Stock-Based Compensation (Components Of SBP And ESUP) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) shares
SBP 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee contributions	$ 3.2
Less diversified contributions	0.7
Total employee stock contributions	2.5
Employer premium contribution to diversified investment accounts
Shares purchased by employees and company match | shares	100,000.0
ESUP 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee contributions	$ 3.8
Less diversified contributions	0.0
Total employee stock contributions	3.8
Employer premium contribution to diversified investment accounts	$ 0.7