Investments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($) Securities	Dec. 26, 2015 USD ($)	Dec. 27, 2014 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Total realized gains on sales of AFS securities	$ 47,633,000	$ 94,778,000	$ 61,390,000
Total realized losses on sales of AFS securities	$ 15,377,000	24,977,000	$ 2,977,000
Number of AFS securities issues contributing to total unrealized loss | Securities	649
Total, Unrealized Losses	$ 66,971,000	$ 40,882,000