| Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] |
The balance of and changes in the components included in AOCI were as follows: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Three Months Ended September 30, | | 2021 | | 2020 | | Foreign Currency Translation | | Cash Flow Hedges | | Pension and Other Postretirement Benefits | | Total | | Foreign Currency Translation | | Cash Flow Hedges | | Pension and Other Postretirement Benefits | | Total | | (Thousands of Dollars) | | Balance as of July 1 | $ | (40,311) | | | $ | (39,467) | | | $ | (12,514) | | | $ | (92,292) | | | $ | (47,962) | | | $ | (44,890) | | | $ | (8,603) | | | $ | (101,455) | | | Other comprehensive (loss) income before reclassification adjustments | (1,684) | | | — | | | — | | | (1,684) | | | 1,594 | | | — | | | — | | | 1,594 | | Net gain on pension costs reclassified into other income, net | — | | | — | | | (187) | | | (187) | | | — | | | — | | | (305) | | | (305) | | Net loss on cash flow hedges reclassified into interest expense, net | — | | | 1,343 | | | — | | | 1,343 | | | — | | | 1,372 | | | — | | | 1,372 | | Other | — | | | — | | | 2 | | | 2 | | | — | | | — | | | 3 | | | 3 | | | Other comprehensive (loss) income | (1,684) | | | 1,343 | | | (185) | | | (526) | | | 1,594 | | | 1,372 | | | (302) | | | 2,664 | | | Balance as of September 30 | $ | (41,995) | | | $ | (38,124) | | | $ | (12,699) | | | $ | (92,818) | | | $ | (46,368) | | | $ | (43,518) | | | $ | (8,905) | | | $ | (98,791) | |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Nine Months Ended September 30, | | 2021 | | 2020 | | Foreign
Currency
Translation | | Cash Flow
Hedges | | Pension and
Other
Postretirement
Benefits | | Total | | Foreign
Currency
Translation | | Cash Flow
Hedges | | Pension and
Other
Postretirement
Benefits | | Total | | (Thousands of Dollars) | | Balance as of January 1 | $ | (42,362) | | | $ | (42,150) | | | $ | (12,144) | | | $ | (96,656) | | | $ | (43,772) | | | $ | (16,124) | | | $ | (8,000) | | | $ | (67,896) | | | Other comprehensive income (loss) before reclassification adjustments | 367 | | | — | | | — | | | 367 | | | (2,596) | | | (30,291) | | | — | | | (32,887) | | Net gain on pension costs reclassified into other income, net | — | | | — | | | (560) | | | (560) | | | — | | | — | | | (915) | | | (915) | | Net loss on cash flow hedges reclassified into interest expense, net | — | | | 4,026 | | | — | | | 4,026 | | | — | | | 2,897 | | | — | | | 2,897 | | Other | — | | | — | | | 5 | | | 5 | | | — | | | — | | | 10 | | | 10 | | | Other comprehensive income (loss) | 367 | | | 4,026 | | | (555) | | | 3,838 | | | (2,596) | | | (27,394) | | | (905) | | | (30,895) | | | Balance as of September 30 | $ | (41,995) | | | $ | (38,124) | | | $ | (12,699) | | | $ | (92,818) | | | $ | (46,368) | | | $ | (43,518) | | | $ | (8,905) | | | $ | (98,791) | |
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| Distributions Made to Limited Partner, by Distribution [Table Text Block] |
Distributions on our Series A, B and C Preferred Units are payable out of any legally available funds, accrue and are cumulative from the original issuance dates, and are payable on the 15th day (or next business day) of each of March, June, September and December of each year to holders of record on the first business day of each payment month as follows (until the distribution rate changes to a floating rate): | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Units | | | | | | | | | | Fixed Distribution Rate Per Unit Per Quarter | | Fixed Distribution
Per Quarter | | Date at Which Distribution
Rate Becomes Floating | | | | | | | | | | | | | (Thousands of Dollars) | | | | Series A Preferred Units | | | | | | | | | | $ | 0.53125 | | | $ | 4,813 | | | December 15, 2021 | | Series B Preferred Units | | | | | | | | | | $ | 0.47657 | | | $ | 7,339 | | | June 15, 2022 | | Series C Preferred Units | | | | | | | | | | $ | 0.56250 | | | $ | 3,881 | | | December 15, 2022 |
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| Distributions Made to Limited Partner, by Distribution [Table Text Block] |
The following table summarizes information about quarterly cash distributions declared for our common limited partners: | | | | | | | | | | | | | | | | | | | | | | | | | | | | Quarter Ended | | Cash Distributions
Per Unit | | Total Cash
Distributions | | Record Date | | Payment Date | | | | | (Thousands of Dollars) | | | | | | September 30, 2021 | | $ | 0.40 | | | $ | 43,814 | | | November 8, 2021 | | November 12, 2021 | | June 30, 2021 | | $ | 0.40 | | | $ | 43,814 | | | August 6, 2021 | | August 12, 2021 | | March 31, 2021 | | $ | 0.40 | | | $ | 43,834 | | | May 10, 2021 | | May 14, 2021 | | December 31, 2020 | | $ | 0.40 | | | $ | 43,787 | | | February 8, 2021 | | February 12, 2021 |
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