The Progressive Corporation (PGR) 10-Q 5 Nov 15 2015 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information $ in Millions	9 Months Ended
	Sep. 30, 2015USD ($)shares
Document Document And Entity Information [Abstract]
Unrecorded Unconditional Purchase Obligation	$ 63.6
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	Sep. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q3
Amendment Flag	false
Trading Symbol	PGR
Entity Common Stock, Shares Outstanding | shares	584,544,245

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenues
Net premiums earned		$ 5,070.6	$ 4,540.1	$ 14,732.7	$ 13,455.9
Period over prior year period percent change in net premiums earned		12.00%		9.00%
Investment income		$ 117.5	101.7	$ 335.9	304.2
Period over prior year period percent change in investment income		16.00%		10.00%
Other-than-temporary impairment (OTTI) losses:
Net impairment losses recognized in earnings		$ (13.6)	(0.1)	$ (23.2)	(0.1)
Net realized gains (losses) on securities		$ (2.2)	38.3	$ 116.4	198.1
Period over prior year period percent change in net realized gains (losses) on securities		(106.00%)		(41.00%)
Total net realized gains (losses) on securities		$ (15.8)	38.2	$ 93.2	198
Period over prior year period percent change in total net realized gains (losses) on securities		(141.00%)		(53.00%)
Fees and other revenues		$ 79.3	75.9	$ 227.9	223.1
Period over prior year period percent change in fees and other revenues		4.00%		2.00%
Service revenues		$ 23.1	15	$ 63.6	38.8
Period over prior year period percent change in service revenues		54.00%		64.00%
Gains (Losses) on Extinguishment of Debt		$ (0.9)	(4.8)	$ (0.9)	(4.8)
Period over prior year period percent change in gains (losses) on extinguishment of debt		(81.00%)		(81.00%)
Total revenues		$ 5,273.8	4,766.1	$ 15,452.4	14,215.2
Period over prior year period percent change in total revenues		11.00%		9.00%
Expenses
Losses and loss adjustment expenses		$ 3,654.3	3,291.8	$ 10,640.1	9,766.8
Period over prior year period percent change in losses and loss adjustment expenses		11.00%		9.00%
Policy acquisition costs		$ 423.2	375.2	$ 1,219.9	1,119
Period over prior year period percent change in policy acquisition costs		13.00%		9.00%
Other underwriting expenses		$ 707.5	609.2	$ 2,020.3	1,831.3
Period over prior year period percent change in other underwriting expenses		16.00%		10.00%
Investment expenses		$ 4.9	3.9	$ 15.9	14
Period over prior year period percent change in investment expenses		26.00%		14.00%
Service expenses		$ 20.4	13.5	$ 56.8	36.1
Period over prior year period percent change in service expenses		51.00%		57.00%
Interest expense		$ 34.5	30.7	$ 101.9	87
Period over prior year period percent change in interest expense		12.00%		17.00%
Total expenses		$ 4,844.8	4,324.3	$ 14,054.9	12,854.2
Period over prior year period percent change in total expenses		12.00%		9.00%
Net Income
Income before income taxes		$ 429	441.8	$ 1,397.5	1,361
Period over prior year period percent change in income before income taxes		(3.00%)		3.00%
Provision for income taxes		$ 142.5	145.7	$ 446.9	450.2
Period over prior year period percent change in provision for income taxes		(2.00%)		(1.00%)
Period over prior year period percent change in net income		(3.00%)		4.00%
Net Income (Loss) Attributable to Noncontrolling Interest		$ 8.2	0	$ 13.4	0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		286.5	296.1	950.6	910.8
Net Income (Loss) Attributable to Parent		$ 278.3	296.1	$ 937.2	910.8
Period over Prior Year Period Percent Change Net Income Attributable to Parent		(6.00%)		3.00%
Net unrealized gains (losses) on securities:
Total net unrealized gains (losses) on securities		$ (130.1)	(65.1)	$ (244.5)	23.2
Period over prior year period percent change in total net unrealized gains (losses) on securities		100.00%
Net unrealized gains (losses) on forecasted transactions		$ (0.4)	(0.7)	$ (9.4)	(2.3)
Period over prior year period percent change in net unrealized gains on forecasted transactions		(43.00%)		309.00%
Foreign currency translation adjustment		$ (0.7)	(0.4)	$ (1.2)	0.1
Period over prior year period percent change in foreign currency translation adjustment		75.00%
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest		$ (131.2)	(66.2)	(255.1)	21
Period over prior year period percent change in other comprehensive income (loss)		98.00%
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest		$ (1.6)	0	1.2	0
Comprehensive income		$ 145.5	$ 229.9	$ 683.3	$ 931.8
Period over prior year period percent change in comprehensive income		(37.00%)		(27.00%)
Computation of Net Income Per Share
Average shares outstanding - Basic (shares)		585.2	589.8	586.1	591.6
Period over prior year period percent change in average shares outstanding - basic		(1.00%)		(1.00%)
Net effect of dilutive stock-based compensation (shares)		3.9	3.9	3.7	4.1
Period over prior year period percent change in net effect of dilutive stock-based compensation		0.00%		(10.00%)
Total equivalent shares - Diluted (shares)		589.1	593.7	589.8	595.7
Period over prior year period percent change in total equivalent shares - diluted		(1.00%)		(1.00%)
Basic: Net income per share (USD per share)		$ 0.48	$ 0.50	$ 1.60	$ 1.54
Period over prior year period percent change in basic: net income per share		(5.00%)		4.00%
Diluted: Net income per share (USD per share)		$ 0.47	0.50	$ 1.59	1.53
Period over prior year period percent change in diluted: net income per share		(5.00%)		4.00%
Dividends declared per share (USD per share)	[1]	$ 0	$ 0	$ 0	$ 0
[1]	1Progressive maintains an annual dividend program. See Note 8 - Dividends for further discussion.See notes to consolidated financial statements.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Investments - Available-for-sale, at fair value:
Fixed maturities (amortized cost: $15,539.6, $13,090.0, and $13,374.2)		$ 15,622.1	$ 13,549.2	$ 13,269.4
Equity securities:
Nonredeemable preferred stocks (cost: $652.4, $532.8, and $590.4)		775.6	827.5	763.3
Common equities (cost: $1,487.0, $1,278.4, and $1,289.2)		2,483.9	2,492.3	2,379.4
Short-term investments (amortized cost: $2,132.0, $2,671.1, and $2,149.0)		2,132	2,149	2,671.1
Total investments at fair value	[1],[2]	21,013.6	19,018	19,083.2
Cash		194.5	108.4	90.6
Accrued investment income		103.6	87.3	81.9
Premiums receivable, net of allowance for doubtful accounts of $153.3, $143.6, and $152.2		4,139.8	3,537.5	3,705.6
Reinsurance recoverables, including $46.1, $39.4, and $46.0 on paid losses and loss adjustment expenses		1,415	1,231.9	1,165.9
Prepaid reinsurance premiums		221.7	85.3	92.3
Deferred acquisition costs		590.8	457.2	488.3
Property and equipment, net of accumulated depreciation of $758.8, $715.9, and $731.0		1,024.1	960.6	954
Goodwill		446.4	1.6	1.6
Intangible assets, net of accumulated amortization of $31.8, $0.6, and $0.6		510.5	11.3	11.3
Other assets		275	288.5	251.3
Total assets		29,935	25,787.6	25,926
Liabilities
Unearned premiums		6,971.9	5,440.1	5,777
Loss and loss adjustment expense reserves		9,827.2	8,857.4	8,728.4
Net deferred income taxes		85.7	98.9	57.4
Dividends payable		0	404.1	0
Accounts payable, accrued expenses, and other liabilities		2,431	1,893.8	2,263.6
Debt, Long-term and Short-term, Combined Amount	[3]	2,714.3	2,164.7	2,164.3
Total liabilities		22,030.1	18,859	18,990.7
Redeemable noncontrolling interest (NCI)		442.9	0	0
Common Shares, $1.00 par value (authorized 900.0; issued 797.6, including treasury shares of 213.0, 208.4, and 209.8)		584.6	587.8	589.2
Paid-in capital		1,197.3	1,184.3	1,169.9
Retained earnings		4,910.9	4,133.4	4,203.5
Accumulated other comprehensive income, net of tax:
Net unrealized gains (losses) on securities		777.4	1,021.9	970.2
Net unrealized gains (losses) on forecasted transactions		(7.9)	1.5	1.8
Foreign currency translation adjustment		(1.5)	(0.3)	0.7
Accumulated other comprehensive (income) loss attributable to noncontrolling interest		1.2	0	0
Total accumulated other comprehensive income		769.2	1,023.1	972.7
Total shareholders’ equity		7,462	6,928.6	6,935.3
Total liabilities, redeemable NCI, and shareholders’ equity		$ 29,935	$ 25,787.6	$ 25,926
[1]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at September 30, 2015, $149.9 million was included in "other liabilities," compared to $158.0 million and $31.3 million at September 30, 2014 and December 31, 2014
[2]	The total fair value of the portfolio at September 30, 2015 and 2014, and December 31, 2014 included $1.0 billion, $1.3 billion, and $1.9 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.See notes to consolidated financial statements.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions, $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Fixed maturities, amortized cost	$ 15,539.6	$ 13,374.2	$ 13,090
Nonredeemable preferred stocks, cost	652.4	590.4	532.8
Common equities, cost	1,487	1,289.2	1,278.4
Short-term investments, amortized cost	2,132	2,149	2,671.1
Premiums receivable, allowance for doubtful accounts	153.3	152.2	143.6
Reinsurance recoverables, paid losses and loss adjustment expenses	46.1	46	39.4
Property and equipment, accumulated depreciation	$ 758.8	$ 731	$ 715.9
Common Shares, par value (USD per share)	$ 1	$ 1	$ 1
Common Shares, authorized (shares)	900	900	900
Common Shares, issued (shares)	797.6	797.6	797.6
Common Shares, treasury shares (shares)	213	209.8	208.4

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
Balance, Beginning of period at Dec. 31, 2013		$ 595.8	$ 1,142	$ 3,500	$ 951.7
Net income available to Progressive	$ 910.8			910.8
Other comprehensive income (loss)	21				21
Tax benefit from exercise/vesting of equity-based compensation			12.8
Treasury shares purchased		(9.6)	(18.7)	(206.4)
Net restricted equity awards (issued) (vested) forfeited		3	(3)
Cash dividends declared on common shares				1.1
Amortization of equity-based compensation			38.4
Reinvested dividends on restricted stock units			(1.6)	(1.6)
Other				(3.6)
Balance, End of period at Sep. 30, 2014	6,935.3	589.2	1,169.9	4,203.5	972.7
Accumulated other comprehensive (income) loss attributable to noncontrolling interest	0
Redeemable noncontrolling interest (NCI)	0		0
Accumulated other comprehensive (income) loss attributable to noncontrolling interest	0
Redeemable noncontrolling interest (NCI)	0
Balance, Beginning of period at Dec. 31, 2014	6,928.6	587.8	1,184.3	4,133.4	1,023.1
Net income available to Progressive	937.2			937.2
Other comprehensive income (loss)	(253.9)				(255.1)
Tax benefit from exercise/vesting of equity-based compensation			15
Treasury shares purchased		(6.3)	(12.9)	(155.7)
Net restricted equity awards (issued) (vested) forfeited		3.1	(3.1)
Cash dividends declared on common shares				0
Amortization of equity-based compensation			45.9
Reinvested dividends on restricted stock units			(0.1)	(0.1)
Other				(4.1)
Balance, End of period at Sep. 30, 2015	7,462	$ 584.6	1,197.3	$ 4,910.9	$ 769.2
Accumulated other comprehensive (income) loss attributable to noncontrolling interest	1.2
Redeemable noncontrolling interest (NCI)	$ 442.9		$ (31.8)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014
Statement of Cash Flows [Abstract]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		$ 950.6	$ 910.8
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation		76.1	71.8
Amortization of intangible assets		31.2	0
Amortization of fixed-income securities		71.2	59.5
Amortization of equity-based compensation		45.9	38.4
Net realized (gains) losses on securities		(93.2)	(198)
Net (gains) losses on disposition of property and equipment		0.5	4.2
Changes in:
Premiums receivable		(573.2)	(394.9)
Reinsurance recoverables		(128.8)	(75.7)
Prepaid reinsurance premiums		10.1	(17.4)
Deferred acquisition costs		(69)	(40.7)
Income taxes		(92.1)	82.1
Unearned premiums		982.7	602.4
Loss and loss adjustment expense reserves		705.8	248.7
Accounts payable, accrued expenses, and other liabilities		218.7	333.1
Other, net		22.1	28.4
Net cash provided by operating activities		2,159.5	1,657.5
Gains (Losses) on Extinguishment of Debt		(0.9)	(4.8)
Purchases:
Fixed maturities		(7,106.7)	(5,774.5)
Equity securities		(461.3)	(250.7)
Sales:
Fixed maturities		3,639.8	4,342
Equity securities		251.8	500.2
Maturities, paydowns, calls, and other:
Fixed maturities		2,469.4	1,714.5
Equity securities		12	14.2
Net sales (purchases) of short-term investments		60.4	(1,397.9)
Net unsettled security transactions		118.6	96.7
Purchases of property and equipment		(86.6)	(73.6)
Payments to Acquire Businesses, Net of Cash Acquired		(752.7)	0
Payments to Acquire Additional Interest in Subsidiaries		(12.6)	0
Sales of property and equipment		8.7	4.5
Net cash used in investing activities		(1,859.2)	(824.6)
Cash Flows From Financing Activities
Tax benefit from vesting of equity-based compensation		15	12.8
Proceeds from debt issuance		382	344.7
Dividends paid to shareholders	[1]	(403.6)	(892.6)
Acquisition of treasury shares		(174.9)	(234.7)
Net cash used in financing activities		(213.5)	(818.7)
Repayments of Debt		13.6	0
Effect of exchange rate changes on cash		(0.7)	1.3
Increase in cash		86.1	15.5
Cash, Beginning of year		108.4	75.1
Cash, End of period		194.5	90.6
Early Repayment of Subordinated Debt		$ 18.4	$ 48.9
[1]	Progressive maintains an annual dividend program. See Note 8 - Dividends for further discussion.See notes to consolidated financial statements.

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation — The consolidated financial statements include the accounts of The Progressive Corporation, its subsidiaries, a mutual insurance company affiliate, and a limited partnership investment affiliate. During the second quarter 2015, Progressive acquired a controlling interest in ARX Holding Corp. (ARX), which wholly owns or controls insurance and non-insurance subsidiaries and affiliates. As of September 30, 2015 , Progressive owns 69.1% of the outstanding capital stock of ARX. All of Progressive's other subsidiaries and affiliates are wholly owned or controlled. Beginning April 1, 2015, we consolidated 100% of ARX's financial information into our results of operations, financial condition, and cash flows. The minority shareholders of ARX retain a 30.9% interest in the operating results of ARX. These interests are reflected in our comprehensive income statements as "Net income/Other comprehensive income attributable to noncontrolling interest (NCI)." As part of a related stockholders' agreement, Progressive has the ability to "call" the remaining outstanding shares to achieve 100% ownership in ARX by the end of the second quarter of 2021. In addition, the minority ARX shareholders have the right to “put” their ARX shares to Progressive by that date. 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. The redeemable noncontrolling interest was initially recorded at fair value of $411.5 million , representing the minority shares at the net acquisition price adjusted for the fair value of the put and call rights. The value of the put and call rights on the acquisition date was based on an internally developed modified binomial model. Subsequent changes to the redeemable noncontrolling interest are based on the maximum redemption value at the end of the reporting period, as determined in accordance with the stockholders' agreement. The 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 September 30, 2015 , 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 our Annual Report on Form 10-K for the year ended December 31, 2014 . 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 September 30, 2015 and December 31, 2014, and $13.4 million at September 30, 2014.

Investments

Investments	9 Months Ended
	Sep. 30, 2015
Investments Schedule [Abstract]
Investments	Investments — Our securities are reported at fair value, with the changes in fair value of these securities (other than hybrid securities and derivative instruments) reported as a component of accumulated other comprehensive income, net of deferred income taxes. The changes in fair value of the hybrid securities and derivative instruments are recorded as a component of net realized gains (losses) on securities. The following tables present the composition of our investment portfolio by major security type, consistent with our classification of how we manage, monitor, and measure the portfolio: ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) 1 Fair Value % of Value September 30, 2015 Fixed maturities: U.S. government obligations $ 2,028.2 $ 10.1 $ 0 $ 0 $ 2,038.3 9.7 % State and local government obligations 3,025.0 47.1 (4.2 ) 0 3,067.9 14.6 Foreign government obligations 19.3 0 0 0 19.3 0.1 Corporate debt securities 3,797.4 23.4 (21.4 ) 0.1 3,799.5 18.1 Residential mortgage-backed securities 1,801.8 26.2 (18.4 ) (0.2 ) 1,809.4 8.6 Agency residential pass-through obligations 112.2 0.1 (0.4 ) 0 111.9 0.5 Commercial mortgage-backed securities 2,641.4 31.1 (9.3 ) 0.4 2,663.6 12.7 Other asset-backed securities 1,859.3 4.1 (1.5 ) 0.5 1,862.4 8.9 Redeemable preferred stocks 255.0 17.6 (22.8 ) 0 249.8 1.2 Total fixed maturities 15,539.6 159.7 (78.0 ) 0.8 15,622.1 74.4 Equity securities: Nonredeemable preferred stocks 652.4 138.3 (14.8 ) (0.3 ) 775.6 3.7 Common equities 1,487.0 1,031.9 (35.0 ) 0 2,483.9 11.8 Short-term investments 2,132.0 0 0 0 2,132.0 10.1 Total portfolio 2,3 $ 19,811.0 $ 1,329.9 $ (127.8 ) $ 0.5 $ 21,013.6 100.0 % ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) 1 Fair Value % of Value September 30, 2014 Fixed maturities: U.S. government obligations $ 3,033.2 $ 33.6 $ (3.9 ) $ 0 $ 3,062.9 16.0 % State and local government obligations 2,124.2 49.5 (0.9 ) 0 2,172.8 11.4 Foreign government obligations 20.2 0 0 0 20.2 0.1 Corporate debt securities 2,501.8 30.7 (13.1 ) (0.3 ) 2,519.1 13.2 Residential mortgage-backed securities 1,460.6 36.9 (10.1 ) (0.9 ) 1,486.5 7.8 Commercial mortgage-backed securities 2,143.8 33.8 (5.1 ) 0 2,172.5 11.4 Other asset-backed securities 1,546.0 5.0 (0.6 ) 0.2 1,550.6 8.1 Redeemable preferred stocks 260.2 28.8 (4.2 ) 0 284.8 1.5 Total fixed maturities 13,090.0 218.3 (37.9 ) (1.0 ) 13,269.4 69.5 Equity securities: Nonredeemable preferred stocks 532.8 218.4 (7.2 ) 19.3 763.3 4.0 Common equities 1,278.4 1,107.7 (6.7 ) 0 2,379.4 12.5 Short-term investments 2,671.1 0 0 0 2,671.1 14.0 Total portfolio 2,3 $ 17,572.3 $ 1,544.4 $ (51.8 ) $ 18.3 $ 19,083.2 100.0 % ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) 1 Fair Value % of Value December 31, 2014 Fixed maturities: U.S. government obligations $ 2,641.1 $ 27.3 $ (1.3 ) $ 0 $ 2,667.1 14.0 % State and local government obligations 2,095.7 44.6 (1.1 ) 0 2,139.2 11.2 Foreign government obligations 14.2 0 0 0 14.2 0.1 Corporate debt securities 2,813.9 32.9 (10.4 ) 0.3 2,836.7 14.9 Residential mortgage-backed securities 1,635.5 34.5 (10.8 ) (0.7 ) 1,658.5 8.7 Commercial mortgage-backed securities 2,278.7 39.3 (2.6 ) 0.2 2,315.6 12.2 Other asset-backed securities 1,634.9 3.8 (0.8 ) 0.8 1,638.7 8.6 Redeemable preferred stocks 260.2 24.7 (5.7 ) 0 279.2 1.5 Total fixed maturities 13,374.2 207.1 (32.7 ) 0.6 13,549.2 71.2 Equity securities: Nonredeemable preferred stocks 590.4 201.1 (6.4 ) 42.4 827.5 4.4 Common equities 1,289.2 1,213.2 (10.1 ) 0 2,492.3 13.1 Short-term investments 2,149.0 0 0 0 2,149.0 11.3 Total portfolio 2,3 $ 17,402.8 $ 1,621.4 $ (49.2 ) $ 43.0 $ 19,018.0 100.0 % 1 Represents net holding period gains (losses) on certain hybrid securities (discussed below). 2 Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at September 30, 2015 , $149.9 million was included in "other liabilities," compared to $158.0 million and $31.3 million at September 30, 2014 and December 31, 2014 , respectively. 3 The total fair value of the portfolio at September 30, 2015 and 2014 , and December 31, 2014 included $1.0 billion , $1.3 billion , and $1.9 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 hold any repurchase transactions where we lent collateral at September 30, 2015 , September 30, 2014 , or December 31, 2014 . To the extent our repurchase transactions were with the same counterparty and subject to an enforceable master netting arrangement, we could elect to offset 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. Also included in short-term investments are reverse repurchase commitment transactions, where we loan cash to approved counterparties and receive U.S. Treasury Notes pledged as collateral against the cash borrowed. Our exposure to credit risk is limited due to the nature of the collateral (i.e., U.S. Treasury Notes) received. We have counterparty exposure on these trades in the event of a counterparty default to the extent the general collateral security's value is below the amount of cash we delivered to acquire the collateral. The short-term duration of the transactions (primarily overnight) reduces that exposure. We had no open reverse repurchase commitments at September 30, 2015 , September 30, 2014 , or December 31, 2014 . For the nine months ended September 30, 2015 , our largest outstanding balance of reverse repurchase commitments was $275.0 million , which was open for one day; the average daily balance of reverse repurchase commitments was $129.7 million over a period of 37 days. Hybrid Securities Included in our fixed-maturity and equity securities are hybrid securities, which are reported at fair value: September 30, December 31, (millions) 2015 2014 Fixed maturities: Corporate debt securities $ 89.4 $ 138.5 $ 139.8 Residential mortgage-backed securities 117.7 116.8 120.7 Commercial mortgage-backed securities 17.7 0 31.2 Other asset-backed securities 11.9 13.5 13.7 Total fixed maturities 236.7 268.8 305.4 Equity securities: Nonredeemable preferred stocks 54.1 93.4 122.3 Total hybrid securities $ 290.8 $ 362.2 $ 427.7 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 $3.3 million as of September 30, 2015 , 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. 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 Holding Corp. and transferred our previous 5% preferred stock investment in ARX to a component of our total ownership interest (see Note 15 – Acquisition for further discussion). This transfer was offset by purchases of new hybrid securities since September 30, 2014 . Fixed Maturities The composition of fixed maturities by maturity at September 30, 2015 , was: (millions) Cost Fair Value Less than one year $ 4,699.3 $ 4,717.3 One to five years 6,826.1 6,855.9 Five to ten years 3,843.8 3,871.0 Ten years or greater 170.4 177.9 Total $ 15,539.6 $ 15,622.1 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 September 30, 2015 , we had $92.8 million of gross unrealized losses in our fixed-income securities (i.e., fixed-maturity securities, nonredeemable preferred stocks, and short-term investments) and $35.0 million in our common equities. We currently do not intend to sell the fixed-income securities and determined that it is more likely than not that we will not be required to sell these securities for the period of time necessary to recover their cost bases. A review of our fixed-income securities indicated that the issuers were current with respect to their interest obligations and that there was no evidence of any deterioration of the current cash flow projections that would indicate we would not receive the remaining principal at maturity. For common equities, 89% of our common stock portfolio was indexed to the Russell 1000; as such, this portfolio may contain securities in a loss position for an extended period of time, subject to possible write-downs, as described below. We may retain these securities as long as the portfolio and index correlation remain similar. To the extent there is issuer-specific deterioration, we may write-down the securities of that issuer. The remaining 11% of our common stocks were part of a managed equity strategy selected and administered by external investment advisors. If our review of loss position securities indicates there was a fundamental, or market, impairment on these securities that was determined to be other-than-temporary, we would recognize a write-down in accordance with our stated policy. The following tables show the composition of gross unrealized losses by major security type and by the length of time that individual securities have been in a continuous unrealized loss position: Total No. of Sec. Total Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Unrealized Losses No. of Sec. Fair Unrealized Losses September 30, 2015 Fixed maturities: U.S. government obligations 0 $ 0 $ 0 0 $ 0 $ 0 0 $ 0 $ 0 State and local government obligations 349 637.1 (4.2 ) 328 551.4 (3.7 ) 21 85.7 (0.5 ) Corporate debt securities 140 1,596.5 (21.4 ) 125 1,292.1 (15.7 ) 15 304.4 (5.7 ) Residential mortgage-backed securities 141 1,205.9 (18.4 ) 76 535.8 (4.1 ) 65 670.1 (14.3 ) Agency residential pass-through obligations 54 67.6 (0.4 ) 54 67.6 (0.4 ) 0 0 0 Commercial mortgage-backed securities 127 1,100.0 (9.3 ) 99 813.8 (7.6 ) 28 286.2 (1.7 ) Other asset-backed securities 60 845.5 (1.5 ) 53 764.0 (0.9 ) 7 81.5 (0.6 ) Redeemable preferred stocks 9 214.8 (22.8 ) 6 121.8 (7.1 ) 3 93.0 (15.7 ) Total fixed maturities 880 5,667.4 (78.0 ) 741 4,146.5 (39.5 ) 139 1,520.9 (38.5 ) Equity securities: Nonredeemable preferred stocks 14 376.9 (14.8 ) 9 197.6 (2.5 ) 5 179.3 (12.3 ) Common equities 136 211.6 (35.0 ) 132 209.1 (34.4 ) 4 2.5 (0.6 ) Total equity securities 150 588.5 (49.8 ) 141 406.7 (36.9 ) 9 181.8 (12.9 ) Total portfolio 1,030 $ 6,255.9 $ (127.8 ) 882 $ 4,553.2 $ (76.4 ) 148 $ 1,702.7 $ (51.4 ) Total No. of Sec. Total Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Unrealized Losses No. of Sec. Fair Unrealized Losses September 30, 2014 Fixed maturities: U.S. government obligations 19 $ 627.0 $ (3.9 ) 9 $ 211.0 $ (0.7 ) 10 $ 416.0 $ (3.2 ) State and local government obligations 31 181.8 (0.9 ) 11 89.7 (0.1 ) 20 92.1 (0.8 ) Corporate debt securities 50 891.4 (13.1 ) 42 744.5 (9.7 ) 8 146.9 (3.4 ) Residential mortgage-backed securities 62 725.8 (10.1 ) 24 290.5 (1.8 ) 38 435.3 (8.3 ) Agency residential pass-through obligations 0 0 0 0 0 0 0 0 0 Commercial mortgage-backed securities 72 894.5 (5.1 ) 61 787.3 (2.9 ) 11 107.2 (2.2 ) Other asset-backed securities 38 650.8 (0.6 ) 36 624.7 (0.4 ) 2 26.1 (0.2 ) Redeemable preferred stocks 2 70.5 (4.2 ) 0 0 0 2 70.5 (4.2 ) Total fixed maturities 274 4,041.8 (37.9 ) 183 2,747.7 (15.6 ) 91 1,294.1 (22.3 ) Equity securities: Nonredeemable preferred stocks 7 206.3 (7.2 ) 4 118.6 (4.0 ) 3 87.7 (3.2 ) Common equities 39 57.5 (6.7 ) 37 45.7 (5.4 ) 2 11.8 (1.3 ) Total equity securities 46 263.8 (13.9 ) 41 164.3 (9.4 ) 5 99.5 (4.5 ) Total portfolio 320 $ 4,305.6 $ (51.8 ) 224 $ 2,912.0 $ (25.0 ) 96 $ 1,393.6 $ (26.8 ) 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, 2014 Fixed maturities: U.S. government obligations 11 $ 428.2 $ (1.3 ) 5 $ 150.7 $ (0.3 ) 6 $ 277.5 $ (1.0 ) State and local government obligations 46 234.2 (1.1 ) 28 177.9 (0.4 ) 18 56.3 (0.7 ) Corporate debt securities 53 843.2 (10.4 ) 43 647.5 (6.1 ) 10 195.7 (4.3 ) Residential mortgage-backed securities 70 844.2 (10.8 ) 33 465.2 (3.1 ) 37 379.0 (7.7 ) Agency residential pass-through obligations 0 0 0 0 0 0 0 0 0 Commercial mortgage-backed securities 63 723.4 (2.6 ) 54 667.5 (1.4 ) 9 55.9 (1.2 ) Other asset-backed securities 44 741.8 (0.8 ) 42 715.7 (0.7 ) 2 26.1 (0.1 ) Redeemable preferred stocks 3 103.0 (5.7 ) 1 33.0 (1.0 ) 2 70.0 (4.7 ) Total fixed maturities 290 3,918.0 (32.7 ) 206 2,857.5 (13.0 ) 84 1,060.5 (19.7 ) Equity securities: Nonredeemable preferred stocks 8 231.4 (6.4 ) 5 143.2 (3.6 ) 3 88.2 (2.8 ) Common equities 20 68.4 (10.1 ) 19 61.8 (9.6 ) 1 6.6 (0.5 ) Total equity securities 28 299.8 (16.5 ) 24 205.0 (13.2 ) 4 94.8 (3.3 ) Total portfolio 318 $ 4,217.8 $ (49.2 ) 230 $ 3,062.5 $ (26.2 ) 88 $ 1,155.3 $ (23.0 ) Since both September 30, 2014 and December 31, 2014 , the number of securities in our fixed-maturity portfolio with unrealized losses increased, primarily reflecting 460 securities added to the portfolio as a result of our acquisition of a controlling interest in ARX during the second quarter 2015, and reflect declines in the prices of these securities since the acquisition date averaging approximately 0.6% of their total cost. 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 September 30, 2015 in the table above are current with respect to required principal and interest payments. Since December 31, 2014 , our nonredeemable preferred stocks with unrealized losses increased to 14 securities, averaging approximately 4% 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 nine months of 2015. 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: September 30, December 31, (millions) 2015 2014 Fixed maturities: Residential mortgage-backed securities $ (43.3 ) $ (44.1 ) $ (44.1 ) Commercial mortgage-backed securities (0.6 ) (0.6 ) (0.6 ) Total fixed maturities $ (43.9 ) $ (44.7 ) $ (44.7 ) The following tables provide rollforwards of the amounts related to credit losses recognized in earnings for the periods ended September 30, 2015 and 2014 , 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 September 30, 2015 Mortgage-Backed (millions) Residential Commercial Total Balance at June 30, 2015 $ 14.0 $ 0.4 $ 14.4 Reductions for securities sold/matured (1.4 ) 0 (1.4 ) Change in recoveries of future cash flows expected to be collected 1 (1.7 ) 0 (1.7 ) Balance at September 30, 2015 $ 10.9 $ 0.4 $ 11.3 Nine Months Ended September 30, 2015 Mortgage-Backed (millions) Residential Commercial Total Balance at December 31, 2014 $ 12.7 $ 0.4 $ 13.1 Reductions for securities sold/matured (1.4 ) 0 (1.4 ) Change in recoveries of future cash flows expected to be collected 1 (0.4 ) 0 (0.4 ) Balance at September 30, 2015 $ 10.9 $ 0.4 $ 11.3 Three Months Ended September 30, 2014 Mortgage-Backed (millions) Residential Commercial Total Balance at June 30, 2014 $ 13.0 $ 0.4 $ 13.4 Reductions for securities sold/matured (0.1 ) 0 (0.1 ) Change in recoveries of future cash flows expected to be collected 1 0.1 0 0.1 Balance at September 30, 2014 $ 13.0 $ 0.4 $ 13.4 Nine Months Ended September 30, 2014 Mortgage-Backed (millions) Residential Commercial Total Balance at December 31, 2013 $ 19.2 $ 0.4 $ 19.6 Reductions for securities sold/matured (0.1 ) 0 (0.1 ) Change in recoveries of future cash flows expected to be collected 1 (6.1 ) 0 (6.1 ) Balance at September 30, 2014 $ 13.0 $ 0.4 $ 13.4 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. 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 nine months ended September 30, 2015 or 2014 . Realized Gains (Losses) The components of net realized gains (losses) for the three and nine months ended September 30, were: Three Months Nine Months (millions) 2015 2014 2015 2014 Gross realized gains on security sales Fixed maturities: U.S. government obligations $ 2.7 $ 2.5 $ 17.1 $ 13.2 State and local government obligations 0.5 3.8 0.5 8.2 Corporate and other debt securities 3.2 0.9 19.1 33.8 Residential mortgage-backed securities 4.4 0.2 4.6 2.2 Commercial mortgage-backed securities 0.9 5.2 15.3 14.8 Redeemable preferred stocks 0 2.3 0.1 2.7 Total fixed maturities 11.7 14.9 56.7 74.9 Equity securities: Nonredeemable preferred stocks 3.7 20.9 53.9 80.0 Common equities 13.2 4.6 43.7 97.0 Subtotal gross realized gains on security sales 28.6 40.4 154.3 251.9 Gross realized losses on security sales Fixed maturities: U.S. government obligations 0 (1.3 ) (0.9 ) (6.4 ) State and local government obligations (0.1 ) (0.3 ) (0.1 ) (0.5 ) Corporate and other debt securities (0.9 ) 0 (2.2 ) (2.3 ) Residential mortgage-backed securities 0 0 0 (0.2 ) Commercial mortgage-backed securities (0.1 ) (1.4 ) (1.1 ) (8.2 ) Redeemable preferred stocks 0 0 0 (3.2 ) Total fixed maturities (1.1 ) (3.0 ) (4.3 ) (20.8 ) Equity securities: Nonredeemable preferred stocks (0.1 ) 0 (1.5 ) 0 Common equities (0.8 ) 0 (1.5 ) (3.4 ) Subtotal gross realized losses on security sales (2.0 ) (3.0 ) (7.3 ) (24.2 ) Net realized gains (losses) on security sales Fixed maturities: U.S. government obligations 2.7 1.2 16.2 6.8 State and local government obligations 0.4 3.5 0.4 7.7 Corporate and other debt securities 2.3 0.9 16.9 31.5 Residential mortgage-backed securities 4.4 0.2 4.6 2.0 Commercial mortgage-backed securities 0.8 3.8 14.2 6.6 Redeemable preferred stocks 0 2.3 0.1 (0.5 ) Total fixed maturities 10.6 11.9 52.4 54.1 Equity securities: Nonredeemable preferred stocks 3.6 20.9 52.4 80.0 Common equities 12.4 4.6 42.2 93.6 Subtotal net realized gains (losses) on security sales 26.6 37.4 147.0 227.7 Other-than-temporary impairment losses Equity securities: Common equities (13.6 ) (0.1 ) (23.0 ) (0.1 ) Subtotal other-than-temporary impairment losses (13.6 ) (0.1 ) (23.0 ) (0.1 ) Other gains (losses) Hybrid securities (1.3 ) (1.8 ) (1.9 ) 5.7 Derivative instruments (27.7 ) (0.7 ) (29.2 ) (39.9 ) Litigation settlements 0.2 3.4 0.3 4.6 Subtotal other gains (losses) (28.8 ) 0.9 (30.8 ) (29.6 ) Total net realized gains (losses) on securities $ (15.8 ) $ 38.2 $ 93.2 $ 198.0 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 in our equity portfolio. Net Investment Income The components of net investment income for the three and nine months ended September 30, were: Three Months Nine Months (millions) 2015 2014 2015 2014 Fixed maturities: U.S. government obligations $ 6.2 $ 11.3 $ 22.5 $ 36.3 State and local government obligations 16.9 12.8 45.0 38.2 Foreign government obligations 0.1 0.1 0.3 0.3 Corporate debt securities 28.0 19.5 75.1 60.3 Residential mortgage-backed securities 13.5 11.3 39.5 32.5 Agency residential pass-through obligations 0.7 0 1.4 0 Commercial mortgage-backed securities 18.3 16.5 54.0 49.2 Other asset-backed securities 5.7 4.2 16.2 12.1 Redeemable preferred stocks 3.7 3.7 11.3 11.7 Total fixed maturities 93.1 79.4 265.3 240.6 Equity securities: Nonredeemable preferred stocks 11.0 9.4 32.4 28.6 Common equities 12.7 12.5 36.7 34.1 Short-term investments 0.7 0.4 1.5 0.9 Investment income 117.5 101.7 335.9 304.2 Investment expenses (4.9 ) (3.9 ) (15.9 ) (14.0 ) Net investment income $ 112.6 $ 97.8 $ 320.0 $ 290.2 Trading Securities At September 30, 2015 and 2014 , and December 31, 2014 , we did not hold any trading securities and did not have any net realized gains (losses) on trading securities for the three and nine months ended September 30, 2015 and 2014 . 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 September 30, 2015 and 2014 , and December 31, 2014 , and for the three and nine months ended September 30, 2015 and 2014 : (millions) Balance Sheet 2 Comprehensive Income Statement Assets (Liabilities) Pretax Net Realized Gains (Losses) Notional Value 1 Three Months Ended Nine Months Ended September 30, Dec. 31, September 30, Dec. 31, September 30, September 30, Derivatives designated as: 2015 2014 2014 Purpose Classification 2015 2014 2014 2015 2014 2015 2014 Hedging instruments Closed: Ineffective cash flow hedge $ 18 $ 44 $ 44 Manage interest rate risk NA $ 0 $ 0 $ 0 $ 0.2 $ 0.5 $ 0.2 $ 0.5 Non-hedging instruments Assets: Interest rate swaps 0 750 750 Manage portfolio duration Investments— fixed maturities 0 37.0 15.8 0 (1.2 ) 0 (40.4 ) Liabilities: Interest rate swaps 750 0 0 Manage portfolio duration Other liabilities (6.3 ) 0 0 (27.9 ) 0 (31.2 ) 0 Closed: U.S. Treasury Note futures 505 0 0 Manage portfolio duration NA 0 0 0 0 0 1.8 0 Total NA NA NA $ (6.3 ) $ 37.0 $ 15.8 $ (27.7 ) $ (0.7 ) $ (29.2 ) $ (39.9 ) 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. NA= Not Applicable CASH FLOW HEDGES We entered into forecasted debt issuance hedges to hedge against a possible rise in interest rates in conjunction with the $400 million of 3.70% Senior Notes issued in January 2015 and the $350 million of 4.35% Senior Notes issued in April 2014. Upon issuance, we closed these hedges and recognized, as part of accumulated other comprehensive income, a pretax loss of $12.9 million in January 2015 and of $1.6 million in April 2014. Our ineffective cash flow hedge, which is reflected in the table above, resulted from the repurchase of a portion of our 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 during 2015 and 2014 , and we reclassified the unrealized gain on forecasted transactions to net realized gains on securities. 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 September 30, 2015 and 2014 , and December 31, 2014 , 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. As interest rates fell during 2015, we recorded a fair value loss on our interest rate swap positions at September 30, 2015 ; the total fair value decline year to date was $22.1 million . During the second quarter 2015, we entered into U.S. treasury futures by selling contracts and we recognized a net realized gain of $1.8 million for the nine months ended September 30, 2015 ; all positions were closed at the end of the third quarter. The net realized gain was the result of overall rising interest rates during the period that the contracts were held. As of September 30, 2015 , the balance of the cash collateral that we delivered to the applicable counterparties on the interest rate swaps was $9.6 million . As of September 30, 2014 and December 31, 2014 , the balance of the cash collateral that we had received from the applicable counterparties on the interest rate swap positions was $31.8 million and $16.1 million , respectively.

Fair Value

Fair Value	9 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Fair Value	Fair Value — We have categorized our financial instruments, based on the degree of subjectivity inherent in the method by which they are valued, into a fair value hierarchy of three levels, as follows: • Level 1 : Inputs are unadjusted quoted prices in active markets for identical instruments at the measurement date (e.g., U.S. government obligations, active exchange-traded equity securities, and certain short-term securities). • Level 2 : Inputs (other than quoted prices included within Level 1) that are observable for the instrument either directly or indirectly (e.g., certain corporate and municipal bonds and certain preferred stocks). This includes: (i) quoted prices for similar instruments in active markets, (ii) quoted prices for identical or similar instruments in markets that are not active, (iii) inputs other than quoted prices that are observable for the instruments, and (iv) inputs that are derived principally from or corroborated by observable market data by correlation or other means. • Level 3 : Inputs that are unobservable. Unobservable inputs reflect our subjective evaluation about the assumptions market participants would use in pricing the financial instrument (e.g., certain structured securities and privately held investments). Determining the fair value of the investment portfolio is the responsibility of management. As part of the responsibility, we evaluate whether a market is distressed or inactive in determining the fair value for our portfolio. We review certain market level inputs to evaluate whether sufficient activity, volume, and new issuances exist to create an active market. Based on this evaluation, we concluded that there was sufficient activity related to the sectors and securities for which we obtained valuations. The composition of the investment portfolio by major security type and our outstanding debt was: Fair Value (millions) Level 1 Level 2 Level 3 Total Cost September 30, 2015 Fixed maturities: U.S. government obligations $ 2,038.3 $ 0 $ 0 $ 2,038.3 $ 2,028.2 State and local government obligations 0 3,067.9 0 3,067.9 3,025.0 Foreign government obligations 19.3 0 0 19.3 19.3 Corporate debt securities 0 3,798.5 1.0 3,799.5 3,797.4 Subtotal 2,057.6 6,866.4 1.0 8,925.0 8,869.9 Asset-backed securities: Residential mortgage-backed 0 1,809.4 0 1,809.4 1,801.8 Agency residential pass-through obligations 0 111.9 0 111.9 112.2 Commercial mortgage-backed 0 2,653.3 10.3 2,663.6 2,641.4 Other asset-backed 0 1,862.4 0 1,862.4 1,859.3 Subtotal asset-backed securities 0 6,437.0 10.3 6,447.3 6,414.7 Redeemable preferred stocks: Financials 0 88.1 0 88.1 71.8 Utilities 0 56.0 0 56.0 65.1 Industrials 0 105.7 0 105.7 118.1 Subtotal redeemable preferred stocks 0 249.8 0 249.8 255.0 Total fixed maturities 2,057.6 13,553.2 11.3 15,622.1 15,539.6 Equity securities: Nonredeemable preferred stocks: Financials 158.7 616.9 0 775.6 652.4 Subtotal nonredeemable preferred stocks 158.7 616.9 0 775.6 652.4 Common equities: Common stocks 2,483.6 0 0 2,483.6 1,486.7 Other risk investments 0 0 0.3 0.3 0.3 Subtotal common equities 2,483.6 0 0.3 2,483.9 1,487.0 Total fixed maturities and equity securities 4,699.9 14,170.1 11.6 18,881.6 17,679.0 Short-term investments 2,007.0 125.0 0 2,132.0 2,132.0 Total portfolio $ 6,706.9 $ 14,295.1 $ 11.6 $ 21,013.6 $ 19,811.0 Debt $ 0 $ 2,727.5 $ 171.7 $ 2,899.2 $ 2,714.3 Fair Value (millions) Level 1 Level 2 Level 3 Total Cost September 30, 2014 Fixed maturities: U.S. government obligations $ 3,062.9 $ 0 $ 0 $ 3,062.9 $ 3,033.2 State and local government obligations 0 2,172.8 0 2,172.8 2,124.2 Foreign government obligations 20.2 0 0 20.2 20.2 Corporate debt securities 0 2,519.1 0 2,519.1 2,501.8 Subtotal 3,083.1 4,691.9 0 7,775.0 7,679.4 Asset-backed securities: Residential mortgage-backed 0 1,486.5 0 1,486.5 1,460.6 Agency residential pass-through obligations 0 0 0 0 0 Commercial mortgage-backed 0 2,160.0 12.5 2,172.5 2,143.8 Other asset-backed 0 1,550.6 0 1,550.6 1,546.0 Subtotal asset-backed securities 0 5,197.1 12.5 5,209.6 5,150.4 Redeemable preferred stocks: Financials 0 100.3 0 100.3 77.3 Utilities 0 65.3 0 65.3 65.0 Industrials 0 119.2 0 119.2 117.9 Subtotal redeemable preferred stocks 0 284.8 0 284.8 260.2 Total fixed maturities 3,083.1 10,173.8 12.5 13,269.4 13,090.0 Equity securities: Nonredeemable preferred stocks: Financials 220.0 496.6 46.7 763.3 532.8 Subtotal nonredeemable preferred stocks 220.0 496.6 46.7 763.3 532.8 Common equities: Common stocks 2,379.0 0 0 2,379.0 1,278.0 Other risk investments 0 0 0.4 0.4 0.4 Subtotal common equities 2,379.0 0 0.4 2,379.4 1,278.4 Total fixed maturities and equity securities 5,682.1 10,670.4 59.6 16,412.1 14,901.2 Short-term investments 2,393.7 277.4 0 2,671.1 2,671.1 Total portfolio $ 8,075.8 $ 10,947.8 $ 59.6 $ 19,083.2 $ 17,572.3 Debt $ 0 $ 2,475.1 $ 0 $ 2,475.1 $ 2,164.3 Fair Value (millions) Level 1 Level 2 Level 3 Total Cost December 31, 2014 Fixed maturities: U.S. government obligations $ 2,667.1 $ 0 $ 0 $ 2,667.1 $ 2,641.1 State and local government obligations 0 2,139.2 0 2,139.2 2,095.7 Foreign government obligations 14.2 0 0 14.2 14.2 Corporate debt securities 0 2,836.7 0 2,836.7 2,813.9 Subtotal 2,681.3 4,975.9 0 7,657.2 7,564.9 Asset-backed securities: Residential mortgage-backed 0 1,658.5 0 1,658.5 1,635.5 Agency residential pass-through obligations 0 0 0 0 0 Commercial mortgage-backed 0 2,304.0 11.6 2,315.6 2,278.7 Other asset-backed 0 1,638.7 0 1,638.7 1,634.9 Subtotal asset-backed securities 0 5,601.2 11.6 5,612.8 5,549.1 Redeemable preferred stocks: Financials 0 97.9 0 97.9 77.3 Utilities 0 65.3 0 65.3 65.0 Industrials 0 116.0 0 116.0 117.9 Subtotal redeemable preferred stocks 0 279.2 0 279.2 260.2 Total fixed maturities 2,681.3 10,856.3 11.6 13,549.2 13,374.2 Equity securities: Nonredeemable preferred stocks: Financials 204.1 554.1 69.3 827.5 590.4 Subtotal nonredeemable preferred stocks 204.1 554.1 69.3 827.5 590.4 Common equities: Common stocks 2,491.9 0 0 2,491.9 1,288.8 Other risk investments 0 0 0.4 0.4 0.4 Subtotal common equities 2,491.9 0 0.4 2,492.3 1,289.2 Total fixed maturities and equity securities 5,377.3 11,410.4 81.3 16,869.0 15,253.8 Short-term investments 1,937.0 212.0 0 2,149.0 2,149.0 Total portfolio $ 7,314.3 $ 11,622.4 $ 81.3 $ 19,018.0 $ 17,402.8 Debt $ 0 $ 2,527.5 $ 0 $ 2,527.5 $ 2,164.7 Our portfolio valuations, excluding short-term investments, classified as either Level 1 or Level 2 in the above tables are priced exclusively by external sources, including: pricing vendors, dealers/market makers, and exchange-quoted prices. We did not have any transfers between Level 1 and Level 2 during the first nine months of 2015 . During the first quarter of 2014 , we had two nonredeemable preferred stocks with a value of $41.7 million that were transferred from Level 2 to Level 1 due to the availability of a consistent exchange price; this was the only transfer during 2014 . We recognize transfers between levels at the end of the reporting period. Our short-term security holdings classified as Level 1 are highly liquid, actively marketed, and have a very short duration, primarily 30 days or less to redemption. These securities are held at their original cost, adjusted for any accretion of discount, since that value very closely approximates what an active market participant would be willing to pay for such securities. The remainder of our short-term securities are classified as Level 2 and are not priced externally since these securities continually trade at par value. These securities are classified as Level 2 since they are primarily longer-dated auction securities issued by municipalities that contain a redemption put feature back to the auction pool with a redemption period typically less than seven days. The auction pool is created by a liquidity provider and if the auction is not available at the end of the seven days, we have the right to put the security back to the issuer at par. At September 30, 2015 , vendor-quoted prices represented 47% of our Level 1 classifications (excluding short-term investments), compared to 54% and 50% at September 30, 2014 and December 31, 2014 , 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 September 30, 2014 was due to a reduction of U.S. Treasury Notes. At September 30, 2015 and 2014 , and December 31, 2014 , vendor-quoted prices comprised 97% , 96% , and 97% , respectively, of our Level 2 classifications (excluding short-term investments), while dealer-quoted prices represented 3% , 4% , 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 security 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 Progressive (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 September 30, 2015 and 2014 , and December 31, 2014 , securities in our fixed-maturity portfolio listed as Level 3 were comprised substantially of securities that were either: (i) private placements, (ii) thinly held and/or traded securities, or (iii) non-investment-grade or non-rated securities with little liquidity. Based on these factors, it was difficult to independently verify observable market inputs that were used to generate the external valuations we received. Despite the lack of sufficient observable market information for our Level 3 securities, we believe the valuations received in conjunction with our procedures for evaluating third-party prices support the fair values reported in the financial statements. At September 30, 2015 , our corporate portfolio included two internally priced securities. These securities were priced at cost since we expect them to be fully redeemed by the end of 2015; therefore, any difference between cost and fair value is immaterial. At September 30, 2014 , we held one private preferred equity security (our 5% equity interest in ARX Holding Corp.) with a value of $46.7 million that was priced internally. The same security had a value of $69.3 million at December 31, 2014 . The increase in value was due primarily to a higher price to book ratio multiple included in the terms of the stock purchase agreement we entered into during December 2014 to purchase a majority interest in ARX Holding Corp. This was the only internally-priced security in the portfolio at both September 30, 2014 and December 31, 2014 . We review the prices from our external sources for reasonableness using internally developed assumptions to derive prices for the securities, which are then compared to the prices we received. During 2015 or 2014 , there were no material assets or liabilities measured at fair value on a nonrecurring basis. Based on our review, all 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 and nine months ended September 30, 2015 and 2014 : Level 3 Fair Value Three Months Ended September 30, 2015 (millions) Fair Value at June 30, 2015 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain) Loss on Sales Change in Valuation Net Transfers In (Out) Fair Value at September 30, 2015 Fixed maturities: Corporate debt securities $ 1.0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 1.0 Asset-backed securities: Residential mortgage-backed 0 0 0 0 0 0 0 0 Commercial mortgage-backed 10.9 (0.4 ) 0 0 0 (0.2 ) 0 10.3 Total fixed maturities 11.9 (0.4 ) 0 0 0 (0.2 ) 0 11.3 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 $ 12.2 $ (0.4 ) $ 0 $ 0 $ 0 $ (0.2 ) $ 0 $ 11.6 Level 3 Fair Value Nine Months Ended September 30, 2015 (millions) Fair Value at Dec. 31, 2014 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain) Loss on Sales Change in Valuation Net Transfers In (Out) Fair Value at September 30, 2015 Fixed maturities: Corporate debt securities $ 0 $ 0 $ 1.0 $ 0 $ 0 $ 0 $ 0 $ 1.0 Asset-backed securities: Residential mortgage-backed 0 0 0 0 0 0 0 0 Commercial mortgage-backed 11.6 (1.0 ) 0 0 0 (0.3 ) 0 10.3 Total fixed maturities 11.6 (1.0 ) 1.0 0 0 (0.3 ) 0 11.3 Equity securities: Nonredeemable preferred stocks: Financials 1 69.3 0 0 0 (39.4 ) (1.4 ) (28.5 ) 0 Common equities: Other risk investments 0.4 0 0 0 0 (0.1 ) 0 0.3 Total Level 3 securities $ 81.3 $ (1.0 ) $ 1.0 $ 0 $ (39.4 ) $ (1.8 ) $ (28.5 ) $ 11.6 1 The $69.3 million decrease during the year reflects the reclassification of our 5% interest in ARX Holding Corp. upon acquisition of a controlling interest in ARX. The $39.4 million reflects our inception-to-date gain recognized, including the $1.4 million reduction in valuation that occurred during the first six months of 2015. Level 3 Fair Value Three Months Ended September 30, 2014 (millions) Fair Value at June 30, 2014 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain) Loss on Sales Change in Valuation Net Transfers In (Out) 1 Fair Value at September 30, 2014 Fixed maturities: Corporate debt securities $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Asset-backed securities: Residential mortgage-backed 0 0 0 0 0 0 0 0 Commercial mortgage-backed 27.6 (1.2 ) 0 0 0 (0.3 ) (13.6 ) 12.5 Total fixed maturities 27.6 (1.2 ) 0 0 0 (0.3 ) (13.6 ) 12.5 Equity securities: Nonredeemable preferred stocks: Financials 2 43.8 0 0 0 0 2.9 0 46.7 Common equities: Other risk investments 0.5 (0.1 ) 0 0 0 0 0 0.4 Total Level 3 securities $ 71.9 $ (1.3 ) $ 0 $ 0 $ 0 $ 2.6 $ (13.6 ) $ 59.6 1 The $13.6 million was transferred out of Level 3 and into Level 2 due to an improvement in the security's underlying collateral and an increase in liquidity and market activity in comparable securities. 2 The $2.9 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. Level 3 Fair Value Nine Months Ended September 30, 2014 (millions) Fair Value at Dec. 31, 2013 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain) Loss on Sales Change in Valuation Net Transfers In (Out) 1 Fair Value at September 30, 2014 Fixed maturities: Corporate debt securities $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Asset-backed securities: Residential mortgage-backed 0.2 0 0 (0.1 ) 0.1 (0.2 ) 0 0 Commercial mortgage-backed 29.0 (3.0 ) 0 0 0 0.1 (13.6 ) 12.5 Total fixed maturities 29.2 (3.0 ) 0 (0.1 ) 0.1 (0.1 ) (13.6 ) 12.5 Equity securities: Nonredeemable preferred stocks: Financials 2 39.0 0 0 0 0 7.7 0 46.7 Common equities: Other risk investments 0.5 (0.1 ) 0 0 0 0 0 0.4 Total Level 3 securities $ 68.7 $ (3.1 ) $ 0 $ (0.1 ) $ 0.1 $ 7.6 $ (13.6 ) $ 59.6 1 The $13.6 million was transferred out of Level 3 and into Level 2 due to an improvement in the security's underlying collateral and an increase in liquidity and market activity in comparable securities. 2 The $7.7 million represents net holding period gains on a hybrid security, which is reflected in net realized gains (losses) on securities in the comprehensive income statement. The following tables provide a summary of the quantitative information about Level 3 fair value measurements for our applicable securities at September 30, 2015 and 2014 , and December 31, 2014 : Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at September 30, 2015 Valuation Technique Unobservable Input Unobservable Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 10.3 External vendor Prepayment rate 1 0 Total fixed maturities 10.3 Equity securities: Nonredeemable preferred stocks: Financials 0 NA NA NA Subtotal Level 3 securities 10.3 Pricing exemption securities 2 1.3 Total Level 3 securities $ 11.6 NA = Not Applicable. We did not hold any nonredeemable preferred stock Level 3 securities at September 30, 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. Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at September 30, 2014 Valuation Technique Unobservable Input Unobservable Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 12.5 External vendor Prepayment rate 1 0 Total fixed maturities 12.5 Equity securities: Nonredeemable preferred stocks: Financials 46.7 Multiple of tangible net book value Price to book ratio multiple 1.9 Subtotal Level 3 securities 59.2 Pricing exemption securities 2 0.4 Total Level 3 securities $ 59.6 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, 2014 Valuation Technique Unobservable Input Unobservable Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 11.6 External vendor Prepayment rate 1 0 Total fixed maturities 11.6 Equity securities: Nonredeemable preferred stocks: Financials 69.3 Multiple of tangible net book value Price to book ratio multiple 2.6 Subtotal Level 3 securities 80.9 Pricing exemption securities 2 0.4 Total Level 3 securities $ 81.3 1 Assumes that one security has 0% of the principal amount of the underlying loans that will be paid off prematurely in each year. 2 The fair values for these securities were 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	9 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
Debt	Debt — Debt consisted of: September 30, 2015 September 30, 2014 December 31, 2014 (millions) Carrying Value Fair Value Carrying Value Fair Value Carrying Value Fair Value 3.75% Senior Notes due 2021 $ 498.1 $ 534.5 $ 497.8 $ 527.9 $ 497.8 $ 535.6 6 5/8% Senior Notes due 2029 295.6 379.5 295.4 390.9 295.5 400.6 6.25% Senior Notes due 2032 394.9 489.3 394.8 510.3 394.8 527.9 4.35% Senior Notes due 2044 346.4 345.7 346.3 352.7 346.3 378.9 3.70% Senior Notes due 2045 395.0 358.0 0 0 0 0 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 612.6 620.5 630.0 693.3 630.3 684.5 Other debt instruments 171.7 171.7 0 0 0 0 Total $ 2,714.3 $ 2,899.2 $ 2,164.3 $ 2,475.1 $ 2,164.7 $ 2,527.5 During the third quarter of 2015 and 2014, we repurchased, in the open market, $18.4 million and $44.3 million , respectively, in aggregate principal amount of our 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 (the "6.70% Debentures"). Since the amount paid exceeded the carrying value of the debt we repurchased, we recognized losses on these extinguishments of $0.9 million during 2015 and $4.8 million during 2014. In addition, for the portion of the 6.70% Debentures we repurchased, we reclassified $0.2 million on a pretax basis, of the unrealized gain on forecasted transactions from accumulated other comprehensive income on the balance sheet to net realized gains on securities on the comprehensive income statement during 2015 and $0.5 million during 2014. In January 2015, we issued $400 million of our 3.70% Senior Notes due 2045 (the “3.70% Senior Notes”) and, in April 2014, we issued $350 million of our 4.35% Senior Notes due 2044 (the “4.35% Senior Notes”) in underwritten public offerings. We received proceeds, after deducting underwriter's discounts and commissions, of approximately $394.9 million and $346.3 million , respectively. In addition, we incurred expenses of approximately $0.8 million and $0.7 million , respectively, related to the issuances. Upon issuance of the 3.70% Senior Notes and 4.35% Senior Notes, we also closed forecasted debt issuance hedges, which were entered into to hedge against a possible rise in interest rates, and recognized a $12.9 million and a $1.6 million pretax loss, respectively, as part of accumulated other comprehensive income (loss); the losses will be recognized as an adjustment to interest expense and amortized over the applicable life of the 3.70% and 4.35% Senior Notes. The other debt instruments consist of ARX debt acquired during the second quarter 2015 through Progressive's acquisition of a controlling interest in ARX. 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. At September 30, 2015, the other debt instruments consist of: Type of debt instrument Number of Instruments Carrying Value Stated Maturity Date(s) Term loans 2 $93.3 December 2018 and 2019 Junior subordinated notes 1 2 41.3 June 2036 and 2037 Senior notes 4 24.0 Various 2 Surplus note 1 13.1 November 2021 Total $171.7 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 junior subordinated notes and senior notes have no restrictive financial covenants. The term loans require ARX and its subsidiaries to maintain specified debt leverage and fixed charge coverage ratios, as well as maintain a minimum risk-based capital ratio and minimum financial strength and credit ratings, as provided by A.M. Best Company, Inc. As of September 30, 2015, ARX was in compliance with these covenants. The only restriction on the surplus note is for ARX to maintain at least $50 million of surplus, which it met at September 30, 2015. Monthly interest and principal payments are made on the term loans, with interest calculated based on the 30-day London Interbank Offered Rate (LIBOR) plus 2.25% . Principal payments of $25.0 million are required to be paid during the next twelve months on these term loans. The term loans are secured by 100% of the outstanding common stock of four subsidiaries of ARX. Interest on the junior subordinated notes and the senior notes is paid quarterly at a floating rate tied to the three-month LIBOR rate. Principal and interest on the surplus note is payable pursuant to a schedule permitted by the Florida Office of Insurance Regulation, and interest is set quarterly based upon the 10-year U.S. treasury bond rate. Principal payments of $2.2 million are due during the next twelve months on the surplus note. The junior subordinated notes and senior notes can be redeemed, in whole or in part, at the option of ARX at par, plus accrued and unpaid interest, on any interest payment date. Pursuant to agreements entered into by ARX relating to the trust preferred securities transactions, ARX established trusts that are 100% owned by ARX. The trusts, which are the holders of the junior subordinated notes, issued trust preferred securities to third parties. The shares in the trusts are not transferable. The trusts are considered special purpose variable interest entities for which ARX is not the primary beneficiary and, therefore, they are accounted for under the equity method of accounting and not consolidated with ARX. Our ownership interest of $1.3 million in the variable interest entities is reported as a component of "other assets" on our consolidated balance sheets. 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 . The prior line of credit, entered into in the first quarter 2014, has expired. The Line of Credit is on substantially the same terms and conditions as the prior line of credit. Subject to the terms and conditions of the Line of Credit documents, advances under the Line of Credit (if any) will bear interest at a variable rate equal to the higher of PNC's Prime Rate or the sum of the Federal Funds Open Rate plus 50 basis points. Each advance 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. Prepayments are permitted without penalty. All advances under the Line of Credit are subject to PNC's discretion. We had no borrowings under the Line of Credit or the prior line of credit during the first nine months of 2015 or throughout 2014 .

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes — At September 30, 2015 and 2014, and December 31, 2014, 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 and nine months ended September 30, 2015 , the effective tax rate was 33.2% and 32.0% , respectively, compared to 33.0% and 33.1% for the same periods last year. The year-over-year decrease in the effective rate on a year-to-date basis is primarily due to the reversal of approximately $14 million of deferred taxes associated with the appreciation of our previous 5% investment in ARX Holding Corp. as a result of our acquisition of a controlling interest in ARX. For the nine months ended September 30, 2015, there have been no material changes in our uncertain tax positions.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	9 Months Ended
	Sep. 30, 2015
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: Nine Months Ended September 30, (millions) 2015 2014 Income taxes $ 513.1 $ 355.0 Interest 90.3 74.7

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2015
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 property 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 homeowners, general liability, and workers’ compensation insurance through our programs with ASI and unaffiliated insurance companies. All segment revenues are generated from external customers. We evaluate the profitability of our Property segment based on pretax underwriting profit (loss), which is consistent with our other operating segments. At September 30, 2015 , $2.3 billion of assets, including intangible assets, were allocated to the Property segment. We are still in the process of determining the allocation of goodwill to our operating segments. We do not allocate our other assets to operating segments. Following are the operating results for the respective periods: Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 (millions) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Personal Lines Agency $ 2,284.6 $ 169.4 $ 2,235.2 $ 147.0 $ 6,805.5 $ 535.8 $ 6,680.7 $ 468.5 Direct 2,069.5 100.9 1,848.9 107.6 6,056.7 287.2 5,435.1 294.3 Total Personal Lines 1 4,354.1 270.3 4,084.1 254.6 12,862.2 823.0 12,115.8 762.8 Commercial Lines 511.3 77.8 456.0 85.1 1,467.0 239.5 1,340.1 204.4 Property 2 205.2 17.2 0 0 403.9 18.2 0 0 Other indemnity 0 (0.4 ) 0 0.1 (0.4 ) (0.4 ) 0 (5.3 ) Total underwriting operations 5,070.6 364.9 4,540.1 339.8 14,732.7 1,080.3 13,455.9 961.9 Fees and other revenues 3 79.3 NA 75.9 NA 227.9 NA 223.1 NA Service businesses 23.1 2.7 15.0 1.5 63.6 6.8 38.8 2.7 Investments 4 101.7 96.8 139.9 136.0 429.1 413.2 502.2 488.2 Gains (losses) on extinguishment of debt (0.9 ) (0.9 ) (4.8 ) (4.8 ) (0.9 ) (0.9 ) (4.8 ) (4.8 ) Interest expense NA (34.5 ) NA (30.7 ) NA (101.9 ) NA (87.0 ) Consolidated total $ 5,273.8 $ 429.0 $ 4,766.1 $ 441.8 $ 15,452.4 $ 1,397.5 $ 14,215.2 $ 1,361.0 NA = Not Applicable 1 Personal auto insurance accounted for 92% of the total Personal Lines segment net premiums earned for the three months ended September 30, 2015 and the nine months ended September 30, 2015 and 2014 and accounted for 91% for the three months ended September 30, 2014; insurance for our special lines products (e.g., motorcycles, ATVs, RVs, mobile 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 Holding Corp. For the three months and nine months ended September 30, 2015, amounts include $15.0 million and $30.0 million , respectively, of amortization/depreciation expense associated with the acquisition of a controlling interest in ARX Holding Corp. Although this expense is included in our Property segment, it is not reported in the consolidated results of ARX Holding Corp. and, therefore, will not affect the value of the noncontrolling interest. 3 Pretax profit (loss) for fees and other revenues is 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. Combined ratio is the complement of the underwriting margin. Following are the underwriting margins/combined ratios for our underwriting operations for the respective periods: Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Under-writing Combined Ratio Under-writing Combined Ratio Under-writing Margin Combined Ratio Under-writing Margin Combined Ratio Personal Lines Agency 7.4 % 92.6 6.6 % 93.4 7.9 % 92.1 7.0 % 93.0 Direct 4.9 95.1 5.8 94.2 4.7 95.3 5.4 94.6 Total Personal Lines 6.2 93.8 6.2 93.8 6.4 93.6 6.3 93.7 Commercial Lines 15.2 84.8 18.6 81.4 16.3 83.7 15.2 84.8 Property 1 8.4 91.6 0 0 4.5 95.5 0 0 Other indemnity 2 NM NM NM NM NM NM NM NM Total underwriting operations 7.2 % 92.8 7.5 % 92.5 7.3 % 92.7 7.1 % 92.9 1 Included in both the three and nine months ended September 30, 2015, is 7.3 points and 7.4 points, respectively, of amortization/depreciation expense associated with the acquisition of a controlling interest in ARX Holding Corp. 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	9 Months Ended
	Sep. 30, 2015
Text Block [Abstract]
Dividends	Dividends — We maintain a policy of paying an annual variable dividend that, if declared, would be paid 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), subject to the limitations discussed below. The target percentage is determined by our Board of Directors on an annual basis and announced to shareholders and the public. In December 2014 , the Board determined the target percentage for 2015 to be 33-1/3 % of annual after-tax underwriting income, which is unchanged from the 2014 target percentage. Underwriting income will include the results of ARX and its subsidiaries subsequent to April 1, 2015 , the date of acquisition. The Gainshare factor can range from zero to two and is determined by comparing our operating performance 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 recalibrated every year, the structure of the Gainsharing program generally remains the same. On a year-to-date basis, as of September 30, 2015 , the Gainshare factor was 1.53 . Since the final factor will be determined based on our results for the full year, the final factor may vary from the current factor. The Gainshare factor excludes the results of our Property business. 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 paid under our annual variable dividend policy. For the nine months ended September 30, 2015, our comprehensive income was $683.3 million , which is less than the $702.2 million of after-tax underwriting income for the same period. However, the ultimate decisions on whether or not a dividend will be paid, and the amount of any dividend, are in the discretion of the Board of Directors. If a dividend for 2015 were to be paid, the Board would likely declare the 2015 annual dividend in December 2015 , with a record date in early 2016 and payment shortly thereafter. Following is a summary of our shareholder dividends, both variable and special, that were paid in the last two years: (millions, except per share amounts) Amount Dividend Type Declared Paid Per Share Total Annual – Variable December 2014 February 2015 $ 0.6862 $ 404.1 Annual – Variable December 2013 February 2014 0.4929 293.9 Special December 2013 February 2014 1.0000 596.3

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2015
Equity [Abstract]
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) — The components of other comprehensive income (loss), including reclassification adjustments by income statement line item, were as follows: Components of Changes in Accumulated Other Comprehensive Income (after tax) (millions) Pretax total accumulated other comprehensive income Total tax (provision) benefit After tax total accumulated other comprehensive income Total net unrealized gains (losses) on securities Net unrealized gains on forecasted transactions Foreign currency translation adjustment Loss attributable to NCI Balance at June 30, 2015 $ 1,393.3 $ (491.3 ) $ 902.0 $ 907.5 $ (7.5 ) $ (0.8 ) $ 2.8 Other comprehensive income (loss) before reclassifications: Investment securities (190.6 ) 66.5 (124.1 ) (124.1 ) 0 0 0 Forecasted transactions 0 0 0 0 0 0 0 Foreign currency translation adjustment (1.1 ) 0.4 (0.7 ) 0 0 (0.7 ) 0 Loss attributable to noncontrolling interest (NCI) (2.5 ) 0.9 (1.6 ) 0 0 0 (1.6 ) Total other comprehensive income (loss) before reclassifications (194.2 ) 67.8 (126.4 ) (124.1 ) 0 (0.7 ) (1.6 ) Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (13.6 ) 4.8 (8.8 ) (8.8 ) 0 0 0 Net realized gains (losses) on securities 23.0 (8.1 ) 14.9 14.8 0.1 0 0 Interest expense 0.4 (0.1 ) 0.3 0 0.3 0 0 Total reclassification adjustment for amounts realized in net income 9.8 (3.4 ) 6.4 6.0 0.4 0 0 Total other comprehensive income (loss) (204.0 ) 71.2 (132.8 ) (130.1 ) (0.4 ) (0.7 ) (1.6 ) Balance at September 30, 2015 $ 1,189.3 $ (420.1 ) $ 769.2 $ 777.4 $ (7.9 ) $ (1.5 ) $ 1.2 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 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 (252.8 ) 84.6 (168.2 ) (168.2 ) 0 0 0 Forecasted transactions (12.8 ) 4.4 (8.4 ) 0 (8.4 ) 0 0 Foreign currency translation adjustment (2.0 ) 0.8 (1.2 ) 0 0 (1.2 ) 0 Loss attributable to noncontrolling interest (NCI) 1.8 (0.6 ) 1.2 0 0 0 1.2 Total other comprehensive income (loss) before reclassifications (265.8 ) 89.2 (176.6 ) (168.2 ) (8.4 ) (1.2 ) 1.2 Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (23.2 ) 8.2 (15.0 ) (15.0 ) 0 0 0 Net realized gains (losses) on securities 140.7 (49.3 ) 91.4 91.3 0.1 0 0 Interest expense 1.4 (0.5 ) 0.9 0 0.9 0 0 Total reclassification adjustment for amounts realized in net income 118.9 (41.6 ) 77.3 76.3 1.0 0 0 Total other comprehensive income (loss) (384.7 ) 130.8 (253.9 ) (244.5 ) (9.4 ) (1.2 ) 1.2 Balance at September 30, 2015 $ 1,189.3 $ (420.1 ) $ 769.2 $ 777.4 $ (7.9 ) $ (1.5 ) $ 1.2 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 Loss attributable to NCI Balance at June 30, 2014 $ 1,598.2 $ (559.3 ) $ 1,038.9 $ 1,035.3 $ 2.5 $ 1.1 $ 0 Other comprehensive income (loss) before reclassifications: Investment securities (62.5 ) 21.9 (40.6 ) (40.6 ) 0 0 0 Forecasted transactions 0 0 0 0 0 0 0 Foreign currency translation adjustment (0.5 ) 0.1 (0.4 ) 0 0 (0.4 ) 0 Loss attributable to noncontrolling interest (NCI) 0 0 0 0 0 0 0 Total other comprehensive income (loss) before reclassifications (63.0 ) 22.0 (41.0 ) (40.6 ) 0 (0.4 ) 0 Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (0.1 ) 0 (0.1 ) (0.1 ) 0 0 0 Net realized gains (losses) on securities 38.3 (13.4 ) 24.9 24.6 0.3 0 0 Interest expense 0.5 (0.1 ) 0.4 0 0.4 0 0 Total reclassification adjustment for amounts realized in net income 38.7 (13.5 ) 25.2 24.5 0.7 0 0 Total other comprehensive income (loss) (101.7 ) 35.5 (66.2 ) (65.1 ) (0.7 ) (0.4 ) 0 Balance at September 30, 2014 $ 1,496.5 $ (523.8 ) $ 972.7 $ 970.2 $ 1.8 $ 0.7 $ 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 Loss attributable to NCI Balance at December 31, 2013 $ 1,464.1 $ (512.4 ) $ 951.7 $ 947.0 $ 4.1 $ 0.6 $ 0 Other comprehensive income (loss) before reclassifications: Investment securities 258.2 (90.3 ) 167.9 167.9 0 0 0 Forecasted transactions (1.6 ) 0.6 (1.0 ) 0 (1.0 ) 0 0 Foreign currency translation adjustment 0.3 (0.2 ) 0.1 0 0 0.1 0 Loss attributable to noncontrolling interest (NCI) 0 0 0 0 0 0 0 Total other comprehensive income (loss) before reclassifications 256.9 (89.9 ) 167.0 167.9 (1.0 ) 0.1 0 Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (0.1 ) 0 (0.1 ) (0.1 ) 0 0 0 Net realized gains (losses) on securities 223.1 (78.0 ) 145.1 144.8 0.3 0 0 Interest expense 1.5 (0.5 ) 1.0 0 1.0 0 0 Total reclassification adjustment for amounts realized in net income 224.5 (78.5 ) 146.0 144.7 1.3 0 0 Total other comprehensive income (loss) 32.4 (11.4 ) 21.0 23.2 (2.3 ) 0.1 0 Balance at September 30, 2014 $ 1,496.5 $ (523.8 ) $ 972.7 $ 970.2 $ 1.8 $ 0.7 $ 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 $1.8 million (pretax) into income during the next 12 months, related to net unrealized gains on forecasted transactions.

Litigation

Litigation	9 Months Ended
	Sep. 30, 2015
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 September 30, 2015. 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 Annual Report to Shareholders for the year ended December 31, 2014, (the "Annual Report to Shareholders"), which is included as Exhibit 13 to our Annual Report on Form 10-K for 2014. 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 to our consolidated financial statements in our Annual Report to Shareholders.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies — During the first nine months of 2015 , the noncancelable operating lease commitments and noncancelable purchase obligations for Progressive have not changed materially from those discussed in our Annual Report on Form 10-K for the year ended December 31, 2014 . During the second quarter 2015, ASI entered into several multiple-layer property catastrophe excess of loss reinsurance contracts with various reinsurers with terms ranging from one to two years. The deposits remaining to be paid on these contracts were $63.6 million as of September 30, 2015. As of September 30, 2015, ARX had no other material lease commitments or noncancelable purchase obligations.

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interest (Notes)	9 Months Ended
	Sep. 30, 2015
Temporary Equity Disclosure [Abstract]
Redeemable Noncontrolling Interest	Redeemable Noncontrolling Interest - The components of redeemable noncontrolling interest (NCI) at September 30, 2015, were: ($ in millions) Balance at March 31, 2015 $ 0 Fair value at date of acquisition 411.5 Net income attributable to NCI 13.4 Other comprehensive loss attributable to NCI (1.2 ) Purchase of shares from NCI (12.6 ) Change in redemption value of NCI 31.8 Balance at September 30, 2015 $ 442.9

New Accounting Standards (Notes

New Accounting Standards (Notes)	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
New Accounting Standards	New Accounting Standards — In April 2015, the Financial Accounting Standards Board (FASB) issued an accounting standard update (ASU) related to the balance sheet presentation of the cost of issuing debt. This standard requires that all costs incurred to issue debt be presented in the balance sheet as a direct deduction from the carrying value of the debt. In August 2015, the FASB further amended this ASU to clarify the treatment of debt issuance costs related to lines-of-credit arrangements. Registrants can elect to defer and present debt issuance costs related to a line of credit as an asset and subsequently amortize the costs ratably over the term of the line-of-credit arrangement, regardless of whether there are any outstanding borrowings on the arrangement. This ASU, which is required to be applied on a retrospective basis, is effective for fiscal years beginning after December 15, 2015 (2016 for calendar-year companies), with early adoption permitted. We have historically deducted the majority of our debt issuance costs from the carrying value of the debt; therefore, we do not expect this standard to have a significant impact on our financial condition, cash flows, or results of operations. In April 2015, the FASB issued an ASU to clarify guidance around accounting for fees paid in a cloud computing arrangement. The standard prescribes when a cloud computing arrangement should be treated as software and when it should be treated as a service contract based on whether the arrangement includes a software license. This ASU, which allows for both prospective and retrospective methods of adoption, will be effective for annual periods (including interim periods within those annual periods), beginning after December 15, 2015. We are currently evaluating the impact the guidance will have on our financial statements. In May 2015, the FASB issued an ASU related to disclosures about short duration contracts. The disclosures are intended to provide users of financial statements with more transparent information about an insurance entity's initial claim estimates and subsequent adjustments to those estimates, the methodologies and judgments used to estimate claims, and the timing, frequency, and severity of claims. This standard, which is required to be applied on a retrospective basis, is effective for fiscal years beginning after December 15, 2015 (2016 for calendar-year companies), except for those disclosures that require application only to the current period (e.g., information about significant changes in estimation methodologies and assumptions made in calculating the claim liability for short-duration contracts). Early adoption is permitted. We are currently analyzing the impact of the new disclosures. In May 2015, the FASB also issued an ASU related to investments measured at net asset value (NAV). The intent is to exclude investments measured at NAV from the fair value hierarchy. This guidance is effective for annual and interim periods after December 15, 2015 (January 2016 for calendar-year companies). We do not value our securities at NAV; therefore, this standard will not impact our financial condition, cash flows, or results of operations.

Reclassification (Notes)

Reclassification (Notes)	9 Months Ended
	Sep. 30, 2015
Accounting Changes and Error Corrections [Abstract]
Reclassification	Reclassification — For the periods ended September 30, 2014 and December 31, 2014, 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.

Acquisitions (Notes)

Acquisitions (Notes)	9 Months Ended
	Sep. 30, 2015
Business Combinations [Abstract]
Acquisition	Acquisition — On April 1, 2015, The Progressive Corporation acquired approximately 63.2% of the outstanding capital stock of ARX Holding Corp. (ARX), the parent company of American Strategic Insurance Corp., other subsidiaries and affiliates (ASI), primarily from non-management shareholders. Later in the second quarter, Progressive purchased an additional 0.9% of ARX capital stock from certain employee shareholders. The total cost to acquire these shares was approximately $890 million and was funded with available cash. Prior to the acquisition, we held a 5% interest in ARX as part of our investment portfolio. During the second quarter 2015, we recognized a $2.0 million loss to reflect the net acquisition cost attributable to this holding. This loss was reported in net realized gains (losses) on securities in the comprehensive income statement. At September 30, 2015, our total ownership interest in ARX was 69.1% . The property business written by ASI accounted for approximately 4% of our total net premiums written during the third quarter 2015. As part of the acquisition, we recorded approximately $470 million of goodwill. Goodwill was calculated as the excess of the purchase price over the estimated fair values of the assets and liabilities acquired, and represents the future economic benefits arising from other assets acquired that could not be individually identified and separately recognized. As a result of the ARX acquisition, we are able to build on the pre-existing relationship we had with ASI to expand on our bundling strategy in the Agency channel. During the third quarter 2015, we completed our analysis related to the fair value of the loss and loss adjustment expense reserves recorded as of the acquisition date. As a result, we recognized a $42.0 million fair value reduction to loss and loss adjustment expense reserves acquired, and a related $15.5 million fair value increase in state and federal deferred taxes acquired, resulting in a net decrease of $26.5 million to the carrying value of goodwill. In September 2015, we adopted the newly issued ASU related to Business Combinations, which simplifies the accounting for measurement-period adjustments. As such, we were able to record the goodwill adjustment in our third quarter 2015 financial statements rather than retrospectively adjusting our previously issued financial statements. As part of the acquisition, we recorded approximately $520 million of other intangible assets; the other intangible assets will be amortized over an average life of about 9 years . The following table reports the intangible assets by asset category as of September 30, 2015: ($ in millions) Category Value at Acquisition Accumulated Amortization Useful Life Policies in force 256.2 18.3 7 years Agency relationships 159.2 5.7 14 years Software 69.1 4.3 8 years ASI Trade name 34.8 1.7 10 years Agent licenses 1.1 0 Indefinite Total $ 520.4 $ 30.0 Including the adjustment made during the third quarter, all assets and liabilities are recorded at fair value at the date of acquisition. If additional new information is obtained within 12 months from the date of acquisition about facts and circumstances that existed at the acquisition date, we will adjust the amounts previously recorded. For income tax purposes, the historical tax bases of the acquired assets and assumed liabilities carried over and were not recorded at fair value; therefore, no tax-basis goodwill was created. At the date of acquisition, ARX had total fair value assets of $1.8 billion , including investment securities of $1.2 billion , cash and cash equivalents of $183 million and prepaid reinsurance premiums of $146 million , and fair value liabilities of $1.2 billion , consisting of unearned premiums of $550 million , loss and loss adjustment expense reserves of $264 million , and debt of $185 million . All of ARX's contingencies were recognized as of the acquisition date. Subsequent to the date of acquisition, our consolidated results included total revenue and net income from ARX of $215.5 million and $26.8 million , respectively, for the third quarter 2015, and $423.7 million and $43.5 million , respectively, for the nine months ended September 30, 2015.

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2015
Investments Schedule [Abstract]
Investment Portfolio by Major Security Type	The following tables present the composition of our investment portfolio by major security type, consistent with our classification of how we manage, monitor, and measure the portfolio: ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) 1 Fair Value % of Value September 30, 2015 Fixed maturities: U.S. government obligations $ 2,028.2 $ 10.1 $ 0 $ 0 $ 2,038.3 9.7 % State and local government obligations 3,025.0 47.1 (4.2 ) 0 3,067.9 14.6 Foreign government obligations 19.3 0 0 0 19.3 0.1 Corporate debt securities 3,797.4 23.4 (21.4 ) 0.1 3,799.5 18.1 Residential mortgage-backed securities 1,801.8 26.2 (18.4 ) (0.2 ) 1,809.4 8.6 Agency residential pass-through obligations 112.2 0.1 (0.4 ) 0 111.9 0.5 Commercial mortgage-backed securities 2,641.4 31.1 (9.3 ) 0.4 2,663.6 12.7 Other asset-backed securities 1,859.3 4.1 (1.5 ) 0.5 1,862.4 8.9 Redeemable preferred stocks 255.0 17.6 (22.8 ) 0 249.8 1.2 Total fixed maturities 15,539.6 159.7 (78.0 ) 0.8 15,622.1 74.4 Equity securities: Nonredeemable preferred stocks 652.4 138.3 (14.8 ) (0.3 ) 775.6 3.7 Common equities 1,487.0 1,031.9 (35.0 ) 0 2,483.9 11.8 Short-term investments 2,132.0 0 0 0 2,132.0 10.1 Total portfolio 2,3 $ 19,811.0 $ 1,329.9 $ (127.8 ) $ 0.5 $ 21,013.6 100.0 % ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) 1 Fair Value % of Value September 30, 2014 Fixed maturities: U.S. government obligations $ 3,033.2 $ 33.6 $ (3.9 ) $ 0 $ 3,062.9 16.0 % State and local government obligations 2,124.2 49.5 (0.9 ) 0 2,172.8 11.4 Foreign government obligations 20.2 0 0 0 20.2 0.1 Corporate debt securities 2,501.8 30.7 (13.1 ) (0.3 ) 2,519.1 13.2 Residential mortgage-backed securities 1,460.6 36.9 (10.1 ) (0.9 ) 1,486.5 7.8 Commercial mortgage-backed securities 2,143.8 33.8 (5.1 ) 0 2,172.5 11.4 Other asset-backed securities 1,546.0 5.0 (0.6 ) 0.2 1,550.6 8.1 Redeemable preferred stocks 260.2 28.8 (4.2 ) 0 284.8 1.5 Total fixed maturities 13,090.0 218.3 (37.9 ) (1.0 ) 13,269.4 69.5 Equity securities: Nonredeemable preferred stocks 532.8 218.4 (7.2 ) 19.3 763.3 4.0 Common equities 1,278.4 1,107.7 (6.7 ) 0 2,379.4 12.5 Short-term investments 2,671.1 0 0 0 2,671.1 14.0 Total portfolio 2,3 $ 17,572.3 $ 1,544.4 $ (51.8 ) $ 18.3 $ 19,083.2 100.0 % ($ in millions) Cost Gross Unrealized Gains Gross Losses Net (Losses) 1 Fair Value % of Value December 31, 2014 Fixed maturities: U.S. government obligations $ 2,641.1 $ 27.3 $ (1.3 ) $ 0 $ 2,667.1 14.0 % State and local government obligations 2,095.7 44.6 (1.1 ) 0 2,139.2 11.2 Foreign government obligations 14.2 0 0 0 14.2 0.1 Corporate debt securities 2,813.9 32.9 (10.4 ) 0.3 2,836.7 14.9 Residential mortgage-backed securities 1,635.5 34.5 (10.8 ) (0.7 ) 1,658.5 8.7 Commercial mortgage-backed securities 2,278.7 39.3 (2.6 ) 0.2 2,315.6 12.2 Other asset-backed securities 1,634.9 3.8 (0.8 ) 0.8 1,638.7 8.6 Redeemable preferred stocks 260.2 24.7 (5.7 ) 0 279.2 1.5 Total fixed maturities 13,374.2 207.1 (32.7 ) 0.6 13,549.2 71.2 Equity securities: Nonredeemable preferred stocks 590.4 201.1 (6.4 ) 42.4 827.5 4.4 Common equities 1,289.2 1,213.2 (10.1 ) 0 2,492.3 13.1 Short-term investments 2,149.0 0 0 0 2,149.0 11.3 Total portfolio 2,3 $ 17,402.8 $ 1,621.4 $ (49.2 ) $ 43.0 $ 19,018.0 100.0 % 1 Represents net holding period gains (losses) on certain hybrid securities (discussed below). 2 Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at September 30, 2015 , $149.9 million was included in "other liabilities," compared to $158.0 million and $31.3 million at September 30, 2014 and December 31, 2014 , respectively. 3 The total fair value of the portfolio at September 30, 2015 and 2014 , and December 31, 2014 included $1.0 billion , $1.3 billion , and $1.9 billion , respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.
Hybrid Securities	Included in our fixed-maturity and equity securities are hybrid securities, which are reported at fair value: September 30, December 31, (millions) 2015 2014 Fixed maturities: Corporate debt securities $ 89.4 $ 138.5 $ 139.8 Residential mortgage-backed securities 117.7 116.8 120.7 Commercial mortgage-backed securities 17.7 0 31.2 Other asset-backed securities 11.9 13.5 13.7 Total fixed maturities 236.7 268.8 305.4 Equity securities: Nonredeemable preferred stocks 54.1 93.4 122.3 Total hybrid securities $ 290.8 $ 362.2 $ 427.7
Composition of Fixed Maturities by Maturity	The composition of fixed maturities by maturity at September 30, 2015 , was: (millions) Cost Fair Value Less than one year $ 4,699.3 $ 4,717.3 One to five years 6,826.1 6,855.9 Five to ten years 3,843.8 3,871.0 Ten years or greater 170.4 177.9 Total $ 15,539.6 $ 15,622.1
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 September 30, 2015 Fixed maturities: U.S. government obligations 0 $ 0 $ 0 0 $ 0 $ 0 0 $ 0 $ 0 State and local government obligations 349 637.1 (4.2 ) 328 551.4 (3.7 ) 21 85.7 (0.5 ) Corporate debt securities 140 1,596.5 (21.4 ) 125 1,292.1 (15.7 ) 15 304.4 (5.7 ) Residential mortgage-backed securities 141 1,205.9 (18.4 ) 76 535.8 (4.1 ) 65 670.1 (14.3 ) Agency residential pass-through obligations 54 67.6 (0.4 ) 54 67.6 (0.4 ) 0 0 0 Commercial mortgage-backed securities 127 1,100.0 (9.3 ) 99 813.8 (7.6 ) 28 286.2 (1.7 ) Other asset-backed securities 60 845.5 (1.5 ) 53 764.0 (0.9 ) 7 81.5 (0.6 ) Redeemable preferred stocks 9 214.8 (22.8 ) 6 121.8 (7.1 ) 3 93.0 (15.7 ) Total fixed maturities 880 5,667.4 (78.0 ) 741 4,146.5 (39.5 ) 139 1,520.9 (38.5 ) Equity securities: Nonredeemable preferred stocks 14 376.9 (14.8 ) 9 197.6 (2.5 ) 5 179.3 (12.3 ) Common equities 136 211.6 (35.0 ) 132 209.1 (34.4 ) 4 2.5 (0.6 ) Total equity securities 150 588.5 (49.8 ) 141 406.7 (36.9 ) 9 181.8 (12.9 ) Total portfolio 1,030 $ 6,255.9 $ (127.8 ) 882 $ 4,553.2 $ (76.4 ) 148 $ 1,702.7 $ (51.4 ) Total No. of Sec. Total Gross Unrealized Losses Less than 12 Months 12 Months or Greater ($ in millions) No. of Sec. Fair Unrealized Losses No. of Sec. Fair Unrealized Losses September 30, 2014 Fixed maturities: U.S. government obligations 19 $ 627.0 $ (3.9 ) 9 $ 211.0 $ (0.7 ) 10 $ 416.0 $ (3.2 ) State and local government obligations 31 181.8 (0.9 ) 11 89.7 (0.1 ) 20 92.1 (0.8 ) Corporate debt securities 50 891.4 (13.1 ) 42 744.5 (9.7 ) 8 146.9 (3.4 ) Residential mortgage-backed securities 62 725.8 (10.1 ) 24 290.5 (1.8 ) 38 435.3 (8.3 ) Agency residential pass-through obligations 0 0 0 0 0 0 0 0 0 Commercial mortgage-backed securities 72 894.5 (5.1 ) 61 787.3 (2.9 ) 11 107.2 (2.2 ) Other asset-backed securities 38 650.8 (0.6 ) 36 624.7 (0.4 ) 2 26.1 (0.2 ) Redeemable preferred stocks 2 70.5 (4.2 ) 0 0 0 2 70.5 (4.2 ) Total fixed maturities 274 4,041.8 (37.9 ) 183 2,747.7 (15.6 ) 91 1,294.1 (22.3 ) Equity securities: Nonredeemable preferred stocks 7 206.3 (7.2 ) 4 118.6 (4.0 ) 3 87.7 (3.2 ) Common equities 39 57.5 (6.7 ) 37 45.7 (5.4 ) 2 11.8 (1.3 ) Total equity securities 46 263.8 (13.9 ) 41 164.3 (9.4 ) 5 99.5 (4.5 ) Total portfolio 320 $ 4,305.6 $ (51.8 ) 224 $ 2,912.0 $ (25.0 ) 96 $ 1,393.6 $ (26.8 ) 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, 2014 Fixed maturities: U.S. government obligations 11 $ 428.2 $ (1.3 ) 5 $ 150.7 $ (0.3 ) 6 $ 277.5 $ (1.0 ) State and local government obligations 46 234.2 (1.1 ) 28 177.9 (0.4 ) 18 56.3 (0.7 ) Corporate debt securities 53 843.2 (10.4 ) 43 647.5 (6.1 ) 10 195.7 (4.3 ) Residential mortgage-backed securities 70 844.2 (10.8 ) 33 465.2 (3.1 ) 37 379.0 (7.7 ) Agency residential pass-through obligations 0 0 0 0 0 0 0 0 0 Commercial mortgage-backed securities 63 723.4 (2.6 ) 54 667.5 (1.4 ) 9 55.9 (1.2 ) Other asset-backed securities 44 741.8 (0.8 ) 42 715.7 (0.7 ) 2 26.1 (0.1 ) Redeemable preferred stocks 3 103.0 (5.7 ) 1 33.0 (1.0 ) 2 70.0 (4.7 ) Total fixed maturities 290 3,918.0 (32.7 ) 206 2,857.5 (13.0 ) 84 1,060.5 (19.7 ) Equity securities: Nonredeemable preferred stocks 8 231.4 (6.4 ) 5 143.2 (3.6 ) 3 88.2 (2.8 ) Common equities 20 68.4 (10.1 ) 19 61.8 (9.6 ) 1 6.6 (0.5 ) Total equity securities 28 299.8 (16.5 ) 24 205.0 (13.2 ) 4 94.8 (3.3 ) Total portfolio 318 $ 4,217.8 $ (49.2 ) 230 $ 3,062.5 $ (26.2 ) 88 $ 1,155.3 $ (23.0 )
Total Non-Credit Portion of Other-Than-Temporary Impairment Recorded in Accumulated Other Comprehensive Income, Reflecting 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: September 30, December 31, (millions) 2015 2014 Fixed maturities: Residential mortgage-backed securities $ (43.3 ) $ (44.1 ) $ (44.1 ) Commercial mortgage-backed securities (0.6 ) (0.6 ) (0.6 ) Total fixed maturities $ (43.9 ) $ (44.7 ) $ (44.7 )
OTTI Credit Losses Recognized in Earnings	The following tables provide rollforwards of the amounts related to credit losses recognized in earnings for the periods ended September 30, 2015 and 2014 , 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 September 30, 2015 Mortgage-Backed (millions) Residential Commercial Total Balance at June 30, 2015 $ 14.0 $ 0.4 $ 14.4 Reductions for securities sold/matured (1.4 ) 0 (1.4 ) Change in recoveries of future cash flows expected to be collected 1 (1.7 ) 0 (1.7 ) Balance at September 30, 2015 $ 10.9 $ 0.4 $ 11.3 Nine Months Ended September 30, 2015 Mortgage-Backed (millions) Residential Commercial Total Balance at December 31, 2014 $ 12.7 $ 0.4 $ 13.1 Reductions for securities sold/matured (1.4 ) 0 (1.4 ) Change in recoveries of future cash flows expected to be collected 1 (0.4 ) 0 (0.4 ) Balance at September 30, 2015 $ 10.9 $ 0.4 $ 11.3 Three Months Ended September 30, 2014 Mortgage-Backed (millions) Residential Commercial Total Balance at June 30, 2014 $ 13.0 $ 0.4 $ 13.4 Reductions for securities sold/matured (0.1 ) 0 (0.1 ) Change in recoveries of future cash flows expected to be collected 1 0.1 0 0.1 Balance at September 30, 2014 $ 13.0 $ 0.4 $ 13.4 Nine Months Ended September 30, 2014 Mortgage-Backed (millions) Residential Commercial Total Balance at December 31, 2013 $ 19.2 $ 0.4 $ 19.6 Reductions for securities sold/matured (0.1 ) 0 (0.1 ) Change in recoveries of future cash flows expected to be collected 1 (6.1 ) 0 (6.1 ) Balance at September 30, 2014 $ 13.0 $ 0.4 $ 13.4 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.
Components of Net Realized Gains (Losses)	The components of net realized gains (losses) for the three and nine months ended September 30, were: Three Months Nine Months (millions) 2015 2014 2015 2014 Gross realized gains on security sales Fixed maturities: U.S. government obligations $ 2.7 $ 2.5 $ 17.1 $ 13.2 State and local government obligations 0.5 3.8 0.5 8.2 Corporate and other debt securities 3.2 0.9 19.1 33.8 Residential mortgage-backed securities 4.4 0.2 4.6 2.2 Commercial mortgage-backed securities 0.9 5.2 15.3 14.8 Redeemable preferred stocks 0 2.3 0.1 2.7 Total fixed maturities 11.7 14.9 56.7 74.9 Equity securities: Nonredeemable preferred stocks 3.7 20.9 53.9 80.0 Common equities 13.2 4.6 43.7 97.0 Subtotal gross realized gains on security sales 28.6 40.4 154.3 251.9 Gross realized losses on security sales Fixed maturities: U.S. government obligations 0 (1.3 ) (0.9 ) (6.4 ) State and local government obligations (0.1 ) (0.3 ) (0.1 ) (0.5 ) Corporate and other debt securities (0.9 ) 0 (2.2 ) (2.3 ) Residential mortgage-backed securities 0 0 0 (0.2 ) Commercial mortgage-backed securities (0.1 ) (1.4 ) (1.1 ) (8.2 ) Redeemable preferred stocks 0 0 0 (3.2 ) Total fixed maturities (1.1 ) (3.0 ) (4.3 ) (20.8 ) Equity securities: Nonredeemable preferred stocks (0.1 ) 0 (1.5 ) 0 Common equities (0.8 ) 0 (1.5 ) (3.4 ) Subtotal gross realized losses on security sales (2.0 ) (3.0 ) (7.3 ) (24.2 ) Net realized gains (losses) on security sales Fixed maturities: U.S. government obligations 2.7 1.2 16.2 6.8 State and local government obligations 0.4 3.5 0.4 7.7 Corporate and other debt securities 2.3 0.9 16.9 31.5 Residential mortgage-backed securities 4.4 0.2 4.6 2.0 Commercial mortgage-backed securities 0.8 3.8 14.2 6.6 Redeemable preferred stocks 0 2.3 0.1 (0.5 ) Total fixed maturities 10.6 11.9 52.4 54.1 Equity securities: Nonredeemable preferred stocks 3.6 20.9 52.4 80.0 Common equities 12.4 4.6 42.2 93.6 Subtotal net realized gains (losses) on security sales 26.6 37.4 147.0 227.7 Other-than-temporary impairment losses Equity securities: Common equities (13.6 ) (0.1 ) (23.0 ) (0.1 ) Subtotal other-than-temporary impairment losses (13.6 ) (0.1 ) (23.0 ) (0.1 ) Other gains (losses) Hybrid securities (1.3 ) (1.8 ) (1.9 ) 5.7 Derivative instruments (27.7 ) (0.7 ) (29.2 ) (39.9 ) Litigation settlements 0.2 3.4 0.3 4.6 Subtotal other gains (losses) (28.8 ) 0.9 (30.8 ) (29.6 ) Total net realized gains (losses) on securities $ (15.8 ) $ 38.2 $ 93.2 $ 198.0
Components of Net Investment Income	The components of net investment income for the three and nine months ended September 30, were: Three Months Nine Months (millions) 2015 2014 2015 2014 Fixed maturities: U.S. government obligations $ 6.2 $ 11.3 $ 22.5 $ 36.3 State and local government obligations 16.9 12.8 45.0 38.2 Foreign government obligations 0.1 0.1 0.3 0.3 Corporate debt securities 28.0 19.5 75.1 60.3 Residential mortgage-backed securities 13.5 11.3 39.5 32.5 Agency residential pass-through obligations 0.7 0 1.4 0 Commercial mortgage-backed securities 18.3 16.5 54.0 49.2 Other asset-backed securities 5.7 4.2 16.2 12.1 Redeemable preferred stocks 3.7 3.7 11.3 11.7 Total fixed maturities 93.1 79.4 265.3 240.6 Equity securities: Nonredeemable preferred stocks 11.0 9.4 32.4 28.6 Common equities 12.7 12.5 36.7 34.1 Short-term investments 0.7 0.4 1.5 0.9 Investment income 117.5 101.7 335.9 304.2 Investment expenses (4.9 ) (3.9 ) (15.9 ) (14.0 ) Net investment income $ 112.6 $ 97.8 $ 320.0 $ 290.2
Derivative Instruments	The following table shows the status of our derivative instruments at September 30, 2015 and 2014 , and December 31, 2014 , and for the three and nine months ended September 30, 2015 and 2014 : (millions) Balance Sheet 2 Comprehensive Income Statement Assets (Liabilities) Pretax Net Realized Gains (Losses) Notional Value 1 Three Months Ended Nine Months Ended September 30, Dec. 31, September 30, Dec. 31, September 30, September 30, Derivatives designated as: 2015 2014 2014 Purpose Classification 2015 2014 2014 2015 2014 2015 2014 Hedging instruments Closed: Ineffective cash flow hedge $ 18 $ 44 $ 44 Manage interest rate risk NA $ 0 $ 0 $ 0 $ 0.2 $ 0.5 $ 0.2 $ 0.5 Non-hedging instruments Assets: Interest rate swaps 0 750 750 Manage portfolio duration Investments— fixed maturities 0 37.0 15.8 0 (1.2 ) 0 (40.4 ) Liabilities: Interest rate swaps 750 0 0 Manage portfolio duration Other liabilities (6.3 ) 0 0 (27.9 ) 0 (31.2 ) 0 Closed: U.S. Treasury Note futures 505 0 0 Manage portfolio duration NA 0 0 0 0 0 1.8 0 Total NA NA NA $ (6.3 ) $ 37.0 $ 15.8 $ (27.7 ) $ (0.7 ) $ (29.2 ) $ (39.9 ) 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. NA= Not Applicable

Fair Value (Tables)

Fair Value (Tables)	9 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Composition of Investment Portfolio by Major Security Type	The composition of the investment portfolio by major security type and our outstanding debt was: Fair Value (millions) Level 1 Level 2 Level 3 Total Cost September 30, 2015 Fixed maturities: U.S. government obligations $ 2,038.3 $ 0 $ 0 $ 2,038.3 $ 2,028.2 State and local government obligations 0 3,067.9 0 3,067.9 3,025.0 Foreign government obligations 19.3 0 0 19.3 19.3 Corporate debt securities 0 3,798.5 1.0 3,799.5 3,797.4 Subtotal 2,057.6 6,866.4 1.0 8,925.0 8,869.9 Asset-backed securities: Residential mortgage-backed 0 1,809.4 0 1,809.4 1,801.8 Agency residential pass-through obligations 0 111.9 0 111.9 112.2 Commercial mortgage-backed 0 2,653.3 10.3 2,663.6 2,641.4 Other asset-backed 0 1,862.4 0 1,862.4 1,859.3 Subtotal asset-backed securities 0 6,437.0 10.3 6,447.3 6,414.7 Redeemable preferred stocks: Financials 0 88.1 0 88.1 71.8 Utilities 0 56.0 0 56.0 65.1 Industrials 0 105.7 0 105.7 118.1 Subtotal redeemable preferred stocks 0 249.8 0 249.8 255.0 Total fixed maturities 2,057.6 13,553.2 11.3 15,622.1 15,539.6 Equity securities: Nonredeemable preferred stocks: Financials 158.7 616.9 0 775.6 652.4 Subtotal nonredeemable preferred stocks 158.7 616.9 0 775.6 652.4 Common equities: Common stocks 2,483.6 0 0 2,483.6 1,486.7 Other risk investments 0 0 0.3 0.3 0.3 Subtotal common equities 2,483.6 0 0.3 2,483.9 1,487.0 Total fixed maturities and equity securities 4,699.9 14,170.1 11.6 18,881.6 17,679.0 Short-term investments 2,007.0 125.0 0 2,132.0 2,132.0 Total portfolio $ 6,706.9 $ 14,295.1 $ 11.6 $ 21,013.6 $ 19,811.0 Debt $ 0 $ 2,727.5 $ 171.7 $ 2,899.2 $ 2,714.3 Fair Value (millions) Level 1 Level 2 Level 3 Total Cost September 30, 2014 Fixed maturities: U.S. government obligations $ 3,062.9 $ 0 $ 0 $ 3,062.9 $ 3,033.2 State and local government obligations 0 2,172.8 0 2,172.8 2,124.2 Foreign government obligations 20.2 0 0 20.2 20.2 Corporate debt securities 0 2,519.1 0 2,519.1 2,501.8 Subtotal 3,083.1 4,691.9 0 7,775.0 7,679.4 Asset-backed securities: Residential mortgage-backed 0 1,486.5 0 1,486.5 1,460.6 Agency residential pass-through obligations 0 0 0 0 0 Commercial mortgage-backed 0 2,160.0 12.5 2,172.5 2,143.8 Other asset-backed 0 1,550.6 0 1,550.6 1,546.0 Subtotal asset-backed securities 0 5,197.1 12.5 5,209.6 5,150.4 Redeemable preferred stocks: Financials 0 100.3 0 100.3 77.3 Utilities 0 65.3 0 65.3 65.0 Industrials 0 119.2 0 119.2 117.9 Subtotal redeemable preferred stocks 0 284.8 0 284.8 260.2 Total fixed maturities 3,083.1 10,173.8 12.5 13,269.4 13,090.0 Equity securities: Nonredeemable preferred stocks: Financials 220.0 496.6 46.7 763.3 532.8 Subtotal nonredeemable preferred stocks 220.0 496.6 46.7 763.3 532.8 Common equities: Common stocks 2,379.0 0 0 2,379.0 1,278.0 Other risk investments 0 0 0.4 0.4 0.4 Subtotal common equities 2,379.0 0 0.4 2,379.4 1,278.4 Total fixed maturities and equity securities 5,682.1 10,670.4 59.6 16,412.1 14,901.2 Short-term investments 2,393.7 277.4 0 2,671.1 2,671.1 Total portfolio $ 8,075.8 $ 10,947.8 $ 59.6 $ 19,083.2 $ 17,572.3 Debt $ 0 $ 2,475.1 $ 0 $ 2,475.1 $ 2,164.3 Fair Value (millions) Level 1 Level 2 Level 3 Total Cost December 31, 2014 Fixed maturities: U.S. government obligations $ 2,667.1 $ 0 $ 0 $ 2,667.1 $ 2,641.1 State and local government obligations 0 2,139.2 0 2,139.2 2,095.7 Foreign government obligations 14.2 0 0 14.2 14.2 Corporate debt securities 0 2,836.7 0 2,836.7 2,813.9 Subtotal 2,681.3 4,975.9 0 7,657.2 7,564.9 Asset-backed securities: Residential mortgage-backed 0 1,658.5 0 1,658.5 1,635.5 Agency residential pass-through obligations 0 0 0 0 0 Commercial mortgage-backed 0 2,304.0 11.6 2,315.6 2,278.7 Other asset-backed 0 1,638.7 0 1,638.7 1,634.9 Subtotal asset-backed securities 0 5,601.2 11.6 5,612.8 5,549.1 Redeemable preferred stocks: Financials 0 97.9 0 97.9 77.3 Utilities 0 65.3 0 65.3 65.0 Industrials 0 116.0 0 116.0 117.9 Subtotal redeemable preferred stocks 0 279.2 0 279.2 260.2 Total fixed maturities 2,681.3 10,856.3 11.6 13,549.2 13,374.2 Equity securities: Nonredeemable preferred stocks: Financials 204.1 554.1 69.3 827.5 590.4 Subtotal nonredeemable preferred stocks 204.1 554.1 69.3 827.5 590.4 Common equities: Common stocks 2,491.9 0 0 2,491.9 1,288.8 Other risk investments 0 0 0.4 0.4 0.4 Subtotal common equities 2,491.9 0 0.4 2,492.3 1,289.2 Total fixed maturities and equity securities 5,377.3 11,410.4 81.3 16,869.0 15,253.8 Short-term investments 1,937.0 212.0 0 2,149.0 2,149.0 Total portfolio $ 7,314.3 $ 11,622.4 $ 81.3 $ 19,018.0 $ 17,402.8 Debt $ 0 $ 2,527.5 $ 0 $ 2,527.5 $ 2,164.7
Summary of Changes in Fair Value Associated With Level 3 Assets	The following tables provide a summary of changes in fair value associated with Level 3 assets for the three and nine months ended September 30, 2015 and 2014 : Level 3 Fair Value Three Months Ended September 30, 2015 (millions) Fair Value at June 30, 2015 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain) Loss on Sales Change in Valuation Net Transfers In (Out) Fair Value at September 30, 2015 Fixed maturities: Corporate debt securities $ 1.0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 1.0 Asset-backed securities: Residential mortgage-backed 0 0 0 0 0 0 0 0 Commercial mortgage-backed 10.9 (0.4 ) 0 0 0 (0.2 ) 0 10.3 Total fixed maturities 11.9 (0.4 ) 0 0 0 (0.2 ) 0 11.3 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 $ 12.2 $ (0.4 ) $ 0 $ 0 $ 0 $ (0.2 ) $ 0 $ 11.6 Level 3 Fair Value Nine Months Ended September 30, 2015 (millions) Fair Value at Dec. 31, 2014 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain) Loss on Sales Change in Valuation Net Transfers In (Out) Fair Value at September 30, 2015 Fixed maturities: Corporate debt securities $ 0 $ 0 $ 1.0 $ 0 $ 0 $ 0 $ 0 $ 1.0 Asset-backed securities: Residential mortgage-backed 0 0 0 0 0 0 0 0 Commercial mortgage-backed 11.6 (1.0 ) 0 0 0 (0.3 ) 0 10.3 Total fixed maturities 11.6 (1.0 ) 1.0 0 0 (0.3 ) 0 11.3 Equity securities: Nonredeemable preferred stocks: Financials 1 69.3 0 0 0 (39.4 ) (1.4 ) (28.5 ) 0 Common equities: Other risk investments 0.4 0 0 0 0 (0.1 ) 0 0.3 Total Level 3 securities $ 81.3 $ (1.0 ) $ 1.0 $ 0 $ (39.4 ) $ (1.8 ) $ (28.5 ) $ 11.6 1 The $69.3 million decrease during the year reflects the reclassification of our 5% interest in ARX Holding Corp. upon acquisition of a controlling interest in ARX. The $39.4 million reflects our inception-to-date gain recognized, including the $1.4 million reduction in valuation that occurred during the first six months of 2015. Level 3 Fair Value Three Months Ended September 30, 2014 (millions) Fair Value at June 30, 2014 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain) Loss on Sales Change in Valuation Net Transfers In (Out) 1 Fair Value at September 30, 2014 Fixed maturities: Corporate debt securities $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Asset-backed securities: Residential mortgage-backed 0 0 0 0 0 0 0 0 Commercial mortgage-backed 27.6 (1.2 ) 0 0 0 (0.3 ) (13.6 ) 12.5 Total fixed maturities 27.6 (1.2 ) 0 0 0 (0.3 ) (13.6 ) 12.5 Equity securities: Nonredeemable preferred stocks: Financials 2 43.8 0 0 0 0 2.9 0 46.7 Common equities: Other risk investments 0.5 (0.1 ) 0 0 0 0 0 0.4 Total Level 3 securities $ 71.9 $ (1.3 ) $ 0 $ 0 $ 0 $ 2.6 $ (13.6 ) $ 59.6 1 The $13.6 million was transferred out of Level 3 and into Level 2 due to an improvement in the security's underlying collateral and an increase in liquidity and market activity in comparable securities. 2 The $2.9 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. Level 3 Fair Value Nine Months Ended September 30, 2014 (millions) Fair Value at Dec. 31, 2013 Calls/ Maturities/ Paydowns Purchases Sales Net Realized (Gain) Loss on Sales Change in Valuation Net Transfers In (Out) 1 Fair Value at September 30, 2014 Fixed maturities: Corporate debt securities $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Asset-backed securities: Residential mortgage-backed 0.2 0 0 (0.1 ) 0.1 (0.2 ) 0 0 Commercial mortgage-backed 29.0 (3.0 ) 0 0 0 0.1 (13.6 ) 12.5 Total fixed maturities 29.2 (3.0 ) 0 (0.1 ) 0.1 (0.1 ) (13.6 ) 12.5 Equity securities: Nonredeemable preferred stocks: Financials 2 39.0 0 0 0 0 7.7 0 46.7 Common equities: Other risk investments 0.5 (0.1 ) 0 0 0 0 0 0.4 Total Level 3 securities $ 68.7 $ (3.1 ) $ 0 $ (0.1 ) $ 0.1 $ 7.6 $ (13.6 ) $ 59.6 1 The $13.6 million was transferred out of Level 3 and into Level 2 due to an improvement in the security's underlying collateral and an increase in liquidity and market activity in comparable securities. 2 The $7.7 million represents net holding period gains on a hybrid security, which is reflected in net realized gains (losses) on securities in the comprehensive income statement.
Summary of Quantitative Information about Level 3 Fair Value Measurements	The following tables provide a summary of the quantitative information about Level 3 fair value measurements for our applicable securities at September 30, 2015 and 2014 , and December 31, 2014 : Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at September 30, 2015 Valuation Technique Unobservable Input Unobservable Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 10.3 External vendor Prepayment rate 1 0 Total fixed maturities 10.3 Equity securities: Nonredeemable preferred stocks: Financials 0 NA NA NA Subtotal Level 3 securities 10.3 Pricing exemption securities 2 1.3 Total Level 3 securities $ 11.6 NA = Not Applicable. We did not hold any nonredeemable preferred stock Level 3 securities at September 30, 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. Quantitative Information about Level 3 Fair Value Measurements ($ in millions) Fair Value at September 30, 2014 Valuation Technique Unobservable Input Unobservable Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 12.5 External vendor Prepayment rate 1 0 Total fixed maturities 12.5 Equity securities: Nonredeemable preferred stocks: Financials 46.7 Multiple of tangible net book value Price to book ratio multiple 1.9 Subtotal Level 3 securities 59.2 Pricing exemption securities 2 0.4 Total Level 3 securities $ 59.6 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, 2014 Valuation Technique Unobservable Input Unobservable Fixed maturities: Asset-backed securities: Commercial mortgage-backed $ 11.6 External vendor Prepayment rate 1 0 Total fixed maturities 11.6 Equity securities: Nonredeemable preferred stocks: Financials 69.3 Multiple of tangible net book value Price to book ratio multiple 2.6 Subtotal Level 3 securities 80.9 Pricing exemption securities 2 0.4 Total Level 3 securities $ 81.3 1 Assumes that one security has 0% of the principal amount of the underlying loans that will be paid off prematurely in each year. 2 The fair values for these securities were determined with unobservable inputs not reasonably available to us.

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
Debt Table	Debt consisted of: September 30, 2015 September 30, 2014 December 31, 2014 (millions) Carrying Value Fair Value Carrying Value Fair Value Carrying Value Fair Value 3.75% Senior Notes due 2021 $ 498.1 $ 534.5 $ 497.8 $ 527.9 $ 497.8 $ 535.6 6 5/8% Senior Notes due 2029 295.6 379.5 295.4 390.9 295.5 400.6 6.25% Senior Notes due 2032 394.9 489.3 394.8 510.3 394.8 527.9 4.35% Senior Notes due 2044 346.4 345.7 346.3 352.7 346.3 378.9 3.70% Senior Notes due 2045 395.0 358.0 0 0 0 0 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 612.6 620.5 630.0 693.3 630.3 684.5 Other debt instruments 171.7 171.7 0 0 0 0 Total $ 2,714.3 $ 2,899.2 $ 2,164.3 $ 2,475.1 $ 2,164.7 $ 2,527.5
Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block]	At September 30, 2015, the other debt instruments consist of: Type of debt instrument Number of Instruments Carrying Value Stated Maturity Date(s) Term loans 2 $93.3 December 2018 and 2019 Junior subordinated notes 1 2 41.3 June 2036 and 2037 Senior notes 4 24.0 Various 2 Surplus note 1 13.1 November 2021 Total $171.7 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 Inform25

Supplemental Cash Flow Information (Tables)	9 Months Ended
	Sep. 30, 2015
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information Table	Cash includes only bank demand deposits. We paid the following in the respective periods: Nine Months Ended September 30, (millions) 2015 2014 Income taxes $ 513.1 $ 355.0 Interest 90.3 74.7

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2015
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 September 30, Nine Months Ended September 30, 2015 2014 2015 2014 (millions) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Revenues Pretax Profit (Loss) Personal Lines Agency $ 2,284.6 $ 169.4 $ 2,235.2 $ 147.0 $ 6,805.5 $ 535.8 $ 6,680.7 $ 468.5 Direct 2,069.5 100.9 1,848.9 107.6 6,056.7 287.2 5,435.1 294.3 Total Personal Lines 1 4,354.1 270.3 4,084.1 254.6 12,862.2 823.0 12,115.8 762.8 Commercial Lines 511.3 77.8 456.0 85.1 1,467.0 239.5 1,340.1 204.4 Property 2 205.2 17.2 0 0 403.9 18.2 0 0 Other indemnity 0 (0.4 ) 0 0.1 (0.4 ) (0.4 ) 0 (5.3 ) Total underwriting operations 5,070.6 364.9 4,540.1 339.8 14,732.7 1,080.3 13,455.9 961.9 Fees and other revenues 3 79.3 NA 75.9 NA 227.9 NA 223.1 NA Service businesses 23.1 2.7 15.0 1.5 63.6 6.8 38.8 2.7 Investments 4 101.7 96.8 139.9 136.0 429.1 413.2 502.2 488.2 Gains (losses) on extinguishment of debt (0.9 ) (0.9 ) (4.8 ) (4.8 ) (0.9 ) (0.9 ) (4.8 ) (4.8 ) Interest expense NA (34.5 ) NA (30.7 ) NA (101.9 ) NA (87.0 ) Consolidated total $ 5,273.8 $ 429.0 $ 4,766.1 $ 441.8 $ 15,452.4 $ 1,397.5 $ 14,215.2 $ 1,361.0 NA = Not Applicable 1 Personal auto insurance accounted for 92% of the total Personal Lines segment net premiums earned for the three months ended September 30, 2015 and the nine months ended September 30, 2015 and 2014 and accounted for 91% for the three months ended September 30, 2014; insurance for our special lines products (e.g., motorcycles, ATVs, RVs, mobile 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 Holding Corp. For the three months and nine months ended September 30, 2015, amounts include $15.0 million and $30.0 million , respectively, of amortization/depreciation expense associated with the acquisition of a controlling interest in ARX Holding Corp. Although this expense is included in our Property segment, it is not reported in the consolidated results of ARX Holding Corp. and, therefore, will not affect the value of the noncontrolling interest. 3 Pretax profit (loss) for fees and other revenues is 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/combined ratios for our underwriting operations for the respective periods: Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Under-writing Combined Ratio Under-writing Combined Ratio Under-writing Margin Combined Ratio Under-writing Margin Combined Ratio Personal Lines Agency 7.4 % 92.6 6.6 % 93.4 7.9 % 92.1 7.0 % 93.0 Direct 4.9 95.1 5.8 94.2 4.7 95.3 5.4 94.6 Total Personal Lines 6.2 93.8 6.2 93.8 6.4 93.6 6.3 93.7 Commercial Lines 15.2 84.8 18.6 81.4 16.3 83.7 15.2 84.8 Property 1 8.4 91.6 0 0 4.5 95.5 0 0 Other indemnity 2 NM NM NM NM NM NM NM NM Total underwriting operations 7.2 % 92.8 7.5 % 92.5 7.3 % 92.7 7.1 % 92.9 1 Included in both the three and nine months ended September 30, 2015, is 7.3 points and 7.4 points, respectively, of amortization/depreciation expense associated with the acquisition of a controlling interest in ARX Holding Corp. 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)	9 Months Ended
	Sep. 30, 2015
Dividends [Abstract]
Dividends	Following is a summary of our shareholder dividends, both variable and special, that were paid in the last two years: (millions, except per share amounts) Amount Dividend Type Declared Paid Per Share Total Annual – Variable December 2014 February 2015 $ 0.6862 $ 404.1 Annual – Variable December 2013 February 2014 0.4929 293.9 Special December 2013 February 2014 1.0000 596.3

Other Comprehensive Income (L28

Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2015
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 Loss attributable to NCI Balance at June 30, 2015 $ 1,393.3 $ (491.3 ) $ 902.0 $ 907.5 $ (7.5 ) $ (0.8 ) $ 2.8 Other comprehensive income (loss) before reclassifications: Investment securities (190.6 ) 66.5 (124.1 ) (124.1 ) 0 0 0 Forecasted transactions 0 0 0 0 0 0 0 Foreign currency translation adjustment (1.1 ) 0.4 (0.7 ) 0 0 (0.7 ) 0 Loss attributable to noncontrolling interest (NCI) (2.5 ) 0.9 (1.6 ) 0 0 0 (1.6 ) Total other comprehensive income (loss) before reclassifications (194.2 ) 67.8 (126.4 ) (124.1 ) 0 (0.7 ) (1.6 ) Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (13.6 ) 4.8 (8.8 ) (8.8 ) 0 0 0 Net realized gains (losses) on securities 23.0 (8.1 ) 14.9 14.8 0.1 0 0 Interest expense 0.4 (0.1 ) 0.3 0 0.3 0 0 Total reclassification adjustment for amounts realized in net income 9.8 (3.4 ) 6.4 6.0 0.4 0 0 Total other comprehensive income (loss) (204.0 ) 71.2 (132.8 ) (130.1 ) (0.4 ) (0.7 ) (1.6 ) Balance at September 30, 2015 $ 1,189.3 $ (420.1 ) $ 769.2 $ 777.4 $ (7.9 ) $ (1.5 ) $ 1.2 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 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 (252.8 ) 84.6 (168.2 ) (168.2 ) 0 0 0 Forecasted transactions (12.8 ) 4.4 (8.4 ) 0 (8.4 ) 0 0 Foreign currency translation adjustment (2.0 ) 0.8 (1.2 ) 0 0 (1.2 ) 0 Loss attributable to noncontrolling interest (NCI) 1.8 (0.6 ) 1.2 0 0 0 1.2 Total other comprehensive income (loss) before reclassifications (265.8 ) 89.2 (176.6 ) (168.2 ) (8.4 ) (1.2 ) 1.2 Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (23.2 ) 8.2 (15.0 ) (15.0 ) 0 0 0 Net realized gains (losses) on securities 140.7 (49.3 ) 91.4 91.3 0.1 0 0 Interest expense 1.4 (0.5 ) 0.9 0 0.9 0 0 Total reclassification adjustment for amounts realized in net income 118.9 (41.6 ) 77.3 76.3 1.0 0 0 Total other comprehensive income (loss) (384.7 ) 130.8 (253.9 ) (244.5 ) (9.4 ) (1.2 ) 1.2 Balance at September 30, 2015 $ 1,189.3 $ (420.1 ) $ 769.2 $ 777.4 $ (7.9 ) $ (1.5 ) $ 1.2 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 Loss attributable to NCI Balance at June 30, 2014 $ 1,598.2 $ (559.3 ) $ 1,038.9 $ 1,035.3 $ 2.5 $ 1.1 $ 0 Other comprehensive income (loss) before reclassifications: Investment securities (62.5 ) 21.9 (40.6 ) (40.6 ) 0 0 0 Forecasted transactions 0 0 0 0 0 0 0 Foreign currency translation adjustment (0.5 ) 0.1 (0.4 ) 0 0 (0.4 ) 0 Loss attributable to noncontrolling interest (NCI) 0 0 0 0 0 0 0 Total other comprehensive income (loss) before reclassifications (63.0 ) 22.0 (41.0 ) (40.6 ) 0 (0.4 ) 0 Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (0.1 ) 0 (0.1 ) (0.1 ) 0 0 0 Net realized gains (losses) on securities 38.3 (13.4 ) 24.9 24.6 0.3 0 0 Interest expense 0.5 (0.1 ) 0.4 0 0.4 0 0 Total reclassification adjustment for amounts realized in net income 38.7 (13.5 ) 25.2 24.5 0.7 0 0 Total other comprehensive income (loss) (101.7 ) 35.5 (66.2 ) (65.1 ) (0.7 ) (0.4 ) 0 Balance at September 30, 2014 $ 1,496.5 $ (523.8 ) $ 972.7 $ 970.2 $ 1.8 $ 0.7 $ 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 Loss attributable to NCI Balance at December 31, 2013 $ 1,464.1 $ (512.4 ) $ 951.7 $ 947.0 $ 4.1 $ 0.6 $ 0 Other comprehensive income (loss) before reclassifications: Investment securities 258.2 (90.3 ) 167.9 167.9 0 0 0 Forecasted transactions (1.6 ) 0.6 (1.0 ) 0 (1.0 ) 0 0 Foreign currency translation adjustment 0.3 (0.2 ) 0.1 0 0 0.1 0 Loss attributable to noncontrolling interest (NCI) 0 0 0 0 0 0 0 Total other comprehensive income (loss) before reclassifications 256.9 (89.9 ) 167.0 167.9 (1.0 ) 0.1 0 Less: Reclassification adjustment for amounts realized in net income by income statement line item: Net impairment losses recognized in earnings (0.1 ) 0 (0.1 ) (0.1 ) 0 0 0 Net realized gains (losses) on securities 223.1 (78.0 ) 145.1 144.8 0.3 0 0 Interest expense 1.5 (0.5 ) 1.0 0 1.0 0 0 Total reclassification adjustment for amounts realized in net income 224.5 (78.5 ) 146.0 144.7 1.3 0 0 Total other comprehensive income (loss) 32.4 (11.4 ) 21.0 23.2 (2.3 ) 0.1 0 Balance at September 30, 2014 $ 1,496.5 $ (523.8 ) $ 972.7 $ 970.2 $ 1.8 $ 0.7 $ 0

Redeemable Noncontrolling Int29

Redeemable Noncontrolling Interest (Tables)	9 Months Ended
	Sep. 30, 2015
Temporary Equity Disclosure [Abstract]
Redeemable Noncontrolling Interest	The components of redeemable noncontrolling interest (NCI) at September 30, 2015, were: ($ in millions) Balance at March 31, 2015 $ 0 Fair value at date of acquisition 411.5 Net income attributable to NCI 13.4 Other comprehensive loss attributable to NCI (1.2 ) Purchase of shares from NCI (12.6 ) Change in redemption value of NCI 31.8 Balance at September 30, 2015 $ 442.9

Acquisitions (Tables)

Acquisitions (Tables)	9 Months Ended
	Sep. 30, 2015
Business Combinations [Abstract]
Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination [Table Text Block]	The following table reports the intangible assets by asset category as of September 30, 2015: ($ in millions) Category Value at Acquisition Accumulated Amortization Useful Life Policies in force 256.2 18.3 7 years Agency relationships 159.2 5.7 14 years Software 69.1 4.3 8 years ASI Trade name 34.8 1.7 10 years Agent licenses 1.1 0 Indefinite Total $ 520.4 $ 30.0

Basis of Presentation Basis of

Basis of Presentation Basis of Presentation-Additional Information (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Disposal Group, Including Discontinued Operation, Assets, Current [Abstract]
Assets Held-for-sale, Property, Plant and Equipment	$ 8.7	$ 8.7	$ 13.4

Basis of Presentation Business

Basis of Presentation Business Acquisition (Details) - USD ($) $ in Millions	Sep. 30, 2015	Apr. 01, 2015	Dec. 31, 2014	Sep. 30, 2014
Business Acquisition [Line Items]
Fair value at date of acquisition		$ 411.5
Assets Held-for-sale, Property, Plant and Equipment	$ 8.7		$ 8.7	$ 13.4
ARX Holding Corp. [Member]
Business Acquisition [Line Items]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage	69.10%
Noncontrolling Interest [Member]
Business Acquisition [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	30.90%
Fair value at date of acquisition		$ 411.5

Investments Investment Portfoli

Investments Investment Portfolio by Major Security Type (Detail) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Schedule of Available-for-sale Securities [Line Items]
Cost	[1],[2]	$ 19,811	$ 17,402.8	$ 17,572.3
Gross Unrealized Gains	[1],[2]	1,329.9	1,621.4	1,544.4
Gross Unrealized Losses	[1],[2]	(127.8)	(49.2)	(51.8)
Net Realized Gains (Losses)	[1],[2],[3]	0.5	43	18.3
Total investments at fair value	[1],[2]	$ 21,013.6	$ 19,018	$ 19,083.2
% of Total Fair Value	[1],[2]	100.00%	100.00%	100.00%
Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 15,539.6	$ 13,374.2	$ 13,090
Gross Unrealized Gains		159.7	207.1	218.3
Gross Unrealized Losses		(78)	(32.7)	(37.9)
Net Realized Gains (Losses)	[3]	0.8	0.6	(1)
Total investments at fair value		$ 15,622.1	$ 13,549.2	$ 13,269.4
% of Total Fair Value		74.40%	71.20%	69.50%
Fixed maturities | U.S. government obligations
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 2,028.2	$ 2,641.1	$ 3,033.2
Gross Unrealized Gains		10.1	27.3	33.6
Gross Unrealized Losses		0	(1.3)	(3.9)
Net Realized Gains (Losses)	[3]	0	0	0
Total investments at fair value		$ 2,038.3	$ 2,667.1	$ 3,062.9
% of Total Fair Value		9.70%	14.00%	16.00%
Fixed maturities | State and local government obligations
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 3,025	$ 2,095.7	$ 2,124.2
Gross Unrealized Gains		47.1	44.6	49.5
Gross Unrealized Losses		(4.2)	(1.1)	(0.9)
Net Realized Gains (Losses)	[3]	0	0	0
Total investments at fair value		$ 3,067.9	$ 2,139.2	$ 2,172.8
% of Total Fair Value		14.60%	11.20%	11.40%
Fixed maturities | Foreign government obligations
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 19.3	$ 14.2	$ 20.2
Gross Unrealized Gains		0	0	0
Gross Unrealized Losses		0	0	0
Net Realized Gains (Losses)	[3]	0	0	0
Total investments at fair value		$ 19.3	$ 14.2	$ 20.2
% of Total Fair Value		0.10%	0.10%	0.10%
Fixed maturities | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 3,797.4	$ 2,813.9	$ 2,501.8
Gross Unrealized Gains		23.4	32.9	30.7
Gross Unrealized Losses		(21.4)	(10.4)	(13.1)
Net Realized Gains (Losses)	[3]	0.1	0.3	(0.3)
Total investments at fair value		$ 3,799.5	$ 2,836.7	$ 2,519.1
% of Total Fair Value		18.10%	14.90%	13.20%
Fixed maturities | Residential mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 1,801.8	$ 1,635.5	$ 1,460.6
Gross Unrealized Gains		26.2	34.5	36.9
Gross Unrealized Losses		(18.4)	(10.8)	(10.1)
Net Realized Gains (Losses)	[3]	(0.2)	(0.7)	(0.9)
Total investments at fair value		$ 1,809.4	$ 1,658.5	$ 1,486.5
% of Total Fair Value		8.60%	8.70%	7.80%
Fixed maturities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 112.2
Gross Unrealized Gains		0.1
Gross Unrealized Losses		(0.4)
Net Realized Gains (Losses)	[3]	0
Total investments at fair value		$ 111.9
% of Total Fair Value		0.50%
Fixed maturities | Commercial mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 2,641.4	$ 2,278.7	$ 2,143.8
Gross Unrealized Gains		31.1	39.3	33.8
Gross Unrealized Losses		(9.3)	(2.6)	(5.1)
Net Realized Gains (Losses)	[3]	0.4	0.2	0
Total investments at fair value		$ 2,663.6	$ 2,315.6	$ 2,172.5
% of Total Fair Value		12.70%	12.20%	11.40%
Fixed maturities | Other asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 1,859.3	$ 1,634.9	$ 1,546
Gross Unrealized Gains		4.1	3.8	5
Gross Unrealized Losses		(1.5)	(0.8)	(0.6)
Net Realized Gains (Losses)	[3]	0.5	0.8	0.2
Total investments at fair value		$ 1,862.4	$ 1,638.7	$ 1,550.6
% of Total Fair Value		8.90%	8.60%	8.10%
Fixed maturities | Redeemable preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 255	$ 260.2	$ 260.2
Gross Unrealized Gains		17.6	24.7	28.8
Gross Unrealized Losses		(22.8)	(5.7)	(4.2)
Net Realized Gains (Losses)	[3]	0	0	0
Total investments at fair value		$ 249.8	$ 279.2	$ 284.8
% of Total Fair Value		1.20%	1.50%	1.50%
Equity securities | Nonredeemable preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 652.4	$ 590.4	$ 532.8
Gross Unrealized Gains		138.3	201.1	218.4
Gross Unrealized Losses		(14.8)	(6.4)	(7.2)
Net Realized Gains (Losses)	[3]	(0.3)	42.4	19.3
Total investments at fair value		$ 775.6	$ 827.5	$ 763.3
% of Total Fair Value		3.70%	4.40%	4.00%
Equity securities | Common equities
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 1,487	$ 1,289.2	$ 1,278.4
Gross Unrealized Gains		1,031.9	1,213.2	1,107.7
Gross Unrealized Losses		(35)	(10.1)	(6.7)
Net Realized Gains (Losses)	[3]	0	0	0
Total investments at fair value		$ 2,483.9	$ 2,492.3	$ 2,379.4
% of Total Fair Value		11.80%	13.10%	12.50%
Short-term investments
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 2,132	$ 2,149	$ 2,671.1
Gross Unrealized Gains		0	0	0
Gross Unrealized Losses		0	0	0
Net Realized Gains (Losses)	[3]	0	0	0
Total investments at fair value		$ 2,132	$ 2,149	$ 2,671.1
% of Total Fair Value		10.10%	11.30%	14.00%
[1]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at September 30, 2015, $149.9 million was included in "other liabilities," compared to $158.0 million and $31.3 million at September 30, 2014 and December 31, 2014
[2]	The total fair value of the portfolio at September 30, 2015 and 2014, and December 31, 2014 included $1.0 billion, $1.3 billion, and $1.9 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) on certain hybrid securities (discussed below).

Investments Investment Portfo34

Investments Investment Portfolio by Major Security Type (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Investments, Debt and Equity Securities [Abstract]
Net unsettled security transactions offset in other liabilities	$ 149.9	$ 31.3	$ 158
Securities in the portfolio of a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions	$ 1,000	$ 1,900	$ 1,300

Investments Hybrid Securities (

Investments Hybrid Securities (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Hybrid Securities [Line Items]
Hybrid securities	$ 290.8	$ 427.7	$ 362.2
Fixed maturities
Hybrid Securities [Line Items]
Hybrid securities	236.7	305.4	268.8
Fixed maturities | Corporate debt securities
Hybrid Securities [Line Items]
Hybrid securities	89.4	139.8	138.5
Fixed maturities | Residential mortgage-backed securities
Hybrid Securities [Line Items]
Hybrid securities	117.7	120.7	116.8
Fixed maturities | Commercial mortgage-backed securities
Hybrid Securities [Line Items]
Hybrid securities	17.7	31.2	0
Fixed maturities | Other asset-backed securities
Hybrid Securities [Line Items]
Hybrid securities	11.9	13.7	13.5
Equity securities | Nonredeemable preferred stocks
Hybrid Securities [Line Items]
Hybrid securities	$ 54.1	$ 122.3	$ 93.4

Investments Composition of Fixe

Investments Composition of Fixed Maturities by Maturity (Detail) $ in Millions	Sep. 30, 2015USD ($)
Available for sale, cost
Less than one year	$ 4,699.3
One to five years	6,826.1
Five to ten years	3,843.8
Ten years or greater	170.4
Total	15,539.6	[1]
Available for sale, Fair value
Less than one year	4,717.3
One to five years	6,855.9
Five to ten years	3,871
Ten years or greater	177.9
Total	$ 15,622.1	[1]
[1]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjcwZTFhZmZmNGIwODQ1YzY5ZDFhZjhhMzY2MmE0MzI3fFRleHRTZWxlY3Rpb246ODBBOUE1MzEzNDkzQTY2MzRENUI4NTQ2RDIxODdEQjYM}

Investments Composition of Fi37

Investments Composition of Fixed Maturities by Maturity (Parenthetical) (Detail) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Schedule of Available-for-sale Securities [Line Items]
Open interest rate swap positions	[1]	$ (6.3)	$ 15.8	$ 37
[1]	To the extent we hold both derivative assets and liabilities with the same counterparty that are subject to an enforceable master netting arrangement, we expect that we will report them on a gross basis on our balance sheets, consistent with our historical presentation.

Investments Gross Unrealized lo

Investments Gross Unrealized losses by Major Security (Detail) $ in Millions	Sep. 30, 2015USD ($)	Dec. 31, 2014USD ($)	Sep. 30, 2014USD ($)
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	1,030	318	320
Total Fair Value	$ 6,255.9	$ 4,217.8	$ 4,305.6
Gross Unrealized Losses	$ (127.8)	$ (49.2)	$ (51.8)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	882	230	224
Less than 12 Months Fair Value	$ 4,553.2	$ 3,062.5	$ 2,912
Less than 12 Months Unrealized Losses	$ (76.4)	$ (26.2)	$ (25)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	148	88	96
12 Months or Greater Fair Value	$ 1,702.7	$ 1,155.3	$ 1,393.6
12 Months or Greater Unrealized Losses	$ (51.4)	$ (23)	$ (26.8)
Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	880	290	274
Total Fair Value	$ 5,667.4	$ 3,918	$ 4,041.8
Gross Unrealized Losses	$ (78)	$ (32.7)	$ (37.9)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	741	206	183
Less than 12 Months Fair Value	$ 4,146.5	$ 2,857.5	$ 2,747.7
Less than 12 Months Unrealized Losses	$ (39.5)	$ (13)	$ (15.6)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	139	84	91
12 Months or Greater Fair Value	$ 1,520.9	$ 1,060.5	$ 1,294.1
12 Months or Greater Unrealized Losses	$ (38.5)	$ (19.7)	$ (22.3)
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	0	11	19
Total Fair Value	$ 0	$ 428.2	$ 627
Gross Unrealized Losses	$ 0	$ (1.3)	$ (3.9)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	0	5	9
Less than 12 Months Fair Value	$ 0	$ 150.7	$ 211
Less than 12 Months Unrealized Losses	$ 0	$ (0.3)	$ (0.7)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	0	6	10
12 Months or Greater Fair Value	$ 0	$ 277.5	$ 416
12 Months or Greater Unrealized Losses	$ 0	$ (1)	$ (3.2)
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	349	46	31
Total Fair Value	$ 637.1	$ 234.2	$ 181.8
Gross Unrealized Losses	$ (4.2)	$ (1.1)	$ (0.9)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	328	28	11
Less than 12 Months Fair Value	$ 551.4	$ 177.9	$ 89.7
Less than 12 Months Unrealized Losses	$ (3.7)	$ (0.4)	$ (0.1)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	21	18	20
12 Months or Greater Fair Value	$ 85.7	$ 56.3	$ 92.1
12 Months or Greater Unrealized Losses	$ (0.5)	$ (0.7)	$ (0.8)
Fixed maturities | Corporate debt securities
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	140	53	50
Total Fair Value	$ 1,596.5	$ 843.2	$ 891.4
Gross Unrealized Losses	$ (21.4)	$ (10.4)	$ (13.1)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	125	43	42
Less than 12 Months Fair Value	$ 1,292.1	$ 647.5	$ 744.5
Less than 12 Months Unrealized Losses	$ (15.7)	$ (6.1)	$ (9.7)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	15	10	8
12 Months or Greater Fair Value	$ 304.4	$ 195.7	$ 146.9
12 Months or Greater Unrealized Losses	$ (5.7)	$ (4.3)	$ (3.4)
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	141	70	62
Total Fair Value	$ 1,205.9	$ 844.2	$ 725.8
Gross Unrealized Losses	$ (18.4)	$ (10.8)	$ (10.1)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	76	33	24
Less than 12 Months Fair Value	$ 535.8	$ 465.2	$ 290.5
Less than 12 Months Unrealized Losses	$ (4.1)	$ (3.1)	$ (1.8)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	65	37	38
12 Months or Greater Fair Value	$ 670.1	$ 379	$ 435.3
12 Months or Greater Unrealized Losses	$ (14.3)	$ (7.7)	$ (8.3)
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	54	0	0
Total Fair Value	$ 67.6	$ 0	$ 0
Gross Unrealized Losses	$ (0.4)	$ 0	$ 0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	54	0	0
Less than 12 Months Fair Value	$ 67.6	$ 0	$ 0
Less than 12 Months Unrealized Losses	$ (0.4)	$ 0	$ 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 | Commercial mortgage-backed securities
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	127	63	72
Total Fair Value	$ 1,100	$ 723.4	$ 894.5
Gross Unrealized Losses	$ (9.3)	$ (2.6)	$ (5.1)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	99	54	61
Less than 12 Months Fair Value	$ 813.8	$ 667.5	$ 787.3
Less than 12 Months Unrealized Losses	$ (7.6)	$ (1.4)	$ (2.9)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	28	9	11
12 Months or Greater Fair Value	$ 286.2	$ 55.9	$ 107.2
12 Months or Greater Unrealized Losses	$ (1.7)	$ (1.2)	$ (2.2)
Fixed maturities | Other asset-backed securities
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	60	44	38
Total Fair Value	$ 845.5	$ 741.8	$ 650.8
Gross Unrealized Losses	$ (1.5)	$ (0.8)	$ (0.6)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	53	42	36
Less than 12 Months Fair Value	$ 764	$ 715.7	$ 624.7
Less than 12 Months Unrealized Losses	$ (0.9)	$ (0.7)	$ (0.4)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	7	2	2
12 Months or Greater Fair Value	$ 81.5	$ 26.1	$ 26.1
12 Months or Greater Unrealized Losses	$ (0.6)	$ (0.1)	$ (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	3	2
Total Fair Value	$ 214.8	$ 103	$ 70.5
Gross Unrealized Losses	$ (22.8)	$ (5.7)	$ (4.2)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	6	1	0
Less than 12 Months Fair Value	$ 121.8	$ 33	$ 0
Less than 12 Months Unrealized Losses	$ (7.1)	$ (1)	$ 0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	3	2	2
12 Months or Greater Fair Value	$ 93	$ 70	$ 70.5
12 Months or Greater Unrealized Losses	$ (15.7)	$ (4.7)	$ (4.2)
Equity securities
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	150	28	46
Total Fair Value	$ 588.5	$ 299.8	$ 263.8
Gross Unrealized Losses	$ (49.8)	$ (16.5)	$ (13.9)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	141	24	41
Less than 12 Months Fair Value	$ 406.7	$ 205	$ 164.3
Less than 12 Months Unrealized Losses	$ (36.9)	$ (13.2)	$ (9.4)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	9	4	5
12 Months or Greater Fair Value	$ 181.8	$ 94.8	$ 99.5
12 Months or Greater Unrealized Losses	$ (12.9)	$ (3.3)	$ (4.5)
Equity securities | Nonredeemable preferred stocks
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	14	8	7
Total Fair Value	$ 376.9	$ 231.4	$ 206.3
Gross Unrealized Losses	$ (14.8)	$ (6.4)	$ (7.2)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	9	5	4
Less than 12 Months Fair Value	$ 197.6	$ 143.2	$ 118.6
Less than 12 Months Unrealized Losses	$ (2.5)	$ (3.6)	$ (4)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	5	3	3
12 Months or Greater Fair Value	$ 179.3	$ 88.2	$ 87.7
12 Months or Greater Unrealized Losses	$ (12.3)	$ (2.8)	$ (3.2)
Equity securities | Common equities
Investments, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	136	20	39
Total Fair Value	$ 211.6	$ 68.4	$ 57.5
Gross Unrealized Losses	$ (35)	$ (10.1)	$ (6.7)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	132	19	37
Less than 12 Months Fair Value	$ 209.1	$ 61.8	$ 45.7
Less than 12 Months Unrealized Losses	$ (34.4)	$ (9.6)	$ (5.4)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	4	1	2
12 Months or Greater Fair Value	$ 2.5	$ 6.6	$ 11.8
12 Months or Greater Unrealized Losses	$ (0.6)	$ (0.5)	$ (1.3)

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	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
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)	$ (44.7)	$ (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)	(44.1)	(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		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Securities Sold		$ 1.4	$ 0.1	$ 1.4	$ 0.1
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance		14.4	13.4	13.1	19.6
Change in recoveries of future cash flows expected to be collected	[1]	(1.7)	0.1	(0.4)	(6.1)
Ending balance		11.3	13.4	11.3	13.4
Residential mortgage-backed securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Securities Sold		1.4	0.1	1.4	0.1
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance		14	13	12.7	19.2
Change in recoveries of future cash flows expected to be collected	[1]	(1.7)	0.1	(0.4)	(6.1)
Ending balance		10.9	13	10.9	13
Commercial mortgage-backed securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Securities Sold		0	0	0	0
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance		0.4	0.4	0.4	0.4
Change in recoveries of future cash flows expected to be collected	[1]	0	0	0	0
Ending balance		$ 0.4	$ 0.4	$ 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		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	$ 28.6	$ 40.4	$ 154.3	$ 251.9
Gross realized losses on securities sales	(2)	(3)	(7.3)	(24.2)
Net realized gains (losses) on securities sales	26.6	37.4	147	227.7
Other-than-temporary impairment losses	(13.6)	(0.1)	(23)	(0.1)
Total net realized gains (losses) on securities	(15.8)	38.2	93.2	198
Fixed maturities
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	11.7	14.9	56.7	74.9
Gross realized losses on securities sales	(1.1)	(3)	(4.3)	(20.8)
Net realized gains (losses) on securities sales	10.6	11.9	52.4	54.1
Fixed maturities | U.S. government obligations
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	2.7	2.5	17.1	13.2
Gross realized losses on securities sales	0	(1.3)	(0.9)	(6.4)
Net realized gains (losses) on securities sales	2.7	1.2	16.2	6.8
Fixed maturities | State and local government obligations
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	0.5	3.8	0.5	8.2
Gross realized losses on securities sales	(0.1)	(0.3)	(0.1)	(0.5)
Net realized gains (losses) on securities sales	0.4	3.5	0.4	7.7
Fixed maturities | Corporate And Other Debt Securities
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	3.2	0.9	19.1	33.8
Gross realized losses on securities sales	(0.9)	0	(2.2)	(2.3)
Net realized gains (losses) on securities sales	2.3	0.9	16.9	31.5
Fixed maturities | Residential mortgage-backed securities
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	4.4	0.2	4.6	2.2
Gross realized losses on securities sales	0	0	0	(0.2)
Net realized gains (losses) on securities sales	4.4	0.2	4.6	2
Fixed maturities | Commercial mortgage-backed securities
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	0.9	5.2	15.3	14.8
Gross realized losses on securities sales	(0.1)	(1.4)	(1.1)	(8.2)
Net realized gains (losses) on securities sales	0.8	3.8	14.2	6.6
Fixed maturities | Redeemable preferred stocks
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	0	2.3	0.1	2.7
Gross realized losses on securities sales	0	0	0	(3.2)
Net realized gains (losses) on securities sales	0	2.3	0.1	(0.5)
Equity securities | Nonredeemable preferred stocks
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	3.7	20.9	53.9	80
Net realized gains (losses) on securities sales	3.6	20.9	52.4	80
Equity securities | Common equities
Gain (Loss) on Investments [Line Items]
Gross realized gains on securities sales	13.2	4.6	43.7	97
Gross realized losses on securities sales	(0.8)	0	(1.5)	(3.4)
Net realized gains (losses) on securities sales	12.4	4.6	42.2	93.6
Other-than-temporary impairment losses	(13.6)	(0.1)	(23)	(0.1)
Hybrid and Derivative Instruments and Litigation Settlements
Gain (Loss) on Investments [Line Items]
Other gains (losses)	(28.8)	0.9	(30.8)	(29.6)
Hybrid and Derivative Instruments and Litigation Settlements | Litigation Settlements
Gain (Loss) on Investments [Line Items]
Other gains (losses)	0.2	3.4	0.3	4.6
Hybrid and Derivative Instruments and Litigation Settlements | Hybrid Preferred Stock
Gain (Loss) on Investments [Line Items]
Other gains (losses)	(1.3)	(1.8)	(1.9)	5.7
Hybrid and Derivative Instruments and Litigation Settlements | Derivative Instruments
Gain (Loss) on Investments [Line Items]
Other gains (losses)	(27.7)	(0.7)	(29.2)	(39.9)
Equity securities | Nonredeemable preferred stocks
Gain (Loss) on Investments [Line Items]
Gross realized losses on securities sales	$ (0.1)	$ 0	$ (1.5)	$ 0

Investments Components of Net I

Investments Components of Net Investment Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Net Investment Income [Line Items]
Investment income	$ 117.5	$ 101.7	$ 335.9	$ 304.2
Investment expenses	(4.9)	(3.9)	(15.9)	(14)
Net Investment Income	112.6	97.8	320	290.2
Fixed maturities
Net Investment Income [Line Items]
Investment income	93.1	79.4	265.3	240.6
Fixed maturities | U.S. government obligations
Net Investment Income [Line Items]
Investment income	6.2	11.3	22.5	36.3
Fixed maturities | State and local government obligations
Net Investment Income [Line Items]
Investment income	16.9	12.8	45	38.2
Fixed maturities | Foreign government obligations
Net Investment Income [Line Items]
Investment income	0.1	0.1	0.3	0.3
Fixed maturities | Corporate debt securities
Net Investment Income [Line Items]
Investment income	28	19.5	75.1	60.3
Fixed maturities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Net Investment Income [Line Items]
Investment income	0.7	0	1.4	0
Fixed maturities | Residential mortgage-backed securities
Net Investment Income [Line Items]
Investment income	13.5	11.3	39.5	32.5
Fixed maturities | Commercial mortgage-backed securities
Net Investment Income [Line Items]
Investment income	18.3	16.5	54	49.2
Fixed maturities | Other asset-backed securities
Net Investment Income [Line Items]
Investment income	5.7	4.2	16.2	12.1
Fixed maturities | Redeemable preferred stocks
Net Investment Income [Line Items]
Investment income	3.7	3.7	11.3	11.7
Equity securities | Nonredeemable preferred stocks
Net Investment Income [Line Items]
Investment income	11	9.4	32.4	28.6
Equity securities | Common equities
Net Investment Income [Line Items]
Investment income	12.7	12.5	36.7	34.1
Short-term investments
Net Investment Income [Line Items]
Investment income	$ 0.7	$ 0.4	$ 1.5	$ 0.9

Investments Derivative Instrume

Investments Derivative Instruments (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Derivative [Line Items]
Balance Sheet - Fair Value	[1]	$ (6.3)	$ 37	$ (6.3)	$ 37	$ 15.8
Income Statement - Net Realized Gain (Loss) on Securities		(27.7)	(0.7)	(29.2)	(39.9)
Designated as Hedging Instruments | Closed Positions | Ineffective Cash Flow Hedge
Derivative [Line Items]
Notional Value	[2]	18	44	18	44	$ 44
Purpose						Manage  interest  rate risk
Balance Sheet - Fair Value	[1]	0	0	0	0	$ 0
Income Statement - Net Realized Gain (Loss) on Securities		0.2	0.5	0.2	0.5
Not Designated as Hedging Instrument [Member] | Closed Positions | Future [Member]
Derivative [Line Items]
Notional Value	[2]	505	0	$ 505	0	0
Purpose				Manage  portfolio duration
Balance Sheet - Fair Value	[1]	0	0	$ 0	0	0
Income Statement - Net Realized Gain (Loss) on Securities		0	0	1.8	0
Not Designated as Hedging Instrument [Member] | Assets | Interest rate swaps | Fixed maturities
Derivative [Line Items]
Notional Value	[2]	0	750	$ 0	$ 750	$ 750
Purpose				Manage  portfolio duration	Manage portfolio duration	Manage portfolio duration
Balance Sheet - Fair Value	[1]	0	37	$ 0	$ 37	$ 15.8
Income Statement - Net Realized Gain (Loss) on Securities		0	(1.2)	0	(40.4)
Not Designated as Hedging Instrument [Member] | Assets | Future [Member] | Fixed maturities
Derivative [Line Items]
Notional Value	[2]		0		0
Not Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member] | Interest rate swaps | Fixed maturities
Derivative [Line Items]
Notional Value	[2]	750	0	$ 750	0	0
Purpose				Manage  portfolio duration
Balance Sheet - Fair Value	[1]	(6.3)	0	$ (6.3)	0	$ 0
Income Statement - Net Realized Gain (Loss) on Securities		$ (27.9)	$ 0	$ (31.2)	$ 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		9 Months Ended		12 Months Ended
		Jan. 26, 2015USD ($)	Apr. 25, 2014USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Dec. 31, 2014USD ($)	Apr. 01, 2015	Jun. 18, 2007
Schedule of Investments [Line Items]
Open reverse repurchase commitments				$ 0		$ 0		$ 0
Gross unrealized losses				$ 127,800,000	$ 51,800,000	$ 127,800,000	$ 51,800,000	$ 49,200,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions				1,030	320	1,030	320	318
Trading securities				$ 0	$ 0	$ 0	$ 0	$ 0
Net realized gains (losses) on securities				(2,200,000)	38,300,000	116,400,000	198,100,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest				286,500,000	296,100,000	950,600,000	910,800,000
Balance Sheet - Fair Value	[1]			$ (6,300,000)	37,000,000	(6,300,000)	37,000,000	15,800,000
Largest Outstanding Balance of Reverse Repurchase Agreements						$ 275,000,000
RRP Largest Outstanding Balance Number of Days Open						1 day
Reverse Repurchase Agreement Average Daily Balance						$ 129,700,000
3.70% Senior Notes due 2045
Schedule of Investments [Line Items]
Additional Expenses Related to the Issuance		$ 800,000
Debt Instrument, Issuance Date		Jan. 26, 2015
Debt Instrument, Face Amount		$ 400,000,000
Debt Instrument, Interest Rate, Stated Percentage		3.70%		3.70%		3.70%				6.70%
Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss)		$ 12,900,000
4.35% Senior Notes due 2044
Schedule of Investments [Line Items]
Additional Expenses Related to the Issuance			$ 700,000
Debt Instrument, Issuance Date			Apr. 25, 2014
Debt Instrument, Face Amount			$ 350,000,000
Debt Instrument, Interest Rate, Stated Percentage			4.35%	4.35%		4.35%
Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss)			$ 1,600,000
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%
Repurchase of debt, face amount						$ 18,400,000	44,300,000
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 | Net unrealized gains on forecasted transactions
Schedule of Investments [Line Items]
Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss)						(200,000)		(500,000)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest						0	0
Future [Member]
Schedule of Investments [Line Items]
Derivative, Gain (Loss) on Derivative, Net						1,800,000
Fixed Income Securities
Schedule of Investments [Line Items]
Gross unrealized losses				$ 92,800,000		92,800,000
Equity securities
Schedule of Investments [Line Items]
Gross unrealized losses				$ 49,800,000	$ 13,900,000	$ 49,800,000	$ 13,900,000	$ 16,500,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions				150	46	150	46	28
Equity securities | Common equities
Schedule of Investments [Line Items]
Gross unrealized losses				$ 35,000,000	$ 6,700,000	$ 35,000,000	$ 6,700,000	$ 10,100,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions				136	39	136	39	20
Equity securities | Nonredeemable preferred stocks
Schedule of Investments [Line Items]
Gross unrealized losses				$ 14,800,000	$ 7,200,000	$ 14,800,000	$ 7,200,000	$ 6,400,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions				14	7	14	7	8
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Percentage Decline				4.00%		4.00%
Fixed maturities
Schedule of Investments [Line Items]
Gross unrealized losses				$ 78,000,000	$ 37,900,000	$ 78,000,000	$ 37,900,000	$ 32,700,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions				880	274	880	274	290
Fixed maturities | State and local government obligations
Schedule of Investments [Line Items]
Gross unrealized losses				$ 4,200,000	$ 900,000	$ 4,200,000	$ 900,000	$ 1,100,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions				349	31	349	31	46
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%		1.00%
Realized investment losses						$ 3,300,000
Gross unrealized losses				$ 21,400,000	$ 13,100,000	$ 21,400,000	$ 13,100,000	$ 10,400,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions				140	50	140	50	53
Interest rate swaps
Schedule of Investments [Line Items]
Derivative, Gain (Loss) on Derivative, Net						$ 22,100,000
Cash collateral received from counterparties					$ 31,800,000		$ 31,800,000	$ 16,100,000
Collateral Delivered to Counterparties on Derivative Instruments				$ 9,600,000		9,600,000
Categories of Investments, Marketable Securities, Trading Securities
Schedule of Investments [Line Items]
Net realized gains (losses) on securities				$ 0	0	$ 0	0
Russell One Thousand | Equity securities | Common equities
Schedule of Investments [Line Items]
Percentage of common stock portfolio				89.00%		89.00%
Managed Equity Strategy | Equity securities | Common equities
Schedule of Investments [Line Items]
Percentage of common stock portfolio				11.00%		11.00%
Not Designated as Hedging Instrument [Member] | Future [Member] | Closed Positions
Schedule of Investments [Line Items]
Notional Value	[2]			$ 505,000,000	0	$ 505,000,000	0	0
Balance Sheet - Fair Value	[1]			0	0	0	0	0
Not Designated as Hedging Instrument [Member] | Future [Member] | Fixed maturities | Assets
Schedule of Investments [Line Items]
Notional Value	[2]				0		0
Not Designated as Hedging Instrument [Member] | Interest rate swaps | Fixed maturities | Assets
Schedule of Investments [Line Items]
Notional Value	[2]			0	750,000,000	0	750,000,000	750,000,000
Balance Sheet - Fair Value	[1]			0	37,000,000	0	37,000,000	15,800,000
Designated as Hedging Instruments | Ineffective Cash Flow Hedge | Closed Positions
Schedule of Investments [Line Items]
Notional Value	[2]			18,000,000	44,000,000	18,000,000	44,000,000	44,000,000
Balance Sheet - Fair Value	[1]			$ 0	$ 0	$ 0	$ 0	$ 0
ARX Holding Corp. [Member]
Schedule of Investments [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions				460		460
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Percentage Decline				0.60%		0.60%
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest				$ 26,800,000		$ 43,500,000
Ownership interest held prior to acquisition (percent)									5.00%
[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.

Fair Value Composition of Inves

Fair Value Composition of Investment Portfolio by Major Security Type (Detail) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Fair Value Measurements [Line Items]
Total investments at fair value	[1],[2]	$ 21,013.6	$ 19,018	$ 19,083.2
Long-Term Debt, Fair Value		2,899.2	2,527.5	2,475.1
Debt		2,714.3	2,164.7	2,164.3
Fixed maturities
Fair Value Measurements [Line Items]
Total investments at fair value		15,622.1	13,549.2	13,269.4
Fixed maturities | Redeemable preferred stocks
Fair Value Measurements [Line Items]
Total investments at fair value		249.8	279.2	284.8
Fixed maturities | Redeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Total investments at fair value		88.1	97.9	100.3
Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value Measurements [Line Items]
Total investments at fair value		56	65.3	65.3
Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value Measurements [Line Items]
Total investments at fair value		105.7	116	119.2
Fixed maturities | Debt Securities
Fair Value Measurements [Line Items]
Total investments at fair value		8,925	7,657.2	7,775
Fixed maturities | Debt Securities | U.S. government obligations
Fair Value Measurements [Line Items]
Total investments at fair value		2,038.3	2,667.1	3,062.9
Fixed maturities | Debt Securities | State and local government obligations
Fair Value Measurements [Line Items]
Total investments at fair value		3,067.9	2,139.2	2,172.8
Fixed maturities | Debt Securities | Foreign government obligations
Fair Value Measurements [Line Items]
Total investments at fair value		19.3	14.2	20.2
Fixed maturities | Debt Securities | Corporate debt securities
Fair Value Measurements [Line Items]
Total investments at fair value		3,799.5	2,836.7	2,519.1
Fixed maturities | Asset-backed Securities
Fair Value Measurements [Line Items]
Total investments at fair value		6,447.3	5,612.8	5,209.6
Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities
Fair Value Measurements [Line Items]
Total investments at fair value		1,809.4	1,658.5	1,486.5
Fixed maturities | Asset-backed Securities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value Measurements [Line Items]
Total investments at fair value		111.9	0	0
Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities
Fair Value Measurements [Line Items]
Total investments at fair value		2,663.6	2,315.6	2,172.5
Fixed maturities | Asset-backed Securities | Other asset-backed securities
Fair Value Measurements [Line Items]
Total investments at fair value		1,862.4	1,638.7	1,550.6
Equity securities | Nonredeemable preferred stocks
Fair Value Measurements [Line Items]
Total investments at fair value		775.6	827.5	763.3
Equity securities | Nonredeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Total investments at fair value		775.6	827.5	763.3
Equity securities | Common equities
Fair Value Measurements [Line Items]
Total investments at fair value		2,483.9	2,492.3	2,379.4
Equity securities | Common equities | Common equities
Fair Value Measurements [Line Items]
Total investments at fair value		2,483.6	2,491.9	2,379
Equity securities | Common equities | Other risk investments
Fair Value Measurements [Line Items]
Total investments at fair value		0.3	0.4	0.4
Total Fixed Maturities and Equity Securities
Fair Value Measurements [Line Items]
Total investments at fair value		18,881.6	16,869	16,412.1
Short-term investments
Fair Value Measurements [Line Items]
Total investments at fair value		2,132	2,149	2,671.1
Fair Value, Inputs, Level 1
Fair Value Measurements [Line Items]
Total investments at fair value		6,706.9	7,314.3	8,075.8
Long-Term Debt, Fair Value		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities
Fair Value Measurements [Line Items]
Total investments at fair value		2,057.6	2,681.3	3,083.1
Fair Value, Inputs, Level 1 | Fixed maturities | Redeemable preferred stocks
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Redeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Debt Securities
Fair Value Measurements [Line Items]
Total investments at fair value		2,057.6	2,681.3	3,083.1
Fair Value, Inputs, Level 1 | Fixed maturities | Debt Securities | U.S. government obligations
Fair Value Measurements [Line Items]
Total investments at fair value		2,038.3	2,667.1	3,062.9
Fair Value, Inputs, Level 1 | Fixed maturities | Debt Securities | State and local government obligations
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Debt Securities | Foreign government obligations
Fair Value Measurements [Line Items]
Total investments at fair value		19.3	14.2	20.2
Fair Value, Inputs, Level 1 | Fixed maturities | Debt Securities | Corporate debt securities
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Asset-backed Securities
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Asset-backed Securities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 1 | Fixed maturities | Asset-backed Securities | Other asset-backed securities
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 1 | Equity securities | Nonredeemable preferred stocks
Fair Value Measurements [Line Items]
Total investments at fair value		158.7	204.1	220
Fair Value, Inputs, Level 1 | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Total investments at fair value		158.7	204.1	220
Fair Value, Inputs, Level 1 | Equity securities | Common equities
Fair Value Measurements [Line Items]
Total investments at fair value		2,483.6	2,491.9	2,379
Fair Value, Inputs, Level 1 | Equity securities | Common equities | Common equities
Fair Value Measurements [Line Items]
Total investments at fair value		2,483.6	2,491.9	2,379
Fair Value, Inputs, Level 1 | Equity securities | Common equities | Other risk investments
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 1 | Total Fixed Maturities and Equity Securities
Fair Value Measurements [Line Items]
Total investments at fair value		4,699.9	5,377.3	5,682.1
Fair Value, Inputs, Level 1 | Short-term investments
Fair Value Measurements [Line Items]
Total investments at fair value		2,007	1,937	2,393.7
Fair Value, Inputs, Level 2
Fair Value Measurements [Line Items]
Total investments at fair value		14,295.1	11,622.4	10,947.8
Long-Term Debt, Fair Value		2,727.5	2,527.5	2,475.1
Fair Value, Inputs, Level 2 | Fixed maturities
Fair Value Measurements [Line Items]
Total investments at fair value		13,553.2	10,856.3	10,173.8
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks
Fair Value Measurements [Line Items]
Total investments at fair value		249.8	279.2	284.8
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Total investments at fair value		88.1	97.9	100.3
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value Measurements [Line Items]
Total investments at fair value		56	65.3	65.3
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value Measurements [Line Items]
Total investments at fair value		105.7	116	119.2
Fair Value, Inputs, Level 2 | Fixed maturities | Debt Securities
Fair Value Measurements [Line Items]
Total investments at fair value		6,866.4	4,975.9	4,691.9
Fair Value, Inputs, Level 2 | Fixed maturities | Debt Securities | U.S. government obligations
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 2 | Fixed maturities | Debt Securities | State and local government obligations
Fair Value Measurements [Line Items]
Total investments at fair value		3,067.9	2,139.2	2,172.8
Fair Value, Inputs, Level 2 | Fixed maturities | Debt Securities | Foreign government obligations
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 2 | Fixed maturities | Debt Securities | Corporate debt securities
Fair Value Measurements [Line Items]
Total investments at fair value		3,798.5	2,836.7	2,519.1
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities
Fair Value Measurements [Line Items]
Total investments at fair value		6,437	5,601.2	5,197.1
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities
Fair Value Measurements [Line Items]
Total investments at fair value		1,809.4	1,658.5	1,486.5
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value Measurements [Line Items]
Total investments at fair value		111.9	0	0
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities
Fair Value Measurements [Line Items]
Total investments at fair value		2,653.3	2,304	2,160
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities | Other asset-backed securities
Fair Value Measurements [Line Items]
Total investments at fair value		1,862.4	1,638.7	1,550.6
Fair Value, Inputs, Level 2 | Equity securities | Nonredeemable preferred stocks
Fair Value Measurements [Line Items]
Total investments at fair value		616.9	554.1	496.6
Fair Value, Inputs, Level 2 | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Total investments at fair value		616.9	554.1	496.6
Fair Value, Inputs, Level 2 | Equity securities | Common equities
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 2 | Equity securities | Common equities | Common equities
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 2 | Equity securities | Common equities | Other risk investments
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 2 | Total Fixed Maturities and Equity Securities
Fair Value Measurements [Line Items]
Total investments at fair value		14,170.1	11,410.4	10,670.4
Fair Value, Inputs, Level 2 | Short-term investments
Fair Value Measurements [Line Items]
Total investments at fair value		125	212	277.4
Fair Value, Inputs, Level 3
Fair Value Measurements [Line Items]
Total investments at fair value		11.6	81.3	59.6
Long-Term Debt, Fair Value		171.7	0	0
Fair Value, Inputs, Level 3 | Fixed maturities
Fair Value Measurements [Line Items]
Total investments at fair value		11.3	11.6	12.5
Fair Value, Inputs, Level 3 | Fixed maturities | Redeemable preferred stocks
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Redeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Debt Securities
Fair Value Measurements [Line Items]
Total investments at fair value		1	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Debt Securities | U.S. government obligations
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Debt Securities | State and local government obligations
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Debt Securities | Foreign government obligations
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Debt Securities | Corporate debt securities
Fair Value Measurements [Line Items]
Total investments at fair value		1	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities
Fair Value Measurements [Line Items]
Total investments at fair value		10.3	11.6	12.5
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities
Fair Value Measurements [Line Items]
Total investments at fair value		10.3	11.6	12.5
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Other asset-backed securities
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks
Fair Value Measurements [Line Items]
Total investments at fair value		0	69.3	46.7
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Total investments at fair value		0	69.3	46.7
Fair Value, Inputs, Level 3 | Equity securities | Common equities
Fair Value Measurements [Line Items]
Total investments at fair value		0.3	0.4	0.4
Fair Value, Inputs, Level 3 | Equity securities | Common equities | Common equities
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Fair Value, Inputs, Level 3 | Equity securities | Common equities | Other risk investments
Fair Value Measurements [Line Items]
Total investments at fair value		0.3	0.4	0.4
Fair Value, Inputs, Level 3 | Total Fixed Maturities and Equity Securities
Fair Value Measurements [Line Items]
Total investments at fair value		11.6	81.3	59.6
Fair Value, Inputs, Level 3 | Short-term investments
Fair Value Measurements [Line Items]
Total investments at fair value		0	0	0
Carrying (Reported) Amount, Fair Value Disclosure
Fair Value Measurements [Line Items]
Total investments at fair value		19,811	17,402.8	17,572.3
Debt		2,714.3	2,164.7	2,164.3
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities
Fair Value Measurements [Line Items]
Total investments at fair value		15,539.6	13,374.2	13,090
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks
Fair Value Measurements [Line Items]
Total investments at fair value		255	260.2	260.2
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Total investments at fair value		71.8	77.3	77.3
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks | Utilities
Fair Value Measurements [Line Items]
Total investments at fair value		65.1	65	65
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks | Industrials
Fair Value Measurements [Line Items]
Total investments at fair value		118.1	117.9	117.9
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities
Fair Value Measurements [Line Items]
Total investments at fair value		8,869.9	7,564.9	7,679.4
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities | U.S. government obligations
Fair Value Measurements [Line Items]
Total investments at fair value		2,028.2	2,641.1	3,033.2
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities | State and local government obligations
Fair Value Measurements [Line Items]
Total investments at fair value		3,025	2,095.7	2,124.2
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities | Foreign government obligations
Fair Value Measurements [Line Items]
Total investments at fair value		19.3	14.2	20.2
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities | Corporate debt securities
Fair Value Measurements [Line Items]
Total investments at fair value		3,797.4	2,813.9	2,501.8
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities
Fair Value Measurements [Line Items]
Total investments at fair value		6,414.7	5,549.1	5,150.4
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities
Fair Value Measurements [Line Items]
Total investments at fair value		1,801.8	1,635.5	1,460.6
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value Measurements [Line Items]
Total investments at fair value		112.2	0	0
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities
Fair Value Measurements [Line Items]
Total investments at fair value		2,641.4	2,278.7	2,143.8
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities | Other asset-backed securities
Fair Value Measurements [Line Items]
Total investments at fair value		1,859.3	1,634.9	1,546
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Nonredeemable preferred stocks
Fair Value Measurements [Line Items]
Total investments at fair value		652.4	590.4	532.8
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value Measurements [Line Items]
Total investments at fair value		652.4	590.4	532.8
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities
Fair Value Measurements [Line Items]
Total investments at fair value		1,487	1,289.2	1,278.4
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities | Common equities
Fair Value Measurements [Line Items]
Total investments at fair value		1,486.7	1,288.8	1,278
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities | Other risk investments
Fair Value Measurements [Line Items]
Total investments at fair value		0.3	0.4	0.4
Carrying (Reported) Amount, Fair Value Disclosure | Total Fixed Maturities and Equity Securities
Fair Value Measurements [Line Items]
Total investments at fair value		17,679	15,253.8	14,901.2
Carrying (Reported) Amount, Fair Value Disclosure | Short-term investments
Fair Value Measurements [Line Items]
Total investments at fair value		$ 2,132	$ 2,149	$ 2,671.1
[1]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at September 30, 2015, $149.9 million was included in "other liabilities," compared to $158.0 million and $31.3 million at September 30, 2014 and December 31, 2014
[2]	The total fair value of the portfolio at September 30, 2015 and 2014, and December 31, 2014 included $1.0 billion, $1.3 billion, and $1.9 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			9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014		Sep. 30, 2015	Sep. 30, 2014		Dec. 31, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total investments at fair value	[1],[2]	$ 21,013.6	$ 19,083.2		$ 21,013.6	$ 19,083.2		$ 19,018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value		12.2	71.9		81.3	68.7
Calls/ Maturities/ Paydowns		(0.4)	(1.3)		(1)	(3.1)
Purchases		0	0		1	0
Sales		0	0		0	(0.1)
Net Realized (Gain) Loss on Sales		0	0		(39.4)	0.1
Change in Valuation		(0.2)	2.6		(1.8)	7.6
Net Transfers in (out)		0	(13.6)	[3]	(28.5)	(13.6)	[4]
Ending Fair value		11.6	59.6		11.6	59.6
Fixed maturities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value		11.9	27.6		11.6	29.2
Calls/ Maturities/ Paydowns		(0.4)	(1.2)		(1)	(3)
Purchases		0	0		1	0
Sales		0	0		0	(0.1)
Net Realized (Gain) Loss on Sales		0	0		0	0.1
Change in Valuation		(0.2)	(0.3)		(0.3)	(0.1)
Net Transfers in (out)		0	(13.6)	[3]	0	(13.6)	[4]
Ending Fair value		11.3	12.5		11.3	12.5
Fixed maturities | Debt Securities | Corporate debt securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value		1	0		0	0
Calls/ Maturities/ Paydowns		0	0		0	0
Purchases		0	0		1	0
Sales		0	0		0	0
Net Realized (Gain) Loss on Sales		0	0		0	0
Change in Valuation		0	0		0	0
Net Transfers in (out)		0	0	[3]	0	0	[4]
Ending Fair value		1	0		1	0
Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value		0	0		0	0.2
Calls/ Maturities/ Paydowns		0	0		0	0
Purchases		0	0		0	0
Sales		0	0		0	(0.1)
Net Realized (Gain) Loss on Sales		0	0		0	0.1
Change in Valuation		0	0		0	(0.2)
Net Transfers in (out)		0	0	[3]	0	0	[4]
Ending Fair value		0	0		0	0
Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value		10.9	27.6		11.6	29
Calls/ Maturities/ Paydowns		(0.4)	(1.2)		(1)	(3)
Purchases		0	0		0	0
Sales		0	0		0	0
Net Realized (Gain) Loss on Sales		0	0		0	0
Change in Valuation		(0.2)	(0.3)		(0.3)	0.1
Net Transfers in (out)		0	(13.6)	[3]	0	(13.6)	[4]
Ending Fair value		10.3	12.5		10.3	12.5
Equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value		0	43.8	[5]	69.3	39	[5]
Calls/ Maturities/ Paydowns		0	0	[5]	0	0	[5]
Purchases		0	0	[5]	0	0	[5]
Sales		0	0	[5]	0	0	[5]
Net Realized (Gain) Loss on Sales		0	0	[5]	(39.4)	0	[5]
Change in Valuation		0	2.9	[5]	(1.4)	7.7	[5]
Net Transfers in (out)		0	0	[3],[5]	(28.5)	0	[4],[5]
Ending Fair value		0	46.7	[5]	0	46.7	[5]
Equity securities | Common equities | Other risk investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value		0.3	0.5		0.4	0.5
Calls/ Maturities/ Paydowns		0	(0.1)		0	(0.1)
Purchases		0	0		0	0
Sales		0	0		0	0
Net Realized (Gain) Loss on Sales		0	0		0	0
Change in Valuation		0	0		(0.1)	0
Net Transfers in (out)		0	0	[3]	0	0	[4]
Ending Fair value		0.3	0.4		0.3	0.4
Fair Value, Inputs, Level 1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total investments at fair value		6,706.9	8,075.8		6,706.9	8,075.8		7,314.3
Fair Value, Inputs, Level 2
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total investments at fair value		14,295.1	10,947.8		14,295.1	10,947.8		11,622.4
Fair Value, Inputs, Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total investments at fair value		11.6	59.6		11.6	59.6		81.3
Carrying (Reported) Amount, Fair Value Disclosure
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total investments at fair value		$ 19,811	$ 17,572.3		$ 19,811	$ 17,572.3		$ 17,402.8
[1]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at September 30, 2015, $149.9 million was included in "other liabilities," compared to $158.0 million and $31.3 million at September 30, 2014 and December 31, 2014
[2]	The total fair value of the portfolio at September 30, 2015 and 2014, and December 31, 2014 included $1.0 billion, $1.3 billion, and $1.9 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.
[3]	The $13.6 million was transferred out of Level 3 and into Level 2 due to an improvement in the security's underlying collateral and an increase in liquidity and market activity in comparable securities.
[4]	The $13.6 million was transferred out of Level 3 and into Level 2 due to an improvement in the security's underlying collateral and an increase in liquidity and market activity in comparable securities.
[5]	The $69.3 million decrease during the year reflects the reclassification of our 5% interest in ARX Holding Corp. upon acquisition of a controlling interest in ARX. The $39.4 million reflects our inception-to-date gain recognized, including the $1.4 million reduction in valuation that occurred during the first six months of 2015.

Fair Value Summary of Changes47

Fair Value Summary of Changes in Fair Value Associated With Level 3 Assets (Parenthetical) (Detail) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)Investment		Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)Investment
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net realized gains (losses) on securities	$ (2.2)	$ 38.3		$ 116.4	$ 198.1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	0		39.4	(0.1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0.2	(2.6)		1.8	(7.6)
Equity securities | Nonredeemable preferred stocks | Financials
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)				(69.3)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	0	[1]	39.4	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0	(2.9)	[1]	1.4	(7.7)	[1]
Equity securities | Nonredeemable preferred stocks | Hybrid Securities | Financials
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net realized gains (losses) on securities		2.9			7.7
Fixed maturities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	0		0	(0.1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0.2	0.3		0.3	0.1
Asset-backed Securities | Fixed maturities | Residential mortgage-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	0		0	(0.1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0	0		0	0.2
Asset-backed Securities | Fixed maturities | Commercial mortgage-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	0		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	$ 0.2	$ 0.3		$ 0.3	$ (0.1)
Internal Pricing | Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Number of securities | Investment		1			1
[1]	The $69.3 million decrease during the year reflects the reclassification of our 5% interest in ARX Holding Corp. upon acquisition of a controlling interest in ARX. The $39.4 million reflects our inception-to-date gain recognized, including the $1.4 million reduction in valuation that occurred during the first six months of 2015.

Fair Value Summary of Quantitat

Fair Value Summary of Quantitative Information about Level 3 Fair Value Measurements (Detail) $ in Millions		9 Months Ended				12 Months Ended
		Sep. 30, 2015USD ($)Investment		Sep. 30, 2014USD ($)Investment		Dec. 31, 2014USD ($)Investment
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	[1],[2]	$ 21,013.6		$ 19,083.2		$ 19,018
Fair Value, Inputs, Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value		11.6		59.6		81.3
External Pricing | Fair Value, Inputs, Level 3 | Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value		$ 10.3		$ 12.5		$ 11.6
External Pricing | Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities | Prepayment Rate Zero Percent
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Number of securities | Investment		1		1		1
Fair Value		$ 10.3		$ 12.5		$ 11.6
Valuation Technique		External vendor		External vendor		External vendor
Unobservable Input, prepayment rate		0.00%		0.00%		0.00%
Internal Pricing | Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Number of securities | Investment				1
Fair Value				$ 46.7		$ 69.3
Internal Pricing | Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks | Financials
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value		$ 0		$ 46.7		$ 69.3
Valuation Technique				Multiple of tangible net book value		Multiple of tangible net book value
Unobservable Input, price to book ratio multiple				1.9		2.6
Subtotal Level 3 Securities | Fair Value, Inputs, Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value		10.3		$ 59.2		$ 80.9
Third Party Pricing Exemption Securities | Fair Value, Inputs, Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value		$ 1.3	[3]	$ 0.4	[4]	$ 0.4	[5]
[1]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at September 30, 2015, $149.9 million was included in "other liabilities," compared to $158.0 million and $31.3 million at September 30, 2014 and December 31, 2014
[2]	The total fair value of the portfolio at September 30, 2015 and 2014, and December 31, 2014 included $1.0 billion, $1.3 billion, and $1.9 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) $ in Millions		3 Months Ended	9 Months Ended
		Sep. 30, 2014USD ($)Investment	Sep. 30, 2015USD ($)Investment	Apr. 01, 2015	Dec. 31, 2014USD ($)
Fair Value Measurements [Line Items]
Quoted prices percentage of fair value assets	[1],[2]	100.00%	100.00%		100.00%
Portfolio	[1],[2]	$ 19,083.2	$ 21,013.6		$ 19,018
Fair Value, Inputs, Level 1
Fair Value Measurements [Line Items]
Portfolio		$ 8,075.8	$ 6,706.9		$ 7,314.3
Fair Value, Inputs, Level 1 | Vendor Quoted Pricing
Fair Value Measurements [Line Items]
Quoted prices percentage of fair value assets		54.00%	47.00%		50.00%
Fair Value, Inputs, Level 2
Fair Value Measurements [Line Items]
Portfolio		$ 10,947.8	$ 14,295.1		$ 11,622.4
Fair Value, Inputs, Level 2 | Vendor Quoted Pricing
Fair Value Measurements [Line Items]
Quoted prices percentage of fair value assets		96.00%	97.00%		97.00%
Fair Value, Inputs, Level 2 | Dealer Quoted Pricing
Fair Value Measurements [Line Items]
Quoted prices percentage of fair value assets		4.00%	3.00%		3.00%
Fair Value, Inputs, Level 3
Fair Value Measurements [Line Items]
Portfolio		$ 59.6	$ 11.6		$ 81.3
Nonredeemable preferred stocks | Equity securities
Fair Value Measurements [Line Items]
Number of securities transferred out of Level 2 into Level 1 | Investment		2	0
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount		$ 41.7
Nonredeemable preferred stocks | Fair Value, Inputs, Level 3 | Equity securities | Internal Pricing
Fair Value Measurements [Line Items]
Number of securities | Investment		1
Portfolio		$ 46.7			$ 69.3
Corporate debt securities | Fair Value, Inputs, Level 3 | Fixed maturities | Internal Pricing
Fair Value Measurements [Line Items]
Number of securities | Investment			2
ARX Holding Corp. [Member]
Fair Value Measurements [Line Items]
Ownership interest held prior to acquisition (percent)				5.00%
[1]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at September 30, 2015, $149.9 million was included in "other liabilities," compared to $158.0 million and $31.3 million at September 30, 2014 and December 31, 2014
[2]	The total fair value of the portfolio at September 30, 2015 and 2014, and December 31, 2014 included $1.0 billion, $1.3 billion, and $1.9 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) $ in Millions		1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
		Jan. 26, 2015USD ($)	Apr. 25, 2014USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Dec. 31, 2014USD ($)
Debt Instrument [Line Items]
Carrying Value				$ 2,714.3	$ 2,164.3	$ 2,714.3	$ 2,164.3	$ 2,164.7
Fair Value				2,899.2	2,475.1	2,899.2	2,475.1	2,527.5
Debt, Long-term and Short-term, Combined Amount	[1]			2,714.3	2,164.3	2,714.3	2,164.3	2,164.7
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest				286.5	296.1	950.6	910.8
3.75% Senior Notes due 2021
Debt Instrument [Line Items]
Carrying Value				498.1	497.8	498.1	497.8	497.8
Fair Value				534.5	527.9	534.5	527.9	535.6
6 5/8% Senior Notes due 2029
Debt Instrument [Line Items]
Carrying Value				295.6	295.4	295.6	295.4	295.5
Fair Value				379.5	390.9	379.5	390.9	400.6
6.25% Senior Notes due 2032
Debt Instrument [Line Items]
Carrying Value				394.9	394.8	394.9	394.8	394.8
Fair Value				489.3	510.3	489.3	510.3	527.9
4.35% Senior Notes due 2044
Debt Instrument [Line Items]
Carrying Value				346.4	346.3	346.4	346.3	346.3
Fair Value				345.7	352.7	345.7	352.7	378.9
Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss)			$ (1.6)
Debt Instrument, Face Amount			$ 350
3.70% Senior Notes due 2045
Debt Instrument [Line Items]
Carrying Value				395	0	395	0	0
Fair Value				358	0	358	0	0
Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss)		$ (12.9)
Debt Instrument, Face Amount		$ 400
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067
Debt Instrument [Line Items]
Extinguishment of Debt, Amount						18.4	44.3
Carrying Value				612.6	630	612.6	630	630.3
Fair Value				620.5	693.3	620.5	693.3	684.5
Other Debt Instruments [Member]
Debt Instrument [Line Items]
Carrying Value				171.7	0	171.7	0	0
Fair Value					$ 0		0	0
Debt, Long-term and Short-term, Combined Amount				$ 171.7		171.7
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067
Debt Instrument [Line Items]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest						0	$ 0
Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss)						$ 0.2		$ 0.5
Notes Payable, Other Payables [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Number of debt instruments				2,000,000		2,000,000
Debt, Long-term and Short-term, Combined Amount				$ 93.3		$ 93.3
Trust Preferred Debt Securities [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Carrying Value				$ 41.3		$ 41.3
Number of debt instruments				2,000,000		2,000,000
Senior Notes [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Carrying Value				$ 24		$ 24
Number of debt instruments				4,000,000		4,000,000
Surplus Note [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Number of debt instruments				1,000,000		1,000,000
Debt, Long-term and Short-term, Combined Amount				$ 13.1		$ 13.1
[1]	1Consists of both short-term and long-term debt. See Note 4 - Debt.See notes to consolidated financial statements.

Debt (Parenthetical) (Details)

Debt (Parenthetical) (Details) - USD ($) $ in Millions	1 Months Ended
	Jan. 26, 2015	Apr. 25, 2014	Sep. 30, 2015	Jun. 18, 2007
3.75% Senior Notes due 2021
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			3.75%
6 5/8% Senior Notes due 2029
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			6.625%
6.25% Senior Notes due 2032
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			6.25%
4.35% Senior Notes due 2044
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		4.35%	4.35%
Debt Instrument, Face Amount		$ 350
Proceeds from Debt, Net of Issuance Costs		346.3
Additional Expenses Related to the Issuance		$ 0.7
3.70% Senior Notes due 2045
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.70%		3.70%	6.70%
Debt Instrument, Face Amount	$ 400
Proceeds from Debt, Net of Issuance Costs	394.9
Additional Expenses Related to the Issuance	$ 0.8
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			6.70%

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 26, 2015	Apr. 25, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2015	Jun. 18, 2007
Debt Instrument [Line Items]
(Gains) losses on extinguishment of debt			$ 900,000	$ 4,800,000	$ 900,000	$ 4,800,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest			286,500,000	$ 296,100,000	950,600,000	910,800,000
Discretionary Line of Credit
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			100,000,000		$ 100,000,000		$ 100,000,000
Line of Credit Facility, Interest Rate Description					advances under the Line of Credit (if any) will bear interest at a variable rate equal to the higher of PNC's Prime Rate or the sum of the Federal Funds Open Rate plus 50 basis points.		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		$ 0
Discretionary Line of Credit | Federal Funds Rate
Debt Instrument [Line Items]
Additional percentage on variable rate basis					0.50%		0.50%
3.70% Senior Notes due 2045
Debt Instrument [Line Items]
Debt Instrument, Issuance Date	Jan. 26, 2015
Debt Instrument, Face Amount	$ 400,000,000
Debt Instrument, Interest Rate, Stated Percentage	3.70%		3.70%		3.70%				6.70%
Proceeds from Debt, Net of Issuance Costs	$ 394,900,000
Additional Expenses Related to the Issuance	800,000
Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss)	$ (12,900,000)
4.35% Senior Notes due 2044
Debt Instrument [Line Items]
Debt Instrument, Issuance Date		Apr. 25, 2014
Debt Instrument, Face Amount		$ 350,000,000
Debt Instrument, Interest Rate, Stated Percentage		4.35%	4.35%		4.35%
Proceeds from Debt, Net of Issuance Costs		$ 346,300,000
Additional Expenses Related to the Issuance		700,000
Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss)		$ (1,600,000)
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			6.70%		6.70%
Repurchase of debt, face amount					$ 18,400,000	44,300,000
(Gains) losses on extinguishment of debt					900,000	4,800,000	$ 4,800,000
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 | Net unrealized gains on forecasted transactions
Debt Instrument [Line Items]
Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss)					200,000		$ 500,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest					0	$ 0
Surplus Note [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Minimum surplus requirement under debt covenant			$ 50,000,000
Debt principal expected to be paid								$ 2,200,000
London Interbank Offered Rate (LIBOR) [Member] | Notes Payable, Other Payables [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Additional percentage on variable rate basis			2.25%
Other Assets [Member]
Debt Instrument [Line Items]
Ownership interest in the variable interest entities			$ 1,300,000		$ 1,300,000
Scenario, Forecast [Member] | Notes Payable, Other Payables [Member] | Other Debt Instruments [Member]
Debt Instrument [Line Items]
Debt principal expected to be paid								$ 25,000,000

Income Taxes Effective Tax Rate

Income Taxes Effective Tax Rate (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Apr. 01, 2015
Investments, Owned, Federal Income Tax Note [Line Items]
Effective Income Tax Rate Reconciliation, Percent	33.20%	33.00%	32.00%	33.10%
Deferred income tax expense (benefit)			$ 14
ARX Holding Corp. [Member]
Investments, Owned, Federal Income Tax Note [Line Items]
Ownership interest held prior to acquisition (percent)					5.00%

Supplemental Cash Flow Inform54

Supplemental Cash Flow Information (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Supplemental Cash Flow Elements [Abstract]
Income taxes	$ 513.1	$ 355
Interest	$ 90.3	$ 74.7

Segment Information Operating R

Segment Information Operating Results (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting Information [Line Items]
Segment Reporting, Asymmetrical Allocations to Segments		2.3
Revenues		$ 5,273.8	$ 4,766.1	$ 15,452.4	$ 14,215.2
Pretax Profit (Loss)		$ 429	$ 441.8	$ 1,397.5	$ 1,361
Underwriting Operations
Segment Reporting Information [Line Items]
Combined Ratio		92.80%	92.50%	92.70%	92.90%
Revenues		$ 5,070.6	$ 4,540.1	$ 14,732.7	$ 13,455.9
Pretax Profit (Loss)		$ 364.9	$ 339.8	$ 1,080.3	$ 961.9
Underwriting Operations | Personal Lines
Segment Reporting Information [Line Items]
Combined Ratio		93.80%	93.80%	93.60%	93.70%
Revenues	[1]	$ 4,354.1	$ 4,084.1	$ 12,862.2	$ 12,115.8
Pretax Profit (Loss)	[1]	$ 270.3	$ 254.6	$ 823	$ 762.8
Underwriting Operations | Personal Lines | Agency Channel
Segment Reporting Information [Line Items]
Combined Ratio		92.60%	93.40%	92.10%	93.00%
Revenues		$ 2,284.6	$ 2,235.2	$ 6,805.5	$ 6,680.7
Pretax Profit (Loss)		$ 169.4	$ 147	$ 535.8	$ 468.5
Underwriting Operations | Personal Lines | Direct Channel
Segment Reporting Information [Line Items]
Combined Ratio		95.10%	94.20%	95.30%	94.60%
Revenues		$ 2,069.5	$ 1,848.9	$ 6,056.7	$ 5,435.1
Pretax Profit (Loss)		$ 100.9	$ 107.6	$ 287.2	$ 294.3
Underwriting Operations | Commercial Lines
Segment Reporting Information [Line Items]
Combined Ratio		84.80%	81.40%	83.70%	84.80%
Revenues		$ 511.3	$ 456	$ 1,467	$ 1,340.1
Pretax Profit (Loss)		$ 77.8	$ 85.1	$ 239.5	$ 204.4
Underwriting Operations | Property, Liability and Casualty Insurance Product Line [Member]
Segment Reporting Information [Line Items]
Combined Ratio		91.60%	0.00%	95.50%	0.00%
Revenues		$ 205.2	$ 0	$ 403.9	$ 0
Pretax Profit (Loss)		17.2	0	18.2	0
Underwriting Operations | Other Indemnity
Segment Reporting Information [Line Items]
Revenues		0	0	(0.4)	0
Pretax Profit (Loss)		(0.4)	0.1	(0.4)	(5.3)
Fees and Other Revenues
Segment Reporting Information [Line Items]
Revenues	[2]	79.3	75.9	227.9	223.1
Service Businesses
Segment Reporting Information [Line Items]
Revenues		23.1	15	63.6	38.8
Pretax Profit (Loss)		2.7	1.5	6.8	2.7
Investments
Segment Reporting Information [Line Items]
Revenues	[3]	101.7	139.9	429.1	502.2
Pretax Profit (Loss)	[3]	96.8	136	413.2	488.2
Gains Losses On Extinguishment Of Debt Net Of Expenses [Member]
Segment Reporting Information [Line Items]
Revenues		(0.9)	(4.8)	(0.9)	(4.8)
Pretax Profit (Loss)		(0.9)	(4.8)	(0.9)	(4.8)
Interest Expense
Segment Reporting Information [Line Items]
Pretax Profit (Loss)		$ (34.5)	$ (30.7)	$ (101.9)	$ (87)
[1]	Personal auto insurance accounted for 92% of the total Personal Lines segment net premiums earned for the three months ended September 30, 2015 and the nine months ended September 30, 2015 and 2014 and accounted for 91% for the three months ended September 30, 2014; insurance for our special lines products (e.g., motorcycles, ATVs, RVs, mobile homes, watercraft, and snowmobiles) accounted for the balance of the Personal Lines net premiums earned.
[2]	Pretax profit (loss) for fees and other revenues is allocated to operating segments.
[3]	Revenues represent recurring investment income and total net realized gains (losses) on securities; pretax profit is net of investment expenses.

Segment Information Operating56

Segment Information Operating Results (Parenthetical) (Detail)	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Underwriting Operations | Personal Lines | Personal Auto
Segment Reporting Information [Line Items]
Personal auto insurance percentage of the total personal lines segment net premiums earned	92.00%	91.00%

Segment Information Underwritin

Segment Information Underwriting Margins and Combined Ratios for our Underwriting Operations (Detail) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015USD ($)	Sep. 30, 2014	Sep. 30, 2015USD ($)	Sep. 30, 2014
Segment Reporting Information [Line Items]
Other Depreciation and Amortization	$ 15		$ 30
Underwriting Operations
Segment Reporting Information [Line Items]
Underwriting Margin	7.20%	7.50%	7.30%	7.10%
Underwriting Operations | Personal Lines
Segment Reporting Information [Line Items]
Underwriting Margin	6.20%	6.20%	6.40%	6.30%
Underwriting Operations | Personal Lines | Agency Channel
Segment Reporting Information [Line Items]
Underwriting Margin	7.40%	6.60%	7.90%	7.00%
Underwriting Operations | Personal Lines | Direct Channel
Segment Reporting Information [Line Items]
Underwriting Margin	4.90%	5.80%	4.70%	5.40%
Underwriting Operations | Commercial Lines
Segment Reporting Information [Line Items]
Underwriting Margin	15.20%	18.60%	16.30%	15.20%
Underwriting Operations | Property, Liability and Casualty Insurance Product Line [Member]
Segment Reporting Information [Line Items]
Underwriting Margin	8.40%	0.00%	4.50%	0.00%
Combined Ratio	7.4

Dividends Dividends (Details)

Dividends Dividends (Details) - USD ($)	1 Months Ended
	Feb. 13, 2015	Feb. 28, 2014
Annual variable dividend
Dividends [Line Items]
Dividend paid per share (USD per share)	$ 0.6862	$ 0.4929
Payments of Ordinary Dividends, Common Stock	$ 404.1	$ 293.9
Special dividend
Dividends [Line Items]
Dividend paid per share (USD per share)		$ 1
Payments of Ordinary Dividends, Common Stock		$ 596.3

Dividends - Additional Informat

Dividends - Additional Information (Detail) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)
Dividends [Abstract]
Target percentage used to determine annual variable dividend	33.00%		33.00%
Gainshare factor used to determine annual variable dividend range, minimum	0		0
Gainshare factor used to determine annual variable dividend range, maximum	2		2
Gainshare factor used to determine annual variable dividend	1.53		1.53
Comprehensive income	$ 145.5	$ 229.9	$ 683.3	$ 931.8
After-tax underwriting income			$ 702.2

Other Comprehensive Income (L60

Other Comprehensive Income (Loss) Components of Other Comprehensive Income (Loss) Including Reclassification Adjustments by Income Statement (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]
Pre tax total accumulated other comprehensive income, beginning balance	$ 1,393.3	$ 1,598.2	$ 1,574	$ 1,464.1
Investment securities, pre tax	(190.6)	(62.5)	(252.8)	258.2
Forecasted transactions, pre tax	0	0	(12.8)	(1.6)
Foreign currency translation adjustment, pre tax	(1.1)	(0.5)	(2)	0.3
Total other comprehensive income (loss) before reclassifications, pre tax	(194.2)	(63)	(265.8)	256.9
Total reclassification adjustment for amounts realized in net income, pre tax	9.8	38.7	118.9	224.5
Total other comprehensive income (loss), pre tax	(204)	(101.7)	(384.7)	32.4
Pre tax total accumulated other comprehensive income, ending balance	1,189.3	1,496.5	1,189.3	1,496.5
Accumulated Other Comprehensive Income (Loss), Tax [Roll Forward]
Accumulated other comprehensive income loss tax (Provision) benefit, beginning balance	(491.3)	(559.3)	(550.9)	(512.4)
Investment securities, Total tax (provision) benefit	66.5	21.9	84.6	(90.3)
Forecasted transactions, Total tax (provision) benefit	0	0	4.4	0.6
Foreign currency translation adjustment, Total tax (provision) benefit	0.4	0.1	0.8	(0.2)
Total other comprehensive income (loss) before reclassifications, Total tax (provision) benefit	67.8	22	89.2	(89.9)
Total reclassification adjustment for amounts realized in net income, Total tax (provision) benefit	(3.4)	(13.5)	(41.6)	(78.5)
Total other comprehensive income (loss), Total tax (provision) benefit	71.2	35.5	130.8	(11.4)
Accumulated other comprehensive income loss tax (Provision) benefit, ending balance	(420.1)	(523.8)	(420.1)	(523.8)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
After tax total accumulated other comprehensive income, beginning balance	902	1,038.9	1,023.1	951.7
Investment securities, after tax	(124.1)	(40.6)	(168.2)	167.9
Forecasted transactions, after tax	0	0	(8.4)	(1)
Foreign currency translation adjustment, after tax	(0.7)	(0.4)	(1.2)	0.1
Total other comprehensive income (loss) before reclassifications, after tax	126.4	41	176.6	(167)
Total reclassification adjustment for amounts realized in net income, after tax	6.4	25.2	77.3	146
Other comprehensive income (loss)	132.8	66.2	253.9	(21)
After tax total accumulated other comprehensive income, ending balance	769.2	972.7	769.2	972.7
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Noncontrolling Interest	(2.5)	0	1.8	0
Other Comprehensive Income (Loss), Tax, Portion Attributable to Noncontrolling Interest	0.9	0	(0.6)	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	(1.6)	0	1.2	0
Net impairment losses recognized in earnings	(13.6)	(0.1)	(23.2)	(0.1)
Net realized gains (losses) on securities	(2.2)	38.3	116.4	198.1
Interest expense	34.5	30.7	101.9	87
Accumulated other comprehensive income after tax
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive income (loss)			255.1	(21)
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	907.5	1,035.3	1,021.9	947
Investment securities, after tax	(124.1)	(40.6)	(168.2)	167.9
Forecasted transactions, after tax	0	0	0	0
Foreign currency translation adjustment, after tax	0	0	0	0
Total other comprehensive income (loss) before reclassifications, after tax	124.1	40.6	168.2	(167.9)
Total reclassification adjustment for amounts realized in net income, after tax	6	24.5	76.3	144.7
Other comprehensive income (loss)	130.1	65.1	244.5	(23.2)
After tax total accumulated other comprehensive income, ending balance	777.4	970.2	777.4	970.2
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	0	0	0	0
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	(7.5)	2.5	1.5	4.1
Investment securities, after tax	0	0	0	0
Forecasted transactions, after tax	0	0	(8.4)	(1)
Foreign currency translation adjustment, after tax	0	0	0	0
Total other comprehensive income (loss) before reclassifications, after tax	0	0	8.4	1
Total reclassification adjustment for amounts realized in net income, after tax	0.4	0.7	1	1.3
Other comprehensive income (loss)	0.4	0.7	9.4	2.3
After tax total accumulated other comprehensive income, ending balance	(7.9)	1.8	(7.9)	1.8
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	0	0	0	0
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
After tax total accumulated other comprehensive income, beginning balance	(0.8)	1.1	(0.3)	0.6
Investment securities, after tax	0	0	0	0
Forecasted transactions, after tax	0	0	0	0
Foreign currency translation adjustment, after tax	(0.7)	(0.4)	(1.2)	0.1
Total other comprehensive income (loss) before reclassifications, after tax	0.7	0.4	1.2	(0.1)
Total reclassification adjustment for amounts realized in net income, after tax	0	0	0	0
Other comprehensive income (loss)	0.7	0.4	1.2	(0.1)
After tax total accumulated other comprehensive income, ending balance	(1.5)	0.7	(1.5)	0.7
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	0	0	0	0
Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
After tax total accumulated other comprehensive income, beginning balance	2.8	0	0	0
Investment securities, after tax	0	0	0	0
Forecasted transactions, after tax	0	0	0	0
Foreign currency translation adjustment, after tax	0	0	0	0
Total other comprehensive income (loss) before reclassifications, after tax	(1.6)	0	1.2	0
Total reclassification adjustment for amounts realized in net income, after tax	0	0	0	0
Other comprehensive income (loss)	(1.6)	0	1.2	0
After tax total accumulated other comprehensive income, ending balance	1.2	0	1.2	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	1.6	0	(1.2)	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	(13.6)	(0.1)	(23.2)	(0.1)
Net realized gains (losses) on securities	23	38.3	140.7	223.1
Interest expense	0.4	0.5	1.4	1.5
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	4.8	0	8.2	0
Net realized gains (losses) on securities	(8.1)	(13.4)	(49.3)	(78)
Interest expense	(0.1)	(0.1)	(0.5)	(0.5)
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	(8.8)	(0.1)	(15)	(0.1)
Net realized gains (losses) on securities	14.9	24.9	91.4	145.1
Interest expense	0.3	0.4	0.9	1
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	(8.8)	(0.1)	(15)	(0.1)
Net realized gains (losses) on securities	14.8	24.6	91.3	144.8
Interest expense	0	0	0	0
Reclassification out of Accumulated Other Comprehensive Income | Net unrealized gains on forecasted transactions
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net impairment losses recognized in earnings	0	0	0	0
Net realized gains (losses) on securities	0.1	0.3	0.1	0.3
Interest expense	0.3	0.4	0.9	1
Reclassification out of Accumulated Other Comprehensive Income | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net impairment losses recognized in earnings	0	0	0	0
Net realized gains (losses) on securities	0	0	0	0
Interest expense	0	0	0	0
Reclassification out of Accumulated Other Comprehensive Income | Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net impairment losses recognized in earnings	0	0	0	0
Net realized gains (losses) on securities	0	0	0	0
Interest expense	$ 0	$ 0	$ 0	$ 0

Other Comprehensive Income (L61

Other Comprehensive Income (Loss) Components of Other Comprehensive Income (Loss) Including Reclassification Adjustments by Income Statement (Parenthetical) (Detail) $ in Millions	Sep. 30, 2015USD ($)
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	$ 1.8

Redeemable Noncontrolling Int62

Redeemable Noncontrolling Interest (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Apr. 01, 2015
Temporary Equity Disclosure [Abstract]
Balance at March 31, 2015			$ 0
Fair value at date of acquisition					$ 411.5
Net income attributable to NCI	$ 13.4
Other comprehensive loss attributable to NCI	1.6	$ 0	(1.2)	$ 0
Purchase of shares from NCI	(12.6)
Change in redemption value of NCI	31.8
Balance at September 30, 2015	$ 442.9	$ 0	$ 442.9	$ 0

Acquisitions (Details)

Acquisitions (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Apr. 01, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Provision for income taxes	$ 142.5	$ 145.7	$ 446.9	$ 450.2
Goodwill	446.4	1.6	446.4	1.6		$ 1.6
Revenues	5,273.8	4,766.1	15,452.4	14,215.2
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 286.5	$ 296.1	$ 950.6	$ 910.8
ARX Holding Corp. [Member]
Business Acquisition [Line Items]
Interest acquired (percent)					63.20%
Additional interest acquired (percent)	0.90%
Cost of interest acquired	$ 890
Ownership interest held prior to acquisition (percent)					5.00%
Loss recognized to reflect the net acquisition cost attributable to interest held prior	$ 2
Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage	69.10%		69.10%
Goodwill	$ 26.5		$ 26.5		$ 470
Losses and loss adjustment expenses	42
Goodwill, Subsequent Recognition of Deferred Tax Asset	15.5
Value at acquisition	520.4		520.4
Total assets acquired					1,800
Investment securities acquired					1,200
Cash and cash equivalents acquired					183
Prepaid reinsurance premiums acquired					146
Libilities assumed in acquisition					1,200
Unearned premiums acquired					550
Loss and loss adjustment expense reserves acquired					264
Debt acquired					$ 185
Revenues	215.5		423.7
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 26.8		$ 43.5
Sales Revenue, Segment [Member] | ARX Holding Corp. [Member]
Business Acquisition [Line Items]
Percentage of total net premiums written (percent)	4.00%

Acquisitions Schedule of Intang

Acquisitions Schedule of Intangible Assets by Category (Details) - USD ($) $ in Millions	Apr. 01, 2015	Sep. 30, 2015
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life	9 years
Policies in Force [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life		7 years
Agency Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life		14 years
Computer Software, Intangible Asset [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life		8 years
Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life		10 years
ARX Holding Corp. [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Value at acquisition		$ 520.4
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Accumulated Amortization		30
ARX Holding Corp. [Member] | Policies in Force [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Value at acquisition		256.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Accumulated Amortization		18.3
ARX Holding Corp. [Member] | Agency Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Value at acquisition		159.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Accumulated Amortization		5.7
ARX Holding Corp. [Member] | Computer Software, Intangible Asset [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Value at acquisition		69.1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Accumulated Amortization		4.3
ARX Holding Corp. [Member] | Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Value at acquisition		34.8
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Accumulated Amortization		1.7
ARX Holding Corp. [Member] | Licensing Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Value at acquisition		1.1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Accumulated Amortization		$ 0