Accounts Receivable, Net of Allowance (Schedule of Accounts Receivable, Net of Allowance) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounts Receivable, Net of Allowance
Contract billings	$ 437,300	$ 669,700
Retainage	148,800	162,200
Cost and earnings in excess of billings	332,700	485,600
Accounts receivable, gross	918,800	1,317,500
Less allowance for doubtful accounts	(7,700)	(13,900)	$ (15,700)
Accounts receivable, net	$ 911,106	$ 1,303,552