Stock-Based Compensation (Schedule of Fair Value of the Restricted Stock Awards Granted During the Periods) (Details) - Restricted Stock [Member] - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2019		Jun. 30, 2018		Jun. 30, 2019		Jun. 30, 2018
Time Vested [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	74,284		49,312		999,957		888,810
Estimated fair value (in millions)	$ 0.9	[1]	$ 1.0	[1]	$ 15.5	[2]	$ 17.1	[2]
Time Vested [Member] | Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	1,500		5,000		927,173		844,498
Estimated fair value (in millions)	$ 0.0	[1]	$ 0.1	[1]	$ 14.6	[2]	$ 16.2	[2]
Percentage of shares granted expected to be distributed	95.00%		95.00%		95.00%		95.00%
Time Vested [Member] | Non-employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	72,784		44,312		72,784		44,312
Estimated fair value (in millions)	$ 0.9	[1]	$ 0.9	[1]	$ 0.9	[2]	$ 0.9	[2]
Percentage of shares granted expected to be distributed	100.00%		100.00%		100.00%		100.00%
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	0		0		424,070		362,070
Estimated fair value (in millions)	$ 0.0	[1]	$ 0.0	[1]	$ 7.1	[2]	$ 7.3	[2]
Performance Shares [Member] | Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	0		0		424,070		362,070
Estimated fair value (in millions)	$ 0.0	[1]	$ 0.0	[1]	$ 7.1	[2]	$ 7.3	[2]
Percentage of shares granted expected to be distributed					54.00%		74.00%
Performance Shares [Member] | Non-employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	0		0		0		0
Estimated fair value (in millions)	$ 0.0	[1]	$ 0.0	[1]	$ 0.0	[2]	$ 0.0	[2]

[1] The performance shares represent 100% of the grant date fair value. (We recognize the grant date fair value minus estimated forfeitures.)

[2] The performance shares represent 100% of the grant date fair value. (We recognize the grant date fair value minus estimated forfeitures.)