Significant Accounting Policies - Inventories (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Inventory [Line Items]
Inventories	$ 81.9	$ 68.1
Sugar inventories
Inventory [Line Items]
Inventories	23.3	16.8
Asphalt
Inventory [Line Items]
Inventories	21.3	17.9
Processed rock, portland cement, and sand
Inventory [Line Items]
Inventories	15.7	12.9
Work in progress
Inventory [Line Items]
Inventories	2.8	2.7
Retail merchandise
Inventory [Line Items]
Inventories	1.5	1.8
Parts, materials and supplies inventories
Inventory [Line Items]
Inventories	$ 17.3	$ 16.0