Derivatives and Hedge Accounting - Additional Information (Detail) £ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2016 GBP (£)	Dec. 31, 2015 GBP (£)
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative losses which could be reclassified into earnings within the next 12 months	$ 1,781
Maximum outstanding term of cash flow hedges (in months)	45 months
Gain/(losses) that reclassified from AOCI into earning for discontinued hedging transactions	$ 0	$ 0
Derivatives Designated as Hedging Instruments | Derivatives in Cash Flow Hedging Relationships | Foreign Currency Exchange Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Foreign exchange contracts outstanding	218,545	230,894
Derivatives not Designated as Hedging Instruments | Foreign Currency Exchange Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Foreign exchange contracts outstanding	$ 71,318	$ 61,641	£ 11,153	£ 13,256