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Share and Unit-based Plans - Stock Units Roll Forward Activity (Details) - Stock units
12 Months Ended
Dec. 31, 2019
$ / shares
shares
Dec. 31, 2018
$ / shares
shares
Dec. 31, 2017
$ / shares
shares
Share-based Payment Arrangement [Abstract]      
Number of common shares into which units can be converted (shares) 1    
Shares or Units      
Balance at beginning of year (shares) | shares 129,457 151,355 148,428
Granted (shares) | shares 160,932 87,983 86,827
Vested (shares) | shares (85,157) (108,991) (81,205)
Forfeited (shares) | shares (5,245) (890) (2,695)
Balance at end of year (shares) | shares 199,987 129,457 151,355
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]      
Balance at beginning of year (in dollars per share) | $ / shares $ 64.21 $ 73.32 $ 78.53
Granted (in dollars per share) | $ / shares 37.44 58.79 66.46
Vested (in dollars per share) | $ / shares 62.84 74.04 75.62
Forfeited (in dollars per share) | $ / shares 51.48 68.81 69.57
Balance at end of year (in dollars per share) | $ / shares $ 43.59 $ 64.21 $ 73.32