Summary of Notional Amounts of Outstanding Foreign Exchange Forward Contracts, Designated as Net Investment Hedges (Detail) - Net Investment Hedging [Member] € in Millions, ¥ in Millions, £ in Millions, $ in Millions	Dec. 31, 2016 EUR (€)	Dec. 31, 2016 GBP (£)	Dec. 31, 2015 EUR (€)	Dec. 31, 2015 GBP (£)	Dec. 31, 2015 JPY (¥)	Dec. 31, 2015 USD ($)
Contracts to Sell GBP for Euros [Member] | Buy [Member]
Derivative [Line Items]
Derivative Notional Amount | €	€ 26.4		€ 29.1
Contracts to Sell GBP for Euros [Member] | Sell [Member]
Derivative [Line Items]
Derivative Notional Amount | £		£ 22.1		£ 21.2
Contracts to Sell Japanese Yen for USD [Member] | Buy [Member]
Derivative [Line Items]
Derivative Notional Amount | $						$ 161.8
Contracts to Sell Japanese Yen for USD [Member] | Sell [Member]
Derivative [Line Items]
Derivative Notional Amount | ¥					¥ 19,400.0