Segment Information (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011	Sep. 30, 2011
Segment reporting, asset reconciling
Total assets	$ 5,441,072		$ 5,441,072		$ 5,003,891
Revenues from external customers
Total operating revenue	769,982	604,406	1,502,570	1,199,048
Investments and corporate operations
Segment reporting, asset reconciling
Total assets	857,884		857,884		757,101
Continuing operations
Segment reporting, asset reconciling
Total assets	5,433,510		5,433,510		4,996,362
Discontinuing operations
Segment reporting, asset reconciling
Total assets	7,562		7,562		7,529
United States
Revenues from external customers
Total operating revenue	699,741	535,582	1,362,092	1,054,622
Colombia
Revenues from external customers
Total operating revenue	19,660	19,758	39,325	38,575
Ecuador
Revenues from external customers
Total operating revenue	13,939	8,092	26,575	20,117
Argentina
Revenues from external customers
Total operating revenue	11,701	11,889	24,108	24,898
Other Foreign
Revenues from external customers
Total operating revenue	24,941	29,085	50,470	60,836
Contract Drilling
Segment reporting, asset reconciling
Total assets	4,575,626		4,575,626		4,239,261
Revenues from external customers
Total operating revenue	766,313	600,729	1,495,619	1,191,368
U.S. Land
Segment reporting, asset reconciling
Total assets	4,035,650		4,035,650		3,719,387
Revenues from external customers
Total operating revenue	658,804	495,459	1,276,583	972,277
Offshore
Segment reporting, asset reconciling
Total assets	138,415		138,415		151,656
Revenues from external customers
Total operating revenue	43,421	50,586	94,213	95,453
International Land
Segment reporting, asset reconciling
Total assets	366,960		366,960		333,142
Revenues from external customers
Total operating revenue	64,088	54,684	124,823	123,638
Other.
Segment reporting, asset reconciling
Total assets	34,601		34,601		35,076
Revenues from external customers
Total operating revenue	3,669	3,677	6,951	7,680
Reportable and other
Revenues from external customers
Total operating revenue	$ 769,982	$ 604,406	$ 1,502,570	$ 1,199,048