Debt - Debt Summary (Parenthetical) (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Weighted Average Interest Rate	1.60%	1.90%
Debt	$ 17,135,668	$ 16,849,076
GBP
Debt Instrument [Line Items]
Weighted Average Interest Rate	2.20%	2.20%
Debt	$ 1,005,266	$ 1,019,480
Percentage of outstanding debt	5.90%	6.10%
CAD
Debt Instrument [Line Items]
Weighted Average Interest Rate	2.70%	2.70%
Debt	$ 283,751	$ 285,708
Percentage of outstanding debt	1.70%	1.70%
EUR
Debt Instrument [Line Items]
Weighted Average Interest Rate	1.10%	1.40%
Debt	$ 6,877,873	$ 6,549,676
Percentage of outstanding debt	40.00%	38.80%
JPY
Debt Instrument [Line Items]
Weighted Average Interest Rate	0.80%	0.80%
Debt	$ 3,146,736	$ 2,877,247
Percentage of outstanding debt	18.40%	17.10%
USD
Debt Instrument [Line Items]
Weighted Average Interest Rate	2.60%	2.80%
Debt	$ 5,822,042	$ 6,116,965
Percentage of outstanding debt	34.00%	36.30%