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Short Term Investments - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jul. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Gain (Loss) on Investments [Line Items]
Realized gains on sales of short-term investments, trading securities		$ 3	$ 4	$ 4
Unrealized holding loss on short-term investment		$ 0	0	$ 0
Gain on structured notes			$ 118
Senior Notes
Gain (Loss) on Investments [Line Items]
Senior notes coupon rate	1.65%
Effective interest rate	1.65%
Par value	$ 4,000
Investment maturity date	2016-07	2016-07

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Effective Interest Rate

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Investment, Maturity, Month and Year

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Senior Notes Coupon Interest

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity, expected to be converted to cash, sold or exchanged within one year or the normal operating cycle.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26626-111562

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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 225
-Section S99
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This item represents the gain realized during the period from the sale of trading securities.

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