Common Stock Incentive Plan - Restricted Stock Activity (Details) - Restricted stock - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Number of shares
Outstanding nonvested shares, beginning of year	219,482	259,698	307,821
Shares granted	133,052	103,473	87,327
Shares vested	(124,505)	(141,486)	(126,363)
Shares forfeited	(15,399)	(2,203)	(9,087)
Outstanding nonvested shares, end of each period	212,630	219,482	259,698
Weighted average price
Outstanding nonvested shares, beginning of year (in dollars per share)	$ 63.69	$ 58.39	$ 53.44
Shares granted (in dollars per share)	64.27	67.84	69.83
Shares vested (in dollars per share)	61.57	56.94	54.45
Shares forfeited (in dollars per share)	65.09	66.48	55.71
Outstanding nonvested shares, end of each period (in dollars per share)	$ 65.20	$ 63.69	$ 58.39