Pension and Other Postretirement Benefit Plans

The Corporation's retirement plans include a qualified pension plan, a nonqualified pension plan, a nonqualified postretirement benefit plan, a 401(k) savings plan, and a multi-employer defined benefit plan.

Qualified and Nonqualified Pension Plans and Nonqualified Postretirement Benefit Plans

The components of net periodic benefit cost for the Corporation’s qualified and nonqualified pension plans and nonqualified postretirement benefit plan are as follows:



	Three Months Ended June 30,						Six Months Ended June 30,
(Dollars in thousands)	2017			2016			2017			2016
Defined Benefit Pension Plans
Service cost	$	234		$	277		$	467		$	554
Interest cost	1,301			1,358			2,603			2,716
Expected return on plan assets	(2,217		)	(2,140		)	(4,434		)	(4,281		)
Amortization of unrecognized net loss	579			572			1,157			1,144
Net periodic benefit cost (income)	$	(103	)	$	67		$	(207	)	$	133
Postretirement Benefit Plan
Service cost	$	1		$	2		$	2		$	4
Interest cost	23			33			47			66
Amortization of prior service cost	—			29			—			58
Amortization of unrecognized net gain	(40		)	(25		)	(81		)	(49		)
Net periodic benefit cost (income)	$	(16	)	$	39		$	(32	)	$	79

The Corporation did not make a contribution to the pension plan during the three and six months ended June 30, 2017 or 2016. The discount rates used to compute the Corporation's qualified and nonqualified pension plan expense are 4.22% and 3.63%, respectively, for 2017. The discount rate used to compute the Corporation's nonqualified postretirement benefit plan for 2017 is 3.79%.

401(k) Savings Plan

401(k) Savings Plan expense for the Corporation’s match of participants’ base compensation contributions and a 4.0% of eligible pay contribution to employees who are not grandfathered under the pension plan was $2.4 million and $1.4 million for the three months ended June 30, 2017 and 2016, respectively, and $5.0 million and $2.7 million for the six months ended June 30, 2017 and 2016, respectively. The Corporation's base compensation match equals 50.0% of the participants' elective deferrals on the first 4.0% of the participants' base compensation up to the maximum amount allowed under the Internal Revenue Code.

Multi-Employer Defined Benefit Plan

In conjunction with the April 1, 2015 acquisition of Monarch, the Corporation acquired a participation in the Pentegra Defined Benefit Plan for Financial Institutions (Pentegra DB Plan), a qualified defined benefit pension plan. Employee benefits for Monarch employees under the Plan were frozen effective April 1, 2004. The Pentegra DB Plan operates as a multi-employer plan for accounting purposes and as a multiple-employer plan under the Employee Retirement Income Security Act of 1974 and the Internal Revenue Code (IRC). The Pentegra DB Plan is a single plan under IRC Section 413(c) and, as a result, all of the plan's assets stand behind all of the plan's liabilities. Accordingly, contributions made by a participating employer may be used to provide benefits to participants of other participating employers. No contributions were made by the Corporation to the Pentegra DB Plan for the three and six months ended June 30, 2017 and 2016.