Segment Information - Schedule of Financial Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Segment Reporting Information [Line Items]
Revenues:	$ 443,562	$ 358,857
Operating expenses:	208,252	181,667
Net operating income:	235,310	241,073
Management fees and other income	19,957	15,645
General and administrative expense	(29,762)	(23,540)
Depreciation and amortization expense	(67,906)	(58,599)
Gain on real estate transactions	0	63,883
Interest expense	(42,538)	(40,695)
Interest income	18,989	12,304
Equity in earnings and dividend income from unconsolidated real estate entities	9,097	6,956
Income tax expense	(3,141)	(4,137)
Net income	217,717	215,501
Operating Segments
Segment Reporting Information [Line Items]
Revenues:	423,605	343,212
Operating expenses:	110,584	99,528
Net operating income:	313,021	243,684
Self-Storage Operations | Operating Segments
Segment Reporting Information [Line Items]
Revenues:	379,808	303,593
Operating expenses:	103,542	92,367
Net operating income:	276,266	211,226
Tenant Reinsurance | Operating Segments
Segment Reporting Information [Line Items]
Revenues:	43,797	39,619
Operating expenses:	7,042	7,161
Net operating income:	$ 36,755	$ 32,458