CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Gamma Knife, accumulated depreciation	$ 634,000usnu_GammaKnifeAccumulatedDepreciation	$ 475,000usnu_GammaKnifeAccumulatedDepreciation
Leasehold improvements, accumulated depreciation	$ 276,000	$ 197,000
STOCKHOLDERS' EQUITY
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	25,000,000us-gaap_CommonStockSharesAuthorized	25,000,000us-gaap_CommonStockSharesAuthorized
Common stock, shares issued (in shares)	7,797,185us-gaap_CommonStockSharesIssued	7,797,185us-gaap_CommonStockSharesIssued
Common stock, shares outstanding (in shares)	7,797,185us-gaap_CommonStockSharesOutstanding	7,797,185us-gaap_CommonStockSharesOutstanding

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

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Cumulative amount of depreciation related to machinery and equipment that has been recognized in the income statement.

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Cumulative amount of amortization related to leasehold improvements that has been recognized in the income statement.

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