Employee Benefit Plans, Net Periodic Benefit Cost (Details) (Defined Benefit Pension Plan and Benefit Equalization Plan [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Defined Benefit Pension Plan and Benefit Equalization Plan [Member]
Summary of Net Periodic Benefit Cost [Abstract]
Interest cost on projected benefit obligation	$ 4,011		$ 4,526		$ 4,531
Return on plan assets	(4,783)		(5,046)		(4,960)
Recognized net actuarial loss	5,487		4,050		2,818
Net periodic benefit cost	$ 4,715		$ 3,530		$ 2,389
Actuarial Assumptions Used to Determine Net Cost [Abstract]
Discount rate (in hundredths)	4.10%		5.18%		5.84%
Expected return on assets (in hundredths)	7.00%		7.50%		7.50%
Rate of increase in compensation (in hundredths)		[1]		[1]		[1]

[1] n.a.