Notes Receivable and Allowance for Losses - Summary of activity related to allowance for losses (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance		$ 6,765
Ending balance		7,430	$ 6,765
Forgivable Notes Receivable
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance		4,615	3,661
Provisions		1,458	1,742
Recoveries		(96)	(739)
Write-offs		(666)	(752)
Other	[1]	(298)	703
Ending balance		5,013	4,615
Mezzanine & Other Notes Receivable
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance		2,150	2,326
Provisions		861	0
Recoveries		(164)	(176)
Write-offs		(430)	0
Other	[1]	0	0
Ending balance		$ 2,417	$ 2,150

[1] (1) Consists of default rate assumption changes and changes in foreign exchange rates