Shareholders' Equity - Reconciliation of Changes in Parent Company's Total Shareholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Beginning Balance	$ 2,378,098	$ 2,132,894
Net proceeds from issuance of common stock	180,529	21,466
Earned portion of non-vested stock	1,453	1,124
Carrying value less than redemption value on redeemed noncontrolling interest	(4)
Adjustment to redemption value on noncontrolling redeemable Operating Partnership units	(2,358)	5,542
Net income attributable to common shareholders	47,383	36,433
Amortization of terminated hedge included in AOCL	229	229
Dividends	(55,840)	(49,969)
Ending Balance	2,549,490	2,147,719
Common Stock Shares [Member]
Beginning Balance	495	467
Net proceeds from issuance of common stock	18	2
Stock dividend	252
Ending Balance	765	469
Additional Paid-in Capital [Member]
Beginning Balance	2,671,311	2,376,723
Net proceeds from issuance of common stock	180,511	21,464
Earned portion of non-vested stock	1,453	1,124
Stock dividend	(252)
Carrying value less than redemption value on redeemed noncontrolling interest	(4)
Ending Balance	2,853,019	2,399,311
Dividends in Excess of Net Income [Member]
Beginning Balance	(288,667)	(238,338)
Adjustment to redemption value on noncontrolling redeemable Operating Partnership units	(2,358)	5,542
Net income attributable to common shareholders	47,383	36,433
Dividends	(55,840)	(49,969)
Ending Balance	(299,482)	(246,332)
Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance	(5,041)	(5,958)
Amortization of terminated hedge included in AOCL	229	229
Ending Balance	$ (4,812)	$ (5,729)