Pension and Other Postretirement Benefits (Tables)

9 Months Ended

Sep. 30, 2015

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

Schedule of Net Benefit Costs

The net periodic benefit cost for the three and nine months ended September 30, 2015 and 2014 included the following components: 

	Pension Benefits						Postretirement Benefits
	Three Months Ended   September 30,						Three Months Ended   September 30,
Components of Net Periodic Benefit Cost	2015			2014			2015			2014
Service cost	$	6,402		$	5,551		$	626		$	614
Interest cost	6,301			6,704			731			834
Expected return on plan assets	(7,075		)	(6,656		)	—			—
Amortization of:
Net actuarial loss	5,007			4,410			261			317
Prior service cost (gain)	113			238			(545		)	(545		)
Net periodic benefit cost	$	10,748		$	10,247		$	1,073		$	1,220

	Pension Benefits						Postretirement Benefits
	Nine Months Ended   September 30,						Nine Months Ended   September 30,
Components of Net Periodic Benefit Cost	2015			2014			2015			2014
Service cost	$	19,206		$	16,654		$	1,878		$	1,841
Interest cost	18,902			20,113			2,194			2,502
Expected return on plan assets	(21,223		)	(19,968		)	—			—
Amortization of:
Net actuarial loss	15,021			13,229			783			951
Prior service cost (gain)	339			714			(1,635		)	(1,635		)
Settlement loss	—			789			—			—
Net periodic benefit cost	$	32,245		$	31,531		$	3,220		$	3,659