Note 6 - Employee Stock Ownership Plan (Details Textual) - USD ($)	3 Months Ended
Mar. 31, 2019	Dec. 31, 2018	Oct. 11, 2016	Jul. 08, 2005
Loan to Employee Stock Ownership Plan			$ 1,907,160	$ 763,140
Employee Stock Ownership Plan (ESOP), Shares in ESOP, Total	253,412	253,412	190,716	76,314
Sale of Stock, Price Per Share			$ 10	$ 10
Employee Stock Ownership Plan ESOP Interest and Principal Payments from ESOP	$ 239,000

Represents the amount of employee stock ownership plan (ESOP) interest and principal payments from ESOP.

No definition available.

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Namespace Prefix:	ottw_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the amount of loan to employee stock ownership plan.

+ References

No definition available.

+ Details

Name:	ottw_LoanToEmployeeStockOwnershipPlan
Namespace Prefix:	ottw_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Sum of the allocated, committed-to-be-released and suspense shares of the entity held by the plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109244661&loc=d3e17540-113929

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockPricePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant