Derivative Instruments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012
Derivative [Line Items]
Notional amount of interest rate swaps	$ 14.2
Notional amount of nonhedging interest rate swaps	476.7
Interest rate swaps, net liability position	17.9
Collateral posted for interest rate swaps in a net liability position	17.4
Real Estate And Building Materials [Member]
Derivative [Line Items]
Derivative loss from industry concentration	3.8
Education [Member]
Derivative [Line Items]
Derivative loss from industry concentration	3.4
Manufacturing [Member]
Derivative [Line Items]
Derivative loss from industry concentration	$ 2.8

Aggregate notional amount of interest rate swap derivatives not designated as a hedging instrument.

No definition available.

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- Definition

The aggregate fair value amounts of interest rate swaps in a net liability position at the end of the reporting period.

+ References

No definition available.

+ Details

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- Definition

The aggregate value of collateral posted for interest rate swaps in a net liability position as of the end of the reporting period.

+ References

No definition available.

+ Details

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- Details

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- Definition

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 9, 10, 11, 12

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 450

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14435-108349

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 9

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14557-108349

+ Details

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- Definition

Aggregate notional amount of all derivatives designated as a fair value hedging instrument. The notional amount relates to a number of currency units, shares, bushels, pounds, or other units specified in a derivative instrument.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Notional Amount

-URI http://asc.fasb.org/extlink&oid=6519104

+ Details

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