Debt - Debt Summary (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Schedule of Capitalization, Long-term Debt [Line Items]
Weighted Average Interest Rate	4.00%	4.20%
Amount Outstanding	$ 8,529,453	$ 9,011,216
Credit Facilities [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Weighted Average Interest Rate	1.10%	1.20%
Amount Outstanding	38,673	725,483
Senior notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Weighted Average Interest Rate	4.00%	4.50%
Amount Outstanding	6,119,885	5,357,933
Exchangeable senior notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Weighted Average Interest Rate	3.30%	3.30%
Amount Outstanding	447,321	438,481
Secured Mortgage Debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Weighted Average Interest Rate	5.80%	5.60%
Amount Outstanding	1,271,546	1,696,597
Secured mortgage debt of consolidated entities [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Weighted Average Interest Rate	3.90%	4.70%
Amount Outstanding	26,804	239,992
Term Loans [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Weighted Average Interest Rate	1.20%	1.70%
Amount Outstanding	608,533	535,908
Other debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Weighted Average Interest Rate	6.20%	6.20%
Amount Outstanding	$ 16,691	$ 16,822