Defined Benefit Pension Plans

The Corporation maintains a tax-qualified defined benefit pension plan for the benefit of certain eligible employees who were hired prior to October 1, 2007. The Corporation also has non-qualified retirement plans to provide supplemental retirement benefits to certain employees, as defined in the plans. The defined benefit pension plans were previously amended to freeze benefit accruals after a 10-year transition period ending in December 2023.

The defined benefit pension plan is funded on a current basis, in compliance with the requirements of ERISA.

The non-qualified retirement plans provide for the designation of assets in rabbi trusts. Securities available for sale and other short-term investments designated for this purpose, with the carrying value of $11.3 million and $11.7 million are included in the Consolidated Balance Sheets at September 30, 2017 and December 31, 2016, respectively.

The composition of net periodic benefit cost was as follows:



(Dollars in thousands)	Qualified Pension Plan												Non-Qualified Retirement Plans
	Three months						Nine months						Three months				Nine months
Periods ended September 30,	2017			2016			2017			2016			2017		2016		2017		2016
Net Periodic Benefit Cost:
Service cost		$537			$537			$1,611			$1,611			$32		$30		$97		$91
Interest cost	669			644			2,005			1,932			107		108		321		324
Expected return on plan assets	(1,236		)	(1,158		)	(3,707		)	(3,475		)	—		—		—		—
Amortization of prior service (credit) cost	(6		)	(6		)	(17		)	(17		)	—		—		—		—
Recognized net actuarial loss	279			207			836			621			76		62		269		185
Net periodic benefit cost		$243			$224			$728			$672			$215		$200		$687		$600

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 nine months ended September 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