Costs and Estimated Earnings on Uncompleted Contracts (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Costs and Estimated Earnings on Uncompleted Contracts
Costs incurred on uncompleted contracts	$ 3,744,678	$ 3,882,968
Reserve for estimated losses on uncompleted contracts	522	764
Gross profit recognized	446,369	448,928
Costs and Estimated Earnings on Uncompleted Contracts	4,191,569	4,332,660
Less: billings to date	(4,283,851)	(4,449,851)
Net cost and estimated earnings in excess of billings	(92,282)	(117,191)
Amount included in consolidated balance sheet
Costs and estimated earnings in excess of billings	70,288	41,701
Billings in excess of costs and estimated earnings	(162,570)	(158,892)
Net cost and estimated earnings in excess of billings	$ (92,282)	$ (117,191)