Date the equity-based award vests, in CCYY-MM-DD format.

No definition available.

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Namespace Prefix:	bwinb_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Shares distribution period from grant date.

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Period which an executive's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition.

+ References

No definition available.

+ Details

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Namespace Prefix:	bwinb_
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- Details

Name:	bwinb_SummaryOfStockIssuancesAbstract
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Balance Type:	na
Period Type:	duration

- Definition

The total fair value of shares issued during the period under a deferred compensation arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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

- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
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- Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of share instruments newly issued under a share-based compensation plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix:
Data Type:	na
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Period Type:

Restricted Stock (Details) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended		3 Months Ended	12 Months Ended	0 Months Ended
	May 31, 2014	May 31, 2013	Mar. 31, 2015	Dec. 31, 2014	Feb. 04, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares distribution period from grant date			1 year
Value of each share issued (in dollars per share)	$ 25.53	$ 24.30
Summary of stock Issuances [Abstract]
Shares granted (in shares)	17,237	18,106
Vesting Date	May 08, 2015	May 07, 2014
Service Period	7/1/2014 - 6/30/2015	7/1/2013 - 6/30/2014
Restricted Stock Units (RSUs) [Member]
Summary of stock Issuances [Abstract]
Period restricted stocks will vest ratably from date of grant			3 years
Restricted Stock Units (RSUs) [Member] \| Class B [Member] \| Outside Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total value of shares issued			440	$ 440
Restricted Stock Units (RSUs) [Member] \| Class B [Member] \| Executives [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total value of shares issued					$ 853
Shares issued (in shares)					36,646
Value of each share issued (in dollars per share)					$ 23.29