Inventories - Additional Information (Detail) (USD $)	3 Months Ended
	Dec. 31, 2014
Three to Four Years Old Inventory [Member]
Inventory [Line Items]
Cost basis reduction in inventory, percentage	50.00%
Three to Four Years Old Inventory [Member] | Minimum [Member]
Inventory [Line Items]
Inventory, time period on the shelf, years	3 years
Three to Four Years Old Inventory [Member] | Maximum [Member]
Inventory [Line Items]
Inventory, time period on the shelf, years	4 years
Four to Five Years Old Inventory [Member]
Inventory [Line Items]
Cost basis reduction in inventory, percentage	75.00%
Four to Five Years Old Inventory [Member] | Minimum [Member]
Inventory [Line Items]
Inventory, time period on the shelf, years	4 years
Four to Five Years Old Inventory [Member] | Maximum [Member]
Inventory [Line Items]
Inventory, time period on the shelf, years	5 years
Greater Than Five Years Old Inventory [Member]
Inventory [Line Items]
Inventory valuation estimate	0
Greater Than Five Years Old Inventory [Member] | Minimum [Member]
Inventory [Line Items]
Inventory, time period on the shelf, years	5 years