Annual report pursuant to Section 13 and 15(d)

Investments in Marketable Securities - Schedule of Amortized Cost and Fair Value of Marketable Securities, Available-for-Sale, by Contractual Maturity (Detail)

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Investments in Marketable Securities - Schedule of Amortized Cost and Fair Value of Marketable Securities, Available-for-Sale, by Contractual Maturity (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]    
Due in one year or less, Amortized Cost $ 27,484 $ 79,943
Due after one year through five years, Amortized Cost 57,309 28,634
Due after five years through ten years, Amortized Cost 14,992 18,020
Due after ten years, Amortized Cost 5,580 8,604
Amortized Cost 105,365 135,201
Due in one year or less, Fair Value 27,454 79,860
Due after one year through five years, Fair Value 57,144 28,465
Due after five years through ten years, Fair Value 14,841 17,466
Due after ten years, Fair Value 5,490 8,464
Total Fair Value $ 104,929 $ 134,255
Weighted average maturity 3 years 6 months 3 years 3 months 18 days