Equity Method Investments and Variable Interest Entities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Oct. 17, 2017
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Equity Method Investment, Summarized Financial Information, Revenue	$ 89.2		$ 218.3
Equity Method Investment, Summarized Financial Information, Cost of Sales	51.2		120.5
Equity Method Investment, Summarized Financial Information, Depreciation and Amortization	17.0		50.4
Equity Method Investment, Summarized Financial Information, Selling, general and administrative expense	6.8		20.0
Equity Method Investment, Summarized Financial Information, Gain (Loss) on disposal of property, plant and equipment	(1.0)		0.0
Equity Method Investment, Summarized Financial Information, Income (Loss) from Continuing Operations	15.2		27.4
Equity Method Investment, Summarized Financial Information, Interest Expense	(5.7)		(16.9)
Equity Method Investment, Summarized Financial Information, Income Tax Expense (benefit)	3.2		3.6
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	6.3		6.9
Equity in earnings of unconsolidated subsidiary	3.1	$ 0.0	3.4	$ 0.0
Equity Method Investment, Summarized Financial Information [Abstract]
Equity Method Investment, Summarized Financial Information, Current Assets	205.8		205.8		$ 108.6
Equity Method Investment, Summarized Financial Information, Noncurrent Assets	468.8		468.8		459.7
Equity Method Investment, Summarized Financial Information, Assets	674.6		674.6		568.3
Equity Method Investment, Summarized Financial Information, Current Liabilities	107.4		107.4		29.2
Equity Method Investment, Summarized Financial Information, Noncurrent Liabilities	566.3		566.3		545.1
Equity Method Investment, Summarized Financial Information, Liabilities	673.7		673.7		574.3
Contribution to joint venture						$ 357.7
Due from Joint Venture, Initial Amount						$ 357.7
Due from Joint Venture, Total	269.0		269.0		271.3
Long-term note receivable from unconsolidated subsidiary	269.0		269.0		270.2
Interest income	8.0	3.7	22.6	8.9
Revenue from Related Parties	33.4		76.1
Proceeds from disposals of property and equipment			8.1	1.5
Gain (Loss) on Disposition of Property Plant Equipment	$ 1.5	$ 2.8	$ 5.0	$ 9.3
Saudi Arabia Joint Venture [Member] | Parent Company [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	50.00%		50.00%
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Equity in earnings of unconsolidated subsidiary	$ 3.1		$ 3.4
Equity Method Investment, Summarized Financial Information [Abstract]
Accounts Payable, Related Parties	11.3		11.3		10.8
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure [Abstract]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	370.3		370.3		319.5
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	11.3		11.3		10.8
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	359.0		359.0		308.7
Accounts Receivable [Member]
Equity Method Investment, Summarized Financial Information [Abstract]
Due from Joint Ventures, Current					1.1
Accounts Receivable [Member] | Saudi Arabia Joint Venture [Member] | Parent Company [Member]
Equity Method Investment, Summarized Financial Information [Abstract]
Accounts Receivable, Related Parties	59.5		59.5		$ 17.3
Prepaid Expenses and Other Current Assets [Member] | Saudi Arabia Joint Venture [Member] | Parent Company [Member]
Equity Method Investment, Summarized Financial Information [Abstract]
Due from Joint Ventures, Current	7.5		7.5
Rig Management Services [Member]
Equity Method Investment, Summarized Financial Information [Abstract]
Costs and Expenses, Related Party	9.2		31.8
Secondment Revenue [Member]
Equity Method Investment, Summarized Financial Information [Abstract]
Revenue from Related Parties	14.4		36.2
Lease Revenue [Member]
Equity Method Investment, Summarized Financial Information [Abstract]
Revenue from Related Parties	8.0		9.1
Transition Services Revenue [Member]
Equity Method Investment, Summarized Financial Information [Abstract]
Revenue from Related Parties	9.0		26.9
Sales of Supplies [Member]
Equity Method Investment, Summarized Financial Information [Abstract]
Revenue from Related Parties	2.0		3.9
ARO Drilling [Member]
Equity Method Investment, Summarized Financial Information [Abstract]
Proceeds from disposals of property and equipment	5.9		7.6
Gain (Loss) on Disposition of Property Plant Equipment	0.9		0.7
ARO Drilling [Member] | Accounts Receivable [Member]
Equity Method Investment, Summarized Financial Information [Abstract]
Related Party Transaction, Due from (to) Related Party, Current	6.8		6.8
Purchase of Supplies from Joint Venture [Member]
Equity Method Investment, Summarized Financial Information [Abstract]
Costs and Expenses, Related Party	$ 4.4		$ 10.1
Saudi Aramco [Member] | Saudi Arabia Joint Venture [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	50.00%		50.00%
London Interbank Offered Rate (LIBOR) [Member]
Equity Method Investment, Summarized Financial Information [Abstract]
Loans Receivable, Basis Spread on Variable Rate						2.00%
Interest Income [Member] | Saudi Arabia Joint Venture [Member] | Parent Company [Member]
Equity Method Investment, Summarized Financial Information [Abstract]
Interest income	$ 2.8		$ 8.4
Operating Segments [Member]
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Equity in earnings of unconsolidated subsidiary	0.0		0.0
Operating Segments [Member] | ARO Segment [Member]
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Equity in earnings of unconsolidated subsidiary	$ 0.0		$ 0.0