Drilling and Other Property and Equipment - Summary of Cost and Accumulated Depreciation of Drilling and Other Property and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Apr. 23, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment	$ 1,372,711		$ 7,111,718
Less: accumulated depreciation	(43,886)		(2,988,909)
Drilling and other property and equipment, net	1,328,825	$ 1,354,650	4,122,809
Drilling Rigs and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	1,186,100		6,987,630
Land and Buildings [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	9,823		41,072
Office Equipment and Other [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	2,217		$ 83,016
Finance Lease Right of Use Asset [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	$ 174,571