401(k) Plan (Details Textual) - USD ($)	1 Months Ended	12 Months Ended
Jan. 01, 2004	Dec. 31, 2014	Dec. 31, 2013
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent		15.00%
Defined Contribution Plan, Cost Recognized		$ 43,000	$ 46,000
3% Employee Contribution [Member]
Defined Contribution Plan Employee Matched Contributions Percent	3.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	100.00%
2% Employee Contribution [Member]
Defined Contribution Plan Employee Matched Contributions Percent	2.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	50.00%

Defined contribution plan, Employee matched contributions, Percent.

No definition available.

Name:	neph_DefinedContributionPlanEmployeeMatchedContributionsPercent
Namespace Prefix:	neph_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

+ Details

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

- Definition

Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

+ References

No definition available.

+ Details

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

- Details

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Namespace Prefix:
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- Details

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Namespace Prefix:
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Balance Type:
Period Type: