Property Casualty Loss and Loss Expenses

This table summarizes activity for our consolidated property casualty loss and loss expense reserves:



(Dollars in millions)	Three months ended September 30,						Nine months ended September 30,
	2017			2016			2017			2016
Gross loss and loss expense reserves, beginning of period	$	5,213		$	4,918		$	5,035		$	4,660
Less reinsurance recoverable	283			310			298			281
Net loss and loss expense reserves, beginning of period	4,930			4,608			4,737			4,379
Net incurred loss and loss expenses related to:
Current accident year	835			730			2,493			2,261
Prior accident years	(20		)	(40		)	(96		)	(151		)
Total incurred	815			690			2,397			2,110
Net paid loss and loss expenses related to:
Current accident year	411			374			969			848
Prior accident years	314			288			1,145			1,005
Total paid	725			662			2,114			1,853
Net loss and loss expense reserves, end of period	5,020			4,636			5,020			4,636
Plus reinsurance recoverable	280			301			280			301
Gross loss and loss expense reserves, end of period	$	5,300		$	4,937		$	5,300		$	4,937

We use actuarial methods, models and judgment to estimate, as of a financial statement date, the property casualty loss and loss expense reserves required to pay for and settle all outstanding insured claims, including incurred but not reported (IBNR) claims, as of that date. The actuarial estimate is subject to review and adjustment by an inter-departmental committee that includes actuarial, claims, underwriting, loss prevention and accounting management. This committee is familiar with relevant company and industry business, claims and underwriting trends, as well as general economic and legal trends that could affect future loss and loss expense payments. The amount we will actually have to pay for claims can be highly uncertain. This uncertainty, together with the size of our reserves, makes the loss and loss expense reserves our most significant estimate. The reserve for loss and loss expenses in the condensed consolidated balance sheets also included $50 million at September 30, 2017, and

$54 million at September 30, 2016, for certain life and health loss and loss expense reserves.

For the three months ended September 30, 2017, we experienced $20 million of favorable development on prior accident years, including $18 million of favorable development in commercial lines, $3 million of favorable development in excess and surplus lines and $1 million of adverse development in our reinsurance assumed operations. This included $6 million from favorable development of catastrophe losses for the three months ended September 30, 2017. For the three months ended September 30, 2017, we recognized favorable reserve development of $14 million for the workers' compensation line, $7 million for the commercial property line and $5 million for the other commercial lines due to reduced uncertainty of prior accident year loss and loss adjustment expense for these lines. For the three months ended September 30, 2017, we recognized unfavorable reserve development of $8 million for the commercial auto line.

For the nine months ended September 30, 2017, we experienced $96 million of favorable development on prior accident years, including $55 million of favorable development in commercial lines, $13 million of favorable development in personal lines, $25 million of favorable development in excess and surplus lines and $3 million of favorable development in our reinsurance assumed operations. This included $20 million from favorable development of catastrophe losses for the nine months ended September 30, 2017. For the nine months ended September 30, 2017, we recognized favorable reserve development of $44 million for the workers' compensation line, $21 million for the commercial property line and $25 million for the other commercial lines due to reduced uncertainty of prior accident year loss and loss adjustment expense for these lines. For the nine months ended September 30, 2017, we recognized unfavorable reserve development of $27 million for the commercial auto line and $8 million for the commercial casualty line. The unfavorable reserve development for commercial casualty reflected higher large loss activity than prior year.

For the three months ended September 30, 2016, we experienced $40 million of favorable development on prior accident years, including $31 million of favorable development in commercial lines, $4 million of adverse development in personal lines, $12 million of favorable development in excess and surplus lines and $1 million of favorable development in our reinsurance assumed operations. We recognized favorable reserve development during the three months ended September 30, 2016, of $16 million for the workers' compensation line, $7 million for commercial casualty line and $11 million for the other commercial lines due to reduced uncertainty of prior accident year loss and loss adjustment expenses for these lines. We recognized unfavorable reserve development during the three months ended September 30, 2016, of $9 million for the personal auto line and $4 million for the commercial auto line. Both lines developed unfavorably due to higher loss cost effects in recent accident years, resulting in an increase of our reserve estimate for claims that have not yet been settled.

For the nine months ended September 30, 2016, we experienced $151 million of favorable development on prior accident years, including $118 million of favorable development in commercial lines, $4 million of favorable development in personal lines, $27 million of favorable development in excess and surplus lines and $2 million of favorable development in our reinsurance assumed operations. This included $5 million from favorable development of catastrophe losses for the nine months ended September 30, 2016. We recognized favorable reserve development during the nine months ended September 30, 2016, of $52 million for the workers' compensation line, $30 million for the commercial casualty line, $25 million for the commercial property line and $37 million for the other commercial lines due to reduced uncertainty of prior accident year loss and loss adjustment expenses for these lines. We recognized unfavorable reserve development during the nine months ended September 30, 2016, of $26 million for the commercial auto line and $15 million for the personal auto line. Both lines developed unfavorably due to higher loss cost effects in recent accident years, resulting in an increase of our reserve estimate for claims that have not yet settled.