CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Operating activities:
Net income (loss)	$ 243us-gaap_NetIncomeLoss	$ (3,511)us-gaap_NetIncomeLoss
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation of property and equipment	1us-gaap_Depreciation	2us-gaap_Depreciation
Amortization of other assets	52us-gaap_AdjustmentForAmortization	53us-gaap_AdjustmentForAmortization
Noncash stock-based compensation, including stock options and restricted stock	26us-gaap_StockOptionPlanExpense	120us-gaap_StockOptionPlanExpense
Change in fair value of warrant liability	(1,009)us-gaap_FairValueAdjustmentOfWarrants	2,751us-gaap_FairValueAdjustmentOfWarrants
Amortization of debt discount	0	142
Inventory reserve	(2)neph_InventoryFifoReservePeriodCharge	17neph_InventoryFifoReservePeriodCharge
(Gain)/loss on foreign currency transactions	(40)	1
(Increase) decrease in operating assets:
Accounts receivable	(224)	(355)
Inventory	(20)us-gaap_IncreaseDecreaseInInventories	(46)us-gaap_IncreaseDecreaseInInventories
Prepaid expenses and other current assets	22	53
Increase (decrease) in operating liabilities:
Accounts payable	(39)	(40)
Accrued expenses	90	(172)
Deferred revenue	(17)	363
Net cash used in operating activities	(917)	(622)
Financing activities:
Proceeds from issuance of common stock, net of equity issuance costs of $125	0	2,016
Proceeds from exercise of warrants	1us-gaap_ProceedsFromWarrantExercises	1us-gaap_ProceedsFromWarrantExercises
Payment of senior secured note	0us-gaap_RepaymentsOfSeniorDebt	(1,500)us-gaap_RepaymentsOfSeniorDebt
Net cash provided by financing activities	1	517
Effect of exchange rates on cash	(1)	(1)
Net decrease in cash	(917)us-gaap_CashPeriodIncreaseDecrease	(106)us-gaap_CashPeriodIncreaseDecrease
Cash, beginning of period	1,284us-gaap_Cash	579us-gaap_Cash
Cash, end of period	367us-gaap_Cash	473us-gaap_Cash
Supplemental disclosure of cash flow information
Cash paid for interest	$ 14us-gaap_InterestPaid	$ 77us-gaap_InterestPaid

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