10. Other Balance Sheet Information

The following is a summary of accounts receivable at March 31, 2018 and September 30, 2017 (in thousands):


	March 31,		September 30,
	2018		2017
Accounts receivable	$	142,819	$	122,868
Less allowance for doubtful accounts		(1,266)		(1,959)
Less allowance for sales returns		(52)		(81)
Accounts receivable, net	$	141,501	$	120,828

The following is a summary of inventories at March 31, 2018 and September 30, 2017 (in thousands):


	March 31,		September 30,
	2018		2017
Inventories
Raw materials and purchased parts	$	79,633	$	73,819
Work-in-process		17,503		10,548
Finished goods		29,458		22,028
Total inventories	$	126,594	$	106,395

Reserves for excess and obsolete inventory were $21.5 million and $23.5 million, respectively, at March 31, 2018 and September 30, 2017.

At March 31, 2018 and September 30, 2017, the Company had cumulative capitalized direct costs of $5.0 million and $4.7 million, respectively, associated with the development of software for its internal use which are included within "Property, plant and equipment, net" in the accompanying unaudited Consolidated Balance Sheets. During the six months ended March 31, 2018, the Company capitalized direct costs of $0.3 million associated with development of software for its internal use.

The Company establishes reserves for estimated costs of product warranties based on historical information. Product warranty reserves are recorded at the time product revenue is recognized, and retrofit accruals are recorded at the time retrofit programs are established. The Company’s warranty obligation is affected by product failure rates, utilization levels, material usage, service delivery costs incurred in correcting a product failure and supplier warranties on parts delivered to the Company.

The following is a summary of product warranty and retrofit activity on a gross basis for the three and six months ended March 31, 2018 and 2017 (in thousands):


Activity -Three Months Ended March 31, 2018
Balance						Balance
December 31,						March 31,
2017		Accruals		Costs Incurred		2018
$	8,218	$	2,073	$	(2,002)	$	8,289


Activity -Three Months Ended March 31, 2017
Balance						Balance
December 31,						March 31,
2016		Accruals		Costs Incurred		2017
$	6,217	$	2,709	$	(1,853)	$	7,073


Activity -Six Months Ended March 31, 2018
Balance						Balance
September 30,						March 31,
2017		Accruals		Costs Incurred		2018
$	8,054	$	4,409	$	(4,174)	$	8,289


Activity -Six Months Ended March 31, 2017
Balance						Balance
September 30,						March 31,
2016		Accruals		Costs Incurred		2017
$	6,324	$	5,216	$	(4,467)	$	7,073