Retirement Benefit Plans (Schedule of Changes in Plan Assets, Changes in Projected Benefit Obligation, Rate Assumptions, and Components of Net Periodic Benefit Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Change in fair value of plan assets
Fair value of plan assets at beginning of year	$ 25,711
Fair value of plan assets at end of year	17,858	$ 25,711
Pension Plans, Defined Benefit
Change in projected benefit obligation
Benefit obligation at beginning of year	30,210	32,051
Service cost	12	13
Interest cost	1,287	1,273
Liability actuarial (gain) loss	56	(1,699)
Benefits paid	(1,443)	(1,428)
Settlements	(9,335)
Benefit obligation at end of year	20,787	30,210
Change in fair value of plan assets
Fair value of plan assets at beginning of year	25,711	26,337
Return on plan assets	1,403	(422)
Employer contributions	1,522	1,224
Benefits paid	(1,443)	(1,428)
Settlements	(9,335)
Fair value of plan assets at end of year	17,858	25,711
Underfunded status	(2,929)	(4,499)
Supplemental Employee Retirement Plans, Defined Benefit
Change in projected benefit obligation
Benefit obligation at beginning of year	3,962	3,732
Service cost	176	121
Interest cost	175	137
Liability actuarial (gain) loss	183	(24)
Benefits paid	(67)	(4)
Plan amendments	958	0
Benefit obligation at end of year	5,387	3,962
Change in fair value of plan assets
Benefits paid	(67)	(4)
Hourly Employees’ Pension Plan | Pension Plans, Defined Benefit
Change in projected benefit obligation
Benefit obligation at beginning of year	9,649	10,456
Service cost	8	9
Interest cost	401	405
Liability actuarial (gain) loss	(148)	(574)
Benefits paid	(575)	(647)
Settlements	(9,335)
Benefit obligation at end of year	0	9,649
Change in fair value of plan assets
Fair value of plan assets at beginning of year	9,019	9,223
Return on plan assets	119	(149)
Employer contributions	772	592
Benefits paid	(575)	(647)
Settlements	(9,335)
Fair value of plan assets at end of year	0	9,019
Underfunded status	0	(630)
Employees’ Retirement Plan | Pension Plans, Defined Benefit
Change in projected benefit obligation
Benefit obligation at beginning of year	20,561	21,595
Service cost	4	4
Interest cost	886	868
Liability actuarial (gain) loss	204	(1,125)
Benefits paid	(868)	(781)
Settlements	0
Benefit obligation at end of year	20,787	20,561
Change in fair value of plan assets
Fair value of plan assets at beginning of year	16,692	17,114
Return on plan assets	1,284	(273)
Employer contributions	750	632
Benefits paid	(868)	(781)
Settlements	0
Fair value of plan assets at end of year	17,858	16,692
Underfunded status	$ (2,929)	$ (3,869)