Schedule of Estimated Fair Value (Detail) - USD ($) $ in Thousands	Mar. 25, 2018	Dec. 31, 2017
2015 Class Five-Year Notes [Member]
Debt Instrument [Line Items]
Principal Amount	$ 491,250	$ 492,500
Fair Value	490,268	494,470
2015 Ten-Year Notes [Member]
Debt Instrument [Line Items]
Principal Amount	786,000	788,000
Fair Value	811,938	821,884
2017 Five-Year Fixed Rate Notes [Member]
Debt Instrument [Line Items]
Principal Amount	597,000	598,500
Fair Value	583,269	592,515
2017 Ten-Year Fixed Rate Notes [Member]
Debt Instrument [Line Items]
Principal Amount	995,000	997,500
Fair Value	998,980	1,023,435
2017 Five-Year Floating Rate Notes [Member]
Debt Instrument [Line Items]
Principal Amount	298,500	299,250
Fair Value	$ 299,694	$ 300,746