Benefit Plans Benefit Plans Post Retirement Medical Plan Net Periodic Benefit Cost (Details) - Jun. 30, 2015 - Postretirement Medical Plan [Member] - USD ($) $ in Thousands	Total	Total
Components of net periodic benefit cost:
Service cost	$ 93	$ 185
Interest cost	53	106
Amortization of prior service cost	2	4
Net periodic benefit cost	$ 148	$ 295