Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Operating revenues
Drilling services	$ 294,026	$ 630,290	$ 538,807	$ 1,241,688
Other	2,145	3,349	3,741	6,608
Total operating revenues	296,171	633,639	542,548	1,248,296
Operating costs and expenses
Drilling services operating expenses, excluding depreciation and amortization	230,313	417,743	429,002	817,072
Other operating expenses	1,274	1,315	2,636	2,737
Depreciation and amortization	106,417	132,006	213,278	262,137
Research and development	5,334	6,214	10,917	13,092
Selling, general and administrative	39,349	41,978	78,652	91,786
Asset impairment charge	54,284	563,234	54,284	563,234
Restructuring charges	1,608	0	1,746	0
(Gain) loss on sale of assets	18,515	(10,310)	6,179	(14,589)
Total operating costs and expenses	457,094	1,152,180	796,694	1,735,469
Operating loss from continuing operations	(160,923)	(518,541)	(254,146)	(487,173)
Other income (expense)
Interest and dividend income	4,819	3,566	6,698	5,780
Interest expense	(5,759)	(6,095)	(11,898)	(12,195)
Gain (loss) on investment securities	2,520	(12,413)	5,444	(9,592)
Gain on sale of subsidiary	0	0	0	14,963
Other	(577)	(398)	(2,057)	(797)
Total other income (expense)	1,003	(15,340)	(1,813)	(1,841)
Loss from continuing operations before income taxes	(159,920)	(533,881)	(255,959)	(489,014)
Income tax benefit	(36,624)	(113,413)	(54,739)	(99,275)
Loss from continuing operations	(123,296)	(420,468)	(201,220)	(389,739)
Income from discontinued operations before income taxes	2,293	6,067	9,786	13,524
Income tax provision	0	6,139	0	13,720
Income (loss) from discontinued operations	2,293	(72)	9,786	(196)
Net loss	$ (121,003)	$ (420,540)	$ (191,434)	$ (389,935)
Basic earnings (loss) per common share:
Loss from continuing operations (in dollars per share)	$ (1.15)	$ (3.88)	$ (1.87)	$ (3.61)
Income from discontinued operations (in dollars per share)	0.02	0	0.09	0
Net loss (in dollars per share)	(1.13)	(3.88)	(1.78)	(3.61)
Diluted earnings (loss) per common share:
Loss from continuing operations (in dollars per share)	(1.15)	(3.88)	(1.87)	(3.61)
Income from discontinued operations (in dollars per share)	0.02	0	0.09	0
Net loss (in dollars per share)	$ (1.13)	$ (3.88)	$ (1.78)	$ (3.61)
Weighted average shares outstanding:
Basic (in shares)	107,861	108,557	107,738	108,556
Diluted (in shares)	107,861	108,557	107,738	108,556