v3.10.0.1

Investments and Fair Value of Financial Instruments - Short-Term Investment Activity (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Fair Value Disclosures [Abstract]
Proceeds from sale of short-term investments	$ 0	$ 0
Proceeds from maturities and calls of short-term investments	4,113	10,168
Purchases of short-term investments	5,504	1,984
Gross realized gains (losses) on sales of short-term investments	$ 0	$ 0

Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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-Publisher FASB
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-Topic 320
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Amount of cash outflow to acquire investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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Amount of cash inflow from maturity, prepayment and call of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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