Employee Benefit and Deferred Compensation Plans (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Change in benefit obligation
Benefit obligation at beginning of year	$ 27,856,000
Settlements	0	$ 0
Transfer from HeritageBank Pension Plan	0	0
Benefit obligation at end of year	28,012,000	27,856,000
Change in fair value of plan assets
Fair value of plan assets at beginning of year	36,892,000
Contribution by employer	0	0
Settlements	0	0
Fair value of plan assets at end of year	25,241,000	36,892,000
HeritageBank
Change in benefit obligation
Settlements	(11,509,000)	(2,187,000)
Transfer from HeritageBank Pension Plan	1,073,000	0
Change in fair value of plan assets
Settlements	(11,509,000)	(2,187,000)
Pension Benefits
Change in benefit obligation
Benefit obligation at beginning of year	27,856,000	28,087,000
Service cost	0	0	$ 0
Interest cost	1,216,000	1,095,000	1,292,000
Plan participants’ contributions	0	0
Actuarial loss (gain)	(115,000)	605,000
Benefits paid	(2,018,000)	(1,931,000)
Settlements	0	0
Transfer from HeritageBank Pension Plan	(1,073,000)	0
Addition from business combination	0	0
Benefit obligation at end of year	28,012,000	27,856,000	28,087,000
Change in fair value of plan assets
Fair value of plan assets at beginning of year	24,434,000	26,532,000
Actual return on plan assets	1,752,000	(167,000)
Contribution by employer	0	0
Benefits paid	(2,018,000)	(1,931,000)
Settlements	0	0
Expenses paid from plan trust	0	0
Transfer from HeritageBank Pension Plan	1,073,000	0
Addition from business combination	0	0
Fair value of plan assets at end of year	25,241,000	24,434,000	26,532,000
Funded status at end of year	$ (2,771,000)	$ (3,422,000)
Weighted-average assumptions as of December 31
Discount rate (percent)	4.35%	4.56%
Pension Benefits | HeritageBank
Change in benefit obligation
Benefit obligation at beginning of year	$ 12,913,000	$ 0
Service cost	0	0
Interest cost	172,000	305,000
Plan participants’ contributions	0	0
Actuarial loss (gain)	(481,000)	(685,000)
Benefits paid	(22,000)	(15,000)
Addition from business combination	0	15,495,000
Benefit obligation at end of year	0	12,913,000	0
Change in fair value of plan assets
Fair value of plan assets at beginning of year	12,458,000	0
Actual return on plan assets	29,000	(21,000)
Contribution by employer	142,000	0
Benefits paid	(22,000)	(15,000)
Expenses paid from plan trust	(25,000)	0
Transfer from HeritageBank Pension Plan	(1,073,000)	0
Addition from business combination	0	14,681,000
Fair value of plan assets at end of year	0	12,458,000	0
Funded status at end of year	$ 0	$ (455,000)
Weighted-average assumptions as of December 31
Discount rate (percent)	0.00%	4.27%
Other Benefits
Change in benefit obligation
Benefit obligation at beginning of year	$ 1,704,000	$ 1,941,000
Service cost	12,000	17,000	14,000
Interest cost	58,000	60,000	84,000
Plan participants’ contributions	76,000	82,000
Actuarial loss (gain)	(56,000)	(37,000)
Benefits paid	(228,000)	(359,000)
Addition from business combination	0	0
Benefit obligation at end of year	1,566,000	1,704,000	$ 1,941,000
Change in fair value of plan assets
Benefits paid	(228,000)	(359,000)
Funded status at end of year	$ (1,566,000)	$ (1,704,000)
Weighted-average assumptions as of December 31
Discount rate (percent)	3.57%	3.63%