Summary of Significant Accounting Policies - Income (Loss) Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income (Loss) Per Share-Basic and Diluted
Net Income (Loss)	$ 68,111	$ 38,562	$ 391,264	$ 96,341
Less: Net Income (Loss) Attributable to Noncontrolling Interests	428	168	2,693	1,058
Net Income (Loss) Attributable to Iron Mountain Incorporated	$ 67,683	$ 38,394	$ 388,571	$ 95,283
Weighted-average shares—basic (in shares)	289,762,000	288,403,000	289,255,000	288,105,000
Effect of dilutive potential stock options (in shares)	869,600	14,758	522,642	28,723
Effect of dilutive potential restricted stock, RSUs and PUs (in shares)	850,655	392,943	918,954	337,588
Weighted-average shares—diluted (in shares)	291,482,255	288,810,701	290,696,596	288,471,311
Income (Loss) from Continuing Operations, Basic (in dollars per share)	$ 0.23	$ 0.13	$ 1.34	$ 0.33
Income (Loss) from Continuing Operations, Diluted (in dollars per share)	$ 0.23	$ 0.13	$ 1.34	$ 0.33
Antidilutive stock options, RSUs and PUs, excluded from the calculation (in shares)	351,673	5,529,126	1,813,880	5,959,693