CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Operating revenues
Contract drilling	$ 787,421	$ 645,076	$ 650,562
Operating costs and expenses
Contract drilling	347,179	223,565	252,427
Depreciation	70,599	43,597	37,030
General and administrative	49,776	44,407	40,620
Other, net	457	4,847	(1,855)
Total costs and expenses	468,011	316,416	328,222
Operating income	319,410	328,660	322,340
Other income (expense):
Interest expense, net of capitalized interest	(6,460)	(4,530)	(2,725)
Interest income	354	717	364
Other income (expense) total	(6,106)	(3,813)	(2,361)
Income before income taxes	313,304	324,847	319,979
Provision for income taxes	41,133	53,173	62,983
Net income	$ 272,171	$ 271,674	$ 256,996
Earnings per common share (Note 2):
Basic (in dollars per share)	$ 4.17	$ 4.20	$ 3.99
Diluted (in dollars per share)	$ 4.14	$ 4.15	$ 3.95
Average common shares outstanding (Note 2):
Basic (in shares)	65,267	64,754	64,391
Diluted (in shares)	65,781	65,403	65,028