Subsequent Events	9 Months Ended
Sep. 30, 2013
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events The Company has evaluated the period after the balance sheet date, noting no subsequent events or transactions that required recognition or disclosure in the financial statements, other than as noted below. West Williston acquisition. On October 1, 2013, the Company acquired approximately 136,000 net acres in and around its position in North Dakota in its West Williston project area (the “West Williston Acquisition”) for $1,478.6 million, which included a $72.5 million deposit made in September 2013, and is subject to further customary post close adjustments. The Company funded the West Williston Acquisition with proceeds from its issuance of the 2022 Notes and borrowings under its revolving credit facility (see below and Note 7 – Long-Term Debt). The West Williston Acquisition will be accounted for as a business combination. Senior secured revolving line of credit. On October 1, 2013, the Company borrowed an additional $440.0 million under its Second Amended Credit Facility, resulting in total outstanding indebtedness under the Second Amended Credit Facility of $605.2 million and an unused borrowing base capacity of $894.8 million. After the closing of the 2022 Notes and the West Williston Acquisition, the Lenders kept the borrowing base of the Second Amended Credit Facility at $1,500.0 million. Drilling contracts. In October 2013, the Company assumed an additional long-term drilling rig contract as part of the West Williston Acquisition. In the event of early termination under this contract, the Company would be obligated to pay an additional maximum amount of approximately $9.7 million if terminated immediately after execution. Purchase agreements. In October 2013, the Company entered into an agreement to purchase well fracturing equipment. The future obligation under this agreement is $3.6 million.

Subsequent Events

The Company has evaluated the period after the balance sheet date, noting no subsequent events or transactions that required recognition or disclosure in the financial statements, other than as noted below.

West Williston acquisition. On October 1, 2013, the Company acquired approximately 136,000 net acres in and around its position in North Dakota in its West Williston project area (the “West Williston Acquisition”) for $1,478.6 million, which included a $72.5 million deposit made in September 2013, and is subject to further customary post close adjustments. The Company funded the West Williston Acquisition with proceeds from its issuance of the 2022 Notes and borrowings under its revolving credit facility (see below and Note 7 – Long-Term Debt). The West Williston Acquisition will be accounted for as a business combination.

Senior secured revolving line of credit. On October 1, 2013, the Company borrowed an additional $440.0 million under its Second Amended Credit Facility, resulting in total outstanding indebtedness under the Second Amended Credit Facility of $605.2 million and an unused borrowing base capacity of $894.8 million. After the closing of the 2022 Notes and the West Williston Acquisition, the Lenders kept the borrowing base of the Second Amended Credit Facility at $1,500.0 million.

Drilling contracts. In October 2013, the Company assumed an additional long-term drilling rig contract as part of the West Williston Acquisition. In the event of early termination under this contract, the Company would be obligated to pay an additional maximum amount of approximately $9.7 million if terminated immediately after execution.

Purchase agreements. In October 2013, the Company entered into an agreement to purchase well fracturing equipment. The future obligation under this agreement is $3.6 million.