Employee Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2015

Compensation and Retirement Disclosure [Abstract]

Schedule of net periodic cost (benefit)

Net periodic cost (benefit) of the Defined Benefit Pension, Post-Retirement Medical, and Supplemental Executive Retirement plans included in general insurance expenses in the accompanying condensed consolidated statements of income includes the following components:

	Three Months Ended September 30,
	Defined Benefit  Pension Plan						Post-Retirement  Medical Plan						Supplemental Executive Retirement Plan				Total
	2015			2014			2015			2014			2015		2014		2015			2014
Components of net periodic cost (benefit):
Service cost	$	1,521		$	1,364		$	254		$	327		$	70	$	30	$	1,845		$	1,721
Interest cost	5,996			5,824			167			171			531		503		6,694			6,498
Expected return on plan assets	(7,084		)	(7,328		)	—			—			—		—		(7,084		)	(7,328		)
Amortization of unrecognized prior service costs (benefits)	3			12			(395		)	(427		)	233		234		(159		)	(181		)
Amortization of losses (gains) from earlier periods	3,086			885			16			(77		)	166		165		3,268			973
Settlement	—			—			—			—			—		2,666		—			2,666
Net periodic cost (benefit)	$	3,522		$	757		$	42		$	(6	)	$	1,000	$	3,598	$	4,564		$	4,349

	Nine Months Ended September 30,
	Defined Benefit  Pension Plan						Post-Retirement  Medical Plan						Supplemental Executive Retirement Plan				Total
	2015			2014			2015			2014			2015		2014		2015			2014
Components of net periodic cost (benefit):
Service cost	$	4,538		$	3,713		$	781		$	739		$	211	$	440	$	5,530		$	4,892
Interest cost	17,990			17,301			420			431			1,592		1,896		20,002			19,628
Expected return on plan assets	(21,258		)	(21,966		)	—			—			—		—		(21,258		)	(21,966		)
Amortization of unrecognized prior service costs (benefits)	10			38			(1,230		)	(1,280		)	700		700		(520		)	(542		)
Amortization of losses (gains) from earlier periods	9,298			2,174			(298		)	(337		)	497		350		9,497			2,187
Settlement	—			—			—			—			—		2,666		—			2,666
Net periodic cost (benefit)	$	10,578		$	1,260		$	(327	)	$	(447	)	$	3,000	$	6,052	$	13,251		$	6,865

Schedule of contributions to the Defined Benefit Pension Plan and payments made to the Post-Retirement Medical Plan and the Supplemental Executive Retirement Plan

The following table summarizes contributions to the Defined Benefit Pension Plan and payments made to the Post-Retirement Medical Plan and the Supplemental Executive Retirement Plan:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2015		2014		2015		2014
Contributions to the Defined Benefit Pension Plan	$	—	$	6,003	$	—	$	10,717
Payments to the Post-Retirement Medical Plan	576		178		1,100		393
Payments to the Supplemental Executive Retirement Plan	830		14,255		3,995		16,044