Common Stock and Earnings Per Share - Summary of Share Transactions (Detail) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Shares Issued, Beginning Balance	55,056,730	55,056,730	55,056,730
Shares Issued, Ending Balance	55,056,730	55,056,730	55,056,730
Shares in Treasury, Beginning Balance	(5,959,124)	(5,939,508)	(5,161,740)
Accelerated Share Repurchase Program	(653,498)		(780,321)
Purchase of Treasury Stock	(563,830)	(124,109)	(401,038)
Sale of Treasury Stock	11,372	12,968	14,631
Issued for stock options and restricted stock	114,736	91,525	388,960
Shares in Treasury, Ending Balance	(7,050,344)	(5,959,124)	(5,939,508)