Subsequent Events	9 Months Ended
Sep. 30, 2016
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. Derivative instruments. In October 2016, the Company entered into new swaps and two-way and three-way costless collar options for crude oil and natural gas with weighted average floor prices of $51.73 per barrel and $3.38 per MMBtu, respectively. The commodity contracts included total notional amounts of 2,338,000 barrels, 1,219,000 barrels and 93,000 barrels, which settle in 2017, 2018 and 2019, respectively, based on WTI and 668,000 MMBtu and 62,000 MMBtu, which settle in 2017 and 2018, respectively, based on Henry Hub. These derivative instruments do not qualify for and were not designated as hedging instruments for accounting purposes. Credit facility amendment. On October 14, 2016, the Company entered into an amendment to its Credit Facility in connection with the scheduled redetermination of its borrowing base. Following the redetermination, the borrowing base and elected commitments were reaffirmed at $1,150.0 million. The next redetermination of the Company’s borrowing base is scheduled for April 1, 2017. Acquisition. On October 17, 2016, the Company signed a purchase and sale agreement (the “Purchase Agreement”) with SM Energy Company to acquire approximately 55,000 net acres in the Williston Basin for approximately $785.0 million (the “Williston Basin Acquisition”). The effective date for the Williston Basin Acquisition is October 1, 2016 and the transaction is expected to close on December 1, 2016. The transaction is subject to customary closing conditions. The Purchase Agreement contains various purchase price adjustments to be calculated as of the closing date. The Company will fund the Williston Basin Acquisition with the proceeds from its October 2016 public equity offering discussed below and borrowings under its Credit Facility. The Williston Basin Acquisition will be accounted for as a business combination. Sale of common stock. On October 21, 2016, the Company completed a public offering of 55,200,000 shares of its common stock (including 7,200,000 shares issued pursuant to the underwriters’ option to purchase additional common stock) at a purchase price to the public of $10.80 per share. Net proceeds from the offering were approximately $584.0 million, after deducting underwriting discounts and commissions and estimated offering expenses. The Company intends to use the net proceeds to fund a portion of the Williston Basin Acquisition. The offering was not conditioned on the consummation of the Williston Basin Acquisition, and if the Williston Basin Acquisition does not close, the net proceeds will be used for general corporate purposes, which may include funding a portion of the Company’s 2017 capital budget. The offering was made pursuant to an effective shelf registration statement on Form S-3 filed with the SEC on July 15, 2014.

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.

Derivative instruments. In October 2016, the Company entered into new swaps and two-way and three-way costless collar options for crude oil and natural gas with weighted average floor prices of $51.73 per barrel and $3.38 per MMBtu, respectively. The commodity contracts included total notional amounts of 2,338,000 barrels, 1,219,000 barrels and 93,000 barrels, which settle in 2017, 2018 and 2019, respectively, based on WTI and 668,000 MMBtu and 62,000 MMBtu, which settle in 2017 and 2018, respectively, based on Henry Hub. These derivative instruments do not qualify for and were not designated as hedging instruments for accounting purposes.

Credit facility amendment. On October 14, 2016, the Company entered into an amendment to its Credit Facility in connection with the scheduled redetermination of its borrowing base. Following the redetermination, the borrowing base and elected commitments were reaffirmed at $1,150.0 million. The next redetermination of the Company’s borrowing base is scheduled for April 1, 2017.

Acquisition. On October 17, 2016, the Company signed a purchase and sale agreement (the “Purchase Agreement”) with SM Energy Company to acquire approximately 55,000 net acres in the Williston Basin for approximately $785.0 million (the “Williston Basin Acquisition”). The effective date for the Williston Basin Acquisition is October 1, 2016 and the transaction is expected to close on December 1, 2016. The transaction is subject to customary closing conditions. The Purchase Agreement contains various purchase price adjustments to be calculated as of the closing date. The Company will fund the Williston Basin Acquisition with the proceeds from its October 2016 public equity offering discussed below and borrowings under its Credit Facility. The Williston Basin Acquisition will be accounted for as a business combination.

Sale of common stock. On October 21, 2016, the Company completed a public offering of 55,200,000 shares of its common stock (including 7,200,000 shares issued pursuant to the underwriters’ option to purchase additional common stock) at a purchase price to the public of $10.80 per share. Net proceeds from the offering were approximately $584.0 million, after deducting underwriting discounts and commissions and estimated offering expenses. The Company intends to use the net proceeds to fund a portion of the Williston Basin Acquisition. The offering was not conditioned on the consummation of the Williston Basin Acquisition, and if the Williston Basin Acquisition does not close, the net proceeds will be used for general corporate purposes, which may include funding a portion of the Company’s 2017 capital budget. The offering was made pursuant to an effective shelf registration statement on Form S-3 filed with the SEC on July 15, 2014.