Fair Value Measurements and Other-Than-Temporary Impairments - Roll Forward of Amortized Cost Cumulative OTTI Recognized in Earnings and Accumulated Other Comprehensive Loss (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 28, 2013	Dec. 27, 2014
Fair Value Measurements And Other Than Temporary Impairments [Line Items]
Amortized Cost, Beginning Balance		$ 326,149
Amortized Cost, Ending Balance	296,972	326,149
Accumulated Other-than-Temporary Impairment [Member]
Fair Value Measurements And Other Than Temporary Impairments [Line Items]
Amortized Cost, Beginning Balance	2,707
Amortized Cost, Call on investments	(87)
Amortized Cost, Investments sold	(2,620)
Amortized Cost, Ending Balance	0
Cumulative OTTI in Earnings, Beginning Balance	(394)
Cumulative OTTI in Earnings, Call on investments	13
Cumulative OTTI in Earnings, Investments sold	381
Cumulative OTTI in Earnings, Ending Balance	0
Unrealized Gain, Beginning Balance	784
Unrealized gain, Call on investments	(25)
Unrealized Gain, Investments sold	(759)
Unrealized Gain, Ending Balance	0
OTTI Loss in Accumulated Other Comprehensive Loss, Beginning Balance	(618)
OTTI Loss in Accumulated Other Comprehensive Loss, Call on investments	20
OTTI Loss in Accumulated Other Comprehensive Loss, Investments sold	598
OTTI Loss in Accumulated Other Comprehensive Loss, Ending Balance	0
Accumulated Other Comprehensive Income (Loss), Beginning Balance	166
Accumulated Other Comprehensive Income (Loss), Call on investments	(5)
Accumulated Other Comprehensive Income (Loss), Investments sold	(161)
Accumulated Other Comprehensive Income (Loss), Ending Balance	$ 0