Segment Information - Schedule of Financial Information (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Revenues:	$ 474,988		$ 378,630		$ 918,550	$ 737,487
Operating expenses:	213,572		181,801		421,824	363,468
Net operating income:	275,665		196,829		510,975	437,902
Management fees and other income	20,517		14,796		40,474	30,441
Transaction related costs	(1,465)		0		(1,465)	0
General and administrative expense	(31,251)		(26,341)		(61,013)	(49,881)
Depreciation and amortization expense	(69,067)		(59,570)		(136,973)	(118,169)
Gain on real estate transactions	14,249		0		14,249	63,883
Interest expense	(47,466)		(40,240)		(90,004)	(80,935)
Interest income	15,060		12,838		34,049	25,142
Equity in earnings and dividend income from unconsolidated real estate entities	10,190		8,322		19,287	15,278
Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of joint venture partner's interest	0		6,251		0	6,251
Income tax expense	(5,615)		(5,421)		(8,756)	(9,558)
Net income	247,834	$ 217,717	178,579	$ 215,501	465,551	394,080
Operating Segments
Segment Reporting Information [Line Items]
Revenues:	454,471		363,834		878,076	707,046
Operating expenses:	111,789		95,890		222,373	195,418
Net operating income:	342,682		267,944		655,703	511,628
Self-Storage Operations | Operating Segments
Segment Reporting Information [Line Items]
Revenues:	408,044		321,500		787,852	625,093
Operating expenses:	104,252		89,155		207,794	181,522
Net operating income:	303,792		232,345		580,058	443,571
Tenant Reinsurance | Operating Segments
Segment Reporting Information [Line Items]
Revenues:	46,427		42,334		90,224	81,953
Operating expenses:	7,537		6,735		14,579	13,896
Net operating income:	$ 38,890		$ 35,599		$ 75,645	$ 68,057