Summarizes Cost And Estimated Fair Value Of Short Term Fixed Income Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 30, 2016
Fair Value Measurements [Line Items]
Due within one year, Amortized Cost	$ 24,000
Due between one and two years, Amortized Cost	44,000
Total Amortized Cost	68,000
Due within one year, Estimated Fair Value	23,971
Due between one and two years, Estimated Fair Value	43,846
Total Estimated Fair Value	$ 67,817	$ 58,755