Segment Information - Schedule of Financial Information of Business Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Revenues	$ 1,577,362	$ 1,356,212	$ 1,308,454
Operating expenses	742,169	708,147	674,701
Net operating income	975,953	666,140	634,958
Property management fees and other income	66,264	52,129	49,890
General and administrative expense	(102,194)	(96,594)	(89,418)
Depreciation and amortization expense	(241,879)	(224,444)	(219,857)
Gain on real estate transactions	140,760	18,075	1,205
Interest expense	(166,183)	(168,626)	(186,526)
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	0	(3,675)	(4,742)
Interest income	49,703	15,192	7,467
Equity in earnings and dividend income from unconsolidated real estate entities	32,358	22,361	11,274
Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of joint venture partner's interest	6,251	0	0
Income tax expense	(20,324)	(13,810)	(11,308)
Net income	877,758	517,582	451,123
Operating Segments
Segment Reporting Information [Line Items]
Revenues	1,511,098	1,304,083	1,258,564
Operating expenses	398,096	387,109	365,426
Net operating income	1,113,002	916,974	893,138
Operating Segments | Self-Storage Operations
Segment Reporting Information [Line Items]
Revenues	1,340,990	1,157,522	1,130,177
Operating expenses	368,608	360,615	336,050
Net operating income	972,382	796,907	794,127
Operating Segments | Tenant Reinsurance
Segment Reporting Information [Line Items]
Revenues	170,108	146,561	128,387
Operating expenses	29,488	26,494	29,376
Net operating income	$ 140,620	$ 120,067	$ 99,011