Commitments and Contingencies (Details)	6 Months Ended
	Jun. 30, 2012 item
Gaskets mislabeled as being non-asbestos
Commitments and Contingencies
Number of gaskets bought, that might have been mislabeled	29,000
Number of Ferguson customers who have found asbestos in gaskets above the 1% level	4
Gaskets mislabeled as being non-asbestos | Maximum
Commitments and Contingencies
Percentage of asbestos in to be classified as non-asbestos	1.00%
Surety | Minimum
Commitments and Contingencies
Percentage of business which has required bonds	25.00%
Surety | Maximum
Commitments and Contingencies
Percentage of business which has required bonds	35.00%