Financial Instruments and Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Debt (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	$ 8,870,635	$ 9,011,216
Fair Value of Debt	9,504,219	9,586,791
Credit Facilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	119,466	725,483
Fair Value of Debt	119,711	725,679
Senior notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	6,296,308	5,357,933
Fair Value of Debt	6,676,298	5,698,864
Exchangeable senior notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	442,729	438,481
Fair Value of Debt	532,783	514,381
Secured mortgage debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	1,674,488	1,696,597
Fair Value of Debt	1,825,836	1,840,829
Secured mortgage debt of consolidated entities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	238,148	239,992
Fair Value of Debt	248,154	246,324
Term loan and other debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	99,496	552,730
Fair Value of Debt	$ 101,437	$ 560,714