Equity Compensation (401(k) Plan) (Details) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Defined Contribution Plan Disclosure [Line Items] | ||
| Maximum amount of employees' gross pay the employee may contribute (as a percent) | 3.50% | |
| Shares contributed (in shares) | 62,230 | 65,171 |
| Expenses associated with contribution | $ 1.5 | $ 1.4 |
| First 1% of employees' salary | ||
| Defined Contribution Plan Disclosure [Line Items] | ||
| Employer matching contribution (as a percent) | 100.00% | |
| Employees' gross pay for which the employer contributes a matching contribution (as a percent) | 1.00% | |
| Second 5% of employees' salary | ||
| Defined Contribution Plan Disclosure [Line Items] | ||
| Employer matching contribution (as a percent) | 50.00% | |
| Employees' gross pay for which the employer contributes a matching contribution (as a percent) | 5.00% | |