Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2012

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Finite-Lived Intangible Assets

Intangible assets other than goodwill, which are subject to amortization, consist of the following:

	Gross Carrying Amount		Accumulated Amortization			Net Balance
Balance at December 31, 2012
Coal supply agreements	$	91.5	$	(29.0	)	$	62.5
Other intangibles	0.9		—			0.9
	$	92.4	$	(29.0	)	$	63.4
Balance at December 31, 2011
Coal supply agreement	$	84.2	$	(26.3	)	$	57.9