| Dividends Declared [Table Text Block] | The following table summarizes the Company’s cash dividend activity for the nine months ended September 30, 2017 (in thousands, except per share data): 
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  
| Declaration Date |   | Per Share |   | Amount |   | Record Date |   | Payment Date |  
| July 31, 2017 (special) |   | $ | 0.25 | 
 |   | $ | 2,833 | 
 |   | August 21, 2017 |   | August 31, 2017 |  
| July 31, 2017 |   | 0.11 | 
 |   | 1,246 | 
 |   | August 21, 2017 |   | August 31, 2017 |  
| April 24, 2017 (special) |   | 0.35 | 
 |   | 3,964 | 
 |   | May 9, 2017 |   | May 19, 2017 |  
| April 24, 2017 |   | 0.10 | 
 |   | 1,133 | 
 |   | May 9, 2017 |   | May 19, 2017 |  
| January 24, 2017 (special) |   | 0.35 | 
 |   | 3,962 | 
 |   | February 21, 2017 |   | March 3, 2017 |  
| January 24, 2017 |   | 0.09 | 
 |   | 1,019 | 
 |   | February 21, 2017 |   | March 3, 2017 |  
|   |   | $ | 1.25 | 
 |   | $ | 14,157 | 
 |   |   |   |   |  |