Defined Pension Plans (Schedule of Net Periodic Pension Costs) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	$ 3,977	$ 3,003
Interest cost on projected benefit obligation	3,217	3,037
Expected return on plan assets	(4,863)	(4,711)
Net amortization and deferral	1,605	244
Net periodic pension cost	3,936	1,573
Unfunded Supplemental Executive Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	140	136
Interest cost on projected benefit obligation	348	377
Net amortization and deferral	654	431
Net periodic pension cost	$ 1,142	$ 944