Share-Based Compensation Plans - Performance Share Units (Details) - Performance Shares - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Payout Levels (in units):
Threshold Award (in shares)	59,698	61,381	42,361	57,563
Target Award (in shares)	119,395	122,761	84,726	115,125
Outstanding Award (in shares)	238,790	245,522	169,452	230,250
Shares Issued (in shares)				88,807
Payout Achieved Over Performance Period			42,361