Net Revenue - Additional Information (Detail) - TWD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Jan. 01, 2018
Disclosure of contract liabilities [line items]
Revenue from the beginning balance of contract liability	$ 31,770.0
Accrued expenses and other current liabilities [member]
Disclosure of contract liabilities [line items]
Revenue from the beginning balance of contract liability	4,684.0	$ 32,434.8
Estimated sales returns and other allowances	55,406.0
Refund liabilities	$ 22,672.6

The amount of an entity’s obligation to transfer goods or services to a customer for which the entity has received consideration (or the amount is due) from the customer.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 15
-IssueDate 2018-01-01
-Paragraph 105
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=15&date=2018-03-01&anchor=para_105&doctype=Standard
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 15
-IssueDate 2018-01-01
-Paragraph 116
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=15&date=2018-03-01&anchor=para_116_a&doctype=Standard
-URIDate 2018-03-16

Name:	ifrs-full_ContractLiabilities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant