Long-Term Debt and Commitments (Details)	12 Months Ended					12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended
	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2012 Series 2006 A Senior Notes Due 2013 [Member] USD ($)	Dec. 31, 2011 Series 2006 A Senior Notes Due 2013 [Member] USD ($)	Dec. 31, 2012 Floating Rate Series 2006 A Senior Notes Due 2013 [Member] USD ($)	Dec. 31, 2011 Floating Rate Series 2006 A Senior Notes Due 2013 [Member] USD ($)	Dec. 31, 2012 Variable/Fixed Rate Industrial Development Revenue Bonds Due 2012 [Member] USD ($)	Dec. 31, 2011 Variable/Fixed Rate Industrial Development Revenue Bonds Due 2012 [Member] USD ($)	Dec. 31, 2012 Variable/Fixed Rate Industrial Development Revenue Bonds Series 1999 Due 2014 [Member] USD ($)	Dec. 31, 2011 Variable/Fixed Rate Industrial Development Revenue Bonds Series 1999 Due 2014 [Member] USD ($)	Dec. 31, 2012 Installment Obligations [Member] USD ($)	Dec. 31, 2011 Installment Obligations [Member] USD ($)	Dec. 31, 2012 Other Borrowings [Member] USD ($)	Dec. 31, 2011 Other Borrowings [Member] USD ($)	Jan. 31, 2011 Other Borrowings [Member] USD ($)	Jan. 31, 2011 Other Borrowings [Member] CNY
Debt Instrument [Line Items]
Long-term debt, gross	$ 85,455,000	$ 94,001,000		$ 50,000,000	$ 50,000,000	$ 25,000,000	$ 25,000,000	$ 0	$ 8,000,000	$ 8,200,000	$ 8,200,000	$ 1,421,000	$ 1,421,000	$ 834,000	$ 1,380,000	$ 1,600,000	10,600,000
Less: Current maturities	76,977,000	8,552,000
Long-term debt	8,478,000	85,449,000
Interest rate on debt instrument (in hundredths)				5.53%
Maturity date				Oct. 05, 2013		Oct. 05, 2013		Aug. 01, 2012		Nov. 01, 2014
Average interest rates (in hundredths)						0.92%	0.77%	0.22%	0.31%	0.22%	0.31%	4.25%		7.40%
Term of debt instrument (in years)								15		15				3
Cost of land and limestone ore reserves acquired												17,500,000
Cash paid on closing of land and limestone ore reserves acquisition												6,100,000
Principal amount of debt at issuance												11,400,000
Long-term debt maturities [Abstract]
2013	77,000,000
2014	8,500,000
2015	0
2016	0
2017	0
Thereafter	0
Short-term Borrowings [Abstract]
Uncommitted short-term bank credit lines, maximum borrowing capacity	190,700,000
Uncommitted short-term bank credit lines, amount outstanding	7,100,000
Short-term debt	7,111,000	5,846,000
Weighted average interest rate on short-term borrowings (in hundredths)	5.80%	5.30%
Interest costs [Abstract]
Interest costs	3,500,000	3,500,000	3,500,000
Capitalized interest cost	$ 300,000	$ 300,000	$ 200,000