| Schedule of Quarterly Financial Information [Table Text Block] |
The following table summarizes quarterly financial data for the years ended December 31, 2017 and 2016: | | | | | | | | | | | | | | | | | | | | | | First Quarter | | Second Quarter | | Third Quarter | | Fourth Quarter | | Total | | (Thousands of Dollars, Except Per Unit Data) | 2017: | | | | | | | | | | Revenues | $ | 487,430 |
| | $ | 435,488 |
| | $ | 440,566 |
| | $ | 450,535 |
| | $ | 1,814,019 |
| Operating income | $ | 97,139 |
| | $ | 73,404 |
| | $ | 91,717 |
| | $ | 74,018 |
| | $ | 336,278 |
| Net income | $ | 57,940 |
| | $ | 26,250 |
| | $ | 38,592 |
| | $ | 25,182 |
| | $ | 147,964 |
| Basic and diluted net income per common unit | $ | 0.49 |
| | $ | 0.05 |
| | $ | 0.15 |
| | $ | — |
| | $ | 0.64 |
| Cash distributions per unit applicable to common limited partners | $ | 1.095 |
| | $ | 1.095 |
| | $ | 1.095 |
| | $ | 1.095 |
| | $ | 4.380 |
| | | | | | | | | | | 2016: | | | | | | | | | | Revenues | $ | 405,703 |
| | $ | 437,804 |
| | $ | 441,418 |
| | $ | 471,757 |
| | $ | 1,756,682 |
| Operating income | $ | 94,565 |
| | $ | 91,217 |
| | $ | 87,954 |
| | $ | 85,373 |
| | $ | 359,109 |
| Net income (loss) | $ | 57,401 |
| | $ | 52,517 |
| | $ | 51,141 |
| | $ | (11,056 | ) | | $ | 150,003 |
| Basic and diluted net income (loss) per common unit | $ | 0.57 |
| | $ | 0.52 |
| | $ | 0.49 |
| | $ | (0.31 | ) | | $ | 1.27 |
| Cash distributions per unit applicable to common limited partners | $ | 1.095 |
| | $ | 1.095 |
| | $ | 1.095 |
| | $ | 1.095 |
| | $ | 4.380 |
|
The quarterly financial data in the table above includes the impact of a $58.7 million non-cash impairment charge on the Axeon Term Loan in the fourth quarter of 2016. |