Contingencies and Legal Matters (Details) (Germany)	3 Months Ended
Mar. 31, 2015
Germany
Income Taxes
Percentage of salaried employees eligible to be represented by Mining, Chemicals and Energy Trade Union (IG BCE)	50.00%
Percentage of hourly employees eligible to be represented by Mining, Chemicals and Energy Trade Union (IG BCE)	80.00%

Represents the percentage of hourly employees eligible to be represented by Mining, Chemicals and Energy Trade Union (Industriegewerkschaft Bergbau, Chemie and Energie).

No definition available.

Name:	np_PercentageOfHourlyEmployeesEligibleToBeRepresentedByMiningChemicalsAndEnergyTradeUnionIGBCE
Namespace Prefix:	np_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration