DERIVATIVE INSTRUMENTS (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2011	Sep. 30, 2010
Forward Commitments to Sell Fixed-Rate Mortgage Loans [Member]
Derivative [Line Items]
Notional amount	$ 167.5	$ 256.7
Difference in carrying value and fair value, reflecting a loss	2.4	1.2
Commitments To Fund Fixed-Rate Mortgage Loans [Member]
Derivative [Line Items]
Notional amount	177.7	203.8
Difference in carrying value and fair value, reflecting a gain	3.9	3.1
Interest Rate Swap [Member]
Derivative [Line Items]
Notional amount	$ 496.6
Average maturity (in months)	65M
Average interest receive rate (in hundredths)	2.50%
Average interest pay rate (in hundredths)	6.00%

- Definition

The difference in the carrying value and fair value of the derivative instrument, reflecting a gain as of the reporting date.

+ Details

Name:	bxs_DifferenceInCarryingValueAndFairValueReflectingGain
Namespace Prefix:	bxs
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The difference in the carrying value and fair value of the derivative instrument, reflecting a loss as of the reporting date.

+ Details

Name:	bxs_DifferenceInCarryingValueAndFairValueReflectingLoss
Namespace Prefix:	bxs
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Monetary amount specified by the derivative(s). Expressed as an absolute value.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

+ Details

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Namespace Prefix:	invest
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Average fixed interest rate related to the group of interest rate derivatives.

+ Details

Name:	us-gaap_DerivativeAverageFixedInterestRate
Namespace Prefix:	us-gaap
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The average time remaining until maturity on the group of derivatives identified.

+ Details

Name:	us-gaap_DerivativeAverageRemainingMaturity
Namespace Prefix:	us-gaap
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	instant

- Definition

Average variable interest rate related to the group of interest rate derivatives.

+ Details

Name:	us-gaap_DerivativeAverageVariableInterestRate
Namespace Prefix:	us-gaap
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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.

+ Details

Name:	us-gaap_DerivativeLineItems
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration