Pension and Other Postretirement Benefits (Tables)

3 Months Ended

Mar. 31, 2015

Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]

Schedule of Net Benefit Costs

The net periodic benefit cost for the three months ended March 31, 2015 and 2014 included the following components: 

	Pension Benefits						Postretirement Benefits
	Three Months Ended   March 31,						Three Months Ended   March 31,
Components of Net Periodic Benefit Cost	2015			2014			2015			2014
Service cost	$	6,500		$	5,597		$	675		$	625
Interest cost	6,350			6,799			750			825
Expected return on plan assets	(7,025		)	(6,675		)	—			—
Amortization of:
Net actuarial loss	4,924			4,534			251			275
Prior service cost (gain)	113			246			(545		)	(550		)
Settlement loss	—			789			—			—
Net periodic benefit cost	$	10,862		$	11,290		$	1,131		$	1,175