| In millions, except per share items | Dec-31-15 | Dec-31-14 | Dec-31-13 | Dec-31-12 | Dec-31-11 |
| | 10-K | 10-K | 10-K | 10-K/A | S-1/A |
| Cash flows from operating activities | | | | | |
| Net loss | -65.8 | -2.8 | | | |
| |
| Adjustments to reconcile net loss to net cash used in operating activities: | | | | | |
| Depreciation and depletion | 22.5 | 10.1 | 6.4 | | 1.6 |
| Deferred income taxes | -14.0 | -1.5 | -0.3 | | |
| Stock-based compensation | 1.1 | 1.5 | 1.2 | | |
| Accretion of asset retirement obligation | 0.2 | 0.3 | 0.2 | | 0.0 |
| Change in fair value of derivative contracts | -1.0 | 1.9 | | | |
| Loss on asset sales | -2.4 | -2.1 | | | |
| Amortization of debt issuance costs | 0.4 | 0.2 | | | |
| Increase (decrease) in cash attributable to changes in operating assets and liabilities: | | | | | |
| Trade receivables | 0.8 | -0.1 | -0.6 | | -0.9 |
| Prepaid expenses and other assets | 0.1 | 0.1 | -0.1 | | -0.1 |
| Accounts payable and accrued liabilities | 0.0 | -1.1 | 4.3 | | 1.4 |
| Joint interest revenues payable | 0.2 | -0.1 | 0.4 | | -0.1 |
| Net cash (used) in operating activities | 0.8 | 6.6 | | | |
| |
| Cash flows from investing activities | | | | | |
| Net cash (used) in investing activities | 2.0 | -31.4 | -14.4 | | -6.2 |
| |
| Cash flows from financing activities | | | | | |
| Proceeds from notes payable | 9.8 | 24.1 | | | |
| Repayments of notes payable | -13.1 | -1.1 | -10.0 | | 0.0 |
| Deferred offering costs | 0.0 | -0.1 | -0.2 | | |
| Net cash (used) in financing activities | -3.5 | 22.7 | 8.0 | | 4.4 |
| |
| Net decrease in cash | -0.7 | -2.2 | 4.8 | | 0.8 |
| Cash, beginning of period | 3.6 | 5.8 | 1.0 | | |
| Cash, end of period | 2.8 | 3.6 | 5.8 | | 1.8 |
| |
| Supplemental disclosure of cash flow information | | | | | |
| Cash paid during the period for interest | 0.8 | 2.2 | 0.4 | | 0.0 |
| |
| Supplemental disclosure of non-cash investing transactions | | | | | |
| Payables related to oil and natural gas capitalized expenditures | 3.1 | 1.5 | 1.6 | | 0.9 |