Receivables, net



(in thousands)	March 31, 2017		December 31, 2016		March 31, 2016
Construction contracts:
Completed and in progress	$	227,314	$	288,160	$	178,974
Retentions	82,692		84,878		93,495
Total construction contracts	310,006		373,038		272,469
Construction Material sales	25,582		29,357		23,392
Other	15,977		17,523		11,940
Total gross receivables	351,565		419,918		307,801
Less: allowance for doubtful accounts	474		573		318
Total net receivables	$	351,091	$	419,345	$	307,483

Receivables include amounts billed and billable to clients for services provided as of the end of the applicable period and do not bear interest. To the extent costs are not contractually billable or have not been earned, such as claim recovery estimates, the associated revenue is included in costs and estimated earnings in excess of billings or billings in excess of costs and estimated earnings in the condensed consolidated balance sheets. As of March 31, 2017, December 31, 2016 and March 31, 2016, the aggregate claim recovery estimates included in these balances were approximately $12.5 million, $12.3 million and $12.4 million, respectively. Included in other receivables at March 31, 2017, December 31, 2016 and March 31, 2016 were items such as estimated recovery from back charge claims, notes receivable, fuel tax refunds, receivables from vendors and income tax refunds. No such receivables individually exceeded 10% of total net receivables at any of these dates. As of March 31, 2017, December 31, 2016 and March 31, 2016 the estimated recovery from back charge claims included in other receivables was $0.3 million, $0.3 million and $7.0 million, respectively.

Certain construction contracts include retainage provisions. The balances billed but not paid by customers pursuant to these provisions generally become due upon completion and acceptance of the project work or products by the owners. As of March 31, 2017, December 31, 2016 and March 31, 2016, no retention receivable individually exceeded 10% of total net receivables at any of the presented dates, the majority of the retentions receivable are expected to be collected within one year and there were no retentions receivables determined to be uncollectible.