Share-Based Compensation Arrangements (Share Options Activity) (Details) - Stock Options [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Share Options:
Beginning of period	223,853
Granted	47,950	47,725	53,400
Exercised	(29,738)
Forfeited or expired	(19,450)
End of period	222,615	223,853
Options exercisable	87,990
Options expected to vest in future periods	134,625
Weighted Average Exercise Price (in dollars per share):
Beginning of period	$ 38.68
Granted	54.74
Exercised	27.57
Forfeited or expired	46.71
End of period	42.92	$ 38.68
Options exercisable	31.18
Options expected to vest in future periods	$ 50.60
Outstanding Weighted Average Remaining Contractual Term	7 years 1 month 24 days
Exercisable Weighted Average Remaining Contractual Term	4 years 8 months 5 days
Expected to Vest Weighted Average Remaining Contractual Term	8 years 9 months 2 days
Outstanding Aggregate Intrinsic Value	$ 1,790
Exercisable Aggregate Intrinsic Value	1,439
Expected to Vest Aggregate Intrinsic Value	$ 351