Notes Receivable - Interest Income and Payments Received (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	$ 2,878	$ 2,678	$ 8,756	$ 8,197
Payment received relating to notes receivables			13,211	2,560
Notes Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	$ 2,500	$ 2,600	7,700	7,900
Payment received relating to notes receivables			$ 11,300	$ 10,900