Changes in Operations Australia - Arrium (Details) $ in Thousands, AUD in Millions	3 Months Ended			6 Months Ended			12 Months Ended				48 Months Ended
	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 AUD	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2016 AUD	Dec. 31, 2016 USD ($)	Dec. 31, 2015 AUD carload	Dec. 31, 2015 USD ($) carload	Dec. 31, 2014 USD ($)
Operating revenues	$ 501,375		$ 542,219		$ 983,991	$ 939,249
Australian Operations [Member]
Operating revenues	$ 55,283		$ 66,808		107,081	$ 126,750
Asset impairment charges		$ 13,000
Write-off of accounts receivable		$ 8,100		AUD 10.9	$ 8,100
Arrium Limited [Member]
Amount invested in capital project											$ 78,000
Annual carloads transported | carload									8,300	8,300
Operating revenues									AUD 83.0	$ 62,000
Scenario, Forecast [Member] | Arrium Limited [Member]
Operating revenues							AUD 35.0	$ 26,000