Accounts Receivable (Details Textual)	Mar. 31, 2015	Mar. 31, 2014
Receivables [Abstract]
Allowance as a percentage of gross accounts receivable	0.20%	0.30%

Allowance as a percentage of gross accounts receivable

No definition available.

Name:	nvl_AllowanceAsPercentageOfGrossAccountsReceivable
Namespace Prefix:	nvl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant