Credit Facilities - Equipment Loan Facility (Detail) - Equipment Loan Facility	Sep. 05, 2017
Line Of Credit Facility [Line Items]
Weighted-average interest rate	4.53%
Maximum
Line Of Credit Facility [Line Items]
Maturity term	4 years
Minimum
Line Of Credit Facility [Line Items]
Maturity term	3 years

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_LineOfCreditFacilityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration