Employee Benefits (Narrative) (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) employee	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Employee Benefits [Abstract]
Employer matching contribution, percent of employees' pay	100.00%
Maximum annual contribution per employee, percent	4.00%
Participants in employee health plan | employee	2,393
Health care cap per person	$ 200,000
Insured capped maximum exposure health care	12,500,000
Workers' compensation liability	2,300,000	$ 4,600,000	$ 2,800,000
Insured maximum exposure per employee	1,000,000
Aggragate insurance deductable for employees	$ 4,000,000