| Note 12 - Subsequent Event (Details Textual) - Subsequent Event [Member] $ / shares in Units, $ in Millions | Jul. 23, 2018  USD ($)  $ / shares | 
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| Common Stock, Value, Subscriptions | $ | $ 13 | 
| Common Stock, Par or Stated Value Per Share | $ / shares | $ 2.25 | 
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- Definition Face amount or stated value per share of common stock. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Monetary value of common stock allocated to investors to buy shares of a new issue of common stock before they are offered to the public. When stock is sold on a subscription basis, the issuer does not initially receive the total proceeds. In general, the issuer does not issue the shares to the investor until it receives the entire proceeds. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Details 
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