Debt - Debt Summary (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Debt	$ 11,139,415	$ 11,626,831
Credit Facilities [Member]
Debt Instrument [Line Items]
Debt	0	0
Senior Notes [Member]
Debt Instrument [Line Items]
Debt	6,603,070	6,516,392
Term Loan [Member]
Debt Instrument [Line Items]
Debt	1,800,000
Secured Mortgage Debt [Member]
Debt Instrument [Line Items]
Debt	$ 901,071	$ 1,172,473
Debts Of Operating Partnership [Member]
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.20%	3.20%
Debt	$ 11,139,415	$ 11,626,831
Debts Of Operating Partnership [Member] | Credit Facilities [Member]
Debt Instrument [Line Items]
Weighted Average Interest Rate	0.00%	0.00%
Debt	$ 0	$ 0
Debts Of Operating Partnership [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.30%	3.30%
Debt	$ 6,603,070	$ 6,516,392
Debts Of Operating Partnership [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Weighted Average Interest Rate	1.90%	2.10%
Debt	$ 1,829,787	$ 2,100,009
Debts Of Operating Partnership [Member] | Other Debt [Member]
Debt Instrument [Line Items]
Weighted Average Interest Rate	6.20%	6.20%
Debt	$ 14,930	$ 15,448
Debts Of Operating Partnership [Member] | Secured Mortgage Debt [Member]
Debt Instrument [Line Items]
Weighted Average Interest Rate	5.30%	5.10%
Debt	$ 901,071	$ 1,172,473
Debts Of Operating Partnership [Member] | Secured Mortgage Debt of Consolidated Entities [Member]
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.00%	2.90%
Debt	$ 1,790,557	$ 1,822,509