Receivables, Net (Tables)

6 Months Ended

Jun. 30, 2017

Receivables [Abstract]

Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block]

(in thousands)	June 30, 2017		December 31, 2016		June 30, 2016
Construction contracts:
Completed and in progress	$	343,707	$	288,160	$	266,685
Retentions	75,891		84,878		95,415
Total construction contracts	419,598		373,038		362,100
Construction material sales	54,165		29,357		54,277
Other	10,892		17,523		15,227
Total gross receivables	484,655		419,918		431,604
Less: allowance for doubtful accounts	410		573		477
Total net receivables	$	484,245	$	419,345	$	431,127