Defined Benefit Pension Plans Amounts reported in accumulated other comprehensive income (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Amounts reported in accumulated other comprehensive income
Unrecognized net actuarial loss, pretax	$ 2,139	$ 8,086
Unrecognized net actuarial loss, net of tax	(714)	4,919
Unrecognized prior service cost, pretax	214	278
Unrecognized prior service cost, net of tax	(71)	169
Amounts reported in accumulated other comprehensive income, pretax	2,353	8,364
Amounts reported in accumulated other comprehensive income, net of tax	(785)	5,088
Amortization of Costs Expected to be Recognized Next Year
Unrecognized net actuarial loss, pretax	175
Unrecognized net actuarial loss, net of tax	131
Unrecognized prior service cost, pretax	64
Unrecognized prior service cost, net of tax	48
Amortization of costs expected to be recognized next year, pretax	239
Amortization of costs expected to be recognized next year, net of tax	179
For pension plans with accumulated benefit obligations in excess of plan assets
Projected benefit obligation	7,064	19,403	$ 24,833
Accumulated benefit obligation	7,064	19,403
Fair value of plan assets	$ 3,758	$ 7,105	$ 11,509