Share-Based Compensation Arrangements (Share Options Activity) (Details) (Share Options [Member], USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share Options [Member]
Number of Share Options:
Beginning of period	645,797
Granted	54,600	106,775	57,450
Exercised	(258,351)
Forfeited or expired	(13,658)
End of period	428,388	645,797
Options exercisable	206,938
Options expected to vest in future periods	221,450
Weighted Average Exercise Price (in dollars per share):
Beginning of period	$ 23.58
Granted	$ 32.77
Exercised	$ 23.97
Forfeited or expired	$ 24.46
End of period	$ 24.50	$ 23.58
Options exercisable	$ 24.20
Options expected to vest in future periods	$ 24.77
Outstanding Weighted Average Remaining Contractual Term	5 years 11 months
Exercisable Weighted Average Remaining Contractual Term	3 years 4 months 20 days
Expected to Vest Weighted Average Remaining Contractual Term	8 years 3 months 23 days
Outstanding Aggregate Intrinsic Value	$ 5,451
Exercisable Aggregate Intrinsic Value	2,694
Expected to Vest Aggregate Intrinsic Value	$ 2,757