Fair Value of Financial Instruments (Details Textual) (USD $)	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Fair Value Disclosures [Line Items]
Amount of dilutive securities effect on earnings per share warrants	$ (1,009,000)	$ 2,751,000

Amount of increase (decrease) to net income used for calculating diluted earnings per share (EPS), resulting from the assumed warrants outstanding.

No definition available.

Name:	neph_AmountOfDilutiveSecuritiesEffectOnEarningsPerShareWarrants
Namespace Prefix:	neph_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration