Share Based Compensation - Dividend Payments (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | |||
|---|---|---|---|---|---|
Jun. 30, 2019 |
Jun. 30, 2018 |
Jun. 30, 2019 |
Jun. 30, 2018 |
Dec. 31, 2018 |
|
| Share Based Compensation | |||||
| Stock based compensation expense | $ 3.8 | $ 4.0 | $ 5.3 | $ 7.3 | |
| Stock Options and Restricted Shares | |||||
| Share Based Compensation | |||||
| Amount of cash bonuses and distributions related to all dividends previously declared on unvested shares | $ 1.7 | $ 1.7 | $ 1.8 | ||