Related Party Transactions (Details) - Credo - USD ($)	1 Months Ended	12 Months Ended
Feb. 29, 2012	Dec. 31, 2016
Related party transactions
Amount of loan provided by executive officers to related party	$ 250,000
Payment made to related party		$ 4,800,000
Initial amount of gross profits which will be retained by the entity		$ 3,500,000

Represents the amount of loan provided by executive officers to related party as a portion of the seed funding.

No definition available.

Name:	mosy_RelatedPartyTransactionAmountOfLoanGivenByExecutiveOfficersToRelatedParty
Namespace Prefix:	mosy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the amount of initial gross profits from the transactions with related party which will be retained by the reporting entity.

+ References

No definition available.

+ Details

Name:	mosy_RelatedPartyTransactionInitialGrossProfitFromTransactionsWithRelatedPartyToBeRetained
Namespace Prefix:	mosy_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=mosy_CredoSemiconductorHongKongLtdMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: