Represents information pertaining to repurchase price percentage of liquidation value of stock.

No definition available.

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Data Type:	num:percentItemType
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- Definition

Represents the amount of dividends payable to preferred stock holders waived upon redemption of temporary equity.

+ References

No definition available.

+ Details

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Namespace Prefix:	osbc_
Data Type:	xbrli:monetaryItemType
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- Details

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- Definition

The excess of (1) the carrying amount of the preferred stock in the registrant's balance sheet over (2) the fair value of the consideration transferred to the holders of the preferred stock, during the accounting period, which will be added to net earnings to arrive at net earnings available to common shareholders in the calculation of earnings per share.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section S99

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=27010884&loc=d3e42851-122695

+ Details

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

- Definition

Cash received on stock transaction after deduction of issuance costs.

+ References

No definition available.

+ Details

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

- Definition

Number of new stock issued during the period.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

+ Details

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

- Definition

Number of stock bought back by the entity at the exercise price or redemption price.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

+ Details

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Period Type:	duration

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_SeriesBPreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Earnings Per Share - Preferred Stock (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended	0 Months Ended	3 Months Ended	1 Months Ended
	Dec. 31, 2014	Apr. 28, 2014	Jun. 30, 2014	Apr. 30, 2014
Redemption of stock
Net proceeds from sale of common stock	$ 64,331
Benefit from redemptions at below liquidation value	1,348
Benefit from reversal of dividends previously accrued or accumulated and waived by holders upon redemption	5,433
Series B Stock
Redemption of stock
Shares redeemed (in shares)		25,669	25,669
Net proceeds from sale of common stock			64,000
Repurchase price percentage of liquidation value (as a percent)		94.75%	94.75%
Benefit from reversal of dividends previously accrued or accumulated and waived by holders upon redemption			5,400
Common
Redemption of stock
Shares issued				15,525,000
Net proceeds from sale of common stock			$ 64,000