Employee Benefit Plans Employee Benefit Plan (Change in projected benefit obligation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation, January 1	$ 655,822	$ 621,312	$ 651,694
Service cost	137	14,175
Interest cost	27,751	26,669
Actuarial (gain) loss	28,247	(49,007)
Regular benefits paid	(21,625)	(22,558)
Acquisition	0	339
Benefit obligation, December 31	655,822	621,312	651,694	$ 655,822	$ 621,312
Accumulated benefit obligation				637,153	602,830
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation, January 1	592,290	560,817	583,080
Service cost	(1,403)	12,851	4,952
Interest cost	25,263	23,987	23,068
Actuarial (gain) loss	24,928	(42,863)
Regular benefits paid	(17,315)	(16,238)
Benefit obligation, December 31	592,290	560,817	583,080	592,290	560,817
Accumulated benefit obligation				575,024	544,011
Post-Retirement Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation, January 1	19,031	16,637	12,782
Service cost	1,246	1,042	985
Interest cost	713	560	574
Actuarial (gain) loss	1,408	3,360
Regular benefits paid	(973)	(1,446)
Acquisition	0	339
Benefit obligation, December 31	19,031	16,637	12,782	19,031	16,637
Accumulated benefit obligation				19,031	16,637
Supplemental Executive Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation, January 1	44,501	43,858	55,832
Service cost	294	282	586
Interest cost	1,775	2,122	2,528
Actuarial (gain) loss	1,911	(9,504)
Regular benefits paid	(3,337)	(4,874)
Benefit obligation, December 31	$ 44,501	$ 43,858	$ 55,832	44,501	43,858
Accumulated benefit obligation				$ 43,098	$ 42,182