Segment Information (Details 2) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financial information with respect to entity's operations by geographic area
Operating revenues	$ 738,872	$ 847,553	$ 863,305	$ 1,414,707	$ 1,783,836	$ 1,813,762	$ 1,616,981	$ 1,589,618	$ 3,864,437	$ 6,804,197	$ 6,152,015
Property, Plant and Equipment, Net	7,027,802				8,599,125				7,027,802	8,599,125	8,597,813
Goodwill	166,659				173,928				166,659	173,928	512,964
United States
Financial information with respect to entity's operations by geographic area
Operating revenues									1,823,906	4,701,122	4,151,127
Property, Plant and Equipment, Net	3,703,533				5,205,296				3,703,533	5,205,296	5,474,746
Goodwill	54,198				146,310				54,198	146,310	498,149
Outside the U.S
Financial information with respect to entity's operations by geographic area
Operating revenues									2,040,531	2,103,075	2,000,888
Property, Plant and Equipment, Net	3,324,269				3,393,829				3,324,269	3,393,829	3,123,067
Goodwill	$ 112,461				$ 27,618				$ 112,461	$ 27,618	$ 14,815