Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] |
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Consolidated Statements of Income
| | | | | | | | | | | | | For the year ended December 31, 2017 | | | | | | | | | | | | | Revenue | | $ | 132,329 | | | $ | 22,305 | | | $ | 154,634 | | Taxes, other than income taxes | | | 3,161 | | | | (2,896 | ) | | | 265 | | | | | (3,365 | ) | | | 4,331 | | | | 966 | | Net income | | | 76,361 | | | | 20,870 | | | | 97,231 | | Net income per Sub-share Certificate
| | | 9.72 | | | | 2.66 | | | | 12.38 | | | | | | | | | | | | | | |
For the year ended December 31, 201
| | | | | | | | | | | | | Revenue | | $ | 59,911 | | | $ | 6,197 | | | $ | 66,108 | | Taxes, other than income taxes | | | 1,779 | | | | (1,612 | ) | | | 167 | | | | | (4,194 | ) | | | 2,774 | | | | (1,420 | ) | Net income | | | 37,240 | | | | 5,035 | | | | 42,275 | | Net income per Sub-share Certificate
| | | 4.66 | | | | 0.63 | | | | 5.29 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Assets: | | | | | | | | | | | | | Accrued receivables | | $ | 18,205 | | | $ | (433 | ) | | $ | 17,772 | | Deferred tax asset (liability)
| | | 6,992 | | | | (7,106 | ) | | | (114 | ) | | | | | | | | | | | | | | Liabilities and Capital: | | | | | | | | | | | | | Unearned revenue | | $ | 41,375 | | | $ | (33,011 | ) | | $ | 8,364 | | Other taxes payable | | | 433 | | | | (433 | ) | | | — | | Net proceeds from all sources | | | 79,997 | | | | 25,905 | | | | 105,902 | | | | | | | | | | | | | | | | | | | | | | | | | | | | Assets: | | | | | | | | | | | | | Accrued receivables | | $ | 6,550 | | | $ | (277 | ) | | $ | 6,273 | | Deferred tax asset | | | 3,875 | | | | (2,774 | ) | | | 1,101 | | | | | | | | | | | | | | | Liabilities and Capital: | | | | | | | | | | | | | Unearned revenue | | $ | 11,775 | | | $ | (7,809 | ) | | $ | 3,966 | | Other taxes payable | | | 277 | | | | (277 | ) | | | — | | Net proceeds from all sources | | | 48,584 | | | | 5,035 | | | | 53,619 | |
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