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Property, Plant and Equipment - Additional Information (Detail)
$ in Millions
 1 Months Ended 12 Months Ended
May 31, 2020
TWD ($)
Dec. 31, 2021
TWD ($)
Dec. 31, 2021
USD ($)
Dec. 31, 2020
TWD ($)
Dec. 31, 2019
TWD ($)
Disclosure Of Property Plant And Equipment [Line Items]          
Impairment loss on property, plant and equipment   $ 0 $ 0 $ 0 $ 93,000,000
Land [Member] | Property, plant and equipment subject to operating leases [member] | Bottom of Range [Member]          
Disclosure Of Property Plant And Equipment [Line Items]          
Lease period   1 year 1 year    
Land [Member] | Property, plant and equipment subject to operating leases [member] | Top of Range [Member]          
Disclosure Of Property Plant And Equipment [Line Items]          
Lease period   20 years 20 years    
Buildings [Member] | Property, plant and equipment subject to operating leases [member] | Bottom of Range [Member]          
Disclosure Of Property Plant And Equipment [Line Items]          
Lease period   1 year 1 year    
Buildings [Member] | Property, plant and equipment subject to operating leases [member] | Top of Range [Member]          
Disclosure Of Property Plant And Equipment [Line Items]          
Lease period   20 years 20 years    
Assets Used by the Company [Member]          
Disclosure Of Property Plant And Equipment [Line Items]          
Impairment loss on property, plant and equipment   $ 0   0  
Gain (loss) on disposals, property, plant and equipment       1,268,000,000  
Assets Used by the Company [Member] | Land [Member]          
Disclosure Of Property Plant And Equipment [Line Items]          
Carrying amount of trade-out of land       37,000,000  
Assets Used by the Company [Member] | Buildings [Member]          
Disclosure Of Property Plant And Equipment [Line Items]          
Fair value of property, plant and equipment materially different from carrying amount       $ 1,305,000,000  
Chunghwa Precision Test Tech. Co., Ltd. (CHPT) [Member] | Assets Used by the Company [Member]          
Disclosure Of Property Plant And Equipment [Line Items]          
Recoverable amount of asset         0
Impairment loss on property, plant and equipment         89,000,000
Chunghwa System Integration Co., Ltd. (CHSI) [Member] | Assets Used by the Company [Member]          
Disclosure Of Property Plant And Equipment [Line Items]          
Recoverable amount of asset         0
Impairment loss on property, plant and equipment         $ 4,000,000
MOTC [Member] | Assets Used by the Company [Member]          
Disclosure Of Property Plant And Equipment [Line Items]          
Difference between assessed value and construction cost of land $ 1,057,000,000