The Progressive Corporation (PGR) 10-Q 12 Nov 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2013
Entity Registrant Name	'PROGRESSIVE CORP/OH/
Entity Central Index Key	'0000080661
Current Fiscal Year End Date	'--12-31
Entity Filer Category	'Large Accelerated Filer
Document Type	'10-Q
Document Period End Date	30-Sep-13
Document Fiscal Year Focus	'2013
Document Fiscal Period Focus	'Q3
Amendment Flag	'false
Trading Symbol	'PGR
Entity Common Stock, Shares Outstanding	599,996,304

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended				9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Revenues	'		'		'		'
Net premiums earned	$4,303		$4,054.80		$12,759.30		$11,912.40
Period over prior year period percent change in net premiums earned	6.00%		'		7.00%		'
Investment income	107.4		109		310.1		336.2
Period over prior year period percent change in investment income	-1.00%		'		-8.00%		'
Other-than-temporary impairment (OTTI) losses:	'		'		'		'
Total OTTI losses	-1.9		-0.4		-3.6		-6
Period over prior year period percent change in total OTTI losses	375.00%		'		-40.00%		'
Non-credit losses, net of credit losses recognized on previously recorded non-credit OTTI losses	0		0		-0.1		-0.7
Period over prior year period percent change in non-credit losses, net of credit losses recognized on previously recorded non-credit OTTI losses	'		'		-86.00%		'
Net impairment losses recognized in earnings	-1.9		-0.4		-3.7		-6.7
Period over prior year period percent change in net impairment losses recognized in earnings	375.00%		'		-45.00%		'
Net realized gains (losses) on securities	29.8		172.3		245.1		251.4
Period over prior year period percent change in net realized gains (losses) on securities	-83.00%		'		-3.00%		'
Total net realized gains (losses) on securities	27.9		171.9		241.4		244.7
Period over prior year period percent change in total net realized gains (losses) on securities	-84.00%		'		-1.00%		'
Fees and other revenues	76		78.4		215.3		213.5
Period over prior year period percent change in fees and other revenues	-3.00%		'		1.00%		'
Service revenues	11.3		9.9		30.3		28.3
Period over prior year period percent change in service revenues	14.00%		'		7.00%		'
Gains (losses) on extinguishment of debt	-4.3		-0.1		-4.3		-1.8
Period over prior year period percent change in gains (losses) on extinguishment of debt	4200.00%		'		139.00%		'
Total revenues	4,521.30		4,423.90		13,552.10		12,733.30
Period over prior year period percent change in total revenues	2.00%		'		6.00%		'
Expenses	'		'		'		'
Losses and loss adjustment expenses	3,164.20		3,068.20		9,266.70		8,874.30
Period over prior year period percent change in losses and loss adjustment expenses	3.00%		'		4.00%		'
Policy acquisition costs	363.1		357.3		1,086		1,081.40
Period over prior year period percent change in policy acquisition costs	2.00%		'		0.00%		'
Other underwriting expenses	602.3		542.5		1,769		1,681.20
Period over prior year period percent change in other underwriting expenses	11.00%		'		5.00%		'
Investment expenses	5.2		3.3		14.5		11.3
Period over prior year period percent change in investment expenses	58.00%		'		28.00%		'
Service expenses	11.1		9.6		30.1		27.7
Period over prior year period percent change in service expenses	16.00%		'		9.00%		'
Interest expense	30.4		30.6		91.4		93.2
Period over prior year period percent change in interest expense	-1.00%		'		-2.00%		'
Total expenses	4,176.30		4,011.50		12,257.70		11,769.10
Period over prior year period percent change in total expenses	4.00%		'		4.00%		'
Net Income	'		'		'		'
Income before income taxes	345		412.4		1,294.40		964.2
Period over prior year period percent change in income before income taxes	-16.00%		'		34.00%		'
Provision for income taxes	112.6		135.4		428.8		311
Period over prior year period percent change in provision for income taxes	-17.00%		'		38.00%		'
Net income	232.4		277		865.6		653.2
Period over prior year period percent change in net income	-16.00%		'		33.00%		'
Net unrealized gains (losses) on securities:	'		'		'		'
Net non-credit related OTTI losses, adjusted for valuation changes	0		1.7		0.3		4.8
Period over prior year period percent change in net non-credit related OTTI losses, adjusted for valuation changes	'		'		-94.00%		'
Other net unrealized gains (losses) on securities	57.8		60.6		2.4		209
Period over prior year period percent change in other net unrealized gains (losses) on securities	-5.00%		'		-99.00%		'
Total net unrealized gains (losses) on securities	57.8		62.3		2.7		213.8
Period over prior year period percent change in total net unrealized gains (losses) on securities	-7.00%		'		-99.00%		'
Net unrealized gains on forecasted transactions	-0.9		-0.3		-1.6		-1.5
Period over prior year period percent change in net unrealized gains on forecasted transactions	200.00%		'		7.00%		'
Foreign currency translation adjustment	-0.2		0.4		-1.2		0.3
Other comprehensive income (loss)	56.7		62.4		-0.1		212.6
Period over prior year period percent change in other comprehensive income (loss)	-9.00%		'		'		'
Comprehensive income	$289.10		$339.40		$865.50		$865.80
Period over prior year period percent change in comprehensive income	-15.00%		'		0.00%		'
Computation of Net Income Per Share	'		'		'		'
Average shares outstanding - Basic (shares)	598.9		601.9		599.7		604.3
Period over prior year period percent change in average shares outstanding - basic	0.00%		'		-1.00%		'
Net effect of dilutive stock-based compensation (shares)	4.6		4.6		4.2		4.2
Period over prior year period percent change in net effect of dilutive stock-based compensation	0.00%		'		0.00%		'
Total equivalent shares - Diluted (shares)	603.5		606.5		603.9		608.5
Period over prior year period percent change in total equivalent shares - diluted	0.00%		'		-1.00%		'
Basic: Net income per share (USD per share)	$0.39		$0.46		$1.44		$1.08
Period over prior year period percent change in basic: net income per share	-16.00%		'		34.00%		'
Diluted: Net income per share (USD per share)	$0.39		$0.46		$1.43		$1.07
Period over prior year period percent change in diluted: net income per share	-16.00%		'		34.00%		'
Dividends declared per share (USD per share)	$0	[1]	$0	[1]	$0	[1]	$0	[1]
[1]	Progressive maintains an annual dividend program. See Note 8 - Dividends for further discussion.

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2012
In Millions, unless otherwise specified
Investments - Available-for-sale, at fair value:	'		'		'
Fixed maturities (amortized cost: $13,644.9, $11,864.0, and $11,373.9)	$13,797.70		$11,774.10		$12,295.20
Equity securities:	'		'		'
Nonredeemable preferred stocks (cost: $442.1, $430.1, and $404.0)	726		812.4		848.4
Common equities (cost: $1,422.3, $1,101.5, and $1,370.3)	2,326.10		1,899		1,639.20
Short-term investments (amortized cost: $1,146.1, $2,394.1, and $1,990.0)	1,146.10		1,990		2,394.10
Total investments	17,995.90	[1],[2]	16,475.50	[1],[2]	17,176.90	[1],[2]
Cash	100.9		179.1		192.2
Accrued investment income	91.5		90		88.2
Premiums receivable, net of allowance for doubtful accounts of $133.7, $133.5, and $138.6	3,500.80		3,183.70		3,356
Reinsurance recoverables, including $36.4, $32.5, and $38.9 on paid losses and loss adjustment expenses	1,031.90		901		880.5
Prepaid reinsurance premiums	82.6		66.3		72.8
Deferred acquisition costs	474.7		434.5		461.8
Net deferred income taxes	27.4		109.4		105.3
Property and equipment, net of accumulated depreciation of $665.8, $603.7, and $625.0	955.3		933.7		918.2
Other assets	247.9		321.5		235.3
Total assets	24,508.90		22,694.70		23,487.20
Liabilities and Shareholders’ Equity	'		'		'
Unearned premiums	5,477.90		4,930.70		5,203.40
Loss and loss adjustment expense reserves	8,310.30		7,838.40		7,760.20
Accounts payable, accrued expenses, and other liabilities	1,917.50		1,855.50		1,906.30
Debt	2,010.60	[3]	2,063.10	[3]	2,062.70	[3]
Total liabilities	17,716.30		16,687.70		16,932.60
Common Shares, $1.00 par value (authorized 900.0; issued 797.6, 797.7, and 797.7, including treasury shares of 197.6, 193.0, and 193.1)	600		604.6		604.7
Paid-in capital	1,123		1,077		1,048.60
Retained earnings	4,198.70		3,454.40		3,996.20
Accumulated other comprehensive income, net of tax:	'		'		'
Net non-credit related OTTI losses, adjusted for valuation changes	0		-0.3		-0.6
Other net unrealized gains (losses) on securities	865.4		863		897.2
Total net unrealized gains (losses) on securities	865.4		862.7		896.6
Net unrealized gains on forecasted transactions	4.5		6.1		6.4
Foreign currency translation adjustment	1		2.2		2.1
Total accumulated other comprehensive income	870.9		871		905.1
Total shareholders’ equity	6,792.60		6,007		6,554.60
Total liabilities and shareholders’ equity	$24,508.90		$22,694.70		$23,487.20
[1]	The total fair value of the portfolio at September 30, 2013 and 2012, and December 31, 2012 included $1.3 billion, $1.6 billion, and $1.4 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company.
[2]	At September 30, 2013, we had $63.7 million of net unsettled security transactions, including collateral on open derivative positions, recognized in other liabilities, compared to $32.4 million and $90.9 million recognized in other assets at September 30, 2012 and December 31, 2012, respectively.
[3]	Consists of both short- and long-term debt. See Note 4 - Debt.

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
In Millions, except Per Share data, unless otherwise specified
Fixed maturities, amortized cost	$13,644.90	$11,373.90	$11,864
Nonredeemable preferred stocks, cost	442.1	404	430.1
Common equities, cost	1,422.30	1,370.30	1,101.50
Short-term investments, amortized cost	1,146.10	1,990	2,394.10
Premiums receivable, allowance for doubtful accounts	133.7	138.6	133.5
Reinsurance recoverables, paid losses and loss adjustment expenses	36.4	38.9	32.5
Property and equipment, accumulated depreciation	$665.80	$625	$603.70
Common Shares, par value (USD per share)	$1	$1	$1
Common Shares, authorized (shares)	900	900	900
Common Shares, issued (shares)	797.6	797.7	797.7
Common Shares, treasury shares (shares)	197.6	193.1	193

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012
Cash Flows From Operating Activities	'		'
Net income	$865.60		$653.20
Adjustments to reconcile net income to net cash provided by operating activities:	'		'
Depreciation	74.9		69.1
Amortization of fixed-income securities	111.4		145.3
Amortization of equity-based compensation	49.8		45.8
Net realized (gains) losses on securities	-241.4		-244.7
Net (gains) losses on disposition of property and equipment	4.1		4.8
(Gains) losses on extinguishment of debt	4.3		1.8
Changes in:	'		'
Premiums receivable	-317.4		-426.2
Reinsurance recoverables	-130.9		-62.5
Prepaid reinsurance premiums	-16.3		-3
Deferred acquisition costs	-40.2		-28.2
Income taxes	77.3		45.7
Unearned premiums	548		624
Loss and loss adjustment expense reserves	472		514.4
Accounts payable, accrued expenses, and other liabilities	277.4		306.6
Other, net	9.4		19.2
Net cash provided by operating activities	1,748		1,665.30
Purchases:	'		'
Fixed maturities	-6,070.80		-3,997
Equity securities	-260.2		-176.1
Sales:	'		'
Fixed maturities	2,352.80		2,416
Equity securities	308		737.4
Maturities, paydowns, calls, and other:	'		'
Fixed maturities	1,338.70		1,094.10
Equity securities	0		4
Net (purchases) sales of short-term investments—other	843		-842.9
Net unsettled security transactions	154.6		14.5
Purchases of property and equipment	-105.6		-84.2
Sales of property and equipment	2.4		3.4
Net cash used in investing activities	-1,437.10		-830.8
Cash Flows From Financing Activities	'		'
Proceeds from exercise of stock options	0		0.5
Tax benefit from exercise/vesting of equity-based compensation	10.3		5.6
Payment of debt	0		-350
Reacquisition of debt	-58.1		-32.5
Dividends paid to shareholders	-175.6	[1]	-252.4	[1]
Acquisition of treasury shares	-164.8		-170.1
Net cash used in financing activities	-388.2		-798.9
Effect of exchange rate changes on cash	-0.9		0.9
Increase (decrease) in cash	-78.2		36.5
Cash, Beginning of year	179.1		155.7
Cash, End of year	$100.90		$192.20
[1]	Progressive maintains an annual dividend program. See Note 8 - Dividends for further discussion.

Basis_of_Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2013
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. All of the subsidiaries and affiliates are wholly owned or controlled. 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, 2013, 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, 2012.
	Consistent with the presentation in our Annual Report on Form 10-K for the year ended December 31, 2012, we revised the presentation of our Statements of Comprehensive Income for the third quarter and first nine months of 2012, to correctly classify $78.4 million and $213.5 million, respectively, of fees and other revenues as a component of total revenues. Previously, these items were presented net within our other underwriting expenses. These revisions had no effect on the results of operations (net or comprehensive income), financial condition (shareholders’ equity), or cash flows and are not considered to be material.

Investments

Investments	9 Months Ended
	Sep. 30, 2013
Investments	'
	Investments — The following tables present the composition of our investment portfolio by major security type, consistent with our classification of how we manage, monitor, and measure the portfolio:
	($ in millions)	Cost			Gross			Gross			Net			Fair		% of
					Unrealized Gains			Unrealized			Realized			Value		Total
								Losses			Gains					Fair
											(Losses)1					Value
	30-Sep-13
	Fixed maturities:
	U.S. government obligations	$	3,691.20		$	61.8		$	(11.3	)	$	0		$	3,741.70	20.8	%
	State and local government obligations	2,125.70			29.9			(17.0		)	0			2,138.60		11.9
	Foreign government obligations2	15.9			0			0			0			15.9		0.1
	Corporate debt securities	3,118.80			67			(28.9		)	0.7			3,157.60		17.6
	Residential mortgage-backed securities	994.9			31.5			(16.5		)	0			1,009.90		5.6
	Commercial mortgage-backed securities	2,224.10			49			(33.1		)	0			2,240.00		12.4
	Other asset-backed securities	1,143.30			7.4			(2.0		)	0.2			1,148.90		6.4
	Redeemable preferred stocks	331			24.5			(10.4		)	0			345.1		1.9
	Total fixed maturities	13,644.90			271.1			(119.2		)	0.9			13,797.70		76.7
	Equity securities:
	Nonredeemable preferred stocks	442.1			280.5			(4.8		)	8.2			726		4
	Common equities	1,422.30			908.8			(5.0		)	0			2,326.10		12.9
	Short-term investments:
	Other short-term investments	1,146.10			0			0			0			1,146.10		6.4
	Total portfolio3,4	$	16,655.40		$	1,460.40		$	(129.0	)	$	9.1		$	17,995.90	100	%
	($ in millions)	Cost			Gross			Gross			Net			Fair		% of
					Unrealized Gains			Unrealized			Realized			Value		Total
								Losses			Gains					Fair
											(Losses)1					Value
	30-Sep-12
	Fixed maturities:
	U.S. government obligations	$	3,433.70		$	110.4		$	(.1	)	$	0		$	3,544.00	20.6	%
	State and local government obligations	1,898.90			61			(.4		)	0			1,959.50		11.4
	Foreign government obligations	0			0			0			0			0		0
	Corporate debt securities	2,687.80			128.8			(.4		)	6.3			2,822.50		16.4
	Residential mortgage-backed securities	399.5			21.6			(12.4		)	0			408.7		2.4
	Commercial mortgage-backed securities	1,998.20			90.7			(1.3		)	0			2,087.60		12.2
	Other asset-backed securities	1,077.90			14.5			(.1		)	0			1,092.30		6.4
	Redeemable preferred stocks	368			27.1			(14.5		)	0			380.6		2.2
	Total fixed maturities	11,864.00			454.1			(29.2		)	6.3			12,295.20		71.6
	Equity securities:
	Nonredeemable preferred stocks	430.1			416.8			0			1.5			848.4		4.9
	Common equities	1,101.50			543.8			(6.1		)	0			1,639.20		9.6
	Short-term investments:
	Other short-term investments	2,394.10			0			0			0			2,394.10		13.9
	Total portfolio3,4	$	15,789.70		$	1,414.70		$	(35.3	)	$	7.8		$	17,176.90	100	%
	($ in millions)	Cost			Gross			Gross			Net			Fair		% of
					Unrealized Gains			Unrealized			Realized			Value		Total
								Losses			Gains					Fair
											(Losses)1					Value
	31-Dec-12
	Fixed maturities:
	U.S. government obligations	$	2,806.40		$	90.1		$	0		$	0		$	2,896.50	17.6	%
	State and local government obligations	1,914.40			50.6			(.6		)	0			1,964.40		11.9
	Foreign government obligations	0			0			0			0			0		0
	Corporate debt securities	2,982.90			124.7			(1.0		)	6.4			3,113.00		18.9
	Residential mortgage-backed securities	413.4			24			(9.2		)	0			428.2		2.6
	Commercial mortgage-backed securities	1,963.90			84.9			(.1		)	0			2,048.70		12.4
	Other asset-backed securities	936			12.9			(.1		)	(.2		)	948.6		5.8
	Redeemable preferred stocks	356.9			30.5			(12.7		)	0			374.7		2.3
	Total fixed maturities	11,373.90			417.7			(23.7		)	6.2			11,774.10		71.5
	Equity securities:
	Nonredeemable preferred stocks	404			404.6			0			3.8			812.4		4.9
	Common equities	1,370.30			539			(10.3		)	0			1,899.00		11.5
	Short-term investments:
	Other short-term investments	1,990.00			0			0			0			1,990.00		12.1
Total portfolio3,4	$	15,138.20		$	1,361.30		$	(34.0	)	$	10		$	16,475.50	100	%
1Represents net holding period gains (losses) on certain hybrid securities (discussed below).
2Reflects an Australian government obligation at September 30, 2013.
3At September 30, 2013, we had $63.7 million of net unsettled security transactions, including collateral on open derivative positions, recognized in other liabilities, compared to $32.4 million and $90.9 million recognized in other assets at September 30, 2012 and December 31, 2012, respectively.
4The total fair value of the portfolio at September 30, 2013 and 2012, and December 31, 2012 included $1.3 billion, $1.6 billion, and $1.4 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company.
Our other short-term investments include commercial paper, reverse repurchase transactions, and other investments that are expected to mature within one year. We had $278.1 million, $798.1 million, and $581.0 million of open reverse repurchase commitments at September 30, 2013 and 2012, and December 31, 2012, respectively. At these dates, we did not hold any repurchase transactions where we lent collateral. 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. Historically, we have chosen to report these transactions on a gross basis on our balance sheets.
Included in our fixed-maturity and equity securities are hybrid securities, which are reported at fair value:
	September 30,						December 31,
(millions)	2013			2012			2012
Fixed maturities:
Corporate debt securities	$	171.8		$	177.5		$	176.1
Other asset-backed securities	15.3			16.4			16.4
Total fixed maturities	187.1			193.9			192.5
Equity securities:
Nonredeemable preferred stocks	57.3			50.5			52.8
Total hybrid securities	$	244.4		$	244.4		$	245.3
Certain corporate debt securities are accounted for as hybrid securities since they were acquired at a substantial premium and contain a change-in-control put option (derivative) that permits the investor, at its sole option if and when a change in control is triggered, to put the security back to the issuer at a 1% premium to par. Due to this change-in-control put option and the substantial market premium paid to acquire these securities, there is the potential that the election to put, upon the change in control, could result in an acceleration of the remaining premium paid on these securities, which would result in a loss of $12.3 million as of September 30, 2013, 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 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.
The hybrid securities in our nonredeemable preferred stock portfolio are perpetual preferred stocks that have call features with fixed-rate coupons, whereby the change in value of the call features is a component of the overall change in value of the preferred stocks.
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.
Fixed Maturities The composition of fixed maturities by maturity at September 30, 2013, was:
(millions)	Cost			Fair Value
Less than one year	$	2,032.10		$	2,063.10
One to five years	8,610.30			8,767.30
Five to ten years	2,834.80			2,794.50
Ten years or greater	114.2			119.3
Total1	$	13,591.40		$	13,744.20
1Excludes $53.5 million related to our open interest rate swap positions.
Asset-backed securities are classified across the maturity distribution table based upon their projected distribution of cash flows. All other securities that do not have a single maturity date are reported at their expected maturity date. 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, 2013, we had $124.0 million of gross unrealized losses in our fixed-income securities (i.e., fixed-maturity securities, nonredeemable preferred stocks, and short-term investments) and $5.0 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. In addition, 88% 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 12% of our common stocks are part of a managed equity strategy selected and administered by external investment advisors. If our strategy were to change and these securities were determined to be other-than-temporarily impaired, 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:
							Less than 12 Months						12 Months or Greater
(millions)	Total Fair Value			Gross Unrealized Losses			Fair Value			Unrealized Losses			Fair Value		Unrealized Losses
30-Sep-13
Fixed maturities:
U.S. government obligations	$	969.1		$	(11.3	)	$	969.1		$	(11.3	)	$	0	$	0
State and local government obligations	728.3			(17.0		)	666.7			(16.2		)	61.6		(.8		)
Corporate debt securities	1,174.20			(28.9		)	1,113.40			(28.5		)	60.8		(.4		)
Residential mortgage-backed securities	663			(16.5		)	585.5			(12.4		)	77.5		(4.1		)
Commercial mortgage-backed securities	993.3			(33.1		)	993.2			(33.0		)	0.1		(.1		)
Other asset-backed securities	282.8			(2.0		)	282.8			(2.0		)	0		0
Redeemable preferred stocks	158.4			(10.4		)	36.2			(.2		)	122.2		(10.2		)
Total fixed maturities	4,969.10			(119.2		)	4,646.90			(103.6		)	322.2		(15.6		)
Equity securities:
Nonredeemable preferred stocks	123.6			(4.8		)	123.6			(4.8		)	0		0
Common equities	47.3			(5.0		)	43			(4.7		)	4.3		(.3		)
Total equity securities	170.9			(9.8		)	166.6			(9.5		)	4.3		(.3		)
Total portfolio	$	5,140.00		$	(129.0	)	$	4,813.50		$	(113.1	)	$	326.5	$	(15.9	)
	Total Fair Value			Gross Unrealized Losses			Less than 12 Months						12 Months or Greater
(millions)							Fair Value			Unrealized Losses			Fair Value		Unrealized Losses
30-Sep-12
Fixed maturities:
U.S. government obligations	$	83.1		$	(.1	)	$	83.1		$	(.1	)	$	0	$	0
State and local government obligations	61.4			(.4		)	29.1			(.2		)	32.3		(.2		)
Corporate debt securities	35.9			(.4		)	14.2			(.1		)	21.7		(.3		)
Residential mortgage-backed securities	177.2			(12.4		)	30			(.5		)	147.2		(11.9		)
Commercial mortgage-backed securities	44			(1.3		)	31.4			(.1		)	12.6		(1.2		)
Other asset-backed securities	21			(.1		)	9			0			12		(.1		)
Redeemable preferred stocks	164.1			(14.5		)	24.7			(.4		)	139.4		(14.1		)
Total fixed maturities	586.7			(29.2		)	221.5			(1.4		)	365.2		(27.8		)
Equity securities:
Nonredeemable preferred stocks	0			0			0			0			0		0
Common equities	80.8			(6.1		)	54.4			(3.4		)	26.4		(2.7		)
Total equity securities	80.8			(6.1		)	54.4			(3.4		)	26.4		(2.7		)
Total portfolio	$	667.5		$	(35.3	)	$	275.9		$	(4.8	)	$	391.6	$	(30.5	)
	Total Fair Value			Gross Unrealized Losses			Less than 12 Months						12 Months or Greater
(millions)							Fair Value			Unrealized Losses			Fair Value		Unrealized Losses
31-Dec-12
Fixed maturities:
U.S. government obligations	$	0		$	0		$	0		$	0		$	0	$	0
State and local government obligations	162.8			(.6		)	123.1			(.5		)	39.7		(.1		)
Corporate debt securities	128.2			(1.0		)	128.2			(1.0		)	0		0
Residential mortgage-backed securities	149.2			(9.2		)	40.2			(.6		)	109		(8.6		)
Commercial mortgage-backed securities	7.1			(.1		)	2.1			0			5		(.1		)
Other asset-backed securities	25			(.1		)	20.8			0			4.2		(.1		)
Redeemable preferred stocks	155.7			(12.7		)	24.9			0			130.8		(12.7		)
Total fixed maturities	628			(23.7		)	339.3			(2.1		)	288.7		(21.6		)
Equity securities:
Nonredeemable preferred stocks	0			0			0			0			0		0
Common equities	118.2			(10.3		)	100.7			(8.2		)	17.5		(2.1		)
Total equity securities	118.2			(10.3		)	100.7			(8.2		)	17.5		(2.1		)
Total portfolio	$	746.2		$	(34.0	)	$	440		$	(10.3	)	$	306.2	$	(23.7	)
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)	2013			2012			2012
Fixed maturities:
Residential mortgage-backed securities	$	(44.1	)	$	(44.2	)	$	(44.2	)
Commercial mortgage-backed securities	(.9		)	(.9		)	(.9		)
Total fixed maturities	$	(45.0	)	$	(45.1	)	$	(45.1	)
The following tables provide rollforwards of the amounts related to credit losses recognized in earnings for the periods ended September 30, 2013 and 2012, for which portions 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, 2013
	Mortgage-Backed
(millions)	Residential			Commercial			Total
Balance at June 30, 2013	$	26.9		$	0.5		$	27.4
Credit losses for which an OTTI was previously recognized	0			0			0
Credit losses for which an OTTI was not previously recognized	0			0			0
Reductions for securities sold/matured	0			0			0
Change in recoveries of future cash flows expected to be collected1	(2.4		)	(.1		)	(2.5		)
Reductions for previously recognized credit impairments written-down to fair value2	0			0			0
Balance at September 30, 2013	$	24.5		$	0.4		$	24.9
	Nine Months Ended September 30, 2013
	Mortgage-Backed
(millions)	Residential			Commercial			Total
Balance at December 31, 2012	$	27.1		$	0.6		$	27.7
Credit losses for which an OTTI was previously recognized	0			0			0
Credit losses for which an OTTI was not previously recognized	0			0			0
Reductions for securities sold/matured	0			0			0
Change in recoveries of future cash flows expected to be collected1	(2.4		)	(.2		)	(2.6		)
Reductions for previously recognized credit impairments written-down to fair value2	(.2		)	0			(.2		)
Balance at September 30, 2013	$	24.5		$	0.4		$	24.9
	Three Months Ended September 30, 2012
	Mortgage-Backed
(millions)	Residential			Commercial			Total
Balance at June 30, 2012	$	28.1		$	0.7		$	28.8
Credit losses for which an OTTI was previously recognized	0			0			0
Credit losses for which an OTTI was not previously recognized	0			0			0
Reductions for securities sold/matured	0			0			0
Change in recoveries of future cash flows expected to be collected1	(.4		)	(.1		)	(.5		)
Reductions for previously recognized credit impairments written-down to fair value2	0			0			0
Balance at September 30, 2012	$	27.7		$	0.6		$	28.3
	Nine Months Ended September 30, 2012
	Mortgage-Backed
(millions)	Residential			Commercial			Total
Balance at December 31, 2011	$	34.5		$	1.3		$	35.8
Credit losses for which an OTTI was previously recognized	0.1			0			0.1
Credit losses for which an OTTI was not previously recognized	0.2			0			0.2
Reductions for securities sold/matured	0			(.2		)	(.2		)
Change in recoveries of future cash flows expected to be collected1	(3.1		)	(.2		)	(3.3		)
Reductions for previously recognized credit impairments written-down to fair value2	(4.0		)	(.3		)	(4.3		)
Balance at September 30, 2012	$	27.7		$	0.6		$	28.3
1Reflects expected recovery of prior period impairments that will be accreted into income over the remaining life of the security, net of any current quarter decreases in expected cash flows on previously recorded reductions.
2Reflects reductions of prior credit impairments where the current credit impairment requires writing securities down to fair value (i.e., no remaining non-credit loss).
Although we determined that it is more likely than not that we will not be required to sell the securities prior to the recovery of their respective cost bases (which could be maturity), we are required to measure and report the amount of credit losses on the securities that were determined to be other-than-temporarily impaired. In that process, we considered a number of factors and inputs related to the individual securities. The methodology and significant inputs used to measure the amount of credit losses in our portfolio included: current performance indicators on the underlying assets (e.g., delinquency rates, foreclosure rates, and default rates); credit support (via current levels of subordination); historical credit ratings; and updated cash flow expectations based upon these performance indicators. In order to determine the amount of credit loss, if any, the net present value of the cash flows expected (i.e., expected recovery value) was calculated using the current book yield for each security, and was compared to its current amortized value. In the event that the net present value was below the amortized value, a credit loss was deemed to exist, and the security was written down.
Realized Gains/Losses
The components of net realized gains (losses) for the three and nine months ended September 30, were:
	Three Months						Nine months
(millions)	2013			2012			2013			2012
Gross realized gains on security sales
Fixed maturities:
U.S. government obligations	$	3.1		$	0.2		$	6.8		$	9.8
State and local government obligations	0			0			6.8			12.1
Corporate and other debt securities	1.7			23			38.4			49.1
Residential mortgage-backed securities	0.3			0.6			2.4			0.6
Commercial mortgage-backed securities	0.1			9.5			8.4			14
Other asset-backed securities	0			0.9			0			0.9
Redeemable preferred stocks	0			0.1			0			0.5
Total fixed maturities	5.2			34.3			62.8			87
Equity securities:
Nonredeemable preferred stocks	11.9			20.6			113.1			57.5
Common equities	11.1			153.4			26.1			163.2
Subtotal gross realized gains on security sales	28.2			208.3			202			307.7
Gross realized losses on security sales
Fixed maturities:
U.S. government obligations	(.8		)	(.5		)	(2.2		)	(1.4		)
Corporate and other debt securities	(2.1		)	(.6		)	(3.1		)	(.6		)
Commercial mortgage-backed securities	0			0			(.7		)	0
Redeemable preferred stocks	0			(.3		)	(.1		)	(.3		)
Total fixed maturities	(2.9		)	(1.4		)	(6.1		)	(2.3		)
Equity securities:
Nonredeemable preferred stocks	0			(1.1		)	0			(1.1		)
Common equities	(.1		)	(22.5		)	(.4		)	(27.0		)
Subtotal gross realized losses on security sales	(3.0		)	(25.0		)	(6.5		)	(30.4		)
Net realized gains (losses) on security sales
Fixed maturities:
U.S. government obligations	2.3			(.3		)	4.6			8.4
State and local government obligations	0			0			6.8			12.1
Corporate and other debt securities	(.4		)	22.4			35.3			48.5
Residential mortgage-backed securities	0.3			0.6			2.4			0.6
Commercial mortgage-backed securities	0.1			9.5			7.7			14
Other asset-backed securities	0			0.9			0			0.9
Redeemable preferred stocks	0			(.2		)	(.1		)	0.2
Total fixed maturities	2.3			32.9			56.7			84.7
Equity securities:
Nonredeemable preferred stocks	11.9			19.5			113.1			56.4
Common equities	11			130.9			25.7			136.2
Subtotal net realized gains (losses) on security sales	25.2			183.3			195.5			277.3
Other-than-temporary impairment losses
Fixed maturities:
Residential mortgage-backed securities	(.1		)	(.4		)	(.5		)	(1.4		)
Commercial mortgage-backed securities	0			0			0			(.1		)
Total fixed maturities	(.1		)	(.4		)	(.5		)	(1.5		)
Equity securities:
Common equities	(1.8		)	0			(3.2		)	(.7		)
Subtotal other-than-temporary impairment losses	(1.9		)	(.4		)	(3.7		)	(2.2		)
Other gains (losses)
Hybrid securities	3.5			5.2			2.3			12.1
Derivative instruments	(1.2		)	(16.3		)	45			(42.8		)
Litigation settlements	2.3			0.1			2.3			0.3
Subtotal other gains (losses)	4.6			(11.0		)	49.6			(30.4		)
Total net realized gains (losses) on securities	$	27.9		$	171.9		$	241.4		$	244.7
Gross realized gains and losses were predominately the result of sales transactions in our fixed-income portfolio related to movements in credit spreads and interest rates. In addition, gains and losses reflect sales of common stocks, holding period valuation changes on hybrids and derivatives and write-downs for securities determined to be other-than-temporarily impaired in our fixed-maturity and equity portfolios.
Trading Securities At September 30, 2013 and 2012, and December 31, 2012, 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, 2013 and 2012.
Derivative Instruments We have invested in the following derivative exposures at various times: interest rate swaps, asset-backed credit default swaps, U.S. corporate debt credit default swaps, cash flow hedges, and equity options.
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 an 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 (net derivative asset). 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 and cash flows.
The following table shows the status of our derivative instruments at September 30, 2013 and 2012, and December 31, 2012, and for the three and nine months ended September 30, 2013 and 2012; amounts are on a pretax basis:
(millions)												Balance Sheet2									Comprehensive Income Statement
													Assets (Liabilities)								Net Realized
													Fair Value								Gains (Losses) on Securities
	Notional Value1																				Three months ended						Nine months ended
	September 30,						Dec. 31,						September 30,					Dec. 31,			September 30,						September 30,
Derivatives designated as:	2013			2012			2012			Purpose		Classification	2013		2012			2012			2013			2012			2013			2012
Hedging instruments
Closed:
Ineffective cash flow hedge	$	54		$	31		$	31		Manage interest		NA	$	0	$	0		$	0		$	0.8		$	0		$	0.8		$	0.6
										rate risk
Non-hedging instruments
Assets:
Interest rate swaps	750			0			0			Manage portfolio		Investments—	53.5		0			0			(2.0		)	0			48.2			0
										duration		fixed maturities
Corporate credit default swaps	0			25			0			Manage credit risk		Investments—	0		0.3			0			0			(.4		)	0			(.7		)
												fixed maturities
Liabilities:
Interest rate swaps	0			1,263			1,263			Manage portfolio		Other liabilities	0		(101.6		)	(95.5		)	0			(15.9		)	0			(42.7		)
										duration
Closed:
Interest rate swaps	1,263			0			0			Manage portfolio		NA	0		0			0			0			0			(4.0		)	0
										duration
Corporate credit default swaps	0			0			25			Manage credit risk		NA	0		0			0			0			0			0			0
Total	NA			NA			NA						$	53.5	$	(101.3	)	$	(95.5	)	$	(1.2	)	$	(16.3	)	$	45		$	(42.8	)
NA=ot Applicable
1The amounts represent the value held at quarter and year end for open positions and the maximum amount held during the period for closed positions.
2To the extent we hold both derivative assets and liabilities with the same counterparty that are subject to an enforceable master netting arrangement, we expect that we will report them on a gross basis on our balance sheets, consistent with our historical presentation.
CASH FLOW HEDGES
During both the third quarter and first nine months of 2013, we repurchased, in the open market, $54.1 million, in aggregate principal amount of our 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 (the “6.70% Debentures”), compared to $0.5 million, $30.9 million, and $30.9 million, during the third quarter, first nine months, and full year of 2012, respectively. For the portion of the 6.70% Debentures we repurchased, we reclassified $0.8 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 both the third quarter and first nine months of 2013, compared to $0, $0.6 million, and $0.6 million, during the third quarter, first nine months, and full year of 2012, respectively.
INTEREST RATE SWAPS
During the periods ended September 30, 2013 and 2012, and December 31, 2012, we invested in interest rate swap positions, primarily to manage the fixed-income portfolio duration. During the beginning of the second quarter 2013, we opened three ten-year interest rate swap positions; in each case, we are paying a fixed rate and receiving a variable rate, effectively shortening the duration of our fixed-income portfolio. We closed three interest rate swap positions during the beginning of the second quarter 2013. The closed positions were a 9-year interest rate swap position (opened in 2009) and two 5-year interest rate swap positions (opened in 2011); in each case, we were paying a fixed rate and receiving a variable rate.
The fair value gain of $53.5 million, as reflected on the balance sheet, on the $750 million notional value swaps was the result of rising interest rates since the positions were opened, while the fair value losses of $101.6 million and $95.5 million on the $1,263 million notional value swaps resulted from an overall decline in interest rates from the inception of the trades. As of September 30, 2013, the balance of the cash collateral that we had received from the applicable counterparties on the open positions was $49.3 million. As of September 30, 2012 and December 31, 2012, the balance of the cash collateral that we had delivered to the applicable counterparty on the then open positions was $107.2 million and $105.0 million, respectively.
CORPORATE CREDIT DEFAULT SWAPS
Financial Services Sector – We held no credit default swaps in this sector during 2013 or at December 31, 2012. During the three and nine months ended September 30, 2012, we held one position, which was opened during the third quarter 2008, on a corporate issuer within the financial services sector for which we bought credit default protection in the form of a credit default swap for a 5-year time horizon. We held this protection to reduce some of our exposure to additional valuation declines on a preferred stock position of the same issuer. As of September 30, 2012, the balance of the cash collateral that we had received from the counterparty on the then open position was $0.3 million.

Fair_Value

Fair Value	9 Months Ended
	Sep. 30, 2013
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 was:
		Fair Value
	(millions)	Level 1		Level 2			Level 3		Total		Cost
	30-Sep-13
	Fixed maturities:
	U.S. government obligations	$	3,741.70	$	0		$	0	$	3,741.70	$	3,691.20
	State and local government obligations	0		2,138.60			0		2,138.60		2,125.70
	Foreign government obligations	15.9		0			0		15.9		15.9
	Corporate debt securities	0		3,157.60			0		3,157.60		3,118.80
	Subtotal	3,757.60		5,296.20			0		9,053.80		8,951.60
	Asset-backed securities:
	Residential mortgage-backed	0		1,009.70			0.2		1,009.90		994.9
	Commercial mortgage-backed	0		2,208.70			31.3		2,240.00		2,224.10
	Other asset-backed	0		1,148.90			0		1,148.90		1,143.30
	Subtotal asset-backed securities	0		4,367.30			31.5		4,398.80		4,362.30
	Redeemable preferred stocks:
	Financials	0		134.2			0		134.2		115.7
	Utilities	0		65.3			0		65.3		64.9
	Industrials	0		145.6			0		145.6		150.4
	Subtotal redeemable preferred stocks	0		345.1			0		345.1		331
	Total fixed maturities	3,757.60		10,008.60			31.5		13,797.70		13,644.90
	Equity securities:
	Nonredeemable preferred stocks:
	Financials	244		429.1			36.1		709.2		427.9
	Utilities	0		16.8			0		16.8		14.2
	Subtotal nonredeemable preferred stocks	244		445.9			36.1		726		442.1
	Common equities:
	Common stocks	2,287.40		0			0		2,287.40		1,419.20
	Other risk investments	0		0			38.7		38.7		3.1
	Subtotal common equities	2,287.40		0			38.7		2,326.10		1,422.30
	Total fixed maturities and equity securities	6,289.00		10,454.50			106.3		16,849.80		15,509.30
	Short-term investments:
	Other short-term investments	751.5		394.6			0		1,146.10		1,146.10
	Total portfolio	$	7,040.50	$	10,849.10		$	106.3	$	17,995.90	$	16,655.40
	Debt	$	0	$	2,231.40		$	0	$	2,231.40	$	2,010.60
		Fair Value
	(millions)	Level 1		Level 2			Level 3		Total		Cost
	30-Sep-12
	Fixed maturities:
	U.S. government obligations	$	3,544.00	$	0		$	0	$	3,544.00	$	3,433.70
	State and local government obligations	0		1,959.50			0		1,959.50		1,898.90
	Foreign government obligations	0		0			0		0		0
	Corporate debt securities	0		2,822.50			0		2,822.50		2,687.80
	Subtotal	3,544.00		4,782.00			0		8,326.00		8,020.40
	Asset-backed securities:
	Residential mortgage-backed	0		358.8			49.9		408.7		399.5
	Commercial mortgage-backed	0		2,065.00			22.6		2,087.60		1,998.20
	Other asset-backed	0		1,092.00			0.3		1,092.30		1,077.90
	Subtotal asset-backed securities	0		3,515.80			72.8		3,588.60		3,475.60
	Redeemable preferred stocks:
	Financials	0		133.9			0		133.9		120.8
	Utilities	0		66.9			0		66.9		65.9
	Industrials	0		179.8			0		179.8		181.3
	Subtotal redeemable preferred stocks	0		380.6			0		380.6		368
	Total fixed maturities	3,544.00		8,678.40			72.8		12,295.20		11,864.00
	Equity securities:
	Nonredeemable preferred stocks:
	Financials	265.2		524.4			29.3		818.9		407.3
Utilities	0		29.5			0		29.5		22.8
Subtotal nonredeemable preferred stocks	265.2		553.9			29.3		848.4		430.1
Common equities:
Common stocks	1,627.20		0			0		1,627.20		1,098.30
Other risk investments	0		0			12		12		3.2
Subtotal common equities	1,627.20		0			12		1,639.20		1,101.50
Total fixed maturities and equity securities	5,436.40		9,232.30			114.1		14,782.80		13,395.60
Short-term investments:
Other short-term investments	2,120.70		273.4			0		2,394.10		2,394.10
Total portfolio	$	7,557.10	$	9,505.70		$	114.1	$	17,176.90	$	15,789.70
Debt	$	0	$	2,405.90		$	0	$	2,405.90	$	2,062.70
	Fair Value
(millions)	Level 1		Level 2			Level 3		Total		Cost
31-Dec-12
Fixed maturities:
U.S. government obligations	$	2,896.50	$	0		$	0	$	2,896.50	$	2,806.40
State and local government obligations	0		1,964.40			0		1,964.40		1,914.40
Foreign government obligations	0		0			0		0		0
Corporate debt securities	0		3,113.00			0		3,113.00		2,982.90
Subtotal	2,896.50		5,077.40			0		7,973.90		7,703.70
Asset-backed securities:
Residential mortgage-backed	0		382.7			45.5		428.2		413.4
Commercial mortgage-backed	0		2,023.40			25.3		2,048.70		1,963.90
Other asset-backed	0		948.6			0		948.6		936
Subtotal asset-backed securities	0		3,354.70			70.8		3,425.50		3,313.30
Redeemable preferred stocks:
Financials	0		129.7			0		129.7		110.7
Utilities	0		66.7			0		66.7		64.9
Industrials	0		178.3			0		178.3		181.3
Subtotal redeemable preferred stocks	0		374.7			0		374.7		356.9
Total fixed maturities	2,896.50		8,806.80			70.8		11,774.10		11,373.90
Equity securities:
Nonredeemable preferred stocks:
Financials	259.6		494.5			31.9		786		383.3
Utilities	0		26.4			0		26.4		20.7
Subtotal nonredeemable preferred stocks	259.6		520.9			31.9		812.4		404
Common equities:
Common stocks	1,887.00		0			0		1,887.00		1,367.20
Other risk investments	0		0			12		12		3.1
Subtotal common equities	1,887.00		0			12		1,899.00		1,370.30
Total fixed maturities and equity securities	5,043.10		9,327.70			114.7		14,485.50		13,148.20
Short-term investments:
Other short-term investments	1,679.90		310.1			0		1,990.00		1,990.00
Total portfolio	$	6,723.00	$	9,637.80		$	114.7	$	16,475.50	$	15,138.20
Debt	$	0	$	2,394.40		$	0	$	2,394.40	$	2,063.10
Our portfolio valuations 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 third quarter or first nine months of 2013. During 2012, we had one redeemable preferred security with a value of $25.0 million that was transferred from Level 1 to Level 2 as it was no longer traded on an exchange. 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 seven days or less to redemption. These securities are held at their original cost, adjusted for any amortization of discount or premium, since that value very closely approximates what an active market participant would be willing to pay for these 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 of 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, 2013, vendor-quoted prices represented 59% of our Level 1 classifications (excluding short-term investments), compared to 65% at September 30, 2012 and 57% at December 31, 2012. The securities quoted by vendors in Level 1 represent our holdings in U.S. Treasury Notes and an Australian government obligation, 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 an active exchange and our interest rate swap derivative positions that have a very similar market to the U.S. Treasury Note market.
At September 30, 2013, vendor-quoted prices comprised 97% of our Level 2 classifications (excluding short-term investments), while dealer-quoted prices represented 3%, compared to 96% and 4% at September 30, 2012 and 98% and 2% at December 31, 2012. 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 global review of our portfolio by sector to identify securities whose prices appear outside of a reasonable range. We then perform a more detailed review of fair values for securities disclosed as Level 2. We review dealer bids and quotes for these and/or similar securities to determine the market level context for our valuations. We then evaluate inputs relevant for each class of securities disclosed in the preceding hierarchy tables.
For our structured debt securities, including commercial, residential, and asset-backed securities, we evaluate available market-related data for these and similar securities related to collateral, delinquencies, and defaults for historical trends and reasonably estimable projections, as well as historical prepayment rates and current prepayment assumptions and cash flow estimates. We further stratify each class of our structured debt securities into more finite sectors (e.g., planned amortization class, first pay, second pay, senior, subordinated, etc.) and use duration, credit quality, and coupon to determine the appropriate fair value.
For our corporate debt and preferred stock (redeemable and nonredeemable) portfolios, 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, 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 of our securities.
With limited exceptions, 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, 2013 and 2012, and December 31, 2012, 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 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. At September 30, 2013, we held one private common equity security with a value of $38.0 million; the valuation reflects a negotiated sale that is expected to be completed by the end of 2013. At September 30, 2012 and December 31, 2012, the same private common equity security was internally priced with a value of $11.2 million. At September 30, 2013, we held one private preferred equity security, with a value of $36.1 million, that was priced internally. The same security had a value of $29.3 million at September 30, 2012 and $31.9 million at December 31, 2012. At September 30, 2013 and 2012, and December 31, 2012, we did not hold any securities in our fixed-maturity portfolio that were priced internally. Despite the lack of sufficient observable market information, we believe the valuations received in conjunction with our procedures for evaluating third-party prices support the fair values reported in the financial statements.
We 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. 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, 2013 and 2012:
	Level 3 Fair Value
	Three months ended September 30, 2013
(millions)	Fair Value at June 30, 2013		Calls/Maturities/Paydowns			Purchases		Sales		Net Realized (gain)/loss on sales			Change in Valuation			Net			Fair Value at Sept. 30, 2013
																Transfers
																in (out)1
Fixed maturities:
Asset-backed securities:
Residential mortgage-backed	$	157.1	$	(17.0	)	$	0	$	0	$	0		$	1.5		$	(141.4	)	$	0.2
Commercial mortgage-backed	27.6		(.3		)	0		0		0			4			0			31.3
Other asset-backed	0		0			0		0		0			0			0			0
Total fixed maturities	184.7		(17.3		)	0		0		0			5.5			(141.4		)	31.5
Equity securities:
Nonredeemable preferred stocks:
Financials2	34.8		0			0		0		0			1.3			0			36.1
Common equities:
Other risk investments	38.7		0			0		0		0			0			0			38.7
Total Level 3 securities	$	258.2	$	(17.3	)	$	0	$	0	$	0		$	6.8		$	(141.4	)	$	106.3
1The $(141.4) million was transferred out of Level 3 and into Level 2 due to an increase in liquidity and trading volume in the market.
2The $1.3 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, 2013
(millions)	Fair Value at Dec. 31, 2012		Calls/Maturities/Paydowns			Purchases		Sales		Net Realized (gain)/loss on sales			Change in			Net			Fair Value at Sept. 30, 2013
													Valuation			Transfers
																in (out)1
Fixed maturities:
Asset-backed securities:
Residential mortgage-backed	$	45.5	$	(28.6	)	$	125.1	$	0	$	0		$	(.4	)	$	(141.4	)	$	0.2
Commercial mortgage-backed	25.3		(1.1		)	0		0		0			7.1			0			31.3
Other asset-backed	0		0			0		0		0			0			0			0
Total fixed maturities	70.8		(29.7		)	125.1		0		0			6.7			(141.4		)	31.5
Equity securities:
Nonredeemable preferred stocks:
Financials2	31.9		0			0		0		0			4.2			0			36.1
Common equities:
Other risk investments	12		(.1		)	0.3		0		(.5		)	27			0			38.7
Total Level 3 securities	$	114.7	$	(29.8	)	$	125.4	$	0	$	(.5	)	$	37.9		$	(141.4	)	$	106.3
1The $(141.4) million was transferred out of Level 3 and into Level 2 due to an increase in liquidity and trading volume in the market.
2The $4.2 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
	Three months ended September 30, 2012
(millions)	Fair Value at June 30, 2012		Calls/			Purchases		Sales		Net Realized (gain)/loss on sales			Change in			Net			Fair Value at Sept. 30, 2012
			Maturities/										Valuation			Transfers
			Paydowns													in (out)
Fixed maturities:
Asset-backed securities:
Residential mortgage-backed	$	54.5	$	(5.0	)	$	0	$	0	$	0		$	0.4		$	0		$	49.9
Commercial mortgage-backed	23.2		(2.6		)	0		0		0			2			0			22.6
Other asset-backed	1.1		(.8		)	0		0		0			0			0			0.3
Total fixed maturities	78.8		(8.4		)	0		0		0			2.4			0			72.8
Equity securities:
Nonredeemable preferred stocks:
Financials1	0		0			28.5		0		0			0.8			0			29.3
Common equities:
Other risk investments	12.2		(.2		)	0		0		0			0			0			12
Total Level 3 securities	$	91	$	(8.6	)	$	28.5	$	0	$	0		$	3.2		$	0		$	114.1
1The $0.8 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, 2012
(millions)	Fair Value at Dec. 31, 2011		Calls/			Purchases		Sales		Net Realized (gain)/loss on sales			Change in			Net			Fair Value at Sept. 30, 2012
			Maturities/										Valuation			Transfers
			Paydowns													in (out)
Fixed maturities:
Asset-backed securities:
Residential mortgage-backed	$	62.3	$	(12.8	)	$	0	$	0	$	0		$	0.4		$	0		$	49.9
Commercial mortgage-backed	21.3		(2.7		)	0		0		0			4			0			22.6
Other asset-backed	2.6		(2.3		)	0		0		0			0			0			0.3
Total fixed maturities	86.2		(17.8		)	0		0		0			4.4			0			72.8
Equity securities:
Nonredeemable preferred stocks:
Financials1	0		0			28.5		0		0			0.8			0			29.3
Common equities:
Other risk investments	11.5		(.2		)	0		0		0			0.7			0			12
Total Level 3 securities	$	97.7	$	(18.0	)	$	28.5	$	0	$	0		$	5.9		$	0		$	114.1
1The $0.8 million represents net holding period gains on a hybrid security which is reflected in net realized gains (losses) on securities in the comprehensive income statement.
The following tables provide a summary of the quantitative information about Level 3 fair value measurements for our applicable securities at September 30, 2013 and 2012, and December 31, 2012:
	Quantitative Information about Level 3 Fair Value Measurements
($ in millions)	Fair Value at Sept. 30, 2013		Valuation Technique		Unobservable Input	Unobservable
						Input Assumption
Fixed maturities:
Asset-backed securities:
Residential mortgage-backed	$	0.2	External vendor		Prepayment rate1	0
Commercial mortgage-backed	31.3		External vendor		Prepayment rate2	0
Total fixed maturities	31.5
Equity securities:
Nonredeemable preferred stocks:
Financials	36.1		Multiple of tangible net book value		Price to book ratio multiple	1.9
Common equities:
Other risk investments	0
Subtotal Level 3 securities	$	67.6
Pricing exemption securities3	38.7
Total Level 3 securities	$	106.3
1Assumes that one security has 0% of the principal amount of the underlying loans that will be paid off prematurely in each year.
2Assumes that two securities have 0% of the principal amount of the underlying loans that will be paid off prematurely in each year.
3The fair values for $0.7 million of these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us. The remaining $38.0 million reflects a negotiated sale on a private common equity security that is expected to be completed by the end of 2013.
	Quantitative Information about Level 3 Fair Value Measurements
($ in millions)	Fair Value at Sept. 30, 2012		Valuation Technique		Unobservable Input	Unobservable
						Input Assumption
Fixed maturities:
Asset-backed securities:
Residential mortgage-backed	$	15.3	External vendor		Prepayment rate1	0,16
Commercial mortgage-backed	0
Total fixed maturities	15.3
Equity securities:
Nonredeemable preferred stocks:
Financials	29.3		Multiple of tangible net book value		Price to Book Ratio Multiple	1.9
Common equities:
Other risk investments	11.2		Discounted consolidated		Discount for lack of marketability	20	%
			equity
Subtotal Level 3 securities	$	55.8
Pricing exemption securities2	58.3
Total Level 3 securities	$	114.1
1Assumes that two securities have 0% and one security has 16% of the principal amount of the underlying loans that will be paid off prematurely in each year.
2The fair values for these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us.
	Quantitative Information about Level 3 Fair Value Measurements
($ in millions)	Fair Value at Dec. 31, 2012		Valuation Technique		Unobservable Input	Unobservable
						Input Assumption
Fixed maturities:
Asset-backed securities:
Residential mortgage-backed	$	0.2	External vendor		Prepayment rate1	16
Commercial mortgage-backed	25.3		External vendor		Prepayment rate2	0
Total fixed maturities	25.5
Equity securities:
Nonredeemable preferred stocks:
Financials	31.9		Multiple of tangible net book value		Price to book ratio multiple	1.9
Common equities:
Other risk investments	11.2		Discounted consolidated equity		Discount for lack of marketability	20	%
Subtotal Level 3 securities	$	68.6
Pricing exemption securities3	46.1
Total Level 3 securities	$	114.7
1Assumes that one security has 16% of the principal amount of the underlying loans that will be paid off prematurely in each year.
2Assumes that three securities have 0% of the principal amount of the underlying loans that will be paid off prematurely in each year.
3The fair values for these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us.
Due to the relative size of the securities’ fair values compared to the total portfolio’s fair value, any changes in pricing methodology would not have a significant change in valuation that would materially impact net and comprehensive income. During 2013 or 2012, there were no material assets or liabilities measured at fair value on a nonrecurring basis.

Debt

Debt	9 Months Ended
	Sep. 30, 2013
Debt	'
	Debt — Debt consisted of:
		30-Sep-13				30-Sep-12				31-Dec-12
	(millions)	Carrying		Fair		Carrying		Fair		Carrying		Fair
		Value		Value		Value		Value		Value		Value
	7% Notes due 2013	$	150	$	150	$	149.8	$	159	$	149.9	$	157.1
	3.75% Senior Notes due 2021	497.5		516.7		497.3		551		497.3		549.1
	6 5/8% Senior Notes due 2029	295.3		362		295.1		393.7		295.2		385
	6.25% Senior Notes due 2032	394.6		478.2		394.5		521.7		394.5		513.5
	6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067	673.2		724.5		726		780.5		726.2		789.7
	Total	$	2,010.60	$	2,231.40	$	2,062.70	$	2,405.90	$	2,063.10	$	2,394.40
	During both the third quarter and first nine months of 2013, we repurchased, in the open market, $54.1 million in aggregate principal amount of our 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 (the “6.70% Debentures”), compared to repurchases of $0.5 million, $30.9 million, and $30.9 million during the third quarter, first nine months, and full year of 2012, respectively. Since the amount paid exceeded the carrying value of the debt we repurchased, we recognized losses on these extinguishments of $4.3 million during both the third quarter and first nine months of 2013, compared to $0.1 million, $1.8 million, and $1.8 million during the third quarter, first nine months, and full year of 2012, respectively. In addition, for the portion of the 6.70% Debentures we repurchased, we reclassified $0.8 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 both the third quarter and first nine months of 2013, compared to $0, $0.6 million, and $0.6 million during the third quarter, first nine months, and full year of 2012, respectively.
	As of September 30, 2013, our next scheduled debt maturity was $150 million of our 7% Notes due 2013; these Notes were paid at maturity on October 1, 2013.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2013
Income Taxes	'
	Income Taxes — At September 30, 2013 and 2012, and December 31, 2012, we determined that we did not need a valuation allowance on our deferred tax asset. Although realization of the deferred tax asset is not assured, management believes that it is more likely than not that the deferred tax asset 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 nine months ended September 30, 2013, there have been no material changes in our uncertain tax positions.

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information	9 Months Ended
	Sep. 30, 2013
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)	2013		2012
	Income taxes, net of refunds	$	340	$	259.1
	Interest	81.9		92.8

Segment_Information

Segment Information	9 Months Ended
	Sep. 30, 2013
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 by small businesses in the business auto, for-hire transportation, contractor, for-hire specialty, and tow markets. 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 unaffiliated insurance companies. All segment revenues are generated from external customers.
	Following are the operating results for the respective periods:
		Three Months Ended September 30,															Nine Months Ended September 30,
		2013							2012								2013						2012
	(millions)	Revenues				Pretax			Revenues				Pretax				Revenues			Pretax			Revenues			Pretax
						Profit							Profit							Profit						Profit
						(Loss)							(Loss)							(Loss)						(Loss)
	Personal Lines
	Agency	$	2,162.70			$	122		$	2,047.70			$	52.3			$	6,421.40		$	428.4		$	6,032.30		$	237.9
	Direct	1,693.40				107.3			1,582.70				105.9				5,020.40			360.5			4,660.10			193.2
	Total Personal Lines1	3,856.10				229.3			3,630.40				158.2				11,441.80			788.9			10,692.40			431.1
	Commercial Lines	446.8				26.3			424.3				7.5				1,317.30			73.7			1,219.20			61
	Other indemnity	0.1				(6.2		)	0.1				(.5		)		0.2			(9.7		)	0.8			(3.1		)
	Total underwriting operations	4,303.00				249.4			4,054.80				165.2				12,759.30			852.9			11,912.40			489
	Fees and other revenues2	76				NA			78.4				NA				215.3			NA			213.5			NA
	Service businesses	11.3				0.2			9.9				0.3				30.3			0.2			28.3			0.6
	Investments3	135.3				130.1			280.9				277.6				551.5			537			580.9			569.6
	Gains (losses) on extinguishment of debt	(4.3		)		(4.3		)	(.1		)		(.1		)		(4.3		)	(4.3		)	(1.8		)	(1.8		)
	Interest expense	NA				(30.4		)	NA				(30.6		)		NA			(91.4		)	NA			(93.2		)
	Consolidated total	$	4,521.30			$	345		$	4,423.90			$	412.4			$	13,552.10		$	1,294.40		$	12,733.30		$	964.2
	1Personal auto insurance accounted for 91% of the total Personal Lines segment net premiums earned in all periods; 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.
	2Pretax profit (loss) for fees and other revenues are allocated to operating segments.
	3Revenues represent recurring investment income and total net realized gains (losses) on securities; pretax profit is net of investment expenses.
	NA =ot Applicable
	Our management uses underwriting margin and combined ratio as primary measures of underwriting profitability. Underwriting profitability is calculated by subtracting losses and loss adjustment expenses, policy acquisition costs, and other underwriting expenses from the total of net premiums earned and “fees and other revenues.” The underwriting margin is the pretax underwriting profit (loss) expressed as a percentage of net premiums earned (i.e., revenues from underwriting operations). Combined ratio is the complement of the underwriting margin. Following are the underwriting margins/combined ratios for our underwriting operations for the respective periods:
		Three Months Ended September 30,									Nine Months Ended September 30,
		2013					2012				2013					2012
		Under-writing			Combined		Under-writing		Combined		Under-writing			Combined		Under-writing			Combined
		Margin			Ratio		Margin		Ratio		Margin			Ratio		Margin			Ratio
	Personal Lines
	Agency	5.6	%		94.4		2.6	%	97.4		6.7	%		93.3		3.9	%		96.1
	Direct	6.3			93.7		6.7		93.3		7.2			92.8		4.1			95.9
	Total Personal Lines	5.9			94.1		4.4		95.6		6.9			93.1		4			96
	Commercial Lines	5.9			94.1		1.8		98.2		5.6			94.4		5			95
	Other indemnity1	NM			NM		NM		NM		NM			NM		NM			NM
	Total underwriting operations	5.8			94.2		4.1		95.9		6.7			93.3		4.1			95.9
	1Underwriting 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, 2013
Dividends	'
	Dividends — We maintain a policy of paying an annual variable dividend that, if declared, would be payable shortly after the close of the year. This annual variable dividend is based on a target percentage of after-tax underwriting income multiplied by a 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. For 2013, the Board has determined the target percentage to be 33-1/3% of annual after-tax underwriting income, which is unchanged from the 2012 target percentage.
	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, 2013, the Gainshare factor was 1.15. Since the final factor will be determined based on our results for the full year, the final factor may vary from the current factor.
	Our annual dividend program will result in a variable payment to shareholders each year, subject to certain limitations. If the Gainshare factor is zero or if our comprehensive income is less than after-tax underwriting income, no dividend would be payable under our annual variable dividend policy. However, the ultimate decision on whether or not a dividend will be paid is in the discretion of the Board of Directors. If a dividend for 2013 were to be paid, the Board would likely declare the 2013 annual dividend in December 2013, with a record date in January 2014 and payment shortly thereafter. For the nine months ended September 30, 2013, our comprehensive income was $865.5 million, which is higher than the $554.4 million of after-tax underwriting income for the same period.
	We paid dividends per common share of $.2845 and $.4072 in February 2013 and 2012, respectively, under our annual variable dividend policy. These dividends were paid pursuant to declarations made by the Board of Directors in December 2012 and 2011. In addition to the annual variable dividend, the Board of Directors declared a $1.00 per common share special dividend in October 2012, which was paid in November 2012.

Other_Comprehensive_Income_Los

Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2013
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			Total tax			After tax total			Total net			Net			Foreign
		accumulated			(provision)			accumulated			unrealized			unrealized			currency
		other			benefit			other			gains (losses)			gains on			translation
		comprehensive						comprehensive			on securities			forecasted			adjustment
		income						income						transactions1,3
	Balance at June 30, 2013	$	1,252.60		$	(438.4	)	$	814.2		$	807.6		$	5.4		$	1.2
	Other comprehensive income (loss) before reclassifications:
	Investment securities	111.9			(39.2		)	72.7			72.7			0			0
	Net non-credit related OTTI losses, adjusted for valuation changes	0			0			0			0			0			0
	Forecasted transactions	0			0			0			0			0			0
	Foreign currency translation adjustment	(.4		)	0.2			(.2		)	0			0			(.2		)
	Total other comprehensive income (loss) before reclassifications	111.5			(39.0		)	72.5			72.7			0			(.2		)
	Less: Reclassification adjustment for amounts realized in net income by income statement line item:
	Net impairment losses recognized in earnings	(1.9		)	0.7			(1.2		)	(1.2		)	0			0
	Net realized gains (losses) on securities2	25.6			(9.0		)	16.6			16.1			0.5			0
	Interest expense3	0.6			(.2		)	0.4			0			0.4			0
	Total reclassification adjustment for amounts realized in net income	24.3			(8.5		)	15.8			14.9			0.9			0
	Total other comprehensive income (loss)	87.2			(30.5		)	56.7			57.8			(.9		)	(.2		)
	Balance at September 30, 2013	$	1,339.80		$	(468.9	)	$	870.9		$	865.4		$	4.5		$	1
											Components of Changes in
											Accumulated Other
											Comprehensive Income (after tax)
	(millions)	Pretax total			Total tax			After tax total			Total net			Net			Foreign
		accumulated			(provision)			accumulated			unrealized			unrealized			currency
		other			benefit			other			gains (losses)			gains on			translation
		comprehensive						comprehensive			on securities			forecasted			adjustment
		income						income						transactions1,3
	Balance at December 31, 2012	$	1,340.00		$	(469.0	)	$	871		$	862.7		$	6.1		$	2.2
	Other comprehensive income (loss) before reclassifications:
	Investment securities	192.6			(67.4		)	125.2			125.2			0			0
	Net non-credit related OTTI losses, adjusted for	0.4			(.1		)	0.3			0.3			0			0
	valuation changes
	Forecasted transactions	0			0			0			0			0			0
	Foreign currency translation adjustment	(1.9		)	0.7			(1.2		)	0			0			(1.2		)
	Total other comprehensive income (loss) before reclassifications	191.1			(66.8		)	124.3			125.5			0			(1.2		)
	Less: Reclassification adjustment for amounts realized in net income by income statement line item:
	Net impairment losses recognized in earnings	(3.5		)	1.3			(2.2		)	(2.2		)	0			0
	Net realized gains (losses) on securities2	193.2			(67.7		)	125.5			125			0.5			0
	Interest expense3	1.6			(.5		)	1.1			0			1.1			0
	Total reclassification adjustment for amounts realized in net income	191.3			(66.9		)	124.4			122.8			1.6			0
	Total other comprehensive income (loss)	(.2		)	0.1			(.1		)	2.7			(1.6		)	(1.2		)
	Balance at September 30, 2013	$	1,339.80		$	(468.9	)	$	870.9		$	865.4		$	4.5		$	1
	1Entered into for the purpose of managing interest rate risk associated with our debt issuances.
	2During both the third quarter and first nine months of 2013, we reclassified $0.8 million, on a pretax basis, from accumulated other comprehensive income on the balance sheet to net realized gains on securities on the comprehensive income statement, reflecting the portion of the unrealized gain on forecasted transactions that was related to the portion of the 6.70% Debentures repurchased during the period (see Note 4 - Debt for further discussion).
	3We expect to reclassify $2.1 million (pretax) into income during the next 12 months, related to the net unrealized gains on forecasted transactions.

Litigation

Litigation	9 Months Ended
	Sep. 30, 2013
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; 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, 2013. 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 range of loss, if any, at this time, due to the factors discussed in Note 12 - Litigation in our Annual Report to Shareholders. In the event that any one or more of these lawsuits results in a substantial judgment against, or settlement by, Progressive, or if our accruals prove to be inadequate, the resulting liability could have a material effect on our consolidated financial condition, cash flows, and/or results of operations. For a further discussion on our pending litigation and related reserving policies, see Note 12 - Litigation in our Annual Report to Shareholders, which is included as Exhibit 13 to our Annual Report on Form 10-K, for the year ended December 31, 2012.

Reclassifications

Reclassifications	9 Months Ended
	Sep. 30, 2013
Reclassifications	'
	Reclassifications — For the period ended September 30, 2012, we reclassified net deferred income taxes to be reported as a separate line item and income taxes currently payable to be reported as a component of other liabilities to conform with the current year presentation. As a result, total assets and total liabilities increased by $57.9 million, which is not material to the September 30, 2012 Consolidated Balance Sheet.

Investments_Tables

Investments (Tables)	9 Months Ended
	Sep. 30, 2013
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			Gross			Net			Fair		% of
					Unrealized Gains			Unrealized			Realized			Value		Total
								Losses			Gains					Fair
											(Losses)1					Value
	30-Sep-13
	Fixed maturities:
	U.S. government obligations	$	3,691.20		$	61.8		$	(11.3	)	$	0		$	3,741.70	20.8	%
	State and local government obligations	2,125.70			29.9			(17.0		)	0			2,138.60		11.9
	Foreign government obligations2	15.9			0			0			0			15.9		0.1
	Corporate debt securities	3,118.80			67			(28.9		)	0.7			3,157.60		17.6
	Residential mortgage-backed securities	994.9			31.5			(16.5		)	0			1,009.90		5.6
	Commercial mortgage-backed securities	2,224.10			49			(33.1		)	0			2,240.00		12.4
	Other asset-backed securities	1,143.30			7.4			(2.0		)	0.2			1,148.90		6.4
	Redeemable preferred stocks	331			24.5			(10.4		)	0			345.1		1.9
	Total fixed maturities	13,644.90			271.1			(119.2		)	0.9			13,797.70		76.7
	Equity securities:
	Nonredeemable preferred stocks	442.1			280.5			(4.8		)	8.2			726		4
	Common equities	1,422.30			908.8			(5.0		)	0			2,326.10		12.9
	Short-term investments:
	Other short-term investments	1,146.10			0			0			0			1,146.10		6.4
	Total portfolio3,4	$	16,655.40		$	1,460.40		$	(129.0	)	$	9.1		$	17,995.90	100	%
	($ in millions)	Cost			Gross			Gross			Net			Fair		% of
					Unrealized Gains			Unrealized			Realized			Value		Total
								Losses			Gains					Fair
											(Losses)1					Value
	30-Sep-12
	Fixed maturities:
	U.S. government obligations	$	3,433.70		$	110.4		$	(.1	)	$	0		$	3,544.00	20.6	%
	State and local government obligations	1,898.90			61			(.4		)	0			1,959.50		11.4
	Foreign government obligations	0			0			0			0			0		0
	Corporate debt securities	2,687.80			128.8			(.4		)	6.3			2,822.50		16.4
	Residential mortgage-backed securities	399.5			21.6			(12.4		)	0			408.7		2.4
	Commercial mortgage-backed securities	1,998.20			90.7			(1.3		)	0			2,087.60		12.2
	Other asset-backed securities	1,077.90			14.5			(.1		)	0			1,092.30		6.4
	Redeemable preferred stocks	368			27.1			(14.5		)	0			380.6		2.2
	Total fixed maturities	11,864.00			454.1			(29.2		)	6.3			12,295.20		71.6
	Equity securities:
	Nonredeemable preferred stocks	430.1			416.8			0			1.5			848.4		4.9
	Common equities	1,101.50			543.8			(6.1		)	0			1,639.20		9.6
	Short-term investments:
	Other short-term investments	2,394.10			0			0			0			2,394.10		13.9
	Total portfolio3,4	$	15,789.70		$	1,414.70		$	(35.3	)	$	7.8		$	17,176.90	100	%
	($ in millions)	Cost			Gross			Gross			Net			Fair		% of
					Unrealized Gains			Unrealized			Realized			Value		Total
								Losses			Gains					Fair
											(Losses)1					Value
	31-Dec-12
	Fixed maturities:
	U.S. government obligations	$	2,806.40		$	90.1		$	0		$	0		$	2,896.50	17.6	%
	State and local government obligations	1,914.40			50.6			(.6		)	0			1,964.40		11.9
	Foreign government obligations	0			0			0			0			0		0
	Corporate debt securities	2,982.90			124.7			(1.0		)	6.4			3,113.00		18.9
	Residential mortgage-backed securities	413.4			24			(9.2		)	0			428.2		2.6
	Commercial mortgage-backed securities	1,963.90			84.9			(.1		)	0			2,048.70		12.4
	Other asset-backed securities	936			12.9			(.1		)	(.2		)	948.6		5.8
	Redeemable preferred stocks	356.9			30.5			(12.7		)	0			374.7		2.3
	Total fixed maturities	11,373.90			417.7			(23.7		)	6.2			11,774.10		71.5
	Equity securities:
	Nonredeemable preferred stocks	404			404.6			0			3.8			812.4		4.9
	Common equities	1,370.30			539			(10.3		)	0			1,899.00		11.5
	Short-term investments:
	Other short-term investments	1,990.00			0			0			0			1,990.00		12.1
Total portfolio3,4	$	15,138.20		$	1,361.30		$	(34.0	)	$	10		$	16,475.50	100	%
1Represents net holding period gains (losses) on certain hybrid securities (discussed below).
2Reflects an Australian government obligation at September 30, 2013.
3At September 30, 2013, we had $63.7 million of net unsettled security transactions, including collateral on open derivative positions, recognized in other liabilities, compared to $32.4 million and $90.9 million recognized in other assets at September 30, 2012 and December 31, 2012, respectively.
4The total fair value of the portfolio at September 30, 2013 and 2012, and December 31, 2012 included $1.3 billion, $1.6 billion, and $1.4 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company.
Hybrid Securities	'
	Included in our fixed-maturity and equity securities are hybrid securities, which are reported at fair value:
		September 30,						December 31,
	(millions)	2013			2012			2012
	Fixed maturities:
	Corporate debt securities	$	171.8		$	177.5		$	176.1
	Other asset-backed securities	15.3			16.4			16.4
	Total fixed maturities	187.1			193.9			192.5
	Equity securities:
	Nonredeemable preferred stocks	57.3			50.5			52.8
	Total hybrid securities	$	244.4		$	244.4		$	245.3
Composition of Fixed Maturities by Maturity	'
	Fixed Maturities The composition of fixed maturities by maturity at September 30, 2013, was:
	(millions)	Cost			Fair Value
	Less than one year	$	2,032.10		$	2,063.10
	One to five years	8,610.30			8,767.30
	Five to ten years	2,834.80			2,794.50
	Ten years or greater	114.2			119.3
	Total1	$	13,591.40		$	13,744.20
	1Excludes $53.5 million related to our open interest rate swap positions.
Gross Unrealized Losses by Major Security	'
	The following tables show the composition of gross unrealized losses by major security type and by the length of time that individual securities have been in a continuous unrealized loss position:
								Less than 12 Months						12 Months or Greater
	(millions)	Total Fair Value			Gross Unrealized Losses			Fair Value			Unrealized Losses			Fair Value		Unrealized Losses
	30-Sep-13
	Fixed maturities:
	U.S. government obligations	$	969.1		$	(11.3	)	$	969.1		$	(11.3	)	$	0	$	0
	State and local government obligations	728.3			(17.0		)	666.7			(16.2		)	61.6		(.8		)
	Corporate debt securities	1,174.20			(28.9		)	1,113.40			(28.5		)	60.8		(.4		)
	Residential mortgage-backed securities	663			(16.5		)	585.5			(12.4		)	77.5		(4.1		)
	Commercial mortgage-backed securities	993.3			(33.1		)	993.2			(33.0		)	0.1		(.1		)
	Other asset-backed securities	282.8			(2.0		)	282.8			(2.0		)	0		0
	Redeemable preferred stocks	158.4			(10.4		)	36.2			(.2		)	122.2		(10.2		)
	Total fixed maturities	4,969.10			(119.2		)	4,646.90			(103.6		)	322.2		(15.6		)
	Equity securities:
	Nonredeemable preferred stocks	123.6			(4.8		)	123.6			(4.8		)	0		0
	Common equities	47.3			(5.0		)	43			(4.7		)	4.3		(.3		)
	Total equity securities	170.9			(9.8		)	166.6			(9.5		)	4.3		(.3		)
	Total portfolio	$	5,140.00		$	(129.0	)	$	4,813.50		$	(113.1	)	$	326.5	$	(15.9	)
		Total Fair Value			Gross Unrealized Losses			Less than 12 Months						12 Months or Greater
	(millions)							Fair Value			Unrealized Losses			Fair Value		Unrealized Losses
	30-Sep-12
	Fixed maturities:
	U.S. government obligations	$	83.1		$	(.1	)	$	83.1		$	(.1	)	$	0	$	0
	State and local government obligations	61.4			(.4		)	29.1			(.2		)	32.3		(.2		)
	Corporate debt securities	35.9			(.4		)	14.2			(.1		)	21.7		(.3		)
	Residential mortgage-backed securities	177.2			(12.4		)	30			(.5		)	147.2		(11.9		)
	Commercial mortgage-backed securities	44			(1.3		)	31.4			(.1		)	12.6		(1.2		)
	Other asset-backed securities	21			(.1		)	9			0			12		(.1		)
	Redeemable preferred stocks	164.1			(14.5		)	24.7			(.4		)	139.4		(14.1		)
	Total fixed maturities	586.7			(29.2		)	221.5			(1.4		)	365.2		(27.8		)
	Equity securities:
	Nonredeemable preferred stocks	0			0			0			0			0		0
	Common equities	80.8			(6.1		)	54.4			(3.4		)	26.4		(2.7		)
	Total equity securities	80.8			(6.1		)	54.4			(3.4		)	26.4		(2.7		)
	Total portfolio	$	667.5		$	(35.3	)	$	275.9		$	(4.8	)	$	391.6	$	(30.5	)
		Total Fair Value			Gross Unrealized Losses			Less than 12 Months						12 Months or Greater
	(millions)							Fair Value			Unrealized Losses			Fair Value		Unrealized Losses
	31-Dec-12
	Fixed maturities:
	U.S. government obligations	$	0		$	0		$	0		$	0		$	0	$	0
	State and local government obligations	162.8			(.6		)	123.1			(.5		)	39.7		(.1		)
	Corporate debt securities	128.2			(1.0		)	128.2			(1.0		)	0		0
	Residential mortgage-backed securities	149.2			(9.2		)	40.2			(.6		)	109		(8.6		)
	Commercial mortgage-backed securities	7.1			(.1		)	2.1			0			5		(.1		)
	Other asset-backed securities	25			(.1		)	20.8			0			4.2		(.1		)
	Redeemable preferred stocks	155.7			(12.7		)	24.9			0			130.8		(12.7		)
	Total fixed maturities	628			(23.7		)	339.3			(2.1		)	288.7		(21.6		)
	Equity securities:
	Nonredeemable preferred stocks	0			0			0			0			0		0
	Common equities	118.2			(10.3		)	100.7			(8.2		)	17.5		(2.1		)
	Total equity securities	118.2			(10.3		)	100.7			(8.2		)	17.5		(2.1		)
	Total portfolio	$	746.2		$	(34.0	)	$	440		$	(10.3	)	$	306.2	$	(23.7	)
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)	2013			2012			2012
	Fixed maturities:
	Residential mortgage-backed securities	$	(44.1	)	$	(44.2	)	$	(44.2	)
	Commercial mortgage-backed securities	(.9		)	(.9		)	(.9		)
	Total fixed maturities	$	(45.0	)	$	(45.1	)	$	(45.1	)
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, 2013 and 2012, for which portions 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, 2013
		Mortgage-Backed
	(millions)	Residential			Commercial			Total
	Balance at June 30, 2013	$	26.9		$	0.5		$	27.4
	Credit losses for which an OTTI was previously recognized	0			0			0
	Credit losses for which an OTTI was not previously recognized	0			0			0
	Reductions for securities sold/matured	0			0			0
	Change in recoveries of future cash flows expected to be collected1	(2.4		)	(.1		)	(2.5		)
	Reductions for previously recognized credit impairments written-down to fair value2	0			0			0
	Balance at September 30, 2013	$	24.5		$	0.4		$	24.9
		Nine Months Ended September 30, 2013
		Mortgage-Backed
	(millions)	Residential			Commercial			Total
	Balance at December 31, 2012	$	27.1		$	0.6		$	27.7
	Credit losses for which an OTTI was previously recognized	0			0			0
	Credit losses for which an OTTI was not previously recognized	0			0			0
	Reductions for securities sold/matured	0			0			0
	Change in recoveries of future cash flows expected to be collected1	(2.4		)	(.2		)	(2.6		)
	Reductions for previously recognized credit impairments written-down to fair value2	(.2		)	0			(.2		)
	Balance at September 30, 2013	$	24.5		$	0.4		$	24.9
		Three Months Ended September 30, 2012
		Mortgage-Backed
	(millions)	Residential			Commercial			Total
	Balance at June 30, 2012	$	28.1		$	0.7		$	28.8
	Credit losses for which an OTTI was previously recognized	0			0			0
	Credit losses for which an OTTI was not previously recognized	0			0			0
	Reductions for securities sold/matured	0			0			0
	Change in recoveries of future cash flows expected to be collected1	(.4		)	(.1		)	(.5		)
	Reductions for previously recognized credit impairments written-down to fair value2	0			0			0
	Balance at September 30, 2012	$	27.7		$	0.6		$	28.3
		Nine Months Ended September 30, 2012
		Mortgage-Backed
	(millions)	Residential			Commercial			Total
	Balance at December 31, 2011	$	34.5		$	1.3		$	35.8
	Credit losses for which an OTTI was previously recognized	0.1			0			0.1
	Credit losses for which an OTTI was not previously recognized	0.2			0			0.2
	Reductions for securities sold/matured	0			(.2		)	(.2		)
	Change in recoveries of future cash flows expected to be collected1	(3.1		)	(.2		)	(3.3		)
	Reductions for previously recognized credit impairments written-down to fair value2	(4.0		)	(.3		)	(4.3		)
	Balance at September 30, 2012	$	27.7		$	0.6		$	28.3
	1Reflects expected recovery of prior period impairments that will be accreted into income over the remaining life of the security, net of any current quarter decreases in expected cash flows on previously recorded reductions.
	2Reflects reductions of prior credit impairments where the current credit impairment requires writing securities down to fair value (i.e., no remaining non-credit loss).
Components of Net Realized Gains (Losses)	'
	The components of net realized gains (losses) for the three and nine months ended September 30, were:
		Three Months						Nine months
	(millions)	2013			2012			2013			2012
	Gross realized gains on security sales
	Fixed maturities:
	U.S. government obligations	$	3.1		$	0.2		$	6.8		$	9.8
	State and local government obligations	0			0			6.8			12.1
	Corporate and other debt securities	1.7			23			38.4			49.1
	Residential mortgage-backed securities	0.3			0.6			2.4			0.6
	Commercial mortgage-backed securities	0.1			9.5			8.4			14
	Other asset-backed securities	0			0.9			0			0.9
	Redeemable preferred stocks	0			0.1			0			0.5
	Total fixed maturities	5.2			34.3			62.8			87
	Equity securities:
	Nonredeemable preferred stocks	11.9			20.6			113.1			57.5
	Common equities	11.1			153.4			26.1			163.2
	Subtotal gross realized gains on security sales	28.2			208.3			202			307.7
	Gross realized losses on security sales
	Fixed maturities:
	U.S. government obligations	(.8		)	(.5		)	(2.2		)	(1.4		)
	Corporate and other debt securities	(2.1		)	(.6		)	(3.1		)	(.6		)
	Commercial mortgage-backed securities	0			0			(.7		)	0
	Redeemable preferred stocks	0			(.3		)	(.1		)	(.3		)
	Total fixed maturities	(2.9		)	(1.4		)	(6.1		)	(2.3		)
	Equity securities:
	Nonredeemable preferred stocks	0			(1.1		)	0			(1.1		)
	Common equities	(.1		)	(22.5		)	(.4		)	(27.0		)
	Subtotal gross realized losses on security sales	(3.0		)	(25.0		)	(6.5		)	(30.4		)
	Net realized gains (losses) on security sales
	Fixed maturities:
	U.S. government obligations	2.3			(.3		)	4.6			8.4
	State and local government obligations	0			0			6.8			12.1
	Corporate and other debt securities	(.4		)	22.4			35.3			48.5
	Residential mortgage-backed securities	0.3			0.6			2.4			0.6
	Commercial mortgage-backed securities	0.1			9.5			7.7			14
	Other asset-backed securities	0			0.9			0			0.9
	Redeemable preferred stocks	0			(.2		)	(.1		)	0.2
	Total fixed maturities	2.3			32.9			56.7			84.7
	Equity securities:
	Nonredeemable preferred stocks	11.9			19.5			113.1			56.4
	Common equities	11			130.9			25.7			136.2
	Subtotal net realized gains (losses) on security sales	25.2			183.3			195.5			277.3
	Other-than-temporary impairment losses
	Fixed maturities:
	Residential mortgage-backed securities	(.1		)	(.4		)	(.5		)	(1.4		)
	Commercial mortgage-backed securities	0			0			0			(.1		)
	Total fixed maturities	(.1		)	(.4		)	(.5		)	(1.5		)
	Equity securities:
	Common equities	(1.8		)	0			(3.2		)	(.7		)
	Subtotal other-than-temporary impairment losses	(1.9		)	(.4		)	(3.7		)	(2.2		)
	Other gains (losses)
	Hybrid securities	3.5			5.2			2.3			12.1
	Derivative instruments	(1.2		)	(16.3		)	45			(42.8		)
	Litigation settlements	2.3			0.1			2.3			0.3
	Subtotal other gains (losses)	4.6			(11.0		)	49.6			(30.4		)
	Total net realized gains (losses) on securities	$	27.9		$	171.9		$	241.4		$	244.7
Derivative Instruments	'
	The following table shows the status of our derivative instruments at September 30, 2013 and 2012, and December 31, 2012, and for the three and nine months ended September 30, 2013 and 2012; amounts are on a pretax basis:
	(millions)												Balance Sheet2									Comprehensive Income Statement
														Assets (Liabilities)								Net Realized
														Fair Value								Gains (Losses) on Securities
		Notional Value1																				Three months ended						Nine months ended
		September 30,						Dec. 31,						September 30,					Dec. 31,			September 30,						September 30,
	Derivatives designated as:	2013			2012			2012			Purpose		Classification	2013		2012			2012			2013			2012			2013			2012
	Hedging instruments
	Closed:
	Ineffective cash flow hedge	$	54		$	31		$	31		Manage interest		NA	$	0	$	0		$	0		$	0.8		$	0		$	0.8		$	0.6
											rate risk
	Non-hedging instruments
	Assets:
	Interest rate swaps	750			0			0			Manage portfolio		Investments—	53.5		0			0			(2.0		)	0			48.2			0
											duration		fixed maturities
	Corporate credit default swaps	0			25			0			Manage credit risk		Investments—	0		0.3			0			0			(.4		)	0			(.7		)
													fixed maturities
	Liabilities:
	Interest rate swaps	0			1,263			1,263			Manage portfolio		Other liabilities	0		(101.6		)	(95.5		)	0			(15.9		)	0			(42.7		)
											duration
	Closed:
	Interest rate swaps	1,263			0			0			Manage portfolio		NA	0		0			0			0			0			(4.0		)	0
											duration
	Corporate credit default swaps	0			0			25			Manage credit risk		NA	0		0			0			0			0			0			0
	Total	NA			NA			NA						$	53.5	$	(101.3	)	$	(95.5	)	$	(1.2	)	$	(16.3	)	$	45		$	(42.8	)
	NA=ot Applicable
	1The amounts represent the value held at quarter and year end for open positions and the maximum amount held during the period for closed positions.
	2To the extent we hold both derivative assets and liabilities with the same counterparty that are subject to an enforceable master netting arrangement, we expect that we will report them on a gross basis on our balance sheets, consistent with our historical presentation.

Fair_Value_Tables

Fair Value (Tables)	9 Months Ended
	Sep. 30, 2013
Composition of Investment Portfolio by Major Security Type	'
	The composition of the investment portfolio by major security type was:
		Fair Value
	(millions)	Level 1		Level 2			Level 3		Total		Cost
	30-Sep-13
	Fixed maturities:
	U.S. government obligations	$	3,741.70	$	0		$	0	$	3,741.70	$	3,691.20
	State and local government obligations	0		2,138.60			0		2,138.60		2,125.70
	Foreign government obligations	15.9		0			0		15.9		15.9
	Corporate debt securities	0		3,157.60			0		3,157.60		3,118.80
	Subtotal	3,757.60		5,296.20			0		9,053.80		8,951.60
	Asset-backed securities:
	Residential mortgage-backed	0		1,009.70			0.2		1,009.90		994.9
	Commercial mortgage-backed	0		2,208.70			31.3		2,240.00		2,224.10
	Other asset-backed	0		1,148.90			0		1,148.90		1,143.30
	Subtotal asset-backed securities	0		4,367.30			31.5		4,398.80		4,362.30
	Redeemable preferred stocks:
	Financials	0		134.2			0		134.2		115.7
	Utilities	0		65.3			0		65.3		64.9
	Industrials	0		145.6			0		145.6		150.4
	Subtotal redeemable preferred stocks	0		345.1			0		345.1		331
	Total fixed maturities	3,757.60		10,008.60			31.5		13,797.70		13,644.90
	Equity securities:
	Nonredeemable preferred stocks:
	Financials	244		429.1			36.1		709.2		427.9
	Utilities	0		16.8			0		16.8		14.2
	Subtotal nonredeemable preferred stocks	244		445.9			36.1		726		442.1
	Common equities:
	Common stocks	2,287.40		0			0		2,287.40		1,419.20
	Other risk investments	0		0			38.7		38.7		3.1
	Subtotal common equities	2,287.40		0			38.7		2,326.10		1,422.30
	Total fixed maturities and equity securities	6,289.00		10,454.50			106.3		16,849.80		15,509.30
	Short-term investments:
	Other short-term investments	751.5		394.6			0		1,146.10		1,146.10
	Total portfolio	$	7,040.50	$	10,849.10		$	106.3	$	17,995.90	$	16,655.40
	Debt	$	0	$	2,231.40		$	0	$	2,231.40	$	2,010.60
		Fair Value
	(millions)	Level 1		Level 2			Level 3		Total		Cost
	30-Sep-12
	Fixed maturities:
	U.S. government obligations	$	3,544.00	$	0		$	0	$	3,544.00	$	3,433.70
	State and local government obligations	0		1,959.50			0		1,959.50		1,898.90
	Foreign government obligations	0		0			0		0		0
	Corporate debt securities	0		2,822.50			0		2,822.50		2,687.80
	Subtotal	3,544.00		4,782.00			0		8,326.00		8,020.40
	Asset-backed securities:
	Residential mortgage-backed	0		358.8			49.9		408.7		399.5
	Commercial mortgage-backed	0		2,065.00			22.6		2,087.60		1,998.20
	Other asset-backed	0		1,092.00			0.3		1,092.30		1,077.90
	Subtotal asset-backed securities	0		3,515.80			72.8		3,588.60		3,475.60
	Redeemable preferred stocks:
	Financials	0		133.9			0		133.9		120.8
	Utilities	0		66.9			0		66.9		65.9
	Industrials	0		179.8			0		179.8		181.3
	Subtotal redeemable preferred stocks	0		380.6			0		380.6		368
	Total fixed maturities	3,544.00		8,678.40			72.8		12,295.20		11,864.00
	Equity securities:
	Nonredeemable preferred stocks:
	Financials	265.2		524.4			29.3		818.9		407.3
	Utilities	0		29.5			0		29.5		22.8
	Subtotal nonredeemable preferred stocks	265.2		553.9			29.3		848.4		430.1
	Common equities:
	Common stocks	1,627.20		0			0		1,627.20		1,098.30
	Other risk investments	0		0			12		12		3.2
Subtotal common equities	1,627.20		0			12		1,639.20		1,101.50
Total fixed maturities and equity securities	5,436.40		9,232.30			114.1		14,782.80		13,395.60
Short-term investments:
Other short-term investments	2,120.70		273.4			0		2,394.10		2,394.10
Total portfolio	$	7,557.10	$	9,505.70		$	114.1	$	17,176.90	$	15,789.70
Debt	$	0	$	2,405.90		$	0	$	2,405.90	$	2,062.70
	Fair Value
(millions)	Level 1		Level 2			Level 3		Total		Cost
31-Dec-12
Fixed maturities:
U.S. government obligations	$	2,896.50	$	0		$	0	$	2,896.50	$	2,806.40
State and local government obligations	0		1,964.40			0		1,964.40		1,914.40
Foreign government obligations	0		0			0		0		0
Corporate debt securities	0		3,113.00			0		3,113.00		2,982.90
Subtotal	2,896.50		5,077.40			0		7,973.90		7,703.70
Asset-backed securities:
Residential mortgage-backed	0		382.7			45.5		428.2		413.4
Commercial mortgage-backed	0		2,023.40			25.3		2,048.70		1,963.90
Other asset-backed	0		948.6			0		948.6		936
Subtotal asset-backed securities	0		3,354.70			70.8		3,425.50		3,313.30
Redeemable preferred stocks:
Financials	0		129.7			0		129.7		110.7
Utilities	0		66.7			0		66.7		64.9
Industrials	0		178.3			0		178.3		181.3
Subtotal redeemable preferred stocks	0		374.7			0		374.7		356.9
Total fixed maturities	2,896.50		8,806.80			70.8		11,774.10		11,373.90
Equity securities:
Nonredeemable preferred stocks:
Financials	259.6		494.5			31.9		786		383.3
Utilities	0		26.4			0		26.4		20.7
Subtotal nonredeemable preferred stocks	259.6		520.9			31.9		812.4		404
Common equities:
Common stocks	1,887.00		0			0		1,887.00		1,367.20
Other risk investments	0		0			12		12		3.1
Subtotal common equities	1,887.00		0			12		1,899.00		1,370.30
Total fixed maturities and equity securities	5,043.10		9,327.70			114.7		14,485.50		13,148.20
Short-term investments:
Other short-term investments	1,679.90		310.1			0		1,990.00		1,990.00
Total portfolio	$	6,723.00	$	9,637.80		$	114.7	$	16,475.50	$	15,138.20
Debt	$	0	$	2,394.40		$	0	$	2,394.40	$	2,063.10
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, 2013 and 2012:
		Level 3 Fair Value
		Three months ended September 30, 2013
	(millions)	Fair Value at June 30, 2013		Calls/Maturities/Paydowns			Purchases		Sales		Net Realized (gain)/loss on sales			Change in Valuation			Net			Fair Value at Sept. 30, 2013
																	Transfers
																	in (out)1
	Fixed maturities:
	Asset-backed securities:
	Residential mortgage-backed	$	157.1	$	(17.0	)	$	0	$	0	$	0		$	1.5		$	(141.4	)	$	0.2
	Commercial mortgage-backed	27.6		(.3		)	0		0		0			4			0			31.3
	Other asset-backed	0		0			0		0		0			0			0			0
	Total fixed maturities	184.7		(17.3		)	0		0		0			5.5			(141.4		)	31.5
	Equity securities:
	Nonredeemable preferred stocks:
	Financials2	34.8		0			0		0		0			1.3			0			36.1
	Common equities:
	Other risk investments	38.7		0			0		0		0			0			0			38.7
	Total Level 3 securities	$	258.2	$	(17.3	)	$	0	$	0	$	0		$	6.8		$	(141.4	)	$	106.3
	1The $(141.4) million was transferred out of Level 3 and into Level 2 due to an increase in liquidity and trading volume in the market.
	2The $1.3 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, 2013
	(millions)	Fair Value at Dec. 31, 2012		Calls/Maturities/Paydowns			Purchases		Sales		Net Realized (gain)/loss on sales			Change in			Net			Fair Value at Sept. 30, 2013
														Valuation			Transfers
																	in (out)1
	Fixed maturities:
	Asset-backed securities:
	Residential mortgage-backed	$	45.5	$	(28.6	)	$	125.1	$	0	$	0		$	(.4	)	$	(141.4	)	$	0.2
	Commercial mortgage-backed	25.3		(1.1		)	0		0		0			7.1			0			31.3
	Other asset-backed	0		0			0		0		0			0			0			0
	Total fixed maturities	70.8		(29.7		)	125.1		0		0			6.7			(141.4		)	31.5
	Equity securities:
	Nonredeemable preferred stocks:
	Financials2	31.9		0			0		0		0			4.2			0			36.1
	Common equities:
	Other risk investments	12		(.1		)	0.3		0		(.5		)	27			0			38.7
	Total Level 3 securities	$	114.7	$	(29.8	)	$	125.4	$	0	$	(.5	)	$	37.9		$	(141.4	)	$	106.3
	1The $(141.4) million was transferred out of Level 3 and into Level 2 due to an increase in liquidity and trading volume in the market.
	2The $4.2 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
		Three months ended September 30, 2012
	(millions)	Fair Value at June 30, 2012		Calls/			Purchases		Sales		Net Realized (gain)/loss on sales			Change in			Net			Fair Value at Sept. 30, 2012
				Maturities/										Valuation			Transfers
				Paydowns													in (out)
	Fixed maturities:
	Asset-backed securities:
	Residential mortgage-backed	$	54.5	$	(5.0	)	$	0	$	0	$	0		$	0.4		$	0		$	49.9
	Commercial mortgage-backed	23.2		(2.6		)	0		0		0			2			0			22.6
	Other asset-backed	1.1		(.8		)	0		0		0			0			0			0.3
	Total fixed maturities	78.8		(8.4		)	0		0		0			2.4			0			72.8
	Equity securities:
	Nonredeemable preferred stocks:
	Financials1	0		0			28.5		0		0			0.8			0			29.3
	Common equities:
	Other risk investments	12.2		(.2		)	0		0		0			0			0			12
	Total Level 3 securities	$	91	$	(8.6	)	$	28.5	$	0	$	0		$	3.2		$	0		$	114.1
	1The $0.8 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, 2012
	(millions)	Fair Value at Dec. 31, 2011		Calls/			Purchases		Sales		Net Realized (gain)/loss on sales			Change in			Net			Fair Value at Sept. 30, 2012
				Maturities/										Valuation			Transfers
				Paydowns													in (out)
	Fixed maturities:
Asset-backed securities:
Residential mortgage-backed	$	62.3	$	(12.8	)	$	0	$	0	$	0		$	0.4		$	0		$	49.9
Commercial mortgage-backed	21.3		(2.7		)	0		0		0			4			0			22.6
Other asset-backed	2.6		(2.3		)	0		0		0			0			0			0.3
Total fixed maturities	86.2		(17.8		)	0		0		0			4.4			0			72.8
Equity securities:
Nonredeemable preferred stocks:
Financials1	0		0			28.5		0		0			0.8			0			29.3
Common equities:
Other risk investments	11.5		(.2		)	0		0		0			0.7			0			12
Total Level 3 securities	$	97.7	$	(18.0	)	$	28.5	$	0	$	0		$	5.9		$	0		$	114.1
1The $0.8 million represents net holding period gains on a hybrid security which is reflected in net realized gains (losses) on securities in the comprehensive income statement.
Summary of Quantitative Information about Level 3 Fair Value Measurements	'
	The following tables provide a summary of the quantitative information about Level 3 fair value measurements for our applicable securities at September 30, 2013 and 2012, and December 31, 2012:
		Quantitative Information about Level 3 Fair Value Measurements
	($ in millions)	Fair Value at Sept. 30, 2013		Valuation Technique		Unobservable Input	Unobservable
							Input Assumption
	Fixed maturities:
	Asset-backed securities:
	Residential mortgage-backed	$	0.2	External vendor		Prepayment rate1	0
	Commercial mortgage-backed	31.3		External vendor		Prepayment rate2	0
	Total fixed maturities	31.5
	Equity securities:
	Nonredeemable preferred stocks:
	Financials	36.1		Multiple of tangible net book value		Price to book ratio multiple	1.9
	Common equities:
	Other risk investments	0
	Subtotal Level 3 securities	$	67.6
	Pricing exemption securities3	38.7
	Total Level 3 securities	$	106.3
	1Assumes that one security has 0% of the principal amount of the underlying loans that will be paid off prematurely in each year.
	2Assumes that two securities have 0% of the principal amount of the underlying loans that will be paid off prematurely in each year.
	3The fair values for $0.7 million of these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us. The remaining $38.0 million reflects a negotiated sale on a private common equity security that is expected to be completed by the end of 2013.
		Quantitative Information about Level 3 Fair Value Measurements
	($ in millions)	Fair Value at Sept. 30, 2012		Valuation Technique		Unobservable Input	Unobservable
							Input Assumption
	Fixed maturities:
	Asset-backed securities:
	Residential mortgage-backed	$	15.3	External vendor		Prepayment rate1	0,16
	Commercial mortgage-backed	0
	Total fixed maturities	15.3
	Equity securities:
	Nonredeemable preferred stocks:
	Financials	29.3		Multiple of tangible net book value		Price to Book Ratio Multiple	1.9
	Common equities:
	Other risk investments	11.2		Discounted consolidated		Discount for lack of marketability	20	%
				equity
	Subtotal Level 3 securities	$	55.8
	Pricing exemption securities2	58.3
	Total Level 3 securities	$	114.1
	1Assumes that two securities have 0% and one security has 16% of the principal amount of the underlying loans that will be paid off prematurely in each year.
	2The fair values for these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us.
		Quantitative Information about Level 3 Fair Value Measurements
	($ in millions)	Fair Value at Dec. 31, 2012		Valuation Technique		Unobservable Input	Unobservable
							Input Assumption
	Fixed maturities:
	Asset-backed securities:
	Residential mortgage-backed	$	0.2	External vendor		Prepayment rate1	16
	Commercial mortgage-backed	25.3		External vendor		Prepayment rate2	0
	Total fixed maturities	25.5
	Equity securities:
	Nonredeemable preferred stocks:
	Financials	31.9		Multiple of tangible net book value		Price to book ratio multiple	1.9
	Common equities:
	Other risk investments	11.2		Discounted consolidated equity		Discount for lack of marketability	20	%
	Subtotal Level 3 securities	$	68.6
	Pricing exemption securities3	46.1
	Total Level 3 securities	$	114.7
	1Assumes that one security has 16% of the principal amount of the underlying loans that will be paid off prematurely in each year.
	2Assumes that three securities have 0% of the principal amount of the underlying loans that will be paid off prematurely in each year.
	3The fair values for these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us.

Debt_Tables

Debt (Tables)	9 Months Ended
	Sep. 30, 2013
Debt Table	'
	Debt consisted of:
		30-Sep-13				30-Sep-12				31-Dec-12
	(millions)	Carrying		Fair		Carrying		Fair		Carrying		Fair
		Value		Value		Value		Value		Value		Value
	7% Notes due 2013	$	150	$	150	$	149.8	$	159	$	149.9	$	157.1
	3.75% Senior Notes due 2021	497.5		516.7		497.3		551		497.3		549.1
	6 5/8% Senior Notes due 2029	295.3		362		295.1		393.7		295.2		385
	6.25% Senior Notes due 2032	394.6		478.2		394.5		521.7		394.5		513.5
	6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067	673.2		724.5		726		780.5		726.2		789.7
	Total	$	2,010.60	$	2,231.40	$	2,062.70	$	2,405.90	$	2,063.10	$	2,394.40

Supplemental_Cash_Flow_Informa1

Supplemental Cash Flow Information (Tables)	9 Months Ended
	Sep. 30, 2013
Supplemental Cash Flow Information Table	'
	We paid the following in the respective periods:
		Nine Months Ended September 30,
	(millions)	2013		2012
	Income taxes, net of refunds	$	340	$	259.1
	Interest	81.9		92.8

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2013
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,
		2013							2012								2013						2012
	(millions)	Revenues				Pretax			Revenues				Pretax				Revenues			Pretax			Revenues			Pretax
						Profit							Profit							Profit						Profit
						(Loss)							(Loss)							(Loss)						(Loss)
	Personal Lines
	Agency	$	2,162.70			$	122		$	2,047.70			$	52.3			$	6,421.40		$	428.4		$	6,032.30		$	237.9
	Direct	1,693.40				107.3			1,582.70				105.9				5,020.40			360.5			4,660.10			193.2
	Total Personal Lines1	3,856.10				229.3			3,630.40				158.2				11,441.80			788.9			10,692.40			431.1
	Commercial Lines	446.8				26.3			424.3				7.5				1,317.30			73.7			1,219.20			61
	Other indemnity	0.1				(6.2		)	0.1				(.5		)		0.2			(9.7		)	0.8			(3.1		)
	Total underwriting operations	4,303.00				249.4			4,054.80				165.2				12,759.30			852.9			11,912.40			489
	Fees and other revenues2	76				NA			78.4				NA				215.3			NA			213.5			NA
	Service businesses	11.3				0.2			9.9				0.3				30.3			0.2			28.3			0.6
	Investments3	135.3				130.1			280.9				277.6				551.5			537			580.9			569.6
	Gains (losses) on extinguishment of debt	(4.3		)		(4.3		)	(.1		)		(.1		)		(4.3		)	(4.3		)	(1.8		)	(1.8		)
	Interest expense	NA				(30.4		)	NA				(30.6		)		NA			(91.4		)	NA			(93.2		)
	Consolidated total	$	4,521.30			$	345		$	4,423.90			$	412.4			$	13,552.10		$	1,294.40		$	12,733.30		$	964.2
	1Personal auto insurance accounted for 91% of the total Personal Lines segment net premiums earned in all periods; 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.
	2Pretax profit (loss) for fees and other revenues are allocated to operating segments.
	3Revenues represent recurring investment income and total net realized gains (losses) on securities; pretax profit is net of investment expenses.
	NA =ot Applicable
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,
		2013					2012				2013					2012
		Under-writing			Combined		Under-writing		Combined		Under-writing			Combined		Under-writing			Combined
		Margin			Ratio		Margin		Ratio		Margin			Ratio		Margin			Ratio
	Personal Lines
	Agency	5.6	%		94.4		2.6	%	97.4		6.7	%		93.3		3.9	%		96.1
	Direct	6.3			93.7		6.7		93.3		7.2			92.8		4.1			95.9
	Total Personal Lines	5.9			94.1		4.4		95.6		6.9			93.1		4			96
	Commercial Lines	5.9			94.1		1.8		98.2		5.6			94.4		5			95
	Other indemnity1	NM			NM		NM		NM		NM			NM		NM			NM
	Total underwriting operations	5.8			94.2		4.1		95.9		6.7			93.3		4.1			95.9
	1Underwriting 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.

Other_Comprehensive_Income_Los1

Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2013
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			Total tax			After tax total			Total net			Net			Foreign
		accumulated			(provision)			accumulated			unrealized			unrealized			currency
		other			benefit			other			gains (losses)			gains on			translation
		comprehensive						comprehensive			on securities			forecasted			adjustment
		income						income						transactions1,3
	Balance at June 30, 2013	$	1,252.60		$	(438.4	)	$	814.2		$	807.6		$	5.4		$	1.2
	Other comprehensive income (loss) before reclassifications:
	Investment securities	111.9			(39.2		)	72.7			72.7			0			0
	Net non-credit related OTTI losses, adjusted for valuation changes	0			0			0			0			0			0
	Forecasted transactions	0			0			0			0			0			0
	Foreign currency translation adjustment	(.4		)	0.2			(.2		)	0			0			(.2		)
	Total other comprehensive income (loss) before reclassifications	111.5			(39.0		)	72.5			72.7			0			(.2		)
	Less: Reclassification adjustment for amounts realized in net income by income statement line item:
	Net impairment losses recognized in earnings	(1.9		)	0.7			(1.2		)	(1.2		)	0			0
	Net realized gains (losses) on securities2	25.6			(9.0		)	16.6			16.1			0.5			0
	Interest expense3	0.6			(.2		)	0.4			0			0.4			0
	Total reclassification adjustment for amounts realized in net income	24.3			(8.5		)	15.8			14.9			0.9			0
	Total other comprehensive income (loss)	87.2			(30.5		)	56.7			57.8			(.9		)	(.2		)
	Balance at September 30, 2013	$	1,339.80		$	(468.9	)	$	870.9		$	865.4		$	4.5		$	1
											Components of Changes in
											Accumulated Other
											Comprehensive Income (after tax)
	(millions)	Pretax total			Total tax			After tax total			Total net			Net			Foreign
		accumulated			(provision)			accumulated			unrealized			unrealized			currency
		other			benefit			other			gains (losses)			gains on			translation
		comprehensive						comprehensive			on securities			forecasted			adjustment
		income						income						transactions1,3
	Balance at December 31, 2012	$	1,340.00		$	(469.0	)	$	871		$	862.7		$	6.1		$	2.2
	Other comprehensive income (loss) before reclassifications:
	Investment securities	192.6			(67.4		)	125.2			125.2			0			0
	Net non-credit related OTTI losses, adjusted for	0.4			(.1		)	0.3			0.3			0			0
	valuation changes
	Forecasted transactions	0			0			0			0			0			0
	Foreign currency translation adjustment	(1.9		)	0.7			(1.2		)	0			0			(1.2		)
	Total other comprehensive income (loss) before reclassifications	191.1			(66.8		)	124.3			125.5			0			(1.2		)
	Less: Reclassification adjustment for amounts realized in net income by income statement line item:
	Net impairment losses recognized in earnings	(3.5		)	1.3			(2.2		)	(2.2		)	0			0
	Net realized gains (losses) on securities2	193.2			(67.7		)	125.5			125			0.5			0
	Interest expense3	1.6			(.5		)	1.1			0			1.1			0
	Total reclassification adjustment for amounts realized in net income	191.3			(66.9		)	124.4			122.8			1.6			0
	Total other comprehensive income (loss)	(.2		)	0.1			(.1		)	2.7			(1.6		)	(1.2		)
	Balance at September 30, 2013	$	1,339.80		$	(468.9	)	$	870.9		$	865.4		$	4.5		$	1
	1Entered into for the purpose of managing interest rate risk associated with our debt issuances.
	2During both the third quarter and first nine months of 2013, we reclassified $0.8 million, on a pretax basis, from accumulated other comprehensive income on the balance sheet to net realized gains on securities on the comprehensive income statement, reflecting the portion of the unrealized gain on forecasted transactions that was related to the portion of the 6.70% Debentures repurchased during the period (see Note 4 - Debt for further discussion).
	3We expect to reclassify $2.1 million (pretax) into income during the next 12 months, related to the net unrealized gains on forecasted transactions.

Basis_of_Presentation_Addition

Basis of Presentation - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revisions [Line Items]	'	'	'	'
Fees and other revenues	$76	$78.40	$215.30	$213.50

Investment_Portfolio_by_Major_

Investment Portfolio by Major Security Type (Detail) (USD $)	Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2012
In Millions, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	$16,655.40	[1],[2]	$15,138.20	[1],[2]	$15,789.70	[1],[2]
Gross Unrealized Gains	1,460.40	[1],[2]	1,361.30	[1],[2]	1,414.70	[1],[2]
Gross Unrealized Losses	-129	[1],[2]	-34	[1],[2]	-35.3	[1],[2]
Net Realized Gains (Losses)	9.1	[1],[2],[3]	10	[1],[2],[3]	7.8	[1],[2],[3]
Total investments	17,995.90	[1],[2]	16,475.50	[1],[2]	17,176.90	[1],[2]
% of Total Fair Value	100.00%	[1],[2]	100.00%	[1],[2]	100.00%	[1],[2]
Fixed maturities	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	13,644.90		11,373.90		11,864
Gross Unrealized Gains	271.1		417.7		454.1
Gross Unrealized Losses	-119.2		-23.7		-29.2
Net Realized Gains (Losses)	0.9	[3]	6.2	[3]	6.3	[3]
Total investments	13,797.70		11,774.10		12,295.20
% of Total Fair Value	76.70%		71.50%		71.60%
Fixed maturities | U.S. government obligations	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	3,691.20		2,806.40		3,433.70
Gross Unrealized Gains	61.8		90.1		110.4
Gross Unrealized Losses	-11.3		0		-0.1
Net Realized Gains (Losses)	0	[3]	0	[3]	0	[3]
Total investments	3,741.70		2,896.50		3,544
% of Total Fair Value	20.80%		17.60%		20.60%
Fixed maturities | State and local government obligations	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	2,125.70		1,914.40		1,898.90
Gross Unrealized Gains	29.9		50.6		61
Gross Unrealized Losses	-17		-0.6		-0.4
Net Realized Gains (Losses)	0	[3]	0	[3]	0	[3]
Total investments	2,138.60		1,964.40		1,959.50
% of Total Fair Value	11.90%		11.90%		11.40%
Fixed maturities | Foreign government obligations	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	15.9	[4]	0		0
Gross Unrealized Gains	0	[4]	0		0
Gross Unrealized Losses	0	[4]	0		0
Net Realized Gains (Losses)	0	[3],[4]	0	[3]	0	[3]
Total investments	15.9	[4]	0		0
% of Total Fair Value	0.10%	[4]	0.00%		0.00%
Fixed maturities | Corporate debt securities	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	3,118.80		2,982.90		2,687.80
Gross Unrealized Gains	67		124.7		128.8
Gross Unrealized Losses	-28.9		-1		-0.4
Net Realized Gains (Losses)	0.7	[3]	6.4	[3]	6.3	[3]
Total investments	3,157.60		3,113		2,822.50
% of Total Fair Value	17.60%		18.90%		16.40%
Fixed maturities | Residential mortgage-backed securities	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	994.9		413.4		399.5
Gross Unrealized Gains	31.5		24		21.6
Gross Unrealized Losses	-16.5		-9.2		-12.4
Net Realized Gains (Losses)	0	[3]	0	[3]	0	[3]
Total investments	1,009.90		428.2		408.7
% of Total Fair Value	5.60%		2.60%		2.40%
Fixed maturities | Commercial mortgage-backed securities	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	2,224.10		1,963.90		1,998.20
Gross Unrealized Gains	49		84.9		90.7
Gross Unrealized Losses	-33.1		-0.1		-1.3
Net Realized Gains (Losses)	0	[3]	0	[3]	0	[3]
Total investments	2,240		2,048.70		2,087.60
% of Total Fair Value	12.40%		12.40%		12.20%
Fixed maturities | Other asset-backed securities	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	1,143.30		936		1,077.90
Gross Unrealized Gains	7.4		12.9		14.5
Gross Unrealized Losses	-2		-0.1		-0.1
Net Realized Gains (Losses)	0.2	[3]	-0.2	[3]	0	[3]
Total investments	1,148.90		948.6		1,092.30
% of Total Fair Value	6.40%		5.80%		6.40%
Fixed maturities | Redeemable preferred stocks	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	331		356.9		368
Gross Unrealized Gains	24.5		30.5		27.1
Gross Unrealized Losses	-10.4		-12.7		-14.5
Net Realized Gains (Losses)	0	[3]	0	[3]	0	[3]
Total investments	345.1		374.7		380.6
% of Total Fair Value	1.90%		2.30%		2.20%
Equity securities | Nonredeemable preferred stocks	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	442.1		404		430.1
Gross Unrealized Gains	280.5		404.6		416.8
Gross Unrealized Losses	-4.8		0		0
Net Realized Gains (Losses)	8.2	[3]	3.8	[3]	1.5	[3]
Total investments	726		812.4		848.4
% of Total Fair Value	4.00%		4.90%		4.90%
Equity securities | Common equities	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	1,422.30		1,370.30		1,101.50
Gross Unrealized Gains	908.8		539		543.8
Gross Unrealized Losses	-5		-10.3		-6.1
Net Realized Gains (Losses)	0	[3]	0	[3]	0	[3]
Total investments	2,326.10		1,899		1,639.20
% of Total Fair Value	12.90%		11.50%		9.60%
Short-term investments | Other short-term investments	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	1,146.10		1,990		2,394.10
Gross Unrealized Gains	0		0		0
Gross Unrealized Losses	0		0		0
Net Realized Gains (Losses)	0	[3]	0	[3]	0	[3]
Total investments	$1,146.10		$1,990		$2,394.10
% of Total Fair Value	6.40%		12.10%		13.90%
[1]	The total fair value of the portfolio at September 30, 2013 and 2012, and December 31, 2012 included $1.3 billion, $1.6 billion, and $1.4 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company.
[2]	At September 30, 2013, we had $63.7 million of net unsettled security transactions, including collateral on open derivative positions, recognized in other liabilities, compared to $32.4 million and $90.9 million recognized in other assets at September 30, 2012 and December 31, 2012, respectively.
[3]	Represents net holding period gains (losses) on certain hybrid securities (discussed below).
[4]	Reflects an Australian government obligation at September 30, 2013.

Investment_Portfolio_by_Major_1

Investment Portfolio by Major Security Type (Parenthetical) (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Net unsettled security transactions offset in other liabilities	$63,700,000	'	'
Net unsettled security transactions offset in other assets	'	90,900,000	32,400,000
Securities in the portfolio of a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions	$1,300,000,000	$1,400,000,000	$1,600,000,000

Investments_Additional_Informa

Investments - Additional Information (Detail) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

1 Months Ended

3 Months Ended

9 Months Ended

6 Months Ended

6 Months Ended

3 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

In Millions, unless otherwise specified

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Jun. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

Corporate Credit Default Swaps

Corporate Credit Default Swaps

Corporate Credit Default Swaps

Corporate Credit Default Swaps

Interest rate swaps

Interest rate swaps

Interest rate swaps

Interest rate swaps

Interest rate swaps

Interest rate swaps

Interest rate swaps

Interest rate swaps

Categories of Investments, Marketable Securities, Trading Securities

Categories of Investments, Marketable Securities, Trading Securities

Categories of Investments, Marketable Securities, Trading Securities

Categories of Investments, Marketable Securities, Trading Securities

Fixed Income Securities

Equity securities

Equity securities

Equity securities

Equity securities

Equity securities

Equity securities

Equity securities

Equity securities

Fixed maturities

Fixed maturities

Fixed maturities

Fixed maturities

Fixed maturities

Fixed maturities

Interest rate swaps

Interest rate swaps

Interest rate swaps

Interest rate swaps

Interest rate swaps

Interest rate swaps

Interest rate swaps

Interest rate swaps

Interest rate swaps

Net unrealized gains on forecasted transactions

Net unrealized gains on forecasted transactions

Net unrealized gains on forecasted transactions

Net unrealized gains on forecasted transactions

Net unrealized gains on forecasted transactions

Financial Services Sector

Financial Services Sector

Financial Services Sector

Financial Services Sector

Opened in 2013

Opened in 2013

Opened in 2009

Opened in 2011

Common equities

Common equities

Common equities

Russell One Thousand

Managed Equity Strategy

Corporate debt securities

Corporate debt securities

Corporate debt securities

Non-hedging Instruments

Non-hedging Instruments

Non-hedging Instruments

Non-hedging Instruments

Non-hedging Instruments

Non-hedging Instruments

Non-hedging Instruments

Non-hedging Instruments

Non-hedging Instruments

Ten Year Time Horizon

Ten Year Time Horizon

Closed Positions

Closed Positions

Common equities

Common equities

Closed Positions

Closed Positions

Closed Positions

Other Liabilities

Other Liabilities

Other Liabilities

Fixed maturities

Fixed maturities

Fixed maturities

Nine Year Time Horizon

Five Year Time Horizon

Liabilities

Liabilities

Liabilities

Assets

Assets

Assets

Schedule of Investments [Line Items]

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Open reverse repurchase commitments

$278.10

$798.10

$278.10

$798.10

$581

'

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Percentage which the issuer receives the security back at once the change of control is triggered

'

'

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'

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'

'

'

'

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1.00%

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Realized investment losses

'

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12.3

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Gross unrealized losses

129

35.3

129

35.3

34

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'

124

9.8

10.3

6.1

5

10.3

6.1

'

'

119.2

23.7

29.2

28.9

1

0.4

'

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'

'

Percentage of common stock portfolio

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88.00%

12.00%

'

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'

'

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'

'

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'

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'

'

'

'

'

Trading securities

0

0

0

0

0

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Net realized gains (losses) on securities

29.8

172.3

245.1

251.4

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0

0

0

0

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Repurchase of debt, face amount

'

'

'

'

'

54.1

0.5

54.1

30.9

30.9

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Cash flow hedge gain reclassification from accumulated other comprehensive income to net realized gains/losses on securities

'

'

'

'

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'

0.8

0

0.8

0.6

0.6

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'

Number of derivative positions opened during the period

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3

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Derivative maturity, term

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'5 years

'

'5 years

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'10 years

'9 years

'5 years

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Derivative Assets (Liabilities), at Fair Value, Net

-53.5

[1]

101.3

[1]

-53.5

[1]

101.3

[1]

95.5

[1]

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-53.5

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0

[1]

0

[1]

0

[1]

0

[1]

95.5

[1]

101.6

[1]

-53.5

[1]

0

[1]

0

[1]

Notional Value

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1,263

[2]

0

[2]

0

[2]

0

[2]

1,263

[2]

1,263

[2]

750

[2]

0

[2]

0

[2]

Number of derivative positions closed during the period

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3

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1

2

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Cash collateral delivered to the counterparties

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105

107.2

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Number of derivative positions held during the period

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0

1

0

1

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Cash collateral received from counterparties

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$0.30

'

$0.30

'

$49.30

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[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.

Hybrid_Securities_Detail

Hybrid Securities (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
In Millions, unless otherwise specified
Hybrid Securities [Line Items]	'	'	'
Hybrid securities	$244.40	$245.30	$244.40
Fixed maturities	'	'	'
Hybrid Securities [Line Items]	'	'	'
Hybrid securities	187.1	192.5	193.9
Fixed maturities | Corporate debt securities	'	'	'
Hybrid Securities [Line Items]	'	'	'
Hybrid securities	171.8	176.1	177.5
Fixed maturities | Other asset-backed securities	'	'	'
Hybrid Securities [Line Items]	'	'	'
Hybrid securities	15.3	16.4	16.4
Equity securities | Nonredeemable preferred stocks	'	'	'
Hybrid Securities [Line Items]	'	'	'
Hybrid securities	$57.30	$52.80	$50.50

Composition_of_Fixed_Maturitie

Composition of Fixed Maturities by Maturity (Detail) (USD $)	Sep. 30, 2013
In Millions, unless otherwise specified
Available for sale, cost	'
Less than one year	$2,032.10
One to five years	8,610.30
Five to ten years	2,834.80
Ten years or greater	114.2
Total	13,591.40	[1]
Available for sale, Fair value	'
Less than one year	2,063.10
One to five years	8,767.30
Five to ten years	2,794.50
Ten years or greater	119.3
Total	$13,744.20	[1]
[1]	Excludes $53.5 million related to our open interest rate swap positions.

Composition_of_Fixed_Maturitie1

Composition of Fixed Maturities by Maturity (Parenthetical) (Detail) (USD $)	Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2012
In Millions, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Open interest rate swap positions	$53.50	[1]	($95.50)	[1]	($101.30)	[1]
Interest rate swaps	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Open interest rate swap positions	$53.50		'		'
[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.

Gross_Unrealized_losses_by_Maj

Gross Unrealized losses by Major Security (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
In Millions, unless otherwise specified
Investments, Unrealized Loss Position [Line Items]	'	'	'
Total Fair Value	$5,140	$746.20	$667.50
Gross Unrealized Losses	-129	-34	-35.3
Less than 12 Months Fair Value	4,813.50	440	275.9
Less than 12 Months Unrealized Losses	-113.1	-10.3	-4.8
12 Months or Greater Fair Value	326.5	306.2	391.6
12 Months or Greater Unrealized Losses	-15.9	-23.7	-30.5
Fixed maturities	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Total Fair Value	4,969.10	628	586.7
Gross Unrealized Losses	-119.2	-23.7	-29.2
Less than 12 Months Fair Value	4,646.90	339.3	221.5
Less than 12 Months Unrealized Losses	-103.6	-2.1	-1.4
12 Months or Greater Fair Value	322.2	288.7	365.2
12 Months or Greater Unrealized Losses	-15.6	-21.6	-27.8
Fixed maturities | U.S. government obligations	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Total Fair Value	969.1	0	83.1
Gross Unrealized Losses	-11.3	0	-0.1
Less than 12 Months Fair Value	969.1	0	83.1
Less than 12 Months Unrealized Losses	-11.3	0	-0.1
12 Months or Greater Fair Value	0	0	0
12 Months or Greater Unrealized Losses	0	0	0
Fixed maturities | State and local government obligations	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Total Fair Value	728.3	162.8	61.4
Gross Unrealized Losses	-17	-0.6	-0.4
Less than 12 Months Fair Value	666.7	123.1	29.1
Less than 12 Months Unrealized Losses	-16.2	-0.5	-0.2
12 Months or Greater Fair Value	61.6	39.7	32.3
12 Months or Greater Unrealized Losses	-0.8	-0.1	-0.2
Fixed maturities | Corporate debt securities	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Total Fair Value	1,174.20	128.2	35.9
Gross Unrealized Losses	-28.9	-1	-0.4
Less than 12 Months Fair Value	1,113.40	128.2	14.2
Less than 12 Months Unrealized Losses	-28.5	-1	-0.1
12 Months or Greater Fair Value	60.8	0	21.7
12 Months or Greater Unrealized Losses	-0.4	0	-0.3
Fixed maturities | Residential mortgage-backed securities	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Total Fair Value	663	149.2	177.2
Gross Unrealized Losses	-16.5	-9.2	-12.4
Less than 12 Months Fair Value	585.5	40.2	30
Less than 12 Months Unrealized Losses	-12.4	-0.6	-0.5
12 Months or Greater Fair Value	77.5	109	147.2
12 Months or Greater Unrealized Losses	-4.1	-8.6	-11.9
Fixed maturities | Commercial mortgage-backed securities	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Total Fair Value	993.3	7.1	44
Gross Unrealized Losses	-33.1	-0.1	-1.3
Less than 12 Months Fair Value	993.2	2.1	31.4
Less than 12 Months Unrealized Losses	-33	0	-0.1
12 Months or Greater Fair Value	0.1	5	12.6
12 Months or Greater Unrealized Losses	-0.1	-0.1	-1.2
Fixed maturities | Other asset-backed securities	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Total Fair Value	282.8	25	21
Gross Unrealized Losses	-2	-0.1	-0.1
Less than 12 Months Fair Value	282.8	20.8	9
Less than 12 Months Unrealized Losses	-2	0	0
12 Months or Greater Fair Value	0	4.2	12
12 Months or Greater Unrealized Losses	0	-0.1	-0.1
Fixed maturities | Redeemable preferred stocks	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Total Fair Value	158.4	155.7	164.1
Gross Unrealized Losses	-10.4	-12.7	-14.5
Less than 12 Months Fair Value	36.2	24.9	24.7
Less than 12 Months Unrealized Losses	-0.2	0	-0.4
12 Months or Greater Fair Value	122.2	130.8	139.4
12 Months or Greater Unrealized Losses	-10.2	-12.7	-14.1
Equity securities	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Total Fair Value	170.9	118.2	80.8
Gross Unrealized Losses	-9.8	-10.3	-6.1
Less than 12 Months Fair Value	166.6	100.7	54.4
Less than 12 Months Unrealized Losses	-9.5	-8.2	-3.4
12 Months or Greater Fair Value	4.3	17.5	26.4
12 Months or Greater Unrealized Losses	-0.3	-2.1	-2.7
Equity securities | Nonredeemable preferred stocks	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Total Fair Value	123.6	0	0
Gross Unrealized Losses	-4.8	0	0
Less than 12 Months Fair Value	123.6	0	0
Less than 12 Months Unrealized Losses	-4.8	0	0
12 Months or Greater Fair Value	0	0	0
12 Months or Greater Unrealized Losses	0	0	0
Equity securities | Common equities	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Total Fair Value	47.3	118.2	80.8
Gross Unrealized Losses	-5	-10.3	-6.1
Less than 12 Months Fair Value	43	100.7	54.4
Less than 12 Months Unrealized Losses	-4.7	-8.2	-3.4
12 Months or Greater Fair Value	4.3	17.5	26.4
12 Months or Greater Unrealized Losses	($0.30)	($2.10)	($2.70)

Total_NonCredit_Portion_of_Oth

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 $)	9 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
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	($45)	($45.10)	($45.10)
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	-44.1	-44.2	-44.2
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	($0.90)	($0.90)	($0.90)

OTTI_Credit_Losses_Recognized_

OTTI Credit Losses Recognized in Earnings (Detail) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]	'		'		'		'
Beginning balance	$27.40		$28.80		$27.70		$35.80
Credit losses for which an OTTI was previously recognized	0		0		0		0.1
Credit losses for which an OTTI was not previously recognized	0		0		0		0.2
Reductions for securities sold/matured	0		0		0		-0.2
Change in recoveries of future cash flows expected to be collected	-2.5	[1]	-0.5	[1]	-2.6	[1]	-3.3	[1]
Reductions for previously recognized credit impairments written-down to fair value	0	[2]	0	[2]	-0.2	[2]	-4.3	[2]
Ending balance	24.9		28.3		24.9		28.3
Residential mortgage-backed securities	'		'		'		'
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]	'		'		'		'
Beginning balance	26.9		28.1		27.1		34.5
Credit losses for which an OTTI was previously recognized	0		0		0		0.1
Credit losses for which an OTTI was not previously recognized	0		0		0		0.2
Reductions for securities sold/matured	0		0		0		0
Change in recoveries of future cash flows expected to be collected	-2.4	[1]	-0.4	[1]	-2.4	[1]	-3.1	[1]
Reductions for previously recognized credit impairments written-down to fair value	0	[2]	0	[2]	-0.2	[2]	-4	[2]
Ending balance	24.5		27.7		24.5		27.7
Commercial mortgage-backed securities	'		'		'		'
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]	'		'		'		'
Beginning balance	0.5		0.7		0.6		1.3
Credit losses for which an OTTI was previously recognized	0		0		0		0
Credit losses for which an OTTI was not previously recognized	0		0		0		0
Reductions for securities sold/matured	0		0		0		-0.2
Change in recoveries of future cash flows expected to be collected	-0.1	[1]	-0.1	[1]	-0.2	[1]	-0.2	[1]
Reductions for previously recognized credit impairments written-down to fair value	0	[2]	0	[2]	0	[2]	-0.3	[2]
Ending balance	$0.40		$0.60		$0.40		$0.60
[1]	Reflects expected recovery of prior period impairments that will be accreted into income over the remaining life of the security, net of any current quarter decreases in expected cash flows on previously recorded reductions.
[2]	Reflects reductions of prior credit impairments where the current credit impairment requires writing securities down to fair value (i.e., no remaining non-credit loss).

Components_of_Net_Realized_Gai

Components of Net Realized Gains (Losses) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Gain (Loss) on Investments [Line Items]	'	'	'	'
Gross realized gains on securities sales	$28.20	$208.30	$202	$307.70
Gross realized losses on securities sales	-3	-25	-6.5	-30.4
Net realized gains (losses) on securities sales	25.2	183.3	195.5	277.3
Other-than-temporary impairment losses	-1.9	-0.4	-3.7	-2.2
Total net realized gains (losses) on securities	27.9	171.9	241.4	244.7
Fixed maturities	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Gross realized gains on securities sales	5.2	34.3	62.8	87
Gross realized losses on securities sales	-2.9	-1.4	-6.1	-2.3
Net realized gains (losses) on securities sales	2.3	32.9	56.7	84.7
Other-than-temporary impairment losses	-0.1	-0.4	-0.5	-1.5
Fixed maturities | U.S. government obligations	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Gross realized gains on securities sales	3.1	0.2	6.8	9.8
Gross realized losses on securities sales	-0.8	-0.5	-2.2	-1.4
Net realized gains (losses) on securities sales	2.3	-0.3	4.6	8.4
Fixed maturities | State and local government obligations	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Gross realized gains on securities sales	0	0	6.8	12.1
Net realized gains (losses) on securities sales	0	0	6.8	12.1
Fixed maturities | Corporate And Other Debt Securities	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Gross realized gains on securities sales	1.7	23	38.4	49.1
Gross realized losses on securities sales	-2.1	-0.6	-3.1	-0.6
Net realized gains (losses) on securities sales	-0.4	22.4	35.3	48.5
Fixed maturities | Residential mortgage-backed securities	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Gross realized gains on securities sales	0.3	0.6	2.4	0.6
Net realized gains (losses) on securities sales	0.3	0.6	2.4	0.6
Other-than-temporary impairment losses	-0.1	-0.4	-0.5	-1.4
Fixed maturities | Commercial mortgage-backed securities	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Gross realized gains on securities sales	0.1	9.5	8.4	14
Gross realized losses on securities sales	0	0	-0.7	0
Net realized gains (losses) on securities sales	0.1	9.5	7.7	14
Other-than-temporary impairment losses	0	0	0	-0.1
Fixed maturities | Other asset-backed securities	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Gross realized gains on securities sales	0	0.9	0	0.9
Net realized gains (losses) on securities sales	0	0.9	0	0.9
Fixed maturities | Redeemable preferred stocks	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Gross realized gains on securities sales	0	0.1	0	0.5
Gross realized losses on securities sales	0	-0.3	-0.1	-0.3
Net realized gains (losses) on securities sales	0	-0.2	-0.1	0.2
Equity securities | Nonredeemable preferred stocks	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Gross realized gains on securities sales	11.9	20.6	113.1	57.5
Gross realized losses on securities sales	0	-1.1	0	-1.1
Net realized gains (losses) on securities sales	11.9	19.5	113.1	56.4
Equity securities | Common equities	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Gross realized gains on securities sales	11.1	153.4	26.1	163.2
Gross realized losses on securities sales	-0.1	-22.5	-0.4	-27
Net realized gains (losses) on securities sales	11	130.9	25.7	136.2
Other-than-temporary impairment losses	-1.8	0	-3.2	-0.7
Hybrid and Derivative Instruments and Litigation Settlements	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Other gains (losses)	4.6	-11	49.6	-30.4
Hybrid and Derivative Instruments and Litigation Settlements | Hybrid Preferred Stock	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Other gains (losses)	3.5	5.2	2.3	12.1
Hybrid and Derivative Instruments and Litigation Settlements | Derivative Instruments	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Other gains (losses)	-1.2	-16.3	45	-42.8
Hybrid and Derivative Instruments and Litigation Settlements | Litigation Settlements	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Other gains (losses)	$2.30	$0.10	$2.30	$0.30

Derivative_Instruments_Detail

Derivative Instruments (Detail) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
Derivative [Line Items]	'		'		'		'		'
Balance Sheet - Fair Value	$53.50	[1]	($101.30)	[1]	$53.50	[1]	($101.30)	[1]	($95.50)	[1]
Income Statement - Net Realized Gain (Loss) on Securities	-1.2		-16.3		45		-42.8		'
Designated as Hedging Instruments | Closed Positions | Ineffective Cash Flow Hedge	'		'		'		'		'
Derivative [Line Items]	'		'		'		'		'
Notional Value	54	[2]	31	[2]	54	[2]	31	[2]	31	[2]
Purpose	'		'		'Manage interest  rate risk		'		'
Balance Sheet - Fair Value	0	[1]	0	[1]	0	[1]	0	[1]	0	[1]
Income Statement - Net Realized Gain (Loss) on Securities	0.8		0		0.8		0.6		'
Non-hedging Instruments | Closed Positions | Interest rate swaps	'		'		'		'		'
Derivative [Line Items]	'		'		'		'		'
Notional Value	1,263	[2]	0	[2]	1,263	[2]	0	[2]	0	[2]
Purpose	'		'		'Manage portfolio duration		'		'
Balance Sheet - Fair Value	0	[1]	0	[1]	0	[1]	0	[1]	0	[1]
Income Statement - Net Realized Gain (Loss) on Securities	0		0		-4		0		'
Non-hedging Instruments | Closed Positions | Corporate Credit Default Swaps	'		'		'		'		'
Derivative [Line Items]	'		'		'		'		'
Notional Value	0	[2]	0	[2]	0	[2]	0	[2]	25	[2]
Purpose	'		'		'Manage credit risk		'		'
Balance Sheet - Fair Value	0	[1]	0	[1]	0	[1]	0	[1]	0	[1]
Income Statement - Net Realized Gain (Loss) on Securities	0		0		0		0		'
Non-hedging Instruments | Assets | Interest rate swaps | Fixed maturities	'		'		'		'		'
Derivative [Line Items]	'		'		'		'		'
Notional Value	750	[2]	0	[2]	750	[2]	0	[2]	0	[2]
Purpose	'		'		'Manage portfolio duration		'		'
Balance Sheet - Fair Value	53.5	[1]	0	[1]	53.5	[1]	0	[1]	0	[1]
Income Statement - Net Realized Gain (Loss) on Securities	-2		0		48.2		0		'
Non-hedging Instruments | Assets | Corporate Credit Default Swaps | Fixed maturities	'		'		'		'		'
Derivative [Line Items]	'		'		'		'		'
Notional Value	0	[2]	25	[2]	0	[2]	25	[2]	0	[2]
Purpose	'		'		'Manage credit risk		'		'
Balance Sheet - Fair Value	0	[1]	0.3	[1]	0	[1]	0.3	[1]	0	[1]
Income Statement - Net Realized Gain (Loss) on Securities	0		-0.4		0		-0.7		'
Non-hedging Instruments | Liabilities | Interest rate swaps | Other Liabilities	'		'		'		'		'
Derivative [Line Items]	'		'		'		'		'
Notional Value	0	[2]	1,263	[2]	0	[2]	1,263	[2]	1,263	[2]
Purpose	'		'		'Manage portfolio duration		'		'
Balance Sheet - Fair Value	0	[1]	-101.6	[1]	0	[1]	-101.6	[1]	-95.5	[1]
Income Statement - Net Realized Gain (Loss) on Securities	$0		($15.90)		$0		($42.70)		'
[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.

Composition_of_Investment_Port

Composition of Investment Portfolio by Major Security Type (Detail) (USD $)	Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2012
In Millions, unless otherwise specified
Fair Value Measurements [Line Items]	'		'		'
Portfolio	$17,995.90	[1],[2]	$16,475.50	[1],[2]	$17,176.90	[1],[2]
Debt	2,231.40		2,394.40		2,405.90
Fixed maturities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	13,797.70		11,774.10		12,295.20
Fixed maturities | Redeemable preferred stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	345.1		374.7		380.6
Fixed maturities | Redeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	134.2		129.7		133.9
Fixed maturities | Redeemable preferred stocks | Utilities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	65.3		66.7		66.9
Fixed maturities | Redeemable preferred stocks | Industrials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	145.6		178.3		179.8
Fixed maturities | Debt Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	9,053.80		7,973.90		8,326
Fixed maturities | Debt Securities | U.S. government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	3,741.70		2,896.50		3,544
Fixed maturities | Debt Securities | State and local government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,138.60		1,964.40		1,959.50
Fixed maturities | Debt Securities | Foreign government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	15.9		0		0
Fixed maturities | Debt Securities | Corporate debt securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	3,157.60		3,113		2,822.50
Fixed maturities | Asset-backed Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	4,398.80		3,425.50		3,588.60
Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	1,009.90		428.2		408.7
Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,240		2,048.70		2,087.60
Fixed maturities | Asset-backed Securities | Other asset-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	1,148.90		948.6		1,092.30
Equity securities | Nonredeemable preferred stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	726		812.4		848.4
Equity securities | Nonredeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	709.2		786		818.9
Equity securities | Nonredeemable preferred stocks | Utilities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	16.8		26.4		29.5
Equity securities | Common equities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,326.10		1,899		1,639.20
Equity securities | Common equities | Common Stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,287.40		1,887		1,627.20
Equity securities | Common equities | Other risk investments	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	38.7		12		12
Total Fixed Maturities and Equity Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	16,849.80		14,485.50		14,782.80
Short-term investments	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	1,146.10		1,990		2,394.10
Fair Value, Inputs, Level 1	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	7,040.50		6,723		7,557.10
Debt	0		0		0
Fair Value, Inputs, Level 1 | Fixed maturities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	3,757.60		2,896.50		3,544
Fair Value, Inputs, Level 1 | Fixed maturities | Redeemable preferred stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 1 | Fixed maturities | Redeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 1 | Fixed maturities | Redeemable preferred stocks | Utilities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 1 | Fixed maturities | Redeemable preferred stocks | Industrials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 1 | Fixed maturities | Debt Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	3,757.60		2,896.50		3,544
Fair Value, Inputs, Level 1 | Fixed maturities | Debt Securities | U.S. government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	3,741.70		2,896.50		3,544
Fair Value, Inputs, Level 1 | Fixed maturities | Debt Securities | State and local government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 1 | Fixed maturities | Debt Securities | Foreign government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	15.9		0		0
Fair Value, Inputs, Level 1 | Fixed maturities | Debt Securities | Corporate debt securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 1 | Fixed maturities | Asset-backed Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 1 | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 1 | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 1 | Fixed maturities | Asset-backed Securities | Other asset-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 1 | Equity securities | Nonredeemable preferred stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	244		259.6		265.2
Fair Value, Inputs, Level 1 | Equity securities | Nonredeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	244		259.6		265.2
Fair Value, Inputs, Level 1 | Equity securities | Nonredeemable preferred stocks | Utilities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 1 | Equity securities | Common equities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,287.40		1,887		1,627.20
Fair Value, Inputs, Level 1 | Equity securities | Common equities | Common Stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,287.40		1,887		1,627.20
Fair Value, Inputs, Level 1 | Equity securities | Common equities | Other risk investments	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 1 | Total Fixed Maturities and Equity Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	6,289		5,043.10		5,436.40
Fair Value, Inputs, Level 1 | Short-term investments	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	751.5		1,679.90		2,120.70
Fair Value, Inputs, Level 2	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	10,849.10		9,637.80		9,505.70
Debt	2,231.40		2,394.40		2,405.90
Fair Value, Inputs, Level 2 | Fixed maturities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	10,008.60		8,806.80		8,678.40
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	345.1		374.7		380.6
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	134.2		129.7		133.9
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks | Utilities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	65.3		66.7		66.9
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks | Industrials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	145.6		178.3		179.8
Fair Value, Inputs, Level 2 | Fixed maturities | Debt Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	5,296.20		5,077.40		4,782
Fair Value, Inputs, Level 2 | Fixed maturities | Debt Securities | U.S. government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 2 | Fixed maturities | Debt Securities | State and local government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,138.60		1,964.40		1,959.50
Fair Value, Inputs, Level 2 | Fixed maturities | Debt Securities | Foreign government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 2 | Fixed maturities | Debt Securities | Corporate debt securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	3,157.60		3,113		2,822.50
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	4,367.30		3,354.70		3,515.80
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	1,009.70		382.7		358.8
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,208.70		2,023.40		2,065
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities | Other asset-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	1,148.90		948.6		1,092
Fair Value, Inputs, Level 2 | Equity securities | Nonredeemable preferred stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	445.9		520.9		553.9
Fair Value, Inputs, Level 2 | Equity securities | Nonredeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	429.1		494.5		524.4
Fair Value, Inputs, Level 2 | Equity securities | Nonredeemable preferred stocks | Utilities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	16.8		26.4		29.5
Fair Value, Inputs, Level 2 | Equity securities | Common equities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 2 | Equity securities | Common equities | Common Stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 2 | Equity securities | Common equities | Other risk investments	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 2 | Total Fixed Maturities and Equity Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	10,454.50		9,327.70		9,232.30
Fair Value, Inputs, Level 2 | Short-term investments	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	394.6		310.1		273.4
Fair Value, Inputs, Level 3	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	106.3		114.7		114.1
Debt	0		0		0
Fair Value, Inputs, Level 3 | Fixed maturities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	31.5		70.8		72.8
Fair Value, Inputs, Level 3 | Fixed maturities | Redeemable preferred stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 3 | Fixed maturities | Redeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 3 | Fixed maturities | Redeemable preferred stocks | Utilities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 3 | Fixed maturities | Redeemable preferred stocks | Industrials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 3 | Fixed maturities | Debt Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 3 | Fixed maturities | Debt Securities | U.S. government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 3 | Fixed maturities | Debt Securities | State and local government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 3 | Fixed maturities | Debt Securities | Foreign government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 3 | Fixed maturities | Debt Securities | Corporate debt securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	31.5		70.8		72.8
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0.2		45.5		49.9
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	31.3		25.3		22.6
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Other asset-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0.3
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	36.1		31.9		29.3
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	36.1		31.9		29.3
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks | Utilities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 3 | Equity securities | Common equities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	38.7		12		12
Fair Value, Inputs, Level 3 | Equity securities | Common equities | Common Stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 3 | Equity securities | Common equities | Other risk investments	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	38.7		12		12
Fair Value, Inputs, Level 3 | Total Fixed Maturities and Equity Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	106.3		114.7		114.1
Fair Value, Inputs, Level 3 | Short-term investments	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Carrying (Reported) Amount, Fair Value Disclosure	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	16,655.40		15,138.20		15,789.70
Debt	2,010.60		2,063.10		2,062.70
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	13,644.90		11,373.90		11,864
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	331		356.9		368
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	115.7		110.7		120.8
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks | Utilities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	64.9		64.9		65.9
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks | Industrials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	150.4		181.3		181.3
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	8,951.60		7,703.70		8,020.40
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities | U.S. government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	3,691.20		2,806.40		3,433.70
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities | State and local government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,125.70		1,914.40		1,898.90
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities | Foreign government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	15.9		0		0
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities | Corporate debt securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	3,118.80		2,982.90		2,687.80
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	4,362.30		3,313.30		3,475.60
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	994.9		413.4		399.5
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,224.10		1,963.90		1,998.20
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities | Other asset-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	1,143.30		936		1,077.90
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Nonredeemable preferred stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	442.1		404		430.1
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Nonredeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	427.9		383.3		407.3
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Nonredeemable preferred stocks | Utilities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	14.2		20.7		22.8
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	1,422.30		1,370.30		1,101.50
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities | Common Stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	1,419.20		1,367.20		1,098.30
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities | Other risk investments	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	3.1		3.1		3.2
Carrying (Reported) Amount, Fair Value Disclosure | Total Fixed Maturities and Equity Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	15,509.30		13,148.20		13,395.60
Carrying (Reported) Amount, Fair Value Disclosure | Short-term investments	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	$1,146.10		$1,990		$2,394.10
[1]	The total fair value of the portfolio at September 30, 2013 and 2012, and December 31, 2012 included $1.3 billion, $1.6 billion, and $1.4 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company.
[2]	At September 30, 2013, we had $63.7 million of net unsettled security transactions, including collateral on open derivative positions, recognized in other liabilities, compared to $32.4 million and $90.9 million recognized in other assets at September 30, 2012 and December 31, 2012, respectively.

Fair_Value_Additional_Informat

Fair Value - Additional Information (Detail) (USD $)

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

In Millions, unless otherwise specified

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 1

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 2

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

InvestmentPortfolio [Member]

InvestmentPortfolio [Member]

Redeemable preferred stocks

Nonredeemable preferred stocks

Nonredeemable preferred stocks

Nonredeemable preferred stocks

Common equities

Common equities

Common equities

Financials

Financials

Financials

Vendor Quoted Pricing

Vendor Quoted Pricing

Vendor Quoted Pricing

Vendor Quoted Pricing

Vendor Quoted Pricing

Vendor Quoted Pricing

Dealer Quoted Pricing

Dealer Quoted Pricing

Dealer Quoted Pricing

Fixed maturities

Fixed maturities

Fixed maturities

Investment

Investment

Fixed maturities

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Nonredeemable preferred stocks

Nonredeemable preferred stocks

Nonredeemable preferred stocks

Internal Pricing

Internal Pricing

Internal Pricing

Investment

Equity securities

Equity securities

Equity securities

Equity securities

Equity securities

Equity securities

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Investment

Investment

Investment

Internal Pricing

Internal Pricing

Internal Pricing

Internal Pricing

Internal Pricing

Internal Pricing

Equity securities

Equity securities

Equity securities

Investment

Investment

Investment

Investment

Investment

Investment

Internal Pricing

Internal Pricing

Internal Pricing

Fair Value Measurements [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of security transferred out of Level 1 into Level 2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0

0

1

'

'

'

'

'

'

'

'

'

Transferred out of Level 1 into Level 2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$25

'

'

'

'

'

'

'

'

'

Quoted prices percentage of fair value assets

100.00%

[1],[2]

100.00%

[1],[2]

100.00%

[1],[2]

'

'

'

59.00%

57.00%

65.00%

'

'

'

97.00%

98.00%

96.00%

3.00%

2.00%

4.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of securities

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0

0

0

'

'

'

1

1

1

1

1

1

'

'

'

Portfolio

$17,995.90

[1],[2]

$16,475.50

[1],[2]

$17,176.90

[1],[2]

$7,040.50

$6,723

$7,557.10

'

'

'

$10,849.10

$9,637.80

$9,505.70

'

'

'

'

'

'

$106.30

$114.70

$114.10

'

'

'

'

'

'

$36.10

$31.90

$29.30

$38

$11.20

$11.20

$36.10

$31.90

$29.30

[1]

The total fair value of the portfolio at September 30, 2013 and 2012, and December 31, 2012 included $1.3 billion, $1.6 billion, and $1.4 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company.

[2]

At September 30, 2013, we had $63.7 million of net unsettled security transactions, including collateral on open derivative positions, recognized in other liabilities, compared to $32.4 million and $90.9 million recognized in other assets at September 30, 2012 and December 31, 2012, respectively.

Summary_of_Changes_in_Fair_Val

Summary of Changes in Fair Value Associated With Level 3 Assets (Detail) (USD $)	3 Months Ended			9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'	'		'
Beginning Fair Value	$258.20		$91	$114.70		$97.70
Calls/Maturities/Paydowns	-17.3		-8.6	-29.8		-18
Purchases	0		28.5	125.4		28.5
Sales	0		0	0		0
Net Realized (gain)/loss on sales	0		0	-0.5		0
Change in Valuation	6.8		3.2	37.9		5.9
Net Transfers in (out)	-141.4		0	-141.4		0
Ending Fair value	106.3		114.1	106.3		114.1
Equity securities | Nonredeemable preferred stocks | Financials	'		'	'		'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'	'		'
Beginning Fair Value	34.8	[1]	0	31.9	[2]	0
Calls/Maturities/Paydowns	0	[1]	0	0	[2]	0
Purchases	0	[1]	28.5	0	[2]	28.5
Sales	0	[1]	0	0	[2]	0
Net Realized (gain)/loss on sales	0	[1]	0	0	[2]	0
Change in Valuation	1.3	[1]	0.8	4.2	[2]	0.8
Net Transfers in (out)	0	[1]	0	0	[2]	0
Ending Fair value	36.1	[1],[2]	29.3	36.1	[1],[2]	29.3
Equity securities | Common equities | Other risk investments	'		'	'		'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'	'		'
Beginning Fair Value	38.7		12.2	12		11.5
Calls/Maturities/Paydowns	0		-0.2	-0.1		-0.2
Purchases	0		0	0.3		0
Sales	0		0	0		0
Net Realized (gain)/loss on sales	0		0	-0.5		0
Change in Valuation	0		0	27		0.7
Net Transfers in (out)	0		0	0		0
Ending Fair value	38.7		12	38.7		12
Fixed maturities	'		'	'		'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'	'		'
Beginning Fair Value	184.7		78.8	70.8		86.2
Calls/Maturities/Paydowns	-17.3		-8.4	-29.7		-17.8
Purchases	0		0	125.1		0
Sales	0		0	0		0
Net Realized (gain)/loss on sales	0		0	0		0
Change in Valuation	5.5		2.4	6.7		4.4
Net Transfers in (out)	-141.4		0	-141.4		0
Ending Fair value	31.5		72.8	31.5		72.8
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	157.1		54.5	45.5		62.3
Calls/Maturities/Paydowns	-17		-5	-28.6		-12.8
Purchases	0		0	125.1		0
Sales	0		0	0		0
Net Realized (gain)/loss on sales	0		0	0		0
Change in Valuation	1.5		0.4	-0.4		0.4
Net Transfers in (out)	-141.4		0	-141.4		0
Ending Fair value	0.2		49.9	0.2		49.9
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	27.6		23.2	25.3		21.3
Calls/Maturities/Paydowns	-0.3		-2.6	-1.1		-2.7
Purchases	0		0	0		0
Sales	0		0	0		0
Net Realized (gain)/loss on sales	0		0	0		0
Change in Valuation	4		2	7.1		4
Net Transfers in (out)	0		0	0		0
Ending Fair value	31.3		22.6	31.3		22.6
Fixed maturities | Asset-backed Securities | Other asset-backed securities	'		'	'		'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'	'		'
Beginning Fair Value	0		1.1	0		2.6
Calls/Maturities/Paydowns	0		-0.8	0		-2.3
Purchases	0		0	0		0
Sales	0		0	0		0
Net Realized (gain)/loss on sales	0		0	0		0
Change in Valuation	0		0	0		0
Net Transfers in (out)	0		0	0		0
Ending Fair value	$0		$0.30	$0		$0.30
[1]	The $1.3 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.
[2]	The $4.2 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_Changes_in_Fair_Val1

Summary of Changes in Fair Value Associated With Level 3 Assets (Parenthetical) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'	'	'
Net realized gains (losses) on securities	$29.80	$172.30	$245.10	$251.40
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	1.3	0.8	4.2	0.8
Asset-backed Securities | Fixed maturities | Residential mortgage-backed securities	'	'	'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'	'	'
Transfer out of Level 3 and into Level 2	($141.40)	'	($141.40)	'

Summary_of_Quantitative_Inform

Summary of Quantitative Information about Level 3 Fair Value Measurements (Detail) (USD $)	9 Months Ended				12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Fair Value	$17,995.90	[1],[2]	$17,176.90	[1],[2]	$16,475.50	[1],[2]
Fair Value, Inputs, Level 3	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Fair Value	106.3		114.1		114.7
External Pricing | Fair Value, Inputs, Level 3 | Fixed maturities	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Fair Value	31.5		15.3		25.5
External Pricing | Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities | Prepayment Rate Zero Percent	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Number of securities	1		2		'
Fair Value	0.2		15.3		'
Valuation Technique	'External vendor		'External vendor		'
Unobservable Input, prepayment rate	0.00%		0.00%		'
External Pricing | Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities | Prepayment Rate Sixteen Percent	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Number of securities	'		1		1
Fair Value	'		15.3		0.2
Valuation Technique	'		'External vendor		'External vendor
Unobservable Input, prepayment rate	'		16.00%		16.00%
External Pricing | Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Fair Value	'		0		'
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	2		'		3
Fair Value	31.3		'		25.3
Valuation Technique	'External vendor		'		'External vendor
Unobservable Input, prepayment rate	0.00%		'		0.00%
Internal Pricing | Fair Value, Inputs, Level 3 | Fixed maturities	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Number of securities	0		0		0
Internal Pricing | Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Number of securities	1		1		1
Fair Value	36.1		29.3		31.9
Internal Pricing | Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks | Financials	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Fair Value	36.1		29.3		31.9
Valuation Technique	'Multiple of tangible net book value		'Multiple of tangible net book value		'Multiple of tangible net book value
Unobservable Input, price to book ratio multiple	1.9		1.9		1.9
Internal Pricing | Fair Value, Inputs, Level 3 | Equity securities | Common equities	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Number of securities	1		1		1
Fair Value	38		11.2		11.2
Internal Pricing | Fair Value, Inputs, Level 3 | Equity securities | Common equities | Other risk investments	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Fair Value	0		11.2		11.2
Valuation Technique	'		'Discounted consolidated  equity		'Discounted consolidated equity
Unobservable Input, discount for lack of marketability	'		20.00%		20.00%
Subtotal Level 3 Securities | Fair Value, Inputs, Level 3	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Fair Value	67.6		55.8		68.6
Third Party Pricing Exemption Securities | Fair Value, Inputs, Level 3	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Fair Value	38.7	[3]	58.3	[4]	46.1	[4]
Third Party Pricing Exemption Securities | Fair Value, Inputs, Level 3 | Equity securities	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Fair Value	38		'		'
Third Party Pricing Exemption Securities | Fair Value, Inputs, Level 3 | Other Non Binding Externally Priced Securities	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Fair Value	$0.70		'		'
[1]	The total fair value of the portfolio at September 30, 2013 and 2012, and December 31, 2012 included $1.3 billion, $1.6 billion, and $1.4 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company.
[2]	At September 30, 2013, we had $63.7 million of net unsettled security transactions, including collateral on open derivative positions, recognized in other liabilities, compared to $32.4 million and $90.9 million recognized in other assets at September 30, 2012 and December 31, 2012, respectively.
[3]	The fair values for $0.7 million of these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us. The remaining $38.0 million reflects a negotiated sale on a private common equity security that is expected to be completed by the end of 2013.
[4]	The fair values for these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us.

Debt_Detail

Debt (Detail) (USD $)	Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2012
In Millions, unless otherwise specified
Debt Instrument [Line Items]	'		'		'
Carrying Value	$2,010.60	[1]	$2,063.10	[1]	$2,062.70	[1]
Fair Value	2,231.40		2,394.40		2,405.90
7% Notes due 2013	'		'		'
Debt Instrument [Line Items]	'		'		'
Carrying Value	150		149.9		149.8
Fair Value	150		157.1		159
3.75% Senior Notes due 2021	'		'		'
Debt Instrument [Line Items]	'		'		'
Carrying Value	497.5		497.3		497.3
Fair Value	516.7		549.1		551
6 5/8% Senior Notes due 2029	'		'		'
Debt Instrument [Line Items]	'		'		'
Carrying Value	295.3		295.2		295.1
Fair Value	362		385		393.7
6.25% Senior Notes due 2032	'		'		'
Debt Instrument [Line Items]	'		'		'
Carrying Value	394.6		394.5		394.5
Fair Value	478.2		513.5		521.7
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067	'		'		'
Debt Instrument [Line Items]	'		'		'
Carrying Value	673.2		726.2		726
Fair Value	$724.50		$789.70		$780.50
[1]	Consists of both short- and long-term debt. See Note 4 - Debt.

Debt_Additional_Information_De

Debt - Additional Information (Detail) (USD $)

3 Months Ended

9 Months Ended

1 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

In Millions, unless otherwise specified

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Oct. 31, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

7% Notes due 2013

7% Notes due 2013

3.75% Senior Notes due 2021

6 5/8% Senior Notes due 2029

6.25% Senior Notes due 2032

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067

Notes scheduled to be paid in 2013

Net unrealized gains on forecasted transactions

Net unrealized gains on forecasted transactions

Net unrealized gains on forecasted transactions

Net unrealized gains on forecasted transactions

Net unrealized gains on forecasted transactions

Subsequent Event [Member]

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt Instrument, Interest Rate, Stated Percentage

'

'

'

'

7.00%

'

3.75%

6.63%

6.25%

6.70%

'

6.70%

'

'

'

'

'

'

'

Repurchase of debt, face amount

'

'

'

'

'

'

'

'

'

$54.10

$0.50

$54.10

$30.90

$30.90

'

'

'

'

'

(Gains) losses on extinguishment of debt

4.3

0.1

4.3

1.8

'

'

'

'

'

4.3

0.1

4.3

1.8

1.8

'

'

'

'

'

Cash flow hedge gain reclassification from accumulated other comprehensive income to net realized gains/losses on securities

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.8

0

0.8

0.6

0.6

Payment of debt

'

'

$0

$350

'

$150

'

'

'

'

'

'

'

'

'

'

'

'

'

Supplemental_Cash_Flow_Informa2

Supplemental Cash Flow Information (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Schedule of Cash Flow, Supplemental [Line Items]	'	'
Income taxes, net of refunds	$340	$259.10
Interest	$81.90	$92.80

Operating_Results_Detail

Operating Results (Detail) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	$4,521.30		$4,423.90		$13,552.10		$12,733.30
Pretax Profit (Loss)	345		412.4		1,294.40		964.2
Underwriting Operations	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	4,303		4,054.80		12,759.30		11,912.40
Pretax Profit (Loss)	249.4		165.2		852.9		489
Underwriting Operations | Personal Lines	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	3,856.10	[1]	3,630.40	[1]	11,441.80	[1]	10,692.40	[1]
Pretax Profit (Loss)	229.3	[1]	158.2	[1]	788.9	[1]	431.1	[1]
Underwriting Operations | Personal Lines | Agency Channel	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	2,162.70		2,047.70		6,421.40		6,032.30
Pretax Profit (Loss)	122		52.3		428.4		237.9
Underwriting Operations | Personal Lines | Direct Channel	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	1,693.40		1,582.70		5,020.40		4,660.10
Pretax Profit (Loss)	107.3		105.9		360.5		193.2
Underwriting Operations | Commercial Auto	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	446.8		424.3		1,317.30		1,219.20
Pretax Profit (Loss)	26.3		7.5		73.7		61
Underwriting Operations | Other Indemnity	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	0.1		0.1		0.2		0.8
Pretax Profit (Loss)	-6.2		-0.5		-9.7		-3.1
Fees and Other Revenues	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	76	[2]	78.4	[2]	215.3	[2]	213.5	[2]
Service Businesses	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	11.3		9.9		30.3		28.3
Pretax Profit (Loss)	0.2		0.3		0.2		0.6
Investments	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	135.3	[3]	280.9	[3]	551.5	[3]	580.9	[3]
Pretax Profit (Loss)	130.1	[3]	277.6	[3]	537	[3]	569.6	[3]
Gains (losses) on extinguishment of debt	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	-4.3		-0.1		-4.3		-1.8
Pretax Profit (Loss)	-4.3		-0.1		-4.3		-1.8
Interest Expense	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Pretax Profit (Loss)	($30.40)		($30.60)		($91.40)		($93.20)
[1]	Personal auto insurance accounted for 91% of the total Personal Lines segment net premiums earned in all periods; 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 are allocated to operating segments.
[3]	Revenues represent recurring investment income and total net realized gains (losses) on securities; pretax profit is net of investment expenses.

Operating_Results_Parenthetica

Operating Results (Parenthetical) (Detail) (Personal Lines, Personal Auto, Underwriting Operations)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Personal Lines | Personal Auto | Underwriting Operations	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Personal auto insurance percentage of the total personal lines segment net premiums earned	91.00%	91.00%	91.00%	91.00%

Underwriting_Margins_and_Combi

Underwriting Margins and Combined Ratios for our Underwriting Operations (Detail) (Underwriting Operations)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting Information [Line Items]	'	'	'	'
Underwriting Margin	5.80%	4.10%	6.70%	4.10%
Combined Ratio	94.20%	95.90%	93.30%	95.90%
Personal Lines	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Underwriting Margin	5.90%	4.40%	6.90%	4.00%
Combined Ratio	94.10%	95.60%	93.10%	96.00%
Personal Lines | Agency Channel	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Underwriting Margin	5.60%	2.60%	6.70%	3.90%
Combined Ratio	94.40%	97.40%	93.30%	96.10%
Personal Lines | Direct Channel	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Underwriting Margin	6.30%	6.70%	7.20%	4.10%
Combined Ratio	93.70%	93.30%	92.80%	95.90%
Commercial Auto	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Underwriting Margin	5.90%	1.80%	5.60%	5.00%
Combined Ratio	94.10%	98.20%	94.40%	95.00%

Dividends_Additional_Informati

Dividends - Additional Information (Detail) (USD $)	1 Months Ended			3 Months Ended		9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Feb. 28, 2013	Nov. 30, 2012	Feb. 29, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Dividends Payable [Line Items]	'	'	'	'	'	'	'
Target percentage used to determine annual variable dividend	'	'	'	33.33%	'	33.33%	'
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	'	'	'	1.15	'	1.15	'
Comprehensive income	'	'	'	$289.10	$339.40	$865.50	$865.80
After-tax underwriting income	'	'	'	'	'	$554.40	'
Dividend paid	$0.28	$1	$0.41	'	'	'	'

Components_of_Other_Comprehens

Components of Other Comprehensive Income (Loss) Including Reclassification Adjustments by Income Statement (Detail) (USD $)	3 Months Ended			9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]	'		'	'		'
Pre tax total accumulated other comprehensive income, beginning balance	$1,252.60		'	$1,340		'
Investment securities, pre tax	111.9		'	192.6		'
Net non-credit related OTTI losses, adjusted for valuation changes, pre tax	0		'	0.4		'
Forecasted transactions, pre tax	0		'	0		'
Foreign currency translation adjustment, pre tax	-0.4		'	-1.9		'
Total other comprehensive income (loss) before reclassifications, pre tax	111.5		'	191.1		'
Total reclassification adjustment for amounts realized in net income, pre tax	24.3		'	191.3		'
Total other comprehensive income (loss), pre tax	87.2		'	-0.2		'
Pre tax total accumulated other comprehensive income, ending balance	1,339.80		'	1,339.80		'
Accumulated Other Comprehensive Income (Loss), Tax [Roll Forward]	'		'	'		'
Accumulated other comprehensive income loss tax (Provision) benefit, beginning balance	-438.4		'	-469		'
Investment securities, Total tax (provision) benefit	-39.2		'	-67.4		'
Net non-credit related OTTI losses, adjusted for valuation changes, Total tax (provision) benefit	0		'	-0.1		'
Forecasted transactions, Total tax (provision) benefit	0		'	0		'
Foreign currency translation adjustment, Total tax (provision) benefit	0.2		'	0.7		'
Total other comprehensive income (loss) before reclassifications, Total tax (provision) benefit	-39		'	-66.8		'
Total reclassification adjustment for amounts realized in net income, Total tax (provision) benefit	-8.5		'	-66.9		'
Total other comprehensive income (loss), Total tax (provision) benefit	-30.5		'	0.1		'
Accumulated other comprehensive income loss tax (Provision) benefit, ending balance	-468.9		'	-468.9		'
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]	'		'	'		'
After tax total accumulated other comprehensive income, beginning balance	814.2		'	871		'
Investment securities, after tax	72.7		'	125.2		'
Net non-credit related OTTI losses, adjusted for valuation changes, after tax	0		1.7	0.3		4.8
Forecasted transactions, after tax	0		'	0		'
Foreign currency translation adjustment, after tax	-0.2		0.4	-1.2		0.3
Total other comprehensive income (loss) before reclassifications, after tax	72.5		'	124.3		'
Total reclassification adjustment for amounts realized in net income, after tax	15.8		'	124.4		'
Other comprehensive income (loss)	56.7		62.4	-0.1		212.6
After tax total accumulated other comprehensive income, ending balance	870.9		905.1	870.9		905.1
Net impairment losses recognized in earnings	-1.9		-0.4	-3.7		-6.7
Net realized gains (losses) on securities	29.8		172.3	245.1		251.4
Interest expense	30.4		30.6	91.4		93.2
Net unrealized gains (losses) on securities	'		'	'		'
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]	'		'	'		'
After tax total accumulated other comprehensive income, beginning balance	807.6		'	862.7		'
Investment securities, after tax	72.7		'	125.2		'
Net non-credit related OTTI losses, adjusted for valuation changes, after tax	0		'	0.3		'
Forecasted transactions, after tax	0		'	0		'
Foreign currency translation adjustment, after tax	0		'	0		'
Total other comprehensive income (loss) before reclassifications, after tax	72.7		'	125.5		'
Total reclassification adjustment for amounts realized in net income, after tax	14.9		'	122.8		'
Other comprehensive income (loss)	57.8		'	2.7		'
After tax total accumulated other comprehensive income, ending balance	865.4		'	865.4		'
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	5.4	[1],[2]	'	6.1	[1],[2]	'
Investment securities, after tax	0	[1],[2]	'	0	[1],[2]	'
Net non-credit related OTTI losses, adjusted for valuation changes, after tax	0	[1],[2]	'	0	[1],[2]	'
Forecasted transactions, after tax	0	[1],[2]	'	0	[1],[2]	'
Foreign currency translation adjustment, after tax	0	[1],[2]	'	0	[1],[2]	'
Total other comprehensive income (loss) before reclassifications, after tax	0	[1],[2]	'	0	[1],[2]	'
Total reclassification adjustment for amounts realized in net income, after tax	0.9	[1],[2]	'	1.6	[1],[2]	'
Other comprehensive income (loss)	-0.9	[1],[2]	'	-1.6	[1],[2]	'
After tax total accumulated other comprehensive income, ending balance	4.5	[1],[2]	'	4.5	[1],[2]	'
Foreign Currency Translation Adjustments	'		'	'		'
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]	'		'	'		'
After tax total accumulated other comprehensive income, beginning balance	1.2		'	2.2		'
Investment securities, after tax	0		'	0		'
Net non-credit related OTTI losses, adjusted for valuation changes, after tax	0		'	0		'
Forecasted transactions, after tax	0		'	0		'
Foreign currency translation adjustment, after tax	-0.2		'	-1.2		'
Total other comprehensive income (loss) before reclassifications, after tax	-0.2		'	-1.2		'
Total reclassification adjustment for amounts realized in net income, after tax	0		'	0		'
Other comprehensive income (loss)	-0.2		'	-1.2		'
After tax total accumulated other comprehensive income, ending balance	1		'	1		'
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	-1.9		'	-3.5		'
Net realized gains (losses) on securities	25.6	[3]	'	193.2	[3]	'
Interest expense	0.6	[1]	'	1.6	[1]	'
Reclassification out of Accumulated Other Comprehensive Income | Accumulated other comprehensive income tax	'		'	'		'
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]	'		'	'		'
Net impairment losses recognized in earnings	0.7		'	1.3		'
Net realized gains (losses) on securities	-9	[3]	'	-67.7	[3]	'
Interest expense	-0.2	[1]	'	-0.5	[1]	'
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	-1.2		'	-2.2		'
Net realized gains (losses) on securities	16.6	[3]	'	125.5	[3]	'
Interest expense	0.4	[1]	'	1.1	[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	-1.2		'	-2.2		'
Net realized gains (losses) on securities	16.1	[3]	'	125	[3]	'
Interest expense	0	[1]	'	0	[1]	'
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	[1],[2]	'	0	[1],[2]	'
Net realized gains (losses) on securities	0.5	[1],[2],[3]	'	0.5	[1],[2],[3]	'
Interest expense	0.4	[1],[2]	'	1.1	[1],[2]	'
Reclassification out of Accumulated Other Comprehensive Income | Foreign Currency Translation Adjustments	'		'	'		'
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]	'		'	'		'
Net impairment losses recognized in earnings	0		'	0		'
Net realized gains (losses) on securities	0	[3]	'	0	[3]	'
Interest expense	$0	[1]	'	$0	[1]	'
[1]	We expect to reclassify $2.1 million (pretax) into income during the next 12 months, related to the net unrealized gains on forecasted transactions.
[2]	Entered into for the purpose of managing interest rate risk associated with our debt issuances.
[3]	During both the third quarter and first nine months of 2013, we reclassified $0.8 million, on a pretax basis, from accumulated other comprehensive income on the balance sheet to net realized gains on securities on the comprehensive income statement, reflecting the portion of the unrealized gain on forecasted transactions that was related to the portion of the 6.70% Debentures repurchased during the period (see Note 4 - Debt for further discussion).

Components_of_Other_Comprehens1

Components of Other Comprehensive Income (Loss) Including Reclassification Adjustments by Income Statement (Parenthetical) (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
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	$2.10	'	$2.10	'	'
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 | Net unrealized gains on forecasted transactions	'	'	'	'	'
Components Of Other Comprehensive Income Loss [Line Items]	'	'	'	'	'
Cash flow hedge gain reclassification from accumulated other comprehensive income to net realized gains/losses on securities	$0.80	$0	$0.80	$0.60	$0.60

Reclassifications_Additional_I

Reclassifications Additional Information (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2012
Reclassifications [Line Items]	'
Increase in total assets and liabilities due to prior period reclassification adjustment	$57.90