Debt - Debt Summary (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Weighted Average Interest Rate	2.60%	2.70%
Debt	$ 10,706,139	$ 11,089,815
Credit Facilities [Member]
Debt Instrument [Line Items]
Weighted Average Interest Rate	1.50%	3.40%
Debt	$ 26,180	$ 50,500
Senior Notes [Member]
Debt Instrument [Line Items]
Weighted Average Interest Rate	2.70%	2.70%
Debt	$ 8,314,678	$ 8,304,147
Term Loans and Unsecured Other [Member]
Debt Instrument [Line Items]
Weighted Average Interest Rate	0.90%	1.80%
Debt	$ 1,411,343	$ 1,921,428
Secured Mortgage [Member]
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.30%	5.10%
Debt	$ 953,938	$ 813,740