Summary of Significant Accounting Policies - Income (Loss) Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income (Loss) Per Share-Basic and Diluted
Net Income (Loss)	$ 276,522	$ (7,113)	$ 323,153	$ 57,779
Less: Net Income (Loss) Attributable to Noncontrolling Interests	1,237	(27)	2,265	890
Net Income (Loss) Attributable to Iron Mountain Incorporated	$ 275,285	$ (7,086)	$ 320,888	$ 56,889
Weighted-average shares—basic (in shares)	289,247,000	288,071,000	289,001,000	287,955,000
Effect of dilutive potential stock options (in shares)	641,888	0	349,163	35,706
Effect of dilutive potential restricted stock, RSUs and PUs (in shares)	1,190,357	0	953,104	309,911
Weighted-average shares—diluted (in shares)	291,079,245	288,071,000	290,303,267	288,300,617
Income (Loss) from Continuing Operations, Basic (in dollars per share)	$ 0.95	$ (0.02)	$ 1.11	$ 0.20
Income (Loss) from Continuing Operations, Diluted (in dollars per share)	$ 0.95	$ (0.02)	$ 1.11	$ 0.20
Antidilutive stock options, RSUs and PUs, excluded from the calculation (in shares)	381,900	6,836,239	2,544,984	6,174,977