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Net Income and Other Comprehensive Income (Loss) - Other Income and Expenses (Detail)
$ in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2017
TWD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
TWD ($)
Dec. 31, 2015
TWD ($)
Analysis Of Income And Expense [Abstract]        
Loss on disposal of property, plant and equipment $ (107)   $ (48) $ (109)
Impairment loss on property, plant and equipment 0 $ 0 (596) (138)
Reversal of impairment loss 11 0 148 142
Loss on disposal of intangible assets 0 0 0 0
Impairment losses (9) 0 0 0
Other income and expenses $ (105) $ (3) $ (496) $ (105)