Employee Benefit Plan (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	$ 0	$ 684
Interest cost	649	752
Expected return on plan assets	(1,215)	(1,242)
Amortization of net retirement plan actuarial loss	239	586
Amortization of net retirement plan prior service (credit) cost	(4)	(217)
Net periodic benefit (credit) cost	(331)	563
Life and Health [Member]
Components of net periodic benefit cost
Service cost	82	61
Interest cost	77	93
Expected return on plan assets	0	0
Amortization of net retirement plan actuarial loss	1	15
Amortization of net retirement plan prior service (credit) cost	4	4
Net periodic benefit (credit) cost	164	173
SERP Benefits [Member]
Components of net periodic benefit cost
Service cost	72	66
Interest cost	211	240
Expected return on plan assets	0	0
Amortization of net retirement plan actuarial loss	104	130
Amortization of net retirement plan prior service (credit) cost	30	34
Net periodic benefit (credit) cost	$ 417	$ 470