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Junior Subordinated Interest Deferrable Debentures (Details) (USD $)	1 Months Ended		9 Months Ended		1 Months Ended
	Mar. 31, 2011	Apr. 30, 2009	Sep. 30, 2011 year segment entity day trust semiannual quarter	Dec. 31, 2010	Jul. 31, 2011 Trust I	Jun. 30, 2011 Trust I	Mar. 31, 2011 Trust I	Mar. 14, 2011 Trust I
Junior Subordinated Interest Deferrable Debentures
Number of statutory business trusts issuing trust preferred securities			8
Junior subordinated deferrable interest debentures			$ 190,726,000	$ 201,117,000
Maximum number of consecutive semi-annual period available for deferral of interest payment			10
Maximum number of consecutive quarterly period available for deferral of interest payment on Trusts VI, VII, VIII, IX, X, XI and XII			20
Percentage of capital securities issued by trust qualifying as Tier I capital, maximum (as a percent)			25.00%
Capital securities issued by the trust, qualifying as Tier I capital			190,726,000	201,117,000
Junior subordinated deferrable interest debentures, major types of business trusts
Consented amount to repurchase shares	40,000,000	40,000,000					10,400,000
Treasury stock repurchased			$ 256,691,000	$ 250,358,000				$ 11,000,000
Originally permitted semi-annual cash dividend (in dollars per share)								$ 0.33
Securities redeemed					One half	One half

X

- Definition

Represents capital securities issued by trust that is qualified as Tier I capital as on the reporting date.

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X

- Definition

Represents the maximum number of consecutive quarterly periods available to the entity for deferring the payment of interest on Trusts VI, VII, VIII, IX, X, XI and XII.

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X

- Definition

Represents the maximum number of consecutive semi-annual periods available to the entity for deferring the payment of interest on Trust I.

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- Definition

Represents the maximum percentage of capital securities issued by the trust qualifying as Tier I capital on an aggregate basis.

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- Definition

Number of statutory business trusts formed for the purpose of issuing trust preferred securities.

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- Definition

Represents the portion of securities redeemed.

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- 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.

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X

- Definition

The per share amount of a dividend declared, but not paid, as of the financial reporting date.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 32

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

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- Definition

Including the current and noncurrent portions, the carrying value of junior subordinated long-term debt owed to unconsolidated subsidiary trusts as of the balance sheet date. Such debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets and was initially scheduled to be repaid after one year or beyond the normal operating cycle if longer.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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- Definition

The amount authorized by an entity's Board of Directors under a stock repurchase plan.

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- Definition

The amount allocated to treasury stock. Treasury stock is common and preferred shares of an entity that were issued, repurchased by the entity, and are held in its treasury.

+ References

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

-Publisher FASB

-Name FASB Technical Bulletin (FTB)

-Number 85-6

-Paragraph 3

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 30

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23315-112656

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