Carrying amount as of the balance sheet date of amounts expected to be recovered under the terms of insurance contracts.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

Commitments and Contingencies - Additional Information - Transocean (Details) $ in Millions	Sep. 30, 2017 USD ($)	Feb. 28, 2017 vessel
Loss Contingencies [Line Items]
Loss contingency accrual	$ 50.5
Claim from Transocean arising from Towage of Transocean Winner Oil Rig
Loss Contingencies [Line Items]
Loss contingency accrual	1.8
Estimated insurance recovery	$ 1.7
Towage Vessels
Loss Contingencies [Line Items]
Number of vessels \| vessel		1