Employee Benefit Plans (Details 6) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits
Components of the net periodic benefit cost
Service cost	$ 0	$ 236	$ 180
Interest cost	194	182	4,774
Expected return on plan assets	0	0	(7,615)
Recognized net actuarial loss	146	1,516	934
Benefit cost (income)	340	1,934	(1,727)
Postretirement Benefits
Components of the net periodic benefit cost
Service cost	760	900	687
Interest cost	1,549	1,584	1,511
Expected return on plan assets	(355)	(543)	(543)
Recognized net actuarial loss	768	1,517	812
Benefit cost (income)	$ 2,722	$ 3,458	$ 2,467