Debt Debt Capital Leases (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Amount	$ 0
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Capital leases entered into to finance maintenance of way and other vehicles and equipment	$ 0	$ 0	$ 0

The portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a rate subject to change from time to time.

No definition available.

Name:	us-gaap_LongtermDebtPercentageBearingVariableInterestAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant