The Progressive Corporation (PGR) 10-K 29 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Jan. 31, 2016	Jun. 30, 2015
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Trading Symbol	PGR
Entity Registrant Name	PROGRESSIVE CORP/OH/
Entity Central Index Key	80,661
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		584,328,057
Entity Public Float			$ 16,089,731,768

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues
Net premiums earned	$ 19,899.1	$ 18,398.5	$ 17,103.4
Investment income	454.6	408.4	422
Other-than-temporary impairment (OTTI) losses:
Total OTTI losses	(23.8)	(7.9)	(6)
Non-credit losses, net of credit losses recognized on previously recorded non-credit OTTI losses	0	0	(0.1)
Net impairment losses recognized in earnings	(23.8)	(7.9)	(6.1)
Net realized gains (losses) on securities	136.5	232.1	324.5
Total net realized gains (losses) on securities	112.7	224.2	318.4
Fees and other revenues	302	309.1	291.8
Service revenues	86.3	56	39.6
Gains (losses) on extinguishment of debt	(0.9)	(4.8)	(4.3)
Total revenues	20,853.8	19,391.4	18,170.9
Expenses
Losses and loss adjustment expenses	14,342	13,306.2	12,472.4
Policy acquisition costs	1,651.8	1,524	1,451.8
Other underwriting expenses	2,712.1	2,467.1	2,350.9
Investment expenses	22.8	18.9	18.8
Service expenses	77.5	50.9	38.8
Interest expense	136	116.9	118.2
Total expenses	18,942.2	17,484	16,450.9
Net Income
Income before income taxes	1,911.6	1,907.4	1,720
Provision for income taxes	611.1	626.4	554.6
Cash flow hedge gain reclassification from accumulated other comprehensive income to net realized gains/losses on securities	1,300.5	1,281	1,165.4
Net Income (Loss) Attributable to Noncontrolling Interest	32.9	0	0
Net income attributable to Progressive	1,267.6	1,281	1,165.4
Net unrealized gains (losses) on securities:
Net non-credit related OTTI losses, adjusted for valuation changes	0	0	0.3
Other net unrealized gains (losses) on securities	(212.9)	74.9	84
Total net unrealized gains (losses) on securities	(212.9)	74.9	84.3
Net unrealized gains on forecasted transactions	(9.7)	(2.6)	(2)
Foreign currency translation adjustment	(1.2)	(0.9)	(1.6)
Other comprehensive income (loss)	(223.8)	71.4	80.7
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	(1.1)	0	0
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 1,044.9	$ 1,352.4	$ 1,246.1
Computation of Net Income Per Share
Average shares outstanding - Basic (shares)	585.5	590.6	599.1
Net effect of dilutive stock-based compensation (shares)	3.7	4.2	4.5
Total equivalent shares - Diluted (shares)	589.2	594.8	603.6
Basic: Net income per share (USD per share)	$ 2.16	$ 2.17	$ 1.95
Diluted: Net income per share (USD per share)	$ 2.15	$ 2.15	$ 1.93

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Investments - Available-for-sale, at fair value:
Fixed maturities (amortized cost: $15,347.9 and $13,374.2)		$ 15,332.2	$ 13,549.2
Equity securities:
Nonredeemable preferred stocks (cost: $674.2 and $590.4)		782.6	827.5
Common equities (cost: $1,494.3 and $1,289.2)		2,650.5	2,492.3
Short-term investments (amortized cost: $2,172.0 and $2,149.0)		2,172	2,149
Total investments at fair value	[1],[2]	20,937.3	19,018
Cash		224.4	108.4
Accrued investment income		102.2	87.3
Premiums receivable, net of allowance for doubtful accounts of $164.8 and $152.2		3,987.7	3,537.5
Reinsurance recoverables, including $46.1 and $46.0 on paid losses and loss adjustment expenses		1,488.8	1,231.9
Prepaid reinsurance premiums		199.3	85.3
Deferred acquisition costs		564.1	457.2
Property and equipment, net of accumulated depreciation of $778.3 and $731.0		1,037.2	960.6
Intangible Assets, Net (Excluding Goodwill)		494.9	11.3
Other assets		335.8	288.5
Goodwill		447.6	1.6
Total assets		29,819.3	25,787.6
Liabilities and Shareholders' Equity
Unearned premiums		6,621.8	5,440.1
Loss and loss adjustment expense reserves		10,039	8,857.4
Net deferred income taxes		109.3	98.9
Dividends payable		519.2	404.1
Accounts payable, accrued expenses, and other liabilities		2,067.8	1,893.8
Debt, Long-term and Short-term, Combined Amount		2,707.9	2,164.7
Total liabilities		22,065	18,859
Redeemable Noncontrolling Interest, Equity, Carrying Amount		464.9	0
Common shares, $1.00 par value (authorized 900.0; issued 797.6, including treasury shares of 214.0 and 209.8)		583.6	587.8
Paid-in capital		1,218.8	1,184.3
Retained earnings		4,686.6	4,133.4
Accumulated other comprehensive income, net of tax:
Total net unrealized gains (losses) on securities		809	1,021.9
Net unrealized gains on forecasted transactions		(8.2)	1.5
Foreign currency translation adjustment		(1.5)	(0.3)
Stockholders' Equity Attributable to Noncontrolling Interest		1.1	0
Total accumulated other comprehensive income		800.4	1,023.1
Total shareholders' equity		7,289.4	6,928.6
Total liabilities and shareholders' equity		$ 29,819.3	$ 25,787.6
[1]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at December 31, 2015, $23.1 million was included in "other assets," compared to $31.3 million in "other liabilities" at December 31, 2014.
[2]	The total fair value of the portfolio included $1.3 billion and $1.9 billion at December 31, 2015 and 2014, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Fixed maturities, amortized cost	$ 7,289,400,000	$ 6,928,600,000
Nonredeemable preferred stocks, cost	0
Common equities, cost	$ 29,819,300,000	$ 25,787,600,000
Short Term Investments Amortized Cost
Premiums receivable, allowance for doubtful accounts	$ 0
Reinsurance recoverables, paid losses and loss adjustment expenses	2,100,000	$ 0
Finite-Lived Intangible Assets, Accumulated Amortization	47.4	0.6
Property and equipment, accumulated depreciation	$ 46,100,000	$ 46,000,000
Common Shares, par value (USD per share)	$ 1	$ 1
Common Shares, authorized (shares)	900	900
Common Shares, issued (shares)	797.6	797.6
Common Shares, treasury shares (shares)	214	209.8

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity - USD ($) shares in Millions, $ in Millions		Total	Common Shares, $1.00 Par Value	Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income, Net of Tax
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest		$ 0				$ 0
Balance, Beginning of year at Dec. 31, 2012			$ 604.6	$ 1,077	$ 3,454.4	871
Net income attributable to Progressive		1,165.4			1,165.4
Other comprehensive income (loss)		80.7				80.7
Tax benefit from exercise/vesting of equity-based compensation				10.3
Treasury shares purchased	[1]		(11)	(20.4)	(242)
Net restricted equity awards (issued) (vested) forfeited			2.2	(2.2)
Cash dividends declared on common shares ($0.8882, $0.6862, and $1.4929 per share)					(889.2)
Amortization of equity-based compensation				64.9
Reinvested dividends on restricted stock units				12.4	(12.4)
Other					23.8
Balance, End of year at Dec. 31, 2013		6,189.5	595.8	1,142	3,500	951.7
Redeemable Noncontrolling Interest, Equity, Carrying Amount				0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest		0				0
Net income attributable to Progressive		1,281			1,281
Other comprehensive income (loss)		71.4				71.4
Tax benefit from exercise/vesting of equity-based compensation				12.8
Treasury shares purchased	[1]		(11.1)	(21.6)	(238.7)
Net restricted equity awards (issued) (vested) forfeited			3.1	(3.1)
Cash dividends declared on common shares ($0.8882, $0.6862, and $1.4929 per share)					(402.6)
Amortization of equity-based compensation				51.4
Reinvested dividends on restricted stock units				2.8	(2.8)
Other					(3.5)
Balance, End of year at Dec. 31, 2014		6,928.6	587.8	1,184.3	4,133.4	1,023.1
Redeemable Noncontrolling Interest, Equity, Carrying Amount		0		0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest		(1.1)				1.1
Net income attributable to Progressive		1,267.6			1,267.6
Other comprehensive income (loss)		(223.8)				(223.8)
Tax benefit from exercise/vesting of equity-based compensation				16.8
Treasury shares purchased	[1]		(7.3)	(15.2)	(186)
Net restricted equity awards (issued) (vested) forfeited			3.1	(3.1)
Cash dividends declared on common shares ($0.8882, $0.6862, and $1.4929 per share)					(520.5)
Amortization of equity-based compensation				64.5
Reinvested dividends on restricted stock units				5.7	(5.7)
Other					(2.2)
Balance, End of year at Dec. 31, 2015		$ 7,289.4	$ 583.6	1,218.8	$ 4,686.6	$ 800.4
Preferred Stock, Shares Authorized		20
Redeemable Noncontrolling Interest, Equity, Carrying Amount		$ 464.9		$ (34.2)
voting preference shares authorized		$ 5
[1]	In December 2013, we purchased 4.0 million shares at a price of $25.50 per share in a privately negotiated transaction with the "Peter B. Lewis Trust under Agreement dated December 21, 1994, as modified." Mr. Lewis was our non-executive Chairman of the Board until his death in November 2013.

Consolidated Statements of Cha6

Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Preference Shares authorized	20,000,000
Number of shares acquired in a privately negotiated transaction		4,000,000
Treasury Stock Acquired Cost per Share Privately Negotiated Transaction		$ 25.50
Retained Earnings
Cash dividends declared on common shares, per share	$ 0.8882	$ 0.6862	$ 1.4929
Serial Preferred Stock
Preference Shares authorized	20,000,000
Preference Shares issued	0
Preferred Shares outstanding	0
Voting Preferred Stock
Preference Shares authorized	5,000,000
Preference Shares issued	0

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Cash Flows [Abstract]
Cash flow hedge gain reclassification from accumulated other comprehensive income to net realized gains/losses on securities	$ 1,300.5	$ 1,281	$ 1,165.4
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	103.7	97.1	101.3
Amortization of Intangible Assets	46.8	0	0
Amortization of fixed-income securities	98.4	78.2	134
Amortization of equity-based compensation	66.2	51.4	64.9
Net realized (gains) losses on securities	(112.7)	(224.2)	(318.4)
Net (gains) losses on disposition of property and equipment	2	5.4	5.6
(Gains) losses on extinguishment of debt	0.9	4.8	4.3
Changes in:
Premiums receivable	(421.1)	(227.1)	(127.4)
Reinsurance recoverables	(202.6)	(141.7)	(189.2)
Prepaid reinsurance premiums	32.5	(10.4)	(8.6)
Deferred acquisition costs	(42.3)	(9.6)	(13.1)
Income taxes	(107.2)	97.5	57.8
Unearned premiums	632.4	266.4	244.8
Loss and loss adjustment expense reserves	(917.7)	(378)	(641.6)
Accounts payable, accrued expenses, and other liabilities	37.9	92	165
Other, net	(60.2)	(13.2)	(28.1)
Net cash provided by operating activities	2,292.9	1,725.6	1,899.9
Purchases:
Fixed maturities	(9,311.1)	(7,967.5)	(7,100.6)
Equity securities	(647.1)	(369.7)	(322.2)
Sales:
Fixed maturities	4,913.5	5,637.5	3,083.9
Equity securities	402.4	560.1	369.2
Maturities, paydowns, calls, and other:
Fixed maturities	3,579.5	2,296.6	1,859.6
Equity securities	12	14.3	21.5
Net sales (purchases) of short-term investments	20.5	(876)	716.6
Net unsettled security transactions	(8.2)	(30)	152.2
Purchases of property and equipment	(130.7)	(108.1)	(140.4)
Sales of property and equipment	10.6	5.9	3.7
Payments to Acquire Businesses, Net of Cash Acquired	(752.7)	0	0
Payments to Acquire Additional Interest in Subsidiaries	(12.6)	0	0
Net cash used in investing activities	(1,923.9)	(836.9)	(1,356.5)
Cash Flows From Financing Activities
Proceeds from exercise of equity options	0.2	0	0
Tax benefit from exercise/vesting of equity-based compensation	16.8	12.8	10.3
Net proceeds from debt issuance	382	344.7	0
Payment of debt	(20.4)	0	(150)
Reacquisition of debt	(19.3)	(48.9)	(58.1)
Dividends paid to shareholders	(403.6)	(892.6)	(175.6)
Acquisition of treasury shares	(208.5)	(271.4)	(273.4)
Net cash used in financing activities	(252.8)	(855.4)	(646.8)
Effect of exchange rate changes on cash	(0.2)	0	(0.6)
Increase (decrease) in cash	116	33.3	(104)
Cash, Beginning of year	108.4	75.1	179.1
Cash, End of year	$ 224.4	$ 108.4	$ 75.1

SCHEDULE I - Summary Of Investm

SCHEDULE I - Summary Of Investments - Other Than Investments in Related Parties	12 Months Ended
	Dec. 31, 2015
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, 2015 Type of Investment Cost Fair Value Amount At Which Shown In The Balance Sheet Available-for-sale Fixed maturities: Bonds: United States Government and government agencies and authorities $ 2,425.4 $ 2,429.2 $ 2,429.2 States, municipalities, and political subdivisions 2,677.6 2,721.4 2,721.4 Foreign government obligations 18.6 18.6 18.6 Public utilities 140.3 139.7 139.7 Corporate and other debt securities 3,572.9 3,551.9 3,551.9 Asset-backed securities 6,253.1 6,237.1 6,237.1 Redeemable preferred stocks 260.0 234.3 234.3 Total fixed maturities 15,347.9 15,332.2 15,332.2 Equity securities: Common stocks: Public utilities 113.1 151.8 151.8 Banks, trusts, and insurance companies 264.1 484.2 484.2 Industrial, miscellaneous, and all other 1,117.1 2,014.5 2,014.5 Nonredeemable preferred stocks 674.2 782.6 782.6 Total equity securities 2,168.5 3,433.1 3,433.1 Short-term investments 1 2,172.0 2,172.0 2,172.0 Total investments $ 19,688.4 $ 20,937.3 $ 20,937.3 1 Includes $2.5 million in treasury bills issued by the Australian government. 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, 2015 .

SCHEDULE II - Condensed Financi

SCHEDULE II - Condensed Financial Information Of Registrant	12 Months Ended
	Dec. 31, 2015
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, 2015 2014 2013 Revenues Dividends from subsidiaries $ 852.5 $ 1,000.2 $ 1,119.7 Undistributed income (loss) from subsidiaries 500.0 358.3 117.5 Equity in net income of subsidiaries* 1,352.5 1,358.5 1,237.2 Intercompany investment income* 3.9 2.4 2.8 Gains (losses) on extinguishment of debt (0.9 ) (4.8 ) (4.3 ) Other income 1 0 0 2.6 Total revenues 1,355.5 1,356.1 1,238.3 Expenses Interest expense 136.1 120.2 121.2 Deferred compensation 2 5.3 2.8 9.5 Other operating costs and expenses 5.4 4.4 4.0 Total expenses 146.8 127.4 134.7 Income before income taxes 1,208.7 1,228.7 1,103.6 Benefit for income taxes (58.9 ) (52.3 ) (61.8 ) Net income attributable to Progressive 1,267.6 1,281.0 1,165.4 Other comprehensive income (loss) (222.7 ) 71.4 80.7 Comprehensive income attributable to Progressive $ 1,044.9 $ 1,352.4 $ 1,246.1 * Eliminated in consolidation. 1 Represents gain on net death benefit received on life insurance policies. 2 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, 2015 2014 Assets Investment in affiliate $ 5.0 $ 5.0 Investment in subsidiaries* 9,192.3 7,423.5 Receivable from investment subsidiary* 1,200.5 1,677.5 Intercompany receivable* 406.0 413.0 Net deferred income taxes 90.6 74.5 Other assets 124.8 123.9 Total Assets $ 11,019.2 $ 9,717.4 Liabilities and Shareholders’ Equity Accounts payable, accrued expenses, and other liabilities $ 202.7 $ 220.0 Dividend payable 519.2 404.1 Debt 2,543.0 2,164.7 Total liabilities 3,264.9 2,788.8 Redeemable noncontrolling interest (NCI) 464.9 0 Shareholders' Equity Common shares, $1.00 par value (authorized 900.0; issued 797.6, including treasury shares of 214.0 and 209.8) 583.6 587.8 Paid-in capital 1,218.8 1,184.3 Retained earnings 4,686.6 4,133.4 Total accumulated other comprehensive income 800.4 1,023.1 Total shareholders’ equity 7,289.4 6,928.6 Total Liabilities, Redeemable NCI, and Shareholders’ Equity $ 11,019.2 $ 9,717.4 *Eliminated in consolidation. See notes to condensed financial statements. CONDENSED STATEMENTS OF CASH FLOWS THE PROGRESSIVE CORPORATION (PARENT COMPANY) (millions) Years Ended December 31, 2015 2014 2013 Cash Flows From Operating Activities: Net income attributable to Progressive $ 1,267.6 $ 1,281.0 $ 1,165.4 Adjustments to reconcile net income attributable to Progressive to net cash provided by operating activities: Undistributed (income) loss from subsidiaries (500.0 ) (358.3 ) (117.5 ) Amortization of equity-based compensation 2.4 2.2 2.1 (Gains) losses on extinguishment of debt 0.9 4.8 4.3 Changes in: Intercompany receivable 7.0 (105.4 ) (11.4 ) Accounts payable, accrued expenses, and other liabilities (46.2 ) 18.2 19.4 Income taxes 12.3 61.1 (55.8 ) Other, net (3.1 ) 0.4 (16.3 ) Net cash provided by operating activities 740.9 904.0 990.2 Cash Flows From Investing Activities: Additional investments in equity securities of consolidated subsidiaries (40.2 ) (21.1 ) (13.9 ) Investment in affiliate 0.0 0 (4.0 ) Acquisition of ARX (890.1 ) 0 0 (Paid to) received from investment subsidiary 409.1 (29.1 ) (325.5 ) Net cash used in investing activities (521.2 ) (50.2 ) (343.4 ) Cash Flows From Financing Activities: Tax benefit from exercise/vesting of equity-based compensation 16.8 12.8 10.3 Net proceeds from debt issuance 394.9 346.3 0 Payment of debt 0 0 (150.0 ) Reacquisition of debt (19.3 ) (48.9 ) (58.1 ) Dividends paid to shareholders (403.6 ) (892.6 ) (175.6 ) Acquisition of treasury shares (208.5 ) (271.4 ) (273.4 ) Net cash used in financing activities (219.7 ) (853.8 ) (646.8 ) Change in cash 0 0 0 Cash, beginning of year 0 0 0 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 year-end 2015 and 2014 , $1.3 billion and $1.9 billion , respectively, of marketable securities were available in this subsidiary. Non-cash activity includes declared but unpaid dividends, the transfer of the previous 5% ownership interest in ARX to The Progressive Corporation from an investment subsidiary, and the change in redemption value of the redeemable NCI. For the years ended December 31, The Progressive Corporation paid the following: (millions) 2015 2014 2013 Income taxes $ 625.0 $ 515.0 $ 497.0 Interest 128.2 116.0 122.3 Note 2. Income Taxes — The Progressive Corporation files a consolidated federal income tax return with all eligible subsidiaries and acts as an agent for the consolidated tax group when making payments to the Internal Revenue Service. Since The Progressive Corporation owns less than 80% of ARX's outstanding stock, ARX and its subsidiaries are not eligible to file on a consolidated basis with The Progressive Corporation. 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. Note 3. Debt — The information relating to debt is incorporated by reference from Note 4 – Debt in our Annual Report, which is included as Exhibit 13 to this Form 10-K. Note 4. Employee Benefit Plans — The information relating to incentive compensation plans and deferred compensation is incorporated by reference from Note 9 – Employee Benefit Plans in our Annual Report, which is included as Exhibit 13 to this Form 10-K. 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 in our Annual Report, which is included as Exhibit 13 to this Form 10-K.

SCHEDULE III - Supplementary In

SCHEDULE III - Supplementary Insurance Information	12 Months Ended
	Dec. 31, 2015
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 Net written Year ended December 31, 2015: Personal Lines $ 17,294.5 $ 12,748.7 $ 1,331.3 $ 2,379.9 $ 17,703.6 Commercial Lines 1,995.9 1,244.5 219.4 232.6 2,171.2 Property 609.1 349.0 101.1 98.8 689.6 Other indemnity (0.4 ) (0.2 ) 0 0.8 (0.4 ) Total $ 564.1 $ 10,039.0 $ 6,621.8 $ 0 $ 19,899.1 $ 431.8 $ 14,342.0 $ 1,651.8 $ 2,712.1 $ 20,564.0 Year ended December 31, 2014: Personal Lines $ 16,561.0 $ 12,161.2 $ 1,322.9 $ 2,262.6 $ 16,759.2 Commercial Lines 1,837.5 1,133.4 201.1 204.2 1,895.4 Property 0 0 0 0 0 Other indemnity 0 11.6 0 0.3 0 Total $ 457.2 $ 8,857.4 $ 5,440.1 $ 0 $ 18,398.5 $ 389.5 $ 13,306.2 $ 1,524.0 $ 2,467.1 $ 18,654.6 Year ended December 31, 2013: Personal Lines $ 15,341.6 $ 11,194.6 $ 1,257.5 $ 2,149.2 $ 15,569.2 Commercial Lines 1,761.6 1,267.3 194.3 201.2 1,770.5 Property 0 0 0 0 0 Other indemnity 0.2 10.5 0 0.5 0 Total $ 447.6 $ 8,479.7 $ 5,174.5 $ 0 $ 17,103.4 $ 403.2 $ 12,472.4 $ 1,451.8 $ 2,350.9 $ 17,339.7 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

SCHEDULE IV - Reinsurance	12 Months Ended
	Dec. 31, 2015
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, 2015 Premiums earned: Property and liability insurance $ 20,454.1 $ 555.0 $ 0 $ 19,899.1 0 December 31, 2014 Premiums earned: Property and liability insurance $ 18,648.4 $ 249.9 $ 0 $ 18,398.5 0 December 31, 2013 Premiums earned: Property and liability insurance $ 17,317.9 $ 214.5 $ 0 $ 17,103.4 0

SCHEDULE VI-Supplemental Inform

SCHEDULE VI-Supplemental Information Concerning Property - Casualty Insurance Operations	12 Months Ended
	Dec. 31, 2015
Text Block [Abstract]
SCHEDULE VI-Supplemental Information Concerning Property - Casualty Insurance Operations	SCHEDULE VI — SUPPLEMENTAL INFORMATION CONCERNING PROPERTY - CASUALTY INSURANCE OPERATIONS THE PROGRESSIVE CORPORATION AND SUBSIDIARIES (millions) Losses and Loss Adjustment Expenses Incurred Related to Year Ended Current Year Prior Years Paid Losses and Loss Adjustment Expenses December 31, 2015 $ 14,657.1 $ (315.1 ) $ 13,639.6 December 31, 2014 $ 13,330.3 $ (24.1 ) $ 13,068.5 December 31, 2013 $ 12,427.3 $ 45.1 $ 12,014.9 Pursuant to Rule 12-18 of Regulation S-X. See Schedule III for the additional information required in Schedule VI.

Reporting And Accounting Polici

Reporting And Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Reporting And Accounting Policies	REPORTING AND ACCOUNTING POLICIES Nature of Operations The Progressive insurance organization began business in 1937. The Progressive Corporation, an insurance holding company was formed in 1965. 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 (collectively the Progressive Group of Insurance Companies) provide personal and commercial automobile and property insurance, other specialty property-casualty insurance and related services. Our Personal Lines segment writes insurance for personal autos and recreational vehicles through both an independent insurance agency channel and a direct channel. Our Commercial Lines segment writes primary liability and physical damage insurance for automobiles and trucks owned and/or operated predominantly by small businesses through both the independent agency and direct channels. Our Property segment writes personal and commercial property insurance for homeowners, other property owners, and renters, primarily through the independent insurance agency channel. We operate our businesses throughout the United States; we also sell personal auto physical damage and auto property damage liability insurance in Australia. 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. The Progressive Corporation owned 69.2% of the outstanding capital stock of ARX at December 31, 2015. All intercompany accounts and transactions are eliminated in consolidation. 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 (e.g., losses are paid), results may, and will likely, differ from those estimates. Investments Our fixed-maturity securities, equity securities, and short-term investments are accounted for on an available-for-sale basis. See Note 2 – Investments for details regarding the composition of our investment portfolio. 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 . Included in the fixed-maturity portfolio are asset-backed securities. The asset-backed securities 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, non-investment-grade asset-backed securities, 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 based on market expectations and are updated quarterly. Equity securities include common stocks, nonredeemable preferred stocks, and other risk investments, and are reported at fair values. Changes in fair value of these securities, net of deferred income taxes, are reflected as unrealized gains (losses) in accumulated other comprehensive income. To the extent we hold any foreign equities or foreign currency hedges, any change in value due to exchange rate fluctuations would be limited by foreign currency hedges, if any, and would be recognized in income in the current period. Short-term investments may include Eurodollar deposits, commercial paper, repurchase transactions, and other securities expected to mature within one year. In addition, short-term investments can include auction rate securities (i.e., certain municipal bonds and preferred stocks). Due to the nature of auction rate securities, these securities are classified as short-term based upon their expected auction date (generally 7 - 49 days) rather than on their contractual maturity date (which is greater than one year at original issuance). In the event that an auction fails, the security may need to be reclassified from short-term. Changes in fair value of these securities, net of deferred income taxes, are reflected as unrealized gains (losses) in accumulated other comprehensive income. Trading securities are securities bought principally for the purpose of sale in the near term. To the extent we have trading securities, changes in fair value would be recognized in income in the current period. Derivative instruments, which may be used for trading purposes or classified as trading derivatives due to the characteristics of the transaction, are discussed below. Derivative instruments may include futures, options, forward positions, foreign currency forwards, 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: • Changes in fair value of an asset or liability (fair value hedge), • Foreign currency of an investment in a foreign operation (foreign currency hedge), or • Variable cash flows of a forecasted transaction (cash flow hedge). To the extent we have derivatives held for general investment purposes, these derivative instruments are recognized as either assets or liabilities and measured at fair value, with changes in fair value recognized in income as a component of net realized 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. Hedges that are deemed to be effective would be accounted for as follows: • Fair value hedge: changes in fair value of the hedge, as well as the hedged item, would be recognized in income in the period of change while the hedge is in effect. • Foreign currency hedge: changes in fair value of the hedge, as well as the hedged item, would be reflected as a change in translation adjustment as part of accumulated other comprehensive income. Gains and losses on the foreign currency hedge would offset the foreign exchange gains and losses on the foreign investment as they are recognized into income. • Cash flow hedge: 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, the following accounting treatment would be applied: • Fair value hedge: the derivative instrument would continue to be adjusted through income, while the adjustment in the change in value of the hedged item would be reflected as a change in unrealized gains (losses) as part of accumulated other comprehensive income. • Foreign currency hedge: changes in the value of the hedged item would continue to be reflected as a change in translation adjustment as part of accumulated other comprehensive income, but the derivative instrument would be adjusted through income for the current period. • Cash flow hedge: changes in fair value of the derivative instrument would be reported in income for the current period. For all derivative positions, net cash requirements are limited to changes in fair values, which may vary resulting from changes in interest rates, currency exchange rates, and other factors. Exposure to credit risk is limited to the carrying value; collateral may be required to limit credit risk. 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 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 equity market declines, 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 debt 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 comprehensive income statement, with the difference (i.e., non-credit related impairment) recognized as part of our net unrealized gains (losses) in accumulated other comprehensive income. When an equity security (common equity and nonredeemable preferred stock) in our investment portfolio has an unrealized loss in fair value that is deemed to be other-than-temporary, we reduce the book value of such security to its current fair value, recognizing the decline as a realized loss in the comprehensive income statement. Any future changes in fair value, either increases or decreases, are reflected as changes in unrealized gains (losses) as part of accumulated other comprehensive income. Investment income consists of interest, dividends, and amortization. In addition to the discussion above for asset-backed securities, interest is recognized on an accrual basis using the effective yield method. Depending on the nature of the equity instruments, dividends are recorded at either the ex-dividend date or on an accrual basis. 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 derivatives, trading securities, and hybrid instruments (e.g., securities with embedded options, where the option is a feature of the overall change in the value of the instrument). 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 small 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 vehicle 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, we do not establish an allowance for doubtful accounts since 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 cancel the policy if the premiums remain unpaid after receipt of notice 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 that 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 2015 $ 748.3 2014 681.8 2013 619.3 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 and losses. 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 transactions include premium ceded to “Regulated” plans and “Non-Regulated” plans. Regulated plans are plans in which we are required to participate by insurance regulations and include the Michigan Catastrophic Claims Association, Florida Hurricane Catastrophe Fund, North Carolina Reinsurance Facility, state-mandated involuntary plans for commercial vehicles (Commercial Auto Insurance Procedures/Plans - “CAIP”), and federally regulated plans for flood (National Flood Insurance Program). Non-Regulated plans are voluntary contractual arrangements and primarily relate to our Property business. 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 written. 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), write-downs on securities determined to be other-than-temporarily impaired, and derivative instruments), 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. The useful life for computer equipment and laptop computers is 3 years. The useful lives range from 7 to 40 years for buildings, improvements, and integrated components, and 3 to 15 years for all other property and equipment. We evaluate impairment of our property and equipment at least annually and expense any item determined to be impaired. Land and buildings comprised 75% and 77% of total property and equipment at December 31, 2015 and 2014 , respectively. During 2014, the decision was made to sell one property originally purchased for a future Service Center site. At December 31, 2015 and 2014, included in other assets in the consolidated balance sheets is $8.7 million of "held for sale" property, which represents the fair value of this property less the estimated costs to sell. Total capitalized interest, which primarily relates to capitalized software projects, for the years ended December 31, was: (millions) Capitalized Interest 2015 $ 2.4 2014 1.3 2013 0.8 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. Substantially all of the goodwill recorded as of December 31, 2015, relates to the April 1, 2015 acquisition of a controlling interest in ARX. Intangible assets primarily arose through the acquisition of ARX and mainly represent the future premiums that will be recognized from the existing policies and current agency relationships, the value of software acquired, and the value of its trade name, "American Strategic Insurance," in the marketplace. The majority of the intangible assets have finite lives ranging from 7 to 14 years. See Note 15 - Acquisition for further discussion. We evaluate our goodwill for impairment at least annually. 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. 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 or to offset against future premium taxes 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. Other revenues may include revenue from the sale of tax credits, rental income, and other revenue transactions. 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 currently issue time-based and performance-based restricted stock unit awards to key members of management (other than management of ARX and its subsidiaries) 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 unit awards, both time-based and performance-based, at the time a dividend is paid to shareholders. 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 time-based restricted equity awards based on the “qualified retirement” provisions in our equity compensation plans, under which (among other provisions) if the participant is 55 years of age or older and satisfies certain years-of-service requirements, the vesting and distribution of 50% of outstanding time-based restricted equity awards accelerates upon reaching eligibility for a qualified retirement and shortly after the grant date for each subsequent award. For awards granted before March 2013, awards held by an individual who satisfies the "qualified retirement" provisions vest in part upon separation from the company if earlier than the contractual vesting date. ARX 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 current stockholders' agreement, pursuant to which The Progressive Corporation has the right, and can be required, to purchase a portion or all of the shares underlying these awards in 2018 and 2021. See Note 16 - Redeemable Noncontrolling Interest . 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, both our equity and liability awards, for the years ended December 31, was: (millions) 2015 2014 2013 Pretax expense $ 66.2 $ 51.4 $ 64.9 Tax benefit 23.2 18.0 22.7 Net Income Per Share Net income attributable to Progressive is used in our calculation of the per share amounts. Basic net income per share is computed using the weighted average number of common shares outstanding during the reporting period, excluding unvested time-based and performance-based restricted equity awards that are subject to forfeiture. Diluted net income per 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 • certain unvested performance-based restricted equity awards that satisfied contingency conditions for common stock equivalents during the period. Supplemental Cash Flow Information Cash includes only bank demand deposits. Non-cash activity includes declared but unpaid dividends. For the years ended December 31, we paid the following: (millions) 2015 2014 2013 Income taxes $ 701.8 $ 515.0 $ 497.0 Interest 132.0 116.0 122.3 New Accounting Standards In February 2016, the Financial Accounting Standards Board (FASB) released an accounting standards update (ASU) intended to eliminate the off-balance-sheet accounting for leases. The new guidance will require lessees to report their operating leases as both an asset and liability on the statement of financial position and disclose key information about leasing arrangements; the expense recognition will be consistent with existing guidance. The ASU, which is required to be applied on a modified retrospective basis, will be effective for fiscal years (including interim periods within those fiscal years) beginning after December 15, 2018 (2019 for calendar-year companies). We are currently evaluating the impact the guidance will have on our financial statements. In January 2016, the FASB released an ASU intended to improve the recognition and measurement of financial instruments. The new guidance will require the changes in fair value of equity securities to be recognized as a component of net income. The ASU is effective for fiscal years beginning after December 15, 2017 (the first quarter 2018 for calendar-year companies). The new guidance could create more volatility in net income, but will have no impact on comprehensive income. In May 2015, the FASB issued an ASU related to disclosures about short-duration contracts. The disclosures are intended to provide users of financial statements with more transparent information about an insurance entity's initial claim estimates and subsequent adjustments to those estimates, the methodologies and judgments used to estimate claims, and the timing, frequency, and severity of claims. This standard, which is required to be applied on a retrospective basis, is effective for fiscal years beginning after December 15, 2015 (2016 for calendar-year companies), except for those disclosures that require application only to the current period (e.g., information about significant changes in estimation methodologies and assumptions made in calculating the claim liability for short-duration contracts). We are currently evaluating the impact the guidance will have on our financial statements. In May 2015, the FASB issued an ASU related to investments measured at net asset value (NAV). The intent is to exclude certain investments measured at NAV from the fair value hierarchy. This guidance is effective for annual and interim periods after December 15, 2015 (January 2016 for calendar-year companies). We did not hold any securities at December 31, 2015, that were priced at NAV. To the extent we acquire such securities, we will follow the guidance to determine the appropriate treatment in the fair value hierarchy table. In April 2015, the FASB issued an ASU related to the balance sheet presentation of the cost of issuing debt. This standard requires that all costs incurred to issue debt be presented in the balance sheet as a direct deduction from the carrying value of the debt. In August 2015, the FASB further amended this ASU to clarify the treatment of debt issuance costs related to lines-of-credit arrangements. Registrants can elect to defer and present debt issuance costs related to a line of credit as an asset and subsequently amortize the costs ratably over the term of the line-of-credit arrangement, regardless of whether there are any outstanding borrowings on the arrangement. This ASU, which is required to be applied on a retrospective basis, is effective for fiscal years beginning after December 15, 2015 (2016 for calendar-year companies). We have historically deducted the majority of our debt issuance costs from the carrying value of the debt; therefore, we do not expect this standard to have a significant impact on our financial condition, cash flows, or results of operations. In April 2015, the FASB issued an ASU to clarify guidance around accounting for fees paid in a cloud computing arrangement. The standard prescribes when a cloud computing arrangement should be treated as software and when it should be treated as a service contract based on whether the arrangement includes a software license. This ASU, which allows for both prospective and retrospective methods of adoption, will be effective for annual periods (including interim periods within those annual periods) beginning after December 15, 2015 (2016 for calendar-year companies). We adopted this standard on January 1, 2016, 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. Reclassification For the period ended December 31, 2015, we reclassified goodwill and intangible assets out of “other assets” to be reported as separate line items to conform with the current-year presentation. There was no effect on total assets.

Investments

Investments	12 Months Ended
	Dec. 31, 2015
Investments Schedule [Abstract]
Investments	INVESTMENTS Our securities are reported at fair value, with the changes in fair value of these securities (other than hybrid securities and derivative instruments) reported as a component of accumulated other comprehensive income, net of deferred income taxes. The changes in fair value of the hybrid securities and derivative instruments are recorded as a component of net realized gains (losses) on securities. The following tables present the composition of our investment portfolio by major security type, consistent with our internal classification of how we manage, monitor, and measure the portfolio: ($ in millions) Cost Gross Unrealized Gains Gross Unrealized Losses Net Realized Gains (Losses) 1 Fair Value % of Total Fair Value December 31, 2015 Fixed maturities: U.S. government obligations $ 2,425.4 $ 4.4 $ (0.6 ) $ 0 $ 2,429.2 11.6 % State and local government obligations 2,677.6 47.5 (3.7 ) 0 2,721.4 13.0 Foreign government obligations 18.6 0 0 0 18.6 0.1 Corporate debt securities 3,713.2 11.3 (33.0 ) 0.1 3,691.6 17.6 Residential mortgage-backed securities 1,726.0 22.1 (20.6 ) (0.8 ) 1,726.7 8.3 Agency residential pass-through obligations 90.3 0.1 (1.1 ) 0 89.3 0.4 Commercial mortgage-backed securities 2,665.7 16.9 (29.4 ) 0 2,653.2 12.7 Other asset-backed securities 1,771.1 1.4 (5.1 ) 0.5 1,767.9 8.4 Redeemable preferred stocks 260.0 17.6 (43.3 ) 0 234.3 1.1 Total fixed maturities 15,347.9 121.3 (136.8 ) (0.2 ) 15,332.2 73.2 Equity securities: Nonredeemable preferred stocks 674.2 122.8 (15.7 ) 1.3 782.6 3.7 Common equities 1,494.3 1,170.4 (14.2 ) 0 2,650.5 12.7 Short-term investments 2,172.0 0 0 0 2,172.0 10.4 Total portfolio 2,3 $ 19,688.4 $ 1,414.5 $ (166.7 ) $ 1.1 $ 20,937.3 100.0 % ($ in millions) Cost Gross Unrealized Gains Gross Unrealized Losses Net Realized Gains (Losses) 1 Fair Value % of Total Fair Value December 31, 2014 Fixed maturities: U.S. government obligations $ 2,641.1 $ 27.3 $ (1.3 ) $ 0 $ 2,667.1 14.0 % State and local government obligations 2,095.7 44.6 (1.1 ) 0 2,139.2 11.2 Foreign government obligations 14.2 0 0 0 14.2 0.1 Corporate debt securities 2,813.9 32.9 (10.4 ) 0.3 2,836.7 14.9 Residential mortgage-backed securities 1,635.5 34.5 (10.8 ) (0.7 ) 1,658.5 8.7 Agency residential pass-through obligations 0 0 0 0 0 0 Commercial mortgage-backed securities 2,278.7 39.3 (2.6 ) 0.2 2,315.6 12.2 Other asset-backed securities 1,634.9 3.8 (0.8 ) 0.8 1,638.7 8.6 Redeemable preferred stocks 260.2 24.7 (5.7 ) 0 279.2 1.5 Total fixed maturities 13,374.2 207.1 (32.7 ) 0.6 13,549.2 71.2 Equity securities: Nonredeemable preferred stocks 590.4 201.1 (6.4 ) 42.4 827.5 4.4 Common equities 1,289.2 1,213.2 (10.1 ) 0 2,492.3 13.1 Short-term investments 2,149.0 0 0 0 2,149.0 11.3 Total portfolio 2,3 $ 17,402.8 $ 1,621.4 $ (49.2 ) $ 43.0 $ 19,018.0 100.0 % 1 Represents net holding period gains (losses) on certain hybrid securities (discussed below). 2 Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at December 31, 2015 , $23.1 million was included in "other assets," compared to $31.3 million in "other liabilities" at December 31, 2014 . 3 The total fair value of the portfolio included $1.3 billion and $1.9 billion at December 31, 2015 and 2014 , respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions. Short-Term Investments Our short-term investments may include commercial paper and other investments that are expected to mature within one year. At December 31, 2015 and 2014 , we had $2.5 million and $5.7 million , respectively, in treasury bills issued by the Australian government, included in short-term investments. We did not hold any repurchase transactions where we lent collateral at December 31, 2015 or 2014 . To the extent our repurchase transactions were with the same counterparty and subject to an enforceable master netting arrangement, we could elect to offset any such transactions. Consistent with past practice, we would expect to elect not to offset any such transactions and therefore to report these transactions on a gross basis on our balance sheets. Also included in short-term investments are reverse repurchase commitment transactions, where we loan cash to approved counterparties and receive U.S. Treasury Notes pledged as collateral against the cash borrowed. Our exposure to credit risk is limited due to the nature of the collateral (i.e., U.S. Treasury Notes) received. We have counterparty exposure on these trades in the event of a counterparty default to the extent the general collateral security's value is below the amount of cash we delivered to acquire the collateral. The short-term duration of the transactions (primarily overnight) reduces that exposure. We had no open reverse repurchase commitments at December 31, 2015 or December 31, 2014 . During 2015 , our largest outstanding balance of reverse repurchase commitments was $275.0 million , which was open for one day; the average daily balance of reverse repurchase commitments was $135.4 million . Hybrid Securities Included in our fixed-maturity and equity securities are hybrid securities, which are reported at fair value at December 31 : (millions) 2015 2014 Fixed maturities: Corporate debt securities $ 49.1 $ 139.8 Residential mortgage-backed securities 144.3 120.7 Commercial mortgage-backed securities 17.3 31.2 Other asset-backed securities 11.3 13.7 Total fixed maturities 222.0 305.4 Equity securities: Nonredeemable preferred stocks 50.7 122.3 Total hybrid securities $ 272.7 $ 427.7 Certain corporate debt securities are accounted for as hybrid securities since they were acquired at a substantial premium and contain a change-in-control put option (derivative) that permits the investor, at its sole option if and when a change in control is triggered, to put the security back to the issuer at a 1% premium to par. Due to this change-in-control put option and the substantial market premium paid to acquire these securities, there is the potential that the election to put, upon the change in control, would result in an acceleration of the recognition of the remaining premium paid on these securities in our results of operations. This would result in a loss of $1.5 million as of December 31, 2015 , if all of these bonds experienced a simultaneous change in control and we elected to exercise all of our put options. The put feature limits the potential loss in value that could be experienced in the event a corporate action occurs that results in a change in control that materially diminishes the credit quality of the issuer. We are under no obligation to exercise the put option we hold if a change in control occurs. The residential mortgage-backed securities accounted for as hybrid securities are obligations of the issuer with payments of principal based on the performance of a reference pool of loans. This embedded derivative results in the securities incorporating the risk of default from both the issuer and the related loan pool. The commercial mortgage-backed securities in the table above contain fixed interest rate reset features that will increase the coupons in the event the securities are not fully paid off on the anticipated repayment date. These reset features have the potential to more than double our initial purchase yield for each security. The other asset-backed security in the table above represents one hybrid security that was acquired at a deep discount to par due to a failing auction, and contains a put option that allows the investor to put that security back to the auction at par if the auction is restored. This embedded derivative had the potential to more than double our initial investment yield at acquisition. The hybrid securities in our nonredeemable preferred stock portfolio are perpetual preferred stocks with fixed-rate coupons that have call features, whereby the change in value of the call features is a component of the overall change in value of the preferred stocks. In the second quarter 2015, we acquired a controlling interest in ARX and transferred our previous 5% preferred stock investment in ARX to a component of our total ownership interest (see Note 15 – Acquisition for further discussion). At December 31, 2015 , bonds and certificates of deposit in the principal amount of $184.8 million were on deposit to meet state insurance regulatory and/or rating agency requirements. We 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, 2015 or 2014 . At December 31, 2015 , we did not have any debt securities that were non-income producing during the preceding 12 months. Fixed Maturities The composition of fixed maturities by maturity at December 31, 2015 , was: (millions) Cost Fair Value Less than one year $ 4,532.3 $ 4,530.9 One to five years 6,758.0 6,734.7 Five to ten years 3,934.1 3,940.3 Ten years or greater 119.1 121.9 Total 1 $ 15,343.5 $ 15,327.8 1 Excludes $4.4 million related to our open interest rate swap positions. 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 As of December 31, 2015 , we had $152.5 million of gross unrealized losses in our fixed-income securities (i.e., fixed-maturity securities, nonredeemable preferred stocks, and short-term investments) and $14.2 million in our common equities. We currently do not intend to sell the fixed-income securities and determined that it is more likely than not that we will not be required to sell these securities for the period of time necessary to recover their cost bases. A review of our fixed-income securities indicated that the issuers were current with respect to their interest obligations and that there was no evidence of any deterioration of the current cash flow projections that would indicate we would not receive the remaining principal at maturity. For common equities, 96% of our common stock portfolio was indexed to the Russell 1000; as such, this portfolio may contain securities in a loss position for an extended period of time, subject to possible write-downs, as described below. We may retain these securities as long as the portfolio and index correlation remain similar. To the extent there is issuer-specific deterioration, we may write-down the securities of that issuer. The remaining 4% of our common stocks were part of a managed equity strategy selected and administered by an external investment advisor. If our review of loss position securities indicated there was a fundamental or market impairment on these securities that was determined to be other-than-temporary, we would recognize a write-down in accordance with our stated policy. The following tables show the composition of gross unrealized losses by major security type and by the length of time that individual securities have been in a continuous unrealized loss position: Total No. of Sec. Total Value Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Value Unrealized Losses No. of Sec. Fair Value Unrealized Losses December 31, 2015 Fixed maturities: U.S. government obligations 22 $ 897.1 $ (0.6 ) 22 $ 897.1 $ (0.6 ) 0 $ 0 $ 0 State and local government obligations 290 606.7 (3.7 ) 264 500.7 (2.6 ) 26 106.0 (1.1 ) Corporate debt securities 215 2,580.6 (33.0 ) 197 2,294.6 (25.2 ) 18 286.0 (7.8 ) Residential mortgage-backed securities 188 1,294.7 (20.6 ) 115 493.4 (3.7 ) 73 801.3 (16.9 ) Agency residential pass-through obligations 61 84.9 (1.1 ) 61 84.9 (1.1 ) 0 0 0 Commercial mortgage-backed securities 207 2,046.5 (29.4 ) 171 1,694.6 (25.8 ) 36 351.9 (3.6 ) Other asset-backed securities 101 1,548.6 (5.1 ) 92 1,472.0 (4.5 ) 9 76.6 (0.6 ) Redeemable preferred stocks 9 199.4 (43.3 ) 6 119.4 (14.5 ) 3 80.0 (28.8 ) Total fixed maturities 1,093 9,258.5 (136.8 ) 928 7,556.7 (78.0 ) 165 1,701.8 (58.8 ) Equity securities: Nonredeemable preferred stocks 10 301.8 (15.7 ) 5 124.2 (1.7 ) 5 177.6 (14.0 ) Common equities 64 164.8 (14.2 ) 60 161.4 (14.2 ) 4 3.4 0 Total equity securities 74 466.6 (29.9 ) 65 285.6 (15.9 ) 9 181.0 (14.0 ) Total portfolio 1,167 $ 9,725.1 $ (166.7 ) 993 $ 7,842.3 $ (93.9 ) 174 $ 1,882.8 $ (72.8 ) 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, 2014 Fixed maturities: U.S. government obligations 11 $ 428.2 $ (1.3 ) 5 $ 150.7 $ (0.3 ) 6 $ 277.5 $ (1.0 ) State and local government obligations 46 234.2 (1.1 ) 28 177.9 (0.4 ) 18 56.3 (0.7 ) Corporate debt securities 53 843.2 (10.4 ) 43 647.5 (6.1 ) 10 195.7 (4.3 ) Residential mortgage-backed securities 70 844.2 (10.8 ) 33 465.2 (3.1 ) 37 379.0 (7.7 ) Agency residential pass-through obligations 0 0 0 0 0 0 0 0 0 Commercial mortgage-backed securities 63 723.4 (2.6 ) 54 667.5 (1.4 ) 9 55.9 (1.2 ) Other asset-backed securities 44 741.8 (0.8 ) 42 715.7 (0.7 ) 2 26.1 (0.1 ) Redeemable preferred stocks 3 103.0 (5.7 ) 1 33.0 (1.0 ) 2 70.0 (4.7 ) Total fixed maturities 290 3,918.0 (32.7 ) 206 2,857.5 (13.0 ) 84 1,060.5 (19.7 ) Equity securities: Nonredeemable preferred stocks 8 231.4 (6.4 ) 5 143.2 (3.6 ) 3 88.2 (2.8 ) Common equities 20 68.4 (10.1 ) 19 61.8 (9.6 ) 1 6.6 (0.5 ) Total equity securities 28 299.8 (16.5 ) 24 205.0 (13.2 ) 4 94.8 (3.3 ) Total portfolio 318 $ 4,217.8 $ (49.2 ) 230 $ 3,062.5 $ (26.2 ) 88 $ 1,155.3 $ (23.0 ) During 2015 , the number of securities in our fixed-maturity portfolio with unrealized losses increased, primarily reflecting 492 securities that were added to the portfolio as a result of our acquisition of a controlling interest in ARX during the second quarter 2015, and that declined in value between the acquisition date and year-end. The decline in these securities averaged approximately 0.9% of their total cost. The remaining increase in the number of securities is the result of rising interest rates since December 31, 2014 , reflected by the majority of the increase in the less than 12 month segment of the table. We had no material decreases in valuation as a result of credit rating downgrades on our fixed-maturity securities during the year. All of the fixed-maturity securities in an unrealized loss position at December 31, 2015 in the table above are current with respect to required principal and interest payments. Unrealized losses on our nonredeemable preferred stocks related to ten issues with unrealized losses, averaging approximately 5% of our total cost of those securities. A review of these securities concluded that the unrealized losses are market-related adjustments to the values, which were determined not to be other-than-temporary, and we continue to expect to recover our initial investments on these securities. The unrealized losses in our common stock portfolio in the less than 12 months category reflect losses that developed as a result of the decline in the equity market. A review of the securities in a loss position did not uncover fundamental issues with the issuers that would indicate other-than-temporary impairments existed. Additionally, market expectations for recovery in the next 12 months would put the fair values at or above our current book values. Lastly, we determined, as of the balance sheet date, that it was not likely these securities would be sold prior to that recovery. Other-Than-Temporary Impairment (OTTI) The following table shows the total non-credit portion of the OTTI recorded in accumulated other comprehensive income, reflecting the original non-credit loss at the time the credit impairment was determined: December 31, (millions) 2015 2014 Fixed maturities: Residential mortgage-backed securities $ (43.3 ) $ (44.1 ) Commercial mortgage-backed securities (0.6 ) (0.6 ) Total fixed maturities $ (43.9 ) $ (44.7 ) The following tables provide rollforwards of the amounts related to credit losses recognized in earnings for the periods ended December 31, 2015 , 2014 , and 2013 , 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: (millions) Residential Mortgage- Backed Commercial Mortgage- Backed Total Balance at December 31, 2014 $ 12.7 $ 0.4 $ 13.1 Credit losses for which an OTTI was previously recognized 0 0 0 Reductions for securities sold/matured (1.4 ) 0 (1.4 ) Change in recoveries of future cash flows expected to be collected 1,2 1.1 0 1.1 Reductions for previously recognized credit impairments written-down to fair value 3 0 0 0 Balance at December 31, 2015 $ 12.4 $ 0.4 $ 12.8 (millions) Residential Mortgage- Backed Commercial Mortgage- Backed Total Balance at December 31, 2013 $ 19.2 $ 0.4 $ 19.6 Credit losses for which an OTTI was previously recognized 0 0 0 Reductions for securities sold/matured (0.1 ) 0 (0.1 ) Change in recoveries of future cash flows expected to be collected 1,2 (6.4 ) 0 (6.4 ) Reductions for previously recognized credit impairments written-down to fair value 3 0 0 0 Balance at December 31, 2014 $ 12.7 $ 0.4 $ 13.1 (millions) Residential Mortgage- Backed Commercial Mortgage- Backed Total Balance at December 31, 2012 $ 27.1 $ 0.6 $ 27.7 Credit losses for which an OTTI was previously recognized 0.1 0 0.1 Reductions for securities sold/matured 0 0 0 Change in recoveries of future cash flows expected to be collected 1,2 (7.8 ) (0.2 ) (8.0 ) Reductions for previously recognized credit impairments written-down to fair value 3 (0.2 ) 0 (0.2 ) Balance at December 31, 2013 $ 19.2 $ 0.4 $ 19.6 1 Reflects expected recovery of prior period impairments that will be accreted into income over the remaining life of the security. 2 Includes $2.9 million , $4.3 million , and $2.6 million at December 31, 2015 , 2014 , and 2013 , respectively, recognized in income in excess of the cash flows expected to be collected at the time of the write-downs. 3 Reflects reductions of prior credit impairments where the current credit impairment requires writing securities down to fair value (i.e., no remaining non-credit loss). Although we determined that it is more likely than not that we will not 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 credit losses on the securities that were determined to be other-than-temporarily impaired. 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 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 was deemed to exist, and the security was written down. Realized Gains (Losses) The components of net realized gains (losses) for the years ended December 31, were: (millions) 2015 2014 2013 Gross realized gains on security sales Fixed maturities: U.S. government obligations $ 17.5 $ 24.0 $ 8.5 State and local government obligations 7.8 9.3 7.7 Corporate and other debt securities 31.2 37.2 47.7 Residential mortgage-backed securities 4.9 2.7 3.0 Commercial mortgage-backed securities 15.7 17.0 10.0 Redeemable preferred stocks 0.1 2.7 0 Total fixed maturities 77.2 92.9 76.9 Equity securities: Nonredeemable preferred stocks 65.3 90.0 126.3 Common equities 50.4 107.3 68.6 Subtotal gross realized gains on security sales 192.9 290.2 271.8 Gross realized losses on security sales Fixed maturities: U.S. government obligations (0.9 ) (7.6 ) (3.7 ) State and local government obligations (0.3 ) (0.5 ) 0 Corporate and other debt securities (5.0 ) (2.8 ) (6.2 ) Residential mortgage-backed securities (0.4 ) (0.2 ) 0 Agency residential pass-through obligations (0.4 ) 0 0 Commercial mortgage-backed securities (1.3 ) (8.3 ) (1.8 ) Redeemable preferred stocks 0 (3.2 ) (0.1 ) Total fixed maturities (8.3 ) (22.6 ) (11.8 ) Equity securities: Nonredeemable preferred stocks (3.2 ) 0 (0.1 ) Common equities (38.4 ) (7.3 ) (0.6 ) Subtotal gross realized losses on security sales (49.9 ) (29.9 ) (12.5 ) Net realized gains (losses) on security sales Fixed maturities: U.S. government obligations 16.6 16.4 4.8 State and local government obligations 7.5 8.8 7.7 Corporate and other debt securities 26.2 34.4 41.5 Residential mortgage-backed securities 4.5 2.5 3.0 Agency residential pass-through obligations (0.4 ) 0 0 Commercial mortgage-backed securities 14.4 8.7 8.2 Redeemable preferred stocks 0.1 (0.5 ) (0.1 ) Total fixed maturities 68.9 70.3 65.1 Equity securities: Nonredeemable preferred stocks 62.1 90.0 126.2 Common equities 12.0 100.0 68.0 Subtotal net realized gains (losses) on security sales 143.0 260.3 259.3 Other-than-temporary impairment losses Fixed maturities: Residential mortgage-backed securities 0 0 (0.6 ) Total fixed maturities 0 0 (0.6 ) Equity securities: Common equities (8.7 ) (7.2 ) (5.5 ) Subtotal other-than-temporary impairment losses (8.7 ) (7.2 ) (6.1 ) Other gains (losses) Hybrid securities (1.3 ) 30.5 6.4 Derivative instruments (20.7 ) (64.1 ) 56.6 Litigation settlements 0.4 4.7 2.2 Subtotal other gains (losses) (21.6 ) (28.9 ) 65.2 Total net realized gains (losses) on securities $ 112.7 $ 224.2 $ 318.4 Gross realized gains and losses were predominantly the result of sales transactions in our fixed-income portfolio related to movements in credit spreads and interest rates and sales from our equity portfolios. In addition, gains and losses reflect recoveries from litigation settlements and holding period valuation changes on hybrids and derivatives. Also included are write-downs for securities determined to be other-than-temporarily impaired in our fixed-maturity and/or equity portfolios. Net Investment Income The components of net investment income for the years ended December 31, were: (millions) 2015 2014 2013 Fixed maturities: U.S. government obligations $ 28.3 $ 46.2 $ 50.2 State and local government obligations 60.7 50.1 48.0 Foreign government obligations 0.4 0.4 0.2 Corporate debt securities 102.4 82.1 98.8 Residential mortgage-backed securities 52.2 44.9 28.1 Agency residential pass-through obligations 2.1 0 0 Commercial mortgage-backed securities 74.6 66.0 74.8 Other asset-backed securities 22.0 16.7 16.7 Redeemable preferred stocks 15.0 15.5 21.2 Total fixed maturities 357.7 321.9 338.0 Equity securities: Nonredeemable preferred stocks 43.7 38.6 36.2 Common equities 51.0 46.6 45.8 Short-term investments 2.2 1.3 2.0 Investment income 454.6 408.4 422.0 Investment expenses (22.8 ) (18.9 ) (18.8 ) Net investment income $ 431.8 $ 389.5 $ 403.2 The amount of investment income (interest and dividends) we recognize varies from year to year based on the average assets held during the year and the book yields of the securities in our portfolio. The increase in 2015 primarily reflects an increase in average assets, due in large part to profitable underwriting results and the acquisition of a controlling interest in ARX, while the decrease in 2014 was due in part to an increase in short-term investments held and lower yields on securities purchased during the year. Trading Securities At December 31, 2015 and 2014 , we did not hold any trading securities and we did not have any net realized gains (losses) on trading securities for the years ended December 31, 2015 , 2014 , and 2013 . Derivative Instruments For all derivative positions discussed below, realized holding period gains and losses are netted with any upfront cash that may be exchanged under the contract to determine if the net position should be classified either as an asset or liability. To be reported as a net derivative asset and a component of the available-for-sale portfolio, the inception-to-date holding period (realized) gain on the derivative position at period end would have to exceed any upfront cash received. On the other hand, a net derivative liability would include any inception-to-date holding period (realized) loss plus the amount of upfront cash received (or netted, if upfront cash was paid) and would be reported as a component of other liabilities. These net derivative assets/liabilities are not separately disclosed on the balance sheet due to their immaterial effect on our financial condition, cash flows, and results of operations. The following table shows the status of our derivative instruments at December 31, 2015 and 2014 , and for the years ended December 31, 2015 , 2014 , and 2013 : (millions) Balance Sheet 2 Comprehensive Income Statement Notional Value 1 Assets (Liabilities) Fair Value Pretax Net Realized Gains (Losses) Years ended December 31, December 31, December 31, Derivatives designated as: 2015 2014 2013 Purpose Classification 2015 2014 2015 2014 2013 Hedging instruments Closed: Ineffective cash flow hedge $ 18 $ 44 $ 54 Manage NA $ 0 $ 0 $ 0.2 $ 0.5 $ 0.8 Non-hedging instruments Assets: Interest rate swaps 750 750 750 Manage portfolio duration Investments - fixed 4.4 15.8 (23.4 ) (64.6 ) 59.8 Closed: Interest rate swaps 0 0 1,263 Manage NA 0 0 0 0 (4.0 ) U.S. Treasury Note futures 691 0 0 Manage NA 0 0 2.5 0 0 Total NA NA NA $ 4.4 $ 15.8 $ (20.7 ) $ (64.1 ) $ 56.6 1 The amounts represent the value held at year end for open positions and the maximum amount held during the year for closed positions. 2 To the extent we hold both derivative assets and liabilities with the same counterparty that are subject to an enforceable master netting arrangement, we expect that we will report them on a gross basis on our balance sheets, consistent with our historical presentation. NA = Not Applicable CASH FLOW HEDGES We entered into forecasted debt issuance hedges to hedge against a possible rise in interest rates in conjunction with the $400 million of 3.70% Senior Notes issued in January 2015 and the $350 million of 4.35% Senior Notes issued in April 2014. Upon issuance, we closed these hedges and recognized, as part of accumulated other comprehensive income, a pretax loss of $12.9 million in January 2015 and $1.6 million in April 2014. Our ineffective cash flow hedge, which is reflected in the table above, resulted from the repurchase of a portion of our 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 during each of the last three years, and we reclassified the unrealized gain on forecasted transactions to net realized gains on securities. During 2015 , we recognized $1.8 million as a net decrease to interest expense on our closed debt issuance cash flow hedges, compared to $2.0 million during 2014 and $2.1 million during 2013 . See Note 4 – Debt for further discussion. INTEREST RATE SWAPS and U.S. TREASURY FUTURES We use interest rate swaps and treasury futures contracts to manage the fixed-income portfolio duration. At December 31, 2015 , 2014 , and 2013 , we held interest rate swap positions for which we are paying a fixed rate and receiving a variable rate, effectively shortening the duration of our fixed-income portfolio. On the open positions, since inception, interest rates have increased; however, as interest rate swap rates fell during 2015 , our fair value gain decreased by $11.4 million . During 2013, we closed three interest rate swap positions including a 9 -year interest rate swap position (opened in 2009) and two 5 -year interest rate swap positions (opened in 2011); in each case, we were paying a fixed rate and receiving a variable rate, effectively shortening the duration of our fixed-income portfolio. During the second quarter 2015, we entered into U.S. treasury futures by selling contracts, and we recognized a net realized gain of $2.5 million during the year; all positions were closed at December 31, 2015. The net realized gain was the result of overall rising interest rates during the period that the contracts were held. As of December 31, 2015 , 2014, and 2013 , the balance of the cash collateral that we had received from the applicable counterparty on our open positions was $4.9 million , $16.1 million , and $62.7 million , respectively.

Fair Value

Fair Value	12 Months Ended
	Dec. 31, 2015
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, 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, 2015 Fixed maturities: U.S. government obligations $ 2,429.2 $ 0 $ 0 $ 2,429.2 $ 2,425.4 State and local government obligations 0 2,721.4 0 2,721.4 2,677.6 Foreign government obligations 18.6 0 0 18.6 18.6 Corporate debt securities 0 3,691.6 0 3,691.6 3,713.2 Subtotal 2,447.8 6,413.0 0 8,860.8 8,834.8 Asset-backed securities: Residential mortgage-backed 0 1,726.7 0 1,726.7 1,726.0 Agency residential pass-through obligations 0 89.3 0 89.3 90.3 Commercial mortgage-backed 0 2,643.3 9.9 2,653.2 2,665.7 Other asset-backed 0 1,767.9 0 1,767.9 1,771.1 Subtotal asset-backed securities 0 6,227.2 9.9 6,237.1 6,253.1 Redeemable preferred stocks: Financials 0 92.0 0 92.0 76.8 Utilities 0 51.2 0 51.2 65.1 Industrials 0 91.1 0 91.1 118.1 Subtotal redeemable preferred stocks 0 234.3 0 234.3 260.0 Total fixed maturities 2,447.8 12,874.5 9.9 15,332.2 15,347.9 Equity securities: Nonredeemable preferred stocks: Financials 154.9 627.7 0 782.6 674.2 Subtotal nonredeemable preferred stocks 154.9 627.7 0 782.6 674.2 Common equities: Common stocks 2,650.2 0 0 2,650.2 1,494.0 Other risk investments 0 0 0.3 0.3 0.3 Subtotal common equities 2,650.2 0 0.3 2,650.5 1,494.3 Total fixed maturities and equity securities 5,252.9 13,502.2 10.2 18,765.3 17,516.4 Short-term investments 2,056.3 115.7 0 2,172.0 2,172.0 Total portfolio $ 7,309.2 $ 13,617.9 $ 10.2 $ 20,937.3 $ 19,688.4 Debt $ 0 $ 2,722.9 $ 164.9 $ 2,887.8 $ 2,707.9 Fair Value (millions) Level 1 Level 2 Level 3 Total Cost December 31, 2014 Fixed maturities: U.S. government obligations $ 2,667.1 $ 0 $ 0 $ 2,667.1 $ 2,641.1 State and local government obligations 0 2,139.2 0 2,139.2 2,095.7 Foreign government obligations 14.2 0 0 14.2 14.2 Corporate debt securities 0 2,836.7 0 2,836.7 2,813.9 Subtotal 2,681.3 4,975.9 0 7,657.2 7,564.9 Asset-backed securities: Residential mortgage-backed 0 1,658.5 0 1,658.5 1,635.5 Agency residential pass-through obligations 0 0 0 0 0 Commercial mortgage-backed 0 2,304.0 11.6 2,315.6 2,278.7 Other asset-backed 0 1,638.7 0 1,638.7 1,634.9 Subtotal asset-backed securities 0 5,601.2 11.6 5,612.8 5,549.1 Redeemable preferred stocks: Financials 0 97.9 0 97.9 77.3 Utilities 0 65.3 0 65.3 65.0 Industrials 0 116.0 0 116.0 117.9 Subtotal redeemable preferred stocks 0 279.2 0 279.2 260.2 Total fixed maturities 2,681.3 10,856.3 11.6 13,549.2 13,374.2 Equity securities: Nonredeemable preferred stocks: Financials 204.1 554.1 69.3 827.5 590.4 Subtotal nonredeemable preferred stocks 204.1 554.1 69.3 827.5 590.4 Common equities: Common stocks 2,491.9 0 0 2,491.9 1,288.8 Other risk investments 0 0 0.4 0.4 0.4 Subtotal common equities 2,491.9 0 0.4 2,492.3 1,289.2 Total fixed maturities and equity securities 5,377.3 11,410.4 81.3 16,869.0 15,253.8 Short-term investments 1,937.0 212.0 0 2,149.0 2,149.0 Total portfolio $ 7,314.3 $ 11,622.4 $ 81.3 $ 19,018.0 $ 17,402.8 Debt $ 0 $ 2,527.5 $ 0 $ 2,527.5 $ 2,164.7 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. During 2015 , we did not have any transfers between Level 1 and Level 2. During 2014, we had two nonredeemable preferred stocks with a value of $41.7 million that were transferred from Level 2 to Level 1 due to the availability of a consistent exchange price; this was the only transfer during 2014. We recognize transfers between levels at the end of the reporting period. Our short-term security holdings classified as Level 1 are highly liquid, actively marketed, and have a very short duration, primarily 30 days or less to redemption. These securities are held at their original cost, adjusted for any accretion of discount, since that value very closely approximates what an active market participant would be willing to pay for such securities. The remainder of our short-term securities are classified as Level 2 and are not priced externally since these securities continually trade at par value. These securities are classified as Level 2 since they are primarily longer-dated auction securities issued by municipalities that contain a redemption put feature back to the auction pool with a redemption period typically less than seven days. The auction pool is created by a liquidity provider and if the auction is not available at the end of the seven days, we have the right to put the security back to the issuer at par. At December 31, 2015 , vendor-quoted prices represented 49% of our Level 1 classifications (excluding short-term investments), compared to 50% at December 31, 2014 . 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. The year-over-year decline in vendor-quoted Level 1 prices was due to a reduction of U.S. Treasury Notes with the funds deployed primarily to short-term investments. At both December 31, 2015 and 2014 , vendor-quoted prices comprised 97% of our Level 2 classifications (excluding short-term investments), while dealer-quoted prices represented 3% . In our process for selecting a source (e.g., dealer, pricing service) to provide pricing for securities in our portfolio, we reviewed documentation from the sources that detailed the pricing techniques and methodologies used by these sources and determined if their policies adequately considered market activity, either based on specific transactions for the particular security type or based on modeling of securities with similar credit quality, duration, yield, and structure that were recently transacted. Once a source is chosen, we continue to monitor any changes or modifications to their processes by reviewing their documentation on internal controls for pricing and market reviews. We review quality control measures of our sources as they become available to determine if any significant changes have occurred from period to period that might indicate issues or concerns regarding their evaluation or market coverage. As part of our pricing procedures, we obtain quotes from more than one source to help us fully evaluate the market price of securities. However, our internal pricing policy is to use a consistent source for individual securities in order to maintain the integrity of our valuation process. Quotes obtained from the sources are not considered binding offers to transact. Under our policy, when a review of the valuation received from our selected source appears to be outside of what is considered market level activity (which is defined as trading at spreads or yields significantly different than those of comparable securities or outside the general sector level movement without a reasonable explanation), we may use an alternate source’s price. To the extent we determine that it may be prudent to substitute one source’s price for another, we will contact the initial source to obtain an understanding of the factors that may be contributing to the significant price variance, which often leads the source to adjust their pricing input data for future pricing. To allow us to determine if our initial source is providing a price that is outside of a reasonable range, we review our portfolio pricing on a weekly basis. We frequently challenge prices from our sources when a price provided does not match our expectations based on our evaluation of market trends and activity. Initially, we perform a review of our portfolio by sector to identify securities whose prices appear outside of a reasonable range. We then perform a more detailed review of fair values for securities disclosed as Level 2. We review dealer bids and quotes for these and/or similar securities to determine the market level context for our valuations. We then evaluate inputs relevant for each class of securities disclosed in the preceding hierarchy tables. For our structured debt securities, including commercial, residential, and asset-backed securities, we evaluate available market-related data for these and similar securities related to collateral, delinquencies, and defaults for historical trends and reasonably estimable projections, as well as historical prepayment rates and current prepayment assumptions and cash flow estimates. We further stratify each class of our structured debt securities into more finite sectors (e.g., planned amortization class, first pay, second pay, senior, subordinated, etc.) and use duration, credit quality, and coupon to determine if the fair value is appropriate. For our corporate debt and preferred stock (redeemable and nonredeemable) portfolios, as well as the notes and debentures 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 seven 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 received 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 price to a previous market valuation price. 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 each 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 inactivity, and lack of similar securities trading to obtain observable market level inputs), these valuations are more subjective in nature. Certain private equity investments and fixed-income investments included in the Level 3 category are valued using external pricing supplemented by internal review and analysis. After all the valuations are received and our review is complete, if the inputs used by vendors are determined to not contain sufficient observable market information, we will reclassify the affected security valuations to Level 3. At December 31, 2015 and 2014 , securities in our fixed-maturity portfolio listed as Level 3 were comprised substantially of securities that were either: (i) private placements, (ii) thinly held and/or traded securities, or (iii) non-investment-grade or non-rated securities with little liquidity. Based on these factors, it was difficult to independently verify observable market inputs that were used to generate the external valuations we received. Despite the lack of sufficient observable market information for our Level 3 securities, we believe the valuations received, in conjunction with our procedures for evaluating third-party prices, support the fair values reported in the financial statements. We did not hold any internally-priced securities at December 31, 2015 . At December 31, 2014, we held one internally-priced security, a private preferred equity security (our 5% equity interest in ARX) with a value of $69.3 million . We review the prices from our external sources for reasonableness using internally developed assumptions to derive prices for the securities, which are then compared to the prices we received. During 2015 or 2014, there were no material assets or liabilities measured at fair value on a nonrecurring basis. Based on our review, all the prices received from external sources remain unadjusted. The following tables provide a summary of changes in fair value associated with Level 3 assets for the years ended December 31, 2015 and 2014 : Level 3 Fair Value (millions) Fair Value at Dec. 31, 2014 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain)/Loss on Sales Change in Valuation Net Transfers In (Out) Fair Value at Dec. 31, 2015 Fixed maturities: Asset-backed securities: Residential mortgage-backed $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Commercial mortgage-backed 11.6 (1.3 ) 0 0 0 (0.4 ) 0 9.9 Total fixed maturities 11.6 (1.3 ) 0 0 0 (0.4 ) 0 9.9 Equity securities: Nonredeemable preferred stocks: Financials 1 69.3 0 0 0 (39.4 ) (1.4 ) (28.5 ) 0 Common equities: Other risk investments 0.4 0 0 0 0 (0.1 ) 0 0.3 Total Level 3 securities $ 81.3 $ (1.3 ) $ 0 $ 0 $ (39.4 ) $ (1.9 ) $ (28.5 ) $ 10.2 1 The $69.3 million decrease during the year reflects the reclassification of our 5% interest in ARX upon our acquisition of a controlling interest in ARX. The $39.4 million reflects our inception-to-date gain recognized, including the $1.4 million reduction in valuation that occurred during the first six months of 2015. Level 3 Fair Value (millions) Fair Value at Dec. 31, 2013 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain)/Loss on Sales Change in Valuation Net Transfers In (Out) 1 Fair Value at Dec. 31, 2014 Fixed maturities: Asset-backed securities: Residential mortgage-backed $ 0.2 $ 0 $ 0 $ (0.1 ) $ 0.1 $ (0.2 ) $ 0 $ 0 Commercial mortgage-backed 29.0 (3.6 ) 0 0 0 (0.2 ) (13.6 ) 11.6 Total fixed maturities 29.2 (3.6 ) 0 (0.1 ) 0.1 (0.4 ) (13.6 ) 11.6 Equity securities: Nonredeemable preferred stocks: Financials 2 39.0 0 0 0 0 30.3 0 69.3 Common equities: Other risk investments 0.5 (0.1 ) 0 0 0 0 0 0.4 Total Level 3 securities $ 68.7 $ (3.7 ) $ 0 $ (0.1 ) $ 0.1 $ 29.9 $ (13.6 ) $ 81.3 1 The $13.6 million was transferred out of Level 3 and into Level 2 due to an improvement in the security's underlying collateral and an increase in liquidity and market activity in comparable securities. 2 The $30.3 million represents a net holding period gain on our investment in ARX, which is reflected in net realized gains (losses) on securities in the comprehensive income statement. The following table provides a summary of the quantitative information about Level 3 fair value measurements for our applicable securities at December 31 : Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at Dec. 31, 2015 Valuation Technique Unobservable Input Unobservable Input Assumption Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 9.9 External vendor Prepayment rate 1 0 Total fixed maturities 9.9 Equity securities: Nonredeemable preferred stocks: Financials 0 NA NA NA Subtotal Level 3 securities 9.9 Third-party pricing exemption securities 2 0.3 Total Level 3 securities $ 10.2 NA= Not Applicable since we did not hold any nonredeemable preferred stock Level 3 securities at December 31, 2015 . 1 Assumes that one security has 0% of the principal amount of the underlying loans that will be paid off prematurely in each year. 2 The fair values for these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us. Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at Dec. 31, 2014 Valuation Technique Unobservable Input Unobservable Input Assumption Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 11.6 External vendor Prepayment rate 1 0 Total fixed maturities 11.6 Equity securities: Nonredeemable preferred stocks: Financials 69.3 Multiple of tangible net book value Price to book ratio multiple 2.6 Subtotal Level 3 securities 80.9 Third-party pricing exemption securities 2 0.4 Total Level 3 securities $ 81.3 1 Assumes that one security has 0% of the principal amount of the underlying loans that will be paid off prematurely in each year. 2 The fair values for these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us. 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 and comprehensive income.

Debt

Debt	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Debt	DEBT Debt at December 31 consisted of: 2015 2014 (millions) Carrying Value Fair Value Carrying Value Fair Value 3.75% Senior Notes due 2021 (issued: $500.0, August 2011) $ 498.1 $ 528.7 $ 497.8 $ 535.6 6 5/8% Senior Notes due 2029 (issued: $300.0, March 1999) 295.7 376.0 295.5 400.6 6.25% Senior Notes due 2032 (issued: $400.0, November 2002) 395.0 490.6 394.8 527.9 4.35% Senior Notes due 2044 (issued: $350.0, April 2014) 346.4 352.8 346.3 378.9 3.70% Senior Notes due 2045 (issued: $400.0, January 2015) 395.0 362.0 0 0 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 (issued: $1,000.0, June 2007; outstanding: $614.4 and $632.8) 612.8 612.8 630.3 684.5 Other debt instruments 164.9 164.9 0 0 Total $ 2,707.9 $ 2,887.8 $ 2,164.7 $ 2,527.5 The other debt instruments reported in the table above represent ARX indebtedness and consist of: Type of debt instrument Number of Instruments Carrying Value Stated Maturity Date(s) Term loans 2 $ 87.1 December 2018 and 2019 Junior subordinated notes 1 2 41.2 June 2036 and 2037 Senior notes 4 24.0 Various 2 Surplus note 1 12.6 November 2021 Total $ 164.9 1 ARX issued junior subordinated floating rate notes to trusts established by ARX in connection with issuances of trust preferred securities by the trust(discussed below). 2 The senior notes mature in May 2033, April 2034, December 2034, and June 2035. Aggregate required principal payments on debt outstanding at December 31, 2015, are as follows: (millions) Year Payments 2016 $ 27.2 2017 27.2 2018 27.2 2019 13.4 2020 3.0 Thereafter 2,631.3 Total $ 2,729.3 The Progressive Corporation Debt Excluding the other debt instruments, all of the outstanding debt was issued by The Progressive Corporation, the ultimate holding company. The holding company debt 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 Progressive Corporation debt. Interest on all debt issued by The Progressive Corporation is payable semiannually at the stated rates. However, the 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 (the “6.70% Debentures”) will only bear interest at this fixed annual rate through June 14, 2017. Thereafter, the 6.70% Debentures will bear interest at an annual rate equal to the three-month London Interbank Offered Rate (LIBOR) plus 2.0175%, and interest will be payable quarterly until the 6.70% Debentures are redeemed or retired. Except for the 6.70% Debentures, all remaining principal on the Senior Notes is due at the maturity stated in the tables above. The Senior Notes are redeemable, in whole or in part, at any time; however, the redemption price will equal the greater of the principal amount of the Senior Notes or a “make whole” amount calculated by reference to the present values of remaining scheduled principal and interest payments under the Senior Notes. Commencing on June 15, 2017, on each interest payment date, we have the right to redeem the 6.70% Debentures at par. If not previously redeemed, the 6.70% Debentures will become due on June 15, 2037, the scheduled maturity date, but only to the extent that we have received sufficient net proceeds from the sale of certain qualifying capital securities. The Progressive Corporation must use its commercially reasonable efforts, subject to certain market disruption events, to sell enough qualifying capital securities to permit repayment of the 6.70% Debentures in full on the scheduled maturity date or, if sufficient proceeds are not realized from the sale of such qualifying capital securities by such date, on each interest payment date thereafter. Any remaining outstanding principal will be due on June 15, 2067, the final maturity date. The Progressive Corporation issued $400 million of 3.70% Senior Notes due 2045 in January 2015, and $350 million of 4.35% Senior Notes due 2044 in April 2014, in underwritten public offerings. We received proceeds, after deducting underwriter's discounts and commissions, of approximately $394.9 million and $346.3 million , respectively. In addition, we incurred expenses of approximately $0.8 million and $0.7 million , respectively, related to the issuances. Prior to issuance of each of the Senior Notes and 6.70% Debentures, we entered into forecasted debt issuance hedges against possible rises in interest rates. Upon issuance of the applicable debt securities, the hedges were closed and we recognized unrealized gains (losses) as part of accumulated other comprehensive income. We recognize the gains and losses as an adjustment to interest expense and amortize them over the applicable life of the debt securities. The original unrealized gain (loss) at the time of each debt issuance and the unamortized balance at December 31, 2015 , on a pretax basis, of these hedges, were as follows: (millions) Unrealized Gain (Loss) at Debt Issuance Unamortized Balance at December 31, 2015 3.75% Senior Notes $ (5.1 ) $ (3.1 ) 6 5/8% Senior Notes (4.2 ) (3.0 ) 6.25% Senior Notes 5.1 3.9 4.35% Senior Notes (1.6 ) (1.6 ) 3.70% Senior Notes (12.9 ) (12.6 ) 6.70% Debentures 34.4 3.9 The gains (losses) on these hedges are deferred and are being amortized as adjustments to interest expense over the life of the related Senior Notes, and over the 10 -year fixed interest rate term for the 6.70% Debentures. In addition to this amortization, during 2015 and 2014 , we reclassified $0.2 million and $0.5 million , respectively, on a pretax basis, from accumulated other comprehensive income on the balance sheet to net realized gains on securities on the comprehensive income statement, reflecting the portion of the unrealized gain on forecasted transactions that was related to the portion of the 6.70% Debentures repurchased during the periods. During 2015 and 2014, we repurchased, in the open market, $18.4 million and $44.3 million , respectively, in aggregate principal amount of the 6.70% Debentures. Since the amount paid exceeded the carrying value of the debt we repurchased, we recognized losses on these extinguishments of $0.9 million and $4.8 million , respectively. ARX Debt (i.e., Other debt instruments) The other debt instruments were issued by ARX, in which we acquired a controlling interest during the second quarter 2015. ARX, not The Progressive Corporation or any of its other subsidiaries, is responsible for the other debt, which includes amounts that were borrowed and contributed to the capital of ARX's insurance subsidiaries or used, or made available for use, for other business purposes. In estimating the fair value of the other debt instruments, it was determined that the fair value of these notes is equal to the carrying value, based on the current rates offered for debt of similar maturities and interest rates. The term loans require ARX and its subsidiaries to maintain specified debt leverage and fixed charge coverage ratios, as well as maintain a minimum risk-based capital ratio and minimum financial strength and credit ratings, as provided by A.M. Best Company, Inc. As of December 31, 2015, ARX was in compliance with these covenants. The surplus note requires ARX to maintain at least $50 million of surplus, which it met at December 31, 2015. There are no restrictive financial covenants or credit rating triggers on any of the remaining other debt instruments. Monthly interest and principal payments are made on the term loans, with interest calculated based on the 30-day LIBOR plus 2.25% . Principal payments of $25.0 million are required to be paid during the next twelve months on these term loans. The term loans are secured by 100% of the outstanding common stock of four subsidiaries of ARX. Interest on the junior subordinated notes and the senior notes is paid quarterly at a floating rate tied to the three-month LIBOR rate. Principal and interest on the surplus note is payable pursuant to a schedule permitted by the Florida Office of Insurance Regulation, and interest is set quarterly based upon the 10-year U.S. treasury bond rate. Principal payments of $2.2 million are due during the next twelve months on the surplus note. The junior subordinated notes and senior notes can be redeemed, in whole or in part, at the option of ARX at par, plus accrued and unpaid interest, on any interest payment date. Pursuant to agreements entered into by ARX relating to the trust preferred securities transactions, ARX established trusts that are 100% owned by ARX. The trusts, which are the holders of the junior subordinated notes, issued trust preferred securities to third parties. The shares in the trusts are not transferable. The trusts are considered special purpose variable interest entities for which ARX is not the primary beneficiary and, therefore, they are accounted for under the equity method of accounting and not consolidated with ARX. Our ownership interest of $1.3 million in the variable interest entities is reported as a component of "other assets" on our consolidated balance sheets. The Progressive Corporation Line of Credit In March 2015, we renewed the unsecured, discretionary line of credit (the "Line of Credit") with PNC Bank, National Association (PNC) in the maximum principal amount of $100 million . The prior line of credit, entered into in March 2014, has expired. The Line of Credit is on substantially the same terms and conditions as the prior line of credit. Subject to the terms and conditions of the Line of Credit documents, advances under the Line of Credit (if any) will bear interest at a variable rate equal to the higher of PNC's Prime Rate or the sum of the Federal Funds Open Rate plus 50 basis points. Each advance must be repaid on the 30th day after the advance or, if earlier, on April 30, 2016, the expiration date of the Line of Credit. Prepayments are permitted without penalty. All advances under the Line of Credit are subject to PNC's discretion. We had no borrowings under the Line of Credit or the prior line of credit in 2015 or 2014 .

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES The components of our income tax provision were as follows: (millions) 2015 2014 2013 Current tax provision Federal $ 655.3 $ 594.4 $ 460.2 State 14.7 0 0 Deferred tax expense (benefit) Federal (47.7 ) 32.0 94.4 State (11.2 ) 0 0 Total income tax provision $ 611.1 $ 626.4 $ 554.6 As a result of our acquisition of a controlling interest in ARX, state income taxes are now being included in the income tax provision. In prior years, state income taxes were not significant. The provision for income taxes in the accompanying consolidated statements of comprehensive income differed from the statutory rate as follows: ($ in millions) 2015 2014 2013 Income before income taxes $ 1,911.6 $ 1,907.4 $ 1,720.0 Tax at statutory federal rate $ 669.1 35 % $ 667.6 35 % $ 602.0 35 % Tax effect of: Dividends received deduction (19.8 ) (1 ) (18.3 ) (1 ) (17.6 ) (1 ) Exempt interest income (17.8 ) (1 ) (13.8 ) (1 ) (13.1 ) (1 ) Non-taxable gain 1 (13.8 ) (1 ) 0 0 0 0 Tax-deductible dividends (7.9 ) 0 (6.5 ) 0 (13.6 ) (1 ) State income taxes, net of federal taxes 2.3 0 0 0 0 0 Other items, net (1.0 ) 0 (2.6 ) 0 (3.1 ) 0 Total income tax provision $ 611.1 32 % $ 626.4 33 % $ 554.6 32 % 1 Represents the tax effect of holding period gains on the 5% interest in ARX we owned prior to acquisition of a controlling interest on April 1, 2015. 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. At December 31, 2015 and 2014 , the components of the net deferred tax asset (liability) were as follows: (millions) 2015 2014 Federal deferred tax assets: Unearned premiums reserve $ 453.3 $ 378.8 Investment basis differences 40.5 60.6 Non-deductible accruals 231.4 208.0 Loss and loss adjustment expense reserves 75.3 76.9 Hedges on forecasted transactions 4.4 0 Other 9.6 7.5 Federal deferred tax liabilities: Net unrealized gains on securities (436.7 ) (550.3 ) Hedges on forecasted transactions 0 (0.8 ) Deferred acquisition costs (197.4 ) (160.0 ) Property and equipment (110.7 ) (100.9 ) Prepaid expenses (11.9 ) (11.4 ) Intangible assets-ARX acquisition (166.4 ) 0 Deferred gain on extinguishment of debt (2.2 ) (3.0 ) Other (7.0 ) (4.3 ) Net federal deferred tax liability (117.8 ) (98.9 ) Net state deferred tax asset 8.5 0 Net deferred tax liability $ (109.3 ) $ (98.9 ) 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, 2015 or 2014 . At December 31, 2015 and 2014, we had $25.1 million and $49.4 million , respectively, of net taxes payable (included in other liabilities on the balance sheet). The Progressive Corporation and its wholly-owned subsidiaries file a consolidated income tax return. This group has been a participant in the Compliance Assurance Program (CAP) since 2007. Under CAP, the Internal Revenue Service (IRS) begins its examination process for the tax year before the tax return is filed, by examining significant transactions and events as they occur. 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 2012 are closed. The IRS exams for 2012-2014 have been completed. We consider these years to be effectively settled. ARX and its wholly owned subsidiaries file their own consolidated income tax return since we own less than 80% of their outstanding stock. This group was last examined by the IRS for the 2011 and 2012 tax years, which we consider to be effectively settled. The 2013-2015 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 year ended December 31, 2015, $0.1 million of interest and penalties expense has been recorded in the tax provision. For the year ended December 31, 2013, $0.2 million of interest benefit 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, 2015 and 2014 .

Loss And Loss Adjustment Expens

Loss And Loss Adjustment Expense Reserves	12 Months Ended
	Dec. 31, 2015
Loss and Loss Adjustment Expense Reserves Disclosures [Abstract]
Loss And Loss Adjustment Expense Reserves	LOSS AND LOSS ADJUSTMENT EXPENSE RESERVES Activity in the loss and loss adjustment expense reserves is summarized as follows: (millions) 2015 2014 2013 Balance at January 1 $ 8,857.4 $ 8,479.7 $ 7,838.4 Less reinsurance recoverables on unpaid losses 1,185.9 1,045.9 862.1 Net balance at January 1 7,671.5 7,433.8 6,976.3 Net loss and loss adjustment reserves acquired 1 222.4 0 0 Total beginning reserves 7,893.9 7,433.8 6,976.3 Incurred related to: Current year 14,657.1 13,330.3 12,427.3 Prior years (315.1 ) (24.1 ) 45.1 Total incurred 14,342.0 13,306.2 12,472.4 Paid related to: Current year 9,577.3 8,831.5 8,095.0 Prior years 4,062.3 4,237.0 3,919.9 Total paid 13,639.6 13,068.5 12,014.9 Net balance at December 31 8,596.3 7,671.5 7,433.8 Plus reinsurance recoverables on unpaid losses 1,442.7 1,185.9 1,045.9 Balance at December 31 $ 10,039.0 $ 8,857.4 $ 8,479.7 1 Net reserves acquired in ARX acquisition. We experienced favorable reserve development of $315.1 million in 2015 and $24.1 million in 2014, compared to unfavorable reserve development of $45.1 million in 2013, which is reflected as “Incurred related to prior years” in the table above. 2015 • The favorable prior year reserve development was primarily attributable to accident year 2014. • Favorable reserve development occurred in all segments; personal auto businesses experienced approximately 65% of total development, with the remainder split between our Commercial Lines business and Property business. • In our personal auto and Commercial Lines businesses, we incurred favorable case loss reserve development primarily in bodily injury and uninsured motorist bodily injury coverages due to lower than anticipated severity. • In our Property business, development was favorable due to lower than anticipated severity and frequency, primarily in accident years 2014 and 2013. 2014 • The favorable prior year reserve development was primarily attributable to accident year 2010. • Favorable reserve development in our Commercial Lines business was partially offset by unfavorable development in our Agency auto business. Our Direct auto business experienced slightly favorable development. • The favorable reserve development in our Commercial Lines business was primarily related to favorable case reserve development on our high limit policies. • In Agency auto, the unfavorable development was primarily attributable to personal injury protection (PIP) loss reserves and to the adjusting and other loss adjustment expense reserves. 2013 • Approximately 80% of the unfavorable reserve development was attributable to accident year 2011, while the remaining 20% was related to accident year 2012. The aggregate reserve development for accident years 2010 and prior was slightly favorable. • About 55% of our unfavorable reserve development was in our Commercial Lines business, with the remainder split about equally between our Personal Lines business and our run-off businesses. In our Personal Lines business, unfavorable development in our Agency auto channel was offset in large part by favorable development in our Direct auto channel. • The unfavorable reserve development in our Agency auto business was in our IBNR reserves due to higher frequency and severity on late emerging claims, as primarily reflected in the “all other development.” • Lower than anticipated severity costs on case reserves were the primary contributor to the favorable development in our Direct auto business. • In our Commercial Lines business, we experienced unfavorable development due to higher frequency and severity on late emerging claims primarily in our bodily injury coverage for our truck business. • In our other businesses, we experienced unfavorable development primarily due to reserve increases in our run-off professional liability group business based on internal actuarial reviews of our claims history. Because we are primarily an insurer of motor vehicles, we have limited exposure to environmental, asbestos, and general liability claims. We have established reserves for such exposures, in amounts that we believe 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. We write personal and commercial auto and property insurance throughout the United States and could be exposed to hurricanes or other catastrophes. We maintain catastrophic reinsurance coverage on our Property business to help mitigate this risk. 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.

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2015
Reinsurance Disclosures [Abstract]
Reinsurance	REINSURANCE The effect of reinsurance on premiums written and earned for the years ended December 31, was as follows: 2015 2014 2013 (millions) Written Earned Written Earned Written Earned Direct premiums $ 21,086.5 $ 20,454.1 $ 18,914.8 $ 18,648.4 $ 17,562.8 $ 17,317.9 Ceded: Regulated Plans (358.0 ) (362.6 ) (251.9 ) (241.4 ) (216.2 ) (205.4 ) Non-Regulated Plans (164.5 ) (192.4 ) (8.3 ) (8.5 ) (6.9 ) (9.1 ) Total Ceded (522.5 ) (555.0 ) (260.2 ) (249.9 ) (223.1 ) (214.5 ) Net premiums $ 20,564.0 $ 19,899.1 $ 18,654.6 $ 18,398.5 $ 17,339.7 $ 17,103.4 Regulated plans 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 Auto Insurance Procedures/Plans (CAIP) The Non-Regulated plans primarily include amounts ceded on Property business under catastrophic and quota share reinsurance agreements. The increase in the amount of premiums ceded in 2015, compared to the prior years, primarily reflects ARX's reinsurance programs. Losses and loss adjustment expenses were net of reinsurance ceded of $457.3 million in 2015 , $322.7 million in 2014 , and $347.0 million in 2013 . The increase in losses and loss adjustment expenses is related to the Property business. Our prepaid reinsurance premiums and reinsurance recoverables were comprised of the following at December 31: Prepaid Reinsurance Premiums Reinsurance Recoverables ($ in millions) 2015 2014 2015 2014 Regulated Plans: MCCA $ 31.4 16 % $ 32.8 38 % $ 1,217.6 82 % $ 1,018.8 83 % CAIP 37.1 19 26.5 31 134.0 9 110.1 9 NCRF 25.6 13 21.9 26 56.7 4 51.1 4 NFIP 45.0 22 0 0 10.4 1 0 0 Other 0 0 0 0 2.8 0 2.0 0 Total Regulated Plans 139.1 70 81.2 95 1,421.5 96 1,182.0 96 Non-Regulated Plans: Property 52.6 26 0 0 35.5 2 0 0 Other 7.6 4 4.1 5 31.8 2 49.9 4 Total Non-Regulated Plans 60.2 30 4.1 5 67.3 4 49.9 4 Total $ 199.3 100 % $ 85.3 100 % $ 1,488.8 100 % $ 1,231.9 100 % 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 the insurance companies in the applicable state. 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, 2015
Statutory Financial Information Disclosures [Abstract]
Statutory Financial Information	STATUTORY FINANCIAL INFORMATION Consolidated statutory surplus was $7,575.5 million and $6,442.8 million at December 31, 2015 and 2014 , respectively. Statutory net income was $1,333.1 million , $1,289.5 million , and $1,086.3 million for the years ended December 31, 2015 , 2014 , and 2013 , respectively. At December 31, 2015 , $637.6 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 2015 , the insurance subsidiaries paid aggregate cash dividends of $886.5 million to their parent company. Based on the dividend laws currently in effect, the insurance subsidiaries could pay aggregate dividends of $1,325.0 million in 2016 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, 2015
Employee Benefit Plans Disclosures [Abstract]
Employee Benefit Plans	EMPLOYEE BENEFIT PLANS Except to the extent specifically included, references in this Note 9 to Progressive refer to The Progressive Corporation and its subsidiaries other than ARX and its subsidiaries, and references to ARX refer to ARX and its subsidiaries. ARX and its subsidiaries maintain employee benefit plans that are separate from the plans that cover employees of The Progressive Corporation's other subsidiaries. Retirement Plans Progressive has a defined contribution pension plan (401(k) Plan) that covers most of its employees who are United States residents and 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, 2015, the ESOP held 25.2 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 made by Progressive for its 401(k) Plan were $78.4 million , $74.8 million , and $69.9 million for the years ended December 31, 2015, 2014, and 2013, respectively. ARX employees are covered by separate qualified defined contribution plans. Matching contributions of up to 6% of each eligible employee’s compensation are made each pay period. Contributions to these plans, from April 1, 2015, the date The Progressive Corporation acquired a controlling interest in ARX, were $0.7 million. 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 $22.6 million and $22.5 million at December 31, 2015 and 2014, respectively. Postretirement Benefits Progressive provides postretirement health and life insurance benefits to all employees who met requirements as to age and length of service at December 31, 1988. There are approximately 100 people who are eligible for these postretirement benefits. Progressive's funding policy for these benefits is to contribute annually, to a 501(c)(9) trust, the maximum amount that can be deducted for federal income tax purposes. 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 includes a cash bonus program for a limited number of senior executives and Progressive's Gainsharing program for other employees; the structures of these programs are similar in nature. Progressive's equity incentive compensation plans provide for the granting of restricted stock awards and restricted stock unit awards (collectively, “restricted equity awards”) to key members of management. ARX provides cash bonuses to its employees, both annual and periodic, and has an equity compensation plan under which it has 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 16 - Redeemable Noncontrolling Interest . 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 for accounting purposes as liability awards. The amounts charged to income for Progressive and ARX incentive compensation plans for the years ended December 31, were: 2015 2014 2013 (millions) Pretax After Tax Pretax After Tax Pretax After Tax Non-equity incentive plans - cash $ 337.7 $ 219.5 $ 266.2 $ 173.0 $ 234.5 $ 152.4 Equity incentive plans: Equity awards 64.5 41.9 51.4 33.4 64.9 42.2 Liability awards 1.7 1.1 0 0 0 0 The decrease in expense for 2014 reflected adjustments recorded to our performance-based equity awards based on estimates, as of December 31, 2014, of the level of performance expected to be reached. Progressive's 2003 Incentive Plan has expired, and no new awards may be made under this plan; all awards granted prior to the plan’s expiration have vested, been forfeited, or expired, and no awards remain outstanding at December 31, 2015. Progressive's 2010 Equity Incentive Plan, which provides for the granting of equity-based compensation to officers and other key employees, originally authorized awards for up to 18.0 million shares. Progressive's 2015 Equity Incentive Plan, which provides for the granting of equity-based compensation to officers and other key employees, originally authorized awards for up to 13.0 million shares. Since 2010, Progressive has issued restricted stock units as the form of equity awards to Progressive management. The restricted equity awards are issued as either time-based or performance-based awards. The time-based awards vest in equal installments upon the lapse of specified periods of time, typically three, four, and five years . All restricted stock units are settled at or after vesting in Progressive common shares from existing treasury shares on a one-to-one basis. The performance-based awards were granted to our Chief Executive Officer as his sole equity award in each of the last five years, and to approximately 45 other Progressive executives and senior managers in 2015 in addition to their time-based awards, to provide additional incentive to achieve pre-established profitability and growth targets or 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 shares or units that will vest if performance meets a specified target and minimum performance goals that must be achieved for any shares or units to vest. 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 of Grant Vesting range, expressed as a percentage of target Growth of our personal and commercial auto businesses, compared to market 2013-2015 0-250% 2012 and Prior 0-200% Investment results relative to peer group 2012-2015 0-200% Growth in percentage of auto policies bundled with other specified types of policies (granted to two senior executive officers) 2015 0% or 100-200% 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. 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. A summary of all employee restricted equity award activity during the years ended December 31, follows: 2015 2014 2013 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 9,051,564 $ 21.27 9,918,575 $ 20.13 11,625,981 $ 17.80 Add (deduct): Granted 2 2,489,976 25.20 3,542,984 19.32 2,738,809 22.73 Vested (3,682,644 ) 19.53 (4,228,673 ) 16.99 (4,293,605 ) 15.54 Forfeited (133,669 ) 21.63 (181,322 ) 20.75 (152,610 ) 18.28 End of year 3,4 7,725,227 $ 23.37 9,051,564 $ 21.27 9,918,575 $ 20.13 1 Includes both restricted stock units and restricted stock. Upon vesting, all units will be converted on a one-for-one basis into Progressive common shares funded from existing treasury shares. All performance-based awards are included at their target amounts. 2 We reinvest dividend equivalents on restricted stock units. For 2015 , 2014 , and 2013 , the number of units "granted" shown in the table above includes 196,947 , 538,749 , and 161,077 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, 2015 , the number of shares included 2,025,871 performance-based awards at their target amounts. We expect 1,946,565 of these performance-based awards to vest, based upon our current estimate of the likelihood of achieving these pre-determined performance goals. 4 At December 31, 2015 , the total unrecognized compensation cost related to unvested equity awards was $78.3 million , which includes performance-based awards at their currently estimated vesting value. This compensation expense will be recognized into the income statement 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, 2015 , 2014 , and 2013 , was $105.4 million , $109.6 million , and $98.3 million , respectively, based on the actual stock price on the vesting date. As a result of the put and call rights described in Note 16 - 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 since acquisition, follows: 2015 Options Outstanding Number of Shares Weighted Average At acquisition 26,000 $ 513.72 Add (deduct): Exercised 1 (1,005 ) 197.01 End of year 24,995 $ 526.46 Exercisable, end of year 12,995 $ 386.69 1 At the time of exercise, the value earned by the option holders was $1.1 million . 2015 Non-Vested Options Outstanding Number of Shares Weighted Average At acquisition 14,800 $ 675.55 Add (deduct): Vested (2,800 ) 665.85 End of year 1 12,000 $ 677.81 1 At December 31, 2015, the remaining unrecognized compensation cost related to unvested options was $2.9 million and the remaining weighted average vesting period on the unvested awards is 1.72 years. Since the acquisition, we recognized $1.7 million , or $1.1 million after tax, of compensation expense related to ARX's outstanding stock options. Incentive Compensation Plans – Directors Progressive's 2003 Directors Equity Incentive Plan, which provides for the granting of equity-based awards, including restricted stock awards, to non-employee directors, originally authorized awards for up to 1.4 million shares. Through 2015, The Progressive Corporation granted restricted stock awards to its non-employee directors as their sole compensation for serving as members of the Board of Directors. The restricted stock awards are issued as time-based awards. The vesting period (i.e., requisite service period) must be a minimum of six months and one day. The time-based awards granted to date have typically included vesting periods of 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, but always at least equal to six months and one day as required by the terms of the plan. The restricted stock awards 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: 2015 2014 2013 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 81,579 $ 25.45 93,254 $ 26.19 92,957 $ 21.41 Add (deduct): Granted 89,427 27.23 90,649 25.44 93,254 26.19 Vested (81,579 ) 25.45 (93,254 ) 26.19 (92,957 ) 21.41 Forfeited 0 0 (9,070 ) 25.36 0 0 End of year 89,427 $ 27.23 81,579 $ 25.45 93,254 $ 26.19 The aggregate fair value of the restricted stock vested, during the years ended December 31, 2015 , 2014 , and 2013 , was $2.2 million , $2.2 million , and $2.3 million , respectively, based on the actual stock price at time of exercise/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 bonuses 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) 2015 2014 Progressive common shares 1 $ 108.5 $ 83.2 Other investment funds 2 124.8 123.9 Total $ 233.3 $ 207.1 1 Includes 4.4 million and 3.6 million common shares as of December 31, 2015 and 2014 , respectively, to be distributed in common shares. 2 Amount is included in other assets on the balance sheet.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Segment Information	SEGMENT INFORMATION We write personal and commercial auto and property insurance and other specialty property-casualty insurance and provide related services. Our Personal Lines segment writes insurance for personal autos and recreational vehicles. 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 auto businesses throughout the United States and sell personal auto physical damage and auto property damage liability insurance in Australia. For the years ended December 31, 2015 , 2014 , and 2013 , net premiums earned on our Australian business were $15.9 million , $17.1 million , and $13.0 million , respectively. Our Commercial Lines segment writes primary liability and physical damage insurance for automobiles and trucks owned and/or operated predominantly by small businesses in the business auto, for-hire transportation, contractor, for-hire specialty, tow, and for-hire livery markets. This segment operates in 49 states and is distributed through both the independent agency and direct channels. Our Property segment writes insurance for homeowners, other property owners, and renters primarily through the independent agency channel in 31 states and the District of Columbia for personal property and in 4 states for commercial property as of December 31, 2015 (flood insurance is written in 37 states and D.C.). Our Property business primarily consists of the operations of ARX, in which we acquired a controlling interest in the second quarter of 2015. Our other indemnity businesses manage our run-off businesses, including the run-off of our professional liability insurance for community banks. Our service businesses provide insurance-related services, including processing CAIP business, and serving as an agent for homeowners, general liability, and workers’ compensation insurance through our programs with American Strategic Insurance and other subsidiaries of ARX (ASI), and unaffiliated insurance companies. All segment revenues are generated from external customers and we do not have a reliance on any major customer. We evaluate profitability based on pretax underwriting profit (loss) for the Personal Lines, Commercial Lines, and Property segments and for the other indemnity businesses. 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 $103.7 million in 2015 , $97.1 million in 2014 , and $101.3 million in 2013 . 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: 2015 2014 2013 (millions) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Personal Lines Agency $ 9,108.6 $ 713.2 $ 9,087.0 $ 683.0 $ 8,601.5 $ 542.9 Direct 8,185.9 403.4 7,474.0 423.4 6,740.1 473.9 Total Personal Lines 1 17,294.5 1,116.6 16,561.0 1,106.4 15,341.6 1,016.8 Commercial Lines 1,995.9 318.3 1,837.5 315.8 1,761.6 114.1 Property 2 609.1 61.3 0 0 0 0 Other indemnity 3 (0.4 ) (1.0 ) 0 (11.9 ) 0.2 (10.8 ) Total underwriting operations 19,899.1 1,495.2 18,398.5 1,410.3 17,103.4 1,120.1 Fees and other revenues 4 302.0 NA 309.1 NA 291.8 NA Service businesses 86.3 8.8 56.0 5.1 39.6 0.8 Investments 5 567.3 544.5 632.6 613.7 740.4 721.6 Gains (losses) on extinguishment of debt (0.9 ) (0.9 ) (4.8 ) (4.8 ) (4.3 ) (4.3 ) Interest expense NA (136.0 ) NA (116.9 ) NA (118.2 ) Consolidated total $ 20,853.8 $ 1,911.6 $ 19,391.4 $ 1,907.4 $ 18,170.9 $ 1,720.0 NA = Not Applicable 1 Personal auto insurance accounted for 92% of the total Personal Lines segment net premiums earned in 2015 , compared to 92% in 2014 and 91% in 2013 ; insurance for our special lines products (e.g., motorcycles, ATVs, RVs, manufactured homes, watercraft, and snowmobiles) accounted for the balance of the Personal Lines net premiums earned. 2 We began reporting our Property business as a segment on April 1, 2015, when we acquired a controlling interest in ARX; Property business written prior to that date was negligible. During 2015 , amounts include $45.2 million of amortization/depreciation expense 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 Holding Corp. and, therefore, will not affect the value of the noncontrolling interest. 3 Our professional liability group recognized $0.4 million of reinstatement premiums paid to our reinsurers pursuant to their reinsurance contracts during 2015. This premium reduction is reflected in our companywide total results. In total, our run-off businesses generated an underwriting loss of $1.0 million in 2015. 4 Pretax profit (loss) for fees and other revenues are allocated to operating segments. 5 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. Underwriting profitability is calculated by subtracting losses and loss adjustment expenses, policy acquisition costs, and other underwriting expenses from the total of net premiums earned and fees and other revenues. The underwriting margin is the pretax underwriting profit (loss) expressed as a percentage of net premiums earned (i.e., revenues from underwriting operations). Combined ratio is the complement of the underwriting margin. Following are the underwriting margins/combined ratios for our underwriting operations for the years ended December 31: 2015 2014 2013 Underwriting Margin Combined Ratio Underwriting Margin Combined Ratio Underwriting Margin Combined Ratio Personal Lines Agency 7.8 % 92.2 7.5 % 92.5 6.3 % 93.7 Direct 4.9 95.1 5.7 94.3 7.0 93.0 Total Personal Lines 6.5 93.5 6.7 93.3 6.6 93.4 Commercial Lines 15.9 84.1 17.2 82.8 6.5 93.5 Property 1 10.1 89.9 0 0 0 0 Other indemnity 2 NM NM NM NM NM NM Total underwriting operations 7.5 92.5 7.7 92.3 6.5 93.5 1 Included is 7.4 points of amortization/depreciation expense associated with the acquisition of a controlling interest in ARX. 2 Underwriting margins/combined ratios are not meaningful (NM) for our other indemnity businesses due to the low level of premiums earned by, and the variability of loss costs in, such businesses.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2015
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 Total tax (provision) benefit After tax total accumulated other comprehensive income Total net unrealized gains (losses) on securities Net unrealized gains on forecasted transactions Foreign currency translation adjustment Loss attributable to NCI Balance at December 31, 2014 $ 1,574.0 $ (550.9 ) $ 1,023.1 $ 1,021.9 $ 1.5 $ (0.3 ) $ 0 Other comprehensive income (loss) before reclassifications: Investment securities (198.7 ) 67.5 (131.2 ) (131.2 ) 0 0 0 Net non-credit related OTTI losses, adjusted for valuation changes 0 0 0 0 0 0 0 Forecasted transactions (12.9 ) 4.5 (8.4 ) 0 (8.4 ) 0 0 Foreign currency translation adjustment (1.8 ) 0.6 (1.2 ) 0 0 (1.2 ) 0 Loss attributable to noncontrolling interest 1.6 (0.5 ) 1.1 0 0 0 1.1 Total other comprehensive income (loss) before reclassifications (211.8 ) 72.1 (139.7 ) (131.2 ) (8.4 ) (1.2 ) 1.1 Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (23.8 ) 8.4 (15.4 ) (15.4 ) 0 0 0 Net realized gains (losses) on securities 149.7 (52.5 ) 97.2 97.1 0.1 0 0 Interest expense 1.8 (0.6 ) 1.2 0 1.2 0 0 Total reclassification adjustment for amounts realized in net income 127.7 (44.7 ) 83.0 81.7 1.3 0 0 Total other comprehensive income (loss) (339.5 ) 116.8 (222.7 ) (212.9 ) (9.7 ) (1.2 ) 1.1 Balance at December 31, 2015 $ 1,234.5 $ (434.1 ) $ 800.4 $ 809.0 $ (8.2 ) $ (1.5 ) $ 1.1 Components of Changes in Accumulated Other Comprehensive Income (after tax) (millions) Pretax total accumulated other comprehensive income Total tax (provision) benefit After tax total accumulated other comprehensive income Total net unrealized gains (losses) on securities Net unrealized gains on forecasted transactions Foreign currency translation adjustment Loss attributable to NCI Balance at December 31, 2013 $ 1,464.1 $ (512.4 ) $ 951.7 $ 947.0 $ 4.1 $ 0.6 $ 0 Other comprehensive income (loss) before reclassifications: Investment securities 362.1 (126.7 ) 235.4 235.4 0 0 0 Net non-credit related OTTI losses, adjusted for valuation changes 0 0 0 0 0 0 0 Forecasted transactions (1.6 ) 0.6 (1.0 ) 0 (1.0 ) 0 0 Foreign currency translation adjustment (1.3 ) 0.4 (0.9 ) 0 0 (0.9 ) 0 Loss attributable to noncontrolling interest 0 0 0 0 0 0 0 Total other comprehensive income (loss) before reclassifications 359.2 (125.7 ) 233.5 235.4 (1.0 ) (0.9 ) 0 Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (7.7 ) 2.7 (5.0 ) (5.0 ) 0 0 0 Net realized gains (losses) on securities 255.0 (89.2 ) 165.8 165.5 0.3 0 0 Interest expense 2.0 (0.7 ) 1.3 0 1.3 0 0 Total reclassification adjustment for amounts realized in net income 249.3 (87.2 ) 162.1 160.5 1.6 0 0 Total other comprehensive income (loss) 109.9 (38.5 ) 71.4 74.9 (2.6 ) (0.9 ) 0 Balance at December 31, 2014 $ 1,574.0 $ (550.9 ) $ 1,023.1 $ 1,021.9 $ 1.5 $ (0.3 ) $ 0 Components of Changes in Accumulated Other Comprehensive Income (after tax) (millions) Pretax total accumulated other comprehensive income Total tax (provision) benefit After tax total accumulated other comprehensive income Total net unrealized gains (losses) on securities Net unrealized gains on forecasted transactions Foreign currency translation adjustment Loss attributable to NCI Balance at December 31, 2012 $ 1,340.0 $ (469.0 ) $ 871.0 $ 862.7 $ 6.1 $ 2.2 $ 0 Other comprehensive income (loss) before reclassifications: Investment securities 368.2 (128.9 ) 239.3 239.3 0 0 0 Net non-credit related OTTI losses, adjusted for valuation changes 0.4 (0.1 ) 0.3 0.3 0 0 0 Forecasted transactions 0 0 0 0 0 0 0 Foreign currency translation adjustment (2.5 ) 0.9 (1.6 ) 0 0 (1.6 ) 0 Loss attributable to noncontrolling interest 0 0 0 0 0 0 0 Total other comprehensive income (loss) before reclassifications 366.1 (128.1 ) 238.0 239.6 0 (1.6 ) 0 Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (5.7 ) 2.0 (3.7 ) (3.7 ) 0 0 0 Net realized gains (losses) on securities 245.5 (86.0 ) 159.5 159.0 0.5 0 0 Interest expense 2.2 (0.7 ) 1.5 0 1.5 0 0 Total reclassification adjustment for amounts realized in net income 242.0 (84.7 ) 157.3 155.3 2.0 0 0 Total other comprehensive income (loss) 124.1 (43.4 ) 80.7 84.3 (2.0 ) (1.6 ) 0 Balance at December 31, 2013 $ 1,464.1 $ (512.4 ) $ 951.7 $ 947.0 $ 4.1 $ 0.6 $ 0 In an effort to manage interest rate risk, we entered into forecasted transactions on each of The Progressive Corporation's outstanding debt issuances. Upon issuing the debt, the gains (losses) recognized on these cash flow hedges are recorded as unrealized gains (losses) in accumulated other comprehensive income and amortized into interest expense over the term of the related debt issuance. We expect to reclassify $1.9 million (pretax) into income during the next 12 months, related to net unrealized gains on forecasted transactions. To the extent we repurchased any of our outstanding debt, a portion of the unrealized gain (loss) would need to be recognized as a realized gain (loss) since the cash flow hedge is deemed ineffective. During 2015, 2014, and 2013, we repurchased in the open market a portion of our 6.70% Debentures and reclassified $0.2 million , $0.5 million , and $0.8 million , respectively, on a pretax basis, from accumulated other comprehensive income on the balance sheet to net realized gains on securities on the comprehensive income statement (see Note 4 - Debt for further discussion).

Litigation

Litigation	12 Months Ended
	Dec. 31, 2015
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 insurance subsidiaries are named as defendants in a number of class action or individual lawsuits arising out of the operations of the insurance subsidiaries. Other insurance companies face many of these same issues. The lawsuits discussed below are in various stages of development. We plan to contest these suits vigorously, but may pursue settlement negotiations in some cases, if appropriate. The outcomes of pending cases are uncertain at this time. We establish accruals for lawsuits when it is probable that a loss has been or will be incurred and we can reasonably estimate its potential exposure, which may include a range of loss (referred to as a loss that is both “probable and estimable” in the discussion below). As to lawsuits in which the loss is not considered both probable and estimable, or is considered probable but not estimable, we do not establish an accrual in accordance with current accounting guidance. It is generally not possible to determine the exposure associated with our lawsuits 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 the courts in the vast majority of our cases in which 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 is often a function of pleading requirements and may be unrelated to the potential exposure. The following is a discussion of potentially significant pending cases at December 31, 2015, and certain cases resolved during the three-year period then ended. As to the pending cases, although their outcomes are uncertain, in each case we do not believe that the outcome will have a material impact on our consolidated financial condition, cash flows, or results of operations. In addition, we do not consider the losses from the pending cases to be both probable and estimable (except as noted below), and we are unable to estimate a range of loss, if any, at this time, due to the factors discussed above. 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 effect on our consolidated financial condition, cash flows, and/or results of operations. Pending cases at December 31, 2015 that challenge certain of our vehicle insurance subsidiaries' practices, include: • One putative class action alleging we sell personal injury protection (PIP) coverage and pay-related claims at levels lower than allowed by law. • Two patent matters alleging that we infringed on patented technology. • Two putative class action lawsuits alleging that we steer customers to Service Centers and network body shops to have their vehicles repaired. • Six putative class action lawsuits challenging our practice in Florida of adjusting PIP and first-party medical payments. • Three putative class action lawsuits challenging our adjustment of medical bills submitted by insureds in bodily injury claims. • One putative class action lawsuit challenging the manner in which we grant a discount for anti-theft devices. • One putative class action lawsuit alleging that we charged insureds for illusory uninsured motorist/underinsured motorist coverage. • One certified class action lawsuit alleging that we undervalued total loss claims through the use of certain valuation tools. • One conditionally certified collective class action lawsuit alleging we did not pay certain employees for work performed during meal periods. • Four qui tam lawsuits alleging we did not comply with its purported obligation to reimburse Medicare for medical payments made to Medicare beneficiaries. • Thirteen individual lawsuits and one putative class action lawsuit pending as multi-district litigation alleging Progressive and other insurers conspire to suppress body repair shop labor rates. For cases that have settled, but for which settlement is not complete, an accrual has been established at our best estimate of the exposure. Settlements that are complete are fully reflected in our financial statements. The amounts accrued or paid for these settlements were not material to our consolidated financial condition, cash flows, or results of operations. Cases settled during 2015 include: • Two conditionally certified collective class action lawsuits challenging our exempt employee classification for certain claims employees under applicable wage and hour laws. These matters were settled and paid during the year. • One certified class action lawsuit alleging that Progressive’s website did not adequately disclose sufficient information concerning the PIP deductibles when customers indicated they are covered by private health insurance. This matter was settled on a class-wide basis and an accrual established. • One putative class action lawsuit challenging the labor rates our insurance subsidiaries pay to auto body repair shops. This matter was settled on an individual basis and an accrual established. • One putative class action lawsuit challenging our policy form with regard to rejecting uninsured motorist coverage. We established an accrual for this matter in 2014 when it was probable that a loss had been incurred on this lawsuit and we were able to estimate a loss. This matter was settled on a class-wide basis in 2015 for the amount which was accrued. • One putative class action lawsuit alleging that our claims representatives reduced lost wages when settling uninsured and underinsured motorist claims. This matter was settled on a class-wide basis and an accrual was established. Cases settled during 2014 include: • One putative class action lawsuit alleging that Progressive steers customers to Service Centers and network shops to have their vehicles repaired. This matter was settled on an individual basis. • One putative class action lawsuit alleging that Progressive negligently designed, manufactured, and deceptively advertised Snapshot ® in that it purportedly drains a vehicle's battery to the point that the battery is non-functional or diminished in value. This matter was settled on an individual basis. • One putative class action lawsuit alleging that Progressive violated the Telephone Consumer Protection Act in making cell phone calls to insureds. This matter was settled on an individual basis. Cases settled during 2013 include: • One putative class action lawsuit alleging that Progressive did not reimburse any of its insureds who incurred legal fees to recover money from another Progressive insured. This case was accrued for, settled, and paid in 2013. • One putative class action lawsuit alleging that Progressive improperly applies a preferred provider discount to medical payment claims. This case was accrued for and settled in 2013. • One putative class action lawsuit challenging the manner in which Progressive charges premium and assesses total loss claims for commercial vehicle stated amount policies. This case was accrued for, settled, and paid in 2013. • Two putative class action lawsuits challenging Progressive’s practice in Florida of adjusting PIP and first-party medical payments. Both cases were settled on an individual basis. • One putative class action lawsuit that challenged Progressive’s use of certain automated database vendors or software to assist in the adjustment of bodily injury claims where the plaintiffs alleged that these databases or software systematically undervalued the claims; an accrual was established during 2012, and the case was paid in 2013.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES We have 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, 2015 , were as follows: (millions) Commitments 2016 $ 50.4 2017 47.8 2018 37.3 2019 24.7 2020 9.6 Thereafter 1.8 Total $ 171.6 Some of the leases have options to renew at the end of the lease periods. The expense we incurred for the leases disclosed above, as well as other operating leases that may be cancelable or have terms less than one year, was: (millions) Expense 2015 $ 66.6 2014 63.4 2013 64.6 We also have certain noncancelable purchase obligations. The minimum commitment under these agreements at December 31, 2015 , was $408.0 million . During 2015, the insurance operations of ARX entered into several multiple-layer property catastrophe excess of loss reinsurance contracts with various reinsurers with terms ranging from one to two years. The minimum commitment under these contracts was $82.4 million at December 31, 2015. As of December 31, 2015 , we had no open investment funding commitments; we had no uncollateralized lines or letters of credit as of December 31, 2015 or 2014 .

Dividends

Dividends	12 Months Ended
	Dec. 31, 2015
Dividends [Abstract]
Dividends	DIVIDENDS We maintain a policy of paying an annual variable dividend that, if declared, would be payable shortly after the close of the year. This annual variable dividend is based on a target percentage of after-tax underwriting income multiplied by a performance factor (Gainshare factor), determined by reference to the Agency auto, Direct auto, special lines, and Commercial Lines business units, subject to the limitations discussed below. The target percentage is determined by our Board of Directors on an annual basis and announced to shareholders and the public. In December 2014 , the Board determined the target percentage for 2015 to be 33-1/3% of annual after-tax underwriting income, which is unchanged from the target percentage in both 2014 and 2013 . The Gainshare factor can range from zero to two and is determined by comparing our operating performance for the Agency auto, Direct auto, special lines, and Commercial Lines business units for the year to certain predetermined profitability and growth objectives approved by the Compensation Committee of the Board. This Gainshare factor is also used in the annual cash bonus program currently in place for our employees (our “Gainsharing program”). Although reviewed every year, the structure of the Gainsharing program generally remains the same. For 2015 , the Gainshare factor was 1.60 , compared to 1.32 in 2014 and 1.21 in 2013 . Our annual dividend program will result in a variable payment to shareholders each year, subject to certain limitations. If the Gainshare factor is zero or if our comprehensive income is less than after-tax underwriting income, no dividend would be payable under our annual variable dividend policy. In addition, the ultimate decision on whether or not a dividend will be paid is in the discretion of the Board of Directors. The Board could decide to alter our policy, or not to pay the annual variable dividend, at any time prior to the declaration of the dividend for the year. Such an action by the Board could result from, among other reasons, changes in the insurance marketplace, changes in our performance or capital needs, changes in federal income tax laws, disruptions of national or international capital markets, or other events affecting our business, liquidity, or financial position. Following is a summary of our shareholder dividends, both variable and special, that were declared in the last three years: (millions, except per share amounts) Amount Dividend Type Declared Paid Per Total 1 Annual – Variable December 2015 February 2016 $ 0.8882 $ 519.2 Annual – Variable December 2014 February 2015 0.6862 404.1 Annual – Variable December 2013 February 2014 0.4929 293.9 Special December 2013 February 2014 1.0000 596.3 1 Based on shares outstanding as of the record date.

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interest (Notes)	12 Months Ended
	Dec. 31, 2015
Noncontrolling Interest [Abstract]
Noncontrolling Interest Disclosure [Text Block]	16. REDEEMABLE NONCONTROLLING INTEREST In connection with the acquisition of a controlling interest in ARX, The Progressive Corporation entered into a stockholders’ agreement with the other ARX stockholders. The stockholders’ agreement provides the non-Progressive shareholders with rights to put all of their shares to us in two installments, one in early 2018 and one in early 2021. The Progressive Corporation likewise will have the right to call shares from the other ARX shareholders in each of 2018 and 2021. If these rights are exercised in full when available, our ownership stake in ARX capital stock will exceed 80% in 2018 and will reach 100% in 2021. The purchase prices for shares to be purchased by Progressive 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 and December 31, 2017 (for the 2018 put or call purchases) or December 31, 2020 (for the 2021 put or call purchases) 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 two other stockholders. Since the ARX shares are redeemable upon the occurrence of an event that is not solely within the control of Progressive, we have recorded the redeemable noncontrolling interest as mezzanine equity on our consolidated balance sheets. 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. The components of redeemable noncontrolling interest (NCI) at December 31, 2015, were: (millions) Balance at March 31, 2015 $ 0 Fair value at date of acquisition 411.5 Net income attributable to NCI 32.9 Other comprehensive loss attributable to NCI (1.1 ) Purchase of shares from NCI (12.6 ) Change in redemption value of NCI 34.2 Balance at December 31, 2015 $ 464.9

Acquisitions (Notes)

Acquisitions (Notes)	12 Months Ended
	Dec. 31, 2015
Business Combinations [Abstract]
Acquisition	ACQUISITION On April 1, 2015, The Progressive Corporation acquired approximately 63.2% of the outstanding capital stock of ARX, the parent company of ASI, primarily from non-management shareholders. Subsequently, in 2015, we purchased an additional 1.0% of ARX capital stock from certain employee shareholders and option holders. The total cost to acquire these shares was $890.1 million and was funded with available cash. Prior to the acquisition, Progressive held a 5% interest in ARX as part of our investment portfolio. During 2015, we recognized a $2.0 million loss to reflect the net acquisition cost attributable to this holding. This loss was reported in net realized gains (losses) on securities in the comprehensive income statement. At December 31, 2015, Progressive's total ownership interest in ARX was 69.2% . The minority shareholders of ARX retain a 30.8% interest in the operating results of ARX. These interests are reflected in our comprehensive income statements as "Net income/Other comprehensive income attributable to noncontrolling interest (NCI)." The property business written by ASI accounted for approximately 3% of our total net premiums written during 2015. As part of the acquisition, we recorded approximately $470 million of goodwill. Goodwill was calculated as the excess of the purchase price over the estimated fair values 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. As a result of the ARX acquisition, we are able to build on the pre-existing relationship we had with ASI, which began in 2009, to expand on our bundling strategy in the Agency channel. The goodwill has been allocated equally between the ASI property business and our personal auto Agency business. During 2015, subsequent to the date of acquisition, we completed our analysis related to the fair value of the loss and loss adjustment expense reserves recorded as of the acquisition date and we obtained additional information about the state and federal deferred tax liabilities that were recorded as of the acquisition date. As a result, we recognized a $42.0 million fair value reduction to loss and loss adjustment expense reserves acquired, and a related $16.7 million fair value increase in state and federal deferred taxes acquired, resulting in a net decrease of $25.3 million to the carrying value of goodwill. No goodwill impairment charges were recognized during the year. As of December 31, 2015, goodwill associated with the acquisition was $446.0 million . In 2015, we adopted the newly issued accounting standard update related to business combinations, which simplifies the accounting for measurement-period adjustments by allowing us to record any goodwill adjustment prospectively, rather than retrospectively adjusting our previously issued financial statements. As part of the acquisition, we recorded $520.4 million of other intangible assets; the other intangible assets will be amortized over an average life of about 9 years. The following table reports the intangible assets by asset category as of December 31, 2015: ($ in millions) Category Value at Acquisition Accumulated Amortization Useful Life Policies in force $ 256.2 $ 27.5 7 years Agency relationships 159.2 8.5 14 years Software 69.1 6.5 8 years Trade name 34.8 2.6 10 years Agent licenses 1.1 0 Indefinite Total $ 520.4 $ 45.1 All assets and liabilities are recorded at fair value at the date of acquisition, as adjusted during 2015. If additional new information is obtained within 12 months from the date of acquisition about facts and circumstances that existed at the acquisition date, we will adjust the amounts previously recorded. For income tax purposes, the historical tax bases of the acquired assets and assumed liabilities were carried over and were not recorded at fair value; therefore, no tax-basis goodwill was created. At the date of acquisition, ARX had total fair value assets of $1.8 billion , including investment securities of $1.2 billion , cash and cash equivalents of $183 million , and prepaid reinsurance premiums of $146 million , and fair value liabilities of $1.2 billion , including unearned premiums of $550 million , loss and loss adjustment expense reserves of $264 million , and debt of $185 million . All of ARX's known contingencies were recognized as of the acquisition date. Subsequent to the date of acquisition, our consolidated 2015 results included total revenue and net income from ARX of $636.3 million and $106.8 million , respectively.

Reporting And Accounting Poli29

Reporting And Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Nature of Operations	Nature of Operations The Progressive insurance organization began business in 1937. The Progressive Corporation, an insurance holding company was formed in 1965. 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 (collectively the Progressive Group of Insurance Companies) provide personal and commercial automobile and property insurance, other specialty property-casualty insurance and related services. Our Personal Lines segment writes insurance for personal autos and recreational vehicles through both an independent insurance agency channel and a direct channel. Our Commercial Lines segment writes primary liability and physical damage insurance for automobiles and trucks owned and/or operated predominantly by small businesses through both the independent agency and direct channels. Our Property segment writes personal and commercial property insurance for homeowners, other property owners, and renters, primarily through the independent insurance agency channel. We operate our businesses throughout the United States; we also sell personal auto physical damage and auto property damage liability insurance in Australia.
Consolidation Policy	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. The Progressive Corporation owned 69.2% of the outstanding capital stock of ARX at December 31, 2015. All intercompany accounts and transactions are eliminated in consolidation.
Estimates And Assumptions Policy	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 (e.g., losses are paid), results may, and will likely, differ from those estimates.
Investment Policy	Investments Our fixed-maturity securities, equity securities, and short-term investments are accounted for on an available-for-sale basis. See Note 2 – Investments for details regarding the composition of our investment portfolio. 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 . Included in the fixed-maturity portfolio are asset-backed securities. The asset-backed securities 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, non-investment-grade asset-backed securities, 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 based on market expectations and are updated quarterly. Equity securities include common stocks, nonredeemable preferred stocks, and other risk investments, and are reported at fair values. Changes in fair value of these securities, net of deferred income taxes, are reflected as unrealized gains (losses) in accumulated other comprehensive income. To the extent we hold any foreign equities or foreign currency hedges, any change in value due to exchange rate fluctuations would be limited by foreign currency hedges, if any, and would be recognized in income in the current period. Short-term investments may include Eurodollar deposits, commercial paper, repurchase transactions, and other securities expected to mature within one year. In addition, short-term investments can include auction rate securities (i.e., certain municipal bonds and preferred stocks). Due to the nature of auction rate securities, these securities are classified as short-term based upon their expected auction date (generally 7 - 49 days) rather than on their contractual maturity date (which is greater than one year at original issuance). In the event that an auction fails, the security may need to be reclassified from short-term. Changes in fair value of these securities, net of deferred income taxes, are reflected as unrealized gains (losses) in accumulated other comprehensive income. Trading securities are securities bought principally for the purpose of sale in the near term. To the extent we have trading securities, changes in fair value would be recognized in income in the current period. Derivative instruments, which may be used for trading purposes or classified as trading derivatives due to the characteristics of the transaction, are discussed below. Derivative instruments may include futures, options, forward positions, foreign currency forwards, 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: • Changes in fair value of an asset or liability (fair value hedge), • Foreign currency of an investment in a foreign operation (foreign currency hedge), or • Variable cash flows of a forecasted transaction (cash flow hedge). To the extent we have derivatives held for general investment purposes, these derivative instruments are recognized as either assets or liabilities and measured at fair value, with changes in fair value recognized in income as a component of net realized 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. Hedges that are deemed to be effective would be accounted for as follows: • Fair value hedge: changes in fair value of the hedge, as well as the hedged item, would be recognized in income in the period of change while the hedge is in effect. • Foreign currency hedge: changes in fair value of the hedge, as well as the hedged item, would be reflected as a change in translation adjustment as part of accumulated other comprehensive income. Gains and losses on the foreign currency hedge would offset the foreign exchange gains and losses on the foreign investment as they are recognized into income. • Cash flow hedge: 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, the following accounting treatment would be applied: • Fair value hedge: the derivative instrument would continue to be adjusted through income, while the adjustment in the change in value of the hedged item would be reflected as a change in unrealized gains (losses) as part of accumulated other comprehensive income. • Foreign currency hedge: changes in the value of the hedged item would continue to be reflected as a change in translation adjustment as part of accumulated other comprehensive income, but the derivative instrument would be adjusted through income for the current period. • Cash flow hedge: changes in fair value of the derivative instrument would be reported in income for the current period. For all derivative positions, net cash requirements are limited to changes in fair values, which may vary resulting from changes in interest rates, currency exchange rates, and other factors. Exposure to credit risk is limited to the carrying value; collateral may be required to limit credit risk. 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 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 equity market declines, 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 debt 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 comprehensive income statement, with the difference (i.e., non-credit related impairment) recognized as part of our net unrealized gains (losses) in accumulated other comprehensive income. When an equity security (common equity and nonredeemable preferred stock) in our investment portfolio has an unrealized loss in fair value that is deemed to be other-than-temporary, we reduce the book value of such security to its current fair value, recognizing the decline as a realized loss in the comprehensive income statement. Any future changes in fair value, either increases or decreases, are reflected as changes in unrealized gains (losses) as part of accumulated other comprehensive income. Investment income consists of interest, dividends, and amortization. In addition to the discussion above for asset-backed securities, interest is recognized on an accrual basis using the effective yield method. Depending on the nature of the equity instruments, dividends are recorded at either the ex-dividend date or on an accrual basis. 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 derivatives, trading securities, and hybrid instruments (e.g., securities with embedded options, where the option is a feature of the overall change in the value of the instrument).
Insurance Premiums and Receivables Policy	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 small 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 vehicle 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, we do not establish an allowance for doubtful accounts since 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 cancel the policy if the premiums remain unpaid after receipt of notice and write off any remaining balance.
Deferred Acquisition Costs Policy	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 that these costs will be fully recoverable in the near term. We do not defer any advertising costs.
Reserve For Losses And Loss Adjustment Expenses	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 and losses. 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 Policy	Reinsurance Our reinsurance transactions include premium ceded to “Regulated” plans and “Non-Regulated” plans. Regulated plans are plans in which we are required to participate by insurance regulations and include the Michigan Catastrophic Claims Association, Florida Hurricane Catastrophe Fund, North Carolina Reinsurance Facility, state-mandated involuntary plans for commercial vehicles (Commercial Auto Insurance Procedures/Plans - “CAIP”), and federally regulated plans for flood (National Flood Insurance Program). Non-Regulated plans are voluntary contractual arrangements and primarily relate to our Property business. 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 written. See Note 7 - Reinsurance for further discussion.
Income Tax Policy	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), write-downs on securities determined to be other-than-temporarily impaired, and derivative instruments), 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, Plant and Equipment Policy	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. The useful life for computer equipment and laptop computers is 3 years. The useful lives range from 7 to 40 years for buildings, improvements, and integrated components, and 3 to 15 years for all other property and equipment. We evaluate impairment of our property and equipment at least annually and expense any item determined to be impaired. Land and buildings comprised 75% and 77% of total property and equipment at December 31, 2015 and 2014 , respectively. During 2014, the decision was made to sell one property originally purchased for a future Service Center site. At December 31, 2015 and 2014, included in other assets in the consolidated balance sheets is $8.7 million of "held for sale" property, which represents the fair value of this property less the estimated costs to sell.
Goodwill and Intangible Assets, Policy [Policy Text Block]	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. Substantially all of the goodwill recorded as of December 31, 2015, relates to the April 1, 2015 acquisition of a controlling interest in ARX. Intangible assets primarily arose through the acquisition of ARX and mainly represent the future premiums that will be recognized from the existing policies and current agency relationships, the value of software acquired, and the value of its trade name, "American Strategic Insurance," in the marketplace. The majority of the intangible assets have finite lives ranging from 7 to 14 years. See Note 15 - Acquisition for further discussion. We evaluate our goodwill for impairment at least annually. 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.
Guaranty Fund Assessments Policy	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 or to offset against future premium taxes 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. Other revenues may include revenue from the sale of tax credits, rental income, and other revenue transactions.
Non-Insurance Service Business	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 currently issue time-based and performance-based restricted stock unit awards to key members of management (other than management of ARX and its subsidiaries) 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 unit awards, both time-based and performance-based, at the time a dividend is paid to shareholders. 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 time-based restricted equity awards based on the “qualified retirement” provisions in our equity compensation plans, under which (among other provisions) if the participant is 55 years of age or older and satisfies certain years-of-service requirements, the vesting and distribution of 50% of outstanding time-based restricted equity awards accelerates upon reaching eligibility for a qualified retirement and shortly after the grant date for each subsequent award. For awards granted before March 2013, awards held by an individual who satisfies the "qualified retirement" provisions vest in part upon separation from the company if earlier than the contractual vesting date. ARX 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 current stockholders' agreement, pursuant to which The Progressive Corporation has the right, and can be required, to purchase a portion or all of the shares underlying these awards in 2018 and 2021. See Note 16 - Redeemable Noncontrolling Interest . 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.
Net Income Per Share Policy	Net Income Per Share Net income attributable to Progressive is used in our calculation of the per share amounts. Basic net income per share is computed using the weighted average number of common shares outstanding during the reporting period, excluding unvested time-based and performance-based restricted equity awards that are subject to forfeiture. Diluted net income per 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 • certain unvested performance-based restricted equity awards that satisfied contingency conditions for common stock equivalents during the period.
Cash Flow Supplemental Disclosure	Supplemental Cash Flow Information Cash includes only bank demand deposits. Non-cash activity includes declared but unpaid dividends.
New Accounting Pronouncements	New Accounting Standards In February 2016, the Financial Accounting Standards Board (FASB) released an accounting standards update (ASU) intended to eliminate the off-balance-sheet accounting for leases. The new guidance will require lessees to report their operating leases as both an asset and liability on the statement of financial position and disclose key information about leasing arrangements; the expense recognition will be consistent with existing guidance. The ASU, which is required to be applied on a modified retrospective basis, will be effective for fiscal years (including interim periods within those fiscal years) beginning after December 15, 2018 (2019 for calendar-year companies). We are currently evaluating the impact the guidance will have on our financial statements. In January 2016, the FASB released an ASU intended to improve the recognition and measurement of financial instruments. The new guidance will require the changes in fair value of equity securities to be recognized as a component of net income. The ASU is effective for fiscal years beginning after December 15, 2017 (the first quarter 2018 for calendar-year companies). The new guidance could create more volatility in net income, but will have no impact on comprehensive income. In May 2015, the FASB issued an ASU related to disclosures about short-duration contracts. The disclosures are intended to provide users of financial statements with more transparent information about an insurance entity's initial claim estimates and subsequent adjustments to those estimates, the methodologies and judgments used to estimate claims, and the timing, frequency, and severity of claims. This standard, which is required to be applied on a retrospective basis, is effective for fiscal years beginning after December 15, 2015 (2016 for calendar-year companies), except for those disclosures that require application only to the current period (e.g., information about significant changes in estimation methodologies and assumptions made in calculating the claim liability for short-duration contracts). We are currently evaluating the impact the guidance will have on our financial statements. In May 2015, the FASB issued an ASU related to investments measured at net asset value (NAV). The intent is to exclude certain investments measured at NAV from the fair value hierarchy. This guidance is effective for annual and interim periods after December 15, 2015 (January 2016 for calendar-year companies). We did not hold any securities at December 31, 2015, that were priced at NAV. To the extent we acquire such securities, we will follow the guidance to determine the appropriate treatment in the fair value hierarchy table. In April 2015, the FASB issued an ASU related to the balance sheet presentation of the cost of issuing debt. This standard requires that all costs incurred to issue debt be presented in the balance sheet as a direct deduction from the carrying value of the debt. In August 2015, the FASB further amended this ASU to clarify the treatment of debt issuance costs related to lines-of-credit arrangements. Registrants can elect to defer and present debt issuance costs related to a line of credit as an asset and subsequently amortize the costs ratably over the term of the line-of-credit arrangement, regardless of whether there are any outstanding borrowings on the arrangement. This ASU, which is required to be applied on a retrospective basis, is effective for fiscal years beginning after December 15, 2015 (2016 for calendar-year companies). We have historically deducted the majority of our debt issuance costs from the carrying value of the debt; therefore, we do not expect this standard to have a significant impact on our financial condition, cash flows, or results of operations. In April 2015, the FASB issued an ASU to clarify guidance around accounting for fees paid in a cloud computing arrangement. The standard prescribes when a cloud computing arrangement should be treated as software and when it should be treated as a service contract based on whether the arrangement includes a software license. This ASU, which allows for both prospective and retrospective methods of adoption, will be effective for annual periods (including interim periods within those annual periods) beginning after December 15, 2015 (2016 for calendar-year companies). We adopted this standard on January 1, 2016, 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.
Reclassification, Policy [Policy Text Block]	Reclassification For the period ended December 31, 2015, we reclassified goodwill and intangible assets out of “other assets” to be reported as separate line items to conform with the current-year presentation. There was no effect on total assets.

Reporting And Accounting Poli30

Reporting And Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Advertising Costs	Total advertising costs, which are expensed as incurred, for the years ended December 31, were: (millions) Advertising Costs 2015 $ 748.3 2014 681.8 2013 619.3
Interest Capitalized	Total capitalized interest, which primarily relates to capitalized software projects, for the years ended December 31, was: (millions) Capitalized Interest 2015 $ 2.4 2014 1.3 2013 0.8
Equity-based Compensation and Related Tax Benefits	The total compensation expense recognized for equity-based compensation, both our equity and liability awards, for the years ended December 31, was: (millions) 2015 2014 2013 Pretax expense $ 66.2 $ 51.4 $ 64.9 Tax benefit 23.2 18.0 22.7
Supplemental Cash Flow Information	For the years ended December 31, we paid the following: (millions) 2015 2014 2013 Income taxes $ 701.8 $ 515.0 $ 497.0 Interest 132.0 116.0 122.3

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2015
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 internal classification of how we manage, monitor, and measure the portfolio: ($ in millions) Cost Gross Unrealized Gains Gross Unrealized Losses Net Realized Gains (Losses) 1 Fair Value % of Total Fair Value December 31, 2015 Fixed maturities: U.S. government obligations $ 2,425.4 $ 4.4 $ (0.6 ) $ 0 $ 2,429.2 11.6 % State and local government obligations 2,677.6 47.5 (3.7 ) 0 2,721.4 13.0 Foreign government obligations 18.6 0 0 0 18.6 0.1 Corporate debt securities 3,713.2 11.3 (33.0 ) 0.1 3,691.6 17.6 Residential mortgage-backed securities 1,726.0 22.1 (20.6 ) (0.8 ) 1,726.7 8.3 Agency residential pass-through obligations 90.3 0.1 (1.1 ) 0 89.3 0.4 Commercial mortgage-backed securities 2,665.7 16.9 (29.4 ) 0 2,653.2 12.7 Other asset-backed securities 1,771.1 1.4 (5.1 ) 0.5 1,767.9 8.4 Redeemable preferred stocks 260.0 17.6 (43.3 ) 0 234.3 1.1 Total fixed maturities 15,347.9 121.3 (136.8 ) (0.2 ) 15,332.2 73.2 Equity securities: Nonredeemable preferred stocks 674.2 122.8 (15.7 ) 1.3 782.6 3.7 Common equities 1,494.3 1,170.4 (14.2 ) 0 2,650.5 12.7 Short-term investments 2,172.0 0 0 0 2,172.0 10.4 Total portfolio 2,3 $ 19,688.4 $ 1,414.5 $ (166.7 ) $ 1.1 $ 20,937.3 100.0 % ($ in millions) Cost Gross Unrealized Gains Gross Unrealized Losses Net Realized Gains (Losses) 1 Fair Value % of Total Fair Value December 31, 2014 Fixed maturities: U.S. government obligations $ 2,641.1 $ 27.3 $ (1.3 ) $ 0 $ 2,667.1 14.0 % State and local government obligations 2,095.7 44.6 (1.1 ) 0 2,139.2 11.2 Foreign government obligations 14.2 0 0 0 14.2 0.1 Corporate debt securities 2,813.9 32.9 (10.4 ) 0.3 2,836.7 14.9 Residential mortgage-backed securities 1,635.5 34.5 (10.8 ) (0.7 ) 1,658.5 8.7 Agency residential pass-through obligations 0 0 0 0 0 0 Commercial mortgage-backed securities 2,278.7 39.3 (2.6 ) 0.2 2,315.6 12.2 Other asset-backed securities 1,634.9 3.8 (0.8 ) 0.8 1,638.7 8.6 Redeemable preferred stocks 260.2 24.7 (5.7 ) 0 279.2 1.5 Total fixed maturities 13,374.2 207.1 (32.7 ) 0.6 13,549.2 71.2 Equity securities: Nonredeemable preferred stocks 590.4 201.1 (6.4 ) 42.4 827.5 4.4 Common equities 1,289.2 1,213.2 (10.1 ) 0 2,492.3 13.1 Short-term investments 2,149.0 0 0 0 2,149.0 11.3 Total portfolio 2,3 $ 17,402.8 $ 1,621.4 $ (49.2 ) $ 43.0 $ 19,018.0 100.0 % 1 Represents net holding period gains (losses) on certain hybrid securities (discussed below). 2 Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at December 31, 2015 , $23.1 million was included in "other assets," compared to $31.3 million in "other liabilities" at December 31, 2014 . 3 The total fair value of the portfolio included $1.3 billion and $1.9 billion at December 31, 2015 and 2014 , 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-maturity and equity securities are hybrid securities, which are reported at fair value at December 31 : (millions) 2015 2014 Fixed maturities: Corporate debt securities $ 49.1 $ 139.8 Residential mortgage-backed securities 144.3 120.7 Commercial mortgage-backed securities 17.3 31.2 Other asset-backed securities 11.3 13.7 Total fixed maturities 222.0 305.4 Equity securities: Nonredeemable preferred stocks 50.7 122.3 Total hybrid securities $ 272.7 $ 427.7
Composition of Fixed Maturities by Maturity	The composition of fixed maturities by maturity at December 31, 2015 , was: (millions) Cost Fair Value Less than one year $ 4,532.3 $ 4,530.9 One to five years 6,758.0 6,734.7 Five to ten years 3,934.1 3,940.3 Ten years or greater 119.1 121.9 Total 1 $ 15,343.5 $ 15,327.8 1 Excludes $4.4 million related to our open interest rate swap positions.
Gross Unrealized Losses by Major Security	The following tables show the composition of gross unrealized losses by major security type and by the length of time that individual securities have been in a continuous unrealized loss position: Total No. of Sec. Total Value Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Value Unrealized Losses No. of Sec. Fair Value Unrealized Losses December 31, 2015 Fixed maturities: U.S. government obligations 22 $ 897.1 $ (0.6 ) 22 $ 897.1 $ (0.6 ) 0 $ 0 $ 0 State and local government obligations 290 606.7 (3.7 ) 264 500.7 (2.6 ) 26 106.0 (1.1 ) Corporate debt securities 215 2,580.6 (33.0 ) 197 2,294.6 (25.2 ) 18 286.0 (7.8 ) Residential mortgage-backed securities 188 1,294.7 (20.6 ) 115 493.4 (3.7 ) 73 801.3 (16.9 ) Agency residential pass-through obligations 61 84.9 (1.1 ) 61 84.9 (1.1 ) 0 0 0 Commercial mortgage-backed securities 207 2,046.5 (29.4 ) 171 1,694.6 (25.8 ) 36 351.9 (3.6 ) Other asset-backed securities 101 1,548.6 (5.1 ) 92 1,472.0 (4.5 ) 9 76.6 (0.6 ) Redeemable preferred stocks 9 199.4 (43.3 ) 6 119.4 (14.5 ) 3 80.0 (28.8 ) Total fixed maturities 1,093 9,258.5 (136.8 ) 928 7,556.7 (78.0 ) 165 1,701.8 (58.8 ) Equity securities: Nonredeemable preferred stocks 10 301.8 (15.7 ) 5 124.2 (1.7 ) 5 177.6 (14.0 ) Common equities 64 164.8 (14.2 ) 60 161.4 (14.2 ) 4 3.4 0 Total equity securities 74 466.6 (29.9 ) 65 285.6 (15.9 ) 9 181.0 (14.0 ) Total portfolio 1,167 $ 9,725.1 $ (166.7 ) 993 $ 7,842.3 $ (93.9 ) 174 $ 1,882.8 $ (72.8 ) 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, 2014 Fixed maturities: U.S. government obligations 11 $ 428.2 $ (1.3 ) 5 $ 150.7 $ (0.3 ) 6 $ 277.5 $ (1.0 ) State and local government obligations 46 234.2 (1.1 ) 28 177.9 (0.4 ) 18 56.3 (0.7 ) Corporate debt securities 53 843.2 (10.4 ) 43 647.5 (6.1 ) 10 195.7 (4.3 ) Residential mortgage-backed securities 70 844.2 (10.8 ) 33 465.2 (3.1 ) 37 379.0 (7.7 ) Agency residential pass-through obligations 0 0 0 0 0 0 0 0 0 Commercial mortgage-backed securities 63 723.4 (2.6 ) 54 667.5 (1.4 ) 9 55.9 (1.2 ) Other asset-backed securities 44 741.8 (0.8 ) 42 715.7 (0.7 ) 2 26.1 (0.1 ) Redeemable preferred stocks 3 103.0 (5.7 ) 1 33.0 (1.0 ) 2 70.0 (4.7 ) Total fixed maturities 290 3,918.0 (32.7 ) 206 2,857.5 (13.0 ) 84 1,060.5 (19.7 ) Equity securities: Nonredeemable preferred stocks 8 231.4 (6.4 ) 5 143.2 (3.6 ) 3 88.2 (2.8 ) Common equities 20 68.4 (10.1 ) 19 61.8 (9.6 ) 1 6.6 (0.5 ) Total equity securities 28 299.8 (16.5 ) 24 205.0 (13.2 ) 4 94.8 (3.3 ) Total portfolio 318 $ 4,217.8 $ (49.2 ) 230 $ 3,062.5 $ (26.2 ) 88 $ 1,155.3 $ (23.0 )
Total Non-Credit Portion of Other-Than-Temporary Impairment Recorded in Accumulated Other Comprehensive Income, Reflecting Orginal Non-Credit Loss at the Time Credit Impairment	The following table shows the total non-credit portion of the OTTI recorded in accumulated other comprehensive income, reflecting the original non-credit loss at the time the credit impairment was determined: December 31, (millions) 2015 2014 Fixed maturities: Residential mortgage-backed securities $ (43.3 ) $ (44.1 ) Commercial mortgage-backed securities (0.6 ) (0.6 ) Total fixed maturities $ (43.9 ) $ (44.7 )
OTTI Credit Losses Recognized in Earnings	The following tables provide rollforwards of the amounts related to credit losses recognized in earnings for the periods ended December 31, 2015 , 2014 , and 2013 , 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: (millions) Residential Mortgage- Backed Commercial Mortgage- Backed Total Balance at December 31, 2014 $ 12.7 $ 0.4 $ 13.1 Credit losses for which an OTTI was previously recognized 0 0 0 Reductions for securities sold/matured (1.4 ) 0 (1.4 ) Change in recoveries of future cash flows expected to be collected 1,2 1.1 0 1.1 Reductions for previously recognized credit impairments written-down to fair value 3 0 0 0 Balance at December 31, 2015 $ 12.4 $ 0.4 $ 12.8 (millions) Residential Mortgage- Backed Commercial Mortgage- Backed Total Balance at December 31, 2013 $ 19.2 $ 0.4 $ 19.6 Credit losses for which an OTTI was previously recognized 0 0 0 Reductions for securities sold/matured (0.1 ) 0 (0.1 ) Change in recoveries of future cash flows expected to be collected 1,2 (6.4 ) 0 (6.4 ) Reductions for previously recognized credit impairments written-down to fair value 3 0 0 0 Balance at December 31, 2014 $ 12.7 $ 0.4 $ 13.1 (millions) Residential Mortgage- Backed Commercial Mortgage- Backed Total Balance at December 31, 2012 $ 27.1 $ 0.6 $ 27.7 Credit losses for which an OTTI was previously recognized 0.1 0 0.1 Reductions for securities sold/matured 0 0 0 Change in recoveries of future cash flows expected to be collected 1,2 (7.8 ) (0.2 ) (8.0 ) Reductions for previously recognized credit impairments written-down to fair value 3 (0.2 ) 0 (0.2 ) Balance at December 31, 2013 $ 19.2 $ 0.4 $ 19.6 1 Reflects expected recovery of prior period impairments that will be accreted into income over the remaining life of the security. 2 Includes $2.9 million , $4.3 million , and $2.6 million at December 31, 2015 , 2014 , and 2013 , respectively, recognized in income in excess of the cash flows expected to be collected at the time of the write-downs. 3 Reflects reductions of prior credit impairments where the current credit impairment requires writing securities down to fair value (i.e., no remaining non-credit loss).
Components of Net Realized Gains (Losses)	The components of net realized gains (losses) for the years ended December 31, were: (millions) 2015 2014 2013 Gross realized gains on security sales Fixed maturities: U.S. government obligations $ 17.5 $ 24.0 $ 8.5 State and local government obligations 7.8 9.3 7.7 Corporate and other debt securities 31.2 37.2 47.7 Residential mortgage-backed securities 4.9 2.7 3.0 Commercial mortgage-backed securities 15.7 17.0 10.0 Redeemable preferred stocks 0.1 2.7 0 Total fixed maturities 77.2 92.9 76.9 Equity securities: Nonredeemable preferred stocks 65.3 90.0 126.3 Common equities 50.4 107.3 68.6 Subtotal gross realized gains on security sales 192.9 290.2 271.8 Gross realized losses on security sales Fixed maturities: U.S. government obligations (0.9 ) (7.6 ) (3.7 ) State and local government obligations (0.3 ) (0.5 ) 0 Corporate and other debt securities (5.0 ) (2.8 ) (6.2 ) Residential mortgage-backed securities (0.4 ) (0.2 ) 0 Agency residential pass-through obligations (0.4 ) 0 0 Commercial mortgage-backed securities (1.3 ) (8.3 ) (1.8 ) Redeemable preferred stocks 0 (3.2 ) (0.1 ) Total fixed maturities (8.3 ) (22.6 ) (11.8 ) Equity securities: Nonredeemable preferred stocks (3.2 ) 0 (0.1 ) Common equities (38.4 ) (7.3 ) (0.6 ) Subtotal gross realized losses on security sales (49.9 ) (29.9 ) (12.5 ) Net realized gains (losses) on security sales Fixed maturities: U.S. government obligations 16.6 16.4 4.8 State and local government obligations 7.5 8.8 7.7 Corporate and other debt securities 26.2 34.4 41.5 Residential mortgage-backed securities 4.5 2.5 3.0 Agency residential pass-through obligations (0.4 ) 0 0 Commercial mortgage-backed securities 14.4 8.7 8.2 Redeemable preferred stocks 0.1 (0.5 ) (0.1 ) Total fixed maturities 68.9 70.3 65.1 Equity securities: Nonredeemable preferred stocks 62.1 90.0 126.2 Common equities 12.0 100.0 68.0 Subtotal net realized gains (losses) on security sales 143.0 260.3 259.3 Other-than-temporary impairment losses Fixed maturities: Residential mortgage-backed securities 0 0 (0.6 ) Total fixed maturities 0 0 (0.6 ) Equity securities: Common equities (8.7 ) (7.2 ) (5.5 ) Subtotal other-than-temporary impairment losses (8.7 ) (7.2 ) (6.1 ) Other gains (losses) Hybrid securities (1.3 ) 30.5 6.4 Derivative instruments (20.7 ) (64.1 ) 56.6 Litigation settlements 0.4 4.7 2.2 Subtotal other gains (losses) (21.6 ) (28.9 ) 65.2 Total net realized gains (losses) on securities $ 112.7 $ 224.2 $ 318.4
Components of Net Investment Income	The components of net investment income for the years ended December 31, were: (millions) 2015 2014 2013 Fixed maturities: U.S. government obligations $ 28.3 $ 46.2 $ 50.2 State and local government obligations 60.7 50.1 48.0 Foreign government obligations 0.4 0.4 0.2 Corporate debt securities 102.4 82.1 98.8 Residential mortgage-backed securities 52.2 44.9 28.1 Agency residential pass-through obligations 2.1 0 0 Commercial mortgage-backed securities 74.6 66.0 74.8 Other asset-backed securities 22.0 16.7 16.7 Redeemable preferred stocks 15.0 15.5 21.2 Total fixed maturities 357.7 321.9 338.0 Equity securities: Nonredeemable preferred stocks 43.7 38.6 36.2 Common equities 51.0 46.6 45.8 Short-term investments 2.2 1.3 2.0 Investment income 454.6 408.4 422.0 Investment expenses (22.8 ) (18.9 ) (18.8 ) Net investment income $ 431.8 $ 389.5 $ 403.2
Derivative Instruments	The following table shows the status of our derivative instruments at December 31, 2015 and 2014 , and for the years ended December 31, 2015 , 2014 , and 2013 : (millions) Balance Sheet 2 Comprehensive Income Statement Notional Value 1 Assets (Liabilities) Fair Value Pretax Net Realized Gains (Losses) Years ended December 31, December 31, December 31, Derivatives designated as: 2015 2014 2013 Purpose Classification 2015 2014 2015 2014 2013 Hedging instruments Closed: Ineffective cash flow hedge $ 18 $ 44 $ 54 Manage NA $ 0 $ 0 $ 0.2 $ 0.5 $ 0.8 Non-hedging instruments Assets: Interest rate swaps 750 750 750 Manage portfolio duration Investments - fixed 4.4 15.8 (23.4 ) (64.6 ) 59.8 Closed: Interest rate swaps 0 0 1,263 Manage NA 0 0 0 0 (4.0 ) U.S. Treasury Note futures 691 0 0 Manage NA 0 0 2.5 0 0 Total NA NA NA $ 4.4 $ 15.8 $ (20.7 ) $ (64.1 ) $ 56.6 1 The amounts represent the value held at year end for open positions and the maximum amount held during the year for closed positions. 2 To the extent we hold both derivative assets and liabilities with the same counterparty that are subject to an enforceable master netting arrangement, we expect that we will report them on a gross basis on our balance sheets, consistent with our historical presentation. NA = Not Applicable

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
	Dec. 31, 2015
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, 2015 Fixed maturities: U.S. government obligations $ 2,429.2 $ 0 $ 0 $ 2,429.2 $ 2,425.4 State and local government obligations 0 2,721.4 0 2,721.4 2,677.6 Foreign government obligations 18.6 0 0 18.6 18.6 Corporate debt securities 0 3,691.6 0 3,691.6 3,713.2 Subtotal 2,447.8 6,413.0 0 8,860.8 8,834.8 Asset-backed securities: Residential mortgage-backed 0 1,726.7 0 1,726.7 1,726.0 Agency residential pass-through obligations 0 89.3 0 89.3 90.3 Commercial mortgage-backed 0 2,643.3 9.9 2,653.2 2,665.7 Other asset-backed 0 1,767.9 0 1,767.9 1,771.1 Subtotal asset-backed securities 0 6,227.2 9.9 6,237.1 6,253.1 Redeemable preferred stocks: Financials 0 92.0 0 92.0 76.8 Utilities 0 51.2 0 51.2 65.1 Industrials 0 91.1 0 91.1 118.1 Subtotal redeemable preferred stocks 0 234.3 0 234.3 260.0 Total fixed maturities 2,447.8 12,874.5 9.9 15,332.2 15,347.9 Equity securities: Nonredeemable preferred stocks: Financials 154.9 627.7 0 782.6 674.2 Subtotal nonredeemable preferred stocks 154.9 627.7 0 782.6 674.2 Common equities: Common stocks 2,650.2 0 0 2,650.2 1,494.0 Other risk investments 0 0 0.3 0.3 0.3 Subtotal common equities 2,650.2 0 0.3 2,650.5 1,494.3 Total fixed maturities and equity securities 5,252.9 13,502.2 10.2 18,765.3 17,516.4 Short-term investments 2,056.3 115.7 0 2,172.0 2,172.0 Total portfolio $ 7,309.2 $ 13,617.9 $ 10.2 $ 20,937.3 $ 19,688.4 Debt $ 0 $ 2,722.9 $ 164.9 $ 2,887.8 $ 2,707.9 Fair Value (millions) Level 1 Level 2 Level 3 Total Cost December 31, 2014 Fixed maturities: U.S. government obligations $ 2,667.1 $ 0 $ 0 $ 2,667.1 $ 2,641.1 State and local government obligations 0 2,139.2 0 2,139.2 2,095.7 Foreign government obligations 14.2 0 0 14.2 14.2 Corporate debt securities 0 2,836.7 0 2,836.7 2,813.9 Subtotal 2,681.3 4,975.9 0 7,657.2 7,564.9 Asset-backed securities: Residential mortgage-backed 0 1,658.5 0 1,658.5 1,635.5 Agency residential pass-through obligations 0 0 0 0 0 Commercial mortgage-backed 0 2,304.0 11.6 2,315.6 2,278.7 Other asset-backed 0 1,638.7 0 1,638.7 1,634.9 Subtotal asset-backed securities 0 5,601.2 11.6 5,612.8 5,549.1 Redeemable preferred stocks: Financials 0 97.9 0 97.9 77.3 Utilities 0 65.3 0 65.3 65.0 Industrials 0 116.0 0 116.0 117.9 Subtotal redeemable preferred stocks 0 279.2 0 279.2 260.2 Total fixed maturities 2,681.3 10,856.3 11.6 13,549.2 13,374.2 Equity securities: Nonredeemable preferred stocks: Financials 204.1 554.1 69.3 827.5 590.4 Subtotal nonredeemable preferred stocks 204.1 554.1 69.3 827.5 590.4 Common equities: Common stocks 2,491.9 0 0 2,491.9 1,288.8 Other risk investments 0 0 0.4 0.4 0.4 Subtotal common equities 2,491.9 0 0.4 2,492.3 1,289.2 Total fixed maturities and equity securities 5,377.3 11,410.4 81.3 16,869.0 15,253.8 Short-term investments 1,937.0 212.0 0 2,149.0 2,149.0 Total portfolio $ 7,314.3 $ 11,622.4 $ 81.3 $ 19,018.0 $ 17,402.8 Debt $ 0 $ 2,527.5 $ 0 $ 2,527.5 $ 2,164.7
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, 2015 and 2014 : Level 3 Fair Value (millions) Fair Value at Dec. 31, 2014 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain)/Loss on Sales Change in Valuation Net Transfers In (Out) Fair Value at Dec. 31, 2015 Fixed maturities: Asset-backed securities: Residential mortgage-backed $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Commercial mortgage-backed 11.6 (1.3 ) 0 0 0 (0.4 ) 0 9.9 Total fixed maturities 11.6 (1.3 ) 0 0 0 (0.4 ) 0 9.9 Equity securities: Nonredeemable preferred stocks: Financials 1 69.3 0 0 0 (39.4 ) (1.4 ) (28.5 ) 0 Common equities: Other risk investments 0.4 0 0 0 0 (0.1 ) 0 0.3 Total Level 3 securities $ 81.3 $ (1.3 ) $ 0 $ 0 $ (39.4 ) $ (1.9 ) $ (28.5 ) $ 10.2 1 The $69.3 million decrease during the year reflects the reclassification of our 5% interest in ARX upon our acquisition of a controlling interest in ARX. The $39.4 million reflects our inception-to-date gain recognized, including the $1.4 million reduction in valuation that occurred during the first six months of 2015. Level 3 Fair Value (millions) Fair Value at Dec. 31, 2013 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain)/Loss on Sales Change in Valuation Net Transfers In (Out) 1 Fair Value at Dec. 31, 2014 Fixed maturities: Asset-backed securities: Residential mortgage-backed $ 0.2 $ 0 $ 0 $ (0.1 ) $ 0.1 $ (0.2 ) $ 0 $ 0 Commercial mortgage-backed 29.0 (3.6 ) 0 0 0 (0.2 ) (13.6 ) 11.6 Total fixed maturities 29.2 (3.6 ) 0 (0.1 ) 0.1 (0.4 ) (13.6 ) 11.6 Equity securities: Nonredeemable preferred stocks: Financials 2 39.0 0 0 0 0 30.3 0 69.3 Common equities: Other risk investments 0.5 (0.1 ) 0 0 0 0 0 0.4 Total Level 3 securities $ 68.7 $ (3.7 ) $ 0 $ (0.1 ) $ 0.1 $ 29.9 $ (13.6 ) $ 81.3 1 The $13.6 million was transferred out of Level 3 and into Level 2 due to an improvement in the security's underlying collateral and an increase in liquidity and market activity in comparable securities. 2 The $30.3 million represents a net holding period gain on our investment in ARX, which is reflected in net realized gains (losses) on securities in the comprehensive income statement.
Summary of Quantitative Information about Level 3 Fair Value Measurements	The following table provides a summary of the quantitative information about Level 3 fair value measurements for our applicable securities at December 31 : Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at Dec. 31, 2015 Valuation Technique Unobservable Input Unobservable Input Assumption Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 9.9 External vendor Prepayment rate 1 0 Total fixed maturities 9.9 Equity securities: Nonredeemable preferred stocks: Financials 0 NA NA NA Subtotal Level 3 securities 9.9 Third-party pricing exemption securities 2 0.3 Total Level 3 securities $ 10.2 NA= Not Applicable since we did not hold any nonredeemable preferred stock Level 3 securities at December 31, 2015 . 1 Assumes that one security has 0% of the principal amount of the underlying loans that will be paid off prematurely in each year. 2 The fair values for these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us. Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at Dec. 31, 2014 Valuation Technique Unobservable Input Unobservable Input Assumption Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 11.6 External vendor Prepayment rate 1 0 Total fixed maturities 11.6 Equity securities: Nonredeemable preferred stocks: Financials 69.3 Multiple of tangible net book value Price to book ratio multiple 2.6 Subtotal Level 3 securities 80.9 Third-party pricing exemption securities 2 0.4 Total Level 3 securities $ 81.3 1 Assumes that one security has 0% of the principal amount of the underlying loans that will be paid off prematurely in each year. 2 The fair values for these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us.

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2015
Debt Table	Debt at December 31 consisted of: 2015 2014 (millions) Carrying Value Fair Value Carrying Value Fair Value 3.75% Senior Notes due 2021 (issued: $500.0, August 2011) $ 498.1 $ 528.7 $ 497.8 $ 535.6 6 5/8% Senior Notes due 2029 (issued: $300.0, March 1999) 295.7 376.0 295.5 400.6 6.25% Senior Notes due 2032 (issued: $400.0, November 2002) 395.0 490.6 394.8 527.9 4.35% Senior Notes due 2044 (issued: $350.0, April 2014) 346.4 352.8 346.3 378.9 3.70% Senior Notes due 2045 (issued: $400.0, January 2015) 395.0 362.0 0 0 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 (issued: $1,000.0, June 2007; outstanding: $614.4 and $632.8) 612.8 612.8 630.3 684.5 Other debt instruments 164.9 164.9 0 0 Total $ 2,707.9 $ 2,887.8 $ 2,164.7 $ 2,527.5
Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block]	The other debt instruments reported in the table above represent ARX indebtedness and consist of: Type of debt instrument Number of Instruments Carrying Value Stated Maturity Date(s) Term loans 2 $ 87.1 December 2018 and 2019 Junior subordinated notes 1 2 41.2 June 2036 and 2037 Senior notes 4 24.0 Various 2 Surplus note 1 12.6 November 2021 Total $ 164.9 1 ARX issued junior subordinated floating rate notes to trusts established by ARX in connection with issuances of trust preferred securities by the trust(discussed below). 2 The senior notes mature in May 2033, April 2034, December 2034, and June 2035.
Aggregate Principal Payments on Debt Outstanding	Aggregate required principal payments on debt outstanding at December 31, 2015, are as follows: (millions) Year Payments 2016 $ 27.2 2017 27.2 2018 27.2 2019 13.4 2020 3.0 Thereafter 2,631.3 Total $ 2,729.3
Cash Flow Hedging [Member]
Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges Included in Accumulated Other Comprehensive Income	The original unrealized gain (loss) at the time of each debt issuance and the unamortized balance at December 31, 2015 , on a pretax basis, of these hedges, were as follows: (millions) Unrealized Gain (Loss) at Debt Issuance Unamortized Balance at December 31, 2015 3.75% Senior Notes $ (5.1 ) $ (3.1 ) 6 5/8% Senior Notes (4.2 ) (3.0 ) 6.25% Senior Notes 5.1 3.9 4.35% Senior Notes (1.6 ) (1.6 ) 3.70% Senior Notes (12.9 ) (12.6 ) 6.70% Debentures 34.4 3.9

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Components of Income Tax Provision	The components of our income tax provision were as follows: (millions) 2015 2014 2013 Current tax provision Federal $ 655.3 $ 594.4 $ 460.2 State 14.7 0 0 Deferred tax expense (benefit) Federal (47.7 ) 32.0 94.4 State (11.2 ) 0 0 Total income tax provision $ 611.1 $ 626.4 $ 554.6
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: ($ in millions) 2015 2014 2013 Income before income taxes $ 1,911.6 $ 1,907.4 $ 1,720.0 Tax at statutory federal rate $ 669.1 35 % $ 667.6 35 % $ 602.0 35 % Tax effect of: Dividends received deduction (19.8 ) (1 ) (18.3 ) (1 ) (17.6 ) (1 ) Exempt interest income (17.8 ) (1 ) (13.8 ) (1 ) (13.1 ) (1 ) Non-taxable gain 1 (13.8 ) (1 ) 0 0 0 0 Tax-deductible dividends (7.9 ) 0 (6.5 ) 0 (13.6 ) (1 ) State income taxes, net of federal taxes 2.3 0 0 0 0 0 Other items, net (1.0 ) 0 (2.6 ) 0 (3.1 ) 0 Total income tax provision $ 611.1 32 % $ 626.4 33 % $ 554.6 32 %
Components of Net Deferred Tax Assets	At December 31, 2015 and 2014 , the components of the net deferred tax asset (liability) were as follows: (millions) 2015 2014 Federal deferred tax assets: Unearned premiums reserve $ 453.3 $ 378.8 Investment basis differences 40.5 60.6 Non-deductible accruals 231.4 208.0 Loss and loss adjustment expense reserves 75.3 76.9 Hedges on forecasted transactions 4.4 0 Other 9.6 7.5 Federal deferred tax liabilities: Net unrealized gains on securities (436.7 ) (550.3 ) Hedges on forecasted transactions 0 (0.8 ) Deferred acquisition costs (197.4 ) (160.0 ) Property and equipment (110.7 ) (100.9 ) Prepaid expenses (11.9 ) (11.4 ) Intangible assets-ARX acquisition (166.4 ) 0 Deferred gain on extinguishment of debt (2.2 ) (3.0 ) Other (7.0 ) (4.3 ) Net federal deferred tax liability (117.8 ) (98.9 ) Net state deferred tax asset 8.5 0 Net deferred tax liability $ (109.3 ) $ (98.9 )

Loss And Loss Adjustment Expe35

Loss And Loss Adjustment Expense Reserves (Tables)	12 Months Ended
	Dec. 31, 2015
Loss and Loss Adjustment Expense Reserves Disclosures [Abstract]
Activity in Loss and Loss Adjustment Expense Reserves	Activity in the loss and loss adjustment expense reserves is summarized as follows: (millions) 2015 2014 2013 Balance at January 1 $ 8,857.4 $ 8,479.7 $ 7,838.4 Less reinsurance recoverables on unpaid losses 1,185.9 1,045.9 862.1 Net balance at January 1 7,671.5 7,433.8 6,976.3 Net loss and loss adjustment reserves acquired 1 222.4 0 0 Total beginning reserves 7,893.9 7,433.8 6,976.3 Incurred related to: Current year 14,657.1 13,330.3 12,427.3 Prior years (315.1 ) (24.1 ) 45.1 Total incurred 14,342.0 13,306.2 12,472.4 Paid related to: Current year 9,577.3 8,831.5 8,095.0 Prior years 4,062.3 4,237.0 3,919.9 Total paid 13,639.6 13,068.5 12,014.9 Net balance at December 31 8,596.3 7,671.5 7,433.8 Plus reinsurance recoverables on unpaid losses 1,442.7 1,185.9 1,045.9 Balance at December 31 $ 10,039.0 $ 8,857.4 $ 8,479.7 1 Net reserves acquired in ARX acquisition.

Reinsurance (Tables)

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2015
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: 2015 2014 2013 (millions) Written Earned Written Earned Written Earned Direct premiums $ 21,086.5 $ 20,454.1 $ 18,914.8 $ 18,648.4 $ 17,562.8 $ 17,317.9 Ceded: Regulated Plans (358.0 ) (362.6 ) (251.9 ) (241.4 ) (216.2 ) (205.4 ) Non-Regulated Plans (164.5 ) (192.4 ) (8.3 ) (8.5 ) (6.9 ) (9.1 ) Total Ceded (522.5 ) (555.0 ) (260.2 ) (249.9 ) (223.1 ) (214.5 ) Net premiums $ 20,564.0 $ 19,899.1 $ 18,654.6 $ 18,398.5 $ 17,339.7 $ 17,103.4
Prepaid Reinsurance Premiums and Reinsurance Recoverables	Prepaid Reinsurance Premiums Reinsurance Recoverables ($ in millions) 2015 2014 2015 2014 Regulated Plans: MCCA $ 31.4 16 % $ 32.8 38 % $ 1,217.6 82 % $ 1,018.8 83 % CAIP 37.1 19 26.5 31 134.0 9 110.1 9 NCRF 25.6 13 21.9 26 56.7 4 51.1 4 NFIP 45.0 22 0 0 10.4 1 0 0 Other 0 0 0 0 2.8 0 2.0 0 Total Regulated Plans 139.1 70 81.2 95 1,421.5 96 1,182.0 96 Non-Regulated Plans: Property 52.6 26 0 0 35.5 2 0 0 Other 7.6 4 4.1 5 31.8 2 49.9 4 Total Non-Regulated Plans 60.2 30 4.1 5 67.3 4 49.9 4 Total $ 199.3 100 % $ 85.3 100 % $ 1,488.8 100 % $ 1,231.9 100 %

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2015
Amounts Charged to Income for Employees Incentive Compensation Plans	The amounts charged to income for Progressive and ARX incentive compensation plans for the years ended December 31, were: 2015 2014 2013 (millions) Pretax After Tax Pretax After Tax Pretax After Tax Non-equity incentive plans - cash $ 337.7 $ 219.5 $ 266.2 $ 173.0 $ 234.5 $ 152.4 Equity incentive plans: Equity awards 64.5 41.9 51.4 33.4 64.9 42.2 Liability awards 1.7 1.1 0 0 0 0
Assets Held in Deferral Plan Irrevocable Grantor Trust Account	The Deferral Plan Irrevocable Grantor Trust account held the following assets at December 31: (millions) 2015 2014 Progressive common shares 1 $ 108.5 $ 83.2 Other investment funds 2 124.8 123.9 Total $ 233.3 $ 207.1 1 Includes 4.4 million and 3.6 million common shares as of December 31, 2015 and 2014 , respectively, to be distributed in common shares. 2 Amount is included in other assets on the balance sheet.
Employee
Summary of Restricted Stock Activity	A summary of all employee restricted equity award activity during the years ended December 31, follows: 2015 2014 2013 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 9,051,564 $ 21.27 9,918,575 $ 20.13 11,625,981 $ 17.80 Add (deduct): Granted 2 2,489,976 25.20 3,542,984 19.32 2,738,809 22.73 Vested (3,682,644 ) 19.53 (4,228,673 ) 16.99 (4,293,605 ) 15.54 Forfeited (133,669 ) 21.63 (181,322 ) 20.75 (152,610 ) 18.28 End of year 3,4 7,725,227 $ 23.37 9,051,564 $ 21.27 9,918,575 $ 20.13 1 Includes both restricted stock units and restricted stock. Upon vesting, all units will be converted on a one-for-one basis into Progressive common shares funded from existing treasury shares. All performance-based awards are included at their target amounts. 2 We reinvest dividend equivalents on restricted stock units. For 2015 , 2014 , and 2013 , the number of units "granted" shown in the table above includes 196,947 , 538,749 , and 161,077 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, 2015 , the number of shares included 2,025,871 performance-based awards at their target amounts. We expect 1,946,565 of these performance-based awards to vest, based upon our current estimate of the likelihood of achieving these pre-determined performance goals. 4 At December 31, 2015 , the total unrecognized compensation cost related to unvested equity awards was $78.3 million , which includes performance-based awards at their currently estimated vesting value. This compensation expense will be recognized into the income statement 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: 2015 2014 2013 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 81,579 $ 25.45 93,254 $ 26.19 92,957 $ 21.41 Add (deduct): Granted 89,427 27.23 90,649 25.44 93,254 26.19 Vested (81,579 ) 25.45 (93,254 ) 26.19 (92,957 ) 21.41 Forfeited 0 0 (9,070 ) 25.36 0 0 End of year 89,427 $ 27.23 81,579 $ 25.45 93,254 $ 26.19
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 since acquisition, follows: 2015 Options Outstanding Number of Shares Weighted Average At acquisition 26,000 $ 513.72 Add (deduct): Exercised 1 (1,005 ) 197.01 End of year 24,995 $ 526.46 Exercisable, end of year 12,995 $ 386.69 1 At the time of exercise, the value earned by the option holders was $1.1 million . 2015 Non-Vested Options Outstanding Number of Shares Weighted Average At acquisition 14,800 $ 675.55 Add (deduct): Vested (2,800 ) 665.85 End of year 1 12,000 $ 677.81 1 At December 31, 2015, the remaining unrecognized compensation cost related to unvested options was $2.9 million and the remaining weighted average vesting period on the unvested awards is 1.72 years.

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Reconciliation of Revenue and Operating Income from Segments to Consolidated	Following are the operating results for the years ended December 31: 2015 2014 2013 (millions) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Personal Lines Agency $ 9,108.6 $ 713.2 $ 9,087.0 $ 683.0 $ 8,601.5 $ 542.9 Direct 8,185.9 403.4 7,474.0 423.4 6,740.1 473.9 Total Personal Lines 1 17,294.5 1,116.6 16,561.0 1,106.4 15,341.6 1,016.8 Commercial Lines 1,995.9 318.3 1,837.5 315.8 1,761.6 114.1 Property 2 609.1 61.3 0 0 0 0 Other indemnity 3 (0.4 ) (1.0 ) 0 (11.9 ) 0.2 (10.8 ) Total underwriting operations 19,899.1 1,495.2 18,398.5 1,410.3 17,103.4 1,120.1 Fees and other revenues 4 302.0 NA 309.1 NA 291.8 NA Service businesses 86.3 8.8 56.0 5.1 39.6 0.8 Investments 5 567.3 544.5 632.6 613.7 740.4 721.6 Gains (losses) on extinguishment of debt (0.9 ) (0.9 ) (4.8 ) (4.8 ) (4.3 ) (4.3 ) Interest expense NA (136.0 ) NA (116.9 ) NA (118.2 ) Consolidated total $ 20,853.8 $ 1,911.6 $ 19,391.4 $ 1,907.4 $ 18,170.9 $ 1,720.0 NA = Not Applicable 1 Personal auto insurance accounted for 92% of the total Personal Lines segment net premiums earned in 2015 , compared to 92% in 2014 and 91% in 2013 ; insurance for our special lines products (e.g., motorcycles, ATVs, RVs, manufactured homes, watercraft, and snowmobiles) accounted for the balance of the Personal Lines net premiums earned. 2 We began reporting our Property business as a segment on April 1, 2015, when we acquired a controlling interest in ARX; Property business written prior to that date was negligible. During 2015 , amounts include $45.2 million of amortization/depreciation expense 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 Holding Corp. and, therefore, will not affect the value of the noncontrolling interest. 3 Our professional liability group recognized $0.4 million of reinstatement premiums paid to our reinsurers pursuant to their reinsurance contracts during 2015. This premium reduction is reflected in our companywide total results. In total, our run-off businesses generated an underwriting loss of $1.0 million in 2015. 4 Pretax profit (loss) for fees and other revenues are allocated to operating segments. 5 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/combined ratios for our underwriting operations for the years ended December 31: 2015 2014 2013 Underwriting Margin Combined Ratio Underwriting Margin Combined Ratio Underwriting Margin Combined Ratio Personal Lines Agency 7.8 % 92.2 7.5 % 92.5 6.3 % 93.7 Direct 4.9 95.1 5.7 94.3 7.0 93.0 Total Personal Lines 6.5 93.5 6.7 93.3 6.6 93.4 Commercial Lines 15.9 84.1 17.2 82.8 6.5 93.5 Property 1 10.1 89.9 0 0 0 0 Other indemnity 2 NM NM NM NM NM NM Total underwriting operations 7.5 92.5 7.7 92.3 6.5 93.5 1 Included is 7.4 points of amortization/depreciation expense associated with the acquisition of a controlling interest in ARX. 2 Underwriting margins/combined ratios are not meaningful (NM) for our other indemnity businesses due to the low level of premiums earned by, and the variability of loss costs in, such businesses.

Other Comprehensive Income (L39

Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2015
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 Total tax (provision) benefit After tax total accumulated other comprehensive income Total net unrealized gains (losses) on securities Net unrealized gains on forecasted transactions Foreign currency translation adjustment Loss attributable to NCI Balance at December 31, 2014 $ 1,574.0 $ (550.9 ) $ 1,023.1 $ 1,021.9 $ 1.5 $ (0.3 ) $ 0 Other comprehensive income (loss) before reclassifications: Investment securities (198.7 ) 67.5 (131.2 ) (131.2 ) 0 0 0 Net non-credit related OTTI losses, adjusted for valuation changes 0 0 0 0 0 0 0 Forecasted transactions (12.9 ) 4.5 (8.4 ) 0 (8.4 ) 0 0 Foreign currency translation adjustment (1.8 ) 0.6 (1.2 ) 0 0 (1.2 ) 0 Loss attributable to noncontrolling interest 1.6 (0.5 ) 1.1 0 0 0 1.1 Total other comprehensive income (loss) before reclassifications (211.8 ) 72.1 (139.7 ) (131.2 ) (8.4 ) (1.2 ) 1.1 Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (23.8 ) 8.4 (15.4 ) (15.4 ) 0 0 0 Net realized gains (losses) on securities 149.7 (52.5 ) 97.2 97.1 0.1 0 0 Interest expense 1.8 (0.6 ) 1.2 0 1.2 0 0 Total reclassification adjustment for amounts realized in net income 127.7 (44.7 ) 83.0 81.7 1.3 0 0 Total other comprehensive income (loss) (339.5 ) 116.8 (222.7 ) (212.9 ) (9.7 ) (1.2 ) 1.1 Balance at December 31, 2015 $ 1,234.5 $ (434.1 ) $ 800.4 $ 809.0 $ (8.2 ) $ (1.5 ) $ 1.1 Components of Changes in Accumulated Other Comprehensive Income (after tax) (millions) Pretax total accumulated other comprehensive income Total tax (provision) benefit After tax total accumulated other comprehensive income Total net unrealized gains (losses) on securities Net unrealized gains on forecasted transactions Foreign currency translation adjustment Loss attributable to NCI Balance at December 31, 2013 $ 1,464.1 $ (512.4 ) $ 951.7 $ 947.0 $ 4.1 $ 0.6 $ 0 Other comprehensive income (loss) before reclassifications: Investment securities 362.1 (126.7 ) 235.4 235.4 0 0 0 Net non-credit related OTTI losses, adjusted for valuation changes 0 0 0 0 0 0 0 Forecasted transactions (1.6 ) 0.6 (1.0 ) 0 (1.0 ) 0 0 Foreign currency translation adjustment (1.3 ) 0.4 (0.9 ) 0 0 (0.9 ) 0 Loss attributable to noncontrolling interest 0 0 0 0 0 0 0 Total other comprehensive income (loss) before reclassifications 359.2 (125.7 ) 233.5 235.4 (1.0 ) (0.9 ) 0 Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (7.7 ) 2.7 (5.0 ) (5.0 ) 0 0 0 Net realized gains (losses) on securities 255.0 (89.2 ) 165.8 165.5 0.3 0 0 Interest expense 2.0 (0.7 ) 1.3 0 1.3 0 0 Total reclassification adjustment for amounts realized in net income 249.3 (87.2 ) 162.1 160.5 1.6 0 0 Total other comprehensive income (loss) 109.9 (38.5 ) 71.4 74.9 (2.6 ) (0.9 ) 0 Balance at December 31, 2014 $ 1,574.0 $ (550.9 ) $ 1,023.1 $ 1,021.9 $ 1.5 $ (0.3 ) $ 0 Components of Changes in Accumulated Other Comprehensive Income (after tax) (millions) Pretax total accumulated other comprehensive income Total tax (provision) benefit After tax total accumulated other comprehensive income Total net unrealized gains (losses) on securities Net unrealized gains on forecasted transactions Foreign currency translation adjustment Loss attributable to NCI Balance at December 31, 2012 $ 1,340.0 $ (469.0 ) $ 871.0 $ 862.7 $ 6.1 $ 2.2 $ 0 Other comprehensive income (loss) before reclassifications: Investment securities 368.2 (128.9 ) 239.3 239.3 0 0 0 Net non-credit related OTTI losses, adjusted for valuation changes 0.4 (0.1 ) 0.3 0.3 0 0 0 Forecasted transactions 0 0 0 0 0 0 0 Foreign currency translation adjustment (2.5 ) 0.9 (1.6 ) 0 0 (1.6 ) 0 Loss attributable to noncontrolling interest 0 0 0 0 0 0 0 Total other comprehensive income (loss) before reclassifications 366.1 (128.1 ) 238.0 239.6 0 (1.6 ) 0 Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (5.7 ) 2.0 (3.7 ) (3.7 ) 0 0 0 Net realized gains (losses) on securities 245.5 (86.0 ) 159.5 159.0 0.5 0 0 Interest expense 2.2 (0.7 ) 1.5 0 1.5 0 0 Total reclassification adjustment for amounts realized in net income 242.0 (84.7 ) 157.3 155.3 2.0 0 0 Total other comprehensive income (loss) 124.1 (43.4 ) 80.7 84.3 (2.0 ) (1.6 ) 0 Balance at December 31, 2013 $ 1,464.1 $ (512.4 ) $ 951.7 $ 947.0 $ 4.1 $ 0.6 $ 0

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Minimum Commitments under Noncancelable Operating Lease Agreements	The minimum commitments under these agreements at December 31, 2015 , were as follows: (millions) Commitments 2016 $ 50.4 2017 47.8 2018 37.3 2019 24.7 2020 9.6 Thereafter 1.8 Total $ 171.6
Expense Incurred for Leases	The expense we incurred for the leases disclosed above, as well as other operating leases that may be cancelable or have terms less than one year, was: (millions) Expense 2015 $ 66.6 2014 63.4 2013 64.6

Dividends (Tables)

Dividends (Tables)	12 Months Ended
	Dec. 31, 2015
Dividends [Abstract]
Dividends	Following is a summary of our shareholder dividends, both variable and special, that were declared in the last three years: (millions, except per share amounts) Amount Dividend Type Declared Paid Per Total 1 Annual – Variable December 2015 February 2016 $ 0.8882 $ 519.2 Annual – Variable December 2014 February 2015 0.6862 404.1 Annual – Variable December 2013 February 2014 0.4929 293.9 Special December 2013 February 2014 1.0000 596.3 1 Based on shares outstanding as of the record date.

Redeemable Noncontrolling Int42

Redeemable Noncontrolling Interest (Tables)	12 Months Ended
	Dec. 31, 2015
Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interest [Table Text Block]	The components of redeemable noncontrolling interest (NCI) at December 31, 2015, were: (millions) Balance at March 31, 2015 $ 0 Fair value at date of acquisition 411.5 Net income attributable to NCI 32.9 Other comprehensive loss attributable to NCI (1.1 ) Purchase of shares from NCI (12.6 ) Change in redemption value of NCI 34.2 Balance at December 31, 2015 $ 464.9

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2015
Business Combinations [Abstract]
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets Acquired as Part of Business Combination [Table Text Block]	The following table reports the intangible assets by asset category as of December 31, 2015: ($ in millions) Category Value at Acquisition Accumulated Amortization Useful Life Policies in force $ 256.2 $ 27.5 7 years Agency relationships 159.2 8.5 14 years Software 69.1 6.5 8 years Trade name 34.8 2.6 10 years Agent licenses 1.1 0 Indefinite Total $ 520.4 $ 45.1

SCHEDULE I - Summary Of Inves44

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, 2015USD ($)
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	$ 19,688.4
Fair Value	20,937.3
Amount At Which Shown In The Balance Sheet	20,937.3
Fixed maturities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	15,347.9
Fair Value	15,332.2
Amount At Which Shown In The Balance Sheet	15,332.2
Fixed maturities | Bonds | US Government and Government Agencies and Authorities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	2,425.4
Fair Value	2,429.2
Amount At Which Shown In The Balance Sheet	2,429.2
Fixed maturities | Bonds | State and local government obligations
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	2,677.6
Fair Value	2,721.4
Amount At Which Shown In The Balance Sheet	2,721.4
Fixed maturities | Bonds | Foreign government obligations
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	18.6
Fair Value	18.6
Amount At Which Shown In The Balance Sheet	18.6
Fixed maturities | Bonds | Public Utility, Bonds
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	140.3
Fair Value	139.7
Amount At Which Shown In The Balance Sheet	139.7
Fixed maturities | Bonds | Corporate And Other Debt Securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	3,572.9
Fair Value	3,551.9
Amount At Which Shown In The Balance Sheet	3,551.9
Fixed maturities | Bonds | Asset-backed Securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	6,253.1
Fair Value	6,237.1
Amount At Which Shown In The Balance Sheet	6,237.1
Fixed maturities | Redeemable preferred stocks
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	260
Fair Value	234.3
Amount At Which Shown In The Balance Sheet	234.3
Equity securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	2,168.5
Fair Value	3,433.1
Amount At Which Shown In The Balance Sheet	3,433.1
Equity securities | Common Stocks, by Industry | Utilities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	113.1
Fair Value	151.8
Amount At Which Shown In The Balance Sheet	151.8
Equity securities | Common Stocks, by Industry | Financials
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	264.1
Fair Value	484.2
Amount At Which Shown In The Balance Sheet	484.2
Equity securities | Common Stocks, by Industry | Industrials
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,117.1
Fair Value	2,014.5
Amount At Which Shown In The Balance Sheet	2,014.5
Equity securities | Nonredeemable preferred stocks
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	674.2
Fair Value	782.6
Amount At Which Shown In The Balance Sheet	782.6
Short-term investments
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	2,172	[1]
Fair Value	2,172	[1]
Amount At Which Shown In The Balance Sheet	$ 2,172	[1]
[1]	Includes $2.5 million in treasury bills issued by the Australian government.

SCHEDULE I - Summary Of Inves45

SCHEDULE I - Summary Of Investments - Other Than Investments in Related Parties Summary Of Investments - Other than Investments In Related Parties (Parenthetical) (Detail) $ in Millions	Dec. 31, 2015USD ($)
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Fair Value	$ 20,937.3
Cost	19,688.4
Amount At Which Shown In The Balance Sheet	20,937.3
Short-term investments
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Fair Value	2,172	[1]
Cost	2,172	[1]
Amount At Which Shown In The Balance Sheet	2,172	[1]
Short-term investments | Foreign Government Debt
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Fair Value	2.5
Cost	2.5
Amount At Which Shown In The Balance Sheet	$ 2.5
[1]	Includes $2.5 million in treasury bills issued by the Australian government.

SCHEDULE II - Condensed Finan46

SCHEDULE II - Condensed Financial Information Of Registrant Condensed Statements Of Comprehensive Income (Parent Company) (Detail) - USD ($) $ in Millions		9 Months Ended	12 Months Ended
		Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues
Gains (losses) on extinguishment of debt		$ (0.9)	$ (0.9)	$ (4.8)	$ (4.3)
Total revenues			20,853.8	19,391.4	18,170.9
Expenses
Interest expense			136	116.9	118.2
Total expenses			18,942.2	17,484	16,450.9
Income before income taxes			1,911.6	1,907.4	1,720
Provision (benefit) for income taxes			611.1	626.4	554.6
Net income attributable to Progressive			1,267.6	1,281	1,165.4
Other comprehensive income (loss)			(223.8)	71.4	80.7
Comprehensive income			1,044.9	1,352.4	1,246.1
Parent Company
Revenues
Dividends from subsidiaries			852.5	1,000.2	1,119.7
Undistributed income (loss) from subsidiaries			500	358.3	117.5
Equity in net income of subsidiaries	[1]		1,352.5	1,358.5	1,237.2
Intercompany investment income	[1]		3.9	2.4	2.8
Gains (losses) on extinguishment of debt			(0.9)	(4.8)	(4.3)
Other Income	[2]		0	0	2.6
Total revenues			1,355.5	1,356.1	1,238.3
Expenses
Interest expense			136.1	120.2	121.2
Deferred compensation	[3]		5.3	2.8	9.5
Other operating costs and expenses			5.4	4.4	4
Total expenses			146.8	127.4	134.7
Income before income taxes			1,208.7	1,228.7	1,103.6
Provision (benefit) for income taxes			(58.9)	(52.3)	(61.8)
Net income attributable to Progressive			1,267.6	1,281	1,165.4
Other comprehensive income (loss)			(222.7)	71.4	80.7
Comprehensive income			$ 1,044.9	$ 1,352.4	$ 1,246.1
[1]	Eliminated in consolidation.
[2]	Represents gain on net death benefit received on life insurance policies.
[3]	See Note 4 – Employee Benefit Plans in these condensed financial statements.

SCHEDULE II - Condensed Finan47

SCHEDULE II - Condensed Financial Information Of Registrant Condensed Balance Sheets (Parent Company) (Detail) - USD ($) $ in Millions		Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets
Other assets		$ 335.8		$ 288.5
Total assets		29,819.3		25,787.6
Liabilities and Shareholders' Equity
Accounts payable, accrued expenses, and other liabilities		2,067.8		1,893.8
Dividend payable		519.2		404.1
Debt		2,707.9		2,164.7
Total liabilities		22,065		18,859
Redeemable Noncontrolling Interest, Equity, Carrying Amount		464.9	$ 0	0
Common shares, $1.00 par value (authorized 900.0; issued 797.6, including treasury shares of 214.0 and 209.8)		583.6		587.8
Paid-in capital		1,218.8		1,184.3
Retained earnings		4,686.6		4,133.4
Total accumulated other comprehensive income		800.4		1,023.1
Total shareholders' equity		7,289.4		6,928.6	$ 6,189.5
Total liabilities and shareholders' equity		29,819.3		25,787.6
Parent Company
Assets
Investment in affiliate		5		5
Investment in subsidiaries	[1]	9,192.3		7,423.5
Receivable from investment subsidiary	[1]	1,200.5		1,677.5
Intercompany receivable	[1]	406		413
Net deferred income taxes		90.6		74.5
Other assets		124.8		123.9
Total assets		11,019.2		9,717.4
Liabilities and Shareholders' Equity
Accounts payable, accrued expenses, and other liabilities		202.7		220
Dividend payable		519.2		404.1
Debt		2,543		2,164.7
Total liabilities		3,264.9		2,788.8
Redeemable Noncontrolling Interest, Equity, Carrying Amount		464.9		0
Common shares, $1.00 par value (authorized 900.0; issued 797.6, including treasury shares of 214.0 and 209.8)		583.6		587.8
Paid-in capital		1,218.8		1,184.3
Retained earnings		4,686.6		4,133.4
Total accumulated other comprehensive income		800.4		1,023.1
Total shareholders' equity		7,289.4		6,928.6
Total liabilities and shareholders' equity		$ 11,019.2		$ 9,717.4
[1]	Eliminated in consolidation.

SCHEDULE II - Condensed Finan48

SCHEDULE II - Condensed Financial Information Of Registrant Condensed Balance Sheets (Parent Company) (Parenthetical) (Detail) - $ / shares shares in Millions	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Common Shares, par value (USD per share)	$ 1	$ 1
Common Shares, authorized (shares)	900	900
Common Shares, issued (shares)	797.6	797.6
Common Shares, treasury shares (shares)	214	209.8
Parent Company
Condensed Financial Statements, Captions [Line Items]
Common Shares, par value (USD per share)	$ 1	$ 1
Common Shares, authorized (shares)	900	900
Common Shares, issued (shares)	797.6	797.6
Common Shares, treasury shares (shares)	214	209.8

SCHEDULE II - Condensed Finan49

SCHEDULE II - Condensed Financial Information Of Registrant Condensed Statements Of Cash Flows (Parent Company) (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash Flows From Operating Activities:
Net income attributable to Progressive		$ 1,267.6	$ 1,281	$ 1,165.4
Adjustments to reconcile net income attributable to Progressive to net cash provided by operating activities:
Amortization of equity-based compensation		66.2	51.4	64.9
(Gains) losses on extinguishment of debt	$ 0.9	0.9	4.8	4.3
Changes in:
Accounts payable, accrued expenses, and other liabilities		37.9	92	165
Income taxes		(107.2)	97.5	57.8
Other, net		(60.2)	(13.2)	(28.1)
Net cash provided by operating activities		2,292.9	1,725.6	1,899.9
Cash Flows From Investing Activities:
Net cash used in investing activities		(1,923.9)	(836.9)	(1,356.5)
Cash Flows From Financing Activities:
Tax benefit from exercise/vesting of equity-based compensation		16.8	12.8	10.3
Net proceeds from debt issuance		382	344.7	0
Payment of debt		(20.4)	0	(150)
Reacquisition of debt		(19.3)	(48.9)	(58.1)
Acquisition of treasury shares		(208.5)	(271.4)	(273.4)
Net cash used in financing activities		(252.8)	(855.4)	(646.8)
Increase (decrease) in cash		116	33.3	(104)
Cash, Beginning of year	108.4	108.4	75.1	179.1
Cash, End of year		224.4	108.4	75.1
Parent Company
Cash Flows From Operating Activities:
Net income attributable to Progressive		1,267.6	1,281	1,165.4
Adjustments to reconcile net income attributable to Progressive to net cash provided by operating activities:
Undistributed (income) loss from subsidiaries		(500)	(358.3)	(117.5)
Amortization of equity-based compensation		2.4	2.2	2.1
(Gains) losses on extinguishment of debt		0.9	4.8	4.3
Changes in:
Intercompany receivable		7	(105.4)	(11.4)
Accounts payable, accrued expenses, and other liabilities		(46.2)	18.2	19.4
Income taxes		12.3	61.1	(55.8)
Other, net		(3.1)	0.4	(16.3)
Net cash provided by operating activities		740.9	904	990.2
Cash Flows From Investing Activities:
Additional investments in equity securities of consolidated subsidiaries		(40.2)	(21.1)	(13.9)
Investment in affiliate		0	0	(4)
Payments to Acquire Businesses, Gross		(890.1)	0	0
(Paid to) received from investment subsidiary		409.1	(29.1)	(325.5)
Net cash used in investing activities		(521.2)	(50.2)	(343.4)
Cash Flows From Financing Activities:
Tax benefit from exercise/vesting of equity-based compensation		16.8	12.8	10.3
Net proceeds from debt issuance		394.9	346.3	0
Payment of debt		0	0	(150)
Reacquisition of debt		(19.3)	(48.9)	(58.1)
Dividends paid to shareholders		(403.6)	(892.6)	(175.6)
Acquisition of treasury shares		(208.5)	(271.4)	(273.4)
Net cash used in financing activities		(219.7)	(853.8)	(646.8)
Increase (decrease) in cash		0	0	0
Cash, Beginning of year	$ 0	0	0	0
Cash, End of year		$ 0	$ 0	$ 0

SCHEDULE II - Condensed Finan50

SCHEDULE II - Condensed Financial Information Of Registrant Condensed Financial Information Of Registrant - Additional Information (Detail) - USD ($) $ in Billions	Dec. 31, 2015	Dec. 31, 2014
Disclosure Condensed Financial Information Of Registrant Additional Information [Abstract]
Securities Held in Consolidated Non-Insurance Subsidiary	$ 1.3	$ 1.9

SCHEDULE II - Condensed Finan51

SCHEDULE II - Condensed Financial Information Of Registrant Progressive Corporation Cash Paid (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes	$ 701.8	$ 515	$ 497
Interest	132	$ 116	$ 122.3
Parent Company
Income Taxes	625
Interest	$ 128.2

SCHEDULE III - Supplementary 52

SCHEDULE III - Supplementary Insurance Information Supplementary Insurance Information (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	[1]	$ 564.1		$ 457.2		$ 447.6
Future policy benefits, losses, claims, and loss expenses	[1]	10,039		8,857.4		8,479.7
Unearned premiums	[1]	6,621.8		5,440.1		5,174.5
Other policy claims and benefits payable	[1]	0		0		0
Premium revenue		(19,899.1)		(18,398.5)		(17,103.4)
Net investment income		431.8	[1],[2]	389.5	[1],[2]	403.2
Benefits, claims, losses, and settlement expenses		(14,342)		(13,306.2)		(12,472.4)
Amortization of deferred policy acquisition costs		1,651.8		1,524		1,451.8
Other operating expenses		2,712.1		2,467.1		2,350.9
Net premiums written		(20,564)		(18,654.6)		(17,339.7)
Personal Lines
Supplementary Insurance Information, by Segment [Line Items]
Premium revenue		(17,294.5)		(16,561)		(15,341.6)
Benefits, claims, losses, and settlement expenses		(12,748.7)		(12,161.2)		(11,194.6)
Amortization of deferred policy acquisition costs		1,331.3		1,322.9		1,257.5
Other operating expenses		2,379.9		2,262.6		2,149.2
Net premiums written		(17,703.6)		(16,759.2)		(15,569.2)
Commercial Lines
Supplementary Insurance Information, by Segment [Line Items]
Premium revenue		(1,995.9)		(1,837.5)		(1,761.6)
Benefits, claims, losses, and settlement expenses		(1,244.5)		(1,133.4)		(1,267.3)
Amortization of deferred policy acquisition costs		219.4		201.1		194.3
Other operating expenses		232.6		204.2		201.2
Net premiums written		(2,171.2)		(1,895.4)		(1,770.5)
Property, Liability and Casualty Insurance Product Line
Supplementary Insurance Information, by Segment [Line Items]
Premium revenue		(609.1)		0		0
Benefits, claims, losses, and settlement expenses		(349)		0		0
Amortization of deferred policy acquisition costs		101.1		0		0
Other operating expenses		98.8		0		0
Net premiums written		(689.6)		0		0
Other Indemnity
Supplementary Insurance Information, by Segment [Line Items]
Premium revenue		(0.4)		0		(0.2)
Benefits, claims, losses, and settlement expenses		(0.2)		(11.6)		(10.5)
Amortization of deferred policy acquisition costs		0		0		0
Other operating expenses		0.8		0.3		0.5
Net premiums written		$ (0.4)		$ 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 ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	$ 20,454,100,000	$ 18,648,400,000	$ 17,317,900,000
Ceded to Other Companies	555,000,000	249,900,000	214,500,000
Property, Liability and Casualty Insurance Product Line
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	20,454,100,000	18,648,400,000	17,317,900,000
Ceded to Other Companies	555,000,000	249,900,000	214,500,000
Assumed From Other Companies	0	0	0
Net Amount	$ 19,899,100,000	$ 18,398,500,000	$ 17,103,400,000
Percentage of Amount Assumed to Net	0.00%	0.00%	0.00%

SCHEDULE VI-Supplemental Info54

SCHEDULE VI-Supplemental Information Concerning Property - Casualty Insurance Operations Supplemental Information Concerning Property - Casualty Insurance Operations (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure Supplemental Information Concerning Property Casualty Insurance Operations [Abstract]
Losses and Loss Adjustment Expenses Incurred Related to Current Year	$ 14,657.1	$ 13,330.3	$ 12,427.3
Losses and Loss Adjustment Expenses Incurred Related to Prior Years	(315.1)	(24.1)	45.1
Paid Losses and Loss Adjustment Expenses	$ 13,639.6	$ 13,068.5	$ 12,014.9

Reporting And Accounting Poli55

Reporting And Accounting Policies Advertising Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Marketing and Advertising Expense [Abstract]
Advertising Expense	$ 748.3	$ 681.8	$ 619.3

Reporting And Accounting Poli56

Reporting And Accounting Policies Interest Capitalized (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure Interest Capitalized [Abstract]
Capitalized Interest	$ 2.4	$ 1.3	$ 0.8

Reporting And Accounting Poli57

Reporting And Accounting Policies Equity Based Compensation (Detail) - Stock Compensation Plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Incentive Compensation Plans Expense [Line Items]
Pretax expense	$ 66.2	$ 51.4	$ 64.9
Tax benefit	$ 23.2	$ 18	$ 22.7

Reporting And Accounting Poli58

Reporting And Accounting Policies Supplemental Cash Flow Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure Supplemental Cash Flow Information [Abstract]
Income Taxes	$ 701.8	$ 515	$ 497
Interest	$ 132	$ 116	$ 122.3

Reporting And Accounting Poli59

Reporting And Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Significant Accounting Policies [Line Items]
Number of Properties Held for Sale	1
Assets Held-for-Sale, Property, Plant and Equipment	$ 8.7
Lower Limit
Significant Accounting Policies [Line Items]
Auction Rate Securities, Period Between Auction Dates	7 days
Upper Limit
Significant Accounting Policies [Line Items]
Auction Rate Securities, Period Between Auction Dates	49 days
computer equipment and laptop computers
Significant Accounting Policies [Line Items]
Estimated useful lives	3 years
Building, Building Improvements, and Integrated Components | Lower Limit
Significant Accounting Policies [Line Items]
Estimated useful lives	7 years
Building, Building Improvements, and Integrated Components | Upper Limit
Significant Accounting Policies [Line Items]
Estimated useful lives	40 years
Property, Plant and Equipment, Other Types | Lower Limit
Significant Accounting Policies [Line Items]
Estimated useful lives	3 years
Property, Plant and Equipment, Other Types | Upper Limit
Significant Accounting Policies [Line Items]
Estimated useful lives	15 years
Land and Building
Significant Accounting Policies [Line Items]
Land and buildings as a percentage of total property and equipment	75.00%	77.00%
ARX Holding Corp. [Member] | Lower Limit
Significant Accounting Policies [Line Items]
Finite-Lived Intangible Asset, Useful Life	7 years
ARX Holding Corp. [Member] | Upper Limit
Significant Accounting Policies [Line Items]
Finite-Lived Intangible Asset, Useful Life	14 years

Investments Investment Portfoli

Investments Investment Portfolio by Major Security Type (Detail) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Cost	[1],[2]	$ 19,688.4	$ 17,402.8
Gross Unrealized Gains	[1],[2]	1,414.5	1,621.4
Gross Unrealized Losses	[1],[2]	(166.7)	(49.2)
Net Realized Gains (Losses)	[1],[2],[3]	1.1	43
Total investments at fair value	[1],[2]	$ 20,937.3	$ 19,018
% of Total Fair Value	[1],[2]	100.00%	100.00%
Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 15,347.9	$ 13,374.2
Gross Unrealized Gains		121.3	207.1
Gross Unrealized Losses		(136.8)	(32.7)
Net Realized Gains (Losses)	[3]	(0.2)	0.6
Total investments at fair value		$ 15,332.2	$ 13,549.2
% of Total Fair Value		73.20%	71.20%
Fixed maturities | U.S. government obligations
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 2,425.4	$ 2,641.1
Gross Unrealized Gains		4.4	27.3
Gross Unrealized Losses		(0.6)	(1.3)
Net Realized Gains (Losses)	[3]	0	0
Total investments at fair value		$ 2,429.2	$ 2,667.1
% of Total Fair Value		11.60%	14.00%
Fixed maturities | State and local government obligations
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 2,677.6	$ 2,095.7
Gross Unrealized Gains		47.5	44.6
Gross Unrealized Losses		(3.7)	(1.1)
Net Realized Gains (Losses)	[3]	0	0
Total investments at fair value		$ 2,721.4	$ 2,139.2
% of Total Fair Value		13.00%	11.20%
Fixed maturities | Foreign government obligations
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 18.6	$ 14.2
Gross Unrealized Gains		0	0
Gross Unrealized Losses		0	0
Net Realized Gains (Losses)	[3]	0	0
Total investments at fair value		$ 18.6	$ 14.2
% of Total Fair Value		0.10%	0.10%
Fixed maturities | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 3,713.2	$ 2,813.9
Gross Unrealized Gains		11.3	32.9
Gross Unrealized Losses		(33)	(10.4)
Net Realized Gains (Losses)	[3]	0.1	0.3
Total investments at fair value		$ 3,691.6	$ 2,836.7
% of Total Fair Value		17.60%	14.90%
Fixed maturities | Residential mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 1,726	$ 1,635.5
Gross Unrealized Gains		22.1	34.5
Gross Unrealized Losses		(20.6)	(10.8)
Net Realized Gains (Losses)	[3]	(0.8)	(0.7)
Total investments at fair value		$ 1,726.7	$ 1,658.5
% of Total Fair Value		8.30%	8.70%
Fixed maturities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 90.3	$ 0
Gross Unrealized Gains		0.1	0
Gross Unrealized Losses		(1.1)	0
Net Realized Gains (Losses)	[3]	0	0
Total investments at fair value		$ 89.3	$ 0
% of Total Fair Value		0.40%	0.00%
Fixed maturities | Commercial mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 2,665.7	$ 2,278.7
Gross Unrealized Gains		16.9	39.3
Gross Unrealized Losses		(29.4)	(2.6)
Net Realized Gains (Losses)	[3]	0	0.2
Total investments at fair value		$ 2,653.2	$ 2,315.6
% of Total Fair Value		12.70%	12.20%
Fixed maturities | Other asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 1,771.1	$ 1,634.9
Gross Unrealized Gains		1.4	3.8
Gross Unrealized Losses		(5.1)	(0.8)
Net Realized Gains (Losses)	[3]	0.5	0.8
Total investments at fair value		$ 1,767.9	$ 1,638.7
% of Total Fair Value		8.40%	8.60%
Fixed maturities | Redeemable preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 260	$ 260.2
Gross Unrealized Gains		17.6	24.7
Gross Unrealized Losses		(43.3)	(5.7)
Net Realized Gains (Losses)	[3]	0	0
Total investments at fair value		$ 234.3	$ 279.2
% of Total Fair Value		1.10%	1.50%
Equity securities | Nonredeemable preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 674.2	$ 590.4
Gross Unrealized Gains		122.8	201.1
Gross Unrealized Losses		(15.7)	(6.4)
Net Realized Gains (Losses)	[3]	1.3	42.4
Total investments at fair value		$ 782.6	$ 827.5
% of Total Fair Value		3.70%	4.40%
Equity securities | Common equities
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 1,494.3	$ 1,289.2
Gross Unrealized Gains		1,170.4	1,213.2
Gross Unrealized Losses		(14.2)	(10.1)
Net Realized Gains (Losses)	[3]	0	0
Total investments at fair value		$ 2,650.5	$ 2,492.3
% of Total Fair Value		12.70%	13.10%
Short-term investments
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 2,172	$ 2,149
Gross Unrealized Gains		0	0
Gross Unrealized Losses		0	0
Net Realized Gains (Losses)	[3]	0	0
Total investments at fair value		$ 2,172	$ 2,149
% of Total Fair Value		10.40%	11.30%
[1]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at December 31, 2015, $23.1 million was included in "other assets," compared to $31.3 million in "other liabilities" at December 31, 2014.
[2]	The total fair value of the portfolio included $1.3 billion and $1.9 billion at December 31, 2015 and 2014, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.
[3]	Represents net holding period gains (losses) on certain hybrid securities (discussed below).

Investments Investment Portfo61

Investments Investment Portfolio by Major Security Type (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Other Receivables from Broker-Dealers and Clearing Organizations	$ 23.1
Net unsettled security transactions offset in other liabilities		$ 31.3
Securities in the portfolio of a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions	$ 1,300	$ 1,900

Investments Hybrid Securities (

Investments Hybrid Securities (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Hybrid Securities [Line Items]
Hybrid securities	$ 272.7	$ 427.7
Fixed maturities
Hybrid Securities [Line Items]
Hybrid securities	222	305.4
Fixed maturities | Corporate debt securities
Hybrid Securities [Line Items]
Hybrid securities	49.1	139.8
Fixed maturities | Residential mortgage-backed securities
Hybrid Securities [Line Items]
Hybrid securities	144.3	120.7
Fixed maturities | Commercial mortgage-backed securities
Hybrid Securities [Line Items]
Hybrid securities	17.3	31.2
Fixed maturities | Other asset-backed securities
Hybrid Securities [Line Items]
Hybrid securities	11.3	13.7
Equity securities | Nonredeemable preferred stocks
Hybrid Securities [Line Items]
Hybrid securities	$ 50.7	$ 122.3

Investments Composition of Fixe

Investments Composition of Fixed Maturities by Maturity (Detail) $ in Millions	Dec. 31, 2015USD ($)
Available for sale, cost
Less than one year	$ 4,532.3
One to five years	6,758
Five to ten years	3,934.1
Ten years or greater	119.1
Total	15,343.5	[1]
Available for sale, Fair value
Less than one year	4,530.9
One to five years	6,734.7
Five to ten years	3,940.3
Ten years or greater	121.9
Total	$ 15,327.8	[1]
[1]	Excludes $4.4 million related to our open interest rate swap positions.

Investments Composition of Fi64

Investments Composition of Fixed Maturities by Maturity (Parenthetical) (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Open interest rate swap positions	[1]	$ 4.4	$ 15.8
Interest Rate Swaps
Schedule of Available-for-sale Securities [Line Items]
Open interest rate swap positions		$ 4.4
[1]	To the extent we hold both derivative assets and liabilities with the same counterparty that are subject to an enforceable master netting arrangement, we expect that we will report them on a gross basis on our balance sheets, consistent with our historical presentation.

Investments Gross Unrealized lo

Investments Gross Unrealized losses by Major Security (Detail) $ in Millions	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	1,167	318
Total Fair Value	$ 9,725.1	$ 4,217.8
Gross Unrealized Losses	$ (166.7)	$ (49.2)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	993	230
Less than 12 Months Fair Value	$ 7,842.3	$ 3,062.5
Less than 12 Months Unrealized Losses	$ (93.9)	$ (26.2)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	174	88
12 Months or Greater Fair Value	$ 1,882.8	$ 1,155.3
12 Months or Greater Unrealized Losses	$ (72.8)	$ (23)
Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	1,093	290
Total Fair Value	$ 9,258.5	$ 3,918
Gross Unrealized Losses	$ (136.8)	$ (32.7)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	928	206
Less than 12 Months Fair Value	$ 7,556.7	$ 2,857.5
Less than 12 Months Unrealized Losses	$ (78)	$ (13)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	165	84
12 Months or Greater Fair Value	$ 1,701.8	$ 1,060.5
12 Months or Greater Unrealized Losses	$ (58.8)	$ (19.7)
Fixed maturities | U.S. government obligations
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	22	11
Total Fair Value	$ 897.1	$ 428.2
Gross Unrealized Losses	$ (0.6)	$ (1.3)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	22	5
Less than 12 Months Fair Value	$ 897.1	$ 150.7
Less than 12 Months Unrealized Losses	$ (0.6)	$ (0.3)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	0	6
12 Months or Greater Fair Value	$ 0	$ 277.5
12 Months or Greater Unrealized Losses	$ 0	$ (1)
Fixed maturities | State and local government obligations
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	290	46
Total Fair Value	$ 606.7	$ 234.2
Gross Unrealized Losses	$ (3.7)	$ (1.1)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	264	28
Less than 12 Months Fair Value	$ 500.7	$ 177.9
Less than 12 Months Unrealized Losses	$ (2.6)	$ (0.4)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	26	18
12 Months or Greater Fair Value	$ 106	$ 56.3
12 Months or Greater Unrealized Losses	$ (1.1)	$ (0.7)
Fixed maturities | Corporate debt securities
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	215	53
Total Fair Value	$ 2,580.6	$ 843.2
Gross Unrealized Losses	$ (33)	$ (10.4)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	197	43
Less than 12 Months Fair Value	$ 2,294.6	$ 647.5
Less than 12 Months Unrealized Losses	$ (25.2)	$ (6.1)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	18	10
12 Months or Greater Fair Value	$ 286	$ 195.7
12 Months or Greater Unrealized Losses	$ (7.8)	$ (4.3)
Fixed maturities | Residential mortgage-backed securities
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	188	70
Total Fair Value	$ 1,294.7	$ 844.2
Gross Unrealized Losses	$ (20.6)	$ (10.8)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	115	33
Less than 12 Months Fair Value	$ 493.4	$ 465.2
Less than 12 Months Unrealized Losses	$ (3.7)	$ (3.1)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	73	37
12 Months or Greater Fair Value	$ 801.3	$ 379
12 Months or Greater Unrealized Losses	$ (16.9)	$ (7.7)
Fixed maturities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	61	0
Total Fair Value	$ 84.9	$ 0
Gross Unrealized Losses	$ (1.1)	$ 0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	61	0
Less than 12 Months Fair Value	$ 84.9	$ 0
Less than 12 Months Unrealized Losses	$ (1.1)	$ 0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	0	0
12 Months or Greater Fair Value	$ 0	$ 0
12 Months or Greater Unrealized Losses	$ 0	$ 0
Fixed maturities | Commercial mortgage-backed securities
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	207	63
Total Fair Value	$ 2,046.5	$ 723.4
Gross Unrealized Losses	$ (29.4)	$ (2.6)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	171	54
Less than 12 Months Fair Value	$ 1,694.6	$ 667.5
Less than 12 Months Unrealized Losses	$ (25.8)	$ (1.4)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	36	9
12 Months or Greater Fair Value	$ 351.9	$ 55.9
12 Months or Greater Unrealized Losses	$ (3.6)	$ (1.2)
Fixed maturities | Other asset-backed securities
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	101	44
Total Fair Value	$ 1,548.6	$ 741.8
Gross Unrealized Losses	$ (5.1)	$ (0.8)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	92	42
Less than 12 Months Fair Value	$ 1,472	$ 715.7
Less than 12 Months Unrealized Losses	$ (4.5)	$ (0.7)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	9	2
12 Months or Greater Fair Value	$ 76.6	$ 26.1
12 Months or Greater Unrealized Losses	$ (0.6)	$ (0.1)
Fixed maturities | Redeemable preferred stocks
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	9	3
Total Fair Value	$ 199.4	$ 103
Gross Unrealized Losses	$ (43.3)	$ (5.7)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	6	1
Less than 12 Months Fair Value	$ 119.4	$ 33
Less than 12 Months Unrealized Losses	$ (14.5)	$ (1)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	3	2
12 Months or Greater Fair Value	$ 80	$ 70
12 Months or Greater Unrealized Losses	$ (28.8)	$ (4.7)
Equity securities
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	74	28
Total Fair Value	$ 466.6	$ 299.8
Gross Unrealized Losses	$ (29.9)	$ (16.5)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	65	24
Less than 12 Months Fair Value	$ 285.6	$ 205
Less than 12 Months Unrealized Losses	$ (15.9)	$ (13.2)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	9	4
12 Months or Greater Fair Value	$ 181	$ 94.8
12 Months or Greater Unrealized Losses	$ (14)	$ (3.3)
Equity securities | Nonredeemable preferred stocks
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	10	8
Total Fair Value	$ 301.8	$ 231.4
Gross Unrealized Losses	$ (15.7)	$ (6.4)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	5	5
Less than 12 Months Fair Value	$ 124.2	$ 143.2
Less than 12 Months Unrealized Losses	$ (1.7)	$ (3.6)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	5	3
12 Months or Greater Fair Value	$ 177.6	$ 88.2
12 Months or Greater Unrealized Losses	$ (14)	$ (2.8)
Equity securities | Common equities
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	64	20
Total Fair Value	$ 164.8	$ 68.4
Gross Unrealized Losses	$ (14.2)	$ (10.1)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	60	19
Less than 12 Months Fair Value	$ 161.4	$ 61.8
Less than 12 Months Unrealized Losses	$ (14.2)	$ (9.6)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	4	1
12 Months or Greater Fair Value	$ 3.4	$ 6.6
12 Months or Greater Unrealized Losses	$ 0	$ (0.5)

Investments Total Non-Credit Po

Investments Total Non-Credit Portion of Other-Than-Temporary Impairment Recorded in Accumulated Other Comprehensive Income, Reflecting Original Non-Credit Loss at Time Credit Impairment (Detail) - Fixed maturities - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Other Than Temporary Impairment Non Credit Losses Recognized In Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Pre-Tax, Available-for-sale, Debt Securities	$ (43.9)	$ (44.7)
Residential mortgage-backed securities
Other Than Temporary Impairment Non Credit Losses Recognized In Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Pre-Tax, Available-for-sale, Debt Securities	(43.3)	(44.1)
Commercial mortgage-backed securities
Other Than Temporary Impairment Non Credit Losses Recognized In Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Pre-Tax, Available-for-sale, Debt Securities	$ (0.6)	$ (0.6)

Investments OTTI Credit Losses

Investments OTTI Credit Losses Recognized in Earnings (Detail) - Fixed maturities - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance		$ 13.1	$ 19.6	$ 27.7
Credit losses for which an OTTI was previously recognized		0	0	0.1
Reductions for securities sold/matured		(1.4)	(0.1)	0
Change in recoveries of future cash flows expected to be collected	[1],[2]	1.1	(6.4)	(8)
Reductions for previously recognized credit impairments written-down to fair value	[3]	0	0	(0.2)
Ending balance		12.8	13.1	19.6
Residential mortgage-backed securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance		12.7	19.2	27.1
Credit losses for which an OTTI was previously recognized		0	0	0.1
Reductions for securities sold/matured		(1.4)	(0.1)	0
Change in recoveries of future cash flows expected to be collected	[1],[2]	1.1	(6.4)	(7.8)
Reductions for previously recognized credit impairments written-down to fair value	[3]	0	0	(0.2)
Ending balance		12.4	12.7	19.2
Commercial mortgage-backed securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance		0.4	0.4	0.6
Credit losses for which an OTTI was previously recognized		0	0	0
Reductions for securities sold/matured		0	0	0
Change in recoveries of future cash flows expected to be collected	[1],[2]	0	0	(0.2)
Reductions for previously recognized credit impairments written-down to fair value	[3]	0	0	0
Ending balance		$ 0.4	$ 0.4	$ 0.4
[1]	Includes $2.9 million, $4.3 million, and $2.6 million at December 31, 2015, 2014, and 2013, respectively, recognized in income in excess of the cash flows expected to be collected at the time of the write-downs.
[2]	Reflects expected recovery of prior period impairments that will be accreted into income over the remaining life of the security.
[3]	Reflects reductions of prior credit impairments where the current credit impairment requires writing securities down to fair value (i.e., no remaining non-credit loss).

Investments OTTI Credit Losse68

Investments OTTI Credit Losses Recognized in Earnings (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Actual Cash Flow Recovery
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Change in recoveries of future cash flows expected to be collected	$ 2.9	$ 4.3	$ 2.6

Investments Components of Net R

Investments Components of Net Realized Gains (Losses) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	$ 192.9	$ 290.2	$ 271.8
Gross realized losses on securities sales	(49.9)	(29.9)	(12.5)
Net realized gains (losses) on securities sales	143	260.3	259.3
Other-than-temporary impairment losses	(8.7)	(7.2)	(6.1)
Total net realized gains (losses) on securities	112.7	224.2	318.4
Fixed maturities
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	77.2	92.9	76.9
Gross realized losses on securities sales	(8.3)	(22.6)	(11.8)
Net realized gains (losses) on securities sales	68.9	70.3	65.1
Other-than-temporary impairment losses	0	0	(0.6)
Fixed maturities | U.S. government obligations
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	17.5	24	8.5
Gross realized losses on securities sales	(0.9)	(7.6)	(3.7)
Net realized gains (losses) on securities sales	16.6	16.4	4.8
Fixed maturities | State and local government obligations
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	7.8	9.3	7.7
Gross realized losses on securities sales	(0.3)	(0.5)	0
Net realized gains (losses) on securities sales	7.5	8.8	7.7
Fixed maturities | Corporate And Other Debt Securities
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	31.2	37.2	47.7
Gross realized losses on securities sales	(5)	(2.8)	(6.2)
Net realized gains (losses) on securities sales	26.2	34.4	41.5
Fixed maturities | Residential mortgage-backed securities
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	4.9	2.7	3
Gross realized losses on securities sales	(0.4)	(0.2)	0
Net realized gains (losses) on securities sales	4.5	2.5	3
Other-than-temporary impairment losses	0	0	(0.6)
Fixed maturities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Gain (Loss) on Investments [Line Items]
Gross realized losses on securities sales	(0.4)	0	0
Net realized gains (losses) on securities sales	(0.4)	0	0
Fixed maturities | Commercial mortgage-backed securities
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	15.7	17	10
Gross realized losses on securities sales	(1.3)	(8.3)	(1.8)
Net realized gains (losses) on securities sales	14.4	8.7	8.2
Fixed maturities | Redeemable preferred stocks
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	0.1	2.7	0
Gross realized losses on securities sales	0	(3.2)	(0.1)
Net realized gains (losses) on securities sales	0.1	(0.5)	(0.1)
Equity securities | Nonredeemable preferred stocks
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	65.3	90	126.3
Gross realized losses on securities sales	(3.2)	0	(0.1)
Net realized gains (losses) on securities sales	62.1	90	126.2
Equity securities | Common equities
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	50.4	107.3	68.6
Gross realized losses on securities sales	(38.4)	(7.3)	(0.6)
Net realized gains (losses) on securities sales	12	100	68
Other-than-temporary impairment losses	(8.7)	(7.2)	(5.5)
Hybrid and Derivative Instruments and Litigation Settlements
Gain (Loss) on Investments [Line Items]
Other gains (losses)	(21.6)	(28.9)	65.2
Hybrid and Derivative Instruments and Litigation Settlements | Litigation Settlements
Gain (Loss) on Investments [Line Items]
Other gains (losses)	0.4	4.7	2.2
Hybrid and Derivative Instruments and Litigation Settlements | Hybrid Preferred Stock
Gain (Loss) on Investments [Line Items]
Other gains (losses)	(1.3)	30.5	6.4
Hybrid and Derivative Instruments and Litigation Settlements | Derivative Instruments
Gain (Loss) on Investments [Line Items]
Other gains (losses)	$ (20.7)	$ (64.1)	$ 56.6

Investments Components of Net I

Investments Components of Net Investment Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	$ 454.6	$ 408.4	$ 422
Investment expenses	(22.8)	(18.9)	(18.8)
Net investment income	431.8	389.5	403.2
Fixed maturities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	357.7	321.9	338
Fixed maturities | U.S. government obligations
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	28.3	46.2	50.2
Fixed maturities | State and local government obligations
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	60.7	50.1	48
Fixed maturities | Foreign government obligations
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	0.4	0.4	0.2
Fixed maturities | Corporate debt securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	102.4	82.1	98.8
Fixed maturities | Residential mortgage-backed securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	52.2	44.9	28.1
Fixed maturities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	2.1	0	0
Fixed maturities | Commercial mortgage-backed securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	74.6	66	74.8
Fixed maturities | Other asset-backed securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	22	16.7	16.7
Fixed maturities | Redeemable preferred stocks
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	15	15.5	21.2
Equity securities | Nonredeemable preferred stocks
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	43.7	38.6	36.2
Equity securities | Common equities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	51	46.6	45.8
Short-term investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	$ 2.2	$ 1.3	$ 2

Investments Derivative Instrume

Investments Derivative Instruments (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Balance Sheet - Fair Value	[1]	$ 4.4	$ 15.8
Income Statement - Net Realized Gain (Loss) on Securities		(20.7)	(64.1)	$ 56.6
Hedging Instrument | Closed Positions | Ineffective Cash Flow Hedge
Derivative [Line Items]
Notional Value	[2]	$ 18	$ 44	$ 54
Purpose		Manage interest rate risk	Manage interest rate risk	Manage interest rate risk
Balance Sheet - Fair Value	[1]	$ 0	$ 0
Income Statement - Net Realized Gain (Loss) on Securities		0.2	0.5	$ 0.8
Non-hedging Instruments | Closed Positions | Interest Rate Swaps
Derivative [Line Items]
Notional Value	[2]	0	0	$ 1,263
Purpose				Manage portfolio duration
Balance Sheet - Fair Value	[1]	0	0
Income Statement - Net Realized Gain (Loss) on Securities		0	0	$ (4)
Non-hedging Instruments | Closed Positions | Future [Member]
Derivative [Line Items]
Notional Value	[2]	$ 691	0	0
Purpose		Manage portfolio duration
Balance Sheet - Fair Value	[1]	$ 0	0
Income Statement - Net Realized Gain (Loss) on Securities		2.5	0	0
Non-hedging Instruments | Assets | Interest Rate Swaps | Fixed maturities
Derivative [Line Items]
Notional Value	[2]	$ 750	$ 750	$ 750
Purpose		Manage portfolio duration	Manage portfolio duration	Manage portfolio duration
Balance Sheet - Fair Value	[1]	$ 4.4	$ 15.8
Income Statement - Net Realized Gain (Loss) on Securities		$ (23.4)	$ (64.6)	$ 59.8
[1]	To the extent we hold both derivative assets and liabilities with the same counterparty that are subject to an enforceable master netting arrangement, we expect that we will report them on a gross basis on our balance sheets, consistent with our historical presentation.
[2]	The amounts represent the value held at year end for open positions and the maximum amount held during the year for closed positions.

Investments - Additional Inform

Investments - Additional Information (Detail)	1 Months Ended		12 Months Ended
	Jan. 26, 2015USD ($)	Apr. 25, 2014USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Jun. 18, 2007
Schedule of Investments [Line Items]
Short-term Investments			$ 2,172,000,000	$ 2,149,000,000
Open reverse repurchase commitments			0	0
Largest Outstanding Balance of Reverse Repurchase Agreements			$ 275,000,000
RRP Largest Outstanding Balance Number of Days Open			1 day
Reverse Repurchase Agreement Average Daily Balance			$ 135,400,000
Principal amount of bonds and certificates of deposit on deposit to meet state insurance regulatory and/or rating agency requirements			184,800,000
Fair value of fixed-maturity securities that were non-income producing during the preceding 12 months			0
Gross Unrealized Losses			$ 166,700,000	$ 49,200,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions			1,167	318
Trading securities			$ 0	$ 0
Net realized gains (losses) on securities			136,500,000	232,100,000	$ 324,500,000
Senior notes, issuance amount	$ 400,000,000	$ 350,000,000
Debt Instrument, Interest Rate, Stated Percentage	3.70%	4.35%
Reclassification out of Accumulated Other Comprehensive Income
Schedule of Investments [Line Items]
Cash flow hedge gain recognized as an adjustment to interest expense			1,800,000	2,000,000	$ 2,100,000
3.70% Senior Notes due 2045
Schedule of Investments [Line Items]
Unrealized Gain (Loss)	$ (12,900,000)		(12,900,000)
Senior notes, issuance amount	$ 400,000,000		$ 400,000,000	0
Debt Instrument, Interest Rate, Stated Percentage	3.70%		3.70%			6.70%
4.35% Senior Notes due 2044
Schedule of Investments [Line Items]
Unrealized Gain (Loss)		$ (1,600,000)	$ (1,600,000)
Senior notes, issuance amount		$ 350,000,000	$ 350,000,000	350,000,000
Debt Instrument, Interest Rate, Stated Percentage		4.35%	4.35%
Equity securities
Schedule of Investments [Line Items]
Gross Unrealized Losses			$ 29,900,000	$ 16,500,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions			74	28
Equity securities | Common equities
Schedule of Investments [Line Items]
Gross Unrealized Losses			$ 14,200,000	$ 10,100,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions			64	20
Equity securities | Nonredeemable preferred stocks
Schedule of Investments [Line Items]
Gross Unrealized Losses			$ 15,700,000	$ 6,400,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions			10	8
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Percentage Decline			5.00%
Fixed maturities
Schedule of Investments [Line Items]
Gross Unrealized Losses			$ 136,800,000	$ 32,700,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions			1,093	290
Fixed maturities | Corporate debt securities
Schedule of Investments [Line Items]
Percentage which the issuer receives the security back at once the change of control is triggered			1.00%
Realized investment losses			$ 1,500,000
Gross Unrealized Losses			$ 33,000,000	$ 10,400,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions			215	53
Fixed Income Securities
Schedule of Investments [Line Items]
Gross Unrealized Losses			$ 152,500,000
Foreign Government Debt
Schedule of Investments [Line Items]
Short-term Investments			2,500,000	$ 5,700,000
Interest Rate Swaps
Schedule of Investments [Line Items]
Number of derivative positions closed during the period					3
Cash collateral received from counterparty			4,900,000	16,100,000	$ 62,700,000
Interest Rate Swaps | Opened in 2009 | Closed Positions | Nine Year Time Horizon
Schedule of Investments [Line Items]
Number of derivative positions closed during the period					1
Derivative Maturity1					9 years
Interest Rate Swaps | Opened in 2011 | Closed Positions | Five Year Time Horizon
Schedule of Investments [Line Items]
Number of derivative positions closed during the period					2
Derivative Maturity1					5 years
Value Of Securities Of Any One Issuer Excluding US Government Obligations Exceeding 10 % Of Total Shareholders Equity
Schedule of Investments [Line Items]
Aggregate cost or fair value of securities			0	0
Future [Member]
Schedule of Investments [Line Items]
Derivative, Gain (Loss) on Derivative, Net			2,500,000
Categories of Investments, Marketable Securities, Trading Securities
Schedule of Investments [Line Items]
Net realized gains (losses) on securities			$ 0	$ 0	$ 0
Russell One Thousand | Equity securities | Common equities
Schedule of Investments [Line Items]
Percentage of common stock portfolio			96.00%
Managed Equity Strategy | Equity securities | Common equities
Schedule of Investments [Line Items]
Percentage of common stock portfolio			4.00%
Non-hedging Instruments | Interest Rate Swaps | Closed Positions
Schedule of Investments [Line Items]
Purpose					Manage portfolio duration
Non-hedging Instruments | Interest Rate Swaps | Fixed maturities | Assets
Schedule of Investments [Line Items]
Derivative, Loss on Derivative			$ 11,400,000
Purpose			Manage portfolio duration	Manage portfolio duration	Manage portfolio duration
ARX Holding Corp. [Member]
Schedule of Investments [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions			492
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Percentage Decline			0.90%

Fair Value Composition of Inves

Fair Value Composition of Investment Portfolio by Major Security Type (Detail) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Fair Value Measurements [Line Items]
Portfolio	[1],[2]	$ 20,937.3	$ 19,018
Long-term Debt, Fair Value		2,887.8	2,527.5
Debt		2,707.9	2,164.7
Fixed maturities
Fair Value Measurements [Line Items]
Portfolio		15,332.2	13,549.2
Fixed maturities | Redeemable preferred stocks
Fair Value Measurements [Line Items]
Portfolio		234.3	279.2
Fixed maturities | Redeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Portfolio		92	97.9
Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value Measurements [Line Items]
Portfolio		51.2	65.3
Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value Measurements [Line Items]
Portfolio		91.1	116
Fixed maturities | Debt Securities
Fair Value Measurements [Line Items]
Portfolio		8,860.8	7,657.2
Fixed maturities | Debt Securities | U.S. government obligations
Fair Value Measurements [Line Items]
Portfolio		2,429.2	2,667.1
Fixed maturities | Debt Securities | State and local government obligations
Fair Value Measurements [Line Items]
Portfolio		2,721.4	2,139.2
Fixed maturities | Debt Securities | Foreign government obligations
Fair Value Measurements [Line Items]
Portfolio		18.6	14.2
Fixed maturities | Debt Securities | Corporate debt securities
Fair Value Measurements [Line Items]
Portfolio		3,691.6	2,836.7
Fixed maturities | Asset-backed Securities
Fair Value Measurements [Line Items]
Portfolio		6,237.1	5,612.8
Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities
Fair Value Measurements [Line Items]
Portfolio		1,726.7	1,658.5
Fixed maturities | Asset-backed Securities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value Measurements [Line Items]
Portfolio		89.3	0
Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities
Fair Value Measurements [Line Items]
Portfolio		2,653.2	2,315.6
Fixed maturities | Asset-backed Securities | Other asset-backed securities
Fair Value Measurements [Line Items]
Portfolio		1,767.9	1,638.7
Equity securities | Nonredeemable preferred stocks
Fair Value Measurements [Line Items]
Portfolio		782.6	827.5
Equity securities | Nonredeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Portfolio		782.6	827.5
Equity securities | Common equities
Fair Value Measurements [Line Items]
Portfolio		2,650.5	2,492.3
Equity securities | Common equities | Common equities
Fair Value Measurements [Line Items]
Portfolio		2,650.2	2,491.9
Equity securities | Common equities | Other risk investments
Fair Value Measurements [Line Items]
Portfolio		0.3	0.4
Total Fixed Maturities and Equity Securities
Fair Value Measurements [Line Items]
Portfolio		18,765.3	16,869
Short-term investments
Fair Value Measurements [Line Items]
Portfolio		2,172	2,149
Carrying (Reported) Amount, Fair Value Disclosure
Fair Value Measurements [Line Items]
Portfolio		19,688.4	17,402.8
Debt		2,707.9	2,164.7
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities
Fair Value Measurements [Line Items]
Portfolio		15,347.9	13,374.2
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks
Fair Value Measurements [Line Items]
Portfolio		260	260.2
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Portfolio		76.8	77.3
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value Measurements [Line Items]
Portfolio		65.1	65
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value Measurements [Line Items]
Portfolio		118.1	117.9
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities
Fair Value Measurements [Line Items]
Portfolio		8,834.8	7,564.9
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities | U.S. government obligations
Fair Value Measurements [Line Items]
Portfolio		2,425.4	2,641.1
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities | State and local government obligations
Fair Value Measurements [Line Items]
Portfolio		2,677.6	2,095.7
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities | Foreign government obligations
Fair Value Measurements [Line Items]
Portfolio		18.6	14.2
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities | Corporate debt securities
Fair Value Measurements [Line Items]
Portfolio		3,713.2	2,813.9
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities
Fair Value Measurements [Line Items]
Portfolio		6,253.1	5,549.1
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities
Fair Value Measurements [Line Items]
Portfolio		1,726	1,635.5
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value Measurements [Line Items]
Portfolio		90.3	0
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities
Fair Value Measurements [Line Items]
Portfolio		2,665.7	2,278.7
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities | Other asset-backed securities
Fair Value Measurements [Line Items]
Portfolio		1,771.1	1,634.9
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Nonredeemable preferred stocks
Fair Value Measurements [Line Items]
Portfolio		674.2	590.4
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Portfolio		674.2	590.4
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities
Fair Value Measurements [Line Items]
Portfolio		1,494.3	1,289.2
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities | Common equities
Fair Value Measurements [Line Items]
Portfolio		1,494	1,288.8
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities | Other risk investments
Fair Value Measurements [Line Items]
Portfolio		0.3	0.4
Carrying (Reported) Amount, Fair Value Disclosure | Total Fixed Maturities and Equity Securities
Fair Value Measurements [Line Items]
Portfolio		17,516.4	15,253.8
Carrying (Reported) Amount, Fair Value Disclosure | Short-term investments
Fair Value Measurements [Line Items]
Portfolio		2,172	2,149
Fair Value, Inputs, Level 1
Fair Value Measurements [Line Items]
Portfolio		7,309.2	7,314.3
Long-term Debt, Fair Value		0	0
Fair Value, Inputs, Level 1 | Fixed maturities
Fair Value Measurements [Line Items]
Portfolio		2,447.8	2,681.3
Fair Value, Inputs, Level 1 | Fixed maturities | Redeemable preferred stocks
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Redeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Debt Securities
Fair Value Measurements [Line Items]
Portfolio		2,447.8	2,681.3
Fair Value, Inputs, Level 1 | Fixed maturities | Debt Securities | U.S. government obligations
Fair Value Measurements [Line Items]
Portfolio		2,429.2	2,667.1
Fair Value, Inputs, Level 1 | Fixed maturities | Debt Securities | State and local government obligations
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Debt Securities | Foreign government obligations
Fair Value Measurements [Line Items]
Portfolio		18.6	14.2
Fair Value, Inputs, Level 1 | Fixed maturities | Debt Securities | Corporate debt securities
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Asset-backed Securities
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Asset-backed Securities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Asset-backed Securities | Other asset-backed securities
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 1 | Equity securities | Nonredeemable preferred stocks
Fair Value Measurements [Line Items]
Portfolio		154.9	204.1
Fair Value, Inputs, Level 1 | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Portfolio		154.9	204.1
Fair Value, Inputs, Level 1 | Equity securities | Common equities
Fair Value Measurements [Line Items]
Portfolio		2,650.2	2,491.9
Fair Value, Inputs, Level 1 | Equity securities | Common equities | Common equities
Fair Value Measurements [Line Items]
Portfolio		2,650.2	2,491.9
Fair Value, Inputs, Level 1 | Equity securities | Common equities | Other risk investments
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 1 | Total Fixed Maturities and Equity Securities
Fair Value Measurements [Line Items]
Portfolio		5,252.9	5,377.3
Fair Value, Inputs, Level 1 | Short-term investments
Fair Value Measurements [Line Items]
Portfolio		2,056.3	1,937
Fair Value, Inputs, Level 2
Fair Value Measurements [Line Items]
Portfolio		13,617.9	11,622.4
Long-term Debt, Fair Value		2,722.9	2,527.5
Fair Value, Inputs, Level 2 | Fixed maturities
Fair Value Measurements [Line Items]
Portfolio		12,874.5	10,856.3
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks
Fair Value Measurements [Line Items]
Portfolio		234.3	279.2
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Portfolio		92	97.9
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value Measurements [Line Items]
Portfolio		51.2	65.3
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value Measurements [Line Items]
Portfolio		91.1	116
Fair Value, Inputs, Level 2 | Fixed maturities | Debt Securities
Fair Value Measurements [Line Items]
Portfolio		6,413	4,975.9
Fair Value, Inputs, Level 2 | Fixed maturities | Debt Securities | U.S. government obligations
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 2 | Fixed maturities | Debt Securities | State and local government obligations
Fair Value Measurements [Line Items]
Portfolio		2,721.4	2,139.2
Fair Value, Inputs, Level 2 | Fixed maturities | Debt Securities | Foreign government obligations
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 2 | Fixed maturities | Debt Securities | Corporate debt securities
Fair Value Measurements [Line Items]
Portfolio		3,691.6	2,836.7
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities
Fair Value Measurements [Line Items]
Portfolio		6,227.2	5,601.2
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities
Fair Value Measurements [Line Items]
Portfolio		1,726.7	1,658.5
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value Measurements [Line Items]
Portfolio		89.3	0
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities
Fair Value Measurements [Line Items]
Portfolio		2,643.3	2,304
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities | Other asset-backed securities
Fair Value Measurements [Line Items]
Portfolio		1,767.9	1,638.7
Fair Value, Inputs, Level 2 | Equity securities | Nonredeemable preferred stocks
Fair Value Measurements [Line Items]
Portfolio		627.7	554.1
Fair Value, Inputs, Level 2 | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Portfolio		627.7	554.1
Fair Value, Inputs, Level 2 | Equity securities | Common equities
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 2 | Equity securities | Common equities | Common equities
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 2 | Equity securities | Common equities | Other risk investments
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 2 | Total Fixed Maturities and Equity Securities
Fair Value Measurements [Line Items]
Portfolio		13,502.2	11,410.4
Fair Value, Inputs, Level 2 | Short-term investments
Fair Value Measurements [Line Items]
Portfolio		115.7	212
Fair Value, Inputs, Level 3
Fair Value Measurements [Line Items]
Portfolio		10.2	81.3
Long-term Debt, Fair Value		164.9	0
Fair Value, Inputs, Level 3 | Fixed maturities
Fair Value Measurements [Line Items]
Portfolio		9.9	11.6
Fair Value, Inputs, Level 3 | Fixed maturities | Redeemable preferred stocks
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Redeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Debt Securities
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Debt Securities | U.S. government obligations
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Debt Securities | State and local government obligations
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Debt Securities | Foreign government obligations
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Debt Securities | Corporate debt securities
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities
Fair Value Measurements [Line Items]
Portfolio		9.9	11.6
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities
Fair Value Measurements [Line Items]
Portfolio		9.9	11.6
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Other asset-backed securities
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks
Fair Value Measurements [Line Items]
Portfolio		0	69.3
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Portfolio		0	69.3
Fair Value, Inputs, Level 3 | Equity securities | Common equities
Fair Value Measurements [Line Items]
Portfolio		0.3	0.4
Fair Value, Inputs, Level 3 | Equity securities | Common equities | Common equities
Fair Value Measurements [Line Items]
Portfolio		0	0
Fair Value, Inputs, Level 3 | Equity securities | Common equities | Other risk investments
Fair Value Measurements [Line Items]
Portfolio		0.3	0.4
Fair Value, Inputs, Level 3 | Total Fixed Maturities and Equity Securities
Fair Value Measurements [Line Items]
Portfolio		10.2	81.3
Fair Value, Inputs, Level 3 | Short-term investments
Fair Value Measurements [Line Items]
Portfolio		$ 0	$ 0
[1]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at December 31, 2015, $23.1 million was included in "other assets," compared to $31.3 million in "other liabilities" at December 31, 2014.
[2]	The total fair value of the portfolio included $1.3 billion and $1.9 billion at December 31, 2015 and 2014, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.

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, 2015		Dec. 31, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value		$ 81.3		$ 68.7
Calls/ Maturities/ Paydowns		(1.3)		(3.7)
Purchases		0		0
Sales		0		(0.1)
Net Realized (Gain)/Loss on Sales		(39.4)		0.1
Change in Valuation		(1.9)		29.9
Net Transfers In (Out)		(28.5)		(13.6)	[1]
Ending Fair value		10.2		81.3
Fixed maturities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value		11.6		29.2
Calls/ Maturities/ Paydowns		(1.3)		(3.6)
Purchases		0		0
Sales		0		(0.1)
Net Realized (Gain)/Loss on Sales		0		0.1
Change in Valuation		(0.4)		(0.4)
Net Transfers In (Out)		0		(13.6)	[1]
Ending Fair value		9.9		11.6
Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value		0		0.2
Calls/ Maturities/ Paydowns		0		0
Purchases		0		0
Sales		0		(0.1)
Net Realized (Gain)/Loss on Sales		0		0.1
Change in Valuation		0		(0.2)
Net Transfers In (Out)		0		0	[1]
Ending Fair value		0		0
Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value		11.6		29
Calls/ Maturities/ Paydowns		(1.3)		(3.6)
Purchases		0		0
Sales		0		0
Net Realized (Gain)/Loss on Sales		0		0
Change in Valuation		(0.4)		(0.2)
Net Transfers In (Out)		0		(13.6)	[1]
Ending Fair value		9.9		11.6
Equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value	[2]	69.3	[3]	39
Calls/ Maturities/ Paydowns		0	[3]	0	[2]
Purchases		0	[3]	0	[2]
Sales		0	[3]	0	[2]
Net Realized (Gain)/Loss on Sales		(39.4)	[3]	0	[2]
Change in Valuation		(1.4)	[3]	30.3	[2]
Net Transfers In (Out)		(28.5)	[3]	0	[1],[2]
Ending Fair value	[3]	0		69.3	[2]
Equity securities | Common equities | Other risk investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value		0.4		0.5
Calls/ Maturities/ Paydowns		0		(0.1)
Purchases		0		0
Sales		0		0
Net Realized (Gain)/Loss on Sales		0		0
Change in Valuation		(0.1)		0
Net Transfers In (Out)		0		0	[1]
Ending Fair value		$ 0.3		$ 0.4
[1]	The $13.6 million was transferred out of Level 3 and into Level 2 due to an improvement in the security's underlying collateral and an increase in liquidity and market activity in comparable securities.
[2]	The $30.3 million represents a net holding period gain on our investment in ARX, which is reflected in net realized gains (losses) on securities in the comprehensive income statement.
[3]	The $69.3 million decrease during the year reflects the reclassification of our 5% interest in ARX upon our acquisition of a controlling interest in ARX. The $39.4 million reflects our inception-to-date gain recognized, including the $1.4 million reduction in valuation that occurred during the first six months of 2015.

Fair Value Summary of Changes75

Fair Value Summary of Changes in Fair Value Associated With Level 3 Assets (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net realized gains (losses) on securities	$ 136.5		$ 232.1		$ 324.5
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	(39.4)		0.1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	(1.9)		29.9
Fixed maturities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0		0.1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	(0.4)		(0.4)
Equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	(39.4)	[1]	0	[2]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	(1.4)	[1]	30.3	[2]
Equity securities | Nonredeemable preferred stocks | Hybrid Securities | Financials
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)	69.3
Net realized gains (losses) on securities			30.3
Asset-backed Securities | Fixed maturities | Residential mortgage-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transferred out of Level 3 into Level 2			(13.6)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0		0.1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0		(0.2)
Asset-backed Securities | Fixed maturities | Commercial mortgage-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	$ (0.4)		$ (0.2)
[1]	The $69.3 million decrease during the year reflects the reclassification of our 5% interest in ARX upon our acquisition of a controlling interest in ARX. The $39.4 million reflects our inception-to-date gain recognized, including the $1.4 million reduction in valuation that occurred during the first six months of 2015.
[2]	The $30.3 million represents a net holding period gain on our investment in ARX, which is reflected in net realized gains (losses) on securities in the comprehensive income statement.

Fair Value Summary of Quantitat

Fair Value Summary of Quantitative Information about Level 3 Fair Value Measurements (Detail) $ in Millions		12 Months Ended
		Dec. 31, 2015USD ($)Investment		Dec. 31, 2014USD ($)Investment
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	[1],[2]	$ 20,937.3		$ 19,018
Fair Value, Inputs, Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value		10.2		81.3
Fair Value, Inputs, Level 3 | Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value		$ 9.9		$ 11.6
External Pricing | Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities | Prepayment rate zero percent
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Number of securities | Investment		1		1
Fair Value		$ 9.9		$ 11.6
Valuation Technique		External vendor		External vendor
Unobservable Input, prepayment rate		0.00%		0.00%
Internal Pricing | Fair Value, Inputs, Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Number of securities | Investment		0
Internal Pricing | Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Number of securities | Investment				1
Fair Value				$ 69.3
Internal Pricing | Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value		$ 0		$ 69.3
Valuation Technique				Multiple of tangible net book value
Unobservable Input, price to book ratio multiple				2.6
Subtotal Level 3 Securities | Fair Value, Inputs, Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value		9.9		$ 80.9
Third Party Pricing Exemption Securities | Fair Value, Inputs, Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value		$ 0.3	[3]	$ 0.4	[4]
[1]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at December 31, 2015, $23.1 million was included in "other assets," compared to $31.3 million in "other liabilities" at December 31, 2014.
[2]	The total fair value of the portfolio included $1.3 billion and $1.9 billion at December 31, 2015 and 2014, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.
[3]	The fair values for these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us.
[4]	The fair values for these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us.

Fair Value - Additional Informa

Fair Value - Additional Information (Detail) $ in Millions		12 Months Ended
		Dec. 31, 2015USD ($)Investment		Dec. 31, 2014USD ($)Investment
Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		$ 39.4		$ (0.1)
Number of securities transferred out of Level 2 into Level 1 | Investment		0
Quoted prices percentage of fair value assets	[1],[2]	100.00%		100.00%
Portfolio	[1],[2]	$ 20,937.3		$ 19,018
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		1.9		(29.9)
Fair Value, Inputs, Level 1
Fair Value Measurements [Line Items]
Portfolio		$ 7,309.2		$ 7,314.3
Fair Value, Inputs, Level 1 | Vendor Quoted Pricing
Fair Value Measurements [Line Items]
Quoted prices percentage of fair value assets		49.00%		50.00%
Fair Value, Inputs, Level 2
Fair Value Measurements [Line Items]
Portfolio		$ 13,617.9		$ 11,622.4
Fair Value, Inputs, Level 2 | Vendor Quoted Pricing
Fair Value Measurements [Line Items]
Quoted prices percentage of fair value assets		97.00%		97.00%
Fair Value, Inputs, Level 2 | Dealer Quoted Pricing
Fair Value Measurements [Line Items]
Quoted prices percentage of fair value assets		3.00%		3.00%
Fair Value, Inputs, Level 3
Fair Value Measurements [Line Items]
Portfolio		$ 10.2		$ 81.3
Fair Value, Inputs, Level 3 | Internal Pricing
Fair Value Measurements [Line Items]
Number of securities | Investment		0
Nonredeemable preferred stocks | Equity securities
Fair Value Measurements [Line Items]
Number of securities transferred out of Level 2 into Level 1 | Investment				2
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount				$ 41.7
Nonredeemable preferred stocks | Fair Value, Inputs, Level 3 | Equity securities | Internal Pricing
Fair Value Measurements [Line Items]
Number of securities | Investment				1
Portfolio				$ 69.3
Financials | Nonredeemable preferred stocks | Equity securities
Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		$ 39.4	[3]	0	[4]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		1.4	[3]	(30.3)	[4]
Financials | Nonredeemable preferred stocks | Fair Value, Inputs, Level 3 | Equity securities | Internal Pricing
Fair Value Measurements [Line Items]
Portfolio		$ 0		$ 69.3
[1]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at December 31, 2015, $23.1 million was included in "other assets," compared to $31.3 million in "other liabilities" at December 31, 2014.
[2]	The total fair value of the portfolio included $1.3 billion and $1.9 billion at December 31, 2015 and 2014, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.
[3]	The $69.3 million decrease during the year reflects the reclassification of our 5% interest in ARX upon our acquisition of a controlling interest in ARX. The $39.4 million reflects our inception-to-date gain recognized, including the $1.4 million reduction in valuation that occurred during the first six months of 2015.
[4]	The $30.3 million represents a net holding period gain on our investment in ARX, which is reflected in net realized gains (losses) on securities in the comprehensive income statement.

Debt (Detail)

Debt (Detail) $ in Millions	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Debt Instrument [Line Items]
Carrying Value	$ 2,707.9	$ 2,164.7
Fair Value	2,887.8	2,527.5
Debt, Long-term and Short-term, Combined Amount	2,707.9	2,164.7
3.75% Senior Notes due 2021
Debt Instrument [Line Items]
Carrying Value	498.1	497.8
Fair Value	528.7	535.6
6 5/8% Senior Notes due 2029
Debt Instrument [Line Items]
Carrying Value	295.7	295.5
Fair Value	376	400.6
6.25% Senior Notes due 2032
Debt Instrument [Line Items]
Carrying Value	395	394.8
Fair Value	490.6	527.9
4.35% Senior Notes due 2044
Debt Instrument [Line Items]
Carrying Value	346.4	346.3
Fair Value	352.8	378.9
3.70% Senior Notes due 2045
Debt Instrument [Line Items]
Carrying Value	395	0
Fair Value	362	0
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067
Debt Instrument [Line Items]
Carrying Value	612.8	630.3
Fair Value	612.8	684.5
Other Debt Instruments [Member]
Debt Instrument [Line Items]
Debt, Long-term and Short-term, Combined Amount	$ 164.9	$ 0
Notes Payable, Other Payables [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Debt Instrument, Number of Debt Instruments Acquired	2,000,000
Debt, Long-term and Short-term, Combined Amount	$ 87.1
Trust Preferred Debt Securities [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Debt Instrument, Number of Debt Instruments Acquired	2,000,000
Carrying Value	$ 41.2
Senior Notes [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Debt Instrument, Number of Debt Instruments Acquired	4,000,000
Carrying Value	$ 24
Surplus Note [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Debt Instrument, Number of Debt Instruments Acquired	1,000,000
Debt, Long-term and Short-term, Combined Amount	$ 12.6

Debt (Parenthetical) (Detail)

Debt (Parenthetical) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Jan. 26, 2015	Dec. 31, 2014	Apr. 25, 2014	Jun. 18, 2007
Debt Instrument [Line Items]
Senior notes, issuance amount		$ 400,000,000		$ 350,000,000
Debt instrument, outstanding	$ 2,729,300,000
Debt Instrument, Interest Rate, Stated Percentage		3.70%		4.35%
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%
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%
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	$ 350,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.35%			4.35%
3.70% Senior Notes due 2045
Debt Instrument [Line Items]
Senior notes, issuance amount	$ 400,000,000	$ 400,000,000	0
Debt Instrument, Interest Rate, Stated Percentage	3.70%	3.70%			6.70%
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067
Debt Instrument [Line Items]
Senior notes, issuance amount	$ 1,000,000,000		1,000,000,000
Debt instrument, outstanding	$ 614,300,000		$ 632,800,000
Debt Instrument, Interest Rate, Stated Percentage	6.70%
Discretionary Line of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate Description	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.
Long-term Line of Credit	$ 0

Debt Unrealized Gains (Losses)

Debt Unrealized Gains (Losses) From Debt Hedges Included In Accumulated Other (Detail) - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Jan. 26, 2015	Apr. 25, 2014	Dec. 31, 2015
3.75% Senior Notes due 2021
Debt Instrument [Line Items]
Unrealized Gain (Loss)			$ (5.1)
Unamortized Balance			(3.1)
6 5/8% Senior Notes due 2029
Debt Instrument [Line Items]
Unrealized Gain (Loss)			(4.2)
Unamortized Balance			(3)
6.25% Senior Notes due 2032
Debt Instrument [Line Items]
Unrealized Gain (Loss)			5.1
Unamortized Balance			3.9
4.35% Senior Notes due 2044
Debt Instrument [Line Items]
Unrealized Gain (Loss)		$ (1.6)	(1.6)
Unamortized Balance			(1.6)
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067
Debt Instrument [Line Items]
Unrealized Gain (Loss)			34.4
Unamortized Balance			3.9
3.70% Senior Notes due 2045
Debt Instrument [Line Items]
Unrealized Gain (Loss)	$ (12.9)		(12.9)
Unamortized Balance			$ (12.6)

Debt Aggregate Principal Paymen

Debt Aggregate Principal Payments On Debt Outstanding (Detail) $ in Millions	Dec. 31, 2015USD ($)
Debt Disclosure [Abstract]
2,015	$ 27.2
2,016	27.2
2,017	27.2
2,018	13.4
2,019	3
Thereafter	2,631.3
Total	$ 2,729.3

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)	1 Months Ended		3 Months Ended	9 Months Ended			12 Months Ended
	Jan. 26, 2015	Apr. 25, 2014	Sep. 30, 2015	Dec. 31, 2015	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jun. 18, 2007
Debt Instrument [Line Items]
Debt interest payments								Interest on all debt issued by The Progressive Corporation is payable semiannually at the stated rates. However, the 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 (the “6.70% Debentures”) will only bear interest at this fixed annual rate through June 14, 2017. Thereafter, the 6.70% Debentures will bear interest at an annual rate equal to the three-month London Interbank Offered Rate (LIBOR) plus 2.0175%, and interest will be payable quarterly until the 6.70% Debentures are redeemed or retired.
Debt Instrument, Face Amount	$ 400,000,000	$ 350,000,000
Debt Instrument, Interest Rate, Stated Percentage	3.70%	4.35%
Interest payment frequency								Payable semiannually
Payment of debt								$ 20,400,000	$ 0	$ 150,000,000
Gains (losses) on extinguishment of debt					$ (900,000)			(900,000)	(4,800,000)	(4,300,000)
Cash flow hedge gain reclassification from accumulated other comprehensive income to net realized gains/losses on securities								1,300,500,000	1,281,000,000	1,165,400,000
Discretionary Line of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				$ 100,000,000				$ 100,000,000	100,000,000
Line of Credit Facility, Interest Rate Description								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.
Long-term Line of Credit				0				$ 0
Discretionary Line of Credit [Member] | Federal Funds Rate
Debt Instrument [Line Items]
Basis points								0.50%
4.35% Senior Notes due 2044
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 350,000,000		$ 350,000,000				$ 350,000,000	350,000,000
Debt Instrument, Interest Rate, Stated Percentage		4.35%		4.35%				4.35%
Proceeds from Debt, Net of Issuance Costs		$ 346,300,000
Debt Related Commitment Fees and Debt Issuance Costs		700,000
Unrealized Gain (Loss)		$ (1,600,000)						$ (1,600,000)
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 1,000,000,000				$ 1,000,000,000	1,000,000,000
Debt Instrument, Interest Rate, Stated Percentage				6.70%				6.70%
Unrealized Gain (Loss)								$ 34,400,000
Repurchase of debt, face amount					$ 18,400,000	$ 44,300,000
Fixed interest rate term								10 years
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 | Three Month LIBOR
Debt Instrument [Line Items]
Basis points								2.0175%
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 | Net unrealized gains on forecasted transactions
Debt Instrument [Line Items]
Cash flow hedge gain reclassification from accumulated other comprehensive income to net realized gains/losses on securities								$ 200,000	500,000	$ 800,000
3.70% Senior Notes due 2045
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 400,000,000			$ 400,000,000				$ 400,000,000	$ 0
Debt Instrument, Interest Rate, Stated Percentage	3.70%			3.70%				3.70%			6.70%
Proceeds from Debt, Net of Issuance Costs	$ 394,900,000
Debt Related Commitment Fees and Debt Issuance Costs	800,000
Unrealized Gain (Loss)	$ (12,900,000)							$ (12,900,000)
Other Assets [Member]
Debt Instrument [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets				$ 1,300,000				$ 1,300,000
Surplus Note [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Debt Instrument, Periodic Payment, Principal							$ 2,200,000
Debt Instrument, Restrictive Covenant, Minimum Surplus Requirement			$ 50,000,000
Scenario, Forecast [Member] | Notes Payable, Other Payables [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Debt Instrument, Periodic Payment, Principal							$ 25,000,000
London Interbank Offered Rate (LIBOR) [Member] | Notes Payable, Other Payables [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Basis points				2.25%

Income Taxes Components of Inco

Income Taxes Components of Income Tax Provision (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Current State and Local Tax Expense (Benefit)	$ 14.7	$ 0	$ 0
Current Federal Tax Expense (Benefit)	655.3	594.4	460.2
Deferred State and Local Income Tax Expense (Benefit)	(11.2)	0	0
Deferred Federal Income Tax Expense (Benefit)	(47.7)	32	94.4
Income Tax Expense (Benefit)	$ 611.1	$ 626.4	$ 554.6

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, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Income before income taxes	$ 1,911.6	$ 1,907.4	$ 1,720
Tax at statutory rate	669.1	667.6	602
Dividends received deduction	(19.8)	(18.3)	(17.6)
Exempt interest income	(17.8)	(13.8)	(13.1)
Tax-deductible dividends	(7.9)	(6.5)	(13.6)
Other items, net	(1)	(2.6)	(3.1)
Income Tax Expense (Benefit)	$ 611.1	$ 626.4	$ 554.6
Tax at statutory rate	35.00%	35.00%	35.00%
Dividends received deduction	(1.00%)	(1.00%)	(1.00%)
Exempt interest income	(1.00%)	(1.00%)	(1.00%)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	$ (13.8)	$ 0	$ 0
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent	(1.00%)	(0.00%)	(0.00%)
Tax-deductible dividends	(0.00%)	(0.00%)	(1.00%)
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	$ 2.3	$ 0	$ 0
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	(0.00%)	(0.00%)	(0.00%)
Other items, net	0.00%	0.00%	0.00%
Total income tax provision	32.00%	33.00%	32.00%

Income Taxes Components of Net

Income Taxes Components of Net Deferred Tax Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Unearned premiums reserve	$ 453.3	$ 378.8
Investment basis differences	40.5	60.6
Non-deductible accruals	231.4	208
Loss and loss adjustment expense reserves	75.3	76.9
Deferred Tax Assets, Hedging Transactions	4.4	0
Other	9.6	7.5
Deferred tax liabilities:
Net unrealized gains on securities	(436.7)	(550.3)
Hedges on forecasted transactions	0	(0.8)
Deferred acquisition costs	(197.4)	(160)
Property and equipment	(110.7)	(100.9)
Prepaid expenses	(11.9)	(11.4)
Deferred Tax Liabilities, Intangible Assets	(166.4)	0
Deferred gain on extinguishment of debt	(2.2)	(3)
Other	(7)	(4.3)
Deferred Tax Liability, Federal Tax	117.8	98.9
Net deferred tax liability	(109.3)	(98.9)
Deferred Tax Assets, State Taxes	$ 8.5	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Line Items]
Net taxes payable	$ 25.1	$ 49.4
Provision (benefit) for income taxes	(611.1)	(626.4)	$ (554.6)
Interest Expense or Benefit
Income Taxes [Line Items]
Provision (benefit) for income taxes	$ (0.1)	$ 0	$ 0.2

Loss And Loss Adjustment Expe87

Loss And Loss Adjustment Expense Reserves Activity in Loss and loss Adjustment Expense Reserves (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Apr. 01, 2015
Loss and Loss Adjustment Expense Reserves Disclosures [Abstract]
Liability for Unpaid Claims and Claims Adjustment Expense, Adjustments						$ 222.4
Liability for Unpaid Claims and Claims Adjustment Expense, Business Acquisitions	$ 0				$ 0
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balance at beginning of period	7,838.4	$ 8,857.4	$ 8,479.7	$ 7,838.4
Less reinsurance recoverables on unpaid losses	862.1	1,185.9	1,045.9	862.1
Net balance at beginning of period	$ 6,976.3	7,671.5	7,433.8	6,976.3
Incurred related to:
Current year		14,657.1	13,330.3	12,427.3
Prior years		(315.1)	(24.1)	45.1
Total incurred		14,342	13,306.2	12,472.4
Paid related to:
Current year		9,577.3	8,831.5	8,095
Prior years		4,062.3	4,237	3,919.9
Total paid		13,639.6	13,068.5	12,014.9
Net balance at ending of period		8,596.3	7,671.5	7,433.8	6,976.3
Plus reinsurance recoverables on unpaid losses		1,442.7	1,185.9	1,045.9	862.1
Balance at ending of period		$ 10,039	8,857.4	$ 8,479.7	$ 7,838.4
Liability for Unpaid Claims and Claims Adjustment Expense, Net, Adjusted Beginning Balance			$ 7,893.9

Loss And Loss Adjustment Expe88

Loss And Loss Adjustment Expense Reserves Loss And Loss Adjustment Expense Reserves - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Insurance Reserves [Line Items]
Prior years	$ 315.1	$ 24.1	$ (45.1)
Accident Year 2011
Insurance Reserves [Line Items]
Unfavorable development in loss and loss adjustment expense reserves			80.00%
Accident Year 2012
Insurance Reserves [Line Items]
Unfavorable development in loss and loss adjustment expense reserves			20.00%
Commercial Lines
Insurance Reserves [Line Items]
Unfavorable development in loss and loss adjustment expense reserves			55.00%
Personal Lines
Insurance Reserves [Line Items]
percentage of favorable development Loss and Loss adjustment expense reserve	65.00%

Reinsurance Effect of Reinsuran

Reinsurance Effect of Reinsurance on Premiums Written and Earned (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct premiums written	$ 21,086.5	$ 18,914.8	$ 17,562.8
Ceded written	(522.5)	(260.2)	(223.1)
Net premiums written	20,564	18,654.6	17,339.7
Direct premiums earned	20,454.1	18,648.4	17,317.9
Ceded earned	(555)	(249.9)	(214.5)
Net premiums earned	19,899.1	18,398.5	17,103.4
non regulated reinsurance plan [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Ceded written	(164.5)	(8.3)	(6.9)
Ceded earned	(192.4)	(8.5)	(9.1)
Regulated reinsurance plan [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Ceded written	(358)	(251.9)	(216.2)
Ceded earned	$ (362.6)	$ (241.4)	$ (205.4)

Reinsurance Prepaid Reinsurance

Reinsurance Prepaid Reinsurance Premiums and Reinsurance Recoverables (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Ceded Premiums Written	$ 522.5	$ 260.2	$ 223.1
Ceded Premiums Earned	555	249.9	214.5
Prepaid reinsurance premiums	$ 199.3	$ 85.3
Percentage of Prepaid Reinsurance Premiums	100.00%	100.00%
Reinsurance Recoverables	$ 1,488.8	$ 1,231.9
Percentage of Reinsurance Recoverables	100.00%	100.00%
State Reinsurance Plan
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Prepaid reinsurance premiums	$ 139.1	$ 81.2
Percentage of Prepaid Reinsurance Premiums	70.00%	95.00%
Reinsurance Recoverables	$ 1,421.5	$ 1,182
Percentage of Reinsurance Recoverables	96.00%	96.00%
State Reinsurance Plan | Michigan Catastrophic Claims Association
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Prepaid reinsurance premiums	$ 31.4	$ 32.8
Percentage of Prepaid Reinsurance Premiums	16.00%	38.00%
Reinsurance Recoverables	$ 1,217.6	$ 1,018.8
Percentage of Reinsurance Recoverables	82.00%	83.00%
State Reinsurance Plan | Commercial Auto Insurance Procedures Plans
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Prepaid reinsurance premiums	$ 37.1	$ 26.5
Percentage of Prepaid Reinsurance Premiums	19.00%	31.00%
Reinsurance Recoverables	$ 134	$ 110.1
Percentage of Reinsurance Recoverables	9.00%	9.00%
State Reinsurance Plan | North Carolina Reinsurance Facility
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Prepaid reinsurance premiums	$ 25.6	$ 21.9
Percentage of Prepaid Reinsurance Premiums	13.00%	26.00%
Reinsurance Recoverables	$ 56.7	$ 51.1
Percentage of Reinsurance Recoverables	4.00%	4.00%
State Reinsurance Plan | other reinsurance program [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Prepaid reinsurance premiums	$ 0	$ 0
Percentage of Prepaid Reinsurance Premiums	0.00%	0.00%
Reinsurance Recoverables	$ 2.8	$ 2
Percentage of Reinsurance Recoverables	0.00%	0.00%
Federal Reinsurance Plans [Member] | National Flood Insurance Program [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Prepaid reinsurance premiums	$ 45	$ 0
Percentage of Prepaid Reinsurance Premiums	22.00%	0.00%
Reinsurance Recoverables	$ 10.4	$ 0
Percentage of Reinsurance Recoverables	1.00%	0.00%
other reinsurance program [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Prepaid reinsurance premiums	$ 7.6	$ 4.1
Percentage of Prepaid Reinsurance Premiums	4.00%	5.00%
Reinsurance Recoverables	$ 31.8	$ 49.9
Percentage of Reinsurance Recoverables	2.00%	4.00%
Non State Reinsurance Plans
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Prepaid reinsurance premiums	$ 60.2	$ 4.1
Percentage of Prepaid Reinsurance Premiums	30.00%	5.00%
Reinsurance Recoverables	$ 67.3	$ 49.9
Percentage of Reinsurance Recoverables	4.00%	4.00%
Property reinsurance program [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Prepaid reinsurance premiums	$ 52.6	$ 0
Percentage of Prepaid Reinsurance Premiums	26.00%	0.00%
Reinsurance Recoverables	$ 35.5	$ 0
Percentage of Reinsurance Recoverables	2.00%	0.00%
Regulated reinsurance plan [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Ceded Premiums Written	$ 358	$ 251.9	216.2
Ceded Premiums Earned	362.6	241.4	205.4
non regulated reinsurance plan [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Ceded Premiums Written	164.5	8.3	6.9
Ceded Premiums Earned	$ 192.4	$ 8.5	$ 9.1

Reinsurance - Additional Inform

Reinsurance - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance ceded	$ (457.3)	$ (322.7)	$ (347)

Statutory Financial Informati92

Statutory Financial Information - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statutory Financial Information Disclosures [Abstract]
Consolidated statutory policyholders' surplus	$ 7,575.5	$ 6,442.8
Statutory net income	1,333.1	$ 1,289.5	$ 1,086.3
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	637.6
Aggregate cash dividends paid to the parent company by subsidiaries	886.5
Maximum aggregate dividend amount subsidiaries could pay without prior approval from regulatory authorities	$ 1,325

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, 2015	Dec. 31, 2014	Dec. 31, 2013
Incentive Compensation Cash Award
Incentive Compensation Plans Expense [Line Items]
Pretax	$ 337.7	$ 266.2	$ 234.5
After Tax	219.5	173	152.4
Employee Stock [Member]
Incentive Compensation Plans Expense [Line Items]
Pretax	64.5	51.4	64.9
After Tax	41.9	33.4	42.2
Employee Stock Option
Incentive Compensation Plans Expense [Line Items]
Pretax	1.7	0	$ 0
After Tax	$ 1.1	$ 0

Employee Benefit Plans Summary

Employee Benefit Plans Summary of All Employee Restricted Equity Award Activity (Detail) - $ / shares		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Employee Restricted Equity Awards
Number of Shares
Beginning of year	[3]	9,051,564	[1],[2]	9,918,575	[1],[2]	11,625,981
Add (deduct):
Granted	[3],[4]	2,489,976		3,542,984		2,738,809
Vested	[3]	(3,682,644)		(4,228,673)		(4,293,605)
Forfeited	[3]	(133,669)		(181,322)		(152,610)
End of year	[1],[2],[3]	7,725,227		9,051,564		9,918,575
Weighted Average Grant Date Fair Value
Beginning of year		$ 21.27	[1],[2]	$ 20.13	[1],[2]	$ 17.80
Granted	[4]	25.20		19.32		22.73
Vested		19.53		16.99		15.54
Forfeited		21.63		20.75		18.28
End of year	[1],[2]	$ 23.37		$ 21.27		$ 20.13
Employee Restricted Equity Awards Vesting Period [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]		three, four, and five years
[1]	At December 31, 2015, the number of shares included 2,025,871 performance-based awards at their target amounts. We expect 1,946,565 of these performance-based awards to vest, based upon our current estimate of the likelihood of achieving these pre-determined performance goals.
[2]	At December 31, 2015, the total unrecognized compensation cost related to unvested equity awards was $78.3 million, which includes performance-based awards at their currently estimated vesting value. This compensation expense will be recognized into the income statement over the weighted average vesting period of 2.3 years.
[3]	Includes both restricted stock units and restricted stock. Upon vesting, all units will be converted on a one-for-one basis into Progressive common shares funded from existing treasury shares. All performance-based awards are included at their target amounts.
[4]	We reinvest dividend equivalents on restricted stock units. For 2015, 2014, and 2013, the number of units "granted" shown in the table above includes 196,947, 538,749, and 161,077 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.

Employee Benefit Plans Summar95

Employee Benefit Plans Summary of All Employee Restricted Equity Award Activity (Parenthetical) (Detail) - Employee Restricted Equity Awards - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number granted units	[1],[2]	2,489,976	3,542,984	2,738,809
Weighted average grant date fair value	[2]	$ 25.20	$ 19.32	$ 22.73
Unrecognized compensation cost related to unvested equity awards		$ 78.3
Period of recognition of compensation expense related to unvested equity awards		2 years 3 months 15 days
Dividend Equivalent Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number granted units		196,947	538,749	161,077
Weighted average grant date fair value		$ 0	$ 0	$ 0
Performance Based Restricted Equity Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity awards target amount		2,025,871
Equity awards to vest		1,946,565
[1]	Includes both restricted stock units and restricted stock. Upon vesting, all units will be converted on a one-for-one basis into Progressive common shares funded from existing treasury shares. All performance-based awards are included at their target amounts.
[2]	We reinvest dividend equivalents on restricted stock units. For 2015, 2014, and 2013, the number of units "granted" shown in the table above includes 196,947, 538,749, and 161,077 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.

Employee Benefit Plans Summar96

Employee Benefit Plans Summary of all Directors' Restricted Stock Activity (Detail) - Non Employee Director Restricted Equity Awards - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Number of Shares
Beginning of year	81,579	93,254	92,957
Add (deduct):
Granted	89,427	90,649	93,254
Vested	(81,579)	(93,254)	(92,957)
Forfeited	0	(9,070)	0
End of year	89,427	81,579	93,254
Weighted Average Grant Date Fair Value
Beginning of year	$ 25.45	$ 26.19	$ 21.41
Granted	27.23	25.44	26.19
Vested	25.45	26.19	21.41
Forfeited		25.36	0
End of year	$ 27.23	$ 25.45	$ 26.19

Employee Benefit Plans Assets H

Employee Benefit Plans Assets Held in Deferral Plan Irrevocable Grantor Trust Account (Detail) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Assets held in Deferral Plan Irrevocable Grantor Trust account		$ 233.3	$ 207.1
Progressive common shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Assets held in Deferral Plan Irrevocable Grantor Trust account	[1]	108.5	83.2
Other Investment Funds
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Assets held in Deferral Plan Irrevocable Grantor Trust account	[2]	$ 124.8	$ 123.9
[1]	Includes 4.4 million and 3.6 million common shares as of December 31, 2015 and 2014, respectively, to be distributed in common shares.
[2]	Amount is included in other assets on the balance sheet.

Employee Benefit Plans Assets98

Employee Benefit Plans Assets Held in Deferral Plan Irrevocable Grantor Trust Account (Parenthetical) (Detail) - shares shares in Millions	Dec. 31, 2015	Dec. 31, 2014
Progressive common shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares held in Deferral Plan Irrevocable Grantor Trust account to be distributed in-kind	4.4	3.6

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)Personshares	Dec. 31, 2014USD ($)Person	Dec. 31, 2013USD ($)Person	Dec. 31, 2011	Dec. 31, 2010
Employee Benefits Disclosure [Line Items]
Employee Stock Ownership Plan Shares held | shares	25,200,000
Postemployment benefits liability	$ 22.6	$ 22.5
Employee Restricted Equity Awards
Employee Benefits Disclosure [Line Items]
Aggregate fair value of the restricted equity awards that vested during the period	$ 105.4	109.6	$ 98.3
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	$ 2.2	$ 2.2	$ 2.3
ARX employee [Member] | Employee Stock Option
Employee Benefits Disclosure [Line Items]
Allocated Share-based Compensation Expense	1.7
Allocated Share-based Compensation Expense, Net of Tax	$ 1.1
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period | shares	(1,005)
Executive Deferred Compensation Plan
Employee Benefits Disclosure [Line Items]
Common shares reserved for issuance under executive deferred compensation plan | shares	11,100,000
2010 Equity Incentive Plan | Employee Restricted Equity Awards
Employee Benefits Disclosure [Line Items]
Shares authorized | shares	18,000,000
2003 Directors Equity Incentive Plan | Non Employee Director Restricted Equity Awards
Employee Benefits Disclosure [Line Items]
Shares authorized | shares	1,400,000
Performance Based Restricted Equity Awards
Employee Benefits Disclosure [Line Items]
Number of employees, approximately | Person	45	45	45
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%
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%	200.00%	200.00%	200.00%
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%
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%
Other Postretirement Benefit Plans, Defined Benefit
Employee Benefits Disclosure [Line Items]
Number of employees, approximately | Person	100
Defined Contribution Pension Plan 401k
Employee Benefits Disclosure [Line Items]
Matching contributions	$ 78.4	$ 74.8	$ 69.9
Defined Contribution Pension Plan 401k | Upper Limit
Employee Benefits Disclosure [Line Items]
Matching contribution to defined contribution pension plan	6.00%

Employee Benefit Plans Summa100

Employee Benefit Plans Summary of ARX employee stock option plans (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Apr. 01, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 1.1
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to unvested equity awards	$ 2.9
Period of recognition of compensation expense related to unvested equity awards	1 year 8 months 20 days
Employee Stock Option | ARX employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Weighted Average Grant Date Fair Value	$ 665.85
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	24,995	26,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$ 526.46	$ 513.72
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares	12,000	14,800
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value	$ 677.81	$ 675.55
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares	2,800
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	(1,005)
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	$ 197.01
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number	12,995
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 386.69

Employee Benefit Plans Summa101

Employee Benefit Plans Summary of ARX Defined Contribution Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Contribution Pension Plan 401k
Defined Contribution Plan Disclosure [Line Items]
Matching contributions	$ 78.4	$ 74.8	$ 69.9
Defined Contribution Pension Plan Four Zero One K ARX [Domain]
Defined Contribution Plan Disclosure [Line Items]
Matching contributions	$ 0

Segment Information Operating R

Segment Information Operating Results (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Depreciation		$ 103.7	$ 97.1	$ 101.3
Premium Revenue		19,899.1	18,398.5	17,103.4
Revenues		20,853.8	19,391.4	18,170.9
Pretax Profit (Loss)		(1,911.6)	(1,907.4)	(1,720)
Personal Lines
Segment Reporting Information [Line Items]
Premium Revenue		17,294.5	16,561	15,341.6
Commercial Lines
Segment Reporting Information [Line Items]
Premium Revenue		1,995.9	1,837.5	1,761.6
Property, Liability and Casualty Insurance Product Line
Segment Reporting Information [Line Items]
Depreciation		45.2
Premium Revenue		609.1	0	0
Other Indemnity
Segment Reporting Information [Line Items]
Premium Revenue		$ 0.4	$ 0	$ 0.2
Underwriting Operations
Segment Reporting Information [Line Items]
Underwriting Margin		7.50%	7.70%	6.50%
Combined Ratio		92.50%	92.30%	93.50%
Revenues		$ 19,899.1	$ 18,398.5	$ 17,103.4
Pretax Profit (Loss)		$ (1,495.2)	$ (1,410.3)	$ (1,120.1)
Underwriting Operations | Personal Lines
Segment Reporting Information [Line Items]
Underwriting Margin		6.50%	6.70%	6.60%
Combined Ratio		93.50%	93.30%	93.40%
Revenues	[1]	$ 17,294.5	$ 16,561	$ 15,341.6
Pretax Profit (Loss)	[1]	$ (1,116.6)	$ (1,106.4)	$ (1,016.8)
Underwriting Operations | Personal Lines | Agency Channel
Segment Reporting Information [Line Items]
Underwriting Margin		7.80%	7.50%	6.30%
Combined Ratio		92.20%	92.50%	93.70%
Revenues		$ 9,108.6	$ 9,087	$ 8,601.5
Pretax Profit (Loss)		$ (713.2)	$ (683)	$ (542.9)
Underwriting Operations | Personal Lines | Direct Channel
Segment Reporting Information [Line Items]
Underwriting Margin		4.90%	5.70%	7.00%
Combined Ratio		95.10%	94.30%	93.00%
Revenues		$ 8,185.9	$ 7,474	$ 6,740.1
Pretax Profit (Loss)		$ (403.4)	$ (423.4)	$ (473.9)
Underwriting Operations | Commercial Lines
Segment Reporting Information [Line Items]
Underwriting Margin		15.90%	17.20%	6.50%
Combined Ratio		84.10%	82.80%	93.50%
Pretax Profit (Loss)		$ (318.3)	$ (315.8)	$ (114.1)
Underwriting Operations | Property, Liability and Casualty Insurance Product Line
Segment Reporting Information [Line Items]
Underwriting Margin		10.10%	0.00%	0.00%
Combined Ratio		89.90%	0.00%	0.00%
Pretax Profit (Loss)		$ (61.3)	$ 0	$ 0
Underwriting Operations | Other Indemnity
Segment Reporting Information [Line Items]
Pretax Profit (Loss)		1	11.9	10.8
Fees And Other Revenues
Segment Reporting Information [Line Items]
Revenues	[2]	302	309.1	291.8
Service Businesses
Segment Reporting Information [Line Items]
Revenues		86.3	56	39.6
Pretax Profit (Loss)		(8.8)	(5.1)	(0.8)
Investments
Segment Reporting Information [Line Items]
Revenues	[3]	567.3	632.6	740.4
Pretax Profit (Loss)		(544.5)	(613.7)	(721.6)
Gains (losses) on extinguishment of debt
Segment Reporting Information [Line Items]
Revenues		(0.9)	(4.8)	(4.3)
Pretax Profit (Loss)		0.9	4.8	4.3
Interest Expense
Segment Reporting Information [Line Items]
Pretax Profit (Loss)		$ 136	$ 116.9	$ 118.2
[1]	Personal auto insurance accounted for 92% of the total Personal Lines segment net premiums earned in 2015, compared to 92% in 2014 and 91% in 2013; insurance for our special lines products (e.g., motorcycles, ATVs, RVs, manufactured homes, watercraft, and snowmobiles) accounted for the balance of the Personal Lines net premiums earned.
[2]	Pretax profit (loss) for fees and other revenues are allocated to operating segments.
[3]	Revenues represent recurring investment income and total net realized gains (losses) on securities; pretax profit is net of investment expenses.

Segment Information Operatin103

Segment Information Operating Results (Parenthetical) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Personal Lines | Personal Auto | Underwriting Operations
Segment Reporting Information [Line Items]
Personal auto insurance percentage of the total personal lines segment net premiums earned	92.00%	92.00%	91.00%

Segment Information Underwritin

Segment Information Underwriting Margins and Combined Ratios for our Underwriting Operations (Details) - Underwriting Operations	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Underwriting Margin	7.50%	7.70%	6.50%
Combined Ratio	92.50%	92.30%	93.50%
Personal Lines
Segment Reporting Information [Line Items]
Underwriting Margin	6.50%	6.70%	6.60%
Combined Ratio	93.50%	93.30%	93.40%
Personal Lines | Agency Channel
Segment Reporting Information [Line Items]
Underwriting Margin	7.80%	7.50%	6.30%
Combined Ratio	92.20%	92.50%	93.70%
Personal Lines | Direct Channel
Segment Reporting Information [Line Items]
Underwriting Margin	4.90%	5.70%	7.00%
Combined Ratio	95.10%	94.30%	93.00%
Commercial Lines
Segment Reporting Information [Line Items]
Underwriting Margin	15.90%	17.20%	6.50%
Combined Ratio	84.10%	82.80%	93.50%

Segment Information - Additiona

Segment Information - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)Entity	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Segment Reporting Information [Line Items]
Net premiums earned	$ 19,899.1	$ 18,398.5	$ 17,103.4
Depreciation	$ 103.7	97.1	101.3
Underwriting Operations | Personal Lines | Agency Channel | Lower Limit
Segment Reporting Information [Line Items]
Independent insurance agencies and brokerages | Entity	35,000
Australia
Segment Reporting Information [Line Items]
Net premiums earned	$ 15.9	$ 17.1	$ 13

Other Comprehensive Income Comp

Other Comprehensive Income Components of Other Comprehensive Income (Loss) Including Reclassification Adjustments by Income Statement (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Components Of Other Comprehensive Income Loss [Line Items]
AOCI before Tax, Attributable to Parent	$ 1,234.5	$ 1,574	$ 1,464.1	$ 1,340
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]
Investment securities, pre tax	(198.7)	362.1	368.2
Net non-credit related OTTI losses, adjusted for valuation changes, pre tax	0	0	0.4
Forecasted transactions, pre tax	(12.9)	(1.6)	0
Foreign currently translation adjustement, pre tax	(1.8)	(1.3)	(2.5)
Total other comprehensive income (loss) before reclassifications, pre tax	(211.8)	359.2	366.1
Total reclassification adjustment for amounts realized in net income, pre tax	127.7	249.3	242
Total other comprehensive income (loss), pre tax	(339.5)	109.9	124.1
Accumulated Other Comprehensive Income (Loss), Tax [Roll Forward]
Investment securities, Total tax (provision) benefit	67.5	(126.7)	(128.9)
Net non-credit related OTTI losses, adjusted for valuation changes Total tax (provision) benefit	0	0	(0.1)
Forecasted transactions, Total tax (provision) benefit	4.5	0.6	0
Foreign currency traslation adjustment, Total tax (provision) benefit	0.6	0.4	0.9
Total other comprehensive Income (loss) before reclassifications, Total tax (provision) benefit	72.1	(125.7)	(128.1)
Total reclassification adjustment for amounts realized in net income, Total tax (provision) benefit	(44.7)	(87.2)	(84.7)
Total other comprehensive income (loss), Total tax (provision) benefit	116.8	(38.5)	(43.4)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Investment securities, after tax	(131.2)	235.4	239.3
Net non-credit related OTTI losses, adjusted for valuation changes, after tax	0	0	0.3
Forecasted transactions, after tax	(8.4)	(1)	0
Foreign currency translation adjustment, after tax	(1.2)	(0.9)	(1.6)
Total other comprehensive income (loss), before reclassifications, after tax	(139.7)	233.5	238
Total reclassification adjustment for amounts realized in net income, after tax	83	162.1	157.3
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Noncontrolling Interest	1.6	0	0
Other Comprehensive Income (Loss), Tax, Portion Attributable to Noncontrolling Interest	(0.5)	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	1.1	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(222.7)	71.4	80.7
Net impairment losses recognized in earnings	(23.8)	(7.9)	(6.1)
Net realized gains (losses) on securities	136.5	232.1	324.5
Interest expense	136	116.9	118.2
AOCI Tax, Attributable to Parent	(434.1)	(550.9)	(512.4)	(469)
AOCI Net of Tax, Attributable to Parent	800.4	1,023.1	951.7	871
Net unrealized gains (losses) on securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Investment securities, after tax	(131.2)	235.4	239.3
Net non-credit related OTTI losses, adjusted for valuation changes, after tax	0	0	0.3
Forecasted transactions, after tax	0	0	0
Foreign currency translation adjustment, after tax	0	0	0
Total other comprehensive income (loss), before reclassifications, after tax	(131.2)	235.4	239.6
Total reclassification adjustment for amounts realized in net income, after tax	81.7	160.5	155.3
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	0	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(212.9)	74.9	84.3
AOCI Net of Tax, Attributable to Parent	809	1,021.9	947	862.7
Net unrealized gains on forecasted transactions
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Investment securities, after tax	0	0	0
Net non-credit related OTTI losses, adjusted for valuation changes, after tax	0	0	0
Forecasted transactions, after tax	(8.4)	(1)	0
Foreign currency translation adjustment, after tax	0	0	0
Total other comprehensive income (loss), before reclassifications, after tax	(8.4)	(1)	0
Total reclassification adjustment for amounts realized in net income, after tax	1.3	1.6	2
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	0	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(9.7)	(2.6)	(2)
AOCI Net of Tax, Attributable to Parent	(8.2)	1.5	4.1	6.1
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Investment securities, after tax	0	0	0
Net non-credit related OTTI losses, adjusted for valuation changes, after tax	0	0	0
Forecasted transactions, after tax	0	0	0
Foreign currency translation adjustment, after tax	(1.2)	(0.9)	(1.6)
Total other comprehensive income (loss), before reclassifications, after tax	(1.2)	(0.9)	(1.6)
Total reclassification adjustment for amounts realized in net income, after tax	0	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	0	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(1.2)	(0.9)	(1.6)
AOCI Net of Tax, Attributable to Parent	(1.5)	(0.3)	0.6	2.2
Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Investment securities, after tax	0	0	0
Net non-credit related OTTI losses, adjusted for valuation changes, after tax	0	0	0
Forecasted transactions, after tax	0	0	0
Foreign currency translation adjustment, after tax	0	0	0
Total other comprehensive income (loss), before reclassifications, after tax	1.1	0	0
Total reclassification adjustment for amounts realized in net income, after tax	0	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	1.1	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	1.1	0	0
AOCI Net of Tax, Attributable to Parent	1.1	0	0	$ 0
Reclassification out of Accumulated Other Comprehensive Income | Accumulated other comprehesnive income pretax
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net impairment losses recognized in earnings	(23.8)	(7.7)	(5.7)
Net realized gains (losses) on securities	149.7	255	245.5
Interest expense	1.8	2	2.2
Reclassification out of Accumulated Other Comprehensive Income | Accumulated other comprehensive income tax
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net impairment losses recognized in earnings	8.4	2.7	2
Net realized gains (losses) on securities	(52.5)	(89.2)	(86)
Interest expense	(0.6)	(0.7)	(0.7)
Reclassification out of Accumulated Other Comprehensive Income | Accumulated other comprehensive income after tax
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net impairment losses recognized in earnings	(15.4)	(5)	(3.7)
Net realized gains (losses) on securities	97.2	165.8	159.5
Interest expense	1.2	1.3	1.5
Reclassification out of Accumulated Other Comprehensive Income | Net unrealized gains (losses) on securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net impairment losses recognized in earnings	(15.4)	(5)	(3.7)
Net realized gains (losses) on securities	97.1	165.5	159
Interest expense	0	0	0
Reclassification out of Accumulated Other Comprehensive Income | Net unrealized gains on forecasted transactions
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net impairment losses recognized in earnings	0	0	0
Net realized gains (losses) on securities	0.1	0.3	0.5
Interest expense	1.2	1.3	1.5
Reclassification out of Accumulated Other Comprehensive Income | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net impairment losses recognized in earnings	0	0	0
Net realized gains (losses) on securities	0	0	0
Interest expense	0	0	0
Reclassification out of Accumulated Other Comprehensive Income | Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net impairment losses recognized in earnings	0	0	0
Net realized gains (losses) on securities	0	0	0
Interest expense	$ 0	$ 0	$ 0

Other Comprehensive Income C107

Other Comprehensive Income Components of Other Comprehensive Income (Loss) Including Reclassification Adjustments by Income Statement (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Components Of Other Comprehensive Income Loss [Line Items]
Cash flow hedge gain reclassification from accumulated other comprehensive income to net realized gains/losses on securities	$ 1,300.5	$ 1,281	$ 1,165.4
Pre Tax
Components Of Other Comprehensive Income Loss [Line Items]
Net unrealized gains on forecasted transactions, expected to reclassify into income within the next 12 months	1.9
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 | Net unrealized gains on forecasted transactions
Components Of Other Comprehensive Income Loss [Line Items]
Cash flow hedge gain reclassification from accumulated other comprehensive income to net realized gains/losses on securities	$ 0.2	$ 0.5	$ 0.8

Commitments and Contingencies M

Commitments and Contingencies Minimum Commitments under Noncancelable Operating Lease Agreements (Detail) $ in Millions	Dec. 31, 2015USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,015	$ 50.4
2,016	47.8
2,017	37.3
2,018	24.7
2,019	9.6
Thereafter	1.8
Total	$ 171.6

Commitments and Contingencies E

Commitments and Contingencies Expenses Incurred for Leases (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]
Expense	$ 66.6	$ 63.4	$ 64.6

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	Dec. 31, 2015USD ($)
reinsurance contract obligation [Line Items]
Other Commitment	$ 82.4
Minimum commitment under noncancelable purchase obligations	$ 408

Dividends Dividends (Details)

Dividends Dividends (Details) - USD ($) $ / shares in Units, $ in Millions	Feb. 12, 2016	Feb. 13, 2015	Feb. 26, 2014
Annual variable dividend
Common Stock, Dividends, Per Share, Cash Paid		$ 0.6862	$ 0.4929
Payments of Ordinary Dividends, Common Stock		$ 404.1	$ 293.9
Special dividend
Common Stock, Dividends, Per Share, Cash Paid			$ 1
Payments of Ordinary Dividends, Common Stock			$ 596.3
Subsequent Event | Annual variable dividend
Common Stock, Dividends, Per Share, Cash Paid	$ 0.8882
Payments of Ordinary Dividends, Common Stock	$ 519.2

Dividends-Additional Informatio

Dividends-Additional Information (Details)	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Dividends [Abstract]
Target percentage used to determine annual variable dividend	33.33%
Gainshare factor used to determine annual variable dividend range, minimum	0
Gainshare factor used to determine annual variable dividend range, maximum	2
Gainshare factor used to determine annual variable dividend	1.60	1.32	1.21

Subsequent Event Subsequent Eve

Subsequent Event Subsequent Event - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jan. 26, 2015	Dec. 31, 2015	Dec. 31, 2014	Apr. 25, 2014	Jun. 18, 2007
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 400,000,000			$ 350,000,000
Debt Instrument, Interest Rate, Stated Percentage	3.70%			4.35%
3.70% Senior Notes due 2045
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 400,000,000	$ 400,000,000	$ 0
Debt Instrument, Interest Rate, Stated Percentage	3.70%	3.70%			6.70%
Proceeds from Debt, Net of Issuance Costs	$ 394,900,000
Debt Related Commitment Fees and Debt Issuance Costs	800,000
Unrealized Gain (Loss)	$ (12,900,000)	$ (12,900,000)

Redeemable Noncontrolling In114

Redeemable Noncontrolling Interest (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Apr. 01, 2015	Mar. 31, 2015
Noncontrolling Interest [Abstract]
Redeemable Noncontrolling Interest, Equity, Carrying Amount	$ 464.9	$ 0			$ 0
Fair value at date of acquisition				$ 411.5
Net income attributable to NCI	32.9
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	(1.1)	$ 0	$ 0
Purchase of shares from NCI	(12.6)
Change in redemption value of NCI	$ 34.2

Acquisitions (Details)

Acquisitions (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Apr. 01, 2015
Business Acquisition [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	30.80%			30.80%	30.80%
Goodwill	$ 447.6			$ 447.6	$ 447.6	$ 1.6
Revenues					20,853.8	19,391.4	$ 18,170.9
Cash flow hedge gain reclassification from accumulated other comprehensive income to net realized gains/losses on securities					$ 1,300.5	$ 1,281	$ 1,165.4
ARX Holding Corp. [Member]
Business Acquisition [Line Items]
Interest acquired (percentage)								63.20%
Additional Interest acquired (percent)			1.00%
Cost of interest acquired			$ 0
Ownership interest held prior to acquisition (percent)								5.00%
Loss recognized to reflect the net acquisition cost attributable to interest held prior			$ 2
Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage	69.20%			69.20%	69.20%
Goodwill	$ 446			$ 446	$ 446			$ 470
Loss and loss adjustment expense		$ 42		25.3
Goodwill, Subsequent Recognition of Deferred Tax Asset				16.7
Value at acquisition	$ 520.4			520.4	$ 520.4
Total assets acquired								1,800
Investment securities acquired								1,200
Cash and cash equivalents acquired								183
Prepaid reinsurance premium acquired								146
Liability assumed in acquisition								1,200
Unearned premiums acquired								550
Loss and loss adjustment expense reserves acquired								264
Debt acquired								$ 185
Revenues				636.3
Cash flow hedge gain reclassification from accumulated other comprehensive income to net realized gains/losses on securities				$ 106.8
Sales Revenue, Segment [Member] | ARX Holding Corp. [Member]
Business Acquisition [Line Items]
Percentage of total net premium written (percent)	3.00%

Acquisitions Schedule of Intang

Acquisitions Schedule of Intangible Assets by Category (Details) - USD ($) $ in Millions	Apr. 01, 2015	Dec. 31, 2015
Policies in Force [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life		7 years
Agency Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life		14 years
Computer Software, Intangible Asset [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life		8 years
Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life		10 years
ARX Holding Corp. [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Value at acquisition		$ 520.4
Accumulative Amortization		45.1
Useful life	9 years
ARX Holding Corp. [Member] | Policies in Force [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Value at acquisition		256.2
Accumulative Amortization		27.5
ARX Holding Corp. [Member] | Agency Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Value at acquisition		159.2
Accumulative Amortization		8.5
ARX Holding Corp. [Member] | Computer Software, Intangible Asset [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Value at acquisition		69.1
Accumulative Amortization		6.5
ARX Holding Corp. [Member] | Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Value at acquisition		34.8
Accumulative Amortization		2.6
ARX Holding Corp. [Member] | Licensing Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Accumulative Amortization		0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets		$ 1.1