Financial Instruments and Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Debt (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	$ 16,503,458	$ 16,849,076
Fair Value of Debt	16,713,516	18,083,430
Credit Facilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	53,250	171,794
Fair Value of Debt	53,250	171,794
Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	14,433,868	14,275,870
Fair Value of Debt	14,598,729	15,452,381
Term Loans and Unsecured Other [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	1,670,556	1,764,311
Fair Value of Debt	1,687,135	1,785,706
Secured Mortgage [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	345,784	637,101
Fair Value of Debt	$ 374,402	$ 673,549