Summary of Significant Accounting Policies - Income (Loss) Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Income (Loss) Per Share-Basic and Diluted
Net Income (Loss)	$ 148,999	$ 16,233
Less: Net Income (Loss) Attributable to Noncontrolling Interests	5,334	281
Net Income (Loss) Attributable to Iron Mountain Incorporated (utilized in numerator of Earnings Per Share calculation)	$ 143,665	$ 15,952
Weighted-average shares—basic (in shares)	296,848,000	294,507,000
Effect of dilutive potential stock options (in shares)	1,704,000	2,162,000
Effect of dilutive potential RSUs and PUs (in shares)	282,000	591,000
Weighted-average shares—diluted (in shares)	298,834,000	297,260,000
Net Income (Loss) Per Share Attributable to Iron Mountain Incorporated:
Basic (in dollars per share)	$ 0.48	$ 0.05
Diluted (in dollars per share)	$ 0.48	$ 0.05
Antidilutive stock options, RSUs and PUs, excluded from the calculation (in shares)	229,681	98,685