 , we had $60.9 million of gross unrealized losses in our fixed-maturity securities. A review of these securities indicated that the issuers were current with respect to their interest obligations and that there was no evidence of deterioration of the current cash flow projections that would indicate we would not receive the remaining principal at maturity. The following tables show the composition of gross unrealized losses by major security type and by the length of time that individual securities have been in a continuous unrealized loss position: Total No. of Sec. Total Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Unrealized Losses No. of Sec. Fair Unrealized Losses March 31, 2019 Fixed maturities: U.S. government obligations 42 $ 3,174.0 $ (20.6 ) 1 $ 19.9 $ (0.1 ) 41 $ 3,154.1 $ (20.5 ) State and local government obligations 162 567.2 (5.1 ) 10 31.4 0 152 535.8 (5.1 ) Corporate debt securities 153 2,555.7 (19.0 ) 11 175.9 (1.1 ) 142 2,379.8 (17.9 ) Residential mortgage-backed securities 63 299.4 (2.6 ) 15 139.1 (1.1 ) 48 160.3 (1.5 ) Commercial mortgage-backed securities 76 1,294.3 (7.9 ) 13 229.1 (0.9 ) 63 1,065.2 (7.0 ) Other asset-backed securities 142 1,294.0 (4.5 ) 27 296.5 (0.7 ) 115 997.5 (3.8 ) Redeemable preferred stocks 2 31.1 (1.2 ) 0 0 0 2 31.1 (1.2 ) Total fixed maturities 640 $ 9,215.7 $ (60.9 ) 77 $ 891.9 $ (3.9 ) 563 $ 8,323.8 $ (57.0 ) Total No. of Sec. Total Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Unrealized Losses No. of Sec. Fair Unrealized Losses March 31, 2018 Fixed maturities: U.S. government obligations 64 $ 7,933.8 $ (127.4 ) 37 $ 5,954.6 $ (90.7 ) 27 $ 1,979.2 $ (36.7 ) State and local government obligations 426 1,263.7 (16.4 ) 301 890.2 (9.5 ) 125 373.5 (6.9 ) Corporate debt securities 348 5,082.9 (64.8 ) 290 4,515.1 (56.1 ) 58 567.8 (8.7 ) Residential mortgage-backed securities 211 329.3 (4.8 ) 36 112.8 (0.5 ) 175 216.5 (4.3 ) Commercial mortgage-backed securities 131 1,974.8 (24.8 ) 89 1,510.5 (16.2 ) 42 464.3 (8.6 ) Other asset-backed securities 208 1,958.5 (12.9 ) 129 1,439.1 (8.7 ) 79 519.4 (4.2 ) Redeemable preferred stocks 3 26.8 (1.4 ) 2 15.3 (0.4 ) 1 11.5 (1.0 ) Total fixed maturities 1,391 $ 18,569.8 $ (252.5 ) 884 $ 14,437.6 $ (182.1 ) 507 $ 4,132.2 $ (70.4 ) Total No. of Sec. Total Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Unrealized Losses No. of Sec. Fair Unrealized Losses December 31, 2018 Fixed maturities: U.S. government obligations 51 $ 4,438.0 $ (52.1 ) 2 $ 126.6 $ (0.1 ) 49 $ 4,311.4 $ (52.0 ) State and local government obligations 299 972.4 (12.8 ) 49 192.7 (0.3 ) 250 779.7 (12.5 ) Corporate debt securities 368 6,723.3 (125.3 ) 133 2,613.3 (33.4 ) 235 4,110.0 (91.9 ) Residential mortgage-backed securities 228 450.2 (5.1 ) 32 248.8 (0.8 ) 196 201.4 (4.3 ) Commercial mortgage-backed securities 140 2,328.5 (39.0 ) 48 741.2 (8.9 ) 92 1,587.3 (30.1 ) Other asset-backed securities 203 2,691.3 (11.8 ) 84 1,551.7 (3.2 ) 119 1,139.6 (8.6 ) Redeemable preferred stocks 3 48.5 (3.5 ) 1 18.9 (0.6 ) 2 29.6 (2.9 ) Total fixed maturities 1,292 $ 17,652.2 $ (249.6 ) 349 $ 5,493.2 $ (47.3 ) 943 $ 12,159.0 $ (202.3 ) Since both March 31, 2018 and December 31, 2018 , the number of securities in our fixed-maturity portfolio with unrealized losses decreased, primarily due to valuation increases in nearly all sectors as well as sales of securities in our municipal and corporate portfolios. We had no material decreases in valuation as a result of credit rating downgrades and all of the securities in the table above are current with respect to required principal and interest payments. Other-Than-Temporary Impairment (OTTI) The following table shows the total non-credit portion of the OTTI recorded in accumulated other comprehensive income, reflecting the original non-credit loss at the time the credit impairment was determined (i.e., unadjusted for valuation changes subsequent to the original write-down): March 31, December 31, (millions) 2019 2018 Fixed maturities: Residential mortgage-backed securities $ (19.7 ) $ (19.7 ) $ (19.7 ) Commercial mortgage-backed securities (0.1 ) (0.3 ) (0.1 ) Total fixed maturities $ (19.8 ) $ (20.0 ) $ (19.8 ) The following tables provide rollforwards of the amounts related to credit losses recognized in earnings for the periods ended March 31, 2019 and 2018 , for which a portion of the OTTI losses were also recognized in accumulated other comprehensive income at the time the credit impairments were determined and recognized: Three Months Ended March 31, 2019 Mortgage-Backed (millions) Residential Commercial Total Balance at December 31, 2018 $ 0 $ 0.5 $ 0.5 Change in recoveries of future cash flows expected to be collected 1 0 0 0 Balance at March 31, 2019 $ 0 $ 0.5 $ 0.5 Three Months Ended March 31, 2018 Mortgage-Backed (millions) Residential Commercial Total Balance at December 31, 2017 $ 0 $ 0.5 $ 0.5 Change in recoveries of future cash flows expected to be collected 1 0 0 0 Balance at March 31, 2018 $ 0 $ 0.5 $ 0.5 1 Reflects the current period change in the expected recovery of prior impairments that will be accreted into income over the remaining life of the security. Although it is not likely that we will be required to sell the securities prior to the recovery of their respective cost bases (which could be maturity), we are required to measure the amount of potential credit losses on the securities that were in an unrealized loss position. In that process, we considered a number of factors and inputs related to the individual securities. The methodology and significant inputs used to measure the amount of credit losses in our portfolio included: current performance indicators on the business model or underlying assets (e.g., delinquency rates, foreclosure rates, and default rates); credit support (via current levels of subordination); historical credit ratings; and updated cash flow expectations based upon these performance indicators. In order to determine the amount of credit loss, if any, the net present value of the cash flows expected (i.e., expected recovery value) was calculated using the current book yield for each security, and was compared to its current amortized value. In the event that the net present value was below the amortized value, a credit loss would be deemed to exist, and the security would be written down. We did no t have any credit impairment write-downs for the three months ended March 31, 2019 or 2018 . Realized Gains (Losses) The components of net realized gains (losses) for the three months ended March 31, were: Three Months (millions) 2019 2018 Gross realized gains on security sales Available-for-sale securities: U.S. government obligations $ 36.6 $ 0 State and local government obligations 1.6 8.6 Corporate and other debt securities 16.1 0.1 Commercial mortgage-backed securities 0.7 1.7 Redeemable preferred stocks 0 1.1 Total available-for-sale securities 55.0 11.5 Equity securities: Nonredeemable preferred stocks 4.9 3.6 Common equities 4.5 119.9 Total equity securities 9.4 123.5 Subtotal gross realized gains on security sales 64.4 135.0 Gross realized losses on security sales Available-for-sale securities: U.S. government obligations (7.1 ) (8.9 ) State and local government obligations (0.6 ) (1.3 ) Corporate and other debt securities (6.1 ) (3.1 ) Residential mortgage-backed securities (2.3 ) 0 Commercial mortgage-backed securities (2.1 ) (6.3 ) Other asset-backed securities (0.1 ) (0.1 ) Total available-for-sale securities (18.3 ) (19.7 ) Equity securities: Nonredeemable preferred stocks 0 (0.4 ) Common equities 0 (7.9 ) Total equity securities 0 (8.3 ) Subtotal gross realized losses on security sales (18.3 ) (28.0 ) Net realized gains (losses) on security sales Available-for-sale securities: U.S. government obligations 29.5 (8.9 ) State and local government obligations 1.0 7.3 Corporate and other debt securities 10.0 (3.0 ) Residential mortgage-backed securities (2.3 ) 0 Commercial mortgage-backed securities (1.4 ) (4.6 ) Other asset-backed securities (0.1 ) (0.1 ) Redeemable preferred stocks 0 1.1 Total available-for-sale securities 36.7 (8.2 ) Equity securities: Nonredeemable preferred stocks 4.9 3.2 Common equities 4.5 112.0 Total equity securities 9.4 115.2 Subtotal net realized gains (losses) on security sales 46.1 107.0 Net holding period gains (losses) Hybrid securities 10.7 (3.2 ) Equity securities 382.0 (152.0 ) Subtotal net holding period gains (losses) 392.7 (155.2 ) Other-than-temporary impairment losses Other asset impairment (24.3 ) 0 Subtotal other-than-temporary impairment losses (24.3 ) 0 Total net realized gains (losses) on securities $ 414.5 $ (48.2 ) During both the first quarter 2019 and 2018, the majority of our net realized gains (losses) on securities were attributable to valuation changes on our equity and hybrid securities. During the first quarter 2019, we wrote down our remaining investment in three federal renewable energy tax credit fund investments, which were reported in “other assets” on the balance sheet, based on an analysis that our investments in those funds will not generate the cash flows that we anticipated. See Note 5 – Income Taxes for additional discussion. The following table reflects our holding period realized gains (losses) on equity securities recognized for the three months ended March 31, 2019 and 2018 for equity securities held at quarter end: Three Months (millions) 2019 2018 Total net gains (losses) recognized during the period on equity securities $ 391.4 $ (36.8 ) Less: Net gains (losses) recognized on equity securities sold during the period 9.4 115.2 Net holding period gains (losses) recognized during the period on equity securities held at period end $ 382.0 $ (152.0 ) Net Investment Income The components of net investment income for the three months ended March 31, were: Three Months (millions) 2019 2018 Available-for-sale securities: Fixed maturities: U.S. government obligations $ 53.7 $ 39.8 State and local government obligations 9.3 10.0 Corporate debt securities 77.2 36.2 Residential mortgage-backed securities 6.6 6.9 Commercial mortgage-backed securities 31.7 21.2 Other asset-backed securities 26.0 13.6 Redeemable preferred stocks 3.7 2.6 Total fixed maturities 208.2 130.3 Short-term investments 16.0 10.1 Total available-for-sale securities 224.2 140.4 Equity securities: Nonredeemable preferred stocks 15.5 10.9 Common equities 13.2 15.0 Total equity securities 28.7 25.9 Investment income 252.9 166.3 Investment expenses (6.2 ) (6.0 ) Net investment income $ 246.7 $ 160.3 The amount of investment income (interest and dividends) we recognize varies based on the average assets held during the year and the book yields of the securities in our portfolio. The increase in net investment income on a year-over-year basis for the three months ended March 31, 2019 , was due to a combination of an increase in average assets and an increase in portfolio yields. The increase in average assets was due to strong underwriting growth and profitability, as well as the proceeds from debt and preferred stock issuances during 2018, partially offset by our dividend payment during the first quarter 2019, under our former annual variable dividend policy. The increase in portfolio yields was a result of our decision to hold a short-duration portfolio, which allowed us to reinvest significant maturities and paydowns of principal at higher yields as interest rates rose. The portfolio duration at both March 31, 2019 and 2018 was 2.6 years . Trading Securities At March 31, 2019 and 2018 , and December 31, 2018 , we did no t hold any trading securities and did no t have any net realized gains (losses) on trading securities for the three months ended March 31, 2019 and 2018 . Derivative Instruments At March 31, 2019 and 2018 , and December 31, 2018 , we had no

Fair Value

Fair Value	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value	Fair Value — We have categorized our financial instruments, based on the degree of subjectivity inherent in the method by which they are valued, into a fair value hierarchy of three levels, as follows: • Level 1 : Inputs are unadjusted quoted prices in active markets for identical instruments at the measurement date (e.g., U.S. government obligations, which are continually priced on a daily basis, active exchange-traded equity securities, and certain short-term securities). • Level 2 : Inputs (other than quoted prices included within Level 1) that are observable for the instrument either directly or indirectly (e.g., certain corporate and municipal bonds and certain preferred stocks). This includes: (i) quoted prices for similar instruments in active markets, (ii) quoted prices for identical or similar instruments in markets that are not active, (iii) inputs other than quoted prices that are observable for the instruments, and (iv) inputs that are derived principally from or corroborated by observable market data by correlation or other means. • Level 3 : Inputs that are unobservable. Unobservable inputs reflect our subjective evaluation about the assumptions market participants would use in pricing the financial instrument (e.g., certain structured securities and privately held investments). Determining the fair value of the investment portfolio is the responsibility of management. As part of the responsibility, we evaluate whether a market is distressed or inactive in determining the fair value for our portfolio. We review certain market level inputs to evaluate whether sufficient activity, volume, and new issuances exist to create an active market. Based on this evaluation, we concluded that there was sufficient activity related to the sectors and securities for which we obtained valuations. The composition of the investment portfolio by major security type and our outstanding debt was: Fair Value (millions) Level 1 Level 2 Level 3 Total Cost March 31, 2019 Fixed maturities: U.S. government obligations $ 9,770.5 $ 0 $ 0 $ 9,770.5 $ 9,685.6 State and local government obligations 0 1,515.8 0 1,515.8 1,505.5 Corporate debt securities 0 7,978.0 0 7,978.0 7,870.1 Subtotal 9,770.5 9,493.8 0 19,264.3 19,061.2 Asset-backed securities: Residential mortgage-backed 0 613.0 0 613.0 609.9 Commercial mortgage-backed 0 3,853.6 0 3,853.6 3,825.6 Other asset-backed 0 3,839.8 0 3,839.8 3,834.2 Subtotal asset-backed securities 0 8,306.4 0 8,306.4 8,269.7 Redeemable preferred stocks: Financials 0 81.3 0 81.3 79.2 Utilities 0 0 0 0 0 Industrials 10.4 159.5 0 169.9 164.4 Subtotal redeemable preferred stocks 10.4 240.8 0 251.2 243.6 Total fixed maturities 9,780.9 18,041.0 0 27,821.9 27,574.5 Short-term investments 2,510.9 73.8 0 2,584.7 2,584.7 Total available-for-sale securities 12,291.8 18,114.8 0 30,406.6 30,159.2 Equity securities: Nonredeemable preferred stocks: Financials 69.6 955.0 25.1 1,049.7 976.1 Utilities 0 40.7 0 40.7 40.0 Industrials 0 0 5.0 5.0 5.0 Subtotal nonredeemable preferred stocks 69.6 995.7 30.1 1,095.4 1,021.1 Common equities: Common stocks 3,010.2 0 0 3,010.2 1,194.0 Other risk investments 0 0 0.3 0.3 0.3 Subtotal common equities 3,010.2 0 0.3 3,010.5 1,194.3 Total equity securities 3,079.8 995.7 30.4 4,105.9 2,215.4 Total portfolio $ 15,371.6 $ 19,110.5 $ 30.4 $ 34,512.5 $ 32,374.6 Debt $ 0 $ 4,734.8 $ 0 $ 4,734.8 $ 4,405.4 Fair Value (millions) Level 1 Level 2 Level 3 Total Cost March 31, 2018 Fixed maturities: U.S. government obligations $ 8,958.1 $ 0 $ 0 $ 8,958.1 $ 9,081.6 State and local government obligations 0 1,720.1 0 1,720.1 1,732.3 Corporate debt securities 0 6,041.1 0 6,041.1 6,102.6 Subtotal 8,958.1 7,761.2 0 16,719.3 16,916.5 Asset-backed securities: Residential mortgage-backed 0 751.8 0 751.8 746.7 Commercial mortgage-backed 0 2,269.5 0 2,269.5 2,289.8 Other asset-backed 0 2,462.1 0 2,462.1 2,472.4 Subtotal asset-backed securities 0 5,483.4 0 5,483.4 5,508.9 Redeemable preferred stocks: Financials 0 64.0 0 64.0 61.2 Utilities 0 11.6 0 11.6 10.7 Industrials 0 141.8 0 141.8 129.9 Subtotal redeemable preferred stocks 0 217.4 0 217.4 201.8 Total fixed maturities 8,958.1 13,462.0 0 22,420.1 22,627.2 Short-term investments 2,569.5 482.9 0 3,052.4 3,052.4 Total available-for-sale securities 11,527.6 13,944.9 0 25,472.5 25,679.6 Equity securities: Nonredeemable preferred stocks: Financials 78.9 662.0 0 740.9 654.6 Utilities 0 0 0 0 0 Industrials 0 0 5.0 5.0 5.0 Subtotal nonredeemable preferred stocks 78.9 662.0 5.0 745.9 659.6 Common equities: Common stocks 3,032.9 0 0 3,032.9 1,265.2 Other risk investments 0 0 0.3 0.3 0.3 Subtotal common equities 3,032.9 0 0.3 3,033.2 1,265.5 Total equity securities 3,111.8 662.0 5.3 3,779.1 1,925.1 Total portfolio $ 14,639.4 $ 14,606.9 $ 5.3 $ 29,251.6 $ 27,604.7 Debt $ 0 $ 4,048.3 $ 0 $ 4,048.3 $ 3,859.2 Fair Value (millions) Level 1 Level 2 Level 3 Total Cost December 31, 2018 Fixed maturities: U.S. government obligations $ 9,916.5 $ 0 $ 0 $ 9,916.5 $ 9,897.4 State and local government obligations 0 1,649.1 0 1,649.1 1,654.6 Corporate debt securities 0 8,694.3 0 8,694.3 8,808.5 Subtotal 9,916.5 10,343.4 0 20,259.9 20,360.5 Asset-backed securities: Residential mortgage-backed 0 734.4 0 734.4 733.5 Commercial mortgage-backed 0 3,301.6 0 3,301.6 3,332.8 Other asset-backed 0 3,577.3 0 3,577.3 3,585.4 Subtotal asset-backed securities 0 7,613.3 0 7,613.3 7,651.7 Redeemable preferred stocks: Financials 0 78.2 0 78.2 79.3 Utilities 0 0 0 0 0 Industrials 9.5 150.6 0 160.1 164.4 Subtotal redeemable preferred stocks 9.5 228.8 0 238.3 243.7 Total fixed maturities 9,926.0 18,185.5 0 28,111.5 28,255.9 Short-term investments 1,722.1 73.8 0 1,795.9 1,795.9 Total available-for-sale securities 11,648.1 18,259.3 0 29,907.4 30,051.8 Equity securities: Nonredeemable preferred stocks: Financials 71.9 887.1 25.1 984.1 951.6 Utilities 0 44.8 0 44.8 46.0 Industrials 0 0 5.0 5.0 5.0 Subtotal nonredeemable preferred stocks 71.9 931.9 30.1 1,033.9 1,002.6 Common equities: Common stocks 2,625.8 0 0 2,625.8 1,148.6 Other risk investments 0 0 0.3 0.3 0.3 Subtotal common equities 2,625.8 0 0.3 2,626.1 1,148.9 Total equity securities 2,697.7 931.9 30.4 3,660.0 2,151.5 Total portfolio $ 14,345.8 $ 19,191.2 $ 30.4 $ 33,567.4 $ 32,203.3 Debt $ 0 $ 4,532.3 $ 0 $ 4,532.3 $ 4,404.9 Our portfolio valuations, excluding short-term investments, classified as either Level 1 or Level 2 in the above tables are priced exclusively by external sources, including: pricing vendors, dealers/market makers, and exchange-quoted prices. Our short-term security holdings classified as Level 1 are highly liquid, actively marketed, and have a very short duration, primarily 90 days or less to redemption. These securities are held at their original cost, adjusted for any accretion of discount, since that value very closely approximates what an active market participant would be willing to pay for such securities. The remainder of our short-term securities are classified as Level 2 and are not priced externally since these securities continually trade at par value. These securities are classified as Level 2 since they are primarily longer-dated securities issued by municipalities that contain either liquidity facilities or mandatory put features within one year. At March 31, 2019 , vendor-quoted prices represented 77% of our Level 1 classifications (excluding short-term investments), compared to 75% and 79% at March 31, 2018 and December 31, 2018 , respectively. The securities quoted by vendors in Level 1 primarily represent our holdings in U.S. Treasury Notes, which are frequently traded, and the quotes are considered similar to exchange-traded quotes. The balance of our Level 1 pricing comes from quotes obtained directly from trades made on active exchanges. At March 31, 2019 and 2018 , and December 31, 2018 , vendor-quoted prices comprised 99% of our Level 2 classifications in each period (excluding short-term investments), while dealer-quoted prices represented the remaining 1% . In our process for selecting a source (e.g., dealer or pricing service) to provide pricing for securities in our portfolio, we reviewed documentation from the sources that detailed the pricing techniques and methodologies used by these sources and determined if their policies adequately considered market activity, either based on specific transactions for the particular security type or based on modeling of securities with similar credit quality, duration, yield, and structure that were recently transacted. Once a source is chosen, we continue to monitor any changes or modifications to their processes by reviewing their documentation on internal controls for pricing and market reviews. We review quality control measures of our sources as they become available to determine if any significant changes have occurred from period to period that might indicate issues or concerns regarding their evaluation or market coverage. As part of our pricing procedures, we obtain quotes from more than one source to help us fully evaluate the market price of securities. However, our internal pricing policy is to use a consistent source for individual securities in order to maintain the integrity of our valuation process. Quotes obtained from the sources are not considered binding offers to transact. Under our policy, when a review of the valuation received from our selected source appears to be outside of what is considered market level activity (which is defined as trading at spreads or yields significantly different than those of comparable securities or outside the general sector level movement without a reasonable explanation), we may use an alternate source’s price. To the extent we determine that it may be prudent to substitute one source’s price for another, we will contact the initial source to obtain an understanding of the factors that may be contributing to the significant price variance, which often leads the source to adjust their pricing input data for future pricing. To allow us to determine if our initial source is providing a price that is outside of a reasonable range, we review our portfolio pricing on a weekly basis. When necessary, we challenge prices from our sources when a price provided does not match our expectations based on our evaluation of market trends and activity. Initially, we perform a review of our portfolio by sector to identify securities whose prices appear outside of a reasonable range. We then perform a more detailed review of fair values for securities disclosed as Level 2. We review dealer bids and quotes for these and/or similar securities to determine the market level context for our valuations. We then evaluate inputs relevant for each class of securities disclosed in the preceding hierarchy tables. For our structured debt securities, including commercial, residential, and asset-backed securities, we evaluate available market-related data for these and similar securities related to collateral, delinquencies, and defaults for historical trends and reasonably estimable projections, as well as historical prepayment rates and current prepayment assumptions and cash flow estimates. We further stratify each class of our structured debt securities into more finite sectors (e.g., planned amortization class, first pay, second pay, senior, subordinated, etc.) and use duration, credit quality, and coupon to determine if the fair value is appropriate. For our corporate debt and preferred stock (redeemable and nonredeemable) portfolios, as well as the notes issued by The Progressive Corporation (see Note 4 – Debt ), we review securities by duration, coupon, and credit quality, as well as changes in interest rate and credit spread movements within that stratification. The review also includes recent trades, including: volume traded at various levels that establish a market, issuer specific fundamentals, and industry specific economic news as it comes to light. For our municipal securities (e.g., general obligations, revenue, and housing), we stratify the portfolio to evaluate securities by type, coupon, credit quality, and duration to review price changes relative to credit spread and interest rate changes. Additionally, we look to economic data as it relates to geographic location as an indication of price-to-call or maturity predictors. For municipal housing securities, we look to changes in cash flow projections, both historical and reasonably estimable projections, to understand yield changes and their effect on valuation. Lastly, for our short-term securities, we look at acquisition price relative to the coupon or yield. Since our short-term securities are typically 90 days or less to maturity, with the majority listed in Level 2 being 30 days or less to redemption, we believe that acquisition price is the best estimate of fair value. We also review data assumptions as supplied by our sources to determine if that data is relevant to current market conditions. In addition, we independently review each sector for transaction volumes, new issuances, and changes in spreads, as well as the overall movement of interest rates along the yield curve to determine if sufficient activity and liquidity exists to provide a credible source for our market valuations. During each valuation period, we create internal estimations of portfolio valuation (performance returns), based on current market-related activity (i.e., interest rate and credit spread movements and other credit-related factors) within each major sector of our portfolio. We compare our internally generated portfolio results with those generated based on quotes we receive externally and research material valuation differences. We compare our results to index returns for each major sector adjusting for duration and credit quality differences to better understand our portfolio’s results. Additionally, we review on a monthly basis our external sales transactions and compare the actual final market sales prices to previous market valuation prices. This review provides us further validation that our pricing sources are providing market level prices, since we are able to explain significant price changes (i.e., greater than 2%) as known events occur in the marketplace and affect a particular security’s price at sale. This analysis provides us with additional comfort regarding the source’s process, the quality of its review, and its willingness to improve its analysis based on feedback from clients. We believe this effort helps ensure that we are reporting the most representative fair values for our securities. Except as described below, our Level 3 securities are also priced externally; however, due to several factors (e.g., nature of the securities, level of activity, and lack of similar securities trading to obtain observable market level inputs), these valuations are more subjective in nature. Certain private equity investments and fixed-income investments included in the Level 3 category are valued using external pricing supplemented by internal review and analysis. After all the valuations are received and our review is complete, if the inputs used by vendors are determined to not contain sufficient observable market information, we will reclassify the affected security valuations to Level 3. At March 31, 2019 and 2018 , and December 31, 2018 , we did no t have any securities in our fixed-maturity portfolio listed as Level 3. At March 31, 2019 and December 31, 2018 , we held two private nonredeemable preferred securities with a combined value of $30.1 million that were priced internally, compared to one private nonredeemable preferred security with a value of $5.0 million that was priced internally at March 31, 2018 . At March 31, 2019 and 2018 , and December 31, 2018 , we held one Level 3 other risk investment with a value of $0.3 million . To the extent we receive prices from external sources for the Level 3 securities, we would review those prices for reasonableness using internally developed assumptions and then compare our derived prices to the prices we received. During 2019 and 2018, there were no material assets or liabilities measured at fair value on a nonrecurring basis. Based on our review, all prices received from external sources remained unadjusted. Due to the relative size of the Level 3 securities’ fair values compared to the total portfolio’s fair value, any changes in pricing methodology would not have a significant change in valuation that would materially impact net or comprehensive income. The following tables provide a summary of changes in fair value associated with Level 3 assets for the three months ended March 31, 2019 and 2018 : Level 3 Fair Value (millions) Fair Value at Dec. 31, 2018 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain)/Loss on Sales Change in Valuation Net Transfers In (Out) Fair Value at March 31, 2019 Equity securities: Nonredeemable preferred stocks: Financials $ 25.1 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 25.1 Industrials 5.0 0 0 0 0 0 0 5.0 Common equities: Other risk investments 0.3 0 0 0 0 0 0 0.3 Total Level 3 securities $ 30.4 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 30.4 Level 3 Fair Value (millions) Fair Value at Dec. 31, 2017 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain)/Loss on Sales Change in Valuation Net Transfers In (Out) Fair Value at March 31, 2018 Equity securities: Nonredeemable preferred stocks: Financials $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Industrials 5.0 0 0 0 0 0 0 5.0 Common equities: Other risk investments 0.3 0 0 0 0 0 0 0.3 Total Level 3 securities $ 5.3 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 5.3 The following tables provide a summary of the quantitative information about Level 3 fair value measurements for our applicable securities at March 31, 2019 and 2018 , and December 31, 2018 : Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at March 31, 2019 Valuation Technique Unobservable Input Unobservable Input Assumption Equity securities: Nonredeemable preferred stocks: Financials 1 $ 25.1 internal price unadjusted purchase price per share 9.0 Industrials 2 5.0 internal price price-to-sales ratio 5.5 Subtotal Level 3 securities 30.1 Pricing exemption securities 3 0.3 Total Level 3 securities $ 30.4 1 The security was internally-priced since it is privately held. The security was purchased during December 2018 and the value at March 31, 2019 reflects the unadjusted purchase price per share. 2 The security was internally-priced since it is privately held. The price at March 31, 2019 , was calculated using a price-to-sales ratio. 3 The unobservable input is not reasonably available to us. Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at March 31, 2018 Valuation Technique Unobservable Input Unobservable Input Assumption Equity securities: Nonredeemable preferred stocks: Financials $ 0 NA NA NA Industrials 1 5.0 internal price unadjusted purchase price per share 3.9 Subtotal Level 3 securities 5.0 Pricing exemption securities 2 0.3 Total Level 3 securities $ 5.3 NA= Not Available 1 The security was internally-priced since it is privately held. The value at March 31, 2018 reflects the unadjusted purchase price per share. 2 The unobservable input is not reasonably available to us. Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at Dec. 31, 2018 Valuation Technique Unobservable Input Unobservable Input Assumption Equity securities: Nonredeemable preferred stocks: Financials 1 $ 25.1 internal price unadjusted purchase price per share 9.0 Industrials 2 5.0 internal price price-to-sales ratio 5.5 Subtotal Level 3 securities 30.1 Pricing exemption securities 3 0.3 Total Level 3 securities $ 30.4 1 The security was internally-priced since it is privately held. The security was purchased during December 2018 and the value at December 31, 2018 reflects the unadjusted purchase price per share. 2 The security was internally-priced since it is privately held. The price at December 31, 2018, was calculated using a price-to-sales ratio. 3

Debt

Debt	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Debt	Debt — Debt at each of the balance sheet periods consisted of: March 31, 2019 March 31, 2018 December 31, 2018 (millions) Carrying Value Fair Value Carrying Value Fair Value Carrying Value Fair Value 3.75% Senior Notes due 2021 $ 499.2 $ 509.7 $ 498.9 $ 512.1 $ 499.1 $ 506.5 2.45% Senior Notes due 2027 496.6 475.6 496.2 458.3 496.5 455.5 6 5/8% Senior Notes due 2029 296.4 377.8 296.2 370.4 296.4 368.5 4.00% Senior Notes due 2029 544.6 587.9 0 0 544.5 562.4 6.25% Senior Notes due 2032 395.6 508.5 395.4 498.9 395.5 496.6 4.35% Senior Notes due 2044 346.6 371.6 346.5 360.2 346.6 350.2 3.70% Senior Notes due 2045 395.3 389.7 395.2 376.6 395.3 366.7 4.125% Senior Notes due 2047 841.4 885.4 841.3 858.6 841.4 831.9 4.20% Senior Notes due 2048 589.7 628.6 589.5 613.2 589.6 594.0 Total $ 4,405.4 $ 4,734.8 $ 3,859.2 $ 4,048.3 $ 4,404.9 $ 4,532.3 The Progressive Corporation issued $550 million of 4.00% Senior Notes due 2029 (the “ 4.00% Senior Notes”) in October 2018, in an underwritten public offering. The net proceeds from the issuance, after deducting underwriters’ discounts, commissions, and other issuance costs, was $544.5 million . Consistent with the other senior notes issued by Progressive, interest on the 4.00% Senior Notes is payable semiannually, principal is due at maturity, and the note is redeemable, in whole or in part, at any time, subject to a treasury “make whole” provision. During 2018, The Progressive Corporation entered into a new line of credit with PNC Bank, National Association (PNC) in the maximum principal amount of $250 million . This line of credit replaced a previous line of credit that expired in April 2018. The line of credit is on the same terms and conditions as the previous line of credit. Subject to the terms and conditions of the line of credit documents, advances under the line of credit (if any) will bear interest at a variable rate equal to the higher of PNC’s Prime Rate or the sum of the Federal Funds Open Rate plus 50 basis points. Each advance must be repaid on the 30 th day after the advance or, if earlier, on April 30, 2019, the expiration date of the line of credit. Prepayments are permitted without penalty. The line of credit is uncommitted and, as such, all advances are subject to PNC’s discretion. We had no

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes — Deferred tax assets and liabilities are recorded based on the difference between the financial statement and tax bases of assets and liabilities at the enacted tax rates. We review our deferred tax assets regularly for recoverability. At March 31, 2019 and 2018 , and December 31, 2018 , we determined that we did no t need a valuation allowance on our gross deferred tax assets. Although realization of the deferred tax assets is not assured, management believes that it is more likely than not the deferred tax assets will be realized based on our expectation that we will be able to fully utilize the deductions that are ultimately recognized for tax purposes. For the three months ended March 31, 2019 , there have been no material changes in our reserve for uncertain tax positions. The effective tax rate for the three months ended March 31, 2019 was 30.9% , compared to 19.9% for the same period last year. During the first quarter 2019, we increased our provision for income taxes $156.1 million , principally reflecting the total reversal of the tax credits and other tax benefits previously recognized from certain renewable energy investments, plus interest. From 2016 to 2018, we invested in federal renewable energy tax credit funds. In late December 2018 and during the first two months of 2019, we learned of allegations of potential fraudulent conduct by the sponsor of three

Loss and Loss Adjustment Expens

Loss and Loss Adjustment Expense Reserves	3 Months Ended
	Mar. 31, 2019
Loss and Loss Adjustment Expenses Reserves [Abstract]
Loss and Loss Adjustment Expenses Reserves	Loss and Loss Adjustment Expense Reserves — Activity in the loss and loss adjustment expense reserves is summarized as follows: March 31, (millions) 2019 2018 Balance, Beginning of period $ 15,400.8 $ 13,086.9 Less reinsurance recoverables on unpaid losses 2,572.7 2,170.1 Net balance, Beginning of period 12,828.1 10,916.8 Incurred related to: Current year 5,616.4 4,815.2 Prior years 142.6 55.6 Total incurred 5,759.0 4,870.8 Paid related to: Current year 2,517.5 2,217.8 Prior years 2,901.4 2,377.8 Total paid 5,418.9 4,595.6 Net balance, End of period 13,168.2 11,192.0 Plus reinsurance recoverables on unpaid losses 2,708.4 2,137.0 Balance, End of period $ 15,876.6 $ 13,329.0 We experienced unfavorable reserve development of $142.6 million and $55.6 million for the first quarter of 2019 and 2018, respectively, which is reflected as “Incurred related to prior years ” in the table above. First Quarter 2019 • About 40% of the unfavorable prior year reserve development was attributable to accident year 2018, 15% to accident year 2017, and the remainder to accident years 2016 and prior. • Our personal auto products incurred about $111 million of unfavorable loss and loss adjustment expense (LAE) reserve development, with the Agency and Direct auto businesses each contributing about half. The unfavorable development was primarily attributable to late reported losses occurring late 2018 but not reported until 2019, a higher than anticipated frequency of reopened personal injury protection (PIP) claims, primarily in Florida, and increased injury severity reflecting higher medical costs. • Our Commercial Lines and special lines businesses experienced about $22 million and $8 million of unfavorable development, respectively, and our Property business had minimal unfavorable development during the first quarter. First Quarter 2018 • The unfavorable prior year reserve development was attributable to accident years 2017 and 2016, with accident years 2015 and prior recognizing $6 million of favorable development. • Our personal auto businesses incurred about $35 million of unfavorable LAE reserve development, with Agency and Direct auto businesses contributing $24 million and $11 million , respectively. The unfavorable development was primarily due to an increase in reopened PIP claims. • Our Commercial Lines business experienced $19 million of unfavorable development primarily due to late reported losses and higher LAE than anticipated. • Our Property business recognized minimal unfavorable development of $2 million

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	3 Months Ended
	Mar. 31, 2019
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information — Cash and cash equivalents include bank demand deposits and daily overnight reverse repurchase commitments of funds held in bank demand deposit accounts on ARX’s subsidiaries. The amount of reverse repurchase commitments held by ARX’s subsidiaries at March 31, 2019 and 2018 , and December 31, 2018 , were $185.6 million , $166.6 million , and $117.3 million , respectively. Restricted cash on our consolidated balance sheets represents cash that is restricted to pay flood claims under the National Flood Insurance Program’s “Write Your Own” program, for which subsidiaries of ARX are administrators. During the first quarter 2019, non-cash activity includes declared but unpaid common share dividends of $58.4 million (see Note 9 – Dividends for further discussion) and operating lease liabilities arising from obtaining right-of-use assets of $10.9 million (see Note 14 – Leases for further discussion). We paid the following in the respective periods: Three Months Ended March 31, (millions) 2019 2018 Income taxes $ 20.0 $ 0 Interest 53.3 33.3 Operating lease liabilities 18.8 NA

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Segment Information	Segment Information — Our Personal Lines segment writes insurance for personal autos and recreational vehicles (our special lines products). Our Commercial Lines segment writes primary liability, physical damage, and other auto-related insurance for automobiles and trucks owned and/or operated predominantly by small businesses in the business auto, for-hire transportation, contractor, for-hire specialty, tow, and for-hire livery markets. Our Property segment writes residential property insurance for homeowners, other property owners, and renters. Our other indemnity businesses include our run-off businesses. Our service businesses provide insurance-related services, including processing Commercial Automobile Insurance Procedures/Plans (CAIP) business and serving as an agent for homeowners, general liability, and workers’ compensation insurance, among other products, through our programs with ASI and unaffiliated insurance companies. All segment revenues are generated from external customers; all intercompany transactions are eliminated in consolidation. Following are the operating results for the respective periods: Three Months Ended March 31, 2019 2018 (millions) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Personal Lines Agency $ 3,508.5 $ 453.0 $ 3,063.8 $ 409.1 Direct 3,576.3 321.9 3,016.3 298.0 Total Personal Lines 1 7,084.8 774.9 6,080.1 707.1 Commercial Lines 1,013.0 166.6 808.6 94.8 Property 2 362.0 7.7 285.3 28.5 Other indemnity 0 0 0 0.2 Total underwriting operations 8,459.8 949.2 7,174.0 830.6 Fees and other revenues 3 130.2 NA 103.8 NA Service businesses 42.6 4.5 34.2 4.9 Investments 4 667.4 661.2 118.1 112.1 Interest expense NA (47.4 ) NA (36.8 ) Consolidated total $ 9,300.0 $ 1,567.5 $ 7,430.1 $ 910.8 NA = Not applicable 1 Personal auto insurance accounted for 94% of the total Personal Lines segment net premiums earned during the three months ended March 31, 2019 and 2018 ; insurance for our special lines products (e.g., motorcycles, ATVs, RVs, watercraft, and snowmobiles) accounted for the balance of the Personal Lines net premiums earned. 2 For the three months ended March 31, 2019 and 2018, pretax profit (loss) includes $17.9 million and $18.0 million , respectively, of amortization expense predominately associated with the acquisition of a controlling interest in ARX. Although this expense is included in our Property segment, it is not reported in the consolidated results of ARX and, therefore, does not affect the value of net income attributable to noncontrolling interest. 3 Pretax profit (loss) for fees and other revenues is attributable to operating segments. 4 Revenues represent recurring investment income and total net realized gains (losses) on securities; pretax profit is net of investment expense. Our management uses underwriting margin and combined ratio as primary measures of underwriting profitability. Underwriting profitability is calculated by subtracting losses and loss adjustment expenses, policy acquisition costs, and other underwriting expenses from the total of net premiums earned and fees and other revenues. The underwriting margin is the pretax underwriting profit (loss) expressed as a percentage of net premiums earned (i.e., revenues from underwriting operations). Combined ratio is the complement of the underwriting margin. Following are the underwriting margins and combined ratios for our underwriting operations for the respective periods: Three Months Ended March 31, 2019 2018 Underwriting Margin Combined Ratio Underwriting Margin Combined Ratio Personal Lines Agency 12.9 % 87.1 13.4 % 86.6 Direct 9.0 91.0 9.9 90.1 Total Personal Lines 10.9 89.1 11.6 88.4 Commercial Lines 16.4 83.6 11.7 88.3 Property 1 2.1 97.9 10.0 90.0 Total underwriting operations 11.2 88.8 11.6 88.4 1 Included in the three months ended March 31, 2019 and 2018, is 5.0 points and 6.3

Dividends

Dividends	3 Months Ended
	Mar. 31, 2019
Dividends [Abstract]
Dividends	Dividends Common Share Dividends In the first quarter 2019, the Board of Directors declared a dividend of $0.10 per common share, or an estimated $58.4 million in the aggregate, payable April 15, 2019, to shareholders of record at the close of business on April 5, 2019. The Board expects to declare regular, quarterly common share dividends and, on at least an annual basis, to consider declaring an additional common share dividend. Prior to 2019, we had a policy of paying an annual variable dividend (see Note 14 - Dividends in our 2018 Annual Report to Shareholders). Following is a summary of our common share dividends that were declared in 2018 and 2017 under that policy: (millions, except per share amounts) Amount of Common Share Dividends Dividend Type Declared Paid Per Share Accrued 1 Paid 1 Annual – Variable December 2018 February 2019 $ 2.5140 $ 1,467.9 $ 1,467.9 Annual – Variable December 2017 February 2018 1.1247 655.1 654.9 1 Variance between accrued and paid, if any, reflects the difference between the number of estimated and actual shares outstanding as of the record date. Preferred Share Dividends During the first quarter of 2019, the Board declared, and we paid, a $26.875 per share, or $13.4 million , dividend on our Series B Fixed-to-Floating Rate Cumulative Perpetual Serial Preferred Shares, without par value (the “Series B Preferred Shares”). There are 500,000 Series B Preferred Shares outstanding, which are cumulative and have a liquidation preference of $1,000 per share (the “stated amount”). Holders of the Series B Preferred Shares will be entitled to receive cumulative cash dividends semi-annually in March and September, if and when declared by the Board of Directors. Until March 15, 2023 (the “fixed-rate period”), the annual dividend rate is fixed at 5.375% of the stated amount per share. Beginning March 15, 2023, the annual dividend rate switches to a floating rate equal to the three-month LIBOR rate (or, if LIBOR is not available, a substitute rate determined in accordance with the terms of the Series B Preferred Shares) plus a spread of 2.539%

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) — The components of other comprehensive income (loss), including reclassification adjustments by income statement line item, were as follows: Components of Changes in Accumulated Other Comprehensive Income (after tax) (millions) Pretax total accumulated other comprehensive income (loss) Total tax (provision) benefit After tax total accumulated other comprehensive income (loss) Total net unrealized gains (losses) on securities Net unrealized gains (losses) on forecasted transactions (Income) loss attributable to NCI Balance at December 31, 2018 $ (153.0 ) $ 32.1 $ (120.9 ) $ (105.6 ) $ (17.2 ) $ 1.9 Other comprehensive income (loss) before reclassifications: Investment securities 414.5 (87.0 ) 327.5 327.5 0 0 Forecasted transactions 0 0 0 0 0 0 Loss attributable to noncontrolling interest (NCI) (2.9 ) 0.6 (2.3 ) 0 0 (2.3 ) Total other comprehensive income (loss) before reclassifications 411.6 (86.4 ) 325.2 327.5 0 (2.3 ) Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings 0 0 0 0 0 0 Net realized gains (losses) on securities 33.4 (7.0 ) 26.4 26.4 0 0 Interest expense (0.3 ) 0.1 (0.2 ) 0 (0.2 ) 0 Total reclassification adjustment for amounts realized in net income 33.1 (6.9 ) 26.2 26.4 (0.2 ) 0 Total other comprehensive income (loss) 378.5 (79.5 ) 299.0 301.1 0.2 (2.3 ) Balance at March 31, 2019 $ 225.5 $ (47.4 ) $ 178.1 $ 195.5 $ (17.0 ) $ (0.4 ) Components of Changes in Accumulated Other Comprehensive Income (after tax) (millions) Pretax total accumulated other comprehensive income (loss) Total tax (provision) benefit After tax total accumulated other comprehensive income (loss) Total net unrealized gains (losses) on securities Net (Income) loss attributable to NCI Balance at December 31, 2017 $ 1,977.8 $ (695.6 ) $ 1,282.2 $ 1,295.0 $ (14.8 ) $ 2.0 Cumulative effect adjustment (2,006.0 ) 705.8 (1,300.2 ) (1,300.2 ) 0 0 Reclassification of disproportionate amounts 0 (4.3 ) (4.3 ) (1.1 ) (3.2 ) 0 Adjusted balance at December 31, 2017 (28.2 ) 5.9 (22.3 ) (6.3 ) (18.0 ) 2.0 Other comprehensive income (loss) before reclassifications: Investment securities (203.4 ) 42.8 (160.6 ) (160.6 ) 0 0 Forecasted transactions 0 0 0 0 0 0 Loss attributable to noncontrolling interest (NCI) 5.1 (1.1 ) 4.0 0 0 4.0 Total other comprehensive income (loss) before reclassifications (198.3 ) 41.7 (156.6 ) (160.6 ) 0 4.0 Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings 0 0 0 0 0 0 Net realized gains (losses) on securities (7.7 ) 1.6 (6.1 ) (6.1 ) 0 0 Interest expense (0.2 ) 0 (0.2 ) 0 (0.2 ) 0 Total reclassification adjustment for amounts realized in net income (7.9 ) 1.6 (6.3 ) (6.1 ) (0.2 ) 0 Total other comprehensive income (loss) (190.4 ) 40.1 (150.3 ) (154.5 ) 0.2 4.0 Balance at March 31, 2018 $ (218.6 ) $ 46.0 $ (172.6 ) $ (160.8 ) $ (17.8 ) $ 6.0 In an effort to manage interest rate risk, we often enter into forecasted transactions on Progressive’s debt issuances. We expect to reclassify $1.0 million (pretax) into interest expense during the next 12 months, related to net unrealized losses on forecasted transactions (see Note 4 – Debt

Litigation

Litigation	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Litigation	Litigation — The Progressive Corporation and/or its insurance subsidiaries are named as defendants in various lawsuits arising out of claims made under insurance policies written by our insurance subsidiaries in the ordinary course of business. We consider all legal actions relating to such claims in establishing our loss and loss adjustment expense reserves. In addition, The Progressive Corporation and/or its subsidiaries are named as defendants in a number of class action or individual lawsuits that challenge certain of the operations of the subsidiaries. These cases include those alleging damages as a result of our subsidiaries’ practices in evaluating or paying medical or injury claims or benefits, including, but not limited to, personal injury protection, medical payments, and bodily injury benefits; the utilization, content, or appearance of policy documents; labor rates paid to auto body repair shops; wage and hour issues; and cases challenging other aspects of our subsidiaries’ claims, marketing, or sales practices, or other business operations. Other insurance companies face many of these same issues. The nature and volume of litigation to which The Progressive Corporation is subject is similar to that which was disclosed in Note 12 – Litigation in our 2018 Annual Report to Shareholders. We plan to contest the pending lawsuits vigorously, but may pursue settlement negotiations in some cases, as we deem appropriate. The outcomes of pending cases are uncertain at this time. We establish accruals for these lawsuits when it is probable that a loss has been or will be incurred and we can reasonably estimate potential loss exposure, which may include a range of loss. As to lawsuits for which the loss is considered neither probable or estimable, or is considered probable but not estimable, we do not establish an accrual. Nevertheless, we continue to evaluate this pending litigation to determine if any losses not deemed probable and estimable become so, at which point we would establish an accrual at our best estimate of the loss or range of loss. With respect to our pending lawsuits that are not related to claims under insurance policies, the accruals that we have established, if any, were not material at March 31, 2019 or 2018 , and there were no material settlements during the first three months of 2019 or 2018 . For most of these lawsuits, we do not consider any losses to be both probable and estimable, and we are unable to estimate a meaningful range of loss, if any, at this time, due to the factors discussed in Note 12 – Litigation in our 2018 Annual Report to Shareholders. In the event that any one or more of these lawsuits results in a substantial judgment against or settlement by us, or if our accruals (if any) prove to be inadequate by a significant amount, the resulting liability could have a material adverse effect on our consolidated financial condition, cash flows, and/or results of operations. For a further discussion on our pending litigation and related reserving policies, see Note 12 – Litigation in our 2018

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interest	3 Months Ended
	Mar. 31, 2019
Temporary Equity Disclosure [Abstract]
Redeemable Noncontrolling Interest	Redeemable Noncontrolling Interest — In connection with the April 2015 acquisition of a controlling interest in ARX, The Progressive Corporation entered into a stockholders’ agreement with the other ARX stockholders. Pursuant to the stockholders’ agreement, the minority ARX stockholders “put” a portion of their ARX shares to Progressive in 2018, and have the right to put all of their remaining shares to Progressive in 2021. During 2018, minority ARX stockholders put 204,527 shares, including 5,483 shares that were issued upon the exercise of outstanding stock options. Progressive acquired these additional shares, in a cash transaction, for a total cost of $295.9 million . If ARX stockholders do not put all of their shares to Progressive in 2021, Progressive has the ability to “call ” all of the outstanding shares shortly thereafter and to bring its ownership stake to 100% in 2021. See Note 15 – Redeemable Noncontrolling Interest in our 2018 Annual Report to Shareholders for a discussion of the purchase price for shares to be purchased by Progressive pursuant to these put or call rights. At March 31, 2019, Progressive’s share ownership interest in ARX was 86.8% . Since these securities are redeemable upon the occurrence of an event that is not solely within the control of Progressive, we have recorded the redeemable noncontrolling interest (NCI) as mezzanine equity on our consolidated balance sheets, which represents the minority shares at the current estimated purchase price pursuant to the put and call provisions of the stockholders’ agreement. The estimated purchase price is based, in part, on the change in tangible net book value of ARX from December 31, 2014, to the balance sheet dates. In addition to these minority shares, at March 31, 2019 , ARX employees held options to purchase 16,067 ARX shares. These options and any shares issued upon exercise are subject to the stockholders’ agreement, including the “put ” and “call ” rights described above. Until the options are exercised, the underlying obligation of approximately $23.8 million is not recorded as part of redeemable NCI. See Note 9 – Employee Benefit Plans in our 2018 Annual Report to Shareholders for a discussion of our employee stock options. The changes in the components of redeemable NCI were: (millions) March 31, 2019 March 31, 2018 December 31, 2018 Balance, Beginning of period $ 214.5 $ 503.7 $ 503.7 Net income attributable to NCI 4.4 11.8 5.7 Other comprehensive income (loss) attributable to NCI 1 2.3 (4.0 ) (3.3 ) Exercise of employee stock options 0 1.4 9.4 Purchase/change of ARX minority shares 0 0 (298.2 ) Change in redemption value of NCI 0 1.3 (2.8 ) Balance, End of period $ 221.2 $ 514.2 $ 214.5 1

Goodwill and Intangible Assets

Goodwill and Intangible Assets	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill During the three months ended March 31, 2019 , there were no changes to the carrying amount of goodwill. No accumulated goodwill impairment losses exist. Intangible Assets The following table is a summary of the net carrying amount of other intangible assets: (millions) March 31, 2019 March 31, 2018 December 31, 2018 Intangible assets subject to amortization $ 264.3 $ 336.2 $ 282.2 Indefinite-lived intangible assets 1 12.4 12.4 12.4 Total $ 276.7 $ 348.6 $ 294.6 1 Indefinite-lived intangible assets are comprised of state insurance and agent licenses. State insurance licenses were previously subject to amortization under superseded accounting guidance and have $0.6 million of accumulated amortization for all periods presented. Intangible assets subject to amortization consisted of the following: (millions) March 31, 2019 March 31, 2018 December 31, 2018 Category Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Policies in force $ 256.2 $ 146.4 $ 109.8 $ 256.2 $ 109.8 $ 146.4 $ 256.2 $ 137.3 $ 118.9 Agency relationships 159.2 45.5 113.7 159.2 34.2 125.0 159.2 42.6 116.6 Software rights 79.1 42.7 36.4 79.1 32.1 47.0 79.1 40.1 39.0 Trade name 34.8 30.4 4.4 34.8 17.0 17.8 34.8 27.1 7.7 Total $ 529.3 $ 265.0 $ 264.3 $ 529.3 $ 193.1 $ 336.2 $ 529.3 $ 247.1 $ 282.2 Amortization expense was $17.9 million and $18.0 million for the three months ended March 31, 2019 and 2018, respectively. As of March 31, 2019 , the remaining average life of all of our intangible assets is 3.7 years

Leases

Leases	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Leases	Leases — We have certain noncancelable operating leases for office space, computer equipment, and vehicles, all with expected terms greater than one year, that are reported as a component of “other assets” and “accounts payable, accrued expenses, and other liabilities” in our 2019 consolidated balance sheet, at March 31, 2019. The leased assets represent our right to use an underlying asset for the lease term and the lease liabilities represent our obligation to make lease payments arising from the lease. We use an incremental borrowing rate to calculate the present value of the remaining lease payments. At March 31, 2019, we had operating lease assets of $201.6 million and operating lease liabilities of $211.4 million . At March 31, 2019, the following table shows our operating lease liabilities, on an undiscounted basis for the periods indicated, along with key inputs used to discount our lease liabilities, in accordance with the new accounting standard adopted on January 1, 2019 (see Note 15 – New Accounting Standard for further discussion): (millions) 2019 (excluding the three months ended March 31, 2019) $ 55.3 2020 72.7 2021 56.3 2022 25.6 2023 9.6 Thereafter 4.4 Total $ 223.9 Interest (12.5 ) Present value of lease liabilities $ 211.4 Weighted-average remaining term 3.2 years Weighted-average discount rate 3.5 % We had certain noncancelable operating lease commitments with lease terms greater than one year for property and computer equipment. The minimum commitments under these agreements at December 31, 2018, were as follows: (millions) Commitments 2019 $ 64.1 2020 65.5 2021 52.8 2022 24.3 2023 8.5 Thereafter 3.8 Total $ 219.0 We review contracts at inception to determine if it contains a lease and whether the lease qualifies as an operating or financing lease. Operating leases are expensed on a straight-line basis over the term of the lease. For the three months ended March 31, 2019, we incurred operating lease costs of $24.0 million

New Accounting Standards

New Accounting Standards	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
New Accounting Standards	New Accounting Standards Issued In August 2018, the Financial Accounting Standards Board (FASB) issued an Accounting Standards Update (ASU), which provides additional guidance on the requirements for capitalizing and amortizing implementation costs incurred in a cloud computing arrangement that does not include a software license. This ASU will be effective for fiscal years (including interim periods within those fiscal years) beginning after December 15, 2019 (2020 for calendar-year companies). We do not expect this standard to have a material impact on our financial condition, cash flows, or results of operations. In August 2018, the FASB issued an ASU, which amends the disclosure requirements for fair value measurements. The ASU requires companies to disclose the changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period and the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements. The ASU also removes current disclosure requirements for the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, the policy for timing of transfers between levels, and the valuation processes for Level 3 fair value measurements. The ASU is effective for fiscal years beginning after December 15, 2019, and should be applied prospectively for the additions to the disclosure requirements and applied retrospectively to all periods presented for all other amendments. As permitted by the ASU, we elected to partially early adopt the removal of current disclosure requirements and will adopt the new disclosure requirements as of the effective date. We do not expect this standard to have an impact on our financial condition, cash flows, or results of operations. In January 2017, the FASB issued an ASU, which eliminates the requirement to determine the implied fair value of goodwill in measuring an impairment loss. Upon adoption, the measurement of a goodwill impairment will represent the excess of the reporting unit’s carrying value over fair value, limited to the carrying value of goodwill. This ASU is effective for goodwill impairment tests in fiscal years beginning after December 15, 2019 (2020 for calendar-year companies), with early adoption permitted. We do not expect this standard to have a material impact on our financial position or results of operations. In June 2016, the FASB issued an ASU intended to improve the timing, and enhance the accounting and disclosure, of credit losses on financial assets. Additionally, this update will modify the existing accounting guidance related to the impairment evaluation for available-for-sale debt securities and will result in the creation of an allowance for credit losses as a contra asset account. The ASU will require cumulative-effect changes to retained earnings in the period of adoption, if any occur, and will also require prospective changes on previously recorded impairments. This ASU is effective for fiscal years (including interim periods within those fiscal years) beginning after December 15, 2019 (2020 for calendar-year companies), with early adoption permissible (including interim periods within that fiscal year) beginning after December 15, 2018 (2019 for calendar-year companies). While the ASU creates additional accounting complexities related to the recognition of the impairment losses, and subsequent recoveries, through an allowance for credit losses account, we currently do not expect the ASU to have a material impact on our current method of evaluating securities or reinsurance recoverables for credit losses or the timing or recognition of the amounts of the impairment losses. Adopted On January 1, 2019, we adopted the ASU which required lessees to report their operating leases as both an asset and liability on the statement of financial position and to disclose key information about leasing arrangements in the financial statement footnotes. We are reporting our operating leased assets and liabilities as a component of “other assets” and “accounts payable, accrued expenses, and other liabilities,” respectively. We did not restate prior year information. Upon adoption of the ASU, based on our lease portfolio on January 1, 2019, and after applying the practical expedient under which we were not required to reassess any of our existing contracts, classification of our leases, or the initial direct costs for existing leases, we recorded a transition adjustment of $213.0 million for leased assets and $217.6 million for liabilities. The adoption of this ASU had no impact on our results of operations or cash flows. See Note 14 – Leases for further information.

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2019
Investments Schedule [Abstract]
Schedule of Debt and Equity Securities Reconciliation	The following tables present the composition of our investment portfolio by major security type, consistent with our classification of how we manage, monitor, and measure the portfolio. Our securities are reported in our Consolidated Balance Sheets at fair value. The changes in fair value for our fixed-maturity securities (other than hybrid securities) are reported as a component of accumulated other comprehensive income, net of deferred income taxes, in our Consolidated Balance Sheets. The net holding period gains (losses) reported below represent the inception-to-date changes in fair value. The changes in the net holding period gains (losses) between periods for the hybrid securities and equity securities are recorded as a component of net realized gains (losses) on securities in our Consolidated Statements of Comprehensive Income. ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) Fair Value % of Value March 31, 2019 Available-for-sale securities: Fixed maturities: U.S. government obligations $ 9,685.6 $ 105.5 $ (20.6 ) $ 0 $ 9,770.5 28.3 % State and local government obligations 1,505.5 15.4 (5.1 ) 0 1,515.8 4.4 Corporate debt securities 7,870.1 126.3 (19.0 ) 0.6 7,978.0 23.1 Residential mortgage-backed securities 609.9 5.7 (2.6 ) 0 613.0 1.8 Commercial mortgage-backed securities 3,825.6 35.9 (7.9 ) 0 3,853.6 11.2 Other asset-backed securities 3,834.2 10.0 (4.5 ) 0.1 3,839.8 11.1 Redeemable preferred stocks 243.6 9.0 (1.2 ) (0.2 ) 251.2 0.7 Total fixed maturities 27,574.5 307.8 (60.9 ) 0.5 27,821.9 80.6 Short-term investments 2,584.7 0 0 0 2,584.7 7.5 Total available-for-sale securities 30,159.2 307.8 (60.9 ) 0.5 30,406.6 88.1 Equity securities: Nonredeemable preferred stocks 1,021.1 0 0 74.3 1,095.4 3.2 Common equities 1,194.3 0 0 1,816.2 3,010.5 8.7 Total equity securities 2,215.4 0 0 1,890.5 4,105.9 11.9 Total portfolio 1,2 $ 32,374.6 $ 307.8 $ (60.9 ) $ 1,891.0 $ 34,512.5 100.0 % ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) Fair Value % of Value March 31, 2018 Available-for-sale securities: Fixed maturities: U.S. government obligations $ 9,081.6 $ 3.9 $ (127.4 ) $ 0 $ 8,958.1 30.6 % State and local government obligations 1,732.3 4.3 (16.4 ) (0.1 ) 1,720.1 5.9 Corporate debt securities 6,102.6 4.8 (64.8 ) (1.5 ) 6,041.1 20.7 Residential mortgage-backed securities 746.7 9.9 (4.8 ) 0 751.8 2.6 Commercial mortgage-backed securities 2,289.8 4.5 (24.8 ) 0 2,269.5 7.8 Other asset-backed securities 2,472.4 2.4 (12.9 ) 0.2 2,462.1 8.4 Redeemable preferred stocks 201.8 18.6 (1.4 ) (1.6 ) 217.4 0.7 Total fixed maturities 22,627.2 48.4 (252.5 ) (3.0 ) 22,420.1 76.7 Short-term investments 3,052.4 0 0 0 3,052.4 10.4 Total available-for-sale securities 25,679.6 48.4 (252.5 ) (3.0 ) 25,472.5 87.1 Equity securities: Nonredeemable preferred stocks 659.6 0 0 86.3 745.9 2.5 Common equities 1,265.5 0 0 1,767.7 3,033.2 10.4 Total equity securities 1,925.1 0 0 1,854.0 3,779.1 12.9 Total portfolio 1,2 $ 27,604.7 $ 48.4 $ (252.5 ) $ 1,851.0 $ 29,251.6 100.0 % ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) Fair Value % of Value December 31, 2018 Available-for-sale securities: Fixed maturities: U.S. government obligations $ 9,897.4 $ 71.2 $ (52.1 ) $ 0 $ 9,916.5 29.5 % State and local government obligations 1,654.6 7.3 (12.8 ) 0 1,649.1 4.9 Corporate debt securities 8,808.5 13.6 (125.3 ) (2.5 ) 8,694.3 25.9 Residential mortgage-backed securities 733.5 6.0 (5.1 ) 0 734.4 2.2 Commercial mortgage-backed securities 3,332.8 7.8 (39.0 ) 0 3,301.6 9.8 Other asset-backed securities 3,585.4 3.6 (11.8 ) 0.1 3,577.3 10.7 Redeemable preferred stocks 243.7 5.9 (3.5 ) (7.8 ) 238.3 0.7 Total fixed maturities 28,255.9 115.4 (249.6 ) (10.2 ) 28,111.5 83.7 Short-term investments 1,795.9 0 0 0 1,795.9 5.4 Total available-for-sale securities 30,051.8 115.4 (249.6 ) (10.2 ) 29,907.4 89.1 Equity securities: Nonredeemable preferred stocks 1,002.6 0 0 31.3 1,033.9 3.1 Common equities 1,148.9 0 0 1,477.2 2,626.1 7.8 Total equity securities 2,151.5 0 0 1,508.5 3,660.0 10.9 Total portfolio 1,2 $ 32,203.3 $ 115.4 $ (249.6 ) $ 1,498.3 $ 33,567.4 100.0 % 1 Our portfolio reflects the effect of unsettled security transactions; at March 31, 2019 , we had $76.5 million included in “other assets,” compared to $83.6 million and $5.9 million at March 31, 2018 and December 31, 2018 , respectively, included in “other liabilities.” 2 The total fair value of the portfolio at March 31, 2019 and 2018 , and December 31, 2018 , included $1.2 billion , $2.1 billion , and $2.9 billion
Hybrid Instruments Table	Included in our fixed-maturity securities are hybrid securities, which are reported at fair value: March 31, (millions) 2019 2018 December 31, 2018 Fixed maturities: State and local government obligations $ 3.6 $ 3.7 $ 3.6 Corporate debt securities 161.7 86.4 158.9 Other asset-backed securities 4.0 6.1 4.5 Redeemable preferred stocks 85.4 37.8 77.7 Total hybrid securities $ 254.7 $ 134.0 $ 244.7
Investments Classified by Contractual Maturity Date	The composition of fixed maturities by maturity at March 31, 2019 , was: (millions) Cost Fair Value Less than one year $ 4,929.9 $ 4,934.2 One to five years 16,765.4 16,878.8 Five to ten years 5,818.5 5,945.9 Ten years or greater 60.7 63.0 Total $ 27,574.5 $ 27,821.9
Schedule of Unrealized Loss on Investments	The following tables show the composition of gross unrealized losses by major security type and by the length of time that individual securities have been in a continuous unrealized loss position: Total No. of Sec. Total Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Unrealized Losses No. of Sec. Fair Unrealized Losses March 31, 2019 Fixed maturities: U.S. government obligations 42 $ 3,174.0 $ (20.6 ) 1 $ 19.9 $ (0.1 ) 41 $ 3,154.1 $ (20.5 ) State and local government obligations 162 567.2 (5.1 ) 10 31.4 0 152 535.8 (5.1 ) Corporate debt securities 153 2,555.7 (19.0 ) 11 175.9 (1.1 ) 142 2,379.8 (17.9 ) Residential mortgage-backed securities 63 299.4 (2.6 ) 15 139.1 (1.1 ) 48 160.3 (1.5 ) Commercial mortgage-backed securities 76 1,294.3 (7.9 ) 13 229.1 (0.9 ) 63 1,065.2 (7.0 ) Other asset-backed securities 142 1,294.0 (4.5 ) 27 296.5 (0.7 ) 115 997.5 (3.8 ) Redeemable preferred stocks 2 31.1 (1.2 ) 0 0 0 2 31.1 (1.2 ) Total fixed maturities 640 $ 9,215.7 $ (60.9 ) 77 $ 891.9 $ (3.9 ) 563 $ 8,323.8 $ (57.0 ) Total No. of Sec. Total Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Unrealized Losses No. of Sec. Fair Unrealized Losses March 31, 2018 Fixed maturities: U.S. government obligations 64 $ 7,933.8 $ (127.4 ) 37 $ 5,954.6 $ (90.7 ) 27 $ 1,979.2 $ (36.7 ) State and local government obligations 426 1,263.7 (16.4 ) 301 890.2 (9.5 ) 125 373.5 (6.9 ) Corporate debt securities 348 5,082.9 (64.8 ) 290 4,515.1 (56.1 ) 58 567.8 (8.7 ) Residential mortgage-backed securities 211 329.3 (4.8 ) 36 112.8 (0.5 ) 175 216.5 (4.3 ) Commercial mortgage-backed securities 131 1,974.8 (24.8 ) 89 1,510.5 (16.2 ) 42 464.3 (8.6 ) Other asset-backed securities 208 1,958.5 (12.9 ) 129 1,439.1 (8.7 ) 79 519.4 (4.2 ) Redeemable preferred stocks 3 26.8 (1.4 ) 2 15.3 (0.4 ) 1 11.5 (1.0 ) Total fixed maturities 1,391 $ 18,569.8 $ (252.5 ) 884 $ 14,437.6 $ (182.1 ) 507 $ 4,132.2 $ (70.4 ) Total No. of Sec. Total Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Unrealized Losses No. of Sec. Fair Unrealized Losses December 31, 2018 Fixed maturities: U.S. government obligations 51 $ 4,438.0 $ (52.1 ) 2 $ 126.6 $ (0.1 ) 49 $ 4,311.4 $ (52.0 ) State and local government obligations 299 972.4 (12.8 ) 49 192.7 (0.3 ) 250 779.7 (12.5 ) Corporate debt securities 368 6,723.3 (125.3 ) 133 2,613.3 (33.4 ) 235 4,110.0 (91.9 ) Residential mortgage-backed securities 228 450.2 (5.1 ) 32 248.8 (0.8 ) 196 201.4 (4.3 ) Commercial mortgage-backed securities 140 2,328.5 (39.0 ) 48 741.2 (8.9 ) 92 1,587.3 (30.1 ) Other asset-backed securities 203 2,691.3 (11.8 ) 84 1,551.7 (3.2 ) 119 1,139.6 (8.6 ) Redeemable preferred stocks 3 48.5 (3.5 ) 1 18.9 (0.6 ) 2 29.6 (2.9 ) Total fixed maturities 1,292 $ 17,652.2 $ (249.6 ) 349 $ 5,493.2 $ (47.3 ) 943 $ 12,159.0 $ (202.3 )
Non Credit Portion Of Other Than Temporary Impairment Recorded In Accumulated Other Comprehensive Income Table	The following table shows the total non-credit portion of the OTTI recorded in accumulated other comprehensive income, reflecting the original non-credit loss at the time the credit impairment was determined (i.e., unadjusted for valuation changes subsequent to the original write-down): March 31, December 31, (millions) 2019 2018 Fixed maturities: Residential mortgage-backed securities $ (19.7 ) $ (19.7 ) $ (19.7 ) Commercial mortgage-backed securities (0.1 ) (0.3 ) (0.1 ) Total fixed maturities $ (19.8 ) $ (20.0 ) $ (19.8 )
Other than Temporary Impairment, Credit Losses Recognized in Earnings	The following tables provide rollforwards of the amounts related to credit losses recognized in earnings for the periods ended March 31, 2019 and 2018 , for which a portion of the OTTI losses were also recognized in accumulated other comprehensive income at the time the credit impairments were determined and recognized: Three Months Ended March 31, 2019 Mortgage-Backed (millions) Residential Commercial Total Balance at December 31, 2018 $ 0 $ 0.5 $ 0.5 Change in recoveries of future cash flows expected to be collected 1 0 0 0 Balance at March 31, 2019 $ 0 $ 0.5 $ 0.5 Three Months Ended March 31, 2018 Mortgage-Backed (millions) Residential Commercial Total Balance at December 31, 2017 $ 0 $ 0.5 $ 0.5 Change in recoveries of future cash flows expected to be collected 1 0 0 0 Balance at March 31, 2018 $ 0 $ 0.5 $ 0.5 1 Reflects the current period change in the expected recovery of prior impairments that will be accreted into income over the remaining life of the security.
Realized Gain (Loss) on Investments	The components of net realized gains (losses) for the three months ended March 31, were: Three Months (millions) 2019 2018 Gross realized gains on security sales Available-for-sale securities: U.S. government obligations $ 36.6 $ 0 State and local government obligations 1.6 8.6 Corporate and other debt securities 16.1 0.1 Commercial mortgage-backed securities 0.7 1.7 Redeemable preferred stocks 0 1.1 Total available-for-sale securities 55.0 11.5 Equity securities: Nonredeemable preferred stocks 4.9 3.6 Common equities 4.5 119.9 Total equity securities 9.4 123.5 Subtotal gross realized gains on security sales 64.4 135.0 Gross realized losses on security sales Available-for-sale securities: U.S. government obligations (7.1 ) (8.9 ) State and local government obligations (0.6 ) (1.3 ) Corporate and other debt securities (6.1 ) (3.1 ) Residential mortgage-backed securities (2.3 ) 0 Commercial mortgage-backed securities (2.1 ) (6.3 ) Other asset-backed securities (0.1 ) (0.1 ) Total available-for-sale securities (18.3 ) (19.7 ) Equity securities: Nonredeemable preferred stocks 0 (0.4 ) Common equities 0 (7.9 ) Total equity securities 0 (8.3 ) Subtotal gross realized losses on security sales (18.3 ) (28.0 ) Net realized gains (losses) on security sales Available-for-sale securities: U.S. government obligations 29.5 (8.9 ) State and local government obligations 1.0 7.3 Corporate and other debt securities 10.0 (3.0 ) Residential mortgage-backed securities (2.3 ) 0 Commercial mortgage-backed securities (1.4 ) (4.6 ) Other asset-backed securities (0.1 ) (0.1 ) Redeemable preferred stocks 0 1.1 Total available-for-sale securities 36.7 (8.2 ) Equity securities: Nonredeemable preferred stocks 4.9 3.2 Common equities 4.5 112.0 Total equity securities 9.4 115.2 Subtotal net realized gains (losses) on security sales 46.1 107.0 Net holding period gains (losses) Hybrid securities 10.7 (3.2 ) Equity securities 382.0 (152.0 ) Subtotal net holding period gains (losses) 392.7 (155.2 ) Other-than-temporary impairment losses Other asset impairment (24.3 ) 0 Subtotal other-than-temporary impairment losses (24.3 ) 0 Total net realized gains (losses) on securities $ 414.5 $ (48.2 )
Components of Equity Realized Gains (Losses)	The following table reflects our holding period realized gains (losses) on equity securities recognized for the three months ended March 31, 2019 and 2018 for equity securities held at quarter end: Three Months (millions) 2019 2018 Total net gains (losses) recognized during the period on equity securities $ 391.4 $ (36.8 ) Less: Net gains (losses) recognized on equity securities sold during the period 9.4 115.2 Net holding period gains (losses) recognized during the period on equity securities held at period end $ 382.0 $ (152.0 )
Components of Net Investment Income	The components of net investment income for the three months ended March 31, were: Three Months (millions) 2019 2018 Available-for-sale securities: Fixed maturities: U.S. government obligations $ 53.7 $ 39.8 State and local government obligations 9.3 10.0 Corporate debt securities 77.2 36.2 Residential mortgage-backed securities 6.6 6.9 Commercial mortgage-backed securities 31.7 21.2 Other asset-backed securities 26.0 13.6 Redeemable preferred stocks 3.7 2.6 Total fixed maturities 208.2 130.3 Short-term investments 16.0 10.1 Total available-for-sale securities 224.2 140.4 Equity securities: Nonredeemable preferred stocks 15.5 10.9 Common equities 13.2 15.0 Total equity securities 28.7 25.9 Investment income 252.9 166.3 Investment expenses (6.2 ) (6.0 ) Net investment income $ 246.7 $ 160.3

Fair Value (Tables)

Fair Value (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Composition of Investment Portfolio by Major Security Type	The composition of the investment portfolio by major security type and our outstanding debt was: Fair Value (millions) Level 1 Level 2 Level 3 Total Cost March 31, 2019 Fixed maturities: U.S. government obligations $ 9,770.5 $ 0 $ 0 $ 9,770.5 $ 9,685.6 State and local government obligations 0 1,515.8 0 1,515.8 1,505.5 Corporate debt securities 0 7,978.0 0 7,978.0 7,870.1 Subtotal 9,770.5 9,493.8 0 19,264.3 19,061.2 Asset-backed securities: Residential mortgage-backed 0 613.0 0 613.0 609.9 Commercial mortgage-backed 0 3,853.6 0 3,853.6 3,825.6 Other asset-backed 0 3,839.8 0 3,839.8 3,834.2 Subtotal asset-backed securities 0 8,306.4 0 8,306.4 8,269.7 Redeemable preferred stocks: Financials 0 81.3 0 81.3 79.2 Utilities 0 0 0 0 0 Industrials 10.4 159.5 0 169.9 164.4 Subtotal redeemable preferred stocks 10.4 240.8 0 251.2 243.6 Total fixed maturities 9,780.9 18,041.0 0 27,821.9 27,574.5 Short-term investments 2,510.9 73.8 0 2,584.7 2,584.7 Total available-for-sale securities 12,291.8 18,114.8 0 30,406.6 30,159.2 Equity securities: Nonredeemable preferred stocks: Financials 69.6 955.0 25.1 1,049.7 976.1 Utilities 0 40.7 0 40.7 40.0 Industrials 0 0 5.0 5.0 5.0 Subtotal nonredeemable preferred stocks 69.6 995.7 30.1 1,095.4 1,021.1 Common equities: Common stocks 3,010.2 0 0 3,010.2 1,194.0 Other risk investments 0 0 0.3 0.3 0.3 Subtotal common equities 3,010.2 0 0.3 3,010.5 1,194.3 Total equity securities 3,079.8 995.7 30.4 4,105.9 2,215.4 Total portfolio $ 15,371.6 $ 19,110.5 $ 30.4 $ 34,512.5 $ 32,374.6 Debt $ 0 $ 4,734.8 $ 0 $ 4,734.8 $ 4,405.4 Fair Value (millions) Level 1 Level 2 Level 3 Total Cost March 31, 2018 Fixed maturities: U.S. government obligations $ 8,958.1 $ 0 $ 0 $ 8,958.1 $ 9,081.6 State and local government obligations 0 1,720.1 0 1,720.1 1,732.3 Corporate debt securities 0 6,041.1 0 6,041.1 6,102.6 Subtotal 8,958.1 7,761.2 0 16,719.3 16,916.5 Asset-backed securities: Residential mortgage-backed 0 751.8 0 751.8 746.7 Commercial mortgage-backed 0 2,269.5 0 2,269.5 2,289.8 Other asset-backed 0 2,462.1 0 2,462.1 2,472.4 Subtotal asset-backed securities 0 5,483.4 0 5,483.4 5,508.9 Redeemable preferred stocks: Financials 0 64.0 0 64.0 61.2 Utilities 0 11.6 0 11.6 10.7 Industrials 0 141.8 0 141.8 129.9 Subtotal redeemable preferred stocks 0 217.4 0 217.4 201.8 Total fixed maturities 8,958.1 13,462.0 0 22,420.1 22,627.2 Short-term investments 2,569.5 482.9 0 3,052.4 3,052.4 Total available-for-sale securities 11,527.6 13,944.9 0 25,472.5 25,679.6 Equity securities: Nonredeemable preferred stocks: Financials 78.9 662.0 0 740.9 654.6 Utilities 0 0 0 0 0 Industrials 0 0 5.0 5.0 5.0 Subtotal nonredeemable preferred stocks 78.9 662.0 5.0 745.9 659.6 Common equities: Common stocks 3,032.9 0 0 3,032.9 1,265.2 Other risk investments 0 0 0.3 0.3 0.3 Subtotal common equities 3,032.9 0 0.3 3,033.2 1,265.5 Total equity securities 3,111.8 662.0 5.3 3,779.1 1,925.1 Total portfolio $ 14,639.4 $ 14,606.9 $ 5.3 $ 29,251.6 $ 27,604.7 Debt $ 0 $ 4,048.3 $ 0 $ 4,048.3 $ 3,859.2 Fair Value (millions) Level 1 Level 2 Level 3 Total Cost December 31, 2018 Fixed maturities: U.S. government obligations $ 9,916.5 $ 0 $ 0 $ 9,916.5 $ 9,897.4 State and local government obligations 0 1,649.1 0 1,649.1 1,654.6 Corporate debt securities 0 8,694.3 0 8,694.3 8,808.5 Subtotal 9,916.5 10,343.4 0 20,259.9 20,360.5 Asset-backed securities: Residential mortgage-backed 0 734.4 0 734.4 733.5 Commercial mortgage-backed 0 3,301.6 0 3,301.6 3,332.8 Other asset-backed 0 3,577.3 0 3,577.3 3,585.4 Subtotal asset-backed securities 0 7,613.3 0 7,613.3 7,651.7 Redeemable preferred stocks: Financials 0 78.2 0 78.2 79.3 Utilities 0 0 0 0 0 Industrials 9.5 150.6 0 160.1 164.4 Subtotal redeemable preferred stocks 9.5 228.8 0 238.3 243.7 Total fixed maturities 9,926.0 18,185.5 0 28,111.5 28,255.9 Short-term investments 1,722.1 73.8 0 1,795.9 1,795.9 Total available-for-sale securities 11,648.1 18,259.3 0 29,907.4 30,051.8 Equity securities: Nonredeemable preferred stocks: Financials 71.9 887.1 25.1 984.1 951.6 Utilities 0 44.8 0 44.8 46.0 Industrials 0 0 5.0 5.0 5.0 Subtotal nonredeemable preferred stocks 71.9 931.9 30.1 1,033.9 1,002.6 Common equities: Common stocks 2,625.8 0 0 2,625.8 1,148.6 Other risk investments 0 0 0.3 0.3 0.3 Subtotal common equities 2,625.8 0 0.3 2,626.1 1,148.9 Total equity securities 2,697.7 931.9 30.4 3,660.0 2,151.5 Total portfolio $ 14,345.8 $ 19,191.2 $ 30.4 $ 33,567.4 $ 32,203.3 Debt $ 0 $ 4,532.3 $ 0 $ 4,532.3 $ 4,404.9
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation	The following tables provide a summary of changes in fair value associated with Level 3 assets for the three months ended March 31, 2019 and 2018 : Level 3 Fair Value (millions) Fair Value at Dec. 31, 2018 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain)/Loss on Sales Change in Valuation Net Transfers In (Out) Fair Value at March 31, 2019 Equity securities: Nonredeemable preferred stocks: Financials $ 25.1 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 25.1 Industrials 5.0 0 0 0 0 0 0 5.0 Common equities: Other risk investments 0.3 0 0 0 0 0 0 0.3 Total Level 3 securities $ 30.4 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 30.4 Level 3 Fair Value (millions) Fair Value at Dec. 31, 2017 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain)/Loss on Sales Change in Valuation Net Transfers In (Out) Fair Value at March 31, 2018 Equity securities: Nonredeemable preferred stocks: Financials $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Industrials 5.0 0 0 0 0 0 0 5.0 Common equities: Other risk investments 0.3 0 0 0 0 0 0 0.3 Total Level 3 securities $ 5.3 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 5.3
Fair Value Measurement Inputs and Valuation Techniques	The following tables provide a summary of the quantitative information about Level 3 fair value measurements for our applicable securities at March 31, 2019 and 2018 , and December 31, 2018 : Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at March 31, 2019 Valuation Technique Unobservable Input Unobservable Input Assumption Equity securities: Nonredeemable preferred stocks: Financials 1 $ 25.1 internal price unadjusted purchase price per share 9.0 Industrials 2 5.0 internal price price-to-sales ratio 5.5 Subtotal Level 3 securities 30.1 Pricing exemption securities 3 0.3 Total Level 3 securities $ 30.4 1 The security was internally-priced since it is privately held. The security was purchased during December 2018 and the value at March 31, 2019 reflects the unadjusted purchase price per share. 2 The security was internally-priced since it is privately held. The price at March 31, 2019 , was calculated using a price-to-sales ratio. 3 The unobservable input is not reasonably available to us. Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at March 31, 2018 Valuation Technique Unobservable Input Unobservable Input Assumption Equity securities: Nonredeemable preferred stocks: Financials $ 0 NA NA NA Industrials 1 5.0 internal price unadjusted purchase price per share 3.9 Subtotal Level 3 securities 5.0 Pricing exemption securities 2 0.3 Total Level 3 securities $ 5.3 NA= Not Available 1 The security was internally-priced since it is privately held. The value at March 31, 2018 reflects the unadjusted purchase price per share. 2 The unobservable input is not reasonably available to us. Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at Dec. 31, 2018 Valuation Technique Unobservable Input Unobservable Input Assumption Equity securities: Nonredeemable preferred stocks: Financials 1 $ 25.1 internal price unadjusted purchase price per share 9.0 Industrials 2 5.0 internal price price-to-sales ratio 5.5 Subtotal Level 3 securities 30.1 Pricing exemption securities 3 0.3 Total Level 3 securities $ 30.4 1 The security was internally-priced since it is privately held. The security was purchased during December 2018 and the value at December 31, 2018 reflects the unadjusted purchase price per share. 2 The security was internally-priced since it is privately held. The price at December 31, 2018, was calculated using a price-to-sales ratio. 3

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Debt Table	Debt at each of the balance sheet periods consisted of: March 31, 2019 March 31, 2018 December 31, 2018 (millions) Carrying Value Fair Value Carrying Value Fair Value Carrying Value Fair Value 3.75% Senior Notes due 2021 $ 499.2 $ 509.7 $ 498.9 $ 512.1 $ 499.1 $ 506.5 2.45% Senior Notes due 2027 496.6 475.6 496.2 458.3 496.5 455.5 6 5/8% Senior Notes due 2029 296.4 377.8 296.2 370.4 296.4 368.5 4.00% Senior Notes due 2029 544.6 587.9 0 0 544.5 562.4 6.25% Senior Notes due 2032 395.6 508.5 395.4 498.9 395.5 496.6 4.35% Senior Notes due 2044 346.6 371.6 346.5 360.2 346.6 350.2 3.70% Senior Notes due 2045 395.3 389.7 395.2 376.6 395.3 366.7 4.125% Senior Notes due 2047 841.4 885.4 841.3 858.6 841.4 831.9 4.20% Senior Notes due 2048 589.7 628.6 589.5 613.2 589.6 594.0 Total $ 4,405.4 $ 4,734.8 $ 3,859.2 $ 4,048.3 $ 4,404.9 $ 4,532.3

Loss and Loss Adjustment Expe_2

Loss and Loss Adjustment Expense Reserves (Tables)	3 Months Ended
	Mar. 31, 2019
Loss and Loss Adjustment Expenses Reserves [Abstract]
Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block]	Activity in the loss and loss adjustment expense reserves is summarized as follows: March 31, (millions) 2019 2018 Balance, Beginning of period $ 15,400.8 $ 13,086.9 Less reinsurance recoverables on unpaid losses 2,572.7 2,170.1 Net balance, Beginning of period 12,828.1 10,916.8 Incurred related to: Current year 5,616.4 4,815.2 Prior years 142.6 55.6 Total incurred 5,759.0 4,870.8 Paid related to: Current year 2,517.5 2,217.8 Prior years 2,901.4 2,377.8 Total paid 5,418.9 4,595.6 Net balance, End of period 13,168.2 11,192.0 Plus reinsurance recoverables on unpaid losses 2,708.4 2,137.0 Balance, End of period $ 15,876.6 $ 13,329.0

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information (Tables)	3 Months Ended
	Mar. 31, 2019
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information Table	We paid the following in the respective periods: Three Months Ended March 31, (millions) 2019 2018 Income taxes $ 20.0 $ 0 Interest 53.3 33.3 Operating lease liabilities 18.8 NA

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Reconciliation of Revenue and operating Income from Segments to Consolidated	Following are the operating results for the respective periods: Three Months Ended March 31, 2019 2018 (millions) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Personal Lines Agency $ 3,508.5 $ 453.0 $ 3,063.8 $ 409.1 Direct 3,576.3 321.9 3,016.3 298.0 Total Personal Lines 1 7,084.8 774.9 6,080.1 707.1 Commercial Lines 1,013.0 166.6 808.6 94.8 Property 2 362.0 7.7 285.3 28.5 Other indemnity 0 0 0 0.2 Total underwriting operations 8,459.8 949.2 7,174.0 830.6 Fees and other revenues 3 130.2 NA 103.8 NA Service businesses 42.6 4.5 34.2 4.9 Investments 4 667.4 661.2 118.1 112.1 Interest expense NA (47.4 ) NA (36.8 ) Consolidated total $ 9,300.0 $ 1,567.5 $ 7,430.1 $ 910.8 NA = Not applicable 1 Personal auto insurance accounted for 94% of the total Personal Lines segment net premiums earned during the three months ended March 31, 2019 and 2018 ; insurance for our special lines products (e.g., motorcycles, ATVs, RVs, watercraft, and snowmobiles) accounted for the balance of the Personal Lines net premiums earned. 2 For the three months ended March 31, 2019 and 2018, pretax profit (loss) includes $17.9 million and $18.0 million , respectively, of amortization expense predominately associated with the acquisition of a controlling interest in ARX. Although this expense is included in our Property segment, it is not reported in the consolidated results of ARX and, therefore, does not affect the value of net income attributable to noncontrolling interest. 3 Pretax profit (loss) for fees and other revenues is attributable to operating segments. 4
Underwriting Margins and Combined Ratios for our Underwriting Operations	Following are the underwriting margins and combined ratios for our underwriting operations for the respective periods: Three Months Ended March 31, 2019 2018 Underwriting Margin Combined Ratio Underwriting Margin Combined Ratio Personal Lines Agency 12.9 % 87.1 13.4 % 86.6 Direct 9.0 91.0 9.9 90.1 Total Personal Lines 10.9 89.1 11.6 88.4 Commercial Lines 16.4 83.6 11.7 88.3 Property 1 2.1 97.9 10.0 90.0 Total underwriting operations 11.2 88.8 11.6 88.4 1 Included in the three months ended March 31, 2019 and 2018, is 5.0 points and 6.3

Dividends Dividends (Tables)

Dividends Dividends (Tables)	3 Months Ended
	Mar. 31, 2019
Dividends [Abstract]
Dividends	Following is a summary of our common share dividends that were declared in 2018 and 2017 under that policy: (millions, except per share amounts) Amount of Common Share Dividends Dividend Type Declared Paid Per Share Accrued 1 Paid 1 Annual – Variable December 2018 February 2019 $ 2.5140 $ 1,467.9 $ 1,467.9 Annual – Variable December 2017 February 2018 1.1247 655.1 654.9 1

Other Comprehensive Income (L_2

Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Components of Other Comprehensive Income (Loss)	The components of other comprehensive income (loss), including reclassification adjustments by income statement line item, were as follows: Components of Changes in Accumulated Other Comprehensive Income (after tax) (millions) Pretax total accumulated other comprehensive income (loss) Total tax (provision) benefit After tax total accumulated other comprehensive income (loss) Total net unrealized gains (losses) on securities Net unrealized gains (losses) on forecasted transactions (Income) loss attributable to NCI Balance at December 31, 2018 $ (153.0 ) $ 32.1 $ (120.9 ) $ (105.6 ) $ (17.2 ) $ 1.9 Other comprehensive income (loss) before reclassifications: Investment securities 414.5 (87.0 ) 327.5 327.5 0 0 Forecasted transactions 0 0 0 0 0 0 Loss attributable to noncontrolling interest (NCI) (2.9 ) 0.6 (2.3 ) 0 0 (2.3 ) Total other comprehensive income (loss) before reclassifications 411.6 (86.4 ) 325.2 327.5 0 (2.3 ) Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings 0 0 0 0 0 0 Net realized gains (losses) on securities 33.4 (7.0 ) 26.4 26.4 0 0 Interest expense (0.3 ) 0.1 (0.2 ) 0 (0.2 ) 0 Total reclassification adjustment for amounts realized in net income 33.1 (6.9 ) 26.2 26.4 (0.2 ) 0 Total other comprehensive income (loss) 378.5 (79.5 ) 299.0 301.1 0.2 (2.3 ) Balance at March 31, 2019 $ 225.5 $ (47.4 ) $ 178.1 $ 195.5 $ (17.0 ) $ (0.4 ) Components of Changes in Accumulated Other Comprehensive Income (after tax) (millions) Pretax total accumulated other comprehensive income (loss) Total tax (provision) benefit After tax total accumulated other comprehensive income (loss) Total net unrealized gains (losses) on securities Net (Income) loss attributable to NCI Balance at December 31, 2017 $ 1,977.8 $ (695.6 ) $ 1,282.2 $ 1,295.0 $ (14.8 ) $ 2.0 Cumulative effect adjustment (2,006.0 ) 705.8 (1,300.2 ) (1,300.2 ) 0 0 Reclassification of disproportionate amounts 0 (4.3 ) (4.3 ) (1.1 ) (3.2 ) 0 Adjusted balance at December 31, 2017 (28.2 ) 5.9 (22.3 ) (6.3 ) (18.0 ) 2.0 Other comprehensive income (loss) before reclassifications: Investment securities (203.4 ) 42.8 (160.6 ) (160.6 ) 0 0 Forecasted transactions 0 0 0 0 0 0 Loss attributable to noncontrolling interest (NCI) 5.1 (1.1 ) 4.0 0 0 4.0 Total other comprehensive income (loss) before reclassifications (198.3 ) 41.7 (156.6 ) (160.6 ) 0 4.0 Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings 0 0 0 0 0 0 Net realized gains (losses) on securities (7.7 ) 1.6 (6.1 ) (6.1 ) 0 0 Interest expense (0.2 ) 0 (0.2 ) 0 (0.2 ) 0 Total reclassification adjustment for amounts realized in net income (7.9 ) 1.6 (6.3 ) (6.1 ) (0.2 ) 0 Total other comprehensive income (loss) (190.4 ) 40.1 (150.3 ) (154.5 ) 0.2 4.0 Balance at March 31, 2018 $ (218.6 ) $ 46.0 $ (172.6 ) $ (160.8 ) $ (17.8 ) $ 6.0

Redeemable Noncontrolling Int_2

Redeemable Noncontrolling Interest (Tables)	3 Months Ended
	Mar. 31, 2019
Temporary Equity Disclosure [Abstract]
Redeemable Noncontrolling Interest	The changes in the components of redeemable NCI were: (millions) March 31, 2019 March 31, 2018 December 31, 2018 Balance, Beginning of period $ 214.5 $ 503.7 $ 503.7 Net income attributable to NCI 4.4 11.8 5.7 Other comprehensive income (loss) attributable to NCI 1 2.3 (4.0 ) (3.3 ) Exercise of employee stock options 0 1.4 9.4 Purchase/change of ARX minority shares 0 0 (298.2 ) Change in redemption value of NCI 0 1.3 (2.8 ) Balance, End of period $ 221.2 $ 514.2 $ 214.5 1

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Net Carrying Amount of Other Intangible Assets	The following table is a summary of the net carrying amount of other intangible assets: (millions) March 31, 2019 March 31, 2018 December 31, 2018 Intangible assets subject to amortization $ 264.3 $ 336.2 $ 282.2 Indefinite-lived intangible assets 1 12.4 12.4 12.4 Total $ 276.7 $ 348.6 $ 294.6 1 Indefinite-lived intangible assets are comprised of state insurance and agent licenses. State insurance licenses were previously subject to amortization under superseded accounting guidance and have $0.6 million
Intangible Assets Subject to Amortization	Intangible assets subject to amortization consisted of the following: (millions) March 31, 2019 March 31, 2018 December 31, 2018 Category Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Policies in force $ 256.2 $ 146.4 $ 109.8 $ 256.2 $ 109.8 $ 146.4 $ 256.2 $ 137.3 $ 118.9 Agency relationships 159.2 45.5 113.7 159.2 34.2 125.0 159.2 42.6 116.6 Software rights 79.1 42.7 36.4 79.1 32.1 47.0 79.1 40.1 39.0 Trade name 34.8 30.4 4.4 34.8 17.0 17.8 34.8 27.1 7.7 Total $ 529.3 $ 265.0 $ 264.3 $ 529.3 $ 193.1 $ 336.2 $ 529.3 $ 247.1 $ 282.2

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Schedule Of Operating Lease Obligations	The minimum commitments under these agreements at December 31, 2018, were as follows: (millions) Commitments 2019 $ 64.1 2020 65.5 2021 52.8 2022 24.3 2023 8.5 Thereafter 3.8 Total $ 219.0
Lessee, Operating Lease, Liability, Maturity	At March 31, 2019, the following table shows our operating lease liabilities, on an undiscounted basis for the periods indicated, along with key inputs used to discount our lease liabilities, in accordance with the new accounting standard adopted on January 1, 2019 (see Note 15 – New Accounting Standard for further discussion): (millions) 2019 (excluding the three months ended March 31, 2019) $ 55.3 2020 72.7 2021 56.3 2022 25.6 2023 9.6 Thereafter 4.4 Total $ 223.9 Interest (12.5 ) Present value of lease liabilities $ 211.4 Weighted-average remaining term 3.2 years Weighted-average discount rate 3.5 %

Basis of Presentation Basis of

Basis of Presentation Basis of Presentation-Additional Information (Details) $ in Millions	Mar. 31, 2019USD ($)shares	Dec. 31, 2018USD ($)	Mar. 31, 2018USD ($)
Business Acquisition [Line Items]
Assets Held-for-sale, Property, Plant and Equipment | $	$ 52.6	$ 39.3	$ 5.3
ARX Holding Corp.
Business Acquisition [Line Items]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage	86.80%	86.80%	68.90%
Number of Shares Put Pursuant to Stockholders' Agreement | shares	204,527

Investments Investment Portfoli

Investments Investment Portfolio by Major Security Type (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 30,159.2	$ 30,051.8	$ 25,679.6
Gross Unrealized Gains	307.8	115.4	48.4
Gross Unrealized Losses	(60.9)	(249.6)	(252.5)
Net Holding Period Gains (Losses)	0.5	(10.2)	(3)
Total available-for-sale securities	$ 30,406.6	$ 29,907.4	$ 25,472.5
% of Total Fair Value	88.10%	89.10%	87.10%
Equity securities, at Fair Value
Cost	$ 2,215.4	$ 2,151.5	$ 1,925.1
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Net Holding Period Gains (Losses)	1,890.5	1,508.5	1,854
Fair Value	$ 4,105.9	$ 3,660	$ 3,779.1
% of Total Fair Value	11.90%	10.90%	12.90%
Debt and Equity Securities, at Fair Value
Cost	$ 32,374.6	$ 32,203.3	$ 27,604.7
Gross Unrealized Gains	307.8	115.4	48.4
Gross Unrealized Losses	(60.9)	(249.6)	(252.5)
Net Holding Period Gains (Losses)	1,891	1,498.3	1,851
Fair Value	$ 34,512.5	$ 33,567.4	$ 29,251.6
% of Total Fair Value	100.00%	100.00%	100.00%
Unsettled security transactions, receivable	$ 76.5
Unsettled security transactions, payable		$ 5.9	$ 83.6
Total fair value of non-insurance subsidiary portfolio	1,200	2,900	2,100
Nonredeemable preferred stocks
Equity securities, at Fair Value
Cost	1,021.1	1,002.6	659.6
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Net Holding Period Gains (Losses)	74.3	31.3	86.3
Fair Value	$ 1,095.4	$ 1,033.9	$ 745.9
% of Total Fair Value	3.20%	3.10%	2.50%
Common equities
Equity securities, at Fair Value
Cost	$ 1,194.3	$ 1,148.9	$ 1,265.5
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Net Holding Period Gains (Losses)	1,816.2	1,477.2	1,767.7
Fair Value	$ 3,010.5	$ 2,626.1	$ 3,033.2
% of Total Fair Value	8.70%	7.80%	10.40%
Total fixed maturities
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 27,574.5	$ 28,255.9	$ 22,627.2
Gross Unrealized Gains	307.8	115.4	48.4
Gross Unrealized Losses	(60.9)	(249.6)	(252.5)
Net Holding Period Gains (Losses)	0.5	(10.2)	(3)
Total available-for-sale securities	$ 27,821.9	$ 28,111.5	$ 22,420.1
% of Total Fair Value	80.60%	83.70%	76.70%
Total fixed maturities | U.S. government obligations
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 9,685.6	$ 9,897.4	$ 9,081.6
Gross Unrealized Gains	105.5	71.2	3.9
Gross Unrealized Losses	(20.6)	(52.1)	(127.4)
Net Holding Period Gains (Losses)	0	0	0
Total available-for-sale securities	$ 9,770.5	$ 9,916.5	$ 8,958.1
% of Total Fair Value	28.30%	29.50%	30.60%
Total fixed maturities | State and local government obligations
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 1,505.5	$ 1,654.6	$ 1,732.3
Gross Unrealized Gains	15.4	7.3	4.3
Gross Unrealized Losses	(5.1)	(12.8)	(16.4)
Net Holding Period Gains (Losses)	0	0	(0.1)
Total available-for-sale securities	$ 1,515.8	$ 1,649.1	$ 1,720.1
% of Total Fair Value	4.40%	4.90%	5.90%
Total fixed maturities | Corporate debt securities
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 7,870.1	$ 8,808.5	$ 6,102.6
Gross Unrealized Gains	126.3	13.6	4.8
Gross Unrealized Losses	(19)	(125.3)	(64.8)
Net Holding Period Gains (Losses)	0.6	(2.5)	(1.5)
Total available-for-sale securities	$ 7,978	$ 8,694.3	$ 6,041.1
% of Total Fair Value	23.10%	25.90%	20.70%
Total fixed maturities | Residential mortgage-backed securities
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 609.9	$ 733.5	$ 746.7
Gross Unrealized Gains	5.7	6	9.9
Gross Unrealized Losses	(2.6)	(5.1)	(4.8)
Net Holding Period Gains (Losses)	0	0	0
Total available-for-sale securities	$ 613	$ 734.4	$ 751.8
% of Total Fair Value	1.80%	2.20%	2.60%
Total fixed maturities | Commercial mortgage-backed securities
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 3,825.6	$ 3,332.8	$ 2,289.8
Gross Unrealized Gains	35.9	7.8	4.5
Gross Unrealized Losses	(7.9)	(39)	(24.8)
Net Holding Period Gains (Losses)	0	0	0
Total available-for-sale securities	$ 3,853.6	$ 3,301.6	$ 2,269.5
% of Total Fair Value	11.20%	9.80%	7.80%
Total fixed maturities | Other asset-backed securities
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 3,834.2	$ 3,585.4	$ 2,472.4
Gross Unrealized Gains	10	3.6	2.4
Gross Unrealized Losses	(4.5)	(11.8)	(12.9)
Net Holding Period Gains (Losses)	0.1	0.1	0.2
Total available-for-sale securities	$ 3,839.8	$ 3,577.3	$ 2,462.1
% of Total Fair Value	11.10%	10.70%	8.40%
Total fixed maturities | Redeemable preferred stocks
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 243.6	$ 243.7	$ 201.8
Gross Unrealized Gains	9	5.9	18.6
Gross Unrealized Losses	(1.2)	(3.5)	(1.4)
Net Holding Period Gains (Losses)	(0.2)	(7.8)	(1.6)
Total available-for-sale securities	$ 251.2	$ 238.3	$ 217.4
% of Total Fair Value	0.70%	0.70%	0.70%
Short-term investments
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 2,584.7	$ 1,795.9	$ 3,052.4
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Net Holding Period Gains (Losses)	0	0	0
Total available-for-sale securities	$ 2,584.7	$ 1,795.9	$ 3,052.4
% of Total Fair Value	7.50%	5.40%	10.40%

Investments Hybrid Securities (

Investments Hybrid Securities (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Hybrid Instruments [Line Items]
Hybrid securities	$ 254.7	$ 244.7	$ 134
State and local government obligations
Hybrid Instruments [Line Items]
Hybrid securities	3.6	3.6	3.7
Corporate debt securities
Hybrid Instruments [Line Items]
Hybrid securities	161.7	158.9	86.4
Other asset-backed securities
Hybrid Instruments [Line Items]
Hybrid securities	4	4.5	6.1
Redeemable preferred stocks
Hybrid Instruments [Line Items]
Hybrid securities	$ 85.4	$ 77.7	$ 37.8

Investments Composition of Fixe

Investments Composition of Fixed Maturities by Maturity (Detail) - Total fixed maturities $ in Millions	Mar. 31, 2019USD ($)
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Amortized Cost [Abstract]
Less than one year	$ 4,929.9
One to five years	16,765.4
Five to ten years	5,818.5
Ten years or greater	60.7
Cost	27,574.5
Fair Value
Less than one year	4,934.2
One to five years	16,878.8
Five to ten years	5,945.9
Ten years or greater	63
Fair Value	$ 27,821.9

Investments Gross Unrealized lo

Investments Gross Unrealized losses by Major Security (Detail) $ in Millions	Mar. 31, 2019USD ($)security	Dec. 31, 2018USD ($)security	Mar. 31, 2018USD ($)security
No. of Sec.
Total | security	640	1,292	1,391
Less than 12 Months | security	77	349	884
12 Months or Greater | security	563	943	507
Fair Value
Total	$ 9,215.7	$ 17,652.2	$ 18,569.8
Less than 12 Months	891.9	5,493.2	14,437.6
12 Months or Greater	8,323.8	12,159	4,132.2
Unrealized Losses
Total	(60.9)	(249.6)	(252.5)
Less than 12 Months	(3.9)	(47.3)	(182.1)
12 Months or Greater	$ (57)	$ (202.3)	$ (70.4)
U.S. government obligations
No. of Sec.
Total | security	42	51	64
Less than 12 Months | security	1	2	37
12 Months or Greater | security	41	49	27
Fair Value
Total	$ 3,174	$ 4,438	$ 7,933.8
Less than 12 Months	19.9	126.6	5,954.6
12 Months or Greater	3,154.1	4,311.4	1,979.2
Unrealized Losses
Total	(20.6)	(52.1)	(127.4)
Less than 12 Months	(0.1)	(0.1)	(90.7)
12 Months or Greater	$ (20.5)	$ (52)	$ (36.7)
State and local government obligations
No. of Sec.
Total | security	162	299	426
Less than 12 Months | security	10	49	301
12 Months or Greater | security	152	250	125
Fair Value
Total	$ 567.2	$ 972.4	$ 1,263.7
Less than 12 Months	31.4	192.7	890.2
12 Months or Greater	535.8	779.7	373.5
Unrealized Losses
Total	(5.1)	(12.8)	(16.4)
Less than 12 Months	0	(0.3)	(9.5)
12 Months or Greater	$ (5.1)	$ (12.5)	$ (6.9)
Corporate debt securities
No. of Sec.
Total | security	153	368	348
Less than 12 Months | security	11	133	290
12 Months or Greater | security	142	235	58
Fair Value
Total	$ 2,555.7	$ 6,723.3	$ 5,082.9
Less than 12 Months	175.9	2,613.3	4,515.1
12 Months or Greater	2,379.8	4,110	567.8
Unrealized Losses
Total	(19)	(125.3)	(64.8)
Less than 12 Months	(1.1)	(33.4)	(56.1)
12 Months or Greater	$ (17.9)	$ (91.9)	$ (8.7)
Residential mortgage-backed securities
No. of Sec.
Total | security	63	228	211
Less than 12 Months | security	15	32	36
12 Months or Greater | security	48	196	175
Fair Value
Total	$ 299.4	$ 450.2	$ 329.3
Less than 12 Months	139.1	248.8	112.8
12 Months or Greater	160.3	201.4	216.5
Unrealized Losses
Total	(2.6)	(5.1)	(4.8)
Less than 12 Months	(1.1)	(0.8)	(0.5)
12 Months or Greater	$ (1.5)	$ (4.3)	$ (4.3)
Commercial mortgage-backed securities
No. of Sec.
Total | security	76	140	131
Less than 12 Months | security	13	48	89
12 Months or Greater | security	63	92	42
Fair Value
Total	$ 1,294.3	$ 2,328.5	$ 1,974.8
Less than 12 Months	229.1	741.2	1,510.5
12 Months or Greater	1,065.2	1,587.3	464.3
Unrealized Losses
Total	(7.9)	(39)	(24.8)
Less than 12 Months	(0.9)	(8.9)	(16.2)
12 Months or Greater	$ (7)	$ (30.1)	$ (8.6)
Other asset-backed securities
No. of Sec.
Total | security	142	203	208
Less than 12 Months | security	27	84	129
12 Months or Greater | security	115	119	79
Fair Value
Total	$ 1,294	$ 2,691.3	$ 1,958.5
Less than 12 Months	296.5	1,551.7	1,439.1
12 Months or Greater	997.5	1,139.6	519.4
Unrealized Losses
Total	(4.5)	(11.8)	(12.9)
Less than 12 Months	(0.7)	(3.2)	(8.7)
12 Months or Greater	$ (3.8)	$ (8.6)	$ (4.2)
Redeemable preferred stocks
No. of Sec.
Total | security	2	3	3
Less than 12 Months | security	0	1	2
12 Months or Greater | security	2	2	1
Fair Value
Total	$ 31.1	$ 48.5	$ 26.8
Less than 12 Months	0	18.9	15.3
12 Months or Greater	31.1	29.6	11.5
Unrealized Losses
Total	(1.2)	(3.5)	(1.4)
Less than 12 Months	0	(0.6)	(0.4)
12 Months or Greater	$ (1.2)	$ (2.9)	$ (1)

Investments Total Non-Credit Po

Investments Total Non-Credit Portion of Other-Than-Temporary Impairment Recorded in Accumulated Other Comprehensive Income, Reflecting Original Non-Credit Loss at Time Credit Impairment (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Other Than Temporary Impairment Non Credit Losses Recognized In Accumulated Other Comprehensive Income [Line Items]
Non-credit portion of other-than-temporary impairments recognized in accumulated other comprehensive income	$ (19.8)	$ (19.8)	$ (20)
Residential mortgage-backed securities
Other Than Temporary Impairment Non Credit Losses Recognized In Accumulated Other Comprehensive Income [Line Items]
Non-credit portion of other-than-temporary impairments recognized in accumulated other comprehensive income	(19.7)	(19.7)	(19.7)
Commercial mortgage-backed securities
Other Than Temporary Impairment Non Credit Losses Recognized In Accumulated Other Comprehensive Income [Line Items]
Non-credit portion of other-than-temporary impairments recognized in accumulated other comprehensive income	$ (0.1)	$ (0.1)	$ (0.3)

Investments OTTI Credit Losses

Investments OTTI Credit Losses Recognized in Earnings (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance	$ 500,000	$ 500,000
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Changes in Cash Flows	0	0
Ending balance	500,000	500,000
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, No Previous Impairment	0	0
Residential mortgage-backed securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance	0	0
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Changes in Cash Flows	0	0
Ending balance	0	0
Commercial mortgage-backed securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance	500,000	500,000
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Changes in Cash Flows	0	0
Ending balance	$ 500,000	$ 500,000

Investments Components of Net R

Investments Components of Net Realized Gains (Losses) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-Sale, Gross Realized Gains on Sales	$ 55	$ 11.5
Equity Securities, FV-NI, Gross Realized Gains on Sales	9.4	123.5
Debt and Equity Securities, Gross Realized Gains on Sales	64.4	135
Debt Securities, Available-for-Sale, Gross Realized Losses excluding Other-than-Temporary Impairment	(18.3)	(19.7)
Equity Securities, FV-NI, Gross Realized Losses on Sales	0	(8.3)
Debt and Equity Securities, Gross Realized Losses on Sales	(18.3)	(28)
Debt Securities, Available-for-Sale, Realized Gain (Loss) on Sales, Excluding Other-than-Temporary Impairment	36.7	(8.2)
Equity Securities, FV-NI, Net Realized Gain (Loss) on Sales	9.4	115.2
Gross Realized Gain (Loss), excluding Holding Period and OTTI	46.1	107
Unrealized Gain (Loss) on Hybrid Instrument, Net	10.7	(3.2)
Net holding period gains (losses), equity securities	382	(152)
Net Holding Period Realized Gain (Loss)	392.7	(155.2)
Other than Temporary Impairment Losses, Portion Recognized in Earnings, Net of Sales	(24.3)	0
Total net realized gains (losses) on securities	414.5	(48.2)
U.S. government obligations
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-Sale, Gross Realized Gains on Sales	36.6	0
Debt Securities, Available-for-Sale, Gross Realized Losses excluding Other-than-Temporary Impairment	(7.1)	(8.9)
Debt Securities, Available-for-Sale, Realized Gain (Loss) on Sales, Excluding Other-than-Temporary Impairment	29.5	(8.9)
State and local government obligations
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-Sale, Gross Realized Gains on Sales	1.6	8.6
Debt Securities, Available-for-Sale, Gross Realized Losses excluding Other-than-Temporary Impairment	(0.6)	(1.3)
Debt Securities, Available-for-Sale, Realized Gain (Loss) on Sales, Excluding Other-than-Temporary Impairment	1	7.3
Corporate debt securities
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-Sale, Gross Realized Gains on Sales	16.1	0.1
Debt Securities, Available-for-Sale, Gross Realized Losses excluding Other-than-Temporary Impairment	(6.1)	(3.1)
Debt Securities, Available-for-Sale, Realized Gain (Loss) on Sales, Excluding Other-than-Temporary Impairment	10	(3)
Residential mortgage-backed securities
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-Sale, Gross Realized Losses excluding Other-than-Temporary Impairment	(2.3)	0
Debt Securities, Available-for-Sale, Realized Gain (Loss) on Sales, Excluding Other-than-Temporary Impairment	(2.3)	0
Commercial mortgage-backed securities
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-Sale, Gross Realized Gains on Sales	0.7	1.7
Debt Securities, Available-for-Sale, Gross Realized Losses excluding Other-than-Temporary Impairment	(2.1)	(6.3)
Debt Securities, Available-for-Sale, Realized Gain (Loss) on Sales, Excluding Other-than-Temporary Impairment	(1.4)	(4.6)
Other asset-backed securities
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-Sale, Gross Realized Losses excluding Other-than-Temporary Impairment	(0.1)	(0.1)
Debt Securities, Available-for-Sale, Realized Gain (Loss) on Sales, Excluding Other-than-Temporary Impairment	(0.1)	(0.1)
Redeemable preferred stocks
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-Sale, Gross Realized Gains on Sales	0	1.1
Debt Securities, Available-for-Sale, Realized Gain (Loss) on Sales, Excluding Other-than-Temporary Impairment	0	1.1
Nonredeemable preferred stocks
Gain (Loss) on Securities [Line Items]
Equity Securities, FV-NI, Gross Realized Gains on Sales	4.9	3.6
Equity Securities, FV-NI, Gross Realized Losses on Sales	0	(0.4)
Equity Securities, FV-NI, Net Realized Gain (Loss) on Sales	4.9	3.2
Common equities
Gain (Loss) on Securities [Line Items]
Equity Securities, FV-NI, Gross Realized Gains on Sales	4.5	119.9
Equity Securities, FV-NI, Gross Realized Losses on Sales	0	(7.9)
Equity Securities, FV-NI, Net Realized Gain (Loss) on Sales	4.5	112
Other Assets
Gain (Loss) on Securities [Line Items]
Other than Temporary Impairment Losses, Portion Recognized in Earnings, Net of Sales	$ (24.3)	$ 0

Investments Components of Equit

Investments Components of Equity Realized Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Components of Equity Realized Gains (Losses) [Line Items]
Realized Investment Gains (Losses)	$ 391.4	$ (36.8)
Equity Securities, FV-NI, Net Realized Gain (Loss) on Sales	9.4	115.2
Equity Securities, FV-NI, Unrealized Gain (Loss)	$ 382	$ (152)

Investments Components of Net I

Investments Components of Net Investment Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net Investment Income [Line Items]
Gross investment income	$ 252.9	$ 166.3
Investment expenses	(6.2)	(6)
Net Investment Income	246.7	160.3
Total equity securities
Net Investment Income [Line Items]
Gross investment income	28.7	25.9
Total equity securities | Nonredeemable preferred stocks
Net Investment Income [Line Items]
Gross investment income	15.5	10.9
Total equity securities | Common equities
Net Investment Income [Line Items]
Gross investment income	13.2	15
Available-for-sale Securities
Net Investment Income [Line Items]
Gross investment income	224.2	140.4
Short-term investments
Net Investment Income [Line Items]
Gross investment income	16	10.1
Total fixed maturities
Net Investment Income [Line Items]
Gross investment income	208.2	130.3
Total fixed maturities | U.S. government obligations
Net Investment Income [Line Items]
Gross investment income	53.7	39.8
Total fixed maturities | State and local government obligations
Net Investment Income [Line Items]
Gross investment income	9.3	10
Total fixed maturities | Corporate debt securities
Net Investment Income [Line Items]
Gross investment income	77.2	36.2
Total fixed maturities | Residential mortgage-backed securities
Net Investment Income [Line Items]
Gross investment income	6.6	6.9
Total fixed maturities | Commercial mortgage-backed securities
Net Investment Income [Line Items]
Gross investment income	31.7	21.2
Total fixed maturities | Other asset-backed securities
Net Investment Income [Line Items]
Gross investment income	26	13.6
Total fixed maturities | Redeemable preferred stocks
Net Investment Income [Line Items]
Gross investment income	$ 3.7	$ 2.6

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Deposit Assets	$ 250,700,000
Securities Sold under Agreements to Repurchase	0	$ 0	$ 0
Open reverse repurchase commitments	0	0	0
Gross unrealized losses	60,900,000	252,500,000	249,600,000
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, No Previous Impairment	$ 0	$ 0
Investment Portfolio Duration	2 years 7 months 6 days	2 years 7 months 6 days
Trading securities	$ 0	$ 0	0
Trading Securities, Gain (Loss)	0	0
Derivative Assets (Liabilities), at Fair Value, Net	$ 0	$ 0	$ 0

Fair Value Composition of Inves

Fair Value Composition of Investment Portfolio by Major Security Type (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	$ 34,512.5	$ 33,567.4	$ 29,251.6
Fair Value	4,734.8	4,532.3	4,048.3
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	15,371.6	14,345.8	14,639.4
Fair Value	0	0	0
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	19,110.5	19,191.2	14,606.9
Fair Value	4,734.8	4,532.3	4,048.3
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	30.4	30.4	5.3
Fair Value	0	0	0
Available-for-sale Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	30,406.6	29,907.4	25,472.5
Available-for-sale Securities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	12,291.8	11,648.1	11,527.6
Available-for-sale Securities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	18,114.8	18,259.3	13,944.9
Available-for-sale Securities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	4,105.9	3,660	3,779.1
Total equity securities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	3,079.8	2,697.7	3,111.8
Total equity securities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	995.7	931.9	662
Total equity securities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	30.4	30.4	5.3
Total equity securities | Nonredeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	1,095.4	1,033.9	745.9
Total equity securities | Nonredeemable preferred stocks | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	69.6	71.9	78.9
Total equity securities | Nonredeemable preferred stocks | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	995.7	931.9	662
Total equity securities | Nonredeemable preferred stocks | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	30.1	30.1	5
Total equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	1,049.7	984.1	740.9
Total equity securities | Nonredeemable preferred stocks | Financials | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	69.6	71.9	78.9
Total equity securities | Nonredeemable preferred stocks | Financials | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	955	887.1	662
Total equity securities | Nonredeemable preferred stocks | Financials | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	25.1	25.1	0
Total equity securities | Nonredeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	40.7	44.8	0
Total equity securities | Nonredeemable preferred stocks | Utilities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total equity securities | Nonredeemable preferred stocks | Utilities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	40.7	44.8	0
Total equity securities | Nonredeemable preferred stocks | Utilities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total equity securities | Nonredeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	5	5	5
Total equity securities | Nonredeemable preferred stocks | Industrials | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total equity securities | Nonredeemable preferred stocks | Industrials | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total equity securities | Nonredeemable preferred stocks | Industrials | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	5	5	5
Total equity securities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	3,010.5	2,626.1	3,033.2
Total equity securities | Common equities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	3,010.2	2,625.8	3,032.9
Total equity securities | Common equities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total equity securities | Common equities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0.3	0.3	0.3
Total equity securities | Common equities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	3,010.2	2,625.8	3,032.9
Total equity securities | Common equities | Common equities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	3,010.2	2,625.8	3,032.9
Total equity securities | Common equities | Common equities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total equity securities | Common equities | Common equities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total equity securities | Common equities | Other risk investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0.3	0.3	0.3
Total equity securities | Common equities | Other risk investments | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total equity securities | Common equities | Other risk investments | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total equity securities | Common equities | Other risk investments | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0.3	0.3	0.3
Carrying (Reported) Amount, Fair Value Disclosure
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	32,374.6	32,203.3	27,604.7
Long-term Debt	4,405.4	4,404.9	3,859.2
Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	30,159.2	30,051.8	25,679.6
Carrying (Reported) Amount, Fair Value Disclosure | Total equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	2,215.4	2,151.5	1,925.1
Carrying (Reported) Amount, Fair Value Disclosure | Total equity securities | Nonredeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	1,021.1	1,002.6	659.6
Carrying (Reported) Amount, Fair Value Disclosure | Total equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	976.1	951.6	654.6
Carrying (Reported) Amount, Fair Value Disclosure | Total equity securities | Nonredeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	40	46	0
Carrying (Reported) Amount, Fair Value Disclosure | Total equity securities | Nonredeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	5	5	5
Carrying (Reported) Amount, Fair Value Disclosure | Total equity securities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	1,194.3	1,148.9	1,265.5
Carrying (Reported) Amount, Fair Value Disclosure | Total equity securities | Common equities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	1,194	1,148.6	1,265.2
Carrying (Reported) Amount, Fair Value Disclosure | Total equity securities | Common equities | Other risk investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0.3	0.3	0.3
Total fixed maturities | Available-for-sale Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	27,821.9	28,111.5	22,420.1
Total fixed maturities | Available-for-sale Securities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	9,780.9	9,926	8,958.1
Total fixed maturities | Available-for-sale Securities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	18,041	18,185.5	13,462
Total fixed maturities | Available-for-sale Securities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	19,264.3	20,259.9	16,719.3
Total fixed maturities | Available-for-sale Securities | Debt Securities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	9,770.5	9,916.5	8,958.1
Total fixed maturities | Available-for-sale Securities | Debt Securities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	9,493.8	10,343.4	7,761.2
Total fixed maturities | Available-for-sale Securities | Debt Securities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	8,306.4	7,613.3	5,483.4
Total fixed maturities | Available-for-sale Securities | Asset-backed Securities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | Asset-backed Securities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	8,306.4	7,613.3	5,483.4
Total fixed maturities | Available-for-sale Securities | Asset-backed Securities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | U.S. government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	9,770.5	9,916.5	8,958.1
Total fixed maturities | Available-for-sale Securities | U.S. government obligations | Debt Securities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	9,770.5	9,916.5	8,958.1
Total fixed maturities | Available-for-sale Securities | U.S. government obligations | Debt Securities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | U.S. government obligations | Debt Securities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | State and local government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	1,515.8	1,649.1	1,720.1
Total fixed maturities | Available-for-sale Securities | State and local government obligations | Debt Securities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | State and local government obligations | Debt Securities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	1,515.8	1,649.1	1,720.1
Total fixed maturities | Available-for-sale Securities | State and local government obligations | Debt Securities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | Corporate debt securities | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	7,978	8,694.3	6,041.1
Total fixed maturities | Available-for-sale Securities | Corporate debt securities | Debt Securities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | Corporate debt securities | Debt Securities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	7,978	8,694.3	6,041.1
Total fixed maturities | Available-for-sale Securities | Corporate debt securities | Debt Securities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | Residential mortgage-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	613	734.4	751.8
Total fixed maturities | Available-for-sale Securities | Residential mortgage-backed securities | Asset-backed Securities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | Residential mortgage-backed securities | Asset-backed Securities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	613	734.4	751.8
Total fixed maturities | Available-for-sale Securities | Residential mortgage-backed securities | Asset-backed Securities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | Commercial mortgage-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	3,853.6	3,301.6	2,269.5
Total fixed maturities | Available-for-sale Securities | Commercial mortgage-backed securities | Asset-backed Securities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | Commercial mortgage-backed securities | Asset-backed Securities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	3,853.6	3,301.6	2,269.5
Total fixed maturities | Available-for-sale Securities | Commercial mortgage-backed securities | Asset-backed Securities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | Other asset-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	3,839.8	3,577.3	2,462.1
Total fixed maturities | Available-for-sale Securities | Other asset-backed securities | Asset-backed Securities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | Other asset-backed securities | Asset-backed Securities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	3,839.8	3,577.3	2,462.1
Total fixed maturities | Available-for-sale Securities | Other asset-backed securities | Asset-backed Securities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	251.2	238.3	217.4
Total fixed maturities | Available-for-sale Securities | Redeemable preferred stocks | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	10.4	9.5	0
Total fixed maturities | Available-for-sale Securities | Redeemable preferred stocks | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	240.8	228.8	217.4
Total fixed maturities | Available-for-sale Securities | Redeemable preferred stocks | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | Redeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	81.3	78.2	64
Total fixed maturities | Available-for-sale Securities | Redeemable preferred stocks | Financials | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | Redeemable preferred stocks | Financials | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	81.3	78.2	64
Total fixed maturities | Available-for-sale Securities | Redeemable preferred stocks | Financials | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | Redeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	11.6
Total fixed maturities | Available-for-sale Securities | Redeemable preferred stocks | Utilities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | Redeemable preferred stocks | Utilities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	11.6
Total fixed maturities | Available-for-sale Securities | Redeemable preferred stocks | Utilities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Available-for-sale Securities | Redeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	169.9	160.1	141.8
Total fixed maturities | Available-for-sale Securities | Redeemable preferred stocks | Industrials | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	10.4	9.5	0
Total fixed maturities | Available-for-sale Securities | Redeemable preferred stocks | Industrials | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	159.5	150.6	141.8
Total fixed maturities | Available-for-sale Securities | Redeemable preferred stocks | Industrials | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Total fixed maturities | Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	27,574.5	28,255.9	22,627.2
Total fixed maturities | Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	19,061.2	20,360.5	16,916.5
Total fixed maturities | Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	8,269.7	7,651.7	5,508.9
Total fixed maturities | Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities | U.S. government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	9,685.6	9,897.4	9,081.6
Total fixed maturities | Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities | State and local government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	1,505.5	1,654.6	1,732.3
Total fixed maturities | Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities | Corporate debt securities | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	7,870.1	8,808.5	6,102.6
Total fixed maturities | Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities | Residential mortgage-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	609.9	733.5	746.7
Total fixed maturities | Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities | Commercial mortgage-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	3,825.6	3,332.8	2,289.8
Total fixed maturities | Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities | Other asset-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	3,834.2	3,585.4	2,472.4
Total fixed maturities | Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	243.6	243.7	201.8
Total fixed maturities | Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities | Redeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	79.2	79.3	61.2
Total fixed maturities | Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities | Redeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	10.7
Total fixed maturities | Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities | Redeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	164.4	164.4	129.9
Short-term investments | Available-for-sale Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	2,584.7	1,795.9	3,052.4
Short-term investments | Available-for-sale Securities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	2,510.9	1,722.1	2,569.5
Short-term investments | Available-for-sale Securities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	73.8	73.8	482.9
Short-term investments | Available-for-sale Securities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	0	0	0
Short-term investments | Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value	$ 2,584.7	$ 1,795.9	$ 3,052.4

Fair Value Summary of Changes i

Fair Value Summary of Changes in Fair Value Associated with Level 3 Assets (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	$ 30.4	$ 5.3
Calls/ Maturities/ Paydowns	0	0
Purchases	0	0
Sales	0	0
Net Realized (Gain)/Loss on Sales	0	0
Change in Valuation	0	0
Net Transfers In (Out)	0	0
Fair value, ending balance	30.4	5.3
Total equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	25.1	0
Calls/ Maturities/ Paydowns	0	0
Purchases	0	0
Sales	0	0
Net Realized (Gain)/Loss on Sales	0	0
Change in Valuation	0	0
Net Transfers In (Out)	0	0
Fair value, ending balance	25.1	0
Total equity securities | Nonredeemable preferred stocks | Industrials
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	5	5
Calls/ Maturities/ Paydowns	0	0
Purchases	0	0
Sales	0	0
Net Realized (Gain)/Loss on Sales	0	0
Change in Valuation	0	0
Net Transfers In (Out)	0	0
Fair value, ending balance	5	5
Total equity securities | Common equities | Other risk investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	0.3	0.3
Calls/ Maturities/ Paydowns	0	0
Purchases	0	0
Sales	0	0
Net Realized (Gain)/Loss on Sales	0	0
Change in Valuation	0	0
Net Transfers In (Out)	0	0
Fair value, ending balance	$ 0.3	$ 0.3

Fair Value Summary of Quantitat

Fair Value Summary of Quantitative Information about Level 3 Fair Value Measurements (Details) $ / shares in Units, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019USD ($)$ / shares	Mar. 31, 2018USD ($)$ / shares	Dec. 31, 2018USD ($)$ / shares
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, Fair Value	$ 34,512.5	$ 29,251.6	$ 33,567.4
Fair Value, Inputs, Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, Fair Value	30.4	5.3	30.4
Internal Pricing | Nonredeemable preferred stocks | Fair Value, Inputs, Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, Fair Value	30.1	5	30.1
Internal Pricing | Financials | Nonredeemable preferred stocks | Fair Value, Inputs, Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, Fair Value	$ 25.1	0	$ 25.1
Fair Value Inputs, Original Issue Price | $ / shares	$ 9		$ 9
Internal Pricing | Industrials | Nonredeemable preferred stocks | Fair Value, Inputs, Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, Fair Value	$ 5	$ 5	$ 5
Fair Value Inputs, Price-to-Sales Ratio	5.5		5.5
Fair Value Inputs, Original Issue Price | $ / shares		$ 3.9
Total Quantitative Level Three Securities | Fair Value, Inputs, Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, Fair Value	$ 30.1	$ 5	$ 30.1
Third Party Pricing Exemption Securities | Fair Value, Inputs, Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, Fair Value	$ 0.3	$ 0.3	$ 0.3

Fair Value - Additional Informa

Fair Value - Additional Information (Detail)	Mar. 31, 2019USD ($)security	Dec. 31, 2018USD ($)security	Mar. 31, 2018USD ($)security
Fair Value Measurements [Line Items]
Investments, Fair Value	$ 34,512,500,000	$ 33,567,400,000	$ 29,251,600,000
Fair Value, Inputs, Level 1
Fair Value Measurements [Line Items]
Vendor Quoted Prices, Percent of FV Hierarchy Level	77.00%	79.00%	75.00%
Investments, Fair Value	$ 15,371,600,000	$ 14,345,800,000	$ 14,639,400,000
Fair Value, Inputs, Level 2
Fair Value Measurements [Line Items]
Vendor Quoted Prices, Percent of FV Hierarchy Level	99.00%	99.00%	99.00%
Dealer Quoted Prices, Percent of FV Hierarchy Level	1.00%	1.00%	1.00%
Investments, Fair Value	$ 19,110,500,000	$ 19,191,200,000	$ 14,606,900,000
Fair Value, Inputs, Level 3
Fair Value Measurements [Line Items]
Investments, Fair Value	30,400,000	30,400,000	5,300,000
Total fixed maturities | Fair Value, Inputs, Level 3
Fair Value Measurements [Line Items]
Investments, Fair Value	0	0	0
Nonredeemable preferred stocks | Internal Pricing | Fair Value, Inputs, Level 3
Fair Value Measurements [Line Items]
Investments, Fair Value	$ 30,100,000	$ 30,100,000	$ 5,000,000
Number of securities | security	2	2	1
Common equities | Internal Pricing | Fair Value, Inputs, Level 3
Fair Value Measurements [Line Items]
Investments, Fair Value	$ 300,000	$ 300,000	$ 300,000
Number of securities | security	1	1	1

Debt (Detail)

Debt (Detail) - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Debt Instrument [Line Items]
Fair Value		$ 4,734.8	$ 4,532.3	$ 4,048.3
Debt, Long-term and Short-term, Combined Amount	[1]	4,405.4	4,404.9	3,859.2
3.75% Senior Notes due 2021
Debt Instrument [Line Items]
Long-term Debt		499.2	499.1	498.9
Fair Value		509.7	506.5	512.1
2.45% Senior Notes due 2027
Debt Instrument [Line Items]
Long-term Debt		496.6	496.5	496.2
Fair Value		475.6	455.5	458.3
6 5/8% Senior Notes due 2029
Debt Instrument [Line Items]
Long-term Debt		296.4	296.4	296.2
Fair Value		377.8	368.5	370.4
4.00% Senior Notes due 2029
Debt Instrument [Line Items]
Long-term Debt		544.6	544.5	0
Fair Value		587.9	562.4	0
6.25% Senior Notes due 2032
Debt Instrument [Line Items]
Long-term Debt		395.6	395.5	395.4
Fair Value		508.5	496.6	498.9
4.35% Senior Notes due 2044
Debt Instrument [Line Items]
Long-term Debt		346.6	346.6	346.5
Fair Value		371.6	350.2	360.2
3.70% Senior Notes due 2045
Debt Instrument [Line Items]
Long-term Debt		395.3	395.3	395.2
Fair Value		389.7	366.7	376.6
4.125% Senior Notes due 2047
Debt Instrument [Line Items]
Long-term Debt		841.4	841.4	841.3
Fair Value		885.4	831.9	858.6
4.20% Senior Notes due 2048
Debt Instrument [Line Items]
Long-term Debt		589.7	589.6	589.5
Fair Value		$ 628.6	$ 594	$ 613.2
[1]	Consists of long-term debt. See Note 4 – Debt

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 31, 2018	Mar. 31, 2019	Dec. 31, 2018
Discretionary Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 250,000,000
Debt term		30 days
Borrowings outstanding		$ 0	$ 0
3.75% Senior Notes due 2021
Debt Instrument [Line Items]
Debt, stated interest rate		3.75%
2.45% Senior Notes due 2027
Debt Instrument [Line Items]
Debt, stated interest rate		2.45%
4.20% Senior Notes due 2048
Debt Instrument [Line Items]
Debt, stated interest rate		4.20%
6 5/8% Senior Notes due 2029
Debt Instrument [Line Items]
Debt, stated interest rate		6.625%
6.25% Senior Notes due 2032
Debt Instrument [Line Items]
Debt, stated interest rate		6.25%
4.35% Senior Notes due 2044
Debt Instrument [Line Items]
Debt, stated interest rate		4.35%
3.70% Senior Notes due 2045
Debt Instrument [Line Items]
Debt, stated interest rate		3.70%
4.125% Senior Notes due 2047
Debt Instrument [Line Items]
Debt, stated interest rate		4.125%
4.00% Senior Notes due 2029
Debt Instrument [Line Items]
Debt, face amount	$ 550,000,000
Debt, stated interest rate	4.00%	4.00%
Proceeds, net of underwriter's discounts and commissions	$ 544,500,000
Federal Funds Open Rate | Discretionary Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		0.50%

Income Taxes Additional Informa

Income Taxes Additional Information (Details)	3 Months Ended
	Mar. 31, 2019USD ($)Investment	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)
Income Taxes [Line Items]
Valuation allowance	$ 0	$ 0	$ 0
Effective Income Tax Rate Reconciliation, Percent	30.90%	19.90%
Alternative Energy
Income Taxes [Line Items]
Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Amount	$ 156,100,000
Number of Sponsors | Investment	3

Loss and Loss Adjustment Expe_3

Loss and Loss Adjustment Expense Reserves (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Liability for Claims and Claims Adjustment Expense [Line Items]
Loss and loss adjustment expense reserves	$ 15,876.6	$ 13,329	$ 15,400.8	$ 13,086.9
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments and Liability for Unpaid Claims and Claim Adjustment Expense, Other Reconciling Item	2,708.4	2,137	2,572.7	2,170.1
Liability for Unpaid Claims and Claims Adjustment Expense, Net	13,168.2	11,192	$ 12,828.1	$ 10,916.8
Current Year Claims and Claims Adjustment Expense	5,616.4	4,815.2
Prior Year Claims and Claims Adjustment Expense	(142.6)	(55.6)
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	5,759	4,870.8
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	2,517.5	2,217.8
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	2,901.4	2,377.8
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	$ 5,418.9	4,595.6
Short-duration Insurance Contracts, Accident Year 2018 [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Percent of Prior Year Claims and Claims Adjustment Expense	40.00%
Short-duration Insurance Contracts, Accident Year 2017 [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Percent of Prior Year Claims and Claims Adjustment Expense	15.00%
Short-duration Insurance Contracts, Accident Years 2015 and Prior
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		6
Personal Lines | Personal auto businesses
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense	$ (111)	(35)
Personal Lines | Agency Auto
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(24)
Personal Lines | Direct Auto
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(11)
Personal Lines | Special Lines
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense	(8)
Commercial Lines
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense	$ (22)	(19)
Property
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		$ (2)

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Open reverse repurchase commitments	$ 0	$ 0	$ 0
Dividends payable	58,400,000		1,467,900,000	$ 655,100,000
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	10,900,000
Operating Lease, Payments	18,800,000
Income Taxes Paid	20,000,000	0
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	53,300,000	33,300,000
Cash and Cash Equivalents | ARX Holding Corp.
Open reverse repurchase commitments	$ 185,600,000	$ 166,600,000	$ 117,300,000

Segment Information Operating R

Segment Information Operating Results (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 9,300	$ 7,430.1
Pretax Profit (Loss)	1,567.5	910.8
Amortization of intangible assets	17.9	18
Personal Lines | Agency | Underwriting operations
Segment Reporting Information [Line Items]
Revenues	3,508.5	3,063.8
Pretax Profit (Loss)	453	409.1
Personal Lines | Direct | Underwriting operations
Segment Reporting Information [Line Items]
Revenues	3,576.3	3,016.3
Pretax Profit (Loss)	321.9	298
Operating Segments | Underwriting operations
Segment Reporting Information [Line Items]
Revenues	8,459.8	7,174
Pretax Profit (Loss)	949.2	830.6
Operating Segments | Personal Lines | Underwriting operations
Segment Reporting Information [Line Items]
Revenues	7,084.8	6,080.1
Pretax Profit (Loss)	$ 774.9	$ 707.1
Personal auto insurance percentage of the total personal lines segment net premiums earned	94.00%	94.00%
Operating Segments | Commercial Lines | Underwriting operations
Segment Reporting Information [Line Items]
Revenues	$ 1,013	$ 808.6
Pretax Profit (Loss)	166.6	94.8
Operating Segments | Property | Underwriting operations
Segment Reporting Information [Line Items]
Revenues	362	285.3
Pretax Profit (Loss)	7.7	28.5
Amortization of intangible assets	17.9	18
Operating Segments | Other Indemnity | Underwriting operations
Segment Reporting Information [Line Items]
Revenues	0	0
Pretax Profit (Loss)	0	0.2
Segment Reconciling Items | Fees and other revenues
Segment Reporting Information [Line Items]
Revenues	130.2	103.8
Segment Reconciling Items | Service businesses
Segment Reporting Information [Line Items]
Revenues	42.6	34.2
Pretax Profit (Loss)	4.5	4.9
Segment Reconciling Items | Investment income
Segment Reporting Information [Line Items]
Revenues	667.4	118.1
Pretax Profit (Loss)	661.2	112.1
Segment Reconciling Items | Interest expense
Segment Reporting Information [Line Items]
Pretax Profit (Loss)	$ (47.4)	$ (36.8)

Segment Information Underwritin

Segment Information Underwriting Margins and Combined Ratios for our Underwriting Operations (Detail) - Underwriting operations	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Personal Lines | Agency
Segment Reporting Information [Line Items]
Underwriting Margin	12.90%	13.40%
Combined Ratio	87.10%	86.60%
Personal Lines | Direct
Segment Reporting Information [Line Items]
Underwriting Margin	9.00%	9.90%
Combined Ratio	91.00%	90.10%
Operating Segments
Segment Reporting Information [Line Items]
Underwriting Margin	11.20%	11.60%
Combined Ratio	88.80%	88.40%
Operating Segments | Personal Lines
Segment Reporting Information [Line Items]
Underwriting Margin	10.90%	11.60%
Combined Ratio	89.10%	88.40%
Operating Segments | Commercial Lines
Segment Reporting Information [Line Items]
Underwriting Margin	16.40%	11.70%
Combined Ratio	83.60%	88.30%
Operating Segments | Property
Segment Reporting Information [Line Items]
Underwriting Margin	2.10%	10.00%
Combined Ratio	97.90%	90.00%
Combined ratio amortization points	0.050	0.063

Dividends (Details)

Dividends (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		3 Months Ended
	Feb. 28, 2019	Feb. 28, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Dividends paid to common shareholders	$ 1,467.9	$ 654.9	$ 1,467.9	$ 654.9
Dividends payable			$ 58.4		$ 1,467.9	$ 655.1
Annual variable dividend
Common Stock, Dividends, Per Share, Cash Paid	$ 2.5140	$ 1.1247
Series B Preferred Stock
Preferred Stock, Dividends Per Share, Declared			$ 26.875
Dividends, Preferred Stock, Cash			$ 13.4
Series B Preferred Stock | Serial Preferred Stock
Preferred Stock, Dividends Per Share, Declared			$ 26.875	$ 0
Preferred Stock, Shares Issued (shares)			500,000	500,000	500,000

Dividends - Additional Informat

Dividends - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		60 Months Ended
	Mar. 31, 2023	Mar. 31, 2019	Mar. 31, 2018	Mar. 14, 2023	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Common Stock, Dividends, Per Share, Declared		$ 0.10	$ 0
Dividends payable		$ 58.4			$ 1,467.9	$ 655.1
Series B Preferred Stock
Class of Stock [Line Items]
Preferred Stock, Dividends Per Share, Declared		$ 26.875
Dividends, Preferred Stock, Cash		$ 13.4
Preferred Stock, Shares Outstanding (shares)		500,000
Preferred Stock, Liquidation Preference Per Share (USD per share)		$ 1,000
Series B Preferred Stock | Serial Preferred Stock
Class of Stock [Line Items]
Preferred Stock, Dividends Per Share, Declared		$ 26.875	$ 0
Preferred Stock, Shares Outstanding (shares)		500,000	500,000		500,000
Preferred Stock, Liquidation Preference Per Share (USD per share)		$ 1,000	$ 1,000		$ 1,000
Scenario, Forecast | Series B Preferred Stock
Class of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage				5.375%
London Interbank Offered Rate (LIBOR) | Scenario, Forecast | Series B Preferred Stock
Class of Stock [Line Items]
Preferred Stock, Basis Spread on Variable Rate	2.539%

Other Comprehensive Income (L_3

Other Comprehensive Income (Loss) Components of Other Comprehensive Income (Loss) Including Reclassification Adjustments by Income Statement (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]
AOCI before Tax, Attributable to Parent, beginning balance	$ (153)	$ 1,977.8	$ 1,977.8
Pretax Cumulative Effect of New Accounting Principal in Period of Adoption		(2,006)	(2,006)
Pretax Reclassification of Stranded Amounts in AOCI to Retained Earnings		0	0
AOCI before Tax, Attributable to Parent, after Cumulative Effect Adjustment		(28.2)	(28.2)
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, before Tax	414.5	(203.4)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	0	0
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Noncontrolling Interest	(2.9)	5.1
OCI, before Reclassifications, before Tax, Attributable to Parent	411.6	(198.3)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, before Tax	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax	33.4	(7.7)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	(0.3)	(0.2)
Total reclassification adjustment for amounts realized in net income, pre tax	33.1	(7.9)
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent	378.5	(190.4)
AOCI before Tax, Attributable to Parent, ending balance	225.5	(218.6)	(153)
Accumulated Other Comprehensive Income (Loss), Tax [Roll Forward]
AOCI Tax, Attributable to Parent, beginning balance	32.1	(695.6)	(695.6)
Tax, Cumulative Effect of New Accounting Principal in Period of Adoption		705.8	705.8
Tax, Reclassification of Stranded Amounts in AOCI to Retained Earnings		(4.3)	(4.3)
AOCI Tax, Attributable to Parent, After Cumulative Effect Adjustment		5.9	5.9
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax	(87)	42.8
Forecasted transactions, Total tax (provision) benefit	0	0
Other Comprehensive Income (Loss), Tax, Portion Attributable to Noncontrolling Interest	0.6	(1.1)
Other Comprehensive Income (Loss), Available-for-sale Securities, before Reclassification Adjustments, Tax	(86.4)	41.7
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, Tax	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax	(7)	1.6
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	0.1	0
Total reclassification adjustment for amounts realized in net income, Total tax (provision) benefit	(6.9)	1.6
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	(79.5)	40.1
AOCI Tax, Attributable to Parent, ending balance	(47.4)	46	32.1
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
After tax total accumulated other comprehensive income, beginning balance	(120.9)	1,282.2	1,282.2
Cumulative Effect of New Accounting Principle in Period of Adoption		(1,300.2)	(1,300.2)
Reclassification of Stranded Amounts in AOCI to Retained Earnings		(4.3)	(4.3)
AOCI, Net of Tax, After Cumulative Effect Adjustment		(22.3)	(22.3)
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax	327.5	(160.6)
Forecasted transactions, after tax	0	0
Other comprehensive (income) loss attributable to NCI	(2.3)	4	3.3
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	325.2	(156.6)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, Net of Tax	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	26.4	(6.1)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	(0.2)	(0.2)
Total reclassification adjustment for amounts realized in net income, after tax	26.2	(6.3)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	299	(150.3)
After tax total accumulated other comprehensive income, ending balance	178.1	(172.6)	(120.9)
Total net unrealized gains (losses) on securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
After tax total accumulated other comprehensive income, beginning balance	(105.6)	1,295	1,295
Cumulative Effect of New Accounting Principle in Period of Adoption		(1,300.2)	(1,300.2)
Reclassification of Stranded Amounts in AOCI to Retained Earnings		(1.1)	(1.1)
AOCI, Net of Tax, After Cumulative Effect Adjustment		(6.3)	(6.3)
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax	327.5	(160.6)
Forecasted transactions, after tax	0	0
Other comprehensive (income) loss attributable to NCI	0	0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	327.5	(160.6)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, Net of Tax	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	26.4	(6.1)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	0	0
Total reclassification adjustment for amounts realized in net income, after tax	26.4	(6.1)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	301.1	(154.5)
After tax total accumulated other comprehensive income, ending balance	195.5	(160.8)	(105.6)
Net unrealized gains (losses) on forecasted transactions
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
After tax total accumulated other comprehensive income, beginning balance	(17.2)	(14.8)	(14.8)
Cumulative Effect of New Accounting Principle in Period of Adoption		0	0
Reclassification of Stranded Amounts in AOCI to Retained Earnings		(3.2)	(3.2)
AOCI, Net of Tax, After Cumulative Effect Adjustment		(18)	(18)
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax	0	0
Forecasted transactions, after tax	0	0
Other comprehensive (income) loss attributable to NCI	0	0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	0
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, Net of Tax	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	(0.2)	(0.2)
Total reclassification adjustment for amounts realized in net income, after tax	(0.2)	(0.2)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	0.2	0.2
After tax total accumulated other comprehensive income, ending balance	(17)	(17.8)	(17.2)
(Income) loss attributable to NCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
After tax total accumulated other comprehensive income, beginning balance	1.9	2	2
Cumulative Effect of New Accounting Principle in Period of Adoption		0	0
Reclassification of Stranded Amounts in AOCI to Retained Earnings		0	0
AOCI, Net of Tax, After Cumulative Effect Adjustment		2	2
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax	0	0
Forecasted transactions, after tax	0	0
Other comprehensive (income) loss attributable to NCI	(2.3)	4
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(2.3)	4
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, Net of Tax	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	0	0
Total reclassification adjustment for amounts realized in net income, after tax	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(2.3)	4
After tax total accumulated other comprehensive income, ending balance	$ (0.4)	$ 6	$ 1.9

Other Comprehensive Income (L_4

Other Comprehensive Income (Loss) Components of Other Comprehensive Income (Loss) Including Reclassification Adjustments by Income Statement, Additional Information (Detail) $ in Millions	Mar. 31, 2019USD ($)
Statement of Comprehensive Income [Abstract]
Net unrealized gains on forecasted transactions, expected to reclassify into income within the next 12 months	$ 1

Redeemable Noncontrolling Int_3

Redeemable Noncontrolling Interest (Details) $ in Millions		3 Months Ended			12 Months Ended
		Mar. 31, 2019USD ($)shares		Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)	Apr. 01, 2021
Increase (Decrease) in Temporary Equity [Roll Forward]
Balance, Beginning of period		$ 214.5	[1]	$ 503.7	$ 503.7
Net income attributable to NCI		4.4		11.8	5.7
Other comprehensive income (loss) attributable to NCI1		2.3		(4)	(3.3)
Exercise of employee stock options		0		1.4	9.4
Purchase/change of ARX minority shares		0		0	(298.2)
Change in redemption value of NCI		0		1.3	(2.8)
Balance, End of period	[1]	$ 221.2		$ 514.2	$ 214.5
ARX Holding Corp.
Redeemable Noncontrolling Interest [Line Items]
Number of Shares Put Pursuant to Stockholders' Agreement | shares		204,527
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period | shares		5,483
Payments to Acquire Interest in Subsidiaries and Affiliates		$ 295.9
Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage		86.80%		68.90%	86.80%
Shares held in Employee Stock Option Plan, Suspense Shares | shares		16,067
Employee Stock Ownership Plan (ESOP), Deferred Shares, Fair Value		$ 23.8
Scenario, Forecast | ARX Holding Corp.
Redeemable Noncontrolling Interest [Line Items]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage						100.00%
[1]	See Note 12 – Redeemable Noncontrolling Interest for further discussion

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets Goodwill (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Goodwill [Line Items]
Goodwill, Acquired During Period	$ 0
Goodwill, Impaired, Accumulated Impairment Loss	0
Amortization of intangible assets	$ 17,900,000	$ 18,000,000
Weighted Average
Goodwill [Line Items]
Finite-Lived Intangible Assets, Remaining Amortization Period	3 years 8 months 12 days

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Net Carrying Amount of Other Intangible Assets (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Schedule of Other Intangible Assets [Line Items]
Indefinite lived intangible assets	$ 12.4	$ 12.4	$ 12.4
Total	276.7	294.6	348.6
Accumulated amortization	265.6	247.7	193.7
Licensing Agreements
Schedule of Other Intangible Assets [Line Items]
Accumulated amortization	0.6	0.6	0.6
Finite-Lived Intangible Assets
Schedule of Other Intangible Assets [Line Items]
Intangible assets subject to amortization	264.3	282.2	336.2
Accumulated amortization	$ 265	$ 247.1	$ 193.1

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Finite-lived Intangible Assets (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	$ 265.6	$ 247.7	$ 193.7
Policies in force
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	256.2	256.2	256.2
Accumulated Amortization	146.4	137.3	109.8
Net Carrying Amount	109.8	118.9	146.4
Agency relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	159.2	159.2	159.2
Accumulated Amortization	45.5	42.6	34.2
Net Carrying Amount	113.7	116.6	125
Software rights
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	79.1	79.1	79.1
Accumulated Amortization	42.7	40.1	32.1
Net Carrying Amount	36.4	39	47
Trade name
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	34.8	34.8	34.8
Accumulated Amortization	30.4	27.1	17
Net Carrying Amount	4.4	7.7	17.8
Finite-Lived Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	529.3	529.3	529.3
Accumulated Amortization	265	247.1	193.1
Net Carrying Amount	$ 264.3	$ 282.2	$ 336.2

Leases - Additional Information

Leases - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Leases [Abstract]
Operating lease right-of-use asset	$ 201.6
Location of operating lease right-of-use asset in statement of financial position	us-gaap:OtherAssets
Operating lease liabilities	$ 211.4
Location of operating lease liability in statement of financial location	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent
Operating lease costs	$ 24

Leases - Schedule of operating

Leases - Schedule of operating lease maturities (Details) $ in Millions	Mar. 31, 2019USD ($)
Leases [Abstract]
2019	$ 55.3
2020	72.7
2021	56.3
2022	25.6
2023	9.6
Thereafter	4.4
Total	223.9
Total	12.5
Present value of lease liabilities	$ 211.4
Weighted-average remaining term	3 years 2 months 12 days
Weighted-average discount rate	3.50%

Leases Schedule of Operating Le

Leases Schedule of Operating Lease Obligations (Details) $ in Millions	Dec. 31, 2018USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019	$ 64.1
2020	65.5
2021	52.8
2022	24.3
2023	8.5
Thereafter	3.8
Total	$ 219

New Accounting Standards Effect

New Accounting Standards Effect of Standard Change (Details) - USD ($) $ in Millions	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Assets	$ 48,850.3		$ 46,575	$ 41,330.9
Liabilities	$ 36,518.4		$ 35,538.7	$ 30,493.5
Property Subject to Operating Lease [Member] | Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Assets		$ 213
Liabilities		$ 217.6