| In millions, except per share items | Jun-30-18 | Mar-31-18 | Jun-30-17 | Mar-31-17 | Dec-31-16 | Sep-30-16 | Jun-30-16 | Mar-31-16 |
| | 10-Q | 10-Q | 10-Q | 10-Q | 10-K | 10-Q | 10-Q | 10-Q |
| Revenues: | | | | | | | | |
| Service revenues | 1,335.0 | 1,346.0 | 1,277.0 | 1,256.0 | 1,485.0 | 1,252.0 | 1,210.0 | 1,226.0 |
| Service revenues – commodity consideration (Note 2) | 94.0 | 101.0 | | | | | | |
| Product sales | 657.0 | 636.0 | 642.0 | 727.0 | 705.0 | 655.0 | 530.0 | 428.0 |
| Total revenues | 2,086.0 | 2,083.0 | 1,919.0 | 1,983.0 | 2,190.0 | 1,907.0 | 1,740.0 | 1,654.0 |
| Total revenues growth | 8.7% | 5.0% | 10.3% | 19.9% | 9.6% | 6.4% | -4.9% | -3.3% |
| Costs and expenses: | | | | | | | | |
| Product costs | 636.0 | 613.0 | 537.0 | 579.0 | | | | |
| Processing commodity expenses (Note 2) | 26.0 | 35.0 | | | | | | |
| Operating and maintenance expenses | 383.0 | 351.0 | 384.0 | 361.0 | 395.0 | 385.0 | 386.0 | 382.0 |
| Depreciation and amortization expenses | 426.0 | 423.0 | 423.0 | 433.0 | 427.0 | 426.0 | 432.0 | 435.0 |
| Selling, general, and administrative expenses | 136.0 | 138.0 | 154.0 | 156.0 | 163.0 | 147.0 | 139.0 | 181.0 |
| Other (income) expense – net | -1.0 | 31.0 | 9.0 | 4.0 | 11.0 | 59.0 | 24.0 | 30.0 |
| Total costs and expenses | 1,606.0 | 1,591.0 | 1,507.0 | 1,533.0 | 1,588.0 | 1,481.0 | 1,780.0 | 1,345.0 |
| Operating income (loss) | 480.0 | 492.0 | 412.0 | 450.0 | 602.0 | 426.0 | -40.0 | 309.0 |
| Operating margin | 23.0% | 23.6% | 21.5% | 22.7% | 27.5% | 22.3% | -2.3% | 18.7% |
| Equity earnings (losses) | 92.0 | 82.0 | 125.0 | -107.0 | 95.0 | 104.0 | 101.0 | 97.0 |
| Other investing income (loss) – net (Note 4) | 67.0 | 4.0 | 2.0 | 271.0 | | 28.0 | 1.0 | |
| Interest incurred | -224.0 | -218.0 | -214.0 | -221.0 | -234.0 | -236.0 | -239.0 | -240.0 |
| |
| Interest capitalized | | | | | | | | |
| Other income (expense) – net | 21.0 | 15.0 | 15.0 | 49.0 | 19.0 | 16.0 | 12.0 | 15.0 |
| Income (loss) before income taxes | 449.0 | 384.0 | 349.0 | 663.0 | 171.0 | 345.0 | -157.0 | 80.0 |
| Provision (benefit) for income taxes | | | -1.0 | -3.0 | -5.0 | 6.0 | 80.0 | -1.0 |
| Net income (loss) | 449.0 | 384.0 | 348.0 | 660.0 | 166.0 | 351.0 | -77.0 | 79.0 |
| Less: Net income (loss) attributable to noncontrolling interests | 23.0 | 24.0 | 28.0 | 26.0 | 21.0 | 25.0 | 13.0 | 29.0 |
| Net income (loss) attributable to controlling interests | 426.0 | 360.0 | 320.0 | 634.0 | 145.0 | 326.0 | -90.0 | 50.0 |
| |
| Allocation of net income (loss) for calculation of earnings per common unit: | | | | | | | | |
| Net income (loss) attributable to controlling interests | 426.0 | 360.0 | 320.0 | 634.0 | 145.0 | 326.0 | -90.0 | 50.0 |
| Allocation of net income (loss) to Class B units | 8.0 | 7.0 | 6.0 | 11.0 | 18.0 | 7.0 | -8.0 | -4.0 |
| Allocation of net income (loss) to common units | 418.0 | 353.0 | 314.0 | 623.0 | 91.0 | 247.0 | -289.0 | -148.0 |
| |
| Basic earnings (loss) per common unit: | | | | | | | | |
| Net income (loss) per common unit | $0.44 | $0.37 | $0.33 | $0.68 | $0.15 | $0.42 | ($0.49) | ($0.25) |
| |
| Weighted-average number of common units outstanding (thousands) | 957.9 | 957.3 | 955.6 | 919.9 | 592.5 | 591.3 | 588.6 | 588.6 |
| |
| Diluted earnings (loss) per common unit: | | | | | | | | |
| Net income (loss) per common unit | $0.44 | $0.37 | $0.33 | $0.68 | $0.15 | $0.42 | ($0.49) | ($0.25) |
| Weighted-average number of common units outstanding (thousands) | 958.0 | 957.3 | 956.0 | 920.3 | 592.5 | 591.6 | 588.6 | 588.6 |
| Cash distributions per common unit | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| |
| Other comprehensive income (loss): | | | | | | | | |
| Net unrealized gain (loss) from derivative instruments | | | | | | | | |
| Reclassifications into earnings of net derivative instruments (gain) loss | | | | | | | | |
| Other comprehensive income (loss) | | | | | | | | |
| Comprehensive income (loss) | | | | | | | | |
| Less: Comprehensive income attributable to noncontrolling interests | | | | | | | | |
| Comprehensive income (loss) attributable to controlling interests | 411.0 | 362.0 | 319.0 | 637.0 | 145.0 | 420.0 | -85.0 | 122.0 |