Share and Unit-based Plans - Stock Option Activity (Details) - Stock options - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Options
Balance at beginning of year (in shares)	35,565	35,565	35,565
Granted (in shares)	1,950	0	0
Balance at end of year (in shares)	37,515	35,565	35,565
Weighted Average Exercise Price
Balance at beginning of year (in dollars per share)	$ 57.32	$ 57.32	$ 57.32
Granted (in dollars per share)	0	0	0
Balance at end of year (in dollars per share)	$ 54.34	$ 57.32	$ 57.32