Accounts Receivable, Net of Allowance, and Contract Assets and Liabilities (Schedule of Accounts Receivable, Net of Allowance and Contract Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Accounts Receivable, Net of Allowance, and Contract Assets [Abstract]
Contract billings	$ 745,500	$ 687,600
Less allowance for doubtful accounts	(14,300)	(16,300)
Accounts receivable, net of allowance	731,200	671,300
Retainage	372,300	230,200
Costs and earnings in excess of billings	849,800	1,022,500
Retainage and costs and earnings in excess of billings (together, “contract assets”)	1,222,100	1,252,700
Accounts receivable, net	$ 1,953,340	$ 1,923,970