Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Receivables:
Allowance for doubtful receivables	$ 0.8	$ 0.8
Deferred tax liabilities relating to the VEBAs	$ 0.0	$ 127.0
Stockholders' equity:
Preferred Stock, shares authorized	5,000,000	5,000,000
Preferred Stock, shares issued	0	0
Preferred Stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	90,000,000	90,000,000
Common Stock, shares issued	21,277,185	21,197,164
Common stock, shares outstanding	17,134,818	17,607,251
Treasury stock, shares	4,142,367	3,589,913