Stock Based Compensation (Narrative) (Details) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) years $ / shares shares	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares
Number of shares authorized for stock based employee and non-employee compensation plans | shares	13.0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested | $	$ 13.9	$ 16.1	$ 14.3
Employee [Member]
RSUs, vesting period (in years)	5
Director [Member]
RSUs, annual vesting percentage	100.00%
RSUs, vesting period (in years)	1
RSUs, contractual lives (in years)	1
Restricted Stock Units (RSUs) [Member]
Compensation expense recognized | $	$ 11.8	$ 11.7	$ 12.3
Total unrecognized compensation expense | $	$ 6.4
Total unrecognized compensation expense, weighted average recognition period	1 year 7 months
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value | $ / shares	$ 19.31	$ 21.15	$ 16.15
RSUs | $ / shares	$ 18.16	$ 17.26	$ 15.03
2015 Award Date [Member] | Employee [Member]
RSUs, vesting period (in years)	3