Stock-Based Compensation (Schedule Of Stock Unit Information) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Total Units
Non-vested (in shares)	0.6
Granted based on current service (in shares)	0.5
Granted based on future conditions (in shares)	0.5
Vested (in shares)	(0.6)
Difference between maximum and actual payout (in shares)	(0.2)
Non-vested (in shares)	0.8	0.6
Fully vested stock units outstanding (in shares)	3.6
Weighted Average Grant Date Fair Value per Unit
Non-vested, Weighted Average Grant Date Fair Value (in dollars per share)	$ 19.56
Granted based on current service (in dollars per share)	42.71
Granted based on future conditions (in dollars per share)	27.48
Vested (in dollars per share)	42.01
Difference between maximum and actual payout (in dollars per share)	0.00
Non-vested, Weighted Average Grant Date Fair Value (in dollars per share)	$ 38.43	$ 19.56
Aggregate Intrinsic Value
Total non-vested	$ 28.2
Fully vested shares available for issuance	$ 131.8
Performance Stock Unit Awards
Weighted Average Grant Date Fair Value per Unit
Granted based on future conditions (in dollars per share)	$ 40.92
DSU
Total Units
Non-vested (in shares)	0.0
Granted based on current service (in shares)	0.2
Granted based on future conditions (in shares)	0.0
Vested (in shares)	(0.2)
Difference between maximum and actual payout (in shares)	0.0
Non-vested (in shares)	0.0	0.0
ESUP
Total Units
Non-vested (in shares)	0.0
Granted based on current service (in shares)	0.2
Granted based on future conditions (in shares)	0.0
Vested (in shares)	(0.2)
Difference between maximum and actual payout (in shares)	0.0
Non-vested (in shares)	0.0	0.0
PSU
Total Units
Non-vested (in shares)	0.4
Granted based on current service (in shares)	0.0
Granted based on future conditions (in shares)	0.5
Vested (in shares)	0.0
Difference between maximum and actual payout (in shares)	(0.2)
Non-vested (in shares)	0.7	0.4
RSU
Total Units
Non-vested (in shares)	0.1
Granted based on current service (in shares)	0.1
Granted based on future conditions (in shares)	0.0
Vested (in shares)	(0.1)
Difference between maximum and actual payout (in shares)	0.0
Non-vested (in shares)	0.1	0.1
PGI
Total Units
Non-vested (in shares)	0.1
Granted based on current service (in shares)	0.0
Granted based on future conditions (in shares)	0.0
Vested (in shares)	(0.1)
Difference between maximum and actual payout (in shares)	0.0
Non-vested (in shares)	0.0	0.1
Maximum | Performance Stock Unit Awards
Aggregate Intrinsic Value
Base award percentage of total shareholder return	200.00%	175.00%
Maximum | PGI
Aggregate Intrinsic Value
Base award percentage of total shareholder return	250.00%