Acquisitions and Divestitures (CCA PPA) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Mar. 27, 2013
Business Acquisition [Line Items]
Cash payment		$ 988,982	[1]
Other assets	1,884
Asset retirement obligations	(7,209)
Business Acquisition, Purchase Price Allocation, Assets Acquired Less (Liabilities Assumed)	988,982
Proved Properties [Member]
Business Acquisition [Line Items]
Oil and natural gas properties	771,487
Unevaluated Properties [Member]
Business Acquisition [Line Items]
Oil and natural gas properties	$ 222,820

[1] This cash payment was made through a qualified intermediary from cash placed in qualifying trust accounts from a portion of the proceeds received from the Bakken Exchange Transaction (as defined below) in order to enable a like-kind-exchange transaction for federal income tax purposes. As such, this amount is not reflected as a cash payment to purchase oil and natural gas properties in our Unaudited Condensed Consolidated Statement of Cash Flows.