Share-Based Payments - Summary of Restricted Stock Awards and Stock Performance Awards (Details)	6 Months Ended
	Jun. 30, 2021 $ / shares shares
Stock Awards
Shares
Beginning of year (in shares) | shares	128,664
Granted (in shares) | shares	57,650
Vested (in shares) | shares	(46,371)
Forfeited (in shares) | shares	(1,577)
End of year (in shares) | shares	138,366
Weighted Average Grant-Date Fair Value
Beginning of year (in dollars per share) | $ / shares	$ 44.30
Granted (in dollars per share) | $ / shares	43.10
Vested (in dollars per share) | $ / shares	43.04
Forfeited (in dollars per share) | $ / shares	40.77
End of year (in dollars per share) | $ / shares	$ 44.26
Stock Performance Awards
Shares
Beginning of year (in shares) | shares	164,600
Granted (in shares) | shares	79,000
Vested (in shares) | shares	(54,000)
Forfeited (in shares) | shares	0
End of year (in shares) | shares	189,600
Weighted Average Grant-Date Fair Value
Beginning of year (in dollars per share) | $ / shares	$ 42.32
Granted (in dollars per share) | $ / shares	38.34
Vested (in dollars per share) | $ / shares	35.73
Forfeited (in dollars per share) | $ / shares	0
End of year (in dollars per share) | $ / shares	$ 42.54