Detail of Selected Balance Sheet Accounts (Tables)

3 Months Ended

Dec. 31, 2016

Activity in our allowance for doubtful accounts receivable consisted of the following (in thousands):



	Three months ended December 31,
	2016			2015
Balance at beginning of period	$	811		$	746
Bad debt expense (recovery)	(113		)	248
Uncollectible accounts written off, net of recoveries	(28		)	26
Change due to foreign currency translation	(6		)	(10		)
Balance at end of period	$	664		$	1,010

The components of inventories are summarized below (in thousands):



	December 31, 2016		September 30, 2016
Raw materials, parts and subassemblies, net	$	23,161	$	25,525
Work-in-progress	815		996
Total inventories	$	23,976	$	26,521

The components of costs and estimated earnings and related amounts billed on uncompleted contracts are summarized below (in thousands):



	December 31, 2016			September 30, 2016
Costs incurred on uncompleted contracts	$	1,090,422		$	1,088,921
Estimated earnings	350,185			350,125
	1,440,607			1,439,046
Less: Billings to date	(1,420,864		)	(1,416,914		)
Net underbilled position	$	19,743		$	22,132
Included in the accompanying balance sheets under the following captions:
Costs and estimated earnings in excess of billings on uncompleted contracts – underbilled	$	59,951		$	66,106
Billings in excess of costs and estimated earnings on uncompleted contracts – overbilled	(40,208		)	(43,974		)
Net underbilled position	$	19,743		$	22,132

Activity in our product warranty accrual consisted of the following (in thousands):



	Three months ended December 31,
	2016			2015
Balance at beginning of period	$	4,639		$	4,930
Increase to warranty expense	370			1,326
Deduction for warranty charges	(725		)	(1,100		)
Change due to foreign currency translation	(54		)	(51		)
Balance at end of period	$	4,230		$	5,105