Financing Receivables - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Leases [Line Items]
Increase in total financing receivables	$ 17,308	$ (1,514)	$ (6,500)
Total financing receivables	$ 26,540	$ 11,054
Maximum contractual term	3 years
Expected financing receivable term (less than)	1 year
Expiration period of sales type lease	through 2024
Increase in amounts considered past due	$ 900
Minimum
Leases [Line Items]
Current financing receivable terms	3 months
Financial receivable lease term	2 years
Maximum
Leases [Line Items]
Current financing receivable terms	12 months
Financial receivable lease term	7 years
Financing Receivable
Leases [Line Items]
Increase in total financing receivables	$ 15,400