Quarterly report pursuant to Section 13 or 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
 6 Months Ended 12 Months Ended
Jun. 30, 2016
Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]    
Due in one year or less, Amortized Cost $ 81,726 $ 79,943
Due after one year through five years, Amortized Cost 40,259 28,634
Due after five years through ten years, Amortized Cost 15,002 18,020
Due after ten years, Amortized Cost 8,085 8,604
Amortized Cost 145,072 135,201
Due in one year or less, Fair Value 81,775 79,860
Due after one year through five years, Fair Value 40,473 28,465
Due after five years through ten years, Fair Value 15,529 17,466
Due after ten years, Fair Value 8,176 8,464
Total Fair Value $ 145,953 $ 134,255
Weighted average contractual maturity 3 years 3 years 3 months 18 days