Share-Based Compensation (RSU Activity During the Year) (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Outstanding and unvested, beginning balance, in shares	721,639	803,699	835,749
RSUs, granted, in shares	268,465	327,411	372,443
RSUs, vested, in shares	(364,817)	(389,285)	(370,397)
RSUs, cancelled, in shares	(20,947)	(20,186)	(34,096)
Outstanding and unvested, ending balance, in shares	604,340	721,639	803,699
Weighted average grant date fair value, beginning of Period, in dollars per share	$ 78.40	$ 67.09	$ 56.95
Weighted average grant date fair value, granted, in dollars per share	102.98	90.07	81.09
Weighted average grant date fair value, vested, in dollars per share	70.26	64.88	58.56
Weighted average grant date fair value, cancelled, in dollars per share	89.64	77.95	63.79
Weighted average grant date fair value, end of Period, in dollars per share	$ 93.56	$ 78.40	$ 67.09