Benefit Plans 401(K) Plan (Details) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Compensation and Retirement Disclosure [Abstract] | |||
| Number of days of continuous employment to be eligible | 90 days | ||
| Maximum annual contribution by employee | 6.00% | ||
| Employer match | 50.00% | ||
| Contributions by employer | $ 201,000 | $ 192,000 | $ 161,000 |