Earnings Per Share - Additional Information (Detail) - shares shares in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restricted Stock Awards [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Options to purchase common shares not included in the computation of diluted EPS	0.9	0.7	0.7
Stock options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Options to purchase common shares not included in the computation of diluted EPS	0.3	0.3
Options to purchase common shares included in the computation of diluted EPS			0.4