The value (monetary amount) of the award the plaintiff seeks in the legal matter.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Commitments and Contingencies (Details) - USD ($) $ in Millions	Jan. 31, 2019	Sep. 08, 2017
Positive Train Control Patents \| Siemens Industry, Inc. \| Settled Litigation
Loss Contingencies [Line Items]
Damages awarded	$ 5.6
End of Train Patents \| Siemens Industry, Inc. \| Settled Litigation
Loss Contingencies [Line Items]
Damages awarded	$ 1.1
Subsidiaries \| Denver Transit, Installation of Constant Wireless Crossings \| Threatened Litigation
Loss Contingencies [Line Items]
Damages alleged		$ 36.8