Accounts Receivable

6 Months Ended

Jun. 30, 2021

Receivables [Abstract]

Accounts Receivable

3.     Accounts Receivable

(table only in thousands)	June 30, 2021			December 31, 2020
Contract receivables	$	57,560		$	57,435
Trade receivables		11,100			8,721
Allowance for doubtful accounts		(3,010	)		(3,110	)
Total accounts receivable	$	65,650		$	63,046

Balances billed but not paid by customers under retainage provisions in contracts within the Condensed Consolidated Balance Sheets amounted to approximately $1.9 million and $1.5 million at June 30, 2021 and December 31, 2020, respectively. Retainage receivables on contracts in progress are generally collected within a year after contract completion.

Bad debt expense was approximately $0.1 million and $0.4 million for the three-month periods ended June 30, 2021 and 2020, respectively, and $0.1 million and $0.5 million for the six-month periods ended June 30, 2021 and 2020, respectively.