Derivative Instruments And Hedging Activities - Additional Information (Detail) € in Millions, £ in Millions, $ in Millions	Sep. 30, 2017 EUR (€)	Sep. 30, 2017 GBP (£)	Sep. 30, 2017 USD ($)
Sell [Member] | Contracts to Sell US Dollars for GBP [Member]
Derivative [Line Items]
Notional amount | $			$ 471.0
Sell [Member] | Contracts to sell USD for EUR [Member]
Derivative [Line Items]
Notional amount | $			$ 54.3
Buy [Member] | Contracts to Sell US Dollars for GBP [Member]
Derivative [Line Items]
Notional amount | £		£ 356.1
Buy [Member] | Contracts to sell USD for EUR [Member]
Derivative [Line Items]
Notional amount	€ 45.0
Derivatives Designated as Investment Hedges [Member] | Currency Swap [Member] | Cross-Currency Paid [Member] | 2015 Senior Notes [Member]
Derivative [Line Items]
Notional amount	€ 100.0
Derivative, swaption interest rate	1.75%	1.75%	1.75%
Derivatives Designated as Investment Hedges [Member] | Currency Swap [Member] | Cross-Currency Received [Member] | 2015 Senior Notes [Member]
Derivative [Line Items]
Notional amount | $			$ 110.5
Derivative, swaption interest rate	3.945%	3.945%	3.945%
Derivatives Designated as Investment Hedges [Member] | Net Investment Hedging [Member] | 2015 Senior Notes [Member]
Derivative [Line Items]
Notional amount	€ 400.0
Bureau van Dijk (BvD) [Member] | Derivatives Not Designated as Investment Hedges [Member] | Foreign Exchange Option [Member] | Sell [Member] | Contracts to Sell US Dollars for GBP [Member]
Derivative [Line Items]
Notional amount | $			$ 41.0
Bureau van Dijk (BvD) [Member] | Derivatives Not Designated as Investment Hedges [Member] | Foreign Exchange Option [Member] | Sell [Member] | Contracts to sell USD for EUR [Member]
Derivative [Line Items]
Notional amount | $			$ 2,800.0
Bureau van Dijk (BvD) [Member] | Derivatives Not Designated as Investment Hedges [Member] | Foreign Exchange Option [Member] | Buy [Member] | Contracts to Sell US Dollars for GBP [Member]
Derivative [Line Items]
Notional amount | £		£ 31.0
Bureau van Dijk (BvD) [Member] | Derivatives Not Designated as Investment Hedges [Member] | Foreign Exchange Option [Member] | Buy [Member] | Contracts to sell USD for EUR [Member]
Derivative [Line Items]
Notional amount	2,400.0
Bureau van Dijk (BvD) [Member] | Derivatives Not Designated as Investment Hedges [Member] | Foreign Exchange Option [Member] | Call Option [Member]
Derivative [Line Items]
Notional amount	2,700.0
Bureau van Dijk (BvD) [Member] | Derivatives Not Designated as Investment Hedges [Member] | Foreign Exchange Option [Member] | Put Option [Member]
Derivative [Line Items]
Notional amount	€ 2,700.0