Equity Method Investment In ARO - Summarized Financial Data (Details) $ in Millions	3 Months Ended
Jun. 30, 2019 USD ($)
ARO
Equity Method Investment, Summarized Financial Information, Liabilities and Equity [Abstract]
Total assets	$ 667.6
Total liabilities	2.8
Maximum exposure to loss	664.8
Investment Owned, Balance [Abstract]
50% interest in ARO net income	8.4
Amortization of basis differences	(7.8)
Equity in earnings of ARO	0.6
ARO
Related Party Transactions [Abstract]
Lease revenue	18.3
Secondment revenue	15.6
Transition Services revenue	5.2
Total revenue from ARO	39.1
ARO
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Revenues	123.8
Contract drilling (exclusive of depreciation)	78.9
Depreciation	12.4
General and administrative	5.3
Operating income	27.2
Other expense, net	8.7
Provision for income taxes	1.7
Net income	16.8
Equity Method Investment, Summarized Financial Information, Liabilities and Equity [Abstract]
Current assets	434.9
Non-current assets	898.6
Total assets	1,333.5
Current liabilities	227.4
Non-current liabilities	1,030.6
Total liabilities	$ 1,258.0

Difference between amount at which an investment accounted for under the equity method of accounting is carried (reported) on the balance sheet and amount of underlying equity in net assets the reporting Entity has in the investee.

Name:	us-gaap_EquityMethodInvestmentDifferenceBetweenCarryingAmountAndUnderlyingEquity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of assets reported by an equity method investment of the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721683-107760

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33912-111571

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14064-108612