Properties (Detail of Net Properties) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 25, 2015	Dec. 26, 2014
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 41,574	$ 39,343
Accumulated Depreciation	(11,400)	(10,759)
Properties - Net	30,174	28,584
Road - Total [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	27,564	26,125
Accumulated Depreciation	(6,758)	(6,148)
Properties - Net	20,806	19,977
Road - Rail and Other Track Material [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	7,150	6,771
Accumulated Depreciation	(1,414)	(1,400)
Properties - Net	$ 5,736	$ 5,371
Annual Depreciation Rate	2.50%	2.50%
Depreciation Method		Group Life
Road - Ties [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 5,077	$ 4,807
Accumulated Depreciation	(1,147)	(1,060)
Properties - Net	$ 3,930	$ 3,747
Annual Depreciation Rate	3.70%	3.70%
Depreciation Method		Group Life
Road - Grading [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 2,533	$ 2,460
Accumulated Depreciation	(479)	(481)
Properties - Net	$ 2,054	$ 1,979
Annual Depreciation Rate	1.40%	1.40%
Depreciation Method		Group Life
Road - Ballast [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 2,793	$ 2,693
Accumulated Depreciation	(802)	(679)
Properties - Net	$ 1,991	$ 2,014
Annual Depreciation Rate	2.70%	2.70%
Depreciation Method		Group Life
Road - Bridges, Trestles, and Culverts [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 2,238	$ 2,119
Accumulated Depreciation	(283)	(278)
Properties - Net	$ 1,955	$ 1,841
Annual Depreciation Rate	1.60%	1.60%
Depreciation Method		Group Life
Road - Signals and Interlockers [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 2,315	$ 2,103
Accumulated Depreciation	(416)	(356)
Properties - Net	$ 1,899	$ 1,747
Annual Depreciation Rate	4.00%	4.00%
Depreciation Method		Group Life
Road - Buildings [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 1,152	$ 1,102
Accumulated Depreciation	(424)	(377)
Properties - Net	$ 728	$ 725
Annual Depreciation Rate	2.50%	2.50%
Depreciation Method		Group Life
Road - Other [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 4,306	$ 4,070
Accumulated Depreciation	(1,793)	(1,517)
Properties - Net	$ 2,513	$ 2,553
Annual Depreciation Rate	4.20%	4.20%
Depreciation Method		Group Life
Total Equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 11,108	$ 10,108
Accumulated Depreciation	(4,633)	(4,526)
Properties - Net	6,475	5,582
Equipment - Locomotive [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	5,673	5,036
Accumulated Depreciation	(2,461)	(2,325)
Properties - Net	$ 3,212	$ 2,711
Annual Depreciation Rate	3.60%	3.60%
Depreciation Method		Group Life
Equipment - Freight Cars [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 3,362	$ 3,244
Accumulated Depreciation	(1,018)	(1,169)
Properties - Net	$ 2,344	$ 2,075
Annual Depreciation Rate	3.20%	3.20%
Depreciation Method		Group Life
Equipment - Work Equipment and Other [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 2,073	$ 1,828
Accumulated Depreciation	(1,154)	(1,032)
Properties - Net	$ 919	$ 796
Annual Depreciation Rate	7.10%	7.10%
Depreciation Method		Group Life
Land [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 1,858	$ 1,875
Properties - Net	1,858	1,875
Construction in Progress [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	1,003	1,196
Properties - Net	1,003	1,196
Other properties [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	41	39
Accumulated Depreciation	(9)	(85)
Properties - Net	$ 32	$ (46)
Depreciation Method		Straight Line
Minimum [Member] | Road - Total [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated useful life	8 years	8 years
Minimum [Member] | Road - Other [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated useful life	8 years
Minimum [Member] | Total Equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated useful life	3 years	3 years
Minimum [Member] | Other properties [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated useful life	4 years	4 years
Maximum [Member] | Road - Total [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated useful life	90 years	90 years
Maximum [Member] | Road - Grading [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated useful life	90 years
Maximum [Member] | Total Equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated useful life	38 years	38 years
Maximum [Member] | Equipment - Work Equipment and Other [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated useful life	38 years
Maximum [Member] | Other properties [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated useful life	30 years	30 years