CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018	May 24, 2018	May 23, 2018	Dec. 31, 2017
Stockholders’ equity:
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001			$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000	5,000,000	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	30,223	30,223			30,223
Preferred stock, shares outstanding (in shares)	4,540	4,606			2,431
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001		$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	100,000,000	100,000,000	75,000,000	100,000,000
Common stock, shares issued (in shares)	438,116	296,609	6,200,000	61,600,000	115,651
Common stock, shares outstanding (in shares)	438,116	296,609	6,200,000	61,600,000	115,651

Face amount or stated value per share of common stock.

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

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The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.

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Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased, and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt.

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Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

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