Increase decrease in investments in associates accounted for using equity method.

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- Definition

Percentage of ownership interest in associate.

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- Definition

Percentage of voting power held in associate

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Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

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- Definition

The fair value of investments in associates if there are quoted market prices for the investment. [Refer: Associates [member]; Investments in associates]

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- Definition

The amount of investments accounted for using the equity method. The equity method is a method of accounting whereby the investment is initially recognised at cost and adjusted thereafter for the post-acquisition change in the investor's share of net assets of the investee. The investor's profit or loss includes its share of the profit or loss of the investee. The investor's other comprehensive income includes its share of the other comprehensive income of the investee. [Refer: At cost [member]]

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- Definition

The amount of investments in associates accounted for using the equity method. [Refer: Associates [member]; Investments accounted for using equity method]

+ References

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- Definition

The amount of investments in joint ventures accounted for using the equity method. [Refer: Joint ventures [member]; Investments accounted for using equity method]

+ References

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- Definition

The entity's share of the other comprehensive income of associates and joint ventures accounted for using the equity method, net of tax. [Refer: Associates [member]; Investments accounted for using equity method; Joint ventures [member]; Other comprehensive income]

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- Definition

The entity's share of the profit (loss) of associates and joint ventures accounted for using the equity method. [Refer: Associates [member]; Investments accounted for using equity method; Joint ventures [member]; Profit (loss)]

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The entity's share of the total comprehensive income of associates and joint ventures accounted for using the equity method. [Refer: Associates [member]; Joint ventures [member]; Investments accounted for using equity method]

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Investments Accounted for Using Equity Method - Investments in Associates (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)	Dec. 31, 2020 USD ($)	Jun. 30, 2020	Nov. 30, 2019 TWD ($)	Feb. 28, 2019
Disclosure of associates [Line Items]
Investments in associates	$ 6,685,000,000		$ 7,139,000,000
Investment in joint venture	10,000,000		0
Investments accounted for using equity method	6,695,000,000		7,139,000,000		$ 238
The Company’s share of profits	244,000,000	$ 9	459,000,000	$ 509,000,000
Next Commercial Bank Co., Ltd. (“NCB”) [Member]
Disclosure of associates [Line Items]
Investments in associates	3,777,000,000		4,074,000,000				$ 4,190,000,000
Investments accounted for using equity method	$ 3,777,000,000		$ 4,074,000,000
Percentage of ownership in associates	41.90%		41.90%		41.90%		41.90%	41.90%
Percentage of voting rights in associates	42.00%		42.00%		42.00%
Senao Networks, Inc. ("SNI") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 841,000,000		$ 803,000,000
Percentage of ownership in associates	34.00%		34.00%		34.00%
Percentage of voting rights in associates	34.00%		34.00%		34.00%
Fair values based on the closing market prices	$ 1,708,000,000		$ 2,014,000,000
ST-2 Satellite Ventures Pte., Ltd. ("STS") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 488,000,000		$ 501,000,000
Percentage of ownership in associates	38.00%		38.00%		38.00%
Percentage of voting rights in associates	38.00%		38.00%		38.00%
International Integrated Systems, Inc. ("IISI") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 0		$ 335,000,000
Percentage of ownership in associates	0.00%		31.47%		0.00%	31.16%
Percentage of voting rights in associates	0.00%		31.00%		0.00%
Viettel-CHT Co., Ltd. ("Viettel-CHT") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 363,000,000		$ 317,000,000
Percentage of ownership in associates	30.00%		30.00%		30.00%
Percentage of voting rights in associates	30.00%		30.00%		30.00%
Taiwan International Standard Electronics Co., Ltd. ("TISE") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 324,000,000		$ 268,000,000
Percentage of ownership in associates	40.00%		40.00%		40.00%
Percentage of voting rights in associates	40.00%		40.00%		40.00%
Chunghwa PChome Fund I Co., Ltd. ("CPFI") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 193,000,000		$ 194,000,000
Percentage of ownership in associates	50.00%		50.00%		50.00%
Percentage of voting rights in associates	50.00%		50.00%		50.00%
KingwayTek Technology Co., Ltd. ("KWT") - Listed [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 213,000,000		$ 217,000,000
So-net Entertainment Taiwan Limited ("So-net") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 225,000,000		$ 186,000,000
Percentage of ownership in associates	30.00%		30.00%		30.00%
Percentage of voting rights in associates	30.00%		30.00%		30.00%
Taiwan International Ports Logistics Corporation ("TIPL") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 56,000,000		$ 51,000,000
Percentage of ownership in associates	27.00%		27.00%		27.00%
Percentage of voting rights in associates	27.00%		27.00%		27.00%
Click Force Co., Ltd. ("CF") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 33,000,000		$ 37,000,000
Percentage of ownership in associates	49.00%		49.00%		49.00%
Percentage of voting rights in associates	49.00%		49.00%		49.00%
KKBOX Taiwan Co., Ltd. ("KKBOXTW") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 163,000,000		$ 151,000,000
Percentage of ownership in associates	30.00%		30.00%		30.00%
Percentage of voting rights in associates	30.00%		30.00%		30.00%
Alliance Digital Tech Co., Ltd. ("ADT") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 3,000,000		$ 3,000,000
Percentage of ownership in associates	14.00%		14.00%		14.00%
Percentage of voting rights in associates	14.00%		14.00%		14.00%
Cornerstone Ventures Co., Ltd. ("CVC") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 6,000,000		$ 5,000,000
Percentage of ownership in associates	49.00%		49.00%		49.00%
Percentage of voting rights in associates	49.00%		49.00%		49.00%
MeWorks LIMITED (HK) ("MeWorks") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 0		$ 0
Percentage of ownership in associates	0.00%		20.00%		0.00%
Percentage of voting rights in associates	0.00%		20.00%		0.00%
UUPON Inc. ("UUPON") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 0
Increase (decrease) in Investments in associates			$ (3,000,000)
Percentage of ownership in associates	0.00%		22.00%		0.00%
Percentage of voting rights in associates	0.00%		22.00%		0.00%
KingwayTek Technology Co., Ltd. ("KWT") [Member]
Disclosure of associates [Line Items]
Percentage of ownership in associates	22.72%		22.52%		22.72%
Percentage of voting rights in associates	23.00%		23.00%		23.00%
Fair values based on the closing market prices	$ 676,000,000		$ 873,000,000
Associates [Member]
Disclosure of associates [Line Items]
The Company’s share of profits	540,000,000		575,000,000	509,000,000
The Company’s share of other comprehensive income (loss)	(8,000,000)		(3,000,000)	5,000,000
The Company’s share of total comprehensive income	$ 532,000,000		$ 572,000,000	$ 514,000,000