Derivatives and Hedging Activities (Details 5) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Summary of credit risk contingent instruments
NOTIONAL AMOUNT	$ 668,900	$ 623,400
AGGREGATE FAIR VALUE	48,400	42,800
COLLATERAL ASSIGNED	$ 50,300	$ 47,600

Fair value as of the balance sheet date of credit risk derivative assets, net of credit risk derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized on the balance sheet.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13433-108611

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 17

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13495-108611

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant