Shareholders Equity - Summary of Changes in Shareholders Equity (Parenthetical) (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Stockholders Equity Note [Line Items]
Tax provision (benefit) for recognized net actuarial loss (gain)	$ (35)	$ (31)
Unrecognized Pension Benefit Cost [Member]
Stockholders Equity Note [Line Items]
Tax provision (benefit) for recognized net actuarial loss (gain)	$ 35	$ 31
Treasury Stock [Member]
Stockholders Equity Note [Line Items]
Purchase of common shares	52,590	75,246
Common Shares [Member]
Stockholders Equity Note [Line Items]
Issuance of common shares	63,316	77,381
Common Shares Issued to Rabbi Trust [Member]
Stockholders Equity Note [Line Items]
Common shares distributed from rabbi trust	3,727	3,358
Deferred Compensation Liability [Member]
Stockholders Equity Note [Line Items]
Common shares distributed from rabbi trust	3,727	3,358
Retained Earnings [Member]
Stockholders Equity Note [Line Items]
Cash dividends declared per share	$ 0.20	$ 0.20