Employee Benefit and Deferred Compensation Plans - Plan Expense for Non-Contributory Benefit Pension Plan and Post-Retirement Health and Life Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Pension Benefits
Plan expense for noncontributory benefit pension plan and post-retirement health and life plans
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	292	304	876	912
Expected return on plan assets	(485)	(468)	(1,456)	(1,404)
Recognized actuarial loss	101	101	301	303
Settlement/curtailment/termination gains	0	0	0	0
Net periodic benefit (return) cost	(92)	(63)	(279)	(189)
Pension Benefits | Heritage Financial Group
Plan expense for noncontributory benefit pension plan and post-retirement health and life plans
Service cost	0	0	0	0
Interest cost	0	34	0	172
Expected return on plan assets	0	(23)	0	(113)
Recognized actuarial loss	0	0	0	0
Settlement/curtailment/termination gains	0	(780)	0	(780)
Net periodic benefit (return) cost	0	(769)	0	(721)
Other Benefits
Plan expense for noncontributory benefit pension plan and post-retirement health and life plans
Service cost	2	1	6	9
Interest cost	11	14	32	43
Expected return on plan assets	0	0	0	0
Recognized actuarial loss	2	23	5	57
Settlement/curtailment/termination gains	0	0	0	0
Net periodic benefit (return) cost	$ 15	$ 38	$ 43	$ 109