Acquisitions and Divestitures (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012	Dec. 31, 2012
Disposal Group, Including Discontinued Operation, Unclassified Balance Sheet Disclosures [Abstract]
Total assets of Ready-Mix Concrete Operations	$ 0	[1]		$ 27.9
Total liabilities of Ready-Mix Concrete Operations	0	[1]		3.7
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Net loss from discontinued operations	6.6		(0.1)
Ready Mix Concrete Operations
Disposal Group, Including Discontinued Operation, Unclassified Balance Sheet Disclosures [Abstract]
Inventories	0			4.5
Property, plant, and equipment, net	0			16.9
Goodwill	0			6.3
Other	0			0.2
Total assets of Ready-Mix Concrete Operations	0			27.9
Debt	0			3.7
Total liabilities of Ready-Mix Concrete Operations	0			3.7
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues	31.6		29.1
Loss from discontinued operations before income taxes	(0.7)		(0.2)
Income tax benefit	(0.3)		(0.1)
Net loss from discontinued operations	$ (0.4)		$ (0.1)

[1] (unaudited)