Unaudited Condensed Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Statement [Abstract]
Revenues	$ 228,614	$ 210,067	$ 620,683	$ 555,181
Cost of sales	179,395	157,840	477,573	414,138
Gross profit	49,219	52,227	143,110	141,043
Earnings of unconsolidated mines	11,808	11,471	34,187	34,056
Operating expenses
Selling, general and administrative expenses	43,317	51,203	141,751	148,135
Amortization of intangible assets	1,076	767	2,736	1,840
(Gain) loss on sale of assets	(48)	(3,108)	303	(5,381)
Operating Expenses	44,345	48,862	144,790	144,594
Operating profit	16,682	14,836	32,507	30,505
Other (income) expense
Interest expense	1,044	1,509	3,496	4,720
Income from other unconsolidated affiliates	(286)	(383)	(1,013)	(1,166)
Closed mine obligations	266	273	943	1,467
Other net, including interest income	174	(238)	517	229
Other (income) expense	1,198	1,161	3,943	5,250
Income from continuing operations before income tax provision	15,484	13,675	28,564	25,255
Income tax provision	3,159	3,299	6,670	6,724
Income from continuing operations, net of tax	12,325	10,376	21,894	18,531
Income from discontinued operations, net of $1,154 tax benefit and $7,599 tax expense in the three and nine months ended September 30, 2012, respectively	0	27,728	0	66,535
Net income	$ 12,325	$ 38,104	$ 21,894	$ 85,066
Basic Earnings per Share:
Continuing operations (in dollars per share)	$ 1.54	$ 1.24	$ 2.68	$ 2.21
Discontinued operations (in dollars per share)	$ 0.00	$ 3.29	$ 0.00	$ 7.93
Basic earnings per share (in dollars per share)	$ 1.54	$ 4.53	$ 2.68	$ 10.14
Diluted Earnings per Share:
Continuing operations (in dollars per share)	$ 1.54	$ 1.23	$ 2.67	$ 2.21
Discontinued operations (in dollars per share)	$ 0.00	$ 3.29	$ 0.00	$ 7.91
Diluted earnings per share (in dollars per share)	$ 1.54	$ 4.52	$ 2.67	$ 10.12
Dividends per share (in dollars per share)	$ 0.25	$ 0.5475	$ 0.75	$ 1.6275
Basic Weighted Average Shares Outstanding	7,988	8,391	8,173	8,385
Diluted Weighted Average Shares Outstanding	7,996	8,409	8,193	8,401