Property and Equipment (Schedule of Property and Equipment) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
PROPERTY AND EQUIPMENT, AT COST	$ 933.1	$ 13,209.3
Drilling rigs and equipment
Property, Plant and Equipment [Line Items]
PROPERTY AND EQUIPMENT, AT COST	865.6	12,584.4
Work-in-progress
Property, Plant and Equipment [Line Items]
PROPERTY AND EQUIPMENT, AT COST	33.3	446.1
Other
Property, Plant and Equipment [Line Items]
PROPERTY AND EQUIPMENT, AT COST	$ 34.2	$ 178.8

Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.13)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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