Employee Benefits Plans (Details 13) - Other Postretirement Benefits - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Amounts recognized in the Consolidated Balance Sheets
Current liability	$ 1,506	$ 1,624
Noncurrent liability	19,459	20,002
Net amount recognized	20,965	21,626
Amounts recognized in accumulated other comprehensive loss (pre-tax)
Prior service credit	(385)	(616)
Net actuarial gain	(10,186)	(11,825)
Net amount recognized	$ (10,571)	$ (12,441)