Financial Instruments and Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Debt (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	$ 16,518,126	$ 11,905,877
Fair Value of Debt	17,525,319	12,527,858
Credit Facilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	39,733	184,255
Fair Value of Debt	39,733	184,255
Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	14,108,021	9,660,570
Fair Value of Debt	15,053,871	10,228,715
Term Loans and Unsecured Other [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	1,723,473	1,441,882
Fair Value of Debt	1,744,580	1,463,841
Secured Mortgages [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	646,899	619,170
Fair Value of Debt	$ 687,135	$ 651,047