Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure Of Intangible Assets [Abstract]

Summary of Intangible Assets

	December 31
	2017		2018
	NT$		NT$
	(In Millions)
Carrying amount
3G and 4G concession	$	53,469	$	49,512
Computer software		880		959
Goodwill		209		209
Others		325		264
	$	54,883	$	50,944

	3G and 4G Concession			Computer Software			Goodwill			Others			Total
	NT$			NT$			NT$			NT$			NT$
	(In Millions)
Cost
Balance on January 1, 2016	$	59,209		$	3,249		$	236		$	409		$	63,103
Additions-acquired separately		—			277			—			5			282
Disposal		—			(121	)		—			—			(121	)
Effect of foreign exchange difference		—			—			—			—			—
Others		—			3			—			—			3
Balance on December 31, 2016	$	59,209		$	3,408		$	236		$	414		$	63,267
Accumulated amortization and impairment
Balance on January 1, 2016	$	(10,608	)	$	(1,983	)	$	(18	)	$	(47	)	$	(12,656	)
Amortization expenses		(2,805	)		(551	)		—			(23	)		(3,379	)
Disposal		—			121			—			—			121
Impairment losses		—			—			—			—			—
Effect of foreign exchange difference		—			—			—			—			—
Balance on December 31, 2016	$	(13,413	)	$	(2,413	)	$	(18	)	$	(70	)	$	(15,914	)
Cost
Balance on January 1, 2017	$	59,209		$	3,408		$	236		$	414		$	63,267
Additions-acquired separately		10,935			366			—			4			11,305
Disposal		—			(462	)		—			—			(462	)
Effect of foreign exchange difference		—			—			—			—			—
Balance on December 31, 2017	$	70,144		$	3,312		$	236		$	418		$	74,110
Accumulated amortization and impairment
Balance on January 1, 2017	$	(13,413	)	$	(2,413	)	$	(18	)	$	(70	)	$	(15,914	)
Amortization expenses		(3,262	)		(481	)		—			(23	)		(3,766	)
Disposal		—			462			—			—			462
Impairment losses		—			—			(9	)		—			(9	)
Effect of foreign exchange difference		—			—			—			—			—
Balance on December 31, 2017	$	(16,675	)	$	(2,432	)	$	(27	)	$	(93	)	$	(19,227	)
Cost
Balance on January 1, 2018	$	70,144		$	3,312		$	236		$	418		$	74,110
Additions-acquired separately		—			485			—			13			498
Disposal		—			(371	)		—			(58	)		(429	)
Effect of foreign exchange difference		—			—			—			—			—
Balance on December 31, 2018	$	70,144		$	3,426		$	236		$	373		$	74,179
Accumulated amortization and impairment
Balance on January 1, 2018	$	(16,675	)	$	(2,432	)	$	(27	)	$	(93	)	$	(19,227	)
Amortization expenses		(3,957	)		(406	)		—			(23	)		(4,386	)
Disposal		—			371			—			58			429
Impairment losses		—			—			—			(51	)		(51	)
Effect of foreign exchange difference		—			—			—			—			—
Balance on December 31, 2018	$	(20,632	)	$	(2,467	)	$	(27	)	$	(109	)	$	(23,235	)