Earnings Per Common Share - Schedule of Computation of Earnings Per Common Share (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Class of Stock [Line Items]
Net income attributable to common stockholders	$ 95,153,000	$ 87,006,000	$ 183,409,000	$ 169,288,000
Earnings and dividends allocated to participating securities	(193,000)	(207,000)	(371,000)	(403,000)
Earnings for basic computations	94,960,000	86,799,000	183,038,000	168,885,000
Earnings and dividends allocated to participating securities	0	0	(371,365)	0
Income allocated to noncontrolling interest - Preferred Operating Partnership Units and Operating Partnership Units	5,271,000	4,965,000	(10,211,000)	(10,285,000)
Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units)	(572,000)	(704,000)	1,144,000	1,975,000
Net income for diluted computations	$ 99,659,000	$ 91,060,000	$ 192,476,000	$ 177,195,000
Weighted average common shares outstanding:
Average number of common shares outstanding - basic (in shares)	125,874,130	125,673,156	125,823,581	125,639,480
OP Units (in shares)	5,651,878	5,574,364	5,657,592	5,585,218
Unvested restricted stock awards included for treasury stock method (in shares)	0	0	256,733	0
Shares related to exchangeable senior notes and dilutive stock options (in shares)	371,284	660,402	379,348	659,176
Average number of common shares outstanding - diluted (in shares)	132,772,772	132,783,402	132,992,734	132,759,354
Earnings per common share
Basic (in dollars per share)	$ 0.75	$ 0.69	$ 1.45	$ 1.34
Diluted (in dollars per share)	$ 0.75	$ 0.69	$ 1.45	$ 1.33
Series A Units
Weighted average common shares outstanding:
Preferred series units (in shares)	875,480	875,480	875,480	875,480