Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Segment information
External Sales	$ 732,588	$ 594,642
Total Sales	732,588	594,642
Segment Operating Income (Loss)	243,061	180,577
Reconciliation of segment operating income to income from continuing operations before income taxes
Segment operating income	243,061	180,577
Income from asset sales	4,683	2,669
Corporate general and administrative costs and corporate depreciation	(17,205)	(12,520)
Operating income from continuing operations	230,539	170,726
Other income (expense):
Interest and dividend income	336	314
Interest expense	(2,461)	(4,451)
Other	21	166
Total other income (expense)	(2,104)	(3,971)
Income from continuing operations before income taxes	228,435	166,755
Contract Drilling
Segment information
External Sales	729,306	590,639
Total Sales	729,306	590,639
Segment Operating Income (Loss)	244,849	181,728
Reconciliation of segment operating income to income from continuing operations before income taxes
Segment operating income	244,849	181,728
U.S. Land
Segment information
External Sales	617,779	476,818
Total Sales	617,779	476,818
Segment Operating Income (Loss)	224,706	158,361
Reconciliation of segment operating income to income from continuing operations before income taxes
Segment operating income	224,706	158,361
Offshore
Segment information
External Sales	50,792	44,867
Total Sales	50,792	44,867
Segment Operating Income (Loss)	12,204	9,000
Reconciliation of segment operating income to income from continuing operations before income taxes
Segment operating income	12,204	9,000
International Land
Segment information
External Sales	60,735	68,954
Total Sales	60,735	68,954
Segment Operating Income (Loss)	7,939	14,367
Reconciliation of segment operating income to income from continuing operations before income taxes
Segment operating income	7,939	14,367
Other.
Segment information
External Sales	3,282	4,003
Intersegment sales	210	210
Total Sales	3,492	4,213
Segment Operating Income (Loss)	(1,788)	(1,151)
Reconciliation of segment operating income to income from continuing operations before income taxes
Segment operating income	(1,788)	(1,151)
Reportable and other
Segment information
External Sales	732,588	594,642
Intersegment sales	210	210
Total Sales	732,798	594,852
Segment Operating Income (Loss)	243,061	180,577
Reconciliation of segment operating income to income from continuing operations before income taxes
Segment operating income	243,061	180,577
Eliminations
Segment information
Intersegment sales	(210)	(210)
Total Sales	$ (210)	$ (210)