Employee Benefit Plans - SERP Plans (Details) (Supplemental Employee Retirement Plans, Defined Benefit [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Supplemental Employee Retirement Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	$ 69,690	$ 62,891
Defined Benefit Plan, Benefit Obligation	79,432	68,473	61,559
Defined Benefit Plan, Service Cost	2,064	1,525
Defined Benefit Plan, Interest Cost	3,302	3,308
Defined Benefit Plan, Actuarial Net (Gains) Losses	9,273	5,602
Defined Benefit Plan, Benefits Paid	(3,680)	(3,521)
Defined Benefit Plan, Funded Status of Plan	(79,432)	(68,473)
Defined Benefit Plan, Amortization of Gains (Losses)	2,038	787
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	41	41
Defined Benefit Plan, Net Periodic Benefit Cost	7,445	5,661
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	4.00%	4.75%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase	5.00%	5.00%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	4.75%	5.50%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	5.00%	5.00%
Defined Benefit Plan, Expected Future Benefit Payments in Year One	3,992
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	3,956
Defined Benefit Plan, Expected Future Benefit Payments in Year Three	3,915
Defined Benefit Plan, Expected Future Benefit Payments in Year Four	4,134
Defined Benefit Plan, Expected Future Benefit Payments in Year Five	4,079
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	$ 28,124