CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Sep. 30, 2011
Assets, Current [Abstract]
Cash and cash equivalents	$ 77,871	$ 295,002
Accounts receivable	167,186	87,173
Income tax receivable	5,750	5,631
Inventories of materials and supplies	80,290	58,263
Prepaid expenses and deferred costs	39,437	14,862
Total current assets	370,534	460,931
Property and equipment, net	2,537,340	1,887,321
Other receivables	11,875	11,875
Deferred costs and other assets	24,013	15,264
Total assets	2,943,762	2,375,391
Current liabilities:
Accounts payable	83,592	113,021
Accrued liabilities	24,478	30,680
Notes payable	5,148	5,461
Income tax payable	9,711	8,461
Deferred credits	13,738	1,700
Total Current Liabilities	136,667	159,323
Long-term debt	830,000	520,000
Deferred income taxes	8,791	9,780
Deferred credits	8,928	7,910
Other long-term liabilities	19,954	25,591
Total long-term liabilities	867,673	563,281
Commitments and contingencies (Note 12)
Shareholders' equity (Note 8):
Preferred stock, no par value; 1,000 shares authorized, none outstanding	0	0
Common stock, $1.00 par value, 90,000 shares authorized with 65,452 and 64,960 issued and outstanding at September 30, 2012 and 2011, respectively	65,452	64,960
Paid-in capital	160,540	145,084
Retained earnings	1,716,441	1,444,270
Accumulated other comprehensive loss	(3,011)	(1,527)
Total shareholders' equity	1,939,422	1,652,787
Total liabilities and shareholders' equity	$ 2,943,762	$ 2,375,391