Schedule of Fixed Income Securities in Unrealized Loss Positions (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 23, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Losses Less Than 12 Months - Fair Value	$ 171,538
Unrealized Losses Less Than 12 Months - Unrealized	(351)
Unrealized Losses 12 Months or Greater - Fair Value	2,525
Unrealized Losses 12 Months or Greater - Unrealized	(43)
Total - Fair Value	174,063
Total - Unrealized	(394)
Municipal Notes And Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Losses Less Than 12 Months - Fair Value	13,222
Unrealized Losses Less Than 12 Months - Unrealized	(6)
Total - Fair Value	13,222
Total - Unrealized	(6)
US Treasury and Agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Losses Less Than 12 Months - Fair Value	54,331
Unrealized Losses Less Than 12 Months - Unrealized	(18)
Total - Fair Value	54,331
Total - Unrealized	(18)
Government-Sponsored Enterprises
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Losses Less Than 12 Months - Fair Value	3,513
Unrealized Losses Less Than 12 Months - Unrealized	(2)
Total - Fair Value	3,513
Total - Unrealized	(2)
Corporate Notes And Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Losses Less Than 12 Months - Fair Value	65,386
Unrealized Losses Less Than 12 Months - Unrealized	(67)
Unrealized Losses 12 Months or Greater - Fair Value	715
Unrealized Losses 12 Months or Greater - Unrealized	(3)
Total - Fair Value	66,101
Total - Unrealized	(70)
Mortgage Backed Securities- Residential
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Losses 12 Months or Greater - Fair Value	172
Unrealized Losses 12 Months or Greater - Unrealized	(3)
Total - Fair Value	172
Total - Unrealized	(3)
Mortgage Backed Securities - Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Losses Less Than 12 Months - Fair Value	35,086
Unrealized Losses Less Than 12 Months - Unrealized	(258)
Unrealized Losses 12 Months or Greater - Fair Value	1,638
Unrealized Losses 12 Months or Greater - Unrealized	(37)
Total - Fair Value	36,724
Total - Unrealized	$ (295)