Retirement Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost on benefit obligations	$ 2,001	$ 1,857	$ 5,956	$ 5,577
Expected return on plan assets	(2,815)	(3,178)	(8,445)	(9,538)
Recognized net loss	1,420	1,160	4,280	3,480
Net periodic benefit cost	606	(161)	1,791	(481)
Defined Benefit Plan, Plan Assets, Contributions by Employer			10,000
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost on benefit obligations	16	35	48	201
Expected return on plan assets	0	0	0	0
Recognized net loss	4	2,271	11	2,729
Net periodic benefit cost	20	2,306	59	2,930
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost on benefit obligations	22	20	64	59
Expected return on plan assets	0	0	0	0
Recognized net loss	(2)	0	(10)	0
Net periodic benefit cost	$ 20	$ 20	$ 54	$ 59