Summary of Notional Amounts of Outstanding Foreign Exchange Forwards, Net Investment Hedging (Detail) - Dec. 31, 2016 - Net Investment Hedging [Member] - Contracts to Sell GBP for Euros [Member] € in Millions, £ in Millions	EUR (€)	GBP (£)
Sell [Member]
Derivative [Line Items]
Derivative Notional Amount | £		£ 22.1
Buy [Member]
Derivative [Line Items]
Derivative Notional Amount | €	€ 26.4