Unaudited Condensed Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Statement [Abstract]
Revenues	$ 221,714	$ 228,614	$ 599,497	$ 620,683
Cost of sales	175,171	179,395	480,260	477,573
Gross profit	46,543	49,219	119,237	143,110
Earnings of unconsolidated mines	12,064	11,808	36,069	34,187
Operating expenses
Selling, general and administrative expenses	46,373	43,269	145,792	142,054
Amortization of intangible assets	911	1,076	2,667	2,736
Operating expenses	47,284	44,345	148,459	144,790
Operating profit	11,323	16,682	6,847	32,507
Other expense (income)
Interest expense	2,046	1,044	5,450	3,496
Income from other unconsolidated affiliates	(191)	(286)	(159)	(1,013)
Closed mine obligations	316	266	940	943
Other, net, including interest income	86	174	(65)	517
Other (income) expense	2,257	1,198	6,166	3,943
Income before income tax provision (benefit)	9,066	15,484	681	28,564
Income tax provision (benefit)	1,367	3,159	(1,870)	6,670
Net income	$ 7,699	$ 12,325	$ 2,551	$ 21,894
Earnings Per Share [Abstract]
Basic earnings (loss) per share (in dollars per share)	$ 1.02	$ 1.54	$ 0.33	$ 2.68
Diluted earnings (loss) per share (in dollars per share)	$ 1.02	$ 1.54	$ 0.33	$ 2.67
Dividends per share (in dollars per share)	$ 0.2575	$ 0.25	$ 0.765	$ 0.75000
Basic weighted average shares outstanding	7,515	7,988	7,688	8,173
Diluted weighted average shares outstanding	7,533	7,996	7,702	8,193