Contingencies and Legacy Environmental Commitments - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended		12 Months Ended		1 Months Ended			3 Months Ended				9 Months Ended
	Dec. 31, 2012 Location	Dec. 31, 2011	Mar. 31, 2012	Mar. 31, 2013 Forecast [Member]	Jul. 31, 2001 Glen Head, New York [Member]	Dec. 31, 2012 Glen Head, New York [Member]	Dec. 31, 2005 Glen Head, New York [Member]	Jun. 30, 2005 Federal Labs [Member]	Dec. 31, 2003 Federal Labs [Member]	Jun. 30, 1999 Federal Labs [Member]	Dec. 31, 2012 Federal Labs [Member]	Dec. 31, 2012 Federal Labs [Member] Minimum [Member]	Dec. 31, 2012 Federal Labs [Member] Maximum [Member]	Dec. 31, 2012 Other properties [Member]	Dec. 31, 2012 Four environmental proceedings [Member]
Site Contingency [Line Items]
Aggregate environmental liability	$ 12,896		$ 13,535			$ 3,299					$ 5,660			$ 3,937	$ 100
Cost-sharing related to environmental liabilities	1,472		1,500
Environmental costs	939	778	1,177						200
Environmental costs, one year				1,225
Number of locations for participating in environmental assessments and remediation work	9
Time frame for environmental liabilities	30 years											20 years	30 years
Property "held for sale"						3,800
Sale of environmental remediation property					4,000
Appraised value of property					3,300		4,200
Additional environmental remediation expense									$ 200
Percentage of environmental costs paid by Federal Government								45.00%		50.00%