Derivative Financial Instruments (Narrative) (Details) $ in Thousands, CAD in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2015 CAD	Dec. 31, 2014 USD ($)	Dec. 31, 2014 CAD
Derivative [Line Items]
Interest rate derivative assets, at fair value	$ (3)		$ (181)
Foreign exchange contract
Derivative [Line Items]
Notional amount of foreign currency derivatives | CAD		CAD 7.3		CAD 7.2
Derivative, fair value, net	400		(300)
Cash flow hedge gain (loss) to be reclassified within twelve months	300
Interest rate contract | HBB
Derivative [Line Items]
Notional amount of foreign currency derivatives	20,000		20,000
Interest rate derivative assets, at fair value	(100)		(200)
Interest rate cash flow hedge gain (loss) to be reclassified during next twelve months	(100)
Interest rate contract | NACoal
Derivative [Line Items]
Notional amount of foreign currency derivatives	100,000		$ 100,000
Interest rate cash flow hedge gain (loss) to be reclassified during next twelve months	800
Interest rate swap | NACoal
Derivative [Line Items]
Derivative, fair value, net	$ 700