Accounts Receivable, Net of Allowance, and Contract Assets and Liabilities (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Accounts Receivable, Net of Allowance, and Contract Assets and Liabilities [Line Items]
Retainage, expected collection period (in years)	1 year
Contract liabilities	$ 228,388	$ 206,180
Contract with customer liability deferred revenue current	203,000	184,100
Deferred revenue, revenue recognized	159,600	199,200
Non-recourse financing agreement, discount charge	(59,629)	(77,026)	$ (82,571)
Accounts receivable, credit loss expense (reversal)	12,100	1,700
Amounts charged against the allowance	1,700	7,900
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	$ (5,000)	$ (10,100)	$ (11,100)
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%