Reserve for Losses and Loss Expenses (Tables)

12 Months Ended

Dec. 31, 2012

Insurance Loss Reserves [Abstract]

Roll Forward of Reserves for Losses and Loss Expenses

($ in thousands)	2012			2011		2010
Gross reserves for losses and loss expenses, at beginning of year	$	3,144,924		2,830,058		2,745,799
Less: reinsurance recoverable on unpaid losses and loss expenses, at beginning of year	549,490			313,739		271,610
Net reserves for losses and loss expenses, at beginning of year	2,595,434			2,516,319		2,474,189
Incurred losses and loss expenses for claims occurring in the:
Current year	1,146,591			1,113,733		1,025,707
Prior years	(25,601		)	(38,746	)	(43,589	)
Total incurred losses and loss expenses	1,120,990			1,074,987		982,118
Paid losses and loss expenses for claims occurring in the:
Current year	424,496			440,786		378,650
Prior years	632,742			569,944		561,338
Total paid losses and loss expenses	1,057,238			1,010,730		939,988
Acquisition of MUSIC losses and loss expense reserves	—			14,858		—
Net reserves for losses and loss expenses, at end of year	2,659,186			2,595,434		2,516,319
Add: Reinsurance recoverable on unpaid losses and loss expenses, at end of year1	1,409,755			549,490		313,739
Gross reserves for losses and loss expenses at end of year	$	4,068,941		3,144,924		2,830,058

¹ Includes $44.0 million related to the acquisition of MUSIC at December 31, 2011.

Prior Year Development

Favorable/(Unfavorable) Prior Year Development
($ in millions)	2012			2011		2010
General Liability	$	(3	)	12		26
Commercial Automobile	9			13		28
Workers' Compensation	(2		)	(7	)	(22	)
Business Owners' Policies	9			11		3
Commercial Property	3			6		3
Homeowners	9			4		6
Personal Automobile	—			(1	)	(2	)
Other	1			1		2
Total	$	26		39		44

Exposure to Various Environmental Claims

	2012
($ in millions)	Gross		Net
Asbestos	$	9.2	7.8
Landfill sites	13.0		8.1
Leaking underground storage tanks	13.4		11.9
Total	$	35.6	27.8

Roll Forward of Gross and Net Environmental Incurred Losses and Loss Expenses and Related Reserves

	2012					2011				2010
($ in thousands)	Gross			Net		Gross		Net		Gross		Net
Asbestos
Reserves for losses and loss expenses at beginning of year	$	8,412		6,586		9,979		8,167		11,056		9,244
Incurred losses and loss expenses	1,696			2,000		2,014		2,000		(338	)	(338	)
Less: losses and loss expenses paid	(938		)	(795	)	(3,581	)	(3,581	)	(739	)	(739	)
Reserves for losses and loss expenses at the end of year	$	9,170		7,791		8,412		6,586		9,979		8,167
Environmental
Reserves for losses and loss expenses at beginning of year	$	27,600		21,330		33,630		27,599		35,864		28,803
Incurred losses and loss expenses	1,363			1,000		(4,285	)	(4,750	)	1,500		2,276
Less: losses and loss expenses paid	(2,558		)	(2,352	)	(1,745	)	(1,519	)	(3,734	)	(3,480	)
Reserves for losses and loss expenses at the end of year	$	26,405		19,978		27,600		21,330		33,630		27,599
Total Environmental Claims
Reserves for losses and loss expenses at beginning of year	$	36,012		27,916		43,609		35,766		46,920		38,047
Incurred losses and loss expenses	3,059			3,000		(2,271	)	(2,750	)	1,162		1,938
Less: losses and loss expenses paid	(3,496		)	(3,147	)	(5,326	)	(5,100	)	(4,473	)	(4,219	)
Reserves for losses and loss expenses at the end of year	$	35,575		27,769		36,012		27,916		43,609		35,766