Note 8 - Employee Stock Ownership Plan (Details Textual) - USD ($)	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2016
Employee Stock Ownership Plan (ESOP), Compensation Expense	$ 12,000	$ 25,000
Share Price at Formation Date	$ 10	$ 10
Shares Held in Employee Stock Option Plan, Committed-to-be-Released	48,378	48,378
Employee Stock Ownership Plan (ESOP), Deferred Shares, Fair Value	$ 682,000	$ 682,000
Share Price	$ 14.09	$ 14.09

The share price of company stock at the date of formation.

No definition available.

Name:	nwbb_SharePriceAtFormationDate
Namespace Prefix:	nwbb_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of plan compensation cost recognized during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65895303&loc=d3e17540-113929

+ Details

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

- Definition

Fair value of unearned shares held by the employee stock ownership plan (ESOP).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 50
-Paragraph 1
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=65895303&loc=d3e17540-113929

+ Details

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

- Definition

Price of a single share of a number of saleable stocks of a company.

+ References

No definition available.

+ Details

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

- Definition

Number of committed-to-be-released shares held by the Employee Stock Option Plan at balance sheet date. Committed-to-be-released shares are shares that will be released in the future and will be allocated to employees for services rendered in an accounting period. These shares are legally released from suspense and from serving as collateral for ESOP debt as a result of payment of debt service.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=65895303&loc=d3e17540-113929

+ Details

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