Commitments and Contingencies (Details 2)	12 Months Ended
	Dec. 31, 2012 item
Gaskets mislabeled as being non-asbestos
Commitments and Contingencies
Number of gaskets bought, that might have been mislabeled	34,000
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
Surety
Percentage of business which has required bonds	25.00%
Surety | Maximum
Surety
Percentage of business which has required bonds	35.00%