Accounts Receivable (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Accounts Receivable.
Contracts receivable, net of allowance for doubtful accounts of $710 at March 31, 2015 and $540 at December 31, 2014	$ 256,199	$ 287,806
Retention receivable	42,644	49,104
Contracts receivable and retention	298,843	336,910
Other accounts receivable	185	472
Accounts receivable, net	299,028	337,382
Allowance for doubtful accounts	$ 710	$ 540