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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 12 Months Ended
Mar. 31, 2018
USD ($)
bank
$ / shares
shares
Mar. 31, 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     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 $ 45,614 $ 58,844    
Less: Net Income (Loss) Attributable to Noncontrolling Interests 468 382    
Income (loss) from continuing operations (utilized in numerator of Earnings Per Share calculation) 45,146 58,462    
Income (loss) from discontinued operations, net of tax (462) (337)    
Net income (loss) attributable to Iron Mountain Incorporated $ 44,684 $ 58,125    
Weighted-average shares—basic | shares 285,259,000 263,855,000    
Effect of dilutive potential stock options (in shares) | shares 249,564 461,761    
Effect of dilutive potential restricted stock, RSUs and PUs (in shares) | shares 484,314 492,905    
Weighted-average shares—diluted | shares 285,992,878 264,809,666    
Earnings (Losses) per share-basic:        
Income (Loss) from continuing operations (in dollars per share) | $ / shares $ 0.16 $ 0.22    
Total (loss) income discontinued operations (in dollars per share) | $ / shares 0.00 0.00    
Net Income (Loss) Attributable to Iron Mountain Incorporated (in dollars per share) | $ / shares 0.16 0.22    
Earnings (Losses) per share-diluted:        
Income (Loss) from continuing operations (in dollars per share) | $ / shares 0.16 0.22    
Total (loss) income from discontinued operations (in dollars per share) | $ / shares 0.00 0.00    
Net Income (Loss) Attributable to Iron Mountain Incorporated (in dollars per share) | $ / shares $ 0.16 $ 0.22    
Antidilutive stock options, RSUs and PUs, excluded from the calculation (in shares) | shares 3,242,141 2,494,255    
Income Taxes:        
Effective tax rates (as a percent) 2.50% 13.50%    
Income (Loss) From Continuing Operations Before Income Taxes, Minority Interest, and (Gain) Loss on Disposition of Real Estate $ 46,782 $ 68,064    
Provision (Benefit) for Income Taxes $ 1,168 $ 9,220    
Federal statutory tax rate (as a percent) 21.00% 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  
Cash and cash equivalents $ 442,491 295,628 $ 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  
Tax Provision, Increase, Amount   $ 1,764    
Tax Provision, Increase, Percentage   2.50%    
Money Market Funds, at Carrying Value 0   585,000  
Time Deposits, at Carrying Value $ 16,678   $ 24,482