Common Stock and Earnings Per Share - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2018	Dec. 31, 2019
Class Of Stock [Line Items]
Common stock share repurchase program, number of shares authorized to be repurchased	2,000,000	2,000,000	2,000,000
Total number of shares repurchased	653,498	780,321
BAML Share Repurchase Agreement [Member]
Class Of Stock [Line Items]
Aggregate amount of common stock, shares to be repurchase	$ 30,000,000.0	$ 50,000,000.0
Total number of shares repurchased	653,498	780,321