The Progressive Corporation (PGR) 10-Q 5 May 16 2016 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	3 Months Ended
	Mar. 31, 2016shares
Document Document And Entity Information [Abstract]
Entity Registrant Name	PROGRESSIVE CORP/OH/
Entity Central Index Key	80,661
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q1
Amendment Flag	false
Trading Symbol	PGR
Entity Common Stock, Shares Outstanding	582,996,534

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Revenues
Net premiums earned		$ 5,317.4	$ 4,666.3
Period over prior year period percent change in net premiums earned		14.00%
Investment income		$ 118.8	105.1
Period over prior year period percent change in investment income		13.00%
Net realized gains (losses) on securities:
Net impairment losses recognized in earnings		$ 0	(7.9)
Period over prior year period percent change in net premium losses recognized in earnings		(100.00%)
Net realized gains (losses) on securities		$ 17.4	40.9
Period over prior year period percent change in net realized gains (losses) on securities		(57.00%)
Total net realized gains (losses) on securities		$ 17.4	33
Period over prior year period percent change in total net realized gains (losses) on securities		(47.00%)
Fees and other revenues		$ 78.9	73.7
Period over prior year period percent change in fees and other revenues		7.00%
Service revenues		$ 25	17.2
Period over prior year period percent change in service revenues		45.00%
Total revenues		$ 5,557.5	4,895.3
Period over prior year period percent change in total revenues		14.00%
Expenses
Losses and loss adjustment expenses		$ 3,913.4	3,368.6
Period over prior year period percent change in losses and loss adjustment expenses		16.00%
Policy acquisition costs		$ 440.3	379.4
Period over prior year period percent change in policy acquisition costs		16.00%
Other underwriting expenses		$ 755.8	650.4
Period over prior year period percent change in other underwriting expenses		16.00%
Investment expenses		$ 4.8	5.3
Period over prior year period percent change in investment expenses		(9.00%)
Service expenses		$ 21.6	15.9
Period over prior year period percent change in service expenses		36.00%
Interest expense		$ 34.2	32.5
Period over prior year period percent change in interest expense		5.00%
Total expenses		$ 5,170.1	4,452.1
Period over prior year period percent change in total expenses		16.00%
Net Income
Income before income taxes		$ 387.4	443.2
Period over prior year period percent change in income before income taxes		(13.00%)
Provision for income taxes		$ 128.7	147.6
Period over prior year period percent change in provision for income taxes		(13.00%)
Net income		$ 258.7	295.6
Period over prior year period percent change in net income		(12.00%)
Net income attributable to noncontrolling interest (NCI), net of tax		$ 0.5	0
Net income attributable to Progressive		$ 258.2	295.6
Period over prior year period percent change in net income attributable to Progressive		(13.00%)
Other Comprehensive Income (Loss), Net of Tax
Total net unrealized gains (losses) on securities		$ 69.5	35.4
Period over prior year period percent change in total net unrealized gains (losses) on securities		96.00%
Net unrealized gains (losses) on forecasted transactions		$ (0.3)	(8.7)
Period over prior year period percent change in net unrealized gains on forecasted transactions		(97.00%)
Foreign currency translation adjustment		$ 0.5	(0.5)
Period over prior year period percent change in foreign currency translation adjustment		(200.00%)
Other comprehensive income		$ 69.7	26.2
Period over prior year period percent change in other comprehensive income		166.00%
Other comprehensive (income) loss attributable to NCI		$ (2.1)	0
Comprehensive income attributable to Progressive		$ 325.8	$ 321.8
Period over prior year period percent change in comprehensive income		1.00%
Computation of Per Share Earnings
Average shares outstanding - Basic (shares)		583.2	587.6
Period over prior year period percent change in average shares outstanding - basic		(1.00%)
Net effect of dilutive stock-based compensation (shares)		2.3	3.4
Period over prior year period percent change in net effect of dilutive stock-based compensation		(32.00%)
Total equivalent shares - Diluted (shares)		585.5	591
Period over prior year period percent change in total equivalent shares - diluted		(1.00%)
Basic: Net income per share (USD per share)		$ 0.44	$ 0.50
Period over prior year period percent change in basic: net income per share		(12.00%)
Diluted: Net income per share (USD per share)		$ 0.44	0.50
Period over prior year period percent change in diluted: net income per share		(12.00%)
Dividends declared per share (USD per share)	[1]	$ 0	$ 0
[1]	Progressive maintains an annual dividend program. See Note 8 - Dividends for further discussion.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Investments - Available-for-sale, at fair value:
Fixed maturities (amortized cost: $13,892.3, $13,997.5, and $15,347.9)		$ 13,966.4	$ 15,332.2	$ 14,219.8
Equity securities:
Nonredeemable preferred stocks (cost: $731.9, $598.3, and $674.2)		832.2	782.6	828.1
Common equities (cost: $1,524.0, $1,295.0, and $1,494.3)		2,705	2,650.5	2,515.7
Short-term investments (amortized cost: $3,826.9, $2,267.0, and $2,172.0)		3,826.9	2,172	2,267
Total investments	[1],[2]	21,330.5	20,937.3	19,830.6
Cash		209.9	224.4	101.5
Accrued investment income		93.6	102.2	84.7
Premiums receivable, net of allowance for doubtful accounts of $157.6, $138.7, and $164.8		4,378.9	3,987.7	3,777
Reinsurance recoverables, including $59.5, $50.8, and $46.1 on paid losses and loss adjustment expenses		1,568.2	1,488.8	1,257.2
Prepaid reinsurance premiums		216.7	199.3	99.3
Deferred acquisition costs		600	564.1	484
Property and equipment, net of accumulated depreciation of $799.6, $742.7, and $778.3		1,061.9	1,037.2	957.5
Goodwill		447.6	447.6	1.6
Intangible assets, net of accumulated amortization of $62.9, $0.6, and $47.4		479.4	494.9	11.3
Other assets		334.9	335.8	276
Total assets		30,721.6	29,819.3	26,880.7
Liabilities
Unearned premiums		7,140.7	6,621.8	5,854
Loss and loss adjustment expense reserves		10,286.7	10,039	9,001.6
Net deferred income taxes		113.9	109.3	97.2
Dividends payable		0	519.2	0
Accounts payable, accrued expenses, and other liabilities		2,451.4	2,067.8	2,165.9
Debt	[3]	2,701.6	2,707.9	2,560.1
Total liabilities		22,694.3	22,065	19,678.8
Redeemable noncontrolling interest (NCI)2	[4]	467.4	464.9	0
Common shares, $1.00 par value (authorized 900.0; issued 797.6, including treasury shares of 214.6, 210.3, and 214.0)		583	583.6	587.3
Paid-in capital		1,231.3	1,218.8	1,196.7
Retained earnings		4,877.6	4,686.6	4,368.6
Accumulated other comprehensive income, net of tax:
Net unrealized gains (losses) on securities		878.5	809	1,057.3
Net unrealized gains (losses) on forecasted transactions		(8.5)	(8.2)	(7.2)
Foreign currency translation adjustment		(1)	(1.5)	(0.8)
Accumulated other comprehensive (income) loss attributable to noncontrolling interest		(1)	1.1	0
Total accumulated other comprehensive income		868	800.4	1,049.3
Total shareholders’ equity		7,559.9	7,289.4	7,201.9
Total liabilities, redeemable NCI, and shareholders’ equity		$ 30,721.6	$ 29,819.3	$ 26,880.7
[1]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at March 31, 2016, $47.3 million was included in "other liabilities," compared to $95.8 million in "other liabilities" at March 31, 2015 and $23.1 million in "other assets" at December 31, 2015.
[2]	The total fair value of the portfolio at March 31, 2016 and 2015, and December 31, 2015 included $0.7 billion, $1.7 billion, and $1.3 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.
[3]	1Consists of both short-term and long-term debt. See Note 4 - Debt for further discussion.
[4]	2See Note 11 – Redeemable Noncontrolling Interest for further discussion.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Fixed maturities, amortized cost	$ 13,892.3	$ 15,347.9	$ 13,997.5
Nonredeemable preferred stocks, cost	731.9	674.2	598.3
Common equities, cost	1,524	1,494.3	1,295
Short-term investments, amortized cost	3,826.9	2,172	2,267
Premiums receivable, allowance for doubtful accounts	157.6	164.8	138.7
Reinsurance recoverables, paid losses and loss adjustment expenses	59.5	46.1	50.8
Finite-Lived Intangible Assets, Accumulated Amortization	62.9	47.4	0.6
Property and equipment, accumulated depreciation	$ 799.6	$ 778.3	$ 742.7
Common Shares, par value (USD per share)	$ 1	$ 1	$ 1
Common Shares, authorized (shares)	900,000,000	900,000,000	900,000,000
Common Shares, issued (shares)	797,600,000	797,600,000	797,600,000
Common Shares, treasury shares (shares)	214,600,000	214,000,000	210,300,000

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity Statement - USD ($) $ in Millions	Total	Common Shares, $1.00 Par Value	Paid-in Capital	Retained Earnings	Accumulated other comprehensive income after tax	Serial Preferred Shares [Member]	Voting Preference Shares [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred stock, shares authorized (in shares)						20,000,000	5,000,000
Preferred stock, shares issued (in shares)						0	0
Preferred stock, shares outstanding (in shares)						0
Balance, Beginning of period at Dec. 31, 2014		$ 587.8	$ 1,184.3	$ 4,133.4	$ 1,023.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Progressive	$ 295.6			295.6
Tax benefit from vesting of equity-based compensation			6.3
Treasury shares purchased		(2.5)	(5)	(58.4)
Net restricted equity awards (issued)/(vested)/forfeited		2	(2)
Amortization of equity-based compensation			13.1
Reinvested dividends on restricted stock units			0	0
Adjustment to carrying amount of redeemable noncontrolling interest			0
Cash dividends declared on common shares				0
Attributable to noncontrolling interest	0				0
Other comprehensive income	26.2				26.2
Other, net				(2)
Balance, End of period at Mar. 31, 2015	7,201.9	587.3	1,196.7	4,368.6	1,049.3
Balance, Beginning of period at Dec. 31, 2014		587.8	1,184.3	4,133.4	1,023.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Tax benefit from vesting of equity-based compensation	16.8
Balance, End of period at Dec. 31, 2015	7,289.4	583.6	1,218.8	4,686.6	800.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred stock, shares authorized (in shares)						20,000,000	5,000,000
Preferred stock, shares issued (in shares)						0	0
Preferred stock, shares outstanding (in shares)						0
Preferred stock, shares authorized (in shares)						20,000,000	5,000,000
Preferred stock, shares issued (in shares)						0	0
Preferred stock, shares outstanding (in shares)						0
Net income attributable to Progressive	258.2			258.2
Tax benefit from vesting of equity-based compensation			6.6
Treasury shares purchased		(2.3)	(4.8)	(63.2)
Net restricted equity awards (issued)/(vested)/forfeited		1.7	(1.7)
Amortization of equity-based compensation			12.8
Reinvested dividends on restricted stock units			(0.3)	0.3
Adjustment to carrying amount of redeemable noncontrolling interest	(0.1)		(0.1)
Cash dividends declared on common shares				0.2
Attributable to noncontrolling interest	(2.1)				(2.1)
Other comprehensive income	69.7				69.7
Other, net				(4.5)
Balance, End of period at Mar. 31, 2016	$ 7,559.9	$ 583	$ 1,231.3	$ 4,877.6	$ 868
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred stock, shares authorized (in shares)						20,000,000	5,000,000
Preferred stock, shares issued (in shares)						0	0
Preferred stock, shares outstanding (in shares)						0

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Statement of Cash Flows [Abstract]
Net income		$ 258.7	$ 295.6
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation		27.5	23.8
Amortization of intangible assets		15.5	0
Amortization of fixed-income securities		20.5	17.3
Amortization of equity-based compensation		12.8	13.1
Net realized (gains) losses on securities		(17.4)	(33)
Net (gains) losses on disposition of property and equipment		0.1	0.1
Changes in:
Premiums receivable		(391.1)	(239.6)
Reinsurance recoverables		(79.4)	(25.3)
Prepaid reinsurance premiums		(17.4)	(14)
Deferred acquisition costs		(35.9)	(26.8)
Income taxes		91.8	80.6
Unearned premiums		518.6	414.4
Loss and loss adjustment expense reserves		247.6	144.4
Accounts payable, accrued expenses, and other liabilities		200.1	106.9
Other, net		(27.5)	13.6
Net cash provided by operating activities		824.5	771.1
Purchases:
Fixed maturities		(2,468.2)	(3,023.8)
Equity securities		(180.1)	(77.2)
Sales:
Fixed maturities		2,105.9	1,534.6
Equity securities		97.9	88.9
Maturities, paydowns, calls, and other:
Fixed maturities		1,829.8	855.1
Net sales (purchases) of short-term investments		(1,653)	(117.7)
Net unsettled security transactions		70.4	64.5
Purchases of property and equipment		(54.3)	(22.2)
Sales of property and equipment		2	1.4
Net cash used in investing activities		(249.6)	(696.4)
Cash Flows From Financing Activities
Tax benefit from vesting of equity-based compensation		6.6	6.3
Proceeds from debt issuance		0	382
Dividends paid to shareholders	[1]	(519)	(403.6)
Acquisition of treasury shares		(70.3)	(65.9)
Repayments of Debt		(6.8)	0
Net cash used in financing activities		(589.5)	(81.2)
Effect of exchange rate changes on cash		0.1	(0.4)
Decrease in cash		(14.5)	(6.9)
Cash, Beginning of year		224.4	108.4
Cash, End of period		$ 209.9	$ 101.5
[1]	Progressive maintains an annual dividend program. See Note 8 - Dividends for further discussion.

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2016
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation — The accompanying consolidated financial statements include the accounts of The Progressive Corporation and ARX Holding Corp. (ARX), and their respective wholly owned insurance and non-insurance subsidiaries and affiliates, in which Progressive or ARX has a controlling financial interest. The Progressive Corporation owned 69.2% of the outstanding capital stock of ARX at March 31, 2016. All intercompany accounts and transactions are eliminated in consolidation. The consolidated financial statements reflect all normal recurring adjustments that, in the opinion of management, were necessary for a fair statement of the results for the interim periods presented. The results of operations for the period ended March 31, 2016 , are not necessarily indicative of the results expected for the full year. These consolidated financial statements and the notes thereto should be read in conjunction with Progressive’s audited financial statements and accompanying notes included in Exhibit 13 to our Annual Report on Form 10-K for the year ended December 31, 2015 ("2015 Annual Report to Shareholders). Included in other assets in the consolidated balance sheets are properties that are considered "held for sale." The fair value of these properties, less the estimated cost to sell them, was $8.7 million at March 31, 2016 and 2015, and December 31, 2015.

Investments

Investments	3 Months Ended
	Mar. 31, 2016
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 classification of how we manage, monitor, and measure the portfolio. The net holding period gains (losses) represent the amounts realized on our hybrid securities only. ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) 1 Fair Value % of Value March 31, 2016 Fixed maturities: U.S. government obligations $ 1,375.8 $ 12.2 $ 0 $ 0 $ 1,388.0 6.5 % State and local government obligations 2,452.0 57.4 (1.2 ) 0 2,508.2 11.8 Foreign government obligations 21.9 0 0 0 21.9 0.1 Corporate debt securities 3,795.2 50.6 (6.2 ) 0.4 3,840.0 18.0 Residential mortgage-backed securities 1,810.9 19.5 (28.5 ) (0.4 ) 1,801.5 8.4 Agency residential pass-through obligations 46.5 0.2 (0.1 ) 0 46.6 0.2 Commercial mortgage-backed securities 2,418.7 26.4 (18.9 ) 0 2,426.2 11.4 Other asset-backed securities 1,706.3 1.3 (4.2 ) 0.3 1,703.7 8.0 Redeemable preferred stocks 265.0 14.2 (48.9 ) 0 230.3 1.1 Total fixed maturities 13,892.3 181.8 (108.0 ) 0.3 13,966.4 65.5 Equity securities: Nonredeemable preferred stocks 731.9 124.7 (24.4 ) 0 832.2 3.9 Common equities 1,524.0 1,186.7 (5.7 ) 0 2,705.0 12.7 Short-term investments 3,826.9 0 0 0 3,826.9 17.9 Total portfolio 2,3 $ 19,975.1 $ 1,493.2 $ (138.1 ) $ 0.3 $ 21,330.5 100.0 % ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) 1 Fair Value % of Value March 31, 2015 Fixed maturities: U.S. government obligations $ 2,678.1 $ 30.1 $ 0 $ 0 $ 2,708.2 13.7 % State and local government obligations 2,224.8 50.0 (1.0 ) 0 2,273.8 11.5 Foreign government obligations 20.0 0 0 0 20.0 0.1 Corporate debt securities 2,851.6 54.4 (3.8 ) 1.8 2,904.0 14.6 Residential mortgage-backed securities 1,629.2 32.4 (13.1 ) (0.3 ) 1,648.2 8.3 Agency residential pass-through obligations 0 0 0 0 0 0 Commercial mortgage-backed securities 2,437.4 50.1 (1.1 ) 0.7 2,487.1 12.5 Other asset-backed securities 1,896.1 4.9 (0.3 ) 0.8 1,901.5 9.6 Redeemable preferred stocks 260.3 23.3 (6.6 ) 0 277.0 1.4 Total fixed maturities 13,997.5 245.2 (25.9 ) 3.0 14,219.8 71.7 Equity securities: Nonredeemable preferred stocks 598.3 192.5 (5.9 ) 43.2 828.1 4.2 Common equities 1,295.0 1,226.7 (6.0 ) 0 2,515.7 12.7 Short-term investments 2,267.0 0 0 0 2,267.0 11.4 Total portfolio 2,3 $ 18,157.8 $ 1,664.4 $ (37.8 ) $ 46.2 $ 19,830.6 100.0 % ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) 1 Fair Value % of 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 % 1 Represents net holding period gains (losses) realized on certain hybrid securities (discussed below). 2 Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at March 31, 2016 , $47.3 million was included in "other liabilities," compared to $95.8 million in "other liabilities" at March 31, 2015 and $23.1 million in "other assets" at December 31, 2015 . 3 The total fair value of the portfolio at March 31, 2016 and 2015 , and December 31, 2015 included $0.7 billion , $1.7 billion , and $1.3 billion , 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. We did not enter into any repurchase commitment transactions during the first three months of 2016 or 2015 , and we had no open repurchase commitments at March 31, 2016 , March 31, 2015 , or December 31, 2015 . 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 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 March 31, 2016 , March 31, 2015 , or December 31, 2015 . For the three months ended March 31, 2016 , our largest outstanding balance of reverse repurchase commitments was $265.0 million , which was open for one day; the average daily balance of reverse repurchase commitments was $160.7 million . To the extent our repurchase and reverse repurchase transactions were with the same counterparty and subject to an enforceable master netting arrangement, we could elect to offset these transactions. Consistent with past practice, we have elected not to offset these transactions and therefore report these transactions on a gross basis on our balance sheets. Hybrid Securities Included in our fixed-maturity and equity securities are hybrid securities, which are reported at fair value: March 31, December 31, (millions) 2016 2015 Fixed maturities: Corporate debt securities $ 39.2 $ 132.9 $ 49.1 Residential mortgage-backed securities 174.4 111.7 144.3 Commercial mortgage-backed securities 0 18.0 17.3 Other asset-backed securities 10.6 13.1 11.3 Total fixed maturities 224.2 275.7 222.0 Equity securities: Nonredeemable preferred stocks 49.5 137.2 50.7 Total hybrid securities $ 273.7 $ 412.9 $ 272.7 Certain corporate debt securities are accounted for as hybrid securities since they were acquired at a 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 $1.4 million as of March 31, 2016 , if all of the 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. These securities were no longer held at March 31, 2016 . 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 has 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 in our 2015 Annual Report to Shareholders for further discussion). Fixed Maturities The composition of fixed maturities by maturity at March 31, 2016 , was: (millions) Cost Fair Value Less than one year $ 3,604.9 $ 3,596.3 One to five years 7,016.5 7,030.3 Five to ten years 3,195.6 3,259.6 Ten years or greater 75.3 80.2 Total $ 13,892.3 $ 13,966.4 Asset-backed securities are classified in the maturity distribution table based upon their projected cash flows. All other securities which do not have a single maturity date are reported based upon expected average maturity. Contractual maturities may differ from expected maturities because the issuers of the securities may have the right to call or prepay obligations. Gross Unrealized Losses As of March 31, 2016 , we had $132.4 million of gross unrealized losses in our fixed-income securities (i.e., fixed-maturity securities, nonredeemable preferred stocks, and short-term investments) and $5.7 million in our common equities. We currently do not intend to sell the fixed-income securities and determined that it is more likely than not that we will not be required to sell these securities for the period of time necessary to recover their cost bases. A review of our fixed-income securities indicated that the issuers were current with respect to their interest obligations and that there was no evidence of any deterioration of the current cash flow projections that would indicate we would not receive the remaining principal at maturity. For common equities, 95% of our common stock portfolio was indexed to the Russell 1000; as such, this portfolio may contain securities in a loss position for an extended period of time, subject to possible write-downs, as described below. We may retain these securities as long as the portfolio and index correlation remain similar. To the extent there is issuer-specific deterioration, we may write-down the securities of that issuer. The remaining 5% of our common stocks were part of a managed equity strategy selected and administered by an external investment advisor. If our review of loss position securities indicates there was a fundamental, or market, impairment on these securities that was determined to be other-than-temporary, we would recognize a write-down in accordance with our stated policy. The following tables show the composition of gross unrealized losses by major security type and by the length of time that individual securities have been in a continuous unrealized loss position: Total No. of Sec. Total Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Unrealized Losses No. of Sec. Fair Unrealized Losses March 31, 2016 Fixed maturities: U.S. government obligations 5 $ 74.9 $ 0 5 $ 74.9 $ 0 0 $ 0 $ 0 State and local government obligations 112 267.8 (1.2 ) 63 132.8 (0.3 ) 49 135.0 (0.9 ) Corporate debt securities 60 672.3 (6.2 ) 21 169.2 (0.4 ) 39 503.1 (5.8 ) Residential mortgage-backed securities 157 1,345.1 (28.5 ) 52 426.9 (3.9 ) 105 918.2 (24.6 ) Agency residential pass-through obligations 25 9.1 (0.1 ) 3 0.4 0 22 8.7 (0.1 ) Commercial mortgage-backed securities 130 1,185.4 (18.9 ) 49 395.4 (2.2 ) 81 790.0 (16.7 ) Other asset-backed securities 86 1,175.2 (4.2 ) 70 999.3 (3.2 ) 16 175.9 (1.0 ) Redeemable preferred stocks 9 198.8 (48.9 ) 4 88.0 (16.1 ) 5 110.8 (32.8 ) Total fixed maturities 584 4,928.6 (108.0 ) 267 2,286.9 (26.1 ) 317 2,641.7 (81.9 ) Equity securities: Nonredeemable preferred stocks 13 344.4 (24.4 ) 4 79.0 (2.6 ) 9 265.4 (21.8 ) Common equities 73 87.4 (5.7 ) 67 84.3 (5.5 ) 6 3.1 (0.2 ) Total equity securities 86 431.8 (30.1 ) 71 163.3 (8.1 ) 15 268.5 (22.0 ) Total portfolio 670 $ 5,360.4 $ (138.1 ) 338 $ 2,450.2 $ (34.2 ) 332 $ 2,910.2 $ (103.9 ) Total No. of Sec. Total Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Unrealized Losses No. of Sec. Fair Unrealized Losses March 31, 2015 Fixed maturities: U.S. government obligations 1 $ 7.2 $ 0 1 $ 7.2 $ 0 0 $ 0 $ 0 State and local government obligations 57 270.3 (1.0 ) 42 231.8 (0.5 ) 15 38.5 (0.5 ) Corporate debt securities 25 390.3 (3.8 ) 17 242.4 (2.3 ) 8 147.9 (1.5 ) Residential mortgage-backed securities 80 1,013.9 (13.1 ) 34 540.6 (3.1 ) 46 473.3 (10.0 ) Agency residential pass-through obligations 0 0 0 0 0 0 0 0 0 Commercial mortgage-backed securities 59 564.2 (1.1 ) 53 560.8 (1.0 ) 6 3.4 (0.1 ) Other asset-backed securities 30 490.9 (0.3 ) 29 472.4 (0.1 ) 1 18.5 (0.2 ) Redeemable preferred stocks 3 102.1 (6.6 ) 1 33.0 (1.0 ) 2 69.1 (5.6 ) Total fixed maturities 255 2,838.9 (25.9 ) 177 2,088.2 (8.0 ) 78 750.7 (17.9 ) Equity securities: Nonredeemable preferred stocks 5 183.1 (5.9 ) 2 74.5 (2.2 ) 3 108.6 (3.7 ) Common equities 40 58.3 (6.0 ) 40 58.3 (6.0 ) 0 0 0 Total equity securities 45 241.4 (11.9 ) 42 132.8 (8.2 ) 3 108.6 (3.7 ) Total portfolio 300 $ 3,080.3 $ (37.8 ) 219 $ 2,221.0 $ (16.2 ) 81 $ 859.3 $ (21.6 ) Total No. of Sec. Total Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Unrealized Losses No. of Sec. Fair Unrealized Losses December 31, 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 ) Since March 31, 2015 , the number of securities in our fixed-maturity portfolio with unrealized losses increased, primarily reflecting 190 securities 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 March 31, 2016 . The decline in these securities averaged approximately 0.4% of their total cost. The number of fixed-maturity securities with unrealized losses decreased since December 31, 2015 , primarily the result of declining interest rates. We had no material decreases in valuation as a result of credit rating downgrades on our fixed-maturity securities. All of the fixed-maturity securities in an unrealized loss position at March 31, 2016 in the table above are current with respect to required principal and interest payments. Since December 31, 2015 , our nonredeemable preferred stocks with unrealized losses increased to 13 securities, averaging approximately 7% of their total cost. We reviewed these securities and concluded that the unrealized losses are market-related adjustments to the values, which we determined not to be other-than-temporary; we expect to recover our initial investments on these securities. The number of issuers with unrealized losses in our common stock portfolio also increased during the first three months of 2016. 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: March 31, December 31, (millions) 2016 2015 Fixed maturities: Residential mortgage-backed securities $ (43.3 ) $ (44.1 ) $ (43.3 ) Commercial mortgage-backed securities (0.6 ) (0.6 ) (0.6 ) Total fixed maturities $ (43.9 ) $ (44.7 ) $ (43.9 ) The following tables provide rollforwards of the amounts related to credit losses recognized in earnings for the periods ended March 31, 2016 and 2015 , for which a portion of the OTTI losses were also recognized in accumulated other comprehensive income at the time the credit impairments were determined and recognized: Three Months Ended March 31, 2016 Mortgage-Backed (millions) Residential Commercial Total Balance at December 31, 2015 $ 12.4 $ 0.4 $ 12.8 Change in recoveries of future cash flows expected to be collected 1 (0.3 ) 0 (0.3 ) Balance at March 31, 2016 $ 12.1 $ 0.4 $ 12.5 Three Months Ended March 31, 2015 Mortgage-Backed (millions) Residential Commercial Total Balance at December 31, 2014 $ 12.7 $ 0.4 $ 13.1 Change in recoveries of future cash flows expected to be collected 1 (0.5 ) 0 (0.5 ) Balance at March 31, 2015 $ 12.2 $ 0.4 $ 12.6 1 Reflects the current period change in the expected recovery of prior impairments that will be accreted into income over the remaining life of the security. Although we determined 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 potential credit losses on the securities that were in an unrealized loss position. In that process, we considered a number of factors and inputs related to the individual securities. The methodology and significant inputs used to measure the amount of credit losses in our portfolio included: current performance indicators on the 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. We did not have any credit impairment write-downs for the three months ended March 31, 2016 or 2015 . Realized Gains (Losses) The components of net realized gains (losses) for the three months ended March 31, were: Three Months (millions) 2016 2015 Gross realized gains on security sales Fixed maturities: U.S. government obligations $ 14.3 $ 4.9 State and local government obligations 10.9 0 Corporate and other debt securities 12.5 9.1 Residential mortgage-backed securities 0.9 0.1 Commercial mortgage-backed securities 3.6 10.8 Total fixed maturities 42.2 24.9 Equity securities: Nonredeemable preferred stocks 1.6 15.8 Common equities 9.5 17.8 Subtotal gross realized gains on security sales 53.3 58.5 Gross realized losses on security sales Fixed maturities: U.S. government obligations (0.4 ) (0.8 ) State and local government obligations (0.1 ) 0 Corporate and other debt securities (0.4 ) (0.8 ) Commercial mortgage-backed securities (2.7 ) (0.2 ) Total fixed maturities (3.6 ) (1.8 ) Equity securities: Nonredeemable preferred stocks (1.0 ) 0 Common equities (4.9 ) (0.4 ) Subtotal gross realized losses on security sales (9.5 ) (2.2 ) Net realized gains (losses) on security sales Fixed maturities: U.S. government obligations 13.9 4.1 State and local government obligations 10.8 0 Corporate and other debt securities 12.1 8.3 Residential mortgage-backed securities 0.9 0.1 Commercial mortgage-backed securities 0.9 10.6 Total fixed maturities 38.6 23.1 Equity securities: Nonredeemable preferred stocks 0.6 15.8 Common equities 4.6 17.4 Subtotal net realized gains (losses) on security sales 43.8 56.3 Other-than-temporary impairment losses Equity securities: Common equities 0 (7.9 ) Subtotal other-than-temporary impairment losses 0 (7.9 ) Other gains (losses) Hybrid securities (0.7 ) 3.3 Derivative instruments (25.7 ) (18.8 ) Litigation settlements 0 0.1 Subtotal other gains (losses) (26.4 ) (15.4 ) Total net realized gains (losses) on securities $ 17.4 $ 33.0 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. Net Investment Income The components of net investment income for the three months ended March 31, were: Three Months (millions) 2016 2015 Fixed maturities: U.S. government obligations $ 4.8 $ 9.1 State and local government obligations 13.5 11.9 Foreign government obligations 0.1 0.1 Corporate debt securities 28.2 22.9 Residential mortgage-backed securities 12.2 12.8 Agency residential pass-through obligations 0.4 0 Commercial mortgage-backed securities 20.9 16.9 Other asset-backed securities 6.0 5.0 Redeemable preferred stocks 3.8 3.8 Total fixed maturities 89.9 82.5 Equity securities: Nonredeemable preferred stocks 11.8 10.5 Common equities 14.5 11.7 Short-term investments 2.6 0.4 Investment income 118.8 105.1 Investment expenses (4.8 ) (5.3 ) Net investment income $ 114.0 $ 99.8 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 of 13% in first quarter 2016 , compared to first quarter 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. Trading Securities At March 31, 2016 and 2015 , and December 31, 2015 , we did not hold any trading securities and did not have any net realized gains (losses) on trading securities for the three months ended March 31, 2016 and 2015 . 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 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 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 March 31, 2016 and 2015 , and December 31, 2015 , and for the three months ended March 31, 2016 and 2015 : (millions) Balance Sheet 2 Comprehensive Income Statement Assets (Liabilities) Pretax Net Realized Gains (Losses) Notional Value 1 Three Months Ended March 31, Dec. 31, March 31, Dec. 31, March 31, Derivatives designated as: 2016 2015 2015 Purpose Classification 2016 2015 2015 2016 2015 Hedging instruments Closed: Ineffective cash flow hedge $ 0 $ 0 $ 18 Manage interest rate risk NA $ 0 $ 0 $ 0 $ 0 $ 0 Non-hedging instruments Assets: Interest rate swaps 0 750 750 Manage portfolio duration Investments— fixed maturities 0 0.1 4.4 0 (18.8 ) Liabilities: Interest rate swaps 565 0 0 Manage portfolio duration Other liabilities (18.7 ) 0 0 (24.0 ) 0 Closed: Interest rate swaps 185 0 0 Manage portfolio duration NA 0 0 0 (1.9 ) 0 U.S. Treasury Note futures 55 0 691 Manage NA 0 0 0 0.2 0 Total NA NA NA $ (18.7 ) $ 0.1 $ 4.4 $ (25.7 ) $ (18.8 ) NA= Not applicable 1 The amounts represent the value held at quarter and year end for open positions and the maximum amount held during the period 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. CASH FLOW HEDGES 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 2015 , and we reclassified the unrealized gain on forecasted transactions to net realized gains on securities. We entered into a forecasted debt issuance hedge to hedge against a possible rise in interest rates in conjunction with the $400 million of 3.70% Senior Notes issued in January 2015. Upon issuance, we closed the hedge and recognized, as part of accumulated other comprehensive income, a pretax loss of $12.9 million in January 2015. See Note 4 – Debt for further discussion. INTEREST RATE SWAPS and U.S. TREASURY FUTURES We use interest rate swaps and treasury futures contracts primarily to manage the fixed-income portfolio duration. At March 31, 2016 and 2015 , and December 31, 2015 , 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 positions open at March 31, 2016, since inception, interest rates have fallen resulting in a fair value loss and a fair value decrease of $22.0 million since December 31, 2015. During the first quarter 2016, we closed one 10 -year interest rate swap position (opened in 2013) in which we were paying a fixed rate and receiving a variable rate, effectively shortening the duration of our fixed-income portfolio. The net realized loss during the quarter was the result of overall falling interest rates during the period the position was open. During the first quarter 2016, we entered into U.S. treasury futures by selling contracts; all positions were closed at March 31, 2016 . The net realized gain during the quarter was the result of overall rising interest rates during the period that the contracts were held. As of March 31, 2016 and 2015 , the balance of the cash collateral that we delivered to the applicable counterparties on the interest rate swaps was $20.6 million and $4.7 million , respectively. As of December 31, 2015 , the balance of the cash collateral that we had received from the applicable counterparties on the interest rate swap positions was $4.9 million .

Fair Value

Fair Value	3 Months Ended
	Mar. 31, 2016
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 March 31, 2016 Fixed maturities: U.S. government obligations $ 1,388.0 $ 0 $ 0 $ 1,388.0 $ 1,375.8 State and local government obligations 0 2,508.2 0 2,508.2 2,452.0 Foreign government obligations 21.9 0 0 21.9 21.9 Corporate debt securities 0 3,840.0 0 3,840.0 3,795.2 Subtotal 1,409.9 6,348.2 0 7,758.1 7,644.9 Asset-backed securities: Residential mortgage-backed 0 1,801.5 0 1,801.5 1,810.9 Agency residential pass-through obligations 0 46.6 0 46.6 46.5 Commercial mortgage-backed 0 2,416.7 9.5 2,426.2 2,418.7 Other asset-backed 0 1,703.7 0 1,703.7 1,706.3 Subtotal asset-backed securities 0 5,968.5 9.5 5,978.0 5,982.4 Redeemable preferred stocks: Financials 0 91.7 0 91.7 81.8 Utilities 0 51.6 0 51.6 65.1 Industrials 0 87.0 0 87.0 118.1 Subtotal redeemable preferred stocks 0 230.3 0 230.3 265.0 Total fixed maturities 1,409.9 12,547.0 9.5 13,966.4 13,892.3 Equity securities: Nonredeemable preferred stocks: Financials 153.8 678.4 0 832.2 731.9 Subtotal nonredeemable preferred stocks 153.8 678.4 0 832.2 731.9 Common equities: Common stocks 2,704.7 0 0 2,704.7 1,523.7 Other risk investments 0 0 0.3 0.3 0.3 Subtotal common equities 2,704.7 0 0.3 2,705.0 1,524.0 Total fixed maturities and equity securities 4,268.4 13,225.4 9.8 17,503.6 16,148.2 Short-term investments 3,730.0 96.9 0 3,826.9 3,826.9 Total portfolio $ 7,998.4 $ 13,322.3 $ 9.8 $ 21,330.5 $ 19,975.1 Debt $ 0 $ 2,789.2 $ 158.1 $ 2,947.3 $ 2,701.6 Fair Value (millions) Level 1 Level 2 Level 3 Total Cost March 31, 2015 Fixed maturities: U.S. government obligations $ 2,708.2 $ 0 $ 0 $ 2,708.2 $ 2,678.1 State and local government obligations 0 2,273.8 0 2,273.8 2,224.8 Foreign government obligations 20.0 0 0 20.0 20.0 Corporate debt securities 0 2,904.0 0 2,904.0 2,851.6 Subtotal 2,728.2 5,177.8 0 7,906.0 7,774.5 Asset-backed securities: Residential mortgage-backed 0 1,648.2 0 1,648.2 1,629.2 Agency residential pass-through obligations 0 0 0 0 0 Commercial mortgage-backed 0 2,475.7 11.4 2,487.1 2,437.4 Other asset-backed 0 1,901.5 0 1,901.5 1,896.1 Subtotal asset-backed securities 0 6,025.4 11.4 6,036.8 5,962.7 Redeemable preferred stocks: Financials 0 98.2 0 98.2 77.3 Utilities 0 64.4 0 64.4 65.0 Industrials 0 114.4 0 114.4 118.0 Subtotal redeemable preferred stocks 0 277.0 0 277.0 260.3 Total fixed maturities 2,728.2 11,480.2 11.4 14,219.8 13,997.5 Equity securities: Nonredeemable preferred stocks: Financials 181.7 576.5 69.9 828.1 598.3 Subtotal nonredeemable preferred stocks 181.7 576.5 69.9 828.1 598.3 Common equities: Common stocks 2,515.4 0 0 2,515.4 1,294.7 Other risk investments 0 0 0.3 0.3 0.3 Subtotal common equities 2,515.4 0 0.3 2,515.7 1,295.0 Total fixed maturities and equity securities 5,425.3 12,056.7 81.6 17,563.6 15,890.8 Short-term investments 2,267.0 0 0 2,267.0 2,267.0 Total portfolio $ 7,692.3 $ 12,056.7 $ 81.6 $ 19,830.6 $ 18,157.8 Debt $ 0 $ 2,910.9 $ 0 $ 2,910.9 $ 2,560.1 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 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. We did not have any transfers between Level 1 and Level 2 during 2016 or 2015 . 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 March 31, 2016 , vendor-quoted prices represented 37% of our Level 1 classifications (excluding short-term investments), compared to 50% and 49% at March 31, 2015 and December 31, 2015 , respectively. The securities quoted by vendors in Level 1 primarily represent our holdings in U.S. Treasury Notes, which are frequently traded, and the quotes are considered similar to exchange-traded quotes. The balance of our Level 1 pricing comes from quotes obtained directly from trades made on active exchanges. The decline in vendor-quoted Level 1 prices since December 31, 2015 was due to a reduction of U.S. Treasury Notes with the funds deployed primarily to short-term investments. At March 31, 2016 and 2015 , and December 31, 2015 , vendor-quoted prices comprised 98% , 97% , and 97% , respectively, of our Level 2 classifications (excluding short-term investments), while dealer-quoted prices represented 2% , 3% , and 3% , respectively. 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 the source’s process, the quality of its review, and its willingness to improve its analysis based on feedback from clients. We believe this effort helps ensure that we are reporting the most representative fair values for our securities. Except as described below, our Level 3 securities are also priced externally; however, due to several factors (e.g., nature of the securities, level of activity, and lack of similar securities trading to obtain observable market level inputs), these valuations are more subjective in nature. Certain private equity investments and fixed-income investments included in the Level 3 category are valued using external pricing supplemented by internal review and analysis. After all the valuations are received and our review is complete, if the inputs used by vendors are determined to not contain sufficient observable market information, we will reclassify the affected security valuations to Level 3. At March 31, 2016 and 2015 , and December 31, 2015 , 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 March 31, 2016 or December 31, 2015 . At March 31, 2015 , we held one internally-priced security, a private preferred equity security (our 5% equity interest in ARX) with a value of $69.9 million , which was reclassified upon our acquisition of a controlling interest in ARX. 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 2016 or 2015 , there were no material assets or liabilities measured at fair value on a nonrecurring basis. Based on our review, all prices received from external sources remained unadjusted. The following tables provide a summary of changes in fair value associated with Level 3 assets for the three months ended March 31, 2016 and 2015 : Level 3 Fair Value Three Months Ended March 31, 2016 (millions) Fair Value at December 31, 2015 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain) Loss on Sales Change in Valuation Net Transfers In (Out) Fair Value at March 31, 2016 Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 9.9 $ (0.3 ) $ 0 $ 0 $ 0 $ (0.1 ) $ 0 $ 9.5 Total fixed maturities 9.9 (0.3 ) 0 0 0 (0.1 ) 0 9.5 Equity securities: Nonredeemable preferred stocks: Financials 0 0 0 0 0 0 0 0 Common equities: Other risk investments 0.3 0 0 0 0 0 0 0.3 Total Level 3 securities $ 10.2 $ (0.3 ) $ 0 $ 0 $ 0 $ (0.1 ) $ 0 $ 9.8 Level 3 Fair Value Three Months Ended March 31, 2015 (millions) Fair Value at December 31, 2014 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain) Loss on Sales Change in Valuation Net Transfers In (Out) Fair Value at March 31, 2015 Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 11.6 $ (0.2 ) $ 0 $ 0 $ 0 $ 0 $ 0 $ 11.4 Total fixed maturities 11.6 (0.2 ) 0 0 0 0 0 11.4 Equity securities: Nonredeemable preferred stocks: Financials 1 69.3 0 0 0 0 0.6 0 69.9 Common equities: Other risk investments 0.4 0 0 0 0 (0.1 ) 0 0.3 Total Level 3 securities $ 81.3 $ (0.2 ) $ 0 $ 0 $ 0 $ 0.5 $ 0 $ 81.6 1 The $0.6 million represents net holding period gains on a hybrid security, which is reflected in net realized gains (losses) on securities in the comprehensive income statement. The following tables provide a summary of the quantitative information about Level 3 fair value measurements for our applicable securities at March 31, 2016 and 2015 , and December 31, 2015 : Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at March 31, 2016 Valuation Technique Unobservable Input Unobservable Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 9.5 External vendor Prepayment rate 1 0 % Total fixed maturities 9.5 Equity securities: Nonredeemable preferred stocks: Financials 0 NA NA NA Subtotal Level 3 securities 9.5 Pricing exemption securities 2 0.3 Total Level 3 securities $ 9.8 NA = Not applicable, since we did not hold any nonredeemable preferred stock Level 3 securities at March 31, 2016 . 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 determined with unobservable inputs not reasonably available to us. Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at March 31, 2015 Valuation Technique Unobservable Input Unobservable Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 11.4 External vendor Prepayment rate 1 0 Total fixed maturities 11.4 Equity securities: Nonredeemable preferred stocks: Financials 69.9 Multiple of tangible net book value Price to book ratio multiple 2.6 Subtotal Level 3 securities 81.3 Pricing exemption securities 2 0.3 Total Level 3 securities $ 81.6 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 determined with unobservable inputs not reasonably available to us. Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at Dec. 31, 2015 Valuation Technique Unobservable Input Unobservable 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 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 determined with unobservable inputs 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 or comprehensive income.

Debt

Debt	3 Months Ended
	Mar. 31, 2016
Debt Disclosure [Abstract]
Debt	Debt — Debt consisted of: March 31, 2016 March 31, 2015 December 31, 2015 (millions) Carrying Value Fair Value Carrying Value Fair Value Carrying Value Fair Value 3.75% Senior Notes due 2021 $ 498.2 $ 538.4 $ 497.9 $ 542.6 $ 498.1 $ 528.7 6 5/8% Senior Notes due 2029 295.8 388.7 295.6 393.6 295.7 376.0 6.25% Senior Notes due 2032 395.0 509.7 394.9 525.6 395.0 490.6 4.35% Senior Notes due 2044 346.4 377.9 346.3 387.1 346.4 352.8 3.70% Senior Notes due 2045 395.0 388.6 394.9 394.8 395.0 362.0 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 613.1 585.9 630.5 667.2 612.8 612.8 Other debt instruments 158.1 158.1 0 0 164.9 164.9 Total $ 2,701.6 $ 2,947.3 $ 2,560.1 $ 2,910.9 $ 2,707.9 $ 2,887.8 The other debt instruments reported in the table above represent ARX indebtedness and consist of: March 31, 2016 December 31, 2015 Type of debt instrument Number of Instruments Carrying Value Number of Instruments Carrying Stated Maturity Date(s) Term loans 2 $ 80.8 2 $ 87.1 December 2018 and 2019 Junior subordinated notes 1 2 41.2 2 41.2 June 2036 and 2037 Senior notes 4 24.0 4 24.0 Various 2 Surplus note 1 12.1 1 12.6 November 2021 Total $ 158.1 $ 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 trusts (discussed below). 2 The senior notes mature in May 2033, April 2034, December 2034, and June 2035. The Progressive Corporation Debt We did not repurchase any debt securities in the first quarter of 2016 or 2015. During the year ended December 31, 2015, we repurchased, in the open market, $18.4 million in aggregate principal amount of our 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 (the "6.70% Debentures"). ARX Debt (i.e., other debt instruments) The other debt instruments were issued by ARX. 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. Pursuant to agreements entered into by ARX relating to the trust preferred securities transactions, ARX established trusts that are entirely 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 at March 31, 2016 , in the variable interest entities is reported as a component of "other assets" on our consolidated balance sheets. The Progressive Corporation Line of Credit During the first quarter 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 . 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 and the sum of the Federal Funds Open Rate plus 50 basis points. Each advance would need to be repaid on the 30th day after the advance or, if earlier, on April 30, 2016, the expiration date of the Line of Credit. We had no borrowings under the Line of Credit or the prior line of credit during the first three months of 2016 or throughout 2015.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes — At March 31, 2016 and 2015, and December 31, 2015, we determined that we did not need a valuation allowance on our gross deferred tax assets. Although realization of the deferred tax assets is not assured, management believes that it is more likely than not 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. For the three months ended March 31, 2016 , there have been no material changes in our uncertain tax positions or effective tax rate.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	3 Months Ended
	Mar. 31, 2016
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information — Cash includes only bank demand deposits. We paid the following in the respective periods: Three Months Ended March 31, (millions) 2016 2015 Income taxes $ 30.0 $ 60.0 Interest 28.1 19.3

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2016
Segment Reporting [Abstract]
Segment Information	Segment Information — Our Personal Lines segment writes insurance for personal autos and recreational vehicles. 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. Our Property segment writes personal and commercial insurance for homeowners, other property owners, and renters. 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 Commercial Auto Insurance Procedures/Plans (CAIP) business and serving as an agent for property, general liability and business owners policies, 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; all intercompany transactions, including those with ASI, are eliminated in consolidation. Following are the operating results for the respective periods: Three Months Ended March 31, 2016 2015 (millions) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Personal Lines Agency $ 2,347.9 $ 171.4 $ 2,244.5 $ 194.5 Direct 2,220.7 79.5 1,955.4 68.2 Total Personal Lines 1 4,568.6 250.9 4,199.9 262.7 Commercial Lines 548.8 61.1 466.4 78.5 Property 2 200.0 (24.5 ) NA NA Other indemnity 0 (0.7 ) 0 0.4 Total underwriting operations 5,317.4 286.8 4,666.3 341.6 Fees and other revenues 3 78.9 NA 73.7 NA Service businesses 25.0 3.4 17.2 1.3 Investments 4 136.2 131.4 138.1 132.8 Interest expense NA (34.2 ) NA (32.5 ) Consolidated total $ 5,557.5 $ 387.4 $ 4,895.3 $ 443.2 NA = Not applicable 1 Personal auto insurance accounted for 92% of the total Personal Lines segment net premiums earned in both the first quarters of 2016 and 2015; 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. For the three months ended March 31, 2016, pretax loss includes $45.3 million of catastrophe losses and $15.1 million of amortization/depreciation expense associated with the acquisition of a controlling interest in ARX. Although the amortization 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 Pretax profit (loss) for fees and other revenues are allocated to operating segments. 4 Revenues represent recurring investment income and total net realized gains (losses) on securities; pretax profit is net of investment expenses. Our management uses underwriting margin and combined ratio as primary measures of underwriting profitability. Underwriting profitability is calculated by subtracting losses and loss adjustment expenses, policy acquisition costs, and other underwriting expenses from the total of net premiums earned and fees and other revenues. The underwriting margin is the pretax underwriting profit (loss) expressed as a percentage of net premiums earned (i.e., revenues from underwriting operations). Combined ratio is the complement of the underwriting margin. Following are the underwriting margins and combined ratios for our underwriting operations for the respective periods: Three Months Ended March 31, 2016 2015 Under-writing Margin Combined Ratio Under-writing Margin Combined Ratio Personal Lines Agency 7.3 % 92.7 8.7 % 91.3 Direct 3.6 96.4 3.5 96.5 Total Personal Lines 5.5 94.5 6.3 93.7 Commercial Lines 11.1 88.9 16.8 83.2 Property 1 (12.2 ) 112.2 NA NA Other indemnity 2 NM NM NM NM Total underwriting operations 5.4 94.6 7.3 92.7 NA = Not applicable; any Property business written by Progressive prior to April 1, 2015 was negligible. 1 Includes 7.6 points of amortization/depreciation expense associated with the acquisition of a controlling interest in ARX. 2 Underwriting margins and 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.

Dividends

Dividends	3 Months Ended
	Mar. 31, 2016
Text Block [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 (using a 35% tax rate) multiplied by a companywide 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 2015 , the Board determined the target percentage for 2016 to be 33-1/3 % of annual after-tax underwriting income, which is unchanged from the 2015 target percentage. 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. On a year-to-date basis, as of March 31, 2016 , the Gainshare factor was 1.30 . Since the final factor will be determined based on our results for the full year, the final factor may vary from the current factor. 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. For the three months ended March 31, 2016, our comprehensive income was $325.8 million , which is more than the $186.4 million of after-tax underwriting income for the same period. However, the ultimate decision on whether or not a dividend will be paid, and the amount of any dividend, are 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. If a dividend for 2016 were to be paid, the Board would likely declare the 2016 annual dividend in December 2016 , with a record date in early 2017 and payment shortly thereafter. Following is a summary of our shareholder dividends that were declared in the last two years: (millions, except per share amounts) Amount Dividend Type Declared Paid Per Share Total 1 Annual – Variable December 2015 February 2016 $ 0.8882 $ 519.0 Annual – Variable December 2014 February 2015 0.6862 404.1 1 Represents the final amount of dividends declared based on shares outstanding as of the record date.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2016
Equity [Abstract]
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) — The components of other comprehensive income (loss), including reclassification adjustments by income statement line item, were as follows: Components of Changes in Accumulated Other Comprehensive Income (after tax) (millions) Pretax total accumulated other comprehensive income 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 (Income)loss attributable to NCI Balance at December 31, 2015 $ 1,234.5 $ (434.1 ) $ 800.4 $ 809.0 $ (8.2 ) $ (1.5 ) $ 1.1 Other comprehensive income (loss) before reclassifications: Investment securities 142.7 (50.3 ) 92.4 92.4 0 0 0 Net non-credit related OTTI losses, adjusted for valuation changes (0.1 ) 0.1 0 0 0 0 0 Forecasted transactions 0 0 0 0 0 0 0 Foreign currency translation adjustment 0.7 (0.2 ) 0.5 0 0 0.5 0 Loss attributable to noncontrolling interest (NCI) (3.3 ) 1.2 (2.1 ) 0 0 0 (2.1 ) Total other comprehensive income (loss) before reclassifications 140.0 (49.2 ) 90.8 92.4 0 0.5 (2.1 ) Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings 0 0 0 0 0 0 0 Net realized gains (losses) on securities 35.3 (12.4 ) 22.9 22.9 0 0 0 Interest expense 0.5 (0.2 ) 0.3 0 0.3 0 0 Total reclassification adjustment for amounts realized in net income 35.8 (12.6 ) 23.2 22.9 0.3 0 0 Total other comprehensive income (loss) 104.2 (36.6 ) 67.6 69.5 (0.3 ) 0.5 (2.1 ) Balance at March 31, 2016 $ 1,338.7 $ (470.7 ) $ 868.0 $ 878.5 $ (8.5 ) $ (1.0 ) $ (1.0 ) 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 Net unrealized gains on forecasted transactions Foreign currency translation adjustment (Income)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 99.3 (34.7 ) 64.6 64.6 0 0 0 Net non-credit related OTTI losses, adjusted for valuation changes 0 0 0 0 0 0 0 Forecasted transactions (12.8 ) 4.4 (8.4 ) 0 (8.4 ) 0 0 Foreign currency translation adjustment (0.9 ) 0.4 (0.5 ) 0 0 (0.5 ) 0 Loss attributable to noncontrolling interest (NCI) 0 0 0 0 0 0 0 Total other comprehensive income (loss) before reclassifications 85.6 (29.9 ) 55.7 64.6 (8.4 ) (0.5 ) 0 Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (7.9 ) 2.8 (5.1 ) (5.1 ) 0 0 0 Net realized gains (losses) on securities 52.8 (18.5 ) 34.3 34.3 0 0 0 Interest expense 0.5 (0.2 ) 0.3 0 0.3 0 0 Total reclassification adjustment for amounts realized in net income 45.4 (15.9 ) 29.5 29.2 0.3 0 0 Total other comprehensive income (loss) 40.2 (14.0 ) 26.2 35.4 (8.7 ) (0.5 ) 0 Balance at March 31, 2015 $ 1,614.2 $ (564.9 ) $ 1,049.3 $ 1,057.3 $ (7.2 ) $ (0.8 ) $ 0 In an effort to manage interest rate risk, we entered into forecasted transactions on each of our 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.

Litigation

Litigation	3 Months Ended
	Mar. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Litigation	Litigation — The Progressive Corporation and/or its insurance subsidiaries are named as defendants in various lawsuits arising out of claims made under insurance policies written by our insurance subsidiaries in the ordinary course of business. We consider all legal actions relating to such claims in establishing our loss and loss adjustment expense reserves. In addition, The Progressive Corporation and/or its insurance subsidiaries are named as defendants in a number of class action or individual lawsuits arising out of the operations of the insurance subsidiaries. These cases include those alleging damages as a result of our subsidiaries’ practices in evaluating or paying medical or injury claims or benefits, including, but not limited to, personal injury protection, medical payments, and bodily injury benefits; the utilization, content, or appearance of policy documents; labor rates paid to auto body repair shops; wage and hour issues; and cases challenging other aspects of our subsidiaries’ claims or marketing practices or other business operations. Other insurance companies face many of these same issues. We plan to contest the pending lawsuits 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 these 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. 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. With respect to our pending lawsuits that are not related to claims under insurance policies, the accruals that we have established were not material at March 31, 2016. With respect to most of these lawsuits, we do not consider any losses to be both probable and estimable, and we are unable to estimate a meaningful range of loss, if any, at this time, due to the factors discussed in Note 12 - Litigation in our 2015 Annual Report to Shareholders. In the event that any one or more of these lawsuits results in a substantial judgment against, or settlement by, Progressive, or if our accruals prove to be inadequate by a significant amount, the resulting liability could have a material adverse effect on our consolidated financial condition, cash flows, and/or results of operations. For a further discussion on our pending litigation and related reserving policies, see Note 12 - Litigation in our 2015 Annual Report to Shareholders.

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interest (Notes)	3 Months Ended
	Mar. 31, 2016
Temporary Equity Disclosure [Abstract]
Redeemable Noncontrolling Interest	Redeemable Noncontrolling Interest - In connection with the acquisition of a controlling interest in ARX, in the second quarter of 2015, The Progressive Corporation entered into a stockholders’ agreement with the other ARX stockholders. As part of the stockholders’ agreement, the minority ARX shareholders have the right to “put” their ARX shares to Progressive in two installments, one in early 2018 and one in early 2021, and Progressive has the ability to "call" a portion of the outstanding shares at the same times. 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. Since these securities are redeemable upon the occurrence of an event that is not solely within the control of Progressive, we have recorded the redeemable noncontrolling interest as mezzanine equity on our consolidated balance sheets, which represents the minority shares at the current estimated purchase price pursuant to the put and call provisions of the stockholders' agreement. No redeemable noncontrolling interest (NCI) existed at March 31, 2015. The components of redeemable NCI at March 31, 2016, were: ($ in millions) Balance at December 31, 2015 $ 464.9 Net income attributable to NCI 0.5 Other comprehensive income attributable to NCI 2.1 Purchase of shares from NCI 0 Change in redemption value of NCI (0.1 ) Balance at March 31, 2016 $ 467.4

Acquisition (Notes)

Acquisition (Notes)	3 Months Ended
	Mar. 31, 2016
Business Combinations [Abstract]
Acquisition	Acquisition — On April 1, 2015, and subsequently during 2015, The Progressive Corporation acquired capital stock of ARX, the parent company of ASI, primarily from non-management shareholders at a total cost of $890.1 million . At March 31, 2016, Progressive's total ownership interest in ARX was 69.2% . As part of the acquisition, we recorded other intangible assets. The following table reports the intangible assets by asset category as of March 31, 2016: ($ in millions) Date of Acquisition March 31, 2016 Category Value Useful Life Accumulated Amortization Remaining Useful Life Policies in force $ 256.2 7 years $ 36.6 6 years Agency relationships 159.2 14 years 11.4 13 years Software 69.1 8 years 8.6 7 years Trade name 34.8 10 years 3.5 9 years Agent licenses 1.1 Indefinite 0 Indefinite Total $ 520.4 $ 60.1 During the first quarter 2016, we recognized $15.0 million of amortization. As of March 31, 2016, goodwill associated with the acquisition was $446.0 million . No goodwill impairment charges were recognized during the first quarter 2016. Additionally, there were no triggering events during the first quarter 2016 that would have required a change to the carrying amount of goodwill.

New Accounting Standards (Notes

New Accounting Standards (Notes)	3 Months Ended
	Mar. 31, 2016
Accounting Policies [Abstract]
New Accounting Standards	New Accounting Standards Issued In March 2016, the Financial Accounting Standards Board (FASB) issued an accounting standard update (ASU) to simplify the accounting for employee share-based payment transactions. This ASU is effective for fiscal years beginning after December 15, 2016 (2017 for calendar-year companies), with early adoption permitted. Several aspects of the ASU include income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. Under provisions of the ASU: • All excess tax benefits and tax deficiencies should be recognized as income tax expense or benefit in the comprehensive income statement (applied prospectively) and classified in the statement of cash flows as an operating activity (applied using either a prospective or retrospective transition method) • Companies are allowed to decide whether or not to record forfeitures of share-based awards when the forfeiture occurs or to record compensation expense over the vesting period net of estimated forfeitures (applied using a modified retrospective transition method by means of a cumulative-effect adjustment to equity upon adoption) • Companies are permitted to withhold up to the maximum statutory tax rate and still maintain equity classification of share-based awards (applied using a modified retrospective transition method by means of a cumulative-effect adjustment to equity upon adoption) • Companies are required to classify as a financing activity in the statement of cash flows the payment of cash to a taxing authority when the company withholds shares for such purpose (applied retrospectively) We are currently evaluating the impact that this standard will have on our financial condition, cash flows, and results of operations, however, we only expect the change in the accounting for the excess tax benefits/deficiencies to impact our results of operations. Over the last three years, the tax benefit, which is currently being recorded in paid in capital, was $16.8 million in 2015, $12.8 million in 2014, and $10.3 million in 2013. We currently record estimated forfeitures over the vesting period and withhold at the minimum statutory tax rate, and we do not anticipate making any changes upon adoption of the ASU. Adopted In January 2016, we adopted ASU 2015-05, "Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement," which clarifies guidance around accounting for fees paid in a cloud computing arrangement and amended the accounting treatment for the acquisition of licenses from third-parties for internal use software. Progressive adopted this ASU on a prospective basis and will apply the guidance for future cloud computing arrangements that we enter into. Upon adoption, we began including the costs of our fixed-term licenses as part of the total amount of capitalized software developed or acquired for internal use, rather than recording them as prepaid assets, when applicable. We do not expect this standard will have a material impact on our results of operations.

Reclassification (Notes)

Reclassification (Notes)	3 Months Ended
	Mar. 31, 2016
Accounting Changes and Error Corrections [Abstract]
Reclassification	Reclassification — For the period ended March 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 (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2016
Investments Schedule [Abstract]
Investment Portfolio by Major Security Type	The following tables present the composition of our investment portfolio by major security type, consistent with our classification of how we manage, monitor, and measure the portfolio. The net holding period gains (losses) represent the amounts realized on our hybrid securities only. ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) 1 Fair Value % of Value March 31, 2016 Fixed maturities: U.S. government obligations $ 1,375.8 $ 12.2 $ 0 $ 0 $ 1,388.0 6.5 % State and local government obligations 2,452.0 57.4 (1.2 ) 0 2,508.2 11.8 Foreign government obligations 21.9 0 0 0 21.9 0.1 Corporate debt securities 3,795.2 50.6 (6.2 ) 0.4 3,840.0 18.0 Residential mortgage-backed securities 1,810.9 19.5 (28.5 ) (0.4 ) 1,801.5 8.4 Agency residential pass-through obligations 46.5 0.2 (0.1 ) 0 46.6 0.2 Commercial mortgage-backed securities 2,418.7 26.4 (18.9 ) 0 2,426.2 11.4 Other asset-backed securities 1,706.3 1.3 (4.2 ) 0.3 1,703.7 8.0 Redeemable preferred stocks 265.0 14.2 (48.9 ) 0 230.3 1.1 Total fixed maturities 13,892.3 181.8 (108.0 ) 0.3 13,966.4 65.5 Equity securities: Nonredeemable preferred stocks 731.9 124.7 (24.4 ) 0 832.2 3.9 Common equities 1,524.0 1,186.7 (5.7 ) 0 2,705.0 12.7 Short-term investments 3,826.9 0 0 0 3,826.9 17.9 Total portfolio 2,3 $ 19,975.1 $ 1,493.2 $ (138.1 ) $ 0.3 $ 21,330.5 100.0 % ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) 1 Fair Value % of Value March 31, 2015 Fixed maturities: U.S. government obligations $ 2,678.1 $ 30.1 $ 0 $ 0 $ 2,708.2 13.7 % State and local government obligations 2,224.8 50.0 (1.0 ) 0 2,273.8 11.5 Foreign government obligations 20.0 0 0 0 20.0 0.1 Corporate debt securities 2,851.6 54.4 (3.8 ) 1.8 2,904.0 14.6 Residential mortgage-backed securities 1,629.2 32.4 (13.1 ) (0.3 ) 1,648.2 8.3 Agency residential pass-through obligations 0 0 0 0 0 0 Commercial mortgage-backed securities 2,437.4 50.1 (1.1 ) 0.7 2,487.1 12.5 Other asset-backed securities 1,896.1 4.9 (0.3 ) 0.8 1,901.5 9.6 Redeemable preferred stocks 260.3 23.3 (6.6 ) 0 277.0 1.4 Total fixed maturities 13,997.5 245.2 (25.9 ) 3.0 14,219.8 71.7 Equity securities: Nonredeemable preferred stocks 598.3 192.5 (5.9 ) 43.2 828.1 4.2 Common equities 1,295.0 1,226.7 (6.0 ) 0 2,515.7 12.7 Short-term investments 2,267.0 0 0 0 2,267.0 11.4 Total portfolio 2,3 $ 18,157.8 $ 1,664.4 $ (37.8 ) $ 46.2 $ 19,830.6 100.0 % ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) 1 Fair Value % of 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 % 1 Represents net holding period gains (losses) realized on certain hybrid securities (discussed below). 2 Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at March 31, 2016 , $47.3 million was included in "other liabilities," compared to $95.8 million in "other liabilities" at March 31, 2015 and $23.1 million in "other assets" at December 31, 2015 . 3 The total fair value of the portfolio at March 31, 2016 and 2015 , and December 31, 2015 included $0.7 billion , $1.7 billion , and $1.3 billion , respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.
Hybrid Securities	Included in our fixed-maturity and equity securities are hybrid securities, which are reported at fair value: March 31, December 31, (millions) 2016 2015 Fixed maturities: Corporate debt securities $ 39.2 $ 132.9 $ 49.1 Residential mortgage-backed securities 174.4 111.7 144.3 Commercial mortgage-backed securities 0 18.0 17.3 Other asset-backed securities 10.6 13.1 11.3 Total fixed maturities 224.2 275.7 222.0 Equity securities: Nonredeemable preferred stocks 49.5 137.2 50.7 Total hybrid securities $ 273.7 $ 412.9 $ 272.7
Composition of Fixed Maturities by Maturity	The composition of fixed maturities by maturity at March 31, 2016 , was: (millions) Cost Fair Value Less than one year $ 3,604.9 $ 3,596.3 One to five years 7,016.5 7,030.3 Five to ten years 3,195.6 3,259.6 Ten years or greater 75.3 80.2 Total $ 13,892.3 $ 13,966.4
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 Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Unrealized Losses No. of Sec. Fair Unrealized Losses March 31, 2016 Fixed maturities: U.S. government obligations 5 $ 74.9 $ 0 5 $ 74.9 $ 0 0 $ 0 $ 0 State and local government obligations 112 267.8 (1.2 ) 63 132.8 (0.3 ) 49 135.0 (0.9 ) Corporate debt securities 60 672.3 (6.2 ) 21 169.2 (0.4 ) 39 503.1 (5.8 ) Residential mortgage-backed securities 157 1,345.1 (28.5 ) 52 426.9 (3.9 ) 105 918.2 (24.6 ) Agency residential pass-through obligations 25 9.1 (0.1 ) 3 0.4 0 22 8.7 (0.1 ) Commercial mortgage-backed securities 130 1,185.4 (18.9 ) 49 395.4 (2.2 ) 81 790.0 (16.7 ) Other asset-backed securities 86 1,175.2 (4.2 ) 70 999.3 (3.2 ) 16 175.9 (1.0 ) Redeemable preferred stocks 9 198.8 (48.9 ) 4 88.0 (16.1 ) 5 110.8 (32.8 ) Total fixed maturities 584 4,928.6 (108.0 ) 267 2,286.9 (26.1 ) 317 2,641.7 (81.9 ) Equity securities: Nonredeemable preferred stocks 13 344.4 (24.4 ) 4 79.0 (2.6 ) 9 265.4 (21.8 ) Common equities 73 87.4 (5.7 ) 67 84.3 (5.5 ) 6 3.1 (0.2 ) Total equity securities 86 431.8 (30.1 ) 71 163.3 (8.1 ) 15 268.5 (22.0 ) Total portfolio 670 $ 5,360.4 $ (138.1 ) 338 $ 2,450.2 $ (34.2 ) 332 $ 2,910.2 $ (103.9 ) Total No. of Sec. Total Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Unrealized Losses No. of Sec. Fair Unrealized Losses March 31, 2015 Fixed maturities: U.S. government obligations 1 $ 7.2 $ 0 1 $ 7.2 $ 0 0 $ 0 $ 0 State and local government obligations 57 270.3 (1.0 ) 42 231.8 (0.5 ) 15 38.5 (0.5 ) Corporate debt securities 25 390.3 (3.8 ) 17 242.4 (2.3 ) 8 147.9 (1.5 ) Residential mortgage-backed securities 80 1,013.9 (13.1 ) 34 540.6 (3.1 ) 46 473.3 (10.0 ) Agency residential pass-through obligations 0 0 0 0 0 0 0 0 0 Commercial mortgage-backed securities 59 564.2 (1.1 ) 53 560.8 (1.0 ) 6 3.4 (0.1 ) Other asset-backed securities 30 490.9 (0.3 ) 29 472.4 (0.1 ) 1 18.5 (0.2 ) Redeemable preferred stocks 3 102.1 (6.6 ) 1 33.0 (1.0 ) 2 69.1 (5.6 ) Total fixed maturities 255 2,838.9 (25.9 ) 177 2,088.2 (8.0 ) 78 750.7 (17.9 ) Equity securities: Nonredeemable preferred stocks 5 183.1 (5.9 ) 2 74.5 (2.2 ) 3 108.6 (3.7 ) Common equities 40 58.3 (6.0 ) 40 58.3 (6.0 ) 0 0 0 Total equity securities 45 241.4 (11.9 ) 42 132.8 (8.2 ) 3 108.6 (3.7 ) Total portfolio 300 $ 3,080.3 $ (37.8 ) 219 $ 2,221.0 $ (16.2 ) 81 $ 859.3 $ (21.6 ) Total No. of Sec. Total Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Unrealized Losses No. of Sec. Fair Unrealized Losses December 31, 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 Non-Credit Portion of Other-Than-Temporary Impairment Recorded in Accumulated Other Comprehensive Income, Reflecting Original 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: March 31, December 31, (millions) 2016 2015 Fixed maturities: Residential mortgage-backed securities $ (43.3 ) $ (44.1 ) $ (43.3 ) Commercial mortgage-backed securities (0.6 ) (0.6 ) (0.6 ) Total fixed maturities $ (43.9 ) $ (44.7 ) $ (43.9 )
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 March 31, 2016 and 2015 , for which a portion of the OTTI losses were also recognized in accumulated other comprehensive income at the time the credit impairments were determined and recognized: Three Months Ended March 31, 2016 Mortgage-Backed (millions) Residential Commercial Total Balance at December 31, 2015 $ 12.4 $ 0.4 $ 12.8 Change in recoveries of future cash flows expected to be collected 1 (0.3 ) 0 (0.3 ) Balance at March 31, 2016 $ 12.1 $ 0.4 $ 12.5 Three Months Ended March 31, 2015 Mortgage-Backed (millions) Residential Commercial Total Balance at December 31, 2014 $ 12.7 $ 0.4 $ 13.1 Change in recoveries of future cash flows expected to be collected 1 (0.5 ) 0 (0.5 ) Balance at March 31, 2015 $ 12.2 $ 0.4 $ 12.6 1 Reflects the current period change in the expected recovery of prior impairments that will be accreted into income over the remaining life of the security.
Components of Net Realized Gains (Losses)	The components of net realized gains (losses) for the three months ended March 31, were: Three Months (millions) 2016 2015 Gross realized gains on security sales Fixed maturities: U.S. government obligations $ 14.3 $ 4.9 State and local government obligations 10.9 0 Corporate and other debt securities 12.5 9.1 Residential mortgage-backed securities 0.9 0.1 Commercial mortgage-backed securities 3.6 10.8 Total fixed maturities 42.2 24.9 Equity securities: Nonredeemable preferred stocks 1.6 15.8 Common equities 9.5 17.8 Subtotal gross realized gains on security sales 53.3 58.5 Gross realized losses on security sales Fixed maturities: U.S. government obligations (0.4 ) (0.8 ) State and local government obligations (0.1 ) 0 Corporate and other debt securities (0.4 ) (0.8 ) Commercial mortgage-backed securities (2.7 ) (0.2 ) Total fixed maturities (3.6 ) (1.8 ) Equity securities: Nonredeemable preferred stocks (1.0 ) 0 Common equities (4.9 ) (0.4 ) Subtotal gross realized losses on security sales (9.5 ) (2.2 ) Net realized gains (losses) on security sales Fixed maturities: U.S. government obligations 13.9 4.1 State and local government obligations 10.8 0 Corporate and other debt securities 12.1 8.3 Residential mortgage-backed securities 0.9 0.1 Commercial mortgage-backed securities 0.9 10.6 Total fixed maturities 38.6 23.1 Equity securities: Nonredeemable preferred stocks 0.6 15.8 Common equities 4.6 17.4 Subtotal net realized gains (losses) on security sales 43.8 56.3 Other-than-temporary impairment losses Equity securities: Common equities 0 (7.9 ) Subtotal other-than-temporary impairment losses 0 (7.9 ) Other gains (losses) Hybrid securities (0.7 ) 3.3 Derivative instruments (25.7 ) (18.8 ) Litigation settlements 0 0.1 Subtotal other gains (losses) (26.4 ) (15.4 ) Total net realized gains (losses) on securities $ 17.4 $ 33.0
Components of Net Investment Income	The components of net investment income for the three months ended March 31, were: Three Months (millions) 2016 2015 Fixed maturities: U.S. government obligations $ 4.8 $ 9.1 State and local government obligations 13.5 11.9 Foreign government obligations 0.1 0.1 Corporate debt securities 28.2 22.9 Residential mortgage-backed securities 12.2 12.8 Agency residential pass-through obligations 0.4 0 Commercial mortgage-backed securities 20.9 16.9 Other asset-backed securities 6.0 5.0 Redeemable preferred stocks 3.8 3.8 Total fixed maturities 89.9 82.5 Equity securities: Nonredeemable preferred stocks 11.8 10.5 Common equities 14.5 11.7 Short-term investments 2.6 0.4 Investment income 118.8 105.1 Investment expenses (4.8 ) (5.3 ) Net investment income $ 114.0 $ 99.8
Derivative Instruments	The following table shows the status of our derivative instruments at March 31, 2016 and 2015 , and December 31, 2015 , and for the three months ended March 31, 2016 and 2015 : (millions) Balance Sheet 2 Comprehensive Income Statement Assets (Liabilities) Pretax Net Realized Gains (Losses) Notional Value 1 Three Months Ended March 31, Dec. 31, March 31, Dec. 31, March 31, Derivatives designated as: 2016 2015 2015 Purpose Classification 2016 2015 2015 2016 2015 Hedging instruments Closed: Ineffective cash flow hedge $ 0 $ 0 $ 18 Manage interest rate risk NA $ 0 $ 0 $ 0 $ 0 $ 0 Non-hedging instruments Assets: Interest rate swaps 0 750 750 Manage portfolio duration Investments— fixed maturities 0 0.1 4.4 0 (18.8 ) Liabilities: Interest rate swaps 565 0 0 Manage portfolio duration Other liabilities (18.7 ) 0 0 (24.0 ) 0 Closed: Interest rate swaps 185 0 0 Manage portfolio duration NA 0 0 0 (1.9 ) 0 U.S. Treasury Note futures 55 0 691 Manage NA 0 0 0 0.2 0 Total NA NA NA $ (18.7 ) $ 0.1 $ 4.4 $ (25.7 ) $ (18.8 ) NA= Not applicable 1 The amounts represent the value held at quarter and year end for open positions and the maximum amount held during the period 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.

Fair Value (Tables)

Fair Value (Tables)	3 Months Ended
	Mar. 31, 2016
Fair Value Disclosures [Abstract]
Composition of Investment Portfolio by Major Security Type	The composition of the investment portfolio by major security type and our outstanding debt was: Fair Value (millions) Level 1 Level 2 Level 3 Total Cost March 31, 2016 Fixed maturities: U.S. government obligations $ 1,388.0 $ 0 $ 0 $ 1,388.0 $ 1,375.8 State and local government obligations 0 2,508.2 0 2,508.2 2,452.0 Foreign government obligations 21.9 0 0 21.9 21.9 Corporate debt securities 0 3,840.0 0 3,840.0 3,795.2 Subtotal 1,409.9 6,348.2 0 7,758.1 7,644.9 Asset-backed securities: Residential mortgage-backed 0 1,801.5 0 1,801.5 1,810.9 Agency residential pass-through obligations 0 46.6 0 46.6 46.5 Commercial mortgage-backed 0 2,416.7 9.5 2,426.2 2,418.7 Other asset-backed 0 1,703.7 0 1,703.7 1,706.3 Subtotal asset-backed securities 0 5,968.5 9.5 5,978.0 5,982.4 Redeemable preferred stocks: Financials 0 91.7 0 91.7 81.8 Utilities 0 51.6 0 51.6 65.1 Industrials 0 87.0 0 87.0 118.1 Subtotal redeemable preferred stocks 0 230.3 0 230.3 265.0 Total fixed maturities 1,409.9 12,547.0 9.5 13,966.4 13,892.3 Equity securities: Nonredeemable preferred stocks: Financials 153.8 678.4 0 832.2 731.9 Subtotal nonredeemable preferred stocks 153.8 678.4 0 832.2 731.9 Common equities: Common stocks 2,704.7 0 0 2,704.7 1,523.7 Other risk investments 0 0 0.3 0.3 0.3 Subtotal common equities 2,704.7 0 0.3 2,705.0 1,524.0 Total fixed maturities and equity securities 4,268.4 13,225.4 9.8 17,503.6 16,148.2 Short-term investments 3,730.0 96.9 0 3,826.9 3,826.9 Total portfolio $ 7,998.4 $ 13,322.3 $ 9.8 $ 21,330.5 $ 19,975.1 Debt $ 0 $ 2,789.2 $ 158.1 $ 2,947.3 $ 2,701.6 Fair Value (millions) Level 1 Level 2 Level 3 Total Cost March 31, 2015 Fixed maturities: U.S. government obligations $ 2,708.2 $ 0 $ 0 $ 2,708.2 $ 2,678.1 State and local government obligations 0 2,273.8 0 2,273.8 2,224.8 Foreign government obligations 20.0 0 0 20.0 20.0 Corporate debt securities 0 2,904.0 0 2,904.0 2,851.6 Subtotal 2,728.2 5,177.8 0 7,906.0 7,774.5 Asset-backed securities: Residential mortgage-backed 0 1,648.2 0 1,648.2 1,629.2 Agency residential pass-through obligations 0 0 0 0 0 Commercial mortgage-backed 0 2,475.7 11.4 2,487.1 2,437.4 Other asset-backed 0 1,901.5 0 1,901.5 1,896.1 Subtotal asset-backed securities 0 6,025.4 11.4 6,036.8 5,962.7 Redeemable preferred stocks: Financials 0 98.2 0 98.2 77.3 Utilities 0 64.4 0 64.4 65.0 Industrials 0 114.4 0 114.4 118.0 Subtotal redeemable preferred stocks 0 277.0 0 277.0 260.3 Total fixed maturities 2,728.2 11,480.2 11.4 14,219.8 13,997.5 Equity securities: Nonredeemable preferred stocks: Financials 181.7 576.5 69.9 828.1 598.3 Subtotal nonredeemable preferred stocks 181.7 576.5 69.9 828.1 598.3 Common equities: Common stocks 2,515.4 0 0 2,515.4 1,294.7 Other risk investments 0 0 0.3 0.3 0.3 Subtotal common equities 2,515.4 0 0.3 2,515.7 1,295.0 Total fixed maturities and equity securities 5,425.3 12,056.7 81.6 17,563.6 15,890.8 Short-term investments 2,267.0 0 0 2,267.0 2,267.0 Total portfolio $ 7,692.3 $ 12,056.7 $ 81.6 $ 19,830.6 $ 18,157.8 Debt $ 0 $ 2,910.9 $ 0 $ 2,910.9 $ 2,560.1 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
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 three months ended March 31, 2016 and 2015 : Level 3 Fair Value Three Months Ended March 31, 2016 (millions) Fair Value at December 31, 2015 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain) Loss on Sales Change in Valuation Net Transfers In (Out) Fair Value at March 31, 2016 Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 9.9 $ (0.3 ) $ 0 $ 0 $ 0 $ (0.1 ) $ 0 $ 9.5 Total fixed maturities 9.9 (0.3 ) 0 0 0 (0.1 ) 0 9.5 Equity securities: Nonredeemable preferred stocks: Financials 0 0 0 0 0 0 0 0 Common equities: Other risk investments 0.3 0 0 0 0 0 0 0.3 Total Level 3 securities $ 10.2 $ (0.3 ) $ 0 $ 0 $ 0 $ (0.1 ) $ 0 $ 9.8 Level 3 Fair Value Three Months Ended March 31, 2015 (millions) Fair Value at December 31, 2014 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain) Loss on Sales Change in Valuation Net Transfers In (Out) Fair Value at March 31, 2015 Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 11.6 $ (0.2 ) $ 0 $ 0 $ 0 $ 0 $ 0 $ 11.4 Total fixed maturities 11.6 (0.2 ) 0 0 0 0 0 11.4 Equity securities: Nonredeemable preferred stocks: Financials 1 69.3 0 0 0 0 0.6 0 69.9 Common equities: Other risk investments 0.4 0 0 0 0 (0.1 ) 0 0.3 Total Level 3 securities $ 81.3 $ (0.2 ) $ 0 $ 0 $ 0 $ 0.5 $ 0 $ 81.6 1 The $0.6 million represents net holding period gains on a hybrid security, which is reflected in net realized gains (losses) on securities in the comprehensive income statement.
Summary of Quantitative Information about Level 3 Fair Value Measurements	The following tables provide a summary of the quantitative information about Level 3 fair value measurements for our applicable securities at March 31, 2016 and 2015 , and December 31, 2015 : Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at March 31, 2016 Valuation Technique Unobservable Input Unobservable Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 9.5 External vendor Prepayment rate 1 0 % Total fixed maturities 9.5 Equity securities: Nonredeemable preferred stocks: Financials 0 NA NA NA Subtotal Level 3 securities 9.5 Pricing exemption securities 2 0.3 Total Level 3 securities $ 9.8 NA = Not applicable, since we did not hold any nonredeemable preferred stock Level 3 securities at March 31, 2016 . 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 determined with unobservable inputs not reasonably available to us. Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at March 31, 2015 Valuation Technique Unobservable Input Unobservable Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 11.4 External vendor Prepayment rate 1 0 Total fixed maturities 11.4 Equity securities: Nonredeemable preferred stocks: Financials 69.9 Multiple of tangible net book value Price to book ratio multiple 2.6 Subtotal Level 3 securities 81.3 Pricing exemption securities 2 0.3 Total Level 3 securities $ 81.6 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 determined with unobservable inputs not reasonably available to us. Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at Dec. 31, 2015 Valuation Technique Unobservable Input Unobservable 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 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 determined with unobservable inputs not reasonably available to us.

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2016
Debt Disclosure [Abstract]
Debt Table	Debt consisted of: March 31, 2016 March 31, 2015 December 31, 2015 (millions) Carrying Value Fair Value Carrying Value Fair Value Carrying Value Fair Value 3.75% Senior Notes due 2021 $ 498.2 $ 538.4 $ 497.9 $ 542.6 $ 498.1 $ 528.7 6 5/8% Senior Notes due 2029 295.8 388.7 295.6 393.6 295.7 376.0 6.25% Senior Notes due 2032 395.0 509.7 394.9 525.6 395.0 490.6 4.35% Senior Notes due 2044 346.4 377.9 346.3 387.1 346.4 352.8 3.70% Senior Notes due 2045 395.0 388.6 394.9 394.8 395.0 362.0 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 613.1 585.9 630.5 667.2 612.8 612.8 Other debt instruments 158.1 158.1 0 0 164.9 164.9 Total $ 2,701.6 $ 2,947.3 $ 2,560.1 $ 2,910.9 $ 2,707.9 $ 2,887.8
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: March 31, 2016 December 31, 2015 Type of debt instrument Number of Instruments Carrying Value Number of Instruments Carrying Stated Maturity Date(s) Term loans 2 $ 80.8 2 $ 87.1 December 2018 and 2019 Junior subordinated notes 1 2 41.2 2 41.2 June 2036 and 2037 Senior notes 4 24.0 4 24.0 Various 2 Surplus note 1 12.1 1 12.6 November 2021 Total $ 158.1 $ 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 trusts (discussed below). 2 The senior notes mature in May 2033, April 2034, December 2034, and June 2035.

Supplemental Cash Flow Inform24

Supplemental Cash Flow Information (Tables)	3 Months Ended
	Mar. 31, 2016
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information Table	Cash includes only bank demand deposits. We paid the following in the respective periods: Three Months Ended March 31, (millions) 2016 2015 Income taxes $ 30.0 $ 60.0 Interest 28.1 19.3

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2016
Segment Reporting [Abstract]
Reconciliation of Revenue and operating Income from Segments to Consolidated	Following are the operating results for the respective periods: Three Months Ended March 31, 2016 2015 (millions) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Personal Lines Agency $ 2,347.9 $ 171.4 $ 2,244.5 $ 194.5 Direct 2,220.7 79.5 1,955.4 68.2 Total Personal Lines 1 4,568.6 250.9 4,199.9 262.7 Commercial Lines 548.8 61.1 466.4 78.5 Property 2 200.0 (24.5 ) NA NA Other indemnity 0 (0.7 ) 0 0.4 Total underwriting operations 5,317.4 286.8 4,666.3 341.6 Fees and other revenues 3 78.9 NA 73.7 NA Service businesses 25.0 3.4 17.2 1.3 Investments 4 136.2 131.4 138.1 132.8 Interest expense NA (34.2 ) NA (32.5 ) Consolidated total $ 5,557.5 $ 387.4 $ 4,895.3 $ 443.2 NA = Not applicable 1 Personal auto insurance accounted for 92% of the total Personal Lines segment net premiums earned in both the first quarters of 2016 and 2015; 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. For the three months ended March 31, 2016, pretax loss includes $45.3 million of catastrophe losses and $15.1 million of amortization/depreciation expense associated with the acquisition of a controlling interest in ARX. Although the amortization 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 Pretax profit (loss) for fees and other revenues are allocated to operating segments. 4 Revenues represent recurring investment income and total net realized gains (losses) on securities; pretax profit is net of investment expenses.
Underwriting Margins and Combined Ratios for our Underwriting Operations	Following are the underwriting margins and combined ratios for our underwriting operations for the respective periods: Three Months Ended March 31, 2016 2015 Under-writing Margin Combined Ratio Under-writing Margin Combined Ratio Personal Lines Agency 7.3 % 92.7 8.7 % 91.3 Direct 3.6 96.4 3.5 96.5 Total Personal Lines 5.5 94.5 6.3 93.7 Commercial Lines 11.1 88.9 16.8 83.2 Property 1 (12.2 ) 112.2 NA NA Other indemnity 2 NM NM NM NM Total underwriting operations 5.4 94.6 7.3 92.7 NA = Not applicable; any Property business written by Progressive prior to April 1, 2015 was negligible. 1 Includes 7.6 points of amortization/depreciation expense associated with the acquisition of a controlling interest in ARX. 2 Underwriting margins and 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.

Dividends Dividends (Tables)

Dividends Dividends (Tables)	3 Months Ended
	Mar. 31, 2016
Dividends [Abstract]
Dividends	Following is a summary of our shareholder dividends that were declared in the last two years: (millions, except per share amounts) Amount Dividend Type Declared Paid Per Share Total 1 Annual – Variable December 2015 February 2016 $ 0.8882 $ 519.0 Annual – Variable December 2014 February 2015 0.6862 404.1 1 Represents the final amount of dividends declared based on shares outstanding as of the record date.

Other Comprehensive Income (L27

Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2016
Equity [Abstract]
Components of Other Comprehensive Income (Loss)	The components of other comprehensive income (loss), including reclassification adjustments by income statement line item, were as follows: Components of Changes in Accumulated Other Comprehensive Income (after tax) (millions) Pretax total accumulated other comprehensive income 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 (Income)loss attributable to NCI Balance at December 31, 2015 $ 1,234.5 $ (434.1 ) $ 800.4 $ 809.0 $ (8.2 ) $ (1.5 ) $ 1.1 Other comprehensive income (loss) before reclassifications: Investment securities 142.7 (50.3 ) 92.4 92.4 0 0 0 Net non-credit related OTTI losses, adjusted for valuation changes (0.1 ) 0.1 0 0 0 0 0 Forecasted transactions 0 0 0 0 0 0 0 Foreign currency translation adjustment 0.7 (0.2 ) 0.5 0 0 0.5 0 Loss attributable to noncontrolling interest (NCI) (3.3 ) 1.2 (2.1 ) 0 0 0 (2.1 ) Total other comprehensive income (loss) before reclassifications 140.0 (49.2 ) 90.8 92.4 0 0.5 (2.1 ) Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings 0 0 0 0 0 0 0 Net realized gains (losses) on securities 35.3 (12.4 ) 22.9 22.9 0 0 0 Interest expense 0.5 (0.2 ) 0.3 0 0.3 0 0 Total reclassification adjustment for amounts realized in net income 35.8 (12.6 ) 23.2 22.9 0.3 0 0 Total other comprehensive income (loss) 104.2 (36.6 ) 67.6 69.5 (0.3 ) 0.5 (2.1 ) Balance at March 31, 2016 $ 1,338.7 $ (470.7 ) $ 868.0 $ 878.5 $ (8.5 ) $ (1.0 ) $ (1.0 ) 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 Net unrealized gains on forecasted transactions Foreign currency translation adjustment (Income)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 99.3 (34.7 ) 64.6 64.6 0 0 0 Net non-credit related OTTI losses, adjusted for valuation changes 0 0 0 0 0 0 0 Forecasted transactions (12.8 ) 4.4 (8.4 ) 0 (8.4 ) 0 0 Foreign currency translation adjustment (0.9 ) 0.4 (0.5 ) 0 0 (0.5 ) 0 Loss attributable to noncontrolling interest (NCI) 0 0 0 0 0 0 0 Total other comprehensive income (loss) before reclassifications 85.6 (29.9 ) 55.7 64.6 (8.4 ) (0.5 ) 0 Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (7.9 ) 2.8 (5.1 ) (5.1 ) 0 0 0 Net realized gains (losses) on securities 52.8 (18.5 ) 34.3 34.3 0 0 0 Interest expense 0.5 (0.2 ) 0.3 0 0.3 0 0 Total reclassification adjustment for amounts realized in net income 45.4 (15.9 ) 29.5 29.2 0.3 0 0 Total other comprehensive income (loss) 40.2 (14.0 ) 26.2 35.4 (8.7 ) (0.5 ) 0 Balance at March 31, 2015 $ 1,614.2 $ (564.9 ) $ 1,049.3 $ 1,057.3 $ (7.2 ) $ (0.8 ) $ 0

Redeemable Noncontrolling Int28

Redeemable Noncontrolling Interest (Tables)	3 Months Ended
	Mar. 31, 2016
Temporary Equity Disclosure [Abstract]
Redeemable Noncontrolling Interest	The components of redeemable NCI at March 31, 2016, were: ($ in millions) Balance at December 31, 2015 $ 464.9 Net income attributable to NCI 0.5 Other comprehensive income attributable to NCI 2.1 Purchase of shares from NCI 0 Change in redemption value of NCI (0.1 ) Balance at March 31, 2016 $ 467.4

Acquisition (Tables)

Acquisition (Tables)	3 Months Ended
	Mar. 31, 2016
Business Combinations [Abstract]
Intangible Assets Acquired in Acquisition	The following table reports the intangible assets by asset category as of March 31, 2016: ($ in millions) Date of Acquisition March 31, 2016 Category Value Useful Life Accumulated Amortization Remaining Useful Life Policies in force $ 256.2 7 years $ 36.6 6 years Agency relationships 159.2 14 years 11.4 13 years Software 69.1 8 years 8.6 7 years Trade name 34.8 10 years 3.5 9 years Agent licenses 1.1 Indefinite 0 Indefinite Total $ 520.4 $ 60.1

Basis of Presentation Basis of

Basis of Presentation Basis of Presentation-Additional Information (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Disposal Group, Including Discontinued Operation, Assets, Current [Abstract]
Assets Held-for-sale, Property, Plant and Equipment	$ 8.7	$ 8.7	$ 8.7

Basis of Presentation Business

Basis of Presentation Business Acquisition (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Business Acquisition [Line Items]
Assets Held-for-sale, Property, Plant and Equipment	$ 8.7	$ 8.7	$ 8.7
ARX Holding Corp. [Member]
Business Acquisition [Line Items]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage	69.20%

Investments Investment Portfoli

Investments Investment Portfolio by Major Security Type (Detail) - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Cost	[1],[2]	$ 19,975.1	$ 19,688.4	$ 18,157.8
Gross Unrealized Gains	[1],[2]	1,493.2	1,414.5	1,664.4
Gross Unrealized Losses	[1],[2]	(138.1)	(166.7)	(37.8)
Net Realized Gains (Losses)	[1],[2],[3]	0.3	1.1	46.2
Fair Value	[1],[2]	$ 21,330.5	$ 20,937.3	$ 19,830.6
% of Total Fair Value	[1],[2]	100.00%	100.00%	100.00%
Net unsettled security transactions offset in other liabilities		$ 47.3		$ 95.8
Other Receivables from Broker-Dealers and Clearing Organizations			$ 23.1
Securities in the portfolio of a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions		700	1,300	1,700
Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost		13,892.3	15,347.9	13,997.5
Gross Unrealized Gains		181.8	121.3	245.2
Gross Unrealized Losses		(108)	(136.8)	(25.9)
Net Realized Gains (Losses)	[3]	0.3	(0.2)	3
Fair Value		$ 13,966.4	$ 15,332.2	$ 14,219.8
% of Total Fair Value		65.50%	73.20%	71.70%
Fixed maturities | U.S. government obligations
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 1,375.8	$ 2,425.4	$ 2,678.1
Gross Unrealized Gains		12.2	4.4	30.1
Gross Unrealized Losses		0	(0.6)	0
Net Realized Gains (Losses)	[3]	0	0	0
Fair Value		$ 1,388	$ 2,429.2	$ 2,708.2
% of Total Fair Value		6.50%	11.60%	13.70%
Fixed maturities | State and local government obligations
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 2,452	$ 2,677.6	$ 2,224.8
Gross Unrealized Gains		57.4	47.5	50
Gross Unrealized Losses		(1.2)	(3.7)	(1)
Net Realized Gains (Losses)	[3]	0	0	0
Fair Value		$ 2,508.2	$ 2,721.4	$ 2,273.8
% of Total Fair Value		11.80%	13.00%	11.50%
Fixed maturities | Foreign government obligations
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 21.9	$ 18.6	$ 20
Gross Unrealized Gains		0	0	0
Gross Unrealized Losses		0	0	0
Net Realized Gains (Losses)	[3]	0	0	0
Fair Value		$ 21.9	$ 18.6	$ 20
% of Total Fair Value		0.10%	0.10%	0.10%
Fixed maturities | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 3,795.2	$ 3,713.2	$ 2,851.6
Gross Unrealized Gains		50.6	11.3	54.4
Gross Unrealized Losses		(6.2)	(33)	(3.8)
Net Realized Gains (Losses)	[3]	0.4	0.1	1.8
Fair Value		$ 3,840	$ 3,691.6	$ 2,904
% of Total Fair Value		18.00%	17.60%	14.60%
Fixed maturities | Residential mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 1,810.9	$ 1,726	$ 1,629.2
Gross Unrealized Gains		19.5	22.1	32.4
Gross Unrealized Losses		(28.5)	(20.6)	(13.1)
Net Realized Gains (Losses)	[3]	(0.4)	(0.8)	(0.3)
Fair Value		$ 1,801.5	$ 1,726.7	$ 1,648.2
% of Total Fair Value		8.40%	8.30%	8.30%
Fixed maturities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 46.5	$ 90.3	$ 0
Gross Unrealized Gains		0.2	0.1	0
Gross Unrealized Losses		(0.1)	(1.1)	0
Net Realized Gains (Losses)	[3]	0	0	0
Fair Value		$ 46.6	$ 89.3	$ 0
% of Total Fair Value		0.20%	0.40%	0.00%
Fixed maturities | Commercial mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 2,418.7	$ 2,665.7	$ 2,437.4
Gross Unrealized Gains		26.4	16.9	50.1
Gross Unrealized Losses		(18.9)	(29.4)	(1.1)
Net Realized Gains (Losses)	[3]	0	0	0.7
Fair Value		$ 2,426.2	$ 2,653.2	$ 2,487.1
% of Total Fair Value		11.40%	12.70%	12.50%
Fixed maturities | Other asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 1,706.3	$ 1,771.1	$ 1,896.1
Gross Unrealized Gains		1.3	1.4	4.9
Gross Unrealized Losses		(4.2)	(5.1)	(0.3)
Net Realized Gains (Losses)	[3]	0.3	0.5	0.8
Fair Value		$ 1,703.7	$ 1,767.9	$ 1,901.5
% of Total Fair Value		8.00%	8.40%	9.60%
Fixed maturities | Redeemable preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 265	$ 260	$ 260.3
Gross Unrealized Gains		14.2	17.6	23.3
Gross Unrealized Losses		(48.9)	(43.3)	(6.6)
Net Realized Gains (Losses)	[3]	0	0	0
Fair Value		$ 230.3	$ 234.3	$ 277
% of Total Fair Value		1.10%	1.10%	1.40%
Equity securities | Nonredeemable preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 731.9	$ 674.2	$ 598.3
Gross Unrealized Gains		124.7	122.8	192.5
Gross Unrealized Losses		(24.4)	(15.7)	(5.9)
Net Realized Gains (Losses)	[3]	0	1.3	43.2
Fair Value		$ 832.2	$ 782.6	$ 828.1
% of Total Fair Value		3.90%	3.70%	4.20%
Equity securities | Common equities
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 1,524	$ 1,494.3	$ 1,295
Gross Unrealized Gains		1,186.7	1,170.4	1,226.7
Gross Unrealized Losses		(5.7)	(14.2)	(6)
Net Realized Gains (Losses)	[3]	0	0	0
Fair Value		$ 2,705	$ 2,650.5	$ 2,515.7
% of Total Fair Value		12.70%	12.70%	12.70%
Short-term investments
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 3,826.9	$ 2,172	$ 2,267
Gross Unrealized Gains		0	0	0
Gross Unrealized Losses		0	0	0
Net Realized Gains (Losses)	[3]	0	0	0
Fair Value		$ 3,826.9	$ 2,172	$ 2,267
% of Total Fair Value		17.90%	10.40%	11.40%
[1]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at March 31, 2016, $47.3 million was included in "other liabilities," compared to $95.8 million in "other liabilities" at March 31, 2015 and $23.1 million in "other assets" at December 31, 2015.
[2]	The total fair value of the portfolio at March 31, 2016 and 2015, and December 31, 2015 included $0.7 billion, $1.7 billion, and $1.3 billion, 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) realized on certain hybrid securities (discussed below).

Investments Hybrid Securities (

Investments Hybrid Securities (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Hybrid Securities [Line Items]
Hybrid securities	$ 273.7	$ 272.7	$ 412.9
Fixed maturities
Hybrid Securities [Line Items]
Hybrid securities	224.2	222	275.7
Fixed maturities | Corporate debt securities
Hybrid Securities [Line Items]
Hybrid securities	39.2	49.1	132.9
Fixed maturities | Residential mortgage-backed securities
Hybrid Securities [Line Items]
Hybrid securities	174.4	144.3	111.7
Fixed maturities | Commercial mortgage-backed securities
Hybrid Securities [Line Items]
Hybrid securities	0	17.3	18
Fixed maturities | Other asset-backed securities
Hybrid Securities [Line Items]
Hybrid securities	10.6	11.3	13.1
Equity securities | Nonredeemable preferred stocks
Hybrid Securities [Line Items]
Hybrid securities	$ 49.5	$ 50.7	$ 137.2

Investments Composition of Fixe

Investments Composition of Fixed Maturities by Maturity (Detail) $ in Millions	Mar. 31, 2016USD ($)
Available for sale, cost
Less than one year	$ 3,604.9
One to five years	7,016.5
Five to ten years	3,195.6
Ten years or greater	75.3
Total	13,892.3
Available for sale, Fair value
Less than one year	3,596.3
One to five years	7,030.3
Five to ten years	3,259.6
Ten years or greater	80.2
Total	$ 13,966.4

Investments Gross Unrealized lo

Investments Gross Unrealized losses by Major Security (Detail) $ in Millions	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Mar. 31, 2015USD ($)
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	670	1,167	300
Total Fair Value	$ 5,360.4	$ 9,725.1	$ 3,080.3
Gross Unrealized Losses	$ (138.1)	$ (166.7)	$ (37.8)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	338	993	219
Less than 12 Months Fair Value	$ 2,450.2	$ 7,842.3	$ 2,221
Less than 12 Months Unrealized Losses	$ (34.2)	$ (93.9)	$ (16.2)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	332	174	81
12 Months or Greater Fair Value	$ 2,910.2	$ 1,882.8	$ 859.3
12 Months or Greater Unrealized Losses	$ (103.9)	$ (72.8)	$ (21.6)
Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	584	1,093	255
Total Fair Value	$ 4,928.6	$ 9,258.5	$ 2,838.9
Gross Unrealized Losses	$ (108)	$ (136.8)	$ (25.9)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	267	928	177
Less than 12 Months Fair Value	$ 2,286.9	$ 7,556.7	$ 2,088.2
Less than 12 Months Unrealized Losses	$ (26.1)	$ (78)	$ (8)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	317	165	78
12 Months or Greater Fair Value	$ 2,641.7	$ 1,701.8	$ 750.7
12 Months or Greater Unrealized Losses	$ (81.9)	$ (58.8)	$ (17.9)
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	5	22	1
Total Fair Value	$ 74.9	$ 897.1	$ 7.2
Gross Unrealized Losses	$ 0	$ (0.6)	$ 0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	5	22	1
Less than 12 Months Fair Value	$ 74.9	$ 897.1	$ 7.2
Less than 12 Months Unrealized Losses	$ 0	$ (0.6)	$ 0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	0	0	0
12 Months or Greater Fair Value	$ 0	$ 0	$ 0
12 Months or Greater Unrealized Losses	$ 0	$ 0	$ 0
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	112	290	57
Total Fair Value	$ 267.8	$ 606.7	$ 270.3
Gross Unrealized Losses	$ (1.2)	$ (3.7)	$ (1)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	63	264	42
Less than 12 Months Fair Value	$ 132.8	$ 500.7	$ 231.8
Less than 12 Months Unrealized Losses	$ (0.3)	$ (2.6)	$ (0.5)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	49	26	15
12 Months or Greater Fair Value	$ 135	$ 106	$ 38.5
12 Months or Greater Unrealized Losses	$ (0.9)	$ (1.1)	$ (0.5)
Fixed maturities | Corporate debt securities
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	60	215	25
Total Fair Value	$ 672.3	$ 2,580.6	$ 390.3
Gross Unrealized Losses	$ (6.2)	$ (33)	$ (3.8)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	21	197	17
Less than 12 Months Fair Value	$ 169.2	$ 2,294.6	$ 242.4
Less than 12 Months Unrealized Losses	$ (0.4)	$ (25.2)	$ (2.3)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	39	18	8
12 Months or Greater Fair Value	$ 503.1	$ 286	$ 147.9
12 Months or Greater Unrealized Losses	$ (5.8)	$ (7.8)	$ (1.5)
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	157	188	80
Total Fair Value	$ 1,345.1	$ 1,294.7	$ 1,013.9
Gross Unrealized Losses	$ (28.5)	$ (20.6)	$ (13.1)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	52	115	34
Less than 12 Months Fair Value	$ 426.9	$ 493.4	$ 540.6
Less than 12 Months Unrealized Losses	$ (3.9)	$ (3.7)	$ (3.1)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	105	73	46
12 Months or Greater Fair Value	$ 918.2	$ 801.3	$ 473.3
12 Months or Greater Unrealized Losses	$ (24.6)	$ (16.9)	$ (10)
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	25	61	0
Total Fair Value	$ 9.1	$ 84.9	$ 0
Gross Unrealized Losses	$ (0.1)	$ (1.1)	$ 0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	3	61	0
Less than 12 Months Fair Value	$ 0.4	$ 84.9	$ 0
Less than 12 Months Unrealized Losses	$ 0	$ (1.1)	$ 0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	22	0	0
12 Months or Greater Fair Value	$ 8.7	$ 0	$ 0
12 Months or Greater Unrealized Losses	$ (0.1)	$ 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	130	207	59
Total Fair Value	$ 1,185.4	$ 2,046.5	$ 564.2
Gross Unrealized Losses	$ (18.9)	$ (29.4)	$ (1.1)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	49	171	53
Less than 12 Months Fair Value	$ 395.4	$ 1,694.6	$ 560.8
Less than 12 Months Unrealized Losses	$ (2.2)	$ (25.8)	$ (1)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	81	36	6
12 Months or Greater Fair Value	$ 790	$ 351.9	$ 3.4
12 Months or Greater Unrealized Losses	$ (16.7)	$ (3.6)	$ (0.1)
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	86	101	30
Total Fair Value	$ 1,175.2	$ 1,548.6	$ 490.9
Gross Unrealized Losses	$ (4.2)	$ (5.1)	$ (0.3)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	70	92	29
Less than 12 Months Fair Value	$ 999.3	$ 1,472	$ 472.4
Less than 12 Months Unrealized Losses	$ (3.2)	$ (4.5)	$ (0.1)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	16	9	1
12 Months or Greater Fair Value	$ 175.9	$ 76.6	$ 18.5
12 Months or Greater Unrealized Losses	$ (1)	$ (0.6)	$ (0.2)
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	9	3
Total Fair Value	$ 198.8	$ 199.4	$ 102.1
Gross Unrealized Losses	$ (48.9)	$ (43.3)	$ (6.6)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	4	6	1
Less than 12 Months Fair Value	$ 88	$ 119.4	$ 33
Less than 12 Months Unrealized Losses	$ (16.1)	$ (14.5)	$ (1)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	5	3	2
12 Months or Greater Fair Value	$ 110.8	$ 80	$ 69.1
12 Months or Greater Unrealized Losses	$ (32.8)	$ (28.8)	$ (5.6)
Equity securities
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	86	74	45
Total Fair Value	$ 431.8	$ 466.6	$ 241.4
Gross Unrealized Losses	$ (30.1)	$ (29.9)	$ (11.9)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	71	65	42
Less than 12 Months Fair Value	$ 163.3	$ 285.6	$ 132.8
Less than 12 Months Unrealized Losses	$ (8.1)	$ (15.9)	$ (8.2)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	15	9	3
12 Months or Greater Fair Value	$ 268.5	$ 181	$ 108.6
12 Months or Greater Unrealized Losses	$ (22)	$ (14)	$ (3.7)
Equity securities | Nonredeemable preferred stocks
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	13	10	5
Total Fair Value	$ 344.4	$ 301.8	$ 183.1
Gross Unrealized Losses	$ (24.4)	$ (15.7)	$ (5.9)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	4	5	2
Less than 12 Months Fair Value	$ 79	$ 124.2	$ 74.5
Less than 12 Months Unrealized Losses	$ (2.6)	$ (1.7)	$ (2.2)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	9	5	3
12 Months or Greater Fair Value	$ 265.4	$ 177.6	$ 108.6
12 Months or Greater Unrealized Losses	$ (21.8)	$ (14)	$ (3.7)
Equity securities | Common equities
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	73	64	40
Total Fair Value	$ 87.4	$ 164.8	$ 58.3
Gross Unrealized Losses	$ (5.7)	$ (14.2)	$ (6)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	67	60	40
Less than 12 Months Fair Value	$ 84.3	$ 161.4	$ 58.3
Less than 12 Months Unrealized Losses	$ (5.5)	$ (14.2)	$ (6)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	6	4	0
12 Months or Greater Fair Value	$ 3.1	$ 3.4	$ 0
12 Months or Greater Unrealized Losses	$ (0.2)	$ 0	$ 0

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	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Other Than Temporary Impairment Non Credit Losses Recognized In Accumulated Other Comprehensive Income [Line Items]
Non-credit portion of other-than-temporary impairments recognized in accumulated other comprehensive income	$ (43.9)	$ (43.9)	$ (44.7)
Residential mortgage-backed securities
Other Than Temporary Impairment Non Credit Losses Recognized In Accumulated Other Comprehensive Income [Line Items]
Non-credit portion of other-than-temporary impairments recognized in accumulated other comprehensive income	(43.3)	(43.3)	(44.1)
Commercial mortgage-backed securities
Other Than Temporary Impairment Non Credit Losses Recognized In Accumulated Other Comprehensive Income [Line Items]
Non-credit portion of other-than-temporary impairments recognized in accumulated other comprehensive income	$ (0.6)	$ (0.6)	$ (0.6)

Investments OTTI Credit Losses

Investments OTTI Credit Losses Recognized in Earnings (Detail) - Fixed maturities - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance		$ 12.8	$ 13.1
Change in recoveries of future cash flows expected to be collected	[1]	(0.3)	(0.5)
Ending balance		12.5	12.6
Residential mortgage-backed securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance		12.4	12.7
Change in recoveries of future cash flows expected to be collected	[1]	(0.3)	(0.5)
Ending balance		12.1	12.2
Commercial mortgage-backed securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance		0.4	0.4
Change in recoveries of future cash flows expected to be collected	[1]	0	0
Ending balance		$ 0.4	$ 0.4
[1]	Reflects the current period change in the expected recovery of prior impairments that will be accreted into income over the remaining life of the security.

Investments Components of Net R

Investments Components of Net Realized Gains (Losses) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	$ 53.3	$ 58.5
Gross realized losses on securities sales	(9.5)	(2.2)
Net realized gains (losses) on securities sales	43.8	56.3
Other-than-temporary impairment losses	0	(7.9)
Total net realized gains (losses) on securities	17.4	33
Fixed maturities
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	42.2	24.9
Gross realized losses on securities sales	(3.6)	(1.8)
Net realized gains (losses) on securities sales	38.6	23.1
Fixed maturities | U.S. government obligations
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	14.3	4.9
Gross realized losses on securities sales	(0.4)	(0.8)
Net realized gains (losses) on securities sales	13.9	4.1
Fixed maturities | State and local government obligations
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	10.9	0
Gross realized losses on securities sales	(0.1)	0
Net realized gains (losses) on securities sales	10.8	0
Fixed maturities | Corporate And Other Debt Securities
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	12.5	9.1
Gross realized losses on securities sales	(0.4)	(0.8)
Net realized gains (losses) on securities sales	12.1	8.3
Fixed maturities | Residential mortgage-backed securities
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	0.9	0.1
Net realized gains (losses) on securities sales	0.9	0.1
Fixed maturities | Commercial mortgage-backed securities
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	3.6	10.8
Gross realized losses on securities sales	(2.7)	(0.2)
Net realized gains (losses) on securities sales	0.9	10.6
Equity securities | Nonredeemable preferred stocks
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	1.6	15.8
Gross realized losses on securities sales	(1)	0
Net realized gains (losses) on securities sales	0.6	15.8
Equity securities | Common equities
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	9.5	17.8
Gross realized losses on securities sales	(4.9)	(0.4)
Net realized gains (losses) on securities sales	4.6	17.4
Other-than-temporary impairment losses	0	(7.9)
Hybrid and Derivative Instruments and Litigation Settlements
Gain (Loss) on Investments [Line Items]
Other gains (losses)	(26.4)	(15.4)
Hybrid and Derivative Instruments and Litigation Settlements | Litigation Settlements
Gain (Loss) on Investments [Line Items]
Other gains (losses)	0	0.1
Hybrid and Derivative Instruments and Litigation Settlements | Hybrid Preferred Stock
Gain (Loss) on Investments [Line Items]
Other gains (losses)	(0.7)	3.3
Hybrid and Derivative Instruments and Litigation Settlements | Derivative Instruments
Gain (Loss) on Investments [Line Items]
Other gains (losses)	$ (25.7)	$ (18.8)

Investments Components of Net I

Investments Components of Net Investment Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Net Investment Income [Line Items]
Investment income	$ 118.8	$ 105.1
Investment expenses	(4.8)	(5.3)
Net Investment Income	114	99.8
Fixed maturities
Net Investment Income [Line Items]
Investment income	89.9	82.5
Fixed maturities | U.S. government obligations
Net Investment Income [Line Items]
Investment income	4.8	9.1
Fixed maturities | State and local government obligations
Net Investment Income [Line Items]
Investment income	13.5	11.9
Fixed maturities | Foreign government obligations
Net Investment Income [Line Items]
Investment income	0.1	0.1
Fixed maturities | Corporate debt securities
Net Investment Income [Line Items]
Investment income	28.2	22.9
Fixed maturities | Residential mortgage-backed securities
Net Investment Income [Line Items]
Investment income	12.2	12.8
Fixed maturities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Net Investment Income [Line Items]
Investment income	0.4	0
Fixed maturities | Commercial mortgage-backed securities
Net Investment Income [Line Items]
Investment income	20.9	16.9
Fixed maturities | Other asset-backed securities
Net Investment Income [Line Items]
Investment income	6	5
Fixed maturities | Redeemable preferred stocks
Net Investment Income [Line Items]
Investment income	3.8	3.8
Equity securities | Nonredeemable preferred stocks
Net Investment Income [Line Items]
Investment income	11.8	10.5
Equity securities | Common equities
Net Investment Income [Line Items]
Investment income	14.5	11.7
Short-term investments
Net Investment Income [Line Items]
Investment income	$ 2.6	$ 0.4

Investments Derivative Instrume

Investments Derivative Instruments (Detail) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
		Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Derivative [Line Items]
Balance Sheet - Fair Value	[1]	$ (18.7)	$ 0.1	$ 4.4
Income Statement - Net Realized Gain (Loss) on Securities		(25.7)	(18.8)
Designated as Hedging Instruments | Ineffective Cash Flow Hedge [Member]
Derivative [Line Items]
Notional Value	[2]	0	0	$ 18
Purpose				Manage  interest  rate risk
Balance Sheet - Fair Value	[1]	0	0	$ 0
Income Statement - Net Realized Gain (Loss) on Securities		0	0
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Fixed maturities
Derivative [Line Items]
Notional Value	[2]	0	$ 750	$ 750
Purpose			Manage  portfolio duration	Manage portfolio duration
Balance Sheet - Fair Value	[1]	0	$ 0.1	$ 4.4
Income Statement - Net Realized Gain (Loss) on Securities		0	(18.8)
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Other Liabilities [Member]
Derivative [Line Items]
Notional Value	[2]	$ 565	0	0
Purpose		Manage  portfolio duration
Balance Sheet - Fair Value	[1]	$ (18.7)	0	0
Income Statement - Net Realized Gain (Loss) on Securities		(24)	0
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Closed Positions [Member]
Derivative [Line Items]
Notional Value	[2]	$ 185	0	0
Purpose		Manage  portfolio duration
Balance Sheet - Fair Value	[1]	$ 0	0	0
Income Statement - Net Realized Gain (Loss) on Securities		(1.9)	0
Not Designated as Hedging Instrument [Member] | Future [Member] | Closed Positions [Member]
Derivative [Line Items]
Notional Value	[2]	$ 55	0	$ 691
Purpose		Manage  portfolio duration		Manage portfolio duration
Balance Sheet - Fair Value	[1]	$ 0	0	$ 0
Income Statement - Net Realized Gain (Loss) on Securities		$ 0.2	$ 0
[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 quarter and year end for open positions and the maximum amount held during the period for closed positions.

Investments Investments - Addit

Investments Investments - Additional Information (Detail)	1 Months Ended	3 Months Ended
	Jan. 26, 2015USD ($)	Mar. 31, 2016USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2015USD ($)	Apr. 01, 2015	Jun. 18, 2007
Schedule of Investments [Line Items]
Proceeds from (Payments for) in Securities Sold under Agreements to Repurchase		$ 0	$ 0
Securities Sold under Agreements to Repurchase		0	0	$ 0
Open reverse repurchase commitments		0	0	0
Largest Outstanding Balance of Reverse Repurchase Agreements		$ 265,000,000
RRP Largest Outstanding Balance Number of Days Open		1 day
Reverse Repurchase Agreement Average Daily Balance		$ 160,700,000
Gross unrealized losses		$ 138,100,000	$ 37,800,000	$ 166,700,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		670	300	1,167
Trading securities		$ 0	$ 0	$ 0
Net realized gains (losses) on securities		$ 17,400,000	40,900,000
3.70% Senior Notes due 2045
Schedule of Investments [Line Items]
Debt Instrument, Face Amount	$ 400,000,000
Debt Instrument, Interest Rate, Stated Percentage	3.70%	3.70%
Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss)	$ 12,900,000
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067
Schedule of Investments [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.70%				6.70%
Fixed Income Securities
Schedule of Investments [Line Items]
Gross unrealized losses		$ 132,400,000
Equity securities
Schedule of Investments [Line Items]
Gross unrealized losses		$ 30,100,000	$ 11,900,000	$ 29,900,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		86	45	74
Equity securities | Common equities
Schedule of Investments [Line Items]
Gross unrealized losses		$ 5,700,000	$ 6,000,000	$ 14,200,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		73	40	64
Equity securities | Nonredeemable preferred stocks
Schedule of Investments [Line Items]
Gross unrealized losses		$ 24,400,000	$ 5,900,000	$ 15,700,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		13	5	10
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Percentage Decline		7.00%
Fixed maturities
Schedule of Investments [Line Items]
Gross unrealized losses		$ 108,000,000	$ 25,900,000	$ 136,800,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		584	255	1,093
Fixed maturities | State and local government obligations
Schedule of Investments [Line Items]
Gross unrealized losses		$ 1,200,000	$ 1,000,000	$ 3,700,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		112	57	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		$ 1,400,000
Gross unrealized losses		$ 6,200,000	$ 3,800,000	$ 33,000,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		60	25	215
Interest Rate Swap [Member]
Schedule of Investments [Line Items]
Cash collateral received from counterparties				$ 4,900,000
Collateral Delivered to Counterparties on Derivative Instruments		$ 20,600,000	$ 4,700,000
Categories of Investments, Marketable Securities, Trading Securities
Schedule of Investments [Line Items]
Net realized gains (losses) on securities		$ 0	$ 0
Russell One Thousand | Equity securities | Common equities
Schedule of Investments [Line Items]
Percentage of common stock portfolio		95.00%
Managed Equity Strategy | Equity securities | Common equities
Schedule of Investments [Line Items]
Percentage of common stock portfolio		5.00%
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Schedule of Investments [Line Items]
Derivative, Gain (Loss) on Derivative, Net		$ 22,000,000
ARX Holding Corp. [Member]
Schedule of Investments [Line Items]
Ownership interest held prior to acquisition (percent)			5.00%		5.00%
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		190
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Percentage Decline		0.40%
Closed Positions [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Schedule of Investments [Line Items]
Number of derivative positions closed during the period		1
Derivative, Term of Contract		10 years

Fair Value Composition of Inves

Fair Value Composition of Investment Portfolio by Major Security Type (Detail) - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	[1],[2]	$ 21,330.5	$ 20,937.3	$ 19,830.6
Long-Term Debt, Fair Value		2,947.3	2,887.8	2,910.9
Debt		2,701.6	2,707.9	2,560.1
Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		13,966.4	15,332.2	14,219.8
Fixed maturities | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		7,758.1	8,860.8	7,906
Fixed maturities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		5,978	6,237.1	6,036.8
Fixed maturities | U.S. government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		1,388	2,429.2	2,708.2
Fixed maturities | U.S. government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		1,388	2,429.2	2,708.2
Fixed maturities | State and local government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		2,508.2	2,721.4	2,273.8
Fixed maturities | State and local government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		2,508.2	2,721.4	2,273.8
Fixed maturities | Foreign government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		21.9	18.6	20
Fixed maturities | Foreign government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		21.9	18.6	20
Fixed maturities | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		3,840	3,691.6	2,904
Fixed maturities | Corporate debt securities | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		3,840	3,691.6	2,904
Fixed maturities | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		1,801.5	1,726.7	1,648.2
Fixed maturities | Residential mortgage-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		1,801.5	1,726.7	1,648.2
Fixed maturities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		46.6	89.3	0
Fixed maturities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		46.6	89.3	0
Fixed maturities | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		2,426.2	2,653.2	2,487.1
Fixed maturities | Commercial mortgage-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		2,426.2	2,653.2	2,487.1
Fixed maturities | Other asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		1,703.7	1,767.9	1,901.5
Fixed maturities | Other asset-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		1,703.7	1,767.9	1,901.5
Fixed maturities | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		230.3	234.3	277
Fixed maturities | Redeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		91.7	92	98.2
Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		51.6	51.2	64.4
Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		87	91.1	114.4
Equity securities | Nonredeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		832.2	782.6	828.1
Equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		832.2	782.6	828.1
Equity securities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		2,705	2,650.5	2,515.7
Equity securities | Common equities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		2,704.7	2,650.2	2,515.4
Equity securities | Common equities | Other risk investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0.3	0.3	0.3
Total Fixed Maturities and Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		17,503.6	18,765.3	17,563.6
Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		3,826.9	2,172	2,267
Carrying (Reported) Amount, Fair Value Disclosure
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		19,975.1	19,688.4	18,157.8
Debt		2,701.6	2,707.9	2,560.1
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		13,892.3	15,347.9	13,997.5
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		7,644.9	8,834.8	7,774.5
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		5,982.4	6,253.1	5,962.7
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | U.S. government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		1,375.8	2,425.4	2,678.1
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | State and local government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		2,452	2,677.6	2,224.8
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Foreign government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		21.9	18.6	20
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Corporate debt securities | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		3,795.2	3,713.2	2,851.6
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Residential mortgage-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		1,810.9	1,726	1,629.2
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		46.5	90.3	0
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Commercial mortgage-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		2,418.7	2,665.7	2,437.4
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Other asset-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		1,706.3	1,771.1	1,896.1
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		265	260	260.3
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		81.8	76.8	77.3
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		65.1	65.1	65
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		118.1	118.1	118
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Nonredeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		731.9	674.2	598.3
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		731.9	674.2	598.3
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		1,524	1,494.3	1,295
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		1,523.7	1,494	1,294.7
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities | Other risk investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0.3	0.3	0.3
Carrying (Reported) Amount, Fair Value Disclosure | Total Fixed Maturities and Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		16,148.2	17,516.4	15,890.8
Carrying (Reported) Amount, Fair Value Disclosure | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		3,826.9	2,172	2,267
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		7,998.4	7,309.2	7,692.3
Long-Term Debt, Fair Value		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		1,409.9	2,447.8	2,728.2
Fair Value, Inputs, Level 1 | Fixed maturities | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		1,409.9	2,447.8	2,728.2
Fair Value, Inputs, Level 1 | Fixed maturities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | U.S. government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		1,388	2,429.2	2,708.2
Fair Value, Inputs, Level 1 | Fixed maturities | State and local government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Foreign government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		21.9	18.6	20
Fair Value, Inputs, Level 1 | Fixed maturities | Corporate debt securities | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Residential mortgage-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Commercial mortgage-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Other asset-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Redeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 1 | Equity securities | Nonredeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		153.8	154.9	181.7
Fair Value, Inputs, Level 1 | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		153.8	154.9	181.7
Fair Value, Inputs, Level 1 | Equity securities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		2,704.7	2,650.2	2,515.4
Fair Value, Inputs, Level 1 | Equity securities | Common equities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		2,704.7	2,650.2	2,515.4
Fair Value, Inputs, Level 1 | Equity securities | Common equities | Other risk investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 1 | Total Fixed Maturities and Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		4,268.4	5,252.9	5,425.3
Fair Value, Inputs, Level 1 | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		3,730	2,056.3	2,267
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		13,322.3	13,617.9	12,056.7
Long-Term Debt, Fair Value		2,789.2	2,722.9	2,910.9
Fair Value, Inputs, Level 2 | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		12,547	12,874.5	11,480.2
Fair Value, Inputs, Level 2 | Fixed maturities | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		6,348.2	6,413	5,177.8
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		5,968.5	6,227.2	6,025.4
Fair Value, Inputs, Level 2 | Fixed maturities | U.S. government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 2 | Fixed maturities | State and local government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		2,508.2	2,721.4	2,273.8
Fair Value, Inputs, Level 2 | Fixed maturities | Foreign government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 2 | Fixed maturities | Corporate debt securities | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		3,840	3,691.6	2,904
Fair Value, Inputs, Level 2 | Fixed maturities | Residential mortgage-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		1,801.5	1,726.7	1,648.2
Fair Value, Inputs, Level 2 | Fixed maturities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		46.6	89.3	0
Fair Value, Inputs, Level 2 | Fixed maturities | Commercial mortgage-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		2,416.7	2,643.3	2,475.7
Fair Value, Inputs, Level 2 | Fixed maturities | Other asset-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		1,703.7	1,767.9	1,901.5
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		230.3	234.3	277
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		91.7	92	98.2
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		51.6	51.2	64.4
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		87	91.1	114.4
Fair Value, Inputs, Level 2 | Equity securities | Nonredeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		678.4	627.7	576.5
Fair Value, Inputs, Level 2 | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		678.4	627.7	576.5
Fair Value, Inputs, Level 2 | Equity securities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 2 | Equity securities | Common equities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 2 | Equity securities | Common equities | Other risk investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 2 | Total Fixed Maturities and Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		13,225.4	13,502.2	12,056.7
Fair Value, Inputs, Level 2 | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		96.9	115.7	0
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		9.8	10.2	81.6
Long-Term Debt, Fair Value		158.1	164.9	0
Fair Value, Inputs, Level 3 | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		9.5	9.9	11.4
Fair Value, Inputs, Level 3 | Fixed maturities | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		9.5	9.9	11.4
Fair Value, Inputs, Level 3 | Fixed maturities | U.S. government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | State and local government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Foreign government obligations | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Corporate debt securities | Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Residential mortgage-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Commercial mortgage-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		9.5	9.9	11.4
Fair Value, Inputs, Level 3 | Fixed maturities | Other asset-backed securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Redeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	69.9
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	69.9
Fair Value, Inputs, Level 3 | Equity securities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0.3	0.3	0.3
Fair Value, Inputs, Level 3 | Equity securities | Common equities | Common equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0	0	0
Fair Value, Inputs, Level 3 | Equity securities | Common equities | Other risk investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0.3	0.3	0.3
Fair Value, Inputs, Level 3 | Total Fixed Maturities and Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		9.8	10.2	81.6
Fair Value, Inputs, Level 3 | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		$ 0	$ 0	$ 0
[1]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at March 31, 2016, $47.3 million was included in "other liabilities," compared to $95.8 million in "other liabilities" at March 31, 2015 and $23.1 million in "other assets" at December 31, 2015.
[2]	The total fair value of the portfolio at March 31, 2016 and 2015, and December 31, 2015 included $0.7 billion, $1.7 billion, and $1.3 billion, 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	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value	$ 10.2	$ 81.3
Calls/ Maturities/ Paydowns	(0.3)	(0.2)
Purchases	0	0
Sales	0	0
Net Realized (Gain) Loss on Sales	0	0
Change in Valuation	(0.1)	0.5
Net Transfers in (out)	0	0
Ending Fair value	9.8	81.6
Realized investment gains (losses)	17.4	33
Equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value	0	69.3
Calls/ Maturities/ Paydowns	0	0
Purchases	0	0
Sales	0	0
Net Realized (Gain) Loss on Sales	0	0
Change in Valuation	0	0.6	[1]
Net Transfers in (out)	0	0
Ending Fair value	0	69.9
Equity securities | Common equities | Other risk investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value	0.3	0.4
Calls/ Maturities/ Paydowns	0	0
Purchases	0	0
Sales	0	0
Net Realized (Gain) Loss on Sales	0	0
Change in Valuation	0	(0.1)
Net Transfers in (out)	0	0
Ending Fair value	0.3	0.3
Fixed maturities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value	9.9	11.6
Calls/ Maturities/ Paydowns	(0.3)	(0.2)
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
Ending Fair value	9.5	11.4
Asset-backed Securities | Fixed maturities | Commercial mortgage-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value	9.9	11.6
Calls/ Maturities/ Paydowns	(0.3)	(0.2)
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
Ending Fair value	$ 9.5	11.4
Hybrid Securities [Member] | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Realized investment gains (losses)		$ 0.6
[1]	The $0.6 million represents net holding period gains on a hybrid security, 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		3 Months Ended				12 Months Ended
		Mar. 31, 2016USD ($)Investment		Mar. 31, 2015USD ($)Investment		Dec. 31, 2015USD ($)Investment
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities	[1],[2]	$ 21,330.5		$ 19,830.6		$ 20,937.3
Equity securities | Nonredeemable preferred stocks
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities		832.2		828.1		782.6
Equity securities | Nonredeemable preferred stocks | Financials
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities		832.2		828.1		782.6
Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities		13,966.4		14,219.8		15,332.2
Fixed maturities | Residential mortgage-backed securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities		1,801.5		1,648.2		1,726.7
Fixed maturities | Commercial mortgage-backed securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities		2,426.2		2,487.1		2,653.2
Fair Value, Inputs, Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities		9.8		81.6		10.2
Fair Value, Inputs, Level 3 | Third Party Pricing Exemption Securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities		0.3	[3]	0.3	[4]	0.3	[5]
Fair Value, Inputs, Level 3 | Subtotal Level 3 Securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities		$ 9.5		81.3		$ 9.9
Fair Value, Inputs, Level 3 | Internal Pricing
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Number of securities | Investment		0				0
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities		$ 0		$ 69.9		$ 0
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks | Internal Pricing
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Number of securities | Investment				1
Available-for-sale Securities				$ 69.9
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities		0		69.9		0
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks | Financials | Internal Pricing
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities		0		$ 69.9		0
Valuation Technique				Multiple of tangible net book value
Unobservable Input, price to book ratio multiple				2.6
Fair Value, Inputs, Level 3 | Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities		9.5		$ 11.4		9.9
Fair Value, Inputs, Level 3 | Fixed maturities | External Pricing
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities		$ 9.5		$ 11.4		$ 9.9
Fair Value, Inputs, Level 3 | Fixed maturities | Commercial mortgage-backed securities | External Pricing
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Number of securities | Investment		1		1		1
Available-for-sale Securities		$ 9.5		$ 11.4		$ 9.9
Valuation Technique		External vendor		External vendor		External vendor
Unobservable Input, prepayment rate		0.00%		0.00%		0.00%
[1]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at March 31, 2016, $47.3 million was included in "other liabilities," compared to $95.8 million in "other liabilities" at March 31, 2015 and $23.1 million in "other assets" at December 31, 2015.
[2]	The total fair value of the portfolio at March 31, 2016 and 2015, and December 31, 2015 included $0.7 billion, $1.7 billion, and $1.3 billion, 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 determined with unobservable inputs not reasonably available to us.
[4]	The fair values for these securities were determined with unobservable inputs not reasonably available to us.
[5]	The fair values for these securities were determined with unobservable inputs not reasonably available to us.

Fair Value Fair Value - Additio

Fair Value Fair Value - Additional Information (Detail)		Mar. 31, 2016USD ($)Investment	Dec. 31, 2015USD ($)Investment	Apr. 01, 2015	Mar. 31, 2015USD ($)Investment
Fair Value Measurements [Line Items]
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount		$ 0	$ 0		$ 0
Quoted prices percentage of fair value assets	[1],[2]	100.00%	100.00%		100.00%
Available-for-sale Securities	[1],[2]	$ 21,330,500,000	$ 20,937,300,000		$ 19,830,600,000
Fair Value, Inputs, Level 1
Fair Value Measurements [Line Items]
Available-for-sale Securities		7,998,400,000	7,309,200,000		7,692,300,000
Fair Value, Inputs, Level 2
Fair Value Measurements [Line Items]
Available-for-sale Securities		13,322,300,000	13,617,900,000		12,056,700,000
Fair Value, Inputs, Level 3
Fair Value Measurements [Line Items]
Available-for-sale Securities		$ 9,800,000	$ 10,200,000		$ 81,600,000
Equity securities | Nonredeemable preferred stocks
Fair Value Measurements [Line Items]
Quoted prices percentage of fair value assets		3.90%	3.70%		4.20%
Available-for-sale Securities		$ 832,200,000	$ 782,600,000		$ 828,100,000
Equity securities | Nonredeemable preferred stocks | Fair Value, Inputs, Level 1
Fair Value Measurements [Line Items]
Available-for-sale Securities		153,800,000	154,900,000		181,700,000
Equity securities | Nonredeemable preferred stocks | Fair Value, Inputs, Level 2
Fair Value Measurements [Line Items]
Available-for-sale Securities		678,400,000	627,700,000		576,500,000
Equity securities | Nonredeemable preferred stocks | Fair Value, Inputs, Level 3
Fair Value Measurements [Line Items]
Available-for-sale Securities		$ 0	$ 0		$ 69,900,000
Equity securities | Common equities
Fair Value Measurements [Line Items]
Quoted prices percentage of fair value assets		12.70%	12.70%		12.70%
Available-for-sale Securities		$ 2,705,000,000	$ 2,650,500,000		$ 2,515,700,000
Equity securities | Common equities | Fair Value, Inputs, Level 1
Fair Value Measurements [Line Items]
Available-for-sale Securities		2,704,700,000	2,650,200,000		2,515,400,000
Equity securities | Common equities | Fair Value, Inputs, Level 2
Fair Value Measurements [Line Items]
Available-for-sale Securities		0	0		0
Equity securities | Common equities | Fair Value, Inputs, Level 3
Fair Value Measurements [Line Items]
Available-for-sale Securities		$ 300,000	$ 300,000		$ 300,000
ARX Holding Corp. [Member]
Fair Value Measurements [Line Items]
Ownership interest held prior to acquisition (percent)				5.00%	5.00%
Internal Pricing | Fair Value, Inputs, Level 3
Fair Value Measurements [Line Items]
Number of securities | Investment		0	0
Internal Pricing | Equity securities | Nonredeemable preferred stocks | Fair Value, Inputs, Level 3
Fair Value Measurements [Line Items]
Number of securities | Investment					1
Available-for-sale Securities					$ 69,900,000
Dealer Quoted Pricing | Fair Value, Inputs, Level 2
Fair Value Measurements [Line Items]
Quoted prices percentage of fair value assets		2.00%	3.00%		3.00%
Vendor Quoted Pricing | Fair Value, Inputs, Level 1
Fair Value Measurements [Line Items]
Quoted prices percentage of fair value assets		37.00%	49.00%		50.00%
Vendor Quoted Pricing | Fair Value, Inputs, Level 2
Fair Value Measurements [Line Items]
Quoted prices percentage of fair value assets		98.00%	97.00%		97.00%
[1]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at March 31, 2016, $47.3 million was included in "other liabilities," compared to $95.8 million in "other liabilities" at March 31, 2015 and $23.1 million in "other assets" at December 31, 2015.
[2]	The total fair value of the portfolio at March 31, 2016 and 2015, and December 31, 2015 included $0.7 billion, $1.7 billion, and $1.3 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.

Debt (Detail)

Debt (Detail)		3 Months Ended		12 Months Ended
		Mar. 31, 2016USD ($)instrument	Mar. 31, 2015USD ($)	Dec. 31, 2015USD ($)instrument	Jan. 26, 2015	Jun. 18, 2007
Debt Instrument [Line Items]
Carrying Value		$ 2,701,600,000	$ 2,560,100,000	$ 2,707,900,000
Fair Value		2,947,300,000	2,910,900,000	2,887,800,000
Debt, Long-term and Short-term, Combined Amount	[1]	$ 2,701,600,000	2,560,100,000	2,707,900,000
3.75% Senior Notes due 2021
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.75%
Carrying Value		$ 498,200,000	497,900,000	498,100,000
Fair Value		$ 538,400,000	542,600,000	528,700,000
6 5/8% Senior Notes due 2029
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.625%
Carrying Value		$ 295,800,000	295,600,000	295,700,000
Fair Value		$ 388,700,000	393,600,000	376,000,000
6.25% Senior Notes due 2032
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.25%
Carrying Value		$ 395,000,000	394,900,000	395,000,000
Fair Value		$ 509,700,000	525,600,000	490,600,000
4.35% Senior Notes due 2044
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		4.35%
Carrying Value		$ 346,400,000	346,300,000	346,400,000
Fair Value		$ 377,900,000	387,100,000	352,800,000
3.70% Senior Notes due 2045
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.70%			3.70%
Carrying Value		$ 395,000,000	394,900,000	395,000,000
Fair Value		388,600,000	394,800,000	362,000,000
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067
Debt Instrument [Line Items]
Repurchase of debt, face amount		$ 0	0	18,400,000
Debt Instrument, Interest Rate, Stated Percentage		6.70%				6.70%
Carrying Value		$ 613,100,000	630,500,000	612,800,000
Fair Value		585,900,000	667,200,000	612,800,000
Other Debt Instruments [Member]
Debt Instrument [Line Items]
Carrying Value			0
Fair Value			$ 0
Debt, Long-term and Short-term, Combined Amount		$ 158,100,000		$ 164,900,000
Notes Payable, Other Payables [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Number of debt instruments | instrument		2		2
Debt, Long-term and Short-term, Combined Amount		$ 80,800,000		$ 87,100,000
Trust Preferred Debt Securities [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Carrying Value	[2]	$ 41,200,000		$ 41,200,000
Number of debt instruments | instrument		2		2
Senior Notes [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Carrying Value	[3]	$ 24,000,000		$ 24,000,000
Number of debt instruments | instrument		4		4
Surplus Note [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Number of debt instruments | instrument		1		1
Debt, Long-term and Short-term, Combined Amount		$ 12,100,000		$ 12,600,000
[1]	1Consists of both short-term and long-term debt. See Note 4 - Debt for further discussion.
[2]	1 ARX issued junior subordinated floating rate notes to trusts established by ARX in connection with issuances of trust preferred securities by the trusts (discussed below).
[3]	2 The senior notes mature in May 2033, April 2034, December 2034, and June 2035.

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Jun. 18, 2007
Debt Instrument [Line Items]
Line of Credit Facility, Description			Each advance would need to be repaid on the 30th day after the advance or, if earlier, on April 30, 2016, the expiration date of the Line of Credit.
Discretionary Line of Credit
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 100,000,000	$ 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 and the sum of the Federal Funds Open Rate plus 50 basis points.		advances under the Line of Credit (if any) will bear interest at a variable rate equal to the higher of PNC's Prime Rate and the sum of the Federal Funds Open Rate plus 50 basis points.
Line of Credit Facility, Amount Outstanding	0			$ 0
Debt Instrument, Basis Spread on Variable Rate			0.50%		0.50%
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067
Debt Instrument [Line Items]
Repurchase of debt, face amount	$ 0	$ 0		$ 18,400,000
Debt Instrument, Interest Rate, Stated Percentage	6.70%		6.70%			6.70%
Other Assets [Member]
Debt Instrument [Line Items]
Ownership interest in the variable interest entities	$ 1,300,000		$ 1,300,000

Supplemental Cash Flow Inform48

Supplemental Cash Flow Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Supplemental Cash Flow Elements [Abstract]
Income taxes	$ 30	$ 60
Interest	$ 28.1	$ 19.3

Segment Information Operating R

Segment Information Operating Results (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Segment Reporting Information [Line Items]
Revenues		$ 5,557.5	$ 4,895.3
Pretax Profit (Loss)		387.4	443.2
Policyholder Benefits and Claims Incurred, Net, Catastrophic Event		45.3
Other Depreciation and Amortization		15.1
Underwriting Operations
Segment Reporting Information [Line Items]
Revenues		5,317.4	4,666.3
Pretax Profit (Loss)		286.8	341.6
Underwriting Operations | Personal Lines
Segment Reporting Information [Line Items]
Revenues	[1]	4,568.6	4,199.9
Pretax Profit (Loss)		250.9	262.7
Underwriting Operations | Personal Lines | Agency Channel
Segment Reporting Information [Line Items]
Revenues		2,347.9	2,244.5
Pretax Profit (Loss)		171.4	194.5
Underwriting Operations | Personal Lines | Direct Channel
Segment Reporting Information [Line Items]
Revenues		2,220.7	1,955.4
Pretax Profit (Loss)		79.5	68.2
Underwriting Operations | Commercial Lines
Segment Reporting Information [Line Items]
Revenues		548.8	466.4
Pretax Profit (Loss)		61.1	78.5
Underwriting Operations | Property, Liability and Casualty Insurance Product Line [Member]
Segment Reporting Information [Line Items]
Revenues		200
Pretax Profit (Loss)	[2]	(24.5)
Underwriting Operations | Other Indemnity
Segment Reporting Information [Line Items]
Revenues		0	0
Pretax Profit (Loss)		(0.7)	0.4
Fees and Other Revenues
Segment Reporting Information [Line Items]
Revenues	[3]	78.9	73.7
Service Businesses
Segment Reporting Information [Line Items]
Revenues		25	17.2
Pretax Profit (Loss)		3.4	1.3
Investments
Segment Reporting Information [Line Items]
Revenues	[4]	136.2	138.1
Pretax Profit (Loss)	[4]	131.4	132.8
Interest Expense
Segment Reporting Information [Line Items]
Pretax Profit (Loss)		$ (34.2)	$ (32.5)
Personal Auto | Underwriting Operations | Personal Lines
Segment Reporting Information [Line Items]
Personal auto insurance percentage of the total personal lines segment net premiums earned		92.00%	92.00%
[1]	1Personal auto insurance accounted for 92% of the total Personal Lines segment net premiums earned in both the first quarters of 2016 and 2015; 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]	2We 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. For the three months ended March 31, 2016, pretax loss includes $45.3 million of catastrophe losses and $15.1 million of amortization/depreciation expense associated with the acquisition of a controlling interest in ARX. Although the amortization 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]	3Pretax profit (loss) for fees and other revenues are allocated to operating segments.
[4]	4Revenues represent recurring investment income and total net realized gains (losses) on securities; pretax profit is net of investment expenses.

Segment Information Underwritin

Segment Information Underwriting Margins and Combined Ratios for our Underwriting Operations (Detail) - Underwriting Operations		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Segment Reporting Information [Line Items]
Underwriting Margin		5.40%	7.30%
Combined Ratio		94.60%	92.70%
Personal Lines
Segment Reporting Information [Line Items]
Underwriting Margin		5.50%	6.30%
Combined Ratio		94.50%	93.70%
Personal Lines | Agency Channel
Segment Reporting Information [Line Items]
Underwriting Margin		7.30%	8.70%
Combined Ratio		92.70%	91.30%
Personal Lines | Direct Channel
Segment Reporting Information [Line Items]
Underwriting Margin		3.60%	3.50%
Combined Ratio		96.40%	96.50%
Commercial Lines
Segment Reporting Information [Line Items]
Underwriting Margin		11.10%	16.80%
Combined Ratio		88.90%	83.20%
Property, Liability and Casualty Insurance Product Line [Member]
Segment Reporting Information [Line Items]
Underwriting Margin		(12.20%)
Combined Ratio	[1]	112.20%
Combined ratio amortization points		7.6
[1]	1Includes 7.6 points of amortization/depreciation expense associated with the acquisition of a controlling interest in ARX.

Dividends Dividends (Details)

Dividends Dividends (Details) - USD ($) $ / shares in Units, $ in Millions		Feb. 12, 2016	Feb. 13, 2015
Dividends [Abstract]
Dividend paid per share (USD per share)		$ 0.8882	$ 0.6862
Payments of Ordinary Dividends, Common Stock	[1]	$ 519	$ 404.1
[1]	1Represents the final amount of dividends declared based on shares outstanding as of the record date.

Dividends - Additional Informat

Dividends - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2016USD ($)	Mar. 31, 2015USD ($)
Dividends [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	35.00%
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	1.30
Comprehensive income	$ 325.8	$ 321.8
After-tax underwriting income	$ 186.4

Other Comprehensive Income (L53

Other Comprehensive Income (Loss) Components of Other Comprehensive Income (Loss) Including Reclassification Adjustments by Income Statement (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]
Pre tax total accumulated other comprehensive income, beginning balance	$ 1,234.5	$ 1,574
Investment securities, pre tax	142.7	99.3
Net non-credit related OTTI losses, adjusted for valuation changes, pre tax	(0.1)	0
Forecasted transactions, pre tax	0	(12.8)
Foreign currency translation adjustment, pre tax	0.7	(0.9)
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Noncontrolling Interest	(3.3)	0
Total other comprehensive income (loss) before reclassifications, pre tax	140	85.6
Total reclassification adjustment for amounts realized in net income, pre tax	35.8	45.4
Total other comprehensive income (loss), pre tax	104.2	40.2
Pre tax total accumulated other comprehensive income, ending balance	1,338.7	1,614.2
Accumulated Other Comprehensive Income (Loss), Tax [Roll Forward]
Accumulated other comprehensive income loss tax (Provision) benefit, beginning balance	(434.1)	(550.9)
Investment securities, Total tax (provision) benefit	(50.3)	(34.7)
Net non-credit related OTTI losses, adjusted for valuation changes, Total tax (provision) benefit	0.1	0
Forecasted transactions, Total tax (provision) benefit	0	4.4
Foreign currency translation adjustment, Total tax (provision) benefit	(0.2)	0.4
Other Comprehensive Income (Loss), Tax, Portion Attributable to Noncontrolling Interest	1.2	0
Total other comprehensive income (loss) before reclassifications, Total tax (provision) benefit	(49.2)	(29.9)
Total reclassification adjustment for amounts realized in net income, Total tax (provision) benefit	(12.6)	(15.9)
Total other comprehensive income (loss), Total tax (provision) benefit	(36.6)	(14)
Accumulated other comprehensive income loss tax (Provision) benefit, ending balance	(470.7)	(564.9)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
After tax total accumulated other comprehensive income, beginning balance	800.4	1,023.1
Investment securities, after tax	92.4	64.6
Net non-credit related OTTI losses, adjusted for valuation changes, after tax	0	0
Forecasted transactions, after tax	0	(8.4)
Foreign currency translation adjustment, after tax	0.5	(0.5)
Other comprehensive (income) loss attributable to NCI	(2.1)	0
Total other comprehensive income (loss) before reclassifications, after tax	90.8	55.7
Total reclassification adjustment for amounts realized in net income, after tax	23.2	29.5
Other comprehensive income (loss)	67.6	26.2
After tax total accumulated other comprehensive income, ending balance	868	1,049.3
Net impairment losses recognized in earnings	0	(7.9)
Net realized gains (losses) on securities	17.4	40.9
Interest expense	34.2	32.5
Accumulated other comprehensive income after tax
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive (income) loss attributable to NCI	(2.1)	0
Net unrealized gains (losses) on securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
After tax total accumulated other comprehensive income, beginning balance	809	1,021.9
Investment securities, after tax	92.4	64.6
Net non-credit related OTTI losses, adjusted for valuation changes, after tax	0	0
Forecasted transactions, after tax	0	0
Foreign currency translation adjustment, after tax	0	0
Other comprehensive (income) loss attributable to NCI	0	0
Total other comprehensive income (loss) before reclassifications, after tax	92.4	64.6
Total reclassification adjustment for amounts realized in net income, after tax	22.9	29.2
Other comprehensive income (loss)	69.5	35.4
After tax total accumulated other comprehensive income, ending balance	878.5	1,057.3
Net unrealized gains on forecasted transactions
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
After tax total accumulated other comprehensive income, beginning balance	(8.2)	1.5
Investment securities, after tax	0	0
Net non-credit related OTTI losses, adjusted for valuation changes, after tax	0	0
Forecasted transactions, after tax	0	(8.4)
Foreign currency translation adjustment, after tax	0	0
Other comprehensive (income) loss attributable to NCI	0	0
Total other comprehensive income (loss) before reclassifications, after tax	0	(8.4)
Total reclassification adjustment for amounts realized in net income, after tax	0.3	0.3
Other comprehensive income (loss)	(0.3)	(8.7)
After tax total accumulated other comprehensive income, ending balance	(8.5)	(7.2)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
After tax total accumulated other comprehensive income, beginning balance	(1.5)	(0.3)
Investment securities, after tax	0	0
Net non-credit related OTTI losses, adjusted for valuation changes, after tax	0	0
Forecasted transactions, after tax	0	0
Foreign currency translation adjustment, after tax	0.5	(0.5)
Other comprehensive (income) loss attributable to NCI	0	0
Total other comprehensive income (loss) before reclassifications, after tax	0.5	(0.5)
Total reclassification adjustment for amounts realized in net income, after tax	0	0
Other comprehensive income (loss)	0.5	(0.5)
After tax total accumulated other comprehensive income, ending balance	(1)	(0.8)
Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
After tax total accumulated other comprehensive income, beginning balance	1.1	0
Investment securities, after tax	0	0
Net non-credit related OTTI losses, adjusted for valuation changes, after tax	0	0
Forecasted transactions, after tax	0	0
Foreign currency translation adjustment, after tax	0	0
Other comprehensive (income) loss attributable to NCI	(2.1)	0
Total other comprehensive income (loss) before reclassifications, after tax	(2.1)	0
Total reclassification adjustment for amounts realized in net income, after tax	0	0
Other comprehensive income (loss)	(2.1)	0
After tax total accumulated other comprehensive income, ending balance	(1)	0
Reclassification out of Accumulated Other Comprehensive Income | Accumulated other comprehensive income pretax
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net impairment losses recognized in earnings	0	(7.9)
Net realized gains (losses) on securities	35.3	52.8
Interest expense	0.5	0.5
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	0	2.8
Net realized gains (losses) on securities	(12.4)	(18.5)
Interest expense	(0.2)	(0.2)
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	0	(5.1)
Net realized gains (losses) on securities	22.9	34.3
Interest expense	0.3	0.3
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	0	(5.1)
Net realized gains (losses) on securities	22.9	34.3
Interest expense	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
Net realized gains (losses) on securities	0	0
Interest expense	0.3	0.3
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
Net realized gains (losses) on securities	0	0
Interest expense	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
Net realized gains (losses) on securities	0	0
Interest expense	$ 0	$ 0

Other Comprehensive Income (L54

Other Comprehensive Income (Loss) Components of Other Comprehensive Income (Loss) Including Reclassification Adjustments by Income Statement, Additional Information (Detail) $ in Millions	Mar. 31, 2016USD ($)
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

Redeemable Noncontrolling Int55

Redeemable Noncontrolling Interest (Details) - USD ($) $ in Millions		3 Months Ended
		Jun. 30, 2021	Jun. 30, 2018	Mar. 31, 2016	Jun. 30, 2015	Mar. 31, 2015	Apr. 01, 2021	Apr. 01, 2018
Redeemable Noncontrolling Interest [Line Items]
Business Combination, Control Obtained Description					2
Balance at December 31, 2015	[1]			$ 464.9	$ 0
Net income attributable to NCI				0.5
Other comprehensive income attributable to NCI				2.1		$ 0
Purchase of shares from NCI				0
Change in redemption value of NCI				(0.1)
Balance at March 31, 2016	[1]			$ 467.4		$ 0
ARX Holding Corp. [Member]
Redeemable Noncontrolling Interest [Line Items]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage				69.20%
Scenario, Forecast [Member]
Redeemable Noncontrolling Interest [Line Items]
Business Combination, Control Obtained Description		1	1
Scenario, Forecast [Member] | ARX Holding Corp. [Member]
Redeemable Noncontrolling Interest [Line Items]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage							100.00%	80.00%
[1]	2See Note 11 – Redeemable Noncontrolling Interest for further discussion.

Acquisition (Details)

Acquisition (Details) - USD ($)	3 Months Ended		9 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Business Acquisition [Line Items]
Amortization of Intangible Assets	$ 15,500,000	$ 0
Goodwill	$ 447,600,000	$ 1,600,000	$ 447,600,000
ARX Holding Corp. [Member]
Business Acquisition [Line Items]
Cost of interest acquired			$ 890,100,000
Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage	69.20%
Amortization of Intangible Assets	$ 15,000,000
Goodwill	446,000,000
Goodwill, Impairment Loss	$ 0

Acquisition Schedule of Intangi

Acquisition Schedule of Intangible Assets by Category (Details) - USD ($) $ in Millions	Apr. 01, 2015	Mar. 31, 2016
Policies in Force [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		6 years
Remaining Useful Life	7 years
Agency Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		13 years
Remaining Useful Life	14 years
Computer Software, Intangible Asset [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		7 years
Remaining Useful Life	8 years
Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		9 years
Remaining Useful Life	10 years
ARX Holding Corp. [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Value	$ 520.4
Accumulated Amortization		$ 60.1
ARX Holding Corp. [Member] | Policies in Force [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Value	256.2
Accumulated Amortization		36.6
ARX Holding Corp. [Member] | Agency Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Value	159.2
Accumulated Amortization		11.4
ARX Holding Corp. [Member] | Computer Software, Intangible Asset [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Value	69.1
Accumulated Amortization		8.6
ARX Holding Corp. [Member] | Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Value	34.8
Accumulated Amortization		3.5
ARX Holding Corp. [Member] | Licensing Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Value	$ 1.1
Accumulated Amortization		$ 0

New Accounting Standards Effect

New Accounting Standards Effect of Standard Change (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounting Policies [Abstract]
Tax benefit from vesting of equity-based compensation	$ 16.8	$ 12.8	$ 10.3