Fair Value of Financial Instruments (Details 2) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Calculated aggregate value	$ 6,377	$ 7,386	$ 3,109
Weighted average exercise price	$ 0.30	$ 0.30	$ 0.40
Closing price per share of common stock	$ 0.60	$ 0.79	$ 0.42
Volatility	138.00%	165.60%	103.50%
Weighted average remaining expected life (years)	4 years 8 months 12 days	5 years	5 years
Risk-free interest rate	1.40%	1.80%	1.60%
Dividend yield	0.00%	0.00%	0.00%

It denotes the closing price per share of common stock, fair value.

No definition available.

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Namespace Prefix:	neph_
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Balance Type:	na
Period Type:	duration

- Definition

It denotes the amount of calculated aggregate value.

+ References

No definition available.

+ Details

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

- Definition

It denotes the weighted average exercise price, fair value.

+ References

No definition available.

+ Details

Name:	neph_WeightedAverageExercisePriceFairValue
Namespace Prefix:	neph_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Expected dividends to be paid to holders of the underlying shares or financial instruments (expressed as a percentage of the share or instrument's price).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	na
Period Type:	duration

- Definition

Period the instrument, asset or liability is expected to be outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

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Period Type:	duration

- Definition

Measure of dispersion, in percentage terms (for instance, the standard deviation or variance), for a given stock price.

+ References

+ Details

Name:	us-gaap_FairValueAssumptionsExpectedVolatilityRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Risk-free interest rate assumption used in valuing an instrument.

+ References

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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