Financial Instruments and Fair Value Disclosures - Assets Measured at Fair Value on Nonrecurring Basis (Parenthetical) (Detail) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2021 USD ($) Rig	Dec. 31, 2020 USD ($)	Mar. 31, 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