Notes Receivable - Interest Income and Payment Received (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
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	$ 1,451	$ 1,854	$ 2,821	$ 4,225
Notes Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	1,400	$ 1,700	2,700	3,200
Payment received relating to notes receivables			2,800	$ 2,900
Accrued interest receivable	$ 40,900		$ 40,900		$ 40,900