Debt	3 Months Ended
Debt	Mar. 31, 2019
Debt Disclosure [Abstract]
Debt	Debt Credit Facility. The Company has a $600.0 million reserve-based revolving credit facility, which is subject to a $350.0 million borrowing base. This borrowing base is currently under evaluation by the Company and its lenders under the credit facility in connection with the scheduled spring redetermination. The next borrowing base redetermination after this is scheduled for October 1, 2019. The credit facility matures on March 31, 2020. Outstanding borrowings under the credit facility bear interest based on a pricing grid tied to borrowing base utilization of (a) LIBOR plus an applicable margin that varies from 3.00% to 4.00% per annum, or (b) the base rate plus an applicable margin that varies from 2.00% to 3.00% per annum. Interest on base rate borrowings is payable quarterly in arrears and interest on LIBOR borrowings is payable every one, two, three or six months, at the election of the Company. Quarterly, the Company pays commitment fees assessed at annual rates of 0.50% on any available portion of the credit facility. The Company has the right to prepay loans under the credit facility at any time without a prepayment penalty, other than customary “breakage” costs with respect to LIBOR loans. The credit facility is secured by (i) first-priority mortgages on at least 95% of the PV-9 valuation of all proved reserves included in the most recently delivered reserve report of the Company, (ii) a first-priority perfected pledge of substantially all of the capital stock owned by each credit party and equity interests in the Royalty Trusts that are owned by a credit party and (iii) a first-priority perfected security interest in substantially all the cash, cash equivalents, deposits, securities and other similar accounts, and other tangible and intangible assets of the credit parties (including but not limited to as-extracted collateral, accounts receivable, inventory, equipment, general intangibles, investment property, intellectual property, real property and the proceeds of the foregoing). As of the end of each fiscal quarter, the credit facility requires the Company to maintain (i) a maximum consolidated total net leverage ratio, measured as of the end of any fiscal quarter, of no greater than 3.50 to 1.00 and (ii) a minimum consolidated interest coverage ratio, measured as of the end of any fiscal quarter, of no less than 2.25 to 1.00. These financial covenants are subject to customary cure rights. The Company was in compliance with all applicable financial covenants under the credit facility as of March 31, 2019, as its consolidated total net leverage ratio was 0.06 and its consolidated interest coverage ratio was 80.20. The credit facility contains customary affirmative and negative covenants, including as to compliance with laws (including environmental laws, ERISA and anti-corruption laws), maintenance of required insurance, delivery of quarterly and annual financial statements, oil and gas engineering reports, maintenance and operation of property (including oil and gas properties), restrictions on the incurrence of liens, indebtedness, asset dispositions, fundamental changes, restricted payments including dividends and other customary covenants. The Company was in compliance with these covenants as of March 31, 2019. The credit facility includes events of default relating to customary matters, including, among other things, nonpayment of principal, interest or other amounts; violation of covenants; incorrectness of representations and warranties in any material respect; cross-payment default and cross acceleration with respect to indebtedness in an aggregate principal amount of $25.0 million or more; bankruptcy; judgments involving a liability of $25.0 million or more that are not paid; and ERISA events. Many events of default are subject to customary notice and cure periods. The Company had $20.0 million outstanding under the credit facility at March 31, 2019, and $5.2 million in outstanding letters of credit, which reduce availability under the credit facility on a dollar-for-dollar basis. Building Note. In February 2018, the Company fully repaid a note secured by a mortgage on the Company's downtown Oklahoma City real estate (the "Building Note") in the amount of $36.3 million, which was comprised of an initial principal amount of $35.0 million and $1.3 million in in-kind interest costs that were previously added to the principal. An unamortized premium of $1.2 million was recognized as a gain on extinguishment of debt in the unaudited condensed consolidated statement of operations for the three-month period ended March 31, 2018 in connection with the repayment.