Share-Based Arrangements (Stock Options Activity) (Details) - Stock Options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Options, Outstanding [Roll Forward]
Outstanding at beginning of period (in shares)	958,679
Granted (in shares)	226,315
Exercised (in shares)	(201,767)
Forfeited or expired (in shares)	(57,842)
Outstanding at end of period (in shares)	925,385	958,679
Options, Weighted Average Exercise Price [Roll Forward]
Outstanding at beginning of period (in dollars per share)	$ 36.18
Granted (in dollars per share)	51.97
Exercised (in dollars per share)	32.44
Forfeited or expired (in dollars per share)	43.02
Outstanding at end of period (in dollars per share)	$ 40.43	$ 36.18
Options, Additional Disclosures [Abstract]
Weighted-average remaining contractual term - options outstanding	6 years 5 months
Aggregate intrinsic value - options outstanding				$ 17,034
Weighted-average exercise price - options outstanding (in dollars per share)	$ 36.18	$ 36.18		$ 40.43
Options exercisable (in shares)				378,725
Weighted-average remaining contractual term - options exercisable	4 years 5 months
Aggregate intrinsic value - options exercisable				$ 9,571
Weighted-average exercise price - options exercisable (in dollars per share)				$ 33.57
Intrinsic value of options exercised	$ 3,900	$ 3,900	$ 1,000
Options, Fair Value Assumptions and Methodology [Abstract]
Expected option term	5 years	5 years 2 months	5 years 1 month
Expected volatility	19.90%	26.00%	29.00%
Risk-free interest rate	1.90%	1.20%	1.60%
Expected dividend yield	1.60%	1.80%	1.60%
Per share fair value of options granted	$ 8.61	$ 8.63	$ 9.28