Balance Sheet Account Detail (Held-to Maturity Marketable Securities) (Details) $ in Thousands	Dec. 31, 2016 USD ($)
Marketable Securities [Abstract]
Amortized Cost	$ 20,988
Gross Unrealized Gain	2
Gross Unrealized Loss	(21)
Fair Value	20,969
Agency bonds
Marketable Securities [Abstract]
Amortized Cost	6,488
Gross Unrealized Gain	2
Gross Unrealized Loss	0
Fair Value	6,490
Corporate bonds
Marketable Securities [Abstract]
Amortized Cost	10,513
Gross Unrealized Gain	0
Gross Unrealized Loss	(21)
Fair Value	10,492
Commercial paper
Marketable Securities [Abstract]
Amortized Cost	3,987
Gross Unrealized Gain	0
Gross Unrealized Loss	0
Fair Value	$ 3,987

Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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- Definition

Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity.

+ References

+ Details

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- Definition

Amount before other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

+ References

No definition available.

+ Details

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Fair value of investments in debt securities classified as held-to-maturity.

+ References

Reference 1: 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=82897076&loc=d3e27232-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

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