Other Financial Statement Disclosures - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Supplemental Cash Flow Information
Accrued capital expenditures			$ 21,100,000	$ 41,400,000
Interest capitalized in connection with rig construction projects	$ 0	$ 8,700,000	$ 0	$ 16,200,000
Income Taxes
Effective tax rate	9.50%	8.30%	7.30%	10.70%
Material Charges and Other Operating Expenses
Material charges and other operating expenses	$ 0	$ 5,000,000	$ 0	$ 5,000,000