Contents of Significant Accounts - Summary of disposed and derecognized partial equity instrument investments measured at fair value through other comprehensive income (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Disposed And Derecognized Partial Equity Instrument Investments Measured At Fair Value Through Other Comprehensive Income [Abstract]
Fair value on the date of sale	$ 2,348,454	$ 0
Cumulative gains (losses) reclassified to retained earnings due to derecognition	$ (551,903)	$ 0