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Marketable Securities (Amortized Cost And Fair Value Of Marketable Securities) (Details) $ in Thousands | Dec. 31, 2017 USD ($)
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Schedule of Available-for-sale Securities [Line Items] |
Amortized Cost | $ 284,429
Gross Unrealized Gains | 120
Gross Unrealized Losses | (294)
Fair Value | 284,255
Corporate Bonds [Member] |
Schedule of Available-for-sale Securities [Line Items] |
Amortized Cost | 140,969
Gross Unrealized Gains | 96
Gross Unrealized Losses | (179)
Fair Value | 140,886
Certificates Of Deposit [Member] |
Schedule of Available-for-sale Securities [Line Items] |
Amortized Cost | 58,510
Fair Value | 58,510
Commercial Paper - Marketable Securities [Member] |
Schedule of Available-for-sale Securities [Line Items] |
Amortized Cost | 29,171
Fair Value | 29,171
Asset-backed Securities [Member] |
Schedule of Available-for-sale Securities [Line Items] |
Amortized Cost | 22,206
Gross Unrealized Gains | 4
Gross Unrealized Losses | (43)
Fair Value | 22,167
U.S. Government Bonds [Member] |
Schedule of Available-for-sale Securities [Line Items] |
Amortized Cost | 15,619
Gross Unrealized Gains | 11
Gross Unrealized Losses | (19)
Fair Value | 15,611
Agency Bonds [Member] |
Schedule of Available-for-sale Securities [Line Items] |
Amortized Cost | 10,990
Gross Unrealized Gains | 9
Gross Unrealized Losses | (52)
Fair Value | 10,947
Treasury Bills [Member] |
Schedule of Available-for-sale Securities [Line Items] |
Amortized Cost | 6,964
Gross Unrealized Losses | (1)
Fair Value | $ 6,963

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- Definition 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=75030427&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=82897076&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=82896770&loc=d3e26610-111562 + Details
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