Reserve for Loss and Loss Expense

The table below provides a roll forward of reserve for loss and loss expense balances:



	Nine Months ended September 30,
($ in thousands)	2018			2017
Gross reserve for loss and loss expense, at beginning of year	$	3,771,240		3,691,719
Less: reinsurance recoverable on unpaid loss and loss expense, at beginning of year	585,855			611,200
Net reserve for loss and loss expense, at beginning of year	3,185,385			3,080,519
Incurred loss and loss expense for claims occurring in the:
Current year	1,148,032			1,037,079
Prior years	(17,564		)	(33,461	)
Total incurred loss and loss expense	1,130,468			1,003,618
Paid loss and loss expense for claims occurring in the:
Current year	369,036			314,686
Prior years	610,734			581,186
Total paid loss and loss expense	979,770			895,872
Net reserve for loss and loss expense, at end of period	3,336,083			3,188,265
Add: Reinsurance recoverable on unpaid loss and loss expense, at end of period	589,072			647,535
Gross reserve for loss and loss expense at end of period	$	3,925,155		3,835,800

The $111.0 million increase in current year loss and loss expense incurred illustrated in the table above was primarily driven by: (i) non-catastrophe property losses; (ii) an increase in current year loss costs on our commercial automobile line of business; and (iii) an increase in exposure due to premium growth. Non-catastrophe property losses, which increased $61.9 million, to $278.5 million, in Nine Months 2018, were partially related to the early January 2018 deep freeze in our footprint states and a relatively large number of fire losses over the course of the year.

Prior year development in Nine Months 2018 of $17.6 million included $24.0 million of favorable casualty development, partially offset by $6.4 million of unfavorable property development. The favorable casualty development included $53.0 million of development in our workers compensation line of business and $8.0 million in our general liability line of business, partially offset by unfavorable development of $25.0 million in our commercial automobile line of business and $12.0 million in our excess and surplus ("E&S") casualty lines.

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 development of $26.0 million in our commercial automobile line of business, $10.0 million in our E&S segment, and $4.0 million in our personal automobile line of business.

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 2017 Annual Report.