Allowance for Doubtful Accounts - Impaired Notes Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Impaired Notes Receivable
Balance Beginning of Year	$ 10,208	$ 2,892	$ 1,639
Additions	395	9,124	1,267
Deductions	4,132	1,808	14
Balance End of Year	6,471	10,208	2,892
Average Outstanding Balance	$ 8,340	$ 6,550	$ 2,266