Benefit Plans (Tables)

6 Months Ended

Jun. 30, 2013

Compensation And Retirement Disclosure [Abstract]

Components of Net Periodic Pension Expense Related to Qualified and Non-Qualified Plans

The following table sets forth the components of net periodic pension expense related to the qualified and non-qualified plans for the three and six months ended June 30, 2013 and 2012:

	Three Months Ended June 30,						Six Months Ended June 30,
	2013			2012			2013			2012
	(in thousands)
Service cost	$	2,056		$	1,985		$	4,043		$	3,971
Interest cost		1,708			1,620			3,365			3,239
Expected return on plan assets		(3,183	)		(2,233	)		(5,742	)		(4,466	)
Amortization of prior service cost		241			191			443			382
Amortization of actuarial loss		811			587			1,605			1,175
Curtailment loss		750			—			750			—
Total net periodic pension expense	$	2,383		$	2,150		$	4,464		$	4,301