Segment Information (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2014
Segment information
Total assets	$ 6,801,519		$ 6,721,861
Operating revenues	1,056,585	889,152
United States
Segment information
Operating revenues	956,281	788,691
Colombia
Segment information
Operating revenues	23,451	26,730
Argentina
Segment information
Operating revenues	25,083	26,359
Ecuador
Segment information
Operating revenues	15,194	17,800
Other foreign
Segment information
Operating revenues	36,576	29,572
Continued operations
Segment information
Total assets	6,794,122		6,714,655
Discontinued operations
Segment information
Total assets	7,397		7,206
Other
Segment information
Operating revenues	4,180	3,083
Operating segment
Segment information
Total assets	6,281,426		6,027,959
Operating revenues	1,056,807	889,372
Operating segment | U.S. Land
Segment information
Total assets	5,451,403		5,260,810
Operating segment | Offshore
Segment information
Total assets	138,539		137,101
Operating segment | International Land
Segment information
Total assets	650,872		589,968
Operating segment | Other
Segment information
Total assets	40,612		40,080
Operating revenues	4,402	3,303
Investments and corporate operations
Segment information
Total assets	$ 512,696		$ 686,696