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
 3 Months Ended 12 Months Ended
Mar. 31, 2016
Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]    
Due in one year or less, Amortized Cost $ 75,108 $ 79,943
Due after one year through five years, Amortized Cost 30,785 28,634
Due after five years through ten years, Amortized Cost 17,835 18,020
Due after ten years, Amortized Cost 8,207 8,604
Amortized Cost 131,935 135,201
Due in one year or less, Fair Value 75,112 79,860
Due after one year through five years, Fair Value 30,846 28,465
Due after five years through ten years, Fair Value 17,983 17,466
Due after ten years, Fair Value 8,179 8,464
Total Fair Value $ 132,120 $ 134,255
Weighted average contractual maturity 3 years 2 months 12 days 3 years 3 months 18 days