Performance Incentive Plan (Other Grants) (Details)	12 Months Ended
	Dec. 31, 2020 $ / shares shares
Other share grants under the 2017 Plan:
Restricted shares granted (in shares)	35,251
Restricted shares granted, weighted average share price (in dollars per share) | $ / shares	$ 32.27
Shares available under the 2017 Plan for grant, end of period (in shares)	793,843
Directors’ fees
Other share grants under the 2017 Plan:
Restricted shares granted (in shares)	17,596
Restricted shares granted, weighted average share price (in dollars per share) | $ / shares	$ 37.56
Deferred directors’ fees
Other share grants under the 2017 Plan:
Restricted shares granted (in shares)	17,655
Restricted shares granted, weighted average share price (in dollars per share) | $ / shares	$ 37.21