Stock Based Compensation (Outstanding Employee Stock Awards) (Details) - $ / shares	May 15, 2019	May 03, 2019	May 17, 2018	May 18, 2017	Jun. 30, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested shares (in shares)					1,411,303
Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date fair value (in dollars per share)					$ 25.64	$ 23.14
Unvested shares (in shares)					1,411,303	1,227,483
Deferred Stock Awards | Deferred Stock Award, Granted May 18, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted (in shares)				196,036
Grant date fair value (in dollars per share)				$ 21.38
Unvested shares (in shares)					41,341
Deferred Stock Awards | Deferred Stock Award, Granted May 18, 2017 | Year 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage				25.00%
Deferred Stock Awards | Deferred Stock Award, Granted May 18, 2017 | Year 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage				25.00%
Deferred Stock Awards | Deferred Stock Award, Granted May 18, 2017 | Year 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage				25.00%
Deferred Stock Awards | Deferred Stock Award, Granted May 18, 2017 | Year 4
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage				25.00%
Deferred Stock Awards | Deferred Stock Award, Granted May 17, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted (in shares)			271,169
Grant date fair value (in dollars per share)			$ 17.84
Unvested shares (in shares)					109,306
Deferred Stock Awards | Deferred Stock Award, Granted May 17, 2018 | Year 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			25.00%
Deferred Stock Awards | Deferred Stock Award, Granted May 17, 2018 | Year 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			25.00%
Deferred Stock Awards | Deferred Stock Award, Granted May 17, 2018 | Year 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			25.00%
Deferred Stock Awards | Deferred Stock Award, Granted May 17, 2018 | Year 4
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			25.00%
Deferred Stock Awards | Deferred Stock Award, Granted May 15,2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted (in shares)	25,974
Grant date fair value (in dollars per share)	$ 20.79
Unvested shares (in shares)					25,974
Deferred Stock Awards | Deferred Stock Award, Granted May 15,2019 | Board of Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	100.00%
Deferred Stock Awards | Deferred Stock Award, Granted May 3, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted (in shares)		300,825
Grant date fair value (in dollars per share)		$ 21.04
Unvested shares (in shares)					196,633
Deferred Stock Awards | Deferred Stock Award, Granted May 3, 2019 | Year 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		25.00%
Deferred Stock Awards | Deferred Stock Award, Granted May 3, 2019 | Year 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		25.00%
Deferred Stock Awards | Deferred Stock Award, Granted May 3, 2019 | Year 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		25.00%
Deferred Stock Awards | Deferred Stock Award, Granted May 3, 2019 | Year 4
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		25.00%
Performance Share Awards | Performance Share Program Award, Granted May 18, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted (in shares)				0
Grant date fair value (in dollars per share)				$ 30.45
Unvested shares (in shares)					286,670
Performance Share Awards | Performance Share Program Award, Granted May 17, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted (in shares)			0
Grant date fair value (in dollars per share)			$ 23.52
Unvested shares (in shares)					366,032
Performance Share Awards | Performance Share Program Award, Granted May 3, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted (in shares)		0
Grant date fair value (in dollars per share)		$ 29.43
Unvested shares (in shares)					385,347