Capital Stock - Schedule of Change in Treasury Shares (Detail) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Stockholders Equity Note [Abstract]
Beginning balance	1,808,133	9,665
Rabbi trust shares distributed and/or sold	(2,338)	(1,532)
Shares repurchased	8,200,000	1,800,000
Ending balance	10,005,795	1,808,133