Acquisitions (Details) $ / shares in Units, $ in Thousands, shares in Millions						3 Months Ended	12 Months Ended
		Dec. 21, 2016 USD ($) shares	Oct. 04, 2016 USD ($)	Oct. 15, 2014 USD ($)	Sep. 24, 2014 USD ($) a	Dec. 31, 2016 USD ($) a $ / shares	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($) a $ / shares	Dec. 31, 2014 USD ($)
Business Acquisition [Line Items]
Wells in Progress						$ 235,147	$ 235,147	$ 387,432
Proved Oil and Gas Property, Successful Effort Method						5,700,418	5,700,418	7,606,405
Unproved Oil and Gas Property, Successful Effort Method						2,471,947	2,471,947	284,538
Asset Retirement Obligations, Noncurrent						$ (96,134)	$ (96,134)	$ (137,284)
Common Stock, Par or Stated Value Per Share | $ / shares						$ 0.01	$ 0.01	$ 0.01
Payments to Acquire Oil and Gas Property and Equipment							$ 2,183,790	$ 7,984	$ 544,553
Value of common stock from issuance of private placement for an asset acquisition	[1]						$ 437,194	0	$ 0
QStar Acquisition 2016 [Member]
Business Acquisition [Line Items]
Wells in Progress		$ 21,812
Proved Oil and Gas Property, Successful Effort Method		61,614
Unproved Oil and Gas Property, Successful Effort Method		1,537,923
Oil and Gas Property, Successful Effort Method, Gross		1,621,349
Working Capital Acquired		(9,141)
Asset Retirement Obligations, Noncurrent		(7,641)
Acquisition of Oil and Gas Property And Equipment, Consideration Transferred		$ 1,604,567
Stock Issued During Period, Shares, Acquisitions | shares		13.4
Payments to Acquire Oil and Gas Property and Equipment		$ 1,167,373
Value of common stock from issuance of private placement for an asset acquisition	[2]	437,194
Noncash or Part Noncash Acquisition, Value of Assets Acquired		$ 1,604,567
Other Midland Basin Acquisition 2016 [Member]
Business Acquisition [Line Items]
Net acres acquired | a						2,900
Payments to Acquire Oil and Gas Property and Equipment						$ 60,000
Rocky Mountain Acquisition 2014 [Member]
Business Acquisition [Line Items]
Payments to Acquire Oil and Gas Property and Equipment								$ 135,500
Leasehold Acres Consideration to Acquire Unproved Property | a								7,000
Gooseneck Second Prospect Acquisition 2014 [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross				$ 84,836
Proved Oil and Gas Property, Successful Effort Method				54,612
Unproved Oil and Gas Property, Successful Effort Method				29,610
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets				84,222
Working Capital Acquired				2,232
Asset Retirement Obligations, Noncurrent				(1,618)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net				$ 84,836
Gooseneck Prospect Acquisition 2014 [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross					$ 321,807
Proved Oil and Gas Property, Successful Effort Method					203,467
Unproved Oil and Gas Property, Successful Effort Method					126,588
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets					330,055
Working Capital Acquired					(6,135)
Asset Retirement Obligations, Noncurrent					(2,113)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net					$ 321,807
Net acres acquired | a					61,000
Rock Oil Acquisition 2016 [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross			$ 991,038
Wells in Progress			5,672
Proved Oil and Gas Property, Successful Effort Method			81,917
Unproved Oil and Gas Property, Successful Effort Method			913,594
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets			5,338
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets			1,006,521
Working Capital Acquired			(7,888)
Asset Retirement Obligations, Noncurrent			(7,595)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net			$ 991,038

[1] Refer to Note 3 - Acquisitions, Divestitures, and Assets Held for Sale and Note 15 - Equity for additional discussion.

[2] The Company issued approximately 13.4 million shares of common stock, par value $0.01 per share, in a private placement to the sellers in the QStar Acquisition on December 21, 2016. The equity consideration was valued on this date using Level 1 and Level 2 inputs with a discount applied due to the lack of marketability in the near term in accordance with the Lock-Up and Registration Rights Agreement that prohibits the sale of such stock until no earlier than the 90th day after issuance.