Components of net periodic benefit cost

9 Months Ended

Sep. 30, 2013

Components of net periodic benefit cost [Abstract]

Components of net periodic benefit cost

Components of net periodic benefit cost

	Pension Benefits
	Three months ended September 30,						Nine months ended September 30,
	2013			2012			2013			2012
Service cost	$	1,686		$	701		$	3,292		$	2,102
Interest cost	2,903			1,717			6,293			5,153
Expected return on plan assets	(3,723		)	(1,740		)	(7,337		)	(5,222		)
Amortization of prior service cost	30			34			85			103
Amortization of net loss	723			910			2,428			2,731
Curtailment	—			—			(18		)	—
Net periodic benefit cost	$	1,619		$	1,622		$	4,743		$	4,867

	Other Postretirement Benefits ("OPEB")
	Three months ended September 30,						Nine months ended September 30,
	2013			2012			2013			2012
Service cost	$	700		$	448		$	1,862		$	1,343
Interest cost	1,474			1,378			4,230			4,135
Amortization of prior service cost	(998		)	(1,063		)	(2,997		)	(3,188		)
Amortization of net loss	1,157			1,652			3,934			4,956
Curtailment	—			—			(20		)	—
Net periodic benefit cost	$	2,333		$	2,415		$	7,009		$	7,246

Employer contributions

During the nine months ended September 30, 2013, we have made contributions of approximately $8,582 to the qualified defined benefit plans we sponsor.