Revenues - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
Accounts receivable balances	$ 160,214				$ 339,699				$ 160,214	$ 339,699
Amount amortized and recorded in drilling revenue	220,801	$ 207,141	$ 250,380	$ 445,927	492,297	$ 598,452	$ 675,765	$ 704,171	1,124,249	2,470,685	$ 3,326,997
Contract Drilling
Disaggregation Of Revenue [Line Items]
Amount amortized and recorded in drilling revenue									669,126	1,308,350	$ 1,430,492
ASC Topic 606 Revenue from Contracts with Customers
Disaggregation Of Revenue [Line Items]
Accounts receivable balances	158,000				336,000				158,000	336,000
ASC Topic 606 Revenue from Contracts with Customers | Accounts Payable
Disaggregation Of Revenue [Line Items]
Total contract liability	$ 600				$ 2,700				600	2,700
ASC Topic 606 Revenue from Contracts with Customers | Contract Drilling
Disaggregation Of Revenue [Line Items]
Amount amortized and recorded in drilling revenue									$ 100	$ 1,000
Maximum
Disaggregation Of Revenue [Line Items]
Accounts receivable payment terms									60 days
Minimum
Disaggregation Of Revenue [Line Items]
Accounts receivable payment terms									30 days