Notes and Contracts Receivable - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning balance	$ 6,470	$ 7,110	$ 7,927
Provision for losses	3,926	4,055	4,209
Write-offs	(5,018)	(4,695)	(5,026)
Ending balance	$ 5,378	$ 6,470	$ 7,110