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Share capital - Rio Tinto plc - Summary of share capital (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Disclosure Of Classes Of Share Capital [Line Items] |  |  |
Rio Tinto Limited shares were held by Rio Tinto plc | 0 | 0 | 0
Rio Tinto plc [member] |  |  |
Disclosure Of Classes Of Share Capital [Line Items] |  |  |
Issued and fully paid up share capital at beginning balance | $ 224 | $ 224 | $ 230
Shares purchased and cancelled | (4) |  | (6)
Issued and fully paid up share capital at ending balance | $ 220 | $ 224 | $ 224
Number of issued and fully paid up share capital at beginning balance | 1,384,520,000 | 1,384,487,000 | 1,425,378,000
Number of shares held by public at beginning balance | 1,384,520,000 | 1,384,487,000 |
Ordinary shares issued | 26,241 | 33,210 | 21,709
Shares purchased and cancelled | (32,937,000) |  | (40,913,000)
Shares purchased and cancelled | (32,937,109) | 0 | (40,912,881)
Number of issued and fully paid up share capital at ending balance | 1,351,609,000 | 1,384,520,000 | 1,384,487,000
Number of shares held by public at ending balance | 1,351,609,000 | 1,384,520,000 | 1,384,487,000
Rio Tinto plc [member] | Shares held by public [member] |  |  |
Disclosure Of Classes Of Share Capital [Line Items] |  |  |
Number of shares held by public at beginning balance | 1,374,822,000 | 1,374,046,000 | 1,414,147,000
Shares reissued from treasury | 147,000 | 743,000 | 790,000
Rio Tinto Limited shares were held by Rio Tinto plc | 9,551,000 | 9,698,000 | 10,441,000
Number of shares held by public at ending balance | 1,342,058,000 | 1,374,822,000 | 1,374,046,000
Rio Tinto plc [member] | Special voting share [member] |  |  |
Disclosure Of Classes Of Share Capital [Line Items] |  |  |
Other share classes | 1 only | 1 only | 1 only
Rio Tinto plc [member] | DLC dividend share [member] |  |  |
Disclosure Of Classes Of Share Capital [Line Items] |  |  |
Other share classes | 1 only | 1 only | 1 only
Rio Tinto plc [member] | Equalisation share [member] |  |  |
Disclosure Of Classes Of Share Capital [Line Items] |  |  |
Other share classes | 1 only | 1 only | 1 only

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