Investments - Schedule of Available-for-Sale Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Amortized Cost And Fair Value Debt Securities [Abstract]
Original stated term to maturity of available-for-sale- investments, Less than one year	$ 113,040	$ 71,000
Original stated term to maturity of available-for-sale- investments, One to five years	39,459	43,552
Original stated term to maturity of available-for-sale- investments, Five to ten years	800
Original stated term to maturity of available-for-sale- investments, Greater than ten years	2,979	7,723
Original stated term to maturity of available-for-sale- investments, Total	$ 156,278	$ 122,275

Amortized cost and fair value debt securities.

No definition available.

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

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-Publisher FASB
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- Definition

Fair value of available-for-sale debt securities maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition

Fair value of available-for-sale debt securities maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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- Definition

Fair value of available-for-sale debt securities maturing after the tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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- Definition

Fair value of available-for-sale debt securities maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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