Earnings per Share - Composition of Weighted-Average Common Shares (Denominator) Used in Basic and Diluted Earnings Per Share (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Weighted Average Number of Shares Issued, Basic	113,914,902	113,914,902
Average treasury shares (in shares)	(17,718,410)	(15,672,850)
Weighted Average Number of Shares, Deferred Compensation Plans	(55,544)	(38,453)
Average unearned nonvested shares	(114,082)	(79,972)
Weighted average common shares and common stock equivalents used to calculate basic earnings per share (in shares)	96,026,866	98,123,627
Additional common stock equivalents (nonvested stock) used to calculate diluted earnings per share	151,200	196,441
Weighted Average Number Of Additional Shares Deferred Compensation Plan	55,581	41,426
Weighted average common shares and common stock equivalents used to calculate diluted earnings per share (in shares)	96,233,647	98,361,494
Basic Earnings per Share (in dollars per share)	$ 0.41	$ 0.05
Diluted Earnings per Share (in dollars per share)	$ 0.41	$ 0.05