Receivables (Aging of Installment Receivables) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 886	$ 916
0-30 Days Past Due	3	6
31-60 Days Past Due	0	0
61-90 Days Past Due	0	0
90 Days Past Due	3,411	3,569
Total Installment Receivables Past Due	4,300	4,491
U.S.
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	0
0-30 Days Past Due	0	0
31-60 Days Past Due	0	0
61-90 Days Past Due	0	0
90 Days Past Due	3,411	3,566
Total Installment Receivables Past Due	3,411	3,566
CANADA
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	886	916
0-30 Days Past Due	3	6
31-60 Days Past Due	0	0
61-90 Days Past Due	0	0
90 Days Past Due	0	3
Total Installment Receivables Past Due	$ 889	$ 925