Stock-Based Incentive Compensation Plans (Summary of activity for performance shares) (Details) - Performance Shares [Member]	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Shares:
Outstanding as of beginning of year (in shares) | shares	546,225
Granted (in shares) | shares	202,484
Vested (in shares) | shares	(258,384)
Forfeited (in shares) | shares	(19,254)
Outstanding as of end of year (in shares) | shares	471,071
Weighted-Average Grant Date Fair Value
Weighted-average grant date fair value, outstanding as of beginning of year (in dollars per share) | $ / shares	$ 59.46
Weighted-average grant date fair value, granted (in dollars per share) | $ / shares	66.89
Weighted-average grant date fair value, vested (in dollars per share) | $ / shares	31.22
Weighted-average grant date fair value, forfeited (in dollars per share) | $ / shares	80.53
Weighted-average grant date fair value, outstanding as of end of year (in dollars per share) | $ / shares	$ 77.29