Financial Instruments and Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	$ 16,849,076	$ 11,905,877
Fair Value of Debt	18,083,430	12,527,858
Credit Facilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	171,794	184,255
Fair Value of Debt	171,794	184,255
Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	14,275,870	9,660,570
Fair Value of Debt	15,452,381	10,228,715
Term Loans and Unsecured Other Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	1,764,311	1,441,882
Fair Value of Debt	1,785,706	1,463,841
Secured Mortgages [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	637,101	619,170
Fair Value of Debt	$ 673,549	$ 651,047