Condensed Consolidating Financial Information - (Cash Flow) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net cash (used in) / provided by operating activities	$ (24,776)	$ 42,171
Cash flows from investing activities:
Oil and natural gas property additions	(13,335)	(164,211)
Gas processing equipment additions	(1)	(457)
Other asset additions	(164)	(742)
Cash received from sale of assets	20	660
Net cash used in investing activities	(13,480)	(164,750)
Cash flows from financing activities:
Borrowings under senior secured revolving credit facility		425,987
Debt issuance costs		(870)
Shares repurchased	(2)	(174)
Net cash provided by (used in) financing activities	(2)	424,943
Net increase (decrease) in cash and cash equivalents	(38,258)	302,364
Cash and cash equivalents, beginning of period	208,637	3,252
Cash and cash equivalents, end of period	170,379	305,616
Eliminations
Cash flows from investing activities:
Advances to subsidiaries	1	(27)
Net cash used in investing activities	1	(27)
Cash flows from financing activities:
Proceeds from subsidiaries	(1)	27
Net cash provided by (used in) financing activities	(1)	27
Parent Company Issuer | Reportable legal entity
Cash flows from operating activities:
Net cash (used in) / provided by operating activities	(24,776)	42,171
Cash flows from investing activities:
Oil and natural gas property additions	(13,335)	(164,211)
Gas processing equipment additions	(1)	(457)
Other asset additions	(164)	(742)
Cash received from sale of assets	20	660
Net cash used in investing activities	(13,480)	(164,750)
Cash flows from financing activities:
Borrowings under senior secured revolving credit facility		425,987
Debt issuance costs		(870)
Shares repurchased	(2)	(174)
Proceeds from subsidiaries	1	(27)
Net cash provided by (used in) financing activities	(1)	424,916
Net increase (decrease) in cash and cash equivalents	(38,257)	302,337
Cash and cash equivalents, beginning of period	208,636	1,993
Cash and cash equivalents, end of period	170,379	304,330
Guarantor Subsidiaries | Reportable legal entity
Cash flows from investing activities:
Advances to subsidiaries	(1)	27
Net cash used in investing activities	(1)	27
Cash flows from financing activities:
Net increase (decrease) in cash and cash equivalents	(1)	27
Cash and cash equivalents, beginning of period	$ 1	1,259
Cash and cash equivalents, end of period		$ 1,286