Segment Information (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012	Sep. 30, 2012
Segment reporting, asset reconciling
Total assets	$ 6,012,452		$ 6,012,452		$ 5,721,085
Revenues from external customers
Total operating revenue	838,309	769,982	1,682,881	1,502,570
Continuing operations
Segment reporting, asset reconciling
Total assets	6,008,379		6,008,379		5,713,466
Discontinuing operations
Segment reporting, asset reconciling
Total assets	4,073		4,073		7,619
United States
Revenues from external customers
Total operating revenue	742,635	699,741	1,499,120	1,362,092
Colombia
Revenues from external customers
Total operating revenue	24,069	19,660	51,474	39,325
Ecuador
Revenues from external customers
Total operating revenue	15,611	13,939	32,241	26,575
Argentina
Revenues from external customers
Total operating revenue	17,572	11,701	31,168	24,108
Other Foreign
Revenues from external customers
Total operating revenue	38,422	24,941	68,878	50,470
Contract Drilling
Segment reporting, asset reconciling
Total assets	5,275,988		5,275,988		5,083,509
Revenues from external customers
Total operating revenue	835,407	766,313	1,676,422	1,495,619
U.S. Land
Segment reporting, asset reconciling
Total assets	4,627,120		4,627,120		4,422,297
Revenues from external customers
Total operating revenue	685,710	658,804	1,381,740	1,276,583
Offshore
Segment reporting, asset reconciling
Total assets	146,570		146,570		160,135
Revenues from external customers
Total operating revenue	55,605	43,421	113,323	94,213
International Land
Segment reporting, asset reconciling
Total assets	470,054		470,054		467,538
Revenues from external customers
Total operating revenue	94,092	64,088	181,359	124,823
Other.
Segment reporting, asset reconciling
Total assets	32,244		32,244		33,539
Revenues from external customers
Total operating revenue	2,902	3,669	6,459	6,951
Reportable and other
Revenues from external customers
Total operating revenue	838,309	769,982	1,682,881	1,502,570
Investments and corporate operations
Segment reporting, asset reconciling
Total assets	$ 732,391		$ 732,391		$ 629,957