Allowance for Doubtful Accounts - Reserve For Impaired Notes Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reserve for Impaired Notes Receivable
Balance Beginning of Year	$ 3,031	$ 2,019	$ 958
Additions	99	2,489	1,072
Deductions	991	1,477	11
Balance End of Year	$ 2,139	$ 3,031	$ 2,019