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The percentage of cash security the company owes the bank. Which must be maintained as a cash balance in a restricted account.

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Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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Exercise price per share or per unit of warrants or rights outstanding.

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Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.

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Face (par) amount of debt instrument at time of issuance.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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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.

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Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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The net amount of operating interest income (expense).

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Sum of investments and unrestricted cash as of the balance sheet date.

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The amount of expense provided in the period for legal costs incurred on or before the balance sheet date pertaining to resolved, pending or threatened litigation, including arbitration and mediation proceedings.

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Carrying value as of the balance sheet date of loans payable (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion.

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Value of input used to measure outstanding warrant and right embodying unconditional obligation requiring redemption by transferring asset at specified or determinable date or upon event certain to occur.

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Period between issuance and expiration of outstanding warrant and right embodying unconditional obligation requiring redemption by transferring asset at specified or determinable date or upon event certain to occur, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Debt - Term Loan (Details)			1 Months Ended	3 Months Ended									6 Months Ended		12 Months Ended
Debt - Term Loan (Details)	Jan. 28, 2019 USD ($)	Jul. 31, 2018 USD ($) $ / shares shares	Jul. 31, 2017 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($) tranche $ / shares shares	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) tranche $ / shares shares	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Debt
Purchase of additional common stock through warrants \| shares					993,204										993,204
Term of warrants					5 years										5 years
Exercise price of warrant \| $ / shares					$ 10.40										$ 10.40
Interest (expense) income				$ 10,000	$ (178,000)	$ (172,000)	$ (144,000)	$ (160,000)	$ (179,000)	$ (132,000)	$ 13,000	$ 12,000	$ (820,000)	$ (304,000)	$ (654,000)	$ (286,000)	$ 114,000
Outstanding borrowings									$ 8,683,000							8,683,000
Risk Free Interest Rate
Debt
Warrant measurement		2.96			2.0										2.0
Price Volatility
Debt
Warrant measurement		66			65.1										65.1
Expected Term
Debt
Term of warrants		10 years			5 years										5 years
Expected Dividend Rate
Debt
Warrant measurement		0			0										0
Minimum
Debt
Interest rate (as a percentage)					4.50%										4.50%
Debt issue costs					$ 4.25										$ 4.25
Maximum
Debt
Interest rate (as a percentage)					5.50%										5.50%
Debt issue costs					$ 4.5										$ 4.5
Term Loan
Debt
Principal amount					$ 15,000,000										$ 15,000,000
Number of tranches \| tranche					3										3
Interest rate (as a percentage)					5.00%										5.00%
Cash security (as a percentage)															100.00%
Unrestricted cash					$ 18,000,000										$ 18,000,000
Debt discount amortized as interest expenses			$ 100,000
Interest (expense) income		$ 33,000													500,000	$ 300,000
Term Loan \| Subsequent Event
Debt
Debt discount amortized as interest expenses	$ 800,000
Outstanding borrowings	8,900,000
Term Loan \| SVB
Debt
Debt issue costs	$ 1,000,000
Final payment fee (as a percentage)	10.00%
Success fee (as a percentage)	3.50%
Purchase of additional common stock through warrants \| shares		36,000
Term of warrants		10 years
Exercise price of warrant \| $ / shares		$ 7.47
Additional paid in capital upon issuance with offset of loan discount		$ 200,000
Debt discount amortized as interest expenses	$ 800,000
Outstanding borrowings	8,900,000
Term Loan \| SVB \| Subsequent Event
Debt
Debt issue costs	$ 1,000,000
Initial Tranche
Debt
Principal amount					10,000,000										10,000,000
Debt discount amortized as interest expenses															2,000
Legal fees incurred															20,000
Initial Tranche \| SVB
Debt
Fee recorded as discount															10,000
Third Tranche Available Through November 2018
Debt
Principal amount					$ 5,000,000										$ 5,000,000