Employee Pension and Other Postretirement Benefits - Fair Value by Level Within Fair Value Hierarchy Assets by Major Asset Category for Pension Plan and Other Benefits Plan (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended																																																																																																12 Months Ended
	Dec. 31, 2012	Dec. 24, 2011	Dec. 31, 2012 Pension Benefits [Member]	Dec. 31, 2011 Pension Benefits [Member]	Dec. 31, 2012 Pension Benefits [Member] Cash and cash equivalents [Member]	Dec. 31, 2011 Pension Benefits [Member] Cash and cash equivalents [Member]	Dec. 31, 2012 Pension Benefits [Member] U.S. Government securities [Member]	Dec. 31, 2011 Pension Benefits [Member] U.S. Government securities [Member]	Dec. 31, 2012 Pension Benefits [Member] Corporate bonds [Member]	Dec. 31, 2011 Pension Benefits [Member] Corporate bonds [Member]	Dec. 31, 2012 Pension Benefits [Member] Equity securities [Member]	Dec. 31, 2011 Pension Benefits [Member] Equity securities [Member]	Dec. 31, 2012 Pension Benefits [Member] Real estate funds [Member]	Dec. 31, 2011 Pension Benefits [Member] Real estate funds [Member]	Dec. 31, 2012 Pension Benefits [Member] Limited partnership [Member]	Dec. 31, 2011 Pension Benefits [Member] Limited partnership [Member]	Dec. 31, 2012 Pension Benefits [Member] Common collective funds [Member]	Dec. 31, 2011 Pension Benefits [Member] Common collective funds [Member]	Dec. 31, 2012 Pension Benefits [Member] Mutual funds [Member]	Dec. 31, 2011 Pension Benefits [Member] Mutual funds [Member]	Dec. 31, 2012 Pension Benefits [Member] Other [Member]	Dec. 31, 2011 Pension Benefits [Member] Other [Member]	Dec. 31, 2012 Other Postretirement Benefits Plan Investments [Member]	Dec. 31, 2011 Other Postretirement Benefits Plan Investments [Member]	Dec. 31, 2012 Other Postretirement Benefits Plan Investments [Member] U.S. Government securities [Member]	Dec. 31, 2012 Other Postretirement Benefits Plan Investments [Member] Corporate bonds [Member]	Dec. 31, 2012 Other Postretirement Benefits Plan Investments [Member] Common collective funds [Member]	Dec. 31, 2011 Other Postretirement Benefits Plan Investments [Member] Common collective funds [Member]	Dec. 31, 2012 Other Postretirement Benefits Plan Investments [Member] Mutual funds [Member]	Dec. 31, 2011 Other Postretirement Benefits Plan Investments [Member] Mutual funds [Member]	Dec. 31, 2012 Other Postretirement Benefits Plan Investments [Member] Municipal bonds [Member]	Dec. 31, 2012 Other Postretirement Benefits Plan Investments [Member] Pooled separate accounts [Member]	Dec. 31, 2011 Other Postretirement Benefits Plan Investments [Member] Pooled separate accounts [Member]	Dec. 31, 2012 Other Postretirement Benefits Plan Investments [Member] Acquisition [Member]	Dec. 31, 2011 Level 1 [Member] Pension Benefits [Member]	Dec. 31, 2012 Level 1 [Member] Pension Benefits [Member] Cash and cash equivalents [Member]	Dec. 31, 2011 Level 1 [Member] Pension Benefits [Member] Cash and cash equivalents [Member]	Dec. 31, 2012 Level 1 [Member] Pension Benefits [Member] U.S. Government securities [Member]	Dec. 31, 2011 Level 1 [Member] Pension Benefits [Member] U.S. Government securities [Member]	Dec. 31, 2012 Level 1 [Member] Pension Benefits [Member] Corporate bonds [Member]	Dec. 31, 2011 Level 1 [Member] Pension Benefits [Member] Corporate bonds [Member]	Dec. 31, 2012 Level 1 [Member] Pension Benefits [Member] Equity securities [Member]	Dec. 31, 2011 Level 1 [Member] Pension Benefits [Member] Equity securities [Member]	Dec. 31, 2012 Level 1 [Member] Pension Benefits [Member] Real estate funds [Member]	Dec. 31, 2011 Level 1 [Member] Pension Benefits [Member] Real estate funds [Member]	Dec. 31, 2012 Level 1 [Member] Pension Benefits [Member] Limited partnership [Member]	Dec. 31, 2011 Level 1 [Member] Pension Benefits [Member] Limited partnership [Member]	Dec. 31, 2012 Level 1 [Member] Pension Benefits [Member] Common collective funds [Member]	Dec. 31, 2011 Level 1 [Member] Pension Benefits [Member] Common collective funds [Member]	Dec. 31, 2012 Level 1 [Member] Pension Benefits [Member] Mutual funds [Member]	Dec. 31, 2011 Level 1 [Member] Pension Benefits [Member] Mutual funds [Member]	Dec. 31, 2012 Level 1 [Member] Pension Benefits [Member] Other [Member]	Dec. 31, 2011 Level 1 [Member] Pension Benefits [Member] Other [Member]	Dec. 31, 2012 Level 1 [Member] Other Postretirement Benefits Plan Investments [Member]	Dec. 31, 2011 Level 1 [Member] Other Postretirement Benefits Plan Investments [Member]	Dec. 31, 2012 Level 1 [Member] Other Postretirement Benefits Plan Investments [Member] U.S. Government securities [Member]	Dec. 31, 2012 Level 1 [Member] Other Postretirement Benefits Plan Investments [Member] Corporate bonds [Member]	Dec. 31, 2012 Level 1 [Member] Other Postretirement Benefits Plan Investments [Member] Common collective funds [Member]	Dec. 31, 2011 Level 1 [Member] Other Postretirement Benefits Plan Investments [Member] Common collective funds [Member]	Dec. 31, 2012 Level 1 [Member] Other Postretirement Benefits Plan Investments [Member] Mutual funds [Member]	Dec. 31, 2011 Level 1 [Member] Other Postretirement Benefits Plan Investments [Member] Mutual funds [Member]	Dec. 31, 2012 Level 1 [Member] Other Postretirement Benefits Plan Investments [Member] Municipal bonds [Member]	Dec. 31, 2012 Level 1 [Member] Other Postretirement Benefits Plan Investments [Member] Pooled separate accounts [Member]	Dec. 31, 2011 Level 1 [Member] Other Postretirement Benefits Plan Investments [Member] Pooled separate accounts [Member]	Dec. 31, 2012 Level 1 [Member] Other Postretirement Benefits Plan Investments [Member] Acquisition [Member]	Dec. 31, 2011 Level 2 [Member] Pension Benefits [Member]	Dec. 31, 2012 Level 2 [Member] Pension Benefits [Member] Cash and cash equivalents [Member]	Dec. 31, 2011 Level 2 [Member] Pension Benefits [Member] Cash and cash equivalents [Member]	Dec. 31, 2012 Level 2 [Member] Pension Benefits [Member] U.S. Government securities [Member]	Dec. 31, 2011 Level 2 [Member] Pension Benefits [Member] U.S. Government securities [Member]	Dec. 31, 2012 Level 2 [Member] Pension Benefits [Member] Corporate bonds [Member]	Dec. 31, 2011 Level 2 [Member] Pension Benefits [Member] Corporate bonds [Member]	Dec. 31, 2012 Level 2 [Member] Pension Benefits [Member] Equity securities [Member]	Dec. 31, 2011 Level 2 [Member] Pension Benefits [Member] Equity securities [Member]	Dec. 31, 2012 Level 2 [Member] Pension Benefits [Member] Real estate funds [Member]	Dec. 31, 2011 Level 2 [Member] Pension Benefits [Member] Real estate funds [Member]	Dec. 31, 2012 Level 2 [Member] Pension Benefits [Member] Limited partnership [Member]	Dec. 31, 2011 Level 2 [Member] Pension Benefits [Member] Limited partnership [Member]	Dec. 31, 2012 Level 2 [Member] Pension Benefits [Member] Common collective funds [Member]	Dec. 31, 2011 Level 2 [Member] Pension Benefits [Member] Common collective funds [Member]	Dec. 31, 2012 Level 2 [Member] Pension Benefits [Member] Mutual funds [Member]	Dec. 31, 2011 Level 2 [Member] Pension Benefits [Member] Mutual funds [Member]	Dec. 31, 2012 Level 2 [Member] Pension Benefits [Member] Other [Member]	Dec. 31, 2011 Level 2 [Member] Pension Benefits [Member] Other [Member]	Dec. 31, 2012 Level 2 [Member] Other Postretirement Benefits Plan Investments [Member]	Dec. 31, 2011 Level 2 [Member] Other Postretirement Benefits Plan Investments [Member]	Dec. 31, 2012 Level 2 [Member] Other Postretirement Benefits Plan Investments [Member] U.S. Government securities [Member]	Dec. 31, 2012 Level 2 [Member] Other Postretirement Benefits Plan Investments [Member] Corporate bonds [Member]	Dec. 31, 2012 Level 2 [Member] Other Postretirement Benefits Plan Investments [Member] Common collective funds [Member]	Dec. 31, 2011 Level 2 [Member] Other Postretirement Benefits Plan Investments [Member] Common collective funds [Member]	Dec. 31, 2012 Level 2 [Member] Other Postretirement Benefits Plan Investments [Member] Mutual funds [Member]	Dec. 31, 2011 Level 2 [Member] Other Postretirement Benefits Plan Investments [Member] Mutual funds [Member]	Dec. 31, 2012 Level 2 [Member] Other Postretirement Benefits Plan Investments [Member] Municipal bonds [Member]	Dec. 31, 2012 Level 2 [Member] Other Postretirement Benefits Plan Investments [Member] Pooled separate accounts [Member]	Dec. 31, 2011 Level 2 [Member] Other Postretirement Benefits Plan Investments [Member] Pooled separate accounts [Member]	Dec. 31, 2012 Level 2 [Member] Other Postretirement Benefits Plan Investments [Member] Acquisition [Member]	Dec. 31, 2012 Level 3 [Member] Real estate funds [Member]	Dec. 24, 2011 Level 3 [Member] Real estate funds [Member]	Dec. 31, 2012 Level 3 [Member] Limited partnership [Member]	Dec. 24, 2011 Level 3 [Member] Limited partnership [Member]	Dec. 31, 2011 Level 3 [Member] Pension Benefits [Member]	Dec. 31, 2012 Level 3 [Member] Pension Benefits [Member] Cash and cash equivalents [Member]	Dec. 31, 2011 Level 3 [Member] Pension Benefits [Member] Cash and cash equivalents [Member]	Dec. 31, 2012 Level 3 [Member] Pension Benefits [Member] U.S. Government securities [Member]	Dec. 31, 2011 Level 3 [Member] Pension Benefits [Member] U.S. Government securities [Member]	Dec. 31, 2012 Level 3 [Member] Pension Benefits [Member] Corporate bonds [Member]	Dec. 31, 2011 Level 3 [Member] Pension Benefits [Member] Corporate bonds [Member]	Dec. 31, 2012 Level 3 [Member] Pension Benefits [Member] Equity securities [Member]	Dec. 31, 2011 Level 3 [Member] Pension Benefits [Member] Equity securities [Member]	Dec. 31, 2012 Level 3 [Member] Pension Benefits [Member] Real estate funds [Member]	Dec. 31, 2011 Level 3 [Member] Pension Benefits [Member] Real estate funds [Member]	Dec. 31, 2012 Level 3 [Member] Pension Benefits [Member] Limited partnership [Member]	Dec. 31, 2011 Level 3 [Member] Pension Benefits [Member] Limited partnership [Member]	Dec. 31, 2012 Level 3 [Member] Pension Benefits [Member] Common collective funds [Member]	Dec. 31, 2011 Level 3 [Member] Pension Benefits [Member] Common collective funds [Member]	Dec. 31, 2012 Level 3 [Member] Pension Benefits [Member] Mutual funds [Member]	Dec. 31, 2011 Level 3 [Member] Pension Benefits [Member] Mutual funds [Member]	Dec. 31, 2012 Level 3 [Member] Pension Benefits [Member] Other [Member]	Dec. 31, 2011 Level 3 [Member] Pension Benefits [Member] Other [Member]	Dec. 31, 2012 Level 3 [Member] Other Postretirement Benefits Plan Investments [Member]	Dec. 31, 2011 Level 3 [Member] Other Postretirement Benefits Plan Investments [Member]	Dec. 31, 2012 Level 3 [Member] Other Postretirement Benefits Plan Investments [Member] U.S. Government securities [Member]	Dec. 31, 2012 Level 3 [Member] Other Postretirement Benefits Plan Investments [Member] Corporate bonds [Member]	Dec. 31, 2012 Level 3 [Member] Other Postretirement Benefits Plan Investments [Member] Common collective funds [Member]	Dec. 31, 2011 Level 3 [Member] Other Postretirement Benefits Plan Investments [Member] Common collective funds [Member]	Dec. 31, 2012 Level 3 [Member] Other Postretirement Benefits Plan Investments [Member] Mutual funds [Member]	Dec. 31, 2011 Level 3 [Member] Other Postretirement Benefits Plan Investments [Member] Mutual funds [Member]	Dec. 31, 2012 Level 3 [Member] Other Postretirement Benefits Plan Investments [Member] Municipal bonds [Member]	Dec. 31, 2012 Level 3 [Member] Other Postretirement Benefits Plan Investments [Member] Pooled separate accounts [Member]	Dec. 31, 2011 Level 3 [Member] Other Postretirement Benefits Plan Investments [Member] Pooled separate accounts [Member]	Dec. 31, 2012 Level 3 [Member] Other Postretirement Benefits Plan Investments [Member] Acquisition [Member]
Allocation Of Plan Assets Fair Value Hierarchy [Line Items]
Fair value of plan assets, beginning of year	$ 148	$ 114	$ 2,019	$ 1,757																			$ 210																																																																										$ 136	$ 110	$ 12	$ 4
Total Plan Investments				1,757	42	13	214	96	243	133	158	146	156	136	132	70	58	266	1,008	896	16	1	216	172	24	17	9	39	109	96	1	40	37	16	1,075		13		20			158	146							1,008	896			109	96					109	96					534	42		214	76	243	133					114	58	58	266			16	1	107	76	24	17	9	39			1	40	37	16					148									156	136	18	12
Accrued dividends and interest receivable			3
Unrealized gains (losses)	8	11																																																																																															7	10	1	1
Purchases, issuances, sales, and settlements, net	18	23																																																																																															13	16	5	7
Net pending trades			(11)																				(6)
Fair value of plan assets, end of year	$ 174	$ 148	$ 2,019	$ 1,757																			$ 210																																																																										$ 156	$ 136	$ 18	$ 12