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, 2015	Dec. 31, 2014
Change in fair value of plan assets
Fair value of plan assets at beginning of year	$ 26,337
Fair value of plan assets at end of year	25,711	$ 26,337
Pension Plans, Defined Benefit
Change in projected benefit obligation
Benefit obligation at beginning of year	32,051	27,812
Service cost	13	12
Interest cost	1,273	1,274
Liability actuarial loss (gain)	(1,699)	4,352
Benefits paid	(1,428)	(1,399)
Benefit obligation at end of year	30,210	32,051
Change in fair value of plan assets
Fair value of plan assets at beginning of year	26,337	25,274
Return on plan assets	(422)	1,262
Employer contributions	1,224	1,200
Benefits paid	(1,428)	(1,399)
Fair value of plan assets at end of year	25,711	26,337
Underfunded status – December 31, 2015	(4,499)	(5,714)
Supplemental Employee Retirement Plans, Defined Benefit
Change in projected benefit obligation
Benefit obligation at beginning of year	3,732	3,021
Service cost	121	152
Interest cost	137	138
Liability actuarial loss (gain)	(24)	421
Benefits paid	(4)	0
Plan amendments	0	0
Benefit obligation at end of year	3,962	3,732
Change in fair value of plan assets
Benefits paid	(4)	0
Hourly Employees’ Pension Plan | Pension Plans, Defined Benefit
Change in projected benefit obligation
Benefit obligation at beginning of year	10,456	9,477
Service cost	9	8
Interest cost	405	422
Liability actuarial loss (gain)	(574)	1,189
Benefits paid	(647)	(640)
Benefit obligation at end of year	9,649	10,456
Change in fair value of plan assets
Fair value of plan assets at beginning of year	9,223	8,873
Return on plan assets	(149)	442
Employer contributions	592	548
Benefits paid	(647)	(640)
Fair value of plan assets at end of year	9,019	9,223
Underfunded status – December 31, 2015	(630)	(1,233)
Employees’ Retirement Plan | Pension Plans, Defined Benefit
Change in projected benefit obligation
Benefit obligation at beginning of year	21,595	18,335
Service cost	4	4
Interest cost	868	852
Liability actuarial loss (gain)	(1,125)	3,163
Benefits paid	(781)	(759)
Benefit obligation at end of year	20,561	21,595
Change in fair value of plan assets
Fair value of plan assets at beginning of year	17,114	16,401
Return on plan assets	(273)	820
Employer contributions	632	652
Benefits paid	(781)	(759)
Fair value of plan assets at end of year	16,692	17,114
Underfunded status – December 31, 2015	$ (3,869)	$ (4,481)