Quarterly report pursuant to Section 13 or 15(d)

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Financial Statements
Notes to Financial Statements
Accounting Policies
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Notes Details

Note 2 - Equipment Acquisitions and Dispositions (Details Textual)

v3.10.0.1

Note 2 - Equipment Acquisitions and Dispositions (Details Textual) $ in Millions	9 Months Ended
	Sep. 30, 2018 USD ($)
Payments to Acquire Property, Plant, and Equipment, Including Fair Value Hedges	$ 44.6
Proceeds from Sale of Property, Plant, and Equipment, Including Deposits	4.0
Proceeds from Sale of Property, Plant, and Equipment, Excluding Deposits for Future Vessel Sales	3.9
Proceeds from Deposits	0.1
Gain (Loss) on Disposition of Property Plant Equipment, Total	2.0
Increase (Decrease) in Customer Deposits	$ 1.4
Wind Farm Utility Vessel [Member]
Number of Equipment Acquired	2
Number of Equipment Sold	1
Supply Vessels [Member]
Number of Equipment Acquired	2
Liftboats [Member]
Number of Equipment Acquired	6
Anchor Handling Towing Supply [Member]
Number of Equipment Acquired	2
Number of Equipment Sold	1
Fast Support Vessels Previously Retired [Member]
Number of Equipment Sold	1
Supply Vessel Previously Retired [Member]
Number of Equipment Sold	2
Standby Safety Vessels [Member]
Number of Equipment Sold	2
Fast Support Vessels [Member]
Number of Equipment Sold	3

- Definition

Represents the number of of equipment acquired.

+ References

No definition available.

+ Details

Name:	smhi_NumberOfEquipmentAcquired
Namespace Prefix:	smhi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of equipment sold.

+ References

No definition available.

+ Details

Name:	smhi_NumberOfEquipmentSold
Namespace Prefix:	smhi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets, including fair value hedges.

+ References

No definition available.

+ Details

Name:	smhi_PaymentsToAcquirePropertyPlantAndEquipmentIncludingFairValueHedges
Namespace Prefix:	smhi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of cash inflow for receipts of deposits.

+ References

No definition available.

+ Details

Name:	smhi_ProceedsFromDeposits
Namespace Prefix:	smhi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash inflow from the sale of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale, excluding deposits for the future sales of vessels.

+ References

No definition available.

+ Details

Name:	smhi_ProceedsFromSaleOfPropertyPlantAndEquipmentExcludingDepositsForFutureVesselSales
Namespace Prefix:	smhi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash inflow from the sale of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale, including deposits.

+ References

No definition available.

+ Details

Name:	smhi_ProceedsFromSaleOfPropertyPlantAndEquipmentIncludingDeposits
Namespace Prefix:	smhi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of gain (loss) on sale or disposal of property, plant and equipment assets, including oil and gas property and timber property.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

+ Details

Name:	us-gaap_GainLossOnSaleOfPropertyPlantEquipment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The increase (decrease) during the period in the amount of customer money held in customer accounts, including security deposits, collateral for a current or future transactions, initial payment of the cost of acquisition or for the right to enter into a contract or agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

+ Details

Name:	us-gaap_IncreaseDecreaseInCustomerDeposits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=smhi_WindFarmUtilityVesselMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=smhi_SupplyVesselsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=smhi_LiftboatsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=smhi_AnchorHandlingTowingSupplyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=smhi_FastSupportVesselsPreviouslyRetiredMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=smhi_SupplyVesselPreviouslyRetiredMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=smhi_StandbySafetyVesselsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=smhi_FastSupportVesselsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: