Accounts Receivable, net - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2012 Customer
Accounts Receivable Net [Line Items]
Trade receivable payment terms	Payment terms of 15 days or less
Number of customers accounted as percentage of accounts receivable	12
Percentage of net receivables	36.00%
Receivable sales agreement [Member]
Accounts Receivable Net [Line Items]
Contract period	Initial term of this agreement is for one year, with renewal options, but either party has an option to terminate the agreement pursuant to the terms of the agreement
Contract terms	Receive payment from the Bank no later than one business day after the Bank’s acceptance of EDC's offer to sell the accounts receivable.