Notes Receivable - Interest Income and Payment Received (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	$ 1,433	$ 1,540	$ 4,254	$ 5,765
Payment received relating to notes receivables			844	2,985
Notes Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	1,400	$ 1,500	4,100	4,700
Payment received relating to notes receivables			6,400	$ 8,800
Accrued interest receivable	$ 39,500		$ 39,500		$ 40,900