Benefit Plans Benefit Plans (Details Textual) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) yr	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Benefit Plans [Abstract]
Minimum Hours Of Work Required By Participants	1,000
Minimum Age Of Work Required By Participants | yr	18
Maximum Annual Contributions Per Employee, Percent	60.00%
Cost Recognized | $	$ 4.0	$ 3.7	$ 2.8