Investments - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Investments maximum maturity period	5 years
Unrealized losses, net of unrealized gains, on the investments in the bond portfolio	$ (223)	$ (109)
Guarantee Payment of Insurance Claims
Schedule of Available-for-sale Securities [Line Items]
Letters of credit outstanding	59,436
Current Investments
Schedule of Available-for-sale Securities [Line Items]
Investments providing collateral for letters of credit to guarantee insurance claims	48,928
Non-Current Investments
Schedule of Available-for-sale Securities [Line Items]
Investments providing collateral for letters of credit to guarantee insurance claims	17,112
Total non-current investments	$ 61,991