Supplemental Financial Information - Additional Information (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Condensed Balance Sheet Statements, Captions [Line Items]
Contract with customer, liability	$ 98,676	$ 108,861	$ 108,861
Capital expenditures incurred but not yet paid	34,100		25,500	$ 23,600	$ 35,100
Contract drilling services
Condensed Balance Sheet Statements, Captions [Line Items]
Contract with customer, liability	98,700		114,300
Contract with customer, asset	$ 59,800		$ 55,700