Marketable Securities and Fair Value Measurements (Details 2) - Recurring - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Marketable securities and fair value measurements
Total	$ 303,341	$ 362,897
Level 1
Marketable securities and fair value measurements
Total	212,227	362,897
Level 2
Marketable securities and fair value measurements
Total	91,114
Cash equivalents
Marketable securities and fair value measurements
Money market funds	182,227	302,595
Cash equivalents \| Level 1
Marketable securities and fair value measurements
Money market funds	182,227	302,595
Short-term
Marketable securities and fair value measurements
Certificates of deposit	30,000	60,000
Investment securities	16,654
Short-term \| Level 1
Marketable securities and fair value measurements
Certificates of deposit	30,000	60,000
Short-term \| Level 2
Marketable securities and fair value measurements
Investment securities	16,654
Long-term
Marketable securities and fair value measurements
Investment securities	74,460
Long-term \| Level 2
Marketable securities and fair value measurements
Investment securities	$ 74,460
Restricted cash
Marketable securities and fair value measurements
Money market funds		302
Restricted cash \| Level 1
Marketable securities and fair value measurements
Money market funds		$ 302

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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+ References

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- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Trading Securities

-URI http://asc.fasb.org/extlink&oid=6526789

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 35

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e24584-111560

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

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

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Available-for-Sale Securities

-URI http://asc.fasb.org/extlink&oid=6505594

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Subparagraph a, f, g

-Article 7

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Fair value portion of short to medium-term investment available at banks and savings and loan institutions where a customer agrees to lend money to the institution for a certain amount of time and is paid a predetermined rate of interest. Certificates of deposit (CD) are typically Federal Deposit Insurance Corporation (FDIC) insured.

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- Definition

Fair value portion of fund that invests in short-term money-market instruments.

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