Segment Information (Details 5) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Segment Assets
Certain cash and cash equivalents	$ 45,162	$ 108,887	$ 299,412	$ 85,305
Fair value of derivatives	23,127	37,428
Investment in unconsolidated affiliates	888,820	805,633
Total assets	11,359,559	10,980,778
Total segments
Segment Assets
Total assets	11,184,044	10,720,981
Not allocated to segments
Segment Assets
Certain cash and cash equivalents	1
Fair value of derivatives	23,127	37,428
Investment in unconsolidated affiliates	57,777	108,849
Other	94,610	113,520
Marcellus | Total segments
Segment Assets
Total assets	6,106,353	5,749,932
Utica Segment | Total segments
Segment Assets
Total assets	2,270,379	2,163,025
Northeast Segment | Total segments
Segment Assets
Total assets	398,221	445,911
Southwest Segment | Total segments
Segment Assets
Total assets	$ 2,409,091	$ 2,362,113