Benefit Plans - Defined Benefit Plans - Components of Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Supplemental Retirement Plan
Components of net periodic benefit cost:
Service cost	$ 81	$ 133
Interest cost	259	259
Amortization of net actuarial loss	69	60
Net periodic benefit cost	409	452
Split-Dollar Life Insurance Benefit Plan
Components of net periodic benefit cost:
Amortization of prior transition obligation	(18)	(13)
Interest cost	61	62	$ 248
Net periodic benefit cost	$ 43	$ 49