Financial Derivatives and Hedging Activities - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2018
Maximum [Member] | Fair Value, Measurements [Member]
Derivative [Line Items]
Accumulated other comprehensive income realization period	18 months
Minimum [Member] | Fair Value, Measurements [Member]
Derivative [Line Items]
Accumulated other comprehensive income realization period	12 months
Designated as Hedging [Member] | Cash Flow Hedges [Member] | Maximum [Member]
Derivative [Line Items]
Maturities of foreign currency derivative contracts	18 months
Designated as Hedging [Member] | Cash Flow Hedges [Member] | Minimum [Member]
Derivative [Line Items]
Maturities of foreign currency derivative contracts	1 month
Not Designated as Hedging [Member]
Derivative [Line Items]
Maturities of foreign currency derivative contracts	1 month