Pension Plan and Other Postretirement Benefits (Tables)

9 Months Ended

Sep. 30, 2016

Compensation and Retirement Disclosure [Abstract]

Schedule of components of net periodic benefit costs for the pension plans and other postretirement benefits

The following table lists components of net periodic benefit costs for the pension plans and other postretirement benefits. The data listed under “pension plan” includes the qualified pension plan and the non-qualified supplemental executive retirement plan. The data listed under “other benefits” is for all other postretirement benefits.

	Three Months Ended September 30
	Pension Plan						Other Benefits
	2016			2015			2016			2015
Service cost	$	5,594		$	4,715		$	1,045		$	3,043
Interest cost	5,764			5,072			625			2,101
Expected return on plan assets	(5,462		)	(4,770		)	(1,005		)	(908		)
Amortization of prior service cost	1,555			1,502			10			12
Recognized net actuarial loss	1,743			2,308			(482		)	2,182
Net periodic benefit cost	$	9,194		$	8,827		$	193		$	6,430

	Nine Months Ended September 30
	Pension Plan						Other Benefits
	2016			2015			2016			2015
Service cost	$	15,728		$	15,980		$	5,653		$	8,044
Interest cost	16,670			15,078			4,225			5,328
Expected return on plan assets	(16,370		)	(14,354		)	(3,097		)	(2,660		)
Amortization of prior service cost	4,664			4,506			32			34
Recognized net actuarial loss	4,329			7,108			2,041			5,099
Net periodic benefit cost	$	25,021		$	28,318		$	8,854		$	15,845