Accounts Receivable, Net Of Allowance (Schedule Of Accounts Receivable) (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Accounts Receivable, Net Of Allowance [Abstract]
Contract billings	$ 398,800,000	$ 309,800,000
Retainage	43,700,000	32,700,000
Costs and earnings in excess of billings	229,800,000	110,400,000
Accounts receivable, gross	672,300,000	452,900,000
Less allowance for doubtful accounts	(7,700,000)	(8,500,000)	(10,300,000)
Accounts receivable, net	$ 664,629,000	$ 444,363,000