Employee Benefits (Tables)

6 Months Ended

Jun. 30, 2013

Compensation and Retirement Disclosure [Abstract]

Net Periodic Benefit Cost

The components of the net periodic benefit cost for our pension and postretirement benefit plans are as follows:

	Pension Plan						Postretirement Benefit Plan
Three Months Ended June 30,	2013			2012			2013		2012
Net periodic benefit cost
Service cost	$	1,868		$	1,278		$	752	$	496
Interest cost	1,326			1,334			423		398
Expected return on plan assets	(1,550		)	(1,360		)	—		—
Amortization of prior service cost	—			—			—		(8		)
Amortization of net loss	1,105			1,684			138		56
Net periodic benefit cost	$	2,749		$	2,936		$	1,313	$	942

	Pension Plan						Postretirement Benefit Plan
Six Months Ended June 30,	2013			2012			2013		2012
Net periodic benefit cost
Service cost	$	3,150		$	2,069		$	1,505	$	992
Interest cost	2,587			2,524			847		796
Expected return on plan assets	(2,886		)	(2,682		)	—		—
Amortization of prior service cost	—			3			—		(17		)
Amortization of net loss	2,211			2,276			274		112
Net periodic benefit cost	$	5,062		$	4,190		$	2,626	$	1,883