Short Term Investments - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 26, 2015	Dec. 31, 2014
Securities Purchased Under Agreements to Resell and Other Short Term Investment Securities [Line Items]
Short-term investments	$ 64,984	$ 64,995
Weighted average interest rate on U.S. Treasury bills, maximum	1.00%	1.00%
US Treasury Bill Securities
Securities Purchased Under Agreements to Resell and Other Short Term Investment Securities [Line Items]
Short-term investments	$ 65,000	$ 65,000