In millions, except per share items | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 | Dec-31-13 | Dec-31-12 | Dec-31-11 | Dec-31-10 |
| 10-K/A | 10-K/A | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
Operating activities: | | | | | | | | |
Adjustments to reconcile net income (loss) to net cash from operating activities: | | | | | | | | |
Amortization of deferred financing costs and long-term debt premium and discount | | | 11.6 | 2.3 | 2.5 | 1.7 | 1.0 | 0.8 |
Stock-based compensation | | | 12.1 | 16.3 | 14.9 | 9.4 | 7.9 | 6.2 |
Commodity derivative instruments (gain) loss | | | | | | | | |
Commodity derivative settlement gain (loss) | | | | | | | | |
Unrealized contingent payment derivative instrument gain | | | | | | | | |
Change in operating assets and liabilities: | | | | | | | | |
Accounts receivable | | | 21.2 | 36.8 | -16.0 | -15.3 | -16.5 | -17.9 |
Other current assets | | | 0.3 | -0.7 | 0.5 | 0.1 | | |
Accounts payable and accrued expenses | | | -27.2 | -14.3 | 25.9 | -4.9 | 18.6 | 0.4 |
Accrued interest payable | | | 0.0 | | 0.0 | 5.6 | -0.3 | 0.0 |
Net cash provided by operating activities | | | 69.5 | 143.5 | 133.3 | 76.8 | 101.1 | 58.5 |
|
Investing activities: | | | | | | | | |
Oil and gas exploration and development expenditures | | | -67.6 | -183.6 | -261.8 | -212.2 | -169.2 | |
Purchase of other property and equipment | | | -0.1 | -1.9 | -2.5 | -1.5 | -1.2 | -0.5 |
Restricted cash | | | -1.5 | -1.6 | 0.2 | -1.8 | -1.8 | -1.8 |
Other long-term assets | | | 0.1 | | | | -0.2 | 0.3 |
Net cash used in investing activities | | | 199.6 | -175.9 | -405.5 | -447.4 | -217.0 | -69.1 |
|
Financing activities: | | | | | | | | |
Proceeds from bank borrowings | | | 46.5 | 139.5 | | 401.9 | 353.2 | 215.3 |
Repayments of bank borrowings | | | -418.0 | -533.5 | -465.0 | -657.6 | -311.1 | -197.0 |
Proceeds from issuance of senior notes | | | | | | | | |
Repayment of term loan | | | -71.7 | | | | | |
Payment of financing costs | | | -3.7 | -1.0 | -1.9 | -12.3 | -0.2 | -4.0 |
Redemption of restricted stock for employee income taxes | | | -0.2 | -1.7 | -1.6 | -1.1 | -1.1 | |
Net cash provided by financing activities | | | -264.1 | 36.8 | 271.3 | 370.5 | 115.2 | 12.0 |
Net decrease in cash and cash equivalents | | | 4.9 | 4.3 | -0.9 | -0.2 | -0.7 | 1.4 |
Cash and cash equivalents at beginning of period | | | 4.4 | 0.0 | 0.9 | 1.1 | 1.8 | 0.5 |
Cash and cash equivalents at end of period | | | 9.3 | 4.4 | 0.0 | 0.9 | 1.1 | 1.8 |