| In millions, except per share items | Sep-30-18 | Jun-30-18 | Mar-31-18 | Dec-31-17 | Sep-30-17 | Jun-30-17 | Mar-31-17 | Dec-31-16 |
| | 10-Q | 10-Q | 10-Q | 10-K | 10-Q | 10-Q | 10-Q | 10-K |
| Cash flows from operating activities: | | | | | | | | |
| Net income | 174.0 | 118.3 | 146.7 | -29.0 | 70.0 | -19.0 | 67.0 | -10.7 |
| Adjustments to reconcile net income to net cash from operating activities: | | | | | | | | |
| Depreciation and amortization | 34.0 | 33.3 | 33.7 | 33.6 | 34.0 | 31.9 | 34.1 | 33.4 |
| Share-based compensation | 3.0 | 8.1 | 0.9 | 6.5 | 2.0 | 2.9 | 2.1 | 2.2 |
| Other non-cash items | 1.0 | 5.0 | | | 1.0 | 2.0 | | |
| Income from equity method investments, net of distributions | | -0.3 | -0.7 | -0.6 | | | | |
| Changes in assets and liabilities: | | | | | | | | |
| Current assets and liabilities | 43.0 | -91.0 | | | -44.0 | 131.0 | | |
| Non-current assets and liabilities | 1.0 | 4.0 | | | -1.0 | | | |
| Net cash provided by operating activities | 256.0 | 242.1 | 15.9 | -136.4 | 62.0 | 135.9 | 116.1 | 81.4 |
| |
| Cash flows from investing activities: | | | | | | | | |
| Capital expenditures | -18.0 | -16.0 | -16.0 | -33.6 | -18.0 | -28.4 | -19.6 | -18.9 |
| Other investing activities | | 1.0 | | | | -1.0 | | |
| Net cash used in investing activities | -18.0 | -15.1 | -15.9 | -109.5 | -18.0 | -28.0 | -21.0 | -21.3 |
| |
| Cash flows from financing activities: | | | | | | | | |
| Distributions to common unitholders – affiliates | -82.0 | -99.0 | | | | | | |
| Distributions to common unitholders – non-affiliates | -15.0 | -43.0 | | | | | | |
| Other financing activities | -1.0 | -1.0 | | | | -1.0 | | |
| Net cash used in financing activities | -98.0 | -76.1 | -66.9 | -140.7 | | -0.6 | -0.4 | -31.9 |
| Net increase in cash and cash equivalents | 140.0 | 150.9 | -66.9 | -386.6 | 44.0 | 107.3 | 94.7 | 28.2 |
| Cash and cash equivalents, beginning of period | | 0.2 | 173.8 | | | | 314.1 | |
| Cash and cash equivalents, end of period | 140.0 | 151.1 | 106.9 | -386.6 | 44.7 | 106.9 | 408.8 | 28.2 |