Financial Instruments and Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	$ 10,608,294	$ 11,626,831
Fair Value of Debt	11,219,716	12,017,527
Credit Facilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	35,023	0
Fair Value of Debt	35,061	0
Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	6,417,492	6,516,392
Fair Value of Debt	6,935,485	6,801,118
Term Loans and Unsecured Other Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	1,499,001	2,115,457
Fair Value of Debt	1,510,661	2,128,270
Secured Mortgages [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	979,585	1,172,473
Fair Value of Debt	1,055,020	1,262,778
Secured Mortgage of Consolidated Entities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	1,677,193	1,822,509
Fair Value of Debt	$ 1,683,489	$ 1,825,361