The average effective interest rate during the reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 22
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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
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The aggregate interest expense incurred on short-term borrowings including commercial paper and Federal funds purchased and securities sold under agreements to repurchase.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Number Title 12
-Chapter V
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-Paragraph 7
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Sum of the carrying amounts at the balance sheet date of short-term borrowings not otherwise specified in the taxonomy having initial terms less than one year or the normal operating cycle, if longer.

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Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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

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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.

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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.

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Short-Term Borrowings (Schedule Of Short-Term Borrowings And Weighted-Average Interest Rates) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Short-term borrowings	$ 305,205	$ 331,577	$ 305,205	$ 331,577	$ 298,232
Average amount outstanding			348,168
Weighted average interest rate	0.15%		0.15%
Short-term borrowings, Weighted average interest	114	146	258	395
Weighted average interest rate during period	0.00%		0.00%
Weighted average interest rate at end of period			0.14%
Federal Funds Purchased [Member]
Short-term borrowings	1,385		1,385
Average amount outstanding			1,783
Maximum amount outstanding at any month-end			17,178
Weighted average interest rate	0.05%		0.05%
Weighted average interest rate at end of period			0.00%
Repurchase Agreements [Member]
Short-term borrowings	294,709		294,709
Average amount outstanding			337,524
Maximum amount outstanding at any month-end			366,103
Weighted average interest rate	0.15%		0.15%
Weighted average interest rate at end of period			0.14%
Other Short-Term Borrowings [Member]
Short-term borrowings	9,111		9,111
Average amount outstanding			8,861
Maximum amount outstanding at any month-end			10,665
Weighted average interest rate	0.04%		0.04%
Weighted average interest rate at end of period			0.00%
Treasury Funds [Member]
Treasury funds	$ 9,100		$ 9,100