Receivables (Tables)

12 Months Ended

Sep. 30, 2018

Receivables [Abstract]

Receivables

Accounts receivable, net at September 30, 2018 and 2017 consisted of the following:

	September 30,
	2018			2017
	(In thousands)
Billed	$	157,333		$	126,887
Unbilled (1)	54,971			44,640
	212,304			171,527
Less: allowance for doubtful accounts	(3,439		)	(2,941		)
Accounts receivable, net	$	208,865		$	168,586

(1) Represents revenue recorded in excess of amounts billable pursuant to contract provisions and generally become billable at contractually specified dates or upon the attainment of milestones. Unbilled amounts are expected to be realized within one year.

Activity of Allowance for Doubtful Accounts

Activity in the allowance for doubtful accounts was as follows:

	Year Ended September 30,
	2018			2017
	(In thousands)
Balance, beginning of year	$	2,941		$	2,192
Add: expense	623			1,640
Less: write-offs (net of recoveries)	(125		)	(891		)
Balance, end of year	$	3,439		$	2,941