Notes Receivable - Interest Income and Payments Received (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	$ 11,769	$ 10,469	$ 11,818
Payment received relating to notes receivables	13,211	2,560	2,370
Notes Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	10,200	10,100	11,600
Payment received relating to notes receivables	$ 11,300	$ 10,900	$ 11,100