CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands	12 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2013 USD ($)
Cash flows from operating activities:
Net income	$ 432,573	$ 340,822	$ 350,224
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	171,947	147,358	117,510
Amortization	6,299	8,634	5,224
Provision for doubtful accounts and inventory obsolescence	4,286	2,826	5,582
Deferred income tax benefit	(2,747)	(1,270)	(816)
Share-based compensation expense	12,828	14,691	14,231
Asset impairment	60,777	0	0
(Gain) loss on sale of assets	15,303	(34,139)	971
Change in assets and liabilities:
Accounts receivable	(72,575)	(43,965)	(36,330)
Income tax receivable	(2,445)	(1,588)	1,078
Inventories of materials and supplies	(19,068)	(17,220)	(43,254)
Prepaid expenses, deferred costs and other current assets	(3,655)	15,463	(712)
Deferred costs and other assets	5,917	(11,682)	(19,700)
Accounts payable	(11,967)	1,932	11,440
Accrued liabilities	1,637	1,647	1,430
Premium on Senior Notes	0	0	8,500
Income tax payable	(328)	(2,320)	5,863
Deferred credits and other liabilities	5,505	21,431	10,869
Net cash provided by operating activities	604,287	442,620	432,110
Cash flows from investing activities:
Capital expenditures	(448,019)	(975,731)	(745,223)
Net proceeds from sale of assets	(4,402)	61,516	147
Net cash used by investing activities	(452,421)	(914,215)	(745,076)
Cash flows from financing activities:
Proceeds from issuance of long-term debt	225,000	700,000	600,000
Principal payments on long-term debt	(280,000)	(220,000)	(175,000)
Proceeds (repayments) on short-term debt, net	(11,885)	(13,979)	2,923
Repurchase and retirement of common shares	0	0	(107,260)
Dividends paid	(48,562)	0	0
Proceeds from exercise of stock options	1,064	3,688	9,224
Debt issuance costs paid	(3,580)	(6,804)	(6,022)
Net cash provided by financing activities	(117,963)	462,905	323,865
Net increase (decrease) in cash and cash equivalents	33,903	(8,690)	10,899
Cash at beginning of period	80,080	88,770	77,871
Cash at end of period	113,983	80,080	88,770
Cash paid during the period for:
Domestic and foreign income taxes	50,428	55,777	49,105
Interest, net of amounts capitalized	48,209	35,265	21,200
Non-cash activities:
Increase (decrease) in accrued liabilities related to capital expenditures	(9,532)	(2,804)	795
Dividends payable	16,164	16,090	0
Increase in short-term debt related to funding of insurance policies	$ 0	$ 17,793	$ 0