Net Income Per Share (EPS) (Schedule of Weighted Average Number of Shares) (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Basic shares	46,593	47,343	47,906
Contingently issuable shares	58	79	77
Diluted shares	48,226	48,813	49,224
Antidilutive shares	184	136	212
Employee Stock Options [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Share-based awards	151	129	111
Restricted Stock Units [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Share-based awards	1,424	1,262	1,130