Financial Instruments and Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Debt (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	$ 15,666,872	$ 11,905,877
Fair Value of Debt	16,546,209	12,527,858
Credit Facilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	115,108	184,255
Fair Value of Debt	114,633	184,255
Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	13,205,392	9,660,570
Fair Value of Debt	14,025,805	10,228,715
Term Loans and Unsecured Other [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	1,695,026	1,441,882
Fair Value of Debt	1,714,984	1,463,841
Secured Mortgages [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value of Debt	651,346	619,170
Fair Value of Debt	$ 690,787	$ 651,047