Summary of Significant Accounting Policies Schedule of costs and estimated earnings on uncompleted contracts and related amounts billed (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accounting Policies [Abstract]
Costs incurred on uncompleted contracts	$ 7,675,049	$ 7,598,325
Estimated earnings, thereon	876,496	830,622
Costs and estimated earnings on uncompleted contracts	8,551,545	8,428,947
Less: billings to date	8,842,011	8,755,806
Net billings in excess of costs	(290,466)	(326,859)
Costs and estimated earnings in excess of billings on uncompleted contracts	93,061	114,836	88,253
Billings in excess of costs and estimated earnings on uncompleted contracts	$ (383,527)	$ (441,695)	$ (456,690)