Allowance for Doubtful Accounts - Impaired Notes Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Impaired Notes Receivable
Balance Beginning of Year	$ 25,704	$ 6,854	$ 5,685
Additions	3,763	23,382	1,169
Deductions	4,830	4,532	0
Balance End of Year	24,637	25,704	6,854
Average Outstanding Balance	27,554	15,448	6,270
Reserve for Impaired Notes Receivable
Balance Beginning of Year	13,472	2,884	2,419
Additions	3,575	12,526	465
Deductions	4,557	1,938	0
Balance End of Year	$ 12,490	$ 13,472	$ 2,884