Marketable Investments - Summary of Maturity Periods of the Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total	$ 58,565	$ 54,885
Corporate Obligations [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
FY 2015	4,501
FY 2016	25,434
FY 2017	23,632
Thereafter	4,998
Total	$ 58,565	$ 54,885