Stock-Based Incentive Compensation Plans (Summary of activity for performance shares) (Details) - Performance Shares [Member]	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Summary of activity for performance shares [Roll Forward]
Outstanding as of beginning of year (in shares) | shares	556,949
Granted (in shares) | shares	156,676
Vested (in shares) | shares	(137,308)
Forfeited (in shares) | shares	(30,092)
Outstanding as of end of year (in shares) | shares	546,225
Performance shares, additional disclosures [Abstract]
Weighted-average grant date fair value, outstanding as of beginning of year (in dollars per share) | $ / shares	$ 53.65
Weighted-average grant date fair value, granted (in dollars per share) | $ / shares	89.89
Weighted-average grant date fair value, vested (in dollars per share) | $ / shares	68.35
Weighted-average grant date fair value, forfeited (in dollars per share) | $ / shares	69.62
Weighted-average grant date fair value, outstanding as of end of year (in dollars per share) | $ / shares	$ 59.46