v3.3.1.900

Fair Value of Financial Instruments (Fair Value Hierarchy) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	$ 156,891	$ 91,462
Recurring Basis | Fair Value
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	156,891	91,462
Level 1 | Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	0	0
Level 2 | Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	156,891	91,462
Level 3 | Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	0	0
Commercial paper
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	27,794	5,999
Commercial paper | Recurring Basis | Fair Value
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	27,794	5,999
Commercial paper | Level 1 | Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	0	0
Commercial paper | Level 2 | Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	27,794	5,999
Commercial paper | Level 3 | Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	0	0
U.S. government agencies
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	105,926	53,832
U.S. government agencies | Recurring Basis | Fair Value
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	105,926	53,832
U.S. government agencies | Level 1 | Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	0	0
U.S. government agencies | Level 2 | Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	105,926	53,832
U.S. government agencies | Level 3 | Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	0	0
Corporate bonds
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	16,182	15,537
Corporate bonds | Recurring Basis | Fair Value
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	16,182	15,537
Corporate bonds | Level 1 | Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	0	0
Corporate bonds | Level 2 | Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	16,182	15,537
Corporate bonds | Level 3 | Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	0	0
Asset-backed securities
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	6,989	16,094
Asset-backed securities | Recurring Basis | Fair Value
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	6,989	16,094
Asset-backed securities | Level 1 | Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	0	0
Asset-backed securities | Level 2 | Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	6,989	16,094
Asset-backed securities | Level 3 | Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	$ 0	$ 0

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26610-111562

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