Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) (Level 3 [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2010	Dec. 31, 2011
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Auction rate securities, Beginning balance	$ 8,775	$ 6,078
Auction rate securities, Unrealized losses included in earning (other than temporary impairment)	(785)
Auction rate securities, Securities sold during 2011		(1,912)
Auction rate securities, Ending balance	$ 7,990	$ 6,078

This element represents total gains or losses for the period (realized and unrealized), arising from assets measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in earnings or resulted in a change in net asset value.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration