Defined Pension Plans (Schedule of Net Periodic Pension Costs) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	$ 3,073	$ 3,452
Interest cost on projected benefit obligation	3,132	2,819
Expected return on plan assets	(4,958)	(4,469)
Net amortization and deferral	393	1,729
Net periodic pension cost	1,640	3,531
Unfunded Supplemental Executive Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	136	144
Interest cost on projected benefit obligation	377	335
Net amortization and deferral	431	551
Net periodic pension cost	$ 944	$ 1,030