Benefit Plans - Defined Benefit Plans - Components of Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Supplemental Retirement Plan
Components of net periodic benefit cost:
Service cost	$ 133	$ 216	$ 266	$ 432
Interest cost	259	221	518	442
Amortization of net actuarial loss	60	96	120	192
Net periodic benefit cost	452	533	904	1,066
Split-Dollar Life Insurance Benefit Plan
Components of net periodic benefit cost:
Amortization of prior transition obligation	(13)	(44)	(26)	(56)
Interest cost	62	34	124	84	$ 169
Net periodic benefit cost	$ 49	$ (10)	$ 98	$ 28