Earnings per Share - Composition of Weighted-Average Common Shares (Denominator) Used in Basic and Diluted Earnings Per Share (Detail) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Weighted Average Number of Shares Issued, Basic	113,914,902	113,914,902	113,914,902	113,914,902
Average treasury shares (in shares)	(15,788,359)	(15,398,192)	(15,730,604)	(15,345,018)
Weighted Average Number of Shares, Deferred Compensation Plans	(41,426)	(37,411)	(39,939)	(37,411)
Average unearned nonvested shares	(152,784)	(132,625)	(116,379)	(119,981)
Weighted average common shares and common stock equivalents used to calculate basic earnings per share (in shares)	97,932,333	98,346,674	98,027,980	98,412,492
Additional common stock equivalents (nonvested stock) used to calculate diluted earnings per share	173,095	216,524	185,023	201,907
Weighted Average Number Of Additional Shares Deferred Compensation Plan	41,426	37,411	41,426	37,411
Weighted average common shares and common stock equivalents used to calculate diluted earnings per share (in shares)	98,146,854	98,600,609	98,254,429	98,651,810
Basic Earnings per Share (in dollars per share)	$ 0.24	$ 0.28	$ 0.29	$ 0.53
Diluted Earnings per Share (in dollars per share)	$ 0.24	$ 0.28	$ 0.29	$ 0.53