XML 32 R124.htm IDEA: XBRL DOCUMENT v3.20.1
Retirement Benefit Plans - Movements in Fair Value of Plan Assets (Detail) - Fair value of plan assets [member] - TWD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Disclosure of fair value of plan assets [line items]      
Balance, beginning of year $ 4,011.3 $ 3,923.9 $ 3,929.1
Interest income 51.4 63.7 59.1
Remeasurement:      
Return on plan assets (excluding amounts included in net interest expense) 124.4 71.3 (29.3)
Contributions from employer 458.6 226.7 226.9
Benefits paid from plan assets (344.1) (274.3) (261.9)
Balance, end of year $ 4,301.6 $ 4,011.3 $ 3,923.9