Financial Instruments and Fair Value Measurements - Summary of Changes in Other Comprehensive Income (Loss) (Parenthetical) (Detail) $ in Thousands, £ in Millions, € in Billions	3 Months Ended
	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2018 EUR (€)	Mar. 31, 2018 GBP (£)	Dec. 31, 2017 USD ($)	Dec. 31, 2017 EUR (€)	Dec. 31, 2017 GBP (£)
Derivative Instruments Gain Loss [Line Items]
Amount paid for (received from) on the settlement of net investment hedges	$ (4,000)	$ (1,800)
Interest expense reclassified	47,245	72,912
Debt	9,460,177				$ 9,412,631
Amount of gain (loss) included in AOCI	(4,770)	(39,667)
Senior notes	6,700,000
Forward Contracts [Member]
Derivative Instruments Gain Loss [Line Items]
Amount of gain (loss) included in AOCI	9,200	4,100
Foreign Currency Options [Member]
Derivative Instruments Gain Loss [Line Items]
Amount of gain (loss) included in AOCI	15,100	0
Designated As Hedging Instrument [Member] | Forward Contracts [Member]
Derivative Instruments Gain Loss [Line Items]
Debt	3,600,000		€ 3.0		3,600,000	€ 3.1
Designated As Hedging Instrument [Member] | Foreign Currency Options [Member]
Derivative Instruments Gain Loss [Line Items]
Senior notes	295,300			£ 213.7	$ 436,000		£ 323.7
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Derivative Instruments Gain Loss [Line Items]
Interest expense reclassified	1,100	$ 1,400
Amount to be reclassified to interest expense, next 12 months	$ 4,300