Employee Benefit Plans (Schedule of Net Periodic Costs and Other Amounts Recognized in OCI) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,227	$ 1,315	$ 1,169
Interest cost	2,140	2,159	2,051
Expected return on plan assets	(2,866)	(2,771)	(2,497)
Amortization of unrecognized prior service (credit) cost	(124)	(141)	(38)
Amortization of net loss	870
Curtailment credit	(952)		(1,910)
Net periodic cost	295	562	(1,225)
Net (gain) loss arising during period	1,630	11,787	(2,044)
Prior service (credit) cost arising during period	952		(2,770)
Amortization of prior service credit (cost)	124	141	38
Amortization of net actuarial loss	(870)
Total amount recognized in OCI	1,836	11,928	(4,776)
Total recognized in net periodic cost and OCI	2,131	12,490	(6,001)
Supplemental Employee Retirement Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	5,808	5,197	4,661
Interest cost	3,398	3,434	3,728
Amortization of unrecognized prior service (credit) cost	1,697	1,696	1,697
Amortization of net loss	2,028	1,533	1,459
Net periodic cost	12,931	11,860	11,545
Net (gain) loss arising during period	10,752	5,225	4,396
Prior service (credit) cost arising during period			(24)
Amortization of prior service credit (cost)	(1,697)	(1,696)	(1,697)
Amortization of net actuarial loss	(2,028)	(1,533)	(1,459)
Total amount recognized in OCI	7,027	1,996	1,216
Total recognized in net periodic cost and OCI	$ 19,958	$ 13,856	$ 12,761