Defined Benefit Pension Plans (Tables)

6 Months Ended

Jun. 30, 2017

Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]

Components of Net Periodic Benefit Cost

The composition of net periodic benefit cost was as follows:

(Dollars in thousands)	Qualified Pension Plan												Non-Qualified Retirement Plans
	Three months						Six months						Three months				Six months
Periods ended June 30,	2017			2016			2017			2016			2017		2016		2017		2016
Net Periodic Benefit Cost:
Service cost		$537			$537			$1,074			$1,074			$33		$31		$65		$61
Interest cost	667			644			1,336			1,288			107		108		214		216
Expected return on plan assets	(1,235		)	(1,159		)	(2,471		)	(2,317		)	—		—		—		—
Amortization of prior service (credit) cost	(5		)	(5		)	(11		)	(11		)	—		—		—		—
Recognized net actuarial loss	278			207			557			414			128		61		193		123
Net periodic benefit cost		$242			$224			$485			$448			$268		$200		$472		$400

Schedule of Assumptions Used for Net Periodic Benefit Cost

The following table presents the measurement date and weighted-average assumptions used to determine net periodic benefit cost:

	Qualified Pension Plan		Non-Qualified Retirement Plans
For the sixth months ended June 30,	2017	2016	2017	2016
Measurement date	Dec 31, 2016	Dec 31, 2015	Dec 31, 2016	Dec 31, 2015
Equivalent single discount rate for benefit obligations	4.18%	4.48%	3.96%	4.19%
Equivalent single discount rate for service cost	4.29	4.63	4.25	4.59
Equivalent single discount rate for interest cost	3.73	3.88	3.36	3.44
Expected long-term return on plan assets	6.75	6.75	N/A	N/A
Rate of compensation increase	3.75	3.75	3.75	3.75