Changes in Operations Australia Arrium (Details) $ in Thousands, AUD in Millions	3 Months Ended	12 Months Ended						48 Months Ended
	Mar. 31, 2016 USD ($)	Dec. 31, 2017 AUD	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 AUD carload	Dec. 31, 2015 USD ($) carload	Dec. 31, 2014 USD ($)	Dec. 31, 2014 USD ($)
Operating revenues				$ 2,001,527		$ 2,000,401	$ 1,639,012
Provision for Doubtful Accounts				19,655		7,512	5,191
Australian Operations [Member]
Operating revenues				$ 222,586		$ 242,952	$ 313,270
Asset Impairment Charges	$ 13,000
Provision for Doubtful Accounts	$ 8,100
Arrium Limited [Member]
Amount invested in capital project								$ 78,000
Annual carloads transported | carload					8,300	8,300
Operating revenues					AUD 83	$ 62,000
Arrium Limited [Member] | Scenario, Forecast [Member]
Operating revenues		AUD 40	$ 29,000