Incentive Award Plan - Narrative (Details) - USD ($)
$ in Millions |
3 Months Ended |
9 Months Ended |
|
Sep. 30, 2017 |
Sep. 30, 2016 |
Sep. 30, 2017 |
Sep. 30, 2016 |
Dec. 31, 2016 |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
|
|
| Unamortized stock-based compensation expense |
$ 20.6
|
|
$ 20.6
|
|
|
| General and administrative expense |
|
|
|
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
|
|
| Stock-based compensation expense |
$ 2.3
|
$ 3.4
|
13.8
|
$ 7.2
|
|
| General and administrative expense | Chief Executive Officer |
|
|
|
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
|
|
| Stock-based compensation expense |
|
|
6.9
|
|
|
| Non-vested Shares of Restricted Stock |
|
|
|
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
|
|
| Deferred compensation expense |
|
|
$ 9.9
|
|
|
| Outstanding unvested shares |
1,500,000
|
|
1,500,000
|
|
|
| Unamortized stock-based compensation expense |
$ 11.9
|
|
$ 11.9
|
|
|
| Non-vested Shares of Restricted Stock | Executives Officers And Employees |
|
|
|
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
|
|
| Grants in period (in shares) |
|
|
1,100,000
|
|
|
| Performance Shares |
|
|
|
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
|
|
| Approved initial target grant (in shares) |
|
|
900,000
|
|
|
| Minimum required service period (in years) |
|
|
3 years
|
|
|
| Stock-based compensation expense |
|
|
$ 8.7
|
|
|
| Dividend rights accrued |
$ 0.7
|
|
$ 0.7
|
|
$ 0.5
|
| Potential grants in period based on total shareholder return (in shares) |
0
|
|
0
|
|
|
| Unamortized stock-based compensation expense |
$ 8.7
|
|
$ 8.7
|
|
|
| Performance Shares | Minimum |
|
|
|
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
|
|
| Multiplier for shares granted (as a percent) |
|
|
0.00%
|
|
|
| Performance Shares | Maximum |
|
|
|
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
|
|
| Multiplier for shares granted (as a percent) |
|
|
250.00%
|
|
|