Financial Instruments (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended	3 Months Ended
Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Strategic Investments [Member]	Mar. 31, 2012 Strategic Investments [Member]
Financial Instruments (Textual) [Abstract]
Original maturities of commercial paper and short-term debt securities	less than 90 days
Average maturity of marketable securities, months		14 months
Impairment charges			$ 0.3	$ 0.5

Description of the maturity date of the debt instrument including whether the debt matures serially and, if so, a brief description of the serial maturities.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(2))

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

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

Name:	us-gaap_DebtInstrumentMaturityDateDescription
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration