Accounting Policies - Earnings Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Weighted average number of common shares used for basic EPS (in Shares)	33,150,949	34,713,937	36,554,437
Effect of dilutive stock options and restricted and deferred stock unit awards (in Shares)	0	496,493	0
Weighted average number of common shares and dilutive potential common stock used in dilutive EPS (in Shares)	33,150,949	35,210,430	36,554,437
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of EPS (in Shares)	735,577		324,804
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of EPS (in Shares)	73,897	77,807	164,014