Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130532-203044

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130531-203044

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

Name:	us-gaap_ContractWithCustomerLiabilityCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Revenue (Details) - USD ($) $ in Millions	3 Months Ended
Revenue (Details) - USD ($) $ in Millions	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Contract Balances
Unbilled revenue	$ 20.3		$ 26.8
Deferred revenue	$ 1.6		$ 1.1
Product revenue
Disaggregation of revenues
Percentage of revenues	55.00%	51.00%
Rental revenue
Disaggregation of revenues
Percentage of revenues	24.00%	25.00%
Field service and other revenue
Disaggregation of revenues
Percentage of revenues	21.00%	24.00%
United States
Disaggregation of revenues
Percentage of revenues	99.00%