Federal Funds Purchased and Securities Sold under Agreements to Repurchase and Wholesale Borrowings (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Federal Funds Purchased and Securities Sold under Agreements to Repurchase [Member]
Average balance during the year	$ 949,756	$ 925,803	$ 907,015
Weighted-average annual interest rate during the year	0.12%	0.36%	0.49%
Maximum month-end balance	1,104,525	1,014,720	1,034,200
Wholesale Borrowings [Member]
Average balance during the year	175,989	298,835	510,790
Weighted-average annual interest rate during the year	2.51%	2.11%	2.74%
Maximum month-end balance	$ 178,489	$ 327,997	$ 716,091

For the form of debt having an initial term of less than one year or less than the normal operating cycle, if longer, average borrowings during the period.

No definition available.

+ Details

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- Definition

For the form of debt having an initial term of less than one year or less than the normal operating cycle, if longer, maximum month-end borrowings during the period.

+ References

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

-Publisher SEC

-Name Industry Guide

-Number 3

-Section VII

-Subsection 2

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Reflects the calculation as of the balance sheet date of the average interest rate weighted by the amount of short-term debt outstanding by type or by instrument at that time.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19

-Subparagraph b

-Article 5

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