Summary of Significant Accounting Policies - Income (Loss) Per Share - Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income (Loss) Per Share-Basic and Diluted
Income (Loss) from Continuing Operations	$ 343,096	$ 268,211	$ 367,558
Less: Net income (loss) attributable to noncontrolling interests	403	938	1,198
Income (loss) from continuing operations (utilized in numerator of Earnings Per Share calculation)	342,693	267,273	366,360
Income (loss) from discontinued operations, net of tax	0	104	(12,427)
Net Income (Loss) Attributable to Iron Mountain Incorporated	$ 342,693	$ 267,377	$ 353,933
Weighted-average shares—basic (in shares)	288,183,000	286,971,000	285,913,000
Effect of dilutive potential stock options (in shares)	24,903	145,509	234,558
Effect of dilutive potential RSUs and PUs (in shares)	435,287	570,435	505,030
Weighted-average shares—diluted (in shares)	288,643,190	287,686,944	286,652,588
Earnings (losses) per share—basic:
Income (loss) from continuing operations (in dollars per share)	$ 1.19	$ 0.93	$ 1.28
(Loss) income from discontinued operations, net of tax (in dollars per share)	0	0	(0.04)
Net income (loss) attributable to iron mountain incorporated (in dollars per share)	1.19	0.93	1.24
Earnings (losses) per share—diluted:
Income (loss) from continuing operations (in dollars per share)	1.19	0.93	1.28
(Loss) income from discontinued operations, net of tax (in dollars per share)	0	0	(0.04)
Net Income (Loss) Attributable to Iron Mountain Incorporated (in dollars per share)	$ 1.19	$ 0.93	$ 1.23
Antidilutive stock options, RSUs and PUs, excluded from the calculation (in shares)	5,663,981	4,475,745	3,258,078