Equity Compensation (401(k) Plan) (Details)
$ in Millions
9 Months Ended
Sep. 30, 2017
USD ($)
shares
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) | shares 53,159
Expenses associated with contribution | $ $ 1.0
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%