Derivative Financial Instruments - Summary of Outstanding Foreign Exchange Derivatives Designated as Net Investment Hedges of Foreign Currency Risk (Detail) - Sell [Member] - Designated as Hedging Instrument [Member] - Foreign Exchange Forward [Member] - Net Investment Hedges [Member] € in Thousands, £ in Thousands, $ in Thousands, $ in Thousands	Mar. 31, 2019 EUR (€) DerivativeInstrument	Mar. 31, 2019 GBP (£) DerivativeInstrument	Mar. 31, 2019 AUD ($) DerivativeInstrument	Mar. 31, 2019 CAD ($) DerivativeInstrument	Dec. 31, 2018 EUR (€) DerivativeInstrument	Dec. 31, 2018 GBP (£) DerivativeInstrument	Dec. 31, 2018 AUD ($) DerivativeInstrument	Dec. 31, 2018 CAD ($) DerivativeInstrument
CAD [Member]
Derivative [Line Items]
Number of Instruments	2	2	2	2	1	1	1	1
Notional Amount | $				$ 78,700				$ 70,600
GBP [Member]
Derivative [Line Items]
Number of Instruments	3	3	3	3	3	3	3	3
Notional Amount | £		£ 262,000				£ 192,300
EUR [Member]
Derivative [Line Items]
Number of Instruments	1	1	1	1	1	1	1	1
Notional Amount | €	€ 179,600				€ 185,000
AUD [Member]
Derivative [Line Items]
Number of Instruments	4	4	4	4	2	2	2	2
Notional Amount | $			$ 210,700				$ 187,600