Share-based Compensation (Restricted Stock Awards And Restricted Stock Units Activity Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restricted Stock Awards [Member]
Schedule of Restricted Stock Award and Restricted Stock Unit Activity [Line Items]
Grant date fair value of awards	$ 0.2
Unrecognized share-based compensation expense related to unvested awards	$ 0.1
Amortized over a weighted average period	5 months 5 days
RSUs vested in period (shares)	29,000
Restricted Stock Units [Member]
Schedule of Restricted Stock Award and Restricted Stock Unit Activity [Line Items]
Grant date fair value of awards	$ 8.3	$ 8.0	$ 8.2
RSUs vested in period (shares)	764,000
Time-based Restricted Stock Units [Member]
Schedule of Restricted Stock Award and Restricted Stock Unit Activity [Line Items]
Shares authorized for grant	1,100,000	1,000,000	1,200,000
Unrecognized share-based compensation expense related to unvested awards	$ 9.9
Amortized over a weighted average period	1 year 6 months 22 days
RSUs vested in period (shares)	696,083	599,071	437,132
Performance-based Restricted Stock Units [Member]
Schedule of Restricted Stock Award and Restricted Stock Unit Activity [Line Items]
Shares authorized for grant	1,300,000	1,200,000	1,500,000
Unrecognized share-based compensation expense related to unvested awards	$ 3.8
Amortized over a weighted average period	1 year 11 months 9 days
RSUs vested in period (shares)	68,317	31,396	67,893