Financial Instruments and Fair Value Measurements - Debt Instruments with Carrying Values Different than Estimated Fair Values (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior notes	$ 1,917,833	$ 2,810,100
Revolving Credit Facilities and term loans	318,452	398,130
Mortgage indebtedness	1,505,235	641,082
Total indebtedness	3,741,520	3,849,312
Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior notes	1,937,522	2,884,272
Revolving Credit Facilities and term loans	320,218	400,119
Mortgage indebtedness	1,538,103	653,185
Total indebtedness	$ 3,795,843	$ 3,937,576