Debt - Debt Summary (Parenthetical) (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Debt	$ 11,459,223	$ 11,089,815
GBP
Debt Instrument [Line Items]
Debt	$ 610,963	$ 635,972
Percentage of outstanding debt	5.30%	5.80%
CAD
Debt Instrument [Line Items]
Debt	$ 274,275	$ 266,337
Percentage of outstanding debt	2.40%	2.40%
EUR
Debt Instrument [Line Items]
Debt	$ 5,941,549	$ 4,893,693
Percentage of outstanding debt	51.90%	44.10%
JPY
Debt Instrument [Line Items]
Debt	$ 2,108,643	$ 1,951,844
Percentage of outstanding debt	18.40%	17.60%
USD
Debt Instrument [Line Items]
Debt	$ 2,523,793	$ 3,341,969
Percentage of outstanding debt	22.00%	30.10%