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Note 21 - Subsequent Events (Details Textual) - USD ($) $ / shares in Units, $ in Millions | 3 Months Ended | 6 Months Ended | 12 Months Ended |
--- | --- | --- | --- | ---
Mar. 31, 2019 | May 07, 2019 | Dec. 31, 2018 | Oct. 26, 2018
Treasury Stock, Shares, Acquired | 233,700 |  | 913,400 |
Treasury Stock Acquired, Average Cost Per Share | $ 36.80 |  | $ 38.43 |
New Stock Repurchase Program [Member] | Subsequent Event [Member] |  |  |  |
Stock Repurchase Program, Authorized Amount |  | $ 50 |  |
October 26, 2018 Stock Repurchase Program [Member] |  |  |  |
Stock Repurchase Program, Authorized Amount |  |  |  | $ 45
October 26, 2018 Stock Repurchase Program [Member] | Subsequent Event [Member] |  |  |  |
Treasury Stock, Shares, Acquired |  | 1,182,060 |  |
Treasury Stock Acquired, Average Cost Per Share |  | $ 38.07 |  |

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