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

401(k) Savings plan - Additional Information (Detail) - 401 (k) [Member] - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Feb. 28, 2017	Feb. 29, 2016	Dec. 31, 2014
Defined Contribution Plan Disclosure [Line Items]
Contributions to the 401(k) Plan		$ 0.6	$ 0.0
Subsequent Event [Member]
Defined Contribution Plan Disclosure [Line Items]
Contributions to the 401(k) Plan	$ 1.0