Operating Segments (Details) (USD $)
In Millions
3 Months Ended9 Months Ended
Sep. 30, 2011
Sep. 30, 2010
Sep. 30, 2011
Sep. 30, 2010
Dec. 31, 2010
Segment Reporting Information [Line Items]     
Sales to external customers$ 229.1$ 176.0$ 799.6$ 712.6 
Intersegment sales0000 
Shipping and handling cost56.138.8214.9177.7 
Operating earnings (loss)48.632.7155.3143.8 
Depreciation, depletion and amortization16.012.248.836.3 
Total assets (as of end of period)1,125.11,001.31,125.11,001.31,114.3
Salt [Member]
     
Segment Reporting Information [Line Items]     
Sales to external customers175.5136.3635.2573.4 
Intersegment sales0.20.20.70.5 
Shipping and handling cost50.633.9195.5160.8 
Operating earnings (loss)40.530.7131.3129.7 
Depreciation, depletion and amortization10.08.230.424.9 
Total assets (as of end of period)688.6690.2688.6690.2 
Specialty Fertilizer [Member]
     
Segment Reporting Information [Line Items]     
Sales to external customers51.136.8156.0130.9 
Intersegment sales1.20.93.82.8 
Shipping and handling cost5.54.919.416.9 
Operating earnings (loss)19.411.657.443.5 
Depreciation, depletion and amortization5.02.915.08.1 
Total assets (as of end of period)369.9245.0369.9245.0 
Corporate and Other [Member]
     
Segment Reporting Information [Line Items]     
Sales to external customers2.5[1]2.9[1]8.4[1]8.3[1] 
Intersegment sales(1.4)[1](1.1)[1](4.5)[1](3.3)[1] 
Shipping and handling cost0[1]0[1]0[1]0[1] 
Operating earnings (loss)(11.3)[1](9.6)[1](33.4)[1](29.4)[1] 
Depreciation, depletion and amortization1.0[1]1.1[1]3.4[1]3.3[1] 
Total assets (as of end of period)$ 66.6[1]$ 66.1[1]$ 66.6[1]$ 66.1[1] 
[1]"Corporate and Other" includes corporate entities, the records management business and eliminations. Corporate assets include deferred tax assets, deferred financing fees, investments related to the non-qualified retirement plan, and other assets not allocated to the operating segments.