Description of Business - Narrative (Details) storage_rooms in Thousands	12 Months Ended
Dec. 31, 2017 customer storage_rooms country
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating countries (more than) \| country	45
Number of customers \| customer	3,700
Number of service locations \| storage_rooms	25

The number of countries in which the entity operates as of balance sheet date.

No definition available.

Name:	us-gaap_NumberOfCountriesInWhichEntityOperates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant