Accounts Receivable, Net of Allowance, and Contract Assets and Liabilities (Schedule of Accounts Receivable, Net of Allowance, and Contract Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Receivables [Abstract]
Contract billings	$ 860,400	$ 687,600
Less allowance for doubtful accounts	10,100	16,300
Accounts receivable, net of allowance	850,326	671,324
Accounts Receivable, Net of Allowance, and Contract Assets [Abstract]
Retainage	345,200	230,200
Unbilled receivables	679,400	1,022,400
Contract assets	$ 1,024,568	$ 1,252,646