Employee Benefit Plans Employee Benefit Plan (underfunded status) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Under funded status at December 31	$ (202,735)	$ (194,181)
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Under funded status at December 31	(139,203)	(133,686)
Post-Retirement Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Under funded status at December 31	(19,031)	(16,637)
Supplemental Executive Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Under funded status at December 31	$ (44,501)	$ (43,858)