Financial Instruments and Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Debt (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	$ 11,139,415	$ 11,626,831
Fair Value of Debt	11,912,310	12,017,527
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	6,603,070	6,516,392
Fair Value of Debt	7,234,087	6,801,118
Secured Mortgage Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	901,071	1,172,473
Fair Value of Debt	996,779	1,262,778
Term Loans And Other Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	1,844,717	2,115,457
Fair Value of Debt	1,877,264	2,128,270
Secured Mortgage Debt of Consolidated Entities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	1,790,557	1,822,509
Fair Value of Debt	$ 1,804,180	$ 1,825,361