Employee Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2018

BancShares Plan

Defined Benefit Plan Disclosure [Line Items]

Schedule of Net Benefit Costs

BancShares Plan

For the three months ended March 31, 2018 and 2017, the components of net periodic benefit cost are as follows:

	Three months ended March 31
(Dollars in thousands)	2018			2017
Service cost	$	3,429		$	3,376
Interest cost	7,057			7,380
Expected return on assets	(11,957		)	(10,698		)
Amortization of prior service cost	20			52
Amortization of net actuarial loss	3,246			2,234
Net periodic benefit cost	$	1,795		$	2,344

Bancorporation Plan

Defined Benefit Plan Disclosure [Line Items]

Schedule of Net Benefit Costs

Bancorporation Plan

For the three months ended March 31, 2018 and 2017, the components of net periodic benefit cost are as follows:

	Three months ended March 31
(Dollars in thousands)	2018			2017
Service cost	$	662		$	671
Interest cost	1,587			1,683
Expected return on assets	(3,106		)	(2,796		)
Amortization of net actuarial loss	71			214
Net periodic benefit cost	$	(786	)	$	(228	)