The Progressive Corporation (PGR) 10-Q 12 May 14 2014 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2014	Apr. 30, 2014
Document Document And Entity Information [Abstract]	'	'
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	31-Mar-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q1	'
Amendment Flag	'false	'
Trading Symbol	'PGR	'
Entity Common Stock, Shares Outstanding	'	592,006,103

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Revenues	'		'
Net premiums earned	$4,402.30		$4,179.30
Period over prior year period percent change in net premiums earned	5.00%		'
Investment income	103.3		100.5
Period over prior year period percent change in investment income	3.00%		'
Other-than-temporary impairment (OTTI) losses:	'		'
Total OTTI losses	0		-0.2
Period over prior year period percent change in total OTTI losses	-100.00%		'
Non-credit losses, net of credit losses recognized on previously recorded non-credit OTTI losses	0		0
Net impairment losses recognized in earnings	0		-0.2
Period over prior year period percent change in net impairment losses recognized in earnings	-100.00%		'
Net realized gains (losses) on securities	119.4		80.8
Period over prior year period percent change in net realized gains (losses) on securities	48.00%		'
Total net realized gains (losses) on securities	119.4		80.6
Period over prior year period percent change in total net realized gains (losses) on securities	48.00%		'
Fees and other revenues	72.8		68.4
Period over prior year period percent change in fees and other revenues	6.00%		'
Service revenues	9.8		8.4
Period over prior year period percent change in service revenues	17.00%		'
Total revenues	4,707.60		4,437.20
Period over prior year period percent change in total revenues	6.00%		'
Expenses	'		'
Losses and loss adjustment expenses	3,205.90		2,985.50
Period over prior year period percent change in losses and loss adjustment expenses	7.00%		'
Policy acquisition costs	369		358.9
Period over prior year period percent change in policy acquisition costs	3.00%		'
Other underwriting expenses	610.4		585.6
Period over prior year period percent change in other underwriting expenses	4.00%		'
Investment expenses	4.1		4.9
Period over prior year period percent change in investment expenses	-16.00%		'
Service expenses	9.7		8.6
Period over prior year period percent change in service expenses	13.00%		'
Interest expense	26.7		30.6
Period over prior year period percent change in interest expense	-13.00%		'
Total expenses	4,225.80		3,974.10
Period over prior year period percent change in total expenses	6.00%		'
Net Income	'		'
Income before income taxes	481.8		463.1
Period over prior year period percent change in income before income taxes	4.00%		'
Provision for income taxes	160.5		154.5
Period over prior year period percent change in provision for income taxes	4.00%		'
Net income	321.3		308.6
Period over prior year period percent change in net income	4.00%		'
Net unrealized gains (losses) on securities:	'		'
Net non-credit related OTTI losses, adjusted for valuation changes	0		0.2
Period over prior year period percent change in net non-credit related OTTI losses, adjusted for valuation changes	-100.00%		'
Other net unrealized gains (losses) on securities	-0.1		99
Period over prior year period percent change in other net unrealized gains (losses) on securities	-100.00%		'
Total net unrealized gains (losses) on securities	-0.1		99.2
Period over prior year period percent change in total net unrealized gains (losses) on securities	-100.00%		'
Net unrealized gains on forecasted transactions	-0.3		-0.3
Period over prior year period percent change in net unrealized gains on forecasted transactions	0.00%		'
Foreign currency translation adjustment	0		-0.2
Period over prior year period percent change in foreign currency translation adjustment	-100.00%		'
Other comprehensive income (loss)	-0.4		98.7
Period over prior year period percent change in other comprehensive income (loss)	-100.00%		'
Comprehensive income	$320.90		$407.30
Period over prior year period percent change in comprehensive income	-21.00%		'
Computation of Net Income Per Share	'		'
Average shares outstanding - Basic (shares)	593.9		600.6
Period over prior year period percent change in average shares outstanding - basic	-1.00%		'
Net effect of dilutive stock-based compensation (shares)	3.8		3.8
Period over prior year period percent change in net effect of dilutive stock-based compensation	0.00%		'
Total equivalent shares - Diluted (shares)	597.7		604.4
Period over prior year period percent change in total equivalent shares - diluted	-1.00%		'
Basic: Net income per share (USD per share)	$0.54		$0.51
Period over prior year period percent change in basic: net income per share	5.00%		'
Diluted: Net income per share (USD per share)	$0.54		$0.51
Period over prior year period percent change in diluted: net income per share	5.00%		'
Dividends declared per share (USD per share)	$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 $)	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013
In Millions, unless otherwise specified
Investments - Available-for-sale, at fair value:	'		'		'
Fixed maturities (amortized cost: $12,335.8, $11,686.0, and $13,415.3)	$12,506.20		$13,540.40		$12,046.30
Equity securities:	'		'		'
Nonredeemable preferred stocks (cost: $460.7, $412.5, and $445.7)	737.9		711.2		820.6
Common equities (cost: $1,252.7, $1,388.5, and $1,451.1)	2,278.70		2,530.50		2,111.10
Short-term investments (amortized cost: $1,872.9, $2,321.7, and $1,272.6)	1,872.90		1,272.60		2,321.70
Total investments at fair value	17,395.70	[1],[2]	18,054.70	[1],[2]	17,299.70	[1],[2]
Cash	96.7		75.1		110.2
Accrued investment income	82.3		89.8		87.3
Premiums receivable, net of allowance for doubtful accounts of $131.9, $128.1, and $142.4	3,515.90		3,310.70		3,372.30
Reinsurance recoverables, including $34.5, $32.4, and $44.3 on paid losses and loss adjustment expenses	1,111.50		1,090.20		947.5
Prepaid reinsurance premiums	81.8		74.9		72.8
Deferred acquisition costs	466.9		447.6		452.3
Property and equipment, net of accumulated depreciation of $687.1, $642.3, and $680.4	950		960.9		935.9
Net deferred income taxes	0		0		49
Other assets	614.6		304.3		216.5
Total assets	24,315.40		24,408.20		23,543.50
Liabilities and Shareholders’ Equity	'		'		'
Unearned premiums	5,460.10		5,174.50		5,207.30
Loss and loss adjustment expense reserves	8,592.60		8,479.70		7,948.40
Net deferred income taxes	51.1		28.4		0
Dividends payable	0		890.2		0
Accounts payable, accrued expenses, and other liabilities	1,911.70		1,785		1,934.50
Debt	1,861.30	[3]	1,860.90	[3]	2,063.50	[3]
Total liabilities	17,876.80		18,218.70		17,153.70
Common Shares, $1.00 par value (authorized 900.0; issued 797.6, including treasury shares of 204.5, 194.4, and 201.8)	593.1		595.8		603.2
Paid-in capital	1,159		1,142		1,096.90
Retained earnings	3,735.20		3,500		3,720
Accumulated other comprehensive income, net of tax:	'		'		'
Net non-credit related OTTI losses, adjusted for valuation changes	0		0		-0.1
Other net unrealized gains (losses) on securities	946.9		947		962
Total net unrealized gains (losses) on securities	946.9		947		961.9
Net unrealized gains on forecasted transactions	3.8		4.1		5.8
Foreign currency translation adjustment	0.6		0.6		2
Total accumulated other comprehensive income	951.3		951.7		969.7
Total shareholders’ equity	6,438.60		6,189.50		6,389.80
Total liabilities and shareholders’ equity	$24,315.40		$24,408.20		$23,543.50
[1]	The total fair value of the portfolio at March 31, 2014 and 2013, and December 31, 2013 included $0.8 billion, $1.2 billion, and $1.8 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.
[2]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at March 31, 2014, $350.0 million was included in "other assets" and at March 31, 2013 and December 31, 2013, $7.5 million and $61.3 million, respectively, were included in "other liabilities."
[3]	Consists of both short- and long-term debt. See Note 4 - Debt.

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Millions, except Per Share data, unless otherwise specified
Fixed maturities, amortized cost	$12,335.80	$13,415.30	$11,686
Nonredeemable preferred stocks, cost	460.7	445.7	412.5
Common equities, cost	1,252.70	1,451.10	1,388.50
Short-term investments, amortized cost	1,872.90	1,272.60	2,321.70
Premiums receivable, allowance for doubtful accounts	131.9	142.4	128.1
Reinsurance recoverables, paid losses and loss adjustment expenses	34.5	44.3	32.4
Property and equipment, accumulated depreciation	$687.10	$680.40	$642.30
Common Shares, par value (USD per share)	$1	$1	$1
Common Shares, authorized (shares)	900	900	900
Common Shares, issued (shares)	797.6	797.6	797.6
Common Shares, treasury shares (shares)	204.5	201.8	194.4

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Cash Flows From Operating Activities	'		'
Net income	$321.30		$308.60
Adjustments to reconcile net income to net cash provided by operating activities:	'		'
Depreciation	22.8		23.7
Amortization of fixed-income securities	19		40
Amortization of equity-based compensation	15.2		17.8
Net realized (gains) losses on securities	-119.4		-80.6
Net (gains) losses on disposition of property and equipment	2.1		1
Changes in:	'		'
Premiums receivable	-205.2		-188.6
Reinsurance recoverables	-21.3		-46.5
Prepaid reinsurance premiums	-6.9		-6.5
Deferred acquisition costs	-19.3		-17.8
Income taxes	149.6		129.8
Unearned premiums	285.6		276.7
Loss and loss adjustment expense reserves	112.9		110
Accounts payable, accrued expenses, and other liabilities	77		135.1
Other, net	27.2		19.4
Net cash provided by operating activities	660.6		722.1
Purchases:	'		'
Fixed maturities	-1,731.60		-1,950.80
Equity securities	-86.6		-74.1
Sales:	'		'
Fixed maturities	2,107.10		1,257.30
Equity securities	362.5		72.5
Maturities, paydowns, calls, and other:	'		'
Fixed maturities	697		368.6
Equity securities	14.3		16
Net sales (purchases) of short-term investments	-600.4		-331.6
Net unsettled security transactions	-411.3		98.4
Purchases of property and equipment	-16.2		-27.7
Sales of property and equipment	2.2		0.8
Net cash provided by (used in) investing activities	337		-570.6
Cash Flows From Financing Activities	'		'
Tax benefit from exercise/vesting of equity-based compensation	10.7		6.6
Dividends paid to shareholders	-892.6	[1]	-175.6	[1]
Acquisition of treasury shares	-94.7		-51.3
Net cash used in financing activities	-976.6		-220.3
Effect of exchange rate changes on cash	0.6		-0.1
Increase (decrease) in cash	21.6		-68.9
Cash, Beginning of year	75.1		179.1
Cash, End of year	$96.70		$110.20
[1]	Progressive maintains an annual dividend program. See Note 8 - Dividends for further discussion.

Basis_of_Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Basis of Presentation	'
	Basis of Presentation — The consolidated financial statements include the accounts of The Progressive Corporation, its subsidiaries, a mutual insurance company affiliate, and a limited partnership investment affiliate. 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 March 31, 2014, 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, 2013.
	During the first quarter 2014, a decision was made to sell property originally purchased for a future Service Center site. At March 31, 2014, included in other assets in the consolidated balance sheets is $8.7 million of "held for sale" property, which represents the fair value of the property less the estimated costs to sell.

Investments

Investments	3 Months Ended
	Mar. 31, 2014
Investments Schedule [Abstract]	'
Investments	'
	Investments — The following tables present the composition of our investment portfolio by major security type, consistent with our classification of how we manage, monitor, and measure the portfolio:
	($ in millions)	Cost				Gross				Gross				Net				Fair			% of
						Unrealized Gains				Unrealized				Realized				Value			Total
										Losses				Gains							Fair
														(Losses)1							Value
	31-Mar-14
	Fixed maturities:
	U.S. government obligations	$	3,197.80			$	39			$	(6.8	)		$	0			$	3,230.00		18.5	%
	State and local government obligations	2,131.00				33.1				(9.2		)		0				2,154.90			12.4
	Foreign government obligations	17.9				0				0				0				17.9			0.1
	Corporate debt securities	2,461.60				45.4				(7.2		)		1.8				2,501.60			14.4
	Residential mortgage-backed securities	1,286.70				32.6				(11.9		)		0				1,307.40			7.5
	Commercial mortgage-backed securities	2,037.70				41.5				(17.6		)		0				2,061.60			11.9
	Other asset-backed securities	936.2				6.6				(.6		)		0.3				942.5			5.4
	Redeemable preferred stocks	266.9				29.6				(6.2		)		0				290.3			1.7
	Total fixed maturities	12,335.80				227.8				(59.5		)		2.1				12,506.20			71.9
	Equity securities:
	Nonredeemable preferred stocks	460.7				263.7				(1.2		)		14.7				737.9			4.2
	Common equities	1,252.70				1,028.80				(2.8		)		0				2,278.70			13.1
	Short-term investments:
	Other short-term investments	1,872.90				0				0				0				1,872.90			10.8
	Total portfolio2,3	$	15,922.10			$	1,520.30			$	(63.5	)		$	16.8			$	17,395.70		100	%
	($ in millions)	Cost				Gross				Gross				Net				Fair			% of
						Unrealized Gains				Unrealized				Realized				Value			Total
										Losses				Gains							Fair
														(Losses)1							Value
	31-Mar-13
	Fixed maturities:
	U.S. government obligations	$	3,015.60			$	83.6			$	0			$	0			$	3,099.20		17.9	%
	State and local government obligations	1,771.60				42.8				(.5		)		0				1,813.90			10.5
	Foreign government obligations	0				0				0				0				0			0
	Corporate debt securities	2,910.80				100.3				(.9		)		4.1				3,014.30			17.4
	Residential mortgage-backed securities	595.7				33.1				(7.5		)		0				621.3			3.6
	Commercial mortgage-backed securities	2,107.20				76.2				(3.2		)		0				2,180.20			12.6
	Other asset-backed securities	929.2				11				0				0.6				940.8			5.4
	Redeemable preferred stocks	355.9				32.5				(11.8		)		0				376.6			2.2
	Total fixed maturities	11,686.00				379.5				(23.9		)		4.7				12,046.30			69.6
	Equity securities:
	Nonredeemable preferred stocks	412.5				401.7				0				6.4				820.6			4.8
	Common equities	1,388.50				729.6				(7.0		)		0				2,111.10			12.2
	Short-term investments:
	Other short-term investments	2,321.70				0				0				0				2,321.70			13.4
	Total portfolio2,3	$	15,808.70			$	1,510.80			$	(30.9	)		$	11.1			$	17,299.70		100	%
	($ in millions)	Cost				Gross				Gross				Net				Fair			% of
						Unrealized Gains				Unrealized				Realized				Value			Total
										Losses				Gains							Fair
														(Losses)1							Value
	31-Dec-13
	Fixed maturities:
	U.S. government obligations	$	3,630.40			$	48.4			$	(16.6	)		$	0			$	3,662.20		20.3	%
	State and local government obligations	2,247.30				27.1				(18.4		)		0				2,256.00			12.5
	Foreign government obligations	15.6				0				0				0				15.6			0.1
	Corporate debt securities	2,885.00				60.4				(20.4		)		1.6				2,926.60			16.2
	Residential mortgage-backed securities	1,110.10				31.9				(14.1		)		0				1,127.90			6.2
	Commercial mortgage-backed securities	2,154.40				43.9				(37.8		)		0				2,160.50			12
	Other asset-backed securities	1,073.00				6.6				(2.1		)		0.2				1,077.70			6
	Redeemable preferred stocks	299.5				24.1				(9.7		)		0				313.9			1.7
	Total fixed maturities	13,415.30				242.4				(119.1		)		1.8				13,540.40			75
	Equity securities:
	Nonredeemable preferred stocks	445.7				258.7				(4.5		)		11.3				711.2			3.9
	Common equities	1,451.10				1,081.80				(2.4		)		0				2,530.50			14
	Short-term investments:
	Other short-term investments	1,272.60				0				0				0				1,272.60			7.1
Total portfolio2,3	$	16,584.70			$	1,582.90			$	(126.0	)		$	13.1			$	18,054.70		100	%
1Represents net holding period gains (losses) on certain hybrid securities (discussed below).
2Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at March 31, 2014, $350.0 million was included in "other assets" and at March 31, 2013 and December 31, 2013, $7.5 million and $61.3 million, respectively, were included in "other liabilities."
3The total fair value of the portfolio at March 31, 2014 and 2013, and December 31, 2013 included $0.8 billion, $1.2 billion, and $1.8 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.
Our other short-term investments include commercial paper, reverse repurchase transactions, and other investments that are expected to mature within one year. We had $140.0 million, $620.4 million, and $200.0 million of open reverse repurchase commitments at March 31, 2014 and 2013, and December 31, 2013, respectively. At these dates, we had no 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. Consistent with past practice, we 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:
	March 31,								December 31,
(millions)	2014				2013				2013
Fixed maturities:
Corporate debt securities	$	145.7			$	175.7			$	164.2
Other asset-backed securities	13.9				16.6				14.8
Total fixed maturities	159.6				192.3				179
Equity securities:
Nonredeemable preferred stocks	63.8				55.4				60.3
Total hybrid securities	$	223.4			$	247.7			$	239.3
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 $10.0 million as of March 31, 2014, 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 March 31, 2014, was:
(millions)	Cost				Fair Value
Less than one year	$	1,838.30			$	1,874.40
One to five years	7,538.00				7,658.90
Five to ten years	2,849.00				2,855.80
Ten years or greater	58.6				65.2
Total1	$	12,283.90			$	12,454.30
1Excludes $51.9 million related to our open interest rate swap positions.
Asset-backed securities are classified in the maturity distribution table based upon their projected cash flows. All other securities which do not have a single maturity date are reported based upon expected average maturity. Contractual maturities may differ from expected maturities because the issuers of the securities may have the right to call or prepay obligations.
Gross Unrealized Losses As of March 31, 2014, we had $60.7 million of gross unrealized losses in our fixed-income securities (i.e., fixed-maturity securities, nonredeemable preferred stocks, and short-term investments) and $2.8 million in our common equities. We currently do not intend to sell the fixed-income securities and determined that it is more likely than not that we will not be required to sell these securities for the period of time necessary to recover their cost bases. A review of our fixed-income securities indicated that the issuers were current with respect to their interest obligations and that there was no evidence of any deterioration of the current cash flow projections that would indicate we would not receive the remaining principal at maturity. For common equities, 87% of our common stock portfolio was indexed to the Russell 1000; as such, this portfolio may contain securities in a loss position for an extended period of time, subject to possible write-downs, as described below. We may retain these securities as long as the portfolio and index correlation remain similar. The remaining 13% of our common stocks are part of a managed equity strategy selected and administered by external investment advisors. If our review of loss position securities indicates there is a fundamental, or market, impairment on these securities that is determined to be other-than-temporary, we would recognize a write-down in accordance with our stated policy.
The following tables show the composition of gross unrealized losses by major security type and by the length of time that individual securities have been in a continuous unrealized loss position:
	Total No. of Sec.		Total			Gross Unrealized Losses			Less than 12 Months									12 Months or Greater
			Fair
($ in millions)			Value						No. of Sec.		Fair			Unrealized Losses				No. of Sec.	Fair			Unrealized Losses
											Value								Value
31-Mar-14
Fixed maturities:
U.S. government obligations	18		$	930.4		$	(6.8	)	5		$	163.1		$	(.3	)		13	$	767.3		$	(6.5	)
State and local government obligations	106		603			(9.2		)	28		76.8			(.6		)		78	526.2			(8.6		)
Corporate debt securities	31		594.3			(7.2		)	7		101.6			(.4		)		24	492.7			(6.8		)
Residential mortgage-backed securities	66		812.6			(11.9		)	24		359.7			(1.9		)		42	452.9			(10.0		)
Commercial mortgage-backed securities	59		783.7			(17.6		)	19		116.7			(.2		)		40	667			(17.4		)
Other asset-backed securities	8		112.7			(.6		)	4		36.8			(.1		)		4	75.9			(.5		)
Redeemable preferred stocks	3		93.5			(6.2		)	0		0			0				3	93.5			(6.2		)
Total fixed maturities	291		3,930.20			(59.5		)	87		854.7			(3.5		)		204	3,075.50			(56.0		)
Equity securities:
Nonredeemable preferred stocks	3		84.3			(1.2		)	0		0			0				3	84.3			(1.2		)
Common equities	9		34			(2.8		)	7		23.1			(1.6		)		2	10.9			(1.2		)
Total equity securities	12		118.3			(4.0		)	7		23.1			(1.6		)		5	95.2			(2.4		)
Total portfolio	303		$	4,048.50		$	(63.5	)	94		$	877.8		$	(5.1	)		209	$	3,170.70		$	(58.4	)
	Total No. of Sec.		Total			Gross Unrealized Losses			Less than 12 Months									12 Months or Greater
			Fair
($ in millions)			Value						No. of Sec.		Fair			Unrealized Losses				No. of Sec.	Fair			Unrealized Losses
											Value								Value
31-Mar-13
Fixed maturities:
U.S. government obligations	1		$	40		$	0		1		$	40		$	0			0	$	0		$	0
State and local government obligations	29		117.4			(.5		)	20		78.7			(.4		)		9	38.7			(.1		)
Corporate debt securities	15		267.5			(.9		)	15		267.5			(.9		)		0	0			0
Residential mortgage-backed securities	26		180.5			(7.5		)	10		106.7			(2.5		)		16	73.8			(5.0		)
Commercial mortgage-backed securities	21		348.2			(3.2		)	17		343.2			(3.1		)		4	5			(.1		)
Other asset-backed securities	4		49.7			0			4		49.7			0				0	0			0
Redeemable preferred stocks	4		120.6			(11.8		)	1		25			0				3	95.6			(11.8		)
Total fixed maturities	100		1,123.90			(23.9		)	68		910.8			(6.9		)		32	213.1			(17.0		)
Equity securities:
Nonredeemable preferred stocks	0		0			0			0		0			0				0	0			0
Common equities	51		55.1			(7.0		)	38		44.3			(5.7		)		13	10.8			(1.3		)
Total equity securities	51		55.1			(7.0		)	38		44.3			(5.7		)		13	10.8			(1.3		)
Total portfolio	151		$	1,179.00		$	(30.9	)	106		$	955.1		$	(12.6	)		45	$	223.9		$	(18.3	)
	Total No. of Sec.		Total			Gross Unrealized Losses			Less than 12 Months									12 Months or Greater
			Fair
($ in millions)			Value						No. of Sec.		Fair			Unrealized Losses				No. of Sec.	Fair			Unrealized Losses
											Value								Value
31-Dec-13
Fixed maturities:
U.S. government obligations	29		$	1,444.30		$	(16.6	)	28		$	1,434.60		$	(16.3	)		1	$	9.7		$	(.3	)
State and local government obligations	141		844.2			(18.4		)	119		759.3			(17.1		)		22	84.9			(1.3		)
Corporate debt securities	51		997.6			(20.4		)	45		831.1			(17.8		)		6	166.5			(2.6		)
Residential mortgage-backed securities	66		763.5			(14.1		)	45		597.6			(7.9		)		21	165.9			(6.2		)
Commercial mortgage-backed securities	76		1,061.90			(37.8		)	60		809.2			(19.7		)		16	252.7			(18.1		)
Other asset-backed securities	25		287.2			(2.1		)	22		233.3			(1.8		)		3	53.9			(.3		)
Redeemable preferred stocks	4		122.7			(9.7		)	0		0			0				4	122.7			(9.7		)
Total fixed maturities	392		5,521.40			(119.1		)	319		4,665.10			(80.6		)		73	856.3			(38.5		)
Equity securities:
Nonredeemable preferred stocks	7		142.3			(4.5		)	7		142.3			(4.5		)		0	0			0
Common equities	24		59.7			(2.4		)	20		58.5			(2.4		)		4	1.2			0
Total equity securities	31		202			(6.9		)	27		200.8			(6.9		)		4	1.2			0
Total portfolio	423		$	5,723.40		$	(126.0	)	346		$	4,865.90		$	(87.5	)		77	$	857.5		$	(38.5	)
During 2013, the number of our fixed-maturity securities with unrealized losses increased reflecting the decline in prices associated with the general rise in interest rates since March 31, 2013. During the first quarter 2014, the decline in benchmark interest rates for maturities longer than five years and for many non-treasury securities of all maturities reduced the number of fixed-maturity securities we held in our portfolio with unrealized losses at March 31, 2014 since year end. The decline in the number of common equity securities in an unrealized loss position during the last nine months of 2013 and the first quarter 2014, reflects increases in the equity market values, sales of securities, and write-downs in 2013 of a number of securities as a result of our other-than-temporary impairment review process. We had no material decreases in valuation as a result of credit rating downgrades on our fixed-maturity securities during the first quarter 2014. Unrealized losses on our nonredeemable preferred stocks related to three issuers with unrealized losses, averaging approximately 1% of our total cost of those securities. A review of these securities concluded that the unrealized losses are market-related adjustments to the values, which were determined not to be other-than-temporary, and we continue to expect to recover our initial investments on these securities. All of the fixed-maturity securities in an unrealized loss position at March 31, 2014 in the table above are current with respect to required principal and interest payments.
Other-Than-Temporary Impairment (OTTI) The following table shows the total non-credit portion of the OTTI recorded in accumulated other comprehensive income, reflecting the original non-credit loss at the time the credit impairment was determined:
	March 31,								December 31,
(millions)	2014				2013				2013
Fixed maturities:
Residential mortgage-backed securities	$	(44.1	)		$	(44.2	)		$	(44.1	)
Commercial mortgage-backed securities	(.9		)		(.9		)		(.9		)
Total fixed maturities	$	(45.0	)		$	(45.1	)		$	(45.0	)
The following tables provide rollforwards of the amounts related to credit losses recognized in earnings for the periods ended March 31, 2014 and 2013, for which a portion of the OTTI losses were also recognized in accumulated other comprehensive income at the time the credit impairments were determined and recognized:
	Three Months Ended March 31, 2014
	Mortgage-Backed
(millions)	Residential				Commercial				Total
Balance at December 31, 2013	$	19.2			$	0.4			$	19.6
Change in recoveries of future cash flows expected to be collected1	(.1		)		0				(.1		)
Balance at March 31, 2014	$	19.1			$	0.4			$	19.5
	Three Months Ended March 31, 2013
	Mortgage-Backed
(millions)	Residential				Commercial				Total
Balance at December 31, 2012	$	27.1			$	0.6			$	27.7
Change in recoveries of future cash flows expected to be collected1	0.6				(.1		)		0.5
Balance at March 31, 2013	$	27.7			$	0.5			$	28.2
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.
Although 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 months ended March 31, were:
(millions)	2014				2013
Gross realized gains on security sales
Fixed maturities:
U.S. government obligations	$	6.5			$	1.5
State and local government obligations	4.4				6.8
Corporate and other debt securities	23.1				24.1
Residential mortgage-backed securities	1				0.4
Commercial mortgage-backed securities	6.1				4
Total fixed maturities	41.1				36.8
Equity securities:
Nonredeemable preferred stocks	25.9				38.5
Common equities	83				2.7
Subtotal gross realized gains on security sales	150				78
Gross realized losses on security sales
Fixed maturities:
U.S. government obligations	(4.7		)		(.3		)
State and local government obligations	(.1		)		0
Corporate and other debt securities	(2.2		)		(.4		)
Commercial mortgage-backed securities	(2.7		)		0
Redeemable preferred stocks	(3.2		)		(.1		)
Total fixed maturities	(12.9		)		(.8		)
Equity securities:
Common equities	(3.4		)		0
Subtotal gross realized losses on security sales	(16.3		)		(.8		)
Net realized gains (losses) on security sales
Fixed maturities:
U.S. government obligations	1.8				1.2
State and local government obligations	4.3				6.8
Corporate and other debt securities	20.9				23.7
Residential mortgage-backed securities	1				0.4
Commercial mortgage-backed securities	3.4				4
Redeemable preferred stocks	(3.2		)		(.1		)
Total fixed maturities	28.2				36
Equity securities:
Nonredeemable preferred stocks	25.9				38.5
Common equities	79.6				2.7
Subtotal net realized gains (losses) on security sales	133.7				77.2
Other-than-temporary impairment losses
Fixed maturities:
Residential mortgage-backed securities	0				(.1		)
Total fixed maturities	0				(.1		)
Equity securities:
Common equities	0				(.1		)
Subtotal other-than-temporary impairment losses	0				(.2		)
Other gains (losses)
Hybrid securities	3.8				2.3
Derivative instruments	(19.3		)		1.3
Litigation settlements	1.2				0
Subtotal other gains (losses)	(14.3		)		3.6
Total net realized gains (losses) on securities	$	119.4			$	80.6
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, sales from our equity-indexed portfolio during the first quarter 2014, and tax management strategies. In addition, gains and losses reflect recoveries from litigation settlements and holding period valuation changes on hybrids and derivatives. Also included are write-downs for securities determined to be other-than-temporarily impaired in our fixed-maturity and/or equity portfolios.
Net Investment Income  The components of net investment income for the three months ended March 31, were:
(millions)	2014			2013
Fixed maturities:
U.S. government obligations	$	13		$	11.8
State and local government obligations	12.8			11.4
Foreign government obligations	0.1			0
Corporate debt securities	22			25.6
Residential mortgage-backed securities	9.9			4.5
Commercial mortgage-backed securities	16.7			18.7
Other asset-backed securities	4.2			3.5
Redeemable preferred stocks	4.1			5.4
Total fixed maturities	82.8			80.9
Equity securities:
Nonredeemable preferred stocks	9.9			9.2
Common equities	10.4			9.7
Short-term investments:
Other short-term investments	0.2			0.7
Investment income	103.3			100.5
Investment expenses	(4.1		)	(4.9		)
Net investment income	$	99.2		$	95.6
Trading Securities At March 31, 2014 and 2013, and December 31, 2013, we did not hold any trading securities and did not have any net realized gains (losses) on trading securities for the three months ended March 31, 2014 and 2013.
Derivative Instruments For all derivative positions discussed below, realized holding period gains and losses are netted with any upfront cash that may be exchanged under the contract to determine if the net position should be classified either as an asset or liability. To be reported as a net derivative asset and a component of the available-for-sale portfolio, the inception-to-date realized gain on the derivative position at period end would have to exceed any upfront cash received. On the other hand, a net derivative liability would include any inception-to-date realized loss plus the amount of upfront cash received (or netted, if upfront cash was paid) and would be reported as a component of other liabilities. These net derivative assets/liabilities are not separately disclosed on the balance sheet due to their immaterial effect on our financial condition, cash flows, and results of operations.
The following table shows the status of our derivative instruments at March 31, 2014 and 2013, and December 31, 2013, and for the three months ended March 31, 2014 and 2013; 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
	March 31,								Dec. 31,								March 31,							Dec. 31,		March 31,
Derivatives designated as:	2014				2013				2013				Purpose		Classification		2014			2013				2013		2014			2013
Hedging instruments
Closed:
Ineffective cash flow hedge	$	0			$	0			$	54			Manage interest		NA		$	0		$	0			$	0	$	0		$	0
													rate risk
Non-hedging instruments
Assets:
Interest rate swaps	750				0				750				Manage portfolio		Investments—		51.9			0				68.1		(19.3		)	0
													duration		fixed maturities
Liabilities:
Interest rate swaps	0				1,263				0				Manage portfolio		Other liabilities		0			(87.8		)		0		0			1.3
													duration
Closed:
Interest rate swaps	0				0				1,263				Manage portfolio		NA		0			0				0		0			0
													duration
Total	NA				NA				NA								$	51.9		$	(87.8	)		$	68.1	$	(19.3	)	$	1.3
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 report them on a gross basis on our balance sheets, consistent with our historical presentation.
NA=ot Applicable
CASH FLOW HEDGES
We did not repurchase any debt during the quarters ended March 31, 2014 and 2013. During the year ended December 31, 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”). For the portion of the 6.70% Debentures we repurchased during 2013, 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.
INTEREST RATE SWAPS
During the periods ended March 31, 2014 and 2013, and December 31, 2013, we invested in interest rate swap positions primarily to manage the fixed-income portfolio duration. At both March 31, 2014 and December 31, 2013, we held three 10-year interest rate swap positions (opened in the second quarter of 2013) with a total notional value of $750 million. In each case, we are paying a fixed rate and receiving a variable rate, effectively shortening the duration of our fixed-income portfolio. As of March 31, 2014 and December 31, 2013, we recognized inception-to-date fair value gains of $51.9 million and $68.1 million, respectively, on the balance sheet, reflecting rising interest rates since the positions were opened. The decrease in the fair value gain during the first quarter 2014 reflected a decline in the benchmark interest rates.
At March 31, 2013, we held three interest rate swap positions with a total notional value of $1,263 million. These positions included one 9-year interest rate swap position (opened in 2009) and two 5-year interest rate swap positions (opened in 2011); in each case, we were paying a fixed rate and receiving a variable rate, effectively shortening the duration of our fixed-income portfolio. We recognized a fair value loss of $87.8 million on these positions as of March 31, 2013, which resulted from an overall decline in interest rates from the inception of the trades.
As of March 31, 2014 and December 31, 2013, the balance of the cash collateral that we had received from the applicable counterparties on the open positions was $43.3 million and $62.7 million, respectively. As of March 31, 2013, the balance of the cash collateral that we had delivered to the applicable counterparty on the then open positions was $93.5 million.

Fair_Value

Fair Value	3 Months Ended
	Mar. 31, 2014
Fair Value Disclosures [Abstract]	'
Fair Value	'
	Fair Value — We have categorized our financial instruments, based on the degree of subjectivity inherent in the method by which they are valued, into a fair value hierarchy of three levels, as follows:
	•	Level 1: Inputs are unadjusted quoted prices in active markets for identical instruments at the measurement date (e.g., U.S. government obligations, active exchange-traded equity securities, and certain short-term securities).
	•	Level 2: Inputs (other than quoted prices included within Level 1) that are observable for the instrument either directly or indirectly (e.g., certain corporate and municipal bonds and certain preferred stocks). This includes: (i) quoted prices for similar instruments in active markets, (ii) quoted prices for identical or similar instruments in markets that are not active, (iii) inputs other than quoted prices that are observable for the instruments, and (iv) inputs that are derived principally from or corroborated by observable market data by correlation or other means.
	•	Level 3: Inputs that are unobservable. Unobservable inputs reflect our subjective evaluation about the assumptions market participants would use in pricing the financial instrument (e.g., certain structured securities and privately held investments).
	Determining the fair value of the investment portfolio is the responsibility of management. As part of the responsibility, we evaluate whether a market is distressed or inactive in determining the fair value for our portfolio. We review certain market level inputs to evaluate whether sufficient activity, volume, and new issuances exist to create an active market. Based on this evaluation, we concluded that there was sufficient activity related to the sectors and securities for which we obtained valuations.
	The composition of the investment portfolio by major security type and our outstanding debt was:
		Fair Value
	(millions)	Level 1		Level 2			Level 3		Total		Cost
	31-Mar-14
	Fixed maturities:
	U.S. government obligations	$	3,230.00	$	0		$	0	$	3,230.00	$	3,197.80
	State and local government obligations	0		2,154.90			0		2,154.90		2,131.00
	Foreign government obligations	17.9		0			0		17.9		17.9
	Corporate debt securities	0		2,501.60			0		2,501.60		2,461.60
	Subtotal	3,247.90		4,656.50			0		7,904.40		7,808.30
	Asset-backed securities:
	Residential mortgage-backed	0		1,307.40			0		1,307.40		1,286.70
	Commercial mortgage-backed	0		2,033.00			28.6		2,061.60		2,037.70
	Other asset-backed	0		942.5			0		942.5		936.2
	Subtotal asset-backed securities	0		4,282.90			28.6		4,311.50		4,260.60
	Redeemable preferred stocks:
	Financials	0		107.4			0		107.4		84.2
	Utilities	0		65.2			0		65.2		64.9
	Industrials	0		117.7			0		117.7		117.8
	Subtotal redeemable preferred stocks	0		290.3			0		290.3		266.9
	Total fixed maturities	3,247.90		9,229.70			28.6		12,506.20		12,335.80
	Equity securities:
	Nonredeemable preferred stocks:
	Financials	284		411.8			42.1		737.9		460.7
	Utilities	0		0			0		0		0
	Subtotal nonredeemable preferred stocks	284		411.8			42.1		737.9		460.7
	Common equities:
	Common stocks	2,278.30		0			0		2,278.30		1,252.30
	Other risk investments	0		0			0.4		0.4		0.4
	Subtotal common equities	2,278.30		0			0.4		2,278.70		1,252.70
	Total fixed maturities and equity securities	5,810.20		9,641.50			71.1		15,522.80		14,049.20
	Short-term investments:
	Other short-term investments	1,611.70		261.2			0		1,872.90		1,872.90
	Total portfolio	$	7,421.90	$	9,902.70		$	71.1	$	17,395.70	$	15,922.10
	Debt	$	0	$	2,152.50		$	0	$	2,152.50	$	1,861.30
		Fair Value
	(millions)	Level 1		Level 2			Level 3		Total		Cost
	31-Mar-13
	Fixed maturities:
	U.S. government obligations	$	3,099.20	$	0		$	0	$	3,099.20	$	3,015.60
	State and local government obligations	0		1,813.90			0		1,813.90		1,771.60
	Foreign government obligations	0		0			0		0		0
	Corporate debt securities	0		3,014.30			0		3,014.30		2,910.80
	Subtotal	3,099.20		4,828.20			0		7,927.40		7,698.00
	Asset-backed securities:
	Residential mortgage-backed	0		535.7			85.6		621.3		595.7
	Commercial mortgage-backed	0		2,152.90			27.3		2,180.20		2,107.20
	Other asset-backed	0		940.8			0		940.8		929.2
	Subtotal asset-backed securities	0		3,629.40			112.9		3,742.30		3,632.10
	Redeemable preferred stocks:
	Financials	0		132.2			0		132.2		110.7
	Utilities	0		67			0		67		64.9
	Industrials	0		177.4			0		177.4		180.3
	Subtotal redeemable preferred stocks	0		376.6			0		376.6		355.9
	Total fixed maturities	3,099.20		8,834.20			112.9		12,046.30		11,686.00
	Equity securities:
	Nonredeemable preferred stocks:
	Financials	270.3		490.3			33.8		794.4		391.8
Utilities	0		26.2			0		26.2		20.7
Subtotal nonredeemable preferred stocks	270.3		516.5			33.8		820.6		412.5
Common equities:
Common stocks	2,099.10		0			0		2,099.10		1,385.30
Other risk investments	0		0			12		12		3.2
Subtotal common equities	2,099.10		0			12		2,111.10		1,388.50
Total fixed maturities and equity securities	5,468.60		9,350.70			158.7		14,978.00		13,487.00
Short-term investments:
Other short-term investments	1,984.20		337.5			0		2,321.70		2,321.70
Total portfolio	$	7,452.80	$	9,688.20		$	158.7	$	17,299.70	$	15,808.70
Debt	$	0	$	2,397.20		$	0	$	2,397.20	$	2,063.50
	Fair Value
(millions)	Level 1		Level 2			Level 3		Total		Cost
31-Dec-13
Fixed maturities:
U.S. government obligations	$	3,662.20	$	0		$	0	$	3,662.20	$	3,630.40
State and local government obligations	0		2,256.00			0		2,256.00		2,247.30
Foreign government obligations	15.6		0			0		15.6		15.6
Corporate debt securities	0		2,926.60			0		2,926.60		2,885.00
Subtotal	3,677.80		5,182.60			0		8,860.40		8,778.30
Asset-backed securities:
Residential mortgage-backed	0		1,127.70			0.2		1,127.90		1,110.10
Commercial mortgage-backed	0		2,131.50			29		2,160.50		2,154.40
Other asset-backed	0		1,077.70			0		1,077.70		1,073.00
Subtotal asset-backed securities	0		4,336.90			29.2		4,366.10		4,337.50
Redeemable preferred stocks:
Financials	0		102.8			0		102.8		84.2
Utilities	0		65.6			0		65.6		64.9
Industrials	0		145.5			0		145.5		150.4
Subtotal redeemable preferred stocks	0		313.9			0		313.9		299.5
Total fixed maturities	3,677.80		9,833.40			29.2		13,540.40		13,415.30
Equity securities:
Nonredeemable preferred stocks:
Financials	240.8		414.6			39		694.4		431.5
Utilities	0		16.8			0		16.8		14.2
Subtotal nonredeemable preferred stocks	240.8		431.4			39		711.2		445.7
Common equities:
Common stocks	2,530.00		0			0		2,530.00		1,450.60
Other risk investments	0		0			0.5		0.5		0.5
Subtotal common equities	2,530.00		0			0.5		2,530.50		1,451.10
Total fixed maturities and equity securities	6,448.60		10,264.80			68.7		16,782.10		15,312.10
Short-term investments:
Other short-term investments	987.8		284.8			0		1,272.60		1,272.60
Total portfolio	$	7,436.40	$	10,549.60		$	68.7	$	18,054.70	$	16,584.70
Debt	$	0	$	2,073.70		$	0	$	2,073.70	$	1,860.90
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. During the first quarter of 2014, we had two nonredeemable preferred stocks with a value of $41.7 million that were transferred from Level 2 to Level 1 due to the availability of a consistent exchange price. We did not have any transfers between Level 1 and Level 2 during the year ended December 31, 2013. 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 accretion of discount, since that value very closely approximates what an active market participant would be willing to pay for such securities. The remainder of our short-term securities are classified as Level 2 and are not priced externally since these securities continually trade at par value. These securities are classified as Level 2 since they are primarily longer-dated auction securities issued by municipalities that contain a redemption put feature back to the auction pool with a redemption period 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 March 31, 2014, vendor-quoted prices represented 55% of our Level 1 classifications (excluding short-term investments), compared to 57% at March 31, 2013 and 56% at December 31, 2013. The securities quoted by vendors in Level 1 primarily represent our holdings in U.S. Treasury Notes, which are frequently traded and the quotes are considered similar to exchange-traded quotes. The balance of our Level 1 pricing comes from quotes obtained directly from trades made on active exchanges.
At both March 31, 2014 and 2013, vendor-quoted prices comprised 96% of our Level 2 classifications (excluding short-term investments), while dealer-quoted prices represented 4%, compared to 98% and 2% at December 31, 2013. 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 for 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 March 31, 2014 and 2013, and December 31, 2013, 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. Despite the lack of sufficient observable market information for our Level 3 securities, we believe the valuations received in conjunction with our procedures for evaluating third-party prices support the fair values reported in the financial statements.
At both March 31, 2014 and December 31, 2013, we did not have any private common equity securities that were priced internally. At March 31, 2013, we had one private common equity security with a value of $11.2 million that was priced internally; the security was sold prior to the end of 2013. At March 31, 2014, we held one private preferred equity security, with a value of $42.1 million, that was priced internally. The same security had a value of $33.8 million at March 31, 2013 and $39.0 million at December 31, 2013. At March 31, 2014 and 2013, and December 31, 2013, we did not hold any securities in our fixed-maturity portfolio that were priced internally.
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 months ended March 31, 2014 and 2013:
	Level 3 Fair Value
	Three months ended March 31, 2014
(millions)	Fair Value at Dec. 31, 2013		Calls/			Purchases		Sales		Net Realized (Gain)/Loss on Sales		Change in Valuation			Net		Fair Value at March 31, 2014
			Maturities/												Transfers
			Paydowns												In (Out)
Fixed maturities:
Asset-backed securities:
Residential mortgage-backed	$	0.2	$	0		$	0	$	0	$	0	$	(.2	)	$	0	$	0
Commercial mortgage-backed	29		(.5		)	0		0		0		0.1			0		28.6
Total fixed maturities	29.2		(.5		)	0		0		0		(.1		)	0		28.6
Equity securities:
Nonredeemable preferred stocks:
Financials1	39		0			0		0		0		3.1			0		42.1
Common equities:
Other risk investments	0.5		(.1		)	0		0		0		0			0		0.4
Total Level 3 securities	$	68.7	$	(.6	)	$	0	$	0	$	0	$	3		$	0	$	71.1
1The $3.1 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 March 31, 2013
(millions)	Fair Value at Dec. 31, 2012		Calls/			Purchases		Sales		Net Realized (Gain)/Loss on Sales		Change in			Net		Fair Value at March 31, 2013
			Maturities/									Valuation			Transfers
			Paydowns												In (Out)
Fixed maturities:
Asset-backed securities:
Residential mortgage-backed	$	45.5	$	(5.3	)	$	45.2	$	0	$	0	$	0.2		$	0	$	85.6
Commercial mortgage-backed	25.3		(.4		)	0		0		0		2.4			0		27.3
Total fixed maturities	70.8		(5.7		)	45.2		0		0		2.6			0		112.9
Equity securities:
Nonredeemable preferred stocks:
Financials1	31.9		0			0		0		0		1.9			0		33.8
Common equities:
Other risk investments	12		0			0		0		0		0			0		12
Total Level 3 securities	$	114.7	$	(5.7	)	$	45.2	$	0	$	0	$	4.5		$	0	$	158.7
1The $1.9 million represents net holding period gains on a hybrid security which is reflected in net realized gains (losses) on securities in the comprehensive income statement.
The following tables provide a summary of the quantitative information about Level 3 fair value measurements for our applicable securities at March 31, 2014 and 2013, and December 31, 2013:
	Quantitative Information about Level 3 Fair Value Measurements
($ in millions)	Fair Value at March 31, 2014		Valuation Technique		Unobservable Input	Unobservable
						Input Assumption
Fixed maturities:
Asset-backed securities:
Residential mortgage-backed1	$	0	NA		NA	NA
Commercial mortgage-backed	28.6		External vendor		Prepayment rate2	0
Total fixed maturities	28.6
Equity securities:
Nonredeemable preferred stocks:
Financials	42.1		Multiple of tangible net book value		Price to book ratio multiple	1.9
Common equities:
Other risk investments	0
Subtotal Level 3 securities	70.7
Pricing exemption securities3	0.4
Total Level 3 securities	$	71.1
1This security is approaching final maturity and is valued at zero.
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 these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us.
NA=ot Applicable
	Quantitative Information about Level 3 Fair Value Measurements
($ in millions)	Fair Value at March 31, 2013		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	27.4		External vendor		Prepayment rate2	0
Total fixed maturities	27.6
Equity securities:
Nonredeemable preferred stocks:
Financials	33.8		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	72.6
Pricing exemption securities3	86.1
Total Level 3 securities	$	158.7
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.
	Quantitative Information about Level 3 Fair Value Measurements
($ in millions)	Fair Value at Dec. 31, 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	29		External vendor		Prepayment rate2	0
Total fixed maturities	29.2
Equity securities:
Nonredeemable preferred stocks:
Financials	39		Multiple of tangible net book value		Price to book ratio multiple	1.9
Common equities:
Other risk investments	0
Subtotal Level 3 securities	68.2
Pricing exemption securities3	0.5
Total Level 3 securities	$	68.7
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 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 2014 or 2013, there were no material assets or liabilities measured at fair value on a nonrecurring basis.

Debt

Debt	3 Months Ended
	Mar. 31, 2014
Debt Disclosure [Abstract]	'
Debt	'
	Debt — Debt consisted of:
		31-Mar-14				31-Mar-13				31-Dec-13
	(millions)	Carrying		Fair		Carrying		Fair		Carrying		Fair
		Value		Value		Value		Value		Value		Value
	7% Notes due 2013	$	0	$	0	$	149.9	$	154.9	$	0	$	0
	3.75% Senior Notes due 2021	497.6		524.5		497.4		544.7		497.6		509.1
	6 5/8% Senior Notes due 2029	295.4		381.8		295.2		382.6		295.3		359.6
	6.25% Senior Notes due 2032	394.7		501.4		394.5		507.1		394.6		473.7
	6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067	673.6		744.8		726.5		807.9		673.4		731.3
	Total	$	1,861.30	$	2,152.50	$	2,063.50	$	2,397.20	$	1,860.90	$	2,073.70
	In October 2013, we retired the entire $150 million of our 7% Notes at maturity.
	We did not repurchase any debt securities in the first quarter of 2014 or 2013. During the year ended December 31, 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”). Since the amount paid exceeded the carrying value of the debt we repurchased, we recognized losses on these extinguishments of $4.3 million. 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.
	In March 2014, we renewed the unsecured, discretionary line of credit (the "Line of Credit") with PNC Bank, National Association ("PNC") in the maximum principal amount of $100 million. The prior line of credit, entered into in March 2013, has expired. The Line of Credit is on substantially the same terms and conditions as the prior line of credit. Subject to the terms and conditions of the Line of Credit documents, advances under the Line of Credit (if any) will bear interest at a variable rate equal to the higher of PNC's Prime Rate and the sum of the Federal Funds Open Rate plus 50 basis points. Each advance must be repaid on the 30th date after the advance or, if earlier, on March 25, 2015, the expiration date of the Line of Credit. Prepayments are permitted without penalty. All advances under the Line of Credit are subject to PNC's discretion. We had no borrowings under the Line of Credit or the prior line of credit during the first quarter 2014 or throughout 2013.

Income_Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Income Taxes — At March 31, 2014 and 2013, and December 31, 2013, 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 three months ended March 31, 2014, there have been no material changes in our uncertain tax positions.

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information	3 Months Ended
	Mar. 31, 2014
Supplemental Cash Flow Elements [Abstract]	'
Supplemental Cash Flow Information	'
	Supplemental Cash Flow Information — Cash includes only bank demand deposits. We paid the following in the respective periods:
		Three Months Ended March 31,
	(millions)	2014		2013
	Income taxes	$	0	$	18
	Interest	19.3		19.3

Segment_Information

Segment Information	3 Months Ended
	Mar. 31, 2014
Segment Reporting [Abstract]	'
Segment Information	'
	Segment Information — Our Personal Lines segment writes insurance for personal autos and recreational vehicles. Our Commercial Lines segment writes primary liability and physical damage insurance for automobiles and trucks owned and/or operated predominantly by small businesses in the business auto, for-hire transportation, contractor, for-hire specialty, 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 March 31,
		2014						2013
	(millions)	Revenues			Pretax			Revenues		Pretax
					Profit					Profit
					(Loss)					(Loss)
	Personal Lines
	Agency	$	2,203.20		$	178.6		$	2,107.20	$	174.9
	Direct	1,762.20			71			1,641.60		127.2
	Total Personal Lines1	3,965.40			249.6			3,748.80		302.1
	Commercial Lines	436.9			40.9			430.4		15.3
	Other indemnity	0			(.7		)	0.1		0.3
	Total underwriting operations	4,402.30			289.8			4,179.30		317.7
	Fees and other revenues2	72.8			NA			68.4		NA
	Service businesses	9.8			0.1			8.4		(.2		)
	Investments3	222.7			218.6			181.1		176.2
	Interest expense	NA			(26.7		)	NA		(30.6		)
	Consolidated total	$	4,707.60		$	481.8		$	4,437.20	$	463.1
	1Personal auto insurance accounted for 92% and 91% of the total Personal Lines segment net premiums earned in the first quarters of 2014 and 2013, respectively; 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 March 31,
		2014				2013
		Underwriting		Combined		Underwriting		Combined
		Margin		Ratio		Margin		Ratio
	Personal Lines
	Agency	8.1	%	91.9		8.3	%	91.7
	Direct	4		96		7.8		92.2
	Total Personal Lines	6.3		93.7		8.1		91.9
	Commercial Lines	9.4		90.6		3.5		96.5
	Other indemnity1	NM		NM		NM		NM
	Total underwriting operations	6.6		93.4		7.6		92.4
	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	3 Months Ended
	Mar. 31, 2014
Text Block [Abstract]	'
Dividends	'
	Dividends — We maintain a policy of paying an annual variable dividend that, if declared, would be payable shortly after the close of the year. This annual variable dividend is based on a target percentage of after-tax underwriting income 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 2014, the Board has determined the target percentage to be 33-1/3% of annual after-tax underwriting income, which is unchanged from the 2013 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 March 31, 2014, the Gainshare factor was 1.02. 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 2014 were to be paid, the Board would likely declare the 2014 annual dividend in December 2014, with a record date in January 2015 and payment shortly thereafter. For the three months ended March 31, 2014, our comprehensive income was $320.9 million, which is higher than the $188.4 million of after-tax underwriting income for the same period.
	We paid dividends per common share of $.4929 and $.2845 in February 2014 and 2013, respectively, under our annual variable dividend policy. These dividends were paid pursuant to declarations made by the Board of Directors in December 2013 and 2012. In addition to the annual variable dividend, the Board of Directors declared a $1.00 per common share special dividend in December 2013, which was paid in February 2014.

Other_Comprehensive_Income_Los

Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2014
Equity [Abstract]	'
Other Comprehensive Income (Loss)	'
	Other Comprehensive Income (Loss) — The components of other comprehensive income (loss), including reclassification adjustments by income statement line item, were as follows:
											Components of Changes in
											Accumulated Other
											Comprehensive Income (after tax)
	(millions)	Pretax total			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						transactions1,2
	Balance at December 31, 2013	$	1,464.10		$	(512.4	)	$	951.7		$	947		$	4.1		$	0.6
	Other comprehensive income (loss) before reclassifications:
	Investment securities	131.8			(46.1		)	85.7			85.7			0			0
	Net non-credit related OTTI losses, adjusted for	0			0			0			0			0			0
	valuation changes
	Forecasted transactions	0			0			0			0			0			0
	Foreign currency translation adjustment	0			0			0			0			0			0
	Total other comprehensive income (loss) before reclassifications	131.8			(46.1		)	85.7			85.7			0			0
	Less: Reclassification adjustment for amounts realized in net income by income statement line item:
	Net impairment losses recognized in earnings	0			0			0			0			0			0
	Net realized gains (losses) on securities	131.9			(46.1		)	85.8			85.8			0			0
	Interest expense2	0.5			(.2		)	0.3			0			0.3			0
	Total reclassification adjustment for amounts realized in net income	132.4			(46.3		)	86.1			85.8			0.3			0
	Total other comprehensive income (loss)	(.6		)	0.2			(.4		)	(.1		)	(.3		)	0
	Balance at March 31, 2014	$	1,463.50		$	(512.2	)	$	951.3		$	946.9		$	3.8		$	0.6
											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
	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	227.8			(79.7		)	148.1			148.1			0			0
	Net non-credit related OTTI losses, adjusted for	0.3			(.1		)	0.2			0.2			0			0
	valuation changes
	Forecasted transactions	0			0			0			0			0			0
	Foreign currency translation adjustment	(.3		)	0.1			(.2		)	0			0			(.2		)
	Total other comprehensive income (loss) before reclassifications	227.8			(79.7		)	148.1			148.3			0			(.2		)
	Less: Reclassification adjustment for amounts realized in net income by income statement line item:
	Net impairment losses recognized in earnings	(.1		)	0.1			0			0			0			0
	Net realized gains (losses) on securities	75.6			(26.5		)	49.1			49.1			0			0
	Interest expense	0.5			(.2		)	0.3			0			0.3			0
	Total reclassification adjustment for amounts realized in net income	76			(26.6		)	49.4			49.1			0.3			0
	Total other comprehensive income (loss)	151.8			(53.1		)	98.7			99.2			(.3		)	(.2		)
	Balance at March 31, 2013	$	1,491.80		$	(522.1	)	$	969.7		$	961.9		$	5.8		$	2
	1Entered into for the purpose of managing interest rate risk associated with our debt issuances.
	2We 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	3 Months Ended
	Mar. 31, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Litigation	'
	Litigation — The Progressive Corporation and/or its insurance subsidiaries are named as defendants in various lawsuits arising out of claims made under insurance policies written by our insurance subsidiaries in the ordinary course of business. We consider all legal actions relating to such claims in establishing our loss and loss adjustment expense reserves.
	In addition, The Progressive Corporation and/or its insurance subsidiaries are named as defendants in a number of class action or individual lawsuits arising out of the operations of the insurance subsidiaries. These cases include those alleging damages as a result of our subsidiaries’ practices in evaluating or paying medical or injury claims or benefits, including, but not limited to, personal injury protection, medical payments, and bodily injury benefits; the utilization, content, or appearance of policy documents; labor rates paid to auto body repair shops; wage and hour issues; and cases challenging other aspects of our subsidiaries’ claims or marketing practices or other business operations. Other insurance companies face many of these same issues.
	We plan to contest the pending lawsuits vigorously, but may pursue settlement negotiations in some cases, if appropriate. The outcomes of pending cases are uncertain at this time.We establish accruals for these lawsuits when it is probable that a loss has been or will be incurred and we can reasonably estimate its potential exposure, which may include a range of loss. As to lawsuits in which the loss is not considered both probable and estimable, or is considered probable but not estimable, we do not establish an accrual in accordance with current accounting guidance.
	With respect to our pending lawsuits that are not related to claims under insurance policies, the accruals that we have established were not material at March 31, 2014. 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 by a significant amount, 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, 2013.

Subsequent_Event

Subsequent Event	3 Months Ended
	Mar. 31, 2014
Subsequent Events [Abstract]	'
Subsequent Event	'
	Subsequent Event — On April 25, 2014, we issued $350 million of 4.35% Senior Notes due 2044 (the “4.35% Senior Notes”).  We received proceeds of $346.3 million, after deducting underwriter’s discounts and commissions. In addition, we incurred expenses of approximately $0.7 million related to the issuance.  In addition, upon issuance of the 4.35% Senior Notes, we closed a forecasted debt issuance hedge, which was entered into to hedge against a possible rise in interest rates, and recognized a $1.6 million pretax loss as part of accumulated other comprehensive income (loss); the loss will be recognized as an adjustment to interest expense and amortized over the life of the 4.35% Senior Notes.

Investments_Tables

Investments (Tables)	3 Months Ended
	Mar. 31, 2014
Investments Schedule [Abstract]	'
Investment Portfolio by Major Security Type	'
	The following tables present the composition of our investment portfolio by major security type, consistent with our classification of how we manage, monitor, and measure the portfolio:
	($ in millions)	Cost				Gross				Gross				Net				Fair			% of
						Unrealized Gains				Unrealized				Realized				Value			Total
										Losses				Gains							Fair
														(Losses)1							Value
	31-Mar-14
	Fixed maturities:
	U.S. government obligations	$	3,197.80			$	39			$	(6.8	)		$	0			$	3,230.00		18.5	%
	State and local government obligations	2,131.00				33.1				(9.2		)		0				2,154.90			12.4
	Foreign government obligations	17.9				0				0				0				17.9			0.1
	Corporate debt securities	2,461.60				45.4				(7.2		)		1.8				2,501.60			14.4
	Residential mortgage-backed securities	1,286.70				32.6				(11.9		)		0				1,307.40			7.5
	Commercial mortgage-backed securities	2,037.70				41.5				(17.6		)		0				2,061.60			11.9
	Other asset-backed securities	936.2				6.6				(.6		)		0.3				942.5			5.4
	Redeemable preferred stocks	266.9				29.6				(6.2		)		0				290.3			1.7
	Total fixed maturities	12,335.80				227.8				(59.5		)		2.1				12,506.20			71.9
	Equity securities:
	Nonredeemable preferred stocks	460.7				263.7				(1.2		)		14.7				737.9			4.2
	Common equities	1,252.70				1,028.80				(2.8		)		0				2,278.70			13.1
	Short-term investments:
	Other short-term investments	1,872.90				0				0				0				1,872.90			10.8
	Total portfolio2,3	$	15,922.10			$	1,520.30			$	(63.5	)		$	16.8			$	17,395.70		100	%
	($ in millions)	Cost				Gross				Gross				Net				Fair			% of
						Unrealized Gains				Unrealized				Realized				Value			Total
										Losses				Gains							Fair
														(Losses)1							Value
	31-Mar-13
	Fixed maturities:
	U.S. government obligations	$	3,015.60			$	83.6			$	0			$	0			$	3,099.20		17.9	%
	State and local government obligations	1,771.60				42.8				(.5		)		0				1,813.90			10.5
	Foreign government obligations	0				0				0				0				0			0
	Corporate debt securities	2,910.80				100.3				(.9		)		4.1				3,014.30			17.4
	Residential mortgage-backed securities	595.7				33.1				(7.5		)		0				621.3			3.6
	Commercial mortgage-backed securities	2,107.20				76.2				(3.2		)		0				2,180.20			12.6
	Other asset-backed securities	929.2				11				0				0.6				940.8			5.4
	Redeemable preferred stocks	355.9				32.5				(11.8		)		0				376.6			2.2
	Total fixed maturities	11,686.00				379.5				(23.9		)		4.7				12,046.30			69.6
	Equity securities:
	Nonredeemable preferred stocks	412.5				401.7				0				6.4				820.6			4.8
	Common equities	1,388.50				729.6				(7.0		)		0				2,111.10			12.2
	Short-term investments:
	Other short-term investments	2,321.70				0				0				0				2,321.70			13.4
	Total portfolio2,3	$	15,808.70			$	1,510.80			$	(30.9	)		$	11.1			$	17,299.70		100	%
	($ in millions)	Cost				Gross				Gross				Net				Fair			% of
						Unrealized Gains				Unrealized				Realized				Value			Total
										Losses				Gains							Fair
														(Losses)1							Value
	31-Dec-13
	Fixed maturities:
	U.S. government obligations	$	3,630.40			$	48.4			$	(16.6	)		$	0			$	3,662.20		20.3	%
	State and local government obligations	2,247.30				27.1				(18.4		)		0				2,256.00			12.5
	Foreign government obligations	15.6				0				0				0				15.6			0.1
	Corporate debt securities	2,885.00				60.4				(20.4		)		1.6				2,926.60			16.2
	Residential mortgage-backed securities	1,110.10				31.9				(14.1		)		0				1,127.90			6.2
	Commercial mortgage-backed securities	2,154.40				43.9				(37.8		)		0				2,160.50			12
	Other asset-backed securities	1,073.00				6.6				(2.1		)		0.2				1,077.70			6
	Redeemable preferred stocks	299.5				24.1				(9.7		)		0				313.9			1.7
	Total fixed maturities	13,415.30				242.4				(119.1		)		1.8				13,540.40			75
	Equity securities:
	Nonredeemable preferred stocks	445.7				258.7				(4.5		)		11.3				711.2			3.9
	Common equities	1,451.10				1,081.80				(2.4		)		0				2,530.50			14
	Short-term investments:
	Other short-term investments	1,272.60				0				0				0				1,272.60			7.1
Total portfolio2,3	$	16,584.70			$	1,582.90			$	(126.0	)		$	13.1			$	18,054.70		100	%
1Represents net holding period gains (losses) on certain hybrid securities (discussed below).
2Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at March 31, 2014, $350.0 million was included in "other assets" and at March 31, 2013 and December 31, 2013, $7.5 million and $61.3 million, respectively, were included in "other liabilities."
3The total fair value of the portfolio at March 31, 2014 and 2013, and December 31, 2013 included $0.8 billion, $1.2 billion, and $1.8 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.
Hybrid Securities	'
	Included in our fixed-maturity and equity securities are hybrid securities, which are reported at fair value:
		March 31,								December 31,
	(millions)	2014				2013				2013
	Fixed maturities:
	Corporate debt securities	$	145.7			$	175.7			$	164.2
	Other asset-backed securities	13.9				16.6				14.8
	Total fixed maturities	159.6				192.3				179
	Equity securities:
	Nonredeemable preferred stocks	63.8				55.4				60.3
	Total hybrid securities	$	223.4			$	247.7			$	239.3
Composition of Fixed Maturities by Maturity	'
	Fixed Maturities The composition of fixed maturities by maturity at March 31, 2014, was:
	(millions)	Cost				Fair Value
	Less than one year	$	1,838.30			$	1,874.40
	One to five years	7,538.00				7,658.90
	Five to ten years	2,849.00				2,855.80
	Ten years or greater	58.6				65.2
	Total1	$	12,283.90			$	12,454.30
	1Excludes $51.9 million related to our open interest rate swap positions.
Gross Unrealized Losses by Major Security	'
	The following tables show the composition of gross unrealized losses by major security type and by the length of time that individual securities have been in a continuous unrealized loss position:
		Total No. of Sec.		Total			Gross Unrealized Losses			Less than 12 Months									12 Months or Greater
				Fair
	($ in millions)			Value						No. of Sec.		Fair			Unrealized Losses				No. of Sec.	Fair			Unrealized Losses
												Value								Value
	31-Mar-14
	Fixed maturities:
	U.S. government obligations	18		$	930.4		$	(6.8	)	5		$	163.1		$	(.3	)		13	$	767.3		$	(6.5	)
	State and local government obligations	106		603			(9.2		)	28		76.8			(.6		)		78	526.2			(8.6		)
	Corporate debt securities	31		594.3			(7.2		)	7		101.6			(.4		)		24	492.7			(6.8		)
	Residential mortgage-backed securities	66		812.6			(11.9		)	24		359.7			(1.9		)		42	452.9			(10.0		)
	Commercial mortgage-backed securities	59		783.7			(17.6		)	19		116.7			(.2		)		40	667			(17.4		)
	Other asset-backed securities	8		112.7			(.6		)	4		36.8			(.1		)		4	75.9			(.5		)
	Redeemable preferred stocks	3		93.5			(6.2		)	0		0			0				3	93.5			(6.2		)
	Total fixed maturities	291		3,930.20			(59.5		)	87		854.7			(3.5		)		204	3,075.50			(56.0		)
	Equity securities:
	Nonredeemable preferred stocks	3		84.3			(1.2		)	0		0			0				3	84.3			(1.2		)
	Common equities	9		34			(2.8		)	7		23.1			(1.6		)		2	10.9			(1.2		)
	Total equity securities	12		118.3			(4.0		)	7		23.1			(1.6		)		5	95.2			(2.4		)
	Total portfolio	303		$	4,048.50		$	(63.5	)	94		$	877.8		$	(5.1	)		209	$	3,170.70		$	(58.4	)
		Total No. of Sec.		Total			Gross Unrealized Losses			Less than 12 Months									12 Months or Greater
				Fair
	($ in millions)			Value						No. of Sec.		Fair			Unrealized Losses				No. of Sec.	Fair			Unrealized Losses
												Value								Value
	31-Mar-13
	Fixed maturities:
	U.S. government obligations	1		$	40		$	0		1		$	40		$	0			0	$	0		$	0
	State and local government obligations	29		117.4			(.5		)	20		78.7			(.4		)		9	38.7			(.1		)
	Corporate debt securities	15		267.5			(.9		)	15		267.5			(.9		)		0	0			0
	Residential mortgage-backed securities	26		180.5			(7.5		)	10		106.7			(2.5		)		16	73.8			(5.0		)
	Commercial mortgage-backed securities	21		348.2			(3.2		)	17		343.2			(3.1		)		4	5			(.1		)
	Other asset-backed securities	4		49.7			0			4		49.7			0				0	0			0
	Redeemable preferred stocks	4		120.6			(11.8		)	1		25			0				3	95.6			(11.8		)
	Total fixed maturities	100		1,123.90			(23.9		)	68		910.8			(6.9		)		32	213.1			(17.0		)
	Equity securities:
	Nonredeemable preferred stocks	0		0			0			0		0			0				0	0			0
	Common equities	51		55.1			(7.0		)	38		44.3			(5.7		)		13	10.8			(1.3		)
	Total equity securities	51		55.1			(7.0		)	38		44.3			(5.7		)		13	10.8			(1.3		)
	Total portfolio	151		$	1,179.00		$	(30.9	)	106		$	955.1		$	(12.6	)		45	$	223.9		$	(18.3	)
		Total No. of Sec.		Total			Gross Unrealized Losses			Less than 12 Months									12 Months or Greater
				Fair
	($ in millions)			Value						No. of Sec.		Fair			Unrealized Losses				No. of Sec.	Fair			Unrealized Losses
												Value								Value
	31-Dec-13
	Fixed maturities:
	U.S. government obligations	29		$	1,444.30		$	(16.6	)	28		$	1,434.60		$	(16.3	)		1	$	9.7		$	(.3	)
	State and local government obligations	141		844.2			(18.4		)	119		759.3			(17.1		)		22	84.9			(1.3		)
	Corporate debt securities	51		997.6			(20.4		)	45		831.1			(17.8		)		6	166.5			(2.6		)
	Residential mortgage-backed securities	66		763.5			(14.1		)	45		597.6			(7.9		)		21	165.9			(6.2		)
	Commercial mortgage-backed securities	76		1,061.90			(37.8		)	60		809.2			(19.7		)		16	252.7			(18.1		)
	Other asset-backed securities	25		287.2			(2.1		)	22		233.3			(1.8		)		3	53.9			(.3		)
	Redeemable preferred stocks	4		122.7			(9.7		)	0		0			0				4	122.7			(9.7		)
	Total fixed maturities	392		5,521.40			(119.1		)	319		4,665.10			(80.6		)		73	856.3			(38.5		)
	Equity securities:
	Nonredeemable preferred stocks	7		142.3			(4.5		)	7		142.3			(4.5		)		0	0			0
	Common equities	24		59.7			(2.4		)	20		58.5			(2.4		)		4	1.2			0
	Total equity securities	31		202			(6.9		)	27		200.8			(6.9		)		4	1.2			0
	Total portfolio	423		$	5,723.40		$	(126.0	)	346		$	4,865.90		$	(87.5	)		77	$	857.5		$	(38.5	)
Total Non-Credit Portion of Other-Than-Temporary Impairment Recorded in Accumulated Other Comprehensive Income, Reflecting Original Non-Credit Loss at the Time Credit Impairment	'
	The following table shows the total non-credit portion of the OTTI recorded in accumulated other comprehensive income, reflecting the original non-credit loss at the time the credit impairment was determined:
		March 31,								December 31,
	(millions)	2014				2013				2013
	Fixed maturities:
	Residential mortgage-backed securities	$	(44.1	)		$	(44.2	)		$	(44.1	)
	Commercial mortgage-backed securities	(.9		)		(.9		)		(.9		)
	Total fixed maturities	$	(45.0	)		$	(45.1	)		$	(45.0	)
OTTI Credit Losses Recognized in Earnings	'
	The following tables provide rollforwards of the amounts related to credit losses recognized in earnings for the periods ended March 31, 2014 and 2013, for which a portion of the OTTI losses were also recognized in accumulated other comprehensive income at the time the credit impairments were determined and recognized:
		Three Months Ended March 31, 2014
		Mortgage-Backed
	(millions)	Residential				Commercial				Total
	Balance at December 31, 2013	$	19.2			$	0.4			$	19.6
	Change in recoveries of future cash flows expected to be collected1	(.1		)		0				(.1		)
	Balance at March 31, 2014	$	19.1			$	0.4			$	19.5
		Three Months Ended March 31, 2013
		Mortgage-Backed
	(millions)	Residential				Commercial				Total
	Balance at December 31, 2012	$	27.1			$	0.6			$	27.7
	Change in recoveries of future cash flows expected to be collected1	0.6				(.1		)		0.5
	Balance at March 31, 2013	$	27.7			$	0.5			$	28.2
	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.
Components of Net Realized Gains (Losses)	'
	The components of net realized gains (losses) for the three months ended March 31, were:
	(millions)	2014				2013
	Gross realized gains on security sales
	Fixed maturities:
	U.S. government obligations	$	6.5			$	1.5
	State and local government obligations	4.4				6.8
	Corporate and other debt securities	23.1				24.1
	Residential mortgage-backed securities	1				0.4
	Commercial mortgage-backed securities	6.1				4
	Total fixed maturities	41.1				36.8
	Equity securities:
	Nonredeemable preferred stocks	25.9				38.5
	Common equities	83				2.7
	Subtotal gross realized gains on security sales	150				78
	Gross realized losses on security sales
	Fixed maturities:
	U.S. government obligations	(4.7		)		(.3		)
	State and local government obligations	(.1		)		0
	Corporate and other debt securities	(2.2		)		(.4		)
	Commercial mortgage-backed securities	(2.7		)		0
	Redeemable preferred stocks	(3.2		)		(.1		)
	Total fixed maturities	(12.9		)		(.8		)
	Equity securities:
	Common equities	(3.4		)		0
	Subtotal gross realized losses on security sales	(16.3		)		(.8		)
	Net realized gains (losses) on security sales
	Fixed maturities:
	U.S. government obligations	1.8				1.2
	State and local government obligations	4.3				6.8
	Corporate and other debt securities	20.9				23.7
	Residential mortgage-backed securities	1				0.4
	Commercial mortgage-backed securities	3.4				4
	Redeemable preferred stocks	(3.2		)		(.1		)
	Total fixed maturities	28.2				36
	Equity securities:
	Nonredeemable preferred stocks	25.9				38.5
	Common equities	79.6				2.7
	Subtotal net realized gains (losses) on security sales	133.7				77.2
	Other-than-temporary impairment losses
	Fixed maturities:
	Residential mortgage-backed securities	0				(.1		)
	Total fixed maturities	0				(.1		)
	Equity securities:
	Common equities	0				(.1		)
	Subtotal other-than-temporary impairment losses	0				(.2		)
	Other gains (losses)
	Hybrid securities	3.8				2.3
	Derivative instruments	(19.3		)		1.3
	Litigation settlements	1.2				0
	Subtotal other gains (losses)	(14.3		)		3.6
	Total net realized gains (losses) on securities	$	119.4			$	80.6
Components of Net Investment Income	'
	Net Investment Income  The components of net investment income for the three months ended March 31, were:
	(millions)	2014			2013
	Fixed maturities:
	U.S. government obligations	$	13		$	11.8
	State and local government obligations	12.8			11.4
	Foreign government obligations	0.1			0
	Corporate debt securities	22			25.6
	Residential mortgage-backed securities	9.9			4.5
	Commercial mortgage-backed securities	16.7			18.7
	Other asset-backed securities	4.2			3.5
	Redeemable preferred stocks	4.1			5.4
	Total fixed maturities	82.8			80.9
	Equity securities:
	Nonredeemable preferred stocks	9.9			9.2
	Common equities	10.4			9.7
	Short-term investments:
	Other short-term investments	0.2			0.7
	Investment income	103.3			100.5
	Investment expenses	(4.1		)	(4.9		)
	Net investment income	$	99.2		$	95.6
Derivative Instruments	'
	The following table shows the status of our derivative instruments at March 31, 2014 and 2013, and December 31, 2013, and for the three months ended March 31, 2014 and 2013; 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
		March 31,								Dec. 31,								March 31,							Dec. 31,		March 31,
	Derivatives designated as:	2014				2013				2013				Purpose		Classification		2014			2013				2013		2014			2013
	Hedging instruments
	Closed:
	Ineffective cash flow hedge	$	0			$	0			$	54			Manage interest		NA		$	0		$	0			$	0	$	0		$	0
														rate risk
	Non-hedging instruments
	Assets:
	Interest rate swaps	750				0				750				Manage portfolio		Investments—		51.9			0				68.1		(19.3		)	0
														duration		fixed maturities
	Liabilities:
	Interest rate swaps	0				1,263				0				Manage portfolio		Other liabilities		0			(87.8		)		0		0			1.3
														duration
	Closed:
	Interest rate swaps	0				0				1,263				Manage portfolio		NA		0			0				0		0			0
														duration
	Total	NA				NA				NA								$	51.9		$	(87.8	)		$	68.1	$	(19.3	)	$	1.3
	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 report them on a gross basis on our balance sheets, consistent with our historical presentation.
	NA=ot Applicable

Fair_Value_Tables

Fair Value (Tables)	3 Months Ended
	Mar. 31, 2014
Fair Value Disclosures [Abstract]	'
Composition of Investment Portfolio by Major Security Type	'
	The composition of the investment portfolio by major security type and our outstanding debt was:
		Fair Value
	(millions)	Level 1		Level 2			Level 3		Total		Cost
	31-Mar-14
	Fixed maturities:
	U.S. government obligations	$	3,230.00	$	0		$	0	$	3,230.00	$	3,197.80
	State and local government obligations	0		2,154.90			0		2,154.90		2,131.00
	Foreign government obligations	17.9		0			0		17.9		17.9
	Corporate debt securities	0		2,501.60			0		2,501.60		2,461.60
	Subtotal	3,247.90		4,656.50			0		7,904.40		7,808.30
	Asset-backed securities:
	Residential mortgage-backed	0		1,307.40			0		1,307.40		1,286.70
	Commercial mortgage-backed	0		2,033.00			28.6		2,061.60		2,037.70
	Other asset-backed	0		942.5			0		942.5		936.2
	Subtotal asset-backed securities	0		4,282.90			28.6		4,311.50		4,260.60
	Redeemable preferred stocks:
	Financials	0		107.4			0		107.4		84.2
	Utilities	0		65.2			0		65.2		64.9
	Industrials	0		117.7			0		117.7		117.8
	Subtotal redeemable preferred stocks	0		290.3			0		290.3		266.9
	Total fixed maturities	3,247.90		9,229.70			28.6		12,506.20		12,335.80
	Equity securities:
	Nonredeemable preferred stocks:
	Financials	284		411.8			42.1		737.9		460.7
	Utilities	0		0			0		0		0
	Subtotal nonredeemable preferred stocks	284		411.8			42.1		737.9		460.7
	Common equities:
	Common stocks	2,278.30		0			0		2,278.30		1,252.30
	Other risk investments	0		0			0.4		0.4		0.4
	Subtotal common equities	2,278.30		0			0.4		2,278.70		1,252.70
	Total fixed maturities and equity securities	5,810.20		9,641.50			71.1		15,522.80		14,049.20
	Short-term investments:
	Other short-term investments	1,611.70		261.2			0		1,872.90		1,872.90
	Total portfolio	$	7,421.90	$	9,902.70		$	71.1	$	17,395.70	$	15,922.10
	Debt	$	0	$	2,152.50		$	0	$	2,152.50	$	1,861.30
		Fair Value
	(millions)	Level 1		Level 2			Level 3		Total		Cost
	31-Mar-13
	Fixed maturities:
	U.S. government obligations	$	3,099.20	$	0		$	0	$	3,099.20	$	3,015.60
	State and local government obligations	0		1,813.90			0		1,813.90		1,771.60
	Foreign government obligations	0		0			0		0		0
	Corporate debt securities	0		3,014.30			0		3,014.30		2,910.80
	Subtotal	3,099.20		4,828.20			0		7,927.40		7,698.00
	Asset-backed securities:
	Residential mortgage-backed	0		535.7			85.6		621.3		595.7
	Commercial mortgage-backed	0		2,152.90			27.3		2,180.20		2,107.20
	Other asset-backed	0		940.8			0		940.8		929.2
	Subtotal asset-backed securities	0		3,629.40			112.9		3,742.30		3,632.10
	Redeemable preferred stocks:
	Financials	0		132.2			0		132.2		110.7
	Utilities	0		67			0		67		64.9
	Industrials	0		177.4			0		177.4		180.3
	Subtotal redeemable preferred stocks	0		376.6			0		376.6		355.9
	Total fixed maturities	3,099.20		8,834.20			112.9		12,046.30		11,686.00
	Equity securities:
	Nonredeemable preferred stocks:
	Financials	270.3		490.3			33.8		794.4		391.8
	Utilities	0		26.2			0		26.2		20.7
	Subtotal nonredeemable preferred stocks	270.3		516.5			33.8		820.6		412.5
	Common equities:
	Common stocks	2,099.10		0			0		2,099.10		1,385.30
	Other risk investments	0		0			12		12		3.2
Subtotal common equities	2,099.10		0			12		2,111.10		1,388.50
Total fixed maturities and equity securities	5,468.60		9,350.70			158.7		14,978.00		13,487.00
Short-term investments:
Other short-term investments	1,984.20		337.5			0		2,321.70		2,321.70
Total portfolio	$	7,452.80	$	9,688.20		$	158.7	$	17,299.70	$	15,808.70
Debt	$	0	$	2,397.20		$	0	$	2,397.20	$	2,063.50
	Fair Value
(millions)	Level 1		Level 2			Level 3		Total		Cost
31-Dec-13
Fixed maturities:
U.S. government obligations	$	3,662.20	$	0		$	0	$	3,662.20	$	3,630.40
State and local government obligations	0		2,256.00			0		2,256.00		2,247.30
Foreign government obligations	15.6		0			0		15.6		15.6
Corporate debt securities	0		2,926.60			0		2,926.60		2,885.00
Subtotal	3,677.80		5,182.60			0		8,860.40		8,778.30
Asset-backed securities:
Residential mortgage-backed	0		1,127.70			0.2		1,127.90		1,110.10
Commercial mortgage-backed	0		2,131.50			29		2,160.50		2,154.40
Other asset-backed	0		1,077.70			0		1,077.70		1,073.00
Subtotal asset-backed securities	0		4,336.90			29.2		4,366.10		4,337.50
Redeemable preferred stocks:
Financials	0		102.8			0		102.8		84.2
Utilities	0		65.6			0		65.6		64.9
Industrials	0		145.5			0		145.5		150.4
Subtotal redeemable preferred stocks	0		313.9			0		313.9		299.5
Total fixed maturities	3,677.80		9,833.40			29.2		13,540.40		13,415.30
Equity securities:
Nonredeemable preferred stocks:
Financials	240.8		414.6			39		694.4		431.5
Utilities	0		16.8			0		16.8		14.2
Subtotal nonredeemable preferred stocks	240.8		431.4			39		711.2		445.7
Common equities:
Common stocks	2,530.00		0			0		2,530.00		1,450.60
Other risk investments	0		0			0.5		0.5		0.5
Subtotal common equities	2,530.00		0			0.5		2,530.50		1,451.10
Total fixed maturities and equity securities	6,448.60		10,264.80			68.7		16,782.10		15,312.10
Short-term investments:
Other short-term investments	987.8		284.8			0		1,272.60		1,272.60
Total portfolio	$	7,436.40	$	10,549.60		$	68.7	$	18,054.70	$	16,584.70
Debt	$	0	$	2,073.70		$	0	$	2,073.70	$	1,860.90
Summary of Changes in Fair Value Associated With Level 3 Assets	'
	The following tables provide a summary of changes in fair value associated with Level 3 assets for the three months ended March 31, 2014 and 2013:
		Level 3 Fair Value
		Three months ended March 31, 2014
	(millions)	Fair Value at Dec. 31, 2013		Calls/			Purchases		Sales		Net Realized (Gain)/Loss on Sales		Change in Valuation			Net		Fair Value at March 31, 2014
				Maturities/												Transfers
				Paydowns												In (Out)
	Fixed maturities:
	Asset-backed securities:
	Residential mortgage-backed	$	0.2	$	0		$	0	$	0	$	0	$	(.2	)	$	0	$	0
	Commercial mortgage-backed	29		(.5		)	0		0		0		0.1			0		28.6
	Total fixed maturities	29.2		(.5		)	0		0		0		(.1		)	0		28.6
	Equity securities:
	Nonredeemable preferred stocks:
	Financials1	39		0			0		0		0		3.1			0		42.1
	Common equities:
	Other risk investments	0.5		(.1		)	0		0		0		0			0		0.4
	Total Level 3 securities	$	68.7	$	(.6	)	$	0	$	0	$	0	$	3		$	0	$	71.1
	1The $3.1 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 March 31, 2013
	(millions)	Fair Value at Dec. 31, 2012		Calls/			Purchases		Sales		Net Realized (Gain)/Loss on Sales		Change in			Net		Fair Value at March 31, 2013
				Maturities/									Valuation			Transfers
				Paydowns												In (Out)
	Fixed maturities:
	Asset-backed securities:
	Residential mortgage-backed	$	45.5	$	(5.3	)	$	45.2	$	0	$	0	$	0.2		$	0	$	85.6
	Commercial mortgage-backed	25.3		(.4		)	0		0		0		2.4			0		27.3
	Total fixed maturities	70.8		(5.7		)	45.2		0		0		2.6			0		112.9
	Equity securities:
	Nonredeemable preferred stocks:
	Financials1	31.9		0			0		0		0		1.9			0		33.8
	Common equities:
	Other risk investments	12		0			0		0		0		0			0		12
	Total Level 3 securities	$	114.7	$	(5.7	)	$	45.2	$	0	$	0	$	4.5		$	0	$	158.7
	1The $1.9 million represents net holding period gains on a hybrid security which is reflected in net realized gains (losses) on securities in the comprehensive income statement.
Summary of Quantitative Information about Level 3 Fair Value Measurements	'
	The following tables provide a summary of the quantitative information about Level 3 fair value measurements for our applicable securities at March 31, 2014 and 2013, and December 31, 2013:
		Quantitative Information about Level 3 Fair Value Measurements
	($ in millions)	Fair Value at March 31, 2014		Valuation Technique		Unobservable Input	Unobservable
							Input Assumption
	Fixed maturities:
	Asset-backed securities:
	Residential mortgage-backed1	$	0	NA		NA	NA
	Commercial mortgage-backed	28.6		External vendor		Prepayment rate2	0
	Total fixed maturities	28.6
	Equity securities:
	Nonredeemable preferred stocks:
	Financials	42.1		Multiple of tangible net book value		Price to book ratio multiple	1.9
	Common equities:
	Other risk investments	0
	Subtotal Level 3 securities	70.7
	Pricing exemption securities3	0.4
	Total Level 3 securities	$	71.1
	1This security is approaching final maturity and is valued at zero.
	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 these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us.
	NA=ot Applicable
		Quantitative Information about Level 3 Fair Value Measurements
	($ in millions)	Fair Value at March 31, 2013		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	27.4		External vendor		Prepayment rate2	0
	Total fixed maturities	27.6
	Equity securities:
	Nonredeemable preferred stocks:
	Financials	33.8		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	72.6
	Pricing exemption securities3	86.1
	Total Level 3 securities	$	158.7
	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.
		Quantitative Information about Level 3 Fair Value Measurements
	($ in millions)	Fair Value at Dec. 31, 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	29		External vendor		Prepayment rate2	0
	Total fixed maturities	29.2
	Equity securities:
	Nonredeemable preferred stocks:
	Financials	39		Multiple of tangible net book value		Price to book ratio multiple	1.9
	Common equities:
	Other risk investments	0
	Subtotal Level 3 securities	68.2
	Pricing exemption securities3	0.5
	Total Level 3 securities	$	68.7
	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 these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us.

Debt_Tables

Debt (Tables)	3 Months Ended
	Mar. 31, 2014
Debt Disclosure [Abstract]	'
Debt Table	'
	Debt consisted of:
		31-Mar-14				31-Mar-13				31-Dec-13
	(millions)	Carrying		Fair		Carrying		Fair		Carrying		Fair
		Value		Value		Value		Value		Value		Value
	7% Notes due 2013	$	0	$	0	$	149.9	$	154.9	$	0	$	0
	3.75% Senior Notes due 2021	497.6		524.5		497.4		544.7		497.6		509.1
	6 5/8% Senior Notes due 2029	295.4		381.8		295.2		382.6		295.3		359.6
	6.25% Senior Notes due 2032	394.7		501.4		394.5		507.1		394.6		473.7
	6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067	673.6		744.8		726.5		807.9		673.4		731.3
	Total	$	1,861.30	$	2,152.50	$	2,063.50	$	2,397.20	$	1,860.90	$	2,073.70

Supplemental_Cash_Flow_Informa1

Supplemental Cash Flow Information (Tables)	3 Months Ended
	Mar. 31, 2014
Supplemental Cash Flow Elements [Abstract]	'
Supplemental Cash Flow Information Table	'
	We paid the following in the respective periods:
		Three Months Ended March 31,
	(millions)	2014		2013
	Income taxes	$	0	$	18
	Interest	19.3		19.3

Segment_Information_Tables

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2014
Segment Reporting [Abstract]	'
Reconciliation of Revenue and operating Income from Segments to Consolidated	'
	Following are the operating results for the respective periods:
		Three Months Ended March 31,
		2014						2013
	(millions)	Revenues			Pretax			Revenues		Pretax
					Profit					Profit
					(Loss)					(Loss)
	Personal Lines
	Agency	$	2,203.20		$	178.6		$	2,107.20	$	174.9
	Direct	1,762.20			71			1,641.60		127.2
	Total Personal Lines1	3,965.40			249.6			3,748.80		302.1
	Commercial Lines	436.9			40.9			430.4		15.3
	Other indemnity	0			(.7		)	0.1		0.3
	Total underwriting operations	4,402.30			289.8			4,179.30		317.7
	Fees and other revenues2	72.8			NA			68.4		NA
	Service businesses	9.8			0.1			8.4		(.2		)
	Investments3	222.7			218.6			181.1		176.2
	Interest expense	NA			(26.7		)	NA		(30.6		)
	Consolidated total	$	4,707.60		$	481.8		$	4,437.20	$	463.1
	1Personal auto insurance accounted for 92% and 91% of the total Personal Lines segment net premiums earned in the first quarters of 2014 and 2013, respectively; 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 March 31,
		2014				2013
		Underwriting		Combined		Underwriting		Combined
		Margin		Ratio		Margin		Ratio
	Personal Lines
	Agency	8.1	%	91.9		8.3	%	91.7
	Direct	4		96		7.8		92.2
	Total Personal Lines	6.3		93.7		8.1		91.9
	Commercial Lines	9.4		90.6		3.5		96.5
	Other indemnity1	NM		NM		NM		NM
	Total underwriting operations	6.6		93.4		7.6		92.4
	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)	3 Months Ended
	Mar. 31, 2014
Equity [Abstract]	'
Components of Other Comprehensive Income (Loss)	'
	The components of other comprehensive income (loss), including reclassification adjustments by income statement line item, were as follows:
											Components of Changes in
											Accumulated Other
											Comprehensive Income (after tax)
	(millions)	Pretax total			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						transactions1,2
	Balance at December 31, 2013	$	1,464.10		$	(512.4	)	$	951.7		$	947		$	4.1		$	0.6
	Other comprehensive income (loss) before reclassifications:
	Investment securities	131.8			(46.1		)	85.7			85.7			0			0
	Net non-credit related OTTI losses, adjusted for	0			0			0			0			0			0
	valuation changes
	Forecasted transactions	0			0			0			0			0			0
	Foreign currency translation adjustment	0			0			0			0			0			0
	Total other comprehensive income (loss) before reclassifications	131.8			(46.1		)	85.7			85.7			0			0
	Less: Reclassification adjustment for amounts realized in net income by income statement line item:
	Net impairment losses recognized in earnings	0			0			0			0			0			0
	Net realized gains (losses) on securities	131.9			(46.1		)	85.8			85.8			0			0
	Interest expense2	0.5			(.2		)	0.3			0			0.3			0
	Total reclassification adjustment for amounts realized in net income	132.4			(46.3		)	86.1			85.8			0.3			0
	Total other comprehensive income (loss)	(.6		)	0.2			(.4		)	(.1		)	(.3		)	0
	Balance at March 31, 2014	$	1,463.50		$	(512.2	)	$	951.3		$	946.9		$	3.8		$	0.6
											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
	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	227.8			(79.7		)	148.1			148.1			0			0
	Net non-credit related OTTI losses, adjusted for	0.3			(.1		)	0.2			0.2			0			0
	valuation changes
	Forecasted transactions	0			0			0			0			0			0
	Foreign currency translation adjustment	(.3		)	0.1			(.2		)	0			0			(.2		)
	Total other comprehensive income (loss) before reclassifications	227.8			(79.7		)	148.1			148.3			0			(.2		)
	Less: Reclassification adjustment for amounts realized in net income by income statement line item:
	Net impairment losses recognized in earnings	(.1		)	0.1			0			0			0			0
	Net realized gains (losses) on securities	75.6			(26.5		)	49.1			49.1			0			0
	Interest expense	0.5			(.2		)	0.3			0			0.3			0
	Total reclassification adjustment for amounts realized in net income	76			(26.6		)	49.4			49.1			0.3			0
	Total other comprehensive income (loss)	151.8			(53.1		)	98.7			99.2			(.3		)	(.2		)
	Balance at March 31, 2013	$	1,491.80		$	(522.1	)	$	969.7		$	961.9		$	5.8		$	2
	1Entered into for the purpose of managing interest rate risk associated with our debt issuances.
	2We 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_Basis_of

Basis of Presentation Basis of Presentation-Additional Information (Details) (USD $)	Mar. 31, 2014
In Millions, unless otherwise specified
Assets Held-for-sale, Long Lived [Abstract]	'
Assets Held-for-sale, Property, Plant and Equipment	$8.70

Investments_Investment_Portfol

Investments Investment Portfolio by Major Security Type (Detail) (USD $)	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013
In Millions, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	$15,922.10	[1],[2]	$16,584.70	[1],[2]	$15,808.70	[1],[2]
Gross Unrealized Gains	1,520.30	[1],[2]	1,582.90	[1],[2]	1,510.80	[1],[2]
Gross Unrealized Losses	-63.5	[1],[2]	-126	[1],[2]	-30.9	[1],[2]
Net Realized Gains (Losses)	16.8	[1],[2],[3]	13.1	[1],[2],[3]	11.1	[1],[2],[3]
Total investments at fair value	17,395.70	[1],[2]	18,054.70	[1],[2]	17,299.70	[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	12,335.80		13,415.30		11,686
Gross Unrealized Gains	227.8		242.4		379.5
Gross Unrealized Losses	-59.5		-119.1		-23.9
Net Realized Gains (Losses)	2.1	[3]	1.8	[3]	4.7	[3]
Total investments at fair value	12,506.20		13,540.40		12,046.30
% of Total Fair Value	71.90%		75.00%		69.60%
Fixed maturities | U.S. government obligations	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	3,197.80		3,630.40		3,015.60
Gross Unrealized Gains	39		48.4		83.6
Gross Unrealized Losses	-6.8		-16.6		0
Net Realized Gains (Losses)	0	[3]	0	[3]	0	[3]
Total investments at fair value	3,230		3,662.20		3,099.20
% of Total Fair Value	18.50%		20.30%		17.90%
Fixed maturities | State and local government obligations	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	2,131		2,247.30		1,771.60
Gross Unrealized Gains	33.1		27.1		42.8
Gross Unrealized Losses	-9.2		-18.4		-0.5
Net Realized Gains (Losses)	0	[3]	0	[3]	0	[3]
Total investments at fair value	2,154.90		2,256		1,813.90
% of Total Fair Value	12.40%		12.50%		10.50%
Fixed maturities | Foreign government obligations	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	17.9		15.6		0
Gross Unrealized Gains	0		0		0
Gross Unrealized Losses	0		0		0
Net Realized Gains (Losses)	0	[3]	0	[3]	0	[3]
Total investments at fair value	17.9		15.6		0
% of Total Fair Value	0.10%		0.10%		0.00%
Fixed maturities | Corporate debt securities	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	2,461.60		2,885		2,910.80
Gross Unrealized Gains	45.4		60.4		100.3
Gross Unrealized Losses	-7.2		-20.4		-0.9
Net Realized Gains (Losses)	1.8	[3]	1.6	[3]	4.1	[3]
Total investments at fair value	2,501.60		2,926.60		3,014.30
% of Total Fair Value	14.40%		16.20%		17.40%
Fixed maturities | Residential mortgage-backed securities	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	1,286.70		1,110.10		595.7
Gross Unrealized Gains	32.6		31.9		33.1
Gross Unrealized Losses	-11.9		-14.1		-7.5
Net Realized Gains (Losses)	0	[3]	0	[3]	0	[3]
Total investments at fair value	1,307.40		1,127.90		621.3
% of Total Fair Value	7.50%		6.20%		3.60%
Fixed maturities | Commercial mortgage-backed securities	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	2,037.70		2,154.40		2,107.20
Gross Unrealized Gains	41.5		43.9		76.2
Gross Unrealized Losses	-17.6		-37.8		-3.2
Net Realized Gains (Losses)	0	[3]	0	[3]	0	[3]
Total investments at fair value	2,061.60		2,160.50		2,180.20
% of Total Fair Value	11.90%		12.00%		12.60%
Fixed maturities | Other asset-backed securities	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	936.2		1,073		929.2
Gross Unrealized Gains	6.6		6.6		11
Gross Unrealized Losses	-0.6		-2.1		0
Net Realized Gains (Losses)	0.3	[3]	0.2	[3]	0.6	[3]
Total investments at fair value	942.5		1,077.70		940.8
% of Total Fair Value	5.40%		6.00%		5.40%
Fixed maturities | Redeemable preferred stocks	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	266.9		299.5		355.9
Gross Unrealized Gains	29.6		24.1		32.5
Gross Unrealized Losses	-6.2		-9.7		-11.8
Net Realized Gains (Losses)	0	[3]	0	[3]	0	[3]
Total investments at fair value	290.3		313.9		376.6
% of Total Fair Value	1.70%		1.70%		2.20%
Equity securities | Nonredeemable preferred stocks	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	460.7		445.7		412.5
Gross Unrealized Gains	263.7		258.7		401.7
Gross Unrealized Losses	-1.2		-4.5		0
Net Realized Gains (Losses)	14.7	[3]	11.3	[3]	6.4	[3]
Total investments at fair value	737.9		711.2		820.6
% of Total Fair Value	4.20%		3.90%		4.80%
Equity securities | Common equities	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	1,252.70		1,451.10		1,388.50
Gross Unrealized Gains	1,028.80		1,081.80		729.6
Gross Unrealized Losses	-2.8		-2.4		-7
Net Realized Gains (Losses)	0	[3]	0	[3]	0	[3]
Total investments at fair value	2,278.70		2,530.50		2,111.10
% of Total Fair Value	13.10%		14.00%		12.20%
Short-term investments | Other short-term investments	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Cost	1,872.90		1,272.60		2,321.70
Gross Unrealized Gains	0		0		0
Gross Unrealized Losses	0		0		0
Net Realized Gains (Losses)	0	[3]	0	[3]	0	[3]
Total investments at fair value	$1,872.90		$1,272.60		$2,321.70
% of Total Fair Value	10.80%		7.10%		13.40%
[1]	The total fair value of the portfolio at March 31, 2014 and 2013, and December 31, 2013 included $0.8 billion, $1.2 billion, and $1.8 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.
[2]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at March 31, 2014, $350.0 million was included in "other assets" and at March 31, 2013 and December 31, 2013, $7.5 million and $61.3 million, respectively, were included in "other liabilities."
[3]	Represents net holding period gains (losses) on certain hybrid securities (discussed below).

Investments_Investment_Portfol1

Investments Investment Portfolio by Major Security Type (Parenthetical) (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Investments, Debt and Equity Securities [Abstract]	'	'	'
Net unsettled security transactions offset in other assets	$350,000,000	'	'
Net unsettled security transactions offset in other liabilities	'	61,300,000	7,500,000
Securities in the portfolio of a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions	$800,000,000	$1,800,000,000	$1,200,000,000

Investments_Hybrid_Securities_

Investments Hybrid Securities (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Millions, unless otherwise specified
Hybrid Securities [Line Items]	'	'	'
Hybrid securities	$223.40	$239.30	$247.70
Fixed maturities	'	'	'
Hybrid Securities [Line Items]	'	'	'
Hybrid securities	159.6	179	192.3
Fixed maturities | Corporate debt securities	'	'	'
Hybrid Securities [Line Items]	'	'	'
Hybrid securities	145.7	164.2	175.7
Fixed maturities | Other asset-backed securities	'	'	'
Hybrid Securities [Line Items]	'	'	'
Hybrid securities	13.9	14.8	16.6
Equity securities | Nonredeemable preferred stocks	'	'	'
Hybrid Securities [Line Items]	'	'	'
Hybrid securities	$63.80	$60.30	$55.40

Investments_Composition_of_Fix

Investments Composition of Fixed Maturities by Maturity (Detail) (USD $)	Mar. 31, 2014
In Millions, unless otherwise specified
Available for sale, cost	'
Less than one year	$1,838.30
One to five years	7,538
Five to ten years	2,849
Ten years or greater	58.6
Total	12,283.90	[1]
Available for sale, Fair value	'
Less than one year	1,874.40
One to five years	7,658.90
Five to ten years	2,855.80
Ten years or greater	65.2
Total	$12,454.30	[1]
[1]	Excludes $51.9 million related to our open interest rate swap positions.

Investments_Composition_of_Fix1

Investments Composition of Fixed Maturities by Maturity (Parenthetical) (Detail) (USD $)	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013
In Millions, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Open interest rate swap positions	$51.90	[1]	$68.10	[1]	($87.80)	[1]
Interest rate swaps	'		'		'
Schedule of Available-for-sale Securities [Line Items]	'		'		'
Open interest rate swap positions	$51.90		'		'
[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 report them on a gross basis on our balance sheets, consistent with our historical presentation.

Investments_Gross_Unrealized_l

Investments Gross Unrealized losses by Major Security (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Millions, unless otherwise specified
Investments, Unrealized Loss Position [Line Items]	'	'	'
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	303	423	151
Total Fair Value	$4,048.50	$5,723.40	$1,179
Gross Unrealized Losses	-63.5	-126	-30.9
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	94	346	106
Less than 12 Months Fair Value	877.8	4,865.90	955.1
Less than 12 Months Unrealized Losses	-5.1	-87.5	-12.6
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	209	77	45
12 Months or Greater Fair Value	3,170.70	857.5	223.9
12 Months or Greater Unrealized Losses	-58.4	-38.5	-18.3
Fixed maturities	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	291	392	100
Total Fair Value	3,930.20	5,521.40	1,123.90
Gross Unrealized Losses	-59.5	-119.1	-23.9
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	87	319	68
Less than 12 Months Fair Value	854.7	4,665.10	910.8
Less than 12 Months Unrealized Losses	-3.5	-80.6	-6.9
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	204	73	32
12 Months or Greater Fair Value	3,075.50	856.3	213.1
12 Months or Greater Unrealized Losses	-56	-38.5	-17
Fixed maturities | U.S. government obligations	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	18	29	1
Total Fair Value	930.4	1,444.30	40
Gross Unrealized Losses	-6.8	-16.6	0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	5	28	1
Less than 12 Months Fair Value	163.1	1,434.60	40
Less than 12 Months Unrealized Losses	-0.3	-16.3	0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	13	1	0
12 Months or Greater Fair Value	767.3	9.7	0
12 Months or Greater Unrealized Losses	-6.5	-0.3	0
Fixed maturities | State and local government obligations	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	106	141	29
Total Fair Value	603	844.2	117.4
Gross Unrealized Losses	-9.2	-18.4	-0.5
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	28	119	20
Less than 12 Months Fair Value	76.8	759.3	78.7
Less than 12 Months Unrealized Losses	-0.6	-17.1	-0.4
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	78	22	9
12 Months or Greater Fair Value	526.2	84.9	38.7
12 Months or Greater Unrealized Losses	-8.6	-1.3	-0.1
Fixed maturities | Corporate debt securities	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	31	51	15
Total Fair Value	594.3	997.6	267.5
Gross Unrealized Losses	-7.2	-20.4	-0.9
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	7	45	15
Less than 12 Months Fair Value	101.6	831.1	267.5
Less than 12 Months Unrealized Losses	-0.4	-17.8	-0.9
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	24	6	0
12 Months or Greater Fair Value	492.7	166.5	0
12 Months or Greater Unrealized Losses	-6.8	-2.6	0
Fixed maturities | Residential mortgage-backed securities	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	66	66	26
Total Fair Value	812.6	763.5	180.5
Gross Unrealized Losses	-11.9	-14.1	-7.5
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	24	45	10
Less than 12 Months Fair Value	359.7	597.6	106.7
Less than 12 Months Unrealized Losses	-1.9	-7.9	-2.5
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	42	21	16
12 Months or Greater Fair Value	452.9	165.9	73.8
12 Months or Greater Unrealized Losses	-10	-6.2	-5
Fixed maturities | Commercial mortgage-backed securities	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	59	76	21
Total Fair Value	783.7	1,061.90	348.2
Gross Unrealized Losses	-17.6	-37.8	-3.2
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	19	60	17
Less than 12 Months Fair Value	116.7	809.2	343.2
Less than 12 Months Unrealized Losses	-0.2	-19.7	-3.1
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	40	16	4
12 Months or Greater Fair Value	667	252.7	5
12 Months or Greater Unrealized Losses	-17.4	-18.1	-0.1
Fixed maturities | Other asset-backed securities	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	8	25	4
Total Fair Value	112.7	287.2	49.7
Gross Unrealized Losses	-0.6	-2.1	0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	4	22	4
Less than 12 Months Fair Value	36.8	233.3	49.7
Less than 12 Months Unrealized Losses	-0.1	-1.8	0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	4	3	0
12 Months or Greater Fair Value	75.9	53.9	0
12 Months or Greater Unrealized Losses	-0.5	-0.3	0
Fixed maturities | Redeemable preferred stocks	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	3	4	4
Total Fair Value	93.5	122.7	120.6
Gross Unrealized Losses	-6.2	-9.7	-11.8
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	0	0	1
Less than 12 Months Fair Value	0	0	25
Less than 12 Months Unrealized Losses	0	0	0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	3	4	3
12 Months or Greater Fair Value	93.5	122.7	95.6
12 Months or Greater Unrealized Losses	-6.2	-9.7	-11.8
Equity securities	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	12	31	51
Total Fair Value	118.3	202	55.1
Gross Unrealized Losses	-4	-6.9	-7
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	7	27	38
Less than 12 Months Fair Value	23.1	200.8	44.3
Less than 12 Months Unrealized Losses	-1.6	-6.9	-5.7
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	5	4	13
12 Months or Greater Fair Value	95.2	1.2	10.8
12 Months or Greater Unrealized Losses	-2.4	0	-1.3
Equity securities | Nonredeemable preferred stocks	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	3	7	0
Total Fair Value	84.3	142.3	0
Gross Unrealized Losses	-1.2	-4.5	0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	0	7	0
Less than 12 Months Fair Value	0	142.3	0
Less than 12 Months Unrealized Losses	0	-4.5	0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	3	0	0
12 Months or Greater Fair Value	84.3	0	0
12 Months or Greater Unrealized Losses	-1.2	0	0
Equity securities | Common equities	'	'	'
Investments, Unrealized Loss Position [Line Items]	'	'	'
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	9	24	51
Total Fair Value	34	59.7	55.1
Gross Unrealized Losses	-2.8	-2.4	-7
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	7	20	38
Less than 12 Months Fair Value	23.1	58.5	44.3
Less than 12 Months Unrealized Losses	-1.6	-2.4	-5.7
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	2	4	13
12 Months or Greater Fair Value	10.9	1.2	10.8
12 Months or Greater Unrealized Losses	($1.20)	$0	($1.30)

Investments_Total_NonCredit_Po

Investments Total Non-Credit Portion of Other-Than-Temporary Impairment Recorded in Accumulated Other Comprehensive Income, Reflecting Original Non-Credit Loss at Time Credit Impairment (Detail) (Fixed maturities, USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Millions, unless otherwise specified
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)	($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	-44.1	-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)

Investments_OTTI_Credit_Losses

Investments OTTI Credit Losses Recognized in Earnings (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]	'		'
Beginning balance	$19.60		$27.70
Change in recoveries of future cash flows expected to be collected	-0.1	[1]	0.5	[1]
Ending balance	19.5		28.2
Residential mortgage-backed securities	'		'
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]	'		'
Beginning balance	19.2		27.1
Change in recoveries of future cash flows expected to be collected	-0.1	[1]	0.6	[1]
Ending balance	19.1		27.7
Commercial mortgage-backed securities	'		'
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]	'		'
Beginning balance	0.4		0.6
Change in recoveries of future cash flows expected to be collected	0	[1]	-0.1	[1]
Ending balance	$0.40		$0.50
[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.

Investments_Components_of_Net_

Investments Components of Net Realized Gains (Losses) (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Gain (Loss) on Investments [Line Items]	'	'
Gross realized gains on securities sales	$150	$78
Gross realized losses on securities sales	-16.3	-0.8
Net realized gains (losses) on securities sales	133.7	77.2
Other-than-temporary impairment losses	0	-0.2
Total net realized gains (losses) on securities	119.4	80.6
Fixed maturities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Gross realized gains on securities sales	41.1	36.8
Gross realized losses on securities sales	-12.9	-0.8
Net realized gains (losses) on securities sales	28.2	36
Other-than-temporary impairment losses	0	-0.1
Fixed maturities | U.S. government obligations	'	'
Gain (Loss) on Investments [Line Items]	'	'
Gross realized gains on securities sales	6.5	1.5
Gross realized losses on securities sales	-4.7	-0.3
Net realized gains (losses) on securities sales	1.8	1.2
Fixed maturities | State and local government obligations	'	'
Gain (Loss) on Investments [Line Items]	'	'
Gross realized gains on securities sales	4.4	6.8
Gross realized losses on securities sales	-0.1	0
Net realized gains (losses) on securities sales	4.3	6.8
Fixed maturities | Corporate And Other Debt Securities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Gross realized gains on securities sales	23.1	24.1
Gross realized losses on securities sales	-2.2	-0.4
Net realized gains (losses) on securities sales	20.9	23.7
Fixed maturities | Residential mortgage-backed securities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Gross realized gains on securities sales	1	0.4
Net realized gains (losses) on securities sales	1	0.4
Other-than-temporary impairment losses	0	-0.1
Fixed maturities | Commercial mortgage-backed securities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Gross realized gains on securities sales	6.1	4
Gross realized losses on securities sales	-2.7	0
Net realized gains (losses) on securities sales	3.4	4
Fixed maturities | Redeemable preferred stocks	'	'
Gain (Loss) on Investments [Line Items]	'	'
Gross realized losses on securities sales	-3.2	-0.1
Net realized gains (losses) on securities sales	-3.2	-0.1
Equity securities | Nonredeemable preferred stocks	'	'
Gain (Loss) on Investments [Line Items]	'	'
Gross realized gains on securities sales	25.9	38.5
Net realized gains (losses) on securities sales	25.9	38.5
Equity securities | Common equities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Gross realized gains on securities sales	83	2.7
Gross realized losses on securities sales	-3.4	0
Net realized gains (losses) on securities sales	79.6	2.7
Other-than-temporary impairment losses	0	-0.1
Hybrid and Derivative Instruments and Litigation Settlements	'	'
Gain (Loss) on Investments [Line Items]	'	'
Other gains (losses)	-14.3	3.6
Hybrid and Derivative Instruments and Litigation Settlements | Hybrid Preferred Stock	'	'
Gain (Loss) on Investments [Line Items]	'	'
Other gains (losses)	3.8	2.3
Hybrid and Derivative Instruments and Litigation Settlements | Derivative Instruments	'	'
Gain (Loss) on Investments [Line Items]	'	'
Other gains (losses)	-19.3	1.3
Hybrid and Derivative Instruments and Litigation Settlements | Litigation Settlements	'	'
Gain (Loss) on Investments [Line Items]	'	'
Other gains (losses)	$1.20	$0

Investments_Components_of_Net_1

Investments Components of Net Investment Income (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Net Investment Income [Line Items]	'	'
Investment income	$103.30	$100.50
Investment expenses	-4.1	-4.9
Net Investment Income	99.2	95.6
Fixed maturities	'	'
Net Investment Income [Line Items]	'	'
Investment income	82.8	80.9
Fixed maturities | U.S. government obligations	'	'
Net Investment Income [Line Items]	'	'
Investment income	13	11.8
Fixed maturities | State and local government obligations	'	'
Net Investment Income [Line Items]	'	'
Investment income	12.8	11.4
Fixed maturities | Foreign government obligations	'	'
Net Investment Income [Line Items]	'	'
Investment income	0.1	0
Fixed maturities | Corporate debt securities	'	'
Net Investment Income [Line Items]	'	'
Investment income	22	25.6
Fixed maturities | Residential mortgage-backed securities	'	'
Net Investment Income [Line Items]	'	'
Investment income	9.9	4.5
Fixed maturities | Commercial mortgage-backed securities	'	'
Net Investment Income [Line Items]	'	'
Investment income	16.7	18.7
Fixed maturities | Other asset-backed securities	'	'
Net Investment Income [Line Items]	'	'
Investment income	4.2	3.5
Fixed maturities | Redeemable preferred stocks	'	'
Net Investment Income [Line Items]	'	'
Investment income	4.1	5.4
Equity securities | Nonredeemable preferred stocks	'	'
Net Investment Income [Line Items]	'	'
Investment income	9.9	9.2
Equity securities | Common equities	'	'
Net Investment Income [Line Items]	'	'
Investment income	10.4	9.7
Short-term investments | Other short-term investments	'	'
Net Investment Income [Line Items]	'	'
Investment income	$0.20	$0.70

Investments_Derivative_Instrum

Investments Derivative Instruments (Detail) (USD $)	3 Months Ended				12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013
Derivative [Line Items]	'		'		'
Balance Sheet - Fair Value	$51.90	[1]	($87.80)	[1]	$68.10	[1]
Income Statement - Net Realized Gain (Loss) on Securities	-19.3		1.3		'
Designated as Hedging Instruments | Closed Positions | Ineffective Cash Flow Hedge	'		'		'
Derivative [Line Items]	'		'		'
Notional Value	0	[2]	0	[2]	54	[2]
Purpose	'		'		'Manage interest  rate risk
Balance Sheet - Fair Value	0	[1]	0	[1]	0	[1]
Income Statement - Net Realized Gain (Loss) on Securities	0		0		'
Non-hedging Instruments | Closed Positions | Interest rate swaps	'		'		'
Derivative [Line Items]	'		'		'
Notional Value	0	[2]	0	[2]	1,263	[2]
Purpose	'		'		'Manage portfolio duration
Balance Sheet - Fair Value	0	[1]	0	[1]	0	[1]
Income Statement - Net Realized Gain (Loss) on Securities	0		0		'
Non-hedging Instruments | Assets | Interest rate swaps | Fixed maturities	'		'		'
Derivative [Line Items]	'		'		'
Notional Value	750	[2]	0	[2]	750	[2]
Purpose	'Manage portfolio duration		'		'Manage portfolio duration
Balance Sheet - Fair Value	51.9	[1]	0	[1]	68.1	[1]
Income Statement - Net Realized Gain (Loss) on Securities	-19.3		0		'
Non-hedging Instruments | Liabilities | Interest rate swaps | Other Liabilities	'		'		'
Derivative [Line Items]	'		'		'
Notional Value	0	[2]	1,263	[2]	0	[2]
Purpose	'		'Manage portfolio duration		'
Balance Sheet - Fair Value	0	[1]	-87.8	[1]	0	[1]
Income Statement - Net Realized Gain (Loss) on Securities	$0		$1.30		'
[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 report them on a gross basis on our balance sheets, consistent with our historical presentation.
[2]	The amounts represent the value held at quarter and year end for open positions and the maximum amount held during the period for closed positions.

Investments_Investments_Additi

Investments Investments - Additional Information (Detail) (USD $)	3 Months Ended				12 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013
Schedule of Investments [Line Items]	'		'		'
Open reverse repurchase commitments	$140,000,000		$620,400,000		$200,000,000
Gross unrealized losses	63,500,000		30,900,000		126,000,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	303		151		423
Trading securities	0		0		0
Net realized gains (losses) on securities	119,400,000		80,800,000		'
Balance Sheet - Fair Value	51,900,000	[1]	-87,800,000	[1]	68,100,000	[1]
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067	'		'		'
Schedule of Investments [Line Items]	'		'		'
Repurchase of debt, face amount	0		0		54,100,000
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 | Net unrealized gains on forecasted transactions	'		'		'
Schedule of Investments [Line Items]	'		'		'
Cash flow hedge gain reclassification from accumulated other comprehensive income to net realized gains/losses on securities	'		'		800,000
Interest rate swaps	'		'		'
Schedule of Investments [Line Items]	'		'		'
Number of derivative positions held during the period	'		3		'
Balance Sheet - Fair Value	51,900,000		'		'
Cash collateral received from counterparties	43,300,000		'		62,700,000
Cash collateral delivered to the counterparties	'		93,500,000		'
Interest rate swaps | Opened in 2013 | Ten Year Time Horizon	'		'		'
Schedule of Investments [Line Items]	'		'		'
Number of derivative positions held during the period	3		'		3
Derivative Maturity	'10 years		'		'10 years
Interest rate swaps | Opened in 2009 | Nine Year Time Horizon	'		'		'
Schedule of Investments [Line Items]	'		'		'
Number of derivative positions held during the period	'		1		'
Derivative Maturity	'		'9 years		'
Interest rate swaps | Opened in 2011 | Five Year Time Horizon	'		'		'
Schedule of Investments [Line Items]	'		'		'
Number of derivative positions held during the period	'		2		'
Derivative Maturity	'		'5 years		'
Categories of Investments, Marketable Securities, Trading Securities	'		'		'
Schedule of Investments [Line Items]	'		'		'
Net realized gains (losses) on securities	0		0		'
Fixed Income Securities	'		'		'
Schedule of Investments [Line Items]	'		'		'
Gross unrealized losses	60,700,000		'		'
Equity securities	'		'		'
Schedule of Investments [Line Items]	'		'		'
Gross unrealized losses	4,000,000		7,000,000		6,900,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	12		51		31
Equity securities | Common equities	'		'		'
Schedule of Investments [Line Items]	'		'		'
Gross unrealized losses	2,800,000		7,000,000		2,400,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	9		51		24
Equity securities | Nonredeemable preferred stocks	'		'		'
Schedule of Investments [Line Items]	'		'		'
Gross unrealized losses	1,200,000		0		4,500,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	3		0		7
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Percentage Decline	1.00%		'		'
Equity securities | Russell One Thousand | Common equities	'		'		'
Schedule of Investments [Line Items]	'		'		'
Percentage of common stock portfolio	87.00%		'		'
Equity securities | Managed Equity Strategy | Common equities	'		'		'
Schedule of Investments [Line Items]	'		'		'
Percentage of common stock portfolio	13.00%		'		'
Fixed maturities	'		'		'
Schedule of Investments [Line Items]	'		'		'
Gross unrealized losses	59,500,000		23,900,000		119,100,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	291		100		392
Fixed maturities | Corporate debt securities	'		'		'
Schedule of Investments [Line Items]	'		'		'
Percentage which the issuer receives the security back at once the change of control is triggered	1.00%		'		'
Realized investment losses	10,000,000		'		'
Gross unrealized losses	7,200,000		900,000		20,400,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	31		15		51
Interest rate swaps | Non-hedging Instruments | Fixed maturities | Assets	'		'		'
Schedule of Investments [Line Items]	'		'		'
Balance Sheet - Fair Value	51,900,000	[1]	0	[1]	68,100,000	[1]
Notional Value	750,000,000	[2]	0	[2]	750,000,000	[2]
Interest rate swaps | Non-hedging Instruments | Other Liabilities | Liabilities	'		'		'
Schedule of Investments [Line Items]	'		'		'
Balance Sheet - Fair Value	0	[1]	-87,800,000	[1]	0	[1]
Notional Value	$0	[2]	$1,263,000,000	[2]	$0	[2]
[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 report them on a gross basis on our balance sheets, consistent with our historical presentation.
[2]	The amounts represent the value held at quarter and year end for open positions and the maximum amount held during the period for closed positions.

Fair_Value_Composition_of_Inve

Fair Value Composition of Investment Portfolio by Major Security Type (Detail) (USD $)	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013
In Millions, unless otherwise specified
Fair Value Measurements [Line Items]	'		'		'
Portfolio	$17,395.70	[1],[2]	$18,054.70	[1],[2]	$17,299.70	[1],[2]
Debt	2,152.50		2,073.70		2,397.20
Fixed maturities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	12,506.20		13,540.40		12,046.30
Fixed maturities | Redeemable preferred stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	290.3		313.9		376.6
Fixed maturities | Redeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	107.4		102.8		132.2
Fixed maturities | Redeemable preferred stocks | Utilities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	65.2		65.6		67
Fixed maturities | Redeemable preferred stocks | Industrials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	117.7		145.5		177.4
Fixed maturities | Debt Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	7,904.40		8,860.40		7,927.40
Fixed maturities | Debt Securities | U.S. government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	3,230		3,662.20		3,099.20
Fixed maturities | Debt Securities | State and local government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,154.90		2,256		1,813.90
Fixed maturities | Debt Securities | Foreign government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	17.9		15.6		0
Fixed maturities | Debt Securities | Corporate debt securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,501.60		2,926.60		3,014.30
Fixed maturities | Asset-backed Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	4,311.50		4,366.10		3,742.30
Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	1,307.40		1,127.90		621.3
Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,061.60		2,160.50		2,180.20
Fixed maturities | Asset-backed Securities | Other asset-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	942.5		1,077.70		940.8
Equity securities | Nonredeemable preferred stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	737.9		711.2		820.6
Equity securities | Nonredeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	737.9		694.4		794.4
Equity securities | Nonredeemable preferred stocks | Utilities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		16.8		26.2
Equity securities | Common equities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,278.70		2,530.50		2,111.10
Equity securities | Common equities | Common Stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,278.30		2,530		2,099.10
Equity securities | Common equities | Other risk investments	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0.4		0.5		12
Total Fixed Maturities and Equity Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	15,522.80		16,782.10		14,978
Short-term investments	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	1,872.90		1,272.60		2,321.70
Fair Value, Inputs, Level 1	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	7,421.90		7,436.40		7,452.80
Debt	0		0		0
Fair Value, Inputs, Level 1 | Fixed maturities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	3,247.90		3,677.80		3,099.20
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	3,247.90		3,677.80		3,099.20
Fair Value, Inputs, Level 1 | Fixed maturities | Debt Securities | U.S. government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	3,230		3,662.20		3,099.20
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	17.9		15.6		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	284		240.8		270.3
Fair Value, Inputs, Level 1 | Equity securities | Nonredeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	284		240.8		270.3
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	2,278.30		2,530		2,099.10
Fair Value, Inputs, Level 1 | Equity securities | Common equities | Common Stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,278.30		2,530		2,099.10
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	5,810.20		6,448.60		5,468.60
Fair Value, Inputs, Level 1 | Short-term investments	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	1,611.70		987.8		1,984.20
Fair Value, Inputs, Level 2	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	9,902.70		10,549.60		9,688.20
Debt	2,152.50		2,073.70		2,397.20
Fair Value, Inputs, Level 2 | Fixed maturities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	9,229.70		9,833.40		8,834.20
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	290.3		313.9		376.6
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	107.4		102.8		132.2
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks | Utilities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	65.2		65.6		67
Fair Value, Inputs, Level 2 | Fixed maturities | Redeemable preferred stocks | Industrials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	117.7		145.5		177.4
Fair Value, Inputs, Level 2 | Fixed maturities | Debt Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	4,656.50		5,182.60		4,828.20
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	2,154.90		2,256		1,813.90
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	2,501.60		2,926.60		3,014.30
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	4,282.90		4,336.90		3,629.40
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	1,307.40		1,127.70		535.7
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,033		2,131.50		2,152.90
Fair Value, Inputs, Level 2 | Fixed maturities | Asset-backed Securities | Other asset-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	942.5		1,077.70		940.8
Fair Value, Inputs, Level 2 | Equity securities | Nonredeemable preferred stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	411.8		431.4		516.5
Fair Value, Inputs, Level 2 | Equity securities | Nonredeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	411.8		414.6		490.3
Fair Value, Inputs, Level 2 | Equity securities | Nonredeemable preferred stocks | Utilities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		16.8		26.2
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	9,641.50		10,264.80		9,350.70
Fair Value, Inputs, Level 2 | Short-term investments	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	261.2		284.8		337.5
Fair Value, Inputs, Level 3	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	71.1		68.7		158.7
Debt	0		0		0
Fair Value, Inputs, Level 3 | Fixed maturities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	28.6		29.2		112.9
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	28.6		29.2		112.9
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0.2		85.6
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	28.6		29		27.3
Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Other asset-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		0		0
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	42.1		39		33.8
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	42.1		39		33.8
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	0.4		0.5		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	0.4		0.5		12
Fair Value, Inputs, Level 3 | Total Fixed Maturities and Equity Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	71.1		68.7		158.7
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	15,922.10		16,584.70		15,808.70
Debt	1,861.30		1,860.90		2,063.50
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	12,335.80		13,415.30		11,686
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	266.9		299.5		355.9
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	84.2		84.2		110.7
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks | Utilities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	64.9		64.9		64.9
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Redeemable preferred stocks | Industrials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	117.8		150.4		180.3
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	7,808.30		8,778.30		7,698
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities | U.S. government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	3,197.80		3,630.40		3,015.60
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities | State and local government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,131		2,247.30		1,771.60
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities | Foreign government obligations	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	17.9		15.6		0
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Debt Securities | Corporate debt securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,461.60		2,885		2,910.80
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	4,260.60		4,337.50		3,632.10
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	1,286.70		1,110.10		595.7
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	2,037.70		2,154.40		2,107.20
Carrying (Reported) Amount, Fair Value Disclosure | Fixed maturities | Asset-backed Securities | Other asset-backed securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	936.2		1,073		929.2
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Nonredeemable preferred stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	460.7		445.7		412.5
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Nonredeemable preferred stocks | Financials	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	460.7		431.5		391.8
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Nonredeemable preferred stocks | Utilities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0		14.2		20.7
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	1,252.70		1,451.10		1,388.50
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities | Common Stocks	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	1,252.30		1,450.60		1,385.30
Carrying (Reported) Amount, Fair Value Disclosure | Equity securities | Common equities | Other risk investments	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	0.4		0.5		3.2
Carrying (Reported) Amount, Fair Value Disclosure | Total Fixed Maturities and Equity Securities	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	14,049.20		15,312.10		13,487
Carrying (Reported) Amount, Fair Value Disclosure | Short-term investments	'		'		'
Fair Value Measurements [Line Items]	'		'		'
Portfolio	$1,872.90		$1,272.60		$2,321.70
[1]	The total fair value of the portfolio at March 31, 2014 and 2013, and December 31, 2013 included $0.8 billion, $1.2 billion, and $1.8 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.
[2]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at March 31, 2014, $350.0 million was included in "other assets" and at March 31, 2013 and December 31, 2013, $7.5 million and $61.3 million, respectively, were included in "other liabilities."

Fair_Value_Summary_of_Changes_

Fair Value Summary of Changes in Fair Value Associated With Level 3 Assets (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'
Beginning Fair Value	$68.70		$114.70
Calls/ Maturities/ Paydowns	-0.6		-5.7
Purchases	0		45.2
Sales	0		0
Net Realized (gain)/loss on sales	0		0
Change in Valuation	3		4.5
Net Transfers in (out)	0		0
Ending Fair value	71.1		158.7
Fixed maturities	'		'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'
Beginning Fair Value	29.2		70.8
Calls/ Maturities/ Paydowns	-0.5		-5.7
Purchases	0		45.2
Sales	0		0
Net Realized (gain)/loss on sales	0		0
Change in Valuation	-0.1		2.6
Net Transfers in (out)	0		0
Ending Fair value	28.6		112.9
Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities	'		'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'
Beginning Fair Value	0.2		45.5
Calls/ Maturities/ Paydowns	0		-5.3
Purchases	0		45.2
Sales	0		0
Net Realized (gain)/loss on sales	0		0
Change in Valuation	-0.2		0.2
Net Transfers in (out)	0		0
Ending Fair value	0		85.6
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	29		25.3
Calls/ Maturities/ Paydowns	-0.5		-0.4
Purchases	0		0
Sales	0		0
Net Realized (gain)/loss on sales	0		0
Change in Valuation	0.1		2.4
Net Transfers in (out)	0		0
Ending Fair value	28.6		27.3
Equity securities | Nonredeemable preferred stocks | Financials	'		'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'
Beginning Fair Value	39	[1]	31.9	[2]
Calls/ Maturities/ Paydowns	0	[1]	0	[2]
Purchases	0	[1]	0	[2]
Sales	0	[1]	0	[2]
Net Realized (gain)/loss on sales	0	[1]	0	[2]
Change in Valuation	3.1	[1]	1.9	[2]
Net Transfers in (out)	0	[1]	0	[2]
Ending Fair value	42.1	[1]	33.8	[2]
Equity securities | Common equities | Other risk investments	'		'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'
Beginning Fair Value	0.5		12
Calls/ Maturities/ Paydowns	-0.1		0
Purchases	0		0
Sales	0		0
Net Realized (gain)/loss on sales	0		0
Change in Valuation	0		0
Net Transfers in (out)	0		0
Ending Fair value	$0.40		$12
[1]	The $3.1 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 $1.9 million represents net holding period gains on a hybrid security which is reflected in net realized gains (losses) on securities in the comprehensive income statement.

Fair_Value_Summary_of_Changes_1

Fair Value Summary of Changes in Fair Value Associated With Level 3 Assets (Parenthetical) (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'
Net realized gains (losses) on securities	$119,400,000	$80,800,000
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	$3,100,000	$1,900,000

Fair_Value_Summary_of_Quantita

Fair Value Summary of Quantitative Information about Level 3 Fair Value Measurements (Detail) (USD $)	3 Months Ended				12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013
	Investment		Investment		Investment
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Fair Value	$17,395.70	[1],[2]	$17,299.70	[1],[2]	$18,054.70	[1],[2]
Fair Value, Inputs, Level 3	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Fair Value	71.1		158.7		68.7
External Pricing | Fair Value, Inputs, Level 3 | Fixed maturities	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Fair Value	28.6		27.6		29.2
External Pricing | Fair Value, Inputs, Level 3 | Fixed maturities | Asset-backed Securities | Residential mortgage-backed securities	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Fair Value	0	[3]	'		'
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		'
Fair Value	'		0.2		'
Valuation Technique	'		'External vendor		'
Unobservable Input, prepayment rate	'		16.00%		'
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
Fair Value	'		'		0.2
Valuation Technique	'		'		'External vendor
Unobservable Input, prepayment rate	'		'		0.00%
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		2
Fair Value	28.6		27.4		29
Valuation Technique	'External vendor		'External vendor		'External vendor
Unobservable Input, prepayment rate	0.00%		0.00%		0.00%
Internal Pricing | Fair Value, Inputs, Level 3 | 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	42.1		33.8		39
Internal Pricing | Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks | Financials	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Fair Value	42.1		33.8		39
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	0		1		0
Fair Value	'		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		0
Valuation Technique	'		'Discounted consolidated  equity		'
Unobservable Input, discount for lack of marketability	'		20.00%		'
Subtotal Level 3 Securities | Fair Value, Inputs, Level 3	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Fair Value	70.7		72.6		68.2
Third Party Pricing Exemption Securities | Fair Value, Inputs, Level 3	'		'		'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'		'		'
Fair Value	$0.40	[4]	$86.10	[4]	$0.50	[4]
[1]	The total fair value of the portfolio at March 31, 2014 and 2013, and December 31, 2013 included $0.8 billion, $1.2 billion, and $1.8 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.
[2]	Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at March 31, 2014, $350.0 million was included in "other assets" and at March 31, 2013 and December 31, 2013, $7.5 million and $61.3 million, respectively, were included in "other liabilities."
[3]	This security is approaching final maturity and is valued at zero.
[4]	The fair values for these securities were obtained from non-binding external sources where unobservable inputs are not reasonably available to us.

Fair_Value_Fair_Value_Addition

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

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Mar. 31, 2014

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

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Fair Value, Inputs, Level 3

Investment Portfolio

Nonredeemable preferred stocks

Nonredeemable preferred stocks

Nonredeemable preferred stocks

Nonredeemable preferred stocks

Common equities

Common equities

Common equities

Asset-backed Securities

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

Fixed maturities

Fixed maturities

Fixed maturities

Investment

Equity securities

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

Residential mortgage-backed securities

Internal Pricing

Internal Pricing

Internal Pricing

External Pricing

External Pricing

External Pricing

Investment

Equity securities

Equity securities

Equity securities

Equity securities

Equity securities

Equity securities

Fair Value, Inputs, Level 3

Investment

Investment

Investment

Internal Pricing

Internal Pricing

Internal Pricing

Internal Pricing

Internal Pricing

Internal Pricing

Fixed maturities

Investment

Investment

Investment

Investment

Investment

Investment

External Pricing

Fair Value Measurements [Line Items]

'

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Number of securities transferred out of Level 2 into Level 1

'

'

'

'

'

'

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'

'

'

'

'

'

'

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'

'

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2

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Fair Value, Assets, Level 2 to Level 1 Transfers, Amount

'

'

'

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'

'

'

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'

'

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$41.70

'

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'

Number of securities transferred out of Level 1 into Level 2

'

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'

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'

'

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'

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0

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Quoted prices percentage of fair value assets

100.00%

[1],[2]

100.00%

[1],[2]

100.00%

[1],[2]

'

'

'

55.00%

56.00%

57.00%

'

'

'

96.00%

98.00%

96.00%

4.00%

2.00%

4.00%

'

'

'

'

'

'

'

'

'

'

'

'

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'

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'

'

Number of securities

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0

0

0

'

'

'

'

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1

1

1

0

0

1

'

Portfolio

$17,395.70

[1],[2]

$18,054.70

[1],[2]

$17,299.70

[1],[2]

$7,421.90

$7,436.40

$7,452.80

'

'

'

$9,902.70

$10,549.60

$9,688.20

'

'

'

'

'

'

$71.10

$68.70

$158.70

'

'

'

$28.60

$29.20

$27.60

'

'

$42.10

$39

$33.80

'

'

$11.20

$0

[3]

[1]

The total fair value of the portfolio at March 31, 2014 and 2013, and December 31, 2013 included $0.8 billion, $1.2 billion, and $1.8 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.

[2]

Our portfolio reflects the effect of unsettled security transactions and collateral on open derivative positions; at March 31, 2014, $350.0 million was included in "other assets" and at March 31, 2013 and December 31, 2013, $7.5 million and $61.3 million, respectively, were included in "other liabilities."

[3]

This security is approaching final maturity and is valued at zero.

Debt_Detail

Debt (Detail) (USD $)	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013
In Millions, unless otherwise specified
Debt Instrument [Line Items]	'		'		'
Carrying Value	$1,861.30	[1]	$1,860.90	[1]	$2,063.50	[1]
Fair Value	2,152.50		2,073.70		2,397.20
7% Notes due 2013	'		'		'
Debt Instrument [Line Items]	'		'		'
Carrying Value	0		0		149.9
Fair Value	0		0		154.9
3.75% Senior Notes due 2021	'		'		'
Debt Instrument [Line Items]	'		'		'
Carrying Value	497.6		497.6		497.4
Fair Value	524.5		509.1		544.7
6 5/8% Senior Notes due 2029	'		'		'
Debt Instrument [Line Items]	'		'		'
Carrying Value	295.4		295.3		295.2
Fair Value	381.8		359.6		382.6
6.25% Senior Notes due 2032	'		'		'
Debt Instrument [Line Items]	'		'		'
Carrying Value	394.7		394.6		394.5
Fair Value	501.4		473.7		507.1
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067	'		'		'
Debt Instrument [Line Items]	'		'		'
Carrying Value	673.6		673.4		726.5
Fair Value	$744.80		$731.30		$807.90
[1]	Consists of both short- and long-term debt. See Note 4 - Debt.

Debt_Parenthetical_Details

Debt (Parenthetical) (Details)	Mar. 31, 2014
7% Notes due 2013	'
Debt Instrument [Line Items]	'
Debt Instrument, Interest Rate, Stated Percentage	7.00%
3.75% Senior Notes due 2021	'
Debt Instrument [Line Items]	'
Debt Instrument, Interest Rate, Stated Percentage	3.75%
6 5/8% Senior Notes due 2029	'
Debt Instrument [Line Items]	'
Debt Instrument, Interest Rate, Stated Percentage	6.63%
6.25% Senior Notes due 2032	'
Debt Instrument [Line Items]	'
Debt Instrument, Interest Rate, Stated Percentage	6.25%
6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067	'
Debt Instrument [Line Items]	'
Debt Instrument, Interest Rate, Stated Percentage	6.70%

Debt_Additional_Information_De

Debt - Additional Information (Detail) (USD $)	3 Months Ended		3 Months Ended	1 Months Ended	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014	Oct. 31, 2013	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2013
	Discretionary Line of Credit	Discretionary Line of Credit	Discretionary Line of Credit	7% Notes due 2013	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
			Federal Funds Rate					Net unrealized gains on forecasted transactions
Debt Instrument [Line Items]	'	'	'	'	'	'	'	'
Payment of debt	'	'	'	$150,000,000	'	'	'	'
Repurchase of debt, face amount	'	'	'	'	0	0	54,100,000	'
(Gains) losses on extinguishment of debt	'	'	'	'	'	'	4,300,000	'
Cash flow hedge gain reclassification from accumulated other comprehensive income to net realized gains/losses on securities	'	'	'	'	'	'	'	800,000
Line of Credit Facility, Maximum Borrowing Capacity	100,000,000	100,000,000	'	'	'	'	'	'
Line of Credit Facility, Interest Rate Description	'advances under the Line of Credit (if any) will bear interest at a variable rate equal to the higher of PNC's Prime Rate and the sum of the Federal Funds Open Rate plus 50 basis points.	'	'	'	'	'	'	'
Line of Credit Facility, Amount Outstanding	$0	$0	'	'	'	'	'	'
Basis points	'	'	0.50%	'	'	'	'	'

Supplemental_Cash_Flow_Informa2

Supplemental Cash Flow Information (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Supplemental Cash Flow Elements [Abstract]	'	'
Income taxes	$0	$18
Interest	$19.30	$19.30

Segment_Information_Operating_

Segment Information Operating Results (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Segment Reporting Information [Line Items]	'		'
Revenues	$4,707.60		$4,437.20
Pretax Profit (Loss)	481.8		463.1
Underwriting Operations	'		'
Segment Reporting Information [Line Items]	'		'
Revenues	4,402.30		4,179.30
Pretax Profit (Loss)	289.8		317.7
Underwriting Operations | Personal Lines	'		'
Segment Reporting Information [Line Items]	'		'
Revenues	3,965.40	[1]	3,748.80	[1]
Pretax Profit (Loss)	249.6	[1]	302.1	[1]
Underwriting Operations | Personal Lines | Agency Channel	'		'
Segment Reporting Information [Line Items]	'		'
Revenues	2,203.20		2,107.20
Pretax Profit (Loss)	178.6		174.9
Underwriting Operations | Personal Lines | Direct Channel	'		'
Segment Reporting Information [Line Items]	'		'
Revenues	1,762.20		1,641.60
Pretax Profit (Loss)	71		127.2
Underwriting Operations | Commercial Lines	'		'
Segment Reporting Information [Line Items]	'		'
Revenues	436.9		430.4
Pretax Profit (Loss)	40.9		15.3
Underwriting Operations | Other Indemnity	'		'
Segment Reporting Information [Line Items]	'		'
Revenues	0		0.1
Pretax Profit (Loss)	-0.7		0.3
Fees and Other Revenues	'		'
Segment Reporting Information [Line Items]	'		'
Revenues	72.8	[2]	68.4	[2]
Service Businesses	'		'
Segment Reporting Information [Line Items]	'		'
Revenues	9.8		8.4
Pretax Profit (Loss)	0.1		-0.2
Investments	'		'
Segment Reporting Information [Line Items]	'		'
Revenues	222.7	[3]	181.1	[3]
Pretax Profit (Loss)	218.6	[3]	176.2	[3]
Interest Expense	'		'
Segment Reporting Information [Line Items]	'		'
Pretax Profit (Loss)	($26.70)		($30.60)
[1]	Personal auto insurance accounted for 92% and 91% of the total Personal Lines segment net premiums earned in the first quarters of 2014 and 2013, respectively; 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.

Segment_Information_Operating_1

Segment Information Operating Results (Parenthetical) (Detail) (Underwriting Operations, Personal Lines, Personal Auto)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Underwriting Operations | Personal Lines | Personal Auto	'	'
Segment Reporting Information [Line Items]	'	'
Personal auto insurance percentage of the total personal lines segment net premiums earned	92.00%	91.00%

Segment_Information_Underwriti

Segment Information Underwriting Margins and Combined Ratios for our Underwriting Operations (Detail) (Underwriting Operations)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting Information [Line Items]	'	'
Underwriting Margin	6.60%	7.60%
Combined Ratio	93.40%	92.40%
Personal Lines	'	'
Segment Reporting Information [Line Items]	'	'
Underwriting Margin	6.30%	8.10%
Combined Ratio	93.70%	91.90%
Personal Lines | Agency Channel	'	'
Segment Reporting Information [Line Items]	'	'
Underwriting Margin	8.10%	8.30%
Combined Ratio	91.90%	91.70%
Personal Lines | Direct Channel	'	'
Segment Reporting Information [Line Items]	'	'
Underwriting Margin	4.00%	7.80%
Combined Ratio	96.00%	92.20%
Commercial Lines	'	'
Segment Reporting Information [Line Items]	'	'
Underwriting Margin	9.40%	3.50%
Combined Ratio	90.60%	96.50%

Dividends_Additional_Informati

Dividends - Additional Information (Detail) (USD $)	3 Months Ended		1 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Feb. 28, 2014	Feb. 28, 2013	Feb. 28, 2014
			Annual variable dividend	Annual variable dividend	Special dividend
Dividends Payable [Line Items]	'	'	'	'	'
Target percentage used to determine annual variable dividend	33.33%	'	'	'	'
Gainshare factor used to determine annual variable dividend range, minimum	0	'	'	'	'
Gainshare factor used to determine annual variable dividend range, maximum	2	'	'	'	'
Gainshare factor used to determine annual variable dividend	1.02	'	'	'	'
Comprehensive income	$320.90	$407.30	'	'	'
After-tax underwriting income	$188.40	'	'	'	'
Dividend paid per share (USD per share)	'	'	$0.49	$0.28	$1

Other_Comprehensive_Income_Los2

Other Comprehensive Income (Loss) Components of Other Comprehensive Income (Loss) Including Reclassification Adjustments by Income Statement (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]	'		'
Pre tax total accumulated other comprehensive income, beginning balance	$1,464,100,000		$1,340,000,000
Investment securities, pre tax	131,800,000		227,800,000
Net non-credit related OTTI losses, adjusted for valuation changes, pre tax	0		300,000
Forecasted transactions, pre tax	0		0
Foreign currency translation adjustment, pre tax	0		-300,000
Total other comprehensive income (loss) before reclassifications, pre tax	131,800,000		227,800,000
Total reclassification adjustment for amounts realized in net income, pre tax	132,400,000		76,000,000
Total other comprehensive income (loss), pre tax	-600,000		151,800,000
Pre tax total accumulated other comprehensive income, ending balance	1,463,500,000		1,491,800,000
Accumulated Other Comprehensive Income (Loss), Tax [Roll Forward]	'		'
Accumulated other comprehensive income loss tax (Provision) benefit, beginning balance	-512,400,000		-469,000,000
Investment securities, Total tax (provision) benefit	-46,100,000		-79,700,000
Net non-credit related OTTI losses, adjusted for valuation changes, Total tax (provision) benefit	0		-100,000
Forecasted transactions, Total tax (provision) benefit	0		0
Foreign currency translation adjustment, Total tax (provision) benefit	0		100,000
Total other comprehensive income (loss) before reclassifications, Total tax (provision) benefit	-46,100,000		-79,700,000
Total reclassification adjustment for amounts realized in net income, Total tax (provision) benefit	-46,300,000		-26,600,000
Total other comprehensive income (loss), Total tax (provision) benefit	200,000		-53,100,000
Accumulated other comprehensive income loss tax (Provision) benefit, ending balance	-512,200,000		-522,100,000
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]	'		'
After tax total accumulated other comprehensive income, beginning balance	951,700,000		871,000,000
Investment securities, after tax	85,700,000		148,100,000
Net non-credit related OTTI losses, adjusted for valuation changes, after tax	0		200,000
Forecasted transactions, after tax	0		0
Foreign currency translation adjustment, after tax	0		-200,000
Total other comprehensive income (loss) before reclassifications, after tax	85,700,000		148,100,000
Total reclassification adjustment for amounts realized in net income, after tax	86,100,000		49,400,000
Other comprehensive income (loss)	-400,000		98,700,000
After tax total accumulated other comprehensive income, ending balance	951,300,000		969,700,000
Net impairment losses recognized in earnings	0		-200,000
Net realized gains (losses) on securities	119,400,000		80,800,000
Interest expense	26,700,000		30,600,000
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	947,000,000		862,700,000
Investment securities, after tax	85,700,000		148,100,000
Net non-credit related OTTI losses, adjusted for valuation changes, after tax	0		200,000
Forecasted transactions, after tax	0		0
Foreign currency translation adjustment, after tax	0		0
Total other comprehensive income (loss) before reclassifications, after tax	85,700,000		148,300,000
Total reclassification adjustment for amounts realized in net income, after tax	85,800,000		49,100,000
Other comprehensive income (loss)	-100,000		99,200,000
After tax total accumulated other comprehensive income, ending balance	946,900,000		961,900,000
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	4,100,000	[1],[2]	6,100,000	[1]
Investment securities, after tax	0	[1],[2]	0	[1]
Net non-credit related OTTI losses, adjusted for valuation changes, after tax	0	[1],[2]	0	[1]
Forecasted transactions, after tax	0	[1],[2]	0	[1]
Foreign currency translation adjustment, after tax	0	[1],[2]	0	[1]
Total other comprehensive income (loss) before reclassifications, after tax	0	[1],[2]	0	[1]
Total reclassification adjustment for amounts realized in net income, after tax	300,000	[1],[2]	300,000	[1]
Other comprehensive income (loss)	-300,000	[1],[2]	-300,000	[1]
After tax total accumulated other comprehensive income, ending balance	3,800,000	[1],[2]	5,800,000	[1]
Foreign Currency Translation Adjustments	'		'
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]	'		'
After tax total accumulated other comprehensive income, beginning balance	600,000		2,200,000
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		-200,000
Total other comprehensive income (loss) before reclassifications, after tax	0		-200,000
Total reclassification adjustment for amounts realized in net income, after tax	0		0
Other comprehensive income (loss)	0		-200,000
After tax total accumulated other comprehensive income, ending balance	600,000		2,000,000
Reclassification out of Accumulated Other Comprehensive Income | Accumulated other comprehensive income pretax	'		'
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]	'		'
Net impairment losses recognized in earnings	0		-100,000
Net realized gains (losses) on securities	131,900,000		75,600,000
Interest expense	500,000	[2]	500,000
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		100,000
Net realized gains (losses) on securities	-46,100,000		-26,500,000
Interest expense	-200,000	[2]	-200,000
Reclassification out of Accumulated Other Comprehensive Income | Accumulated other comprehensive income after tax	'		'
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]	'		'
Net impairment losses recognized in earnings	0		0
Net realized gains (losses) on securities	85,800,000		49,100,000
Interest expense	300,000	[2]	300,000
Reclassification out of Accumulated Other Comprehensive Income | Net unrealized gains (losses) on securities	'		'
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]	'		'
Net impairment losses recognized in earnings	0		0
Net realized gains (losses) on securities	85,800,000		49,100,000
Interest expense	0	[2]	0
Reclassification out of Accumulated Other Comprehensive Income | Net unrealized gains on forecasted transactions	'		'
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]	'		'
Net impairment losses recognized in earnings	0	[1],[2]	0	[1]
Net realized gains (losses) on securities	0	[1],[2]	0	[1]
Interest expense	300,000	[1],[2]	300,000	[1]
Reclassification out of Accumulated Other Comprehensive Income | Foreign Currency Translation Adjustments	'		'
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]	'		'
Net impairment losses recognized in earnings	0		0
Net realized gains (losses) on securities	0		0
Interest expense	$0	[2]	$0
[1]	Entered into for the purpose of managing interest rate risk associated with our debt issuances.
[2]	We expect to reclassify $2.1 million (pretax) into income during the next 12 months, related to the net unrealized gains on forecasted transactions.

Other_Comprehensive_Income_Los3

Other Comprehensive Income (Loss) Components of Other Comprehensive Income (Loss) Including Reclassification Adjustments by Income Statement (Parenthetical) (Detail) (Pre Tax, USD $)	Mar. 31, 2014
In Millions, unless otherwise specified
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

Subsequent_Event_Additional_In

Subsequent Event - Additional Information (Details) (Subsequent Event, 4.35% Senior Notes due 2044, USD $)	1 Months Ended
	Apr. 25, 2014
Subsequent Event | 4.35% Senior Notes due 2044	'
Debt Instrument [Line Items]	'
Debt Instrument, Issuance Date	25-Apr-14
Debt Instrument, Face Amount	$350,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.35%
Proceeds from Debt, Net of Issuance Costs	346,300,000
Additional Expenses Related to the Issuance	700,000
Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss)	$1,600,000