Accounts Receivable, Net of Allowance, and Contract Assets and Liabilities (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Accounts Receivable, Net of Allowance, and Contract Assets and Liabilities [Line Items]
Retainage, expected collection period (in years)	1 year
Provision for doubtful accounts	$ 1,700	$ 8,600
Amounts charged against the allowance	7,900	500
Contract liabilities	206,180	231,644
Contract with customer liability deferred revenue current	184,100	227,100
Deferred revenue, revenue recognized	199,200
Non-recourse financing agreement, discount charge	(77,026)	(82,571)	$ (61,011)
Receivables, Non-Recourse Arrangement [Member]
Schedule of Accounts Receivable, Net of Allowance, and Contract Assets and Liabilities [Line Items]
Non-recourse financing agreement, discount charge	$ (10,100)	$ (11,100)	$ (6,000)
Minimum [Member]
Schedule of Accounts Receivable, Net of Allowance, and Contract Assets and Liabilities [Line Items]
Retainage, percentage of contract billings	5.00%
Maximum [Member]
Schedule of Accounts Receivable, Net of Allowance, and Contract Assets and Liabilities [Line Items]
Retainage, percentage of contract billings	10.00%