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Fair Value Measurements (Narrative) (Details) - USD ($) | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Fair Value Measurements [Abstract] |  |  |
Transfers of assets and liabilities between level 1, 2, 3 | $ 0 | $ 0 | $ 0

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- Definition Amount of transfers of financial instruments classified in shareholders' equity measured on a recurring basis betwee level 1, 2, 3 of the fair value hierarchy. + References No definition available. + Details
Name: | rdi_FairValueEquityBetweenLevelsOneTwoThreeTransfersAmount
Namespace Prefix: | rdi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_FairValueDisclosuresAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration