Accounts Receivable, Net of Allowance, and Contract Assets and Liabilities (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Schedule of Accounts Receivable, Net of Allowance, and Contract Assets and Liabilities [Line Items]
Provision for credit losses			$ (11,000)	$ 12,300
Contract liabilities	$ 238,853		238,853		$ 228,388
Contract with customer liability, deferred revenue current	217,400		217,400		$ 203,000
Deferred revenue, revenue recognized	19,300		166,100
Non-recourse financing agreement, discount charge	(13,829)	$ (14,808)	(26,288)	(31,812)
Receivables, Non-Recourse Arrangement
Schedule of Accounts Receivable, Net of Allowance, and Contract Assets and Liabilities [Line Items]
Non-recourse financing agreement, discount charge	$ (800)	$ (1,400)	$ (1,500)	$ (3,200)
Minimum
Schedule of Accounts Receivable, Net of Allowance, and Contract Assets and Liabilities [Line Items]
Retainage, percentage of contract billings			5.00%
Maximum
Schedule of Accounts Receivable, Net of Allowance, and Contract Assets and Liabilities [Line Items]
Retainage, percentage of contract billings			10.00%