Reserve for Losses and Loss Expenses Reserves for Losses and Loss Expenses (Tables)

9 Months Ended

Sep. 30, 2017

Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block]



	Nine Months ended September 30,
($ in thousands)	2017			2016
Gross reserves for losses and loss expenses, at beginning of year	$	3,691,719		3,517,728
Less: reinsurance recoverable on unpaid losses and loss expenses, at beginning of year	611,200			551,019
Net reserves for losses and loss expenses, at beginning of year	3,080,519			2,966,709
Incurred losses and loss expenses for claims occurring in the:
Current year	1,037,079			955,347
Prior years	(33,461		)	(43,466	)
Total incurred losses and loss expenses	1,003,618			911,881
Paid losses and loss expenses for claims occurring in the:
Current year	314,686			275,623
Prior years	581,186			547,067
Total paid losses and loss expenses	895,872			822,690
Net reserves for losses and loss expenses, at end of period	3,188,265			3,055,900
Add: Reinsurance recoverable on unpaid losses and loss expenses, at end of period	647,535			630,686
Gross reserves for losses and loss expenses at end of period	$	3,835,800		3,686,586

Prior year development in Nine Months 2017 of $33.5 million was primarily driven by favorable prior year casualty reserve development of $48.3 million in our general liability line of business and $29.3 million in our workers compensation line of business. This was partially offset by unfavorable casualty development of $26.0 million in our commercial automobile line of business, $10.0 million in our Excess and Surplus ("E&S") segment and $4.0 million in our personal automobile line of business.

Prior year development in Nine Months 2016 of $43.5 million was primarily due to favorable casualty reserve development of $36.0 million in our workers compensation line of business and $33.0 million in our general liability line of business. This was partially offset by unfavorable casualty reserve development of $20.0 million in our commercial automobile line of business and $3.0 million in our E&S segment.

For a discussion of the trends and recent developments impacting these lines, refer to the "Critical Accounting Policies and Estimates" section of Item 7. "Management's Discussion and Analysis of Financial Condition and Results of Operations." in our 2016 Annual Report.