Employee Benefit Plans (Details 6) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Benefits
Components of the net periodic benefit cost
Service cost	$ 236	$ 180	$ 0
Interest cost	182	4,774	4,227
Expected return on plan assets	0	(7,615)	(7,005)
Recognized net actuarial loss	1,516	934	1,530
Benefit cost (income)	1,934	(1,727)	(1,248)
Postretirement Benefits
Components of the net periodic benefit cost
Service cost	900	687	841
Interest cost	1,584	1,511	1,366
Expected return on plan assets	(543)	(543)	(543)
Recognized net actuarial loss	1,517	812	1,473
Benefit cost (income)	$ 3,458	$ 2,467	$ 3,137