Contingencies and Legacy Environmental Commitments - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended		12 Months Ended	1 Months Ended			3 Months Ended				6 Months Ended
	Sep. 30, 2013 Location	Sep. 30, 2012	Mar. 31, 2013	Jul. 31, 2001 Glen Head, New York	Sep. 30, 2013 Glen Head, New York	Dec. 31, 2005 Glen Head, New York	Jun. 30, 2005 Federal Labs	Dec. 31, 2003 Federal Labs	Jun. 30, 1999 Federal Labs	Sep. 30, 2013 Federal Labs	Sep. 30, 2013 Federal Labs Minimum	Sep. 30, 2013 Federal Labs Maximum	Sep. 30, 2013 Other Properties
Site Contingency [Line Items]
Aggregate environmental liability	$ 11,049		$ 12,684		$ 3,155					$ 5,292			$ 2,602
Cost-sharing related to environmental liabilities	1,408		1,472
Environmental costs	602	544	1,245					200
Number of locations for participating in environmental assessments and remediation work	10
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%
Reduction in remaining environmental liability	$ 1,207