Commitments and Contingencies (Details) - USD ($) $ in Millions	Aug. 15, 2019	Jan. 31, 2019	Sep. 08, 2017
Siemens Industry, Inc. | Settled Litigation
Loss Contingencies [Line Items]
Damages awarded	$ 14.1
Denver Transit, Installation of Constant Wireless Crossings | Threatened Litigation | Subsidiaries
Loss Contingencies [Line Items]
Damages alleged			$ 36.8
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