Share and Unit-based Plans - Stock Option Activity (Details) - Stock options - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Options
Balance at beginning of year (shares)	35,565	35,565	10,565
Granted (shares)	0	0	25,000
Exercised (in shares)	0	0	0
Balance at end of year (shares)	35,565	35,565	35,565
Weighted Average Exercise Price (in dollars per share)
Balance at beginning of year (in dollars per share)	$ 57.32	$ 57.32	$ 56.77
Granted (in dollars per share)	0	0	57.55
Exercised (in dollars per share)	0	0	0
Balance at end of year (in dollars per share)	$ 57.32	$ 57.32	$ 57.32