Current Marketable Securities Held-to-maturity Securities (Details) (Short-term corporate debt securities, USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Short-term corporate debt securities
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities	$ 4,995	$ 124,873

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity, expected to be converted to cash, sold or exchanged within one year or the normal operating cycle.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26626-111562

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558

Name:	us-gaap_HeldToMaturitySecuritiesCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant