Impairments of Assets - Additional Information (Detail) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2017 Rigs	Jun. 30, 2017 USD ($) Rigs	Jun. 30, 2016 USD ($) Rigs	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Schedule Of Asset Impairment Charges [Line Items]
Loss on impairment of assets | $				$ 71,268	$ 678,145
2017 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs evaluated for impairment	6	7
Number of rigs impaired		2
Loss on impairment of assets | $		$ 71,300		$ 71,300
2016 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs evaluated for impairment			15
Number of rigs impaired			8
Loss on impairment of assets | $			$ 670,000			$ 670,000
Ultra-Deepwater Rigs [Member] | 2017 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs impaired		1
Ultra-Deepwater Rigs [Member] | 2016 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs impaired			3
Deepwater Semisubmersible Rigs [Member] | 2017 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs impaired		1
Deep Water Rigs [Member] | 2016 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs impaired			3
Mid-Water Drilling Rigs [Member] | 2016 Impaired Rigs [Member]
Schedule Of Asset Impairment Charges [Line Items]
Number of rigs impaired			2
Rig Spare Parts and Supplies [Member]
Schedule Of Asset Impairment Charges [Line Items]
Loss on impairment of assets | $			$ 8,100			$ 8,100