Company Information - Additional Information (Detail)	12 Months Ended
Dec. 31, 2014 Segment mi	Dec. 31, 2013 Segment	Dec. 31, 2012 Segment	Dec. 31, 2011 Segment
Accounting Policies [Abstract]
Distance of principal manufacturing and design operations Shenzhen	30ntp_Distance
Number of reportable segments		1us-gaap_NumberOfReportableSegments	2us-gaap_NumberOfReportableSegments	2us-gaap_NumberOfReportableSegments

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

No definition available.

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration