Earnings Per Common Share - Schedule of Computation of Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Line Items]
Net income attributable to common stockholders	$ 87,006	$ 83,044	$ 169,288	$ 165,636
Earnings and dividends allocated to participating securities	(207)	(214)	(403)	(380)
Earnings for basic computations	86,799	82,830	168,885	165,256
Undistributed Earnings, Diluted	0	0	0	380
Income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units) and Operating Partnership	4,965	5,398	10,285	10,872
Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units)	(704)	(1,271)	(1,975)	(2,542)
Net income for diluted computations	$ 91,060	$ 86,957	$ 177,195	$ 173,966
Weighted average common shares outstanding:
Average number of common shares outstanding - basic (in shares)	125,673,156	124,914,467	125,639,480	124,678,293
OP Units (in shares)	5,574,364	5,517,607	5,585,218	5,569,537
Preferred series units (in shares)	875,480	875,480	875,480	875,480
Unvested restricted stock awards included for treasure stock method	0	0	0	309,987
Shares related to exchangeable senior notes and dilutive stock options (in shares)	660,402	718,361	659,176	719,222
Average number of common shares outstanding - diluted (in shares)	132,783,402	132,025,915	132,759,354	132,152,519
Earnings per common share
Basic (in dollars per share)	$ 0.69	$ 0.66	$ 1.34	$ 1.33
Diluted (in dollars per share)	$ 0.69	$ 0.66	$ 1.33	$ 1.32