Summary of Significant Accounting Policies - Income Per Share, Allowance for Doubful Accounts, Income Taxes, and Concentration of Credit Risk (Details) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018 USD ($) bank fund $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares	Jun. 30, 2018 USD ($) bank fund $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) bank fund	Dec. 31, 2016 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Concentration Risk, Number of "Triple A" Rated Money Market Funds | fund	0		0		12
Effective Income Tax Rate Reconciliation Repatriation Of Foreign Earnings, Cash And Liquid Assets					15.50%
Income (Loss) Per Share-Basic and Diluted
Income (loss) from continuing operations	$ 93,903	$ 83,148	$ 139,517	$ 141,992
Less: Net Income (Loss) Attributable to Noncontrolling Interests	142	2,492	610	2,874
Income (loss) from continuing operations (utilized in numerator of Earnings Per Share calculation)	93,761	80,656	138,907	139,118
Income (loss) from discontinued operations, net of tax	(360)	(2,026)	(822)	(2,363)
Net income (loss) attributable to Iron Mountain Incorporated	$ 93,401	$ 78,630	$ 138,085	$ 136,755
Weighted-average shares—basic | shares	285,984,000	264,217,000	285,622,000	264,036,000
Effect of dilutive potential stock options (in shares) | shares	237,708	395,044	243,636	428,403
Effect of dilutive potential restricted stock, RSUs and PUs (in shares) | shares	347,543	318,375	415,929	405,640
Weighted-average shares—diluted | shares	286,569,251	264,930,419	286,281,565	264,870,043
Earnings (Losses) per share-basic:
Income (Loss) from continuing operations (in dollars per share) | $ / shares	$ 0.33	$ 0.31	$ 0.49	$ 0.53
Total (loss) income discontinued operations (in dollars per share) | $ / shares	0.00	(0.01)	0.00	(0.01)
Net Income (Loss) Attributable to Iron Mountain Incorporated (in dollars per share) | $ / shares	0.33	0.30	0.48	0.52
Earnings (Losses) per share-diluted:
Income (Loss) from continuing operations (in dollars per share) | $ / shares	0.33	0.30	0.49	0.53
Total (loss) income from discontinued operations (in dollars per share) | $ / shares	0.00	(0.01)	0.00	(0.01)
Net Income (Loss) Attributable to Iron Mountain Incorporated (in dollars per share) | $ / shares	$ 0.33	$ 0.30	$ 0.48	$ 0.52
Antidilutive stock options, RSUs and PUs, excluded from the calculation (in shares) | shares	3,272,502	2,701,129	3,257,322	2,597,692
Income Taxes:
Effective tax rates (as a percent)	21.90%	18.10%	16.50%	16.20%
Income (Loss) From Continuing Operations Before Income Taxes, Minority Interest, and (Gain) Loss on Disposition of Real Estate	$ 120,308	$ 99,594	$ 167,090	$ 167,658
Provision (Benefit) for Income Taxes	$ 26,405	$ 18,009	$ 27,573	$ 27,229
Federal statutory tax rate (as a percent)		35.00%	21.00%	35.00%	35.00%
Tax Matter Resolution, amount released			$ 14,000
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount				$ 7,511
Concentrations of Credit Risk
Number of global banks with cash, cash equivalent and restricted cash held on deposit | bank	7		7		7
Cash and cash equivalents	$ 188,192	$ 291,019	$ 188,192	$ 291,019	$ 925,699	$ 236,484
Effective Income Tax Rate Reconciliation Repatriation Of Foreign Earnings, Non-Liquid Assets					8.00%
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Liability					$ 186,000
Income Tax Reconciliation Repatriation Of Foreign Earnings, Attributable To REIT					$ 82,000