Debt - Debt Summary (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Schedule of Capitalization, Long-term Debt [Line Items]
Weighted Average Interest Rate	4.40%	4.20%
Amount Outstanding	$ 8,870,635	$ 9,011,216
Credit Facilities [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Weighted Average Interest Rate	1.20%	1.20%
Amount Outstanding	119,466	725,483
Senior notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Weighted Average Interest Rate	4.30%	4.50%
Amount Outstanding	6,296,308	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	442,729	438,481
Secured mortgage debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Weighted Average Interest Rate	5.50%	5.60%
Amount Outstanding	1,674,488	1,696,597
Secured mortgage debt of consolidated entities [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Weighted Average Interest Rate	4.70%	4.70%
Amount Outstanding	238,148	239,992
Term Loan [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Weighted Average Interest Rate	1.50%	1.70%
Amount Outstanding	82,728	535,908
Other debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Weighted Average Interest Rate	6.20%	6.20%
Amount Outstanding	$ 16,768	$ 16,822