Receivables, Net (Tables)

9 Months Ended

Sep. 30, 2017

Receivables [Abstract]

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

(in thousands)	September 30, 2017		December 31, 2016		September 30, 2016
Construction contracts:
Completed and in progress	$	469,416	$	288,160	$	347,320
Retentions	88,650		84,878		97,385
Total construction contracts	558,066		373,038		444,705
Construction material sales	58,920		29,357		50,768
Other	10,412		17,523		17,760
Total gross receivables	627,398		419,918		513,233
Less: allowance for doubtful accounts	317		573		481
Total net receivables	$	627,081	$	419,345	$	512,752