Employee Benefits (Schedule of Net Funded (Unfunded) Status) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Qualified Pension Plan [Member]
Change in Benefit Obligation:
Benefit obligation at beginning of period	$ 67,550	$ 73,149
Service cost	2,148	2,459	$ 2,152
Interest cost	2,576	2,928	2,891
Actuarial (gain) loss	3,888	(5,410)
Benefits paid	(3,072)	(5,430)
Administrative expenses	(139)	(146)
Benefit obligation at end of period	72,951	67,550	73,149
Change in Plan Assets:
Fair value of plan assets at beginning of period	65,710	67,613
Actual return on plan assets	4,788	673
Employer contributions	8,500	3,000
Benefits paid	(3,072)	(5,430)
Administrative expenses	(139)	(146)
Fair value of plan assets at end of period	75,787	65,710	67,613
Funded (unfunded) status at end of period	2,836	(1,840)
Non-Qualified Retirement Plans [Member]
Change in Benefit Obligation:
Benefit obligation at beginning of period	13,015	13,097
Service cost	122	78	46
Interest cost	432	490	478
Actuarial (gain) loss	374	88
Benefits paid	(789)	(738)
Administrative expenses	0	0
Benefit obligation at end of period	13,154	13,015	13,097
Change in Plan Assets:
Fair value of plan assets at beginning of period	0	0
Actual return on plan assets	0	0
Employer contributions	789	738
Benefits paid	(789)	(738)
Administrative expenses	0	0
Fair value of plan assets at end of period	0	0	$ 0
Funded (unfunded) status at end of period	$ (13,154)	$ (13,015)