Postretirement Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2016

Compensation and Retirement Disclosure [Abstract]

Summary of Post-Retirement Benefit Costs by Component

The following tables present a summary of post-retirement benefit costs by component.

Components of Post-Retirement Benefit Costs

	Three Months Ended March 31,
	Pension Benefits						Other Benefits
	2016			2015			2016		2015
Service cost	$	3,894		$	3,990		$	—	$	—
Interest cost	5,432			5,003			212		203
Expected return on assets	(5,782		)	(5,323		)	—		—
Amortization:
Prior service cost	120			81			—		—
Actuarial (gain) loss	2,424			3,534			8		23
Direct recognition of expense	—			—			34		176
Net periodic benefit cost	$	6,088		$	7,285		$	254	$	402

Schedule of Assets at Fair Value for Defined-Benefit Pension Plans

The following table presents assets at fair value for the defined-benefit pension plans at March 31, 2016 and the prior-year end.

Pension Assets by Component

	March 31, 2016			December 31, 2015
	Amount		%	Amount		%
Corporate debt	$	149,670	49	$	146,381	47
Other fixed maturities	655		—	270		—
Equity securities	120,717		39	123,428		40
Short-term investments	13,273		4	15,593		5
Guaranteed annuity contract	17,209		6	17,082		6
Other	5,571		2	4,842		2
Total	$	307,095	100	$	307,596	100