Contingencies and Legacy Environmental Commitments - Additional Information (Detail)	1 Months Ended				3 Months Ended			6 Months Ended		12 Months Ended
	Mar. 31, 2015 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014	Jul. 31, 2001 USD ($)	Jun. 30, 2005	Dec. 31, 2003 USD ($)	Jun. 30, 1999	Sep. 30, 2015 USD ($) Location	Sep. 30, 2014 USD ($)	Mar. 31, 2015 USD ($)
Site Contingency [Line Items]
Aggregate environmental liability	$ 9,255,000							$ 9,086,000		$ 9,255,000
Cost-sharing related to environmental liabilities	1,554,000							1,150,000		1,554,000
Environmental costs								$ 307,000	$ 383,000	946,000
Number of locations for participating in environmental assessments and remediation work | Location								6
Time frame for environmental liabilities								30 years
Real estate held for sale	3,800,000							$ 3,800,000		3,800,000
Decrease in environmental reserve								430,000
Additional Environmental Reserve								430,000
Glen Head, New York
Site Contingency [Line Items]
Aggregate environmental liability								3,157,000
Real estate held for sale								3,800,000
Sale of environmental remediation property				$ 4,000,000
Additional liquidated amount	750,000									$ 750,000
Escrow Deposits Related to Property Sales	530,000
Glen Head, New York | Maximum
Site Contingency [Line Items]
Reduced purchase price	$ 1,000,000
Federal Labs
Site Contingency [Line Items]
Aggregate environmental liability								4,029,000
Environmental costs						$ 200,000
Additional environmental remediation expense						$ 200,000
Percentage of environmental costs paid by Federal Government					45.00%		50.00%
Maximum technical and oversight fees								$ 10,000
Decrease in environmental reserve		$ 412,000
Percentage of environmental costs payable			26.00%
Percentage of environmental costs payable thereafter			33.50%
Federal Labs | Maximum
Site Contingency [Line Items]
Time frame for environmental liabilities								30 years
Federal Labs | Minimum
Site Contingency [Line Items]
Time frame for environmental liabilities								20 years
Placerita, California
Site Contingency [Line Items]
Maximum technical and oversight fees								$ 14,000
Decrease in environmental reserve								430,000
Other Properties
Site Contingency [Line Items]
Aggregate environmental liability								$ 1,900,000