Stock-Based Incentive Plans (Schedule of Performance-Based Restricted Stock and Restricted Stock Units Rollforward) (Details) - Operating performance-based restricted stock units - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Non-vested shares, beginning of year (in shares)	285,669
Granted (in shares)	185,940
Vested, shares (in shares)	(63,305)
Forfeited, shares (in shares)	(27,505)
Non-vested shares, end of year (in shares)	380,799	285,669
Wtd. Avg. Grant Date Fair Value
Balance beginning of year (in dollars per share)	$ 71.02
Granted (in dollars per share)	41.70	$ 98.50	$ 95.62
Vested (in dollars per share)	41.79
Forfeited (in dollars per share)	64.35
Balance end of year (in dollars per share)	$ 56.55	$ 71.02