Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended	12 Months Ended				12 Months Ended					3 Months Ended					12 Months Ended	3 Months Ended
	Mar. 31, 2013 claim LegalMatter	Dec. 31, 2012 LegalMatter	Sep. 30, 2012	Dec. 31, 2012 LegalMatter	Dec. 31, 2011 claim	Dec. 31, 2010 Minimum [Member] LegalMatter	Sep. 30, 2012 Minimum [Member]	Dec. 31, 2010 Maximum [Member] LegalMatter	Dec. 31, 2012 Maximum [Member]	Mar. 31, 2013 Claims that Specify Amount of Damages Sought [Member] LegalMatter	Mar. 31, 2013 Claims that Cite Jurisdictional Amounts [Member] LegalMatter	Mar. 31, 2013 Claims that Specify Amount of Damages Sought not Based on Jurisdictional Requirements [Member] LegalMatter	Mar. 31, 2013 Claims that Specify Amount of Damages Sought not Based on Jurisdictional Requirements [Member] Maximum [Member] LegalMatter	Mar. 31, 2013 Claims that Specify Amount of Damages Sought not Based on Jurisdictional Requirements [Member] Legal Claim 1 [Member] Compensatory [Member]	Mar. 31, 2013 Claims that Specify Amount of Damages Sought not Based on Jurisdictional Requirements [Member] Legal Claim 1 [Member] Punitive [Member]	Mar. 31, 2013 Claims that Specify Amount of Damages Sought not Based on Jurisdictional Requirements [Member] Legal Claim 3 [Member] Punitive [Member]	Mar. 31, 2013 Superfund Sites Proceedings [Member] LegalMatter	Dec. 31, 2012 Superfund Sites Proceedings [Member]	Mar. 31, 2013 PCB Contamination Proceedings [Member]	Mar. 31, 2010 PCB Contamination Proceedings [Member]	Mar. 31, 2013 PCB Contamination Proceedings [Member] Building [Member]
Commitments and Contingencies Disclosure [Line Items]
Number of pending claims	337	319		319						72	264	1					1
Estimated total cleanup costs, cost sharing percentage																	2.00%
Loss contingency, minimum possible loss																	$ 18.8	$ 17.0
Loss contingency, maximum possible loss																	29.6	24.0
Estimated total cleanup costs, accrual	0.4
Estimated total cleanup costs, insurance receivable																	0.3
Remediation and monitoring costs incurred since inception related to the PCB soil and building contamination																			2.5		0.7
PCB contamination of the building, liability recording during the period																			0.3	1.0
Percentage of pending claims												1.00%
Damages sought														20	20	1
Number of defendants						1		833					21
Description of named defendants	Cases involving us typically name 50-300 defendants
Number of claims dismissed	20				93
Number of claims settled	2				16
Claims settlements amount	0.9			6.3
Cost Sharing Agreement, Expiration Period	4 years
Cost Sharing Agreement, expiration date	Jan. 25, 2015
Asbestos-related liabilities, estimated liability		51.4		51.4
Asbestos-related liabilities, estimated insurance recovery		48.3		48.3
Asbestos Forcast Claim Period							5 years		10 years
Environmental Expense and Liabilities		2.9
Environmental Remediation Expense			$ 0.2