v3.8.0.1
Financial Instruments and Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Debt (Detail) - USD ($)
$ in Thousands
Sep. 30, 2017
Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Carrying Value of Debt $ 9,721,065 $ 10,608,294
Fair Value of Debt 10,317,340 11,219,716
Credit Facilities [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Carrying Value of Debt 0 35,023
Fair Value of Debt 0 35,061
Senior Notes [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Carrying Value of Debt 6,874,108 6,417,492
Fair Value of Debt 7,390,221 6,935,485
Term Loans and Unsecured Other Debt [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Carrying Value of Debt 1,634,682 1,499,001
Fair Value of Debt 1,653,113 1,510,661
Secured Mortgages [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Carrying Value of Debt 812,371 979,585
Fair Value of Debt 874,491 1,055,020
Secured Mortgage of Consolidated Entities [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Carrying Value of Debt 399,904 1,677,193
Fair Value of Debt $ 399,515 $ 1,683,489