Stock-Based Compensation Plans - Summary of Performance of Share Activity for Annual Awards (Detail) - Performance Shares [Member] - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Target share pay-out	16,716	10,479	12,971
Actual share pay-out (paid in following year)	19,400	10,479	8,094
Weighted average fair value per share on grant date	$ 223.81	$ 202.04	$ 155.53