Notes and Contracts Receivable Notes and Contracts Receivable - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance, beginning of period	$ 7,110	$ 7,927	$ 6,987
Provision for losses	4,055	4,209	5,152
Write-offs	4,695	5,026	4,212
Balance, end of period	$ 6,470	$ 7,110	$ 7,927