Segment Information - Income by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Segment information
Total Sales	$ 577,484	$ 405,283	$ 1,141,571	$ 773,873
Segment Operating Income (Loss)	24,814	(58,049)	54,501	(83,377)
Other
Segment information
Total Sales	9,313	3,324	15,180	6,435
Segment Operating Income (Loss)	(7,015)	(1,134)	(14,332)	(3,183)
Operating segment
Segment information
Total Sales	577,771	405,491	1,142,078	774,289
Operating segment | Other
Segment information
Total Sales	9,565	3,532	15,652	6,851
Inter-Segment
Segment information
Total Sales	(287)	(208)	(507)	(416)
Inter-Segment | Other
Segment information
Total Sales	252	208	472	416
Contract Drilling:
Segment information
Total Sales	568,171	401,959	1,126,391	767,438
Segment Operating Income (Loss)	31,829	(56,915)	68,833	(80,194)
Contract Drilling: | U.S. Land
Segment information
Total Sales	482,729	330,967	944,369	594,603
Segment Operating Income (Loss)	27,075	(51,850)	51,820	(82,738)
Contract Drilling: | Offshore
Segment information
Total Sales	32,983	36,235	66,349	70,047
Segment Operating Income (Loss)	5,449	5,912	14,174	12,696
Contract Drilling: | International Land
Segment information
Total Sales	52,459	34,757	115,673	102,788
Segment Operating Income (Loss)	(695)	(10,977)	2,839	(10,152)
Contract Drilling: | Operating segment
Segment information
Total Sales	568,206	401,959	1,126,426	767,438
Contract Drilling: | Operating segment | U.S. Land
Segment information
Total Sales	482,764	330,967	944,404	594,603
Contract Drilling: | Operating segment | Offshore
Segment information
Total Sales	32,983	36,235	66,349	70,047
Contract Drilling: | Operating segment | International Land
Segment information
Total Sales	52,459	$ 34,757	115,673	$ 102,788
Contract Drilling: | Inter-Segment
Segment information
Total Sales	35		35
Contract Drilling: | Inter-Segment | U.S. Land
Segment information
Total Sales	$ 35		$ 35