Financial Instruments and Fair Value Disclosures - Assets Measured at Fair Value on Nonrecurring Basis (Parenthetical) (Detail) $ in Thousands	3 Months Ended			4 Months Ended	6 Months Ended	12 Months Ended
	Mar. 31, 2021 Rig	Dec. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Apr. 23, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2020 Rig
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Number of rigs impaired during period | Rig	1					1
Loss on impairment of assets				$ 197,027	$ 774,028
Four Semisubmersible Rigs [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loss on impairment of assets		$ 68,000	$ 774,000