Fair Value Of Financial Instruments (Schedule Of Changes In Fair Value Carrying Values Associated With Level 3 Financial Instruments) (Details) (USD $) In Thousands, unless otherwise specified			3 Months Ended
Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 Corporate Fixed Income Securities [Member]	Mar. 31, 2012 State And Municipal Securities [Member]	Mar. 31, 2012 Auction Rate Securities [Member]	Mar. 31, 2012 Municipal Auction Rate Securities [Member]	Mar. 31, 2012 Other [Member]
Beginning Balance	$ 12,000	$ 12,000	$ 3,742	$ 66,896	$ 103,176	$ 11,729	$ 37,033
Unrealized gains/(losses), Included in changes in net assets			47		451	(65)	704
Unrealized gains/(losses), Included in OCI, Assets				(155)
Realized gains/(losses), Assets			18	118			590
Purchases, Assets			5,246		2,800	2,040	390
Sales, Assets			(2,557)				(735)
Redemptions, Assets				(2,000)	(14,350)	(300)
Transfers, Into Level 3, Assets			227
Transfers, Out of Level 3, Assets			(26)
Net change, Assets			2,955	(2,037)	(11,099)	1,675	949
Ending Balance, Assets	$ 12,000	$ 12,000	$ 6,697	$ 64,859	$ 92,077	$ 13,404	$ 37,982

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Redemptions

No definition available.

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- Definition

Fair Value Measurement with Unobservable Inputs Reconciliation Recurring Basis Realized Asset Gain Loss Included In Earnings

+ References

No definition available.

+ Details

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- Definition

Amount of gain (loss) recognized in earnings, arising from assets measured at fair value on a recurring basis using unobservable inputs (level 3).

+ References

+ Details

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- Definition

Amount of gain (loss) recognized in other comprehensive income, arising from assets measured at fair value on a recurring basis using unobservable inputs (level 3).

+ References

+ Details

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- Definition

Purchases that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ References

+ Details

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- Definition

Sales that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ References

+ Details

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- Definition

Transfers into assets measured at fair value and categorized within Level 3 of the fair value hierarchy that have taken place during the period.

+ References

+ Details

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- Definition

This element represents [net] transfers in to and out of assets measured at fair value on a recurring basis using unobservable inputs (Level 3) which have taken place during the period.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c(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.

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- Definition

Transfers out of assets measured at fair value and categorized within Level 3 of the fair value hierarchy that have taken place during the period.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c

-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.

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