Fair Value of Pension Plan Assets by Level within Fair Value Hierarchy (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 30, 2012		Dec. 25, 2011		Dec. 26, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	$ 2,594,250	[1]	$ 2,518,515	[1]
Fair value of pension plan liabilities	(85,250)	[1]	(128,547)	[1]
Cash and other	43,316	[1]	18,800	[1]
Total net fair value of plan assets	2,552,316	[1]	2,408,768	[1]
U.S. government-related securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	100,140	[1]	50,582	[1]
Mortgage Backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	71,641	[1]	166,922	[1]
Other government bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	30,317	[1]	39,687	[1]
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	137,437	[1]	137,705	[1]
Corporate stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	723,437	[1]	614,975	[1]
Real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	97,385	[1]	93,620	[1]
Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	604,003	[1]	434,693	[1]
Fixed Income
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	193,620	[1]	373,368	[1]
Interest in reg. invest. companies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	128,418	[1]	112,767	[1]
Interest in 103-12 investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	84,956	[1]	79,432	[1]
Partnership/joint venture interests
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	130,995	[1]	128,121	[1]
Hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	236,444	[1]	232,817	[1]
Derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	55,457	[1]	53,826	[1]
Liability to purchase U.S. government and other securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan liabilities	(26,882)	[1]	(71,876)	[1]
Derivative liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan liabilities	(58,368)	[1]	(56,671)	[1]
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	839,478	[1]	731,448	[1]
Fair value of pension plan liabilities	(21)	[1]	(15)	[1]
Cash and other	36,295	[1]	18,135	[1]
Total net fair value of plan assets	875,752	[1]	749,568	[1]
Fair Value, Inputs, Level 1 | U.S. government-related securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	0	[1]
Fair Value, Inputs, Level 1 | Mortgage Backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	0	[1]
Fair Value, Inputs, Level 1 | Other government bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	0	[1]
Fair Value, Inputs, Level 1 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	0	[1]
Fair Value, Inputs, Level 1 | Corporate stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	722,619	[1]	613,976	[1]
Fair Value, Inputs, Level 1 | Real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	0	[1]
Fair Value, Inputs, Level 1 | Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	0	[1]
Fair Value, Inputs, Level 1 | Fixed Income
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	12,630	[1]	24,632	[1]
Fair Value, Inputs, Level 1 | Interest in reg. invest. companies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	104,196	[1]	92,840	[1]
Fair Value, Inputs, Level 1 | Interest in 103-12 investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	0	[1]
Fair Value, Inputs, Level 1 | Partnership/joint venture interests
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	0	[1]
Fair Value, Inputs, Level 1 | Hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	0	[1]
Fair Value, Inputs, Level 1 | Derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	33	[1]	0	[1]
Fair Value, Inputs, Level 1 | Derivative liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan liabilities	(21)	[1]	(15)	[1]
Fair Value, Inputs, Level 1 | Liability to purchase U.S. government and other securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan liabilities	0	[1]	0	[1]
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	1,366,171	[1]	1,404,293	[1]
Fair value of pension plan liabilities	(83,221)	[1]	(126,015)	[1]
Cash and other	7,021	[1]	665	[1]
Total net fair value of plan assets	1,289,971	[1]	1,278,943	[1]
Fair Value, Inputs, Level 2 | U.S. government-related securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	100,140	[1]	50,582	[1]
Fair Value, Inputs, Level 2 | Mortgage Backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	71,641	[1]	165,651	[1]
Fair Value, Inputs, Level 2 | Other government bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	30,317	[1]	38,246	[1]
Fair Value, Inputs, Level 2 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	136,640	[1]	135,635	[1]
Fair Value, Inputs, Level 2 | Corporate stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	818	[1]	999	[1]
Fair Value, Inputs, Level 2 | Real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	0	[1]
Fair Value, Inputs, Level 2 | Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	604,003	[1]	434,693	[1]
Fair Value, Inputs, Level 2 | Fixed Income
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	180,990	[1]	348,736	[1]
Fair Value, Inputs, Level 2 | Interest in reg. invest. companies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	24,222	[1]	19,927	[1]
Fair Value, Inputs, Level 2 | Interest in 103-12 investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	84,956	[1]	79,432	[1]
Fair Value, Inputs, Level 2 | Partnership/joint venture interests
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	0	[1]
Fair Value, Inputs, Level 2 | Hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	77,520	[1]	76,801	[1]
Fair Value, Inputs, Level 2 | Derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	54,924	[1]	53,591	[1]
Fair Value, Inputs, Level 2 | Derivative liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan liabilities	(56,339)	[1]	(54,139)	[1]
Fair Value, Inputs, Level 2 | Liability to purchase U.S. government and other securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan liabilities	(26,882)	[1]	(71,876)	[1]
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	388,601	[1]	382,774	[1]	378,917
Fair value of pension plan liabilities	(2,008)	[1]	(2,517)	[1]
Cash and other	0	[1]	0	[1]
Total net fair value of plan assets	386,593	[1]	380,257	[1]
Fair Value, Inputs, Level 3 | U.S. government-related securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	0	[1]
Fair Value, Inputs, Level 3 | Mortgage Backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	1,271	[1]	0
Fair Value, Inputs, Level 3 | Other government bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	1,441	[1]	1,526
Fair Value, Inputs, Level 3 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	797	[1]	2,070	[1]	5,896
Fair Value, Inputs, Level 3 | Corporate stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	0	[1]
Fair Value, Inputs, Level 3 | Real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	97,385	[1]	93,620	[1]	90,344
Fair Value, Inputs, Level 3 | Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	0	[1]
Fair Value, Inputs, Level 3 | Fixed Income
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	0	[1]
Fair Value, Inputs, Level 3 | Interest in reg. invest. companies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	0	[1]
Fair Value, Inputs, Level 3 | Interest in 103-12 investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	0	[1]	0	[1]
Fair Value, Inputs, Level 3 | Partnership/joint venture interests
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	130,995	[1]	128,121	[1]	117,698
Fair Value, Inputs, Level 3 | Hedge funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	158,924	[1]	156,016	[1]	163,349
Fair Value, Inputs, Level 3 | Derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan assets	500	[1]	235	[1]	104
Fair Value, Inputs, Level 3 | Derivative liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan liabilities	(2,008)	[1]	(2,517)	[1]
Fair Value, Inputs, Level 3 | Liability to purchase U.S. government and other securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan liabilities	0	[1]	0	[1]
Fair Value, Inputs, Level 3 | Derivative liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of pension plan liabilities	$ (2,008)		$ (2,517)		$ (453)

[1] The company uses a Dec. 31 measurement date for its retirement plans.