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Financial Statement Details - Investment Income, Net (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Financial Statement Details [Abstract]
Interest income	$ 704	$ 1,354
Investment amortization accretion expense, net	(201)	(572)
Net realized gains (losses) on investments	2	(3)
Investment income, net	$ 505	$ 779

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Financial statement details.

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Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.7(b))
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Amount after accretion (amortization) of discount (premium), and investment expense, of interest income and dividend income on nonoperating securities.

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of accretion (amortization) of purchase discount (premium) on nonoperating securities.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 225
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The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

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