Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
OPERATING ACTIVITIES:
Net income	$ 736,639	$ 581,045	$ 434,186
Adjustment for (income) loss from discontinued operations	(15,186)	(7,436)	482
Income from continuing operations	721,453	573,609	434,668
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	455,623	387,549	315,468
Provision for bad debt	3,875	205	106
Stock-based compensation	23,271	18,078	12,101
Gain on sale of investment securities	(162,121)		(913)
Income from asset sales	(18,923)	(19,223)	(13,903)
Deferred income tax expense	29,557	196,931	187,651
Other	2,490
Change in assets and liabilities:
Accounts receivable	(4,806)	(160,154)	(2,987)
Inventories	(12,289)	(22,170)	(11,005)
Prepaid expenses and other	5,730	(27,758)	12,623
Accounts payable	(52,076)	54,906	17,362
Accrued liabilities	24,259	195	20,483
Deferred income taxes	(1,673)	(180)	251
Other noncurrent liabilities	(17,371)	(1,592)	6,129
Net cash provided by operating activities from continuing operations	996,999	1,000,396	978,034
Net cash provided by (used in) operating activities from discontinued operations	186	(64)	(482)
Net cash provided by operating activities	997,185	1,000,332	977,552
INVESTING ACTIVITIES:
Capital expenditures	(809,066)	(1,097,680)	(694,264)
Acquisition of TerraVici Drilling Solutions			(4,000)
Proceeds from asset sales	28,026	39,894	26,795
Proceeds from sale of investments	232,221		3,932
Net cash used in investing activities from continuing operations	(548,819)	(1,057,786)	(667,537)
Net cash provided by investing activities from discontinued operations	15,000	7,500
Net cash used in investing activities	(533,819)	(1,050,286)	(667,537)
FINANCING ACTIVITIES:
Payments on long-term debt	(40,000)	(115,000)
Proceeds from line of credit		20,000	10,000
Payments on line of credit		(20,000)	(20,000)
Repurchase of common stock		(77,610)
Dividends paid	(93,053)	(30,049)	(26,741)
Exercise of stock options	13,317	2,673	15,441
Tax withholdings related to net share settlements of restricted stock	(1,677)	(1,514)
Excess tax benefit from stock-based compensation	9,820	3,303	12,511
Net cash used in financing activities	(111,593)	(218,197)	(8,789)
Net increase (decrease) in cash and cash equivalents	351,773	(268,151)	301,226
Cash and cash equivalents, beginning of period	96,095	364,246	63,020
Cash and cash equivalents, end of period	$ 447,868	$ 96,095	$ 364,246