Unaudited Condensed Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Statement [Abstract]
Revenues	$ 200,370	$ 196,017	$ 377,783	$ 392,069
Cost of sales	163,847	148,387	305,089	298,178
Gross profit	36,523	47,630	72,694	93,891
Earnings of unconsolidated mines	11,567	10,281	24,005	22,379
Operating expenses
Selling, general and administrative expenses	50,990	48,489	99,419	98,785
Amortization of intangible assets	991	619	1,756	1,660
Operating Expenses	51,981	49,108	101,175	100,445
Operating profit (loss)	(3,891)	8,803	(4,476)	15,825
Other expense (income)
Interest expense	1,950	1,148	3,404	2,452
(Income) loss from other unconsolidated affiliates	420	(336)	32	(727)
Closed mine obligations	308	272	624	677
Other, net, including interest income	(273)	476	(151)	343
Other (income) expense	2,405	1,560	3,909	2,745
Income (loss) before income tax provision (benefit)	(6,296)	7,243	(8,385)	13,080
Income tax provision (benefit)	(2,672)	2,096	(3,237)	3,511
Net income (loss)	$ (3,624)	$ 5,147	$ (5,148)	$ 9,569
Earnings Per Share [Abstract]
Basic earnings (loss) per share (in dollars per share)	$ (0.47)	$ 0.63	$ (0.66)	$ 1.16
Diluted earnings (loss) per share (in dollars per share)	$ (0.47)	$ 0.63	$ (0.66)	$ 1.16
Dividends per share (in dollars per share)	$ 0.2575	$ 0.25	$ 0.5075	$ 0.50
Basic weighted average shares outstanding	7,712	8,179	7,777	8,259
Diluted weighted average shares outstanding	7,718	8,184	7,787	8,284