Nature of Operations and Basis of Presentation - Additional Information (Detail) - Jun. 30, 2015	Total	Total
Gas Segment [Member]
Business Description and Basis Of Presentation [Line Items]
Percentage of total revenue	28.00%	31.00%
Power And Electro-mechanic Segment [Member]
Business Description and Basis Of Presentation [Line Items]
Percentage of total revenue	72.00%	69.00%