Employee Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2018

BancShares Plan

Defined Benefit Plan Disclosure [Line Items]

Schedule of Net Benefit Costs

BancShares Plan

For the three and nine months endedSeptember 30, 2018 and 2017, the components of net periodic benefit cost are as follows:

	Three months ended September 30						Nine months ended September 30
(Dollars in thousands)	2018			2017			2018			2017
Service cost	$	3,396		$	3,180		$	10,187		$	9,490
Interest cost	7,093			7,283			21,281			21,732
Expected return on assets	(11,966		)	(10,589		)	(35,899		)	(31,594		)
Amortization of prior service cost	19			53			59			158
Amortization of net actuarial loss	3,398			2,214			10,192			6,641
Net periodic benefit cost	$	1,940		$	2,141		$	5,820		$	6,427

Bancorporation Plan

Defined Benefit Plan Disclosure [Line Items]

Schedule of Net Benefit Costs

Bancorporation Plan

For the three and nine months endedSeptember 30, 2018 and 2017, the components of net periodic benefit cost are as follows:

	Three months ended September 30						Nine months ended September 30
(Dollars in thousands)	2018			2017			2018			2017
Service cost	$	643		$	569		$	1,929		$	1,910
Interest cost	1,588			1,624			4,767			4,989
Expected return on assets	(3,106		)	(2,783		)	(9,322		)	(8,375		)
Amortization of net actuarial loss	78			63			235			491
Net periodic benefit cost	$	(797	)	$	(527	)	$	(2,391	)	$	(985	)