The Progressive Corporation (PGR) 10-K 2 Mar 20 2019 FY Annual report Financial data

Cover Page

Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2019	Jan. 31, 2020	Jun. 30, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-09518
Entity Registrant Name	PROGRESSIVE CORP/OH/
Entity Incorporation, State or Country Code	OH
Entity Tax Identification Number	34-0963169
Entity Address, Address Line One	6300 Wilson Mills Road,
Entity Address, City or Town	Mayfield Village,
Entity Address, State or Province	OH
Entity Address, Postal Zip Code	44143
City Area Code	440
Local Phone Number	461-5000
Title of 12(b) Security	Common Shares, $1.00 Par Value
Trading Symbol	PGR
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 46,188,157,681
Entity Common Stock, Shares Outstanding		585,253,659
Entity Central Index Key	0000080661
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2019
Amendment Flag	false
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant’s Proxy Statement for the Annual Meeting of Shareholders to be held on May 8 , 2020 , and the Annual Report to Shareholders of The Progressive Corporation and subsidiaries for the year ended December 31, 2019 , included as Exhibit 13 to this Form 10-K, are incorporated by reference in Parts I, II, III, and IV hereof.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues
Net premiums earned	$ 36,192.4	$ 30,933.3	$ 25,729.9
Investment income	1,042	820.5	563.1
Net realized gains (losses) on securities:
Net realized gains (losses) on security sales	334.6	170.7
Net holding period gains (losses) on securities	757.9	(507.9)
Net impairment losses recognized in earnings	(63.3)	(68.3)	(64.5)
Total net realized gains (losses) on securities	1,029.2	(405.5)
Net realized gains (losses) on security sales			115.7
Net holding period gains (losses) on securities			(1.6)
Total net realized gains (losses) on securities			49.6
Fees and other revenues	563.7	472.2	370.6
Service revenues	195	158.5	126.8
Other gains (losses)	0	0	(1)
Total revenues	39,022.3	31,979	26,839
Expenses
Losses and loss adjustment expenses	25,470.5	21,721	18,808
Policy acquisition costs	3,023.2	2,573.7	2,124.9
Other underwriting expenses	4,975.1	4,195.8	3,480.7
Investment expenses	24.6	24.3	23.9
Service expenses	178.9	134.1	109.5
Interest expense	189.7	166.5	153.1
Total expenses	33,862	28,815.4	24,700.1
Net Income
Income before income taxes	5,160.3	3,163.6	2,138.9
Provision for income taxes	1,180.3	542.6	540.8
Net income	3,980	2,621	1,598.1
Net (income) loss attributable to noncontrolling interest (NCI)	(9.7)	(5.7)	(5.9)
Net income attributable to Progressive	3,970.3	2,615.3	1,592.2
Changes in:
Total net unrealized gains (losses) on fixed-maturity securities	466.4	(99.3)	355.4
Net unrealized losses on forecasted transactions	0.8	0.8	(5.4)
Foreign currency translation adjustment	0	0	1.1
Other comprehensive income (loss)	467.2	(98.5)	351.1
Other comprehensive (income) loss attributable to NCI	(4.6)	3.3	(2.3)
Comprehensive income attributable to Progressive	4,432.9	2,520.1	1,941
Computation of Earnings Per Common Share
Net income attributable to Progressive	3,970.3	2,615.3	1,592.2
Less: Preferred share dividends	26.9	21.4	0
Net income available to common shareholders	$ 3,943.4	$ 2,593.9	$ 1,592.2
Average common shares outstanding - Basic	583.8	582.4	580.8
Net effect of dilutive stock-based compensation	3.4	4.3	4.9
Total average equivalent common shares - Diluted	587.2	586.7	585.7
Basic: Earnings per share (usd per share)	$ 6.75	$ 4.45	$ 2.74
Diluted: Earnings per share (usd per share)	$ 6.72	$ 4.42	$ 2.72

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Assets
Fixed maturities (amortized cost: $32,643.1 and $28,255.9)	$ 33,110.3	$ 28,111.5
Short-term investments (amortized cost: $1,798.8 and $1,795.9)	1,798.8	1,795.9
Total available-for-sale securities	34,909.1	29,907.4
Nonredeemable preferred stocks (cost: $971.3 and $1,002.6)	1,038.9	1,033.9
Common equities (cost: $1,125.5 and $1,148.9)	3,306.3	2,626.1
Total equity securities	4,345.2	3,660
Total investments	39,254.3	33,567.4
Cash and cash equivalents	226.2	69.5
Restricted cash	1.2	5.5
Total cash, cash equivalents, and restricted cash	227.4	75
Accrued investment income	181.3	190.8
Premiums receivable, net of allowance for doubtful accounts of $283.2 and $252.1	7,507.3	6,497.1
Reinsurance recoverables	3,378.9	2,696.1
Prepaid reinsurance premiums	626.5	309.7
Deferred acquisition costs	1,056.5	951.6
Property and equipment, net of accumulated depreciation of $1,138.1 and $1,033.2	1,213.7	1,131.7
Goodwill	452.7	452.7
Intangible assets, net of accumulated amortization of $314.0 and $247.7	228.3	294.6
Net deferred income taxes	0	43.2
Other assets	768.4	365.1
Total assets	54,895.3	46,575
Liabilities
Unearned premiums	12,388.8	10,686.5
Loss and loss adjustment expense reserves	18,105.4	15,400.8
Net deferred income taxes	132.5	0
Accounts payable, accrued expenses, and other liabilities	5,962.7	5,046.5
Debt	4,407.1	4,404.9
Total liabilities	40,996.5	35,538.7
Redeemable noncontrolling interest (NCI)	225.6	214.5
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
Common shares, $1.00 par value (authorized 900.0; issued 797.5, including treasury shares of 212.9 and 214.3)	584.6	583.2
Paid-in capital	1,573.4	1,479
Retained earnings	10,679.6	8,386.6
Accumulated other comprehensive income (loss):
Net unrealized gains (losses) on fixed-maturity securities	360.8	(105.6)
Net unrealized losses on forecasted transactions	(16.4)	(17.2)
Accumulated other comprehensive (income) loss attributable to NCI	(2.7)	1.9
Total accumulated other comprehensive income (loss) attributable to Progressive	341.7	(120.9)
Total shareholders’ equity	13,673.2	10,821.8
Total liabilities, redeemable NCI, and shareholders’ equity	$ 54,895.3	$ 46,575

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fixed maturities, amortized cost	$ 32,643.1	$ 28,255.9
Nonredeemable preferred stocks, cost	971.3	1,002.6
Equity Securities Common Equities Cost	1,125.5	1,148.9
Debt Securities, Available-for-Sale Short Term Investments, Amortized Cost	1,798.8	1,795.9
Premiums receivable, allowance for doubtful accounts	283.2	252.1
Property and equipment, accumulated depreciation	1,138.1	1,033.2
Finite-Lived Intangible Assets, Accumulated Amortization	$ 314	$ 247.7
Common Shares, par value (USD per share)	$ 1	$ 1
Common Shares, authorized (shares)	900,000,000	900,000,000
Common Shares, issued (shares)	797,500,000	797,500,000
Common Shares, treasury shares (shares)	212,900,000	214,300,000
Serial Preferred Stock
Preferred Stock, Shares Authorized	20,000,000	20,000,000
Series B Preferred Stock | Serial Preferred Stock
Preferred Stock, No Par Value	$ 0	$ 0
Preferred Stock, Shares Authorized	500,000	500,000
Preferred Stock, Shares Issued	500,000	500,000
Preferred Stock, Shares Outstanding	500,000	500,000
Preferred Stock, Liquidation Preference Per Share	$ 1,000	$ 1,000

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Millions	Total	Preferred Shares, No Par Value	Common Shares, $1.00 Par Value	Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss) Attributable to Progressive
Balance, beginning of year at Dec. 31, 2016		$ 0	$ 579.9	$ 1,303.4	$ 5,140.4	$ 933.4
Stock Issued During Period, Value, New Issues		0
Treasury shares purchased			(1.5)	(3.4)	(57.6)
Net restricted equity awards issued/vested			3.3	(3.3)
Amortization of equity-based compensation				92.9
Reinvested dividends on restricted stock units				8	(8)
Adjustment to carrying amount of redeemable noncontrolling interest	$ 8.4			(8.4)
Net income attributable to Progressive	1,592.2				1,592.2
Cash dividends declared on common shares ($2.65, $2.5140, and $1.1247 per share)					(654.2)
Cash dividends declared on Serial Preferred Shares, Series B ($53.75, $27.024, and $0 per share)					0
Other, net					18.9
Attributable to noncontrolling interest	(2.3)					(2.3)
Other comprehensive income (loss)						351.1
Balance, end of year at Dec. 31, 2017	9,284.8	0	581.7	1,389.2	6,031.7	1,282.2
Cumulative Effect of New Accounting Principle in Period of Adoption	1,300.2
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-01 [Member]					0	0
Reclassification of Stranded Amounts in AOCI to Equity	7.7
Reclassification of Stranded Amounts in AOCI to Equity | Accounting Standards Update 2018-02 [Member]					0	0
Stock Issued During Period, Value, New Issues		493.9
Treasury shares purchased			(1.4)	(3.3)	(74.3)
Net restricted equity awards issued/vested			2.9	(2.9)
Amortization of equity-based compensation				76.2
Reinvested dividends on restricted stock units				12.2	(12.2)
Adjustment to carrying amount of redeemable noncontrolling interest	(2.8)			7.6
Net income attributable to Progressive	2,615.3				2,615.3
Cash dividends declared on common shares ($2.65, $2.5140, and $1.1247 per share)					(1,466)
Cash dividends declared on Serial Preferred Shares, Series B ($53.75, $27.024, and $0 per share)					(13.5)
Other, net					1.1
Attributable to noncontrolling interest	3.3					(0.1)
Other comprehensive income (loss)						(98.5)
Balance, end of year at Dec. 31, 2018	10,821.8	493.9	583.2	1,479	8,386.6	(120.9)
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-01 [Member]					1,300.2	(1,300.2)
Reclassification of Stranded Amounts in AOCI to Equity | Accounting Standards Update 2018-02 [Member]					4.3	(4.3)
Stock Issued During Period, Value, New Issues		0
Treasury shares purchased			(1.3)	(3.2)	(86.8)
Net restricted equity awards issued/vested			2.7	(2.7)
Amortization of equity-based compensation				90.1
Reinvested dividends on restricted stock units				10.6	(10.6)
Adjustment to carrying amount of redeemable noncontrolling interest	0.3			(0.4)
Net income attributable to Progressive	3,970.3				3,970.3
Cash dividends declared on common shares ($2.65, $2.5140, and $1.1247 per share)					(1,548.4)
Cash dividends declared on Serial Preferred Shares, Series B ($53.75, $27.024, and $0 per share)					(26.8)
Other, net					(4.7)
Attributable to noncontrolling interest	(4.6)					(4.6)
Other comprehensive income (loss)						467.2
Balance, end of year at Dec. 31, 2019	$ 13,673.2	$ 493.9	$ 584.6	$ 1,573.4	10,679.6	341.7
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-01 [Member]					0	0
Reclassification of Stranded Amounts in AOCI to Equity | Accounting Standards Update 2018-02 [Member]					$ 0	$ 0

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Common Stock, Dividends, Per Share, Declared	$ 2.65	$ 2.5140	$ 1.1247
Common Shares, par value (USD per share)	$ 1	$ 1	$ 1
Voting Preferred Stock
Preference Shares authorized	5,000,000	5,000,000	5,000,000
Preferred Stock, Shares Issued	0	0	0
Serial Preferred Stock
Preference Shares authorized	20,000,000	20,000,000
Serial Preferred Stock | Series B Preferred Stock
Preferred Stock, Dividends Per Share, Declared	$ 53.750	$ 27.024	$ 0
Preferred Stock, No Par Value	$ 0	$ 0	$ 0
Preference Shares authorized	500,000	500,000
Preferred Stock, Shares Issued	500,000	500,000

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Cash Flows [Abstract]
Net income	$ 3,980	$ 2,621	$ 1,598.1
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	239.8	190.4	169.9
Amortization of intangible assets	66.3	72	66.2
Net amortization of fixed-income securities	33.3	34.3	86.2
Amortization of equity-based compensation	90.2	77.2	95.4
Net realized (gains) losses on securities	(1,029.2)	405.5	(49.6)
Net (gains) losses on disposition of property and equipment	11	32.1	7.2
Other (gains) losses	0	0	1
Changes in:
Premiums receivable	(1,010.2)	(1,074.6)	(913.2)
Reinsurance recoverables	(682.8)	(422.7)	(388.6)
Prepaid reinsurance premiums	(316.8)	(106.4)	(32.8)
Deferred acquisition costs	(104.9)	(171.1)	(129.3)
Income taxes	227.2	(158.7)	(172.6)
Unearned premiums	1,702.3	1,783	1,434.9
Loss and loss adjustment expense reserves	2,704.6	2,313.9	1,718.8
Accounts payable, accrued expenses, and other liabilities	611.6	746.6	400
Other, net	(260.8)	(57.7)	(134.8)
Net cash provided by operating activities	6,261.6	6,284.8	3,756.8
Purchases:
Fixed maturities	(28,765.2)	(21,153)	(14,587.8)
Equity securities	(379.9)	(538.8)	(255.6)
Sales:
Fixed maturities	18,412.7	7,835.6	5,382.5
Equity securities	471.4	823.5	252.9
Maturities, paydowns, calls, and other:
Fixed maturities	6,145.5	5,099.8	5,215.8
Equity securities	49.9	26.6	50
Net sales of short-term investments	31.5	1,116.3	727.6
Net unsettled security transactions	6	11.7	(33.6)
Purchases of property and equipment	(363.5)	(266)	(155.7)
Sales of property and equipment	53.3	9.4	15.3
Acquisition of an insurance company, net of cash acquired	0	0	(18.1)
Net cash used in investing activities	(4,338.3)	(7,034.9)	(3,406.7)
Cash Flows From Financing Activities
Dividends paid to common shareholders	(1,643.2)	(654.9)	(395.4)
Dividends paid to preferred shareholders	(26.8)	(13.5)	0
Acquisition of treasury shares for restricted stock tax liabilities	(84.4)	(78.6)	(57.6)
Acquisition of treasury shares acquired in open market	(6.9)	(0.4)	(4.9)
Acquisition of additional shares of ARX Holding Corp.	(11.2)	(296.9)	0
Net proceeds from debt issuance	0	1,134	841.1
Net proceeds from issuance of Serial Preferred Shares, Series B	0	493.9	0
Payments of debt	0	(37.1)	(49)
Proceeds from exercise of equity options	1.6	3.3	0.5
Redemption/reacquisition of subordinated debt	0	0	(635.6)
Net cash provided by (used in) financing activities	(1,770.9)	549.8	(300.9)
Effect of exchange rate changes on cash	0	0	(0.3)
Increase (decrease) in cash, cash equivalents, and restricted cash	152.4	(200.3)	48.9
Cash, cash equivalents, and restricted cash - beginning of year	75	275.3	226.4
Cash, cash equivalents, and restricted cash - end of year	$ 227.4	$ 75	$ 275.3

SCHEDULE I - Summary Of Investm

SCHEDULE I - Summary Of Investments - Other Than Investments in Related Parties	12 Months Ended
	Dec. 31, 2019
Text Block [Abstract]
SCHEDULE I - Summary Of Investments - Other Than Investments In Related Parties	SCHEDULE I — SUMMARY OF INVESTMENTS — OTHER THAN INVESTMENTS IN RELATED PARTIES THE PROGRESSIVE CORPORATION AND SUBSIDIARIES (millions) December 31, 2019 Type of Investment Cost Fair Value Amount At Which Shown In The Balance Sheet Fixed maturities: Bonds: United States Government and government agencies and authorities $ 13,100.7 $ 13,251.1 $ 13,251.1 States, municipalities, and political subdivisions 1,686.0 1,713.3 1,713.3 Public utilities 303.8 314.1 314.1 Corporate and other debt securities 6,556.5 6,753.6 6,753.6 Asset-backed securities 10,810.4 10,883.2 10,883.2 Redeemable preferred stocks 185.7 195.0 195.0 Total fixed maturities 32,643.1 33,110.3 33,110.3 Equity securities: Common stocks: Public utilities 81.6 172.7 172.7 Banks, trusts, and insurance companies 220.9 664.9 664.9 Industrial, miscellaneous, and all other 823.0 2,468.7 2,468.7 Nonredeemable preferred stocks 971.3 1,038.9 1,038.9 Total equity securities 2,096.8 4,345.2 4,345.2 Short-term investments $ 1,798.8 $ 1,798.8 $ 1,798.8 Total investments $ 36,538.7 $ 39,254.3 $ 39,254.3 Progressive did not have any securities of any one issuer, excluding U.S. government obligations, with an aggregate cost or fair value exceeding 10% of total shareholders’ equity at December 31, 2019 .

SCHEDULE II - Condensed Financi

SCHEDULE II - Condensed Financial Information Of Registrant	12 Months Ended
	Dec. 31, 2019
Text Block [Abstract]
SCHEDULE II - Condensed Financial Information Of Registrant	SCHEDULE II — CONDENSED FINANCIAL INFORMATION OF REGISTRANT CONDENSED STATEMENTS OF COMPREHENSIVE INCOME THE PROGRESSIVE CORPORATION (PARENT COMPANY) (millions) Years Ended December 31, 2019 2018 2017 Revenues Dividends from subsidiaries $ 2,277.9 $ 939.1 $ 867.3 Undistributed income (loss) from subsidiaries 1,821.3 1,770.7 866.3 Equity in net income of subsidiaries 4,099.2 2,709.8 1,733.6 Intercompany investment income 31.1 39.4 11.3 Gains (losses) on extinguishment of debt 0 0 0.2 Total revenues 4,130.3 2,749.2 1,745.1 Expenses Interest expense 190.4 166.8 151.1 Deferred compensation 1 16.6 7.5 23.2 Other operating costs and expenses 5.5 5.1 4.6 Total expenses 212.5 179.4 178.9 Income before income taxes 3,917.8 2,569.8 1,566.2 Benefit for income taxes 52.5 45.5 26.0 Net income attributable to Progressive 3,970.3 2,615.3 1,592.2 Other comprehensive income (loss) 462.6 (95.2 ) 348.8 Comprehensive income attributable to Progressive $ 4,432.9 $ 2,520.1 $ 1,941.0 1 See Note 4 – Employee Benefit Plans in these condensed financial statements. See notes to condensed financial statements. CONDENSED BALANCE SHEETS THE PROGRESSIVE CORPORATION (PARENT COMPANY) (millions) December 31, 2019 2018 Assets Investment in affiliate $ 5.0 $ 5.0 Investment in subsidiaries 16,186.8 13,652.2 Receivable from investment subsidiary 2,912.0 2,658.9 Intercompany receivable 678.6 651.1 Net deferred income taxes 70.3 68.2 Other assets 303.8 124.2 Total assets $ 20,156.5 $ 17,159.6 Liabilities Accounts payable, accrued expenses, and other liabilities $ 475.2 $ 250.5 Dividend payable 1,375.4 1,467.9 Debt 4,407.1 4,404.9 Total liabilities 6,257.7 6,123.3 Redeemable noncontrolling interest (NCI) 225.6 214.5 Shareholders’ Equity Serial Preferred Shares (authorized 20.0) 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 Common shares, $1.00 par value (authorized 900.0; issued 797.5, including treasury shares of 212.9 and 214.3) 584.6 583.2 Paid-in capital 1,573.4 1,479.0 Retained earnings 10,679.6 8,386.6 Total accumulated other comprehensive income attributable to Progressive 341.7 (120.9 ) Total shareholders’ equity 13,673.2 10,821.8 Total liabilities, redeemable NCI, and shareholders’ equity $ 20,156.5 $ 17,159.6 See notes to condensed financial statements. CONDENSED STATEMENTS OF CASH FLOWS THE PROGRESSIVE CORPORATION (PARENT COMPANY) (millions) Years Ended December 31, 2019 2018 2017 Cash Flows From Operating Activities: Net income attributable to Progressive $ 3,970.3 $ 2,615.3 $ 1,592.2 Adjustments to reconcile net income attributable to Progressive to net cash provided by operating activities: Undistributed (income) loss from subsidiaries (1,821.3 ) (1,770.7 ) (866.3 ) Amortization of equity-based compensation 2.9 2.4 2.1 (Gains) losses on extinguishment of debt 0 0 (0.2 ) Changes in: Intercompany receivable (14.1 ) 77.5 (71.3 ) Accounts payable, accrued expenses, and other liabilities 47.1 (29.6 ) 53.6 Income taxes 175.5 (14.2 ) 37.3 Other, net (179.8 ) 47.8 (22.6 ) Net cash provided by operating activities 2,180.6 928.5 724.8 Cash Flows From Investing Activities: Additional investments in equity securities of consolidated subsidiaries (152.8 ) (178.3 ) (86.7 ) Acquisition of additional shares - ARX (5.4 ) (287.9 ) 0 Acquisition of an insurance company 0 0 (18.7 ) (Paid to) received from investment subsidiary (253.1 ) (1,192.8 ) (344.2 ) Net cash used in investing activities (411.3 ) (1,659.0 ) (449.6 ) Cash Flows From Financing Activities: Net proceeds from debt issuance 0 1,134.0 841.1 Net proceeds from preferred stock issuance 0 493.9 0 Reacquisitions of debt 0 0 (594.4 ) Dividends paid to common shareholders (1,643.2 ) (654.9 ) (395.4 ) Dividends paid to preferred shareholders (26.8 ) (13.5 ) 0 Acquisition of treasury shares for restricted stock tax liabilities (84.4 ) (78.6 ) (57.6 ) Acquisition of treasury shares acquired in open market (6.9 ) (0.4 ) (4.9 ) Loan to ARX Holding Corp. (8.0 ) (150.0 ) (64.0 ) Net cash provided by (used in) financing activities (1,769.3 ) 730.5 (275.2 ) Change in cash, cash equivalents, and restricted cash 0 0 0 Cash, cash equivalents, restricted cash - Beginning of year 0 0 0 Cash, cash equivalents, restricted cash - End of year $ 0 $ 0 $ 0 See notes to condensed financial statements. NOTES TO CONDENSED FINANCIAL STATEMENTS The accompanying condensed financial statements of The Progressive Corporation (parent company) should be read in conjunction with the consolidated financial statements and notes thereto in the Annual Report to Shareholders of The Progressive Corporation and its subsidiaries, which is included as Exhibit 13 to this Form 10-K. Note 1. Statements of Cash Flows — For the purpose of the Statements of Cash Flows, cash includes only bank demand deposits. The Progressive Corporation does not hold any cash but has unrestricted access to funds maintained in a non-insurance investment subsidiary to meet its holding company obligations; at December 31, 2019 , 2018 , and 2017, $3.2 billion , $2.9 billion , and $1.6 billion , respectively, of marketable securities were available in this subsidiary. Non-cash activity includes declared but unpaid dividends, and the change in redemption value of the redeemable NCI. For the years ended December 31, The Progressive Corporation paid the following: (millions) 2019 2018 2017 Income taxes $ 925.0 $ 679.2 $ 669.7 Interest 184.9 153.6 142.2 Note 2. Income Taxes — The Progressive Corporation files a consolidated federal income tax return with its eligible subsidiaries and acts as an agent for the consolidated tax group when making payments to the Internal Revenue Service. Effective April 2018, The Progressive Corporation acquired additional shares of ARX to increase its ownership above 80% . As a result, ARX and its subsidiaries were included in The Progressive Corporation consolidated federal income tax return for the period from April to December 31, 2018. The Progressive Corporation consolidated group’s net income taxes currently payable/recoverable are included in other liabilities/assets, respectively, in the accompanying Condensed Balance Sheets based on the balance at the end of the year. The Progressive Corporation and its eligible subsidiaries have adopted, pursuant to a written agreement, a method of allocating consolidated federal income taxes. Amounts allocated to the eligible subsidiaries under the written agreement are included in “Intercompany Receivable” in the accompanying Condensed Balance Sheets. On December 22, 2017, legislation commonly known as the Tax Cuts and Jobs Act of 2017 (the “2017 Tax Act”) was signed into law. One of the provisions of the 2017 Tax Act reduced the corporate federal income tax rate from 35% to 21% effective January 1, 2018. Pursuant to current accounting guidance, all deferred tax assets and liabilities were revalued at December 31, 2017, to recognize the tax rate that is expected to apply when the tax effects are ultimately recognized in future periods. The impact of revaluing the deferred tax assets and liabilities from 35% to 21% was a net increase to The Progressive Corporation’s income tax expense of $44.7 million in 2017. Note 3. Debt — The information relating to debt is incorporated by reference from Note 4 – Debt in our Annual Report. Note 4. Employee Benefit Plans — The information relating to incentive compensation and deferred compensation plans is incorporated by reference from Note 9 – Employee Benefit Plans in our Annual Report. Note 5. Other Comprehensive Income — On the condensed Statements of Comprehensive Income, other comprehensive income represents activity of the subsidiaries of The Progressive Corporation and includes net unrealized gains (losses) on securities, net unrealized gains on forecasted transactions, and foreign currency translation adjustments. Note 6. Dividends — The information relating to our dividend policy is incorporated by reference from Note 14 – Dividends

SCHEDULE III - Supplementary In

SCHEDULE III - Supplementary Insurance Information	12 Months Ended
	Dec. 31, 2019
Text Block [Abstract]
SCHEDULE III - Supplementary Insurance Information	SCHEDULE III — SUPPLEMENTARY INSURANCE INFORMATION THE PROGRESSIVE CORPORATION AND SUBSIDIARIES (millions) Segment Deferred 1 Future 1 Unearned premiums 1 Other 1 Premium revenue Net 1,2 Benefits, Amortization Other 1 Net premiums written Year ended December 31, 2019: Personal Lines $ 30,210.0 $ 21,329.7 $ 2,273.6 $ 4,227.6 $ 31,102.2 Commercial Lines 4,427.6 3,034.8 481.2 523.5 4,791.8 Property 1,554.8 1,106.0 268.4 224.0 1,683.9 Other indemnity 0 0 0 0 0 Total $ 1,056.5 $ 18,105.4 $ 12,388.8 $ 0 $ 36,192.4 $ 1,017.4 $ 25,470.5 $ 3,023.2 $ 4,975.1 $ 37,577.9 Year ended December 31, 2018: Personal Lines $ 26,034.7 $ 18,389.8 $ 1,964.4 $ 3,563.3 $ 27,157.6 Commercial Lines 3,610.9 2,394.0 396.0 396.0 3,996.4 Property 1,287.7 937.0 213.3 237.2 1,455.9 Other indemnity 0 0.2 0 (0.7 ) 0 Total $ 951.6 $ 15,400.8 $ 10,686.5 $ 0 $ 30,933.3 $ 796.2 $ 21,721.0 $ 2,573.7 $ 4,195.8 $ 32,609.9 Year ended December 31, 2017: Personal Lines $ 21,947.2 $ 16,141.4 $ 1,656.4 $ 2,954.8 $ 22,928.4 Commercial Lines 2,793.9 1,966.4 309.3 335.3 3,112.7 Property 988.8 700.2 159.2 190.4 1,091.0 Other indemnity 0 0 0 0.2 0 Total $ 780.5 $ 13,086.9 $ 8,903.5 $ 0 $ 25,729.9 $ 539.2 $ 18,808.0 $ 2,124.9 $ 3,480.7 $ 27,132.1 1 Progressive does not allocate assets, liabilities, or investment income to operating segments. Expense allocations are based on certain assumptions and estimates primarily related to revenue and volume; stated segment operating results would change if different methods were applied. 2 Excludes total net realized gains (losses) on securities.

SCHEDULE IV - Reinsurance

SCHEDULE IV - Reinsurance	12 Months Ended
	Dec. 31, 2019
Text Block [Abstract]
SCHEDULE IV - Reinsurance	SCHEDULE IV — REINSURANCE THE PROGRESSIVE CORPORATION AND SUBSIDIARIES (millions) Year Ended: Gross Amount Ceded to Assumed Net Amount Percentage December 31, 2019 Premiums earned: Property and liability insurance $ 37,519.7 $ 1,327.3 $ 0 $ 36,192.4 0 % December 31, 2018 Premiums earned: Property and liability insurance $ 31,970.2 $ 1,036.9 $ 0 $ 30,933.3 0 % December 31, 2017 Premiums earned: Property and liability insurance $ 26,425.7 $ 695.8 $ 0 $ 25,729.9 0 %

Reporting and Accounting Polici

Reporting and Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Reporting and Accounting Policies	REPORTING AND ACCOUNTING POLICIES Nature of Operations The Progressive insurance organization began business in 1937. The financial results of The Progressive Corporation include its subsidiaries and affiliates (references to “subsidiaries” in these notes include affiliates as well). Our insurance subsidiaries provide personal and commercial auto insurance, personal residential and commercial property insurance, general liability insurance, and other specialty property-casualty insurance and related services. Our Personal Lines segment writes insurance for personal autos and recreational vehicles, which we refer to as our special lines products. Our Commercial Lines segment writes auto-related primary liability and physical damage insurance, and general liability and property insurance, predominately for small businesses. Our Property segment writes residential property insurance for homeowners, other property owners, and renters. We operate our businesses throughout the United States through both the independent agency and direct channels. Basis of Consolidation and Reporting 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. All intercompany accounts and transactions are eliminated in consolidation. All revenues are generated from external customers and we do not have a reliance on any major customer. The Progressive Corporation owned 87.1% of the outstanding capital stock of ARX at December 31, 2019 , 86.8% at December 31, 2018 , and 69.0% at December 31, 2017 . The increase in Progressive's ownership of ARX in 2018 is primarily due to the minority ARX stockholders exercising their rights to "put" a portion of their shares, including exercised stock options, to Progressive pursuant to the ARX stockholders' agreement. See Note 15 – Redeemable Noncontrolling Interest and Note 17 – Subsequent Event for further discussion. Estimates We are required to make estimates and assumptions when preparing our financial statements and accompanying notes in conformity with accounting principles generally accepted in the United States of America (GAAP). As estimates develop into fact, results may, and will likely, differ from those estimates. Investments Our fixed-maturity securities and short-term investments are accounted for on an available-for-sale basis. Fixed-maturity securities include debt securities and redeemable preferred stocks, which may have fixed or variable principal payment schedules, may be held for indefinite periods of time, and may be used as a part of our asset/liability strategy or sold in response to changes in interest rates, anticipated prepayments, risk/reward characteristics, liquidity needs, or other economic factors. These securities are carried at fair value with the corresponding unrealized gains (losses), net of deferred income taxes, reported in accumulated other comprehensive income. Fair values are obtained from recognized pricing services or are quoted by market makers and dealers, with limited exceptions discussed in Note 3 – Fair Value . Short-term investments may include Eurodollar deposits, commercial paper, repurchase transactions, and other securities expected to mature within one year. From time to time, we may also invest in municipal bonds that have maturity dates that are longer than one year but have either liquidity facilities or mandatory put features within one year. Equity securities include common stocks, nonredeemable preferred stocks, and other risk investments. These securities are carried at fair value, with the changes in fair value reported as a component of net holding period gains (losses) on securities reported in net income. Derivative instruments may include futures, options, forward positions, interest rate swap agreements, and credit default swaps and may be used in the portfolio for general investment purposes or to hedge the exposure to variable cash flows of a forecasted transaction (cash flow hedge). We did no t have any derivatives outstanding at December 31, 2019 and 2018. To the extent we have derivatives held for general investment purposes, these derivative instruments would be recognized as either assets or liabilities and measured at fair value, with changes in fair value recognized in income as a component of net holding period gains (losses) on securities during the period of change. Derivatives designated as hedges are required to be evaluated on established criteria to determine the effectiveness of their correlation to, and ability to reduce the designated risk of, specific securities or transactions. Effectiveness is required to be reassessed regularly. For cash flow hedges that are deemed to be effective, the changes in fair value of the hedge would be reported as a component of accumulated other comprehensive income and subsequently amortized into earnings over the life of the hedged transaction. If a hedge is deemed to become ineffective or discontinued, changes in fair value of the derivative instrument would be reported in income for the current period. For derivatives settled through a clearinghouse, we will need cash to post initial margin and are subject to increases in margin beyond changes in fair value. Exposure to credit risk is limited to the carrying value; collateral may be required to limit credit risk. For bi-lateral derivative positions, net cash requirements are limited to changes in fair values, which may vary as a result of changes in interest rates, currency exchange rates, and other factors. We have elected not to offset fair value amounts that arise from derivative positions with the same counterparty under a master netting arrangement. Investment securities are exposed to various risks such as interest rate, market, credit, and liquidity risk. Fair values of securities fluctuate based on the nature and magnitude of changing market conditions; significant changes in market conditions could materially affect the portfolio’s value in the near term. We regularly monitor our portfolio for price changes, which might indicate potential impairments, and perform detailed reviews of fixed-maturity securities with unrealized losses. In such cases, changes in fair value are evaluated to determine the extent to which such changes are attributable to: (i) fundamental factors specific to the issuer, such as financial condition, business prospects, or other factors, (ii) market-related factors, such as interest rates, or (iii) credit-related losses, where the present value of cash flows expected to be collected are lower than the amortized cost basis of the security. We analyze our investment in fixed-maturity securities that are in a loss position to determine if we intend to sell, or if it is more likely than not that we will be required to sell, the security prior to recovery and, if so, we write down the security to its current fair value, with the entire amount of the write-down recorded to earnings. To the extent that it is more likely than not that we will hold the debt security until recovery (which could be maturity), we determine if any of the decline in value is due to a credit loss (i.e., where the present value of future cash flows expected to be collected is lower than the amortized cost basis of the security) and, if so, we recognize that portion of the impairment as a component of net realized gains (losses) in the consolidated statements of comprehensive income, with the difference (i.e., non-credit related impairment) recognized as part of our net unrealized gains (losses) in accumulated other comprehensive income. For a discussion of the modifications to the accounting guidance relative to the impairment evaluation for available-for-sale securities, which is effective January 1, 2020, see the " New Accounting Standards " section of this Note 1, below. Investment income consists of interest, dividends, and accretion (net of amortization). Interest is recognized on an accrual basis using the effective yield method, except for asset-backed securities, discussed below. Depending on the nature of the equity instruments, dividends are recorded at either the ex-dividend date or on an accrual basis. Asset-backed securities, which are included in our fixed-maturity portfolio, are generally accounted for under the retrospective method. The retrospective method recalculates yield assumptions (based on changes in interest rates or cash flow expectations) historically to the inception of the investment holding period, and applies the required adjustment, if any, to the cost basis, with the offset recorded to investment income. The prospective method is used primarily for interest-only securities, asset-backed securities below high investment-grade status (i.e., below AA-), and certain asset-backed securities with sub-prime loan exposure or where there is a greater risk of non-performance and where it is possible the initial investment may not be substantially recovered. The prospective method requires a calculation of expected future repayments and resets the yield to allow for future period adjustments; no current period impact to investment income or the security’s cost is made based on the cash flow update. Prepayment assumptions are updated quarterly. Realized gains (losses) on securities are computed based on the first-in first-out method and include write-downs on available-for-sale securities considered to have other-than-temporary declines in fair value (excluding non-credit related impairments), as well as holding period valuation changes on equity securities, hybrid instruments (e.g., securities with embedded options, where the option is a feature of the overall change in the value of the instrument), and derivatives. Insurance Premiums and Receivables Insurance premiums written are earned into income on a pro rata basis over the period of risk, based on a daily earnings convention. Accordingly, unearned premiums represent the portion of premiums written that are applicable to the unexpired risk. We provide insurance and related services to individuals and commercial accounts and offer a variety of payment plans. Generally, premiums are collected prior to providing risk coverage, minimizing our exposure to credit risk. For our Personal Lines and Commercial Lines businesses, we perform a policy level evaluation to determine the extent to which the premiums receivable balance exceeds the unearned premiums balance. We then age this exposure to establish an allowance for doubtful accounts based on prior experience. For our Property business, the risk of uncollectibility is relatively low. If premiums are unpaid by the policy due date, we provide advance notice of cancellation in accordance with each state’s requirements and, if the premiums remain unpaid after receipt of notice, cancel the policy and write off any remaining balance. Deferred Acquisition Costs Deferred acquisition costs include commissions, premium taxes, and other variable underwriting and direct sales costs incurred in connection with the successful acquisition or renewal of insurance contracts. These acquisition costs, net of ceding allowances, are deferred and amortized over the policy period in which the related premiums are earned. We consider anticipated investment income in determining the recoverability of these costs. Management believes these costs will be fully recoverable in the near term. We do not defer any advertising costs. Total advertising costs, which are expensed as incurred, for the years ended December 31, were: (millions) Advertising Costs 2019 $ 1,837.3 2018 1,422.4 2017 1,005.4 Loss and Loss Adjustment Expense Reserves Loss reserves represent the estimated liability on claims reported to us, plus reserves for losses incurred but not recorded (IBNR). These estimates are reported net of amounts estimated to be recoverable from salvage and subrogation. Loss adjustment expense reserves represent the estimated expenses required to settle these claims. The methods of making estimates and establishing these reserves are reviewed regularly, and resulting adjustments are reflected in income in the current period. Such loss and loss adjustment expense reserves are susceptible to change in the near term. Reinsurance Our reinsurance activity includes transactions which are categorized as Regulated and Non-Regulated. Regulated refers to plans in which we participate that are governed by insurance regulations and include state-provided reinsurance facilities (e.g., Michigan Catastrophic Claims Association, North Carolina Reinsurance Facility, Florida Hurricane Catastrophe Fund), as well as state-mandated involuntary plans for commercial vehicles (Commercial Automobile Insurance Procedures/Plans – CAIP) and federally regulated plans for flood (National Flood Insurance Program – NFIP); we act as a servicing agent for CAIP and as a participant in the “Write Your Own” program for the NFIP. Non-Regulated includes voluntary contractual arrangements primarily related to our Property business and to the transportation network company business written by our Commercial Lines segment. Prepaid reinsurance premiums are earned on a pro rata basis over the period of risk, based on a daily earnings convention, which is consistent with premiums earned. See Note 7 – Reinsurance for further discussion. Income Taxes The income tax provision is calculated under the balance sheet approach. 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. The principal items giving rise to such differences are investment securities (e.g., net unrealized gains (losses), net holding period gains (losses) on securities, write-downs on securities determined to be other-than-temporarily impaired), loss and loss adjustment expense reserves, unearned premiums reserves, deferred acquisition costs, property and equipment, intangible assets, and non-deductible accruals. We review our deferred tax assets regularly for recoverability. See Note 5 – Income Taxes for further discussion. Property and Equipment Property and equipment are recorded at cost, less accumulated depreciation, and include capitalized software developed or acquired for internal use. Depreciation is recognized over the estimated useful lives of the assets using accelerated methods for computer equipment and the straight-line method for all other fixed assets. We evaluate impairment whenever events or circumstances warrant such a review and write-off the impaired assets if appropriate. The cost and useful lives for property and equipment at December 31, were: ($ in millions) 2019 2018 Useful Lives Land $ 161.6 $ 177.0 NA Buildings, improvements, and integrated components 927.1 928.8 7-40 years Capitalized software 367.1 327.0 3-10 years Software licenses (internal use) 286.8 259.1 1-5 years Computer equipment 223.3 123.2 3 years All other property and equipment 385.9 349.8 3-10 years Total cost 2,351.8 2,164.9 Accumulated depreciation (1,138.1 ) (1,033.2 ) Balance at end of year $ 1,213.7 $ 1,131.7 NA = Not applicable At December 31, 2019 and 2018 , included in other assets in the consolidated balance sheets is $32.9 million and $39.3 million , respectively, of “held for sale” property, which represents the fair value of these properties less the estimated costs to sell. Goodwill and Intangible Assets Goodwill is the excess of the purchase price over the estimated fair value of the assets and liabilities acquired and represents the future economic benefits arising from other assets acquired that could not be individually identified and separately recognized. Intangible assets primarily arose through the acquisition of ARX and mainly represent the future premiums that will be recognized from the policies and agency relationships that existed at the acquisition date. See Note 16 – Goodwill and Intangible Assets for further discussion. We evaluate our goodwill for impairment at least annually using a qualitative approach. If events or changes in circumstances indicate that the carrying value of goodwill or intangible assets may not be recoverable, we will evaluate such items for impairment using a quantitative approach. Guaranty Fund Assessments We are subject to state guaranty fund assessments, which provide for the payment of covered claims or other insurance obligations of insurance companies deemed insolvent. These assessments are accrued after a formal determination of insolvency has occurred, and we have written the premiums on which the assessments will be based. Assessments that are available for recoupment from policyholders are capitalized when incurred; all other assessments are expensed. Fees and Other Revenues Fees and other revenues primarily represent fees collected from policyholders relating to installment charges in accordance with our bill plans, as well as late payment and insufficient funds fees and revenue from ceding commissions. Fees and other revenues are generally earned when invoiced, except for excess ceding commissions, which are earned over the policy period. Service Revenues and Expenses Our service businesses provide insurance-related services. Service revenues and expenses from our commission-based businesses are recorded in the period in which they are earned or incurred. Service revenues generated from processing business for involuntary CAIP plans are earned on a pro rata basis over the term of the related policies. Service expenses related to these CAIP plans are expensed as incurred. Equity-Based Compensation We issue time-based and performance-based restricted stock unit awards to key members of management as our form of equity compensation, and time-based restricted stock awards to non-employee directors. Collectively, we refer to these awards as “restricted equity awards.” Compensation expense for time-based restricted equity awards with installment vesting is recognized over each respective vesting period. For performance-based restricted equity awards, compensation expense is recognized over the respective estimated vesting periods. Dividend equivalent units are credited to outstanding restricted stock unit awards, both time-based and performance-based, at the time a dividend is paid to shareholders and paid upon vesting of the underlying award. We record an estimate for expected forfeitures of restricted equity awards based on our historical forfeiture rates. In addition, we shorten the vesting periods of certain restricted equity awards based on the “qualified retirement” provisions in our equity compensation plans, under which (among other provisions) if the participant satisfies certain age and years-of-service requirements, the vesting and distribution of 50% of outstanding restricted equity awards accelerates upon reaching eligibility for a qualified retirement and shortly after the grant date for each subsequent award. ARX also has nonqualified and incentive stock options outstanding that were issued prior to April 2015 as a form of equity compensation to certain of the officers and employees of ARX and its subsidiaries. These outstanding stock options are subject to the put/call features contained in the ARX stockholders’ agreement, pursuant to which The Progressive Corporation has the right, and can be required, to purchase all the shares underlying these awards. The vested stock options, and the shares issuable upon exercise of the stock options, are also subject to repurchase by ARX if the holder’s employment terminates. See Note 15 – Redeemable Noncontrolling Interest and Note 17 – Subsequent Event for further discussion. These stock options, which are treated for accounting purposes as liability awards, are expensed over the respective vesting periods based on the Black-Scholes value determined at period end. The total compensation expense recognized for equity-based compensation, including both equity and liability awards, for the years ended December 31, was: (millions) 2019 2018 2017 Pretax expense $ 90.2 $ 77.2 $ 95.4 Tax benefit 1 18.9 16.2 33.4 1 Calculated using the corporate federal tax rate of 21% for 2019 and 2018 and 35% for 2017. Earnings Per Common Share Net income attributable to Progressive is reduced by preferred share dividends to determine net income available to common shareholders, and is used in our calculation of the per common share amounts. Basic earnings per common share is computed using the weighted average number of common shares outstanding during the reporting period, excluding unvested time-based restricted stock awards. Diluted earnings per common share includes common stock equivalents assumed outstanding during the period. Our common stock equivalents include the incremental shares assumed to be issued for: • earned but unvested time-based restricted equity awards, and • performance-based restricted equity awards that satisfied certain contingency conditions for unvested common stock equivalents during the period and are highly likely to continue to satisfy the conditions until the date of vesting. 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 by ARX’s subsidiaries, and are not considered part of the investment portfolio. The amount of reverse repurchase commitments held by ARX’s subsidiaries at December 31, 2019 , 2018 , and 2017 , were $46.3 million , $117.3 million , and $247.2 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. For the year ended December 31, 2019, non-cash activity includes declared but unpaid dividends of $1,375.4 million and operating lease liabilities arising from obtaining right-of-use assets of $63.1 million (see Note 13 – Leases for further discussion). Our consolidated statement of cash flows for the year ended December 31, 2018, was revised to correct the classification of our acquisition of additional shares of ARX Holding Corp. from an investing activity to a financing activity; there was no overall impact on the decrease in cash, cash equivalents, and restricted cash that was reported for 2018. For the years ended December 31, we paid the following: (millions) 2019 2018 2017 Income taxes $ 954.3 $ 702.6 $ 715.6 Interest 184.9 154.0 146.3 Operating lease liabilities 84.0 NA NA NA = Not applicable prior to the adoption of the new accounting standard in 2019. Commitments and Contingencies We have certain noncancelable purchase obligations for goods and services with minimum commitments of $857.0 million at December 31, 2019. In addition, we have several multiple-layer property catastrophe reinsurance contracts with various reinsurers with terms ranging from one to three years; the minimum commitment under these agreements at December 31, 2019, was $96.1 million . New Accounting Standards Adopted On January 1, 2019, we adopted the Accounting Standards Update (ASU) that requires 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 13 – Leases for further information. On January 1, 2019, we adopted the ASU related to premium amortization on purchased callable debt securities. Under the ASU, the premium is required to be amortized to the earliest call date, which more closely aligns interest income recorded on bonds held at a premium with the economics of the underlying instrument. We applied the ASU on a modified retrospective basis, as required under the standard. Since we have historically used a yield-to-worst scenario for our securities that were purchased at a premium, and the first call on a premium security most often produces the lowest and most conservative yield, the adoption of this standard did not have an impact on our financial condition, cash flows, or results of operations. Issued In August 2018, the Financial Accounting Standards Board (FASB) issued an 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 is effective for fiscal years (including interim periods within those fiscal years) beginning after December 15, 2019 (2020 for calendar-year companies). We adopted this standard on January 1, 2020, on a prospective basis, and 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 (2020 for calendar-year companies), 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, in 2018, we elected to partially early adopt the removal of current disclosure requirements and adopted the remaining disclosure requirements as of January 1, 2020. Since this standard only affected disclosure, there was no 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. This standard was adopted on January 1, 2020 and is not expected 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. This update modified the existing accounting guidance related to the impairment evaluation for available-for-sale debt securities, reinsurance recoverables, and premiums receivables and could result in the creation of an allowance for credit losses as a contra asset account. The ASU requires a cumulative-effect change to retained earnings in the period of adoption and prospective changes on previously recorded impairments, to the extent applicable. This ASU is effective for fiscal years (including interim periods within those fiscal years) beginning after December 15, 2019 (2020 for calendar-year companies). We adopted this standard as of January 1, 2020. To determine the existence of any credit-related impairment losses on our available-for-sale debt securities, we reviewed all such securities at December 31, 2019, by applying estimates of future cash flows and performance of those securities in a loss position and identifying market-related versus performance-related losses. For our reinsurance recoverables, we assessed the current credit quality and credit outlook for reinsurers with at-risk uncollateralized recoverables. In assessing premium receivables, which are short-term in nature, we assessed customer balances leveraging our current process for analyzing uncollectibility of premium receivables. Based on these analyses, we determined that no allowance for credit losses was necessary relative to our available-for-sale debt securities, reinsurance recoverables, or premiums receivable upon adoption of the ASU.

Investments

Investments	12 Months Ended
	Dec. 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 of the securities. 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 Unrealized Losses Net Holding Period Gains (Losses) Fair Value % of Total Fair Value December 31, 2019 Available-for-sale securities: Fixed maturities: U.S. government obligations $ 13,100.7 $ 194.1 $ (43.7 ) $ 0 $ 13,251.1 33.7 % State and local government obligations 1,686.0 30.0 (2.7 ) 0 1,713.3 4.4 Corporate debt securities 6,860.3 206.6 (0.5 ) 1.3 7,067.7 18.0 Residential mortgage-backed securities 625.0 4.5 (2.0 ) 0 627.5 1.6 Commercial mortgage-backed securities 5,020.7 61.5 (6.0 ) 0 5,076.2 12.9 Other asset-backed securities 5,164.7 16.2 (1.4 ) 0 5,179.5 13.2 Redeemable preferred stocks 185.7 4.1 (1.3 ) 6.5 195.0 0.5 Total fixed maturities 32,643.1 517.0 (57.6 ) 7.8 33,110.3 84.3 Short-term investments 1,798.8 0 0 0 1,798.8 4.6 Total available-for-sale securities 34,441.9 517.0 (57.6 ) 7.8 34,909.1 88.9 Equity securities: Nonredeemable preferred stocks 971.3 0 0 67.6 1,038.9 2.7 Common equities 1,125.5 0 0 2,180.8 3,306.3 8.4 Total equity securities 2,096.8 0 0 2,248.4 4,345.2 11.1 Total portfolio 1,2 $ 36,538.7 $ 517.0 $ (57.6 ) $ 2,256.2 $ 39,254.3 100.0 % ($ in millions) Cost Gross Unrealized Gains Gross Unrealized Losses Net Holding Period Gains (Losses) Fair Value % of Total Fair Value December 31, 2018 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 fixed maturities and short-term 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 available-for-sale 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 net unsettled security transactions; at December 31, 2019 , $11.9 million was included in “other liabilities,” compared to $5.9 million at December 31, 2018 . 2 The total fair value of the portfolio at December 31, 2019 and 2018 included $3.2 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 December 31, 2019 , bonds and certificates of deposit in the principal amount of $281.0 million were on deposit to meet state insurance regulatory requirements. We did no t hold any securities of any one issuer, excluding U.S. government obligations, with an aggregate cost or fair value exceeding 10% of total shareholders’ equity at December 31, 2019 or 2018 . At December 31, 2019 , we did no t hold any debt securities that were non-income producing during the preceding 12 months. 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. Although we did invest in repurchase and reverse repurchase transactions during 2019 and 2018 , we did no t have any open positions at December 31, 2019 or 2018 . To the extent we enter into repurchase or reverse repurchase transactions, consistent with past practice, we would elect not to offset these transactions and would report them on a gross basis on our consolidated 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 maturities are hybrid securities, which are reported at fair value at December 31 : (millions) 2019 2018 Fixed Maturities: State and local government obligations $ 3.5 $ 3.6 Corporate debt securities 91.2 158.9 Other asset-backed securities 2.6 4.5 Redeemable preferred stocks 92.1 77.7 Total hybrid securities $ 189.4 $ 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 a component of realized gains or losses. Fixed Maturities The composition of fixed maturities by maturity at December 31, 2019 , was: (millions) Cost Fair Value Less than one year $ 6,700.1 $ 6,712.6 One to five years 16,898.3 17,158.4 Five to ten years 9,010.8 9,203.9 Ten years or greater 33.9 35.4 Total $ 32,643.1 $ 33,110.3 Asset-backed securities are classified in the maturity distribution table based upon their projected cash flows. All other securities that 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 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 Value Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Value Unrealized Losses No. of Sec. Fair Value Unrealized Losses December 31, 2019 U.S. government obligations 23 $ 5,152.4 $ (43.7 ) 19 $ 5,057.2 $ (43.6 ) 4 $ 95.2 $ (0.1 ) State and local government obligations 67 314.3 (2.7 ) 52 287.5 (2.6 ) 15 26.8 (0.1 ) Corporate debt securities 16 247.6 (0.5 ) 12 191.4 (0.5 ) 4 56.2 0 Residential mortgage-backed securities 41 292.8 (2.0 ) 12 163.7 (0.9 ) 29 129.1 (1.1 ) Commercial mortgage-backed securities 98 1,742.4 (6.0 ) 79 1,400.0 (5.3 ) 19 342.4 (0.7 ) Other asset-backed securities 61 1,000.6 (1.4 ) 43 938.5 (0.9 ) 18 62.1 (0.5 ) Redeemable preferred stocks 1 11.2 (1.3 ) 0 0 0 1 11.2 (1.3 ) Total fixed maturities 307 $ 8,761.3 $ (57.6 ) 217 $ 8,038.3 $ (53.8 ) 90 $ 723.0 $ (3.8 ) Total No. of Sec. Total Fair Value Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Value Unrealized Losses No. of Sec. Fair Value Unrealized Losses December 31, 2018 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 ) During 2019 , the number of securities in our fixed-maturity portfolio with unrealized losses decreased, primarily due to valuation increases in nearly all sectors as interest rates declined and credit spreads tightened. For both 2019 and 2018, we had no material decreases in valuation as a result of credit rating downgrades. A review of the securities in the table above 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. Other-Than-Temporary Impairment (OTTI) At December 31, 2019, 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) was $19.6 million , compared to $19.8 million at December 31, 2018. At December 31, 2019, 2018, and 2017, the balance for the amount related to credit losses recognized in earnings, 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, was $0.5 million . We did no t have any credit loss rollforward activity during 2019 or 2018. The following table shows the rollforward activity for 2017: (millions) Total Total at December 31, 2016 $ 11.5 Credit losses for which an OTTI was not previously recognized 0.4 Reductions for securities sold/matured (11.2 ) Change in recoveries of future cash flows expected to be collected 1 (0.2 ) Total at December 31, 2017 $ 0.5 1 Reflects expected recovery of prior period 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 year ended December 31, 2019 . Realized Gains (Losses) The components of net realized gains (losses) for the years ended December 31, were: (millions) 2019 2018 2017 Gross realized gains on security sales Available-for-sale securities: U.S. government obligations $ 164.4 $ 6.7 $ 6.2 State and local government obligations 6.1 9.5 10.5 Corporate and other debt securities 100.1 2.4 20.3 Residential mortgage-backed securities 0.2 0 23.8 Commercial mortgage-backed securities 8.1 2.0 4.9 Other asset-backed securities 0.8 0.1 0.3 Redeemable preferred stocks 2.2 4.5 8.5 Total available-for-sale securities 281.9 25.2 74.5 Equity securities: Nonredeemable preferred stocks 36.2 4.1 58.4 Common equities 61.7 286.6 43.0 Total equity securities 97.9 290.7 101.4 Subtotal gross realized gains on security sales 379.8 315.9 175.9 Gross realized losses on security sales Available-for-sale securities: U.S. government obligations (20.4 ) (98.7 ) (28.7 ) State and local government obligations (0.7 ) (2.9 ) (0.1 ) Corporate and other debt securities (7.9 ) (10.4 ) (5.1 ) Residential mortgage-backed securities (2.3 ) (0.1 ) (0.4 ) Commercial mortgage-backed securities (2.2 ) (6.3 ) (5.3 ) Other asset-backed securities (0.1 ) (1.1 ) (0.4 ) Redeemable preferred stocks (0.4 ) (0.1 ) (6.4 ) Short-term investments 0 0 (0.2 ) Total available-for-sale securities (34.0 ) (119.6 ) (46.6 ) Equity securities: Nonredeemable preferred stocks (3.2 ) (3.9 ) (5.9 ) Common equities (8.0 ) (21.7 ) (12.2 ) Total equity securities (11.2 ) (25.6 ) (18.1 ) Subtotal gross realized losses on security sales (45.2 ) (145.2 ) (64.7 ) Net realized gains (losses) on security sales Available-for-sale securities: U.S. government obligations 144.0 (92.0 ) (22.5 ) State and local government obligations 5.4 6.6 10.4 Corporate and other debt securities 92.2 (8.0 ) 15.2 Residential mortgage-backed securities (2.1 ) (0.1 ) 23.4 Commercial mortgage-backed securities 5.9 (4.3 ) (0.4 ) Other asset-backed securities 0.7 (1.0 ) (0.1 ) Redeemable preferred stocks 1.8 4.4 2.1 Short-term investments 0 0 (0.2 ) Total available-for-sale securities 247.9 (94.4 ) 27.9 Equity securities: Nonredeemable preferred stocks 33.0 0.2 52.5 Common equities 53.7 264.9 30.8 Total equity securities 86.7 265.1 83.3 Litigation settlements and other gains (losses) 0 0 1.2 Subtotal net realized gains (losses) on security sales 334.6 170.7 112.4 Net holding period gains (losses) Hybrid securities 18.0 (10.4 ) (1.6 ) Equity securities 739.9 (497.5 ) 0 Subtotal net holding period gains (losses) 757.9 (507.9 ) (1.6 ) Other-than-temporary impairment losses Fixed maturities: Commercial mortgage-backed securities 0 0 (0.4 ) Total fixed maturities 0 0 (0.4 ) Equity securities: Common equities 0 0 (11.2 ) Subtotal investment other-than-temporary impairment losses 0 0 (11.6 ) Other asset impairment (63.3 ) (68.3 ) (49.6 ) Subtotal other-than-temporary impairment losses (63.3 ) (68.3 ) (61.2 ) Total net realized gains (losses) on securities $ 1,029.2 $ (405.5 ) $ 49.6 For all three periods, the other asset impairment losses related to federal renewable energy tax credit fund investments, which were reported in “other assets” on the consolidated balance sheets, 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 related to 2019 activity. The following table reflects our holding period realized gains (losses) on equity securities recognized for the respective years ended December 31, for equity securities held at the respective year end: (millions) 2019 2018 Total net gains (losses) recognized during the period on equity securities $ 826.6 $ (232.4 ) Less: Net gains (losses) recognized on equity securities sold during the period 86.7 265.1 Net holding period gains (losses) recognized during the period on equity securities held at period end $ 739.9 $ (497.5 ) Note: Comparative disclosure for 2017 is not meaningful. Net Investment Income The components of net investment income for the years ended December 31, were: (millions) 2019 2018 2017 Available-for-sale securities: Fixed maturities: U.S. government obligations $ 268.6 $ 196.8 $ 72.7 State and local government obligations 36.5 37.7 51.5 Foreign government obligations 0 0 0.3 Corporate debt securities 268.9 217.9 125.2 Residential mortgage-backed securities 21.6 27.6 34.7 Commercial mortgage-backed securities 150.1 93.9 79.6 Other asset-backed securities 117.3 75.7 47.1 Redeemable preferred stocks 19.0 12.3 11.8 Total fixed maturities 882.0 661.9 422.9 Short-term investments 41.7 52.9 37.8 Total available-for-sale securities 923.7 714.8 460.7 Equity securities: Nonredeemable preferred stocks 61.8 45.9 44.1 Common equities 56.5 59.8 58.3 Total equity securities 118.3 105.7 102.4 Investment income 1,042.0 820.5 563.1 Investment expenses (24.6 ) (24.3 ) (23.9 ) Net investment income $ 1,017.4 $ 796.2 $ 539.2 The amount of investment income we recognize varies based on the average assets held during the year and the book yields of the securities in our portfolio. The year-over-year increases in net investment income in 2019 and 2018 , were 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 premium growth, underwriting profitability, and portfolio returns, as well as the proceeds from debt and preferred stock issuances during 2018, partially offset by the payment of common and preferred share dividends and the interest on our debt. The increase in portfolio yields was a result of our decisions to hold a short-duration portfolio, which allowed us to take advantage of opportunities to invest in higher yielding securities with cash from operations, portfolio maturities, and paydowns, and to increase the portfolio duration. The portfolio duration at December 31, 2019 was 3.0 years , compared to 2.8 years and 2.5 years at December 31, 2018 and 2017 , respectively. Derivative Instruments At December 31, 2019 , 2018 , and 2017 , we had no open derivative positions. During both 2019 and 2018 , we reclassified $1.0 million , respectively, of net unrealized losses from accumulated other comprehensive income to interest expense on our closed debt issuance cash flow hedges, compared to net unrealized gains of $0.3 million during 2017 . During March 2017 , we entered into a forecasted debt issuance hedge, against a possible rise in interest rates, in conjunction with the $850 million of 4.125% Senior Notes due 2047 issued in April 2017 . Upon issuance, we closed the hedge and recognized, as part of accumulated other comprehensive income, a pretax unrealized loss of $8.0 million in April 2017 .

Fair Value

Fair Value	12 Months Ended
	Dec. 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 December 31, 2019 Fixed maturities: U.S. government obligations $ 13,251.1 $ 0 $ 0 $ 13,251.1 $ 13,100.7 State and local government obligations 0 1,713.3 0 1,713.3 1,686.0 Corporate debt securities 0 7,067.7 0 7,067.7 6,860.3 Subtotal 13,251.1 8,781.0 0 22,032.1 21,647.0 Asset-backed securities: Residential mortgage-backed 0 627.5 0 627.5 625.0 Commercial mortgage-backed 0 5,076.2 0 5,076.2 5,020.7 Other asset-backed 0 5,179.5 0 5,179.5 5,164.7 Subtotal asset-backed securities 0 10,883.2 0 10,883.2 10,810.4 Redeemable preferred stocks: Financials 0 51.7 0 51.7 51.5 Utilities 0 11.1 0 11.1 10.0 Industrials 11.1 121.1 0 132.2 124.2 Subtotal redeemable preferred stocks 11.1 183.9 0 195.0 185.7 Total fixed maturities 13,262.2 19,848.1 0 33,110.3 32,643.1 Short-term investments 1,797.4 1.4 0 1,798.8 1,798.8 Total available-for-sale securities 15,059.6 19,849.5 0 34,909.1 34,441.9 Equity securities: Nonredeemable preferred stocks: Financials 77.4 850.7 27.1 955.2 891.3 Utilities 0 42.3 0 42.3 39.9 Industrials 0 25.4 16.0 41.4 40.1 Subtotal nonredeemable preferred stocks 77.4 918.4 43.1 1,038.9 971.3 Common equities: Common stocks 3,306.0 0 0 3,306.0 1,125.2 Other risk investments 0 0 0.3 0.3 0.3 Subtotal common equities 3,306.0 0 0.3 3,306.3 1,125.5 Total equity securities 3,383.4 918.4 43.4 4,345.2 2,096.8 Total portfolio $ 18,443.0 $ 20,767.9 $ 43.4 $ 39,254.3 $ 36,538.7 Debt $ 0 $ 5,119.6 $ 0 $ 5,119.6 $ 4,407.1 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 fixed maturities and short-term 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 available-for-sale 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 investments 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 investments 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 December 31, 2019 , vendor-quoted prices represented 80% of our Level 1 classifications (excluding short-term investments), compared to 79% at December 31, 2018 . 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 both December 31, 2019 and 2018 , vendor-quoted prices comprised 99% of our Level 2 classifications (excluding short-term investments), while dealer-quoted prices represented 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. 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 other 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 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 December 31, 2019 and 2018 , we did no t have any securities in our fixed-maturity portfolio listed as Level 3. At December 31, 2019 , we owned three private nonredeemable preferred securities that were priced internally or by a pricing firm and we held two private nonredeemable preferred securities that were priced internally at December 31, 2018 . At both December 31, 2019 and 2018 , we held one Level 3 other risk investment that was priced using the equity method. 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 or 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 years ended December 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 Dec. 31, 2019 Equity securities: Nonredeemable preferred stocks: Financials $ 25.1 $ 0 $ 2.0 $ 0 $ 0 $ 0 $ 0 $ 27.1 Industrials 5.0 0 10.0 0 0 1.0 0 16.0 Common equities: Other risk investments 0.3 0 0 0 0 0 0 0.3 Total Level 3 securities $ 30.4 $ 0 $ 12.0 $ 0 $ 0 $ 1.0 $ 0 $ 43.4 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 Dec. 31, 2018 Equity securities: Nonredeemable preferred stocks: Financials $ 0 $ 0 $ 25.1 $ 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 $ 5.3 $ 0 $ 25.1 $ 0 $ 0 $ 0 $ 0 $ 30.4 The following tables provide a summary of the quantitative information about Level 3 fair value measurements for our applicable securities at December 31 : Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at Dec. 31, 2019 Valuation Technique Unobservable Input Unobservable Input Assumption Equity securities: Nonredeemable preferred stocks: Financials $ 27.1 Pricing firm Recent transaction price 9.0 Industrials 6.0 Pricing firm Performance-based transaction price adjustment 4.8 Industrials 1 10.0 Internal price Unadjusted purchase price 4.9 Subtotal Level 3 securities 43.1 Pricing exemption securities 0.3 Total Level 3 securities $ 43.4 1 The security was purchased in November 2019. 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 9.0 Industrials 5.0 Internal price Price-to-sales ratio 5.5 Subtotal Level 3 securities 30.1 Pricing exemption securities 0.3 Total Level 3 securities $ 30.4 1

Debt

Debt	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Debt	DEBT Debt at December 31, consisted of: 2019 2018 (millions) Carrying Value Fair Value Carrying Value Fair Value 3.75% Senior Notes due 2021 (issued: $500.0, August 2011) $ 499.4 $ 515.6 $ 499.1 $ 506.5 2.45% Senior Notes due 2027 (issued: $500.0, August 2016) 496.9 501.5 496.5 455.5 6 5/8% Senior Notes due 2029 (issued: $300.0, March 1999) 296.6 392.5 296.4 368.5 4.00% Senior Notes due 2029 (issued: $550.0, October 2018) 545.0 614.3 544.5 562.4 6.25% Senior Notes due 2032 (issued: $400.0, November 2002) 395.7 552.6 395.5 496.6 4.35% Senior Notes due 2044 (issued: $350.0, April 2014) 346.7 417.0 346.6 350.2 3.70% Senior Notes due 2045 (issued: $400.0, January 2015) 395.4 434.2 395.3 366.7 4.125% Senior Notes due 2047 (issued: $850.0, April 2017) 841.6 986.1 841.4 831.9 4.20% Senior Notes due 2048 (issued: $600.0, March 2018) 589.8 705.8 589.6 594.0 Total $ 4,407.1 $ 5,119.6 $ 4,404.9 $ 4,532.3 All of the outstanding debt was issued by The Progressive Corporation and includes amounts that were borrowed and contributed to the capital of its insurance subsidiaries or used, or made available for use, for other business purposes. Fair values for these debt instruments are obtained from external sources. There are no restrictive financial covenants or credit rating triggers on the outstanding debt. Interest on all debt is payable semiannually at the stated rates. All principal is due at the stated maturity. Each note is redeemable, in whole or in part, at any time; however, the redemption price will equal the greater of the principal amount of the note or a “make whole” amount calculated by reference to the present values of remaining scheduled principal and interest payments under the note. Aggregate required principal payments on debt outstanding at December 31, 2019 , are as follows: (millions) Year Payments 2020 $ 0 2021 500 2022 0 2023 0 2024 0 Thereafter 3,950 Total $ 4,450 We issued $550 million of 4.00% Senior Notes due 2029 in October 2018 and $600 million of 4.20% Senior Notes due 2048 in March 2018, in underwritten public offerings. The net proceeds from these issuances, after deducting underwriters’ discounts, commissions, and other issuance costs, were approximately $544.5 million and $589.5 million , respectively. Prior to certain issuances of our debt securities, we entered into forecasted transactions to hedge against possible rises in interest rates. When the contracts were closed upon the issuance of the applicable debt securities, we recognized the unrealized gains (losses) on these contracts as part of accumulated other comprehensive income (see Note 1 – Reporting and Accounting Policies for further discussion). These unrealized gains (losses) are being amortized as adjustments to interest expense over the life of the related notes. The following table shows the original gain (loss) recognized at debt issuance and the unamortized balance at December 31, 2019 , on a pretax basis: (millions) Unrealized Gain (Loss) at Debt Issuance Unamortized Balance at December 31, 2019 3.75% Senior Notes $ (5.1 ) $ (1.0 ) 6 5/8% Senior Notes (4.2 ) (2.4 ) 6.25% Senior Notes 5.1 3.3 4.35% Senior Notes (1.6 ) (1.4 ) 3.70% Senior Notes (12.9 ) (11.7 ) 4.125% Senior Notes (8.0 ) (7.6 ) During 2019, we renewed the line of credit with PNC Bank, National Association (PNC) in the maximum principal amount of $250 million on the same terms and conditions as the prior line of credit entered into in 2018. 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, 2020, 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 borrowings under either line of credit in 2019 or 2018.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES The components of our income tax provision were as follows: (millions) 2019 2018 2017 Current tax provision Federal $ 1,104.7 $ 673.1 $ 680.9 State 27.3 21.5 12.8 Deferred tax expense (benefit) Federal 45.3 (145.9 ) (149.4 ) State 3.0 (6.1 ) (3.5 ) Total income tax provision $ 1,180.3 $ 542.6 $ 540.8 The provision for income taxes in the accompanying consolidated statements of comprehensive income differed from the statutory rate as follows: (millions) 2019 2018 2017 Income before income taxes $ 5,160.3 $ 3,163.6 $ 2,138.9 Tax at statutory federal rate $ 1,083.7 21 % $ 664.4 21 % $ 748.6 35 % Tax effect of: Reversal of prior year tax credits 163.2 3 0 0 0 0 Tax credits 1 (43.9 ) (1 ) (76.3 ) (2 ) (52.4 ) (2 ) Stock-based compensation (25.9 ) (1 ) (25.1 ) (1 ) (25.1 ) (1 ) Tax-deductible dividends (14.6 ) 0 (14.6 ) (1 ) (9.7 ) 0 Dividends received deduction 2,3 (10.4 ) 0 (9.7 ) 0 (20.7 ) (1 ) Exempt interest income 3 (3.6 ) 0 (5.9 ) 0 (16.9 ) (1 ) Net deferred tax liability revaluation 4 0 0 0 0 (99.5 ) (5 ) Nondeductible compensation expense 5 8.1 0 (0.2 ) 0 10.1 0 State income taxes, net of federal taxes 24.0 1 12.2 0 6.0 0 Other items, net (0.3 ) 0 (2.2 ) 0 0.4 0 Total income tax provision $ 1,180.3 23 % $ 542.6 17 % $ 540.8 25 % 1 Includes $38.1 million , $71.0 million , and $48.7 million for 2019 , 2018 , and 2017 , respectively, of benefits on investments in federal renewable energy tax credit funds. 2 2019 and 2018 amounts reflect a dividends received deduction percentage of 50% under the 2017 Tax Act. In 2017, the deduction percentage was 70%. 3 2019 and 2018 amounts reflect a proration percentage of 25% for such income attributable to investments held by our insurance companies. In 2017, the proration percentage was 15%. 4 Pursuant to the 2017 Tax Act. 5 Decrease in 2018 reflects our updated interpretation regarding compensation that qualifies for deduction under the 2017 Tax Act based on additional guidance issued. See further discussion below. 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 tax credit fund investments we made from 2016 through 2018, including information about ongoing federal investigations. Based on our investigations and other information that became available to us, we concluded the sponsor had committed fraud through these tax credit funds and that all the tax credits and other tax benefits related to those investments were not valid. As a result, during 2019, we increased our provision for income taxes by $163.2 million ( $252.0 million current income taxes payable, offset by $88.8 million reduction of deferred tax liability), principally reflecting the total reversal of the tax credits and other tax benefits previously recognized from certain renewable energy investments, plus interest. In addition, we paid $100.0 million related to the 2018 tax year, which reduced net taxes payable, and made protective deposits of $152.1 million for tax years 2017 and 2016. The protective deposits are included in other assets on our consolidated balance sheets. As of early 2020, the principals of the sponsor and various other individuals have pleaded guilty to federal criminal charges relating to the fraudulent tax credit funds. On December 22, 2017, legislation commonly known as the Tax Cuts and Jobs Act of 2017 (the “2017 Tax Act”) was signed into law. One of the provisions of the 2017 Tax Act reduced the corporate federal income tax rate from 35% to 21% effective January 1, 2018. Pursuant to current accounting guidance, all deferred tax assets and liabilities at December 31, 2017, were revalued to recognize the tax rate that is expected to apply when the tax effects are ultimately recognized in future periods. The impact of revaluing the deferred tax assets and liabilities from 35% to 21% was a net reduction to income tax expense of $99.5 million in 2017, as disclosed in the table above. As of December 31, 2018, we updated our accounting for the tax effects of the enactment of the 2017 Tax Act, which we were not able to fully complete at December 31, 2017, with regards to the following: • We reversed $3.9 million of the $4.5 million provisional tax amount that we recorded in 2017 related to deductibility of compensation expense for certain covered executives due to uncertainty surrounding the appropriate tax treatment of outstanding performance-based awards at that time. The IRS issued additional guidance during 2018 that clarified the treatment of these awards. We also recorded a benefit of $0.3 million in 2018 related to compensation expense for time-based awards granted to the chief financial officer that we had treated as nondeductible at December 31, 2017. The benefit of both of these amounts is reflected in the nondeductible compensation expense line item in the table above for the 2018 year. • We recorded an increase to the deferred tax asset for loss and loss adjustment expense reserves of $67.1 million and an offsetting deferred tax liability in the same amount for the transition adjustment, which is recognized over an 8-year period as required by the 2017 Tax Act. At December 31, 2017, we did not record any amounts related to the changes in loss reserve discounting required by the 2017 Tax Act since the IRS had not yet published new discount factors based on loss payment patterns and interest rates determined under the 2017 Tax Act and we were unable to make a reasonable estimate. The IRS published the new discount factors in 2018, which allowed us to compute the adjustments. The impact of these amounts are reflected in the 2018 deferred tax assets and liabilities in the table below. Deferred income taxes reflect the effect for financial statement reporting purposes of temporary differences between the financial statement carrying amounts and the tax bases of assets and liabilities. The following table shows the components of the net deferred tax asset (liability) at December 31, 2019 and 2018 , respectively. (millions) 2019 2018 Federal deferred tax assets: Unearned premiums reserve $ 498.2 $ 439.9 Non-deductible accruals 181.8 169.3 Loss and loss adjustment expense reserves 153.3 134.6 Operating lease liabilities 42.3 0 Net unrealized losses on fixed-maturity securities 0 28.2 Hedges on forecasted transactions 4.4 4.6 Other 15.3 16.2 Federal deferred tax liabilities: Net holding period gains on equity securities (472.2 ) (316.8 ) Deferred acquisition costs (221.9 ) (199.8 ) Property and equipment (108.6 ) (85.7 ) Net unrealized gains on fixed-maturity securities (96.5 ) 0 Loss and loss adjustment expense reserve transition adjustment (47.2 ) (58.5 ) Operating lease assets (42.3 ) 0 Intangible assets (38.9 ) (52.2 ) Investment basis differences (1.1 ) (43.3 ) Prepaid expenses (4.8 ) (4.7 ) Other (8.3 ) (8.9 ) Net federal deferred tax asset (liability) (146.5 ) 22.9 Net state deferred tax asset 14.0 20.3 Net deferred tax asset (liability) $ (132.5 ) $ 43.2 Although realization of the deferred tax assets is not assured, management believes that it is more likely than not that 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 and, therefore, no valuation allowance was needed at December 31, 2019 or 2018 . At December 31, 2019 and 2018 , we had $195.5 million and $16.8 million , respectively, of net taxes payable (included in other liabilities on the consolidated balance sheets). The increase in 2019 primarily results from the reversal of the tax credits benefits for 2017 and 2016. The Progressive Corporation and its subsidiaries file a consolidated federal income tax return. Effective April 2018, we acquired additional shares of ARX to increase our ownership above 80% . As a result, ARX and its subsidiaries were first included in The Progressive Corporation consolidated federal income tax return for the period from April 2018 to December 31, 2018. ARX filed a final consolidated federal income tax return with its subsidiaries for the period from January to March 2018. The Progressive Corporation and its eligible subsidiaries participated in the Compliance Assurance Program (CAP) from 2007 through 2018. Under CAP, the IRS begins its examination process for the tax year before the tax return is filed, by examining significant transactions and events as they occur; however, a CAP examination does not include equity investments in pass-through entities in which the taxpayer owns less than 100% (e.g., partnerships, joint ventures, etc.). The goal of the CAP program is to expedite the exam process and to reduce the level of uncertainty regarding a taxpayer’s tax filing positions. All federal income tax years prior to 2016 are closed to examination for The Progressive Corporation. The IRS CAP exams for 2016-2018 for The Progressive Corporation have been completed and the returns were accepted as filed. We consider these years to be effectively settled (other than with respect to equity investments in pass-through entities). The 2019 tax year remains open to examination. For the tax year ended March 2018, and for 2017 and prior years, ARX and its eligible subsidiaries filed their own consolidated federal income tax returns. All tax years prior to 2016 are closed and the 2016, 2017, and short 2018 tax years remain open to examination. The statute of limitations for state income tax purposes generally remains open for three to four years from the return filing date, depending upon the jurisdiction. There has been no significant state income tax audit activity. We recognize interest and penalties, if any, as a component of income tax expense. For the years ended December 31, 2019 , 2018 , and 2017, $9.9 million , $0 , and $0.2 million , respectively, of interest and penalties expense has been recorded in the tax provision. We have not recorded any unrecognized tax benefits, or any related interest and penalties, as of December 31, 2019 and 2018 .

Loss And Loss Adjustment Expens

Loss And Loss Adjustment Expense Reserves	12 Months Ended
	Dec. 31, 2019
Insurance [Abstract]
Loss And Loss Adjustment Expense Reserves	LOSS AND LOSS ADJUSTMENT EXPENSE RESERVES We write personal and commercial auto insurance, residential property insurance, and other specialty property-casualty insurance and related services throughout the United States. As a property-casualty insurance company, we are exposed to hurricanes or other catastrophes. To help mitigate this risk, we maintained excess of loss and aggregate stop-loss reinsurance coverage on our Property business during 2019, 2018, and 2017. Although the occurrence of a major catastrophe could have a significant effect on our monthly or quarterly results, we believe that, based on historical experience, such an event would not be so material as to disrupt the overall normal operations of Progressive. We are unable to predict the frequency or severity of any such events that may occur in the near term or thereafter. As we are primarily an insurer of motor vehicles and residential property, we have limited exposure to environmental, asbestos, and general liability claims. We have established reserves for such exposures, which represent about 0.06% of our total loss and loss adjustment expense reserves. We believe these reserves to be adequate based on information currently known. These claims are not expected to have a material effect on our liquidity, financial condition, cash flows, or results of operations. Loss and Loss Adjustment Expense Reserves Loss and loss adjustment expense (LAE) reserves represent our best estimate of our ultimate liability for losses and LAE relating to events that occurred prior to the end of any given accounting period but have not yet been paid. For our Personal and Commercial Lines vehicle businesses, which represent about 96% of our total carried reserves, we establish loss and LAE reserves after completing reviews at a disaggregated level of grouping. Progressive’s actuarial staff reviews over 400 subsets of business data, which are at a combined state, product, and line coverage level, to calculate the needed loss and LAE reserves. During a reserve review, ultimate loss amounts are estimated using several industry standard actuarial projection methods. These methods take into account historical comparable loss data at the subset level and estimate the impact of various loss development factors, such as the frequency (number of losses per earned car year), severity (dollars of loss per each claim), and average premium (dollars of premium per earned car year), as well as the frequency and severity of loss adjustment expense costs. We begin our review of a set of data by producing multiple estimates of needed reserves, using both paid and incurred data, to determine if a reserve change is required. In the event of a wide variation among results generated by the different projections, our actuarial group will further analyze the data using additional quantitative analysis. Each review develops a point estimate for a relatively small subset of the business, which allows us to establish meaningful reserve levels for that subset. We believe our comprehensive process of reviewing at a subset level provides us more meaningful estimates of our aggregate loss reserves. The actuarial staff completes separate projections of needed case and incurred but not recorded (IBNR) reserves. Since a large majority of the parties involved in an accident report their claims within a short time period after the occurrence, we do not carry a significant amount of IBNR reserves for older accident years. Based on the methodology we use to estimate case reserves for our vehicle businesses, we do not have expected development on reported claims included in our IBNR reserves. We do, however, include anticipated salvage and subrogation recoveries in our IBNR reserves, which could result in negative carried IBNR reserves, primarily in our physical damage reserves. Changes from historical data may reduce the predictiveness of our projected future loss costs. Internal considerations that are process-related, which generally result from changes in our claims organization’s activities, include claim closure rates, the number of claims that are closed without payment, and the level of the claims representatives’ estimates of the needed case reserve for each claim. These changes and their effect on the historical data are studied at the state level versus on a larger, less indicative, countrywide basis. External items considered include the litigation atmosphere, state-by-state changes in medical costs, and the availability of services to resolve claims. These also are better understood at the state level versus at a more macro, countrywide level. The actuarial staff takes these changes into consideration when making their assumptions to determine needed reserve levels. Similar to our vehicle businesses, our actuarial staff analyzes loss and LAE data for our Property business on an accident period basis. Many of the methodologies and key parameters reviewed are similar. In addition, for our Property business, since claims adjusters primarily establish the case reserves, the actuarial staff includes expected development on case reserves as a component of the overall IBNR reserves. Activity in the loss and LAE reserves is summarized as follows: (millions) 2019 2018 2017 Balance at January 1 $ 15,400.8 $ 13,086.9 $ 11,368.0 Less reinsurance recoverables on unpaid losses 2,572.7 2,170.1 1,801.0 Net balance at January 1 12,828.1 10,916.8 9,567.0 Incurred related to: Current year 25,238.2 21,632.5 18,782.1 Prior years 232.3 88.5 25.9 Total incurred 25,470.5 21,721.0 18,808.0 Paid related to: Current year 16,105.0 13,792.1 12,201.5 Prior years 7,300.4 6,017.6 5,256.7 Total paid 23,405.4 19,809.7 17,458.2 Net balance at December 31 14,893.2 12,828.1 10,916.8 Plus reinsurance recoverables on unpaid losses 3,212.2 2,572.7 2,170.1 Balance at December 31 $ 18,105.4 $ 15,400.8 $ 13,086.9 We experienced unfavorable reserve development of $232.3 million , $88.5 million , and $25.9 million in 2019 , 2018 , and 2017 , respectively, which is reflected as “Incurred related to prior years” in the table above. 2019 • Approximately $131 million of the unfavorable prior year reserve development was attributable to accident year 2018, $73 million to accident year 2017, and the remainder to 2016 and prior accident years. • Our personal auto products incurred about $121 million of unfavorable loss and LAE reserve development, with the Agency and Direct auto businesses each contributing about half, primarily reflecting increased injury severity, a higher than anticipated frequency of reopened personal injury protection (PIP) claims, primarily in Florida, and late reported losses occurring late 2018 but not reported until 2019. • Our Commercial Lines business experienced about $83 million of unfavorable development, primarily due to increased injury severity and more emergence of large injury claims than originally anticipated. • Our special lines business experienced about $14 million of unfavorable development, primarily due to less salvage and subrogation recoveries than originally anticipated and increased severity of late reported claims. • Our Property businesses experienced about $12 million of unfavorable development, primarily due to higher than originally anticipated homeowner and dwelling costs and fire liability costs. 2018 • Approximately $99 million of unfavorable prior year reserve development was attributable to accident years 2017 and 2016. This unfavorable development was offset by about $10 million of favorable development attributable to accident year 2015 and prior accident years. • Our personal auto products incurred almost $85 million of unfavorable loss and LAE reserve development, with approximately 70% attributable to the Agency business and 30% attributable to the Direct business, primarily reflecting unfavorable development from reopened Florida PIP claims. • Our special lines and Property businesses experienced about $5 million and $3 million of unfavorable development, respectively, while our commercial auto products had about $4 million of favorable reserve development. 2017 • Approximately $64 million of unfavorable prior year reserve development was attributable to accident years 2016 and 2015. This unfavorable development was offset by $38 million of favorable development attributable to accident year 2014 and prior accident years. • Our personal auto products incurred $70 million of unfavorable loss and LAE reserve development, primarily in the Agency business, in part reflecting an increase in costs related to property damage and higher LAE costs, primarily due to an increase in incentive compensation and defense counsel spend. • Our Property business experienced $37 million in favorable development primarily due to lower severity and frequency than anticipated for accident year 2016 and development of losses eligible to be ceded under our catastrophe bond reinsurance program. • Our commercial auto products had less than $1 million of unfavorable reserve development. Incurred and Paid Claims Development by Accident Year The following tables present our incurred, net of reinsurance, and paid claims development by accident year for the last five years, which generally represents the maximum development period for claims in any of our segments. The tables below include inception-to-date information for companies acquired and wholly exclude companies disposed of, rather than including information from the date of acquisition, or until the date of disposition. We believe the most meaningful presentation of claims development is through the retrospective approach by presenting all relevant historical information for all periods presented. We have elected to present our incurred and paid claims development consistent with our GAAP reportable segments (see Note 10 – Segment Information for a discussion of our segment reporting), with a further disaggregation of our Personal Lines and Commercial Lines claims development between liability and physical damage, since the loss patterns are significantly different between them. The other business primarily includes reserves for our run-off products, which are not considered material, and, therefore, we are not including separate claims development tables. Only 2019 is audited; all prior years are considered required supplementary information and, therefore, are unaudited. Expected development on our case reserves is excluded from the IBNR reserves on our vehicle businesses, as discussed above. For the Property business, the IBNR reserves include expected case development based on the methodology used in establishing the case reserves for that segment. The cumulative number of incurred claims are based on accident coverages (e.g., bodily injury, collision, comprehensive, personal injury protection, property damage) related to opened claims. Coverage counts related to claims closed without payment are excluded from the cumulative number of incurred claims. Personal Lines - Agency - Liability ($ in millions) As of Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance December 31, 2019 For the years ended December 31, Total of IBNR Liabilities Plus Expected Development on Reported Claims Cumulative Number of Incurred Claim Counts Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 3,774.9 $ 3,773.8 $ 3,798.8 $ 3,815.6 $ 3,776.0 $ 0 704,986 2016 4,082.9 4,130.0 4,152.0 4,177.3 62.3 740,385 2017 4,474.8 4,485.8 4,511.1 82.5 779,082 2018 5,141.8 5,182.1 224.2 854,146 2019 5,885.0 871.8 909,050 Total $ 23,531.5 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance For the years ended December 31, Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 1,793.1 $ 2,976.0 $ 3,416.5 $ 3,623.3 $ 3,715.4 2016 1,941.6 3,231.5 3,723.1 3,969.5 2017 2,074.0 3,478.5 4,048.5 2018 2,378.0 4,028.7 2019 2,715.2 Total $ 18,477.3 All outstanding liabilities before 2015, net of reinsurance 1 63.2 Liabilities for claims and claim adjustment expenses, net of reinsurance $ 5,117.4 1 Required supplementary information (unaudited) Personal Lines - Agency - Physical Damage ($ in millions) As of Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance December 31, 2019 For the years ended December 31, Total of IBNR Liabilities Plus Expected Development on Reported Claims Cumulative Number of Incurred Claim Counts Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 2,136.8 $ 2,137.2 $ 2,134.4 $ 2,131.5 $ 2,134.5 $ 0 1,336,520 2016 2,423.4 2,398.9 2,401.8 2,400.1 (3.8 ) 1,399,077 2017 2,635.5 2,638.5 2,643.5 (2.9 ) 1,514,531 2018 2,819.0 2,822.6 (12.3 ) 1,694,380 2019 3,277.9 (167.6 ) 1,872,822 Total $ 13,278.6 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance For the years ended December 31, Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 2,106.2 $ 2,138.1 $ 2,134.4 $ 2,134.1 $ 2,133.6 2016 2,391.0 2,406.9 2,402.1 2,402.2 2017 2,599.8 2,643.2 2,640.9 2018 2,769.1 2,827.4 2019 3,242.5 Total $ 13,246.6 All outstanding liabilities before 2015, net of reinsurance 1 0.4 Liabilities for claims and claim adjustment expenses, net of reinsurance $ 32.4 1 Required supplementary information (unaudited) Personal Lines - Direct - Liability ($ in millions) As of Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance December 31, 2019 For the years ended December 31, Total of IBNR Liabilities Plus Expected Development on Reported Claims Cumulative Number of Incurred Claim Counts Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 3,330.5 $ 3,328.3 $ 3,354.2 $ 3,399.3 $ 3,368.7 $ 0 659,243 2016 3,819.0 3,843.9 3,871.2 3,897.8 53.9 735,653 2017 4,209.5 4,209.9 4,229.3 70.9 772,712 2018 4,904.8 4,980.9 204.4 868,604 2019 5,756.5 811.4 953,154 Total $ 22,233.2 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance For the years ended December 31, Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 1,545.2 $ 2,615.0 $ 3,021.0 $ 3,238.2 $ 3,323.1 2016 1,780.6 2,991.1 3,476.9 3,714.6 2017 1,912.6 3,255.2 3,808.3 2018 2,235.1 3,863.5 2019 2,630.3 Total $ 17,339.8 All outstanding liabilities before 2015, net of reinsurance 1 43.4 Liabilities for claims and claim adjustment expenses, net of reinsurance $ 4,936.8 1 Required supplementary information (unaudited) Personal Lines - Direct - Physical Damage ($ in millions) As of Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance December 31, 2019 For the years ended December 31, Total of IBNR Liabilities Plus Expected Development on Reported Claims Cumulative Number of Incurred Claim Counts Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 2,110.7 $ 2,097.7 $ 2,093.5 $ 2,090.8 $ 2,093.9 $ 0 1,540,071 2016 2,521.0 2,475.4 2,477.7 2,475.6 (4.3 ) 1,676,343 2017 2,750.6 2,743.7 2,749.0 (4.1 ) 1,791,190 2018 3,202.3 3,181.9 (18.8 ) 2,069,525 2019 3,787.9 (237.7 ) 2,282,681 Total $ 14,288.3 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance For the years ended December 31, Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 2,094.7 $ 2,100.1 $ 2,094.7 $ 2,093.7 $ 2,093.1 2016 2,505.0 2,485.8 2,479.3 2,478.5 2017 2,742.1 2,753.5 2,748.4 2018 3,170.0 3,193.8 2019 3,782.6 Total $ 14,296.4 All outstanding liabilities before 2015, net of reinsurance 1 0.4 Liabilities for claims and claim adjustment expenses, net of reinsurance $ (7.7 ) 1 Required supplementary information (unaudited) Commercial Lines - Liability ($ in millions) As of Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance December 31, 2019 For the years ended December 31, Total of IBNR Liabilities Plus Expected Development on Reported Claims Cumulative Number of Incurred Claim Counts Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 897.6 $ 911.1 $ 914.8 $ 899.7 $ 891.3 $ 0 77,819 2016 1,185.8 1,204.8 1,231.1 1,238.9 17.2 92,684 2017 1,374.1 1,366.6 1,393.3 30.8 97,297 2018 1,700.8 1,736.5 97.7 111,146 2019 2,103.1 343.7 124,829 Total $ 7,363.1 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance For the years ended December 31, Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 238.4 $ 501.5 $ 675.0 $ 786.3 $ 848.9 2016 298.6 639.9 886.0 1,073.3 2017 325.8 712.9 1,027.3 2018 382.7 913.4 2019 455.4 Total $ 4,318.3 All outstanding liabilities before 2015, net of reinsurance 1 36.0 Liabilities for claims and claim adjustment expenses, net of reinsurance $ 3,080.8 1 Required supplementary information (unaudited) Commercial Lines - Physical Damage ($ in millions) As of Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance December 31, 2019 For the years ended December 31, Total of IBNR Liabilities Plus Expected Development on Reported Claims Cumulative Number of Incurred Claim Counts Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 274.4 $ 274.1 $ 273.5 $ 272.4 $ 272.4 $ 0 62,593 2016 379.6 379.8 378.2 377.8 (0.7 ) 74,193 2017 415.4 412.1 411.0 (0.6 ) 77,163 2018 475.0 478.2 (2.4 ) 82,183 2019 577.8 (14.3 ) 91,920 Total $ 2,117.2 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance For the years ended December 31, Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 248.5 $ 271.9 $ 272.0 $ 272.2 $ 272.3 2016 336.7 376.9 376.8 377.5 2017 369.0 409.4 409.2 2018 426.0 475.1 2019 516.9 Total $ 2,051.0 All outstanding liabilities before 2015, net of reinsurance 1 0.4 Liabilities for claims and claim adjustment expenses, net of reinsurance $ 66.6 1 Required supplementary information (unaudited) Property Business ($ in millions) As of Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance December 31, 2019 For the years ended December 31, Total of IBNR Liabilities Plus Expected Development on Reported Claims Cumulative Number of Incurred Claim Counts Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 460.0 $ 416.5 $ 403.6 $ 398.8 $ 396.3 $ 0.9 41,998 2016 568.6 541.2 537.1 536.5 5.1 53,665 2017 672.8 680.9 683.4 4.1 72,728 2018 839.0 845.2 34.9 63,243 2019 971.7 160.2 66,824 Total $ 3,433.1 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance For the years ended December 31, Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 280.3 $ 372.8 $ 383.5 $ 390.1 $ 393.5 2016 415.2 498.2 516.9 526.4 2017 506.7 647.1 670.1 2018 595.9 781.2 2019 708.0 Total $ 3,079.2 All outstanding liabilities before 2015, net of reinsurance 1 3.3 Liabilities for claims and claim adjustment expenses, net of reinsurance $ 357.2 1 Required supplementary information (unaudited) The following table reconciles the net incurred and paid claims development tables to the liability for claims and claim adjustment expenses: (millions) 2019 2018 Net outstanding liabilities Personal Lines Agency, Liability $ 5,117.4 $ 4,509.0 Agency, Physical Damage 32.4 43.3 Direct, Liability 4,936.8 4,258.6 Direct, Physical Damage (7.7 ) 18.4 Commercial Lines Liability 3,080.8 2,504.2 Physical Damage 66.6 53.9 Property 357.2 314.7 Other business 30.8 42.9 Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance 13,614.3 11,745.0 Reinsurance recoverable on unpaid claims Personal Lines Agency, Liability 930.7 836.8 Agency, Physical Damage 0 0 Direct, Liability 1,314.1 1,070.4 Direct, Physical Damage 0 0 Commercial Lines Liability 482.6 287.4 Physical Damage 0.5 0 Property 184.1 145.4 Other business 288.1 222.1 Total reinsurance recoverable on unpaid claims 3,200.1 2,562.1 Unallocated claims adjustment expense related to: Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance 1,278.9 1,083.1 Reinsurance recoverable on unpaid claims 12.1 10.6 Total gross liability for unpaid claims and claim adjustment expense $ 18,105.4 $ 15,400.8 The following table shows the average historical claims duration as of December 31, 2019 : (Required Supplementary Information - Unaudited) Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 Personal Lines Agency, Liability 46.3% 31.3% 12.1% 5.7% 2.4% Agency, Physical Damage 98.7 1.5 (0.2) 0 0 Direct, Liability 45.4 31.9 12.6 6.3 2.5 Direct, Physical Damage 100.0 0.2 (0.2) 0 0 Commercial Lines Liability 23.1 28.9 20.8 14.0 7.0 Physical Damage 89.6 9.9 0 0.1 0 Property 73.0 20.4 3.2 1.7 0.9

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2019
Reinsurance Disclosures [Abstract]
Reinsurance	REINSURANCE The effect of reinsurance on premiums written and earned for the years ended December 31, was as follows: 2019 2018 2017 (millions) Written Earned Written Earned Written Earned Direct premiums $ 39,222.0 $ 37,519.7 $ 33,753.1 $ 31,970.2 $ 27,860.7 $ 26,425.7 Ceded premiums: Regulated (711.1 ) (670.8 ) (596.4 ) (557.5 ) (505.9 ) (479.6 ) Non-Regulated (933.0 ) (656.5 ) (546.8 ) (479.4 ) (222.7 ) (216.2 ) Total ceded premiums (1,644.1 ) (1,327.3 ) (1,143.2 ) (1,036.9 ) (728.6 ) (695.8 ) Net premiums $ 37,577.9 $ 36,192.4 $ 32,609.9 $ 30,933.3 $ 27,132.1 $ 25,729.9 Regulated refers to federal or state run plans and primarily include the following: • Federal reinsurance plan • National Flood Insurance Program (NFIP) • State-provided reinsurance facilities • Michigan Catastrophic Claims Association (MCCA) • North Carolina Reinsurance Facility (NCRF) • Florida Hurricane Catastrophe Fund (FHCF) • State-mandated involuntary plans • Commercial Automobile Insurance Procedures/Plans (CAIP) Non-Regulated represents voluntary external reinsurance contracts entered into by the company. These include amounts ceded on our Commercial Lines business primarily related to transportation network company (TNC) business under quota-share reinsurance agreements and amounts ceded on our Property business under catastrophic excess of loss reinsurance agreements and aggregate stop-loss reinsurance agreements. During 2019, we expanded our TNC business to seventeen states, from four states in 2018 and one state in 2017. Our reinsurance recoverables and prepaid reinsurance premiums were comprised of the following at December 31: Reinsurance Recoverables Prepaid Reinsurance Premiums ($ in millions) 2019 2018 2019 2018 Regulated: MCCA $ 2,247.1 67 % $ 1,903.9 71 % $ 71.8 12 % $ 55.3 18 % CAIP 332.4 10 254.7 9 93.8 15 72.9 24 FHCF 1 86.0 3 18.5 1 0 0 0 0 NCRF 84.4 2 78.1 3 33.8 5 34.0 11 NFIP 11.6 0 27.8 1 58.7 9 55.9 18 Other 3.1 0 2.9 0 1.0 0 0.6 0 Total Regulated 2,764.6 82 2,285.9 85 259.1 41 218.7 71 Non-Regulated: Commercial Lines 459.5 14 254.2 10 352.9 56 79.2 25 Property 146.8 4 147.7 5 14.5 3 11.8 4 Other 8.0 0 8.3 0 0 0 0 0 Total Non-Regulated 614.3 18 410.2 15 367.4 59 91.0 29 Total $ 3,378.9 100 % $ 2,696.1 100 % $ 626.5 100 % $ 309.7 100 % 1 Prior year amounts were reclassified from "Other" to conform to the current year presentation. Reinsurance contracts do not relieve us from our obligations to policyholders. Failure of reinsurers to honor their obligations could result in losses to us. Our exposure to losses from the failure of Regulated plans is minimal, since these plans are funded by the federal government or by mechanisms supported by insurance companies in applicable states. We evaluate the financial condition of our other reinsurers and monitor concentrations of credit risk to minimize our exposure to significant losses from reinsurer insolvencies.

Statutory Financial Information

Statutory Financial Information	12 Months Ended
	Dec. 31, 2019
Statutory Financial Information Disclosures [Abstract]
Statutory Financial Information	STATUTORY FINANCIAL INFORMATION Consolidated statutory surplus was $13,671.1 million and $11,571.8 million at December 31, 2019 and 2018 , respectively. Statutory net income was $3,489.7 million , $2,643.0 million , and $1,416.2 million for the years ended December 31, 2019 , 2018 , and 2017 , respectively. At December 31, 2019 , $1,063.2 million of consolidated statutory surplus represented net admitted assets of our insurance subsidiaries and affiliates that are required to meet minimum statutory surplus requirements in such entities’ states of domicile. The companies may be licensed in states other than their states of domicile, which may have higher minimum statutory surplus requirements. Generally, the net admitted assets of insurance companies that, subject to other applicable insurance laws and regulations, are available for transfer to the parent company cannot include the net admitted assets required to meet the minimum statutory surplus requirements of the states where the companies are licensed. During 2019 , the insurance subsidiaries paid aggregate cash dividends of $2,277.9 million to their parent company. Based on the dividend laws in effect at December 31, 2019, the insurance subsidiaries could pay aggregate dividends of $3,319.3 million in 2020 without prior approval from regulatory authorities, provided the dividend payments are not made within 12 months of previous dividends paid by the applicable subsidiary.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2019
Employee Benefit Plans Disclosures [Abstract]
Employee Benefit Plans	EMPLOYEE BENEFIT PLANS Beginning July 1, 2017, employees of ARX and its subsidiaries were included in the benefit plans described below. Prior to July 1, 2017, ARX maintained employee benefit plans that were separate from the plans that covered employees of The Progressive Corporation’s other subsidiaries. References in this Note 9 to Progressive refer to The Progressive Corporation and its subsidiaries, including ARX and its subsidiaries. Retirement Plans Progressive has a defined contribution pension plan (401(k) Plan) that covers employees who have been employed with the company for at least 30 days . Under Progressive’s 401(k) Plan, we match up to a maximum of 6% of an employee’s eligible compensation contributed to the plan. Employee and company matching contributions are invested, at the direction of the employee, in a number of investment options available under the plan, including various mutual funds, a self-directed brokerage option, and a Progressive common stock fund. Progressive’s common stock fund is an employee stock ownership program (ESOP) within the 401(k) Plan. At December 31, 2019, the ESOP held 23.0 million of our common shares, all of which are included in shares outstanding. Dividends on these shares are reinvested in common shares or paid out in cash, at the election of the participant, and the related tax benefit is recorded as part of our tax provision. Matching contributions to these plans for the years ended December 31, 2019, 2018, and 2017 were $120.8 million , $106.8 million , and $97.3 million , respectively. Postemployment Benefits Progressive provides various postemployment benefits to former or inactive employees who meet eligibility requirements, and to their beneficiaries and covered dependents. Postemployment benefits include salary continuation and disability-related benefits, including workers’ compensation and, if elected, continuation of health-care benefits for specified limited periods. The liability for these benefits was $22.2 million and $20.2 million at December 31, 2019 and 2018, respectively. Incentive Compensation Plans – Employees Progressive’s incentive compensation programs include both non-equity incentive plans (cash) and equity incentive plans. Progressive’s cash incentive compensation included an annual cash incentive program (i.e., Gainsharing Program) for virtually all employees. Progressive’s equity incentive compensation plans provide for the granting of restricted stock unit awards to key members of management . Prior to 2019, ARX provided periodic cash bonuses to its employees. ARX also has an equity compensation plan under which it had granted stock option awards, exercisable for shares of ARX common stock, to certain of its key employees. These stock option awards include both nonqualified and incentive stock options; all such stock options are subject to the put and call provisions of the ARX stockholders’ agreement (see Note 15 – Redeemable Noncontrolling Interest and Note 17 – Subsequent Event for further discussion). As a result of these provisions, and the determination that the ultimate settlement of these awards would be in cash, the ARX stock options are treated as liability awards for accounting purposes. The amounts charged to expense for Progressive and ARX incentive compensation plans for the years ended December 31, were: 2019 2018 2017 (millions) Pretax After Tax Pretax After Tax Pretax After Tax Non-equity incentive plans – cash $ 598.4 $ 472.7 $ 539.5 $ 426.2 $ 461.3 $ 299.8 Equity incentive plans: Equity awards 90.1 71.2 76.2 60.2 92.9 60.4 Liability awards 0.1 0.1 1.0 0.8 2.5 1.6 Generally, time-based and performance-based equity awards are expensed pro rata over their respective vesting periods, based on the market value of the awards at the time of grant, with accelerated expense for participants who reach qualified retirement provisions. Performance-based equity awards that contain variable vesting criteria are expensed based on management’s expectation of the percentage of the award, if any, that will ultimately vest. These estimates can change periodically throughout the measurement period. The after-tax amounts are determined using the corporate federal tax rate of 21% for 2019 and 2018, and 35% for 2017. Progressive’s 2015 Equity Incentive Plan, which provides for the granting of equity-based compensation to officers and other key employees, currently has authorized awards for up to 17.0 million shares, which includes 4.0 million shares transferred from the 2010 Equity Incentive Plan in accordance with the terms of the 2015 Equity Incentive Plan. No awards have been granted under the 2010 Equity Incentive Plan since January 2016 and none will be granted in the future. The restricted equity awards are issued as either time-based or performance-based awards. All restricted equity awards are settled at or after vesting in Progressive common shares from existing treasury shares on a one-to-one basis. The time-based awards vest in equal installments upon the lapse of specified periods of time, typically three , four , and five years , absent the retirement provisions in the plan. The performance-based awards were granted to approximately 40 Progressive executives and senior managers in 2019 in addition to their time-based awards to provide additional incentive to achieve pre-established profitability and growth targets, and relative investment performance. Vesting of performance-based awards is contingent upon the achievement of predetermined performance goals within specified time periods. The targets for the performance-based awards, as well as the number of units that ultimately may vest, vary by grant. All performance-based awards include a specified number of units that will vest if performance meets a specified target and minimum performance goals. If at least the minimum performance goals are achieved, the range at which an award can vest is determined by the type of measurement goals included in the award, as follows: Performance Measurement Year(s) of Grant Vesting range (as a percentage of target) Growth of our personal auto and commercial auto businesses and homeowners multi-peril business, each compared to its respective market 2018-2019 0-250% Growth of our personal auto and commercial auto businesses, compared to the combined personal and commercial auto market 2014-2017 0-250% Investment results relative to peer group 2014-2019 0-200% Unit growth in a specified customer segment 2016-2017 0% or 85-150% A summary of all employee restricted equity award activity during the years ended December 31, follows: 2019 2018 2017 Restricted Equity Awards Number of Shares 1 Weighted Average Grant Date Fair Value Number of Shares 1 Weighted Average Grant Date Fair Value Number of Shares 1 Weighted Average Grant Date Fair Value Beginning of year 4,856,356 $ 38.56 5,858,848 $ 30.47 6,951,373 $ 26.18 Add (deduct): Granted 2 1,835,145 49.61 1,876,109 45.55 2,383,475 32.01 Vested (2,691,337 ) 31.85 (2,811,070 ) 26.41 (3,220,671 ) 22.53 Forfeited (121,087 ) 43.98 (67,531 ) 36.10 (255,329 ) 28.03 End of year 3,4 3,879,077 $ 48.28 4,856,356 $ 38.56 5,858,848 $ 30.47 1 Includes restricted stock units. All performance-based awards are included at their target amounts. 2 We reinvest dividend equivalents on restricted stock units. For 2019 , 2018 , and 2017 , the number of units “granted” shown in the table above includes 210,159 , 144,668 , and 157,396 of dividend equivalent units, respectively, at a weighted average grant date fair value of $0 , since the dividends were factored into the grant date fair value of the original grant. 3 At December 31, 2019 , the number of shares included 726,712 performance-based units at their target amounts. We expect 1,740,712 units to vest based upon our current estimates of the likelihood of achieving the pre-determined performance goals applicable to each award. 4 At December 31, 2019 , the total unrecognized compensation cost related to unvested equity awards was $95.9 million , which includes performance-based awards at their currently estimated vesting value. This compensation expense will be recognized into the consolidated statements of comprehensive income over the weighted average vesting period of 2.3 years . The aggregate fair value of the restricted equity awards that vested during the years ended December 31, 2019 , 2018 , and 2017 , was $191.6 million , $162.7 million , and $130.5 million , respectively, based on the actual stock price on the applicable vesting date. As a result of the put and call rights described in Note 15 – Redeemable Noncontrolling Interest , all outstanding stock options awarded to ARX employees prior to April 1, 2015, are treated as liability awards for accounting purposes; however, the awards maintain the specific features per the original award agreements. The value of each option is based upon our good faith estimate of the fair market value as of the end of the reporting period and the pro rata expense is recognized. A summary of all ARX employee stock option activity during the years ended December 31, follows: 2019 2018 2017 Options Outstanding Number of Shares Weighted Average Number of Shares Weighted Average Number of Shares Weighted Average Beginning of year 16,067 $ 588.15 22,550 $ 564.60 24,995 $ 526.46 Add (deduct): Exercised 1 (5,329 ) 353.67 (6,483 ) 506.26 (2,445 ) 174.65 Forfeited (300 ) 803.64 0 0 0 0 End of year 10,438 $ 701.66 16,067 $ 588.15 22,550 $ 564.60 Exercisable, end of year 10,438 $ 701.66 13,967 $ 562.17 17,950 $ 517.75 1 At the time of exercise, the value earned by the option holders was $5.9 million , $6.2 million , and $2.9 million in 2019, 2018, and 2017, respectively. 2019 2018 2017 Non-Vested Options Outstanding Number of Shares Weighted Average Number of Shares Weighted Average Number of Shares Weighted Average Beginning of year 2,100 $ 760.93 4,600 $ 747.45 8,000 $ 712.74 Add (deduct): Vested (1,800 ) 753.82 (2,500 ) 736.12 (3,400 ) 665.79 Forfeited (300 ) 803.64 0 0 0 0 End of year 0 $ 0 2,100 $ 760.93 4,600 $ 747.45 Incentive Compensation Plans – Directors Progressive’s 2017 Directors Equity Incentive Plan, which provides for the granting of equity-based awards, including restricted stock awards, to non-employee directors, was approved by shareholders in 2017 and originally authorized awards for up to 0.5 million shares. The Progressive Corporation permits each non-employee director to indicate a preference to receive either 100% of their compensation in the form of a restricted stock award or 60% in the form of a restricted stock award and 40% in the form of cash. If the director does not state a preference, it is presumed that he or she preferred to receive 100% of their compensation in the form of restricted stock. After considering such preferences, the Compensation Committee of the Board of Directors determines the awards (restricted stock, or restricted stock and cash) for each non-employee director. The restricted stock awards are issued as time-based awards. The vesting period (i.e., requisite service period) is typically 11 months from the date of each grant. To the extent a director is newly appointed during the year, or a director’s committee assignments change, the vesting period may be shorter. Both the restricted stock awards and cash, if elected, are expensed pro rata over their respective vesting periods based on the market value of the awards at the time of grant. A summary of all directors’ restricted stock activity during the years ended December 31, follows: 2019 2018 2017 Restricted Stock Number of Shares Weighted Average Grant Date Fair Value Number of Shares Weighted Average Grant Date Fair Value Number of Shares Weighted Average Grant Date Fair Value Beginning of year 41,706 $ 62.23 53,284 $ 40.54 55,839 $ 33.24 Add (deduct): Granted 38,451 73.43 41,706 62.23 53,284 40.54 Vested (41,706 ) 62.23 (53,284 ) 40.54 (55,839 ) 33.24 End of year 1 38,451 $ 73.43 41,706 $ 62.23 53,284 $ 40.54 1 At December 31, 2019, 2018, and 2017, the remaining unrecognized compensation cost related to restricted stock awards was $0.8 million , $0.9 million , and $0.7 million , respectively. The aggregate fair value of the restricted stock vested, during the years ended December 31, 2019 , 2018 , and 2017 , was $3.0 million , $3.2 million , and $2.2 million , respectively, based on the actual stock price at time of vesting. Deferred Compensation The Progressive Corporation Executive Deferred Compensation Plan (Deferral Plan) permits eligible Progressive executives to defer receipt of some or all of their annual incentive payments and all of their annual equity awards. Deferred cash compensation is deemed invested in one or more investment funds, including Progressive common shares, offered under the Deferral Plan and elected by the participant. All Deferral Plan distributions attributable to deferred cash compensation will be paid in cash. For all equity awards granted in or after March 2005, and deferred pursuant to the Deferral Plan, the deferred amounts are deemed invested in our common shares and are ineligible for transfer to other investment funds in the Deferral Plan; distributions of these deferred awards will be made in Progressive common shares. For all restricted stock awards granted prior to that date, the deferred amounts are eligible to be transferred to any of the investment funds in the Deferral Plan; distributions of these deferred awards will be made in cash. We reserved 11.1 million of our common shares for issuance under the Deferral Plan. An irrevocable grantor trust has been established to provide a source of funds to assist us in meeting our liabilities under the Deferral Plan. The Deferral Plan Irrevocable Grantor Trust account held the following assets at December 31: (millions) 2019 2018 Progressive common shares 1 $ 121.6 $ 114.7 Other investment funds 2 151.2 124.0 Total $ 272.8 $ 238.7 1 Included 3.2 million and 3.6 million common shares as of December 31, 2019 and 2018 , respectively, to be distributed in common shares, and are reported at grant date fair value. 2 Amount is included in other assets on the consolidated balance sheets.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Segment Information	SEGMENT INFORMATION We write personal and commercial auto insurance, personal residential and commercial property insurance, general liability insurance, and other specialty property-casualty insurance and related services. Our Personal Lines segment writes insurance for personal autos and recreational vehicles (our special lines products). The Personal Lines segment is comprised of both the Agency and Direct businesses. The Agency business includes business written by our network of more than 35,000 independent insurance agencies, including brokerages in New York and California, and strategic alliance business relationships (other insurance companies, financial institutions, and national agencies). The Direct business includes business written directly by us online, by phone, or on mobile devices. We operate our Personal Lines businesses throughout the United States. Our Commercial Lines segment writes auto-related primary liability and physical damage insurance, and general liability and property insurance, predominately for small businesses. This segment operates throughout the United States and is distributed through both the independent agency and direct channels. Our Property segment writes residential property insurance for homeowners, other property owners, and renters through both the independent agency and direct channel, and writes flood insurance through the “Write Your Own” program for the National Flood Insurance Program, through the agency channel. Our Property segment operates throughout the majority of the United States. Our service businesses provide insurance-related services, including processing CAIP business and serving as an agent for homeowners, general liability, and workers’ compensation insurance, among other products, through our programs with Progressive Home and unaffiliated insurance companies. We evaluate profitability based on pretax underwriting profit (loss) for the Personal Lines, Commercial Lines, and Property segments. Pretax underwriting profit (loss) is calculated as net premiums earned plus fees and other revenues, less: (i) losses and loss adjustment expenses; (ii) policy acquisition costs; and (iii) other underwriting expenses. Service business pretax profit (loss) is the difference between service business revenues and service business expenses. Expense allocations are based on certain assumptions and estimates primarily related to revenue and volume; stated segment operating results would change if different methods were applied. We do not allocate assets or income taxes to operating segments. In addition, we do not separately identify depreciation expense by segment, and such allocation would be impractical. Companywide depreciation expense was $239.8 million in 2019 , $190.4 million in 2018 , and $169.9 million in 2017 . The accounting policies of the operating segments are the same as those described in Note 1 – Reporting and Accounting Policies . Following are the operating results for the years ended December 31: 2019 2018 2017 (millions) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Personal Lines Agency $ 14,904.1 $ 1,673.2 $ 13,017.2 $ 1,435.7 $ 11,177.6 $ 839.6 Direct 15,305.9 1,181.4 13,017.5 1,088.5 10,769.6 683.7 Total Personal Lines 1 30,210.0 2,854.6 26,034.7 2,524.2 21,947.2 1,523.3 Commercial Lines 4,427.6 458.8 3,610.9 478.6 2,793.9 214.1 Property 2 1,554.8 (26.1 ) 1,287.7 (88.7 ) 988.8 (50.3 ) Other indemnity 0 0 0 0.9 0 (0.2 ) Total underwriting operations 36,192.4 3,287.3 30,933.3 2,915.0 25,729.9 1,686.9 Fees and other revenues 3 563.7 NA 472.2 NA 370.6 NA Service businesses 195.0 16.1 158.5 24.4 126.8 17.3 Investments 4 2,071.2 2,046.6 415.0 390.7 612.7 588.8 Other gains (losses) 0 0 0 0 (1.0 ) (1.0 ) Interest expense NA (189.7 ) NA (166.5 ) NA (153.1 ) Consolidated total $ 39,022.3 $ 5,160.3 $ 31,979.0 $ 3,163.6 $ 26,839.0 $ 2,138.9 NA = Not applicable 1 Personal auto insurance accounted for 94% of the total Personal Lines segment net premiums earned in 2019 and 2018, compared to 93% in 2017 ; 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 During 2019 , 2018 , and 2017 , pretax profit (loss) includes $66.3 million , $72.0 million , and $66.2 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 are allocated to operating segments. 4 Revenues represent recurring investment income and total net realized gains (losses) on securities; pretax profit is net of investment expenses. Our management uses underwriting margin and combined ratio as primary measures of underwriting profitability, as defined above. 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 years ended December 31: 2019 2018 2017 Underwriting Margin Combined Ratio Underwriting Margin Combined Ratio Underwriting Margin Combined Ratio Personal Lines Agency 11.2 % 88.8 11.0 % 89.0 7.5 % 92.5 Direct 7.7 92.3 8.4 91.6 6.3 93.7 Total Personal Lines 9.5 90.5 9.7 90.3 6.9 93.1 Commercial Lines 10.4 89.6 13.3 86.7 7.7 92.3 Property 1 (1.7 ) 101.7 (6.9 ) 106.9 (5.1 ) 105.1 Total underwriting operations 9.1 90.9 9.4 90.6 6.6 93.4 1 Included in 2019 , 2018 , and 2017 , are 4.3 points, 5.6 points, and 6.7 points, respectively, of amortization expense predominately associated with the acquisition of a controlling interest in ARX.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 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, for the years ended December 31, 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 Foreign currency translation adjustment (Income) loss attributable to NCI Balance at December 31, 2018 $ (153.0 ) $ 32.1 $ (120.9 ) $ (105.6 ) $ (17.2 ) $ 0 $ 1.9 Other comprehensive income (loss) before reclassifications: Investment securities 825.8 (174.9 ) 650.9 650.9 0 0 0 Forecasted transactions 0 0 0 0 0 0 0 Foreign currency translation adjustment 0 0 0 0 0 0 0 (Income) loss attributable to noncontrolling interest (NCI) (5.9 ) 1.3 (4.6 ) 0 0 0 (4.6 ) Total other comprehensive income (loss) before reclassifications 819.9 (173.6 ) 646.3 650.9 0 0 (4.6 ) 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 0 Net realized gains (losses) on securities 232.2 (47.7 ) 184.5 184.5 0 0 0 Other gains (losses) 0 0 0 0 0 0 0 Interest expense (1.0 ) 0.2 (0.8 ) 0 (0.8 ) 0 0 Total reclassification adjustment for amounts realized in net income 231.2 (47.5 ) 183.7 184.5 (0.8 ) 0 0 Total other comprehensive income (loss) 588.7 (126.1 ) 462.6 466.4 0.8 0 (4.6 ) Balance at December 31, 2019 $ 435.7 $ (94.0 ) $ 341.7 $ 360.8 $ (16.4 ) $ 0 $ (2.7 ) Components of Changes in Accumulated Other Comprehensive Income (after tax) (millions) Pretax total Total tax After tax total Total net Net Foreign (Income) loss attributable to NCI Balance at December 31, 2017 $ 1,977.8 $ (695.6 ) $ 1,282.2 $ 1,295.0 $ (14.8 ) $ 0 $ 2.0 Cumulative effect adjustment 1 (2,006.0 ) 705.8 (1,300.2 ) (1,300.2 ) 0 0 0 Reclassification of disproportionate amounts 2 (4.3 ) (3.4 ) (7.7 ) (1.1 ) (3.2 ) 0 (3.4 ) Adjusted balance at December 31, 2017 (32.5 ) 6.8 (25.7 ) (6.3 ) (18.0 ) 0 (1.4 ) Other comprehensive income (loss) before reclassifications: Investment securities (224.1 ) 47.0 (177.1 ) (177.1 ) 0 0 0 Forecasted transactions 0 0 0 0 0 0 0 Foreign currency translation adjustment 0 0 0 0 0 0 0 (Income) loss attributable to noncontrolling interest (NCI) 4.3 (1.0 ) 3.3 0 0 0 3.3 Total other comprehensive income (loss) before reclassifications (219.8 ) 46.0 (173.8 ) (177.1 ) 0 0 3.3 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 0 Net realized gains (losses) on securities (98.3 ) 20.5 (77.8 ) (77.8 ) 0 0 0 Other gains (losses) 0 0 0 0 0 0 0 Interest expense (1.0 ) 0.2 (0.8 ) 0 (0.8 ) 0 0 Total reclassification adjustment for amounts realized in net income (99.3 ) 20.7 (78.6 ) (77.8 ) (0.8 ) 0 0 Total other comprehensive income (loss) (120.5 ) 25.3 (95.2 ) (99.3 ) 0.8 0 3.3 Balance at December 31, 2018 $ (153.0 ) $ 32.1 $ (120.9 ) $ (105.6 ) $ (17.2 ) $ 0 $ 1.9 1 Reflects the fair value changes on equity securities as of December 31, 2017, which are reported as realized gains (losses) under the new accounting guidance. See Note 1 – Reporting and Accounting Policies for additional information. 2 Reflects the effect of the change in the U.S. federal tax rate on our available-for-sale fixed-maturity securities and our hedges on forecasted transactions as of December 31, 2017 (see Note 1 – Reporting and Accounting Policies for additional information) and the adjustment to reflect the change in value on (income) loss attributable to NCI in conjunction with the "put" transaction (see Note 15 – Redeemable Noncontrolling Interest for additional information). Components of Changes in Accumulated Other Comprehensive Income (after tax) (millions) Pretax total Total tax After tax total Total net Net Foreign (Income) loss attributable to NCI Total at December 31, 2016 $ 1,439.5 $ (506.1 ) $ 933.4 $ 939.6 $ (9.4 ) $ (1.1 ) $ 4.3 Other comprehensive income (loss) before reclassifications: Investment securities 636.9 (224.0 ) 412.9 412.9 0 0 0 Forecasted transactions (8.0 ) 2.8 (5.2 ) 0 (5.2 ) 0 0 Foreign currency translation adjustment 0.4 (0.1 ) 0.3 0 0 0.3 0 (Income) loss attributable to noncontrolling interest (NCI) (3.5 ) 1.2 (2.3 ) 0 0 0 (2.3 ) Total other comprehensive income (loss) before reclassifications 625.8 (220.1 ) 405.7 412.9 (5.2 ) 0.3 (2.3 ) Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (14.9 ) 5.3 (9.6 ) (9.6 ) 0 0 0 Net realized gains (losses) on securities 103.3 (36.2 ) 67.1 67.1 0 0 0 Other gains (losses) 1 (1.2 ) 0.4 (0.8 ) 0 0 (0.8 ) 0 Interest expense 0.3 (0.1 ) 0.2 0 0.2 0 0 Total reclassification adjustment for amounts realized in net income 87.5 (30.6 ) 56.9 57.5 0.2 (0.8 ) 0 Total other comprehensive income (loss) 538.3 (189.5 ) 348.8 355.4 (5.4 ) 1.1 (2.3 ) Total at December 31, 2017 $ 1,977.8 $ (695.6 ) $ 1,282.2 $ 1,295.0 $ (14.8 ) $ 0 $ 2.0 1 During 2017, we ceased writing insurance in Australia resulting in a loss of $1.2 million relating to the foreign currency translation adjustment. The loss is netted with other gains (losses) on our consolidated statements of comprehensive income for the year end December 31, 2017. In an effort to manage interest rate risk, we often enter into forecasted transactions on Progressive’s debt issuances. We expect to reclassify $1.1 million (pretax) into interest expense during the next 12 months, related to net unrealized losses on forecasted transactions (see Note 4 – Debt

Litigation

Litigation	12 Months Ended
	Dec. 31, 2019
Litigation Disclosures [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. Other insurance companies face many of these same issues. We describe litigation contingencies for which a loss is probable. In addition, we establish accruals for these lawsuits when we can reasonably estimate potential loss exposure, which may include a range of loss, and we will disclose such amount or range of loss if material. As to lawsuits for which the loss 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. We also describe litigation contingencies for which a loss is reasonably possible (but not probable). When disclosing reasonably possible litigation contingencies, we will disclose the amount or range of possible loss, if we are able to make that determination and if material. We review all reasonably possible losses on an ongoing basis to determine whether the likelihood of incurring a loss has become probable, or whether the circumstances have changed such that we may now reasonably estimate a range of loss. We may also be exposed to litigation contingencies that are remote. Remote litigation contingencies are those for which the likelihood of a loss is slight at period end. We do not disclose, or establish accruals for, remote litigation contingencies, but we evaluate these contingencies on an ongoing basis to determine whether the likelihood of a loss has increased. Each year, certain of our pending litigation matters are brought to conclusion. For cases that have settled, but for which settlement is not complete, an accrual is established at our best estimate of the loss exposure. We regularly review these and other accruals to ensure they are adequate, and that there is not the possibility of material losses in excess of our accruals. Settlements that are complete are fully reflected in our financial statements. The amounts accrued and/or paid for settlements during the periods presented were not material to our consolidated financial condition, cash flows, or results of operations. The pending lawsuits summarized below are in various stages of development, and the outcomes are uncertain as of December 31, 2019 . At period end, except to the extent an immaterial accrual has been established, we do not consider the losses from these pending cases to be both probable and estimable, and we are unable to estimate a range of loss at this time. It is not possible to determine loss exposure for a number of reasons, including, without limitation, one or more of the following: liability appears to be remote; putative class action lawsuits generally pose immaterial exposure until a class is actually certified, which, historically, has not been granted by courts in the vast majority of our cases in which class certification has been sought; class definitions are often indefinite and preclude detailed exposure analysis; and complaints rarely state an amount sought as relief, and when such amount is stated, it often is a function of pleading requirements and may be unrelated to the potential exposure. We plan to contest these suits vigorously, but may pursue settlement negotiations in some cases, as we deem appropriate. In the event that any one or more of these cases results in a substantial judgment against, or settlement by, us or if our accruals (if any) prove to be inadequate, the resulting liability could have a material adverse effect on our consolidated financial condition, cash flows, and/or results of operations. Based on information currently known, we do not believe that the outcome of any pending cases described below will have a material impact on our consolidated financial condition, cash flows, and/or results of operations. At December 31, 2019 , pending lawsuits as described above that challenge certain of the operations of our subsidiaries included: Lawsuits seeking class/collective action status : • alleging we sell or charge insureds for illusory coverage or coverage lower than amounts allowed by law for personal injury protection (PIP) coverage and pay related claims at levels lower than allowed by law. • challenging how physical damage claims are handled, adjusted, and ultimately paid, including how we value total loss claims, the payment of fees and taxes associated with total losses, and the payment of diminution damages. • challenging our practice in Florida of adjusting PIP payments. • challenging our assessment of fees. • challenging our adjustment of medical bills submitted by insureds or medical providers in medical claims. • challenging our payment and reimbursement practices to Medicare Advantage Plans on first party medical, PIP, and bodily injury claims. • alleging we improperly sell secondary PIP coverage to Medicare and Medicaid beneficiaries in New Jersey. • challenging our acceptance of uninsured motorist (UM) rejection. • alleging we sell illusory underinsured motorist (UIM) coverage. • alleging that we wrongly pursue subrogation of medical payments paid directly to providers and not to insureds. • alleging that we must pay an insured the pre-loss actual cash value of a totaled vehicle in addition to the value of the salvage vehicle if we take ownership of the salvage vehicle. • alleging legal malpractice by tort counsel appointed by and paid by Progressive to defend our insureds in civil cases. • alleging that we improperly adjust property claims by depreciating labor costs. • alleging that we improperly calculate basic economic loss as it relates to wage loss coverage in New York. • alleging that we violated the Telephone Consumer Protection Act. • challenging certain pay practices with respect to our non-exempt employee population. Lawsuits certified or conditionally certified as class/collective actions : • alleging that we undervalued total loss claims through the use of certain valuation tools. • challenging the manner in which we grant a discount for anti-theft devices. • alleging that we fail to pay overtime to certain employees who we classify as exempt from overtime pay requirements. • challenging our compliance with certain provisions of the California Labor Code with respect to our non-exempt California employee population. Individual lawsuits : • challenging the estimation of physical damage and payment practices for physical damage repairs, and allegations of tortious interference with contract and insurance industry antitrust practice asserted by body shops outside our network program. • claiming that we and other shareholders were overpaid for stock as part of a leveraged buy-out that preceded the entity’s bankruptcy. • claiming patent infringement. • alleging that we are vicariously liable for the fraudulent acts of an agent. • challenging, on a representative basis, certain of our pay practices. • challenging various employment practices.

Leases

Leases	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Leases	LEASES At the beginning of 2019, we adopted the new lease accounting standard that requires operating leases be reported on the balance sheet, on a prospective basis (see Note 1 – Reporting and Accounting Policies for further discussion). Included in our consolidated balance sheet at December 31, 2019, are certain operating leases for office space, computer equipment, and vehicles that are reported as a component of other assets and accounts payable, accrued expenses, and other liabilities. 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 December 31, 2019 , we had operating lease assets of $188.2 million and operating lease liabilities of $201.5 million . At December 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: (millions) Commitments 2020 $ 77.6 2021 64.3 2022 33.1 2023 18.5 2024 11.9 Thereafter 6.1 Total 211.5 Interest (10.0 ) Present value of lease liabilities $ 201.5 Weighted-average remaining term 3.3 years Weighted-average discount rate 3.0 % We review each contract 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. In determining the lease term, we consider the probability of exercising renewal options. We elected to account for leases with both lease and non-lease components as a single lease component and to apply a portfolio approach to account for our vehicle leases. The operating lease expense for the years ended December 31, was as follows: (millions) Expense 2019 $ 102.0 2018 77.3 2017 77.2 Prior to adopting the new lease accounting standard, 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

Dividends

Dividends	12 Months Ended
	Dec. 31, 2019
Dividends [Abstract]
Dividends	DIVIDENDS Following is a summary of our common and preferred share dividends that were declared and/or paid in the last three years: (millions, except per share amounts) Amount Declared Payable Per Share Accrued 1 Common - Annual Variable Dividends: December 2019 January 2020 $ 2.25 $ 1,316.9 December 2018 February 2019 2.5140 1,467.9 December 2017 February 2018 1.1247 655.1 December 2016 February 2017 0.6808 395.4 Common - Quarterly Dividends: December 2019 January 2020 0.10 58.5 August 2019 October 2019 0.10 58.5 May 2019 July 2019 0.10 58.4 February 2019 April 2019 0.10 58.4 Preferred Dividends: August 2019 September 2019 26.875 13.4 February 2019 March 2019 26.875 13.4 August 2018 September 2018 27.024 13.5 1 The accrual is based on an estimate of shares outstanding as of the record date and is recorded as a component of accounts payable, accrued expenses, and other liabilities on the consolidated balance sheets. Common Share Dividends The Board of Directors adopted a policy of declaring regular quarterly common share dividends, and on at least an annual basis, to consider declaring an additional common share dividend, which was effective beginning in 2019. During 2018 and 2017, we maintained a policy of paying an annual variable dividend. Under the policy, the dividend was based on a target percentage of 33-1/3%, as determined by the Board, of after-tax underwriting income multiplied by a performance factor (Gainshare factor). The Gainshare factor was 1.91 and 1.79 for the dividends declared in 2018 and 2017, respectively. Preferred Share Dividends In March 2018, we issued 500,000 Series B Fixed-to-Floating Rate Cumulative Perpetual Serial Preferred Shares, without par value (the “Series B Preferred Shares”), with 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 London Interbank Offered Rate (LIBOR) (or comparable successor base rate) plus a spread of 2.539%

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interest (Notes)	12 Months Ended
	Dec. 31, 2019
Noncontrolling Interest [Abstract]
Noncontrolling Interest Disclosure [Text Block]	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, as of December 31, 2019, had 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 . As of December 31, 2019, 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. Progressive's purchase prices for shares, pursuant to these put or call rights, will be determined by adding (A) the price per share paid at the closing on April 1, 2015, to (B) the product of the change in the fully diluted net tangible book value per share of ARX between December 31 , 2014, a nd December 31, 2020, times a multiple of between 1.0 and 2.0 . The multiple will be determined based on the growth and profitability of ARX’s business over the applicable time period, pursuant to criteria included in the stockholders’ agreement. Among other provisions, the stockholders’ agreement also prohibits ARX from taking a number of actions, including the payment of dividends, without the consent of The Progressive Corporation and one other stockholder. 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, calculated as described above, of the stockholders’ agreement. The redeemable noncontrolling interest was initially recorded at a fair value of $411.5 million , representing the minority shares at the net acquisition price adjusted for the fair value of the put and call rights. The value of the put and call rights on the acquisition date was based on an internally developed modified binomial model. Subsequent changes to the redeemable noncontrolling interest are based on the maximum redemption value at the end of the reporting period, as determined in accordance with the stockholders’ agreement. In addition to these minority shares, at December 31, 2019 , ARX employees held options to purchase 10,438 ARX shares. These options and any shares issued upon exercise are subject to the stockholders’ agreement, including the “put” and “call” rights described above. As the options are not exercised, the underlying obligation of approximately $16.0 million is not recorded as part of redeemable NCI. The changes in the components of redeemable NCI during the years ended December 31, were: (millions) 2019 2018 2017 Balance, beginning of year $ 214.5 $ 503.7 $ 483.7 Net income attributable to NCI 9.7 5.7 5.9 Other comprehensive income (loss) attributable to NCI 1 4.6 (3.3 ) 2.3 Exercise of stock options 7.7 9.4 3.4 Purchase/change of ARX minority shares (11.2 ) (298.2 ) 0 Change in redemption value 0.3 (2.8 ) 8.4 Balance, end of year $ 225.6 $ 214.5 $ 503.7 1 Amount represents the other comprehensive income (loss) attributable to NCI, as reflected on the consolidated statements of comprehensive income; changes in accumulated other comprehensive income (loss) attributable to NCI due to a change in the minority ownership percentage does not impact the amount of redeemable NCI. In February 2020, Progressive and the minority ARX stockholders entered into an agreement requiring Progressive to purchase all remaining minority shares in the second quarter 2020. See Note 17 – Subsequent Event for further discussion.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	GOODWILL AND INTANGIBLE ASSETS Goodwill Goodwill recorded at December 31, 2019 , and 2018 , was $452.7 million . The majority of the goodwill recorded as of December 31, 2019, relates to the April 1, 2015, acquisition of a controlling interest in ARX. No impairment losses have been recorded on any of the outstanding goodwill. Intangible Assets The following table is a summary of the net carrying amount of other intangible assets as of December 31 : (millions) 2019 2018 Intangible assets subject to amortization $ 215.9 $ 282.2 Indefinite-lived intangible assets 1 12.4 12.4 Total $ 228.3 $ 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 both years presented. Intangible assets subject to amortization for the years ended December 31, consisted of the following: (millions) 2019 2018 Category Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Policies in force $ 256.2 $ 173.9 $ 82.3 $ 256.2 $ 137.3 $ 118.9 Agency relationships 159.2 54.0 105.2 159.2 42.6 116.6 Software rights 79.1 50.7 28.4 79.1 40.1 39.0 Trade name 34.8 34.8 0 34.8 27.1 7.7 Total $ 529.3 $ 313.4 $ 215.9 $ 529.3 $ 247.1 $ 282.2 Amortization expense was $66.3 million , $72.0 million , and $66.2 million for the years ended December 31, 2019 , 2018 , and 2017 , respectively. During 2017, we revised our estimate of the economic useful life of our trade name intangible asset from an original life of 10 years to a remaining life of 2 years . The decrease in the useful life reflected the transition of our branding for the Property business, from the ASI trade name to the Progressive brand. The majority of the intangible assets have finite lives, which, at December 31, 2019, had a remaining life range from 2 months to 9 years , with an average remaining life of 3.7 years . The estimated aggregate amortization on these intangible assets for each of the next five years as of December 31, 2019 , follows: (millions) Year Amortization Expense 2020 $ 56.9 2021 56.6 2022 29.2 2023 13.5 2024 11.4

Subsequent Event

Subsequent Event	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Event	SUBSEQUENT EVENT In February 2020, Progressive and the minority ARX stockholders, including employees holding vested stock options, signed a stock purchase agreement requiring Progressive to acquire all outstanding shares and shares to be issued under outstanding stock options. This transaction, which is subject to normal closing conditions, would bring Progressive’s ownership stake to 100% early in the second quarter of 2020, instead of 2021 as originally planned. The total cost of this transaction is estimated to be $242 million .

Reporting and Accounting Poli_2

Reporting and Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Nature Of Operations Policy	Nature of Operations The Progressive insurance organization began business in 1937. The financial results of The Progressive Corporation include its subsidiaries and affiliates (references to “subsidiaries” in these notes include affiliates as well). Our insurance subsidiaries provide personal and commercial auto insurance, personal residential and commercial property insurance, general liability insurance, and other specialty property-casualty insurance and related services. Our Personal Lines segment writes insurance for personal autos and recreational vehicles, which we refer to as our special lines products. Our Commercial Lines segment writes auto-related primary liability and physical damage insurance, and general liability and property insurance, predominately for small businesses. Our Property segment writes residential property insurance for homeowners, other property owners, and renters. We operate our businesses throughout the United States through both the independent agency and direct channels.
Basis of Consolidation and Reporting	Basis of Consolidation and Reporting 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. All intercompany accounts and transactions are eliminated in consolidation. All revenues are generated from external customers and we do not have a reliance on any major customer. The Progressive Corporation owned 87.1% of the outstanding capital stock of ARX at December 31, 2019 , 86.8% at December 31, 2018 , and 69.0% at December 31, 2017 . The increase in Progressive's ownership of ARX in 2018 is primarily due to the minority ARX stockholders exercising their rights to "put" a portion of their shares, including exercised stock options, to Progressive pursuant to the ARX stockholders' agreement. See Note 15 – Redeemable Noncontrolling Interest and Note 17 – Subsequent Event for further discussion.
Estimates	Estimates We are required to make estimates and assumptions when preparing our financial statements and accompanying notes in conformity with accounting principles generally accepted in the United States of America (GAAP). As estimates develop into fact, results may, and will likely, differ from those estimates.
Investments	Investments Our fixed-maturity securities and short-term investments are accounted for on an available-for-sale basis. Fixed-maturity securities include debt securities and redeemable preferred stocks, which may have fixed or variable principal payment schedules, may be held for indefinite periods of time, and may be used as a part of our asset/liability strategy or sold in response to changes in interest rates, anticipated prepayments, risk/reward characteristics, liquidity needs, or other economic factors. These securities are carried at fair value with the corresponding unrealized gains (losses), net of deferred income taxes, reported in accumulated other comprehensive income. Fair values are obtained from recognized pricing services or are quoted by market makers and dealers, with limited exceptions discussed in Note 3 – Fair Value . Short-term investments may include Eurodollar deposits, commercial paper, repurchase transactions, and other securities expected to mature within one year. From time to time, we may also invest in municipal bonds that have maturity dates that are longer than one year but have either liquidity facilities or mandatory put features within one year. Equity securities include common stocks, nonredeemable preferred stocks, and other risk investments. These securities are carried at fair value, with the changes in fair value reported as a component of net holding period gains (losses) on securities reported in net income. Derivative instruments may include futures, options, forward positions, interest rate swap agreements, and credit default swaps and may be used in the portfolio for general investment purposes or to hedge the exposure to variable cash flows of a forecasted transaction (cash flow hedge). We did no t have any derivatives outstanding at December 31, 2019 and 2018. To the extent we have derivatives held for general investment purposes, these derivative instruments would be recognized as either assets or liabilities and measured at fair value, with changes in fair value recognized in income as a component of net holding period gains (losses) on securities during the period of change. Derivatives designated as hedges are required to be evaluated on established criteria to determine the effectiveness of their correlation to, and ability to reduce the designated risk of, specific securities or transactions. Effectiveness is required to be reassessed regularly. For cash flow hedges that are deemed to be effective, the changes in fair value of the hedge would be reported as a component of accumulated other comprehensive income and subsequently amortized into earnings over the life of the hedged transaction. If a hedge is deemed to become ineffective or discontinued, changes in fair value of the derivative instrument would be reported in income for the current period. For derivatives settled through a clearinghouse, we will need cash to post initial margin and are subject to increases in margin beyond changes in fair value. Exposure to credit risk is limited to the carrying value; collateral may be required to limit credit risk. For bi-lateral derivative positions, net cash requirements are limited to changes in fair values, which may vary as a result of changes in interest rates, currency exchange rates, and other factors. We have elected not to offset fair value amounts that arise from derivative positions with the same counterparty under a master netting arrangement. Investment securities are exposed to various risks such as interest rate, market, credit, and liquidity risk. Fair values of securities fluctuate based on the nature and magnitude of changing market conditions; significant changes in market conditions could materially affect the portfolio’s value in the near term. We regularly monitor our portfolio for price changes, which might indicate potential impairments, and perform detailed reviews of fixed-maturity securities with unrealized losses. In such cases, changes in fair value are evaluated to determine the extent to which such changes are attributable to: (i) fundamental factors specific to the issuer, such as financial condition, business prospects, or other factors, (ii) market-related factors, such as interest rates, or (iii) credit-related losses, where the present value of cash flows expected to be collected are lower than the amortized cost basis of the security. We analyze our investment in fixed-maturity securities that are in a loss position to determine if we intend to sell, or if it is more likely than not that we will be required to sell, the security prior to recovery and, if so, we write down the security to its current fair value, with the entire amount of the write-down recorded to earnings. To the extent that it is more likely than not that we will hold the debt security until recovery (which could be maturity), we determine if any of the decline in value is due to a credit loss (i.e., where the present value of future cash flows expected to be collected is lower than the amortized cost basis of the security) and, if so, we recognize that portion of the impairment as a component of net realized gains (losses) in the consolidated statements of comprehensive income, with the difference (i.e., non-credit related impairment) recognized as part of our net unrealized gains (losses) in accumulated other comprehensive income. For a discussion of the modifications to the accounting guidance relative to the impairment evaluation for available-for-sale securities, which is effective January 1, 2020, see the " New Accounting Standards " section of this Note 1, below. Investment income consists of interest, dividends, and accretion (net of amortization). Interest is recognized on an accrual basis using the effective yield method, except for asset-backed securities, discussed below. Depending on the nature of the equity instruments, dividends are recorded at either the ex-dividend date or on an accrual basis. Asset-backed securities, which are included in our fixed-maturity portfolio, are generally accounted for under the retrospective method. The retrospective method recalculates yield assumptions (based on changes in interest rates or cash flow expectations) historically to the inception of the investment holding period, and applies the required adjustment, if any, to the cost basis, with the offset recorded to investment income. The prospective method is used primarily for interest-only securities, asset-backed securities below high investment-grade status (i.e., below AA-), and certain asset-backed securities with sub-prime loan exposure or where there is a greater risk of non-performance and where it is possible the initial investment may not be substantially recovered. The prospective method requires a calculation of expected future repayments and resets the yield to allow for future period adjustments; no current period impact to investment income or the security’s cost is made based on the cash flow update. Prepayment assumptions are updated quarterly. Realized gains (losses) on securities are computed based on the first-in first-out method and include write-downs on available-for-sale securities considered to have other-than-temporary declines in fair value (excluding non-credit related impairments), as well as holding period valuation changes on equity securities, hybrid instruments (e.g., securities with embedded options, where the option is a feature of the overall change in the value of the instrument), and derivatives.
Insurance Premiums and Receivables	Insurance Premiums and Receivables Insurance premiums written are earned into income on a pro rata basis over the period of risk, based on a daily earnings convention. Accordingly, unearned premiums represent the portion of premiums written that are applicable to the unexpired risk. We provide insurance and related services to individuals and commercial accounts and offer a variety of payment plans. Generally, premiums are collected prior to providing risk coverage, minimizing our exposure to credit risk. For our Personal Lines and Commercial Lines businesses, we perform a policy level evaluation to determine the extent to which the premiums receivable balance exceeds the unearned premiums balance. We then age this exposure to establish an allowance for doubtful accounts based on prior experience. For our Property business, the risk of uncollectibility is relatively low. If premiums are unpaid by the policy due date, we provide advance notice of cancellation in accordance with each state’s requirements and, if the premiums remain unpaid after receipt of notice, cancel the policy and write off any remaining balance.
Deferred Acquisition Costs	Deferred Acquisition Costs Deferred acquisition costs include commissions, premium taxes, and other variable underwriting and direct sales costs incurred in connection with the successful acquisition or renewal of insurance
Loss and Loss Adjustment Expense Reserves	Loss and Loss Adjustment Expense Reserves Loss reserves represent the estimated liability on claims reported to us, plus reserves for losses incurred but not recorded (IBNR). These estimates are reported net of amounts estimated to be recoverable from salvage and subrogation. Loss adjustment expense reserves represent the estimated expenses required to settle these claims. The methods of making estimates and establishing these reserves are reviewed regularly, and resulting adjustments are reflected in income in the current period. Such loss and loss adjustment expense reserves are susceptible to change in the near term.
Reinsurance	Reinsurance Our reinsurance activity includes transactions which are categorized as Regulated and Non-Regulated. Regulated refers to plans in which we participate that are governed by insurance regulations and include state-provided reinsurance facilities (e.g., Michigan Catastrophic Claims Association, North Carolina Reinsurance Facility, Florida Hurricane Catastrophe Fund), as well as state-mandated involuntary plans for commercial vehicles (Commercial Automobile Insurance Procedures/Plans – CAIP) and federally regulated plans for flood (National Flood Insurance Program – NFIP); we act as a servicing agent for CAIP and as a participant in the “Write Your Own” program for the NFIP. Non-Regulated includes voluntary contractual arrangements primarily related to our Property business and to the transportation network company business written by our Commercial Lines segment. Prepaid reinsurance premiums are earned on a pro rata basis over the period of risk, based on a daily earnings convention, which is consistent with premiums earned. See Note 7 – Reinsurance for further discussion.
Income Taxes	Income Taxes The income tax provision is calculated under the balance sheet approach. 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. The principal items giving rise to such differences are investment securities (e.g., net unrealized gains (losses), net holding period gains (losses) on securities, write-downs on securities determined to be other-than-temporarily impaired), loss and loss adjustment expense reserves, unearned premiums reserves, deferred acquisition costs, property and equipment, intangible assets, and non-deductible accruals. We review our deferred tax assets regularly for recoverability. See Note 5 – Income Taxes for further discussion.
Property and Equipment	Property and Equipment Property and equipment are recorded at cost, less accumulated depreciation, and include capitalized software developed or acquired for internal use. Depreciation is recognized over the estimated useful lives of the assets using accelerated methods for computer equipment and the straight-line method for all other fixed assets. We evaluate impairment whenever events or circumstances warrant such a review and write-off the impaired assets if appropriate. The cost and useful lives for property and equipment at December 31, were: ($ in millions) 2019 2018 Useful Lives Land $ 161.6 $ 177.0 NA Buildings, improvements, and integrated components 927.1 928.8 7-40 years Capitalized software 367.1 327.0 3-10 years Software licenses (internal use) 286.8 259.1 1-5 years Computer equipment 223.3 123.2 3 years All other property and equipment 385.9 349.8 3-10 years Total cost 2,351.8 2,164.9 Accumulated depreciation (1,138.1 ) (1,033.2 ) Balance at end of year $ 1,213.7 $ 1,131.7 NA = Not applicable At December 31, 2019 and 2018 , included in other assets in the consolidated balance sheets is $32.9 million and $39.3 million , respectively, of “held for sale” property, which represents the fair value of these properties less the estimated costs to sell.
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill is the excess of the purchase price over the estimated fair value of the assets and liabilities acquired and represents the future economic benefits arising from other assets acquired that could not be individually identified and separately recognized. Intangible assets primarily arose through the acquisition of ARX and mainly represent the future premiums that will be recognized from the policies and agency relationships that existed at the acquisition date. See Note 16 – Goodwill and Intangible Assets for further discussion. We evaluate our goodwill for impairment at least annually using a qualitative approach. If events or changes in circumstances indicate that the carrying value of goodwill or intangible assets may not be recoverable, we will evaluate such items for impairment using a quantitative approach.
Guaranty Fund Assessments	Guaranty Fund Assessments We are subject to state guaranty fund assessments, which provide for the payment of covered claims or other insurance obligations of insurance companies deemed insolvent. These assessments are accrued after a formal determination of insolvency has occurred, and we have written the premiums on which the assessments will be based. Assessments that are available for recoupment from policyholders are capitalized when incurred; all other assessments are expensed.
Fees and Other Revenues	Fees and Other Revenues Fees and other revenues primarily represent fees collected from policyholders relating to installment charges in accordance with our bill plans, as well as late payment and insufficient funds fees and revenue from ceding commissions. Fees and other revenues are generally earned when invoiced, except for excess ceding commissions, which are earned over the policy period.
Service Revenues and Expenses	Service Revenues and Expenses Our service businesses provide insurance-related services. Service revenues and expenses from our commission-based businesses are recorded in the period in which they are earned or incurred. Service revenues generated from processing business for involuntary CAIP plans are earned on a pro rata basis over the term of the related policies. Service expenses related to these CAIP plans are expensed as incurred.
Equity-Based Compensation	Equity-Based Compensation We issue time-based and performance-based restricted stock unit awards to key members of management as our form of equity compensation, and time-based restricted stock awards to non-employee directors. Collectively, we refer to these awards as “restricted equity awards.” Compensation expense for time-based restricted equity awards with installment vesting is recognized over each respective vesting period. For performance-based restricted equity awards, compensation expense is recognized over the respective estimated vesting periods. Dividend equivalent units are credited to outstanding restricted stock unit awards, both time-based and performance-based, at the time a dividend is paid to shareholders and paid upon vesting of the underlying award. We record an estimate for expected forfeitures of restricted equity awards based on our historical forfeiture rates. In addition, we shorten the vesting periods of certain restricted equity awards based on the “qualified retirement” provisions in our equity compensation plans, under which (among other provisions) if the participant satisfies certain age and years-of-service requirements, the vesting and distribution of 50% of outstanding restricted equity awards accelerates upon reaching eligibility for a qualified retirement and shortly after the grant date for each subsequent award. ARX also has nonqualified and incentive stock options outstanding that were issued prior to April 2015 as a form of equity compensation to certain of the officers and employees of ARX and its subsidiaries. These outstanding stock options are subject to the put/call features contained in the ARX stockholders’ agreement, pursuant to which The Progressive Corporation has the right, and can be required, to purchase all the shares underlying these awards. The vested stock options, and the shares issuable upon exercise of the stock options, are also subject to repurchase by ARX if the holder’s employment terminates. See Note 15 – Redeemable Noncontrolling Interest and Note 17 – Subsequent Event for further discussion. These stock options, which are treated for accounting purposes as liability awards, are expensed over the respective vesting periods based on the Black-Scholes value determined at period end.
Earnings Per Share	Earnings Per Common Share Net income attributable to Progressive is reduced by preferred share dividends to determine net income available to common shareholders, and is used in our calculation of the per common share amounts. Basic earnings per common share is computed using the weighted average number of common shares outstanding during the reporting period, excluding unvested time-based restricted stock awards. Diluted earnings per common share includes common stock equivalents assumed outstanding during the period. Our common stock equivalents include the incremental shares assumed to be issued for: • earned but unvested time-based restricted equity awards, and • performance-based restricted equity awards that satisfied certain contingency conditions for unvested common stock equivalents during the period and are highly likely to continue to satisfy the conditions until the date of vesting.
Cash Flow, Supplemental Disclosures	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 by ARX’s subsidiaries, and are not considered part of the investment portfolio. The amount of reverse repurchase commitments held by ARX’s subsidiaries at December 31, 2019 , 2018 , and 2017 , were $46.3 million , $117.3 million , and $247.2 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. For the year ended December 31, 2019, non-cash activity includes declared but unpaid dividends of $1,375.4 million and operating lease liabilities arising from obtaining right-of-use assets of $63.1 million (see Note 13 – Leases for further discussion). Our consolidated statement of cash flows for the year ended December 31, 2018, was revised to correct the classification of our acquisition of additional shares of ARX Holding Corp. from an investing activity to a financing activity; there was no overall impact on the decrease in cash, cash equivalents, and restricted cash that was reported for 2018. For the years ended December 31, we paid the following: (millions) 2019 2018 2017 Income taxes $ 954.3 $ 702.6 $ 715.6 Interest 184.9 154.0 146.3 Operating lease liabilities 84.0 NA NA
Commitments and Contingencies	Commitments and Contingencies We have certain noncancelable purchase obligations for goods and services with minimum commitments of $857.0 million at December 31, 2019. In addition, we have several multiple-layer property catastrophe reinsurance contracts with various reinsurers with terms ranging from one to three years; the minimum commitment under these agreements at December 31, 2019, was $96.1 million .
New Accounting Standards	New Accounting Standards Adopted On January 1, 2019, we adopted the Accounting Standards Update (ASU) that requires 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 13 – Leases for further information. On January 1, 2019, we adopted the ASU related to premium amortization on purchased callable debt securities. Under the ASU, the premium is required to be amortized to the earliest call date, which more closely aligns interest income recorded on bonds held at a premium with the economics of the underlying instrument. We applied the ASU on a modified retrospective basis, as required under the standard. Since we have historically used a yield-to-worst scenario for our securities that were purchased at a premium, and the first call on a premium security most often produces the lowest and most conservative yield, the adoption of this standard did not have an impact on our financial condition, cash flows, or results of operations. Issued In August 2018, the Financial Accounting Standards Board (FASB) issued an 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 is effective for fiscal years (including interim periods within those fiscal years) beginning after December 15, 2019 (2020 for calendar-year companies). We adopted this standard on January 1, 2020, on a prospective basis, and 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 (2020 for calendar-year companies), 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, in 2018, we elected to partially early adopt the removal of current disclosure requirements and adopted the remaining disclosure requirements as of January 1, 2020. Since this standard only affected disclosure, there was no 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. This standard was adopted on January 1, 2020 and is not expected 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. This update modified the existing accounting guidance related to the impairment evaluation for available-for-sale debt securities, reinsurance recoverables, and premiums receivables and could result in the creation of an allowance for credit losses as a contra asset account. The ASU requires a cumulative-effect change to retained earnings in the period of adoption and prospective changes on previously recorded impairments, to the extent applicable. This ASU is effective for fiscal years (including interim periods within those fiscal years) beginning after December 15, 2019 (2020 for calendar-year companies). We adopted this standard as of January 1, 2020. To determine the existence of any credit-related impairment losses on our available-for-sale debt securities, we reviewed all such securities at December 31, 2019, by applying estimates of future cash flows and performance of those securities in a loss position and identifying market-related versus performance-related losses. For our reinsurance recoverables, we assessed the current credit quality and credit outlook for reinsurers with at-risk uncollateralized recoverables. In assessing premium receivables, which are short-term in nature, we assessed customer balances leveraging our current process for analyzing uncollectibility of premium receivables. Based on these analyses, we determined that no allowance for credit losses was necessary relative to our available-for-sale debt securities, reinsurance recoverables, or premiums receivable upon adoption of the ASU.

Reporting and Accounting Poli_3

Reporting and Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Advertising Costs	Total advertising costs, which are expensed as incurred, for the years ended December 31, were: (millions) Advertising Costs 2019 $ 1,837.3 2018 1,422.4 2017 1,005.4
Property and Equipment	The cost and useful lives for property and equipment at December 31, were: ($ in millions) 2019 2018 Useful Lives Land $ 161.6 $ 177.0 NA Buildings, improvements, and integrated components 927.1 928.8 7-40 years Capitalized software 367.1 327.0 3-10 years Software licenses (internal use) 286.8 259.1 1-5 years Computer equipment 223.3 123.2 3 years All other property and equipment 385.9 349.8 3-10 years Total cost 2,351.8 2,164.9 Accumulated depreciation (1,138.1 ) (1,033.2 ) Balance at end of year $ 1,213.7 $ 1,131.7 NA = Not applicable
Interest Capitalized
Equity Based Compensation and Related Tax Benefits	The total compensation expense recognized for equity-based compensation, including both equity and liability awards, for the years ended December 31, was: (millions) 2019 2018 2017 Pretax expense $ 90.2 $ 77.2 $ 95.4 Tax benefit 1 18.9 16.2 33.4 1 Calculated using the corporate federal tax rate of 21% for 2019 and 2018 and 35% for 2017.
Supplemental Cash Flow Information	For the years ended December 31, we paid the following: (millions) 2019 2018 2017 Income taxes $ 954.3 $ 702.6 $ 715.6 Interest 184.9 154.0 146.3 Operating lease liabilities 84.0 NA NA

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2019
Investments Schedule [Abstract]
Investment Portfolio by Major Security Type	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 of the securities. 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 Unrealized Losses Net Holding Period Gains (Losses) Fair Value % of Total Fair Value December 31, 2019 Available-for-sale securities: Fixed maturities: U.S. government obligations $ 13,100.7 $ 194.1 $ (43.7 ) $ 0 $ 13,251.1 33.7 % State and local government obligations 1,686.0 30.0 (2.7 ) 0 1,713.3 4.4 Corporate debt securities 6,860.3 206.6 (0.5 ) 1.3 7,067.7 18.0 Residential mortgage-backed securities 625.0 4.5 (2.0 ) 0 627.5 1.6 Commercial mortgage-backed securities 5,020.7 61.5 (6.0 ) 0 5,076.2 12.9 Other asset-backed securities 5,164.7 16.2 (1.4 ) 0 5,179.5 13.2 Redeemable preferred stocks 185.7 4.1 (1.3 ) 6.5 195.0 0.5 Total fixed maturities 32,643.1 517.0 (57.6 ) 7.8 33,110.3 84.3 Short-term investments 1,798.8 0 0 0 1,798.8 4.6 Total available-for-sale securities 34,441.9 517.0 (57.6 ) 7.8 34,909.1 88.9 Equity securities: Nonredeemable preferred stocks 971.3 0 0 67.6 1,038.9 2.7 Common equities 1,125.5 0 0 2,180.8 3,306.3 8.4 Total equity securities 2,096.8 0 0 2,248.4 4,345.2 11.1 Total portfolio 1,2 $ 36,538.7 $ 517.0 $ (57.6 ) $ 2,256.2 $ 39,254.3 100.0 % ($ in millions) Cost Gross Unrealized Gains Gross Unrealized Losses Net Holding Period Gains (Losses) Fair Value % of Total Fair Value December 31, 2018 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 fixed maturities and short-term 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 available-for-sale 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 net unsettled security transactions; at December 31, 2019 , $11.9 million was included in “other liabilities,” compared to $5.9 million at December 31, 2018 . 2 The total fair value of the portfolio at December 31, 2019 and 2018 included $3.2 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.
Hybrid Securities	Included in our fixed maturities are hybrid securities, which are reported at fair value at December 31 : (millions) 2019 2018 Fixed Maturities: State and local government obligations $ 3.5 $ 3.6 Corporate debt securities 91.2 158.9 Other asset-backed securities 2.6 4.5 Redeemable preferred stocks 92.1 77.7 Total hybrid securities $ 189.4 $ 244.7
Composition of Fixed Maturities by Maturity	The composition of fixed maturities by maturity at December 31, 2019 , was: (millions) Cost Fair Value Less than one year $ 6,700.1 $ 6,712.6 One to five years 16,898.3 17,158.4 Five to ten years 9,010.8 9,203.9 Ten years or greater 33.9 35.4 Total $ 32,643.1 $ 33,110.3
Gross Unrealized Losses by Major Security	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 Value Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Value Unrealized Losses No. of Sec. Fair Value Unrealized Losses December 31, 2019 U.S. government obligations 23 $ 5,152.4 $ (43.7 ) 19 $ 5,057.2 $ (43.6 ) 4 $ 95.2 $ (0.1 ) State and local government obligations 67 314.3 (2.7 ) 52 287.5 (2.6 ) 15 26.8 (0.1 ) Corporate debt securities 16 247.6 (0.5 ) 12 191.4 (0.5 ) 4 56.2 0 Residential mortgage-backed securities 41 292.8 (2.0 ) 12 163.7 (0.9 ) 29 129.1 (1.1 ) Commercial mortgage-backed securities 98 1,742.4 (6.0 ) 79 1,400.0 (5.3 ) 19 342.4 (0.7 ) Other asset-backed securities 61 1,000.6 (1.4 ) 43 938.5 (0.9 ) 18 62.1 (0.5 ) Redeemable preferred stocks 1 11.2 (1.3 ) 0 0 0 1 11.2 (1.3 ) Total fixed maturities 307 $ 8,761.3 $ (57.6 ) 217 $ 8,038.3 $ (53.8 ) 90 $ 723.0 $ (3.8 ) Total No. of Sec. Total Fair Value Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Value Unrealized Losses No. of Sec. Fair Value Unrealized Losses December 31, 2018 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 )
OTTI Credit Losses Recognized in Earnings	The following table shows the rollforward activity for 2017: (millions) Total Total at December 31, 2016 $ 11.5 Credit losses for which an OTTI was not previously recognized 0.4 Reductions for securities sold/matured (11.2 ) Change in recoveries of future cash flows expected to be collected 1 (0.2 ) Total at December 31, 2017 $ 0.5 1 Reflects expected recovery of prior period impairments that will be accreted into income over the remaining life of the security.
Components of Net Realized Gains (Losses)	The components of net realized gains (losses) for the years ended December 31, were: (millions) 2019 2018 2017 Gross realized gains on security sales Available-for-sale securities: U.S. government obligations $ 164.4 $ 6.7 $ 6.2 State and local government obligations 6.1 9.5 10.5 Corporate and other debt securities 100.1 2.4 20.3 Residential mortgage-backed securities 0.2 0 23.8 Commercial mortgage-backed securities 8.1 2.0 4.9 Other asset-backed securities 0.8 0.1 0.3 Redeemable preferred stocks 2.2 4.5 8.5 Total available-for-sale securities 281.9 25.2 74.5 Equity securities: Nonredeemable preferred stocks 36.2 4.1 58.4 Common equities 61.7 286.6 43.0 Total equity securities 97.9 290.7 101.4 Subtotal gross realized gains on security sales 379.8 315.9 175.9 Gross realized losses on security sales Available-for-sale securities: U.S. government obligations (20.4 ) (98.7 ) (28.7 ) State and local government obligations (0.7 ) (2.9 ) (0.1 ) Corporate and other debt securities (7.9 ) (10.4 ) (5.1 ) Residential mortgage-backed securities (2.3 ) (0.1 ) (0.4 ) Commercial mortgage-backed securities (2.2 ) (6.3 ) (5.3 ) Other asset-backed securities (0.1 ) (1.1 ) (0.4 ) Redeemable preferred stocks (0.4 ) (0.1 ) (6.4 ) Short-term investments 0 0 (0.2 ) Total available-for-sale securities (34.0 ) (119.6 ) (46.6 ) Equity securities: Nonredeemable preferred stocks (3.2 ) (3.9 ) (5.9 ) Common equities (8.0 ) (21.7 ) (12.2 ) Total equity securities (11.2 ) (25.6 ) (18.1 ) Subtotal gross realized losses on security sales (45.2 ) (145.2 ) (64.7 ) Net realized gains (losses) on security sales Available-for-sale securities: U.S. government obligations 144.0 (92.0 ) (22.5 ) State and local government obligations 5.4 6.6 10.4 Corporate and other debt securities 92.2 (8.0 ) 15.2 Residential mortgage-backed securities (2.1 ) (0.1 ) 23.4 Commercial mortgage-backed securities 5.9 (4.3 ) (0.4 ) Other asset-backed securities 0.7 (1.0 ) (0.1 ) Redeemable preferred stocks 1.8 4.4 2.1 Short-term investments 0 0 (0.2 ) Total available-for-sale securities 247.9 (94.4 ) 27.9 Equity securities: Nonredeemable preferred stocks 33.0 0.2 52.5 Common equities 53.7 264.9 30.8 Total equity securities 86.7 265.1 83.3 Litigation settlements and other gains (losses) 0 0 1.2 Subtotal net realized gains (losses) on security sales 334.6 170.7 112.4 Net holding period gains (losses) Hybrid securities 18.0 (10.4 ) (1.6 ) Equity securities 739.9 (497.5 ) 0 Subtotal net holding period gains (losses) 757.9 (507.9 ) (1.6 ) Other-than-temporary impairment losses Fixed maturities: Commercial mortgage-backed securities 0 0 (0.4 ) Total fixed maturities 0 0 (0.4 ) Equity securities: Common equities 0 0 (11.2 ) Subtotal investment other-than-temporary impairment losses 0 0 (11.6 ) Other asset impairment (63.3 ) (68.3 ) (49.6 ) Subtotal other-than-temporary impairment losses (63.3 ) (68.3 ) (61.2 ) Total net realized gains (losses) on securities $ 1,029.2 $ (405.5 ) $ 49.6
Components of Equity Realized Gains (Losses)	<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;padding-top:8px;text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">The following table reflects our holding period realized gains (losses) on equity securities recognized for the respective years ended December 31, for equity securities held at the respective year end:</font></div><div style="line-height:120%;text-align:left;font-size:10pt;"><div style="padding-left:0px;text-indent:0px;line-height:normal;padding-top:10px;"><table cellpadding="0" cellspacing="0" style="font-family:Times New Roman;font-size:10pt;width:100%;border-collapse:collapse;text-align:left;"><tr><td colspan="7" rowspan="1"></td></tr><tr><td style="width:84%;" rowspan="1" colspan="1"></td><td style="width:1%;" rowspan="1" colspan="1"></td><td style="width:6%;" rowspan="1" colspan="1"></td><td style="width:1%;" rowspan="1" colspan="1"></td><td style="width:1%;" rowspan="1" colspan="1"></td><td style="width:6%;" rowspan="1" colspan="1"></td><td style="width:1%;" rowspan="1" colspan="1"></td></tr><tr><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;font-weight:bold;">(millions)</font></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;font-weight:bold;">2019</font></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;font-weight:bold;">2018</font></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td></tr><tr><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Total net gains (losses) recognized during the period on equity securities</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">$</font></div></td><td style="vertical-align:bottom;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"><div style="text-align:right;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">826.6</font></div></td><td style="vertical-align:bottom;border-top:1px solid #000000;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">$</font></div></td><td style="vertical-align:bottom;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"><div style="text-align:right;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">(232.4</font></div></td><td style="vertical-align:bottom;padding-right:2px;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">)</font></div></td></tr><tr><td style="vertical-align:bottom;background-color:#e5e5e5;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Less: Net gains (losses) recognized on equity securities sold during the period</font></div></td><td colspan="2" style="vertical-align:bottom;background-color:#e5e5e5;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">86.7</font></div></td><td style="vertical-align:bottom;background-color:#e5e5e5;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#e5e5e5;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">265.1</font></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#e5e5e5;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td></tr><tr><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Net holding period gains (losses) recognized during the period on equity securities held at period end</font></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">$</font></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"><div style="text-align:right;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">739.9</font></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;border-top:1px solid #000000;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">$</font></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"><div style="text-align:right;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">(497.5</font></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;padding-right:2px;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">)</font></div></td></tr></table></div></div><div style="line-height:120%;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;">Note: Comparative disclosure for 2017 is not meaningful.</font></div></div>
Components of Net Investment Income	The components of net investment income for the years ended December 31, were: (millions) 2019 2018 2017 Available-for-sale securities: Fixed maturities: U.S. government obligations $ 268.6 $ 196.8 $ 72.7 State and local government obligations 36.5 37.7 51.5 Foreign government obligations 0 0 0.3 Corporate debt securities 268.9 217.9 125.2 Residential mortgage-backed securities 21.6 27.6 34.7 Commercial mortgage-backed securities 150.1 93.9 79.6 Other asset-backed securities 117.3 75.7 47.1 Redeemable preferred stocks 19.0 12.3 11.8 Total fixed maturities 882.0 661.9 422.9 Short-term investments 41.7 52.9 37.8 Total available-for-sale securities 923.7 714.8 460.7 Equity securities: Nonredeemable preferred stocks 61.8 45.9 44.1 Common equities 56.5 59.8 58.3 Total equity securities 118.3 105.7 102.4 Investment income 1,042.0 820.5 563.1 Investment expenses (24.6 ) (24.3 ) (23.9 ) Net investment income $ 1,017.4 $ 796.2 $ 539.2

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
	Dec. 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 December 31, 2019 Fixed maturities: U.S. government obligations $ 13,251.1 $ 0 $ 0 $ 13,251.1 $ 13,100.7 State and local government obligations 0 1,713.3 0 1,713.3 1,686.0 Corporate debt securities 0 7,067.7 0 7,067.7 6,860.3 Subtotal 13,251.1 8,781.0 0 22,032.1 21,647.0 Asset-backed securities: Residential mortgage-backed 0 627.5 0 627.5 625.0 Commercial mortgage-backed 0 5,076.2 0 5,076.2 5,020.7 Other asset-backed 0 5,179.5 0 5,179.5 5,164.7 Subtotal asset-backed securities 0 10,883.2 0 10,883.2 10,810.4 Redeemable preferred stocks: Financials 0 51.7 0 51.7 51.5 Utilities 0 11.1 0 11.1 10.0 Industrials 11.1 121.1 0 132.2 124.2 Subtotal redeemable preferred stocks 11.1 183.9 0 195.0 185.7 Total fixed maturities 13,262.2 19,848.1 0 33,110.3 32,643.1 Short-term investments 1,797.4 1.4 0 1,798.8 1,798.8 Total available-for-sale securities 15,059.6 19,849.5 0 34,909.1 34,441.9 Equity securities: Nonredeemable preferred stocks: Financials 77.4 850.7 27.1 955.2 891.3 Utilities 0 42.3 0 42.3 39.9 Industrials 0 25.4 16.0 41.4 40.1 Subtotal nonredeemable preferred stocks 77.4 918.4 43.1 1,038.9 971.3 Common equities: Common stocks 3,306.0 0 0 3,306.0 1,125.2 Other risk investments 0 0 0.3 0.3 0.3 Subtotal common equities 3,306.0 0 0.3 3,306.3 1,125.5 Total equity securities 3,383.4 918.4 43.4 4,345.2 2,096.8 Total portfolio $ 18,443.0 $ 20,767.9 $ 43.4 $ 39,254.3 $ 36,538.7 Debt $ 0 $ 5,119.6 $ 0 $ 5,119.6 $ 4,407.1 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 fixed maturities and short-term 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 available-for-sale 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
Summary of Changes in Fair Value Associated With Level 3 Assets	The following tables provide a summary of changes in fair value associated with Level 3 assets for the years ended December 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 Dec. 31, 2019 Equity securities: Nonredeemable preferred stocks: Financials $ 25.1 $ 0 $ 2.0 $ 0 $ 0 $ 0 $ 0 $ 27.1 Industrials 5.0 0 10.0 0 0 1.0 0 16.0 Common equities: Other risk investments 0.3 0 0 0 0 0 0 0.3 Total Level 3 securities $ 30.4 $ 0 $ 12.0 $ 0 $ 0 $ 1.0 $ 0 $ 43.4 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 Dec. 31, 2018 Equity securities: Nonredeemable preferred stocks: Financials $ 0 $ 0 $ 25.1 $ 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 $ 5.3 $ 0 $ 25.1 $ 0 $ 0 $ 0 $ 0 $ 30.4
Summary of Quantitative Information about Level 3 Fair Value Measurements	The following tables provide a summary of the quantitative information about Level 3 fair value measurements for our applicable securities at December 31 : Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at Dec. 31, 2019 Valuation Technique Unobservable Input Unobservable Input Assumption Equity securities: Nonredeemable preferred stocks: Financials $ 27.1 Pricing firm Recent transaction price 9.0 Industrials 6.0 Pricing firm Performance-based transaction price adjustment 4.8 Industrials 1 10.0 Internal price Unadjusted purchase price 4.9 Subtotal Level 3 securities 43.1 Pricing exemption securities 0.3 Total Level 3 securities $ 43.4 1 The security was purchased in November 2019. 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 9.0 Industrials 5.0 Internal price Price-to-sales ratio 5.5 Subtotal Level 3 securities 30.1 Pricing exemption securities 0.3 Total Level 3 securities $ 30.4 1 The security was purchased in December 2018.

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Table	Debt at December 31, consisted of: 2019 2018 (millions) Carrying Value Fair Value Carrying Value Fair Value 3.75% Senior Notes due 2021 (issued: $500.0, August 2011) $ 499.4 $ 515.6 $ 499.1 $ 506.5 2.45% Senior Notes due 2027 (issued: $500.0, August 2016) 496.9 501.5 496.5 455.5 6 5/8% Senior Notes due 2029 (issued: $300.0, March 1999) 296.6 392.5 296.4 368.5 4.00% Senior Notes due 2029 (issued: $550.0, October 2018) 545.0 614.3 544.5 562.4 6.25% Senior Notes due 2032 (issued: $400.0, November 2002) 395.7 552.6 395.5 496.6 4.35% Senior Notes due 2044 (issued: $350.0, April 2014) 346.7 417.0 346.6 350.2 3.70% Senior Notes due 2045 (issued: $400.0, January 2015) 395.4 434.2 395.3 366.7 4.125% Senior Notes due 2047 (issued: $850.0, April 2017) 841.6 986.1 841.4 831.9 4.20% Senior Notes due 2048 (issued: $600.0, March 2018) 589.8 705.8 589.6 594.0 Total $ 4,407.1 $ 5,119.6 $ 4,404.9 $ 4,532.3
Aggregate Principal Payments on Debt Outstanding	Aggregate required principal payments on debt outstanding at December 31, 2019 , are as follows: (millions) Year Payments 2020 $ 0 2021 500 2022 0 2023 0 2024 0 Thereafter 3,950 Total $ 4,450
Cash Flow Hedging [Member]
Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges Included in Accumulated Other Comprehensive Income	The following table shows the original gain (loss) recognized at debt issuance and the unamortized balance at December 31, 2019 , on a pretax basis: (millions) Unrealized Gain (Loss) at Debt Issuance Unamortized Balance at December 31, 2019 3.75% Senior Notes $ (5.1 ) $ (1.0 ) 6 5/8% Senior Notes (4.2 ) (2.4 ) 6.25% Senior Notes 5.1 3.3 4.35% Senior Notes (1.6 ) (1.4 ) 3.70% Senior Notes (12.9 ) (11.7 ) 4.125% Senior Notes (8.0 ) (7.6 )

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Components of Income Tax Provision	The components of our income tax provision were as follows: (millions) 2019 2018 2017 Current tax provision Federal $ 1,104.7 $ 673.1 $ 680.9 State 27.3 21.5 12.8 Deferred tax expense (benefit) Federal 45.3 (145.9 ) (149.4 ) State 3.0 (6.1 ) (3.5 ) Total income tax provision $ 1,180.3 $ 542.6 $ 540.8
Reconciliation of Provision (Benefit) for Income Taxes Reported in Consolidated Statements of Income with Tax at Statutory Rate	The provision for income taxes in the accompanying consolidated statements of comprehensive income differed from the statutory rate as follows: (millions) 2019 2018 2017 Income before income taxes $ 5,160.3 $ 3,163.6 $ 2,138.9 Tax at statutory federal rate $ 1,083.7 21 % $ 664.4 21 % $ 748.6 35 % Tax effect of: Reversal of prior year tax credits 163.2 3 0 0 0 0 Tax credits 1 (43.9 ) (1 ) (76.3 ) (2 ) (52.4 ) (2 ) Stock-based compensation (25.9 ) (1 ) (25.1 ) (1 ) (25.1 ) (1 ) Tax-deductible dividends (14.6 ) 0 (14.6 ) (1 ) (9.7 ) 0 Dividends received deduction 2,3 (10.4 ) 0 (9.7 ) 0 (20.7 ) (1 ) Exempt interest income 3 (3.6 ) 0 (5.9 ) 0 (16.9 ) (1 ) Net deferred tax liability revaluation 4 0 0 0 0 (99.5 ) (5 ) Nondeductible compensation expense 5 8.1 0 (0.2 ) 0 10.1 0 State income taxes, net of federal taxes 24.0 1 12.2 0 6.0 0 Other items, net (0.3 ) 0 (2.2 ) 0 0.4 0 Total income tax provision $ 1,180.3 23 % $ 542.6 17 % $ 540.8 25 % 1 Includes $38.1 million , $71.0 million , and $48.7 million for 2019 , 2018 , and 2017 , respectively, of benefits on investments in federal renewable energy tax credit funds. 2 2019 and 2018 amounts reflect a dividends received deduction percentage of 50% under the 2017 Tax Act. In 2017, the deduction percentage was 70%. 3 2019 and 2018 amounts reflect a proration percentage of 25% for such income attributable to investments held by our insurance companies. In 2017, the proration percentage was 15%. 4 Pursuant to the 2017 Tax Act. 5 Decrease in 2018 reflects our updated interpretation regarding compensation that qualifies for deduction under the 2017 Tax Act based on additional guidance issued. See further discussion below.
Components of Net Deferred Tax Assets	The following table shows the components of the net deferred tax asset (liability) at December 31, 2019 and 2018 , respectively. (millions) 2019 2018 Federal deferred tax assets: Unearned premiums reserve $ 498.2 $ 439.9 Non-deductible accruals 181.8 169.3 Loss and loss adjustment expense reserves 153.3 134.6 Operating lease liabilities 42.3 0 Net unrealized losses on fixed-maturity securities 0 28.2 Hedges on forecasted transactions 4.4 4.6 Other 15.3 16.2 Federal deferred tax liabilities: Net holding period gains on equity securities (472.2 ) (316.8 ) Deferred acquisition costs (221.9 ) (199.8 ) Property and equipment (108.6 ) (85.7 ) Net unrealized gains on fixed-maturity securities (96.5 ) 0 Loss and loss adjustment expense reserve transition adjustment (47.2 ) (58.5 ) Operating lease assets (42.3 ) 0 Intangible assets (38.9 ) (52.2 ) Investment basis differences (1.1 ) (43.3 ) Prepaid expenses (4.8 ) (4.7 ) Other (8.3 ) (8.9 ) Net federal deferred tax asset (liability) (146.5 ) 22.9 Net state deferred tax asset 14.0 20.3 Net deferred tax asset (liability) $ (132.5 ) $ 43.2

Loss And Loss Adjustment Expe_2

Loss And Loss Adjustment Expense Reserves (Tables)	12 Months Ended
	Dec. 31, 2019
Insurance [Abstract]
Activity in Loss and Loss Adjustment Expense Reserves	Activity in the loss and LAE reserves is summarized as follows: (millions) 2019 2018 2017 Balance at January 1 $ 15,400.8 $ 13,086.9 $ 11,368.0 Less reinsurance recoverables on unpaid losses 2,572.7 2,170.1 1,801.0 Net balance at January 1 12,828.1 10,916.8 9,567.0 Incurred related to: Current year 25,238.2 21,632.5 18,782.1 Prior years 232.3 88.5 25.9 Total incurred 25,470.5 21,721.0 18,808.0 Paid related to: Current year 16,105.0 13,792.1 12,201.5 Prior years 7,300.4 6,017.6 5,256.7 Total paid 23,405.4 19,809.7 17,458.2 Net balance at December 31 14,893.2 12,828.1 10,916.8 Plus reinsurance recoverables on unpaid losses 3,212.2 2,572.7 2,170.1 Balance at December 31 $ 18,105.4 $ 15,400.8 $ 13,086.9
Short-duration Insurance Contracts, Claims Development	Only 2019 is audited; all prior years are considered required supplementary information and, therefore, are unaudited. Expected development on our case reserves is excluded from the IBNR reserves on our vehicle businesses, as discussed above. For the Property business, the IBNR reserves include expected case development based on the methodology used in establishing the case reserves for that segment. The cumulative number of incurred claims are based on accident coverages (e.g., bodily injury, collision, comprehensive, personal injury protection, property damage) related to opened claims. Coverage counts related to claims closed without payment are excluded from the cumulative number of incurred claims. Personal Lines - Agency - Liability ($ in millions) As of Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance December 31, 2019 For the years ended December 31, Total of IBNR Liabilities Plus Expected Development on Reported Claims Cumulative Number of Incurred Claim Counts Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 3,774.9 $ 3,773.8 $ 3,798.8 $ 3,815.6 $ 3,776.0 $ 0 704,986 2016 4,082.9 4,130.0 4,152.0 4,177.3 62.3 740,385 2017 4,474.8 4,485.8 4,511.1 82.5 779,082 2018 5,141.8 5,182.1 224.2 854,146 2019 5,885.0 871.8 909,050 Total $ 23,531.5 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance For the years ended December 31, Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 1,793.1 $ 2,976.0 $ 3,416.5 $ 3,623.3 $ 3,715.4 2016 1,941.6 3,231.5 3,723.1 3,969.5 2017 2,074.0 3,478.5 4,048.5 2018 2,378.0 4,028.7 2019 2,715.2 Total $ 18,477.3 All outstanding liabilities before 2015, net of reinsurance 1 63.2 Liabilities for claims and claim adjustment expenses, net of reinsurance $ 5,117.4 1 Required supplementary information (unaudited) Personal Lines - Agency - Physical Damage ($ in millions) As of Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance December 31, 2019 For the years ended December 31, Total of IBNR Liabilities Plus Expected Development on Reported Claims Cumulative Number of Incurred Claim Counts Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 2,136.8 $ 2,137.2 $ 2,134.4 $ 2,131.5 $ 2,134.5 $ 0 1,336,520 2016 2,423.4 2,398.9 2,401.8 2,400.1 (3.8 ) 1,399,077 2017 2,635.5 2,638.5 2,643.5 (2.9 ) 1,514,531 2018 2,819.0 2,822.6 (12.3 ) 1,694,380 2019 3,277.9 (167.6 ) 1,872,822 Total $ 13,278.6 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance For the years ended December 31, Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 2,106.2 $ 2,138.1 $ 2,134.4 $ 2,134.1 $ 2,133.6 2016 2,391.0 2,406.9 2,402.1 2,402.2 2017 2,599.8 2,643.2 2,640.9 2018 2,769.1 2,827.4 2019 3,242.5 Total $ 13,246.6 All outstanding liabilities before 2015, net of reinsurance 1 0.4 Liabilities for claims and claim adjustment expenses, net of reinsurance $ 32.4 1 Required supplementary information (unaudited) Personal Lines - Direct - Liability ($ in millions) As of Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance December 31, 2019 For the years ended December 31, Total of IBNR Liabilities Plus Expected Development on Reported Claims Cumulative Number of Incurred Claim Counts Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 3,330.5 $ 3,328.3 $ 3,354.2 $ 3,399.3 $ 3,368.7 $ 0 659,243 2016 3,819.0 3,843.9 3,871.2 3,897.8 53.9 735,653 2017 4,209.5 4,209.9 4,229.3 70.9 772,712 2018 4,904.8 4,980.9 204.4 868,604 2019 5,756.5 811.4 953,154 Total $ 22,233.2 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance For the years ended December 31, Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 1,545.2 $ 2,615.0 $ 3,021.0 $ 3,238.2 $ 3,323.1 2016 1,780.6 2,991.1 3,476.9 3,714.6 2017 1,912.6 3,255.2 3,808.3 2018 2,235.1 3,863.5 2019 2,630.3 Total $ 17,339.8 All outstanding liabilities before 2015, net of reinsurance 1 43.4 Liabilities for claims and claim adjustment expenses, net of reinsurance $ 4,936.8 1 Required supplementary information (unaudited) Personal Lines - Direct - Physical Damage ($ in millions) As of Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance December 31, 2019 For the years ended December 31, Total of IBNR Liabilities Plus Expected Development on Reported Claims Cumulative Number of Incurred Claim Counts Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 2,110.7 $ 2,097.7 $ 2,093.5 $ 2,090.8 $ 2,093.9 $ 0 1,540,071 2016 2,521.0 2,475.4 2,477.7 2,475.6 (4.3 ) 1,676,343 2017 2,750.6 2,743.7 2,749.0 (4.1 ) 1,791,190 2018 3,202.3 3,181.9 (18.8 ) 2,069,525 2019 3,787.9 (237.7 ) 2,282,681 Total $ 14,288.3 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance For the years ended December 31, Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 2,094.7 $ 2,100.1 $ 2,094.7 $ 2,093.7 $ 2,093.1 2016 2,505.0 2,485.8 2,479.3 2,478.5 2017 2,742.1 2,753.5 2,748.4 2018 3,170.0 3,193.8 2019 3,782.6 Total $ 14,296.4 All outstanding liabilities before 2015, net of reinsurance 1 0.4 Liabilities for claims and claim adjustment expenses, net of reinsurance $ (7.7 ) 1 Required supplementary information (unaudited) Commercial Lines - Liability ($ in millions) As of Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance December 31, 2019 For the years ended December 31, Total of IBNR Liabilities Plus Expected Development on Reported Claims Cumulative Number of Incurred Claim Counts Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 897.6 $ 911.1 $ 914.8 $ 899.7 $ 891.3 $ 0 77,819 2016 1,185.8 1,204.8 1,231.1 1,238.9 17.2 92,684 2017 1,374.1 1,366.6 1,393.3 30.8 97,297 2018 1,700.8 1,736.5 97.7 111,146 2019 2,103.1 343.7 124,829 Total $ 7,363.1 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance For the years ended December 31, Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 238.4 $ 501.5 $ 675.0 $ 786.3 $ 848.9 2016 298.6 639.9 886.0 1,073.3 2017 325.8 712.9 1,027.3 2018 382.7 913.4 2019 455.4 Total $ 4,318.3 All outstanding liabilities before 2015, net of reinsurance 1 36.0 Liabilities for claims and claim adjustment expenses, net of reinsurance $ 3,080.8 1 Required supplementary information (unaudited) Commercial Lines - Physical Damage ($ in millions) As of Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance December 31, 2019 For the years ended December 31, Total of IBNR Liabilities Plus Expected Development on Reported Claims Cumulative Number of Incurred Claim Counts Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 274.4 $ 274.1 $ 273.5 $ 272.4 $ 272.4 $ 0 62,593 2016 379.6 379.8 378.2 377.8 (0.7 ) 74,193 2017 415.4 412.1 411.0 (0.6 ) 77,163 2018 475.0 478.2 (2.4 ) 82,183 2019 577.8 (14.3 ) 91,920 Total $ 2,117.2 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance For the years ended December 31, Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 248.5 $ 271.9 $ 272.0 $ 272.2 $ 272.3 2016 336.7 376.9 376.8 377.5 2017 369.0 409.4 409.2 2018 426.0 475.1 2019 516.9 Total $ 2,051.0 All outstanding liabilities before 2015, net of reinsurance 1 0.4 Liabilities for claims and claim adjustment expenses, net of reinsurance $ 66.6 1 Required supplementary information (unaudited) Property Business ($ in millions) As of Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance December 31, 2019 For the years ended December 31, Total of IBNR Liabilities Plus Expected Development on Reported Claims Cumulative Number of Incurred Claim Counts Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 460.0 $ 416.5 $ 403.6 $ 398.8 $ 396.3 $ 0.9 41,998 2016 568.6 541.2 537.1 536.5 5.1 53,665 2017 672.8 680.9 683.4 4.1 72,728 2018 839.0 845.2 34.9 63,243 2019 971.7 160.2 66,824 Total $ 3,433.1 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance For the years ended December 31, Accident Year 2015 1 2016 1 2017 1 2018 1 2019 2015 $ 280.3 $ 372.8 $ 383.5 $ 390.1 $ 393.5 2016 415.2 498.2 516.9 526.4 2017 506.7 647.1 670.1 2018 595.9 781.2 2019 708.0 Total $ 3,079.2 All outstanding liabilities before 2015, net of reinsurance 1 3.3 Liabilities for claims and claim adjustment expenses, net of reinsurance $ 357.2 1 Required supplementary information (unaudited)
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability	The following table reconciles the net incurred and paid claims development tables to the liability for claims and claim adjustment expenses: (millions) 2019 2018 Net outstanding liabilities Personal Lines Agency, Liability $ 5,117.4 $ 4,509.0 Agency, Physical Damage 32.4 43.3 Direct, Liability 4,936.8 4,258.6 Direct, Physical Damage (7.7 ) 18.4 Commercial Lines Liability 3,080.8 2,504.2 Physical Damage 66.6 53.9 Property 357.2 314.7 Other business 30.8 42.9 Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance 13,614.3 11,745.0 Reinsurance recoverable on unpaid claims Personal Lines Agency, Liability 930.7 836.8 Agency, Physical Damage 0 0 Direct, Liability 1,314.1 1,070.4 Direct, Physical Damage 0 0 Commercial Lines Liability 482.6 287.4 Physical Damage 0.5 0 Property 184.1 145.4 Other business 288.1 222.1 Total reinsurance recoverable on unpaid claims 3,200.1 2,562.1 Unallocated claims adjustment expense related to: Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance 1,278.9 1,083.1 Reinsurance recoverable on unpaid claims 12.1 10.6 Total gross liability for unpaid claims and claim adjustment expense $ 18,105.4 $ 15,400.8
Short-duration Insurance Contracts, Schedule of Historical Claims Duration	The following table shows the average historical claims duration as of December 31, 2019 : (Required Supplementary Information - Unaudited) Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 Personal Lines Agency, Liability 46.3% 31.3% 12.1% 5.7% 2.4% Agency, Physical Damage 98.7 1.5 (0.2) 0 0 Direct, Liability 45.4 31.9 12.6 6.3 2.5 Direct, Physical Damage 100.0 0.2 (0.2) 0 0 Commercial Lines Liability 23.1 28.9 20.8 14.0 7.0 Physical Damage 89.6 9.9 0 0.1 0 Property 73.0 20.4 3.2 1.7 0.9

Reinsurance (Tables)

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2019
Reinsurance Disclosures [Abstract]
Effect of Reinsurance on Premiums Written and Earned	The effect of reinsurance on premiums written and earned for the years ended December 31, was as follows: 2019 2018 2017 (millions) Written Earned Written Earned Written Earned Direct premiums $ 39,222.0 $ 37,519.7 $ 33,753.1 $ 31,970.2 $ 27,860.7 $ 26,425.7 Ceded premiums: Regulated (711.1 ) (670.8 ) (596.4 ) (557.5 ) (505.9 ) (479.6 ) Non-Regulated (933.0 ) (656.5 ) (546.8 ) (479.4 ) (222.7 ) (216.2 ) Total ceded premiums (1,644.1 ) (1,327.3 ) (1,143.2 ) (1,036.9 ) (728.6 ) (695.8 ) Net premiums $ 37,577.9 $ 36,192.4 $ 32,609.9 $ 30,933.3 $ 27,132.1 $ 25,729.9
Prepaid Reinsurance Premiums and Reinsurance Recoverables	Our reinsurance recoverables and prepaid reinsurance premiums were comprised of the following at December 31: Reinsurance Recoverables Prepaid Reinsurance Premiums ($ in millions) 2019 2018 2019 2018 Regulated: MCCA $ 2,247.1 67 % $ 1,903.9 71 % $ 71.8 12 % $ 55.3 18 % CAIP 332.4 10 254.7 9 93.8 15 72.9 24 FHCF 1 86.0 3 18.5 1 0 0 0 0 NCRF 84.4 2 78.1 3 33.8 5 34.0 11 NFIP 11.6 0 27.8 1 58.7 9 55.9 18 Other 3.1 0 2.9 0 1.0 0 0.6 0 Total Regulated 2,764.6 82 2,285.9 85 259.1 41 218.7 71 Non-Regulated: Commercial Lines 459.5 14 254.2 10 352.9 56 79.2 25 Property 146.8 4 147.7 5 14.5 3 11.8 4 Other 8.0 0 8.3 0 0 0 0 0 Total Non-Regulated 614.3 18 410.2 15 367.4 59 91.0 29 Total $ 3,378.9 100 % $ 2,696.1 100 % $ 626.5 100 % $ 309.7 100 % 1 Prior year amounts were reclassified from "Other" to conform to the current year presentation.

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2019
Amounts Charged to Income for Employees Incentive Compensation Plans	The amounts charged to expense for Progressive and ARX incentive compensation plans for the years ended December 31, were: 2019 2018 2017 (millions) Pretax After Tax Pretax After Tax Pretax After Tax Non-equity incentive plans – cash $ 598.4 $ 472.7 $ 539.5 $ 426.2 $ 461.3 $ 299.8 Equity incentive plans: Equity awards 90.1 71.2 76.2 60.2 92.9 60.4 Liability awards 0.1 0.1 1.0 0.8 2.5 1.6
Assets Held in Deferral Plan Irrevocable Grantor Trust Account	The Deferral Plan Irrevocable Grantor Trust account held the following assets at December 31: (millions) 2019 2018 Progressive common shares 1 $ 121.6 $ 114.7 Other investment funds 2 151.2 124.0 Total $ 272.8 $ 238.7 1 Included 3.2 million and 3.6 million common shares as of December 31, 2019 and 2018 , respectively, to be distributed in common shares, and are reported at grant date fair value. 2 Amount is included in other assets on the consolidated balance sheets.
Employee
Summary of Restricted Stock Activity	A summary of all employee restricted equity award activity during the years ended December 31, follows: 2019 2018 2017 Restricted Equity Awards Number of Shares 1 Weighted Average Grant Date Fair Value Number of Shares 1 Weighted Average Grant Date Fair Value Number of Shares 1 Weighted Average Grant Date Fair Value Beginning of year 4,856,356 $ 38.56 5,858,848 $ 30.47 6,951,373 $ 26.18 Add (deduct): Granted 2 1,835,145 49.61 1,876,109 45.55 2,383,475 32.01 Vested (2,691,337 ) 31.85 (2,811,070 ) 26.41 (3,220,671 ) 22.53 Forfeited (121,087 ) 43.98 (67,531 ) 36.10 (255,329 ) 28.03 End of year 3,4 3,879,077 $ 48.28 4,856,356 $ 38.56 5,858,848 $ 30.47 1 Includes restricted stock units. All performance-based awards are included at their target amounts. 2 We reinvest dividend equivalents on restricted stock units. For 2019 , 2018 , and 2017 , the number of units “granted” shown in the table above includes 210,159 , 144,668 , and 157,396 of dividend equivalent units, respectively, at a weighted average grant date fair value of $0 , since the dividends were factored into the grant date fair value of the original grant. 3 At December 31, 2019 , the number of shares included 726,712 performance-based units at their target amounts. We expect 1,740,712 units to vest based upon our current estimates of the likelihood of achieving the pre-determined performance goals applicable to each award. 4 At December 31, 2019 , the total unrecognized compensation cost related to unvested equity awards was $95.9 million , which includes performance-based awards at their currently estimated vesting value. This compensation expense will be recognized into the consolidated statements of comprehensive income over the weighted average vesting period of 2.3 years .
Director
Summary of Restricted Stock Activity	A summary of all directors’ restricted stock activity during the years ended December 31, follows: 2019 2018 2017 Restricted Stock Number of Shares Weighted Average Grant Date Fair Value Number of Shares Weighted Average Grant Date Fair Value Number of Shares Weighted Average Grant Date Fair Value Beginning of year 41,706 $ 62.23 53,284 $ 40.54 55,839 $ 33.24 Add (deduct): Granted 38,451 73.43 41,706 62.23 53,284 40.54 Vested (41,706 ) 62.23 (53,284 ) 40.54 (55,839 ) 33.24 End of year 1 38,451 $ 73.43 41,706 $ 62.23 53,284 $ 40.54 1 At December 31, 2019, 2018, and 2017, the remaining unrecognized compensation cost related to restricted stock awards was $0.8 million , $0.9 million , and $0.7 million , respectively.
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding and Exercisable [Table Text Block]	A summary of all ARX employee stock option activity during the years ended December 31, follows: 2019 2018 2017 Options Outstanding Number of Shares Weighted Average Number of Shares Weighted Average Number of Shares Weighted Average Beginning of year 16,067 $ 588.15 22,550 $ 564.60 24,995 $ 526.46 Add (deduct): Exercised 1 (5,329 ) 353.67 (6,483 ) 506.26 (2,445 ) 174.65 Forfeited (300 ) 803.64 0 0 0 0 End of year 10,438 $ 701.66 16,067 $ 588.15 22,550 $ 564.60 Exercisable, end of year 10,438 $ 701.66 13,967 $ 562.17 17,950 $ 517.75 1 At the time of exercise, the value earned by the option holders was $5.9 million , $6.2 million , and $2.9 million in 2019, 2018, and 2017, respectively. 2019 2018 2017 Non-Vested Options Outstanding Number of Shares Weighted Average Number of Shares Weighted Average Number of Shares Weighted Average Beginning of year 2,100 $ 760.93 4,600 $ 747.45 8,000 $ 712.74 Add (deduct): Vested (1,800 ) 753.82 (2,500 ) 736.12 (3,400 ) 665.79 Forfeited (300 ) 803.64 0 0 0 0 End of year 0 $ 0 2,100 $ 760.93 4,600 $ 747.45

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Reconciliation of Revenue and Operating Income from Segments to Consolidated	Following are the operating results for the years ended December 31: 2019 2018 2017 (millions) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Personal Lines Agency $ 14,904.1 $ 1,673.2 $ 13,017.2 $ 1,435.7 $ 11,177.6 $ 839.6 Direct 15,305.9 1,181.4 13,017.5 1,088.5 10,769.6 683.7 Total Personal Lines 1 30,210.0 2,854.6 26,034.7 2,524.2 21,947.2 1,523.3 Commercial Lines 4,427.6 458.8 3,610.9 478.6 2,793.9 214.1 Property 2 1,554.8 (26.1 ) 1,287.7 (88.7 ) 988.8 (50.3 ) Other indemnity 0 0 0 0.9 0 (0.2 ) Total underwriting operations 36,192.4 3,287.3 30,933.3 2,915.0 25,729.9 1,686.9 Fees and other revenues 3 563.7 NA 472.2 NA 370.6 NA Service businesses 195.0 16.1 158.5 24.4 126.8 17.3 Investments 4 2,071.2 2,046.6 415.0 390.7 612.7 588.8 Other gains (losses) 0 0 0 0 (1.0 ) (1.0 ) Interest expense NA (189.7 ) NA (166.5 ) NA (153.1 ) Consolidated total $ 39,022.3 $ 5,160.3 $ 31,979.0 $ 3,163.6 $ 26,839.0 $ 2,138.9 NA = Not applicable 1 Personal auto insurance accounted for 94% of the total Personal Lines segment net premiums earned in 2019 and 2018, compared to 93% in 2017 ; 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 During 2019 , 2018 , and 2017 , pretax profit (loss) includes $66.3 million , $72.0 million , and $66.2 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 are allocated to operating segments. 4 Revenues represent recurring investment income and total net realized gains (losses) on securities; pretax profit is net of investment expenses.
Underwriting Margins and Combined Ratios for our Underwriting Operations	Following are the underwriting margins and combined ratios for our underwriting operations for the years ended December 31: 2019 2018 2017 Underwriting Margin Combined Ratio Underwriting Margin Combined Ratio Underwriting Margin Combined Ratio Personal Lines Agency 11.2 % 88.8 11.0 % 89.0 7.5 % 92.5 Direct 7.7 92.3 8.4 91.6 6.3 93.7 Total Personal Lines 9.5 90.5 9.7 90.3 6.9 93.1 Commercial Lines 10.4 89.6 13.3 86.7 7.7 92.3 Property 1 (1.7 ) 101.7 (6.9 ) 106.9 (5.1 ) 105.1 Total underwriting operations 9.1 90.9 9.4 90.6 6.6 93.4 1 Included in 2019 , 2018 , and 2017 , are 4.3 points, 5.6 points, and 6.7 points, respectively, of amortization expense predominately associated with the acquisition of a controlling interest in ARX.

Other Comprehensive Income (L_2

Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 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, for the years ended December 31, 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 Foreign currency translation adjustment (Income) loss attributable to NCI Balance at December 31, 2018 $ (153.0 ) $ 32.1 $ (120.9 ) $ (105.6 ) $ (17.2 ) $ 0 $ 1.9 Other comprehensive income (loss) before reclassifications: Investment securities 825.8 (174.9 ) 650.9 650.9 0 0 0 Forecasted transactions 0 0 0 0 0 0 0 Foreign currency translation adjustment 0 0 0 0 0 0 0 (Income) loss attributable to noncontrolling interest (NCI) (5.9 ) 1.3 (4.6 ) 0 0 0 (4.6 ) Total other comprehensive income (loss) before reclassifications 819.9 (173.6 ) 646.3 650.9 0 0 (4.6 ) 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 0 Net realized gains (losses) on securities 232.2 (47.7 ) 184.5 184.5 0 0 0 Other gains (losses) 0 0 0 0 0 0 0 Interest expense (1.0 ) 0.2 (0.8 ) 0 (0.8 ) 0 0 Total reclassification adjustment for amounts realized in net income 231.2 (47.5 ) 183.7 184.5 (0.8 ) 0 0 Total other comprehensive income (loss) 588.7 (126.1 ) 462.6 466.4 0.8 0 (4.6 ) Balance at December 31, 2019 $ 435.7 $ (94.0 ) $ 341.7 $ 360.8 $ (16.4 ) $ 0 $ (2.7 ) Components of Changes in Accumulated Other Comprehensive Income (after tax) (millions) Pretax total Total tax After tax total Total net Net Foreign (Income) loss attributable to NCI Balance at December 31, 2017 $ 1,977.8 $ (695.6 ) $ 1,282.2 $ 1,295.0 $ (14.8 ) $ 0 $ 2.0 Cumulative effect adjustment 1 (2,006.0 ) 705.8 (1,300.2 ) (1,300.2 ) 0 0 0 Reclassification of disproportionate amounts 2 (4.3 ) (3.4 ) (7.7 ) (1.1 ) (3.2 ) 0 (3.4 ) Adjusted balance at December 31, 2017 (32.5 ) 6.8 (25.7 ) (6.3 ) (18.0 ) 0 (1.4 ) Other comprehensive income (loss) before reclassifications: Investment securities (224.1 ) 47.0 (177.1 ) (177.1 ) 0 0 0 Forecasted transactions 0 0 0 0 0 0 0 Foreign currency translation adjustment 0 0 0 0 0 0 0 (Income) loss attributable to noncontrolling interest (NCI) 4.3 (1.0 ) 3.3 0 0 0 3.3 Total other comprehensive income (loss) before reclassifications (219.8 ) 46.0 (173.8 ) (177.1 ) 0 0 3.3 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 0 Net realized gains (losses) on securities (98.3 ) 20.5 (77.8 ) (77.8 ) 0 0 0 Other gains (losses) 0 0 0 0 0 0 0 Interest expense (1.0 ) 0.2 (0.8 ) 0 (0.8 ) 0 0 Total reclassification adjustment for amounts realized in net income (99.3 ) 20.7 (78.6 ) (77.8 ) (0.8 ) 0 0 Total other comprehensive income (loss) (120.5 ) 25.3 (95.2 ) (99.3 ) 0.8 0 3.3 Balance at December 31, 2018 $ (153.0 ) $ 32.1 $ (120.9 ) $ (105.6 ) $ (17.2 ) $ 0 $ 1.9 1 Reflects the fair value changes on equity securities as of December 31, 2017, which are reported as realized gains (losses) under the new accounting guidance. See Note 1 – Reporting and Accounting Policies for additional information. 2 Reflects the effect of the change in the U.S. federal tax rate on our available-for-sale fixed-maturity securities and our hedges on forecasted transactions as of December 31, 2017 (see Note 1 – Reporting and Accounting Policies for additional information) and the adjustment to reflect the change in value on (income) loss attributable to NCI in conjunction with the "put" transaction (see Note 15 – Redeemable Noncontrolling Interest for additional information). Components of Changes in Accumulated Other Comprehensive Income (after tax) (millions) Pretax total Total tax After tax total Total net Net Foreign (Income) loss attributable to NCI Total at December 31, 2016 $ 1,439.5 $ (506.1 ) $ 933.4 $ 939.6 $ (9.4 ) $ (1.1 ) $ 4.3 Other comprehensive income (loss) before reclassifications: Investment securities 636.9 (224.0 ) 412.9 412.9 0 0 0 Forecasted transactions (8.0 ) 2.8 (5.2 ) 0 (5.2 ) 0 0 Foreign currency translation adjustment 0.4 (0.1 ) 0.3 0 0 0.3 0 (Income) loss attributable to noncontrolling interest (NCI) (3.5 ) 1.2 (2.3 ) 0 0 0 (2.3 ) Total other comprehensive income (loss) before reclassifications 625.8 (220.1 ) 405.7 412.9 (5.2 ) 0.3 (2.3 ) Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (14.9 ) 5.3 (9.6 ) (9.6 ) 0 0 0 Net realized gains (losses) on securities 103.3 (36.2 ) 67.1 67.1 0 0 0 Other gains (losses) 1 (1.2 ) 0.4 (0.8 ) 0 0 (0.8 ) 0 Interest expense 0.3 (0.1 ) 0.2 0 0.2 0 0 Total reclassification adjustment for amounts realized in net income 87.5 (30.6 ) 56.9 57.5 0.2 (0.8 ) 0 Total other comprehensive income (loss) 538.3 (189.5 ) 348.8 355.4 (5.4 ) 1.1 (2.3 ) Total at December 31, 2017 $ 1,977.8 $ (695.6 ) $ 1,282.2 $ 1,295.0 $ (14.8 ) $ 0 $ 2.0

(Tables)

(Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Minimum Commitments under Noncancelable Operating Lease Agreements	At December 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: (millions) Commitments 2020 $ 77.6 2021 64.3 2022 33.1 2023 18.5 2024 11.9 Thereafter 6.1 Total 211.5 Interest (10.0 ) Present value of lease liabilities $ 201.5 Weighted-average remaining term 3.3 years Weighted-average discount rate 3.0 %
Expense Incurred for Leases	The operating lease expense for the years ended December 31, was as follows: (millions) Expense 2019 $ 102.0 2018 77.3 2017 77.2
Schedule Of Operating Lease Obligations [Table Text Block]	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

Dividends (Tables)

Dividends (Tables)	12 Months Ended
	Dec. 31, 2019
Dividends [Abstract]
Dividends	Following is a summary of our common and preferred share dividends that were declared and/or paid in the last three years: (millions, except per share amounts) Amount Declared Payable Per Share Accrued 1 Common - Annual Variable Dividends: December 2019 January 2020 $ 2.25 $ 1,316.9 December 2018 February 2019 2.5140 1,467.9 December 2017 February 2018 1.1247 655.1 December 2016 February 2017 0.6808 395.4 Common - Quarterly Dividends: December 2019 January 2020 0.10 58.5 August 2019 October 2019 0.10 58.5 May 2019 July 2019 0.10 58.4 February 2019 April 2019 0.10 58.4 Preferred Dividends: August 2019 September 2019 26.875 13.4 February 2019 March 2019 26.875 13.4 August 2018 September 2018 27.024 13.5 1 The accrual is based on an estimate of shares outstanding as of the record date and is recorded as a component of accounts payable, accrued expenses, and other liabilities on the consolidated balance sheets.

Redeemable Noncontrolling Int_2

Redeemable Noncontrolling Interest (Tables)	12 Months Ended
	Dec. 31, 2019
Noncontrolling Interest [Abstract]
Redeemable Noncontrolling Interest [Table Text Block]	The changes in the components of redeemable NCI during the years ended December 31, were: (millions) 2019 2018 2017 Balance, beginning of year $ 214.5 $ 503.7 $ 483.7 Net income attributable to NCI 9.7 5.7 5.9 Other comprehensive income (loss) attributable to NCI 1 4.6 (3.3 ) 2.3 Exercise of stock options 7.7 9.4 3.4 Purchase/change of ARX minority shares (11.2 ) (298.2 ) 0 Change in redemption value 0.3 (2.8 ) 8.4 Balance, end of year $ 225.6 $ 214.5 $ 503.7 1 Amount represents the other comprehensive income (loss) attributable to NCI, as reflected on the consolidated statements of comprehensive income; changes in accumulated other comprehensive income (loss) attributable to NCI due to a change in the minority ownership percentage does not impact the amount of redeemable NCI.

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 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 as of December 31 : (millions) 2019 2018 Intangible assets subject to amortization $ 215.9 $ 282.2 Indefinite-lived intangible assets 1 12.4 12.4 Total $ 228.3 $ 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 both years presented.
Intangible Assets Subject to Amortization	Intangible assets subject to amortization for the years ended December 31, consisted of the following: (millions) 2019 2018 Category Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Policies in force $ 256.2 $ 173.9 $ 82.3 $ 256.2 $ 137.3 $ 118.9 Agency relationships 159.2 54.0 105.2 159.2 42.6 116.6 Software rights 79.1 50.7 28.4 79.1 40.1 39.0 Trade name 34.8 34.8 0 34.8 27.1 7.7 Total $ 529.3 $ 313.4 $ 215.9 $ 529.3 $ 247.1 $ 282.2
Amortization on Intangible Assets	The estimated aggregate amortization on these intangible assets for each of the next five years as of December 31, 2019 , follows: (millions) Year Amortization Expense 2020 $ 56.9 2021 56.6 2022 29.2 2023 13.5 2024 11.4

SCHEDULE I - Summary Of Inves_2

SCHEDULE I - Summary Of Investments - Other Than Investments in Related Parties Summary Of Investments - Other than Investments In Related Parties (Detail) $ in Millions	Dec. 31, 2019USD ($)
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	$ 36,538.7
Fair Value	39,254.3
Amount At Which Shown In The Balance Sheet	39,254.3
Fixed maturities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	32,643.1
Fair Value	33,110.3
Amount At Which Shown In The Balance Sheet	33,110.3
Fixed maturities | US Government Agencies and Authorities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	13,100.7
Fair Value	13,251.1
Amount At Which Shown In The Balance Sheet	13,251.1
Fixed maturities | State and local government obligations
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	1,686
Fair Value	1,713.3
Amount At Which Shown In The Balance Sheet	1,713.3
Fixed maturities | Public Utilities, Bonds
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	303.8
Fair Value	314.1
Amount At Which Shown In The Balance Sheet	314.1
Fixed maturities | Corporate And Other Debt Securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	6,556.5
Fair Value	6,753.6
Amount At Which Shown In The Balance Sheet	6,753.6
Fixed maturities | Asset-backed Securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	10,810.4
Fair Value	10,883.2
Amount At Which Shown In The Balance Sheet	10,883.2
Fixed maturities | Redeemable preferred stocks
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	185.7
Fair Value	195
Amount At Which Shown In The Balance Sheet	195
Equity securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	2,096.8
Fair Value	4,345.2
Amount At Which Shown In The Balance Sheet	4,345.2
Equity securities | Utilities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	81.6
Fair Value	172.7
Amount At Which Shown In The Balance Sheet	172.7
Equity securities | Financials
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	220.9
Fair Value	664.9
Amount At Which Shown In The Balance Sheet	664.9
Equity securities | Industrials
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	823
Fair Value	2,468.7
Amount At Which Shown In The Balance Sheet	2,468.7
Equity securities | Nonredeemable preferred stocks
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	971.3
Fair Value	1,038.9
Amount At Which Shown In The Balance Sheet	1,038.9
Short-term investments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	1,798.8
Fair Value	1,798.8
Amount At Which Shown In The Balance Sheet	$ 1,798.8

SCHEDULE II - Condensed Finan_2

SCHEDULE II - Condensed Financial Information Of Registrant Condensed Statements Of Comprehensive Income (Parent Company) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues
Total revenues		$ 39,022.3	$ 31,979	$ 26,839
Expenses
Interest expense		189.7	166.5	153.1
Total expenses		33,862	28,815.4	24,700.1
Income before income taxes		5,160.3	3,163.6	2,138.9
Benefit for income taxes		(1,180.3)	(542.6)	(540.8)
Net income attributable to Progressive		3,970.3	2,615.3	1,592.2
Comprehensive income attributable to Progressive		4,432.9	2,520.1	1,941
Parent Company
Revenues
Dividends from subsidiaries		2,277.9	939.1	867.3
Undistributed income (loss) from subsidiaries		1,821.3	1,770.7	866.3
Equity in net income of subsidiaries		4,099.2	2,709.8	1,733.6
Intercompany investment income		31.1	39.4	11.3
Gains (losses) on extinguishment of debt		0	0	0.2
Total revenues		4,130.3	2,749.2	1,745.1
Expenses
Interest expense		190.4	166.8	151.1
Deferred compensation	[1]	16.6	7.5	23.2
Other operating costs and expenses		5.5	5.1	4.6
Total expenses		212.5	179.4	178.9
Income before income taxes		3,917.8	2,569.8	1,566.2
Benefit for income taxes		52.5	45.5	26
Net income attributable to Progressive		3,970.3	2,615.3	1,592.2
Other comprehensive income (loss)		462.6	(95.2)	348.8
Comprehensive income attributable to Progressive		$ 4,432.9	$ 2,520.1	$ 1,941
[1]	See Note 4 – Employee Benefit Plans in these condensed financial statements.

SCHEDULE II - Condensed Finan_3

SCHEDULE II - Condensed Financial Information Of Registrant Condensed Balance Sheets (Parent Company) (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets
Net deferred income taxes	$ 0	$ 43.2
Other assets	768.4	365.1
Total assets	54,895.3	46,575
Liabilities and Shareholders' Equity
Accounts payable, accrued expenses, and other liabilities	5,962.7	5,046.5
Debt	4,407.1	4,404.9
Total liabilities	40,996.5	35,538.7
Redeemable noncontrolling interest (NCI)	225.6	214.5	$ 503.7	$ 483.7
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
Common shares, $1.00 par value (authorized 900.0; issued 797.5, including treasury shares of 212.9 and 214.3)	584.6	583.2
Paid-in capital	1,573.4	1,479
Retained earnings	10,679.6	8,386.6
Total accumulated other comprehensive income attributable to Progressive	341.7	(120.9)	1,282.2	$ 933.4
Total shareholders’ equity	13,673.2	10,821.8	$ 9,284.8
Total liabilities, redeemable NCI, and shareholders’ equity	54,895.3	46,575
Parent Company
Assets
Investment in affiliate	5	5
Investment in subsidiaries	16,186.8	13,652.2
Receivable from investment subsidiary	2,912	2,658.9
Intercompany receivable	678.6	651.1
Net deferred income taxes	70.3	68.2
Other assets	303.8	124.2
Total assets	20,156.5	17,159.6
Liabilities and Shareholders' Equity
Accounts payable, accrued expenses, and other liabilities	475.2	250.5
Dividends payable	1,375.4	1,467.9
Debt	4,407.1	4,404.9
Total liabilities	6,257.7	6,123.3
Redeemable noncontrolling interest (NCI)	225.6	214.5
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
Common shares, $1.00 par value (authorized 900.0; issued 797.5, including treasury shares of 212.9 and 214.3)	584.6	583.2
Paid-in capital	1,573.4	1,479
Retained earnings	10,679.6	8,386.6
Total accumulated other comprehensive income attributable to Progressive	341.7	(120.9)
Total shareholders’ equity	13,673.2	10,821.8
Total liabilities, redeemable NCI, and shareholders’ equity	$ 20,156.5	$ 17,159.6

SCHEDULE II - Condensed Finan_4

SCHEDULE II - Condensed Financial Information Of Registrant Condensed Balance Sheets (Parent Company) (Phantom) (Detail) - $ / shares	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Common Shares, par value (USD per share)	$ 1	$ 1		$ 1
Common Shares, authorized (shares)	900,000,000	900,000,000
Common Shares, issued (shares)	797,500,000	797,500,000
Common Shares, treasury shares (shares)	212,900,000	214,300,000
Parent Company
Condensed Financial Statements, Captions [Line Items]
Common Shares, par value (USD per share)	$ 1	$ 1
Common Shares, authorized (shares)	900,000,000	900,000,000
Common Shares, issued (shares)	797,500,000	797,500,000
Common Shares, treasury shares (shares)	212,900,000	214,300,000
Series B Preferred Stock
Condensed Financial Statements, Captions [Line Items]
Preferred Stock, Shares Issued			500,000
Preferred Stock, Liquidation Preference Per Share			$ 1,000
Serial Preferred Stock
Condensed Financial Statements, Captions [Line Items]
Preferred Stock, Shares Authorized	20,000,000	20,000,000
Serial Preferred Stock | Parent Company
Condensed Financial Statements, Captions [Line Items]
Preferred Stock, Shares Authorized	20,000,000	20,000,000
Serial Preferred Stock | Series B Preferred Stock
Condensed Financial Statements, Captions [Line Items]
Preferred Stock, No Par Value	$ 0	$ 0		$ 0
Preferred Stock, Shares Authorized	500,000	500,000
Preferred Stock, Shares Issued	500,000	500,000
Preferred Stock, Shares Outstanding	500,000	500,000
Preferred Stock, Liquidation Preference Per Share	$ 1,000	$ 1,000
Serial Preferred Stock | Series B Preferred Stock | Parent Company
Condensed Financial Statements, Captions [Line Items]
Preferred Stock, No Par Value	$ 0	$ 0
Preferred Stock, Shares Authorized	500,000	500,000
Preferred Stock, Shares Issued	500,000	500,000
Preferred Stock, Shares Outstanding	500,000	500,000
Preferred Stock, Liquidation Preference Per Share	$ 1,000	$ 1,000

SCHEDULE II - Condensed Finan_5

SCHEDULE II - Condensed Financial Information Of Registrant Condensed Statements Of Cash Flows (Parent Company) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flows From Operating Activities:
Net income attributable to Progressive	$ 3,970.3	$ 2,615.3	$ 1,592.2
Adjustments to reconcile net income attributable to Progressive to net cash provided by operating activities:
Amortization of equity-based compensation	90.2	77.2	95.4
Changes in:
Accounts payable, accrued expenses, and other liabilities	611.6	746.6	400
Income taxes	227.2	(158.7)	(172.6)
Other, net	(260.8)	(57.7)	(134.8)
Net cash provided by operating activities	6,261.6	6,284.8	3,756.8
Cash Flows From Investing Activities:
Payments to Acquire Additional Interest in Subsidiaries	(11.2)	(296.9)	0
Net cash used in investing activities	(4,338.3)	(7,034.9)	(3,406.7)
Cash Flows From Financing Activities:
Net proceeds from debt issuance	0	1,134	841.1
Net proceeds from preferred stock issuance	0	493.9	0
Reacquisitions of debt	0	0	(635.6)
Dividends paid to common shareholders	(1,643.2)	(654.9)	(395.4)
Dividends paid to preferred shareholders	(26.8)	(13.5)	0
Acquisition of treasury shares for restricted stock tax liabilities	(84.4)	(78.6)	(57.6)
Acquisition of treasury shares acquired in open market	(6.9)	(0.4)	(4.9)
Net cash provided by (used in) financing activities	(1,770.9)	549.8	(300.9)
Change in cash, cash equivalents, and restricted cash	152.4	(200.3)	48.9
Cash, cash equivalents, and restricted cash - beginning of year	75	275.3	226.4
Cash, cash equivalents, and restricted cash - end of year	227.4	75	275.3
Parent Company
Cash Flows From Operating Activities:
Net income attributable to Progressive	3,970.3	2,615.3	1,592.2
Adjustments to reconcile net income attributable to Progressive to net cash provided by operating activities:
Undistributed (income) loss from subsidiaries	(1,821.3)	(1,770.7)	(866.3)
Amortization of equity-based compensation	2.9	2.4	2.1
(Gains) losses on extinguishment of debt	0	0	(0.2)
Changes in:
Intercompany receivable	(14.1)	77.5	(71.3)
Accounts payable, accrued expenses, and other liabilities	47.1	(29.6)	53.6
Income taxes	175.5	(14.2)	37.3
Other, net	(179.8)	47.8	(22.6)
Net cash provided by operating activities	2,180.6	928.5	724.8
Cash Flows From Investing Activities:
Additional investments in equity securities of consolidated subsidiaries	(152.8)	(178.3)	(86.7)
Payments to Acquire Additional Interest in Subsidiaries	(5.4)	(287.9)	0
Acquisition of business	0	0	(18.7)
(Paid to) received from investment subsidiary	(253.1)	(1,192.8)	(344.2)
Net cash used in investing activities	(411.3)	(1,659)	(449.6)
Cash Flows From Financing Activities:
Net proceeds from debt issuance	0	1,134	841.1
Net proceeds from preferred stock issuance	0	493.9	0
Reacquisitions of debt	0	0	(594.4)
Dividends paid to common shareholders	(1,643.2)	(654.9)	(395.4)
Dividends paid to preferred shareholders	(26.8)	(13.5)	0
Acquisition of treasury shares for restricted stock tax liabilities	(84.4)	(78.6)	(57.6)
Acquisition of treasury shares acquired in open market	(6.9)	(0.4)	(4.9)
Loan to ARX Holding Corp.	(8)	(150)	(64)
Net cash provided by (used in) financing activities	(1,769.3)	730.5	(275.2)
Change in cash, cash equivalents, and restricted cash	0	0	0
Cash, cash equivalents, and restricted cash - beginning of year	0	0	0
Cash, cash equivalents, and restricted cash - end of year	$ 0	$ 0	$ 0

SCHEDULE II - Condensed Finan_6

SCHEDULE II - Condensed Financial Information Of Registrant Condensed Financial Information Of Registrant - Additional Information (Detail) - USD ($) $ in Billions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Significant Accounting Policies [Line Items]
Securities Held In Consolidated Non-Insurance Subsidiary	$ 3.2	$ 2.9
Parent Company
Significant Accounting Policies [Line Items]
Securities Held In Consolidated Non-Insurance Subsidiary	$ 3.2	$ 2.9	$ 1.6

SCHEDULE II - Condensed Finan_7

SCHEDULE II - Condensed Financial Information Of Registrant Progressive Corporation Cash Paid (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income taxes	$ 954.3	$ 702.6	$ 715.6
Interest	184.9	154	146.3
Parent Company
Income taxes	925	679.2	669.7
Interest	$ 184.9	$ 153.6	$ 142.2

SCHEDULE II - Condensed Finan_8

SCHEDULE II - Condensed Financial Information Of Registrant Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Apr. 30, 2018
Income Taxes [Line Items]
Benefit for income taxes	$ 44.7
Lower Limit | ARX and subsidiaries
Income Taxes [Line Items]
Noncontrolling interest, ownership percentage (less than)		80.00%

SCHEDULE III - Supplementary _2

SCHEDULE III - Supplementary Insurance Information Supplementary Insurance Information (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	[1]	$ 1,056.5	$ 951.6	$ 780.5
Future policy benefits, losses, claims, and loss expenses	[1]	18,105.4	15,400.8	13,086.9
Unearned premiums	[1]	12,388.8	10,686.5	8,903.5
Other policy claims and benefits payable	[1]	0	0	0
Premium revenue		36,192.4	30,933.3	25,729.9
Net investment income	[1],[2]	1,017.4	796.2	539.2
Benefits, claims, losses, and settlement expenses		25,470.5	21,721	18,808
Amortization of deferred policy acquisition costs		3,023.2	2,573.7	2,124.9
Other operating expenses		4,975.1	4,195.8	3,480.7
Net Premiums Written		37,577.9	32,609.9	27,132.1
Personal Lines
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Premium revenue		30,210	26,034.7	21,947.2
Benefits, claims, losses, and settlement expenses		21,329.7	18,389.8	16,141.4
Amortization of deferred policy acquisition costs		2,273.6	1,964.4	1,656.4
Other operating expenses		4,227.6	3,563.3	2,954.8
Net Premiums Written		31,102.2	27,157.6	22,928.4
Commercial Lines
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Premium revenue		4,427.6	3,610.9	2,793.9
Benefits, claims, losses, and settlement expenses		3,034.8	2,394	1,966.4
Amortization of deferred policy acquisition costs		481.2	396	309.3
Other operating expenses		523.5	396	335.3
Net Premiums Written		4,791.8	3,996.4	3,112.7
Property, Liability and Casualty Insurance Product Line
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Premium revenue		1,554.8	1,287.7	988.8
Benefits, claims, losses, and settlement expenses		1,106	937	700.2
Amortization of deferred policy acquisition costs		268.4	213.3	159.2
Other operating expenses		224	237.2	190.4
Net Premiums Written		1,683.9	1,455.9	1,091
Other Indemnity
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Premium revenue		0	0	0
Benefits, claims, losses, and settlement expenses		0	0.2	0
Amortization of deferred policy acquisition costs		0	0	0
Other operating expenses		0	(0.7)	0.2
Net Premiums Written		$ 0	$ 0	$ 0
[1]	Progressive does not allocate assets, liabilities, or investment income to operating segments.
[2]	Excludes total net realized gains (losses) on securities.

SCHEDULE IV - Reinsurance Reins

SCHEDULE IV - Reinsurance Reinsurance (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount	$ 37,519.7	$ 31,970.2	$ 26,425.7
Ceded to Other Companies	1,327.3	1,036.9	695.8
Property, Liability and Casualty Insurance Product Line
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount	37,519.7	31,970.2	26,425.7
Ceded to Other Companies	1,327.3	1,036.9	695.8
Assumed From Other Companies	0	0	0
Net Amount	$ 36,192.4	$ 30,933.3	$ 25,729.9
Percentage of Amount Assumed to Net	0.00%	0.00%	0.00%

Reporting and Accounting Poli_4

Reporting and Accounting Policies - Advertising Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Advertising costs	$ 1,837.3	$ 1,422.4	$ 1,005.4

Reporting and Accounting Poli_5

Reporting and Accounting Policies Property, Plant, and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 2,351.8	$ 2,164.9
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(1,138.1)	(1,033.2)
Property and equipment, net of accumulated depreciation of $1,138.1 and $1,033.2	1,213.7	1,131.7
Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	927.1	928.8
Property, Plant and Equipment, Other Types [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	385.9	349.8
Software Development [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	367.1	327
Software and Software Development Costs [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	286.8	259.1
Land [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	161.6	177
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 223.3	$ 123.2
Property, Plant and Equipment, Useful Life	3 years
Lower Limit | Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	7 years
Lower Limit | Property, Plant and Equipment, Other Types [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Lower Limit | Software Development [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Lower Limit | Software and Software Development Costs [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	1 year
Upper Limit | Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	40 years
Upper Limit | Property, Plant and Equipment, Other Types [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Upper Limit | Software Development [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Upper Limit | Software and Software Development Costs [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years

Reporting and Accounting Poli_6

Reporting and Accounting Policies - Capitalized Interest (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Capitalized interest	$ 1.7	$ 1.8	$ 2.8

Reporting and Accounting Poli_7

Reporting and Accounting Policies - Compensation Expense Recognized for Equity-Based Compensation (Details) - Stock compensation plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pretax expense	$ 90.2	$ 77.2	$ 95.4
Tax benefit1	$ 18.9	$ 16.2	$ 33.4

Reporting and Accounting Poli_8

Reporting and Accounting Policies - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Income taxes	$ 954.3	$ 702.6	$ 715.6
Interest	184.9	$ 154	$ 146.3
Operating Lease, Payments	$ 84

Reporting and Accounting Poli_9

Reporting and Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Apr. 01, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net	$ 0	$ 0
Held for sale property	$ 32,900,000	39,300,000
Accelerated vesting percentage	50.00%
Open reverse repurchase commitments	$ 0	$ 0
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	63,100,000
Unrecorded Unconditional Purchase Obligation	$ 857,000,000
ARX Holding Corp.
Property, Plant and Equipment [Line Items]
Equity interest percentage	87.10%	86.80%		69.00%
Cash and Cash Equivalents [Member] | ARX Holding Corp.
Property, Plant and Equipment [Line Items]
Open reverse repurchase commitments	$ 46,300,000	$ 117,300,000		$ 247,200,000
Lower Limit | ARX Holding Corp.
Property, Plant and Equipment [Line Items]
Equity interest percentage			80.00%
Common Stock [Member]
Property, Plant and Equipment [Line Items]
Dividends payable	1,375,400,000
unrecorded unconditional purchase obligations reinsurance [Member] | Lower Limit
Property, Plant and Equipment [Line Items]
Other Commitment	$ 96,100,000

Investments Investment Portfoli

Investments Investment Portfolio by Major Security Type (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 34,441.9	$ 30,051.8
Gross Unrealized Gains	517	115.4
Gross Unrealized Losses	(57.6)	(249.6)
Net Holding Period Gains (Losses)	7.8	(10.2)
Fair Value	$ 34,909.1	$ 29,907.4
% of Total Fair Value	88.90%	89.10%
Equity Securities, at Fair Value
Cost	$ 2,096.8	$ 2,151.5
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Net Holding Period Gains (Losses)	2,248.4	1,508.5
Fair Value	$ 4,345.2	$ 3,660
% of Total Fair Value	11.10%	10.90%
Debt and Equity Securities, at Fair Value
Cost	$ 36,538.7	$ 32,203.3
Gross Unrealized Gains	517	115.4
Gross Unrealized Losses	(57.6)	(249.6)
Net Holding Period Gains (Losses)	2,256.2	1,498.3
Fair Value	$ 39,254.3	$ 33,567.4
% of Total Fair Value	100.00%	100.00%
Other Payables to Broker-Dealers and Clearing Organizations	$ 11.9	$ 5.9
Securities Held In Consolidated Non-Insurance Subsidiary	3,200	2,900
Nonredeemable preferred stocks
Equity Securities, at Fair Value
Cost	971.3	1,002.6
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Net Holding Period Gains (Losses)	67.6	31.3
Fair Value	$ 1,038.9	$ 1,033.9
% of Total Fair Value	2.70%	3.10%
Common equities
Equity Securities, at Fair Value
Cost	$ 1,125.5	$ 1,148.9
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Net Holding Period Gains (Losses)	2,180.8	1,477.2
Fair Value	$ 3,306.3	$ 2,626.1
% of Total Fair Value	8.40%	7.80%
Fixed maturities
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 32,643.1	$ 28,255.9
Gross Unrealized Gains	517	115.4
Gross Unrealized Losses	(57.6)	(249.6)
Net Holding Period Gains (Losses)	7.8	(10.2)
Fair Value	$ 33,110.3	$ 28,111.5
% of Total Fair Value	84.30%	83.70%
Fixed maturities | U.S. government obligations
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 13,100.7	$ 9,897.4
Gross Unrealized Gains	194.1	71.2
Gross Unrealized Losses	(43.7)	(52.1)
Net Holding Period Gains (Losses)	0	0
Fair Value	$ 13,251.1	$ 9,916.5
% of Total Fair Value	33.70%	29.50%
Fixed maturities | State and local government obligations
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 1,686	$ 1,654.6
Gross Unrealized Gains	30	7.3
Gross Unrealized Losses	(2.7)	(12.8)
Net Holding Period Gains (Losses)	0	0
Fair Value	$ 1,713.3	$ 1,649.1
% of Total Fair Value	4.40%	4.90%
Fixed maturities | Corporate debt securities
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 6,860.3	$ 8,808.5
Gross Unrealized Gains	206.6	13.6
Gross Unrealized Losses	(0.5)	(125.3)
Net Holding Period Gains (Losses)	1.3	(2.5)
Fair Value	$ 7,067.7	$ 8,694.3
% of Total Fair Value	18.00%	25.90%
Fixed maturities | Residential mortgage-backed securities
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 625	$ 733.5
Gross Unrealized Gains	4.5	6
Gross Unrealized Losses	(2)	(5.1)
Net Holding Period Gains (Losses)	0	0
Fair Value	$ 627.5	$ 734.4
% of Total Fair Value	1.60%	2.20%
Fixed maturities | Commercial mortgage-backed securities
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 5,020.7	$ 3,332.8
Gross Unrealized Gains	61.5	7.8
Gross Unrealized Losses	(6)	(39)
Net Holding Period Gains (Losses)	0	0
Fair Value	$ 5,076.2	$ 3,301.6
% of Total Fair Value	12.90%	9.80%
Fixed maturities | Other asset-backed securities
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 5,164.7	$ 3,585.4
Gross Unrealized Gains	16.2	3.6
Gross Unrealized Losses	(1.4)	(11.8)
Net Holding Period Gains (Losses)	0	0.1
Fair Value	$ 5,179.5	$ 3,577.3
% of Total Fair Value	13.20%	10.70%
Fixed maturities | Redeemable preferred stocks
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 185.7	$ 243.7
Gross Unrealized Gains	4.1	5.9
Gross Unrealized Losses	(1.3)	(3.5)
Net Holding Period Gains (Losses)	6.5	(7.8)
Fair Value	$ 195	$ 238.3
% of Total Fair Value	0.50%	0.70%
Short-term investments
Debt Securities, Available-for-Sale, at Fair Value
Cost	$ 1,798.8	$ 1,795.9
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Net Holding Period Gains (Losses)	0	0
Fair Value	$ 1,798.8	$ 1,795.9
% of Total Fair Value	4.60%	5.40%

Investments Hybrid Securities (

Investments Hybrid Securities (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Hybrid Securities [Line Items]
Hybrid securities	$ 189.4	$ 244.7
State and local government obligations
Hybrid Securities [Line Items]
Hybrid securities	3.5	3.6
Corporate debt securities
Hybrid Securities [Line Items]
Hybrid securities	91.2	158.9
Other asset-backed securities
Hybrid Securities [Line Items]
Hybrid securities	2.6	4.5
Redeemable preferred stocks
Hybrid Securities [Line Items]
Hybrid securities	$ 92.1	$ 77.7

Investments Composition of Fixe

Investments Composition of Fixed Maturities by Maturity (Detail) - Fixed maturities $ in Millions	Dec. 31, 2019USD ($)
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost [Abstract]
Less than one year	$ 6,700.1
One to five years	16,898.3
Five to ten years	9,010.8
Ten years or greater	33.9
Cost	32,643.1
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value [Abstract]
Less than one year	6,712.6
One to five years	17,158.4
Five to ten years	9,203.9
Ten years or greater	35.4
Debt Securities, Available-for-Sale	$ 33,110.3

Investments Gross Unrealized lo

Investments Gross Unrealized losses by Major Security (Detail) $ in Millions	Dec. 31, 2019USD ($)security	Dec. 31, 2018USD ($)security
Number of Securities
Total | security	307	1,292
Less than 12 Months | security	217	349
12 Months or Greater | security	90	943
Fair Value
Total	$ 8,761.3	$ 17,652.2
Less than 12 Months	8,038.3	5,493.2
12 Month or Greater	723	12,159
Gross Unrealized Losses
Total	57.6	249.6
Less than 12 Months	53.8	47.3
12 Months or Greater	$ 3.8	$ 202.3
U.S. government obligations
Number of Securities
Total | security	23	51
Less than 12 Months | security	19	2
12 Months or Greater | security	4	49
Fair Value
Total	$ 5,152.4	$ 4,438
Less than 12 Months	5,057.2	126.6
12 Month or Greater	95.2	4,311.4
Gross Unrealized Losses
Total	43.7	52.1
Less than 12 Months	43.6	0.1
12 Months or Greater	$ 0.1	$ 52
State and local government obligations
Number of Securities
Total | security	67	299
Less than 12 Months | security	52	49
12 Months or Greater | security	15	250
Fair Value
Total	$ 314.3	$ 972.4
Less than 12 Months	287.5	192.7
12 Month or Greater	26.8	779.7
Gross Unrealized Losses
Total	2.7	12.8
Less than 12 Months	2.6	0.3
12 Months or Greater	$ 0.1	$ 12.5
Corporate debt securities
Number of Securities
Total | security	16	368
Less than 12 Months | security	12	133
12 Months or Greater | security	4	235
Fair Value
Total	$ 247.6	$ 6,723.3
Less than 12 Months	191.4	2,613.3
12 Month or Greater	56.2	4,110
Gross Unrealized Losses
Total	0.5	125.3
Less than 12 Months	0.5	33.4
12 Months or Greater	$ 0	$ 91.9
Residential mortgage-backed securities
Number of Securities
Total | security	41	228
Less than 12 Months | security	12	32
12 Months or Greater | security	29	196
Fair Value
Total	$ 292.8	$ 450.2
Less than 12 Months	163.7	248.8
12 Month or Greater	129.1	201.4
Gross Unrealized Losses
Total	2	5.1
Less than 12 Months	0.9	0.8
12 Months or Greater	$ 1.1	$ 4.3
Commercial mortgage-backed securities
Number of Securities
Total | security	98	140
Less than 12 Months | security	79	48
12 Months or Greater | security	19	92
Fair Value
Total	$ 1,742.4	$ 2,328.5
Less than 12 Months	1,400	741.2
12 Month or Greater	342.4	1,587.3
Gross Unrealized Losses
Total	6	39
Less than 12 Months	5.3	8.9
12 Months or Greater	$ 0.7	$ 30.1
Other asset-backed securities
Number of Securities
Total | security	61	203
Less than 12 Months | security	43	84
12 Months or Greater | security	18	119
Fair Value
Total	$ 1,000.6	$ 2,691.3
Less than 12 Months	938.5	1,551.7
12 Month or Greater	62.1	1,139.6
Gross Unrealized Losses
Total	1.4	11.8
Less than 12 Months	0.9	3.2
12 Months or Greater	$ 0.5	$ 8.6
Redeemable preferred stocks
Number of Securities
Total | security	1	3
Less than 12 Months | security	0	1
12 Months or Greater | security	1	2
Fair Value
Total	$ 11.2	$ 48.5
Less than 12 Months	0	18.9
12 Month or Greater	11.2	29.6
Gross Unrealized Losses
Total	1.3	3.5
Less than 12 Months	0	0.6
12 Months or Greater	$ 1.3	$ 2.9

Investments OTTI Credit Losses

Investments OTTI Credit Losses Recognized in Earnings (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2017
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance	$ 500,000
Ending balance	500,000	$ 500,000
Fixed maturities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance		11,500,000
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, No Previous Impairment	$ 0	400,000
Reductions for securities sold/matured		(11,200,000)
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Changes in Cash Flows		(200,000)
Ending balance		$ 500,000

Investments Components of Net R

Investments Components of Net Realized Gains (Losses) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-sale, Realized Gain	$ 281.9	$ 25.2
Equity Securities, FV-NI, Realized Gain	97.9	290.7
Debt and Equity Securities, Realized Gains	379.8	315.9
Gross realized gains on securities sales			$ 175.9
Debt Securities, Available-for-sale, Realized Loss	(34)	(119.6)
Equity Securities, FV-NI, Realized Loss	(11.2)	(25.6)
Debt and Equity Securities, Realized Losses	(45.2)	(145.2)
Available-for-sale Securities, Gross Realized Losses			(64.7)
Debt Securities, Available-for-sale, Realized Gain (Loss), Excluding Other-than-temporary Impairment	247.9	(94.4)
Equity Securities, FV-NI, Realized Gain (Loss)	86.7	265.1
Net realized gains (losses) on security sales	334.6	170.7
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments			115.7
Realized Gain on Litigation Settlements	0	0	1.2
Available-for-sale Securities, Gross Realized Gain (Loss) and Litigation, Excluding Other than Temporary Impairments			112.4
Unrealized Gain (Loss) on Hybrid Instrument, Net	18	(10.4)	(1.6)
Equity Securities, FV-NI, Unrealized Gain (Loss)	739.9	(497.5)
Net holding period gains (losses) on securities	757.9	(507.9)
Other than Temporary Impairment Losses, Portion Recognized in Earnings, Net of Sales, Debt and Equity Securities	0	0	11.6
Other than Temporary Impairment Losses, Portion Recognized in Earnings, Net of Sales	(63.3)	(68.3)	(61.2)
Total net realized gains (losses) on securities	1,029.2	(405.5)
Total net realized gains (losses) on securities			49.6
U.S. government obligations
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-sale, Realized Gain	164.4	6.7
Debt Securities, Available-for-sale, Realized Loss	(20.4)	(98.7)
Debt Securities, Available-for-sale, Realized Gain (Loss), Excluding Other-than-temporary Impairment	144	(92)
State and local government obligations
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-sale, Realized Gain	6.1	9.5
Debt Securities, Available-for-sale, Realized Loss	(0.7)	(2.9)
Debt Securities, Available-for-sale, Realized Gain (Loss), Excluding Other-than-temporary Impairment	5.4	6.6
Corporate debt securities
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-sale, Realized Gain	100.1	2.4
Debt Securities, Available-for-sale, Realized Loss	(7.9)	(10.4)
Debt Securities, Available-for-sale, Realized Gain (Loss), Excluding Other-than-temporary Impairment	92.2	(8)
Residential mortgage-backed securities
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-sale, Realized Gain	0.2	0
Debt Securities, Available-for-sale, Realized Loss	(2.3)	(0.1)
Debt Securities, Available-for-sale, Realized Gain (Loss), Excluding Other-than-temporary Impairment	(2.1)	(0.1)
Commercial mortgage-backed securities
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-sale, Realized Gain	8.1	2
Debt Securities, Available-for-sale, Realized Loss	(2.2)	(6.3)
Debt Securities, Available-for-sale, Realized Gain (Loss), Excluding Other-than-temporary Impairment	5.9	(4.3)
Other than Temporary Impairment Losses, Portion Recognized in Earnings, Net of Sales, Debt and Equity Securities	0	0
Other asset-backed securities
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-sale, Realized Gain	0.8	0.1
Debt Securities, Available-for-sale, Realized Loss	(0.1)	(1.1)
Debt Securities, Available-for-sale, Realized Gain (Loss), Excluding Other-than-temporary Impairment	0.7	(1)
Redeemable preferred stocks
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-sale, Realized Gain	2.2	4.5
Debt Securities, Available-for-sale, Realized Loss	(0.4)	(0.1)
Debt Securities, Available-for-sale, Realized Gain (Loss), Excluding Other-than-temporary Impairment	1.8	4.4
Short-term investments
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-sale, Realized Loss	0	0
Debt Securities, Available-for-sale, Realized Gain (Loss), Excluding Other-than-temporary Impairment	0	0
Nonredeemable preferred stocks
Gain (Loss) on Securities [Line Items]
Equity Securities, FV-NI, Realized Gain	36.2	4.1
Equity Securities, FV-NI, Realized Loss	(3.2)	(3.9)
Equity Securities, FV-NI, Realized Gain (Loss)	33	0.2
Common equities
Gain (Loss) on Securities [Line Items]
Equity Securities, FV-NI, Realized Gain	61.7	286.6
Equity Securities, FV-NI, Realized Loss	(8)	(21.7)
Equity Securities, FV-NI, Realized Gain (Loss)	53.7	264.9
Other than Temporary Impairment Losses, Portion Recognized in Earnings, Net of Sales, Debt and Equity Securities	0	0	11.2
Fixed Maturities and Short Term [Member]
Gain (Loss) on Securities [Line Items]
Gross realized gains on securities sales			74.5
Available-for-sale Securities, Gross Realized Losses			(46.6)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments			27.9
Fixed Maturities and Short Term [Member] | U.S. government obligations
Gain (Loss) on Securities [Line Items]
Gross realized gains on securities sales			6.2
Available-for-sale Securities, Gross Realized Losses			(28.7)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments			(22.5)
Fixed Maturities and Short Term [Member] | State and local government obligations
Gain (Loss) on Securities [Line Items]
Gross realized gains on securities sales			10.5
Available-for-sale Securities, Gross Realized Losses			(0.1)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments			10.4
Fixed Maturities and Short Term [Member] | Corporate debt securities
Gain (Loss) on Securities [Line Items]
Gross realized gains on securities sales			20.3
Available-for-sale Securities, Gross Realized Losses			(5.1)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments			15.2
Fixed Maturities and Short Term [Member] | Residential mortgage-backed securities
Gain (Loss) on Securities [Line Items]
Gross realized gains on securities sales			23.8
Available-for-sale Securities, Gross Realized Losses			(0.4)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments			23.4
Fixed Maturities and Short Term [Member] | Commercial mortgage-backed securities
Gain (Loss) on Securities [Line Items]
Gross realized gains on securities sales			4.9
Available-for-sale Securities, Gross Realized Losses			(5.3)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments			(0.4)
Fixed Maturities and Short Term [Member] | Other asset-backed securities
Gain (Loss) on Securities [Line Items]
Gross realized gains on securities sales			0.3
Available-for-sale Securities, Gross Realized Losses			(0.4)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments			(0.1)
Fixed Maturities and Short Term [Member] | Redeemable preferred stocks
Gain (Loss) on Securities [Line Items]
Gross realized gains on securities sales			8.5
Available-for-sale Securities, Gross Realized Losses			(6.4)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments			2.1
Fixed Maturities and Short Term [Member] | Short-term investments
Gain (Loss) on Securities [Line Items]
Available-for-sale Securities, Gross Realized Losses			(0.2)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments			(0.2)
Fixed maturities
Gain (Loss) on Securities [Line Items]
Other than Temporary Impairment Losses, Portion Recognized in Earnings, Net of Sales, Debt and Equity Securities	0	0	0.4
Fixed maturities | Commercial mortgage-backed securities
Gain (Loss) on Securities [Line Items]
Other than Temporary Impairment Losses, Portion Recognized in Earnings, Net of Sales, Debt and Equity Securities			0.4
Equity securities
Gain (Loss) on Securities [Line Items]
Gross realized gains on securities sales			101.4
Available-for-sale Securities, Gross Realized Losses			(18.1)
Equity Securities, FV-NI, Realized Gain (Loss)	86.7	265.1
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments			83.3
Equity Securities, FV-NI, Unrealized Gain (Loss)	739.9	(497.5)
Equity securities | Nonredeemable preferred stocks
Gain (Loss) on Securities [Line Items]
Gross realized gains on securities sales			58.4
Available-for-sale Securities, Gross Realized Losses			(5.9)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments			52.5
Equity securities | Common equities
Gain (Loss) on Securities [Line Items]
Gross realized gains on securities sales			43
Available-for-sale Securities, Gross Realized Losses			(12.2)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments			30.8
Other Assets [Member]
Gain (Loss) on Securities [Line Items]
Other than Temporary Impairment Losses, Portion Recognized in Earnings, Net of Sales	$ (63.3)	$ (68.3)	$ (49.6)

Investments Components of Equit

Investments Components of Equity Realized Gains (Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Components of Equity Realized Gains (Losses) [Line Items]
Equity Securities, FV-NI, Realized Gain (Loss)	$ 86.7	$ 265.1
Equity Securities, FV-NI, Unrealized Gain (Loss)	739.9	(497.5)
Equity securities
Components of Equity Realized Gains (Losses) [Line Items]
Equity Securities, FV-NI, Gain (Loss)	826.6	(232.4)
Equity Securities, FV-NI, Realized Gain (Loss)	86.7	265.1
Equity Securities, FV-NI, Unrealized Gain (Loss)	$ 739.9	$ (497.5)

Investments Components of Net I

Investments Components of Net Investment Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross Investment Income, Operating	$ 1,042	$ 820.5	$ 563.1
Investment expenses	(24.6)	(24.3)	(23.9)
Net investment income	1,017.4	796.2	539.2
Available-for-sale Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross Investment Income, Operating	923.7	714.8	460.7
Equity securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross Investment Income, Operating	118.3	105.7	102.4
Equity securities | Nonredeemable preferred stocks
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross Investment Income, Operating	61.8	45.9	44.1
Equity securities | Common equities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross Investment Income, Operating	56.5	59.8	58.3
Fixed maturities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross Investment Income, Operating	882	661.9	422.9
Fixed maturities | U.S. government obligations
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross Investment Income, Operating	268.6	196.8	72.7
Fixed maturities | State and local government obligations
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross Investment Income, Operating	36.5	37.7	51.5
Fixed maturities | Foreign government obligations
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross Investment Income, Operating	0	0	0.3
Fixed maturities | Corporate debt securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross Investment Income, Operating	268.9	217.9	125.2
Fixed maturities | Residential mortgage-backed securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross Investment Income, Operating	21.6	27.6	34.7
Fixed maturities | Commercial mortgage-backed securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross Investment Income, Operating	150.1	93.9	79.6
Fixed maturities | Other asset-backed securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross Investment Income, Operating	117.3	75.7	47.1
Fixed maturities | Redeemable preferred stocks
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross Investment Income, Operating	19	12.3	11.8
Short-term investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross Investment Income, Operating	$ 41.7	$ 52.9	$ 37.8

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Apr. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Principal amount of bonds and certificates of deposit on deposit to meet state insurance regulatory and/or rating agency requirements		$ 281,000,000
Securities exceeding 10% of Shareholders' Equity		0	$ 0
Fair value of fixed-maturity securities that were non-income producing during the preceding 12 months		0
Securities Sold under Agreements to Repurchase		0	0
Open reverse repurchase commitments		0	0
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Pre-Tax, Available-for-sale, Debt Securities		19,600,000	19,800,000
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held		500,000	500,000	$ 500,000
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Period Increase (Decrease)		$ 0	$ 0
Investment Portfolio Duration		3 years	2 years 9 months 18 days	2 years 6 months
Derivative Assets (Liabilities), at Fair Value, Net		$ 0	$ 0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax		(1,000,000)	(1,000,000)	$ 300,000
4.125% Senior Notes due 2047
Schedule of Investments [Line Items]
Senior notes, issuance amount	$ 850,000,000	$ 850,000,000	850,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.125%	4.125%
Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss)	$ 8,000,000
Fixed maturities
Schedule of Investments [Line Items]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held				500,000	$ 11,500,000
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, No Previous Impairment		$ 0		400,000
Non-hedging Instruments | Interest Rate Swaps
Schedule of Investments [Line Items]
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	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 39,254.3	$ 33,567.4
Long-term Debt, Fair Value	5,119.6	4,532.3
Available-for-sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	34,909.1	29,907.4
Available-for-sale Securities [Member] | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	33,110.3	28,111.5
Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	22,032.1	20,259.9
Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member] | U.S. government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	13,251.1	9,916.5
Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member] | State and local government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,713.3	1,649.1
Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member] | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	7,067.7	8,694.3
Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	10,883.2	7,613.3
Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	627.5	734.4
Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	5,076.2	3,301.6
Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities | Other asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	5,179.5	3,577.3
Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	195	238.3
Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	51.7	78.2
Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	11.1	0
Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	132.2	160.1
Available-for-sale Securities [Member] | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,798.8	1,795.9
Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	4,345.2	3,660
Equity securities | Nonredeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,038.9	1,033.9
Equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	955.2	984.1
Equity securities | Nonredeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	42.3	44.8
Equity securities | Nonredeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	41.4	5
Equity securities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	3,306.3	2,626.1
Equity securities | Common equities | Common Stocks, by Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	3,306	2,625.8
Equity securities | Common equities | Other risk investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0.3	0.3
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	18,443	14,345.8
Long-term Debt, Fair Value	0	0
Fair Value, Inputs, Level 1 | Available-for-sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	15,059.6	11,648.1
Fair Value, Inputs, Level 1 | Available-for-sale Securities [Member] | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	13,262.2	9,926
Fair Value, Inputs, Level 1 | Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	13,251.1	9,916.5
Fair Value, Inputs, Level 1 | Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member] | U.S. government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	13,251.1	9,916.5
Fair Value, Inputs, Level 1 | Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member] | State and local government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 1 | Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member] | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 1 | Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 1 | Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 1 | Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 1 | Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities | Other asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 1 | Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	11.1	9.5
Fair Value, Inputs, Level 1 | Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 1 | Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 1 | Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	11.1	9.5
Fair Value, Inputs, Level 1 | Available-for-sale Securities [Member] | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,797.4	1,722.1
Fair Value, Inputs, Level 1 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	3,383.4	2,697.7
Fair Value, Inputs, Level 1 | Equity securities | Nonredeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	77.4	71.9
Fair Value, Inputs, Level 1 | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	77.4	71.9
Fair Value, Inputs, Level 1 | Equity securities | Nonredeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 1 | Equity securities | Nonredeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 1 | Equity securities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	3,306	2,625.8
Fair Value, Inputs, Level 1 | Equity securities | Common equities | Common Stocks, by Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	3,306	2,625.8
Fair Value, Inputs, Level 1 | Equity securities | Common equities | Other risk investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	20,767.9	19,191.2
Long-term Debt, Fair Value	5,119.6	4,532.3
Fair Value, Inputs, Level 2 | Available-for-sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	19,849.5	18,259.3
Fair Value, Inputs, Level 2 | Available-for-sale Securities [Member] | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	19,848.1	18,185.5
Fair Value, Inputs, Level 2 | Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	8,781	10,343.4
Fair Value, Inputs, Level 2 | Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member] | U.S. government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 2 | Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member] | State and local government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,713.3	1,649.1
Fair Value, Inputs, Level 2 | Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member] | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	7,067.7	8,694.3
Fair Value, Inputs, Level 2 | Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	10,883.2	7,613.3
Fair Value, Inputs, Level 2 | Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	627.5	734.4
Fair Value, Inputs, Level 2 | Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	5,076.2	3,301.6
Fair Value, Inputs, Level 2 | Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities | Other asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	5,179.5	3,577.3
Fair Value, Inputs, Level 2 | Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	183.9	228.8
Fair Value, Inputs, Level 2 | Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	51.7	78.2
Fair Value, Inputs, Level 2 | Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	11.1	0
Fair Value, Inputs, Level 2 | Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	121.1	150.6
Fair Value, Inputs, Level 2 | Available-for-sale Securities [Member] | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1.4	73.8
Fair Value, Inputs, Level 2 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	918.4	931.9
Fair Value, Inputs, Level 2 | Equity securities | Nonredeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	918.4	931.9
Fair Value, Inputs, Level 2 | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	850.7	887.1
Fair Value, Inputs, Level 2 | Equity securities | Nonredeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	42.3	44.8
Fair Value, Inputs, Level 2 | Equity securities | Nonredeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	25.4	0
Fair Value, Inputs, Level 2 | Equity securities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 2 | Equity securities | Common equities | Common Stocks, by Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 2 | Equity securities | Common equities | Other risk investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	43.4	30.4
Long-term Debt, Fair Value	0	0
Fair Value, Inputs, Level 3 | Available-for-sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3 | Available-for-sale Securities [Member] | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3 | Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3 | Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member] | U.S. government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3 | Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member] | State and local government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3 | Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member] | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3 | Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3 | Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3 | Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3 | Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities | Other asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3 | Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3 | Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3 | Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3 | Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3 | Available-for-sale Securities [Member] | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	43.4	30.4
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	43.1	30.1
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	27.1	25.1
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	16	5
Fair Value, Inputs, Level 3 | Equity securities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0.3	0.3
Fair Value, Inputs, Level 3 | Equity securities | Common equities | Common Stocks, by Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Inputs, Level 3 | Equity securities | Common equities | Other risk investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0.3	0.3
Carrying (Reported) Amount, Fair Value Disclosure
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	36,538.7	32,203.3
Carrying Value	4,407.1	4,404.9
Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	34,441.9	30,051.8
Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities [Member] | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	32,643.1	28,255.9
Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	21,647	20,360.5
Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member] | U.S. government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	13,100.7	9,897.4
Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member] | State and local government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,686	1,654.6
Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities [Member] | Fixed maturities | Debt Securities [Member] | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	6,860.3	8,808.5
Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	10,810.4	7,651.7
Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	625	733.5
Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	5,020.7	3,332.8
Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities [Member] | Fixed maturities | Asset-backed Securities | Other asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	5,164.7	3,585.4
Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	185.7	243.7
Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	51.5	79.3
Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	10	0
Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities [Member] | Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	124.2	164.4
Carrying (Reported) Amount, Fair Value Disclosure | Available-for-sale Securities [Member] | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,798.8	1,795.9
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,096.8	2,151.5
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Nonredeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	971.3	1,002.6
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	891.3	951.6
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Nonredeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	39.9	46
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Nonredeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	40.1	5
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,125.5	1,148.9
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities | Common Stocks, by Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,125.2	1,148.6
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities | Other risk investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 0.3	$ 0.3

Fair Value Summary of Changes i

Fair Value Summary of Changes in Fair Value Associated With Level 3 Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value	$ 30.4	$ 5.3
Calls/ Maturities/ Paydowns	0	0
Purchases	12	25.1
Sales	0	0
Net Realized (Gain)/Loss on Sales	0	0
Change in Valuation	1	0
Net Transfers In (Out)	0	0
Ending Fair value	43.4	30.4
Equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value	25.1	0
Calls/ Maturities/ Paydowns	0	0
Purchases	2	25.1
Sales	0	0
Net Realized (Gain)/Loss on Sales	0	0
Change in Valuation	0	0
Net Transfers In (Out)	0	0
Ending Fair value	27.1	25.1
Equity securities | Nonredeemable preferred stocks | Industrials
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value	5	5
Calls/ Maturities/ Paydowns	0	0
Purchases	10	0
Sales	0	0
Net Realized (Gain)/Loss on Sales	0	0
Change in Valuation	1	0
Net Transfers In (Out)	0	0
Ending Fair value	16	5
Equity securities | Common equities | Other risk investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value	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
Ending Fair value	$ 0.3	$ 0.3

Fair Value Summary of Quantitat

Fair Value Summary of Quantitative Information about Level 3 Fair Value Measurements (Detail) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)$ / shares	Dec. 31, 2018USD ($)$ / shares
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 39,254.3	$ 33,567.4
Fair Value, Inputs, Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	43.4	30.4
Fair Value, Inputs, Level 3 | Third Party Pricing Exemption Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	0.3	0.3
Fair Value, Inputs, Level 3 | Total Quantitative Level Three Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	43.1	30.1
Financials | Fair Value, Inputs, Level 3 | Nonredeemable preferred stocks | Internal Pricing
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value		$ 25.1
Fair Value Inputs, Original Issue Price | $ / shares		$ 9
Financials | Fair Value, Inputs, Level 3 | Nonredeemable preferred stocks | Third Party Pricing Firm [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 27.1
Fair Value Inputs, Recent Transaction Price | $ / shares	$ 9
Industrials | Fair Value, Inputs, Level 3 | Nonredeemable preferred stocks | Internal Pricing
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 10	$ 5
Fair Value Inputs, Price-to-Sales Ratio		5.5
Fair Value Inputs, Original Issue Price | $ / shares	$ 4.9
Industrials | Fair Value, Inputs, Level 3 | Nonredeemable preferred stocks | Third Party Pricing Firm [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 6
Fair Value Inputs, Performance Based Price Adjustment | $ / shares	$ 4.8

Fair Value - Additional Informa

Fair Value - Additional Information (Detail)	Dec. 31, 2019USD ($)security	Dec. 31, 2018USD ($)security
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 39,254,300,000	$ 33,567,400,000
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Vendor Quoted Prices, Percent of FV Hierarchy Level	80.00%	79.00%
Fair Value	$ 18,443,000,000	$ 14,345,800,000
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Vendor Quoted Prices, Percent of FV Hierarchy Level	99.00%	99.00%
Dealer Quoted Prices, Percent of FV Hierarchy Level	1.00%	1.00%
Fair Value	$ 20,767,900,000	$ 19,191,200,000
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	43,400,000	30,400,000
Fixed maturities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 0	$ 0
Nonredeemable preferred stocks | Internal Pricing | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of securities | security	3	2
Common equities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of securities | security	1	1

Debt (Detail)

Debt (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Fair Value	$ 5,119.6	$ 4,532.3
Debt, Long-term and Short-term, Combined Amount	4,407.1	4,404.9
3.75% Senior Notes due 2021
Debt Instrument [Line Items]
Carrying Value	499.4	499.1
Fair Value	515.6	506.5
2.45% Senior Notes Due 2027
Debt Instrument [Line Items]
Carrying Value	496.9	496.5
Fair Value	501.5	455.5
6 5/8% Senior Notes due 2029
Debt Instrument [Line Items]
Carrying Value	296.6	296.4
Fair Value	392.5	368.5
4.00% Senior Notes due 2029
Debt Instrument [Line Items]
Carrying Value	545	544.5
Fair Value	614.3	562.4
6.25% Senior Notes due 2032
Debt Instrument [Line Items]
Carrying Value	395.7	395.5
Fair Value	552.6	496.6
4.35% Senior Notes due 2044
Debt Instrument [Line Items]
Carrying Value	346.7	346.6
Fair Value	417	350.2
3.70% Senior Notes due 2045
Debt Instrument [Line Items]
Carrying Value	395.4	395.3
Fair Value	434.2	366.7
4.125% Senior Notes due 2047
Debt Instrument [Line Items]
Carrying Value	841.6	841.4
Fair Value	986.1	831.9
4.20% Senior Notes due 2048
Debt Instrument [Line Items]
Carrying Value	589.8	589.6
Fair Value	$ 705.8	$ 594

Debt (Phantom) (Detail)

Debt (Phantom) (Detail) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Oct. 31, 2018	Mar. 31, 2018	Apr. 30, 2017
3.75% Senior Notes due 2021
Debt Instrument [Line Items]
Senior notes, issuance amount	$ 500,000,000	$ 500,000,000
Debt Instrument, Interest Rate, Stated Percentage	3.75%
2.45% Senior Notes Due 2027
Debt Instrument [Line Items]
Senior notes, issuance amount	$ 500,000,000	500,000,000
Debt Instrument, Interest Rate, Stated Percentage	2.45%
6 5/8% Senior Notes due 2029
Debt Instrument [Line Items]
Senior notes, issuance amount	$ 300,000,000	300,000,000
Debt Instrument, Interest Rate, Stated Percentage	6.625%
4.00% Senior Notes due 2029
Debt Instrument [Line Items]
Senior notes, issuance amount	$ 550,000,000	550,000,000	$ 550,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.00%		4.00%
6.25% Senior Notes due 2032
Debt Instrument [Line Items]
Senior notes, issuance amount	$ 400,000,000	400,000,000
Debt Instrument, Interest Rate, Stated Percentage	6.25%
4.35% Senior Notes due 2044
Debt Instrument [Line Items]
Senior notes, issuance amount	$ 350,000,000	350,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.35%
3.70% Senior Notes due 2045
Debt Instrument [Line Items]
Senior notes, issuance amount	$ 400,000,000	400,000,000
Debt Instrument, Interest Rate, Stated Percentage	3.70%
4.125% Senior Notes due 2047
Debt Instrument [Line Items]
Senior notes, issuance amount	$ 850,000,000	850,000,000			$ 850,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.125%				4.125%
4.20% Senior Notes due 2048
Debt Instrument [Line Items]
Senior notes, issuance amount	$ 600,000,000	$ 600,000,000		$ 600,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.20%			4.20%

Debt Aggregate Principal Paymen

Debt Aggregate Principal Payments On Debt Outstanding (Detail) $ in Millions	Dec. 31, 2019USD ($)
Debt Disclosure [Abstract]
Debt Instrument, Periodic Payment, Principal in Next Twelve Months	$ 0
Long-term Debt, Maturities, Repayments of Principal in Year Two	500
Long-Term Debt, Maturities, Repayments of Principal in Year Three	0
Long-Term Debt, Maturities, Repayments of Principal in Year Four	0
Long-Term Debt, Maturities, Repayments of Principal in Year Five	0
Long-Term Debt, Maturities, Repayments of Principal after Year Five	3,950
Total	$ 4,450

Debt Unrealized Gains (Losses)

Debt Unrealized Gains (Losses) From Debt Hedges Included In Accumulated Other (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Apr. 30, 2017	Jan. 31, 2015	Apr. 30, 2014	Aug. 31, 2011	Nov. 30, 2002	Mar. 31, 1999
Debt Instrument [Line Items]
Unrealized Gain (Loss)	$ (16.4)	$ (17.2)
3.75% Senior Notes due 2021
Debt Instrument [Line Items]
Unrealized Gain (Loss)	(1)					$ (5.1)
6 5/8% Senior Notes due 2029
Debt Instrument [Line Items]
Unrealized Gain (Loss)	(2.4)							$ (4.2)
6.25% Senior Notes due 2032
Debt Instrument [Line Items]
Unrealized Gain (Loss)	3.3						$ 5.1
4.35% Senior Notes due 2044
Debt Instrument [Line Items]
Unrealized Gain (Loss)	(1.4)				$ (1.6)
3.70% Senior Notes due 2045
Debt Instrument [Line Items]
Unrealized Gain (Loss)	(11.7)			$ (12.9)
4.125% Senior Notes due 2047
Debt Instrument [Line Items]
Unrealized Gain (Loss)	$ (7.6)		$ (8)

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)	1 Months Ended		12 Months Ended
	Oct. 31, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Discretionary Line of Credit
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 250,000,000
Debt Instrument, Term			30 days
Proceeds from Lines of Credit			$ 0	$ 0
4.00% Senior Notes due 2029
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 550,000,000		$ 550,000,000	550,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.00%		4.00%
Proceeds from Debt, Net of Issuance Costs	$ 544,500,000
4.20% Senior Notes due 2048
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 600,000,000	$ 600,000,000	$ 600,000,000
Debt Instrument, Interest Rate, Stated Percentage		4.20%	4.20%
Proceeds from Debt, Net of Issuance Costs		$ 589,500,000
Federal Funds Rate [Member] | Discretionary Line of Credit
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate			0.50%

Income Taxes Components of Inco

Income Taxes Components of Income Tax Provision (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Current Federal Tax Expense (Benefit)	$ 1,104.7	$ 673.1	$ 680.9
Current State and Local Tax Expense (Benefit)	27.3	21.5	12.8
Deferred Federal Income Tax Expense (Benefit)	45.3	(145.9)	(149.4)
Deferred State and Local Income Tax Expense (Benefit)	3	(6.1)	(3.5)
Total income tax provision	$ 1,180.3	$ 542.6	$ 540.8

Income Taxes Reconciliation of

Income Taxes Reconciliation of Provision (Benefit) for income Taxes Reported in Consolidated Statements Of Income with Tax at Statutory Rate (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income before income taxes	$ 5,160.3	$ 3,163.6	$ 2,138.9
Tax at statutory federal rate	1,083.7	664.4	748.6
Tax Adjustments, Settlements, and Unusual Provisions	163.2	0	0
Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Amount	(43.9)	(76.3)	(52.4)
Stock-based compensation	(25.9)	(25.1)	(25.1)
Tax-deductible dividends	(14.6)	(14.6)	(9.7)
Dividends received deduction	(10.4)	(9.7)	(20.7)
Exempt interest income	(3.6)	(5.9)	(16.9)
Net deferred tax liability revaluation	0	0	(99.5)
Nondeductible compensation expense	8.1	(0.2)	10.1
State income taxes, net of federal taxes	24	12.2	6
Other items, net	(0.3)	(2.2)	0.4
Total income tax provision	$ 1,180.3	$ 542.6	$ 540.8
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Tax at statutory federal rate	21.00%	21.00%	35.00%
Tax adjustments, settlements, and unusual provisions, percentage	3.00%	0.00%	0.00%
Tax credits	(1.00%)	(2.00%)	(2.00%)
Stock-based compensation	(1.00%)	(1.00%)	(1.00%)
Tax-deductible dividends	0.00%	(1.00%)	0.00%
Dividends received deduction	0.00%	0.00%	(1.00%)
Exempt interest income	0.00%	0.00%	(1.00%)
Net deferred tax liability revaluation	0.00%	0.00%	(5.00%)
Nondeductible compensation expense	0.00%	0.00%	0.00%
State income taxes, net of federal taxes	1.00%	0.00%	0.00%
Other items, net	0.00%	0.00%	0.00%
Total income tax provision	23.00%	17.00%	25.00%

Income Taxes Components of Net

Income Taxes Components of Net Deferred Tax Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Federal deferred tax assets:
Unearned premiums reserve	$ 498.2	$ 439.9
Non-deductible accruals	181.8	169.3
Loss and loss adjustment expense reserves	153.3	134.6
Deferred Tax Assets, Leasing Arrangements	42.3	0
Net unrealized losses on fixed-maturity securities	0	28.2
Hedges on forecasted transactions	4.4	4.6
Other	15.3	16.2
Federal deferred tax liabilities:
Net holding period gains on equity securities	(472.2)	(316.8)
Deferred acquisition costs	(221.9)	(199.8)
Property and equipment	(108.6)	(85.7)
Deferred Tax Liabilities, Unrealized Gains on Trading Securities	(96.5)	0
Loss and loss adjustment expense reserve transition adjustment	(47.2)	(58.5)
Deferred Tax Liabilities, Leasing Arrangements	(42.3)	0
Intangible assets	(38.9)	(52.2)
Investment basis differences	(1.1)	(43.3)
Prepaid expenses	(4.8)	(4.7)
Other	(8.3)	(8.9)
Deferred Tax Liability, Federal Tax	(146.5)
Net federal deferred tax asset (liability)		22.9
Net state deferred tax asset	14	20.3
Deferred Tax Liabilities, Net	(132.5)	0
Net deferred income taxes	$ 0	$ 43.2

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Mar. 31, 2019Investment	Apr. 01, 2018
Income Taxes [Line Items]
Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Amount	$ 43,900,000	$ 76,300,000	$ 52,400,000
Tax Adjustments, Settlements, and Unusual Provisions	163,200,000	0	0
Net taxes payable	195,500,000	16,800,000
Provision for income taxes	1,180,300,000	542,600,000	540,800,000
Tax cuts and jobs act, reduction in income tax expense related to revaluing deferred tax assets and liabilities			99,500,000
Tax cuts and jobs act, provisional tax amount related to deductibility of executive compensation expense		(3,900,000)	4,500,000
Stock-based compensation	25,900,000	25,100,000	25,100,000
Net deferred income taxes	0	43,200,000
Deferred Tax Liabilities, Net	132,500,000	0
Deferred tax assets valuation allowance	0	0
Interest and Penalties [Member]
Income Taxes [Line Items]
Provision for income taxes	$ 9,900,000	0	$ 200,000
Chief Financial Officer [Member]
Income Taxes [Line Items]
Stock-based compensation		300,000
Liability for Claims and Claims Adjustment Expense [Member]
Income Taxes [Line Items]
Net deferred income taxes		67,100,000
Deferred Tax Liabilities, Net		$ 67,100,000
ARX Holding Corp.
Income Taxes [Line Items]
Equity interest percentage	87.10%	86.80%	69.00%
ARX Holding Corp. | Lower Limit
Income Taxes [Line Items]
Equity interest percentage					80.00%
Alternative Energy [Member]
Income Taxes [Line Items]
Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Amount	$ 38,100,000	$ 71,000,000	$ 48,700,000
Number of Investments | Investment				3
Tax Adjustments, Settlements, and Unusual Provisions	163,200,000
Net taxes payable	252,000,000
Net deferred income taxes	88,800,000
Provision for income taxes	100,000,000
Protective Deposits	$ 152,100,000

Loss And Loss Adjustment Expe_3

Loss And Loss Adjustment Expense Reserves Activity in Loss and loss Adjustment Expense Reserves (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balance at beginning of period	$ 15,400.8	$ 13,086.9	$ 11,368
Less reinsurance recoverables on unpaid losses	2,572.7	2,170.1	1,801
Net balance at beginning of period	12,828.1	10,916.8	9,567
Incurred related to:
Current year	25,238.2	21,632.5	18,782.1
Prior years	232.3	88.5	25.9
Total incurred	25,470.5	21,721	18,808
Paid related to:
Current year	16,105	13,792.1	12,201.5
Prior years	7,300.4	6,017.6	5,256.7
Total paid	23,405.4	19,809.7	17,458.2
Net balance at ending of period	14,893.2	12,828.1	10,916.8
Plus reinsurance recoverables on unpaid losses	3,212.2	2,572.7	2,170.1
Balance at ending of period	$ 18,105.4	$ 15,400.8	$ 13,086.9

Loss And Loss Adjustment Expe_4

Loss And Loss Adjustment Expense Reserves Loss And Loss Adjustment Expense Reserves - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)data_subset	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Number of subsets of business data reviewed (over) | data_subset	400
Reserve development, prior years	$ 232.3	$ 88.5	$ 25.9
2018
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Reserve development, prior years	131
2017
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Reserve development, prior years	73
Short-duration Insurance Contracts, Accident Years 2017 and 2016 [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Reserve development, prior years		99
Short-duration Insurance Contracts, Accident Years 2015 and Prior [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Reserve development, prior years		(10)
Short-duration Insurance Contracts, Accident Year 2016 and 2015 [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Reserve development, prior years			64
Short-duration Insurance Contracts, Accident Years 2014 and Prior [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Reserve development, prior years			(38)
Commercial Lines Segment
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Reserve development, prior years	83	(4)	1
Property Segment
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Reserve development, prior years	$ 12	3	(37)
environmental, asbestos, and general liability [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Percentage of reserves	0.06%
Auto
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Percentage of reserves	96.00%
Personal Auto | Personal Lines Segment
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Reserve development, prior years	$ 121	85	$ 70
Special Lines [Member] | Personal Lines Segment
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Reserve development, prior years	$ 14	$ 5
Agency Channel | Personal Auto | Personal Lines Segment
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Percent of personal auto Prior Year Claims and Claims Adjustment Expense		70.00%
Direct Channel | Personal Auto | Personal Lines Segment
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Percent of personal auto Prior Year Claims and Claims Adjustment Expense		30.00%

Loss And Loss Adjustment Expe_5

Loss And Loss Adjustment Expense Reserves Incurred and Paid Claims Development with IBNR and Claim Counts (Details) $ in Millions	Dec. 31, 2019USD ($)claim	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Claims Development [Line Items]
Liabilities for claims and claim adjustment expenses, net of reinsurance	$ 13,614.3	$ 11,745
Commercial Lines - Physical Damage | Commercial Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,117.2
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,051
All outstanding liabilities before 2015, net of reinsurance1	0.4
Liabilities for claims and claim adjustment expenses, net of reinsurance	66.6	53.9
Commercial Lines - Liability | Commercial Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	7,363.1
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	4,318.3
All outstanding liabilities before 2015, net of reinsurance1	36
Liabilities for claims and claim adjustment expenses, net of reinsurance	3,080.8	2,504.2
Property | Property Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	3,433.1
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	3,079.2
All outstanding liabilities before 2015, net of reinsurance1	3.3
Liabilities for claims and claim adjustment expenses, net of reinsurance	357.2	314.7
2015 | Commercial Lines - Physical Damage | Commercial Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	272.4	272.4	$ 273.5	$ 274.1	$ 274.4
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 0
Cumulative Number of Incurred Claim Counts | claim	62,593
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 272.3	272.2	272	271.9	248.5
2015 | Commercial Lines - Liability | Commercial Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	891.3	899.7	914.8	911.1	897.6
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 0
Cumulative Number of Incurred Claim Counts | claim	77,819
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 848.9	786.3	675	501.5	238.4
2015 | Property | Property Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	396.3	398.8	403.6	416.5	460
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 0.9
Cumulative Number of Incurred Claim Counts | claim	41,998
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 393.5	390.1	383.5	372.8	280.3
2016 | Commercial Lines - Physical Damage | Commercial Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	377.8	378.2	379.8	379.6
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ (0.7)
Cumulative Number of Incurred Claim Counts | claim	74,193
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 377.5	376.8	376.9	336.7
2016 | Commercial Lines - Liability | Commercial Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	1,238.9	1,231.1	1,204.8	1,185.8
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 17.2
Cumulative Number of Incurred Claim Counts | claim	92,684
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 1,073.3	886	639.9	298.6
2016 | Property | Property Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	536.5	537.1	541.2	568.6
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 5.1
Cumulative Number of Incurred Claim Counts | claim	53,665
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 526.4	516.9	498.2	415.2
2017 | Commercial Lines - Physical Damage | Commercial Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	411	412.1	415.4
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ (0.6)
Cumulative Number of Incurred Claim Counts | claim	77,163
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 409.2	409.4	369
2017 | Commercial Lines - Liability | Commercial Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	1,393.3	1,366.6	1,374.1
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 30.8
Cumulative Number of Incurred Claim Counts | claim	97,297
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 1,027.3	712.9	325.8
2017 | Property | Property Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	683.4	680.9	672.8
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 4.1
Cumulative Number of Incurred Claim Counts | claim	72,728
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 670.1	647.1	506.7
2018 | Commercial Lines - Physical Damage | Commercial Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	478.2	475
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ (2.4)
Cumulative Number of Incurred Claim Counts | claim	82,183
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 475.1	426
2018 | Commercial Lines - Liability | Commercial Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	1,736.5	1,700.8
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 97.7
Cumulative Number of Incurred Claim Counts | claim	111,146
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 913.4	382.7
2018 | Property | Property Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	845.2	839
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 34.9
Cumulative Number of Incurred Claim Counts | claim	63,243
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 781.2	595.9
2019 | Commercial Lines - Physical Damage | Commercial Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	577.8
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ (14.3)
Cumulative Number of Incurred Claim Counts | claim	91,920
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 516.9
2019 | Commercial Lines - Liability | Commercial Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,103.1
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 343.7
Cumulative Number of Incurred Claim Counts | claim	124,829
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 455.4
2019 | Property | Property Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	971.7
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 160.2
Cumulative Number of Incurred Claim Counts | claim	66,824
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 708
Agency Channel | Personal Lines - Liability | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	23,531.5
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	18,477.3
All outstanding liabilities before 2015, net of reinsurance1	63.2
Liabilities for claims and claim adjustment expenses, net of reinsurance	5,117.4	4,509
Agency Channel | Personal Lines - Physical Damage | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	13,278.6
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	13,246.6
All outstanding liabilities before 2015, net of reinsurance1	0.4
Liabilities for claims and claim adjustment expenses, net of reinsurance	32.4	43.3
Agency Channel | 2015 | Personal Lines - Liability | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	3,776	3,815.6	3,798.8	3,773.8	3,774.9
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 0
Cumulative Number of Incurred Claim Counts | claim	704,986
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 3,715.4	3,623.3	3,416.5	2,976	1,793.1
Agency Channel | 2015 | Personal Lines - Physical Damage | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,134.5	2,131.5	2,134.4	2,137.2	2,136.8
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 0
Cumulative Number of Incurred Claim Counts | claim	1,336,520
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 2,133.6	2,134.1	2,134.4	2,138.1	2,106.2
Agency Channel | 2016 | Personal Lines - Liability | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	4,177.3	4,152	4,130	4,082.9
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 62.3
Cumulative Number of Incurred Claim Counts | claim	740,385
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 3,969.5	3,723.1	3,231.5	1,941.6
Agency Channel | 2016 | Personal Lines - Physical Damage | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,400.1	2,401.8	2,398.9	2,423.4
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ (3.8)
Cumulative Number of Incurred Claim Counts | claim	1,399,077
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 2,402.2	2,402.1	2,406.9	2,391
Agency Channel | 2017 | Personal Lines - Liability | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	4,511.1	4,485.8	4,474.8
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 82.5
Cumulative Number of Incurred Claim Counts | claim	779,082
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 4,048.5	3,478.5	2,074
Agency Channel | 2017 | Personal Lines - Physical Damage | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,643.5	2,638.5	2,635.5
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ (2.9)
Cumulative Number of Incurred Claim Counts | claim	1,514,531
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 2,640.9	2,643.2	2,599.8
Agency Channel | 2018 | Personal Lines - Liability | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	5,182.1	5,141.8
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 224.2
Cumulative Number of Incurred Claim Counts | claim	854,146
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 4,028.7	2,378
Agency Channel | 2018 | Personal Lines - Physical Damage | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,822.6	2,819
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ (12.3)
Cumulative Number of Incurred Claim Counts | claim	1,694,380
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 2,827.4	2,769.1
Agency Channel | 2019 | Personal Lines - Liability | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	5,885
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 871.8
Cumulative Number of Incurred Claim Counts | claim	909,050
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 2,715.2
Agency Channel | 2019 | Personal Lines - Physical Damage | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	3,277.9
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ (167.6)
Cumulative Number of Incurred Claim Counts | claim	1,872,822
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 3,242.5
Direct Channel | Personal Lines - Liability | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	22,233.2
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	17,339.8
All outstanding liabilities before 2015, net of reinsurance1	43.4
Liabilities for claims and claim adjustment expenses, net of reinsurance	4,936.8	4,258.6
Direct Channel | Personal Lines - Physical Damage | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	14,288.3
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	14,296.4
All outstanding liabilities before 2015, net of reinsurance1	0.4
Liabilities for claims and claim adjustment expenses, net of reinsurance	(7.7)	18.4
Direct Channel | 2015 | Personal Lines - Liability | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	3,368.7	3,399.3	3,354.2	3,328.3	3,330.5
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 0
Cumulative Number of Incurred Claim Counts | claim	659,243
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 3,323.1	3,238.2	3,021	2,615	1,545.2
Direct Channel | 2015 | Personal Lines - Physical Damage | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,093.9	2,090.8	2,093.5	2,097.7	2,110.7
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 0
Cumulative Number of Incurred Claim Counts | claim	1,540,071
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 2,093.1	2,093.7	2,094.7	2,100.1	$ 2,094.7
Direct Channel | 2016 | Personal Lines - Liability | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	3,897.8	3,871.2	3,843.9	3,819
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 53.9
Cumulative Number of Incurred Claim Counts | claim	735,653
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 3,714.6	3,476.9	2,991.1	1,780.6
Direct Channel | 2016 | Personal Lines - Physical Damage | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,475.6	2,477.7	2,475.4	2,521
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ (4.3)
Cumulative Number of Incurred Claim Counts | claim	1,676,343
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 2,478.5	2,479.3	2,485.8	$ 2,505
Direct Channel | 2017 | Personal Lines - Liability | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	4,229.3	4,209.9	4,209.5
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 70.9
Cumulative Number of Incurred Claim Counts | claim	772,712
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 3,808.3	3,255.2	1,912.6
Direct Channel | 2017 | Personal Lines - Physical Damage | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,749	2,743.7	2,750.6
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ (4.1)
Cumulative Number of Incurred Claim Counts | claim	1,791,190
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 2,748.4	2,753.5	$ 2,742.1
Direct Channel | 2018 | Personal Lines - Liability | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	4,980.9	4,904.8
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 204.4
Cumulative Number of Incurred Claim Counts | claim	868,604
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 3,863.5	2,235.1
Direct Channel | 2018 | Personal Lines - Physical Damage | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	3,181.9	3,202.3
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ (18.8)
Cumulative Number of Incurred Claim Counts | claim	2,069,525
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 3,193.8	$ 3,170
Direct Channel | 2019 | Personal Lines - Liability | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	5,756.5
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 811.4
Cumulative Number of Incurred Claim Counts | claim	953,154
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 2,630.3
Direct Channel | 2019 | Personal Lines - Physical Damage | Personal Lines Segment
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	3,787.9
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ (237.7)
Cumulative Number of Incurred Claim Counts | claim	2,282,681
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 3,782.6

Loss And Loss Adjustment Expe_6

Loss And Loss Adjustment Expense Reserves Reconciliation of the Claims Development to the Liability for Claims and Claim Adjustment Expenses (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	$ 13,614.3	$ 11,745
Total reinsurance recoverable on unpaid claims	3,200.1	2,562.1
Unallocated claims adjustment expense related to:	1,278.9	1,083.1
Total gross liability for unpaid claims and claim adjustment expense	18,105.4	15,400.8	$ 13,086.9	$ 11,368
Other business
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	30.8	42.9
Total reinsurance recoverable on unpaid claims	288.1	222.1
Commercial Lines Segment | Commercial Lines - Liability
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	3,080.8	2,504.2
Total reinsurance recoverable on unpaid claims	482.6	287.4
Commercial Lines Segment | Commercial Lines - Physical Damage
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	66.6	53.9
Total reinsurance recoverable on unpaid claims	0.5	0
Property Segment | Property
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	357.2	314.7
Total reinsurance recoverable on unpaid claims	184.1	145.4
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claim Adjustment Expense, Other Reconciling Item	12.1	10.6
Agency Channel | Personal Lines Segment | Personal Lines - Liability
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	5,117.4	4,509
Total reinsurance recoverable on unpaid claims	930.7	836.8
Agency Channel | Personal Lines Segment | Personal Lines - Physical Damage
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	32.4	43.3
Total reinsurance recoverable on unpaid claims	0	0
Direct Channel | Personal Lines Segment | Personal Lines - Liability
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	4,936.8	4,258.6
Total reinsurance recoverable on unpaid claims	1,314.1	1,070.4
Direct Channel | Personal Lines Segment | Personal Lines - Physical Damage
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	(7.7)	18.4
Total reinsurance recoverable on unpaid claims	$ 0	$ 0

Loss And Loss Adjustment Expe_7

Loss And Loss Adjustment Expense Reserves Historical Claims Duration (Details)	Dec. 31, 2019
Personal Lines Segment | Agency Channel | Personal Lines - Liability
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	46.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	31.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	12.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	5.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	2.40%
Personal Lines Segment | Agency Channel | Personal Lines - Physical Damage
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	98.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	1.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	(0.20%)
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	0.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	0.00%
Personal Lines Segment | Direct Channel | Personal Lines - Liability
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	45.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	31.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	12.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	6.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	2.50%
Personal Lines Segment | Direct Channel | Personal Lines - Physical Damage
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	100.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	0.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	(0.20%)
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	0.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	0.00%
Commercial Lines Segment | Commercial Lines - Liability
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	23.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	28.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	20.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	14.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	7.00%
Commercial Lines Segment | Commercial Lines - Physical Damage
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	89.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	9.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	0.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	0.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	0.00%
Property Segment | Property
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	73.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	20.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	3.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	1.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	0.90%

Reinsurance Effect of Reinsuran

Reinsurance Effect of Reinsurance on Premiums Written and Earned (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct premiums written	$ 39,222	$ 33,753.1	$ 27,860.7
Ceded written	(1,644.1)	(1,143.2)	(728.6)
Net premiums written	37,577.9	32,609.9	27,132.1
Direct premiums earned	37,519.7	31,970.2	26,425.7
Ceded earned	(1,327.3)	(1,036.9)	(695.8)
Net premiums earned	36,192.4	30,933.3	25,729.9
non regulated reinsurance plan [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Ceded written	(933)	(546.8)	(222.7)
Ceded earned	(656.5)	(479.4)	(216.2)
Regulated reinsurance plan [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Ceded written	(711.1)	(596.4)	(505.9)
Ceded earned	$ (670.8)	$ (557.5)	$ (479.6)

Reinsurance Prepaid Reinsurance

Reinsurance Prepaid Reinsurance Premiums and Reinsurance Recoverables (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Reinsurance Recoverables, Including Reinsurance Premium Paid	$ 3,378.9	$ 2,696.1
Percentage Of Total Reinsurance Recoverables	100.00%	100.00%
Prepaid reinsurance premiums	$ 626.5	$ 309.7
Percentage Of Total Prepaid Reinsurance Premiums	100.00%	100.00%
State Reinsurance Plans [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Reinsurance Recoverables, Including Reinsurance Premium Paid	$ 2,764.6	$ 2,285.9
Percentage Of Total Reinsurance Recoverables	82.00%	85.00%
Prepaid reinsurance premiums	$ 259.1	$ 218.7
Percentage Of Total Prepaid Reinsurance Premiums	41.00%	71.00%
State Reinsurance Plans [Member] | Michigan Catastrophic Claims Association [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Reinsurance Recoverables, Including Reinsurance Premium Paid	$ 2,247.1	$ 1,903.9
Percentage Of Total Reinsurance Recoverables	67.00%	71.00%
Prepaid reinsurance premiums	$ 71.8	$ 55.3
Percentage Of Total Prepaid Reinsurance Premiums	12.00%	18.00%
State Reinsurance Plans [Member] | Commercial Auto Insurance Procedures Plans [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Reinsurance Recoverables, Including Reinsurance Premium Paid	$ 332.4	$ 254.7
Percentage Of Total Reinsurance Recoverables	10.00%	9.00%
Prepaid reinsurance premiums	$ 93.8	$ 72.9
Percentage Of Total Prepaid Reinsurance Premiums	15.00%	24.00%
State Reinsurance Plans [Member] | Florida Hurricane Catastrophe Fund [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Reinsurance Recoverables, Including Reinsurance Premium Paid	$ 86	$ 18.5
Percentage Of Total Reinsurance Recoverables	3.00%	1.00%
Prepaid reinsurance premiums	$ 0	$ 0
Percentage Of Total Prepaid Reinsurance Premiums	0.00%	0.00%
State Reinsurance Plans [Member] | North Carolina Reinsurance Facility [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Reinsurance Recoverables, Including Reinsurance Premium Paid	$ 84.4	$ 78.1
Percentage Of Total Reinsurance Recoverables	2.00%	3.00%
Prepaid reinsurance premiums	$ 33.8	$ 34
Percentage Of Total Prepaid Reinsurance Premiums	5.00%	11.00%
State Reinsurance Plans [Member] | other reinsurance program [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Reinsurance Recoverables, Including Reinsurance Premium Paid	$ 3.1	$ 2.9
Percentage Of Total Reinsurance Recoverables	0.00%	0.00%
Prepaid reinsurance premiums	$ 1	$ 0.6
Percentage Of Total Prepaid Reinsurance Premiums	0.00%	0.00%
Federal Reinsurance Plans [Member] | National Flood Insurance Program [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Reinsurance Recoverables, Including Reinsurance Premium Paid	$ 11.6	$ 27.8
Percentage Of Total Reinsurance Recoverables	0.00%	1.00%
Prepaid reinsurance premiums	$ 58.7	$ 55.9
Percentage Of Total Prepaid Reinsurance Premiums	9.00%	18.00%
Commercial Lines reinsurance program [Member] [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Reinsurance Recoverables, Including Reinsurance Premium Paid	$ 459.5	$ 254.2
Percentage Of Total Reinsurance Recoverables	14.00%	10.00%
Prepaid reinsurance premiums	$ 352.9	$ 79.2
Percentage Of Total Prepaid Reinsurance Premiums	56.00%	25.00%
Property reinsurance program [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Reinsurance Recoverables, Including Reinsurance Premium Paid	$ 146.8	$ 147.7
Percentage Of Total Reinsurance Recoverables	4.00%	5.00%
Prepaid reinsurance premiums	$ 14.5	$ 11.8
Percentage Of Total Prepaid Reinsurance Premiums	3.00%	4.00%
other reinsurance program [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Reinsurance Recoverables, Including Reinsurance Premium Paid	$ 8	$ 8.3
Percentage Of Total Reinsurance Recoverables	0.00%	0.00%
Prepaid reinsurance premiums	$ 0	$ 0
Percentage Of Total Prepaid Reinsurance Premiums	0.00%	0.00%
Non State Reinsurance Plans [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Reinsurance Recoverables, Including Reinsurance Premium Paid	$ 614.3	$ 410.2
Percentage Of Total Reinsurance Recoverables	18.00%	15.00%
Prepaid reinsurance premiums	$ 367.4	$ 91
Percentage Of Total Prepaid Reinsurance Premiums	59.00%	29.00%

Reinsurance - Additional Inform

Reinsurance - Additional Information (Detail) - state	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Transportation Network Company [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Number of States in which Entity Operates	17	4	1

Statutory Financial Informati_2

Statutory Financial Information - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statutory Financial Information Disclosures [Abstract]
Consolidated statutory policyholders' surplus	$ 13,671.1	$ 11,571.8
Statutory net income	3,489.7	$ 2,643	$ 1,416.2
Consolidated statutory policyholders' surplus, net admitted assets of insurance subsidiaries and affiliate that are required to meet minimum statutory surplus requirements in such entities' states of domicile	1,063.2
Aggregate cash dividends paid to the parent company by subsidiaries	2,277.9
Maximum aggregate dividend amount subsidiaries could pay without prior approval from regulatory authorities	$ 3,319.3

Employee Benefit Plans Amounts

Employee Benefit Plans Amounts Charged to Income for employees Incentive Compensation Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Incentive Compensation Cash Award
Incentive Compensation Plans Expense [Line Items]
Pretax	$ 598.4	$ 539.5	$ 461.3
After Tax	472.7	426.2	299.8
Employee Stock
Incentive Compensation Plans Expense [Line Items]
Pretax	90.1	76.2	92.9
After Tax	71.2	60.2	60.4
Employee Stock Option
Incentive Compensation Plans Expense [Line Items]
Pretax	0.1	1	2.5
After Tax	$ 0.1	$ 0.8	$ 1.6

Employee Benefit Plans Summary

Employee Benefit Plans Summary of All Employee Restricted Equity Award Activity (Detail) - Employee Restricted Equity Awards - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of Shares
Beginning of year	4,856,356	5,858,848	6,951,373
Add (deduct):
Granted	1,835,145	1,876,109	2,383,475
Vested	(2,691,337)	(2,811,070)	(3,220,671)
Forfeited	(121,087)	(67,531)	(255,329)
End of year	3,879,077	4,856,356	5,858,848
Weighted Average Grant Date Fair Value
Beginning of year	$ 38.56	$ 30.47	$ 26.18
Granted	49.61	45.55	32.01
Vested	31.85	26.41	22.53
Forfeited	43.98	36.10	28.03
End of year	$ 48.28	$ 38.56	$ 30.47
Unrecognized compensation cost related to unvested equity awards	$ 95.9
Period of recognition of compensation expense related to unvested equity awards	2 years 3 months 18 days
Dividend Equivalent Units
Add (deduct):
Granted	210,159	144,668	157,396
Weighted Average Grant Date Fair Value
Granted	$ 0	$ 0	$ 0
Performance Shares
Weighted Average Grant Date Fair Value
Target shares	726,712
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Expected To Vest Number	1,740,712

Employee Benefit Plans Summar_2

Employee Benefit Plans Summary of ARX employee stock option plans (Details) - Employee Stock Option - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	10,438	16,067	22,550	24,995
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$ 701.66	$ 588.15	$ 564.60	$ 526.46
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	(5,329)	(6,483)	(2,445)
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	$ 353.67	$ 506.26	$ 174.65
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	(300)	0	0
Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price	$ 803.64	$ 0	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number	10,438	13,967	17,950
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 701.66	$ 562.17	$ 517.75
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 5.9	$ 6.2	$ 2.9
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares	0	2,100	4,600	8,000
Share-based Compensation Arrangement by Share-based Payment Award, Option, Nonvested, Weighted Average Exercise Price	$ 0	$ 760.93	$ 747.45	$ 712.74
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares	(1,800)	(2,500)	(3,400)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Weighted Average Grant Date Fair Value	$ 753.82	$ 736.12	$ 665.79
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Number of Shares	300	0	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Weighted Average Grant Date Fair Value	$ 803.64	$ 0	$ 0

Employee Benefit Plans Summar_3

Employee Benefit Plans Summary of all Directors' Restricted Stock Activity (Detail) - Non Employee Director Restricted Equity Awards - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to unvested equity awards	$ 0.8	$ 0.9	$ 0.7
Number of Shares
Beginning of year	41,706	53,284	55,839
Add (deduct):
Granted	38,451	41,706	53,284
Vested	(41,706)	(53,284)	(55,839)
End of year	38,451	41,706	53,284
Weighted Average Grant Date Fair Value
Beginning of year	$ 62.23	$ 40.54	$ 33.24
Granted	73.43	62.23	40.54
Vested	62.23	40.54	33.24
End of year	$ 73.43	$ 62.23	$ 40.54

Employee Benefit Plans Assets H

Employee Benefit Plans Assets Held in Deferral Plan Irrevocable Grantor Trust Account (Detail) - USD ($) shares in Millions, $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Assets held in Deferral Plan Irrevocable Grantor Trust account	$ 272.8	$ 238.7
Other Investment Funds
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Assets held in Deferral Plan Irrevocable Grantor Trust account	151.2	124
Common Stock [Member] | Progressive common shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Assets held in Deferral Plan Irrevocable Grantor Trust account	$ 121.6	$ 114.7
Deferred Compensation Arrangement with Individual, Shares Authorized for Issuance	3.2	3.6

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)Personshares	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Benefits Disclosure [Line Items]
Minimum employment period for benefits	30 days
Postemployment benefits liability | $	$ 22.2	$ 20.2
Compensation, Percentage	100.00%
Employee Restricted Equity Awards
Employee Benefits Disclosure [Line Items]
Aggregate fair value of the restricted equity awards that vested during the period | $	$ 191.6	162.7	$ 130.5
Non Employee Director Restricted Equity Awards
Employee Benefits Disclosure [Line Items]
Vesting period of grants to date	11 months
Total pretax intrinsic value of options exercised and restricted stock vested | $	$ 3	$ 3.2	$ 2.2
Executive Deferred Compensation Plan
Employee Benefits Disclosure [Line Items]
Common shares reserved for issuance under executive deferred compensation plan	11,100,000
2017 Directors Equity Incentive Plan | Non Employee Director Restricted Equity Awards
Employee Benefits Disclosure [Line Items]
Shares authorized	500,000
Equity Incentive Plan Twenty Ten [Member]
Employee Benefits Disclosure [Line Items]
Shares authorized	0
share based compensation arrangement by share based payment award, number of shares transferred	4,000,000
Equity Incentive Plan Twenty Fifteen [Domain]
Employee Benefits Disclosure [Line Items]
Shares authorized	17,000,000
Performance Based Restricted Equity Awards
Employee Benefits Disclosure [Line Items]
Estimated Number Of Participants | Person	40
Performance Based Restricted Equity Awards | Insurance Operating Results | Lower Limit
Employee Benefits Disclosure [Line Items]
Performance-based awards granted vesting percentage of the award amount	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%
Performance Based Restricted Equity Awards | Insurance Operating Results | Upper Limit
Employee Benefits Disclosure [Line Items]
Performance-based awards granted vesting percentage of the award amount	250.00%	250.00%	250.00%	250.00%	250.00%	250.00%
Performance Based Restricted Equity Awards | Investment Results | Lower Limit
Employee Benefits Disclosure [Line Items]
Performance-based awards granted vesting percentage of the award amount	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%
Performance Based Restricted Equity Awards | Investment Results | Upper Limit
Employee Benefits Disclosure [Line Items]
Performance-based awards granted vesting percentage of the award amount	200.00%	200.00%	200.00%	200.00%	200.00%	200.00%
Performance Based Restricted Equity Awards | Unit growth in a particular customer segment [Member] | Lower Limit
Employee Benefits Disclosure [Line Items]
Performance-based awards granted vesting percentage of the award amount			85.00%	85.00%
Performance Based Restricted Equity Awards | Unit growth in a particular customer segment [Member] | Upper Limit
Employee Benefits Disclosure [Line Items]
Performance-based awards granted vesting percentage of the award amount			150.00%	150.00%
Performance Based Restricted Equity Awards | Unit growth in a particular customer segment, performance objective not achieved
Employee Benefits Disclosure [Line Items]
Performance-based awards granted vesting percentage of the award amount			0.00%	0.00%
Defined Contribution Pension Plan 401k
Employee Benefits Disclosure [Line Items]
Matching contributions | $	$ 120.8	$ 106.8	$ 97.3
Defined Contribution Pension Plan 401k | Upper Limit
Employee Benefits Disclosure [Line Items]
Matching contribution to defined contribution pension plan	6.00%
Cash [Member]
Employee Benefits Disclosure [Line Items]
Compensation, Percentage	40.00%
Non Employee Director Restricted Equity Awards
Employee Benefits Disclosure [Line Items]
Compensation, Percentage	60.00%
Vesting tranche one | Employee Restricted Equity Awards
Employee Benefits Disclosure [Line Items]
Vesting period of grants to date	3 years
Vesting tranche two | Employee Restricted Equity Awards
Employee Benefits Disclosure [Line Items]
Vesting period of grants to date	4 years
Vesting tranche three | Employee Restricted Equity Awards
Employee Benefits Disclosure [Line Items]
Vesting period of grants to date	5 years
Common Stock [Member]
Employee Benefits Disclosure [Line Items]
Employee Stock Ownership Plan Shares held	23,000,000

Segment Information Operating R

Segment Information Operating Results (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues	$ 39,022.3	$ 31,979	$ 26,839
Pretax Profit (Loss)	5,160.3	3,163.6	2,138.9
Personal Lines Segment | Agency Channel | Underwriting Operations
Segment Reporting Information [Line Items]
Revenues	14,904.1	13,017.2	11,177.6
Pretax Profit (Loss)	1,673.2	1,435.7	839.6
Personal Lines Segment | Direct Channel | Underwriting Operations
Segment Reporting Information [Line Items]
Revenues	15,305.9	13,017.5	10,769.6
Pretax Profit (Loss)	1,181.4	1,088.5	683.7
Operating Segments | Underwriting Operations
Segment Reporting Information [Line Items]
Revenues	36,192.4	30,933.3	25,729.9
Pretax Profit (Loss)	3,287.3	2,915	1,686.9
Operating Segments | Personal Lines Segment | Underwriting Operations
Segment Reporting Information [Line Items]
Revenues	30,210	26,034.7	21,947.2
Pretax Profit (Loss)	2,854.6	2,524.2	1,523.3
Operating Segments | Commercial Lines Segment | Underwriting Operations
Segment Reporting Information [Line Items]
Revenues	4,427.6	3,610.9	2,793.9
Pretax Profit (Loss)	458.8	478.6	214.1
Operating Segments | Property Segment | Underwriting Operations
Segment Reporting Information [Line Items]
Revenues	1,554.8	1,287.7	988.8
Pretax Profit (Loss)	(26.1)	(88.7)	(50.3)
Operating Segments | Other Indemnity | Underwriting Operations
Segment Reporting Information [Line Items]
Revenues	0	0	0
Pretax Profit (Loss)	0	0.9	(0.2)
Segment Reconciling Items | Fees And Other Revenues
Segment Reporting Information [Line Items]
Revenues	563.7	472.2	370.6
Segment Reconciling Items | Service Businesses
Segment Reporting Information [Line Items]
Revenues	195	158.5	126.8
Pretax Profit (Loss)	16.1	24.4	17.3
Segment Reconciling Items | Investments
Segment Reporting Information [Line Items]
Revenues	2,071.2	415	612.7
Pretax Profit (Loss)	2,046.6	390.7	588.8
Segment Reconciling Items | Other gains (losses)
Segment Reporting Information [Line Items]
Revenues	0	0	(1)
Pretax Profit (Loss)	0	0	(1)
Segment Reconciling Items | Interest Expense
Segment Reporting Information [Line Items]
Pretax Profit (Loss)	$ (189.7)	$ (166.5)	$ (153.1)

Segment Information Operating_2

Segment Information Operating Results (Phantom) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Amortization of intangible assets	$ 66.3	$ 72	$ 66.2
Personal Lines Segment | Underwriting Operations | Operating Segments
Segment Reporting Information [Line Items]
Personal auto insurance percentage of the total personal lines segment net premiums earned	94.00%	94.00%	93.00%
Property Segment | Underwriting Operations | Operating Segments
Segment Reporting Information [Line Items]
Amortization of intangible assets	$ 66.3	$ 72	$ 66.2

Segment Information Underwritin

Segment Information Underwriting Margins and Combined Ratios for our Underwriting Operations (Details) - Underwriting Operations	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Personal Lines Segment | Agency Channel
Segment Reporting Information [Line Items]
Underwriting Margin	11.20%	11.00%	7.50%
Combined Ratio	88.80%	89.00%	92.50%
Personal Lines Segment | Direct Channel
Segment Reporting Information [Line Items]
Underwriting Margin	7.70%	8.40%	6.30%
Combined Ratio	92.30%	91.60%	93.70%
Operating Segments
Segment Reporting Information [Line Items]
Underwriting Margin	9.10%	9.40%	6.60%
Combined Ratio	90.90%	90.60%	93.40%
Operating Segments | Personal Lines Segment
Segment Reporting Information [Line Items]
Underwriting Margin	9.50%	9.70%	6.90%
Combined Ratio	90.50%	90.30%	93.10%
Operating Segments | Commercial Lines Segment
Segment Reporting Information [Line Items]
Underwriting Margin	10.40%	13.30%	7.70%
Combined Ratio	89.60%	86.70%	92.30%
Operating Segments | Property Segment
Segment Reporting Information [Line Items]
Underwriting Margin	(1.70%)	(6.90%)	(5.10%)
Combined Ratio	101.70%	106.90%	105.10%
Combined ratio amortization points	0.043	0.056	0.067

Segment Information - Additiona

Segment Information - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)Entity	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Segment Reporting Information [Line Items]
Depreciation | $	$ 239.8	$ 190.4	$ 169.9
Operating Segments | Personal Lines Segment | Agency Channel | Lower Limit
Segment Reporting Information [Line Items]
Independent insurance agencies and brokerages | Entity	35,000

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	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]
AOCI before Tax, Attributable to Parent, beginning balance	$ (153)	$ 1,977.8	$ 1,439.5
Pretax Cumulative Effect of New Accounting Principal in Period of Adoption		(2,006)
Pretax Reclassification of Stranded Amounts in AOCI to Equity		(4.3)
AOCI before Tax, Attributable to Parent, after Cumulative Effect Adjustment and Reclassification of Stranded Amounts		(32.5)
Unrealized Holding Gain (Loss) on Securities Arising During the Period, before tax	825.8	(224.1)	636.9
Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	0	0	(8)
Foreign Currently Translation Adjustment, before tax	0	0	0.4
Portion Attributable to Noncontrolling Interest, before tax	(5.9)	4.3	(3.5)
Total other comprehensive income (loss) before reclassifications, before tax	819.9	(219.8)	625.8
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, before Tax	0	0	(14.9)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax	232.2	(98.3)	103.3
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, before Tax	0	0	(1.2)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	(1)	(1)	0.3
Total reclassification adjustment for amounts realized in net income, before tax	231.2	(99.3)	87.5
Total other comprehensive income, before tax	588.7	(120.5)	538.3
AOCI before Tax, Attributable to Parent, ending balance	435.7	(153)	1,977.8
Accumulated Other Comprehensive Income (Loss), Tax [Roll Forward]
AOCI Tax, Attributable to Parent, beginning balance	32.1	(695.6)	(506.1)
Tax, Cumulative Effect of New Accounting Principal in Period of Adoption		705.8
Tax, Reclassification of Stranded Amounts in AOCI to Equity		(3.4)
AOCI Tax, Attributable to Parent, After Cumulative Effect Adjustment and Reclassification of Stranded Amounts		6.8
Unrealized Holding Gain (Loss) on Securities Arising During the Period, tax	(174.9)	47	(224)
Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	0	0	2.8
Foreign currency translation adjustment, tax	0	0	(0.1)
Portion Attributable to Noncontrolling Interest, tax	1.3	(1)	1.2
Total Other Comprehensive Income (Loss), before Reclassification Adjustments, Tax	(173.6)	46	(220.1)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, Tax	0	0	5.3
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax	(47.7)	20.5	(36.2)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Tax	0	0	0.4
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	0.2	0.2	(0.1)
Total reclassification adjustment for amounts realized in net income, Total tax (provisions) benefit	(47.5)	20.7	(30.6)
Total other comprehensive income, Total tax (provision) benefit	(126.1)	25.3	(189.5)
AOCI Tax, Attributable to Parent, ending balance	(94)	32.1	(695.6)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
After tax total accumulated other comprehensive income, beginning balance	(120.9)	1,282.2	933.4
Cumulative Effect of New Accounting Principle in Period of Adoption		(1,300.2)
Reclassification of Stranded Amounts in AOCI to Equity		(7.7)
AOCI, Net of Tax, After Cumulative Effect Adjustment and Reclassification of Stranded Amounts		(25.7)
Unrealized Holding Gain (Loss) on Securities Arising During Period, after tax	650.9	(177.1)	412.9
Unrealized Gain (Loss) on Derivatives Arising During Period, after tax	0	0	(5.2)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	0	0	0.3
Other comprehensive (income) loss attributable to NCI	(4.6)	3.3	(2.3)
Total other comprehensive income (loss), before reclassifications, after tax	646.3	(173.8)	405.7
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, Net of Tax	0	0	(9.6)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	184.5	(77.8)	67.1
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax	0	0	(0.8)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	(0.8)	(0.8)	0.2
Total reclassification adjustment for amounts realized in net income, Net of tax	183.7	(78.6)	56.9
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	462.6	(95.2)	348.8
After tax total accumulated other comprehensive income, ending balance	341.7	(120.9)	1,282.2
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	939.6
Cumulative Effect of New Accounting Principle in Period of Adoption		(1,300.2)
Reclassification of Stranded Amounts in AOCI to Equity		(1.1)
AOCI, Net of Tax, After Cumulative Effect Adjustment and Reclassification of Stranded Amounts		(6.3)
Unrealized Holding Gain (Loss) on Securities Arising During Period, after tax	650.9	(177.1)	412.9
Unrealized Gain (Loss) on Derivatives Arising During Period, after tax	0	0	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	0	0	0
Other comprehensive (income) loss attributable to NCI	0	0	0
Total other comprehensive income (loss), before reclassifications, after tax	650.9	(177.1)	412.9
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, Net of Tax	0	0	(9.6)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	184.5	(77.8)	67.1
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax	0	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	0	0	0
Total reclassification adjustment for amounts realized in net income, Net of tax	184.5	(77.8)	57.5
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	466.4	(99.3)	355.4
After tax total accumulated other comprehensive income, ending balance	360.8	(105.6)	1,295
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
After tax total accumulated other comprehensive income, beginning balance	(17.2)	(14.8)	(9.4)
Cumulative Effect of New Accounting Principle in Period of Adoption		0
Reclassification of Stranded Amounts in AOCI to Equity		(3.2)
AOCI, Net of Tax, After Cumulative Effect Adjustment and Reclassification of Stranded Amounts		(18)
Unrealized Holding Gain (Loss) on Securities Arising During Period, after tax	0	0	0
Unrealized Gain (Loss) on Derivatives Arising During Period, after tax	0	0	(5.2)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	0	0	0
Other comprehensive (income) loss attributable to NCI	0	0	0
Total other comprehensive income (loss), before reclassifications, after tax	0	0	(5.2)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, Net of Tax	0	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	0	0	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax	0	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	(0.8)	(0.8)	0.2
Total reclassification adjustment for amounts realized in net income, Net of tax	(0.8)	(0.8)	0.2
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	0.8	0.8	(5.4)
After tax total accumulated other comprehensive income, ending balance	(16.4)	(17.2)	(14.8)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
After tax total accumulated other comprehensive income, beginning balance	0	0	(1.1)
Cumulative Effect of New Accounting Principle in Period of Adoption		0
Reclassification of Stranded Amounts in AOCI to Equity		0
AOCI, Net of Tax, After Cumulative Effect Adjustment and Reclassification of Stranded Amounts		0
Unrealized Holding Gain (Loss) on Securities Arising During Period, after tax	0	0	0
Unrealized Gain (Loss) on Derivatives Arising During Period, after tax	0	0	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	0	0	0.3
Other comprehensive (income) loss attributable to NCI	0	0	0
Total other comprehensive income (loss), before reclassifications, after tax	0	0	0.3
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, Net of Tax	0	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	0	0	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax	0	0	(0.8)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	0	0	0
Total reclassification adjustment for amounts realized in net income, Net of tax	0	0	(0.8)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	0	0	1.1
After tax total accumulated other comprehensive income, ending balance	0	0	0
Noncontrolling Interest
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
After tax total accumulated other comprehensive income, beginning balance	1.9	2	4.3
Cumulative Effect of New Accounting Principle in Period of Adoption		0
Reclassification of Stranded Amounts in AOCI to Equity		(3.4)
AOCI, Net of Tax, After Cumulative Effect Adjustment and Reclassification of Stranded Amounts		(1.4)
Unrealized Holding Gain (Loss) on Securities Arising During Period, after tax	0	0	0
Unrealized Gain (Loss) on Derivatives Arising During Period, after tax	0	0	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	0	0	0
Other comprehensive (income) loss attributable to NCI	(4.6)	3.3	(2.3)
Total other comprehensive income (loss), before reclassifications, after tax	(4.6)	3.3	(2.3)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, Net of Tax	0	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	0	0	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax	0	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	0	0	0
Total reclassification adjustment for amounts realized in net income, Net of tax	0	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(4.6)	3.3	(2.3)
After tax total accumulated other comprehensive income, ending balance	$ (2.7)	$ 1.9	$ 2

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	Dec. 31, 2019USD ($)
Statement of Comprehensive Income [Abstract]
Net unrealized losses on forecasted transactions, expected to reclassify into interest expense within the next 12 months	$ 1.1

Leases - Schedule of operating

Leases - Schedule of operating lease maturities (Detail) $ in Millions	Dec. 31, 2019USD ($)
Leases [Abstract]
2020	$ 77.6
2021	64.3
2022	33.1
2023	18.5
2024	11.9
Thereafter	6.1
Total	211.5
Interest	(10)
Present value of lease liabilities	$ 201.5
Weighted-average remaining term	3 years 3 months 18 days
Weighted-average discount rate	3.00%

Leases Expenses Incurred for Le

Leases Expenses Incurred for Leases (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Leases [Abstract]
Expense	$ 102	$ 77.3	$ 77.2

- Additional Information (Detai

- Additional Information (Detail) $ in Millions	Dec. 31, 2019USD ($)
Leases [Abstract]
Operating Lease, Right-of-Use Asset	$ 188.2
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssets
Operating Lease, Liability	$ 201.5
Operating Lease, Liability, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent

Leases Schedule Of Operating Le

Leases Schedule Of Operating Lease Obligations (Details) $ in Millions	Dec. 31, 2018USD ($)
Leases [Abstract]
Operating Leases, Future Minimum Payments Due, Next Twelve Months	$ 64.1
Operating Leases, Future Minimum Payments, Due in Two Years	65.5
Operating Leases, Future Minimum Payments, Due in Three Years	52.8
Operating Leases, Future Minimum Payments, Due in Four Years	24.3
Operating Leases, Future Minimum Payments, Due in Five Years	8.5
Operating Leases, Future Minimum Payments, Due Thereafter	3.8
Operating Leases, Future Minimum Payments Due	$ 219

Dividends Dividends (Details)

Dividends Dividends (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended										12 Months Ended
	Dec. 31, 2019	Oct. 31, 2019	Sep. 30, 2019	Jul. 31, 2019	Apr. 30, 2019	Mar. 31, 2019	Feb. 28, 2019	Sep. 30, 2018	Feb. 28, 2018	Feb. 28, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Aug. 31, 2019	Jun. 30, 2019	Aug. 31, 2018	Dec. 31, 2016
Common Stock, Dividends, Per Share, Declared											$ 2.65	$ 2.5140	$ 1.1247
Quarterly dividend [Member]
Common Stock, Dividends, Per Share, Declared	$ 0.10
Common Stock, Dividends, Per Share, Cash Paid		$ 0.10		$ 0.10	$ 0.10
Annual variable dividend
Common Stock, Dividends, Per Share, Declared	$ 2.25
Common Stock, Dividends, Per Share, Cash Paid							$ 2.5140		$ 1.1247	$ 0.6808
Series B Preferred Stock
Dividends payable							$ 13.4							$ 13.4		$ 13.5
Preferred Stock, Dividends, Per Share, Cash Paid			$ 26.875			$ 26.875		$ 27.024
Common Stock [Member]
Dividends payable	$ 1,375.4										$ 1,375.4
Common Stock [Member] | Quarterly dividend [Member]
Dividends payable	58.5		$ 58.5			$ 58.4					58.5				$ 58.4
Common Stock [Member] | Annual variable dividend
Dividends payable	$ 1,316.9										$ 1,316.9	$ 1,467.9	$ 655.1				$ 395.4

Dividends-Additional Informatio

Dividends-Additional Information (Details) - $ / shares	1 Months Ended	60 Months Ended
	Mar. 31, 2023	Mar. 14, 2023	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Dividends Payable [Line Items]
Target percentage used to determine annual variable dividend			33.33%		33.33%
Gainshare factor used to determine annual variable dividend			1.91		1.79
Series B Preferred Stock
Dividends Payable [Line Items]
Preferred Stock, Shares Issued				500,000
Preferred Stock, Liquidation Preference Per Share				$ 1,000
Forecast | Series B Preferred Stock
Dividends Payable [Line Items]
Preferred Stock, Dividend Rate, Percentage		5.375%
London Interbank Offered Rate (LIBOR) [Member] | Forecast | Series B Preferred Stock
Dividends Payable [Line Items]
Preferred Stock, Basis Spread on Variable Rate	2.539%

Redeemable Noncontrolling Int_3

Redeemable Noncontrolling Interest (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)voteshares	Dec. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)	Apr. 01, 2021	Apr. 01, 2018	Apr. 01, 2015USD ($)
Redeemable Noncontrolling Interest [Line Items]
Number of stockholder votes to approve actions | vote	1
Fair value at date of acquisition						$ 411.5
Increase (Decrease) in Temporary Equity [Roll Forward]
Balance, Beginning of year	$ 214.5	$ 503.7	$ 483.7
Net income attributable to NCI	9.7	5.7	5.9
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	4.6	(3.3)	2.3
Stock Issued During Period, Value, Stock Options Exercised Attributable to Redeemable Noncontrolling Interest	7.7	9.4	3.4
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	(11.2)	(298.2)	0
Adjustment to carrying amount of redeemable noncontrolling interest	0.3	(2.8)	8.4
Balance, End of year	$ 225.6	$ 214.5	$ 503.7
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
Equity interest percentage	87.10%	86.80%	69.00%
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number | shares	10,438
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 16
ARX Holding Corp. | Forecast
Redeemable Noncontrolling Interest [Line Items]
Equity interest percentage				100.00%
Lower Limit
Redeemable Noncontrolling Interest [Line Items]
Multiple for determining purchase price of shares	1
Lower Limit | ARX Holding Corp.
Redeemable Noncontrolling Interest [Line Items]
Equity interest percentage					80.00%
Upper Limit
Redeemable Noncontrolling Interest [Line Items]
Multiple for determining purchase price of shares	2

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Net Carrying Amount of Other Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Accumulated Amortization	$ 314	$ 247.7
Indefinite-lived Intangible Assets (Excluding Goodwill)	12.4	12.4
Total	228.3	294.6
Finite-Lived Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Accumulated Amortization	313.4	247.1
Intangible assets subject to amortization	215.9	282.2
Licenses
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Accumulated Amortization	$ 0.6	$ 0.6

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Finite-lived Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	$ 314	$ 247.7
Policies in force
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	256.2	256.2
Accumulated Amortization	173.9	137.3
Net Carrying Amount	82.3	118.9
Agency relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	159.2	159.2
Accumulated Amortization	54	42.6
Net Carrying Amount	105.2	116.6
Software rights
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	79.1	79.1
Accumulated Amortization	50.7	40.1
Net Carrying Amount	28.4	39
Trade name
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	34.8	34.8
Accumulated Amortization	34.8	27.1
Net Carrying Amount	0	7.7
Finite-Lived Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	529.3	529.3
Accumulated Amortization	313.4	247.1
Net Carrying Amount	$ 215.9	$ 282.2

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets Goodwill and Intangible Assets - Amortization (Details) $ in Millions	Dec. 31, 2019USD ($)
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Finite- Lived Intangible Assets, Amortization Expense, Next Twelve Months	$ 56.9
Finite-Lived Intangible Assets, Amortization Expense, Year Two	56.6
Finite-Lived Intangible Assets, Amortization Expense, Year Three	29.2
Finite-Lived Intangible Assets, Amortization Expense, Year Four	13.5
Finite-Lived Intangible Assets, Amortization Expense, Year Five	$ 11.4

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets Goodwill (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Goodwill	$ 452,700,000	$ 452,700,000
Goodwill, Impaired, Accumulated Impairment Loss	0
Amortization of intangible assets	$ 66,300,000	$ 72,000,000	$ 66,200,000
Weighted Average [Member]
Goodwill [Line Items]
Finite-Lived Intangible Assets, Remaining Amortization Period	3 years 8 months 12 days
Trade name
Goodwill [Line Items]
Intangible assets finite lives			10 years
Finite-Lived Intangible Asset, Revised Useful Life			2 years
ARX Holding Corp. | Lower Limit
Goodwill [Line Items]
Intangible assets finite lives	2 months
ARX Holding Corp. | Upper Limit
Goodwill [Line Items]
Intangible assets finite lives	9 years

Subsequent Event (Details)

Subsequent Event (Details) - ARX Holding Corp. - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2018	Apr. 01, 2021	Dec. 31, 2019	Dec. 31, 2017
Subsequent Event [Line Items]
Equity interest percentage		86.80%		87.10%	69.00%
Payments to Acquire Interest in Subsidiaries and Affiliates		$ 295.9
Forecast
Subsequent Event [Line Items]
Equity interest percentage			100.00%
Subsequent Event | Forecast
Subsequent Event [Line Items]
Equity interest percentage	100.00%
Payments to Acquire Interest in Subsidiaries and Affiliates	$ 242