Guarantor and Non-Guarantor Financial Information - Cash Flows (Details) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS
Net cash provided by (used in) operating activities	$ 615,410	$ 1,151,556
INVESTING ACTIVITIES:
Capital expenditures	(219,549)	(971,602)
Purchase of short-term investments	(36,958)
Proceeds from sales of short-term investments	32,681
Proceeds from asset sales	12,804	17,757
Net cash used in investing activities	(211,022)	(953,845)
FINANCING ACTIVITIES:
Proceeds from senior notes, net of discount		497,125
Debt issuance costs	(32)	(5,202)
Proceeds on short-term debt		1,002
Payments on short-term debt		(1,002)
Net increase in bank overdraft		10,824
Dividends paid	(224,040)	(223,827)
Repurchase of common stock		(59,654)
Exercise of stock options, net of tax withholding	483	(609)
Tax withholdings related to net share settlements of restricted stock	(3,912)	(5,104)
Excess tax benefit from stock-based compensation	761	2,969
Net cash provided by (used in) financing activities	(226,740)	216,522
Net increase in cash and cash equivalents	177,648	414,233
Cash and cash equivalents, beginning of period	729,384	360,307
Cash and cash equivalents, end of period	907,032	774,540
Guarantor/Parent | Reportable Legal Entities
CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS
Net cash provided by (used in) operating activities	4,127	66,448
INVESTING ACTIVITIES:
Capital expenditures	(15,515)	(18,708)
Intercompany transfers	15,515	18,708
Proceeds from asset sales	8	1
Net cash used in investing activities	8	1
FINANCING ACTIVITIES:
Dividends paid	(224,040)	(223,827)
Intercompany transfers	224,040	223,827
Repurchase of common stock		(59,654)
Exercise of stock options, net of tax withholding	483	(609)
Tax withholdings related to net share settlements of restricted stock	(3,912)	(5,104)
Excess tax benefit from stock-based compensation	(788)	91
Net cash provided by (used in) financing activities	(4,217)	(65,276)
Net increase in cash and cash equivalents	(82)	1,173
Cash and cash equivalents, beginning of period	(838)	(2,050)
Cash and cash equivalents, end of period	(920)	(877)
Issuer Subsidiary | Reportable Legal Entities
CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS
Net cash provided by (used in) operating activities	631,371	1,068,214
INVESTING ACTIVITIES:
Capital expenditures	(200,611)	(911,844)
Intercompany transfers	(15,515)	(18,708)
Purchase of short-term investments	(36,958)
Proceeds from sales of short-term investments	32,681
Proceeds from asset sales	10,956	16,804
Net cash used in investing activities	(209,447)	(913,748)
FINANCING ACTIVITIES:
Proceeds from senior notes, net of discount		497,125
Debt issuance costs	(32)	(5,202)
Intercompany transfers	(224,040)	(223,827)
Excess tax benefit from stock-based compensation	1,351	2,853
Net cash provided by (used in) financing activities	(222,721)	270,949
Net increase in cash and cash equivalents	199,203	425,415
Cash and cash equivalents, beginning of period	693,273	329,655
Cash and cash equivalents, end of period	892,476	755,070
Non-Guarantor Subsidiaries | Reportable Legal Entities
CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS
Net cash provided by (used in) operating activities	(20,088)	16,894
INVESTING ACTIVITIES:
Capital expenditures	(3,423)	(41,050)
Proceeds from asset sales	1,840	952
Net cash used in investing activities	(1,583)	(40,098)
FINANCING ACTIVITIES:
Proceeds on short-term debt		1,002
Payments on short-term debt		(1,002)
Net increase in bank overdraft		10,824
Excess tax benefit from stock-based compensation	198	25
Net cash provided by (used in) financing activities	198	10,849
Net increase in cash and cash equivalents	(21,473)	(12,355)
Cash and cash equivalents, beginning of period	36,949	32,702
Cash and cash equivalents, end of period	$ 15,476	$ 20,347