Segment Information - Income Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2015
Segment information
Total assets	$ 7,130,274		$ 7,147,242
Operating revenues	487,847	$ 1,060,787
United States
Segment information
Operating revenues	409,506	956,281
Colombia
Segment information
Operating revenues	6,743	23,937
Argentina
Segment information
Operating revenues	49,786	28,476
Ecuador
Segment information
Operating revenues	3,940	13,890
Other foreign
Segment information
Operating revenues	17,872	38,203
Continued operations
Segment information
Total assets	7,121,825		7,139,145
Discontinued operations.
Segment information
Total assets	8,449		8,097
Other
Segment information
Operating revenues	3,968	4,180
Operating segment
Segment information
Total assets	6,019,687		6,152,140
Operating revenues	488,066	1,061,009
Operating segment | U.S. Land
Segment information
Total assets	5,321,369		5,429,179
Operating segment | Offshore
Segment information
Total assets	116,563		118,852
Operating segment | International Land
Segment information
Total assets	544,257		565,712
Operating segment | Other
Segment information
Total assets	37,498		38,397
Operating revenues	4,187	$ 4,402
Investments and corporate operations
Segment information
Total assets	$ 1,102,138		$ 987,005