Financial Instruments and Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	$ 11,626,831	$ 9,336,977
Fair Value of Debt	12,017,527	10,080,157
Credit Facilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	0	0
Fair Value of Debt	0	0
Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	6,516,392	6,046,965
Fair Value of Debt	6,801,118	6,593,657
Exchangeable Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	0	456,373
Fair Value of Debt	0	511,931
Secured Mortgage Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	1,172,473	1,042,628
Fair Value of Debt	1,262,778	1,173,488
Term Loans and Other Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	2,115,457	584,124
Fair Value of Debt	2,128,270	591,810
Secured Mortgage Debt of Consolidated Entities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	1,822,509	1,206,887
Fair Value of Debt	$ 1,825,361	$ 1,209,271