Employee Benefit Plans - Summary of pre tax amounts recognized in comprehensive loss (Details 3) - Retirement Income Plan - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Net loss (gain)	$ 2,039	$ (1,621)	$ 10,745
Amortization of net loss	(799)	(790)	(531)
Net transition obligation (asset)
Amount recognized in accumulated other comprehensive loss	$ 1,240	$ (2,411)	$ 10,214