Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Benefit Plan
Change in Projected Benefit Obligation:
Beginning Balance	$ 56,201	$ 42,138
Service Cost	2,198	1,574	1,396
Interest Cost	2,417	2,261	2,228
Actuarial Loss	3,833	12,047
Benefits Paid	(1,832)	(1,819)
Ending Balance	62,817	56,201	42,138
Other Benefits Plan
Change in Projected Benefit Obligation:
Beginning Balance	43,121	29,605
Service Cost	1,784	1,306
Interest Cost	1,868	1,604
Actuarial Loss	4,425	11,121
Benefits Paid	(590)	(515)
Ending Balance	$ 50,608	$ 43,121