Earnings per Share - Composition of Weighted-Average Common Shares (Denominator) Used in Basic and Diluted Earnings Per Share (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Weighted Average Number of Shares, Deferred Compensation Plans	37,496	37,411	37,411
Weighted average common shares issued	113,914,902	113,914,902	111,809,880
Average treasury shares	(15,447,299)	(14,747,687)	(16,463,079)
Average unearned nonvested shares	(112,320)	(93,641)	(89,334)
Weighted average common shares and common stock equivalents used to calculate basic earnings per share	98,317,787	99,036,163	95,220,056
Additional common stock equivalents (nonvested stock) used to calculate diluted earnings per share	231,957	149,939	73,570
Weighted average common shares and common stock equivalents used to calculate diluted earnings per share	98,588,164	99,223,513	95,331,037
Weighted Average Number Of Additional Shares Deferred Compensation Plan	38,420	37,411	37,411
Basic Earnings Per Share (in dollars per share)	$ 1.07	$ 1.09	$ 0.58
Diluted Earnings Per Share (in dollars per share)	$ 1.07	$ 1.08	$ 0.58