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Additional Information of Expenses by Nature - Summary of Additional Information of Expenses by Nature (Detail)
$ in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2017
TWD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
TWD ($)
Dec. 31, 2015
TWD ($)
Expense by nature [line items]        
Depreciation of property, plant and equipment $ 255,796.0 $ 8,630.1 $ 220,085.0 $ 219,303.4
Amortization of intangible assets 4,346.7 146.6 3,743.4 3,202.2
Research and development costs expensed as incurred 80,732.5 $ 2,723.8 71,207.7 65,544.6
Defined contribution plans 2,369.9   2,164.9 2,002.6
Defined benefit plans 271.5   272.2 278.9
Post-employment benefits 2,641.4   2,437.1 2,281.5
Other employee benefits 101,488.7   97,248.0 88,929.4
Employee benefits expenses 104,130.1   99,685.1 91,210.9
Cost of revenue [member]        
Expense by nature [line items]        
Depreciation of property, plant and equipment 235,985.2   203,476.8 204,126.2
Amortization of intangible assets 2,135.5   2,028.5 1,642.1
Defined benefit plans 175.3   177.0 189.5
Employee benefits expenses 61,026.1   58,493.5 52,983.2
Operating expenses [member]        
Expense by nature [line items]        
Depreciation of property, plant and equipment 19,746.3   16,583.1 15,152.2
Amortization of intangible assets 2,211.2   1,714.9 1,560.1
Employee benefits expenses 43,104.0   41,191.6 38,227.7
Other operating income and expenses [member]        
Expense by nature [line items]        
Depreciation of property, plant and equipment $ 64.5   $ 25.1 $ 25.0