Income Taxes - Additional Information (Detail) $ in Millions	9 Months Ended
Oct. 31, 2015 USD ($)
Income Tax Disclosure [Abstract]
Net state deferred tax assets	$ 4
Acquisition and disposition ownership interest period	3 years

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from state taxes.

No definition available.

Name:	us-gaap_DeferredTaxAssetsStateTaxes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant