Derivative Financial Instruments - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2018
Derivative [Line Items]
Foreign currency exchange contracts reclassified date	2019-06
Foreign Exchange Risk Management [Member]
Derivative [Line Items]
Hedging effectiveness	100.00%
Foreign Exchange Risk Management [Member] | Maximum [Member]
Derivative [Line Items]
Foreign exchange forward contracts maturity	1 year