Accounts Receivable (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Accounts Receivable.
Contracts receivable, net of allowance for doubtful accounts of $480 at June 30, 2016 and December 31, 2015, respectively	$ 280,033	$ 288,300
Retention receivable	36,901	31,396
Contracts receivable and retention	316,934	319,696
Other accounts receivable	1,140	892
Accounts receivable, net	318,074	320,588
Allowance for doubtful accounts	$ 480	$ 480