Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2014
Properties
Properties depreciation method by asset class	Accounting policy for depreciation Railroad properties are carried at cost less accumulated depreciation including asset impairment write-downs. The cost of properties, including those under capital leases, net of asset impairment write-downs, is depreciated on a straight-line basis over their estimated service lives, measured in years, except for rail which is measured in millions of gross ton miles. The Company follows the group method of depreciation whereby a single composite depreciation rate is applied to the gross investment in a class of similar assets, despite small differences in the service life or salvage value of individual property units within the same asset class. The Company uses approximately 40 different depreciable asset classes.         For all depreciable assets, the depreciation rate is based on the estimated service lives of the assets. Assessing the reasonableness of the estimated service lives of properties requires judgment and is based on currently available information, including periodic depreciation studies conducted by the Company. The Company’s U.S. properties are subject to comprehensive depreciation studies as required by the Surface Transportation Board (STB) and are conducted by external experts. Depreciation studies for Canadian properties are not required by regulation and are conducted internally. Studies are performed on specific asset groups on a periodic basis. Changes in the estimated service lives of the assets and their related composite depreciation rates are implemented prospectively.         The service life of the rail asset is based on expected future usage of the rail in its existing condition, determined using railroad industry research and testing (based on rail characteristics such as weight, curvature and metallurgy), less the rail asset’s usage to date. The annual composite depreciation rate for rail assets is determined by dividing the estimated annual number of gross tons carried over the rail by the estimated service life of the rail measured in millions of gross ton miles. The Company amortizes the cost of rail grinding over the remaining life of the rail asset, which includes the incremental life extension generated by rail grinding.
Pensions
Postretirement benefits amortization of cumulative net actuarial gains and losses excess threshold	10.00%
Finite Lived Intangible Assets [Line Items]
Intangible assets amortization method	straight-line basis
Minimum [Member]
Finite Lived Intangible Assets [Line Items]
Intangible asset useful life	40 years
Maximum [Member]
Finite Lived Intangible Assets [Line Items]
Intangible asset useful life	50 years