RETIREMENT BENEFITS AND ASSETS HELD IN TRUST

Retirement Plan Benefits

We have a qualified retirement plan for eligible employees, comprised of a traditional final average pay plan and a cash balance plan. The traditional final average pay plan is noncontributory, covers select employees, and provides retirement benefits based on the employees’ years of benefit service, average final compensation and age at retirement. The cash balance plan is also noncontributory, covers substantially all employees, and provides retirement benefits based on eligible compensation and interest credits. While we are obligated to fund the retirement plan by contributing the minimum amount required by the Employee Retirement Income Security Act of 1974, as amended, it is our practice to contribute the maximum allowable amount as defined by section 404 of the Internal Revenue Code. We contributed $6.9 million to the defined benefit retirement plan relating to the 2012 plan year in June 2013.

We also have two supplemental nonqualified, noncontributory, retirement benefit plans for selected management employees. The plans provide for benefits that supplement those provided by our other retirement plans. We contributed $0.6 million to these supplemental nonqualified, noncontributory, retirement benefit plans in June 2013. We do not expect to make any additional contributions with respect to these plans in 2013.

Net pension cost includes the following components:



	Three months ended						Nine months ended
	September 30,						September 30,
(in thousands)	2013			2012			2013			2012
Service cost	$	1,315		$	1,040		$	3,946		$	3,120
Interest cost	698			647			2,094			1,942
Expected return on plan assets	(717		)	(569		)	(2,151		)	(1,708		)
Amortization of prior service cost	(10		)	(11		)	(31		)	(32		)
Amortization of unrecognized loss	679			868			2,036			2,603
Net pension cost	$	1,965		$	1,975		$	5,894		$	5,925

Other Postretirement Benefits

We provide certain postretirement health care, dental, and life insurance benefits for employees who may become eligible for these benefits. We contributed $1.0 million to the postretirement benefit plan in September 2013. We expect to contribute up to an additional $1.5 million to the postretirement benefit plan in 2013.

Net postretirement cost includes the following components:



	Three months ended						Nine months ended
	September 30,						September 30,
(in thousands)	2013			2012			2013			2012
Service cost	$	1,443		$	1,358		$	4,330		$	4,075
Interest cost	390			388			1,171			1,164
Expected return on plan assets	(353		)	(254		)	(1,061		)	(762		)
Amortization of prior service cost	—			31			—			93
Amortization of unrecognized loss	55			134			165			401
Net postretirement cost	$	1,535		$	1,657		$	4,605		$	4,971

Defined Contribution Plan

We also sponsor a defined contribution retirement savings plan. Participation in this plan is available to substantially all employees. We match employee contributions up to certain predefined limits based upon eligible compensation and the employee’s contribution rate. The cost of this plan was $0.7 million for the three months ended September 30, 2013 and 2012, and $3.1 million and $2.4 million for the nine months ended September 30, 2013 and 2012, respectively.