Temporarily Impaired Available for Sale Securities by Time Period Impaired (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 28, 2015	Dec. 27, 2014
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 1,406,960	$ 1,902,997
Less Than 12 Months, Unrealized Losses	14,397	15,174
12 Months or Longer, Fair Value	159,335	167,718
12 Months or Longer, Unrealized Losses	3,685	4,514
Total, Fair Value	1,566,295	2,070,715
Total, Unrealized Losses	18,082	19,688
Tax exempt bonds
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	602,522	689,909
Less Than 12 Months, Unrealized Losses	2,696	2,359
12 Months or Longer, Fair Value	82,148	93,454
12 Months or Longer, Unrealized Losses	942	1,652
Total, Fair Value	684,670	783,363
Total, Unrealized Losses	3,638	4,011
Taxable bonds
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	522,279	936,512
Less Than 12 Months, Unrealized Losses	1,250	3,666
12 Months or Longer, Fair Value	69,398	68,035
12 Months or Longer, Unrealized Losses	423	926
Total, Fair Value	591,677	1,004,547
Total, Unrealized Losses	1,673	4,592
Restricted investments
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	168,879	169,224
Less Than 12 Months, Unrealized Losses	1,121	776
12 Months or Longer, Fair Value	0	0
12 Months or Longer, Unrealized Losses	0	0
Total, Fair Value	168,879	169,224
Total, Unrealized Losses	1,121	776
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	113,280	107,352
Less Than 12 Months, Unrealized Losses	9,330	8,373
12 Months or Longer, Fair Value	7,789	6,229
12 Months or Longer, Unrealized Losses	2,320	1,936
Total, Fair Value	121,069	113,581
Total, Unrealized Losses	$ 11,650	$ 10,309