Employee Benefit Plans Employee Benefit Plan (change in plan assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Value of plan assets, January 1	$ 427,131	$ 443,962
Actual return on plan assets	43,271	(593)
Employer contributions	4,310	6,320
Regular benefits paid	(21,625)	(22,558)
Value of plan assets, December 31	453,087	427,131
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Value of plan assets, January 1	427,131	443,962
Actual return on plan assets	43,271	(593)
Employer contributions	0	0
Regular benefits paid	(17,315)	(16,238)
Value of plan assets, December 31	453,087	427,131
Post-Retirement Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	973	1,446
Regular benefits paid	(973)	(1,446)
Supplemental Executive Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	3,337	4,874
Regular benefits paid	$ (3,337)	$ (4,874)