Contingencies and Legacy Environmental Commitments - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended		12 Months Ended	1 Months Ended		1 Months Ended	3 Months Ended			6 Months Ended
	Sep. 30, 2014 Location	Sep. 30, 2013	Mar. 31, 2014	Jul. 31, 2001 Glen Head, New York	Sep. 30, 2014 Glen Head, New York	Mar. 31, 2014 Federal Labs	Jun. 30, 2005 Federal Labs	Dec. 31, 2003 Federal Labs	Jun. 30, 1999 Federal Labs	Sep. 30, 2014 Federal Labs	Sep. 30, 2014 Federal Labs Minimum	Sep. 30, 2014 Federal Labs Maximum	Sep. 30, 2014 Other Properties
Site Contingency [Line Items]
Aggregate environmental liability	$ 9,677		$ 10,323		$ 3,158					$ 4,344			$ 2,175
Cost-sharing related to environmental liabilities	1,344		1,918
Environmental costs	383	602	1,487					200
Number of locations for participating in environmental assessments and remediation work	7
Time frame for environmental liabilities	30 years										20 years	30 years
Real estate held for sale	3,800		3,800		3,800
Sale of environmental remediation property				4,000
Additional environmental remediation expense								200
Percentage of environmental costs paid by Federal Government							45.00%		50.00%
Maximum technical and oversight fees										10
Decrease in environmental reserve	$ 412									$ 412
Percentage of environmental costs payable						26.00%
Percentage of environmental costs payable thereafter						33.50%