Accounts Receivable

6 Months Ended

Jun. 30, 2018

Receivables [Abstract]

Accounts Receivable

3. Accounts Receivable

(Table only in thousands)	June 30, 2018			December 31, 2017
Contract receivables	$	63,990		$	60,543
Trade receivables		8,040			11,603
Allowance for doubtful accounts		(4,234	)		(4,156	)
Total accounts receivable	$	67,796		$	67,990

Balances billed but not paid by customers under retainage provisions in contracts within the Condensed Consolidated Balance Sheets amounted to approximately $2.6 million and $2.5 million at June 30, 2018 and December 31, 2017, respectively. Retainage receivables on contracts in progress are generally collected within a year after contract completion.

Bad debt expense was $0.5 million and $0.7 million for the three-month periods ended June 30, 2018 and 2017, respectively, and $0.6 million and $1.0 million for the six-month periods ended June 30, 2018 and 2017, respectively.