Financial Instruments (Details Textual)	9 Months Ended	12 Months Ended
Sep. 30, 2015	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Original maturities of commercial paper and short-term debt securities	less than 90 days
Overnight reverse repurchase agreements, percent of total assets	0.90%	2.10%
Average maturity of marketable securities, months	13 months	15 months

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 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

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