Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Operating revenues
Drilling services	$ 1,761,714	$ 2,785,557	$ 2,474,458
Other	12,213	12,933	12,810
Total operating revenues	1,773,927	2,798,490	2,487,268
Operating costs and expenses
Drilling services operating expenses, excluding depreciation and amortization	1,184,788	1,803,204	1,647,557
Other operating expenses	5,777	5,382	5,053
Depreciation and amortization	481,885	562,803	583,802
Research and development	21,645	27,467	18,167
Selling, general and administrative	167,513	194,416	199,257
Asset impairment charge	563,234	224,327	23,128
Restructuring charges	16,047	0	0
Gain on sale of assets	(46,775)	(39,691)	(22,660)
Total operating costs and expenses	2,394,114	2,777,908	2,454,304
Operating income (loss) from continuing operations	(620,187)	20,582	32,964
Other income (expense)
Interest and dividend income	7,304	9,468	8,017
Interest expense	(24,474)	(25,188)	(24,265)
Gain (loss) on investment securities	(8,720)	(54,488)	1
Gain on sale of subsidiary	14,963	0	0
Other	(5,384)	(1,596)	(876)
Total other income (expense)	(16,311)	(71,804)	(17,123)
Income (loss) from continuing operations before income taxes	(636,498)	(51,222)	15,841
Income tax benefit	(140,106)	(18,712)	(477,169)
Income (loss) from continuing operations	(496,392)	(32,510)	493,010
Income from discontinued operations before income taxes	30,580	32,848	23,389
Income tax provision	28,685	33,994	33,727
Income (loss) from discontinued operations	1,895	(1,146)	(10,338)
Net income (loss)	$ (494,497)	$ (33,656)	$ 482,672
Basic earnings (loss) per common share:
Income (loss) from continuing operations (in dollars per share)	$ (4.62)	$ (0.33)	$ 4.49
Income (loss) from discontinued operations (in dollars per share)	0.02	(0.01)	(0.10)
Net income (loss) (in dollars per share)	(4.60)	(0.34)	4.39
Diluted earnings (loss) per common share:
Income (loss) from continuing operations (in dollars per share)	(4.62)	(0.33)	4.47
Income (loss) from discontinued operations (in dollars per share)	0.02	(0.01)	(0.10)
Net income (loss) (in dollars per share)	$ (4.60)	$ (0.34)	$ 4.37
Weighted average shares outstanding:
Basic (in shares)	108,009	109,216	108,851
Diluted (in shares)	108,009	109,216	109,387