Investments in Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 19,326	$ 26,643
Gross Unrealized Gain	7	6
Gross Unrealized Loss	(18)	(9)
Fair Value	19,315	26,640
Marketable securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	17,688	23,089
Gross Unrealized Gain	7	6
Gross Unrealized Loss	(13)	(5)
Fair Value	17,682	23,090
Marketable securities \| U.S. Government and agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,029	12,716
Gross Unrealized Gain		2
Gross Unrealized Loss	(6)	(2)
Fair Value	7,023	12,716
Marketable securities \| Corporate and other debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,659	10,373
Gross Unrealized Gain	7	4
Gross Unrealized Loss	(7)	(3)
Fair Value	10,659	10,374
Long-term marketable securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,638	3,554
Gross Unrealized Loss	(5)	(4)
Fair Value	1,633	3,550
Long-term marketable securities \| U.S. Government and agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	838	1,228
Gross Unrealized Loss	(2)
Fair Value	836	1,228
Long-term marketable securities \| Corporate and other debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	800	2,326
Gross Unrealized Loss	(3)	(4)
Fair Value	$ 797	$ 2,322

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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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
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-Section 50
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-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
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+ References

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 210.5-02.2)
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