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Line of credit - Additional Information (Detail)
$ in Millions
1 Months Ended
Mar. 31, 2014
USD ($)
Line of Credit Facility [Line Items]  
Line of Credit Facility, Interest Rate During Period 3.00%
Line of Credit Facility, Expiration Date Jun. 30, 2016
Letter of Credit  
Line of Credit Facility [Line Items]  
Line of Credit Facility, Amount Outstanding $ 5.0