| In millions, except per share items | Sep-30-14 | Jun-30-14 | Mar-31-14 | Dec-31-13 | Sep-30-13 | Jun-30-13 | Mar-31-13 | Dec-31-12 |
| | 10-Q | 10-Q | 10-Q | 10-K | 10-Q | 10-Q | 10-Q | 10-K |
| Cash flows from operating activities: | | | | | | | | |
| Net income | 37.2 | -65.3 | -14.4 | | 33.9 | 55.4 | -8.2 | |
| Adjustments to reconcile net income to net cash from operating activities: | | | | | | | | |
| Depreciation, depletion and amortization | 93.2 | 60.6 | 29.8 | | 85.5 | 57.5 | 30.8 | |
| Accretion of asset retirement obligations | 6.5 | 4.3 | 2.1 | | 5.4 | 3.5 | 1.7 | |
| Recognition of unit-based awards | 5.8 | 3.4 | 1.7 | | 5.1 | 3.2 | 1.0 | |
| Loss (gain) on derivative contracts, net | 20.2 | 91.2 | 23.6 | | 14.4 | -34.2 | 16.1 | -42.9 |
| Cash received (paid) on settlement of derivative contracts | 1.2 | -2.9 | -0.3 | | 13.1 | 14.4 | 8.2 | |
| Gain on deferred Class B unit obligation | -6.9 | | | | | | | |
| Other items | 6.1 | 4.2 | 1.6 | | 3.4 | 3.0 | 1.4 | |
| Changes in operating assets and liabilities: | | | | | | | | |
| Accounts receivable and other assets | -16.1 | -24.7 | -0.3 | -21.8 | -20.7 | -14.1 | -15.0 | -8.5 |
| Accounts payable and other liabilities | -12.7 | -3.7 | -7.1 | | 1.6 | 4.5 | -2.2 | |
| Net cash provided by operating activities | 134.5 | 79.1 | 42.2 | | 141.8 | 93.2 | 33.9 | |
| |
| Cash flows from investing activities: | | | | | | | | |
| Additions to oil and natural gas properties | -119.4 | -73.2 | -29.8 | -88.2 | -65.9 | -39.0 | -18.5 | -127.4 |
| Acquisitions | -44.3 | -40.4 | -29.0 | -128.2 | -101.7 | -2.2 | 2.3 | -468.0 |
| Divestitures of oil and gas properties | 1.3 | | | | | | | |
| Proceeds from sale of available-for-sale securities | 3.7 | 0.9 | 0.6 | | 4.6 | | | |
| Purchases of available-for-sale securities | -3.6 | -0.2 | -0.2 | -6.0 | -4.3 | | | |
| Net cash used in investing activities | -162.7 | -113.1 | -58.4 | -218.2 | -167.2 | -41.2 | -16.2 | -592.3 |
| |
| Cash flows from financing activities: | | | | | | | | |
| Proceeds from issuance of units | | | | | 0.1 | 0.1 | | |
| Management incentive fee to the general partner | -1.4 | -1.4 | -1.4 | -3.4 | -2.0 | -0.7 | | -7.7 |
| Distributions to unitholders | -106.6 | -71.0 | -35.4 | -141.6 | -106.2 | -70.8 | -32.3 | -96.5 |
| Units withheld for employee payroll tax obligation | -1.0 | -0.6 | 0.0 | -0.6 | | 0.0 | 0.0 | -0.3 |
| Proceeds from bank borrowings | 178.0 | 123.0 | 63.0 | | 150.0 | 15.0 | | |
| Repayments on bank borrowings | -38.0 | -23.0 | | -35.0 | -20.0 | -5.0 | | -506.5 |
| Deferred financing costs | | | | -2.0 | -1.8 | -1.8 | -1.8 | -8.9 |
| Other | | | | | -0.4 | -0.9 | | |
| Net cash (used in) provided by financing activities | 31.0 | 27.0 | 26.2 | | 19.6 | -64.2 | -33.9 | |
| |
| Increase (decrease) in cash | 2.8 | -6.9 | 9.9 | -18.5 | -5.8 | -12.2 | -16.3 | |
| Cash and cash equivalents at beginning of period | 13.4 | 13.4 | 13.4 | | 31.8 | 31.8 | 31.8 | |
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| Cash and cash equivalents at ending of period | | | | | | | | |