Annual report pursuant to Section 13 and 15(d)

Note 2 - Summary of Significant Accounting Policies - Adoption Impact of New Accounting Pronouncement Related to Revenue Recognition (Details)

v3.8.0.1
Note 2 - Summary of Significant Accounting Policies - Adoption Impact of New Accounting Pronouncement Related to Revenue Recognition (Details) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Revenue $ 38,321 $ 42,497 $ 27,358 $ 24,238 $ 17,573 $ 14,273 $ 16,196 $ 11,898 $ 132,329 $ 59,911 $ 79,415
Taxes, other than income taxes                 3,161 1,779 1,477
Income taxes — deferred                 (3,365) (4,194) (186)
Net income $ 18,361 $ 26,405 $ 16,711 $ 14,885 $ 10,907 $ 8,929 $ 10,123 $ 7,280 $ 76,361 $ 37,240 $ 50,039
Net income per Sub-share Certificate (in dollars per share) $ 2.35 $ 3.36 $ 2.12 $ 1.88 $ 1.37 $ 1.12 $ 1.26 $ 0.90 $ 9.72 $ 4.66 $ 6.10
ASSETS                      
Accrued receivables $ 18,205       $ 6,550       $ 18,205 $ 6,550  
Deferred tax asset (liability) 6,992       3,875       6,992 3,875  
LIABILITIES AND CAPITAL                      
Unearned revenue 41,375       11,775       41,375 11,775  
Other taxes payable 433       277       433 277  
Net proceeds from all sources 79,997       48,584       79,997 48,584  
Accounting Standards Update 2014-09 [Member]                      
Revenue                 154,634 66,108  
Taxes, other than income taxes                 265 167  
Income taxes — deferred                 966 (1,420)  
Net income                 $ 97,231 $ 42,275  
Net income per Sub-share Certificate (in dollars per share)                 $ 12.38 $ 5.29  
ASSETS                      
Accrued receivables 17,772       6,273       $ 17,772 $ 6,273  
Deferred tax asset (liability) (114)       1,101       (114) 1,101  
LIABILITIES AND CAPITAL                      
Unearned revenue 8,364       3,966       8,364 3,966  
Other taxes payable              
Net proceeds from all sources 105,902       53,619       105,902 53,619  
Scenario, Previously Reported [Member] | Accounting Standards Update 2014-09 [Member]                      
Revenue                 132,329 59,911  
Taxes, other than income taxes                 3,161 1,779  
Income taxes — deferred                 (3,365) (4,194)  
Net income                 $ 76,361 $ 37,240  
Net income per Sub-share Certificate (in dollars per share)                 $ 9.72 $ 4.66  
ASSETS                      
Accrued receivables 18,205       6,550       $ 18,205 $ 6,550  
Deferred tax asset (liability) 6,992       3,875       6,992 3,875  
LIABILITIES AND CAPITAL                      
Unearned revenue 41,375       11,775       41,375 11,775  
Other taxes payable 433       277       433 277  
Net proceeds from all sources 79,997       48,584       79,997 48,584  
Restatement Adjustment [Member] | Accounting Standards Update 2014-09 [Member]                      
Revenue                 22,305 6,197  
Taxes, other than income taxes                 (2,896) (1,612)  
Income taxes — deferred                 4,331 2,774  
Net income                 $ 20,870 $ 5,035  
Net income per Sub-share Certificate (in dollars per share)                 $ 2.66 $ 0.63  
ASSETS                      
Accrued receivables (433)       (277)       $ (433) $ (277)  
Deferred tax asset (liability) (7,106)       (2,774)       (7,106) (2,774)  
LIABILITIES AND CAPITAL                      
Unearned revenue (33,011)       (7,809)       (33,011) (7,809)  
Other taxes payable (433)       (277)       (433) (277)  
Net proceeds from all sources $ 25,905       $ 5,035       $ 25,905 $ 5,035