Impairment of Assets - Additional Information (Detail) $ in Thousands	3 Months Ended		4 Months Ended	9 Months Ended		12 Months Ended
	Mar. 31, 2021 Rig	Mar. 31, 2020 Rig	Apr. 23, 2021 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2020 Rig
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs impaired during period	1					1
Impairment of asset | $			$ 197,027		$ 774,028
2021 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs evaluated for impairment	3
Number of rigs impaired during period	1
Impairment of asset | $			$ 197,000
2020 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs evaluated for impairment		5
Number of rigs impaired during period		4
Impairment of asset | $				$ 774,000