Earnings Per Share - Number of Potential Common Shares that have been Excluded from Computation of Diluted Earnings Per Share for Indicated Period Due to Their Anti-Dilutive Nature (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Potential common shares	1,082	1,233	1,379